Thessaloniki, Greece

The Aristotle University of Thessaloniki is among the oldest and most prestigious higher education institutions of Greece. It is the largest university in Greece and in the Balkans. It is named after the philosopher Aristotle, who was born in Stageira, about 55 km east of Thessaloniki. Its campus covers 230,000 square metres in the centre of Thessaloniki, with additional educational and administrative facilities elsewhere.More than 95,000 students study at the Aristotle University, 86,000 in undergraduate programmes and 9,000 in postgraduate programmes. The Teaching and Research Staff number 2,248 people , the Scientific Teaching Staff number 84 and the Special Laboratory Teaching Staff 275 people. They are supported by 309 members of the Special Technical Laboratory for teaching services and the 1028 administrative staff.The language of instruction is Greek, although there are programs in foreign languages and courses for international students, which are carried out in English, French, German, and Italian. Wikipedia.

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Aristotle University of Thessaloniki and PAVLIDIS & Partners Co. | Date: 2017-02-01

Method for snail extract acquisition, more particularly of Cornu aspersum, comprising at least two steps, being remarkable in that a first step for obtaining the extract consists of a non stressful snail extract acquisition, wherein a batch of snails is selected which are brought to move by crawling on a set of surface means, particularly glass plates, under a set of predetermined conditions including moisture, temperature and duration, yielding a quantity of clear pedal mucus, which is removed from said surface means and placed into receptacles. It is followed by a further step consisting of drying with a subsequent resuspension step of the produced snail extract, resp. of a centrifugation of said snail extract.

Mitri G.H.,Association for Forests | Gitas I.Z.,Aristotle University of Thessaloniki
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

The aim of this paper is to investigate whether it is possible to accurately map postfire vegetation recovery on the Mediterranean island of Thasos by employing Earth Observing-1 (EO-1) Hyperion imagery and object-based classification. Specific objectives include the following: 1) locating and mapping areas of forest regeneration and other vegetation recovery and distinguishing among them; 2) distinguishing between Pinus brutia regeneration and Pinus nigra regeneration within the area of forest regeneration; and 3) examining whether it is possible to distinguish between areas of forest regeneration (Pinus brutia, Pinus nigra) and mature forest. The data used in this study consist of satellite images, field-spectroradiometry measurements, and field observations of the homogenous revegetated areas. The methodology comprised four consecutive steps. The first step involved preprocessing of the Hyperion image and field data. Subsequently, an object-oriented model was developed, which involved three steps, namely, image segmentation, object training, and object classification. The process resulted in the separation of five classes ("brutia mature," "nigra mature," "brutia regeneration," "nigra regeneration," and "other vegetation"). The accuracy assessment revealed very promising results (approximately 75.81% overall accuracy, with a Kappa Index of Agreement of 0.689). Some classification confusion involving the classes of Pinus brutia regeneration and Pinus nigra regeneration was recorded. This could be attributed to the absence of large homogenous areas of regenerated pine trees. The main conclusion drawn in this paper was that object-based classification can be used to accurately map postfire vegetation recovery using EO-1 Hyperion imagery. © 2009 IEEE.

Papanagiotou P.,Aristotle University of Thessaloniki | Tzimitra-Kalogianni I.,Aristotle University of Thessaloniki | Melfou K.,TEI of Western Macedonia Florina branch
Meat Science | Year: 2013

Expected quality is believed to be one of the most important factors that influence consumers' intention to purchase food. The present study seeks to explore the concept of pork meat expected quality and compare it with self-stated consumer intention to purchase pork meat. The aim is attempted by means of a field research conducted in Greece, following a conjoint analytic procedure. Results show that quality expectations comply with intention to buy pork, in many aspects. However, several differences have been identified. More specifically, country of origin and marbling appear to be more important for respondents' purchase decisions than they are for their quality evaluations, while the opposite appears to be true for price. Finally, socio-demographic factors such as gender, level of education, place of purchase and consumption habits seem to influence perceptions. © 2012.

Yiantsios S.G.,Aristotle University of Thessaloniki | Higgins B.G.,University of California at Davis
Physics of Fluids | Year: 2010

In film coating and other applications involving thin liquid films, surfactants are typically employed to suppress the usually undesirable instabilities driven by surface phenomena. Yet, in the present study a mechanism of Marangoni instability in evaporating thin films is presented and analyzed, which has its origin on the effects of a soluble surfactant. As the film thins due to evaporation, thickness perturbations lead to surfactant concentration perturbations, which in turn drive film motion and tend to enhance uneven drying. A thin-film analysis is applied and evolution equations for the film thickness and the surfactant concentration are derived and analyzed by the techniques of linear stability and numerical simulation. In the linear analysis a nonautonomous system is obtained for the film thickness and surfactant concentration perturbations, which shows that the instability will manifest itself provided that an appropriate Marangoni number is relatively large and the surfactant solubility in the bulk is large as well. On the other hand, low solubility in the bulk, diffusion, and the effect of surfactant on interfacial mobility through the surface viscosity are found to suppress disturbance growth. Direct numerical simulations of the full nonlinear evolution equations confirm those results and add to the picture obtained for the physical system behavior. Estimates of the relevant dimensionless parameters suggest that the conditions for instability may be met in relatively thick films, on the order of tens of microns, for which the effects of molecular forces and disjoining pressure are not dominant. Moreover, the stabilizing effects of diffusion and interfacial mobility are not likely to become significant unless the films are much thinner, i.e., on the order of 1 μm or below. © 2010 American Institute of Physics.

Samolada M.C.,Taki Oikonomidi | Zabaniotou A.A.,Aristotle University of Thessaloniki
Resources, Conservation and Recycling | Year: 2014

A debate is still open on issues of waste to energy methodologies aiming to answer to questions of particular relevance, such as whether the concept of SRF/RDF production can be applied directly to MSW through the Mechanical-Biological Treatment (MBT) process, when selective collection acts as a virtual pre-treatment of the same, or if the use of SRF/RDF as alternative fuel in cement kilns is the most sustainable solution. In this study, two scenarios were analyzed and compared: (a) the use of SRF in a new dedicated thermal plant for electricity production and (b) the use of SRF as an alternative fuel in an existing cement plant. The comparative assessment was based on principles of Sustainable Waste Management embracing technical and cost issues, environmental protection, industrial ecology and symbiosis. The application of SWOT analysis showed that the use of SRF in cement kilns is more sustainable compared to its use in a new dedicated plant for electricity production. © 2013 Elsevier B.V. All rights reserved.

Irakli M.N.,Greek National Agricultural Research Foundation | Samanidou V.F.,Aristotle University of Thessaloniki | Papadoyannis I.N.,Aristotle University of Thessaloniki
Journal of Separation Science | Year: 2011

The increasing interest in antioxidant properties of cereal and cereal-based products has prompted the development of a simple and reliable HPLC method for the simultaneous determination of important phytochemicals like tocopherols (T), tocotrienols (T3) and carotenoids. Separation was carried out on a Nucleosil 100 C 18 column, 5 μm (250 × 4.6 mm) thermostated at 25°C, using a linear gradient elution system starting with methanol and ending with a mixture of methanol-isopropanol-acetonitrile. All separated compounds including the internal standard (α-tocopherol acetate) were eluted within 16 min and detected by dual detection: fluorescence for tocopherols and tocotrienols at 290 nm excitation and 320 nm emission and UV-vis photodiode array detection for lutein and β-carotene at 450 nm. Detection limits ranged from 0.2 μg/g (β-carotene) to 1.60 μg/g (α-tocopherol). The intra- and inter-assay coefficients of variation were calculated by using cereals with different levels of lipophilic antioxidants. The extraction method involved sample saponification and clean-up by solid-phase extraction (SPE). The extraction recoveries obtained using OASIS HLB SPE cartridges and dichloromethane as eluent were in the range of 90.2-110.1%, with RSD lower than 10%. The method was successfully applied to cereals: durum wheat, bread wheat, rice, barley, oat, rye, corn and triticale. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Karaoulis M.C.,Aristotle University of Thessaloniki | Kim J.H.,Korea Institute of Geoscience and Mineral Resources | Tsourlos P.I.,Aristotle University of Thessaloniki
Journal of Applied Geophysics | Year: 2011

Techniques that incorporate regularization in space and time have been proposed to reduce inversion artifacts that may lead a misinterpretation of geophysical monitoring data. Applying this time regularization, however, may result in a model too smoothly carrying in the time domain. To alleviate this problem, we propose an algorithm for inverting time-lapse resistivity monitoring data.Here the time regularization is not considered to be constant between different time steps but is now allowed to vary depending on the degree of spatial resistivity changes occurring between different monitoring stages. Two methods are proposed to assign different time Lagrangian values, one based on a pre-estimation during execution time, and one using a-priori information. Both methods require a threshold to characterize the significance of the observed resistivity changes with time. We performed numerous numerical experiments using synthetic data to provide reasonable threshold values. Synthetic data tests illustrate that the new algorithm, named 4D Active Time Constrained (4D-ATC), produces in most cases improved time-lapse images when compared with existing techniques. Further the applicability of the new scheme is demonstrated with real data. Overall, the new algorithm is shown to be a useful tool for processing time-lapse resistivity data, which can be used with minor modifications to other types of time-lapse geophysical data. © 2010 Elsevier B.V.

Papa A.,Aristotle University of Thessaloniki | Velo E.,National Institute of Public Health | Bino S.,National Institute of Public Health
Clinical Microbiology and Infection | Year: 2011

Sandflies were collected in two districts of Albania and tested for a probable phlebovirus infection. A novel phlebovirus, provisionally named Adria virus, was detected in 2/12 pools, both trapped in a region close to the Adriatic Sea. The new virus is genetically closer (similarity 77.1% at nucleotide level) to Arbia virus, which belongs to the Salehabad serocomplex. Its distribution and probable pathogenicity to humans remain to be elucidated. © 2010 The Authors. Clinical Microbiology and Infection © 2010 European Society of Clinical Microbiology and Infectious Diseases.

Pazaitou-Panayiotou K.,Theagenion Cancer Hospital | Polyzos S.A.,Aristotle University of Thessaloniki | Mantzoros C.S.,Beth Israel Deaconess Medical Center
Obesity Reviews | Year: 2013

The incidence of thyroid cancer has been rising over the past few decades along with a parallel increase in obesity. Observational studies have provided evidence for a potential association between the two. By contrast, clinical data for a link between type 2 diabetes mellitus, a condition strongly associated with obesity, and thyroid cancer are limited and largely not supportive of such an association. Obesity leads to hypoadiponectinemia, a pro-inflammatory state, and insulin resistance, which, in turn, leads to high circulating insulin and insulin-like growth factor-1 levels, thereby possibly increasing the risk for thyroid cancer. Thus, insulin resistance possibly plays a pivotal role in underlying the observed association between obesity and thyroid cancer, potentially leading to the development and/or progression of thyroid cancer, through its interconnections with other factors including insulin-like growth factor-1, adipocytokines/cytokines and thyroid-stimulating hormone. In this review, epidemiological and clinical evidence and potential mechanisms underlying the proposed association between obesity and thyroid cancer risk are reviewed. If the association between obesity and thyroid cancer demonstrated in observational studies proves to be causal, targeting obesity (and/or downstream mediators of risk) could be of importance in the prevention and management of thyroid cancer. © 2013 International Association for the Study of Obesity.

Triantafyllakos G.,Aristotle University of Thessaloniki | Palaigeorgiou G.,T.E.I. Kavalas | Tsoukalas I.A.,Aristotle University of Thessaloniki
Computers and Education | Year: 2011

In this paper, we present a framework for the development of collaborative design games that can be employed in participatory design sessions with students for the design of educational applications. The framework is inspired by idea generation theory and the design games literature, and guides the development of board games which, through the use of adequate stimuli, rules and props, facilitate students in extracting and expressing their needs, desires and prospects regarding future educational software. To evaluate the proposed framework three studies were conducted. The first study aimed at the design of a web learning platform with the participation of 62 undergraduate higher education students in 13 design sessions; in the second study, a structured design approach was employed (12 sessions, 54 students) with the same design objective for comparison reasons; in the third study, the framework was deployed for the design of an electronic assessment application so as to examine its applicability in different learning domains (8 design sessions, 28 students). Students were very positive regarding both their participation and experience with the design games, and the needs elicited. The games favored a quick, broad exploration of the design space and facilitated the elicitation of numerous diverse needs and ideas, almost twice as many as produced by the structured approach. They also facilitated the creation of an informal atmosphere and limited the effects of common social influences on idea generation, such as social loafing, evaluation apprehension and production blocking. The three studies indicated that the proposed framework may simplify the development and employment of effective and efficient participatory design sessions in educational settings. © 2010 Elsevier Ltd. All rights reserved.

Goudakos J.K.,Aristotle University of Thessaloniki | Markou K.D.,Aristotle University of Thessaloniki
Clinical Otolaryngology | Year: 2011

Clin. Otolaryngol. 2011, 36, 212-220 Background: Endoscopic trans-sphenoidal surgery has been increasingly replacing microscopic surgery as the state of the art trans-sphenoidal approach. Objective of review: To assess the efficacy and safety of pure endoscopic approach in comparison with microscopic approach in pituitary surgery. Type of review: Literature review and meta-analysis. Search strategy: Systematic literature searches of MEDLINE (1952-10th February 2010), EMBASE (1974-10th February 2010) and the Cochrane Central Register of Controlled Trials to the 10th February 2010. Evaluation method: Review of all English-language studies comparing endoscopic and microscopic techniques. Results: Eleven relevant studies were identified with a total of 806 patients, 369 of whom had endoscopic surgery and 437 microscopic surgery. The initial remission rate of hypersecretion of functioning adenomas was not significantly different between the endoscopic and the microscopic group [(OR: 1.34(95% CI: 0.73-2.47); P=0.35; 66% remission rate in endoscopic group versus 60% in microscopic)].The proportion of patients with complete tumour removal was not significantly different in the endoscopic group than in the microscopic group [(OR: 0.83, (95% CI: 0.52-1.33); P=0.44]. The rate of CSF leak attributable to the surgical method did not differ significantly between endoscopic and microscopic group. Post-operative diabetes insipidus was less frequent in those having endoscopic surgery [15%versus 28%P=0.003]. Regarding the other intra cranial and nasal complications attributable to surgical technique, the occurrence rate in endoscopic group was significant lower compared with microscopic group (13%versus 1.2% respectively, P<0.05). Patients in the endoscopic group had significant shorter postoperative hospital stay with a range from 3.7 to 4.4days, than those of microscopic group with a range from 5.4 to 5.7days [(WMD: -1.53, (95% CI: -2.30 to -0.77); P<0.00001)]. Conclusions: Notwithstanding its limitations, the present systematic review, based on the currently available evidence, suggests that endoscopic trans-sphenoidal pituitary surgery is associated with similar rates of complete tumour excision and remission rates. Endoscopic surgery was associated with fewer complications related to surgical technique and a shorter hospital stay. © 2011 Blackwell Publishing Ltd.

Papana A.,Aristotle University of Thessaloniki | Kugiumtzis D.,Aristotle University of Thessaloniki | Larsson P.G.,University of Oslo
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

Measures of the direction and strength of the interdependence between two time series are evaluated and modified to reduce the bias in the estimation of the measures, so that they give zero values when there is no causal effect. For this, point shuffling is employed as used in the frame of surrogate data. This correction is not specific to a particular measure and it is implemented here on measures based on state space reconstruction and information measures. The performance of the causality measures and their modifications is evaluated on simulated uncoupled and coupled dynamical systems and for different settings of embedding dimension, time series length, and noise level. The corrected measures, and particularly the suggested corrected transfer entropy, turn out to stabilize at the zero level in the absence of a causal effect and detect correctly the direction of information flow when it is present. The measures are also evaluated on electroencephalograms (EEG) for the detection of the information flow in the brain of an epileptic patient. The performance of the measures on EEG is interpreted in view of the results from the simulation study. © 2011 American Physical Society.

News Article | November 30, 2016

Researchers at the University of Surrey have achieved record power conversion efficiencies for large area organic solar cells. In recent years scientists have been attempting to increase the efficiency of these cells to allow commercial applications such as integration into a building's glass façade, generating electricity to power the building. The research was led by the University of Surrey's Advanced Technology Institute (ATI) in collaboration with Oxford University, Aristotle University of Thessaloniki (Greece), and University of Stuttgart (Germany). The project is part of SMARTONICS, a four-year European Commission FP7 programme aimed at developing large-scale pilot lines for the fabrication and printing of organic polymer solar cells. The results, published in Advanced Electronic Materials, demonstrate that dependencies between the chemical and physical properties of the photoactive layer's building blocks within organic solar cells determine the efficiency of these solar cells. By using a well-known and low cost electron donating material (P3HT) in combination with an electron accepting material (ICBA) for the photosensitive layer of the organic solar cells, the research team discovered that different ICBA samples consist of dissimilar isomeric mixtures (isomers are molecules with the same number of atoms of each element, but with the atoms differently arranged). These characteristics are critical for the formation kinetics and spatial arrangement of P3HT and ICBA in their photosensitive blend and lead to varying power conversion efficiencies. Tailoring the fabrication process based on these findings, the research team were able to improve the efficiency of their solar cells from 2.2% up to 6.7%. This is one of the highest efficiencies to have been reported for P3HT blends on a large-area device. Professor Ravi Silva, corresponding author and Director of the ATI commented, "Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells - and more so when the organic is P3HT, the fruit fly for organic solar cells. Not only are they flexible, lightweight and environmentally-friendly, they are also design-friendly because they can be semi-transparent and printed in different colours and shapes. In addition, in contrast to their inorganic competitors, they convert efficiently indirect sunlight, which makes them an ideal material to power devices on the move, such as for the Internet of Things. Our group is looking to expand research in this field, with more PhD students and researchers, which will have such a positive impact on society." PhD student Dimitar Kutsarov, the paper's lead author, said, "The research represents a significant step forward in the understanding of the characteristics of materials with isomeric properties, which will lead to a future improvement of the efficiency of organic solar cells. We know now how important the spatial arrangement of the isomeric molecules is and will, therefore, be able to push the efficiency of P3HT-based solar cells further. Our findings will be used for the fabrication of meters long organic solar cells as part of the successful completion of the collaborative European project SMARTONICS."

News Article | November 30, 2016

Researchers at the University of Surrey have achieved record power conversion efficiencies for large area organic solar cells. In recent years scientists have been attempting to increase the efficiency of these cells to allow commercial applications such as integration into a building's glass façade, generating electricity to power the building. The research was led by the University of Surrey's Advanced Technology Institute (ATI) in collaboration with Oxford University, Aristotle University of Thessaloniki (Greece), and University of Stuttgart (Germany). The project is part of SMARTONICS, a four-year European Commission FP7 programme aimed at developing large-scale pilot lines for the fabrication and printing of organic polymer solar cells. The results, published in Advanced Electronic Materials, demonstrate that dependencies between the chemical and physical properties of the photoactive layer's building blocks within organic solar cells determine the efficiency of these solar cells. By using a well-known and low cost electron donating material (P3HT) in combination with an electron accepting material (ICBA) for the photosensitive layer of the organic solar cells, the research team discovered that different ICBA samples consist of dissimilar isomeric mixtures (isomers are molecules with the same number of atoms of each element, but with the atoms differently arranged). These characteristics are critical for the formation kinetics and spatial arrangement of P3HT and ICBA in their photosensitive blend and lead to varying power conversion efficiencies. Tailoring the fabrication process based on these findings, the research team were able to improve the efficiency of their solar cells from 2.2% up to 6.7%. This is one of the highest efficiencies to have been reported for P3HT blends on a large-area device. Professor Ravi Silva, corresponding author and Director of the ATI commented, "Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells - and more so when the organic is P3HT, the fruit fly for organic solar cells. Not only are they flexible, lightweight and environmentally-friendly, they are also design-friendly because they can be semi-transparent and printed in different colours and shapes. In addition, in contrast to their inorganic competitors, they convert efficiently indirect sunlight, which makes them an ideal material to power devices on the move, such as for the Internet of Things. Our group is looking to expand research in this field, with more PhD students and researchers, which will have such a positive impact on society." PhD student Dimitar Kutsarov, the paper's lead author, said, "The research represents a significant step forward in the understanding of the characteristics of materials with isomeric properties, which will lead to a future improvement of the efficiency of organic solar cells. We know now how important the spatial arrangement of the isomeric molecules is and will, therefore, be able to push the efficiency of P3HT-based solar cells further. Our findings will be used for the fabrication of meters long organic solar cells as part of the successful completion of the collaborative European project SMARTONICS."

News Article | November 30, 2016

The research was led by the University of Surrey's Advanced Technology Institute (ATI) in collaboration with Oxford University, Aristotle University of Thessaloniki (Greece), and University of Stuttgart (Germany). The project is part of SMARTONICS, a four-year European Commission FP7 programme aimed at developing large-scale pilot lines for the fabrication and printing of organic polymer solar cells. The results, published in Advanced Electronic Materials, demonstrate that dependencies between the chemical and physical properties of the photoactive layer's building blocks within organic solar cells determine the efficiency of these solar cells. By using a well-known and low cost electron donating material (P3HT) in combination with an electron accepting material (ICBA) for the photosensitive layer of the organic solar cells, the research team discovered that different ICBA samples consist of dissimilar isomeric mixtures (isomers are molecules with the same number of atoms of each element, but with the atoms differently arranged). These characteristics are critical for the formation kinetics and spatial arrangement of P3HT and ICBA in their photosensitive blend and lead to varying power conversion efficiencies. Tailoring the fabrication process based on these findings, the research team were able to improve the efficiency of their solar cells from 2.2% up to 6.7%. This is one of the highest efficiencies to have been reported for P3HT blends on a large-area device. Professor Ravi Silva, corresponding author and Director of the ATI commented, "Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells – and more so when the organic is P3HT, the fruit fly for organic solar cells. Not only are they flexible, lightweight and environmentally-friendly, they are also design-friendly because they can be semi-transparent and printed in different colours and shapes. In addition, in contrast to their inorganic competitors, they convert efficiently indirect sunlight, which makes them an ideal material to power devices on the move, such as for the Internet of Things. Our group is looking to expand research in this field, with more PhD students and researchers, which will have such a positive impact on society." PhD student Dimitar Kutsarov, the paper's lead author, said, "The research represents a significant step forward in the understanding of the characteristics of materials with isomeric properties, which will lead to a future improvement of the efficiency of organic solar cells. We know now how important the spatial arrangement of the isomeric molecules is and will, therefore, be able to push the efficiency of P3HT-based solar cells further. Our findings will be used for the fabrication of meters long organic solar cells as part of the successful completion of the collaborative European project SMARTONICS." Explore further: New way to make low-cost solar cell technology More information: Dimitar I. Kutsarov et al. Achieving 6.7% Efficiency in P3HT/Indene-CBisadduct Solar Cells through the Control of Vertical Volume Fraction Distribution and Optimized Regio-Isomer Ratios, Advanced Electronic Materials (2016). DOI: 10.1002/aelm.201600362

News Article | December 1, 2016

Abstract: •Research from the University of Surrey reveals scientists are able to improve the efficiency of solar cells more than threefold •The solar cells are a flexible, lightweight and environmentally-friendly and have the capacity to be printed in different colours and shapes •The solar cells are a contrast to their inorganic competitors as they also convert efficiently indirect sunlight, making them ideal material to power devices on the move, such as for the Internet of Things Researchers at the University of Surrey have achieved record power conversion efficiencies for large area organic solar cells. In recent years scientists have been attempting to increase the efficiency of these cells to allow commercial applications such as integration into a building's glass façade, generating electricity to power the building. The research was led by the University of Surrey's Advanced Technology Institute (ATI) in collaboration with Oxford University, Aristotle University of Thessaloniki (Greece), and University of Stuttgart (Germany). The project is part of SMARTONICS, a four-year European Commission FP7 programme aimed at developing large-scale pilot lines for the fabrication and printing of organic polymer solar cells. The results, published in Advanced Electronic Materials, demonstrate that dependencies between the chemical and physical properties of the photoactive layer's building blocks within organic solar cells determine the efficiency of these solar cells. By using a well-known and low cost electron donating material (P3HT) in combination with an electron accepting material (ICBA) for the photosensitive layer of the organic solar cells, the research team discovered that different ICBA samples consist of dissimilar isomeric mixtures (isomers are molecules with the same number of atoms of each element, but with the atoms differently arranged). These characteristics are critical for the formation kinetics and spatial arrangement of P3HT and ICBA in their photosensitive blend and lead to varying power conversion efficiencies. Tailoring the fabrication process based on these findings, the research team were able to improve the efficiency of their solar cells from 2.2% up to 6.7%. This is one of the highest efficiencies to have been reported for P3HT blends on a large-area device. Professor Ravi Silva, corresponding author and Director of the ATI commented, "Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells - and more so when the organic is P3HT, the fruit fly for organic solar cells. Not only are they flexible, lightweight and environmentally-friendly, they are also design-friendly because they can be semi-transparent and printed in different colours and shapes. In addition, in contrast to their inorganic competitors, they convert efficiently indirect sunlight, which makes them an ideal material to power devices on the move, such as for the Internet of Things. Our group is looking to expand research in this field, with more PhD students and researchers, which will have such a positive impact on society." PhD student Dimitar Kutsarov, the paper's lead author, said, "The research represents a significant step forward in the understanding of the characteristics of materials with isomeric properties, which will lead to a future improvement of the efficiency of organic solar cells. We know now how important the spatial arrangement of the isomeric molecules is and will, therefore, be able to push the efficiency of P3HT-based solar cells further. Our findings will be used for the fabrication of meters long organic solar cells as part of the successful completion of the collaborative European project SMARTONICS." For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Agency: Cordis | Branch: FP7 | Program: | Phase: | Award Amount: 3.21M | Year: 2008

eInfrastructure in Europe has reached a mature state where the GEANT network forms a backbone on top of which a distributed computing infrastructure - the Grid - provides processing and storage services for eScience research. The South-East European eInfrastructure initiatives are committed to ensuring equal participation of the less-resourced countries of the region in European trends. SEEREN initiative has established a regional network and its GEANT connection and the SEE-GRID initiative the regional Grid. Hereby proposed SEE-GRID-SCI will leverage the SEE eInfrastructure to enable new scientific collaborations among SEE user communities. SEE-GRID-SCI will stimulate widespread integrated eInfrastructure uptake by new cross-border user groups extending over the region, fostering collaboration and providing advanced capabilities to more researchers, with an emphasis on strategic groups in seismology, meteorology and environmental protection. The initiative thus aims to have a catalytic and structuring effect on a variety of user communities that currently do not directly benefit from the available eInfrastructures. In parallel, it will enlarge the regional eInfrastructure to cater for demands of the communities: a number of new Grid clusters and countries will be added, engaging a wider range of players and expanding the provider pool. Finally, SEE-GRID-SCI will help mature and stabilise the National Grid Initiatives in the region, allowing them to join the new era of longer-term sustainable Grid infrastructure in Europe. In this context, SEE-GRID-SCI will aim to attract political and financial support for materializing the eInfrastructure vision. In longer term, SEE-GRID-SCI aspires to contribute to the stabilisation and development of South-East Europe, by easing the digital divide and stimulating eInfrastructure development and adoption by new user communities, thus enabling collaborative high-quality research across a spectrum of scientific fields.

Michalakis K.,National and Kapodistrian University of Athens | Mintziori G.,Aristotle University of Thessaloniki | Kaprara A.,Aristotle University of Thessaloniki | Tarlatzis B.C.,Aristotle University of Thessaloniki | Goulis D.G.,Aristotle University of Thessaloniki
Metabolism: Clinical and Experimental | Year: 2013

The aim of this narrative review is to provide current evidence for the interaction between obesity, metabolic syndrome (MS) and reproductive axis. Gonadotropin-releasing hormone (GnRH) pulses and, consequently, normal function of reproductive (hypothalamus-pituitary-gonadal) axis depend on normal energy balance, which presupposes sufficient food intake, reasonable energy consumption and average thermoregulatory costs. In case of an energy imbalance, reproductive dysfunction may occur. In young women, excessive leanness is accompanied by puberty delay, whereas premature puberty might be a manifestation of obesity. In a similar way, obesity in men affects fertility. Excess adipose tissue results in increased conversion of testosterone to estradiol, which may lead to secondary hypogonadism through reproductive axis suppression. Moreover, oxidative stress at the level of the testicular micro-environment may result in decreased spermatogenesis and sperm damage. Products of the adipocyte, such as leptin, adiponectin and resistin, and gut peptides, such as ghrelin, are considered to be crucial in the interaction between energy balance and reproduction. Finally, an indirect evidence for the interplay between MS and reproductive axis is the fact that when treating components of one, parameters of the other can be improved as well. These therapeutic interventions include lifestyle modifications, pharmacological agents, such as sex hormone replacement therapy, and surgical procedures. Although many issues remain unclear, the elucidation of the complex interaction between MS and reproductive axis will have obvious clinical implications in the therapeutic approach of both entities. © 2013 Elsevier Inc.

Casasanto D.,Max Planck Institute for Psycholinguistics | Fotakopoulou O.,Aristotle University of Thessaloniki | Boroditsky L.,Stanford University
Cognitive Science | Year: 2010

What is the relationship between space and time in the human mind? Studies in adults show an asymmetric relationship between mental representations of these basic dimensions of experience: Representations of time depend on space more than representations of space depend on time. Here we investigated the relationship between space and time in the developing mind. Native Greek-speaking children watched movies of two animals traveling along parallel paths for different distances or durations and judged the spatial and temporal aspects of these events (e.g., Which animal went for a longer distance, or a longer time?). Results showed a reliable cross-dimensional asymmetry. For the same stimuli, spatial information influenced temporal judgments more than temporal information influenced spatial judgments. This pattern was robust to variations in the age of the participants and the type of linguistic framing used to elicit responses. This finding demonstrates a continuity between space-time representations in children and adults, and informs theories of analog magnitude representation. Copyright © 2010 Cognitive Science Society, Inc. All rights reserved.

Cholongitas E.,Aristotle University of Thessaloniki | Papatheodoridis G.V.,National and Kapodistrian University of Athens
World Journal of Gastroenterology | Year: 2013

The progress in treatment against hepatitis B virus (HBV) with the development of effective and well tolerated nucleotide analogues (NAs) has improved the outcome of patients with HBV decompensated cirrhosis and has prevented post-transplant HBV recurrence. This review summarizes updated issues related to the management of patients with HBV infection before and after liver transplantation (LT). A literature search using the PubMed/Medline databases and consensus documents was performed. Pre-transplant therapy has been initially based on lamivudine, but entecavir and tenofovir represent the currently recommended first-line NAs for the treatment of patients with HBV decompensated cirrhosis. After LT, the combination of HBV immunoglobulin (HBIG) and NA is considered as the standard of care for prophylaxis against HBV recurrence. The combination of HBIG and lamivudine is related to higher rates of HBV recurrence, compared to the HBIG and entecavir or tenofovir combination. In HBIG-free prophylactic regimens, entecavir and tenofovir should be the first-line options. The choice of treatment for HBV recurrence depends on prior prophylactic therapy, but entecavir and tenofovir seem to be the most attractive options. Finally, liver grafts from hepatitis B core antibody (anti-HBc) positive donors can be safely used in hepatitis B surface antigen negative, preferentially anti-HBc/anti-hepatitis B surface antibody positive recipients. © 2013 Baishideng Publishing Group Co., Limited. All rights reserved.

Kimiskidis V.K.,Aristotle University of Thessaloniki | Valentin A.,King's College London | Valentin A.,King's College | Kalviainen R.,Kuopio University Hospital
Current Opinion in Neurology | Year: 2014

Purpose of review: The aim is to critically review recent advances emerging from the application of transcranial magnetic stimulation (TMS) as a research and clinical tool in the field of epilepsy. Recent findings: A number of TMS-electromyography (EMG) and TMS-electroencephalography (EEG) studies have identified distinct changes of cortical excitability associated with specific epilepsy syndromes and in asymptomatic siblings of patients with epilepsy. Pharmaco-TMS studies have shed additional light on the effects of traditional and recently introduced antiepileptic drugs on excitatory and inhibitory brain microcircuits as well as cortical plasticity mechanisms. In addition, stronger evidence has emerged that TMS may serve as a biomarker with prognostic (i.e. predicting response to pharmacologic or surgical interventions) and diagnostic potential (for instance aiding in the noninvasive localization of the epileptogenic zone). Finally, the role of repetitive TMS in the therapeutic management of drug-resistant epilepsies and refractory status epilepticus has been further defined and is expected to become more prominent by the optimization of the stimulation parameters. Summary: TMS has provided important insight into the pathophysiological substrate of human epilepsies and emerges as a valuable tool with diagnostic, prognostic and therapeutic potential. The recent advent of TMS-EEG can be reasonably expected to contribute further significant advances to the field of epilepsy.

Pipili C.L.,National and Kapodistrian University of Athens | Papatheodoridis G.V.,National and Kapodistrian University of Athens | Cholongitas E.C.,Aristotle University of Thessaloniki
Kidney International | Year: 2013

Although the prevalence of chronic hepatitis B virus (HBV) infection in patients with chronic kidney disease remains low in developed countries, clinicians should be aware of the rationale for treatment in this setting. This patient population presents particular features and various complicating conditions requiring special treatment strategies. Interferon, the standard treatment for HBV infection, has been poorly tolerated by patients with chronic kidney disease, has presented relatively low efficacy, and has posed renal transplant recipients under the risk of acute rejection. The advent of effective nucleos(t)ide analogs (NAs) has offered the opportunity to minimize the consequences of HBV infection in HBV-positive patients with chronic kidney disease. Combination with immunosuppressive agents might be considered in cases of rapid renal function deterioration and/or severe proteinuria. Among the newer NAs, entecavir may be preferred, because of its high potency, high genetic barrier to resistance, and favorable renal safety profile. However, entecavir presented low efficacy in case of lamivudine or telbivudine resistance, and thus tenofovir may be a better option in that setting. All HBsAg-positive candidates should be treated with NAs before renal transplantation in order to maintain undetectable HBV DNA, reduce liver fibrosis, and prevent hepatic decompensation after renal transplantation. This review summarizes updated issues related to treatment of chronic HBV infection in all categories of population with chronic kidney disease (those exhibiting HBV-associated glomerular disease, those treated with hemodialysis, as well as renal transplant candidates, donors, and recipients). © 2013 International Society of Nephrology.

Kandarakis S.A.,National and Kapodistrian University of Athens | Piperi C.,National and Kapodistrian University of Athens | Topouzis F.,Aristotle University of Thessaloniki | Papavassiliou A.G.,National and Kapodistrian University of Athens
Progress in Retinal and Eye Research | Year: 2014

Advanced glycation end products (AGEs) have been implicated in vision loss associated with macula degeneration, cataract formation, diabetic retinopathy and glaucoma.This pathogenic potential is mainly attributed to their accumulation in ocular tissues where they mediate aberrant crosslinking of extracellular matrix proteins and disruption of endothelial junctional complexes that affects cell permeability, mediates angiogenesis and breakdown of the inner blood-retinal barrier. Furthermore, AGEs severely affect cellular metabolism by disrupting ATP production, enhancing oxidative stress and modulating gene expression of anti-angiogenic and anti-inflammatory genes. Elucidation of AGE-induced mechanisms of action in different eye compartments will help in the understanding of the complex cellular and molecular processes associated with eye diseases. Several pharmaceutical agents with anti-glycating and anti-oxidant properties as well as AGE crosslink 'breakers' have been currently applied to eye diseases. The role of diet and the beneficial effects of certain nutriceuticals provide an alternative way to manage chronic visual disorders that affect the quality of life of millions of people. © 2014 Elsevier Ltd.

Katsarou A.,National and Kapodistrian University of Athens | Armenaka M.C.,Aristotle University of Thessaloniki
Journal of the European Academy of Dermatology and Venereology | Year: 2011

We review the particular characteristics of atopic dermatitis (AD) in adult life, and compare findings with those of AD in childhood. AD affects 1-3% of adults world-wide, and can present as adult-onset AD, or as infantile/childhood AD that persists, or recurs after many years. Eczema in adults usually exists for years, compromising quality of life, sex life and occupational choices. The flexural areas, shoulders, head-and-neck, and hands are typically affected. In elderly adults, eczematous erythroderma is common. The intrinsic (non-IgE-allergic) eczema subtype affects 5-15% of cases. Classical food allergy has a low importance, although non-IgE-mediated and pseudoallergic reactions can cause eczema. Sensitivity to aeroallergens, especially dust mite, is demonstrated in the majority of adult AD patients, including elderly adults, by immunoglobulin E-mediated tests and/or atopy patch tests. Occupational allergic and irritant contact dermatitis is increased. In adults, as in children, Staphylococcus aureus colonization is very high, whereas adult skin is more heavily colonized with Malassezia yeasts. Immediate and delayed sensitization to Malassezia sympodialis is specific for intrinsic and extrinsic AD, occurring especially in head-and-neck eczema. Concerning therapy, older patients are prone to certain adverse drug effects. In conclusion, differences exist between childhood and adult disease. As we should be seeing more adults with AD in the future, there is a need for more clinical and immunological studies in older patients. © 2010 European Academy of Dermatology and Venereology.

Theodoridou I.,TU Darmstadt | Papadopoulos A.M.,Aristotle University of Thessaloniki | Hegger M.,TU Darmstadt
Energy Policy | Year: 2012

Designing measures for the reduction of energy consumption in urban areas is a complex venture indeed. In terms of urban sustainability, such measures affect energy efficiency as well as environmental, economic and social aspects. Numerous publications dealt with such methodological approaches in the past, whilst the subject of sustainable urban areas and cities is constantly gaining interest. Furthermore, energy performance depends on building density, occupancy and consumer profile, climatic conditions, not least construction quality, factors linked, directly or not, to socioeconomic aspects. Greek cities are known for their density, their polymorphic structure and their complexity. Thus, planning energy conservation measures is a difficult task, demanding a precise methodological approach, which will embody most of these aspects to a great extent. This paper proposes a methodology on how to manage Greek cities in terms of their energy efficiency, emphasizing on the residential stock. © 2012 Elsevier Ltd.

Kioutsioukis I.,Aristotle University of Thessaloniki | Melas D.,Aristotle University of Thessaloniki | Zerefos C.,National and Kapodistrian University of Athens
International Journal of Climatology | Year: 2010

This article focuses on extreme events of high and low temperatures and precipitation and their amplitude and frequency changes over the last 50 years in Greece. Sixteen climate indices have been calculated and their trends were analysed to identify possible changes over a network of measurement stations covering the region quite homogeneously. Furthermore, the changes in the probability distribution of the indices were examined. In addition, we analyzed the temporal evolution of the amplitude and frequency of extreme events through the parameters of extreme value distribution. The temporal stability of the fitted distributions is examined and the spatial distribution of their trend as well as the changes in the 5-year return levels is investigated. Half of the examined climatic indices exhibit significant regional trend; most of them are sole functions of minimum temperature or precipitation. A shift was found in the tail distribution of the peak minimum temperatures, with the 5-year return value in the last quartile of the twientieth century to be equal to the 7-year return value in the previous quartile. Warming was also apparent for the maximum temperature, mainly in the summer months, but of smaller magnitude. Total precipitation shifted towards drier climate over the domain while extreme rainfall events exhibit increased variability without following any coherent regional pattern. The changes in the peak temperature extremes are most sensitive to the changes in the location of the distribution of annual extremes. Changes in the precipitation extremes are associated with changes in both the scale and location of the fitted distribution. The highest range of change was found for the scale parameter for both temperature and precipitation extremes, pointing out that the most influenced factor is the interannual variability of the extremes. © 2009 Royal Meteorological Society.

Dalamaga M.,National and Kapodistrian University of Athens | Chou S.H.,Beth Israel Deaconess Medical Center | Shields K.,Beth Israel Deaconess Medical Center | Papageorgiou P.,Beth Israel Deaconess Medical Center | And 3 more authors.
Cell Metabolism | Year: 2013

Since its discovery as an adipocyte-secreted hormone, leptin has been found to impact food intake, energy homeostasis, and metabolism through its effects on the central nervous system and peripheral organs. Recent research indicates that leptin may also be involved in cognition, immune function, and bone metabolism. These findings place leptin at the intersection of neuroendocrinology and metabolism, and possibly immune function, and render it an appealing therapeutic target for several niche areas of unmet clinical need. Current evidence regarding classic and emerging roles of leptin as well as the pros and cons of its potential clinical use are summarized herein. © 2013 Elsevier Inc.

Kotzampassi K.,Aristotle University of Thessaloniki | Giamarellos-Bourboulis E.J.,National and Kapodistrian University of Athens | Giamarellos-Bourboulis E.J.,Friedrich - Schiller University of Jena
International Journal of Antimicrobial Agents | Year: 2012

According to current definitions, probiotics are live microorganisms that, when ingested in adequate quantities, exert a health benefit to the host. The action of probiotics in the host is exerted by three mechanisms: modulation of the content of gut microbiota; maintenance of the integrity of the gut barrier and prevention of bacterial translocation; and modulation of the local immune response by the gut-associated immune system. Regarding their role for the prevention and treatment of infectious diseases, adequate evidence coming from randomised clinical trials (RCTs) is available for antibiotic-associated diarrhoea (AAD), Clostridium difficile infection (CDI), acute gastroenteritis and infectious complications following admission to the Intensive Care Unit (ICU). Existing evidence supports their role for decreasing the incidence of AAD and CDI when administered in parallel with antimicrobials. They also shorten the duration of symptoms when administered in paediatric populations with acute gastroenteritis, particularly of rotavirus aetiology. Available evidence is not sufficient to support administration for the management of CDI. Regarding populations of critically ill patients, data from many RCTs suggest a decrease of infectious complications by starting feeding with probiotics following ICU admission, with the exception of patients suffering from severe pancreatitis. However, it should be underscored that all analysed RCTs are characterised by marked heterogeneity regarding the type of administered probiotic species, precluding robust recommendations. © 2012 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Bamidis P.D.,Aristotle University of Thessaloniki | Vivas A.B.,University of Sheffield | Styliadis C.,Aristotle University of Thessaloniki | Frantzidis C.,Aristotle University of Thessaloniki | And 4 more authors.
Neuroscience and Biobehavioral Reviews | Year: 2014

Maintaining a healthy brain is a critical factor for the quality of life of elderly individuals and the preservation of their independence. Challenging aging brains through cognitive training and physical exercises has shown to be effective against age-related cognitive decline and disease. But how effective are such training interventions? What is the optimal combination/strategy? Is there enough evidence from neuropsychological observations, animal studies, as well as, structural and functional neuroimaging investigations to interpret the underlying neurobiological mechanisms responsible for the observed neuroplasticity of the aging brain? This piece of work summarizes recent findings toward these questions, but also highlights the role of functional brain connectivity work, an emerging discipline for future research in healthy aging and the study of the underlying mechanisms across the life span. The ultimate aim is to conclude on recommended multimodal training, in light of contemporary trends in the design of exergaming interventions. The latter issue is discussed in conjunction with building up neuroscientific knowledge and envisaged future research challenges in mapping, understanding and training the aging brain. © 2014 Elsevier Ltd.

Mangera A.,Sheffield Teaching Hospitals NHS Trust | Apostolidis A.,Aristotle University of Thessaloniki | Andersson K.E.,Wake forest University | Dasgupta P.,King's College London | And 4 more authors.
European Urology | Year: 2014

Context Botulinum toxin A (BoNTA) has received regulatory approval for use in neurogenic detrusor overactivity (NDO) and overactive bladder (OAB), but it remains unlicensed in other lower urinary tract symptoms (LUTS) indications such as nonneurogenic LUTS in men with benign prostatic enlargement (LUTS/BPE), bladder pain syndrome (BPS), and detrusor sphincter dyssynergia (DSD). Objective To compare statistically the outcomes of high level of evidence (LE) studies with placebo using BoNTA for LUTS indications; NDO, OAB, LUTS/BPE, BPS and DSD. Evidence acquisition We conducted a systematic review of the published literature on PubMed, Scopus, and Embase reporting on BoNTA use in LUTS dysfunction. Statistical comparison was made between high LE studies with placebo and low LE studies. Evidence synthesis In adult NDO, there are significantly greater improvements with BoNTA in daily incontinence and catheterisation episodes (-63% and -18%, respectively; p < 0.01), and the urodynamic parameters of maximum cystometric capacity (MCC), reflex volume, and maximum detrusor pressure (MDP) (68%, 61%, and -42%, respectively; all p < 0.01). In OAB, BoNTA leads to significant improvements in bladder diary parameters such as daily frequency (-29%), daily urgency (-38%), and daily incontinence (-59%) (all p < 0.02). The urodynamic parameters of MCC and MDP improved by 58% (p = 0.04) and -29% (p = 0.002), respectively. The risk of urinary tract infection was significantly increased from placebo at 21% versus 7% (p < 0.001), respectively; the risk of intermittent self-catherisation increased from 0% to 12% (p < 0.001). Men with LUTS/BPE showed no significant improvements in International Prostate Symptom Score, maximum flow rate, or prostate volume. There were insufficient data for statistical analysis in DSD, BPS, and paediatric studies. Low LE studies were found to overestimate the effects of BoNTA in all indications, but differences from high LE studies were significant in only a few parameters. Conclusions BoNTA significantly improves all symptoms and urodynamic parameters in NDO and OAB. The effect of BoNTA in treating LUTS dysfunction appears to be overestimated in lower as opposed to higher LE studies. © 2013 European Association of Urology.

Preshaw P.M.,Northumbria University | Alba A.L.,Hospital Of Jove | Herrera D.,Complutense University of Madrid | Jepsen S.,University of Bonn | And 3 more authors.
Diabetologia | Year: 2012

Periodontitis is a common chronic inflammatory disease characterised by destruction of the supporting structures of the teeth (the periodontal ligament and alveolar bone). It is highly prevalent (severe periodontitis affects 10-15% of adults) and has multiple negative impacts on quality of life. Epidemiological data confirm that diabetes is a major risk factor for periodontitis; susceptibility to periodontitis is increased by approximately threefold in people with diabetes. There is a clear relationship between degree of hyperglycaemia and severity of periodontitis. The mechanisms that underpin the links between these two conditions are not completely understood, but involve aspects of immune functioning, neutrophil activity, and cytokine biology. There is emerging evidence to support the existence of a two-way relationship between diabetes and periodontitis, with diabetes increasing the risk for periodontitis, and periodontal inflammation negatively affecting glycaemic control. Incidences of macroalbuminuria and end-stage renal disease are increased twofold and threefold, respectively, in diabetic individuals who also have severe periodontitis compared to diabetic individuals without severe periodontitis. Furthermore, the risk of cardiorenal mortality (ischaemic heart disease and diabetic nephropathy combined) is three times higher in diabetic people with severe periodontitis than in diabetic people without severe periodontitis. Treatment of periodontitis is associated with HbA1c reductions of approximately 0.4%. Oral and periodontal health should be promoted as integral components of diabetes management. © 2011 The Author(s).

Cholongitas E.,Aristotle University of Thessaloniki | Papatheodoridis G.V.,National and Kapodistrian University of Athens
American Journal of Transplantation | Year: 2013

The combination of hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogues [NA(s)] is considered as the standard of care for prophylaxis against HBV recurrence after liver transplantation (LT), but the optimal protocol is controversial. We evaluated the efficacy of the newer NAs with high genetic barrier (hgbNA) [i.e. entecavir (ETV) or tenofovir (TDF)] with or without HBIG as prophylaxis against HBV recurrence after LT. In total, 519 HBV liver transplant recipients from 17 studies met the inclusion criteria and they were compared to those under lamivudine (LAM) and HBIG who had been selected in our previous review. Patients under HBIG and LAM developed HBV recurrence (115/1889 or 6.1%): (a) significantly more frequently compared to patients under HBIG and a hgbNA [1.0% (3/303), p < 0.001], and (b) numerically but not significantly more frequently compared to the patients who received a newer NA after discontinuation of HBIG [3.9% (4/102), p = 0.52]. The use of a hgbNA without any HBIG offered similar antiviral prophylaxis compared to HBIG and LAM combination, if the definition of HBV recurrence was based on HBV DNA detectability [0.9% vs. 3.8%, p = 0.11]. Our findings favor the use of HBIG and a hgbNA instead of HBIG and LAM combined prophylaxis against HBV recurrence after LT. The authors find that the use of hepatitis B immunoglobulin and a newer nucleos(t)ide analogue with high genetic barrier provides the best prophylaxis against HBV recurrence after liver transplantation. See related article by Di Costanzo et al (page 348). © Copyright 2012 The American Society of Transplantation and the American Society of Transplant Surgeons.

Kouretsis A.P.,Aristotle University of Thessaloniki | Stathakopoulos M.,Aristotle University of Thessaloniki | Stavrinos P.C.,National and Kapodistrian University of Athens
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The similarity between Finsler and Riemann geometry is an intriguing starting point to extend general relativity. The lack of quadratic restriction over the line element (color) naturally generalizes the Riemannian case and breaks the local symmetries of general relativity. In addition, the Finsler manifold is enriched with new geometric entities, and all the classical identities are suitably extended. We investigate the covariant kinematics of a medium formed by a timelike congruence. After a brief view in the general case, we impose particular geometric restrictions to get some analytic insight. A central role to our analysis plays the Lie derivative, where even in the case of irrotational Killing vectors the bundle still deforms. We demonstrate an example of an isotropic and exponentially expanding cross section that finally deflates or forms a caustic. Furthermore, using the 1+3 covariant formalism we investigate the expansion dynamics of the congruence. For certain geometric restrictions we retrieve the Raychaudhuri equation where a color-curvature coupling is revealed. The condition to prevent the focusing of neighboring particles is given and is more likely to be fulfilled in highly curved regions. Then, we introduce the Levi-Civita connection for the osculating Riemannian metric and develop a (spatially) isotropic and homogeneous dustlike model with a nonsingular bounce. © 2012 American Physical Society.

Kopanos G.M.,Polytechnic University of Catalonia | Puigjaner L.,Polytechnic University of Catalonia | Georgiadis M.C.,Aristotle University of Thessaloniki
Omega | Year: 2012

The production and logistics operations planning in real-life single- or multi-site semicontinuous food industries is addressed in this work. A discrete/continuous-time mixed integer programming model, based on the definition of families of products, is developed for the problem in question. A remarkable feature of the proposed approach is that in the production planning problem timing and sequencing decisions are taken for product families rather than for products. However, material balances are realized for every specific product, thus permitting the detailed optimization of production, inventory, and transportation costs. Changeovers are also explicitly taken into account and optimized. Moreover, alternative transportation modes are considered for the delivery of final products from production sites to distribution centers. The efficiency and the applicability of the proposed approach is demonstrated by solving to optimality two industrial-size case studies, for an emerging real-life Greek dairy industry. © 2011 Elsevier Ltd.

Floros G.,Aristotle University of Thessaloniki | Floros G.,Applied Technology Internet | Siomos K.,Applied Technology Internet
Psychiatry Research | Year: 2013

This paper presents a cross-sectional study of a large, high-school Greek student sample (N=1971) with the aim to examine adolescent motives for participating in social networking (SN) for a possible link with parenting style and cognitions related to Internet addiction disorder (IAD). Exploratory statistics demonstrate a shift from the prominence of online gaming to social networking for this age group. A regression model provides with the best linear combination of independent variables useful in predicting participation in SN. Results also include a validated model of negative correlation between optimal parenting on the one hand and motives for SN participation and IAD on the other. Examining cognitions linked to SN may assist in a better understanding of underlying adolescent wishes and problems. Future research may focus in the patterns unveiled among those adolescents turning to SN for the gratification of basic unmet psychological needs. The debate on the exact nature of IAD would benefit from the inclusion of SN as a possible online activity where addictive phenomena may occur. © 2013 Elsevier Ireland Ltd.

Pataka A.,Aristotle University of Thessaloniki | Riha R.L.,Royal Infirmary
Current Cardiology Reports | Year: 2013

The obstructive sleep apnea syndrome (OSAS) is associated with the development/worsening of cardiovascular disease. OSAS is considered to be an independent risk factor for hypertension and is linked to increased mortality in the context of coronary heart disease, the development of cardiac arrhythmias and increased risk of developing mild pulmonary hypertension. OSAS is also associated with cerebrovascular mortality and morbidity. In heart failure, OSAS can lead to worsening of symptoms. Treatment of OSAS using positive airways pressure therapy (PAP) has been shown in randomized, controlled trials in selected populations to reduce some, but not all of these cardiovascular and cerebrovascular risks. Unequivocal evidence of causality for OSAS in the development, progression, and outcomes of these disorders in all individuals suffering from them, is lacking. Good quality long-term morbidity and mortality data for the effects of OSAS on cardiometabolic health and the impact of PAP treatment are likewise limited. © Springer Science+Business Media New York 2013.

Vorria P.,Aristotle University of Thessaloniki | Ntouma M.,Aristotle University of Thessaloniki | Rutter M.,King's College London
Development and Psychopathology | Year: 2015

The aim of the study was to examine possible influences on individual differences in adolescence in response to early institutional care in infancy not involving either generalized privation or subnutrition. Fifty-two adopted adolescents aged 13 years who received institutional care in infancy at the Metera Babies Centre and 36 adolescents of the same age who were raised in their biological families participated in the study. Adolescents' attachment relationships, cognition, behavioral adjustment and use of psychological services were assessed. Marked heterogeneity in outcomes was found. No predictive effects were found for preinstitutional features or for adoptive circumstances. By contrast a large effect was found for institutional care extending beyond the age of 2 years and for quality of institutional care as experienced at an individual level. There was a close association between prolonged institutional care and disorganized attachment while in the institution, but the main institutional effect derived from the length of time in the institution. Copyright © Cambridge University Press 2015.

Gkaliagkousi E.,Aristotle University of Thessaloniki | Ferro A.,King's College London
Frontiers in Bioscience | Year: 2011

Nitric oxide (NO) exerts important protective actions on the cardiovascular system. Generated from L-arginine by the action of endothelial (or type 3) nitric oxide synthase (NOS3), NO regulates vascular tone in humans and causes endothelium-dependent vasodilation. Additionally endothelium-derived NO exerts antioxidant, antiproliferative and anti-inflammatory properties, thus playing an important role in inhibiting the atherosclerotic process. With regard to effects on platelet function, NO produced by both endothelial cells and platelets has important antithrombotic effects by decreasing platelet activation, a phenomenon which contributes importantly to the thrombotic tendency which accompanies a variety of cardiovascular disease states. Additionally, by inhibiting platelet activation, NO prevents heterotypic aggregation between platelets and monocytes, thereby reducing monocyte-platelet aggregates in the circulation which are believed to play an important pathophysiological role in the initiation and progression of atherosclerosis. New therapeutic interventions aimed at improving NO availability have been investigated in animal as well as in vitro studies and show considerable promise, but it remains to be seen whether such therapies will be equally efficacious in humans clinically.

Theodoridou I.,TU Darmstadt | Papadopoulos A.M.,Aristotle University of Thessaloniki | Hegger M.,TU Darmstadt
Energy and Buildings | Year: 2011

The latest developments in the field of energy supply, along with the major issue of the environment protection, set new priorities and yardsticks concerning the energy policies implemented worldwide. The development and implementation of effective energy conservation policies has been a target of the European Union ever since the days when it was still called European Economic Community. In this framework, and despite the successes already monitored, the need for further energy conservation in the building sector is a both an aim and a tool. Emphasis is being placed on the residential building stock and the improvement of its energy performance. Greece has been one of the last countries to adopt the Directive on the Energy Performance of Buildings. A thorough research regarding the nature of the Greek residential building stock helps in highlighting the problems associated with this delay, but also the perspectives for catching up with the other EU member states and achieving the aims set for the coming years. This paper aims at providing detailed information on the residential urban building stock, as determined in a field study in typical big and smaller Greek cities. © 2011 Elsevier B.V. All rights reserved.

Theodoridou I.,TU Darmstadt | Papadopoulos A.M.,Aristotle University of Thessaloniki | Hegger M.,TU Darmstadt
Energy and Buildings | Year: 2011

Based on the European Directive on the Energy Performance of Buildings a new regulation framework has recently been implemented in Greece, aiming at the CO2 emissions reduction caused by the building sector. Given the fact that almost 71% of the Greek buildings were constructed before the implementation of the first Thermal Insulation Regulation (TIR), emphasis must be laid upon the existing building stock. Moreover, 83% of this stock consists of residential buildings, indicating the large potential in energy conservation. In order to plan and promote the respective energy renovation scenarios, a thorough analysis of the Greek building stock has to be carried out, especially regarding the urban built environment. In order to achieve this, a classification of the dominating multifamily building typology is being presented and characteristic examples are being studied. © 2011 Elsevier B.V. All rights reserved.

Mitrakis N.E.,European Commission - Joint Research Center Ispra | Mitrakis N.E.,Aristotle University of Thessaloniki | Theocharis J.B.,Aristotle University of Thessaloniki
Information Sciences | Year: 2012

In this article, an efficient structure learning algorithm is proposed for the development of self-organizing neuro-fuzzy multilayered classifiers (SONeFMUC). These classifiers are hierarchical structures comprising small-scale fuzzy-neuron classifiers (FNCs), interconnected along multiple layers. At each layer, parent FNCs are combined to construct a descendant FNC at the next layer with enhanced classification qualities. The SONeFMUC structure is progressively expanded by generating new layers based on the principles of the Group Method of Data Handling (GMDH) algorithm, which is appropriately adapted to handle classification tasks. Traditional GMDH proceeds blindly to the construction of all possible parent FNC pairs from the previous layer to obtain the individuals in the next layer without paying due attention to the diversity of the FNC combinations. However, previous experimentation shows that a large number of descendant FNCs exhibit similar or slightly better classification capabilities than their parent FNCs. This causes an increase of the computational cost required for structure learning, without a direct impact on the accuracy of the obtained models. In this paper, a modified version of GMDH is devised for effective identification of the SONeFMUC structure. We incorporate the Proportion of Specific Agreement (Ps) as a means to evaluate the diversity of the FNC pairs. In the devised method, only complementary FNCs are combined, i.e., FNCs which commit errors at different pattern subspaces, to construct a descendant FNC at the next layer. Accordingly, a computational reduction is achieved while high classification accuracy is maintained. The efficiency of the proposed structure learning is tested on a diverse set of benchmark datasets using land cover classification from multispectral images as a real-world application. © 2011 Elsevier Inc. All rights reserved.

Pipili C.,Laiki Merimna | Cholongitas E.,Aristotle University of Thessaloniki | Papatheodoridis G.,National and Kapodistrian University of Athens
Alimentary Pharmacology and Therapeutics | Year: 2014

Background The treatment of chronic hepatitis B (CHB) in patients with chronic kidney disease (CKD) is based on nucleoside (lamivudine, telbivudine, entecavir) or nucleotide (adefovir, tenofovir) analogues (NAs), but it may be complex and the information is scarce. Entecavir and tenofovir represent the currently recommended first-line NAs for NA-naive CHB patients, while tenofovir is the NA of choice for CHB patients with resistance to nucleosides. Aim To review the efficacy and safety of NAs in adult CHB patients with CKD and to provide reasonable recommendations for their optimal management. Methods Literature search in PubMed/Medline and manual search of relevant articles, reviews and book chapters. Results NAs are cleared by kidneys and their dosage should be adjusted in patients with creatinine clearance <50 mL/min. There are concerns about nephrotoxic potential of the nucleotides, particularly adefovir, while improvements of creatinine clearance have been reported under telbivudine. Most existing data in CHB patients with CKD are for lamivudine and, less frequently, for other NAs, mostly entecavir. Besides CHB, NA should be used in case of immunosuppressive therapy in any HBsAg-positive patient with CKD including renal transplant (RT) recipients and in anti-HBs-positive recipients of kidney grafts from HBsAg-positive donors. Conclusions Chronic hepatitis B patients with chronic kidney disease receiving nucleoside analogues should be followed carefully for treatment efficacy and renal safety. Despite the absence of strong data, entecavir and telbivudine seem to be the preferred options for nucleoside analogue-naive CHB patients with chronic kidney disease, depending on viraemia and severity of renal dysfunction. More studies are certainly needed in this setting. © 2013 John Wiley & Sons Ltd.

Charmousis C.,University Paris - Sud | Iosifidis D.,Aristotle University of Thessaloniki
Journal of Physics: Conference Series | Year: 2015

Studying a certain sub class of higher order Horndeski (scalar-tensor) theories we discuss a method discovered recently permitting analytic black hole solutions with a non trivial and regular scalar field. One of the solutions found has de Sitter asymptotics and self tunes the bulk cosmological constant. Using the aforementioned method we find and analyse new black hole solutions which can also have de Sitter asymptotics. By looking at small deviations of the integration constant responsible for self tuning we discuss the robustness of the self tuning mechanism. We find that neighboring solutions to the one previously found present also self tuning properties with unaltered effective cosmological constant. © Published under licence by IOP Publishing Ltd.

Baltas A.E.,Aristotle University of Thessaloniki | Dervos A.N.,Hydroeconomy Karditsa
Renewable Energy | Year: 2012

Greece has adopted measures to support renewable energy sources ensuring the simplification of the licensing procedures. A regulatory framework is presented for the determination of the appropriate areas and the constraints for the installation of renewable energy projects, categorised by activity (wind farms, small hydroelectric projects, photovoltaic parks), based on the available national data. The sites that are infeasible for installation are defined. Regarding the spatial planning of wind farms, the national territory is divided into major categories based on the exploitable wind potential and particular spatial and environmental characteristics. Criteria are set for the installation of wind farms in the mainland and for their integration into the landscape in such a way that the visual effect has the least possible impact. The cases of installation at inhabited islands and marine areas are also reported. Regarding the spatial planning of Small Hydroelectric Projects, the water districts with exploitable hydraulic potential and restrictions concerning the capacity of the water stream are defined. Criteria are set for the installation of these projects in such a way that the environmental burden is low, taking into account technical and geological constraints. Privileged areas for the installation of biomass/biogas and geothermal energy projects are also reported. © 2012 Elsevier Ltd.

Kouretsis A.P.,Aristotle University of Thessaloniki | Stathakopoulos M.,1 Anastasiou Genadiou Street | Stavrinos P.C.,National and Kapodistrian University of Athens
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We construct a cosmological toy model based on a Finslerian structure of space-time. In particular, we are interested in a specific Finslerian Lorentz violating theory based on a curved version of Cohen and Glashow's very special relativity. The osculation of a Finslerian manifold to a Riemannian manifold leads to the limit of relativistic cosmology, for a specified observer. A modified flat Friedmann-Robertson-Walker cosmology is produced. The analogue of a zero energy particle unfolds some special properties of the dynamics. The kinematical equations of motion are affected by local anisotropies. Seeds of Lorentz violations may trigger density inhomogeneities to the cosmological fluid. © 2010 The American Physical Society.

Karayiannidis Y.,KTH Royal Institute of Technology | Doulgeri Z.,Aristotle University of Thessaloniki
Robotics and Autonomous Systems | Year: 2012

The problem of robot joint position control with prescribed performance guarantees is considered; the control objective is the error evolution within prescribed performance bounds in both problems of regulation and tracking. The proposed controllers do not utilize either the robot dynamic model or any approximation structures and are composed by simple PID or PD controllers enhanced by a proportional term of a transformed error through a transformation related gain. Under a sufficient condition for the damping gain, the proposed controllers are able to guarantee (i) predefined minimum speed of convergence, maximum steady state error and overshoot concerning the position error and (ii) uniformly ultimate boundedness (UUB) of the velocity error. The use of the integral term reduces residual errors allowing the proof of asymptotic convergence of both velocity and position errors to zero for the regulation problem under constant disturbances. Performance is a priori guaranteed irrespective of the selection of the control gain values. Simulation results of a three dof spatial robotic manipulator and experimental results of one dof manipulator are given to confirm the theoretical findings. © 2011 Elsevier B.V. All rights reserved.

Floros G.,Aristotle University of Thessaloniki | Floros G.,Applied Technology Internet | Siomos K.,Applied Technology Internet
Cyberpsychology, Behavior, and Social Networking | Year: 2012

In this study, we attempt to identify motives pivotal in choices made regarding online and offline game genres and assess whether they are meaningful predictors of Internet addiction. A separate goal was to determine how an assessment of Internet-related cognitions compares to criteria-based research instruments on Internet addiction, and demonstrate its clinical usefulness. We are using data from a cross-sectional study of the entire adolescent student population aged 12-18 of the island of Kos. Results indicate that specific game genres and motives for choosing a game are important predictors of Internet addiction, even after accounting for sociodemographic and Internet-use-related variables. Gender differences are not statistically important when we account for genre choices and motives for choosing them. Boys' thought content tends to revolve more around their Internet use compared to girls. Several patterns of motives to play specific genres were identified with the help of a canonical correlation analysis, demonstrating the fact that the simple observation of overt behavior is not enough to deduce the meaning of these actions for the individual. Using multiple measures of online addiction, examining genre preferences and underlying motives for choosing a game can be helpful in reaching a better understanding of the individual game player. © Copyright 2012, Mary Ann Liebert, Inc.

Amer P.R.,AbacusBio Ltd | Banos G.,Aristotle University of Thessaloniki
Journal of Dairy Science | Year: 2010

The aim of this study was to evaluate and quantify the importance of avoiding overlap between training and testing subsets of data when evaluating the effectiveness of predictions of genetic merit based on genetic markers. Genomic selection holds great potential for increasing the accuracy of selection in young bulls and is likely to lead quickly to more widespread use of these young bulls with a shorter generation interval and faster genetic improvement. Practical implementations of genomic selection in dairy cattle commonly involve results of national genetic evaluations being used as the dependent variable to evaluate the predictive ability of genetic markers. Selection index theory was used to demonstrate how ignoring correlations among errors of prediction between animals in training and testing sets could result in overestimates of accuracy of genomic predictions. Correlations among errors of prediction occur when estimates of genetic merit of training animals used in prediction are taken from the same genetic evaluation as estimates for validation of animals. Selection index theory was used to show a substantial degree of error correlation when animals used for testing genomic predictions are progeny of training animals, when heritability is low, and when the number of recorded progeny for both training and testing animals is low. Even when training involves a dependent variable that is not influenced by the progeny records of testing animals (i.e., historic proofs), error correlations can still result from records of relatives of training animals contributing to both the historic proofs and the predictions of genetic merit of testing animals. A simple simulation was used to show how an error correlation could result in spurious confirmation of predictive ability that was overestimated in the training population because of ascertainment bias. Development of a method of testing genomic selection predictions that allows unbiased testing when training and testing variables are estimated breeding values from the same genetic evaluation would simplify training and testing of genomic predictions. In the meantime, a 4-step approach for separating records used for training from those used for testing after correction of fixed effects is suggested when use of progeny averages of adjusted records (e.g., daughter yield deviations) would result in inefficient use of the information available in the data. © 2010 American Dairy Science Association.

Cholongitas E.,Aristotle University of Thessaloniki | Papatheodoridisb G.V.,National and Kapodistrian University of Athens
Annals of Gastroenterology | Year: 2014

Major changes have emerged during the last few years in the therapy of patients with chronic hepatitis C (CHC). Several direct acting antiviral agents (DAAs) have been developed showing potent activity against hepatitis C virus (HCV) and incrementally improving the rates of sustained virological response (SVR), even in difficult-to-treat CHC patients. Sofosbuvir, a new nucleotide analog, HCV NS5B polymerase inhibitor, represents the first key step towards the new era in the management of CHC, since it is the first approved DAA with excellent tolerability and favorable pharmacokinetic profile, limited potential for drug interactions, potent antiviral activity and high genetic barrier against all HCV genotypes. Sofosbuvir has recently become commercially available in combination with ribavirin, with or without pegylated interferon, achieving high SVR rates after 12-24 weeks of therapy. Finally, since interferon-free regimens are close to becoming the new standard of care in CHC patients, sofosbuvir has an ideal profile to be the cornerstone antiviral agent, especially in difficult-to-treat CHC patients, given in combination with other new DAAs. This review summarizes the main updated issues related to the efficacy and safety of sofosbuvir-containing regimens in CHC patients. © 2014 Hellenic Society of Gastroenterology.

Yannopoulos S.,Aristotle University of Thessaloniki | Spiliotis M.,National and Kapodistrian University of Athens
Water Resources Management | Year: 2013

Reliability analysis of water distribution systems is a complex task, as it requires both definition and calculation of several reliability measures. In this paper, a methodology for evaluating water distribution system reliability is developed and demonstrated on a simple water distribution network based on the minimum cut-set approach. In general, the definition of the minimum cut-set can arise either from the mechanical reliability or from the concept of hydraulic reliability. In the case of mechanical reliability, a new method based on graph theory is developed, in order to determine the minimum cut-set. This method is based on the counting of paths between nodes. Furthermore, the general concept of reliability is proposed, to include apart from the mechanical reliability, more generally, the pressure availability at nodes as a main hydraulic property. Based on the pressure availability, the sense of hydraulic availability can be expressed as a fuzzy set, while the combination of the water unavailability of the nodes can be achieved by using fuzzy averaging aggregator. Finally, an overall reliability index is proposed based on both the hydraulic and the mechanical reliability. An illustrative example is developed to indicate the methodology. © 2012 Springer Science+Business Media Dordrecht.

News Article | February 24, 2017

Mild cognitive impairment (MCI), a condition that often predates Alzheimer's disease (AD), can be remotely detected through a self-administered virtual reality brain training game. Thessaloniki, Greece, February 23, 2017 - Greek researchers demonstrated the potential of a self-administered virtual supermarket cognitive training game for remotely detecting mild cognitive impairment (MCI), without the need for an examiner, among a sample of older adults. MCI patients suffer from cognitive problems and often encounter difficulties in performing complex activities such as financial planning. They are at a high risk for progressing to dementia however early detection of MCI and suitable interventions can stabilize the patients' condition and prevent further decline. It has been shown that virtual reality game-based applications and especially virtual supermarkets can detect MCI. Past studies have utilized user performance in such applications along with data from standardized neuropsychological tests in order to detect MCI. The team that conducted this study was the first scientific team to achieve reliable MCI detection using a virtual reality game-based application on its own. In that previous study , administration of the virtual super market (VSM) exercise was conducted by an examiner. The present study eliminated the need for an examiner by calculating the average performance of older adults using a special version of the VSM application, the VSM Remote Assessment Routine (VSM-RAR), at home on their own, for a period of one month. It is the first instance where a self-administered virtual reality application was used to detect MCI with a high degree of reliability. The research team included scientists from the Aristotle University of Thessaloniki (AUTH), the Centre for Research and Technology Hellas/Information Technologies Institute (CERTH/ITI), the Greek Association of Alzheimer's Disease and Related Disorders (GAADRD) and the Network Aging Research (NAR) of the University of Heidelberg. In an article published in the Journal of Alzheimer's Disease, the researchers have indicated that the virtual supermarket remote assessment routine (VSM-RAR) application displayed a correct classification rate (CCR) of 91.8% improving VSM's CCR as assessed in the previous VSM study while achieving a level of diagnostic accuracy similar to the most accurate standardized neuropsychological tests, which are considered the gold standard for MCI detection. Self-administered computerized cognitive training exercises/games are gaining popularity among older adults as an easy and enjoyable means of maintaining cognitive health. Such applications are especially popular among older adults who consider themselves healthy and are not inclined to visit specialized memory clinics for cognitive assessment. If self-administered games and exercises could also detect cognitive disorders, initial cognitive screening could be conducted remotely. The wide implementation of this method of remote screening would facilitate the detection of cognitive impairment at the MCI stage thus allowing for more efficient therapeutic interventions. This preliminary study indicates that automated, remote MCI screening is feasible. This method could be utilized to screen the majority of the older adult population, as it dramatically lowers examination-related costs. The social and economic benefits, especially caregiver and healthcare service burden, of the early detection of cognitive disorders could be enormous. At the same time, as older adults are becoming increasingly computer savvy, it is important to create software that meets their needs and allows them to remain healthy and active. Out team continues its research on the VSM with the aim of improving its usability, shortening its administration time and supplementing the science behind VSM with additional data. The Journal of Alzheimer's Disease is an international multidisciplinary journal to facilitate progress in understanding the etiology, pathogenesis, epidemiology, genetics, behavior, treatment and psychology of Alzheimer's disease. The journal publishes research reports, reviews, short communications, book reviews, and letters-to-the-editor. Groundbreaking research that has appeared in the journal includes novel therapeutic targets, mechanisms of disease and clinical trial outcomes. The Journal of Alzheimer's Disease has an Impact Factor of 3.612 according to Thomson Reuters' 2013 Journal Citation Reports. It is ranked #22 on the Index Copernicus Top 100 Journal List. The Journal is published by IOS Press.

Trigas P.,Agricultural University of Athens | Panitsa M.,University of Ioannina | Tsiftsis S.,Aristotle University of Thessaloniki
PLoS ONE | Year: 2013

Understanding diversity patterns along environmental gradients and their underlying mechanisms is a major topic in current biodiversity research. In this study, we investigate for the first time elevational patterns of vascular plant species richness and endemism on a long-isolated continental island (Crete) that has experienced extensive post-isolation mountain uplift. We used all available data on distribution and elevational ranges of the Cretan plants to interpolate their presence between minimum and maximum elevations in 100-m elevational intervals, along the entire elevational gradient of Crete (0-2400 m). We evaluate the influence of elevation, area, mid-domain effect, elevational Rapoport effect and the post-isolation mountain uplift on plant species richness and endemism elevational patterns. Furthermore, we test the influence of the island condition and the post-isolation mountain uplift to the elevational range sizes of the Cretan plants, using the Peloponnese as a continental control area. Total species richness monotonically decreases with increasing elevation, while endemic species richness has a unimodal response to elevation showing a peak at mid-elevation intervals. Area alone explains a significant amount of variation in species richness along the elevational gradient. Mid-domain effect is not the underlying mechanism of the elevational gradient of plant species richness in Crete, and Rapoport's rule only partly explains the observed patterns. Our results are largely congruent with the post-isolation uplift of the Cretan mountains and their colonization mainly by the available lowland vascular plant species, as high-elevation specialists are almost lacking from the Cretan flora. The increase in the proportion of Cretan endemics with increasing elevation can only be regarded as a result of diversification processes towards Cretan mountains (especially mid-elevation areas), supported by elevation-driven ecological isolation. Cretan plants have experienced elevational range expansion compared to the continental control area, as a result of ecological release triggered by increased species impoverishment with increasing elevation. © 2013 Trigas et al.

Koufaki P.,Heriot - Watt University | Kouidi E.,Aristotle University of Thessaloniki
Sports Medicine | Year: 2010

Chronic kidney disease (CKD) is becoming a serious health problem throughout the world and is one of the most potent known risk factors for cardiovascular disease. Deterioration of physical function is accelerated in patients with CKD to levels that significantly impact on clinically and patient-important outcomes such as morbidity, employment, quality of life and, ultimately, survival. However, meaningful interpretation of the existing physical function-related literature in adult patients with CKD is hindered, possibly due to inconsistent choice of methodology, assessment tools and reporting of data. The current comprehensive review of the literature aims to provide the theoretical rationale and framework for physical function assessment and to identify the prevailing approaches to (i) the characterization (classification and terminology), (ii) interpretation, and (iii) reporting of physical function assessment in people with CKD. Comprehensive assessment of physical function can provide important information about the presence of 'physiological impairment' at a body systems level (exercise tolerance under well controlled, laboratory-based procedures), 'functional limitations' (physical performance during tasks imitating usual daily, personal or occupational tasks) and 'functional disability' (via self-reported physical functioning in the context of a socio-cultural environment). The selection of physical function assessment tools should be guided by the primary purpose of the assessment (e.g. research or routine clinical monitoring), by the overall scientific 'soundness' of the chosen tool (e.g. validity, utility, reproducibility, responsiveness characteristics) and by operational factors (e.g. patient collaboration, cost, personnel expertise). Recommendations for tests, methods and protocols are therefore presented, for the assessment of cardiorespiratory and muscular fitness, physical performance and self-reported physical functioning. These recommendations are based on synthesis of available information as derived from controlled exercise training interventions in adult patients with CKD. Special considerations for physical function assessment and suggestions for future research are also addressed. Such an information synthesis might promote greater standardization of the physical function assessment of patients with CKD in routine clinical care or research settings. This would potentially lead to generation of adequate scientific decision-making criteria to help researchers and healthcare providers in selecting the most appropriate measures according to the physical function areas assessed, and to accurately and meaningfully characterize and compare patients responses to therapeutic interventions. © 2010 Adis Data Information BV. All rights reserved.

Marcellin P.,French Institute of Health and Medical Research | Gane E.,Auckland City Hospital | Buti M.,Hospital General Universitari Vall dHebron and ehd | Afdhal N.,Beth Israel Deaconess Medical Center | And 11 more authors.
The Lancet | Year: 2013

Background: Whether long-term suppression of replication of hepatitis B virus (HBV) has any beneficial effect on regression of advanced liver fibrosis associated with chronic HBV infection remains unclear. We aimed to assess the effects on fibrosis and cirrhosis of at least 5 years' treatment with tenofovir disoproxil fumarate (DF) in chronic HBV infection. Methods: After 48 weeks of randomised double-blind comparison (trials NCT00117676 and NCT00116805) of tenofovir DF with adefovir dipivoxil, participants (positive or negative for HBeAg) were eligible to enter a 7-year study of open-label tenofovir DF treatment, with a pre-specified repeat liver biopsy at week 240. We assessed histological improvement (≥2 point reduction in Knodell necroinflammatory score with no worsening of fibrosis) and regression of fibrosis (≥1 unit decrease by Ishak scoring system). Findings: Of 641 patients who received randomised treatment, 585 (91%) entered the open-label phase, and 489 (76%) completed 240 weeks. 348 patients (54%) had biopsy results at both baseline and week 240. 304 (87%) of the 348 had histological improvement, and 176 (51%) had regression of fibrosis at week 240 (p<0·0001). Of the 96 (28%) patients with cirrhosis (Ishak score 5 or 6) at baseline, 71 (74%) no longer had cirrhosis (≥1 unit decrease in score), whereas three of 252 patients without cirrhosis at baseline progressed to cirrhosis at year 5 (p<0·0001). Virological breakthrough occurred infrequently and was not due to resistance to tenofovir DF. The safety profile was favourable: 91 (16%) patients had adverse events but only nine patients had serious events related to the study drug. Interpretation: In patients with chronic HBV infection, up to 5 years of treatment with tenofovir DF was safe and effective. Long-term suppression of HBV can lead to regression of fibrosis and cirrhosis. Funding: Gilead Sciences. © 2013 Elsevier Ltd.

Veloukas T.,Aristotle University of Thessaloniki | Markoglou A.N.,Agricultural University of Athens | Karaoglanidis G.S.,Aristotle University of Thessaloniki
Plant Disease | Year: 2013

Succinate dehydrogenase inhibiting (SDHI) fungicides constitute a relatively novel fungicide group used for gray mold control caused mainly by Botrytis cinerea. Shortly after registration, resistance was observed in fungal populations that correlated with several mutations in the succinate dehydrogenase complex (complex II). In the current study, 30 B. cinerea isolates possessing five different mutations at three different codons of SdhB (P225F, N230I, and H272L/R/Y) were characterized for their sensitivities to eight SDHI fungicides. The results show different sensitivities and cross-resistance patterns between structurally different SDHIs. P225F mutants were resistant in vitro to all SDHIs tested. Similarly, isolates possessing the H272L mutation were highly resistant to boscalid but showed low to moderate levels of resistance to other SDHIs. The N230I mutants were moderately resistant to boscalid, fluopyram, and fluxapyroxad and showed low resistance levels to isopyrazam, bixafen, fenfuram, benodanil, and carboxin. The H272R mutants showed moderate levels of resistance to boscalid and low resistance levels to isopyrazam, fenfuram, and carboxin but remained sensitive to fluopyram, bixafen, fluxapyroxad, and benodanil. Similarly, the H272Y showed moderate levels of resistance to boscalid and very low resistance levels to isopyrazam, bixafen, fenfuram, and carboxin but showed increased sensitivity to benodanil and fluopyram. Boscalid provided moderate to high control of H272R/Y and N230I mutants in detached fruit assays but provided little control against the H272L and P225F mutants. In contrast, fluopyram controlled H272R/Y mutants and provided moderate levels of control toward H272L, N230I, and P225F mutants. Our findings suggest that sensitivity to SDHIs may vary greatly, dependent on the point mutation in the sdhb subunit. © 2013 The American Phytopathological Society.

Papadopoulos P.M.,Aristotle University of Thessaloniki | Lagkas T.D.,University of Western Macedonia | Demetriadis S.N.,Aristotle University of Thessaloniki
Computers and Education | Year: 2012

This study provides field research evidence on the efficiency of a "free-selection" peer review assignment protocol as compared to the typically implemented "assigned-pair" protocol. The study employed 54 sophomore students who were randomly assigned into three groups: Assigned-Pair (AP) (the teacher assigns student works for review to student pairs), Free-Selection (FS) (students are allowed to freely explore and select peer work for review).; No Review (NR) (control group). AP and FS student groups studied and reviewed peer work in the domain of Computer Networking, supported by a web-based environment designed to facilitate the two peer review protocols. Our results indicate that students following the Free Selection protocol demonstrate (a) better domain learning outcomes.; (b) better reviewer skills, compared to the AP condition. Overall, the study analyzes the benefits and shortcomings of the FS vs AP review assignment protocol, providing evidence that the FS condition can be multiply beneficial to students who engage in peer review activities. © 2012 Elsevier Ltd. All rights reserved.

Anastopoulos I.,Agricultural University of Athens | Kyzas G.Z.,Aristotle University of Thessaloniki | Kyzas G.Z.,Technological Educational Institute of Kavala
Journal of Molecular Liquids | Year: 2014

This work summarizes the recently published literature (after 2010) regarding the use of agricultural peels for dye adsorption. The use of peels in decontamination technology is very promising given the near zero-cost for the synthesis of those adsorbents. Banana, orange, and potato peels are the most used types of biomass reported in literature. However, other peels such as pomegranate, citrus, grapefruit, yam, and garlic have been also investigated as potential dye adsorbents. The equilibrium data were analyzed and their fitting to known models (Langmuir, Freundlich, etc.) was discussed in details. Similarly, kinetic modeling applied in those studies was commented comparing the equations used (pseudo-first, -second order, etc.). Thermodynamic aspects also are discussed indicating that in many cases the process was spontaneous (ΔG < 0) and endothermic (ΔH > 0) or exothermic (ΔH < 0). © 2014 Elsevier B.V.

Ovid'Ko I.A.,Saint Petersburg State University | Sheinerman A.G.,Russian Academy of Sciences | Aifantis E.C.,Aristotle University of Thessaloniki
Acta Materialia | Year: 2011

A new mechanism of fracture toughness enhancement in nanocrystalline metals and ceramics is suggested. The mechanism represents the cooperative grain boundary (GB) sliding and stress-driven GB migration process near the tips of growing cracks. It is shown that this mechanism can increase the critical stress intensity factor for crack growth in nanocrystalline materials by a factor of three or more and thus considerably enhances the fracture toughness of such materials. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Kontogianni A.D.,University of Western Macedonia | Emmanouilides C.J.,Aristotle University of Thessaloniki
ICES Journal of Marine Science | Year: 2014

This paper investigates the economic valuations individuals make about the degradation of the marine ecosystem in the Gulf of Lion, in the western Mediterranean. A choice experiment has been conducted to quantify in monetary terms the social costs associated with two key aspects of degradation of the marine ecosystem: (i) the loss of critical habitats, and (ii) the risk of jellyfish outbreaks. We apply choice models to analyse the preference structure of residents and visitors for alternative ecosystem resilience scenarios. The focus of the modelling approach is on inference about welfare valuations and their relationship to the characteristics of the participants in the choice experiment, their perceptions of the importance of ecosystem services, attitudes to tourism, and trust in environmental policy-making institutions. We detected a number of significant linear and non-linear effects, and discuss the implications of our findings for marine environment protection policies. © 2013 International Council for the Exploration of the Sea 2014. All rights reserved.

Molassiotis A.,Aristotle University of Thessaloniki | Fotopoulos V.,Cyprus University of Technology
Plant Signaling and Behavior | Year: 2011

Reactive oxygen species (rOS) and reactive nitrogen species (rNS) constitute key features underpinning the dynamic nature of cell signaling systems in plants. Despite their importance in many aspects of cell biology, our understanding of oxidative and especially of nitrosative signaling and their regulation remains poorly understood. Early reports have established that rOS and rNS coordinately regulate plant defense responses to biotic stress. in addition, evidence has accumulated demonstrating that there is a strong cross-talk between oxidative and nitrosative signaling upon abiotic stress conditions. The goal of this mini-review is to provide latest findings showing how both rOS and rNS comprise a coordinated oxidative and nitrosative signaling network that modulates cellular responses in response to environmental stimuli. © 2011 Landes Bioscience.

Sotiriadis A.,Aristotle University of Thessaloniki | Papatheodorou S.I.,Cyprus University of Technology | Martins W.P.,University of Sao Paulo
Ultrasound in Obstetrics and Gynecology | Year: 2016

Although commonly overlooked during the writing and reporting process, most readers will look at only the abstract, so it is essential to convey as much quantitative information as possible, given the space limitations set by the journal. Suggested subheadings include 'Introduction' (specifying the current state of knowledge in the field, the gap that this study aims to cover, i.e. objectives), 'Methods' (search strategy, eligibility criteria, outcomes and statistical analysis), 'Results' (study selection and main results with numerical estimates) and 'Conclusion' (clinical interpretation of results and suggestions for future research). © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Michopoulos A.,Aristotle University of Thessaloniki | Zachariadis T.,Cyprus University of Technology | Kyriakis N.,Aristotle University of Thessaloniki
Energy | Year: 2013

This article reports on the performance of a ground source heat pump system installed in a New Municipality Hall in Northern Greece over an eight-year operation period. The system consists of a vertical ground heat exchanger, 21 boreholes in 80 m depth, 11 water-to-water heat pump units. Basic parameters of its operation are continuously monitoring by a data acquisition system. Based on these recordings, heat transfer flows from/to the building and the ground were calculated in order to estimate the performance of the system. It is found that the maximum ground heat exchanger load reaches 50 W/m in heating operation while in cooling mode it ranges between 20 and 210 W/m. The Weekly Performance Factor of the heat pumps as well as the Seasonal Energy Efficiency Ratio were found to be between 5.0-6.2 and 4.5-5.5 in heating mode and 4.1-5.9 and 3.6-4.5 in cooling mode, respectively. Compared to a conventional heating and cooling system for this building, the ground source heat pump consumes 25.7% less primary energy and emits lower CO2 and NOx emissions by 22.7% and 99.6% respectively, but its SO2 emissions are 18.4% higher. © 2012 Elsevier Ltd.

Sotiriadis A.,Aristotle University of Thessaloniki | Papatheodorou S.,Cyprus University of Technology | Eleftheriades M.,Prenatal Diagnostic Center | Makrydimas G.,University of Ioannina
Ultrasound in Obstetrics and Gynecology | Year: 2013

Objective: To pool published data regarding the sensitivity and specificity of nuchal translucency (NT) in the diagnosis of major congenital heart defects (CHDs) in fetuses with normal karyotype. Methods: MEDLINE and Scopus searches using combinations of the terms 'nuchal' and 'cardiac*' were complemented by perusal of references of the retrieved articles and an additional automated search using the 'search for related articles' function on PubMed. Only fetuses with normal karyotype and major CHDs were analyzed. Weighted estimates were made and summary receiver-operating characteristics curves were constructed. Results: The analysis included 20 studies (205 232 fetuses; 537 cases with major CHDs). The pooled sensitivity and specificity of NT > 95th centile for diagnosis of major CHDs was 44.4% (95% CI, 39.5-49.5) and 94.5% (95% CI, 94.4-94.6), respectively. The pooled sensitivity and specificity of NT > 99th centile was 19.5% (95% CI, 15.9-23.5) and 99.1% (95% CI, 99.1-99.2), respectively. For the subgroup of studies in which NT was measured by Fetal Medicine Foundation-certified operators, the pooled sensitivity and specificity of NT > 95th centile was 45.6% (95% CI, 39.6-51.7) and 94.7% (95% CI, 94.6-94.9), respectively. The corresponding estimates for NT > 99th centile were 21.0% (95%CI, 16.5-26.1) and 99.2% (95% CI, 99.2-99.3). The pooled positive likelihood ratio for NT > 99th centile was 30.5 (95% CI, 24.3-38.6). There was high across-studies heterogeneity for most estimates. Conclusion Approximately 44% of chromosomally normal fetuses with CHDs have NT > 95th centile and 20% have NT > 99th centile. However, there is high heterogeneity across studies, which largely remains even in subgroup analyses of studies of apparently similar design, potentially indicating the presence of some residual unidentified bias. © 2013 ISUOG. Published by John Wiley & Sons Ltd.

Nikita E.,Aristotle University of Thessaloniki | Nikita E.,Wiener Laboratory
American Journal of Physical Anthropology | Year: 2014

The current article explores whether the application of generalized linear models (GLM) and generalized estimating equations (GEE) can be used in place of conventional statistical analyses in the study of ordinal data that code an underlying continuous variable, like entheseal changes. The analysis of artificial data and ordinal data expressing entheseal changes in archaeological North African populations gave the following results. Parametric and nonparametric tests give convergent results particularly for P values <0.1, irrespective of whether the underlying variable is normally distributed or not under the condition that the samples involved in the tests exhibit approximately equal sizes. If this prerequisite is valid and provided that the samples are of equal variances, analysis of covariance may be adopted. GLM are not subject to constraints and give results that converge to those obtained from all nonparametric tests. Therefore, they can be used instead of traditional tests as they give the same amount of information as them, but with the advantage of allowing the study of the simultaneous impact of multiple predictors and their interactions and the modeling of the experimental data. However, GLM should be replaced by GEE for the study of bilateral asymmetry and in general when paired samples are tested, because GEE are appropriate for correlated data. Am J Phys Anthropol 153:473-483, 2014. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.

Aristotle University of Thessaloniki, Karagiannidis, Lioumpas and Michalopoulos | Date: 2010-08-04

This invention relates to a method for combining signals received by a diversity receiver means comprising at least two branches, said signals transmitting symbols through a multi-paths channel, comprising the steps of combining (4) the signals after their processing in individual branches and demodulating and detecting the transmitted symbols. Said method is remarkable in that said processing comprises a co-phasing step (2) consisting of estimating the phase changes induced by the channel at the received signal, with reference to the transmitted signal, and weighting of each signal by a co-phasing coefficient based on said estimation, with all received signals being co-phased, and an optimization step consisting of estimating the mean value and the variance of the signal to noise ratio at said branch, using sampling techniques, and the weighting (3) of the received signals by an optimization coefficient calculated from said mean value and variance. It also relates to said diversity receiver.

Voultsiadou Eleni E.,Aristotle University of Thessaloniki
Journal of Ethnopharmacology | Year: 2010

Aim of the study: Marine organisms are currently investigated for the therapeutic potential of their natural products with very promising results. The human interest for their use in healing practices in the Eastern Mediterranean goes back to the antiquity. An attempt is made in the present work to investigate the therapeutic properties of marine invertebrates and the ways they were used in the medical practice during the dawn of the western medicine. Methods: The classical Greek texts of the Ancient Greek (Classical, Hellenistic and Roman) and early Byzantine period were studied and the data collected were analysed in order to extract detailed information on the parts of animal bodies and the ways they were used for healing purposes. Results and discussion: Thirty-eight marine invertebrates were recorded for their therapeutic properties and uses in 40 works of 20 classical authors, covering a time period of 11 centuries (5th c. BC to 7th c. AD). The identified taxa were classified into 7 phyla and 11 classes of the animal kingdom, while molluscs were the dominant group. Marine invertebrates were more frequently used for their properties relevant to digestive, genitourinary and skin disorders. Flesh, broth, skeleton, or other special body parts of the animals were prepared as drinks, collyria, suppositories, cataplasms, compresses, etc. Conclusions: Marine invertebrates were well known for their therapeutic properties and had a prominent role in the medical practice during the Ancient Greek and the early Byzantine period. The diversity of animal species and their medicinal uses reflect the maritime nature of the Greek civilization, which flourished on the coasts and islands of the Aegean Sea. Most of them were common species exploited by humans for food or other everyday uses. © 2010 Elsevier Ireland Ltd.

Goula A.M.,Aristotle University of Thessaloniki
Journal of Food Engineering | Year: 2013

In this work, ultrasound-assisted extraction was employed to extract oil from pomegranate seeds. Seed particle size, extraction temperature, solvent/solid ratio, amplitude level, and pulse duration/pulse interval ratio were the factors investigated with respect to extraction yield using a central composite design. The optimum operating conditions were found to be: seed particle size, 0.2 mm; extraction temperature, 20°C; solvent/solid ratio, 20/1; amplitude level, 60%; pulse duration/pulse interval ratio, 5/15. Under these optimized conditions, the predicted value for extraction yield was 59.8%. A second-order kinetic model was successfully developed for describing the mechanism of ultrasound extraction under different processing parameters. © 2012 Elsevier Ltd. All rights reserved.

Mademlis C.,Aristotle University of Thessaloniki | Kioskeridis I.,Alexander Technological Educational Institute of Thessaloniki
IEEE Transactions on Industrial Electronics | Year: 2010

The problem of high-precision position control in switched reluctance motor (SRM) drives is investigated in this paper. Advanced proportionalintegral and proportionaldifferential controllers for speed and position controls, respectively, are adopted. A gain-scheduling technique is adopted in the speed controller design for providing high dynamic performance and precise position control. In order to improve the set-point tracking, a low-pass filter is included in the position controller. The proposed four-quadrant control scheme is based on the average torque control method. The turn-on and turn-off angles are online determined through simple formulas so as to reduce the torque ripple at an acceptable level over a wide speed range. This is important since the position precision is highly influenced from the motor torque ripple. Experimental results of the SRM dynamic response are presented to verify the theoretical considerations and to demonstrate the effectiveness of the proposed control scheme. © 2006 IEEE.

Ganias K.,Aristotle University of Thessaloniki
Fisheries Research | Year: 2013

Despite its importance in applied fish reproductive biology the fecundity pattern (determinate vs. indeterminate) is still an open question for many fish stocks, often hindering the selection of the appropriate egg production method for the estimation of stock spawning biomass. As a rule of thumb it is considered that cold-water, capital breeders with short spawning periods are determinate spawners while warm-water, income breeders with extended spawning periods are indeterminate spawners. However, the exact biological and/or ecological mechanisms that lead to the one, the other or intermediate patterns are still uncertain. The present review describes the evolving concepts on fish fecundity patterns and overviews the important theoretical and methodological advances on the assessment of fish fecundity. This information is subsequently used to provide refined lines of evidence on the correct designation of the fecundity pattern of fish stocks. Finally, this review attempts to shed light on the possible links between the fecundity pattern and the specific environmental conditions encompassed by fish stocks and suggest future perspectives and conceptual models that could be developed in order to better explain and predict the fecundity pattern in fishes. © 2012 Elsevier B.V.

Mavrodi A.,Aristotle University of Thessaloniki | Paraskevas G.,Aristotle University of Thessaloniki
International Journal of Cardiology | Year: 2014

According to their writings, ancient Greek physicians had explored the anatomy of the heart. Although pre-Hippocratic medicine, which relied on religion and mysticism, has nothing more to present than implausible theories and speculations, younger physicians thanks to their animal dissections were able to depict the heart with detail. Hippocratic "On the Heart", Aristotle's, Herophilus', Erasistratus' and Galen's writings provide us with the necessary data to take a look at the anatomy of the heart as it was described back then. Despite of some confusing passages in their writings and some erroneous notions, the heart was described with relative accuracy. In the years after antiquity and in the Middle Age the only information about the anatomy of the heart could be derived from the ancient Greek works and only anatomists of the Renaissance managed to displace them. In this paper we present the knowledge of all known ancient Greek physicians about the heart, with emphasis on its anatomy. © 2014 Elsevier Ireland Ltd.

Giagazoglou P.,Aristotle University of Thessaloniki
Infants and Young Children | Year: 2013

The aim of this study was to examine and describe the effect of gender and socioeconomic status (SES) on preschool-aged children's overall development. Two hundred fifty-five preschoolers (125 boys and 130 girls), with a mean age of 56 ± 9 months, were randomly selected from day care centers and kindergartens of different areas of Northern Greece. In terms of SES, the sample was divided to 3 groups (75 children coming from high-SES, 110 mid-SES, and 70 low-SES families) according to parental education, occupational status, and family income, which have been suggested as stable measures of SES. The overall development of children was assessed using the 6 scales of the Griffiths Test No. II. Two-way analysis of variance designs demonstrated no significant Group × Gender interaction (p >.05), whereas a post hoc analysis revealed that children coming from high-SES families had better scores on all domains of development examined than children of the other 2 SES groups (p <.001). With respect to gender differences, no significant main effect on the General Developmental Quotient and on the Performance subscale (p >.05) was noticed, whereas there was a significant main effect noted in the remaining 5 scales. The findings of this study suggest that the related factors of SES and gender should be considered in the interpretation of Griffiths scales' performance, because they could prove to be important aspects that affect young children's general functioning. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams &Wilkins.

Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
IEEE Transactions on Power Systems | Year: 2011

Market clearing has always been an issue of great interest and research as liberalized electricity markets evolved over time in many countries. As trading in electricity evolves rapidly, multi-area power exchanges appear to substitute the local markets. The tie-lines constitute a significant parameter in multi-area power exchanges, since congestion leads to price differentiation. Prices are affected by physical (e.g., network) constraints, yet they should sometimes follow regulatory policy rules, which do not necessarily reflect or depend on physical characteristics. Until now, all approaches in clearing a multi-area power dispatch (or a multi-area market) are based on a zonal or nodal pricing model, which is applied uniformly to both production and demand within the same zone (or at each node). These approaches are not able to deal with complex pricing rules, which impose price discrimination for supply or demand entities within the same area. This paper presents a mathematical approach for the solution of a multi-area dispatch, in which production and demand of the same area may be cleared in different prices. The main principle is the formulation of a mixed complementarity problem for the system equilibrium conditions, in which supply and demand are associated to explicitly or implicitly defined prices. Illustrative implementations and test results for a simple five-zone system and the 73-bus IEEE RTS-96 are presented. © 2011 IEEE.

Baslis C.G.,Aristotle University of Thessaloniki | Bakirtzis A.G.,Aristotle University of Thessaloniki
IEEE Transactions on Power Systems | Year: 2011

A yearly stochastic self-scheduling model for a price-maker hydro producer is presented. In the short term, the producer aims at maximizing profits in the day-ahead market. Residual demand curves model the producer's interaction with his competitors and the load demand. A modification of the residual demand curve is proposed to enable the definition of optimal pumped-hydro bids. Multistage stochastic programming provides hedging against the mid-term uncertainty of inflows, load demand, and competitors' offers. The proposed method models the impact of short-term profit maximization decisions on mid-term scheduling within a compact stochastic mixed integer linear programming (MILP) approach. A test case with a three-stage, 90-scenario stochastic tree and data of the Greek Power System is presented. Results provide insight on both mid-term reservoir management and short-term market-based operation and indicate the feasibility of solving a very large-scale scheduling problem as a unique MILP using a commercial solver. The role of forward contracts in mitigating market power is also analyzed. © 2006 IEEE.

Pitilakis D.,Aristotle University of Thessaloniki | Clouteau D.,École Centrale Paris
Bulletin of Earthquake Engineering | Year: 2010

An equivalent linear substructure approximation of the soil-foundation-structure interaction is proposed in this paper. Based on the inherent linearity of the approach, the solution of the structural and the soil domain is obtained simultaneously, incorporating the effects of the primary and secondary soil nonlinearities. The proposed approximation is established theoretically and then validated against centrifuge benchmark soil-foundation-structure interaction tests. The equivalent linear substructure approximation is proved to simulate efficiently the effects of the nonlinear soil behavior on the soil-foundation-structure system under a strong earthquake ground motion. © 2009 Springer Science+Business Media B.V.

Katsiki N.,Aristotle University of Thessaloniki | Mikhailidis D.P.,University College London | Wierzbicki A.S.,St Thomas Hospital
Current Opinion in Cardiology | Year: 2013

PURPOSE OF REVIEW: We comment on the associations between epicardial adiposity and cardiovascular disease (CVD) and associated risk factors. The effects of lifestyle measures and CVD drugs on cardiac adipose tissue are also discussed. RECENT FINDINGS: Epicardial adipose tissue exerts cardioprotective properties; however, in cases of pathological enlargement, epicardial fat can lead to myocardial inflammation and dysfunction as well as left ventricular hypertrophy and coronary artery disease (CAD) due to paracrine actions that include increased production of reactive oxygen species, atherogenic and inflammatory cytokines. Cardiac adiposity is associated with CAD, obesity, type 2 diabetes, metabolic syndrome, nonalcoholic fatty liver disease, and chronic kidney disease, as well as with CVD risk factors such as lipids, hypertension, obesity markers, and carotid atherosclerosis. SUMMARY: Due to its anatomical and functional proximity to the coronary circulation, epicardial adipose tissue may represent an even more direct CVD risk marker than central adiposity. Lifestyle measures and certain drugs may affect its thickness, although there are limited data currently available. The clinical implications of epicardial fat in daily practice remain to be established in future studies. © 2013 Wolters Kluwer Health | Lippincott Williams &Wilkins.

Katragkou A.,Aristotle University of Thessaloniki | Roilides E.,Aristotle University of Thessaloniki
Current Opinion in Infectious Diseases | Year: 2011

Purpose of review: Invasive fungal infections are an escalating problem in paediatrics. The purpose of this review is to update the recent evidence on antifungal treatment options as well as to provide an outline of best practices in treating children. Recent findings: Candida and Aspergillus species are the leading causes of invasive fungal infections in paediatric patients. Invasive fungal infections are associated with significant morbidity and mortality and preemptive antifungal therapy has been found to improve survival. Although novel antifungal agents (echinocandins and second generation triazoles) and treatment strategies based on surrogate markers (galactomannan and beta-glucan) have established utility in treating adults, limited data are available to guide paediatricians when managing children with invasive fungal infections. The collective findings of the up-to-date data show that treatment recommendations are similar for paediatric and adult patients. Progress has been made in describing pharmacokinetics and safety of voriconazole and echinocandins, respectively, while further efficacy, safety and pharmacokinetic trials are ongoing. Summary: The current guidelines, proposed mainly for adults with invasive fungal infections, are likely applicable also to paediatric patients, but prior to making definitive recommendations more pharmacokinetic and phase III trials are needed. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Youlatos D.,Aristotle University of Thessaloniki
Mammalian Biology | Year: 2010

The present report aims to quantify the use of zygodactylous (opposability of digits II to III) grasping in relation to positional modes and support size and orientation, in the highly arboreal, walking/climbing woolly opossum, Caluromys philander. For this purpose, four captive adult C. philander were intensively video-recorded and their positional behavior, hand grasp, and support size and orientation use were analyzed frame-by-frame. Overall, C. philander used a zygodactylous grasp in 81.3±1.2% of bouts. In terms of support features, this grasp was particularly common on (a) supports that could be wholly and partly held by the animals' hand and (b) vertical supports in particular. In a comparable manner, zygodactyly dominated during above-support positional modes, but was significantly less used during bridging and suspension. The results show that zygodactyly provided an above-support secure and steady grasp on relatively unstable arboreal supports, by aligning the hand with the main axis of the support. This very likely assisted in controlling over the applied torques during cautious quadrupedal and climbing activities with extended hand contact that characterizes the locomotor strategy of C. philander. These observations need to be further tested by more detailed kinetic studies and on a larger sample of arboreal didelphids. © 2009 Deutsche Gesellschaft für Säugetierkunde.

Real-time PCR (RTiPCR) assays including enrichment stage were evaluated for the rapid detection of Listeria monocytogenes, Salmonella spp. and Escherichia coli O157:H7 in raw ingredients and ready-to-eat products using molecular beacon probes available as commercial kits (WARNEX Genevision, Canada & AES Chemunex detection system, France). The accuracy of the assays was evaluated analyzing 1032 naturally contaminated food samples in combination to the conventional cultural methods. Presence/absence testing of the above pathogens was performed in 25g samples of each product. In case of L.monocytogenes of 39 positive RTiPCR samples, 37 were confirmed by the cultural method (based on McNemar's test the difference between the two methods is insignificant). The highest incidence of L.monocytogenes in food products was found in desserts and the second highest in frozen pastries. None of the samples were cultural positive but negative in the RTiPCR test. One among the 343 investigated samples was positive for Salmonella spp. by RTiPCR and the cultural method. Out of 333 samples analyzed for E.coli O157:H7 no positive sample was detected. RTiPCR-based methods proved to be powerful tools for fast, sensitive and accurate pathogen detection in raw food ingredients and ready-to-eat products. © 2013 Elsevier Ltd.

Androulidakis Y.S.,Aristotle University of Thessaloniki | Kourafalou V.H.,University of Miami
Journal of Geophysical Research: Oceans | Year: 2011

The outflow of Waters of Black Sea origin (BSW) through the Dardanelles Strait is the strongest buoyant input for the North Aegean Sea (NAS). Two opposing flows exist across the Dardanelles exit: a lighter, upper layer outflow (BSW) and a denser, deeper layer inflow (waters of Mediterranean origin). This study examines the processes influencing the plume development and evolution. The complex topography of the receiving basin (NAS) plays a significant role on the preferred BSW pathways that are controlled by the buoyancy and wind forcing. A high-resolution numerical model, the NAS-HYCOM (Hybrid Coordinate Ocean Model), is implemented to perform process-oriented experiments that examine the relative role of the forcing factors and topographic effects. Three major pathways are identified. In the absence of wind, an anticyclonic bulge is formed inducing a Westward Jet that is topographically guided between two islands near the outflow. Topography also controls the development of a buoyancy-driven Coastal Current and a Rim Current along the North Aegean shelf areas. Comparison of model results to analytical calculations suggests that topography modifies the formation and the ballooning of the anticyclonic bulge, which are controlled by the outflow rate, the resulting stratification and Coriolis. Experiments also employ several wind directions and magnitudes in combination with different outflow characteristics. The study elucidates the importance of the Aegean morphology on the processes controlling the coupling to the Black Sea. The BSW are found to influence both deep and shelf Aegean basins, along their overall cyclonic pathway toward the eastern Mediterranean. Copyright 2011 by the American Geophysical Union.

Mallidis I.,Aristotle University of Thessaloniki | Dekker R.,Erasmus University Rotterdam | Vlachos D.,Aristotle University of Thessaloniki
Journal of Transport Geography | Year: 2012

The consideration of environmental issues has emerged as a topic of critical importance for today's globalized supply chains. The purpose of this paper is to develop a strategic-tactical decision support model to assist managers in evaluating the impact of environmental issues, related to transportation emissions, on the transport geography of a region. Specifically we provide a model that addresses: (i) supply chain network design, including port of entry and transportation mode, and (ii) decisions on using dedicated versus shared warehouses and transportation. The applicability of the proposed methodology is examined through the development of a sustainable supply chain network in the South-Eastern Europe region. The results indicate that in most cases using shared warehouses from Third Party Logistics operators improves both the cost and the environmental performance of a company. In all cases shared use of transportation operations minimizes the amount of CO 2 and PM emissions generated, while dedicated use minimizes costs. © 2012 Elsevier Ltd.

New taxonomic study of the " old collection" of Carnivora from Petralona Cave, associated to the well-known hominid skull, housed in the Geology School of the Thessaloniki Aristotle University since 1960, revealed 11 species (Canis arnensis, Lycaon lycaonoides, Vulpes praeglacialis, Ursus deningeri, U. spelaeus, U. arctos, Pliocrocuta perrieri, Pachycrocuta brevirostris, Crocuta crocuta, Panthera leo spelaea, and Felis silvestris), which are described in detail. The species composition is typical of the eastern part of the European Mediterranean and may be divided into three biostratigraphic assemblages: early Middle Pleistocene, late Middle Pleistocene and Late Pleistocene. © 2010 Elsevier Masson SAS.

Tsilingiridis G.,Aristotle University of Thessaloniki | Martinopoulos G.,Aristotle University of Thessaloniki
Renewable Energy | Year: 2010

The effort to reduce the dependence on imported crude oil in Greece, after the oil crises in the '70s, has resulted, among others, in a total installed area of 3.57 million m2 solar collectors in 2007, making Greece one of the pioneers in the use of domestic solar hot water system (DSHWS) worldwide. In the present work, the contribution of DSHWS to the reduction of conventional energy and greenhouse gases and other air pollutant emissions in Greece from its early years in mid '70s up to now is assessed. DSHWS market penetration, solar system technological changes and development and demographic changes in association with the climatic conditions in all regions of the country have been taken into account in order to calculate energy conservation and emissions reduction. The results show that the conserved energy ranges from 21.27 GW hel (0.1% of the domestic sector energy use) in 1978 to 1513 GW hel (2.4%) in 2007, resulting in an abatement of CO2 emissions, which for the year 2000 was 1.67 Mt, exceeding by 76% the objectives of the Greek Program of "Climatic Change", which indicated savings of 0.95 Mt CO2 for 2000. Moreover DSHWS maximum technical potential is assessed to be about three times the current installed area, showing that they can play an important role in energy end environmental policy of the country. © 2009 Elsevier Ltd. All rights reserved.

The sustainable development of Protected Areas (PAs) depends on several conditions; a tight legal framework that respects the EU and international legislation on one hand and the participation of the local community on the other hand are of utmost importance. This paper presents the legal framework for PAs in Greece with regard to the PA of Lake Kerkini and explores the role of the local community in promoting the sustainable development of the area. It points out that although the study area is a declared National Park, it faces severe environmental problems due to particular reasons. It also identifies the regulatory and governance gaps at national and local level, and finally, it proposes the necessary steps for promoting sustainable development and protecting the natural resources of the study area. Copyright © 2014 Inderscience Enterprises Ltd.

Kehagias A.,Aristotle University of Thessaloniki
Information Sciences | Year: 2011

In this paper we study the connections between three related concepts which have appeared in the fuzzy literature: fuzzy intervals, fuzzy numbers and fuzzy interval numbers (FIN's). We show that these three concepts are very closely related. We propose a new definition which encompasses the three previous ones and proceeds to study the properties ensuing from this definition. Given a reference lattice (X,⊆), we define fuzzy intervals to be the fuzzy sets such that their p-cuts are closed intervals of (X,⊆). We show that, given a complete lattice (X,⊆), the collection of its fuzzy intervals is a complete lattice. Furthermore we show that, if (X,⊆) is completely distributive, then the lattice of its fuzzy intervals is distributive. Finally we introduce a new inclusion measure, which can be used to quantify the degree in which a fuzzy interval is contained in another, an approach which is particularly valuable in engineering applications. © 2010 Elsevier Inc. All rights reserved.

Komninos N.,Aristotle University of Thessaloniki
Intelligent Buildings International | Year: 2011

This article discusses the spatial intelligence of cities, the use of information communication technologies (ICTs) and institutional frameworks that support innovation ecosystems of cities and increase the problem-solving capability of communities and cities. It is based on three case studies on Bletchley Park, Cyberport Hong Kong and Smart Amsterdam, which highlight different architectures of spatial intelligence: (1) orchestration intelligence that stems from collaboration within a community and integration of people's skills, know-how, and collective and machine intelligence, (2) amplification intelligence based on learning, up-skilling and talent cultivation using open technology platforms and ICT infrastructure offered by the city, and (3) instrumentation intelligence based on streams of information generated from the functioning of cities, which enable more informed decisions to be taken by citizens and organizations. The article contributes to understanding different processes that make communities more intelligent, and how collective intelligence, people-driven innovation and use of smart devices advance the efficiency, operation and governance of cities. © 2011 Taylor & Francis.

Vologiannidis S.,Aristotle University of Thessaloniki | Antoniou E.N.,Alexander Technological Educational Institute of Thessaloniki
Mathematics of Control, Signals, and Systems | Year: 2011

In Antoniou and Vologiannidis, a new family of companion forms associated with a regular polynomial matrix T (s) has been presented, using products of permutations of n elementary matrices, generalizing similar results presented in Fiedler (Linear Algebra Its Appl 371:325-331, 2003) where the scalar case was considered. In this paper, extending this "permuted factors" approach, we present a broader family of companion-like linearizations, using products of up to n(n -1)/2 elementary matrices, where n is the degree of the polynomial matrix. Under given conditions, the proposed linearizations can be shown to consist of block entries where the coefficients of the polynomialmatrix appear intact. Additionally, we provide a criterion for those linearizations to be block symmetric. We also illustrate several new block symmetric linearizations of the original polynomial matrix T (s), where in some of them the constraint of nonsingularity of the constant term and the coefficient of maximum degree are not a prerequisite. © Springer-Verlag London Limited 2011.

Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
IEEE Transactions on Power Systems | Year: 2011

The integration of the spot electricity markets in Europe shall lead to multi-area power exchanges that will substitute the local markets. In such scheme, market prices are affected by physical (e.g., network) constraints, yet they should sometimes follow regulatory policy rules, which do not necessarily reflect or depend on physical characteristics. In some cases, complex pricing rules should be implemented, which impose price discrimination for supply and demand entities within the same area. The methodology presented in this paper enables the balancing of supply and demand in a multi-area market considering energy and reserve bids, under complex pricing rules, which mix energy and reserve prices. A demand bid corresponds to the whole cost a demand entity is willing to pay for its participation in the energy market, including the cost for the procurement of the necessary reserves. The approach attains price integration of energy and reserves markets, simultaneous settlement of energy and reserves, and significant decrease of the payments through the uplift accounts. The main principle is the formulation of a mixed complementarity problem for the system equilibrium conditions, in which supply and demand are associated to explicitly or implicitly defined prices, which may be different even in the same zone. © 2006 IEEE.

Vasilakou D.,Aristotle University of Thessaloniki | Karagiannis T.,Aristotle University of Thessaloniki | Athanasiadou E.,Aristotle University of Thessaloniki | Mainou M.,Aristotle University of Thessaloniki | And 5 more authors.
Annals of Internal Medicine | Year: 2013

Background: Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new class of antidiabetic drugs. Purpose: To assess the efficacy and safety of SGLT2 inhibitors in adults with type 2 diabetes. Data Sources: MEDLINE, EMBASE, and the Cochrane Library from inception through April 2013 without language restrictions; regulatory authorities' reports; and gray literature. Study Selection: Randomized trials comparing SGLT2 inhibitors with placebo or other medication for type 2 diabetes. Data Extraction: Three reviewers extracted or checked data for study characteristics, outcomes of interest, and risk of bias, and 3 reviewers summarized strength of evidence using the Grading of Recommendations Assessment, Development and Evaluation approach. Data Synthesis: Sodium-glucose cotransporter 2 inhibitors were compared with placebo in 45 studies (n=11 232) and with active comparators in 13 studies (n=5175). They had a favorable effect on hemoglobin A1c level (mean difference vs. placebo, -0.66% [95% CI, -0.73% to -0.58%]; mean difference vs. active comparators, -0.06% [CI, -0.18% to 0.05%]). Sensitivity analyses incorporating unpublished data showed similar effect estimates. Compared with other agents, SGLT2 inhibitors reduced body weight (mean difference, -1.80 kg [CI, -3.50 to -0.11 kg]) and systolic blood pressure (mean difference, -4.45 mm Hg [CI, -5.73 to -3.18 mm Hg]). Urinary and genital tract infections were more common with SGLT2 inhibitors (odds ratios, 1.42 [CI, 1.06 to 1.90] and 5.06 [CI, 3.44 to 7.45], respectively). Hypoglycemic risk was similar to that of other agents. Results for cardiovascular outcomes and death were inconclusive. An imbalance in incidence of bladder and breast cancer was noted with dapagliflozin compared with control. Limitation: Most trials were rated as high risk of bias because of missing data and last-observation-carried-forward methods. Conclusion: Sodium-glucose cotransporter 2 inhibitors may improve short-term outcomes in adults with type 2 diabetes, but effects on long-term outcomes and safety are unclear. © 2013 American College of Physicians.

Panayiotou C.,Aristotle University of Thessaloniki
Journal of Chemical Thermodynamics | Year: 2012

The partial solvation parameters (PSP) have been defined recently, on the basis of the insight derived from modern quantum chemical calculations, in an effort to overcome some of the inherent restrictions of the original definition of solubility parameter and expand its range of applications. The present work continues along these lines and introduces two new solvation parameters, the van der Waals and the polarity/refractivity ones, which may replace both of the former dispersion and polar PSPs. Thus, one may use either the former scheme of PSPs (dispersion, polar, acidic, and basic) or, equivalently, the new scheme (van der Waals, polarity/refractivity, acidic, basic). The new definitions are made in a simple and straightforward manner and, thus, the strength and appeal of the widely accepted concept of solubility parameter is preserved. The inter-relations of the various PSPs are critically discussed and their values are tabulated for a variety of common substances. The advantage of the new scheme of PSPs is the bridge that makes with the corresponding Abraham's LSER descriptors. With this bridge, one may exchange information between PSPs, LSER experimental scales, and quantum mechanics calculations such as via the COSMO-RS theory. The proposed scheme is a predictive one and it is applicable to, both, homo-solvated and hetero-solvated compounds. The new scheme is tested for the calculation of activity coefficients at infinite dilution, for octanol/water partition coefficients, and for the prediction of miscibility of some pharmaceuticals in various solvents. The perspectives from bridging LSER and solubility parameter approaches are discussed. © 2012 Elsevier Ltd. All rights reserved.

Bechlioulis C.P.,Aristotle University of Thessaloniki | Rovithakis G.A.,Aristotle University of Thessaloniki
IEEE Transactions on Automatic Control | Year: 2010

We consider the tracking problem of unknown, robustly stabilizable, multi-input multi-output (MIMO), affine in the control, nonlinear systems with guaranteed prescribed performance. By prescribed performance we mean that the tracking error converges to a predefined arbitrarily small residual set, with convergence rate no less than a prespecified value, exhibiting maximum overshoot as well as undershoot less than some sufficiently small preassigned constants. Utilizing an output error transformation, we obtain a transformed system whose robust stabilization is proven necessary and sufficient to achieve prescribed performance guarantees for the output tracking error of the original system, provided that initially the transformed system is well defined. Consequently, a switching robust control Lyapunov function (RCLF)-based adaptive, state feedback controller is designed, to solve the stated problem. The proposed controller is continuous and successfully overcomes the problem of computing the control law when the approximation model becomes uncontrollable. Simulations illustrate the approach. © 2010 IEEE.

Hatzimouratidis K.,Aristotle University of Thessaloniki | Hatzichristou D.,Aristotle University of Thessaloniki
Current Diabetes Reports | Year: 2014

Erectile dysfunction (ED) is highly prevalent affecting at least 50 % of men with diabetes mellitus (DM). DM may cause ED through a number of pathophysiological pathways. These include neuropathy, endothelial dysfunction, cavernosal smooth muscle structural/functional changes, and hormonal changes. Lifestyle changes, diabetes control, and treatment of hypogonadism are important as the first step in ED management since there is no curative treatment for ED. Phosphodiesterase type 5 inhibitors (PDE5i) are the first-line treatment option. Intracavernous administration of vasoactive drugs is commonly used as a second-line medical treatment when PDE5i have failed. Alprostadil is the most widely used drug in this second-line setting. The combination of papaverine, phentolamine, and alprostadil represents the most efficacious intracavernous pharmacologic treatment option that may save non-responders to alprostadil. Penile prosthesis implantation can be considered in treatment refractory cases, with excellent functional and safety results in the properly informed patients. © 2014, Springer Science+Business Media New York.

Fountoulakis K.N.,Aristotle University of Thessaloniki
Annals of General Psychiatry | Year: 2010

The present work represents a detailed description of our current understanding and knowledge of the epidemiology, etiopathogenesis and clinical manifestations of mood disorders, their comorbidity and overlap, and the effect of variables such as gender and age. This review article is largely based on the 'Mood disorders' chapter of the Wikibooks Textbook of Psychiatry © 2010 Fountoulakis; licensee BioMed Central Ltd.

Patetsini E.,Aristotle University of Thessaloniki | Dimitriadis V.K.,Aristotle University of Thessaloniki | Kaloyianni M.,Aristotle University of Thessaloniki
Aquatic Toxicology | Year: 2013

The present study examines the influence of environmentally relevant concentrations of two pesticides, chlorpyrifos and penoxsulam on mussel physiological status. For this reason, lysosomal membrane stability (LMS), reactive oxygen species (ROS), DNA damage, protein carbonylation (PCC) and antioxidant capacity (TAC) in hemaolymph and hemocytes of the mussels was measured. Mussels were exposed to a range of concentrations of the pesticides chlorpyrifos and penoxsulam and the response of animals to the destabilization of lysosomal membrane in hemocytes (LMS) was studied. Subsequently, the half maximal effective concentration (EC50) for both pesticides was calculated. The animals were subsequently exposed for 0, 1, 3, 5, 7, 15 and 30 days to 10 times less concentration than EC50 of each pesticide (0.05 μg/l) and changes in LMS, ROS, DNA damage, protein carbonylation and antioxidant capacity of mussels was evaluated. Our results showed a significant change in the response of mussels for all parameters tested after 30 days exposure, in relation to the controls. The pesticides at the environmental concentrations used induced changes to the animal physiology through causing oxidative stress and lysosomal abnormalities and their usage in the agriculture demands great care. In addition, the results show that ROS, DNA damage, protein carbonylation and antioxidant capacity could constitute, after further investigation, reliable biomarkers for the evaluation of pollution or other environmental stressors. © 2012 Elsevier B.V.

Zotos E.E.,Aristotle University of Thessaloniki
Meccanica | Year: 2016

The case of the planar circular restricted three-body problem where one of the two primaries has a stronger gravitational field with respect to the classical Newtonian field is investigated. We consider the case where two primaries have the same mass, so as the the only difference between them to be the strength of the gravitational field which is controlled by the power p of the potential. A thorough numerical analysis takes place in several types of two dimensional planes in which we classify initial conditions of orbits into three main categories: (1) bounded, (2) escaping and (3) collision. Our results reveal that the power of the gravitational potential has a huge impact on the nature of orbits. Interpreting the collision motion as leaking in the phase space we related our results to both chaotic scattering and the theory of leaking Hamiltonian systems. We successfully located the escape as well as the collision basins and we managed to correlate them with the corresponding escape and collision time of the orbits. We hope our contribution to be useful for a further understanding of the escape and collision properties of motion in this interesting version of the restricted three-body problem. © 2016 Springer Science+Business Media Dordrecht

Daqing L.,Bar - Ilan University | Kosmidis K.,Justus Liebig University | Kosmidis K.,Aristotle University of Thessaloniki | Bunde A.,Justus Liebig University | Havlin S.,Bar - Ilan University
Nature Physics | Year: 2011

The dimension of a system is one of the most fundamental quantities to characterize its structure and basic physical properties. Diffusion and vibrational excitations, for example, as well as the universal features of a system near a critical point depend crucially on its dimension. However, in the theory of complex networks the concept of dimension has been rarely discussed. Here we study models for spatially embedded networks and show how their dimension can be determined. Our results indicate that networks characterized by a broad distribution of link lengths have a dimension higher than that of the embedding space. We illustrate our findings using the global airline network and the Internet and argue that although these networks are embedded in two-dimensional space they should be regarded as systems with dimension close to 3 and 4.5, respectively. We show that the network dimension is a key concept to understand not only network topology, but also dynamical processes on networks, such as diffusion and critical phenomena including percolation. © 2011 Macmillan Publishers Limited. All rights reserved.

Doneva D.D.,University of Tübingen | Doneva D.D.,Bulgarian Academy of Science | Yazadjiev S.S.,University of Tübingen | Yazadjiev S.S.,Sofia University | And 2 more authors.
Astrophysical Journal Letters | Year: 2014

It was shown recently that normalized relations between the moment of inertia (I), the quadrupole moment (Q), and the tidal deformability (Love number) exist and for slowly rotating neutron stars they are almost independent of the equation of state (EOS). We extend the computation of the I-Q relation to models rotating up to the mass-shedding limit and show that the universality of the relations is lost. With increasing rotation rate, the normalized I-Q relation departs significantly from its slow-rotation limit, deviating up to 40% for neutron stars and up to 75% for strange stars. The deviation is also EOS dependent and for a broad set of hadronic and strange matter EOSs the spread due to rotation is comparable to the spread due to the EOS, if one considers sequences with fixed rotational frequency. Still, for a restricted sample of modern realistic EOSs one can parameterize the deviations from universality as a function of rotation only. The previously proposed I-Love-Q relations should thus be used with care, because they lose their universality in astrophysical situations involving compact objects rotating faster than a few hundred Hz. © 2014. The American Astronomical Society. All rights reserved..

Lazarides G.,Aristotle University of Thessaloniki
AIP Conference Proceedings | Year: 2012

It is shown that, in supergravity models of inflation where the gauge kinetic function of a gauge field is modulated by the inflaton, we can obtain a new inflationary attractor solution, in which the roll-over of the inflaton suffers additional impedance due to the vector field backreaction. As a result, directions of the scalar potential which, due to strong Kähler corrections, become too steep and curved to normally support slow-roll inflation can now naturally do so. This solves the infamous η problem of inflation in supergravity and also keeps the spectral index of the curvature perturbation mildly red despite η of order unity. This mechanism is applied to a model of hybrid inflation in supergravity with a generic Kähler potential. The spectral index of the curvature perturbation is found to be 0.97 - 0.98, in excellent agreement with data. The gauge field can act as vector curvaton generating statistical anisotropy in the curvature perturbation. However, this anisotropy could be possibly observable only if the gauge coupling constant is unnaturally small. © 2012 American Institute of Physics.

Papageorgiou G.Z.,Aristotle University of Thessaloniki | Tsanaktsis V.,Aristotle University of Thessaloniki | Bikiaris D.N.,Aristotle University of Thessaloniki
Physical Chemistry Chemical Physics | Year: 2014

Poly(ethylene-2,5-furandicarboxylate) (PEF) is a new alipharomatic polyester that can be prepared from monomers derived from renewable resources like furfural and hydroxymethylfurfural. For this reason it has gained high interest recently. In the present work it was synthesized from the dimethylester of 2,5-furandicarboxylic acid and ethylene glycol by applying the two-stage melt polycondensation method. The thermal behavior of PEF was studied in comparison to its terephthalate and naphthalate homologues poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN), which were also synthesized following the same procedure. The equilibrium melting point of PEF was found to be 265 °C while the heat of fusion for the pure crystalline PEF was estimated to be about 137 J g-1. The crystallization kinetics was analyzed using various models. PET showed faster crystallization rates than PEN and this in turn showed faster crystallization than PEF, under both isothermal and non-isothermal conditions. The spherulitic morphology of PEF during isothermal crystallization was investigated by polarized light microscopy (PLM). A large nucleation density and a small spherulite size were observed for PEF even at low supercoolings, in contrast to PET or PEN. Thermogravimetric analysis indicated that PEF is thermally stable up to 325 °C and the temperature for the maximum degradation rate was 438 °C. These values were a little lower than those for PET or PEN. © 2014 the Partner Organisations.

Mavromatis T.,Aristotle University of Thessaloniki
Theoretical and Applied Climatology | Year: 2014

The present study aims at forecasting hard wheat (Triticum turgidum L. var. durum) yield in northern Greece, a season prior to harvest. It is based on (a) crop simulated, with CERES-Wheat indicators at four planting dates and (b) reported crop yields at two regional levels (three NUTS2 [Nomenclature of Units for Territorial Statistics] and 16 NUTS3 regions), for the years 1979-2006. Principal component analysis (PCA) was applied to explore major patterns of joint variability in 20 crop simulated agroclimatic indicators of the growing season before harvest. Stepwise regression and hindcast were employed for the selection of the modes identified by PCA as predictors in multivariate linear regression models used for forecasting yield a season ahead of harvest. Forecasting skill varied to a large extent by spatial scale and planting date. When the simulation results aggregated to the larger spatial level (NUTS2), the yield forecasting skill, in terms of R2, was rated as high (ranging from 0.48 to 0.73) in three out of four planting dates for Central Macedonia and in one planting (R 2 = 0.57) for Thrace. Harvest index, nitrogen leaching and related soil water crop simulated output of the previous season, were the most important predictors. No forecasting skill was found in the third NUTS2 region. The performance of the regression models substantially deteriorated at the higher resolution spatial level (NUTS3). In four regions only (including the one where CERES-Wheat was calibrated) yield forecasting skill was moderate (R 2 > 0.25). The results demonstrate the potential of this approach for regional crop yield forecasting before the beginning of the cropping season. However, crop model calibration is required before its application. © 2013 Springer-Verlag Wien.

Kostopoulos D.S.,Aristotle University of Thessaloniki
Acta Palaeontologica Polonica | Year: 2014

A morphological reappraisal of Middle Miocene and Early Pliocene antelopes with homonymously twisted horncores (i.e., with the left horncore twisted clockwise from the base up) and an additional re-description of some critical Greek specimens allows a revision of the current taxonomy at the species and genus level. A parsimony analysis recognizes Hispanodorcas, Oioceros, Samodorcas, Samotragus, Paraoioceros, and Urmiatherium as distinct lineages of the subtribe Oiocerina. The latter emerged during the Astaracian (ca. 14-11.5 Ma), and radiated in Eurasia during the mid-late Vallesian (ca. 10-9 Ma), resulting in a great variety of genera with unique combinations of morpho-ecological adaptations. The suprageneric relationships of Oiocerina are poorly understood, but their closest ancestors possibly lie within or close to the Middle Miocene "hypsodontines", and inside Antilopinae. © 2014 D.S. Kostopoulos.

Zouboulis A.I.,Aristotle University of Thessaloniki | Tzoupanos N.,Aristotle University of Thessaloniki
Desalination | Year: 2010

An alternative preparation procedure for polyaluminium chloride (PAC), a common inorganic coagulant, is presented in this paper. The proposed procedure is based on the use of granular aluminium metal, a common by-product of several aluminium-processing secondary industries, instead of using Al2O3 (or of using a mineral containing Al2O3) which is commonly applied by most industrial producers, and exhibits important benefits such as energy and time saving during the preparation procedure. Several efforts have been made to produce the pre-polymerized coagulant with properties, similar to the properties of a commercially available PAC solution, using appropriate, commonly found laboratory equipment and without the application of extreme conditions (in terms of temperature or pressure). The laboratory prepared PAClab was characterized mainly by means of aluminium content, basicity, density and aluminium species distribution. Furthermore, the coagulation performance of PAClab was evaluated for the treatment of contaminated tap water and of wastewater samples and it was compared with the performance of a commercially available PAC solution. Finally, the coagulation-flocculation kinetics was examined with the use of Photometric Dispersion Analyzer instrument (PDA) and the floc growth rates between the two coagulants were compared. The results suggest that PAC can be alternatively produced under mild conditions, resulting in a product with better properties than the commercial PAC used for comparison. Additionally, if the preparation takes place in industrial scale, a greater improvement is further feasible, due to the common equipment used, instead of using e.g. autoclaving. © 2009 Elsevier B.V. All rights reserved.

Tsinidis G.,Aristotle University of Thessaloniki | Pitilakis K.,Aristotle University of Thessaloniki | Trikalioti A.D.,Aristotle University of Thessaloniki
Acta Geotechnica | Year: 2014

The paper summarizes the numerical simulation of the round robin numerical test on tunnels performed in Aristotle University of Thessaloniki. The main issues of the numerical simulation are presented along with representative comparisons of the computed response with the recorded data. For the simulation, the finite element method is implemented, using ABAQUS. The analyses are performed on prototype-scale models under plane strain conditions. While the tunnel behavior is assumed to be elastic, the soil nonlinear behavior during shaking is modeled using a simplified kinematic hardening model combined with a von Mises failure criterion and an associated plastic flow rule. The model parameters are adequately calibrated using available laboratory test results for the specific fraction of sand. The soil-tunnel interface is also accounted and simulated adequately. The effect of the interface friction on the tunnel response is investigated for one test case, as this parameter seems to affect significantly the tunnel lining axial forces. Finally, the internal forces of the tunnel lining are also evaluated with available closed-form solutions, usually used in the preliminary stages of design and compared with the experimental data and the numerical predictions. The numerical analyses can generally reproduce reasonably well the recorded response. Any differences between the experimental data and the numerical results are mainly attributed to the simplification of the used model and to differences between the assumed and the actual mechanical properties of the soil and the tunnel during the test. © 2013 Springer-Verlag Berlin Heidelberg.

Karteris M.,Aristotle University of Thessaloniki | Papadopoulos A.M.,Aristotle University of Thessaloniki
Energy Policy | Year: 2013

The Law 3468/2006 provided for first time in 2006 appealing feed-in tariff (FiT) incentives for photovoltaics (PVs) in Greece. The response of the national market was immediate in less than 2 years' time. Two subsequent laws formed an even more attractive investment and licensing context both for field and building installations, by introducing additional guarantees and improved grid-connection procedures. However, the unexpectedly large amount of applications submitted until 2011, with aggregate PV capacities which exceeded the national target for 2020 caused continuously tremendous delays in grid-connection processes. Undoubtedly, the effectiveness of this legislative framework cannot be judged solely by the response of prospective investors. In that sense, main objectives of this paper are to present and discuss about the effective provisions as well as the major weaknesses of the FiT legislation in Greece since 2006, associated mainly with its attractiveness to investors and its cost-effectiveness towards preserving and supporting the Greek PV market. The paper concludes with a technoeconomic assessment, which evaluates PV projects' viability, especially those ones whose provision of grid-connection offer was postponed several times. © 2012 Elsevier Ltd.

Nenadis N.,Aristotle University of Thessaloniki | Tsimidou M.Z.,Aristotle University of Thessaloniki
Food Research International | Year: 2012

The present study focuses on the examination of the radical scavenging activity trend of some natural hydroxybenzaldehydes and their corresponding acids with the aid of DFT/B3LYP. Values of computed molecular descriptors (bond dissociation enthalpy, BDE; ionization potential, IP; proton affinity, PA; electron transfer energy, ETE) characterizing the hydrogen atom or electron donating efficiency of parent compounds and ions were discussed considering published experimental findings for the radical scavenging activity of the same compounds using various methods (Rancimat, crocin bleaching, trolox equivalent antioxidant capacity and 2,2-diphenyl-1-picrylhydrazyl assays). Calculations in the gas and/or liquid phase (benzene, methanol, water) were performed to approximate the activity in a lipid substrate or in solution. BDE values could predict the activity of the compounds when hydrogen atom transfer prevailed. Thus, protocatechuic (1) aldehyde, syringaldehyde (2) and their respective acids (1', 2') were predicted to be the most efficient hydrogen atom donors, in line with Rancimat data. In polar media, where electron donation should be favored for hydroxybenzaldehydes, experimental findings could not always be supported by molecular descriptors. Combined information from various descriptors, as shown for DPPH. data, could justify the higher efficiency of 1 over that of 1' and 2'. The results document further the use of computed molecular descriptors as a green tool that can facilitate antioxidant activity studies and selection of efficient antioxidants. © 2012 Elsevier Ltd.

Mantzouridou F.,Aristotle University of Thessaloniki | Spanou A.,Aristotle University of Thessaloniki | Kiosseoglou V.,Aristotle University of Thessaloniki
Food Research International | Year: 2012

The technological properties of inulin were exploited to develop a physically stable dressing emulsion able to sustain the viability of the probiotic microorganism Lactobacillus paracasei subsp. paracasei DC412, both during storage as well as under conditions simulating those of the human gastrointestinal (GI) tract environment. Cell viability, following their entrapment inside the oil droplets of three emulsion systems differing in the type of emulsifier used (egg yolk, gum arabic/xanthan and whey protein isolate), was found to be lower than that of cells freely suspended in the continuous phase of a yolk-stabilized dressing emulsion, especially in the presence of inulin. This emulsion system was investigated further by applying response surface methodology to establish the relationships between the main factors, storage time, and inulin and yolk content, on one hand, and the response variables, probiotic count before and after treatment with GI track enzyme fluids, consistency index and creaming stability, on the other. © 2011 Elsevier Ltd.

Ganias K.,Aristotle University of Thessaloniki
Fisheries Research | Year: 2012

The postovulatory follicles' method or POFs method was introduced by Hunter and Goldberg in the start of the 80s and still remains the most popular method for estimating population spawning frequency in wild populations of multiple spawners. During these last thirty years the method has been applied to more than 50 fish stocks almost all around the world's oceans. Even though the method was initially designed for the stock of northern anchovy, Engraulis mordax, it has now been applied not only to other multiple spawning clupeoids (ca. 40% of total applications) but also to a large number of other fish taxa. Despite its popularity the method can be quite inaccurate when its criteria are applied to other species and populations without prior validation. Four important sources of bias in the application of the method were identified: bias related to POF staging, bias in POF ageing, sampling bias and bias in the estimation of spawning fraction. Apart from all these potential sources of bias the method is quite costly and labor-intensive because it needs large number of adult samples, much histology and many work-hours from experienced personnel. In that respect, the development of alternative methodology for estimating spawning frequency seems worthwhile. © 2011 Elsevier B.V.

Dimou M.,Aristotle University of Thessaloniki
Apidologie | Year: 2012

In the last few years, many studies have used airborne pollen to record the flowering season of plants. However, the airborne pollen found in traps does not always originate from or reflect the flowering period of the taxa from the studied surroundings. This study compared aerobiological, melissopalynological and flowering phenological data obtained from olive trees. The results of the study suggest that pollen loads collected by honeybees can be used as an alternative method to airborne pollen to record the flowering phenological phases and to provide accurate results. © 2011 INRA, DIB and Springer-Verlag, France.

Fountoulakis K.N.,Aristotle University of Thessaloniki | Kontis D.,Psychiatric Hospital of Attica | Gonda X.,Semmelweis University | Yatham L.N.,University of British Columbia
Bipolar Disorders | Year: 2013

Objective: Rapid cycling is associated with longer illness duration and greater illness severity in bipolar disorder. The aim of the present study was to review the existing published randomized trials investigating the effect of treatment on patients with rapid cycling bipolar disorder. Methods: A MEDLINE search was conducted using combinations of the following key words: bipolar and rapid or rapid-cycling or rapid cycling and randomized. The search was conducted through July 16, 2011, and no conference proceedings were included. Results: The search returned 206 papers and ultimately 25 papers were selected for review. Only six randomized, controlled trials specifically designed to study a rapid cycling population were found. Most data were derived from post hoc analyses of trials that had included rapid cyclers. The literature suggested that: (i) rapid cycling patients perform worse in the follow-up period; (ii) lithium and anticonvulsants have comparable efficacies; (iii) there is inconclusive evidence on the comparative acute or prophylactic efficacy of the combination of anticonvulsants versus anticonvulsant monotherapy; (iv) aripiprazole, olanzapine, and quetiapine are effective against acute bipolar episodes; (v) olanzapine and quetiapine appear to be equally effective to anticonvulsants during acute treatment; (vi) aripiprazole and olanzapine appear promising for the maintenance of response of rapid cyclers; and (vii) there might be an association between antidepressant use and the presence of rapid cycling. Conclusion: The literature examining the pharmacological treatment of rapid cycling is still sparse and therefore there is no clear consensus with respect to its optimal pharmacological management. Clinical trials specifically studying rapid cycling are needed in order to unravel the appropriate management of rapid cycling bipolar disorder. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

Tsioras P.A.,Aristotle University of Thessaloniki
Small-scale Forestry | Year: 2012

The aim of this study was to examine the perception of forestry experts and forest workers on the status of the forest workers in Greece. A postal questionnaire was distributed to 115 experts on forest operations in Greece, and 106 forest workers were interviewed in the context of this study. According to the majority of the study participants, there is lack of interest on behalf of the State and the most pressing problems are income-related. The effectiveness of seminars organized during the last years is under question, since they did not result in fewer or less severe accidents. Despite the mentioned problems, the interviewed forest workers are reluctant to change their jobs, indicating a possible potential for maintaining or even increasing employment in forestry, which would warrant further study. The organization of a forest workers' training system along with institutional changes can significantly improve the quality and the employment conditions of the Greek forest operations' sector. © 2011 Steve Harrison, John Herbohn.

A confirmatory high performance liquid chromatography method for the determination of six penicillin antibiotics and three amphenicol antibiotics in gilthead seabream (Sparus Aurata) tissue was developed. Ampicillin (AMP), penicillin G (PG), penicillin V (PV), oxacillin (OXA), cloxacillin (CLO), dicloxacillin (DICLO), thiamphenicol (TAP), florfenicol (FFC) and chloramphenicol (CAP) were separated on an Inertsil, C8 (250 × 4 mm, 5 μm) column by gradient elution with a mobile phase consisting of ammonium acetate 0.05 M and acetonitrile at 25 °C. Diode array detection with monitoring at 225 nm (for the determination of AMP, PG, PV, TAP and FFC), 240 nm (for OXA, CLO and DICLO) and 278 nm (for CAP) was applied. Examined antibiotics were isolated from gilthead seabream tissue by liquid-liquid extraction and further clean-up was performed by solid phase extraction using Oasis HLB (200 mg/6 mL) cartridges. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity according to the European Union Decision 2002/657/EC. © 2012 Elsevier Ltd. All rights reserved.

Gougouli M.,Aristotle University of Thessaloniki | Koutsoumanis K.P.,Aristotle University of Thessaloniki
International Journal of Food Microbiology | Year: 2013

The relation between germination time and lag time of mycelium growth of individual spores was studied by combining microscopic and macroscopic techniques. The radial growth of a large number (100-200) of Penicillium expansum and Aspergillus niger mycelia originating from single spores was monitored macroscopically at isothermal conditions ranging from 0 to 30°C and 10 to 41.5°C, respectively. The radial growth curve for each mycelium was fitted to a linear model for the estimation of mycelium lag time. The results showed that the lag time varied significantly among single spores. The cumulative frequency distributions of the lag times were fitted to the modified Gompertz model and compared with the respective distributions for the germination time, which were obtained microscopically. The distributions of the measured mycelium lag time were found to be similar to the germination time distributions under the same conditions but shifted in time with the lag times showing a significant delay compared to germination times. A numerical comparison was also performed based on the distribution parameters λm and λg, which indicate the time required from the spores to start the germination process and the completion of the lag phase, respectively. The relative differences %(λm-λg)/λm were not found to be significantly affected by temperatures tested with mean values of 72.5±5.1 and 60.7±2.1 for P. expansum for A. niger, respectively. In order to investigate the source of the above difference, a time-lapse microscopy method was developed providing videos with the behavior of single fungal spore from germination until mycelium formation. The distances of the apexes of the first germ tubes that emerged from the swollen spore were measured in each frame of the videos and these data were expressed as a function of time. The results showed that in the early hyphal development, the measured radii appear to increase exponentially, until a certain time, where growth becomes linear. The two phases of hyphal development can explain the difference between germination and lag time. Since the lag time is estimated from the extrapolation of the regression line of the linear part of the graph only, its value is significantly higher than the germination time, tG. The relation of germination and lag time was further investigated by comparing their temperature dependence using the Cardinal Model with Inflection. The estimated values of the cardinal parameters (Tmin, Topt, and Tmax) for 1/λg were found to be very close to the respective values for 1/λm, indicating similar temperature dependence between them. © 2012 Elsevier B.V.

Sofianidis G.,Aristotle University of Thessaloniki
Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science | Year: 2012

This study investigated how the dancer's level of expertise and the type of auditory guidance provided influence the kinematic profile of the lower limbs during traditional dance performance. Ten experts in traditional Greek dance (age: 25±3.29 years, five males and five females) and eleven novice participants (age: 26.45±3.88 years, six males and five females), all Greek natives, performed a series of Greek and Irish dance steps with auditory guidance of the metrics (verbal counting) and the music of the respective dances. An electromagnetic tracking system sampled (at 100 Hz) the angular displacement of the two lower legs about the Mediolateral axis during dance performance. Segment rotations were analyzed in the time and frequency domain. Expert dancers displayed significantly lower variability of lower leg rotation and stronger interlimb coupling when compared to novice performers. In novice performers, the power of the lower limb angular displacement extended to higher frequencies when dance performance was guided by music compared to metrical guidance. The addition of music and the origin of the dance interfered with performance for novices but not experienced dancers. Kinematic analysis of the lower limbs may open a new window for the investigation of learning and auditory guidance effects on dance performance.

Zaharis Z.D.,Aristotle University of Thessaloniki
Progress in Electromagnetics Research | Year: 2012

The present paper is a study of adaptive beamforming (ABF) techniques applied to antenna arrays. The structure of these techniques is based on Taguchi's Optimization (TagO) method. The high convergence speed and the ability to reach near-optimal solutions by adjusting only one parameter make the Taguchi's method an attractive choice for real time implementations like the case of ABF. Modifications are proposed in order to enhance the applicability of the TagO algorithm and decrease the computational time needed by the algorithm to terminate. The TagO method is used here to construct an ABF technique that aims at steering the main lobe of a uniform linear array towards a signal of interest, under the constraint of low side lobe level (SLL) or the constraint of placing radiation pattern nulls towards respective interference signals. Properly defined fitness functions must be minimized by the TagO algorithm to satisfy respectively the above mentioned constraints. The TagO-based ABF technique is compared with typical beamforming methods, like the Sample Matrix Inversion (SMI) and Maximum Likelihood (ML) ones, and with two evolutionary ABF techniques based on Particle Swarm Optimization (PSO) and Differential Evolution (DE), respectively. The comparison is performed regarding the convergence speed, the ability to achieve better fitness values in less time, the ability to properly steer the main lobe and finally the null-steering ability or the SLL control depending on the constraint type. The results exhibit the superiority of the TagO-based technique.

Papadopoulos T.G.,Aristotle University of Thessaloniki | Rekanos I.T.,Aristotle University of Thessaloniki
IEEE Transactions on Antennas and Propagation | Year: 2012

A time-domain inverse scattering method for the reconstruction of inhomogeneous dispersive media described by the Debye model is presented. The method aims to the simultaneous reconstruction of the spatial distributions of the optical and static permittivity as well as of the relaxation time. The reconstruction of the scatterer is based on the minimization of a cost functional, which describes the difference between measured and estimated values of the electric field. The fulfillment of the Maxwell's curl equations is set as constraint by means of Lagrange multipliers in an augmented functional. The Fréchet derivatives with respect to the scatterer properties are derived analytically and can be utilized by any gradientbased optimization technique. The proposed reconstruction technique is based on the Polak-Ribière nonlinear conjugate-gradient algorithm, while the finite-difference time-domain (FDTD) method is employed for the solution of the direct and the adjoint electromagnetic problem. Numerical results for the reconstruction of one-dimensional layered scatterers illustrate the performance of the proposed method. © 2011 IEEE.

Rekanos I.T.,Aristotle University of Thessaloniki
IEEE Microwave and Wireless Components Letters | Year: 2012

A finite-difference time-domain (FDTD) method for modeling wave propagation in Havriliak-Negami dispersive media is presented. In such media, the time-domain representation of the polarization relation involves time derivatives of fractional orders. Hence, the direct application of the FDTD method meets significant difficulties. In the proposed method, an auxiliary differential equation of integer order that approximates the polarization relation is derived. This approximation is based on Padé approximants of the relative complex permittivity. As a result the auxiliary differential equation can be easily discretized by means of finite differences and then included within the standard FDTD scheme. The efficiency of the proposed method is demonstrated by simulating the propagation of wideband pulses. © 2006 IEEE.

Rekanos I.T.,Aristotle University of Thessaloniki
IEEE Transactions on Antennas and Propagation | Year: 2012

Two finite-difference time-domain (FDTD) schemes based on the use of auxiliary differential equations are proposed for modeling time-domain wave propagation in dispersive Davidson-Cole media. The main difficulty in FDTD implementations for such media is the appearance of fractional derivatives in the time-domain polarization relation. To circumvent this difficulty, the relative complex permittivity of the medium is approximated by Padé approximants resulting in auxiliary differential equations of integer order. Moreover, it is proven that under certain conditions the Padé approximation is equivalent to one given by a sum of Debye terms. Hence, an alternative set of auxiliary differential equations is derived. Over a wideband frequency domain, the comparisons between analytical and calculated values of the relative complex permittivity as well as of the transfer function inside the dispersive medium illustrate the efficiency of both FDTD schemes. © 2006 IEEE.

Kaifas T.N.,Aristotle University of Thessaloniki
IEEE Transactions on Antennas and Propagation | Year: 2012

The current work proposes a direct rational function fitting method, employing cylindrical waves alone, for the accurate evaluation of Sommerfeld integrals for planar multilayered structures. Three are the key points of the effort. 1) Until now, relative works require the extraction of the quasi-static/asymptotic terms, and branch cut/continuous wave contribution explicitly. In the current one, the explicit treatment of those terms is avoided. The proposed methodology is based on the direct fitting of the spectrum of the Green's function by rational functions. Thus, it provides the spatial Green's function solely in terms of cylindrical waves. 2) The effectiveness, robustness and accuracy improvement of the rational function fit rely upon the proper sampling of the spectrum. This accurate fitting is possible because instead of avoiding large variations of the spectral kernel, we introduce proper paths to include more variation, and thus more spectrum information, before we apply the modified VECTFIT algorithm. 3) Furthermore, proper weighting of the VECTFIT is proposed in order to guide the algorithm in providing increased accuracy in specific desired areas of the horizontal distance between the source and observation points. Armed with the above the direct rational function fitting method provides accurate results both for the near and far-field regions. Various examples, among them the correct treatment of a two branch case, are given that prove the excellent performance and robustness of the proposed approach. © 2006 IEEE.

Fitsios D.,Aristotle University of Thessaloniki | Vyrsokinos K.,Center for Research and Technology Hellas | Miliou A.,Aristotle University of Thessaloniki | Pleros N.,Aristotle University of Thessaloniki
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2012

We demonstrate analytical frequency-domain transfer function expressions for an optical random access memory (RAM) cell that employs two SOA-based ON/OFF switches and two coupled SOA-MZI gates forming an optical flip-flop. Our theoretical model relies on first-order perturbation theory approximations applied for the first time to coupled optical switching structures, resulting to an optical RAM cell frequency response that allows for a qualitative and quantitative analysis of optical RAM memory speed and performance characteristics and their dependence on certain RAM cell device parameters. We show that the transfer function of an optical RAM cell and its incorporated flip-flop device exhibits periodic resonance frequencies resembling the behavior of optical ring resonator configurations. Its free spectral range is mainly dictated by the length of the waveguide that enables the coupling of the two SOA-MZI gates, yielding this coupling length as the dominant memory speed determining factor. The obtained results are in close agreement with experimental observations, demonstrating that optimized RAM cell designs with waveguide coupling lengths lower than 5 mm can enable RAM operation at memory speeds well beyond 40 GHz. © 2011 IEEE.

Mironidis G.K.,Aristotle University of Thessaloniki | Savopoulou-Soultani M.,Aristotle University of Thessaloniki
Journal of Thermal Biology | Year: 2010

Under natural conditions insects are occasionally subjected to thermal stresses. Data concerning the effects of these temperature extremes on tolerance and on life history parameters of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) have been lacking. This study investigated the effects of heat shock temperatures and exposure pattern on survival and on reproductive parameters of H. armigera adults. Adults were exposed to four high temperatures (40, 42.5, 45 and 46.5°C) for time periods ranging from 1.5 to 540min, depending on the temperature treatment and then insects were returned to normal temperature conditions. The survival rate of both sexes declined with the increase in the time of exposure at all high temperatures examined. The lethal time needed to cause mortality in 50% and 90% of the adult population decreased rapidly with the increase in the temperature from 40 to 46.5°C. Mean adult longevity declined significantly with the increase in the exposure time at all heat-shock treatments tested. The values of parameters of fecundity were found to be inversely related to the exposure time of the adults to high temperatures. No eggs were oviposited by adults of H. armigera exposed to 40, 42.5 and 45°C for 360, 120 and 15min, respectively, while adults exposed to 42.5, 45 and 46.5°C for 90, 12.5 and 5min, respectively, did not mate successfully. As the heat shock response is vital for H. armigera adults living in a variable environment, our findings can be used to develop a more profound understanding on the potential for this insect to evolve in response to environmental changes. © 2009 Elsevier Ltd.

Menelaou M.,Aristotle University of Thessaloniki | Georgoula K.,Aristotle University of Thessaloniki | Simeonidis K.,University of Thessaly | Dendrinou-Samara C.,Aristotle University of Thessaloniki
Dalton Transactions | Year: 2014

Nickel ferrite nanoparticles were synthesized via a facile solvothermal approach. Oleylamine (OAm) was used in all synthetic procedures as a stabilizing agent and solvent. By varying the polarity of the solvents, hydrophobic NiFe2O4 nanoparticles coated with OAm of relatively similar sizes (9-11.7 nm) and in a range of magnetization values (32.0-53.5 emu g-1) were obtained. The as-prepared hydrophobic nanoparticles were characterized by XRD, TEM, SEM, TGA and VSM and converted to hydrophilic by two different approaches. The addition of a positively charged ligand (cetyltrimethyl ammonium bromide, CTAB) and the ligand exchange procedure (2,3-dimercaptosuccinic acid, DMSA) have been successfully applied. The aqueous suspensions of NiFe2O4@CTAB and NiFe2O 4@DMSA showed good colloidal stability after a long period of time. The different surface modification affected both the NMR relaxometric measurements and the hyperthermia effects. In both techniques CTAB modification demonstrated higher r2 relaxivity (278.9 s-1 mM -1 in an NMR spectrometer at 11.7 T) and SAR values (423.4 W g -1 at an applied AC field with a particle concentration of 0.5 mg mL-1). The results indicate that a coating with a larger molecule as CTAB under the same size, shape and magnetization of NiFe2O 4 NPs gave rise to NMR relaxometric properties and heating efficacy. © 2014 The Royal Society of Chemistry.

Hatzimouratidis K.,Aristotle University of Thessaloniki
European urology | Year: 2010

Erectile dysfunction (ED) and premature ejaculation (PE) are the two most prevalent male sexual dysfunctions. To present the updated version of 2009 European Association of Urology (EAU) guidelines on ED and PE. A systematic review of the recent literature on the epidemiology, diagnosis, and treatment of ED and PE was performed. Levels of evidence and grades of recommendation were assigned. ED is highly prevalent, and 5-20% of men have moderate to severe ED. ED shares common risk factors with cardiovascular disease. Diagnosis is based on medical and sexual history, including validated questionnaires. Physical examination and laboratory testing must be tailored to the patient's complaints and risk factors. Treatment is based on phosphodiesterase type 5 inhibitors (PDE5-Is), including sildenafil, tadalafil, and vardenafil. PDE5-Is have high efficacy and safety rates, even in difficult-to-treat populations such as patients with diabetes mellitus. Treatment options for patients who do not respond to PDE5-Is or for whom PDE5-Is are contraindicated include intracavernous injections, intraurethral alprostadil, vacuum constriction devices, or implantation of a penile prosthesis. PE has prevalence rates of 20-30%. PE may be classified as lifelong (primary) or acquired (secondary). Diagnosis is based on medical and sexual history assessing intravaginal ejaculatory latency time, perceived control, distress, and interpersonal difficulty related to the ejaculatory dysfunction. Physical examination and laboratory testing may be needed in selected patients only. Pharmacotherapy is the basis of treatment in lifelong PE, including daily dosing of selective serotonin reuptake inhibitors and topical anaesthetics. Dapoxetine is the only drug approved for the on-demand treatment of PE in Europe. Behavioural techniques may be efficacious as a monotherapy or in combination with pharmacotherapy. Recurrence is likely to occur after treatment withdrawal. These EAU guidelines summarise the present information on ED and PE. The extended version of the guidelines is available at the EAU Web site ( Copyright © 2010 European Association of Urology. Published by Elsevier B.V. All rights reserved.

Mantzouridou F.,Aristotle University of Thessaloniki | Tsimidou M.Z.,Aristotle University of Thessaloniki
FEMS Yeast Research | Year: 2010

The constructed strains AM63, having an extra copy of the HMG2 gene with a K6R stabilizing mutation in Hmg2p expressed under the control of the inducible galactose promoter and stably integrated into the chromosomal HO locus, and AM64, a derivative of AM63 with an additional deletion of the ERG6 gene, were used as tools to test the squalene accumulation capacity of Saccharomyces cerevisiae. Kinetic data indicated high squalene levels in the early stages of semi-anaerobic cultivation of these strains. The stable Hmg2p induced a strong increase in the squalene pool and a smaller increase in the lanosterol pool. In AM63, the squalene content was ∼20-fold higher than in the wild-type EGY48 parental strain. In AM64, the combined Hmg2p stabilization and ERG6 deletion did not further enhance squalene accumulation, as lack of ergosterol feedback inhibition led to an elevated transfer of surplus squalene into C27 sterols. The obtained maximum capacity of the selected strains to accumulate squalene and our observations provide a further understanding of the regulation of ergosterol pathway and may also be used as a reference value for its production using food-grade strains of S. cerevisiae. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Zotos E.E.,Aristotle University of Thessaloniki
Monthly Notices of the Royal Astronomical Society | Year: 2014

The aim of this work is to explore the escape process of three-dimensional orbits in a star cluster rotating around its parent galaxy in a circular orbit. The gravitational field of the cluster is represented by a smooth, spherically symmetric Plummer potential, while the tidal approximation was used to model the steady tidal field of the galaxy. We conduct a thorough numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. It is of particular interest to locate the escape basins towards the two exit channels and relate them with the corresponding escape times of the orbits. For this purpose, we split our investigation into three cases depending on the initial value of the z-coordinate which was used for launching the stars. The most noticeable finding is that the majority of stars initiated very close to the primary (x, y) plane move in chaotic orbits and they remain trapped for vast time intervals, while orbits with relatively high values of z0 on the other hand, form well-defined basins of escape. It was also observed, that for energy levels close to the critical escape energy the escape rates of orbits are large, while for much higher values of energy most of the orbits have low escape periods or they escape immediately to infinity. We hope our outcomes to be useful for a further understanding of the dissolution process and the escape mechanism in open star clusters. © 2014 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.

Semaltianos N.G.,Aristotle University of Thessaloniki
Critical Reviews in Solid State and Materials Sciences | Year: 2010

This review concerns nanoparticles collected in the form of nanopowder or a colloidal solution by laser ablating a solid target that lies in a gaseous or a liquid environment. The paper discusses the advantages of the method as compared with other methods for nanoparticle synthesis, outlines the factors on which the properties of the produced nanoparticles depend, explains the mechanisms and models involved in the generation of nanoparticles by laser ablation, clarifies the differences between nanoparticle generation in gaseous and liquid environments, presents some experimental desigins and equipment used by the several groups for nanoparticle generation by laser ablation, describes the techniques used for tuning the width of the nanoparticles size distribution, and finally presents a few interesting examples of nanoparticles generated by laser ablation. © 2010 Taylor and Francis Group, LLC.

Evaggelopoulou E.N.,Aristotle University of Thessaloniki | Samanidou V.F.,Aristotle University of Thessaloniki
Food Chemistry | Year: 2013

A confirmatory high pressure liquid chromatographic method for the determination of seven quinolone antibiotics in tissue of Atlantic salmon (Salmo salar L.) was developed. Ciprofloxacin (CIP), danofloxacin (DAN), enrofloxacin (ENR), sarafloxacin (SAR), oxolinic acid (OXO), nalidixic acid (NAL) and flumequine (FLU) were separated on a Perfectsil ODS-2 120 (250 mm × 4 mm, 5 μm) column by gradient elution with a mobile phase consisting of 0.1% trifluoroacetic acid (pH = 1), acetonitrile and methanol at 25 °C within 22 min. Analytes were monitored at 255 nm (for the determination of OXO, NAL and FLU) and 275 nm (for CIP, DAN, ENR and SAR) by means of photodiode array detector. Examined quinolones were isolated from salmon tissue by extraction with citrate buffer solution (pH = 4.7) and purified by solid phase extraction using Oasis HLB (200 mg/6 mL) cartridges. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity according to the European Union Decision 2002/657/EC. The accuracy of the method was additionally proved by its application to certified reference material of salmon tissue (BCR® 725). © 2012 Elsevier Ltd. All rights reserved.

Bikiaris D.N.,Aristotle University of Thessaloniki | Triantafyllidis K.S.,Aristotle University of Thessaloniki
Materials Letters | Year: 2013

HDPE nanocomposites containing 0.5, 1, 2.5 and 5 wt% of copper nanofibers (Cu-nanofibers) were prepared by the melt-mixing method and exhibited enhanced tensile strength, Young's modulus, and oxygen barrier as well as antibacterial properties. These improvements were attributed to the small size of Cu-nanofibers and their fine dispersion into the HDPE matrix. © 2012 Elsevier B.V.

Karatasos K.,Aristotle University of Thessaloniki
Journal of Physical Chemistry B | Year: 2013

Fully atomistic molecular dynamics simulations were employed in order to examine in detail the self-assembly characteristics and the complexation behavior of the anticancer drug doxorubicin with PEGylated hyperbranched polyesters in an aqueous environment. We have examined two variants of the polymeric compound by altering the length of the hydrophilic poly(ethylene glycol) arms attached to the hydrophobic hyperbranched core. By comparing the clustering properties of the drug molecules in a polymer-free system to those in the polymer-containing models, we were able to assess the effects related to the presence and to the structural features of the polymer moiety. In addition, we have distinguished the effects associated with the neutral and protonated drug molecules separately. It was found that, in the presence of the polymeric material, the drug molecules formed clusters preferentially close to the polymer's periphery, the characteristics of which depended on the structural details of the polymeric host and on the charge of the drug molecules. Hydrogen bonding was found to contribute to the polymer/drug complexation, with the nature of the prevailing donor/acceptor pairs depending on the charge of the drug. Dynamic analysis of the drugs' motion revealed that in the polymer-containing systems the drug molecules experienced a larger degree of confinement within the formed clusters compared to that describing their polymer-free analogues, while the structural coherence of the clusters was found to be more persistent in the system with the larger poly(ethylene glycol) arms. The results described in this work, through the monitoring of both static and dynamic aspects of the self-association and the complexation behavior of the neutral and charged molecules of doxorubicin with the polymeric host, may help toward the elucidation of the key parameters that are involved in the formation of effective polymer-based carriers for drug molecules of the anthracycline family used in cancer chemotherapy. © 2013 American Chemical Society.

The mechanisms of stress tolerance in sessile animals, such as molluscs, can offer fundamental insights into the adaptation of organisms for a wide range of environmental challenges. One of the best studied processes at the molecular level relevant to stress tolerance is the heat shock response in the genus Mytilus. We focus on the upstream region of Mytilus galloprovincialis Hsp90 genes and their structural and functional associations, using comparative genomics and network inference. Sequence comparison of this region provides novel evidence that the transcription of Hsp90 is regulated via a dense region of transcription factor binding sites, also containing a region with similarity to the Gamera family of LINE-like repetitive sequences and a genus-specific element of unknown function. Furthermore, we infer a set of gene networks from tissue-specific expression data, and specifically extract an Hsp class-associated network, with 174 genes and 2,226 associations, exhibiting a complex pattern of expression across multiple tissue types. Our results (i) suggest that the heat shock response in the genus Mytilus is regulated by an unexpectedly complex upstream region, and (ii) provide new directions for the use of the heat shock process as a biosensor system for environmental monitoring.

Valla V.,Aristotle University of Thessaloniki
Advances in Experimental Medicine and Biology | Year: 2013

Optimal blood glucose control and the restoration of the physiological insulin secretion is a current medical challenge and will account for an overall cardiovascular morbidity and mortality related to diabetes mellitus complications. Continuous Subcutaneous Insulin Infusion (CSII) is the first step to the development of the so-called "artificial pancreas" and is intended to restore blood glucose levels and the frequency of hypoglycemic episodes. CSII using an external pump, offers both a better glycemic profile compared to multiple daily insulin injections (MDI) and a broader flexibility in everyday activities. The advantages of insulin pumps, i.e., basal delivery consistency, adjustable basal rates and low insulin depots also contribute to its reported clinical superiority. However, experience with CSII indicates that candidate patients should be carefully selected, thoroughly educated and vividly motivated to improve their blood glucose control. © 2012 Landes Bioscience and Springer Science+Business Media.

Malea P.,Aristotle University of Thessaloniki | Kevrekidis T.,Democritus University of Thrace
Science of the Total Environment | Year: 2013

Novel information on the biological fate of trace elements in seagrass ecosystems is provided. Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V concentrations in five compartments (blades, sheaths, vertical rhizomes, main axis plus additional branches, roots) of the seagrass Cymodocea nodosa, as well as in seawater and sediments from the Thessaloniki Gulf, Greece were determined monthly. Uni- and multivariate data analyses were applied. Leaf compartments and roots displayed higher Al, Mo, Ni and Se annual mean concentrations than rhizomes, B was highly accumulated in blades and Cr in sheaths; As, Ba, Sr and Tl contents did not significantly vary among plant compartments. A review summarizing reported element concentrations in seagrasses has revealed that C. nodosa sheaths display a high Cr accumulation capacity. Most element concentrations in blades increased in early mid-summer and early autumn with blade size and age, while those in sheaths peaked in late spring-early summer and autumn when sheath size was the lowest; elevated element concentrations in seawater in late spring and early-mid autumn, possibly as a result of elevated rainfall and associated run-off from the land, may have also contributed to the observed variability. Element concentrations in rhizomes and roots generally displayed a temporary increase in late autumn, which was concurrent with high rainfall, low wind speed associated with reduced hydrodynamism, and elevated sediment element levels. The bioaccumulation factor based on element concentrations in seagrass compartments and sediments was lower than 1 except for B, Ba, Mo, Se and Sr in all compartments, Cr in sheaths and U in roots. Blade V concentration positively correlated with sediment V concentration, suggesting that C. nodosa could be regarded as a bioindicator for V. Our findings can contribute to the design of biomonitoring programs and the development of predictive models for rational management of seagrass meadows. © 2013.

Sargianou M.,Aristotle University of Thessaloniki
Expert review of anti-infective therapy | Year: 2013

Crimean-Congo hemorrhagic fever (CCHF), a viral disease with high fatality rate, is endemic in many countries in Europe, the Middle East, Asia and Africa. It is transmitted to humans either by tick bite or by direct contact with blood or tissues of viremic patients or livestock. Aim of the present study was to review the main epidemiological characteristics of the disease worldwide, with special attempt to show the epidemiological and behavioral factors that play a role in acquisition of the infection. It is obvious that these factors differ among countries, and the knowledge and understanding of the transmission routes in each region facilitates the implementation of proper control measures, the awareness enhancement and the prevention of the disease.

Tzamalis A.,Aristotle University of Thessaloniki
Retina | Year: 2016

PURPOSE:: To describe the safety and efficacy of removing posteriorly dislocated lens fragments with the use of intravitreal ultrasonic fragmentation through a limbal, clear cornea self-sealing incision. METHODS:: Patients presenting with posteriorly luxated nuclei were enrolled in this prospective case series. Preoperative examination included evaluation of the corneal endothelium by means of specular microscopy. A 3-port 25+ pars plana vitrectomy was initially performed. Following vitrectomy, sclerotomies were sealed using scleral plugs and a limbal/clear corneal incision was performed for the insertion of the fragmatome probe. The incision was slightly larger (1 mm) than the diameter of the fragmatome probe (20 gauge = 0.81 mm) to avoid wound overheating. At the end of the procedure, an appropriate intraocular lens either sulcus-fixated or angle-supported was implanted. Primary outcome measures were mean postoperative best-corrected visual acuity, intraoperative or postoperative complications, and intraoperative challenging features. RESULTS:: In all eyes, fragmentation was completed successfully with a mean total ultrasound time of 113.4 seconds. Nucleus density was ≥3 in all cases (mean ± SD = 3.8 ± 0.4). Intraoperative challenges included viewing difficulties because of corneal distortion, fragment turbulence, and leakage through the limbal incision potentially compromising fundus visualization. There was statistically nonsignificant reduction in endothelial cell density ranging between 1932 ± 187 cells per square millimeter preoperatively to 1789 ± 213 cells per square millimeter at the first month postoperatively (P = 0.79). CONCLUSION:: Clear corneal, sutureless ultrasonic fragmentation seems to be a novel, safe, and efficient method for the removal of hard posteriorly dislocated lens fragments, sparing the need for a 20-gauge scleral port. © 2016 by Ophthalmic Communications Society, Inc.

Petridis H.P.,Aristotle University of Thessaloniki
The European journal of esthetic dentistry : official journal of the European Academy of Esthetic Dentistry | Year: 2012

The purpose of this systematic review was to compare the survival and complication rates of ceramic veneers produced with different techniques and materials after a minimum follow-up time of 5 years. A literature search was conducted, using electronic databases, relevant references, citations and journal researching, for clinical studies reporting on the survival of ceramic veneers fabricated with different techniques and materials with a mean followup time of at least 5 years. The search period spanned from January 1980 up to October 2010. Event rates were calculated for the following complications associated with ceramic veneers: fracture, debonding, marginal discoloration, marginal integrity, and caries. Summary estimates, and 5-year event rates were reported. Comparison between subgroups of different materials, as well as statistical significance, was calculated using a mixed effects model. Nine studies were selected for final analysis over an initial yield of 409 titles. No study directly compared the incidence of complications between ceramic veneers fabricated from different materials. Four of the included studies reported on the survival of ceramic veneers made out of feldspathic ceramics; four studies were on glass-ceramic veneers and one study included veneers fabricated from both materials. The mean observation time ranged between 5 and 10 years. Overall, the 5-year complication rates were low, with the exception of studies reporting on extended ceramic veneers. The most frequent complication reported was marginal discoloration (9% at 5 years), followed by marginal integrity (3.9-7.7% at 5 years). There was no statistically significant difference in the event rates between the subgroups of different materials (feldspathic vs. glass-ceramic). The results of this systematic review showed that ceramic veneers fabricated from feldspathic or glass-ceramics have an adequate clinical survival for at least 5 years of clinical service, with very low complication rates.

Karagkiozaki V.,Aristotle University of Thessaloniki
Journal of Nanoparticle Research | Year: 2013

Atherosclerosis is a multifactorial disease and many different approaches have been attempted for its accurate diagnosis and treatment. The disease is induced by a low-grade inflammatory process in the vascular wall, leading through a cascade of events to the eventual formation of atheromatous plaque and arterial stenosis. Different types of cells participate in the process making more difficult to recognize the potential cellular targets within the plaques for their effective treatment. The rise of nanomedicine over the last decade has provided new types of drug delivery nanosystems that are able to be delivered to a specific diseased site of the vessel for imaging while simultaneously act as therapeutic agents. In this paper, a review of the recent advances in nanomedicine that has provided novel insights to the disease diagnosis and treatment will be given in line with different nanotechnology-based approaches to advance the cardiovascular stents. The main complications of bare metal stents such as restenosis and of drug-eluting stents which is the late stent thrombosis are analyzed to comprehend the demand for emerging therapeutic strategies based on nanotechnology. © 2013 Springer Science+Business Media Dordrecht.

Dimitrakopulos G.P.,Aristotle University of Thessaloniki
Applied Physics Letters | Year: 2012

The heteroepitaxy of semipolar s-plane (1101) InN grown directly on r-plane sapphire by plasma-assisted molecular beam epitaxy is studied using transmission electron microscopy techniques. The epitaxial relationship is determined to be (1101) InN (1102)Al 2O 3, [1120] InN [2021]Al 2O 3, [1102 ] InN ∼ [0221Al 2O 3, which ensures a 0.7 misfit along [1120] InN. Two orientation variants are identified. Proposed geometrical factors contributing to the high density of basal stacking faults, partial dislocations, and sphalerite cubic pockets include the misfit accommodation and reduction, as well as the accommodation of lattice twist. © 2012 American Institute of Physics.

Koufos G.D.,Aristotle University of Thessaloniki
Integrative Zoology | Year: 2014

Knowledge on the Villafranchian faunas of Greece was limited for a long time, but over the past 3 decades several new fossiliferous sites have been discovered and new material has been unearthed. The carnivores constitute a remarkable part of this material and their study has provided useful information for the taxonomy, chronology and palaeoecology. The Villafranchian carnivoran guild includes numerous taxa belonging to various families. Some of them are interesting as they are differentiated from the other Eurasian families. They cover the entire Villafranchian but the mass is known from the Middle to the Epi-Villafranchian (EVC). Despite the discontinuous data, they provide useful biochronological results. The coexistence of Pliocrocuta perrieri and Pachycrocuta brevirostris in the locality of Gerakarou 1 is strong evidence for the Middle Villafranchian (MVC)/Late Villafranchian (LVC) boundary. The composition of the Villafranchian carnivores suggests that the canids predominate, while the felids, hyenids and mustelids are well represented; the ursids are represented by a single taxon, the well-known Ursus etruscus, which seems to be common during the entire Villafranchian. The carnivoran guild structure and the multivariate analysis of the Greek Villafranchian carnivoran assemblages (MVC, LVC and EVC) in comparison with modern assembalges from open and closed environments indicate a relatively open landscape, which is in agreement with previous results for the Villafranchian of Greece. During the EVC there is a faunal renewal that is related to a more open and dry environment, like savannah bushland/grassland. © 2013 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.

Karras S.,Aristotle University of Thessaloniki
European Journal of Clinical Nutrition | Year: 2016

Despite high levels of sunshine, maternal hypovitaminosis D during pregnancy is prevalent in the Mediterranean region. The aim of this study is to systematically review trials that investigated vitamin D concentrations during pregnancy in this region, in order to determine predictors of hypovitaminosis D and explain this phenomenon. After applying inclusion/exclusion criteria, 15 studies were entered into the systematic review involving 2649 pregnant women and 820 neonates. The main outcome was maternal vitamin D status, assessed by serum 25-hydroxy-vitamin D (25(OH)D) concentrations. Possible predictors of the outcome included maternal age, body mass index (BMI), race, socioeconomic status, skin type, gestational age, sun exposure, calcium and vitamin D intake and supplementation, smoking status, parity and season of delivery. Studies differed widely in vitamin D deficiency criteria, method of measurement and outcomes. The prevalence of vitamin D insufficiency ranges from 9.3 to 41.4%, whereas that of vitamin D deficiency from 22.7 to 90.3%. A positive association with 25(OH)D concentrations exists for light skin color, white race, uncovered dressing pattern, maternal vitamin D supplementation and season of gestation (spring/summer). An inverse association exists for BMI and gestational age, whereas data for smoking and socioeconomic status are controversial. We concluded that vitamin D deficiency in pregnancy seems to be quite common, even in the Mediterranean region. Racial, social and cultural habits, as well as the absence of preventive supplementation/dietary strategies, seem to negate the benefits of sun exposure.European Journal of Clinical Nutrition advance online publication, 2 March 2016; doi:10.1038/ejcn.2016.12. © 2016 Macmillan Publishers Limited

Moschakis T.,Aristotle University of Thessaloniki | Murray B.S.,University of Leeds | Biliaderis C.G.,Aristotle University of Thessaloniki
Food Hydrocolloids | Year: 2010

The influence of chitosan and gum arabic mixtures on the behaviour of o/w emulsions has been investigated at pH = 3.0. The emulsion behaviour, properties and microstructure were found to be greatly dependent on the precise gum arabic to chitosan ratio. Mixing of gum arabic with chitosan leads to the formation of coacervates of a size dependent on their ratio. Incorporation of low gum arabic to chitosan weight ratios into whey protein-coated emulsions causes depletion flocculation and gravity-induced phase separation. Increasing the polysaccharide weight ratio further, a droplet network with a rather high viscosity (at low shear stress) is generated, which prevents or even inhibits phase separation. At even higher gum arabic to chitosan ratios, the emulsion droplets were immobilised into clusters of an insoluble ternary matrix. Although the emulsion droplet charge had the same sign as that of the coacervates, clusters of oil droplets in a ternary matrix were generated. A mechanism to explain the behaviour of the whey protein-stabilised o/w emulsions is described on the basis of confocal and phase contrast microscopic observations, rheological data, zeta potential measurements, particle size analysis and visual assessment of the macroscopic phase separation events. © 2009 Elsevier Ltd. All rights reserved.

Zygouris S.,Aristotle University of Thessaloniki | Tsolaki M.,Aristotle University of Thessaloniki
American Journal of Alzheimer's Disease and other Dementias | Year: 2015

Objective: This article is a review of computerized tests and batteries used in the cognitive assessment of older adults. Method: A literature search on Medline followed by cross-referencing yielded a total of 76 citations. Results: Seventeen test batteries were identified and categorized according to their scope. Computerized adaptive testing (CAT) and the Cambridge Cognitive Examination CAT battery as well as 3 experimental batteries and an experimental test are discussed in separate sections. All batteries exhibit strengths associated with computerized testing such as standardization of administration, accurate measurement of many variables, automated record keeping, and savings of time and costs. Discriminant validity and testretest reliability were well documented for most batteries while documentation of other psychometric properties varied. Conclusion: The large number of available batteries can be beneficial to the clinician or researcher; however, care should be taken in order to choose the correct battery for each application. © The Author(s) 2014 Reprints and permission:

Baltzis K.B.,Aristotle University of Thessaloniki
Wireless Personal Communications | Year: 2012

Geometrically based models are commonly used for the study, analysis and simulation of the wireless propagation channel. This paper presents a two-dimensional geometric scattering model for the description of the angle of arrival (AoA) distribution in mobile environments. In our approach, scatterers are uniformly distributed in hollow ellipses around each communication node. We derive closed-form expressions for the probability density function of the azimuth AoA of the incoming multipaths at each unit and investigate the impact of scatterer distribution on the angular spread of the received signal. Simulation results verify the accuracy of the model. Finally, we show that the proposed method is a generalization of popular geometric channel models. © Springer Science+Business Media, LLC. 2011.

Stavropoulos G.G.,Aristotle University of Thessaloniki
Fuel Processing Technology | Year: 2011

Liquid-solid adsorption kinetic data are mostly interpreted by a limited number of rate equations, (pseudo-first, pseudo-second order and Elovich). Besides, a fundamental tool in heterogeneous reactions, the Langmuir theory of adsorption, is used almost exclusively to model equilibrium isotherms but, surprisingly, not kinetics. Considering the limited applicability of the mentioned kinetic models, especially in estimating kinetic constants and predicting adsorption mechanism, it seems more reasonable to apply the Langmuir kinetic equation in modeling the liquid phase adsorption. In the diffusion-free regime, by constructing the experimental equilibrium isotherm of a system, one can easily check the validity of the Langmuir model. Afterwards, kinetic constants can be readily calculated and used to predict adsorption performance under different operating conditions. The proposed procedure was tested in the experimental results of cyanide adsorption in activated carbon to verify the applicability of the Langmuir adsorption mechanism and estimate the equilibrium and kinetic constants. © 2011 Elsevier B.V. All rights reserved.

Michailides C.,Aristotle University of Thessaloniki | Angelides D.C.,Aristotle University of Thessaloniki
Applied Ocean Research | Year: 2012

In the present paper, linear hydroelastic analysis is performed for the assessment of the behavior of a Flexible Floating Breakwater (FFB), which represents not only a structure for shore protection but also a device for wave energy production with the utilization of a linear hydraulic Power Take-Off mechanism (PTO). The linear hydroelastic analysis is conducted in frequency domain with a radiation/diffraction 3D hydrodynamic model considering the effect of the flexibility of the FFB as well as the damping associated with the energy extraction by the PTO mechanism. A framework for this analysis is proposed and demonstrated, which includes three components: (a) a 3D structural model for an initial eigenvalue analysis, (b) a 3D hydrodynamic model for the hydroelastic analysis and (c) a numerical analysis for the calculation of the forces associated with the PTO and, also, for the estimation of the generated power. FFB consists of a grid of flexible floating modules connected flexibly in two directions by: (a) connectors with known properties and (b) hydraulic Power Take-Off mechanisms with known linear damping characteristics. The PTO mechanisms can be oriented in any possible direction in space. The investigation of the FFBs' behavior is executed for two grids with different number of modules as well as for different combinations of translational and rotational stiffness of the FFB's connectors and different damping coefficients of PTO. The combined effect of wave energy extraction, behavior and a desired level of protection by the FFB is illustrated. © 2011 Elsevier Ltd.

Kontoleon K.J.,Aristotle University of Thessaloniki
Energy and Buildings | Year: 2012

This paper aims at introducing an improved methodology for the dynamic modelling of buildings by the thermal networks method. This methodology employs, as a tool, the commonly used ASHRAE clear sky model to allow for the calculation of the external faade radiation and the distribution of the penetrating solar flux on the internal surface-nodes of the zone. The zone considered has an entirely glazed faade with a varying type of glazing and its enclosure is a rectangle parallelipipedic. The incident solar radiation is determined for building surface azimuths ranging from east to west in 45°step increments. The mathematical formulation of this solar-angle dependent lumped capacitance thermal model is based on the nodal approach and is updated in 15 min time increments. The proposed methodology provides more insight to help understand the impact of opaque and glazed faade orientations and layer-formation on energy consumption. Results from annual energy performance calculations vs glazed-faade orientation, for various glazing systems, are given for a building zone location in the Mediterranean region. Depending on the building faade orientation and climatic conditions, proper selection of the type of glazing can reduce the annual building energy consumption. © 2012 Elsevier B.V. All rights reserved.

Bechlioulis C.P.,Aristotle University of Thessaloniki | Doulgeri Z.,Aristotle University of Thessaloniki | Rovithakis G.A.,Aristotle University of Thessaloniki
Automatica | Year: 2012

In this paper, we consider the problem of force/position tracking for a robot with revolute joints in compliant contact with a kinematically known planar surface. A novel controller is designed capable of guaranteeing, for an a priori known nonsingular initial robot condition, (i) certain predefined minimum speed of response, maximum steady state error as well as overshoot concerning the force/position tracking errors, (ii) contact maintenance and (iii) bounded closed loop signals. No information regarding either the robot dynamic model or the force deformation model is required and no approximation structures are utilized to estimate them. As the tracking performance is a priori guaranteed irrespectively of the control gains selection, the only concern is to adopt those values that lead to reasonable input torques. Finally, a comparative simulation study on a 6-DOF robot illustrates the performance of the proposed controller. © 2011 Elsevier Ltd. All rights reserved.

Stylianidis K.C.,Aristotle University of Thessaloniki
Open Construction and Building Technology Journal | Year: 2012

Although it is well documented that infills significantly affect the dynamic characteristics and the seismic response of the bare basic structural system, codes are reluctant to encourage consideration of infills as main structural elements, mainly due to structural uncertainties and computational complexities. Part of the uncertainties are due to the very many parameters affecting the behavior of the system, such as infill materials, reinforcing of infills, connection to the surrounding frame, geometry, relative stiffness and strength, local construction techniques etc. In the present paper three successive experimental programs, conducted at the R/C and Masonry Structures Laboratory of the Aristotle University, are described, commented and discussed. All of them refer to single-storey one-bay 1:3 scale R/C moment resisting frames. The first program consisted of 18 specimens, 2 bare and 16 unreinforced masonry (URM) infilled. The second program was an extension and a supplement of the previous one. It consisted of 20 more specimens, 6 bare and 14 URM infilled. The third program was directed towards the investigation of quick and low cost strengthening methods of R/C frames damaged by earthquakes, using several infill techniques. For this purpose 10 of the damaged specimens of the first program were repaired and strengthened. © K.C. Stylianidis.

Sperdouli I.,Aristotle University of Thessaloniki | Moustakas M.,Aristotle University of Thessaloniki
Plant Biology | Year: 2012

Using chlorophyll (chl) fluorescence imaging, we studied the effect of mild (MiDS), moderate (MoDS) and severe (SDS) drought stress on photosystem II (PSII) photochemistry of 4-week-old Arabidopsis thaliana. Spatio-temporal heterogeneity in all chl fluorescence parameters was maintained throughout water stress. After exposure to drought stress, maximum quantum yield of PSII photochemistry (F v/F m) and quantum efficiency of PSII photochemistry (Φ PSΙΙ) decreased less in the proximal (base) than in the distal (tip) leaf. The chl fluorescence parameter F v/F m decreased less after MoDS than MiDS. Under MoDS, the antioxidant mechanism of A. thaliana leaves seemed to be sufficient in scavenging reactive oxygen species, as evident by the decreased lipid peroxidation, the more excitation energy dissipated by non-photochemical quenching (NPQ) and decreased excitation pressure (1-q p). Arabidopsis leaves appear to function normally under MoDS, but do not seem to have particular metabolic tolerance mechanisms under MiDS and SDS, as revealed by the level of lipid peroxidation and decreased quantum yield for dissipation after down-regulation in PSII (Φ NPQ), indicating that energy dissipation by down-regulation did not function and electron transport (ETR) was depressed. The simultaneous increased quantum yield of non-regulated energy dissipation (Φ NO) indicated that both the photochemical energy conversion and protective regulatory mechanism were insufficient. The non-uniform photosynthetic pattern under drought stress may reflect different zones of leaf anatomy and mesophyll development. The data demonstrate that the effect of different degrees of drought stress on A. thaliana leaves show spatio-temporal heterogeneity, implying that common single time point or single point leaf analyses are inadequate. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.

Michailidis N.,Aristotle University of Thessaloniki
Materials Science and Engineering A | Year: 2011

Metal foams can be used as structural materials for impact energy absorption applications, due to the extended plateau stress they exert under compressive loads. The compressive behaviour of Ni-foams was studied by experimental and computational methods at various strain rates. The geometry of the porous material was reconstructed based on X-ray computed tomography measurements and used in a FEM simulation software package, facilitating large unconstrained plastic deformation, to determine its response under variable strain rates. SEM in situ compression tests were employed to measure the load-displacement response of the foam, while allowing the acquisition of images illustrating the deformed metal foam struts. The results of the study indicated that the introduced FEM model provides reliable insight with regard to the response of metal foams under various compressive strain rates. Additionally, the FEM model facilitates a holistic overview of the deformation phenomena occurring within the porous structure on both macro- and micro-scales. © 2011 Elsevier B.V.

Aifantis E.C.,Aristotle University of Thessaloniki
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2011

The term "gradient nanomechanics" is used here to designate a generalized continuum mechanics framework accounting for "bulk- surface" interactions in the form of extra gradient terms that enter in the balance laws or the evolution equations of the relevant constitutive variables that govern behavior at the nanoscale. In the case of nanopolycrystals, the grain boundaries may be viewed either as sources/sinks of "effective" mass and internal force or as a separate phase, interacting with the bulk phase that it surrounds, and supporting its own fields, balance laws, and constitutive equations reflecting this interaction. In either view, a further common assumption introduced is that the constitutive interaction between bulk and "interface" phases enters in the form of higher order gradient terms, independently of the details of the underlying physical mechanisms that bring these terms about. The effectiveness of the approach is shown by considering certain benchmark problems for nanoelasticity, nanoplasticity, and nanodiffusion for which standard continuum mechanics theory fails to model the observed behavior. Its implications to interpreting size-dependent stress-strain curves for nanopolycrystals with varying grain size are also discussed. © 2011 The Minerals, Metals & Materials Society and ASM International.

Kantartzis N.V.,Aristotle University of Thessaloniki
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields | Year: 2012

A hybrid unconditionally stable time-domain technique for the precise analysis and wideband performance characterization of 3D microwave systems is developed in this paper. Founded on a nontraditional differential discretization basis, the proposed technique launches a class of robust operators via an error-controllable procedure that offers enhanced spectral resolution and optimal spatial stencils. The key asset of the frequency-dependent algorithm is the novel high-order nonstandard approximators, whose tensorial properties preserve the hyperbolic character of Maxwell's equations. In this manner, the resulting formulation remains completely explicit and generates effective dual meshes free of artificial vector parasites and spurious modes. Moreover, the preceding schemes are fruitfully hybridized, in the context of nonoverlapping subspaces, with an alternating-direction implicit finite-element time-domain method in an effort to handle abruptly varying media boundaries and intricate geometries. Hence, an extensive decrease of dispersion errors is achieved, even when time-steps are chosen appreciably beyond stability limits. These advanced simulation competences are successfully applied to diverse real-world setups and composite configurations, thus validating the efficiency and universality of the proposed methodology. Copyright © 2012 John Wiley & Sons, Ltd.

Symeonidis P.,Aristotle University of Thessaloniki
IEEE Transactions on Systems, Man, and Cybernetics: Systems | Year: 2016

Social tagging systems (STSs) allow users to annotate information items (songs, pictures, etc.) to provide them item/tag or even user recommendations. STSs consist of three main types of entities: 1) users; 2) items; and 3) tags. These data usually are represented by a three-order tensor, on which Tucker decomposition (TD) models are performed, such as higher order singular value decomposition. However, TD models require cubic computations for the tensor decomposition. Furthermore, TD models suffer from sparsity that incurs in social tagging data. Thus, TD models have limited applicability to large-scale datasets, due to their computational complexity and data sparsity. In this paper, we use two different ways to compute similarity/distance between tags (i.e., the term frequency - inverse document frequency vector space model and the semantic similarity of tags using the ontology of WordNet). Moreover, to reduce the size of the tensor's dimensions and its data sparsity, we use clustering methods (i.e., ${k}$ -means, spectral clustering, etc.) for discovering tag clusters, which are the intermediaries between a user's profile and items. Thus, instead of inserting the tag dimension in the tensor, we insert the tag cluster dimension, which is smaller and has less noise, resulting to better item recommendation accuracy. We perform experimental comparison of the proposed method against a state-of-the-art item recommendation algorithm with two real datasets ( and BibSonomy). Our results show significant improvements in terms of effectiveness and efficiency. © 2013 IEEE.

Karatzas K.D.,Aristotle University of Thessaloniki
Environmental Engineering and Management Journal | Year: 2010

The Air Quality Management problem calls for detailed, case-specific knowledge and requires, due to legal mandates, the development of operational, environmental parameter related, incident forecasting. Both targets can be met by applying Artificial Intelligence (AI) methods, and by employing relevant computational algorithms that are capable of producing reliable results. The current paper provides with an overview of the problem domain, identifies goals and proposes methods that may be employed in order to effectively deal with real world environmental management - air quality problems.

Dimoulas C.A.,Aristotle University of Thessaloniki
IEEE Transactions on Multimedia | Year: 2016

This paper presents the novel sound-field localization and visualization techniques for audiovisual spatial audio analysis, content description, and management. The method focuses on topographic analysis and mapping of gastro-intestinal motility (GIM) through multichannel recording of abdominal sounds (AS). Related research has attempted to study GIM physiology patterns and diagnose specific abnormalities or diseases. In this context, a new AS source localization method is implemented and evaluated. Sound imaging and spatiotemporal mapping utilities are deployed next by means of sound level distribution images. Novel audio description and management is introduced for the analysis automation of prolonged AS recordings, facilitating smart content browsing with audiovisual summarization and highlighting. The proposed modalities can be utilized in multimedia healthcare applications, where multimodal monitoring of GIM and other psychophysiological parameters can be combined for the study of human digestive patterns and their relation to other factors (i.e., subjects' medical history, nutrition, medication, psychological state, and others). The adopted methodology of spatial audio analysis introduces a generic framework that can be efficiently applied to various sound localization and imaging tasks, which are encountered both in bioacoustics and in contemporary multimedia involving multichannel/3D audio. © 2016 IEEE.

Rekanos I.T.,Aristotle University of Thessaloniki
IEEE Antennas and Wireless Propagation Letters | Year: 2012

Recently, a novel finite-difference time-domain (FDTD) scheme has been proposed for modeling wave propagation in Cole-Cole dispersive media (Abdullah , IEEE Antennas Wireless Propag. Lett., vol. 11, pp. 281-284, 2012). The scheme is based on the approximation of the fractional derivative, which appears in the polarization relation, by means of a semi-local method. This approach ends up to an approximate time-domain polarization relation given by a first-order differential equation with nonconstant coefficients. As a result, this scheme is very attractive because it has very limited storage demands compared to all the previously reported schemes. However, in this letter, it is shown that the proposed scheme is actually untrustworthy. This criticism is based on both analytical and numerical evidences and illustrates that the semi-local approximation of fractional derivatives is very poor. © 2011 IEEE.

Mitoulis S.A.,Aristotle University of Thessaloniki
Engineering Structures | Year: 2012

Abutments are not only earth-retaining systems as they also participate to the earthquake resisting system (ERS) of the bridge, under certain design considerations. Current research mainly focuses on the assessment of the performance of integral abutment bridges, while only a few studies dealt with the design of bridges with seat-type abutments accounting for their seismic contribution. Along these lines, a comparative study on seat-type abutment bridges was performed. The scope of the study was to identify possible differences in their seismic response affecting significant design parameters that are the displacements of the deck and the bending moments of the piers. The study employed three real bridges of variable total lengths, openings at the expansion joints, backfill models and moderate to strong earthquake excitations. Non-linear dynamic time history analysis was performed. The study showed that the strong participation of the abutment and the backfill soil can reduce effectively the seismic demand of bridges. However, attention should be given in bridges with tall piers, whose seismic forces can be increased under certain design conditions. © 2012 Elsevier Ltd.

Mergos P.E.,Aristotle University of Thessaloniki | Kappos A.J.,Aristotle University of Thessaloniki
Engineering Structures | Year: 2012

A new beam-column model is developed for the seismic analysis of reinforced concrete (R/C) structures. This finite element consists of two interacting, gradual spread inelasticity sub-elements representing inelastic flexural and shear response and two rotational springs at the ends of the member to model anchorage slip effects. The flexural sub-element is able to capture gradual spread of flexural yielding in plastic hinge regions of R/C members. The shear sub-element interacts throughout the analysis with the flexural sub-element, in the location of the plastic hinge regions, in order to capture gradual spread of inelastic shear deformations as well as degradation of shear strength with curvature ductility demand based on an analytical procedure proposed herein. The skeleton curves and hysteretic behaviour in all three deformation mechanisms are determined on the basis of analytical procedures and hysteretic models found to match adequately the experimental results. Empirical formulae are proposed for the shear distortion at onset of stirrup yielding and onset of shear failure. The proposed element is implemented in the general finite element code for damage analysis of R/C structures IDARC and is validated against experimental results involving R/C column and frame specimens failing in shear subsequent to yielding in flexure. It is shown that the model can capture well the hysteretic response and predict reliably the type of failure of these specimens. © 2012 Elsevier Ltd.

Hadjidimitriou S.K.,Aristotle University of Thessaloniki | Hadjileontiadis L.J.,Aristotle University of Thessaloniki
IEEE Transactions on Biomedical Engineering | Year: 2012

Affective phenomena, as reflected through brain activity, could constitute an effective index for the detection of music preference. In this vein, this paper focuses on the discrimination between subjects electroencephalogram (EEG) responses to self-assessed liked or disliked music, acquired during an experimental procedure, by evaluating different feature extraction approaches and classifiers to this end. Feature extraction is based on time-frequency (TF) analysis by implementing three TF techniques, i.e., spectrogram, Zhao-Atlas-Marks distribution and Hilbert-Huang spectrum (HHS). Feature estimation also accounts for physiological parameters that relate to EEG frequency bands, reference states, time intervals, and hemispheric asymmetries. Classification is performed by employing four classifiers, i.e., support vector machines, k-nearest neighbors (k-NN), quadratic and Mahalanobis distance-based discriminant analyses. According to the experimental results across nine subjects, best classification accuracy {86.52 (±0.76)} was achieved using k-NN and HHS-based feature vectors (FVs) representing a bilateral average activity, referred to a resting period, in β (13-30Hz) and γ (30-49Hz) bands. Activity in these bands may point to a connection between music preference and emotional arousal phenomena. Furthermore, HHS-based FVs were found to be robust against noise corruption. The outcomes of this study provide early evidence and pave the way for the development of a generalized brain computer interface for music preference recognition. © 2012 IEEE.

Zotos E.E.,Aristotle University of Thessaloniki
International Journal of Non-Linear Mechanics | Year: 2016

We consider the planar circular equilateral restricted four body-problem where a test particle of infinitesimal mass is moving under the gravitational attraction of three primary bodies which move on circular orbits around their common center of gravity, such that their configuration is always an equilateral triangle. The case where all three primaries have equal masses is numerically investigated. A thorough numerical analysis takes place in the configuration (x,y) as well as in the (x,y) space in which we classify initial conditions of orbits into four main categories: (i) bounded regular orbits, (ii) trapped chaotic orbits, (iii) escaping orbits and (iv) collision orbits. Interpreting the collision motion as leaking in the phase space we related our results to both chaotic scattering and the theory of leaking Hamiltonian systems. We successfully located the escape and the collision basins and we managed to correlate them with the corresponding escape and collision times of orbits. We hope our contribution to be useful for a further understanding of the escape and collision properties of motion in this interesting dynamical system. © 2016 Elsevier Ltd

Kazakis N.,Aristotle University of Thessaloniki | Voudouris K.S.,Aristotle University of Thessaloniki
Journal of Hydrology | Year: 2015

In the present study the DRASTIC method was modified to estimate vulnerability and pollution risk of porous aquifers to nitrate. The qualitative parameters of aquifer type, soil and impact of the vadose zone were replaced with the quantitative parameters of aquifer thickness, nitrogen losses from soil and hydraulic resistance. Nitrogen losses from soil were estimated based on climatic, soil and topographic data using indices produced by the GLEAMS model. Additionally, the class range of each parameter and the final index were modified using nitrate concentration correlation with four grading methods (natural breaks, equal interval, quantile and geometrical intervals). For this reason, seventy-seven (77) groundwater samples were collected and analyzed for nitrate. Land uses were added to estimate the pollution risk to nitrates. The two new methods, DRASTIC-PA and DRASTIC-PAN, were then applied in the porous aquifer of Anthemountas basin together with the initial versions of DRASTIC and the LOSN-PN index. The two modified methods displayed the highest correlations with nitrate concentrations. The two new methods provided higher discretisation of the vulnerability and pollution risk, whereas the high variance of the (ANOVA) F statistic confirmed the increase of the average concentrations of NO3-, increasing from low to high between the vulnerability and pollution risk classes. The importance of the parameters of hydraulic resistance of the vadose zone, aquifer thickness and land use was confirmed by single-parameter sensitivity analysis. © 2015 Elsevier B.V.

Papadopoulos K.G.,ABB | Margaris N.I.,Aristotle University of Thessaloniki
Journal of Process Control | Year: 2013

An automatic tuning method for the PID controller in single-input-single- output control loops involving processes with conjugate complex poles is presented. The development of the method lies in the principle of the well known Magnitude Optimum criterion and considers two fundamental constraints met frequently in many industry applications; (1) the existence of a poor process model and (2) access to the output of the process and not to its states. The presentation of the method is carried out in two steps. Over the first step, the straightforward PID tuning via the Magnitude Optimum criterion in the ideal case of a known single input-single output linear process model reveals a feature of the method called 'the preservation of the shape of the step and frequency response' of the final closed-loop control system. This shape is characterized by specific performance in terms of overshoot (4.4%), settling and rise time of the closed-loop control system. Over the second step, the PID controller parameters are tuned automatically so that the aforementioned performance is achieved. In this case, the existence of a poor process model is adopted assuming access to its output and not to its states. For applying the method an open-loop experiment of the process is carried out which serves for (1) initializing the algorithm and (2) determining the two zeros of the proposed PID controller. The method starts with I-Lag control action to the process by tuning the integral gain. After this tuning is over, the parasitic time constant of the closed-loop system is estimated. I-Lag control is then turned into PID control and the integrator's time constant of the PID controller is tuned accordingly, so that the shape of the control loop's output exhibits the aforementioned performance. Since the tuning of the PID controller is based on the Magnitude Optimum criterion, optimal disturbance rejection is expected to be achieved at the output of the controlled process. The potential of the proposed method is justified via simulation examples for two benchmark process models met frequently in various industry applications. © 2013 Elsevier Ltd. All rights reserved.

Dermanis A.,Aristotle University of Thessaloniki
Applied Geomatics | Year: 2011

The rigorous approach to plane deformation developed by the author is extended to the case of curved surfaces and is applied to the monitoring of surface-like constructions by repeated surveys. From coordinates of discrete points at two survey epochs, interpolation of the displacements produces displacement functions expressed in terms of surface curvilinear coordinates, which can be used for the computation of coordinate-invariant deformation parameters which are meaningful from the strength-of-materials point of view. In addition, it is shown how to incorporate information from additional in situ measurements by strainmeters, extensiometers, tiltmeters, etc. in the interpolation process. The computed invariant parameters at any surface point are the dilatation, the maximum shear strain, and the maximum bending expressed in terms of the maximum change of radius curvature among all surface directions. In addition to the theoretical tools, a complete algorithm is presented for direct practical implementation. © Società Italiana di Fotogrammetria e Topografia (SIFET) 2011..

Nikolaidis A.K.,Aristotle University of Thessaloniki | Achilias D.S.,Aristotle University of Thessaloniki | Karayannidis G.P.,Aristotle University of Thessaloniki
Industrial and Engineering Chemistry Research | Year: 2011

The effect of the amount of nanofiller and type of organic modifier in organomodified montmorillonite (OMMT)/poly(methyl methacrylate) (PMMA) nanocomposites prepared by in situ bulk polymerization was investigated. Several commercial OMMTs under the tradename Cloisite were used. The structure and morphology of the prepared materials were investigated by means of wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. It was found that the presence of OMMT enhances polymerization kinetics especially in the gel-effect region, while sodium MMT acts rather as a reaction retarder. The presence of the nanofiller increased the thermal stability of the nanocomposites, as measured by thermogravimetric analysis (TGA) and their glass transition temperature, measured by differential scanning calorimetry (DSC), as well as their average molecular weight measured by gel permeation chromatography (GPC). Tensile measurements using a dynamometer revealed an increase in the Young's modulus with the amount of the nanofiller accompanied by a decrease in the tensile strength and elongation at break. Overall, the best performance was found for the nanocomposites of PMMA with Cloisite 25A. © 2010 American Chemical Society.

Roilides E.,Aristotle University of Thessaloniki
Early Human Development | Year: 2011

Invasive candidiasis is associated with high morbidity and mortality in neonates and children. The incidence of invasive candidiasis is greater in children than in adults and is particularly high in neonates. Main risk factors are multiple antibiotics, central venous catheters, parenteral nutrition, immunodepression, low birth weight, fungal colonization, and necrotizing enterocolitis. Successful management of IFIs relies on early recognition and rapid initiation of effective treatment. © 2011 Elsevier Ltd.

Moussas P.A.,Aristotle University of Thessaloniki | Zouboulis A.I.,Aristotle University of Thessaloniki
Separation and Purification Technology | Year: 2012

Latest developments on the synthesis of novel coagulants have reported the formation of reagents constituting of both inorganic and organic materials. In this study, the preparation of new composite reagents was achieved, by combining the inorganic pre-polymerized iron-based polyferric sulfate (PFS) with the cationic polyelectrolyte (CP) poly-dimethyl-diallyl-ammonium chloride (PDMDAAC) under different CP/Fe weight ratio. The reagents were prepared by using two different methods: co-polymerization and composite polymerization. Moreover, they were characterized in terms of typical properties, stability and morphological analysis (XRD, FTIR, SEM). Their coagulation performance was evaluating by treating low and high turbid (kaolin-humic acid) suspensions, while the usage of the Photometric Dispersion Analysis (PDA) apparatus enabled the investigation of the applied coagulation mechanisms. The results show that the new coagulants present improved coagulation properties, including an excellent stability. Coagulation experiments reveal that the PFS-CP composite reagent exhibits a superior coagulation performance, when compared to conventional coagulants. PDA analysis shows that the improvement of kinetic parameters with increasing CP/Fe ratio (especially in comparison with PFS) is attributed to the nature and properties of the cationic polymer. © 2012 Elsevier B.V. All rights reserved.

Galanis N.,Aristotle University of Thessaloniki
Clinical Journal of Sport Medicine | Year: 2014

Judo is a combat sport with high risk of injury. We present a rare case of traumatic left posterior sternoclavicular (SC) joint dislocation, inflicted to a 12-year-old boy during a judo contest. An extensive literature review did not reveal any case of posterior SC joint dislocation in judo. The patient was treated with closed reduction under general anesthesia. At 2-year follow-up, his left upper extremity had full range of motion, and he did not complain of any residual symptoms. He decided to discontinue judo training; however, he participates in other physically demanding sports. Although not often encountered, posterior SC joint dislocation is a challenging and critical medical problem that can be fatal if not promptly diagnosed and treated on time and should be considered in the differential diagnosis of trauma-related anterior chest pain.

Veloukas T.,Aristotle University of Thessaloniki | Karaoglanidis G.S.,Aristotle University of Thessaloniki
Pest Management Science | Year: 2012

Background: Succinate dehydrogenase inhibitors (SDHIs) constitute a fungicide class with increasing relevance in crop protection. These fungicides could play a crucial role in successful management of grey mould disease. In the present study the effect of fluopyram, a novel SDHI fungicide, on several developmental stages of Botrytis cinerea was determined in vitro, and the protective and curative activity against the pathogen was determined on strawberry fruit. Furthermore, fungal baseline sensitivity was determined in a set of 192 pathogen isolates. Results: Inhibition of germ tube elongation was found to be the most sensitive growth stage affected by fluopyram, while mycelial growth was found to be the least sensitive growth stage. Fluopyram provided excellent protective activity against B. cinerea when applied at 100 μg mL -1 96, 48 or 24 h before the artificial inoculation of the strawberry fruit. Similarly, fluopyram showed a high curative activity when it was applied at 100 μg mL -1 24 h post-inoculation, but, when applications were conducted 48 or 96 h post-inoculation, disease control efficacy was modest or low. The measurement of baseline sensitivity showed that it was unimodal in all the populations tested. The individual EC 50 values for fluopyram ranged from 0.03 to 0.29 μg mL -1. In addition, no correlation was found between sensitivity to fluopyram and sensitivity to other fungicides, including cyprodinil, fenhexamid, fludioxonil, iprodione, boscalid and pyraclostrobin. Conclusions: The obtained biological activity, baseline sensitivity and cross-resistance relationship data suggest that fluopyram could play a key role in grey mould management in the near future and encourage its introduction into spray programmes. © 2011 Society of Chemical Industry.

Kyzas G.Z.,Aristotle University of Thessaloniki | Lazaridis N.K.,Aristotle University of Thessaloniki | Bikiaris D.N.,Aristotle University of Thessaloniki
Carbohydrate Polymers | Year: 2013

In this study, two types of novel molecularly imprinted polymers (MIPs) were prepared, for toxic and carcinogenic dyes adsorption. Substrates of the polymeric matrix of the two MIPs were β-cyclodextrin and chitosan. The conditions in the polymerization/imprinting stage and in the rebinding/adsorption step were optimized. The effect of a range of parameters (polymer, cross-linker, and initiator concentrations, reaction time and pH) on the selectivity and adsorption capacity of the dye-MIPs were investigated. Their dye rebinding properties were demonstrated by equilibrium batch experiments (fitting with Freundlich model) and their kinetic rates were exported by the pseudo-first order model. Additionally, a thermodynamic evaluation was carried out through the determination of enthalpy, entropy, and free energy. The selectivity of MIPs was elucidated by their different rebinding capabilities in a trichromatic mixture (composed of related structurally dyes). Regeneration/reuse of the dye-loaded polymers was evaluated via sequential adsorption-desorption cycles. © 2012 Elsevier Ltd.

Goula A.M.,Aristotle University of Thessaloniki | Adamopoulos K.G.,Aristotle University of Thessaloniki
Drying Technology | Year: 2012

A new technique for lycopene microencapsulation by spray drying using dehumidified air as the drying medium was developed and the optimum operating conditions for encapsulation efficiency were determined. A pilot-scale spray dryer was employed for the spray-drying process. The modification made to the original design consisted of connecting the dryer inlet air intake to an absorption air dryer. The dextrose equivalent (DE) of maltodextrin, ratio of core to wall material, feed temperature, inlet air temperature, drying air flow rate, and compressed air flow rate were the factors investigated with respect to encapsulation efficiency. The resulting microcapsules were evaluated in terms of moisture content, bulk density, rehydration ability, lycopene isomerization, and storage stability. The optimum operating conditions were found to be as follows: ratio of core to wall material, 1:3.3; feed temperature, 52°C; inlet air temperature, 147°C. Under these conditions, the maximum encapsulation efficiency was about 93%. The use of dehumidified air was proven to be an effective way of increasing lycopene encapsulation efficiency. © 2012 Copyright Taylor and Francis Group, LLC.

Tzoupanos N.D.,Aristotle University of Thessaloniki | Zouboulis A.I.,Aristotle University of Thessaloniki
Water Research | Year: 2011

The development of the Inorganic Polymeric Flocculants (IPFs) can be regarded as significant progress in the coagulation-flocculation field. However, the IPFs may be less efficient when compared to the organic polymers (polyelectrolytes) regarding their aggregation abilities. In order to increase further their flocculation efficiency, the combination of a cationic IPF (polyaluminium chloride, PACl) and an anionic polyelectrolyte in one unique reagent is proposed in this study. During this investigation, several composite coagulants were prepared, which differ on the preparation method and polyelectrolyte content. Major typical properties of the prepared coagulants were examined, i.e. pH, turbidity, conductivity, Al species distribution. The composition, structure and morphology of the composite coagulants were studied in detail as well, with the application of FT-IR, XRD and SEM techniques. Their coagulation performance was investigated in the treatment of a model water sample (simulating surface water) and compared to the respective coagulation performance of PACl and the polyelectrolyte applied as separated reagents (common procedure). Finally, the kinetics of coagulation was studied with application of the Photometric Dispersion Analyser (PDA). From the results, it was revealed that interactions take place between the Al species and the polyelectrolyte molecules, which probably lead to the formation of new, " composite" species. The properties of the composite coagulants are significantly affected by these interactions, leading to more effective water treatment. The simplification of the overall treatment process and the cost-effectiveness are considered as the major advantages of the composite coagulants. © 2011 Elsevier Ltd.

Cholongitas E.,Aristotle University of Thessaloniki | Tziomalos K.,Aristotle University of Thessaloniki | Pipili C.,Laiki Merimna
World Journal of Gastroenterology | Year: 2015

The development of effective nucleos(t)ide analogs (NAs) against hepatitis B virus (HBV) has improved the outcome of patients with chronic hepatitis B (CHB). This review updates issues related to the management of CHB patients included in special populations. Entecavir (ETV) and tenofovir (TDF) represent the currently recommended first-line NAs in patients with HBV decompensated cirrhosis. The combination of HBV immunoglobulin (usually for a finite duration) and NA is considered the standard of care for prophylaxis against HBV recurrence after liver transplantation. TDF is the best choice for hemodialysis patients and in patients with chronic kidney disease with nucleoside resistance. ETV and telbivudine are the preferred options in naïve renal transplant recipients and with low viremia levels, respectively. All hepatitis B surface antigen (HBsAg)-positive candidates should be treated with NAs before renal transplantation to achieve undetectable HBV DNA at the time of transplantation. Conventional interferon or NAs can also be used in children, on the basis of well-established therapeutic indication. Pregnant women at high risk of perinatal transmission could be treated with lamivudine, telbivudine or TDF in the last trimester of pregnancy. HBsAg-positive patients under immunosuppression should receive NA preemptively (regardless of HBV DNA levels) up to 12 mo after its cessation. In HBsAg negative, anti-HBc positive patients under immunosuppression, further studies are needed to form a final conclusion; however, it seems that anti-HBV prophylaxis is justified in such patients with hematological diseases and/or for those receiving rituximab-containing regimens, regardless of their anti-HBs or serum HBV DNA status. © The Author(s) 2015.

Sazou D.,Aristotle University of Thessaloniki | Saltidou K.,Aristotle University of Thessaloniki | Pagitsas M.,Aristotle University of Thessaloniki
Electrochimica Acta | Year: 2012

The effect of donor density, N D on the critical localized breakdown potential, E b of the passivity on Ti was investigated in bromide-containing aqueous solutions. Oxide films of approximately fixed thickness were galvanostatically grown on Ti in 0.5 M H 2SO 4 at various current densities. The N D was estimated using Mott-Schottky analysis. The stable localized breakdown induced by bromides manifested itself in potentiodynamic current-potential curves by a sudden current increase at E b. The passive film on Ti is n-type and oxygen vacancies were considered as majority defects. The E b tends to decrease as the oxygen vacancy and bromide concentration increases. Additionally, the E b of anodically grown films was found to increase with the potential scan rate, inversely of the behavior observed for the native oxide on Ti, but in concert with corresponding relationships followed by other metals/alloys and predicted by the point defect model (PDM). Physico-electrochemical processes leading to growth and breakdown of passivity on Ti can be understood in terms of a PDM. The higher susceptibility of titanium oxide to local breakdown in presence of bromides than chlorides is interpreted by considering electrochemical reactions occurring at the TiO 2solution interface and their effect on film surface and bulk properties upon increasing the potential during the positive-going potential scan. Finally, it should be noted that a further understanding on the mechanism of bromide-induced passivity breakdown on Ti might be useful to achieve optimized anodization conditions for ordered oxide nanostructures with desired properties in electrolytes other than fluorides and perhaps at lower anodization potentials. © 2012 Elsevier Ltd. All rights reserved.

Dimitriadis C.A.,Aristotle University of Thessaloniki
Advances in peritoneal dialysis. Conference on Peritoneal Dialysis | Year: 2011

This paper reviews the issues associated with the reproductive system in the special population of female patients with end-stage renal disease on peritoneal dialysis (PD). We summarize current knowledge concerning cancer screening tests, elective and urgent gynecologic procedures, and the issues of menstruation, contraception, pregnancy, and delivery in these patients. Finally, we present the potential effects of gynecologic problems on PD and the complications of PD that can present with symptoms of the female genitalia.

Papadopoulou S.K.,Aristotle University of Thessaloniki | Panayiotou C.,Aristotle University of Thessaloniki
Journal of Chromatography A | Year: 2012

The thermodynamic characterization of a fluorinated methacrylic homopolymer was conducted by means of inverse gas chromatography (IGC) at infinite dilution. The polymer under study, poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate) (PHFIMA) was synthesized via a free radical polymerization reaction and was properly characterized prior to IGC measurements. The IGC characterization encompassed the calculation of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficients and the Flory-Huggins interaction parameters of 15 probes. Moreover, the total and partial solubility parameters of the polymer were determined. The impact of the temperature and the chemical nature of the probes on the aforementioned thermodynamic parameters are discussed. Results demonstrate that PHFIMA is insoluble in almost every tested solvent, with the exception of chloroform, due to its proton donor character which is favorable for the formation of hydrogen bonds with the fluorine groups and the oxygen atoms of the carbonyl groups (proton acceptors) of the polymer. Furthermore, the total and dispersive solubility parameters descend in a linear manner with the increase of temperature, whereas the polar and hydrogen bonding solubility parameters increase when temperature rises, probably due to the conformational changes of the polymer on the solid support. © 2012 Elsevier B.V.

Iosifidis A.,Aristotle University of Thessaloniki | Tefas A.,Aristotle University of Thessaloniki | Pitas I.,Aristotle University of Thessaloniki
IEEE Transactions on Information Forensics and Security | Year: 2012

In this paper, a novel view invariant person identification method based on human activity information is proposed. Unlike most methods proposed in the literature, in which walk (i.e., gait) is assumed to be the only activity exploited for person identification, we incorporate several activities in order to identify a person. A multicamera setup is used to capture the human body from different viewing angles. Fuzzy vector quantization and linear discriminant analysis are exploited in order to provide a discriminant activity representation. Person identification, activity recognition, and viewing angle specification results are obtained for all the available cameras independently. By properly combining these results, a view-invariant activity-independent person identification method is obtained. The proposed approach has been tested in challenging problem setups, simulating real application situations. Experimental results are very promising. © 2006 IEEE.

Katsiki N.,Aristotle University of Thessaloniki | Athyros V.G.,Aristotle University of Thessaloniki | Karagiannis A.,Aristotle University of Thessaloniki | Mikhailidis D.P.,University College London
Current Pharmaceutical Design | Year: 2014

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide. T2DM is associated with both microvascular (neuropathy, nephropathy and retinopathy) and macrovascular complications [coronary artery disease (CAD), stroke, carotid artery disease and peripheral artery disease (PAD)]. Apart from acting on diabetic dyslipidemia, statins were shown to exert beneficial effects on several diabetic complications as well as other cardiovascular (CVD) risk predictors such as endothelial dysfunction, inflammation, oxidative stress, chronic kidney disease (CKD), non-alcoholic fatty liver disease (NAFLD), metabolic syndrome (MetS), obstructive sleep apnea syndrome (OSAS) and hyperuricemia. Several clinical trials involving T2DM patients have reported significant reductions in coronary and cerebrovascular events following statin treatment. However, a modest statin-related risk of new-onset diabetes (NOD) has been reported but that did outweigh the benefit of CVD risk reduction in high-risk individuals. Overall, statin use is beneficial and should be recommended in diabetic patients to target their increased CVD risk. © 2014 Bentham Science Publishers.

Fountoulakis K.N.,Aristotle University of Thessaloniki
British Journal of Psychiatry | Year: 2016

The prevailing picture in both the scientific literature and mass media is that the increase in unemployment acts as a generic risk factor on the entire population and increases the rate of suicide, suggesting that the socioeconomic environment is the determining factor and measures to improve it are the most suitable in the struggle to reduce the number of suicides. As a result, 'horizontal' actions targeting the general population are proposed rather than 'vertical' actions that target specific vulnerable groups. This is not only a mistake but it also constitutes a kind of 'reverse' stigma which deprives mental health patients of their right to receive special and targeted benefits, interventions and care, and deprives mental healthcare of valuable resources. © The Royal College of Psychiatrists 2016.

Tsakmakidis I.A.,Aristotle University of Thessaloniki
Small Ruminant Research | Year: 2010

Although the application of modern technologies and techniques in ram semen evaluation is not as widespread as in domesticated animal species, developments have been reported. Improvements in extenders and cryo-protectants have contributed to extended ram semen preservation and better results of ovine artificial insemination. For these reasons, semen evaluation process offering high accuracy and reliability of the results is needed more than in the past. Major advancements have been made on ram semen analysis by using computer assisted semen analyzers. Moreover, evaluation of sperm function in depth as the estimation of sperm mitochondrial status, sperm nucleus chromatin integrity and sperm ability to bind and/or fertilize an oocyte have recently been included to ram semen assessment. This review emphasizes to recent development in these technologies that start to show satisfactory diagnostic value for ram semen evaluation, as well as to their relation with field fertility. © 2010 Elsevier B.V.

Polizopoulou Z.S.,Aristotle University of Thessaloniki
Small Ruminant Research | Year: 2010

The evaluation of sheep complete blood cell count (CBC) can be of significant aid to clinical examination. Accurate assessment of haematologic data depends on the proper collection, preparation and transportation of blood samples. Blood should be drawn from animals at rest, calm and well restrained at the time of sampling, in order to avoid artifactual changes, such as a stress leucogram caused by endogenous steroid or epinephrine release or haemolysis from traumatic collection. Proper venipuncture is important to avoid contamination by tissue thromboplastin, which encourages clot formation and invalidates haemostatic function tests. Tubes must be filled to capacity to ensure the proper blood-anticoagulant ratio. When haemostasis tests are indicated, blood should be carefully transferred to vials containing anticoagulant, in order to prevent haemolysis, which precludes the use of evacuated tubes. Blood samples for haematologic studies are best processed as soon as possible after collection, but if a delay is expected they should be refrigerated at 4°C and for a maximum period of 24. h (with the exception of platelet counts which should be performed within 4-6. h after sample collection), while air-dried blood smears must be prepared immediately after sampling to be stained with Wright or any modified Romanovsky stain. Complete blood counts can be performed either manually or with the aid of sophisticated instrumentation. Automated haematology instruments provide rapid cell counts of blood, haemoglobin calculation, potentially useful erythrocyte indices, but they cannot detect morphologic abnormalities and haemoparasites. Red blood cell counting and morphological changes are useful when evaluating anaemia. The differential white blood cell count is more important than the total white blood cell count, because increases and decreases in individual cell types may occur simultaneously, leaving total count unchanged. Overall, CBC can provide valuable information to the sheep clinician. Moreover, evaluation of a well-prepared blood film is an essential adjunct to interpretation of all cell counts, allowing detection of significant morphologic abnormalities or presence of haemoparasites. © 2010 Elsevier B.V.

Michopoulos A.,Aristotle University of Thessaloniki | Papakostas K.T.,Aristotle University of Thessaloniki | Kyriakis N.,Aristotle University of Thessaloniki
Applied Energy | Year: 2011

The HVAC systems utilizing renewable energy sources are one of the main contributors towards the fossil fuel dependency reduction. Among these, the ground source heat pump systems, especially those based on vertical ground heat exchanger, are very attractive, due to their high efficiency.The size of the systems depends on the building (geometry, construction materials, orientation etc. but also usage and internal gains), on the ground thermophysical characteristics, on the climatology of the area and on the ground heat exchanger design and construction. As a result, the ground heat exchanger length required for heating may result significantly different from the one required for cooling. In this work, the ground heat exchanger lengths required for heating and cooling are calculated for two model-buildings, a residential and an office one, located at 40 different Greek cities, covering a wide range of country's climate conditions. Assuming that a ratio of these lengths in the 0.8-1.2 range is required for efficient long-term operation of the autonomous GSHP system with minimum installation cost, the results suggest that autonomous systems may be used in areas with the heating degree-days in the 800-950. K-days range. In hotter climates with less than 800 heating degree-days, the GSHP system should be supplemented by a conventional cooling system, while in colder climates with more than 950 heating degree-days a conventional heating system supplement is required. © 2010 Elsevier Ltd.

Giarma C.,Aristotle University of Thessaloniki | Aravantinos D.,Aristotle University of Thessaloniki
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2011

An estimation of moisture loading severity for building components in Greece was attempted. Annual driving rain indices were calculated for 31 stations spread all over the country, based on the average annual rainfall and wind speed values derived from data, published by Hellenic National Meteorological Service. The analysis revealed that the majority of the locations are sheltered from driving rain. A driving rain map for Greece was produced. A second set of annual driving rain indices were calculated for these sites, based on average monthly data. The relationship between these two sets of indices for the 31 locations was best approximated by a hyperbolic function. Thessaloniki, a city in northern Greece, was further studied using average annual and daily data provided by the Institute of Meteorology and Climatology, A.U.Th. For Thessaloniki, the exposure estimated from daily data was bigger than the one resulting from annual data. Finally, a moisture index for the comparison of building components' exposure to moisture, with the drying potential also being considered, was calculated for the 31 sites studied and a ranking of these sites' climates in terms of moisture loading on buildings was obtained. The drying potential's contribution to this ranking is very important. © 2010 Elsevier Ltd.

Kostarigka A.K.,Aristotle University of Thessaloniki | Rovithakis G.A.,Aristotle University of Thessaloniki
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2011

A neural network output feedback/observer-free continuous controller for multiple-input-multiple-output uncertain nonlinear systems is designed, which is capable of guaranteeing prescribed performance bounds on the system output, as well as the boundedness of all other closed-loop signals, despite the presence of additive external disturbances and unmodeled dynamics. The assumptions that were made concern the satisfaction of an unboundedness observability property and an output Lagrange stability condition of the unmodeled dynamics subsystem and that the nominal system is output feedback equivalent to a strictly passive one. Simulations on an induction motor system illustrate the approach. © 2006 IEEE.

Zotou A.,Aristotle University of Thessaloniki | Vasiliadou C.,Aristotle University of Thessaloniki
Journal of Separation Science | Year: 2010

A new, rapid, sensitive and selective HPLC method with fluorescence detection is described for the simultaneous determination of 12 sulfonamides, in the presence of putrescine as internal standard, after pre-column derivatization with fluorescamine. The drugs were separated on a Chromolith Performance RP-18 column (100 × 4.6 mm), using a gradient elution with a binary mobile phase of methanol/0.05M acetate buffer (pH 3.4). Linearity of derivatization was obtained for concentrations from 3.0 to 300 μg/L in standard solutions. The whole procedure was evaluated and fully validated, according to the European Union Decision 2002/657/EC, for the determination of sulfonamides in turkey muscle and hen eggs following SPE. The LODs varied from 2 to 17 μg/kg in turkey and 2 to 15 μg/kg in egg samples. The average recoveries ranged between 96.9-108.6% in turkey muscle and 96.0-108.4% in egg samples, respectively. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

Tsoumakas G.,Aristotle University of Thessaloniki | Spyromitros-Xioufis E.,Aristotle University of Thessaloniki | Vilcek J.,Aristotle University of Thessaloniki | Vlahavas I.,Aristotle University of Thessaloniki
Journal of Machine Learning Research | Year: 2011

MULAN is a Java library for learning from multi-label data. It offers a variety of classification, ranking, thresholding and dimensionality reduction algorithms, as well as algorithms for learning from hierarchically structured labels. In addition, it contains an evaluation framework that calculates a rich variety of performance measures. © 2011 Grigorios Tsoumakas, Eleftherios Spyromitros-Xioufis, Jozef Vilcek and Ioannis Vlahavas.

Baltzis K.B.,Aristotle University of Thessaloniki
Progress in Electromagnetics Research | Year: 2011

This paper presents a geometrically based method for the calculation of the node-to-node distance distribution function in circular-shaped networks. In our approach, this function is obtained from the intersection volume of a sphere and an ellipsoid. The method is valid for both overlapping and non-overlapping networks. Simulation results and comparisons with methods in the literature demonstrate the efficacy of the approach. The relation between networks geometric parameters and distance statistics is explored. As an application example, we model distance-dependent path loss and investigate the impact of channel characteristics and networks size on signal absorption. The aforementioned model is a useful and low-complexity tool for system-level modeling and simulation of mobile communication systems.

Meditskos G.,Aristotle University of Thessaloniki | Bassiliades N.,Aristotle University of Thessaloniki
Expert Systems with Applications | Year: 2011

The increasing number of Web 2.0 applications, such as wikis or social networking sites, indicates a movement to large-scale collaborative and social Web activities. Users can share information, add value to Web applications by using them or aggregate data from different sources creating Web applications (mashups) using specialized tools (mashup tools). However, Web 2.0 is not a new technology, but it rather embraces a new philosophy, treating the Internet as a platform. Several issues related to the Semantic Web vision, such as interoperability or machine understandable data semantics, are not tackled by Web 2.0. In this paper, we present our effort to combine semantic Web services (SWS) discovery frameworks, UDDI repositories and existing mashup tools in order to enhance the procedure of developing mashups with semantic mashup discovery capabilities. Towards this end, we introduce a social-oriented extension of OWL-S advertisements, their mapping algorithm on UDDI repositories and a semantic mashup discovery algorithm. Finally, we elaborate on the way our framework has been realized using the Yahoo Pipes mashup tool. © 2010 Elsevier Ltd. All rights reserved.

Syrris V.,Aristotle University of Thessaloniki | Petridis V.,Aristotle University of Thessaloniki
Information Sciences | Year: 2011

This work describes a computational approach for a typical machine-vision application, that of human action recognition from video streams. We present a method that has the following advantages: (a) no human intervention in pre-processing stages, (b) a reduced feature set, (c) modularity of the recognition system and (d) control of the model's complexity in acceptable for real-time operation levels. Representation of each video frame and feature extraction procedure are formulated in the lattice theory context. The recognition system consists of two components: an ensemble of neural network predictors which correspond to the training video sequences and one classifier, based on the PREMONN approach, capable of deciding at each time instant which known video source has potentially generated a new sequence of frames. Extensive experimental study on three well known benchmarks validates the flexibility and robustness of the proposed approach. © 2010 Elsevier Inc. All rights reserved.

Liaskos C.K.,Aristotle University of Thessaloniki | Petridou S.G.,Aristotle University of Thessaloniki | Papadimitriou G.I.,Aristotle University of Thessaloniki
IEEE/ACM Transactions on Networking | Year: 2011

A main design issue in a wireless data broadcasting system is to choose between push-based and pull-based logic: The former is used as a low-cost solution, while the latter is preferred when performance is of utmost importance. Therefore, the most significant advantage of a push system is the minimal cost. This fact implies that hardware limitations do exist in the case of push systems. As a consequence, every related proposed algorithm should primarily be cost-effective. This attribute, however, has been overlooked in related research. In this paper, popular broadcast scheduling approaches are tested from an implementation cost aspect, and the results render them only conditionally realizable. Moreover, a new, cost-effective, adaptivity oriented schedule constructor is proposed as a realistic, minimal-cost solution. © 2006 IEEE.

Deliyanni E.,Aristotle University of Thessaloniki | Bandosz T.J.,City College of New York
Journal of Hazardous Materials | Year: 2011

Micro/mesoporous activated carbon was oxidized and used either as received or after modification as a support for the deposition of iron oxyhydroxide. The prepared samples were applied as adsorbents of arsenate from water phase. The initial materials and those after adsorption were characterized using adsorption of nitrogen, - potentiometric titration, FTIR, EDX, XRD, AAS, and thermal analysis. The results obtained suggest that oxidation of the carbon support increases significantly the amount of iron oxyhydroxide species deposited on the surface and thus decreases their dispersions and the efficiency of arsenate immobilization in the carbon pore system. Iron hydroxyoxides react with arsenate forming salts. Moreover, a meso/microporous carbon surface contributes to changes in the toxicity of arsenic via reduction of As(V) to As(III). This is visible in the increased degree of carbon oxidation. © 2010 Elsevier B.V.

Polyzos S.A.,Aristotle University of Thessaloniki | Polyzos S.A.,Beth Israel Deaconess Medical Center | Kountouras J.,Aristotle University of Thessaloniki | Mantzoros C.S.,Beth Israel Deaconess Medical Center
Metabolism: Clinical and Experimental | Year: 2015

Leptin, the first described adipokine, interplays with hepatic metabolism. The aim of this review was to summarize available data on the association between leptin and nonalcoholic fatty liver disease (NAFLD). Leptin has a potential dual action on NAFLD experimental models, exerting a possible anti-steatotic, but also a proinflammatory and profibrogenic action. Observational clinical studies have shown higher or similar leptin levels between simple steatosis and nonalcoholic steatohepatitis (NASH) compared with controls. Interventional studies showed that circulating leptin diminishes together with body mass index after successful weight loss following lifestyle modifications or bariatric surgery. Studies providing evidence for the effect of other medications on leptin levels in NAFLD populations are limited and of low power. Data from small studies claim that recombinant leptin administration had a possibly beneficial effect on steatosis, but not fibrosis, in NAFLD patients with hypoleptinemia. Although the aforementioned dual leptin action has not yet been validated in humans, leptin administration in NAFLD patients with normoleptinemia or hyperleptinemia is discouraged. Further well-controlled studies in cautiously selected populations are needed to elucidate whether leptin has any prognostic and therapeutic role in NAFLD patients. © 2015 Elsevier Inc. All rights reserved.

Babas E.,Aristotle University of Thessaloniki
International journal of gynecological cancer : official journal of the International Gynecological Cancer Society | Year: 2010

When apoptosis is disrupted, the transformed cells can survive, proliferate, and evolve into a malignancy. The strictly conserved caspase genes and the reliable experimental data clearly show that some caspases play a crucial role in apoptosis even if some of them have no apoptotic activity and others exhibit both apoptotic and nonapoptotic properties. Although caspase-2 belongs to initiator caspases, its normal role remains unclear. Experimental studies have shown that it is primarily necessary for the execution of apoptosis in mutagenic cells. Human caspase-5 is classified as an inflammatory caspase, although its substrate has not been identified yet. In this research, the activities of caspase-2 and caspase-5 have been estimated during the progression of human cervical malignancy. The experimental material includes human cervical tissue samples (normal and pathological) and blood serum samples of the corresponding tissue donors, where enzyme activities have been measured colorimetrically. Both caspases' activities showed the highest increase, statistically significant (P < 0.01, by t test) compared with the controls, in the low-grade squamous intraepithelial lesion tissues. Caspase-2 of all pathological tissues was proved more active than the controls. Serum caspases' activities were significantly lower than those of the tissues. Serum caspase-2's activity in patients with low-grade squamous intraepithelial lesion stage showed no statistically significant increase compared with the controls. Serum caspase-5's activity of all patients with malignancy stages was presented elevated, whereas that of the serum of patients with cervical cancer had the highest activity (P < 0.01, by t test). The changes of caspase-2 and caspase-5 activities could be indicative of their involvement in the cervical malignancy mechanisms.

Baloyannis S.J.,Aristotle University of Thessaloniki
International Journal of Alzheimer's Disease | Year: 2011

Morphological alterations of mitochondria may play an important role in the pathogenesis of Alzheimer's disease, been associated with oxidative stress and Aβ-peptide-induced toxicity. We proceeded to estimation of mitochondria on electron micrographs of autopsy specimens of Alzheimer's disease. We found substantial morphological and morphometric changes of the mitochondria in the neurons of the hippocampus, the neocortex, the cerebellar cortex, the thalamus, the globus pallidus, the red nucleus, the locus coeruleus, and the climbing fibers. The alterations consisted of considerable changes of the cristae, accumulation of osmiophilic material, and modification of the shape and size. Mitochondrial alterations were prominent in neurons, which showed a depletion of dendritic spines and loss of dendritic branches. Mitochondrial alterations are not related with the accumulation of amyloid deposits, but are prominent whenever fragmentation of the Golgi apparatus exists. Morphometric analysis showed also that mitochondria are significantly reduced in neurons, which demonstrated synaptic pathology. © 2011 Stavros J. Baloyannis.

Kyzas G.Z.,Aristotle University of Thessaloniki | Travlou N.A.,Aristotle University of Thessaloniki | Deliyanni E.A.,Aristotle University of Thessaloniki
Colloids and Surfaces B: Biointerfaces | Year: 2014

The present study focuses on the role of chitosan (CS) as nanofiller of graphite oxide (GO) in order to prepare composite materials with improved Hg(II) adsorption properties. The removal of Hg(II) from aqueous solutions was studied using adsorbents as graphite oxide (GO), graphite oxide nanofilled with chitosan (GO/CS) and magnetic chitosan (GO/mCS). Many possible interactions between materials and Hg(II) were observed after adsorption and explained via characterization with various techniques (SEM/EDAX, FTIR, XRD, DTG). The adsorption evaluation was done studying various parameters as the effect of pH (both in adsorption and desorption), contact time (pseudo-second order fitting), temperature (isotherms at 25, 45, 65°C), in line with a brief thermodynamic analysis (δG0, δH0, δS0). The maximum adsorption capacity (fitting with Langmuir model) of GO at 25°C was Qmax=187mg/g, while after the CS nanofilling (formation of the composite GO/CS), Qmax was increased to 381mg/g with a further enhancement for GO/mCS (Qmax=397mg/g). © 2013 Elsevier B.V.

With the rapid development of nanotechnologies and nanomaterials since 1990s, the studies on polymer-based nanocomposites have been extensively focused on their properties' enhancement. Among these, it is well known that nanoparticles can also enhance thermal degradation of nanocomposites. This review is focused on highlighting the effect of different nanoparticles, their dispersion and the used modifiers, on polymer thermal stability. The whole range of polycondensation polymer matrices is covered. Most of these polymers have reactive end groups which can interact with inorganic nanoparticles surface. Hydrogen or covalent bonds can be formed, which can increase the adhesion of nanoparticles with the polymer matrix, resulting in higher dispersion degrees. This, in most cases, leads to substantial enhancement of thermal decomposition properties. Only in nanocomposites containing montmorillonite there are conflicting results and accelerating degradation was also reported. Organoclays also have similar effects on polymers thermal stability and in this case the achieved clay dispersion (intercalated-exfoliated), as well as the used modifier, can alter the thermal decomposition of polymers. The used amount of nanoparticles plays an important role on the thermal stability of nanocomposites. In most cases thermal stability enhancement takes place at low loading (4-5 wt%) of nanoparticles, while at higher contents thermal stabilization becomes progressively smaller. © 2011 Elsevier B.V. All rights reserved.

Chrissafis K.,Aristotle University of Thessaloniki | Bikiaris D.,Aristotle University of Thessaloniki
Thermochimica Acta | Year: 2011

Polymer nanocomposites are an important class of polymers that have wide application in a number of different industrial sectors and thus organic/inorganic nanocomposite materials have been extensively studied in the last few decades. Inorganic nanoscale fillers, which are considered to be very important, include layered silicates (such as montmorillonite), nanotubes (mainly carbon nanotubes, CNTs), fullerenes, SiO2, metal oxides (e.g., TiO2, Fe2O3, Al2O 3), nanoparticles of metals (e.g., Au, Ag), polyhedral oligomeric silsesquioxane (POSS), semiconductors (e.g., PbS, CdS), carbon black, nanodiamonds, etc. Among the effects of different nanoparticles on polymer properties, many research works evaluate the effect of nanoparticles on polymer thermal stability and fewer papers are dealing with the decomposition mechanism. Thermal stability is mainly studied using TGA, TGA-MS, TGA-FTIR and other techniques. This review highlights the major findings of the effect of different nanoparticles in polymer thermal stability. The whole range of addition polymer matrices is covered, i.e., thermoplastics, thermosets and elastomers. Thermal decomposition kinetics is also a part of this review. The thermal degradation mechanism of these nanocomposites is generally considered to be related to the kind of used nanoparticles and its amount, the structure of the char formed during polymer degradation, the gas impermeability of inorganic nanoparticles, which inhibit the formation and escape of volatile byproducts during degradation and the interactions between inorganic nanoparticles and polymer reactive groups. © 2011 Elsevier B.V. All rights reserved.

Misaelides P.,Aristotle University of Thessaloniki
Microporous and Mesoporous Materials | Year: 2011

The natural zeolites have already found extensive applications to the environmental remediation and restoration. The most of these applications are based on their ion-exchange properties. This contribution provides a short review of the recent literature concerning the utilization of natural zeolites and their modified forms in the separation, binding and chemical stabilization of hazardous inorganic, organic and radioactive species in soils and aqueous systems. The advantages and eventual disadvantages of the techniques are also discussed. © 2011 Elsevier Inc. All rights reserved.

Gika H.,Aristotle University of Thessaloniki | Theodoridis G.,Aristotle University of Thessaloniki
Bioanalysis | Year: 2011

Blood represents a very important biological fluid and has been the target of continuous and extensive research for diagnostic, or health and drug monitoring reasons. Recently, metabonomics/metabolomics have emerged as a new and promising 'omics' platform that shows potential in biomarker discovery, especially in areas such as disease diagnosis, assessment of drug efficacy or toxicity. Blood is collected in various establishments in conditions that are not standardized. Next, the samples are prepared and analyzed using different methodologies or tools. When targeted analysis of key molecules (e.g., a drug or its metabolite[s]) is the aim, enforcement of certain measures or additional analyses may correct and harmonize these discrepancies. In omics fields such as those performed by holistic analytical approaches, no such rules or tools are available. As a result, comparison or correlation of results or data fusion becomes impractical. However, it becomes evident that such obstacles should be overcome in the near future to allow for large-scale studies that involve the assaying of samples from hundreds of individuals. In this case the effect of sample handling and preparation becomes very serious, in order to avoid wasting months of work from experts and expensive instrument time. The present review aims to cover the different methodologies applied to the pretreatment of blood prior to LC-MS metabolomic/metabonomic studies. The article tries to critically compare the methods and highlight issues that need to be addressed. © 2011 Future Science Ltd.

Assael M.J.,Aristotle University of Thessaloniki | Mylona S.K.,Aristotle University of Thessaloniki
Journal of Chemical and Engineering Data | Year: 2013

The design and operation of a new vibrating-wire viscometer for the measurement of high-viscosity liquids (50 to 125) mPa·s, and up to 18 MPa are described. The design of the instrument is based on a complete theory so that it is possible to make absolute measurements. The viscosity of liquid diisodecyl phthalate (DIDP) is measured at temperatures between (293 and 363) K and pressures between (0.1 and 18) MPa with an absolute uncertainty of ± 1.5 %. © 2013 American Chemical Society.

Kontogiorgis C.,Aristotle University of Thessaloniki | Hadjipavlou-Litina D.,Aristotle University of Thessaloniki
Current Medicinal Chemistry | Year: 2010

Thromboxane A2 (TxA2), a bioactive metabolite of the Arachidonic acid (AA), is a potent mediator of platelet aggregation, vasoconstriction and bronchoconstriction. It plays an important role in major human diseases, such as myocardial infraction, unstable angina, pregnancy-induced hypertension and preeclampsia, thrombosis and thrombotic disorders, pulmonary hypertension, asthma, septic shock, atherosclerosis, lupus nephritis, and Raynaud's phenomenon. Thus, TxA2 is a therapeutic target for many research groups. A number of TXA(2) receptor antagonists as well as thromboxane synthase inhibitors have been developed. In this research we review and evaluate new quantitative structure activity relationships of thromboxane synthase inhibitors and thromboxane receptor antagonists, using the C-QSAR program of Biobyte. Lipophicity, as Clog P is a significant physicochemical parameter for this biological response. CMR/MR molar refractivity as well as sterimol parameters seemed to be important as well Molecular Volume. Electronic effects with the exception of σ Hammett's constant are not found to govern the biological activity. The derived equations will be very helpful for the design of new potent molecules. © 2010 Bentham Science Publishers Ltd.

Youlatos D.,Aristotle University of Thessaloniki | Meldrum J.,Idaho State University
Anatomical Record | Year: 2011

Modern platyrrhines exhibit a remarkable diversity of locomotor and postural adaptations, which evolved along multiple trajectories since the initial immigration to the island continent of South America. We trace this diversification by reviewing the available paleontological and neontological data for postcranial morphology and ecological adaptation. Fossil platyrrhines are notably diverse, from the Oligocene Branisella, to the varied Patagonian early Miocene quadurpedal-leaping and quadrupedal-climbing fossils of disputed affinities, on through the rich middle Miocene Colombian quadurpedal-leaping forms. More recent taxa exhibit even more derived positional patterns, from the largest suspensory atelids in Pleistocene Brazil, to the remarkable Antillean radiation with suspensory forms and also semiterrestrial species, with postcranial morphology convergent on some Old World monkeys. Field studies of positional behavior of modern platyrrhines set the framework for a spectrum of locomotor adaptations. Central within this spectrum is a cluster of medium-sized species with generalized locomotion (quadrupedal-leaping). At opposite poles lie the more derived conditions: large-bodied species exhibiting locomotor specializations for climbing-suspension; small-bodied species exhibiting adaptations for claw climbing and leaping. This behavior-based spectrum of locomotor diversification is similarly evident in a morphology-based pattern, that is, that produced by the shape of the talus. The implications of the record of platyrrhine postcranial evolution for the competing hypotheses of platyrrhine phylogenetic patterns, the "long lineage hypothesis" and the "stem platyrrhine hypothesis," are considered. © 2011 Wiley Periodicals, Inc.

The aim of the present study is the comparative examination of accumulation and detoxification of Cu and Hg in digestive gland and gills of mussels Mytilus galloprovincialis, using atomic absorption spectrophotometry and autometallography. Mussels were exposed to 0.08mgL-1 Cu, 0.08mgL-1 Hg, as well as to a mixture of 0.08mgL-1 Hg and 0.08mgL-1 Cu for 11d. After the experimental exposure, animals were kept under laboratory conditions for a detoxification period of 7d. An antagonistic effect of Cu against to Hg accumulation was noted in the digestive gland of mussels after the experimental exposure, as well as after the detoxification period, supporting the protective role of Cu against to Hg toxicity in this tissue. Digestive gland was suggested as a main organ for Hg accumulation and gills as a target position for Cu accumulation. Additionally, lower time was evaluated for Hg detoxification in the digestive gland and gills of mussels, in relation to those addressed for Cu detoxification in the same tissues. The evaluation of black silver deposits (BSD) extent performed in digestive gland and gills was suggested as a less sensitive approach, in relation to atomic absorption spectrophotometry (AAS), to indentify the concentration of heavy metals in tissues of mussels. The toxic effects of Hg, Cu and a mixture of them on lysosomal system of the digestive cells are also discussed. © 2011 Elsevier Ltd.

Veresoglou S.D.,Free University of Berlin | Menexes G.,Aristotle University of Thessaloniki | Rillig M.C.,Free University of Berlin
Mycorrhiza | Year: 2012

Arbuscular mycorrhizas (AM) are ubiquitous root symbioses with often pervasive effects on the plant host, one of which may be above- and belowground biomass allocation. A meta-analysis was conducted on 516 trials that were described in 90 available articles to examine whether AM colonization could result in a modification of partitioning of plant biomass in shoots and roots. It was hypothesized that alleviating plant nutrient limitations could result in a decrease of root to shoot (R/S) ratio in AM plants or, alternatively, the direction of shifts in the R/S ratio would be determined by the changes in total dry biomass. In our analysis, we considered four types of stresses: drought stress, single heavy metal stress, multiple heavy metal stress, and other potential abiotic plant stress factors. When disregarding any factors that could regulate effects, including stress status and mode of propagation, the overall AM effect was a significant modification of biomass towards shoot growth. However, the responses of stressed and clonally propagated plants differed from those of seed-grown unstressed plants. Our meta-analysis detected a considerable decline in the R/S ratio when plants were grown from seeds in the absence of abiotic stresses. Moreover, we demonstrate that additional regulators of the AM-mediated impact on R/S ratio were presence of competition from other plants, plant growth outcome of the symbiosis, growth substrate volume, experimental duration, and the identities of both plant and AM fungus. Our results indicate that a prediction of AM effects on R/S allocation becomes more accurate when considering regulators, most notably propagation mode and stress. We discuss possible mechanisms through which stress and other regulators may operate. © 2011 Springer-Verlag.

Groll A.H.,University Childrens Hospital | Tragiannidis A.,Aristotle University of Thessaloniki
Clinical Microbiology and Infection | Year: 2010

Paediatric age groups display important differences in host biology, predisposing conditions, epidemiology and presentation of fungal infections relative to the adult population. During the past decade, several new antifungal agents have been developed. Although not all of these agents are yet approved for children, the paediatric development of antifungal agents has moved forwards in an exemplary manner. Invasive fungal infections will remain important causes of morbidity and mortality in immunocompromised paediatric patients. Whereas the availability of new therapeutic options is an important advance, antifungal therapy has become increasingly complex, and a thorough understanding of the available antifungal armamentarium is essential for the successful management of the individual patient. This article provides an update on the pharmacokinetics, safety and dosing of antifungal agents in paediatric patients, and their clinical indications. © 2010 The Author Clinical Microbiology and Infection © 2010 European Society of Clinical Microbiology and Infectious Diseases.

Papadopoulou L.C.,Aristotle University of Thessaloniki | Tsiftsoglou A.S.,Aristotle University of Thessaloniki
Pharmaceutical Research | Year: 2011

Protein therapy is considered an alternative approach to gene therapy for treatment of genetic-metabolic disorders. Human protein therapeutics (PTs), developed via recombinant DNA technology and used for the treatment of these illnesses, act upon membrane-bound receptors to achieve their pharmacological response. On the contrary, proteins that normally act inside the cells cannot be developed as PTs in the conventional way, since they are not able to "cross" the plasma membrane. Furthermore, in mitochondrial disorders, attributed either to depleted or malfunctioned mitochondrial proteins, PTs should also have to reach the subcellular mitochondria to exert their therapeutic potential. Nowadays, there is no effective therapy for mitochondrial disorders. The development of PTs, however, via the Protein Transduction Domain (PTD) technology offered new opportunities for the deliberate delivery of human recombinant proteins inside eukaryotic subcellular organelles. To this end, mitochondrial disorders could be clinically encountered with the delivery of human mitochondrial proteins (engineered via recombinant DNA and PTD technologies) at specific intramitochondrial sites to exert their function. Overall, PTD-mediated Protein Replacement Therapy emerges as a suitable model system for the therapeutic approach for mitochondrial disorders. © Springer Science+Business Media, LLC 2011.

Mittas N.,Aristotle University of Thessaloniki | Angelis L.,Aristotle University of Thessaloniki
Empirical Software Engineering | Year: 2012

Background: Regression Error Characteristic (REC) curves provide a visualization tool, able to characterize graphically the prediction power of alternative predictive models. Due to the benefits of using such a visualization description of the whole distribution of error, REC analysis was recently introduced in software cost estimation to aid the decision of choosing the most appropriate cost estimation model during the management of a forthcoming project. Aims: Although significant information can be retrieved from a readable graph, REC curves are not able to assess whether the divergences between the alternative error functions can constitute evidence for a statistically significant difference. Method: In this paper, we propose a graphical procedure that utilizes (a) the process of repetitive permutations and (b) and the maximum vertical deviation between two comparative Regression Error Characteristic curves in order to conduct a hypothesis test for assessing the statistical significance of error functions. Results: In our case studies, the data used come from software projects and the models compared are cost prediction models. The results clearly showed that the proposed statistical test is necessary in order to assess the significance of the superiority of a prediction model, since it provides an objective criterion for the distances between the REC curves. Moreover, the procedure can be easily applied to any dataset where the objective is the prediction of a response variable of interest and the comparison of alternative prediction techniques in order to select the best strategy. Conclusions: The proposed hypothesis test, accompanying an informative graphical tool, is more easily interpretable than the conventional parametric and non-parametric statistical procedures. Moreover, it is free from normality assumptions of the error distributions when the samples are small-sized and highly skewed. Finally, the proposed graphical test can be applied to the comparisons of any alternative prediction methods and models and also to any other validation procedure. © 2011 Springer Science+Business Media, LLC.

Gika H.G.,Aristotle University of Thessaloniki | Wilson I.D.,Imperial College London
Bioanalysis | Year: 2014

Alcohol-related disorders are multifaceted since ethanol can induce profound metabolic perturbations when taken in excess. Global metabolic profiling strategies may aid the understanding of ethanol-related effects by shedding light on these metabolic changes and potentially revealing unknown mechanisms of ethanol toxicity. Here an overview of studies designed to explore the effects of alcohol (ethanol) consumption using holistic metabolite profiling approaches (metabonomics/metabolomics) is presented, demonstrating the potential of this methodology. The analytical technologies used (NMR, GC-MS and LC-MS), have been applied to the profiling of serum, plasma, urine and tissues, obtained from animal models or humans, after exposure to alcohol. From the metabolic profiling data of a range of biological samples, a number of endogenous metabolites have been proposed as potential ethanol consumption-related biomarkers. The biomarkers suggested by these studies, and the biochemical insights that they provide for understanding the effects of ethanol mechanisms of toxicity, are discussed. © 2014 Future Science Ltd.

Kontoleon K.J.,Aristotle University of Thessaloniki | Eumorfopoulou E.A.,Aristotle University of Thessaloniki
Building and Environment | Year: 2010

The aim of the present work is to analyse thoroughly the influence of the orientation and proportion (covering percentage) of plant-covered wall sections on the thermal behaviour of typical buildings in the Greek region during the summer period. As to the effect of construction parameters, the layer position of masonry/insulation has been also considered. The investigation has been carried out using a thermal-network model that adequately simulates the building zone under assumption; its validation was based on experimental results from a recently reported study. The model makes provision for several heat-flow paths in order to take into account the leaf cover on the external wall surface, heat transfer through the surfaces that constitute the building envelope, and natural ventilation. The influence of orientation and covering percentage of plant foliage for walls with different configurations was studied using representative outdoor environmental data for the zone location at a specific time period. © 2009 Elsevier Ltd. All rights reserved.

Tzamkiozis T.,Aristotle University of Thessaloniki | Ntziachristos L.,Aristotle University of Thessaloniki | Samaras Z.,Aristotle University of Thessaloniki
Atmospheric Environment | Year: 2010

This paper examines the impact of the emission control and fuel technology development on the emissions of gaseous and, in particular, PM pollutants from diesel passenger cars. Three cars in five configurations in total were measured, and covered the range from Euro 1 to Euro 4 standards. The emission control ranged from no aftertreatment in the Euro 1 case, an oxidation catalyst in Euro 2, two oxidation catalysts and exhaust gas recirculation in Euro 3 and Euro 4, while a catalyzed diesel particle filter (DPF) fitted in the Euro 4 car led to a Euro 4 + DPF configuration. Both certification test and real-world driving cycles were employed. The results showed that CO and HC emissions were much lower than the emission standard over the hot-start real-world cycles. However, vehicle technologies from Euro 2 to Euro 4 exceeded the NOx and PM emission levels over at least one real-world cycle. The NOx emission level reached up to 3.6 times the certification level in case of the Euro 4 car. PM were up to 40% and 60% higher than certification level for the Euro 2 and Euro 3 cars, while the Euro 4 car emitted close or slightly below the certification level over the real-world driving cycles. PM mass reductions from Euro 1 to Euro 4 were associated with a relevant decrease in the total particle number, in particular over the certification test. This was not followed by a respective reduction in the solid particle number which remained rather constant between the four technologies at 0.86 × 1014 km-1 (coefficient of variation 9%). As a result, the ratio of solid vs. total particle number ranged from ∼50% in Euro 1-100% in Euro 4. A significant reduction of more than three orders of magnitude in solid particle number is achieved with the introduction of the DPF. However, the potential for nucleation mode formation at high speed from the DPF car is an issue that needs to be considered in the over all assessment of its environmental benefit. Finally, comparison of the mobility and aerodynamic diameters of airborne particles led to fractal dimensions dropping from 2.60 (Euro 1) to 2.51 (Euro 4), denoting a more loose structure with improving technology. © 2009 Elsevier Ltd. All rights reserved.

Georgiadis K.,Aristotle University of Thessaloniki
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010

The undrained bearing capacity of foundations on or near slopes is commonly calculated using empirical equations or from design charts which have been produced based on limit equilibrium or upper bound plasticity calculations. Many of the available methods do not take account of important parameters that affect the undrained bearing capacity factor, such as the distance of the footing from the slope, the slope height, or the soil properties. This paper presents finite element analyses of strip footings on or near undrained soil slopes performed in order to investigate the influence of the various parameters that affect undrained bearing capacity. The results of the analyses are compared to available methods. It is found that while some of these methods compare well with the finite element results for certain combinations of geometrical parameters and soil properties, they cannot produce sufficiently accurate results as they either do not take account of all of the affecting parameters or are generally not conservative. Based on the finite element results, design charts, equations, and a design procedure are proposed for the calculation of the undrained bearing capacity factor Nc as a function of the undrained shear strength and the bulk unit weight of the soil, the footing width, the distance of the footing from the slope, the slope angle and the slope height. © 2010 ASCE.

Kappos A.J.,Aristotle University of Thessaloniki | Panagopoulos G.,Aristotle University of Thessaloniki
Structure and Infrastructure Engineering | Year: 2010

The latest developments of a methodology developed by the authors and their co-workers for estimating direct losses from earthquakes in reinforced concrete (R/C) buildings are presented; they concern the derivation of capacity curves and vulnerability (fragility) curves in terms of peak ground acceleration (PGA), as well as spectral displacement, for all types of R/C buildings that are common in Greece. The vulnerability assessment methodology is based on the hybrid approach, which combines statistical data with appropriately processed results from nonlinear dynamic or static analyses that permit interpolation and (under certain conditions) extrapolation of statistical data to PGAs and/or spectral displacements for which no data is available. A detailed discussion of the limitations of the hybrid approach is provided, along with a proposal for improving the quality of results by applying a weighting technique to both the analytical and the statistical input data. © 2010 Taylor & Francis.

Mitoulis S.A.,Aristotle University of Thessaloniki | Tegos I.A.,Aristotle University of Thessaloniki
Bulletin of Earthquake Engineering | Year: 2010

The current design of seismically isolated bridges usually combines the use of bearings and stoppers, as a second line of defence. The stoppers allow the development of the in-service movements of the bridge deck, without transmitting significant loads to the piers and their foundations, while during earthquake they transmit the entire seismic action. Despite the fact that stoppers, which restrain the transverse seismic movements of the deck, are used frequently in seismically isolated bridges, the use of longitudinal stoppers is relatively rare, mainly due to the large in-service constraint movements of bridges. The present paper proposes a new type of external longitudinal stoppers, which are installed in stiff sub-structures-boundaries, aiming at limiting the bridge seismic movements. The parametric investigation, which was conducted in order to identify the seismic efficiency of the external stoppers, showed that the interaction of the bridge with the stiff boundaries can lead to significant reductions in the seismic movements of the bridge. Serviceability is appropriately arranged in the paper by expansion joints and approach slabs. © 2010 Springer Science+Business Media B.V.

Itziou A.,Aristotle University of Thessaloniki | Dimitriadis V.K.,Aristotle University of Thessaloniki
Science of the Total Environment | Year: 2011

The present study aimed to enrich the group of sentinel organisms of terrestrial pollution biomonitoring, by investigating the efficacy of the land snail Eobania vermiculata. For this reason, a package of biomarkers was performed on land snails E. vermiculata collected from polluted areas in the field or treated with heavy metals in the laboratory. The biomarkers used were neutral red lysosomal retention assay of the haemocytes, acetylcholinesterase activity in the digestive gland and the haemolymph, and metallothionein content of the digestive gland. Moreover, the morphometric changes in the lysosomal system and the morphometric alterations of the neutral lipids were also investigated. In addition, the content of cadmium, lead and copper was evaluated in the digestive gland of the snails. The results revealed appreciable alterations in the biomarker values both in field- and laboratory-conditions, accompanied by significant correlations among the biomarkers. Therefore, this exploratory study suggests the utility of E. vermiculata as a sentinel organism for biomonitoring the biologic impact of terrestrial pollution, and supports the package's efficacy of the selected biomarkers. © 2010 Elsevier B.V.

Panagakis Y.,Aristotle University of Thessaloniki | Kotropoulos C.,Aristotle University of Thessaloniki | Arce G.R.,University of Delaware
IEEE Transactions on Audio, Speech and Language Processing | Year: 2010

Motivated by psychophysiological investigations on the human auditory system, a bio-inspired two-dimensional auditory representation of music signals is exploited, that captures the slow temporal modulations. Although each recording is represented by a second-order tensor (i.e., a matrix), a third-order tensor is needed to represent a music corpus. Non-negative multilinear principal component analysis (NMPCA) is proposed for the unsupervised dimensionality reduction of the third-order tensors. The NMPCA maximizes the total tensor scatter while preserving the non-negativity of auditory representations. An algorithm for NMPCA is derived by exploiting the structure of the Grassmann manifold. The NMPCA is compared against three multilinear subspace analysis techniques, namely the non-negative tensor factorization, the high-order singular value decomposition, and the multilinear principal component analysis as well as their linear counterparts, i.e., the non-negative matrix factorization, the singular value decomposition, and the principal components analysis in extracting features that are subsequently classified by either support vector machine or nearest neighbor classifiers. Three different sets of experiments conducted on the GTZAN and the ISMIR2004 Genre datasets demonstrate the superiority of NMPCA against the aforementioned subspace analysis techniques in extracting more discriminating features, especially when the training set has small cardinality. The best classification accuracies reported in the paper exceed those obtained by the state-of-the-art music genre classification algorithms applied to both datasets. © 2006 IEEE.

This study addresses the issue of urban sprawl through the perspective of simulation modeling. CA model's ability to simulate urban patterns and processes of urban expansion in a realistic way has been widely investigated, but the influence of macro-scale factors and processes has often been neglected. A CA-based model is proposed linking macro-scale processes to micro-dynamics in order to simulate the urban sprawl process. The model allocates new urban land in a disaggregated field of land units (cells) taking into account a) a wide range of demographic, accessibility, socioeconomic, environmental and urban planning data b) a set of local characteristics of cells and neighborhood interactions. The application of the model to real-world data is based on a multiple regression model quantifying the influence of macro-scale factors and on an automatic calibration process based on historical data where local coefficient scores for different areas are determined. An application in the urban agglomeration of Thessaloniki in Greece is presented, where the model is calibrated for the period 1990e2010 and is used to explore urban expansion until 2030. The conclusions force us to recognize the need for further research into the way CA-based integrated modeling could act as a land-use policy development tool. © 2011 Elsevier Ltd.

Papastefanou C.,Aristotle University of Thessaloniki
Radiation Measurements | Year: 2010

Radon flux measurements were carried out at three radon stations along an active fault zone in the Langadas basin, Northern Greece by various techniques for earthquake prediction studies. Specially made devices with alpha track-etch detectors (ATDs) were installed by using LR-115, type II, non-strippable cellulose nitrate films (integrating method of measurements). Continuous monitoring of radon gas exhaling from the ground was also performed by using silicon diode detectors, Barasol and Clipperton type, in association with various probes and sensors including simultaneously registration of the meteorological parameters, such as precipitation height (rainfall events), temperature and barometric pressure. The obtained radon data were studied in parallel with the data of seismic events, such as the magnitude, ML of earthquakes, the epicentral distance, the hypocentral distance and the energy released during the earthquake event occurred at the fault zone during the period of measurements to find out any association between the rad on flux and the meteorological and seismological parameters. Seismic events with magnitude ML ≥ 4.0 appeared to be preceded by large precursory signals produced a well-defined "anomaly" (peak) of radon flux prior to the event. In the results, the radon peaks in the obtained spectra appeared to be sharp and narrow. The rise time of a radon peak, that is the time period from the onset of a radon peak until the time of radon flux maximum is about a week, while the after time, that is the time interval between the time of radon flux maximum and the time of a seismic event ranges from about 3 weeks or more. © 2010 Elsevier Ltd. All rights reserved.

Papamichos E.,Aristotle University of Thessaloniki
European Journal of Environmental and Civil Engineering | Year: 2010

Experimental results from sand production hollow cylinders tests are presented for cavity failure and sand production quantification. The effects of important parameters such as the sandstone class, stress rate, fluid flow rate, and time are presented and show how they influence sand production. A model for hydro-mechanical erosion of porous rocks is presented as it is applied to the sand production problem in hydrocarbon production. The model is based on a continuum theory for erosion, which regards the continuum as a threephase medium and establishes a set of mass balance equations for the various phases. The solution requires an additional equation in the form of a constitutive or evolution law for the sand rate. Erosion is coupled with the mechanical behavior of a sand-producing cavity, and leads to enlargement of the erosion zone. Finally, multiphase flow and its effect on sand production is presented experimentally and theoretically by analyzing water invasion in the sand production test. © 2010 Lavoisier, Paris.

Damos P.,Aristotle University of Thessaloniki
Journal of Economic Entomology | Year: 2013

This work studies for first time the effect of constant temperatures (15, 20, 25, 30 and 35°C) on the demography of Anarsia lineatella Zeller (Lepidoptera: Gelechiidae) based on jackknife and bootstrap randomization methods. Male and female longevity was substantially reduced at the higher temperatures in contrast to intermediate and lower temperatures. According to a second order polynomial regression function, high correlations were observed between temperatures and the age of first reproduction as well as temperature and oviposition times. Net reproductive rate was highest at 25°C and 74.172, while the intrinsic rate of increase displayed its highest values at 30°C and was estimated to be 0.238. Birth rate and finite capacity of increase were higher at 30°C and estimated to be 0.235 and 1.268, respectively. Mean generation time and doubling time varied significantly with temperature and the shortest mean generation and doubling time was obtained at 30°C (25.566 and 2.909 d respectively). Life expectancy had its lowest value 10.3 d at 25°C, whereas cohorts that were maintained at 20 and 15°C increased their life expectation approximately three to sixfold. © 2013 Entomological Society of America.

Angeli S.D.,Aristotle University of Thessaloniki | Monteleone G.,ENEA | Giaconia A.,ENEA | Lemonidou A.A.,Aristotle University of Thessaloniki
International Journal of Hydrogen Energy | Year: 2014

The methane steam reforming (MSR) technology is the oldest and the most vital route to convert CH4 into H2. The conventional process usually operates in a high temperature range of 973-1173 K due to the highly endothermic nature of the reforming reaction. Necessity to increase the energy efficiency leads to the development of processes operating at low temperature and of highly active and coke resistant catalysts. An active catalyst which can provide high reforming reaction rates at low temperature (<823 K) is therefore required. This work summarizes the latest developments on catalysts for methane steam reforming at low reaction temperature. Three major groups of materials are considered, nickel-based, noble metal-based and bimetallic catalysts. In each section the strategies proposed by several authors to enhance the performance of catalysts are discussed. An overview of the kinetic models developed for the description of the catalytic performance is also included. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Tsapkini K.,Johns Hopkins University | Tsapkini K.,Aristotle University of Thessaloniki | Rapp B.,Johns Hopkins University
Cortex | Year: 2010

We report on an investigation of the cognitive functions of an individual with a resection of the left fusiform gyrus. This individual and a group of control participants underwent testing to examine the question of whether or not there are neural substrates within the left fusiform gyrus that are dedicated to orthographic processing. We evaluated the modality specificity (written vs spoken language) and the category specificity (written language vs other visual categories) of this individual's impairments. The results clearly reveal deficits affecting lexical processes in both reading and spelling. Specifically, we find disruption of normal, rapid access to meaning from print in reading and of accurate retrieval of the spellings of words from their meaning in writing. These deficits stand in striking contrast with intact processing of spoken language and categories of visual stimuli such as line drawings of objects and faces. The modality and category specificity of the deficits provide clear evidence of neural substrates within the left-mid-fusiform gyrus that are specialized and necessary for normal orthographic processing. © 2009 Elsevier Srl. All rights reserved.

Tzanavaras P.D.,Aristotle University of Thessaloniki
Instrumentation Science and Technology | Year: 2012

In this study, a new, green analytical method is proposed for the determination of N-acetylcysteine (NAC) in pharmaceutical formulations. The analyte was separated from the samples matrix using a 100% aqueous mobile phase [0.05% v/v CH 3COOH+1mmolL -1 ethylenediaminetetraacetic acid (EDTA) in water] and a suitable analytical column (Prevail reversed phase column). Detection was carried out at 285nm after on-line post-column derivatization (PCD) with methyl-propiolate (MP) in alkaline medium. Method development included both chromatographic and reaction parameters, while validation was based on international recommendations. The developed analytical scheme excludes the use of organic modifiers from all steps of pretreatment/analysis and offers adequate figures of merit for the quality control (assay and content uniformity) of NAC-containing formulations. Copyright © Taylor & Francis Group, LLC.

Kachrimanis K.,Aristotle University of Thessaloniki
Pharmaceutical research | Year: 2012

To investigate the dehydration of carbamazepine dihydrate, combining kinetics and crystal water dynamics with electronic structure calculations. Thermal microscopy, moisture sorption, and thermogravimetric analysis (TGA) were applied to evaluate the effects on relative humidity (RH) and temperature, while crystal water dynamics were monitored by 2D-FTIR correlation spectroscopy (2DCOS) and the nature of the H-bonding network was investigated by 3D-periodic DFT calculations. It was found that the dihydrate is unstable below 40% RH and/or above the glass transition temperature (T g ∼ 53°C). At room temperature, amorphous carbamazepine is formed at RH ∼ 0%, form I at RH ∼ 10%, and mixtures of forms I and III at higher RH. Above the T g , the dehydration yields partially crystalline mixtures of forms I and IV between 50-100°C, and form I above 100°C. In all cases, the amorphous product crystallizes to form IV. Thermal analysis and 2DCOS revealed a biphasic dehydration process. Kinetic modelling suggests a diffusion-controlled dehydration below T g and reaction interface-controlled kinetics above T g . The dehydration consists of two overlapping water removal processes, with the water molecule attached to the amide C=O departing faster, probably due to the destabilizing effect of anti-bonding interactions between the water H1s and the carbonyl O2p orbital.

Bozini T.,Aristotle University of Thessaloniki
The International journal of oral & maxillofacial implants | Year: 2011

To systematically review clinical studies on prosthodontic complication rates of implant fixed dental prostheses in edentulous patients after an observation period of at least 5 years. A literature search was conducted using different electronic databases. Specific terms were used for the database search, which spanned the years 1990 to 2008. The search was augmented by using the option of "related articles" as well as by hand searching of references and relevant journals. Relevant studies were selected according to predetermined inclusion and exclusion criteria. Agreement between reviewers was determined by using Cohen kappa coefficients. The initial database search yielded 8,216 relevant titles. Following the filtering process, 19 studies were finally selected. No study directly compared the incidence of prosthodontic complications of complete implant-supported metal-ceramic versus metal-acrylic resin fixed prostheses in the completely edentulous patient. Studies of metal-ceramic prostheses were scarce and short term. Metal-acrylic resin complete implant fixed prostheses presented with various prosthodontic complications after long-term function. The most frequent complications were veneer fracture and material wear.

Myresiotis C.K.,Aristotle University of Thessaloniki | Vryzas Z.,Democritus University of Thrace | Papadopoulou-Mourkidou E.,Aristotle University of Thessaloniki
Biodegradation | Year: 2012

A laboratory study was conducted to investigate the influence of four PGPR strains on the degradation of five soil applied pesticides and their effects on bacterial growth. Interactions of Bacillus subtilis GB03, Bacillus subtilis FZB24, Bacillus amyloliquefaciens IN937a and Bacillus pumilus SE34 with two concentrations of acibenzolar-S-methyl, metribuzin, napropamide, propamocarb hydrochloride and thiamethoxam in liquid culture and soil microcosm were studied. The degradation of acibenzolar-S-methyl by all PGPR tested in low and high concentration, was 5.4 and 5.7 times, respectively, faster than that in non-inoculated liquid culture medium. At the end of the 72-h liquid cultured experiments, 8-18, 9-11, 15-36 and 11-22% of metribuzin, napropamide, propamocarb hydrochloride and thiamethoxam, respectively, had disappeared from PGPR inoculated medium. Under the soil microcosm experimental conditions, the half-lives of acibenzolar-S-methyl incubated in the presence of PGPR strains spiked at 1.0 and 10.0 mg kg -1 were 10.3-16.4 and 9.2-15.9 days, respectively, markedly lower compared with >34.2 days in the control. From the rest pesticides studied degradation of propamocarb hydrochloride and thiamethoxam was enhanced in the presence of B. amyloliquefaciens IN937a and B. pumilus SE34. Acibenzolar-S-methyl, propamocarb hydrochloride and thiamethoxam significantly increased the PGPR growth. However, the stimulatory effect was related to the level of pesticide spiked. © 2011 Springer Science+Business Media B.V.

Theodorou E.C.,Aristotle University of Thessaloniki | Theodorou M.C.,Aristotle University of Thessaloniki | Kyriakidis D.A.,Aristotle University of Thessaloniki
Metabolic Engineering | Year: 2012

AtoSC two-component system plays a pivotal role in many regulatory indispensable Escherichia coli processes. AtoSCDAEB regulon, comprising the AtoSC system and the atoDAEB operon, regulates the short-chain fatty acids catabolism. We report here, that AtoSC up-regulates the high-molecular weight PHB biosynthesis, in recombinant phaCAB + E. coli, with the Cupriavidus necator phaCAB operon. PHB accumulation was maximized upon the acetoacetate-mediated induction of AtoSC, under glucose 1% w/v, resulting in a yield of 1.73g/l with a biopolymer content of 64.5% w/w. The deletion of the atoSC locus, in the ΔatoSC strains, resulted in a 5 fold reduction of PHB accumulation, which was restored by the extrachromosomal introduction of the AtoSC system. The deletion of the atoDAEB operon triggered a significant decrease in PHB synthesis in ΔatoDAEB strains. However, the acetoacetate-induced AtoSC system in those strains increased PHB to 1.55g/l, while AtoC expression increased PHB to 1.4g/l upon acetoacetate. The complementation of the ΔatoDAEB phenotype was achieved by the extrachromosomal introduction of the atoSCDAEB regulon. The individual inhibition of Β-oxidation and mainly fatty-acid biosynthesis pathways by acrylic acid or cerulenin respectively, reduced PHB biosynthesis. Under those conditions the introduction of the atoSC locus or the atoSCDAEB regulon was capable to up-regulate the biopolymer accumulation. The concurrent inhibition of both the fatty acids metabolic pathways eliminated PHB production. PHB up-regulation in phaCAB + E. coli, by AtoSC signaling through atoDAEB operon and its participation in the fatty acids metabolism interplay, provide additional perceptions of AtoSC critical involvement in E. coli regulatory processes towards the biotechnologically improved polyhydroxyalkanoates biosynthesis. © 2012 Elsevier Inc.

Karageorgou E.G.,Aristotle University of Thessaloniki | Samanidou V.F.,Aristotle University of Thessaloniki
Journal of Separation Science | Year: 2010

Ultrasound-assisted matrix solid-phase dispersion (MSPD) was applied to isolate eight cephalosporins (cefadroxil, cefaclor, cephalexin, cefotaxime, cefazolin, cefuroxime, cefoperazone and ceftiofur) from milk. Multi-residue analysis was subsequently performed by HPLC-diode array detection. Extraction yield by matrix solid-phase dispersion using Nexus sorbent was higher than various investigated SPE protocols. Three analytical columns, two conventional silica based and one monolithic, were compared based on resolution, peak shape and retention time. The optimum method using Chromolith RP-18e (100x4.6 mm) achieved separation in less than 16 min. Method validation was performed according to the European Union Decision 2002/657/EC, determining linearity, selectivity, stability, decision limit, detection capability, accuracy and precision. RSD values observed were lower than 15.3%. Recovery rates of examined antimicrobials from milk ranged from 93.8 to 101.9% for cefadroxil, from 94.7 to 103.6% for cefaclor, from 93.4 to 106.6% for cephalexine, from 104.1 to 115.3% for cefotaxime, from 97.1 to 105.6% for cefazolin, from 97.4 to 108.6% for cefuroxime, from 98.8 to 103.4% for cefoperazone and from 95.5 to 103.6% for ceftiofur. Correlation coefficients ranged from 0.9926 to 0.9999. CC b values were in the range from 103.5 to 112.3 μg/kg for analytes with a maximum residue limit of 100 μg/kg and from 54.4 to 56.3 μg/kg for those with a maximum residue limit of 50 μg/kg. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Michailides C.,Aristotle University of Thessaloniki | Angelides D.C.,Aristotle University of Thessaloniki
Engineering Structures | Year: 2015

In the present paper, a multi objective optimization process of a novel Flexible Floating Structure (FFS) subjected to regular and irregular incident waves is developed and presented. The FFS introduced here is considered as an effective structure capable for both wave energy production, with the utilization of a linear hydraulic Power Take-Off (PTO) mechanism, and protection effectiveness. FFS consists of a grid of floating modules connected flexibly in two directions by PTOs with known linear damping characteristics and by connectors with known properties. The optimization process includes two distinct optimization stages; the first one is related with the identification of the optimal set of non dominated solutions and the second one with the selection of the optimum design configuration of the FFS. The performance criteria considered for the selection of the optimum design of the FFS are the produced power, the protection effectiveness and the structural integrity of structural parts that compose the FFS and more specifically of the connectors of the floating modules of the FFS. The performance criteria are thoroughly depended upon design variables, continuous and discrete, associated with the excitation and the characteristics of the structure. The optimization process, based on genetic algorithms and global criterion method, is developed and applied for specific predefined wave field characteristics in order to properly address the characteristics of the structure toward a most preferable (optimum) design. The results that are obtained demonstrate the suitability of the proposed optimization process and the capability of the novel introduced FFS to operate up to a desired level for both wave energy production and protection effectiveness. © 2014 Elsevier Ltd.

Askes H.,University of Sheffield | Aifantis E.C.,Aristotle University of Thessaloniki
International Journal of Solids and Structures | Year: 2011

In this paper, we discuss various formats of gradient elasticity and their performance in static and dynamic applications. Gradient elasticity theories provide extensions of the classical equations of elasticity with additional higher-order spatial derivatives of strains, stresses and/or accelerations. We focus on the versatile class of gradient elasticity theories whereby the higher-order terms are the Laplacian of the corresponding lower-order terms. One of the challenges of formulating gradient elasticity theories is to keep the number of additional constitutive parameters to a minimum. We start with discussing the general Mindlin theory, that in its most general form has 903 constitutive elastic parameters but which were reduced by Mindlin to three independent material length scales. Further simplifications are often possible. In particular, the Aifantis theory has only one additional parameter in statics and opens up a whole new field of analytical and numerical solution procedures. We also address how this can be extended to dynamics. An overview of length scale identification and quantification procedures is given. Finite element implementations of the most commonly used versions of gradient elasticity are discussed together with the variationally consistent boundary conditions. Details are provided for particular formats of gradient elasticity that can be implemented with simple, linear finite element shape functions. New numerical results show the removal of singularities in statics and dynamics, as well as the size-dependent mechanical response predicted by gradient elasticity. © 2011 Elsevier Ltd. All rights reserved.

Groll A.H.,University of Munster | Castagnola E.,Instituto Giannina Gaslini | Cesaro S.,Pediatric Hematology Oncology | Dalle J.-H.,University Paris Diderot | And 6 more authors.
The Lancet Oncology | Year: 2014

Invasive opportunistic fungal diseases (IFDs) are important causes of morbidity and mortality in paediatric patients with cancer and those who have had an allogeneic haemopoietic stem-cell transplantation (HSCT). Apart from differences in underlying disorders and comorbidities relative to those of adults, IFDs in infants, children, and adolescents are unique with respect to their epidemiology, the usefulness of diagnostic methods, the pharmacology and dosing of antifungal agents, and the absence of interventional phase 3 clinical trials for guidance of evidence-based decisions. To better define the state of knowledge on IFDs in paediatric patients with cancer and allogeneic HSCT and to improve IFD diagnosis, prevention, and management, the Fourth European Conference on Infections in Leukaemia (ECIL-4) in 2011 convened a group that reviewed the scientific literature on IFDs and graded the available quality of evidence according to the Infectious Diseases Society of America grading system. The final considerations and recommendations of the group are summarised in this manuscript. © 2014 Elsevier Ltd.

Kimiskidis V.K.,Aristotle University of Thessaloniki
Revue Neurologique | Year: 2016

In recent years, a number of novel brain-stimulation techniques have been developed (such as TMS-EEG, TMS-fMRI and TMS-NIRS), yet they remain underutilized in the field of epilepsy. Accumulating evidence suggests that transcranial magnetic stimulation (TMS) combined with electroencephalography (TMS-EEG) is a highly relevant technique for exploration of the pathophysiology of human epilepsies as well as a promising biomarker with diagnostic and prognostic potential. Results.-In genetic generalized epilepsies, TMS-EEG has provided pathophysiological insight by revealing quasi-stable, covert states of excitability, a subclass of which is associated with the generation of TMS-induced epileptiform discharges (EDs). In focal epilepsy, TMSinduced EDs were successfully employed to identify the epileptogenic zone. In addition, TMS trains applied during focal EDs can terminate them, and appear to restore the effective connectivity of the brain network significantly altered by EDs. This abortive effect of TMS on EDs may possibly serve as a biomarker of response to invasive neuromodulatory techniques. Conclusion.-TMS-EEG-based stimulation paradigms can provide insight into the mechanisms underlying human epilepsies and, thus, warrant further study as diagnostic and prognostic biomarkers. © 2016 Elsevier Masson SAS.

Volos C.K.,Hellenic Army Academy | Kyprianidis I.M.,Aristotle University of Thessaloniki | Stouboulos I.N.,Aristotle University of Thessaloniki
Signal Processing | Year: 2013

This paper presents a novel image encryption scheme, which uses a chaotic True Random Bits Generator (TRBG). The chaotic TRBG is based on the coexistence of two different synchronization phenomena. The first one is the well-known complete chaotic synchronization while the second one is a recently new proposed synchronization phenomenon, the inverse π-lag synchronization. This coexistence is observed in the case of two mutually coupled identical nonlinear circuits. The nonlinear circuit, which is used, produces double-scroll chaotic attractors. The initial conditions of the coupled system and the values of the circuit's parameters serve as the private key of the proposed cryptographic scheme. In order to face the challenge of using this chaotic TRBG in such cryptographic schemes, the produced bits sequence is subjected to statistical tests which are the well-known Federal Information Processing Standards-140-2. This bits sequence has then been used to encrypt and decrypt gray-scale images. Also, the security analysis of the encrypted image demonstrates the high security of the proposed encryption scheme. © 2012 Elsevier B.V. All rights reserved.

Katsanos E.I.,Aristotle University of Thessaloniki | Sextos A.G.,Aristotle University of Thessaloniki
Advances in Engineering Software | Year: 2013

Current practice enables the design and assessment of structures in earthquake prone areas by performing time history analysis with the use of appropriately selected strong ground motions. This study presents a Matlab-based software environment, which is integrated with a finite element analysis package, and aims to improve the efficiency of earthquake ground motion selection by accounting for the variability of critical structural response quantities. This additional selection criterion, which is tailored to the specific structure studied, leads to more reliable estimates of the mean structural response quantities used in design, while fulfils the criteria already prescribed by the European and US seismic codes and guidelines. To demonstrate the applicability of the software environment developed, an existing irregular, multi-storey, reinforced concrete building is studied for a wide range of seismic scenarios. The results highlight the applicability of the software developed and the benefits of applying a structure-specific criterion in the process of selecting suites of earthquake motions for the seismic design and assessment. © 2013 Elsevier Ltd. All rights reserved.

Bechlioulis C.P.,Aristotle University of Thessaloniki | Rovithakis G.A.,Aristotle University of Thessaloniki
International Journal of Adaptive Control and Signal Processing | Year: 2013

Adaptive dynamic surface control (ADSC) design was proposed as an alternative to adaptive backstepping, capable of curing the 'explosion of complexity' problem, caused by the repeated differentiations of the so called intermediate control signals. However, as it is clearly demonstrated in this work, ADSC schemes are sensitive to modeling uncertainties and/or additive external disturbances. In fact, it is shown that a uniformly bounded exogenous perturbation of unknown upper bound may easily destabilize the closed-loop system. Subsequently, a constructive methodology based on the recently developed by the authors prescribed performance control technique, is proposed, which combined with an ADSC design, results in a modified scheme possessing significantly increased robustness properties. Simulation studies illustrate the approach. Copyright © 2012 John Wiley & Sons, Ltd.

Exarhopoulos S.,Aristotle University of Thessaloniki | Raphaelides S.N.,Aristotle University of Thessaloniki
Journal of Cereal Science | Year: 2012

A series of starch-fatty acid samples were prepared using three types of starches differing in their amylose content i.e. maize, pea and amylomaize and three fatty acids differing in their chain length; i.e. myristic, palmitic and stearic. Two different modes of heating the starch systems were employed; i.e. either prior to the addition of the acid to starch aqueous dispersions or after heating the dispersions at the predetermined temperatures 75, 85 or 98°C. Light and SEM microscopic examination indicated that amylose-fatty acid interactions taken place during starch gelatinization retarded the destruction of the granules depending on the heating temperature. XRD studies revealed that the degree of crystallinity exhibited by the starch samples was dependent on the amylose content, the fatty acid chain length and the modes of heating employed. © 2011 Elsevier Ltd.

Georgiadis P.,Aristotle University of Thessaloniki | Politou A.,Aristotle University of Thessaloniki
Computers and Industrial Engineering | Year: 2013

Drum-Buffer-Rope-based production planning and control (PPC) approaches provide production managers with effective tools to manage production disruptions and improve operational performance. The corner stone of these approaches is the proper selection of time-buffers which are considered as exogenously defined constant. However, the majority of real-world manufacturing systems are characterized by the dynamic change of demand and by stochastic production times. This fact calls for a dynamic approach in supporting the decision making on time-buffer policies. To this end, we study a capacitated, single-product, three-operation, flow-shop manufacturing system. We propose a dynamic time-buffer control mechanism for short/medium-term PPC with adaptive response to demand changes and robustness to sudden disturbances in both internal and external shop environment. By integrating the control mechanism into the flow-shop system, we develop a system dynamics model to support the decision-making on time-buffer policies. Using the model, we study the effect of policies on shop performance by means of analysis of variance. Extensive numerical investigation reveals the insensitivity of time-buffer policies to key factors related to demand, demand due date and operational characteristics such as protective capacity and production times. © 2013 Elsevier Ltd. All rights reserved.

Psomas G.,Aristotle University of Thessaloniki | Kessissoglou D.P.,Aristotle University of Thessaloniki
Dalton Transactions | Year: 2013

The structural features of copper(ii), nickel(ii), cobalt(ii) and zinc(ii) complexes with the antimicrobial drugs quinolones and non-steroidal anti-inflammatory drugs (NSAIDs) as ligands are discussed. The binding properties of these complexes to biomolecules (calf-thymus DNA, bovine or human serum albumin) are presented and evaluated. The biological activity (antimicrobial, antioxidant and antiproliferative) of selected complexes is investigated. Further perspectives concerning the synthesis and the biological activity of novel complexes with quinolones or NSAIDs attractive to synthetic chemists, biochemists and/or biologists are presented. © 2013 The Royal Society of Chemistry.

Zotos E.E.,Aristotle University of Thessaloniki
Research in Astronomy and Astrophysics | Year: 2012

We study the behavior of orbits in two different galactic dynamical models, describing the motion in the central parts of a triaxial elliptical galaxy with a dense nucleus. Numerical experiments show that both models display regular motion together with extended chaotic regions. A detailed investigation of the properties of motion is made for the 2D and 3D Hamiltonian systems, using a number of different dynamical parameters, such as the Poincaré surface of a section, the maximal Lyapunov Characteristic Exponent, the S(c) spectrum, the S(w) spectrum and the P(f) indicator. The numerical calculations suggest that the properties of motion in both potentials are very similar. Our results show that one may use different kinds of gravitational potentials in order to describe the motion in triaxial galaxies while obtaining quantitatively similar results. © 2012 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.

Zotos E.E.,Aristotle University of Thessaloniki
Research in Astronomy and Astrophysics | Year: 2012

We use a composite gravitational galactic model consisting of a disk, a halo, a massive nucleus and a strong nuclear bar, in order to study the connections between global and local parameters in a realistic dynamical system. The local model is constructed from a two-dimensional perturbed harmonic oscillator and can be derived by expanding the global model in the vicinity of the central stable Lagrange equilibrium point. The frequencies of oscillations are not arbitrary, but they are connected with all the parameters involved with the global model. Moreover, the value of the local energy is also connected with the value of the global energy. Low and high energy stars in the global model display chaotic motion. Comparison with previous research reveals that the presence of the massive nucleus is responsible for the chaotic motion of the low energy stars. In the local motion, the low energy stars show interesting resonance phenomena, but the chaotic motion, if any, is negligible. On the contrary, the high energy stars do not show bounded motion in the local model. This is an indication of particular activity near the center of galaxies possessing massive nuclei. © 2012 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.

Valagiannopoulos C.A.,Aalto University | Tsitsas N.L.,Aristotle University of Thessaloniki
Radio Science | Year: 2012

Eliminating the electromagnetic interaction of a device with its background is a topic which attracts considerable attention both from a theoretical as well as from an experimental point of view. In this work, we analyze an infinite two-dimensional planar microstrip antenna, excited by an incident plane wave, and propose its potential operation as a low-profile receiving antenna, by suitably adjusting the parameters of its cloaking superstrate. We impose a semi-analytic integral equation method to determine the scattering characteristics of the microstrip antenna. The method utilizes the explicit expressions of the Green's function of the strip-free microstrip and yields the surface strip's current as the solution of a suitable linear system. Subsequently, the antenna's far-field response is obtained. Numerical results are presented for the achieved low profile of the receiving antenna, by choosing suitably the cloaking superstrate parameters. It is demonstrated that for specific cloaking parameters the scattered field by the antenna is considerably reduced, while the received signal from the antenna is maintained at sensible levels. We point out that the material values achieving this reduction correspond to a superstrate filled with an -near-zero or a low-index metamaterial. Finally, the variations of the device reaction for various superstrates are depicted, concluding that for optimized superstrate's parameters, the reaction values are significantly reduced, while at distinct scattering angles even approach zero.

Zotos E.E.,Aristotle University of Thessaloniki
New Astronomy | Year: 2012

In the present article, we use an axially symmetric galactic gravitational model with a disk-halo and a spherical nucleus, in order to investigate the transition from regular to chaotic motion for stars moving in the meridian (r,z) plane. We study in detail the transition from regular to chaotic motion, in two different cases: the time independent model and the time evolving model. In both cases, we explored all the available range regarding the values of the main involved parameters of the dynamical system. In the time dependent model, we follow the evolution of orbits as the galaxy develops a dense and massive nucleus in its core, as mass is transported exponentially from the disk to the galactic center. We apply the classical method of the Poincaré (r,p r) phase plane, in order to distinguish between ordered and chaotic motion. The Lyapunov Characteristic Exponent is used, to make an estimation of the degree of chaos in our galactic model and also to help us to study the time dependent model. In addition, we construct some numerical diagrams in which we present the correlations between the main parameters of our galactic model. Our numerical calculations indicate, that stars with values of angular momentum L z less than or equal to a critical value L zc, moving near to the galactic plane, are scattered to the halo upon encountering the nuclear region and subsequently display chaotic motion. A linear relationship exists between the critical value of the angular momentum L zc and the mass of the nucleus M n. Furthermore, the extent of the chaotic region increases as the value of the mass of the nucleus increases. Moreover, our simulations indicate that the degree of chaos increases linearly, as the mass of the nucleus increases. A comparison is made between the critical value L zc and the circular angular momentum L z0 at different distances from the galactic center. In the time dependent model, there are orbits that change their orbital character from regular to chaotic and vise versa and also orbits that maintain their character during the galactic evolution. These results strongly indicate that the ordered or chaotic nature of orbits, depends on the presence of massive objects in the galactic cores of the galaxies. Our results suggest, that for disk galaxies with massive and prominent nuclei, the low angular momentum stars in the associated central regions of the galaxy, must be in predominantly chaotic orbits. Some theoretical arguments to support the numerically derived outcomes are presented. Comparison with similar previous works is also made. © 2012 Elsevier B.V. All rights reserved.

Panayiotou C.,Aristotle University of Thessaloniki
Journal of Physical Chemistry B | Year: 2012

The recently(1, 2) introduced partial solvation parameters (PSPs) are molecular descriptors that combine elements from quantum mechanics with the QSPR/LSER/solvatochromic and solubility parameter approaches. Basic regularities and universalities exhibited by PSPs are examined in this work and the concepts of homosolvation, heterosolvation and solvation energy density are quantified. A simple consistent thermodynamic framework is developed, through which the validity of the PSP approach is tested. The predictions are compared with experimental phase equilibrium data that span the full composition range from the pure fluid state to infinite dilution. They include vapor-liquid equilibria of fluids interacting with strong specific forces, dissolution of solids/liquids in various solvents and probe/oligomer or probe/polymer interactions as typically determined by inverse gas-chromatography. These applications show the potential of the PSP approach not only to reasonably predict a variety of properties of classes of complex systems but, also, to shed light to challenging aspects of intermolecular interactions. The perspectives of this unified approach to solution thermodynamics are discussed. © 2012 American Chemical Society.

Zotos E.E.,Aristotle University of Thessaloniki
Publications of the Astronomical Society of Australia | Year: 2012

In the present article, we investigate the behavior of orbits in a time-independent axially symmetric galactic-type potential. This dynamical model can be considered to describe the motion in the central parts of a galaxy, for values of energies larger than the energy of escape. We use the classical surface-of-section method in order to visualize and interpret the structure of the phase space of the dynamical system. Moreover, the Lyapunov characteristic exponent is used in order to make an estimation of the degree of chaoticity of the orbits in our galactic model. Our numerical calculations suggest that in this galactic-type potential there are two kinds of orbits, (i) escaping orbits and (ii) trapped orbits, which do not escape at all. Furthermore, a large number of orbits of the dynamical system display chaotic motion. Among the chaotic orbits, there are orbits that escape quickly and also orbits that remain trapped for vast time intervals. When the value of a test particle's energy slightly exceeds the energy of escape, the number of trapped regular orbits increases as the value of the angular momentum increases. Therefore, the extent of the chaotic regions observed in the phase plane decreases as the energy value increases. Moreover, we calculate the average value of the escape period of chaotic orbits and try to correlate it with the value of the energy and also with the maximum value of the z component of the orbits. In addition, we find that the value of the Lyapunov characteristic exponent corresponding to each chaotic region for different values of energy increases exponentially as the energy increases. Some theoretical arguments are presented in order to support the numerically obtained outcomes. © 2012 Astronomical Society of Australia.

Tsioras P.A.,Aristotle University of Thessaloniki
IForest | Year: 2010

This study aims at examining the perspectives of the Greek forest workers and the benefits that will be derived from the introduction of a forest workers' training system. A postal questionnaire was distributed to 115 experts on forest operations nationwide, and personal interviews were conducted with 106 forest workers in 13 prefectures of Greece. The questionnaire was completed by 99 forestry experts with long experience on forestry issues all over Greece. The majority of the participants believed that there is a lack of interest on behalf of the State and that the most pressing problems are income- related. The results indicate that the number of forest workers will continue to decline unless specific measures are taken. Changes in the forest management systems are necessary since the present status has not lived up to the expectations. The introduction of a forest workers' training system is expected to bring professionalism to the sector of forest operations, increase the overall productivity and improve the perspectives of the forestry workforce in Greece. © iForest-Biogeosciences and Forestry.

Tsagas C.G.,Aristotle University of Thessaloniki | Tsagas C.G.,Albanova University Center
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2012

Recent surveys indicate coherent large-scale peculiar motions, commonly referred to as 'dark flows', considerably stronger than expected. At the same time, an increasing number of reports suggest the presence of a weak dipolar anisotropy in the supernova data. The Universe seems to accelerate slightly faster in one direction and equally slower in the opposite. Also, this 'cosmological axis' lies fairly close to the cosmic microwave background dipole. Since apparent, dipole-like, anisotropies are the trademark signature of peculiarmotions, we consider the possibility that these, seemingly unconnected, observations are actually related. In the process, we find that observers living inside a dark flow could experience locally accelerated expansion in a globally decelerating Universe. Moreover, to these observers, the acceleration should appear slightly faster in one direction and equally slower in the opposite, as if there is a preferred axis in the universe. When combined, these results open, in principle at least, the theoretical possibility of addressing the supernova data and the cosmic acceleration by appealing to dark flows rather than dark energy. © 2012 The Author Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Andreadou N.,Aristotle University of Thessaloniki | Pavlidou F.-N.,Aristotle University of Thessaloniki
IEEE Transactions on Power Delivery | Year: 2010

Power-line communications (PLC) have gained a lot of scientific interest over the past years. In this paper, a practical noise model is proposed that best describes the noise conditions on an orthogonal frequency-division multiplexing PLC system. The noise present on a power-line system is divided in five categories which are grouped into two classes: 1) the generalized background and 2) the impulsive noise. In this paper, all of the components comprising the noise are precisely depicted on a computer simulation system. The statistical properties regarding all component parameters are taken into account and used in our model. By this way, the real conditions on a PLC channel can be portrayed in the most precise way. This model is tested on a PLC channel and its performance in terms of bit-error rate versus the Eb/N o value is obtained. For reasons of completeness, we examine how two of the model's components affect the system's performance by altering their vital parameters. In order to accomplish this, we take various values for these parameters and we check their influence on the system. Furthermore, we apply a popular noise model, such as Middleton's noise model and we compare the performance obtained by both noise models. © 2009 IEEE.

Gill H.S.,University of Oxford | Grammatopoulos G.,University of Oxford | Adshead S.,Aristotle University of Thessaloniki | Tsialogiannis E.,Aristotle University of Thessaloniki | And 2 more authors.
Trends in Molecular Medicine | Year: 2012

Theoretical, desirable features of second-generation metal-on-metal (MoM) hip prostheses have led to their widespread use. However, the bearing surfaces, consisting of complex cobalt-chromium alloys, are subject to wear and the release of cobalt and chromium (CoCr) nanoparticles. These nanoparticles can reduce cellular viability, induce DNA damage, lead to chromosomal aberrations, and possibly stimulate increased metal hypersensitivity. Clinically, the effects can be both local (soft-tissue reactions) and systemic (arthroprosthetic cobaltism). This review assesses the literature concerning the in vitro and in vivo cytotoxic, genotoxic, and immunotoxic effects of CoCr wear particles, which is increasingly important in view of the large number of MoM arthroplasties performed. © 2011 Elsevier Ltd.

Kyriakidis I.,Aristotle University of Thessaloniki | Papa A.,Aristotle University of Thessaloniki
Virus Research | Year: 2013

It is generally accepted that the pathogenesis of hantavirus infections is the result of virus-mediated host immune response. Hantaviruses, and mainly Dobrava-Belgrade virus, are present in Greece, and cause to humans hemorrhagic fever with renal syndrome (HFRS). Serum IL-6, IL-8, IL-10, TNF-α and sTNFR1 levels were measured in 29 HFRS Greek patients. Significant higher sTNFR1, IL-6, IL-8 and IL-10 levels were observed in severe than in mild/moderate cases, while TNF-α did not seem to be associated with disease severity. Correlations between cytokine levels and their fluctuation over time after onset of the illness, along with comparisons from previously published data on the field, led in building an immune response pattern for HFRS. © 2013 Elsevier B.V.

Demoulias C.,Aristotle University of Thessaloniki
Electric Power Systems Research | Year: 2010

A new simple analytical method for the calculation of the optimum inverter size in grid-connected PV plants in any location is presented. The derived analytical expressions contain only four unknown parameters, three of which are related to the inverter and one is related to the location and to the nominal power of the PV plant. All four parameters can be easily estimated from data provided by the inverter manufacturer and from freely available climate data. Additionally, analytical expressions for the calculation of the annual energy injected into the ac grid for a given PV plant with given inverter, are also provided. Moreover, an expression for the effective annual efficiency of an inverter is given. The analytical method presented here can be a valuable tool to design engineers for comparing different inverters without having to perform multiple simulations, as is the present situation. The validity of the proposed analytical model was tested through comparison with results obtained by detailed simulations and with measured data. © 2010 Elsevier B.V. All rights reserved.

Zotos E.E.,Aristotle University of Thessaloniki
Nonlinear Dynamics | Year: 2015

The escape dynamics in a simple analytical gravitational model which describes the motion of stars in a Seyfert galaxy is investigated in detail. We conduct a thorough numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion, we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points L1 and L2 and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the physical (x,y) and in the phase (x,x˙) space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the considered escape basins with the total orbital energy, with the remarkable presence of fractal basin boundaries along all the escape regimes. It was also observed that for energy levels close to the critical escape energy, the escape rates of orbits are large, while for much higher values of energy most of the orbits have low escape periods or they escape immediately to infinity. We also present evidence obtained through numerical simulations that our model can describe the formation and the evolution of the observed spiral structure in Seyfert galaxies. We hope our outcomes to be useful for a further understanding of the escape mechanism in galaxies with active nuclei. © 2015, Springer Science+Business Media Dordrecht.

Vogiatzis C.G.,Aristotle University of Thessaloniki | Zachariadis G.A.,Aristotle University of Thessaloniki
Analytica Chimica Acta | Year: 2014

Metallomics is a relatively new branch of omics with a growing interest. The study of metallomes is becoming more focused in certain metabolites and the screening of various categories of analytes using a robust analytical methodology is more than appealing. In this context, when dealing with the challenge of identifying a certain species or specify a particular molecular structure, tandem mass spectrometry (MS/MS) is a reliable tool. Moreover, MS/MS instrumentation is recommended in hyphenated chromatographic techniques with MS detection such as LC-MS, where primary molecular species suffer minor fragmentation (soft-ionization techniques). ICP-MS is widely used in metallomics with its main advantages being the provided high sensitivity and selectivity. Usually, analyzes utilize ICP-MS as the main detection. Its role in proteomics is significant as an alternating choice for protein and peptide quantifications.In this review, we discuss modern trends and applications of MS/MS in the important and growing field of metallomics. These reports concern the identification, characterization and determination of various metal species such as metalloproteins, metallo-DNA adducts, metal-labeled molecules and other metal binding biomolecules. Such assays also present new and interesting hyphenated instrumentation and novel sophisticated apparatus. In addition, we designate the role of ICP-MS in the mentioned contributions and in the same scope we highlight some general analytical strategies. © 2014 Elsevier B.V.

Gika H.G.,Aristotle University of Thessaloniki | Theodoridis G.A.,Aristotle University of Thessaloniki | Plumb R.S.,Imperial College London | Wilson I.D.,Imperial College London
Journal of Pharmaceutical and Biomedical Analysis | Year: 2014

Based on publication and citation numbers liquid chromatography (LC-MS) has become the major analytical technology in the field of global metabolite profiling. This dominance reflects significant investments from both the research community and instrument manufacturers. Here an overview of the approaches taken for LC-MS-based metabolomics research is given, describing critical steps in the realisation of such studies: study design and its needs, specific technological problems to be addressed and major obstacles in data treatment and biomarker identification. The current state of the art for LC-MS-based analysis in metabonomics/metabolomics is described including recent developments in liquid chromatography, mass spectrometry and data treatment as these are applied in metabolomics underlining the challenges, limitations and prospects for metabolomics research. Examples of the application of metabolite profiling in the life sciences focusing on disease biomarker discovery are highlighted. In addition, new developments and future prospects are described. © 2013 Elsevier B.V.

Malousi A.,Aristotle University of Thessaloniki | Kouidou S.,Aristotle University of Thessaloniki
Molecular Genetics and Genomics | Year: 2012

DNA methylation is presently accepted as a tentative regulatory parameter in splicing. Recently, we reported significant methylation differences among various exonic splicing-enhancing elements and alternative splicing events, based on CpG methylation data from the Human Epigenome Project for chromosomes 6, 20 and 22. Presently, using a different computational approach and the same database, we report: (a) significant increase of hypermethylation in intronic and exonic sequences close to acceptor sites, relative to overall introns and exons, respectively (1,973 CpGs examined); (b) frequent CpGs, mostly hypomethylated, in donors and infrequent CpGs mostly hypermethylated, in acceptors; and (c) hypermethylation in cassette exons which are occasionally spliced and have weaker average splicing potential, relative to constitutive exons (p < 0.0001). CpGs are hypomethylated in non-coding exons (only 16 % hypermethylation). Single-exon genes, similarly to first exons, frequently contain hypomethylated CpGs, while in internal and last exons CpGs are more frequently hypermethylated. Methylation is also more frequent in strange introns and splice sites processed by the minor spliceosome, e.g., ATAC, (p < 0.0001 in all cases), but not in sites of incomplete processing, e.g., retained introns or bleeding exons, (p = 0.706 and p = 0.313, respectively). Most Alus, which are known to contribute to transcript presentation, are heavily methylated, in contrast with other Alus, e.g., AluJo and mammalian interspersed repetitive elements which have been previously associated with alternative expression. These results elucidate the role of intragenic methylation in association with alternative splicing and facilitate the evaluation of genomic variations/polymorphisms and the development of tools for the prediction of alternative splicing events. © The Author(s) 2012.

Kyzas G.Z.,Aristotle University of Thessaloniki | Deliyanni E.A.,Aristotle University of Thessaloniki | Matis K.A.,Aristotle University of Thessaloniki
Journal of Chemical Technology and Biotechnology | Year: 2014

Graphene oxide, particularly as magnetic particles, has recently been used as an adsorbent for wastewater treatment in applications such as heavy metals separation (mercury, cadmium, copper, chromium, arsenic) and also organics (antibiotics, dyes, i.e. Reactive black 5, etc.). Selected examples will be given in the present review-mostly from the literature. The following themes are examined among others: the synthesis route (impregnation, co-precipitation), kinetics of adsorption, thermodynamics, isotherm studies and applications in comparison with other adsorbents. © 2013 Society of Chemical Industry.

Humaidan P.,The Fertility Clinic | Quartarolo J.,Schering | Papanikolaou E.G.,Aristotle University of Thessaloniki
Fertility and Sterility | Year: 2010

Objective: To reevaluate ovarian hyperstimulation syndrome (OHSS) prevention techniques and provide a classification system for grading OHSS and evidence-based treatment strategies for preventing OHSS. Design: A literature search was conducted in PubMed for articles published in the last 5 years using the keywords "controlled ovarian stimulation," "controlled ovarian hyperstimulation," "ovarian hyperstimulation syndrome," "OHSS," "prevention," "chorionic gonadotropin," "hCG," "GnRH agonist," "GnRH antagonist," "coasting," and "cryopreservation." We reviewed randomized controlled trials (RCTs), retrospective studies, pilot studies, case studies, reviews, and meta-analyses. Result(s): There is a shortage of large, prospective RCTs reporting OHSS prediction and prevention strategies. Our review showed that risk factors such as antral follicle count and baseline anti-Müllerian hormone level may identify women at high OHSS risk. Preventative strategies that appear highly effective at reducing or preventing OHSS include GnRH antagonist protocols and the use of GnRH agonists to trigger final oocyte maturation. Moreover, alternative therapies, such as dopamine receptor agonists (Cabergoline), have also emerged as potential new treatment modalities in the management of this disease. Conclusion(s): These findings suggest that current treatment guidelines should be updated to incorporate findings from recent literature that show that GnRH antagonist protocols consistently reduce OHSS and that GnRH agonist triggering has considerable promise in preventing OHSS, although further RCTs will be needed to confirm this. © 2010 American Society for Reproductive Medicine.

Karageorgou E.,Aristotle University of Thessaloniki | Samanidou V.,Aristotle University of Thessaloniki
Journal of Chromatography A | Year: 2014

Analytical method validation is a vital step following method development for ensuring reliable and accurate method performance. Among examined figures of merit, robustness/ruggedness study allows us to test performance characteristics of the analytical process when operating conditions are altered either deliberately or not. This study yields useful information, being a fundamental part of method validation. Since many experiments are required, this step is high demanding in time and consumables. In order to avoid the difficult task of performing too many experiments the Youden test which makes use of fractional factorial designs and has been proved to be a very effective approach. The main advantage of Youden test is the fact that it keeps the required time and effort to a minimum, since only a limited number of determinations have to be made, using combinations of the chosen investigated factors. Typical applications of this robustness test found in literature covering a wide variety of sample matrices are briefly discussed in this review. © 2014 Elsevier B.V.

Samaras I.K.,Aristotle University of Thessaloniki | Hassapis G.D.,Aristotle University of Thessaloniki | Gialelis J.V.,University of Patras | Gialelis J.V.,Industrial Systems Institute
IEEE Transactions on Industrial Informatics | Year: 2013

In this paper, a modification of the protocol stack of the device profile for web services (DPWS) is proposed which can be applied in wireless sensor networks (WSNs) that comply with the IPv6 over low-power wireless personal area networks (6LoWPAN) architecture. The modification is based on a new format for the DPWS message exchanges without prohibiting the usage of the web services (WS) and the extensible markup language (XML) set of rules. The modified DPWS was implemented on the SunSPOT wireless sensor mote (WSM) and it was observed that it processes XML documents with a mean computation time less by 53% than the respective computation time of the DPWS while it consumes less EEPROM and RAM by 84% and 85%, respectively. Furthermore, its network performance was assessed by testing it over a real 6LoWPAN-based WSN with its maximum number of WSMs being 12. In order to validate these results and extend them to larger-scale 6LoWPAN-based WSNs, the network simulator 2 (NS-2) was used by enhancing it with a developed 6LoWPAN object. The NS-2 was also utilized for comparing the modified DPWS, the DPWS and a binary-based DPWS in terms of packet delivery ratio and maximum transmission delay. Simulation results have shown that the modified DPWS presents better performance than the DPWS and offers inferior results only when it is compared with the binary-based DPWS which, however, does not retain the WSs interoperability feature as it does not use XML documents. © 2005-2012 IEEE.

Panayiotou C.,Aristotle University of Thessaloniki
Physical Chemistry Chemical Physics | Year: 2012

The present work reconsiders a classical and universally accepted concept of physical chemistry, the solubility parameter. Based on the insight derived from modern quantum chemical calculations, a new definition of solubility parameter is proposed, which overcomes some of the inherent restrictions of the original definition and expands its range of applications. The original single solubility parameter is replaced by four partial solvation parameters reflecting the dispersion, the polar, the acidic and the basic character of the chemical compounds as expressed either in their pure state or in mixtures. Simple rules are adopted for the definition and calculation of these four parameters and their values are tabulated for a variety of common substances. In contrast, however, to the well known Hansen solubility parameters, their design and evaluation does not rely exclusively on the basic rule of "similarity matching" for solubility but it makes also use of the other basic rule of compatibility, namely, the rule of "complementarity matching". This complementarity matching becomes particularly operational with the sound definition of the acidic and basic components of the solvation parameter based on the third σ-moments of the screening charge distributions of the quantum mechanics-based COSMO-RS theory. The new definitions are made in a simple and straightforward manner, thus, preserving the strength and appeal of solubility parameter stemming from its simplicity. The new predictive method has been applied to a variety of solubility data for systems of pharmaceuticals and polymers. The results from quantum mechanics calculations are critically compared with the results from Abraham's acid/base descriptors. © 2011 The Owner Societies.

Triantafyllidis K.S.,Aristotle University of Thessaloniki | Deliyanni E.A.,Aristotle University of Thessaloniki
Chemical Engineering Journal | Year: 2014

Adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from solutions in hexadecane was investigated on three commercial nanoporous activated carbons of different origin and nature, which possessed either microporous or combined micro/mesoporous structures, and their oxidized counterparts. The initial and exhausted carbons were characterized using the nitrogen porosimetry at 77. K, thermal analysis, Boehm titration, and FTIR. The capacity for 4,6-DMDBT removal increases with an increase in the volume of pores with size similar to that of 4,6-DMDBT molecules, which is about 6. Å. Functional groups present on the surface of larger pores contribute to adsorption via polar interactions. © 2013 Elsevier B.V.

Iosifidis A.,Aristotle University of Thessaloniki | Tefas A.,Aristotle University of Thessaloniki | Pitas I.,Aristotle University of Thessaloniki
Signal Processing | Year: 2013

In this paper, we present a view-independent action recognition method exploiting a low computational-cost volumetric action representation. Binary images depicting the human body during action execution are accumulated in order to produce the so-called action volumes. A novel time-invariant action representation is obtained by exploiting the circular shift invariance property of the magnitudes of the Discrete Fourier Transform coefficients. The similarity of an action volume with representative action volumes is exploited in order to map it to a lower-dimensional feature space that preserves the action class properties. Discriminant learning is, subsequently, employed for further dimensionality reduction and action class discrimination. By using such an action representation, the proposed approach performs fast action recognition. By combining action recognition results coming from different view angles, high recognition rates are obtained. The proposed method is extended to interaction recognition, i.e., to human action recognition involving two persons. The proposed approach is evaluated on a publicly available action recognition database using experimental settings simulating situations that may appear in real-life applications, as well as on a new nutrition support action recognition database. © 2012 Elsevier B.V.

Papadopoulos K.G.,ABB | Papastefanaki E.N.,Intracom | Margaris N.I.,Aristotle University of Thessaloniki
IEEE Transactions on Industrial Electronics | Year: 2013

The problem of designing PID type-III control loops is investigated. On a theoretical basis and if frequency domain modeling of the control loop is followed, type-III control loops are characterized by the presence of three pure integrators in the open-loop transfer function. Therefore, such a control scheme has the advantage of tracking fast reference signals since it exhibits zero steady-state position, velocity, and acceleration error. This advantage is considered critical in many industry applications, i.e., control of electrical motor drives and control of power converters, since it allows the output variable, i.e., current or speed, to track perfectly step, ramp, and parabolic reference signals. The proposed PID control law has the following characteristics: 1) it consists of analytical expressions that involve all modeled process parameters; 2) it can be straightforwardly applied to any process regardless of its complexity since, for its development, a generalized transfer function process model is employed consisting of n poles and m zeros plus unknown time delay d; and 3) it allows for accurate investigation of the performance of the control action to exogenous and internal disturbances in the control loop and investigation of different operating points. For justifying the potential of the proposed control law, several examples of process models met in many industry applications are investigated. © 1982-2012 IEEE.

Stefanidou M.,Aristotle University of Thessaloniki
Revista Romana de Materiale/ Romanian Journal of Materials | Year: 2013

Repair mortars based on lime known as "traditional" mortars have been applied the last decades in monuments and historic buildings as the best solution in terms of compatibility. However, problems of durability have been arising due to their weak structure and easy fracture pattern. In order to improve their durability, the new developed tools of nanotechnology are tested in order to strengthen the structure of repair mortars and restrict the durability problems. In the present work, nano-SiO2 of approximately 14nm in diameter is added in lime- natural pozzolana binders, which are the most common used binders of the "traditional" mortars, in different percentages in order to study the micro and nano structure of the produced pastes using Scanning and Transmission Electron Microscopy. Additionally, their mechanical and physical properties are tested from 3 up to the age of 28 days. From the study derives that nano-modified limepozzolana binders have a dense structure with reduced large pores and increased strength. Additionally, the catalytic role of nano-particles to crystal formation is confirmed.

Andreou E.,Aristotle University of Thessaloniki
Renewable Energy | Year: 2014

The paper presents the results of shading analysis which was carried out as part of a wider comparative analysis of two sites with different characteristics in terms of street geometry and urban density. The first experiment site was a traditional settlement in the island of Tinos, Greece, and the second was a relatively newly built part of the capital city of the island. Also a parametric shading analysis was carried out in order to examine a number of parameters that influence shading conditions in urban canyons.The paper aims in analyzing the effect of parameters such as urban layout, street geometry and orientation on solar access and shading conditions, which strongly affect urban canyon microclimate. The results of shading simulations are compared to the results of experimental measurements of air and surface temperatures and to parametric thermal analysis results. The conclusions can contribute in the formulation of urban design guidelines. © 2013 Elsevier Ltd.

Taplidou S.A.,Aristotle University of Thessaloniki | Hadjileontiadis L.J.,Aristotle University of Thessaloniki
IEEE Transactions on Biomedical Engineering | Year: 2010

Wheezes are musical breath sounds, which usually imply an existing pulmonary obstruction, such as asthma and chronic obstructive pulmonary disease (COPD). Although many studies have addressed the problem of wheeze detection, a limited number of scientific works has focused in the analysis of wheeze characteristics, and in particular, their time-varying nonlinear characteristics. In this study, an effort is made to reveal and statistically analyze the nonlinear characteristics of wheezes and their evolution over time, as they are reflected in the quadratic phase coupling of their harmonics. To this end, the continuous wavelet transform (CWT) is used in combination with third-order spectra to define the analysis domain, where the nonlinear interactions of the harmonics of wheezes and their time variations are revealed by incorporating instantaneous wavelet bispectrum and bicoherence, which provide with the instantaneous biamplitude and biphase curves. Based on this nonlinear information pool, a set of 23 features is proposed for the nonlinear analysis of wheezes. Two complementary perspectives, i.e., general and detailed, related to average performance and to localities, respectively, were used in the construction of the feature set, in order to embed trends and local behaviors, respectively, seen in the nonlinear interaction of the harmonic elements of wheezes over time. The proposed feature set was evaluated on a dataset of wheezes, acquired from adult patients with diagnosed asthma and COPD from a lung sound database. The statistical evaluation of the feature set revealed discrimination ability between the two pathologies for all data subgroupings. In particular, when the total breathing cycle was examined, all 23 features, but one, showed statistically significant difference between the COPD and asthma pathologies, whereas for the subgroupings of inspiratory and expiratory phases, 18 out of 23 and 22 out of 23 features exhibited discrimination power, respectively. This paves the way for the use of the wavelet higher order spectral features as an input vector to an efficient classifier. Apparently, this would integrate the intrinsic characteristics of wheezes within computerized diagnostic tools toward their more efficient evaluation. © 2006 IEEE.

Mavromatis T.,Aristotle University of Thessaloniki
Agricultural Systems | Year: 2016

The present study aims at forecasting hard wheat (Triticum turgidum L. var. durum) yield at seven prediction dates (planting and six 30-day intervals after planting) prior to harvest in northern Greece. It is based on (a) reported crop yields at two relatively high spatial resolution regional levels (three NUTS2 (Nomenclature of Units for Territorial Statistics) and 16 NUTS3 regions) and (b) crop agroclimatic indicators simulated with CERES-Wheat, at four planting dates, for the years 1979-2006. Principal component analysis (PCA) was applied to explore major patterns of joint variability in a number of simulated crop agroclimatic indicators at the selected prediction dates during growing season. Stepwise regression and hindcast were employed for the selection of the modes identified by PCA as predictors in multivariate linear models used for yield forecast. Yield forecasting skill varied to a large extent by the spatial scale, planting date and timing of forecast. When the simulation results were aggregated to the larger spatial level (NUTS2), the cross-validated forecasting skill was rated as moderate in Central Macedonia (CM) (R2=43%) and Thrace (THR) (R2=35.9%) and as low in West Macedonia (WM) (R2=21.5%). Soil water availability to plants was the most important indicator. Except for THR, these forecasts were achieved three months before harvest in CM and four in WM. Compared with the NUTS2 level, yield predictions at the higher resolution spatial level (NUTS3) worsened in 11 and 12 out of 16 NUTS3 regions in terms of R2 and RMSE, respectively. The results demonstrate the potential of this approach and the suitability of CERES-Wheat for regional crop yield forecasting in northern Greece. © 2015 Elsevier B.V.

Pagonis V.,McDaniel College | Kitis G.,Aristotle University of Thessaloniki
Physica Status Solidi (B) Basic Research | Year: 2012

Typical materials used in thermoluminescence (TL) dosimetry exhibit the following common characteristics: (i) the temperature of glow peak maximum of individual glow peaks remains practically constant over a wide dose range, (ii) there are no systematic changes in the glow curve shapes with the irradiation dose, and (iii) higher order kinetics is rarely seen in dosimetric materials, while first-order kinetics is a common occurrence in experimental TL work. Theoretical explanation of these experimental characteristics is an open topic of TL research. In the present work these three characteristics are studied by using several models of increasing complexity. The simplest model studied is based on the empirical analytical general order (GO) expressions, followed by two commonly used models, the well-known one trap one recombination center models (OTOR) and the interactive multiple trap system (IMTS). Previous researchers have studied the behavior of these models using arbitrary values of the kinetic parameters in the models, and by varying these parameters within limited physically reasonable ranges. In this paper, a new method of analyzing the results from such models is presented, in which the average behavior of real dosimetric materials is simulated by allowing simultaneous random variations of the kinetic parameters, within several orders of magnitude. The simulation results lead to the conclusion that the presence of many competitive processes during the heating stage of TL, may be correlated to the remarkable stability of the glow curve shapes exhibited by most materials, and to the prevalence of first-order kinetics. This correlation is demonstrated further by a series of simulations in which the number of competitor traps is increased systematically, by adding up to 12 competitor traps in the IMTS model. As the number of competitor traps increases, the average behavior of the TL glow curves tends progressively toward first-order kinetics, and this in turn results in very small average variations in the shape of the TL glow peak. The simulation results in this paper provide a convincing demonstration and explanation of the stability of the shape of TL glow curves in dosimetric materials, and for the prevalence of first-order kinetics in TL. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boboridis K.G.,Aristotle University of Thessaloniki
Pediatric endocrinology reviews : PER | Year: 2010

Thyroid eye disease manifests as orbital inflammation resulting in extraocular muscle enlargement and orbital fat proliferation. This causes exophthalmos, ocular motility impairment and eyelid retraction. Numerous surgical procedures have been introduced for correction of exophthalmos by removal of bony walls. The limited success and high complication rate of the early methods lead to the evolution of an alternative procedure for reduction of retrobulbar volume by removal of intraorbital fat. The indications for this procedure extended from orbital decompression to compressive optic neuropathy with satisfactory results. The moderate complication rate and the fact that orbits with predominant muscle enlargement respond purely to this technique leads to the evolution of a combined procedure with orbital fat removal and bony wall decompression. The scattered published evidence comprising retrospective case series highlights the need for prospective controlled clinical trials in order to improve patient care and clinical practice.

Tsolaki M.,Aristotle University of Thessaloniki
European Journal of Clinical Nutrition | Year: 2014

Aging is the major risk factor for the development of human neurodegenerative maladies such as Alzheimer's, Huntington's and Parkinson's diseases (PDs) and prion disorders, all of which stem from toxic protein aggregation. All of these diseases are correlated with cognitive decline. Cognitive Decline is a dynamic state from normal cognition of aging to dementia. According to the original criteria for Alzheimer's Disease (AD) (1984), a clinical diagnosis was possible only when someone was already demented. The prevalence rates of Cognitive Decline (mild cognitive impairment plus dementia) are very high now and will be higher in future because of the increasing survival time of people. Many neurological and psychiatric diseases are correlated with cognitive decline. Diagnosis of cognitive decline is mostly clinical (clinical criteria), but there are multiple biomarkers that could help us mostly in research programs such as short or long, paper and pencil or computerized neuropsychological batteries for cognition, activities of daily living and behavior, electroencephalograph, event-related potentials, and imaging-structural magnetic resonance imaging (MRI) and functional (fMRI, Pittsburgh bound positron emission tomography, FDG-PET, single photon emission computerized tomography and imaging of tau pathology)-cerebrospinal fluid proteins (Abeta, tau and phospho-tau in AD and -synuclein (Syn) for PD). Blood biomarkers need more studies to confirm their usefulness. Genetic markers are also studied but until now are not used in clinical praxis. Finally, in everyday clinical praxis and in research workout for early detection of cognitive decline, the combination of biomarkers is useful. © 2014 Macmillan Publishers Limited.

Valla V.,Aristotle University of Thessaloniki
Experimental diabetes research | Year: 2010

AIM: Inadequately controlled diabetes accounts for chronic complications and increases mortality. Its therapeutic management aims in normal HbA1C, prandial and postprandial glucose levels. This review discusses diabetes management focusing on the latest insulin analogues, alternative insulin delivery systems and the artificial pancreas. RESULTS: Intensive insulin therapy with multiple daily injections (MDI) allows better imitation of the physiological rhythm of insulin secretion. Longer-acting, basal insulin analogues provide concomitant improvements in safety, efficacy and variability of glycaemic control, followed by low risks of hypoglycaemia. Continuous subcutaneous insulin infusion (CSII) provides long-term glycaemic control especially in type 1 diabetic patients, while reducing hypoglycaemic episodes and glycaemic variability. Continuous subcutaneous glucose monitoring (CGM) systems provide information on postprandial glucose excursions and nocturnal hypo- and/or hyperglycemias. This information enhances treatment options, provides a useful tool for self-monitoring and allows safer achievement of treatment targets. In the absence of a cure-like pancreas or islets transplants, artificial "closed-loop" systems mimicking the pancreatic activity have been also developed. CONCLUSIONS: Individualized treatment plans for insulin initiation and administration mode are critical in achieving target glycaemic levels. Progress in these fields is expected to facilitate and improve the quality of life of diabetic patients.

Luneski A.,Aristotle University of Thessaloniki
Methods of information in medicine | Year: 2010

BACKGROUND: Affective computing (AC) is concerned with emotional interactions performed with and through computers. It is defined as "computing that relates to, arises from, or deliberately influences emotions". AC enables investigation and understanding of the relation between human emotions and health as well as application of assistive and useful technologies in the medical domain. OBJECTIVES: 1) To review the general state of the art in AC and its applications in medicine, and 2) to establish synergies between the research communities of AC and medical informatics. METHODS: Aspects related to the human affective state as a determinant of the human health are discussed, coupled with an illustration of significant AC research and related literature output. Moreover, affective communication channels are described and their range of application fields is explored through illustrative examples. RESULTS: The presented conferences, European research projects and research publications illustrate the recent increase of interest in the AC area by the medical community. Tele-home healthcare, AmI, ubiquitous monitoring, e-learning and virtual communities with emotionally expressive characters for elderly or impaired people are few areas where the potential of AC has been realized and applications have emerged. CONCLUSIONS: A number of gaps can potentially be overcome through the synergy of AC and medical informatics. The application of AC technologies parallels the advancement of the existing state of the art and the introduction of new methods. The amount of work and projects reviewed in this paper witness an ambitious and optimistic synergetic future of the affective medicine field.

Despite the great commercial and economic importance of mussels, Mytilus galloprovincialis (Bivalvia, Mollusca) in Greece, little information is available concerning their population genetic structure. We used RAPD markers to examine genetic differentiation and potential impact of aquaculture practices and other anthropogenic activities on the genetic structure of two cultivated and eight wild mussel populations collected from one Turkish and nine Greek coast sites. Five random decamer primers were chosen, among 34 tested, for the analysis of 433 individuals. Eighty-eight bands (genetic loci) were scored, all of which were polymorphic. No indication of reduced genetic variability was observed in the cultured populations. In contrast, a loss in genetic diversity was observed in populations from two localities (Canakkale and Kalochori) that are heavily polluted by chemical contaminants. FST analyses and exact tests revealed significant heterogeneity among M. galloprovincialis population samples, although their genetic divergence seemed to be independent of geographic distances. Anthropogenic activities, i.e., marine pollution and transplantation of mussels, appear to have played an important role in shaping patterns of genetic diversity and differentiation among Greek M. galloprovincialis populations.

Siskos S.,Aristotle University of Thessaloniki
Proceedings - IEEE Annual Symposium on VLSI, ISVLSI 2010 | Year: 2010

A simple current mirror using floating-gate MOS transistors (FGMOS) operating in the linear region is used in this work, to design a built-in current sensor (BICS). The important feature in this application is that the voltage drop across the sensing device can be reduced to almost zero value (less than 50 mV). This makes the proposed BICS appropriate for modern very low supply voltage applications. The proposed BICS in conjunction with an RMS-to-DC converter and a novel current window comparator can be used to efficiently achieve supply current monitoring of analog and mixed-signal circuit testing. © 2010 IEEE.

Erdman S.E.,Massachusetts Institute of Technology | Poutahidis T.,Aristotle University of Thessaloniki
Toxicologic Pathology | Year: 2010

Risk for developing cancer rises substantially as a result of poorly regulated inflammatory responses to pathogenic bacterial infections. Anti-inflammatory CD4+ regulatory cells (TREG) function to restore immune homeostasis during chronic inflammatory disorders. It seems logical that TREG cells would function to reduce risk of inflammation-associated cancer in the bowel by down-regulating inflammation. It is widely believed, however, that TREG function in cancer mainly to suppress protective anticancer inflammatory responses. Thus roles for inflammation, TREG cells, and gut bacteria in cancer are paradoxical and are the subject of controversy. Our accumulated data build upon the "hygiene hypothesis" model in which gastrointestinal (GI) infections lead to changes in TREG that reduce inflammation-associated diseases. Ability of TREG to inhibit or suppress cancer depends upon gut bacteria and IL-10, which serve to maintain immune balance and a protective anti-inflammatory TREG phenotype. However, under poorly regulated pro-inflammatory conditions, TREG fail to inhibit and may instead contribute to a T helper (Th)-17-driven procarcinogenic process, a cancer state that is reversible by down-regulation of inflammation and interleukin (IL)-6. Consequently, hygienic individuals with a weakened IL-10-and TREG-mediated inhibitory loop are highly susceptible to the carcinogenic consequences of elevated inflammation and show more frequent inflammation-associated cancers. Taken together, these data help explain the paradox of inflammation and T REG in cancer and indicate that targeted stimulation of T REG may promote health and significantly reduce risk of cancer. Copyright © 2010 by The Author(s).

Damalas C.A.,Democritus University of Thrace | Eleftherohorinos I.G.,Aristotle University of Thessaloniki
International Journal of Environmental Research and Public Health | Year: 2011

Pesticides are widely used in agricultural production to prevent or control pests, diseases, weeds, and other plant pathogens in an effort to reduce or eliminate yield losses and maintain high product quality. Although pesticides are developed through very strict regulation processes to function with reasonable certainty and minimal impact on human health and the environment, serious concerns have been raised about health risks resulting from occupational exposure and from residues in food and drinking water. Occupational exposure to pesticides often occurs in the case of agricultural workers in open fields and greenhouses, workers in the pesticide industry, and exterminators of house pests. Exposure of the general population to pesticides occurs primarily through eating food and drinking water contaminated with pesticide residues, whereas substantial exposure can also occur in or around the home. Regarding the adverse effects on the environment (water, soil and air contamination from leaching, runoff, and spray drift, as well as the detrimental effects on wildlife, fish, plants, and other non-target organisms), many of these effects depend on the toxicity of the pesticide, the measures taken during its application, the dosage applied, the adsorption on soil colloids, the weather conditions prevailing after application, and how long the pesticide persists in the environment. Therefore, the risk assessment of the impact of pesticides either on human health or on the environment is not an easy and particularly accurate process because of differences in the periods and levels of exposure, the types of pesticides used (regarding toxicity and persistence), and the environmental characteristics of the areas where pesticides are usually applied. Also, the number of the criteria used and the method of their implementation to assess the adverse effects of pesticides on human health could affect risk assessment and would possibly affect the characterization of the already approved pesticides and the approval of the new compounds in the near future. Thus, new tools or techniques with greater reliability than those already existing are needed to predict the potential hazards of pesticides and thus contribute to reduction of the adverse effects on human health and the environment. On the other hand, the implementation of alternative cropping systems that are less dependent on pesticides, the development of new pesticides with novel modes of action and improved safety profiles, and the improvement of the already used pesticide formulations towards safer formulations (e.g., microcapsule suspensions) could reduce the adverse effects of farming and particularly the toxic effects of pesticides. In addition, the use of appropriate and well-maintained spraying equipment along with taking all precautions that are required in all stages of pesticide handling could minimize human exposure to pesticides and their potential adverse effects on the environment. © 2011 by the authors.

Aryal M.,Aristotle University of Thessaloniki | Liakopoulou-Kyriakides M.,Aristotle University of Thessaloniki
Environmental monitoring and assessment | Year: 2015

Heavy metals are among the most common pollutants found in the environment. Health problems due to the heavy metal pollution become a major concern throughout the world, and therefore, various treatment technologies such as reverse osmosis, ion exchange, solvent extraction, chemical precipitation, and adsorption are adopted to reduce or eliminate their concentration in the environment. Biosorption is a cost-effective and environmental friendly technique, and it can be used for detoxification of heavy metals in industrial effluents as an alternative treatment technology. Biosorption characteristics of various bacterial species are reviewed here with respect to the results reported so far. The role of physical, chemical, and biological modification of bacterial cells for heavy metal removal is presented. The paper evaluates the different kinetic, equilibrium, and thermodynamic models used in bacterial sorption of heavy metals. Biomass characterization and sorption mechanisms as well as elution of metal ions and regeneration of biomass are also discussed.

Nicolaidis A.,Aristotle University of Thessaloniki
Journal of Cosmology and Astroparticle Physics | Year: 2010

We study the photon axion mixing in the presence of large extra dimensions. The eigenvalues and eigenstates of the mixing matrix are analyzed and we establish the resonance condition for the total conversion of a high energy photon into a Kaluza-Klein (KK) axion state. This resonant transition, a photon transformed into a KK axion traveling freely through the bulk and converting back into a photon, may provide a plausible explanation for the transparency of the universe to energetic photons. If the brane we live in is curved, then there are shortcuts through the bulk, which the axion can take. Within our model, the photons having the appropriate resonance energy are using the axionic shortcut and arrive earlier compared to the photons which follow the geodesic on the brane. We suggest that such axionic shortcuts are at the root of the dispersion of time arrival of photons observed by the MAGIC telescope. We indicate also the cosmological significance of the existence of axionic shortcuts for the photon. © 2010 IOP Publishing Ltd and SISSA.

Meimaroglou D.,Aristotle University of Thessaloniki | Kiparissides C.,Aristotle University of Thessaloniki
Macromolecules | Year: 2010

A novel stochastic algorithm isdescribed for the accurate prediction of the detailed molecular topology of highly branched polymer chains. Stochastic topological polymer chain simulations are carried out in conjunction with a polymerization kinetic MC simulator. Contrary to previous efforts on the stochastic simulation of topological features of branched polymer chains, the present approach does not apply any simplifying assumptions regarding the distributional form of "live" and "dead" polymer chain populations. The proposed stochastic approach takes explicitly into account the effects of various diffusional limitations in the termination and propagation rate constants (i.e., gel-and glass-effect) as well as the effect of branching density on the kinetics of various reactions (i.e., transfer to polymer and chain scission reactions). To demonstrate the predictive capabilities of the proposed stochastic approach, the free-radical polymerization of ethylene in an industrial high-pressure tubular reactor is investigated. It is shown that the present stochastic kinetic/topology algorithm can provide detailed information on the topological features of highly branched polymer chains (i.e, long-and short-chain branching distributions, segment seniority and priority distributions, etc.). The topological information, obtained by the application of the stochastic kinetic/topology algorithm, is then used together with a 3-D molecular random-walk simulator to predict the 3-D random spatial configurations of branched polymer chains as well as some important rheological parameters (i.e., the mean radius of gyration, Rg, the mean hydrodynamic radius, Rh, and the average branching factor, g) of low-density polyethylene. © 2010 American Chemical Society.

Kyzas G.Z.,Aristotle University of Thessaloniki | Kostoglou M.,Aristotle University of Thessaloniki | Lazaridis N.K.,Aristotle University of Thessaloniki
Langmuir | Year: 2010

The scope of the present work is the study of the adsorption behavior of two dyes of different nature/class on several chitosan derivatives. The adsorbents used were grafted with different functional groups (carboxyl, amido, sulfonate, N-vinylimidazole) to increase their adsorption capacity and cross-linked to improve their mechanical resistance. This complete kinetic analysis was realized at 25,45, and 65 °C to observe the effect of temperature on adsorption rates for each adsorbent-adsórbate system. Activated carbon was also used as an adsorbent for reference/comparison. The experimental equilibrium data were successfully fitted to the Langmuir-Freundlich (L-F) isotherms, presenting high correlation coefficients (R2 ~ 0.998). A detailed pore-surface diffusion with local adsorption-desorption model has been developed to describe the adsorption kinetics in chitosan adsorbents. The existence of kinetic data in several temperatures assists in recognizing the diffusion mechanism in the adsorbent particles. The findings on diffusion mechanisms and the corresponding coefficients, from using the model to match the experimental data, are compatible with the expected adsorbent-dye interactions based on their chemical structure. © 2010 American Chemical Society.

Oikonomou V.K.,Aristotle University of Thessaloniki
Astrophysics and Space Science | Year: 2015

As is known, in modified cosmological theories of gravity many of the cosmologies which could not be generated by standard Einstein gravity, can be consistently described by (Formula presented.) theories. Using known reconstruction techniques, we investigate which (Formula presented.) theories can lead to a Hubble parameter describing two types of cosmological bounces, the superbounce model, related to supergravity and non-supersymmetric models of contracting ekpyrosis and also the Loop Quantum Cosmology modified ekpyrotic model. Since our method is an approximate method, we investigate the problem at large and small curvatures. As we evince, both models yield power law reconstructed (Formula presented.) gravities, with the most interesting new feature being that both lead to accelerating cosmologies, in the large curvature approximation. The mathematical properties of the some Friedmann-Robertson-Walker spacetimes (Formula presented.), that describe superbounce-like cosmologies are also pointed out, with regards to the group of curvature collineations (Formula presented.). © 2015, Springer Science+Business Media Dordrecht.

Zotos E.E.,Aristotle University of Thessaloniki
Astrophysics and Space Science | Year: 2015

We numerically investigate the orbital dynamics of a spacecraft, or a comet, or an asteroid in the Pluto-Charon system in a scattering region around Charon using the planar circular restricted three-body problem. The test particle can move in bounded orbits around Charon or escape through the necks around the Lagrangian points L1 and L2 or even collide with the surface of Charon. We explore four of the five possible Hill’s regions configurations depending on the value of the Jacobi constant which is of course related with the total orbital energy. We conduct a thorough numerical analysis on the phase space mixing by classifying initial conditions of orbits and distinguishing between three types of motion: (i) bounded, (ii) escaping and (iii) collisional. In particular, we locate the different basins and we relate them with the corresponding spatial distributions of the escape and collision times. Our results reveal the high complexity of this planetary system. Furthermore, the numerical analysis shows a strong dependence of the properties of the considered basins with the total orbital energy, with a remarkable presence of fractal basin boundaries along all the regimes. Our results are compared with earlier ones regarding the Saturn-Titan planetary system. © 2015, Springer Science+Business Media Dordrecht.

Kyzas G.Z.,Aristotle University of Thessaloniki | Bikiaris D.N.,Aristotle University of Thessaloniki
Marine Drugs | Year: 2015

Chitosan is considered to be one of the most promising and applicable materials in adsorption applications. The existence of amino and hydroxyl groups in its molecules contributes to many possible adsorption interactions between chitosan and pollutants (dyes, metals, ions, phenols, pharmaceuticals/drugs, pesticides, herbicides, etc.). These functional groups can help in establishing positions for modification. Based on the learning from previously published works in literature, researchers have achieved a modification of chitosan with a number of different functional groups. This work summarizes the published works of the last three years (2012-2014) regarding the modification reactions of chitosans (grafting, cross-linking, etc.) and their application to adsorption of different environmental pollutants (in liquid-phase). © 2015 by the authors licensee MDPI Basel Switzerland.

Papa A.,Aristotle University of Thessaloniki | Xanthopoulou K.,Aristotle University of Thessaloniki | Gewehr S.,Eco Development | Mourelatos S.,Eco Development
Clinical Microbiology and Infection | Year: 2011

A human outbreak of West Nile virus (WNV) infections occurred in 2010 in central Macedonia, northern Greece. Most cases were observed close to four rivers forming a large Delta, a major Mediterranean wetland. WNV lineage 2 sequences were obtained from two pools of Culex pipiens mosquitoes trapped in sites where encephalitis cases occurred a few days before the trapping. The Greek strain showed the highest homology to Hungarian and South African strains, differing from the Russian WNV lineage 2 strain, which suggests that at least two lineage 2 strains have been introduced and established in Europe, causing severe disease to humans. © 2011 European Society of Clinical Microbiology and Infectious Diseases.

Kostoglou M.,Aristotle University of Thessaloniki | Karabelas A.J.,Center for Research and Technology Hellas
Journal of Colloid and Interface Science | Year: 2011

Modeling incipient crystallization (" scaling" ) in desalination membrane modules is a very difficult task due to several complications arising from the interplay of physico-chemical solution conditions (leading to supersaturation) with the flow field and related transport processes, including solid phase generation phenomena and membrane surface geometrical changes caused by the developing discrete particles. Although eventually all these aspects must be included in a comprehensive process model, it is fruitful to isolate and tackle them separately, thereby improving our understanding and developing techniques which will facilitate the ensuing synthesis of an integrated modeling framework. The focus in this work is on solid phase generation phenomena accounting for the membrane surface geometrical changes. A mean field model is developed that includes bulk and surface particle nucleation and growth processes. The relative importance of the two types of processes is analyzed. It is shown that, if thick concentration boundary layers exist around surface particles, the mean field theory-although not strictly valid-can be approximately used to estimate the transport coefficients, in conjunction with a unit cell problem for transport processes around a single surface particle. The unit cell problem is formulated and typical results for the flow and concentration field therein are presented as well as the corresponding mass transfer coefficients. © 2011 Elsevier Inc.

Kostoglou M.,Aristotle University of Thessaloniki | Karapantsios T.D.,Aristotle University of Thessaloniki
Advances in Colloid and Interface Science | Year: 2015

The term liquid bridge refers to the specific silhouette of a liquid volume when it is placed between two solid surfaces. Liquid bridges have been studied extensively both theoretically and experimentally during the last century due to their significance in many technological applications. It is worth noticing that even today new technological applications based on liquid bridges continue to appear. A liquid bridge has a well-defined surface configuration dictated by a rigid theoretical foundation so the potential of its utilization as a tool to study surface properties of liquids is apparent. However, it is very scarce in literature that the use of liquid bridges is suggested as an alternative to the well-established drop techniques (pendant/sessile drop). The present work (i) presents the theoretical background for setting up a liquid-bridge based surface property estimation problem, (ii) describes the required experimental equipment and procedures and (iii) performs a thorough literature review on the subject. A case with particular interest is that of liquid bridges made of electrically conducting liquids forming between two conducting solids; such a liquid bridge presents an integral electrical conductance value which is sensitive to the specific silhouette of the bridge. This enables the use of this integral conductance as shape descriptor instead of the conventional image processing techniques. Several attempts in literature for the estimation of liquid surface tension, liquid-solid contact angle and surfactant induced surface elasticity for conducting or non/conducting liquids are presented and the prospects of the technique are discussed. © 2014 Elsevier B.V. All rights reserved.

Manoukas G.,Aristotle University of Thessaloniki | Athanatopoulou A.,Aristotle University of Thessaloniki | Avramidis I.,Aristotle University of Thessaloniki
Earthquake Spectra | Year: 2011

In this paper, a new energy-based pushover procedure is presented in order to achieve an approximate estimation of structural performance under strong earthquakes. The steps of the proposed methodology are quite similar to those of the well-known displacement modification method. However, the determination of the characteristics of the equivalent single-degree-of-freedom (E-SDOF) system is based on a different rational concept. Its main idea is to determine the E-SDOF system by equating the external work of the lateral loads acting on the multi-degree-of-freedom (MDOF) system under consideration to the strain energy of the E-SDOF system. After a brief outline of the theoretical background, a representative numerical example is given. Finally, the accuracy of the proposed method is evaluated by an extensive parametric study which shows that, in general, it provides better results compared to those produced by other similar procedures. © 2011, Earthquake Engineering Research Institute.

Thermou G.E.,Aristotle University of Thessaloniki | Pantazopoulou S.J.,Democritus University of Thrace
Earthquake Engineering and Structural Dynamics | Year: 2011

The seismic vulnerability of old multi-storey reinforced concrete (R.C.) buildings reinforced with substandard details is assessed as a function of interstorey drift demand imposed by the design earthquake while considering brittle termination of elastic response of the critical members of the structure due to a premature shear failure. Interstorey drift demand is related to column and wall translational stiffnesses which are expressed through analytical derivations in terms of the floor area ratios of gravity and lateral load bearing members in the critical floor. Interstorey drift capacity is related to the available transverse reinforcement and the axial load ratio of the vertical members. The significance of the area ratio of vertical members in the typical floor as an index of vulnerability is explored with reference to the limitations in the value of axial load ratio used in R.C. design in order to secure ductile flexural behavior, and also with reference to the stability index of gravity load bearing members. Interstorey Drift Spectra are derived for the existing R.C. buildings suitable for rapid seismic vulnerability screening but also as a guide for rehabilitation of the existing structures. Lightly reinforced or substandard reinforced concrete buildings that reportedly collapsed during previous earthquakes are used as example case studies in order to calibrate the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.

Anagnostopoulou C.,Aristotle University of Thessaloniki
Theoretical and Applied Climatology | Year: 2016

Drought over the Greek region is characterized by a strong seasonal cycle and large spatial variability. Dry spells longer than 10 consecutive days mainly characterize the duration and the intensity of Greek drought. Moreover, an increasing trend of the frequency of drought episodes has been observed, especially during the last 20 years of the 20th century. Moreover, the most recent regional circulation models (RCMs) present discrepancies compared to observed precipitation, while they are able to reproduce the main patterns of atmospheric circulation. In this study, both a statistical and a dynamical downscaling approach are used to quantify drought episodes over Greece by simulating the Standardized Precipitation Index (SPI) for different time steps (3, 6, and 12 months). A statistical downscaling technique based on artificial neural network is employed for the estimation of SPI over Greece, while this drought index is also estimated using the RCM precipitation for the time period of 1961–1990. Overall, it was found that the drought characteristics (intensity, duration, and spatial extent) were well reproduced by the regional climate models for long term drought indices (SPI12) while ANN simulations are better for the short-term drought indices (SPI3). © 2016 Springer-Verlag Wien

Praidou A.,Aristotle University of Thessaloniki
Current diabetes reviews | Year: 2010

Diabetic retinopathy is considered one of the vision-threatening diseases among working-age population. The pathogenesis of the disease is regarded multifactorial and complex: capillary basement membrane thickening, loss of pericytes, microaneuryms, loss of endothelial cells, blood retinal barrier breakdown and other anatomic lesions might contribute to macular edema and/or neovascularization the two major and sight threatening complications of diabetic retinopathy. A number of proangiogenic, angiogenic and antiangiogenic factors are involved in the pathogenesis and progression of diabetic retinal disease, Vascular Endothelial Growth Factor (VEGF) being one of the most important. Other growth factors, which are known to participate in the pathogenesis of the disease, are: Platelet Derived Growth Factor (PDGF), Fibroblast Growth Factor (FGF), Hepatocyte Growth Factor (HGF), Transforming Growth Factor (TGF), Placental Endothelial Cell Growth Factor (PlGF), Connective Tissue Growth Factor (CTGF). Other molecules that are involved in the disease mechanisms are: intergrins, angiopoietins, protein kinase C (PKC), ephrins, interleukins, leptin, angiotensin, monocyte chemotactic protein (MCP), vascular cell adhesion molecule (VCAM), tissue plasminogen activator (TPA), and extracellular matrix metalloproteinases (ECM-MMPs). However, the intraocular concentration of angiogenic factors is counterbalanced by the ocular synthesis of several antioangiogenic factors such as pigment epithelial derived factor (PEDF), angiostatin, endostatin, thrombospondin, steroids, atrial natriuretic peptide (ANP), inteferon, aptamer, monoclonal antibodies, VEGF receptor blocker, VEGF gene suppressors, intracellular signal transduction inhibitors, and extracellular matrix antagonists. Growth stimulation or inhibition by these factors depends on the state of development and differentiation of the target tissue. The mechanisms of angiogenesis factor action are very different and most factors are multipotential; they stimulate proliferation or differentiation of endothelial cells. This review attempts to briefly outline the knowledge about peptide growth factor involvement in diabetic retinopathy. Further ongoing research may provide better understanding of molecular mechanisms, disease pathogenesis and therapeutic interactions.

Tsitsas N.L.,Aristotle University of Thessaloniki
Applied Computational Electromagnetics Society Journal | Year: 2012

Electromagnetic wave propagation phenomena in nonlinear metamaterials are investigated for waves propagating either in the left-handed frequency band or in the frequency band gaps. In the left-handed band, we implement directly the reductive perturbation method to Faraday's and Ampére's laws and derive a second-and a thirdorder nonlinear Schrödinger (NLS) equation, describing solitons of moderate and ultra-short pulse widths, respectively. Then, we find necessary conditions and derive exact bright and dark soliton solutions of these equations. On the other hand, in the frequency band gaps with negative linear effective permittivity and positive permeability (where linear electromagnetic waves are evanescent), we derive two short-pulse equations (SPEs) for the high- and low-frequency band gaps. The structure of the SPEs solutions is discussed, and connections with the NLS soliton solutions are presented. Numerical simulations of the SPEs solutions are included and compared with those of the reduced wave equations. Directions towards the modelling of wave propagation in nonlinear chiral metamaterials are pointed out. © 2012 ACES.

Georgaca E.,Aristotle University of Thessaloniki
Journal of Mental Health | Year: 2014

Background. Discourse analytic approaches to mental distress have been developed in the last two decades as part of the broader social constructionist movement in psychology. Aims. The paper reviews existing discourse analytic studies on issues pertaining to mental distress, aiming to identify strengths and gaps in the existing literature as well as to assess their contribution to conceptualizing and managing distress. Method. Discourse analytic and social constructionist studies of different aspects of mental distress, conducted within the field of psychology, were identified and reviewed. Results. The studies reviewed have been organized in four themes: (a) exploring users' accounts and experiences, (b) examining professional accounts and practices, (c) focusing on mental health-related public texts and (d) deconstructing clinical categories. Conclusions. The main function of discourse analytic studies on mental distress has been to highlight the historically contingent and socially constructed character of professional forms of knowledge and practice. More specifically, this research trend has highlighted the discursive resources drawn upon to conceptualize mental distress, the discursive practices through which specific versions of distress are constructed and the discursive effects of these constructions for institutions, subjectivity and social practices. © 2014 Shadowfax Publishing and Informa UK Limited.

Erdman S.E.,Massachusetts Institute of Technology | Poutahidis T.,Massachusetts Institute of Technology | Poutahidis T.,Aristotle University of Thessaloniki
International Journal of Cancer | Year: 2010

Chronic inflammation is essential for cancer growth and metastasis. It follows that factors reducing inflammation would abrogate cancer and restore tissue health. However, roles for anti-inflammatory CD4+ regulatory cells (TREG) in cancer are enigmatic and controversial. Our recent data reveal that TREG may function in cancer similarly to inflammatory bowel disease or multiple sclerosis, whereby TREG accumulate but lack potency to restore tissue homeostasis under inflammatory conditions. Interestingly, early life exposures to diverse environmental organisms reinforce a protective TREG phenotype that inhibits cancer. In contrast, hygienic individuals with few exposures earlier in life suffer from a dysregulated TREG feedback loop. Consequently, hygienic subjects have increased risk of malignancy later in life. This cancer condition is reversible by blocking underlying inflammation. Taken together, these data help explain increased inflammation-associated cancer rates in hygienic societies and identify targets to abrogate cancer and restore overall health. © 2010 UICC.

Karatasos K.,Aristotle University of Thessaloniki
Macromolecules | Year: 2014

We explore by means of molecular dynamics (MD) simulations mixtures of graphene with hyperbranched polyesters (Boltorn) of two different pseudogenerations in a wide range of temperatures. Static and dynamic features of the polymeric component are probed in order to assess the effects of the presence of graphene in the polymer's behavior, while we also examine the structural rearrangement of the graphene sheets in the presence of a noncrystallizable highly branched polymeric component. Our results show that graphene platelets are forming stacks comprised by a small number of flakes (typically 2-3) which are dispersed within the polymeric matrix. The characteristics of the spatial arrangement of the graphene planes and that of the formed clusters (including their relative orientation) depend sensitively on the temperature and on the size of the hyperbranched component. From the dynamic point of view, a significant slowing down is detected both in local and in global polymer dynamics in composite systems. The strong dynamic slowing down is accompanied by the occurrence of a glass-like transition at a considerably higher temperature compared to that characterizing the respective pristine polymer systems. We believe that the results reported in the present study capture also generic characteristics of the behavior of such materials and therefore could be exploited for a better control of the mechanical and thermal characteristics of hyperbranched polymer/graphene systems in a more general aspect. © 2014 American Chemical Society.

Tema E.,University of Turin | Kondopoulou D.,Aristotle University of Thessaloniki
Geophysical Journal International | Year: 2011

The first archaeomagnetic secular variation (SV) curves for the whole Southern Balkan Peninsula are presented. These are based on all data within a 700 km circle centred at Thessaloniki (40.60oN, 23.00oE). This data set consists of 325 directional and 625 intensity data mainly from Greece, Bulgaria, Serbia and southern Hungary. Some data from southern Italy are also included. The sliding moving window technique, was used to calculate a continuous SV curve for intensity while the directional SV curves were calculated using the bivariate extension of the Fisher statistics. These curves are well constrained and clearly show the main features of the geomagnetic field variation in this region during the last eight millennia. Comparisons with the predictions of the SCHA.DIF.3K and SCHA.DIF.8K regional and the CALS7K.2 and ARCH3K.1 global geomagnetic field models show a good agreement for the last 3000 years but differences for older times. The Balkan SV curves identify several rapid changes of the geomagnetic field in eastern Europe and can be used as reference curves for archaeomagnetic dating in the Balkan Peninsula. © 2011 The Authors Geophysical Journal International © 2011 RAS.

Georgiadou V.,Aristotle University of Thessaloniki | Dendrinou-Samara C.,Aristotle University of Thessaloniki
European Journal of Inorganic Chemistry | Year: 2014

CoFe2O4 magnetic nanoparticles (MNPs) were synthesized in a new synthetic system from metal acetylacetonates in the presence of octadecylamine (ODA) in autoclaves with subcritical water. By altering the water extent and ratio of the precursors, four samples were isolated. High crystallinity MNPs of various sizes (26, 15, 18, 9 nm) and saturation magnetization (71, 87, 93, 64 emu g-1) were formed. The organic coating was characterized by FTIR spectroscopy, 1H NMR and 13C NMR spectroscopy, and thermogravimetric analysis (TGA), and the free amine groups were detected by a ninhydrin assay. Under the present conditions, the CoFe2O4 MNPs were covered by a bilayer consisting of N-octadecylamide and ODA. The MNPs were converted into fluorescence probes through the formation of a sulfonamide bond between ODA and sulforhodamine B (SRB). NMR relaxometric measurements were performed for MNPs modified with SRB, cetyltrimethylammonium bromide, and by 2,3-dimercaptosuccinic acid. The bimodal magnetic fluorescent MNPs showed relaxivity values of up to r2 = 219.5 mM-1 s-1, which renders them promising as dual agents. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tsilipakos O.,Aristotle University of Thessaloniki | Kriezis E.E.,Aristotle University of Thessaloniki
Journal of the Optical Society of America B: Optical Physics | Year: 2014

Optical bistability with a hybrid silicon-plasmonic configuration consisting of a nonlinear traveling-wave (disk) resonator side-coupled with a bus waveguide is theoretically investigated. The nonlinear response is studied with a theoretical framework combining perturbation theory and temporal coupled-mode theory. For the CW case, a general closed-form expression is derived. The effect of the parameters entering in the expression on the bistability curve is thoroughly investigated, and the physical system is accordingly designed so as to exhibit minimum power threshold for bistability and maximumextinction ratio between bistable states. Finally, the temporal dynamics are assessed. The system can toggle between bistable states in approximately 5 ps and is thus suitable for ultrafast memory and switching applications. © 2014 Optical Society of America.

Papadopoulos V.N.,Aristotle University of Thessaloniki
Techniques in coloproctology | Year: 2011

Several factors have been considered important for the decision between diversion and primary repair in the surgical management of colorectal injuries. The aim of this study is to clarify whether patients with colorectal injuries need diversion or not. From 2008 to 2010, ten patients with colorectal injuries were surgically treated by primary repair or by a staged repair. The patients were five men and five women, with median age 40 years (20-55). Two men and two women had rectal injuries, while 6 patients had colon injuries. The mechanism of trauma in two patients was firearm injuries, in two patients was a stab injury, in four patients was a motor vehicle accident, in one woman was iatrogenic injury during vaginal delivery, and one case was the transanal foreign body insertion. Primary repair was possible in six patients, while diversion was necessary in four patients. Primary repair should be attempted in the initial surgical management of all penetrating colon and intraperitoneal rectal injuries. Diversion of colonic injuries should only be considered if the colon tissue itself is inappropriate for repair due to severe edema or ischemia. The role of diversion in the management of unrepaired extraperitoneal rectal injuries and in cases with anal sphincter injuries is mandatory.

Nikolaou K.,Biomedical science Research Center Alexander Fleming | Tsagaratou A.,Biomedical science Research Center Alexander Fleming | Tsagaratou A.,Aristotle University of Thessaloniki | Eftychi C.,Biomedical science Research Center Alexander Fleming | And 3 more authors.
Cancer Cell | Year: 2012

The tumor suppressor cylindromatosis (CYLD) inhibits the NFκB and mitogen-activated protein kinase (MAPK) activation pathways by deubiquitinating upstream regulatory factors. Here we show that liver-specific disruption of CYLD triggers hepatocyte cell death in the periportal area via spontaneous and chronic activation of TGF-β activated kinase 1 (TAK1) and c-Jun N-terminal kinase (JNK). This is followed by hepatic stellate cell and Kupffer cell activation, which promotes progressive fibrosis, inflammation, tumor necrosis factor (TNF) production, and expansion of hepatocyte apoptosis toward the central veins. At later stages, compensatory proliferation results in the development of cancer foci featuring re-expression of oncofetal hepatic and stem cell-specific genes. The results demonstrate that, in the liver, CYLD acts as an important regulator of hepatocyte homeostasis, protecting cells from spontaneous apoptosis by preventing uncontrolled TAK1 and JNK activation. © 2012 Elsevier Inc.