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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.

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

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.

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.

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.

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.

Pantzartzi C.,Aristotle University of Thessaloniki
PLoS computational biology | Year: 2010

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.

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.

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.

Triantafyllou A.,Aristotle University of Thessaloniki
Rural and remote health | Year: 2010

INTRODUCTION: Hypertension is a major public health problem and its prevalence increases with age. Despite an aging population, only a limited number of population-based studies, and fewer Greek studies, have focused exclusively on the elderly. The objective of this study was to investigate the prevalence, awareness, treatment and control of hypertension in the rural residents of Paliouri village in Greece who were aged 65 years and older. METHODS: In total there were 171 participants (response rate 89.5%). Six blood pressure (BP) measurements were obtained in two visits and hypertension was defined as a mean systolic BP >or= 140 mmHg and/or mean diastolic BP >or= 90 mmHg, and/or current use of an antihypertensive medication. RESULTS: The prevalence of hypertension was 89%. Of the 137 hypertensive patients, 89.8% were aware of their disease, 89.1% were receiving treatment, and the hypertension of 32.8% was controlled. Awareness of hypertension was significantly higher among those with a high frequency of BP measurements, a history of coronary or other chronic disease, lower education, and those living with a spouse. CONCLUSION: The findings indicate that hypertension is highly prevalent in this Greek elderly population. Similarly high is the awareness and treatment of hypertension. However, the control rates were relatively low, suggesting that the local health system requires a greater orientation to the prevention and control of hypertension.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Kotzekidou P.,Aristotle University of Thessaloniki
Food Microbiology | Year: 2013

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.

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.

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.

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 http://en.wikibooks.org/wiki/Textbook_of_Psychiatry/Mood_Disorders. © 2010 Fountoulakis; licensee BioMed Central Ltd.

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.

Pitilakis D.,Aristotle University of Thessaloniki | Clouteau D.,Ecole 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.

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.

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.

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.

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.

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.

Manou D.B.,Aristotle University of Thessaloniki
International Journal of Sustainable Society | Year: 2014

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Siddiqui M.N.,King Fahd University of Petroleum and Minerals | Redhwi H.H.,King Fahd University of Petroleum and Minerals | Achilias D.S.,Aristotle University of Thessaloniki
Journal of Analytical and Applied Pyrolysis | Year: 2012

In this study, the methanolic pyrolysis (methanolysis) of poly(ethylene terephthalate) (PET) taken from waste soft-drink bottles, under microwave irradiation, is proposed as a recycling method with substantial energy saving. The reaction was carried out with methanol with and without the use of zinc acetate as catalyst in a sealed microwave reactor in which the pressure and temperature were controlled and recorded. Experiments under constant temperature or microwave power were carried out at several time intervals. The main product dimethyl-terephthalate was analyzed and identified by FTIR and DSC measurements. It was found that PET depolymerization, is favored by increasing temperature, time and microwave power. High degrees of depolymerization were measured at temperatures near 180°C and at microwave power higher than 150 W. Most of the degradation was found to occur during the initial 5-10 min. Compared to conventional pyrolysis methods, microwave irradiation during methanolic pyrolysis of PET certainly results in shorter reaction times supporting thus the conclusion that this method is a very beneficial one for the recycling of PET wastes. © 2012 Elsevier B.V.

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.

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.

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..

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.

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 (http://www.uroweb.org/nc/professional-resources/guidelines/online/). Copyright © 2010 European Association of Urology. Published by Elsevier B.V. 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.

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.

Valagiannopoulos C.A.,Aalto University | Tsitsas N.L.,Aristotle University of Thessaloniki

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
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.

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.

Groll A.H.,University of Munster | Castagnola E.,Infectious Diseases Unit | 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.

Fu J.,Auburn University | Kyzas G.Z.,Technological Educational Institute of Kavala | Kyzas G.Z.,Aristotle University of Thessaloniki
Cuihua Xuebao/Chinese Journal of Catalysis | Year: 2014

Wet air oxidation (WAO), a liquid phase reaction between organic materials in water and oxygen, is one of the most economical and technologically viable advanced oxidation processes for wastewater treatment, particularly toxic and high organic content wastewater. WAO is the liquid phase oxidation of organics or oxidizable inorganic components at elevated temperatures (125-320°C) and pressures (0.5-20 MPa) using gaseous oxygen (or air) as oxidant. In the past two decades, the WAO process was widely studied and applied in the treatment of dye wastewater. Compared to conventional WAO, catalytic WAO processes have higher efficiency and use moderate reaction conditions. The catalysts included homogenous and heterogeneous types. The key points that need to be solved are recycling of homogenous catalysts and better stability of heterogeneous catalysts. In the present review, the technological processes are first introduced, then some research history and hotspots of WAO research are presented, and finally, its application in the treatment of dye wastewater in the past two decades is summarized to reveal the impressive changes in modes, trends, and conditions used. The application includes model pollutant studies and wastewater tests. © 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

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.

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.

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.

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.

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.

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.

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.

Kiratzi A.A.,Aristotle University of Thessaloniki
Turkish Journal of Earth Sciences | Year: 2011

On 6 September 2009 (GMT 21:49) a moderate Mw5.4 earthquake sequence burst at the eastern border of Albania with the Former Yugoslav Republic of Macedonia (FYROM). Th e main shock was located ~6 km north of the epicentre of the 30 November 1967 Mw6.2 Dibra (or Debar) earthquake, which caused loss of life and considerable damage to buildings. We use broad band waveforms recorded by the Hellenic Unified Seismic Network (HUSN), which receives real-time waveforms from the neighbouring networks, to compute focal mechanisms, obtain the slip model and derive the ShakeMap of the mainshock. The focal mechanisms of 18 of the stronger events of the sequence, obtained through time-domain moment tensor inversion, indicate that deformation is taken up by NNE-SSW-trending normal faults, in agreement with the ~E-W extension previously identified within the Albanian orogen. Our results show that the 2009 main shock ruptured a roughly 9 km normal fault at a depth of 6 km, which strikes at 194° and dips west at ~45°. The slip of the main shock was confined to a single patch of ~9 km × 6 km, the average slip was 5 cm and the peak slip was 18 cm. The slip model was incorporated in a forward modelling scheme to simulate the ground motion distribution in the near field. The ShakeMap thus obtained, based on the distribution of Peak Ground Velocity at phantom stations, outlines the mesoseismal area within the Dibra and Bulqiza districts in Albania, in accordance with macroseismic observations. Th e region aff ected by the 2009 sequence, together with the seismogenic region of the 1967 Dibra event, form a roughly NNE-SSW-trending structure which is an active seismotectonic zone in eastern Albania constituting a threat for nearby urban areas. © TÜBİTAK.

Koufos G.D.,Aristotle University of Thessaloniki
Estudios Geologicos | Year: 2011

The Miocene carnivore assemblage of Greece includes a great number of taxa, described in numerous articles since the first decades of the 19th Century. The present article is a revision of all these taxa, providing information about their history, localities, age, as well as their stratigraphic distribution and palaeoenvironment. The Early/Middle Miocene carnivore record of Greece is poor as the available fossiliferous sites and material are rare. However, the Late Miocene one is quite rich, including numerous taxa. The Miocene localities with carnivores and their age are given in a stratigraphic table covering the European Mammal zones from MN 4 to MN 13. The type locality, holotype, and some historical and morphological remarks are given for each taxon. Several carnivore taxa were erected from Greek material and new photos of their holotypes are given. The stratigraphic distribution of the Greek carnivore taxa indicates that they are covering the time span from ∼19.0-5.3Ma. The majority of the Miocene taxa (Adcrocuta, Hyaenictitherium, Plioviverrops, Protictitherium, Ictitherium, Indarctos, Dinocrocuta, Promephitis) disappeared at the end of Miocene. The composition of the Early/Middle Miocene carnivore assemblage of Greece includes mainly viverrids (Lophocyon, Euboictis), while the hyaenids, percrocutids, felids and mustelids are very few. On the contrary the Late Miocene assemblage is richer, including more subfamilies and species; the hyaenids and mustelids dominate, while the viverrids are absent. The Late Miocene carnivore guild structure is similar to that of the modern Serengeti, indicating a relatively open, savannah-like environment.

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.

Skendros P.,Democritus University of Thrace | Boura P.,Aristotle University of Thessaloniki
OIE Revue Scientifique et Technique | Year: 2013

Resistance to intracellular bacterial pathogens such as Brucella spp. relies on cell-mediated immunity, which involves activation of the bactericidal mechanisms of antigen-presenting cells (macrophages and dendritic cells) and the subsequent expansion of antigen-specific CD4+ and CD8+ T-cell clones. Brucella antigens induce the production of T helper type 1 (Th1) cytokines, and an adequate Th1 immune response is critical for the clearance of Brucella infection. Studies on experimental and human brucellosis indicate that interferon-γ (IFNy) is the principal cytokine active against Brucella infection. On the other hand, Brucella has evolutionarily developed diverse evasion strategies to avoid the host's innate and adaptive immunity in order to establish an intracellular niche for long-term parasitism. Disturbances of the Thl response and anergy have been described in patients with chronic brucellosis, and are associated with poor outcome. Accordingly, chronic brucellosis represents a challenge for the study of immune mechanisms against Brucella and the development of novel therapeutic or vaccination approaches.

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.

Tranos M.D.,Aristotle University of Thessaloniki
Journal of Geodynamics | Year: 2011

In Central and Eastern Macedonia of Northern Greece large NW-SE trending basins filled up mainly with terrestrial sediments developed during the Neogene over the Alpine basement rocks. Among them, the Strymon basin was established along the NNW-SSE trending Strouma/Strymon Lineament which formed over the tectonic boundary of the Serbomacedonian and Rhodope massifs, both representing the hinterland of the Hellenic orogen. The present study suggests that the Strymon basin was not formed as a syn-detachment basin over the Strymon Valley Detachment Fault, considered to have caused exhumation of the Rhodope massif metamorphic complex. Instead, transpressional s.l. tectonics dominated the region in the Late Oligocene-Early Miocene and it progressively changed into a wrench tectonics under which the Strymon basin has been initiated in the Middle Miocene. The basin continued to develop further under a short-lived NW-SE extension in the Middle-Late Miocene. The whole deformation is attributed to the late-stage collisional processes between the Apulia and Eurasia plates. The prevalent NE-SW extension has been constrained later on in the Late Miocene and Pliocene times activating both low-angle and high-angle NW-SE trending faults and causing the regional tilting towards the SW of the mountain fault blocks (i.e., mountain chains). From Quaternary onwards, the Strymon basin has been separated from the Strymonikos Gulf basin due to an N-S extension that mainly activates E-W striking normal faults. © 2010 Elsevier Ltd.

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.

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.

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.

Samaras A.G.,University of Bologna | Koutitas C.G.,Aristotle University of Thessaloniki
Geomorphology | Year: 2014

Coastal morphology evolves as the combined result of both natural- and human- induced factors that cover a wide range of spatial and temporal scales of effect. Areas in the vicinity of natural stream mouths are of special interest, as the direct connection with the upstream watershed extends the search for drivers of morphological evolution from the coastal area to the inland as well. Although the impact of changes in watersheds on the coastal sediment budget is well established, references that study concurrently the two fields and the quantification of their connection are scarce. In the present work, the impact of land-use changes in a watershed on coastal erosion is studied for a selected site in North Greece. Applications are based on an integrated approach to quantify the impact of watershed management on coastal morphology through numerical modeling. The watershed model SWAT and a shoreline evolution model developed by the authors (PELNCON-M) are used, evaluating with the latter the performance of the three longshore sediment transport rate formulae included in the model formulation. Results document the impact of crop abandonment on coastal erosion (agricultural land decrease from 23.3% to 5.1% is accompanied by the retreat of ~. 35. m in the vicinity of the stream mouth) and show the effect of sediment transport formula selection on the evolution of coastal morphology. Analysis denotes the relative importance of the parameters involved in the dynamics of watershed-coast systems, and - through the detailed description of a case study - is deemed to provide useful insights for researchers and policy-makers involved in their study. © 2014 Elsevier B.V.

Zotos E.E.,Aristotle University of Thessaloniki
Nonlinear Dynamics | Year: 2014

In this work, we try to shed some light to the nature of orbits in a three-dimensional (3D) potential of a perturbed harmonic oscillator with eight possible channels of escape, which was chosen as an interesting example of open 3D Hamiltonian systems. In particular, we conduct a thorough numerical investigation distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering unbounded motion for several values of the energy. In an attempt to discriminate safely and with certainty between ordered and chaotic motion, we use the Smaller ALingment Index (SALI) detector, computed by integrating numerically the basic equations of motion as well as the variational equations. Of particular interest is to locate the basins of escape toward the different escape channels and connect them with the corresponding escape periods of the orbits. We split our study into three different cases depending on the initial value of the z coordinate which was used for launching the test particles. We found that when the orbits are started very close to the primary (x, y) plane the respective grids exhibit a high degree of fractalization, while on the other hand for orbits with relatively high values of z0 several well-formed basins of escape emerge thus reducing significantly the fractalization of the grids. It was also observed that for values of energy very close to the escape energy the escape times of orbits are large, while for energy levels much higher than the escape energy the vast majority of orbits escape extremely fast or even immediately to infinity. We hope our outcomes to be useful for a further understanding of the escape process in open 3D Hamiltonian systems. © 2014 Springer Science+Business Media Dordrecht.

Tsoukala E.,Aristotle University of Thessaloniki | Mol D.,Natural History Museum
Quaternary International | Year: 2016

Two different species of Early Villafranchian proboscideans were contemporaneous in Milia (Grevena, Western Macedonia, Greece): the large zygodont, Borson's mastodon, Mammut borsoni (Hays, 1834), and the smaller gomphothere, the mastodon of Auvergne, Anancus arvernensis (Croizet et Jobert, 1828), the former being predominant. Since 1996 partial skeletons and a large number of isolated skeletal elements of the zygodonts have been excavated from Aliakmon River sand deposits in Milia. The skeletons include substantial portions of the cranium with left and right molars (M2, M3); two complete pairs of the longest upper tusks ever recorded in the world (4.39 m and 5.02 m) and the most complete mandible in Europe, with the two entire lower tusks in anatomical position, as well as two almost-complete mandibles with dentition (m2 + m3); and post-cranials. These partial skeletons represent very robust male individuals in the prime of their life at time of death. In this paper, we describe a new partial skeleton and we discuss the evolutionary position of the specimens among mammutids, the stratigraphy and the paleoenvironment. The enriched Milia zygodont material is compared with other European specimens in order to get a better understanding of its extinction. © 2014 Elsevier Ltd and INQUA.

Papageorgiou G.P.,University of Thessaly | Mouratidis A.,Aristotle University of Thessaloniki
Structure and Infrastructure Engineering | Year: 2014

Transportation authorities managing road networks have to define threshold values of acceptance for pavement surface characteristics. This procedure is either based on relevant experience or drawn from a combination of subjective ranking and monitoring data. Rare are the references of an analytical procedure to define these threshold values with respect to the operational criteria of a road network: safety, comfort, environment and economy. Several road management agencies worldwide apply specific limit values for each pavement feature. Conversely, other authorities do not prescribe acceptance limits at all, allowing for high variability of local factors such as traffic and climatic conditions. In either case, the analytical approach to reliably define limit values is missing. In this study, a methodology to provide threshold values for pavement surface characteristics is presented. Three most important measurable characteristics of pavement conditions, skid resistance, roughness and rutting, are herein analysed. This analysis is carried out by introducing, respectively, suitable parameters, namely the sideway force coefficient, the International Roughness Index and the rutting depth. The objective is to outline a comprehensive methodology for determining threshold values for indicators that portray pavement condition. The proposed methodology attempts to define these limit values by spotting abrupt change in terms of safety or significant increase in negative effects to road users. Relative graphs are given correlating the aforesaid characteristics with safety and travel cost features. The overall analysis is based on the evidence of an 'inflection' point at each correlation curve, adequately interpreted to provide the threshold values in question. © 2013 Taylor & Francis.

Draziotis K.A.,Aristotle University of Thessaloniki
Information Processing Letters | Year: 2016

We provide an attack to (EC)DSA digital signature built upon Coppersmith's method. We prove that, if a,k are the private and ephemeral key, respectively, of the (EC)DSA scheme and (k-1modq)2a < 0.262·q1.157, then we can efficiently find a. © 2016 Elsevier B.V. All rights reserved.

Kimiskidis V.K.,Aristotle University of Thessaloniki
European Neurology | Year: 2010

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique which, over the last 25 years, has greatly expanded from a simple method for stimulating the motor cortex to an invaluable tool with multiple research, diagnostic and even therapeutic applications. In this review, we discuss the use of repetitive TMS as a means of suppressing cortical hyperexcitability in drug-resistant epilepsies. The theoretical background and the experimental evidence in favor of this novel therapeutic approach are presented, and a number of open-label and controlled studies in patients with various forms of focal epilepsy are reviewed. It is concluded that, although the therapeutic effects of repetitive TMS in epilepsy appear rather limited, further clinical testing of this rapidly evolving technology is warranted. Copyright © 2010 S. Karger AG, Basel.

Zotos E.E.,Aristotle University of Thessaloniki
Astronomy and Astrophysics | Year: 2014

Aims. The distinction between regular and chaotic motion in galaxies is undoubtedly an issue of paramount importance. We explore the nature of orbits of stars moving in the meridional plane (R,z) of an axially symmetric galactic model with a disk, a spherical nucleus, and a flat biaxial dark matter halo component. In particular, we study the influence of all the involved parameters of the dynamical system by computing both the percentage of chaotic orbits and the percentages of orbits of the main regular resonant families in each case. Methods. To distinguish between ordered and chaotic motion, we use the smaller alignment index (SALI) method to extensive samples of orbits by numerically integrating the equations of motion as well as the variational equations. Moreover, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Two cases are studied for every parameter: (i) the case where the halo component is prolate and (ii) the case where an oblate dark halo is present. Results. Our numerical investigation indicates that all the dynamical quantities affect, more or less, the overall orbital structure. It was observed that the mass of the nucleus, the halo flattening parameter, the scale length of the halo, the angular momentum, and the orbital energy are the most influential quantities, while the effect of all the other parameters is much weaker. It was also found that all the parameters corresponding to the disk only have a minor influence on the nature of orbits. Furthermore, some other quantities, such as the minimum distance to the origin, the horizontal, and the vertical force, were tested as potential chaos detectors. Our analysis revealed that only general information can be obtained from these quantities. We also compared our results with early related work. © ESO, 2014.

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.

Tsiouris V.,Aristotle University of Thessaloniki
Avian Pathology | Year: 2016

The intestinal ecosystem of poultry has been inevitably changed as a result of the ban of antimicrobial growth promoters. The re-emergence of necrotic enteritis has been the most significant threat for the poultry industry, which, in clinical form, causes high mortality and in subclinical forms, affects growth and feed conversion. It is one of the most common and economically devastating bacterial diseases in modern broiler flocks in terms of performance, welfare and mortality. Necrotic enteritis is a multi-factorial disease process, in which a number of co-factors are usually required to precipitate an outbreak of the disease. Although, Clostridium perfringens has been identified as the aetiological agent of the disease, the predisposing factors that lead to over-proliferation of C. perfringens and the subsequent progression to disease are poorly understood. Any factor that causes stress in broiler chicks could suppress the immune system and disturb the balance of the intestinal ecosystem, in such a way that the risk of a necrotic enteritis (NE) outbreak increases. Poultry management could significantly affect the pathogenesis of NE. In particular, feed restriction and coccidiosis vaccination can protect against NE, while extreme house temperature, feed mycotoxins and high stocking density predispose to NE. It becomes really important to understand the pathogenesis of the disease, as well as to clarify the interactions between husbandry, nutritional and infectious factors and the outbreak of necrotic enteritis. This is necessary and extremely important in order to develop managerial strategies at the farm level to control the incidence and severity of the disease in the post-antibiotic era. © 2016 Houghton Trust 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

IEEE Transactions on Biomedical Engineering | Year: 2015

A novel approach in tonic cold pain characterization, based on electroencephalograph (EEG) data analysis using wavelet higher order spectral (WHOS) features, is presented here. The proposed WHOS-based feature space extends the relative power spectrum-based (phase blind) approaches reported so far a step forward; this is realized via dynamic monitoring of the nonlinerities of the EEG brain response to tonic cold pain stimuli by capturing the change in the underlying quadratic phase coupling at the bifrequency wavelet bispectrum/bicoherence domain due to the change of the pain level. Three pain characterization scenarios were formed and experimentally tested involving WHOS-based analysis of EEG data, acquired from 17 healthy volunteers that were subjected to trials of tonic cold pain stimuli. The experimental and classification analysis results, based on four well-known classifiers, have shown that the WHOS-based features successfully discriminate relax from pain status, provide efficient identification of the transition from relax to mild and/or severe pain status, and translate the subjective perception of pain to an objective measure of pain endurance. These findings seem quite promising and pave the way for adopting WHOS-based approaches to pain characterization under other types of pain, e.g., chronic pain and various clinical scenarios. © 1964-2012 IEEE.

Stamelos I.,Aristotle University of Thessaloniki
Journal of Systems and Software | Year: 2010

This paper explores the area of bad practices, namely anti-patterns, and their consequences in software project management (SPM). The paper surveys the multitude of anti-patterns that have been reported and documented up to now and stresses the need for tools to formally represent SPM anti-patterns, proposing specific formalisms for such purpose, namely Bayesian Belief Networks, Ontologies and Social Networks. It is also explained how the Web can provide an opportunity for capturing, storing, disseminating and ultimately avoiding SPM anti-patterns. As a consequence, anti-patterns may provide an excellent tool for educating active and future software managers. Finally, conclusions and future research trends are given. © 2009 Elsevier Inc. All rights reserved.

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.

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.

Manolis A.,Asclepeion General Hospital | Doumas M.,Aristotle University of Thessaloniki
Current Hypertension Reports | Year: 2012

Sexual dysfunction is frequently encountered in hypertensive patients. Available data indicates that sexual dysfunction is more frequent in treated than in untreated patients, generating the hypothesis that antihypertensive therapy might be associated with sexual dysfunction. Several lines of evidence suggest that differences between antihypertensive drugs exist regarding their effects on sexual function. Older antihypertensive drugs (diuretics, beta blockers) exert detrimental effects on erectile function whereas newer drugs (nebivolol, angiotensin receptor blockers) have neutral or even beneficial effects. Phosphodiesterase (PDE)-5 inhibitors are effective in hypertensive patients and can be safely administered even when multidrug regimes are used. Precautions need to be taken with alpha blockers or patients with uncontrolled high-risk hypertension, while co-administration with nitrates is contraindicated. © Springer Science+Business Media, LLC 2012.

Bechlioulis C.P.,National Technical University of Athens | Rovithakis G.A.,Aristotle University of Thessaloniki
Automatica | Year: 2014

A universal, approximation-free state feedback control scheme is designed for unknown pure feedback systems, capable of guaranteeing, for any initial system condition, output tracking with prescribed performance and bounded closed loop signals. By prescribed performance, it is meant that the output error converges to a predefined arbitrarily small residual set, with convergence rate no less than a certain prespecified value, having maximum overshoot less than a preassigned level. The proposed state feedback controller isolates the aforementioned output performance characteristics from control gains selection and exhibits strong robustness against model uncertainties, while completely avoiding the explosion of complexity issue raised by backstepping-like approaches that are typically employed to the control of pure feedback systems. In this respect, a low complexity design is achieved. Moreover, the controllability assumptions reported in the relevant literature are further relaxed, thus enlarging the class of pure feedback systems that can be considered. Finally, simulation studies clarify and verify the approach. © 2014 Elsevier Ltd. All rights reserved.

Tziomalos T.,Aristotle University of Thessaloniki
World Journal of Hepatology | Year: 2010

Chronic hepatitis B (CHB) is a major risk factor for hepatocellular carcinoma (HCC). The prevention of HCC is of paramount importance in patients with CHB, particularly in those with cirrhosis. Antiviral treatment can potentially reduce the risk for HCC since it suppresses viral replication, induces HBeAg seroconversion and improves liver histology. However, most evidence supporting a protective effect of antiviral treatment originates from non-randomized or retrospective studies and is limited to conventional interferon and lamivudine. There is a paucity of data on the effects of pegylated interferon and "newer" oral agents (telbivudine, tenofovir, entecavir) on HCC risk. However, it should be emphasized that the existing randomized control studies in patients with CHB were relatively short-term and not designed to assess the effects of antiviral treatment on HCC risk. Since viral load directly correlates with HCC risk, it is reasonable to hypothesize that the reduction in viral load with antiviral treatment will also lower the risk of HCC. This benefit might become more readily apparent with the newer agents used in the management of CHB which are more effective and have a more favorable resistance profile. © 2010 Baishideng.

Nodler K.,University of Gottingen | Voutsa D.,Aristotle University of Thessaloniki | Licha T.,University of Gottingen
Marine Pollution Bulletin | Year: 2014

Polar anthropogenic organic micropollutants are frequently detected in freshwater and discharged on large scale into marine systems. In this work the results of 153 samples collected from the shorelines of the Baltic Sea (Germany), Northern Adriatic Sea (Italy), Aegean Sea and Dardanelles (Greece & Turkey), San Francisco Bay (USA), Pacific Ocean (USA), Mediterranean Sea (Israel), and Balearic Sea (Spain) are presented. The samples were analyzed for various classes of micropollutants such as pharmaceuticals, corrosion inhibitors, biocides, and stimulants. Caffeine, paraxanthine, theobromine, tolyltriazole, 1H-benzotriazole, and atrazine were detected in. >50% of all samples. The detection frequencies of carbamazepine, iopamidol, diuron, sulfamethoxazole, paracetamol, theophylline, and atenolol were between 20% and 32%. As caffeine is linked to untreated wastewater, the widespread occurrence of raw sewage in marine environments and thus potentially elevated nutrient concentrations and risk for the presence of wastewater-related pathogens is remarkable. © 2014 Elsevier Ltd.

Morozov N.F.,Russian Academy of Sciences | Ovid'ko I.A.,Russian Academy of Sciences | Sheinerman A.G.,Russian Academy of Sciences | Aifantis E.C.,Aristotle University of Thessaloniki
Journal of the Mechanics and Physics of Solids | Year: 2010

A theoretical model is suggested which describes the effect of special rotational deformation on crack growth in deformed nanocrystalline ceramics and metals. Within the model, the special rotational deformation (driven by the external stress concentrated near the tip of a mode I crack) occurs in a nanograin through formation of immobile disclinations whose strengths gradually increase during the formation process conducted by grain boundary sliding and diffusion. The special rotational deformation releases, in part, local stresses near the crack tip, thus serving as a toughening mechanism in nanocrystalline materials. The effects of the special rotational deformation on the growth of pre-existent, comparatively large cracks in nanocrystal-line metals and ceramics are estimated. © 2010 Elsevier Ltd. All rights reserved.

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.

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.

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.

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.

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.

Papagianni M.,Aristotle University of Thessaloniki
Microbial Cell Factories | Year: 2012

This paper gives an overview of the recent advances in engineering the central carbon metabolism of the industrially important bacteria Escherichia coli, Bacillus subtilis, Corynobacterium glutamicum, Streptomyces spp., Lactococcus lactis and other lactic acid bacteria. All of them are established producers of important classes of products, e.g. proteins, amino acids, organic acids, antibiotics, high-value metabolites for the food industry and also, promising producers of a large number of industrially or therapeutically important chemicals. Optimization of existing or introduction of new cellular processes in these microorganisms is often achieved through manipulation of targets that reside at major points of central metabolic pathways, such as glycolysis, gluconeogenesis, the pentose phosphate pathway and the tricarboxylic acid cycle with the glyoxylate shunt. Based on the huge progress made in recent years in biochemical, genetic and regulatory studies, new fascinating engineering approaches aim at ensuring an optimal carbon and energy flow within central metabolism in order to achieve optimized metabolite production. © 2012 Papagianni; licensee BioMed Central Ltd.

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.

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.

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.

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.

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.

Giantsis I.A.,Aristotle University of Thessaloniki
Genetics and molecular research : GMR | Year: 2012

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.

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.

Zabaniotou A.,Aristotle University of Thessaloniki
Sustainable Energy Technologies and Assessments | Year: 2014

The present study is focusing on the CHP generation by agro biomass thermochemical derived gases and liquids, as feedstock for hydrogen-rich gas production and consecutively, power generation by using fuel cells mainly of the SOFC type. Objectives encompass analysis, integration of processes and synergies along with estimation of selected agro residues physicochemical characteristics, suitability and implication in decentralized CHP systems of thermochemical conversion in conjunction with SOFC. Estimation of the conjugated system energy efficiency by using data from olive kernel steam gasification is also reported. The integration of agro biomass gasification with SOFC offers the potential of highly efficient and renewable power generation. From the perspective of the integrated process, power density and fuel characteristics determine the overall efficiency of SOFCs. © 2014 Elsevier Ltd.

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.

Papastefanou C.,Aristotle University of Thessaloniki

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.

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.

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.

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.

Christaki E.,Aristotle University of Thessaloniki
Research Journal of Biotechnology | Year: 2012

An important field of research today is the control of biological damages such as oxidative stress and oxidative rancidity caused by free radicals. Natural antioxidants can be used because of their health benefits against oxidative stress which is involved in the pathology of several diseases in living organisms. Moreover, antioxidants have been used in the food industry to prevent oxidative rancidity which represents one of the major causes of food deterioration. Poultry meat is particular susceptible to lipid oxidation due to its high content in polyunsaturated fatty acids. Over the last several years much attention has been focused on herbs, spices, plants and especially aromatic plants like oregano, rosemary, thyme and saffron which are traditionally used in folk medicine. These plants have many bioactive compounds and particularly polyphenols which are known for their antioxidative capacity. Therefore, they have been used in poultry diets as a simple and convenient strategy to introduce natural antioxidants into meat. Nowadays, the consumer demand for natural products has created an interest in the use of plant derived antioxidants in poultry nutrition.

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.

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.

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.

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.

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

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.

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.

Vassilikos V.P.,Aristotle University of Thessaloniki
Telemedicine journal and e-health : the official journal of the American Telemedicine Association | Year: 2010

Radiofrequency catheter ablation (RFA) is an effective treatment of arrhythmias. However, patients often remain symptomatic after the procedure. We aimed to assess the arrhythmia recurrence after successful RFA in relation to patients' symptoms using transtelephonic loop recorders. Thirty-six consecutive patients (age 50 +/- 14 years, 17 males/19 females) were enrolled after successful RFA for atrioventricular (AV) nodal reentrant tachycardia (n = 21), AV reentrant tachycardia (n = 8), atrial tachycardia (n = 2), atrial fibrillation/flutter (n = 4), and ventricular tachycardia (n = 1). During 23 +/- 6 days of follow-up, 679 events were recorded, 246 of which were true arrhythmic events, mostly (56%) asymptomatic. The vast majority of these true arrhythmic events were due to trivial arrhythmias (extrasystoles or sinus tachycardia), equally distributed among symptomatic and asymptomatic episodes. Arrhythmia relapse was shown in four patients, who had a total of nine episodes, eight of which were symptomatic. No high degree AV block was detected. Overall, symptom recurrence had low sensitivity (44%) and high specificity (95%) for the detection of any arrhythmia, and high sensitivity (89%) but low specificity (58%) for the detection of relapse. In conclusion, transtelephonic monitoring was a useful tool for the assessment of symptoms after RFA and its use may be reserved for the most symptomatic patients to detect a relapse or to reassure them for the benign nature of their symptoms.

Psyllaki A.,University of Crete | Lykakis I.N.,Aristotle University of Thessaloniki | Stratakis M.,University of Crete
Tetrahedron | Year: 2012

Gold nanoparticles supported on TiO 2 (0.8-1.4 mol %) catalyze the β-(E) regioselective hydrosilylation of a variety of functionalized terminal alkynes with alkylhydrosilanes in 1,2-dichloroethane (70 °C). The product yields are excellent, and the reaction times relatively short, while almost equimolar amounts of alkynes and hydrosilanes can be used. Minor side-products in up to 35% relative yield of cis-oxidative (dehydrogenative) disilylation, an unprecedented reaction pathway, are formed in the cases of the less hindered hydrosilanes and alkynes. Triethoxysilane reacts faster and affords apart from β-(E) addition products, minor α-hydrosilylation regio-isomers in upto 15% relative yield. Internal alkynes are generally less reactive or even unreactive. It is proposed that cationic Au(I) species stabilized by the support are the reactive catalytic sites, forming in the presence of hydrosilanes either silyl-Au(III)-H (hydrosilylation pathway) or Au(III)-disilyl species (dehydrogenative disilylation pathway). Regarding the mechanism of hydrosilylation, kinetic experiments are in agreement with silyl carbometallation of the triple bond in the rate determining step of the reaction. © 2012 Elsevier Ltd. All rights reserved.

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

We explore the escape dynamics in open Hamiltonian systems with multiple channels of escape continuing the work initiated in Part I. A thorough numerical investigation is conducted distinguishing between trapped (ordered and chaotic) and escaping orbits. The determination of the location of the basins of escape toward the different escape channels and their correlations with the corresponding escape periods of the orbits is undoubtedly an issue of paramount importance. We consider four different cases depending on the perturbation function which controls the number of escape channels on the configuration space. In every case, we computed extensive samples of orbits in both the configuration and the phase space by numerically integrating the equations of motion as well as the variational equations. It was found that in all examined cases, regions of non-escaping motion coexist with several basins of escape. The larger escape periods have been measured for orbits with initial conditions in the vicinity of the fractal structure, while the lowest escape rates belong to orbits with initial conditions inside the basins of escape. In addition, we related the model potential with applications in the field of reactive multichannel scattering. We hope that our numerical analysis will be useful for a further understanding of the escape mechanism of orbits in open Hamiltonian systems with two degrees of freedom. © 2015 Springer Science+Business Media Dordrecht

Kosma C.I.,University of Ioannina | Lambropoulou D.A.,Aristotle University of Thessaloniki | Albanis T.A.,University of Ioannina
Journal of Hazardous Materials | Year: 2010

A monitoring study was carried out for the four seasons over 1-year monitoring period (March 2006-March 2007) to investigate the residues of 11 pharmaceuticals and personal care products (PPCPs) belonging to various therapeutic categories. The selected areas of the study were the municipal and hospital wastewater treatment plants (WWTPs) of Ioannina city, located in Western Greece. The most common pre-treatment technique for pharmaceuticals, solid-phase extraction (SPE), was used for the isolation and pre-concentration of the target analytes. The samples were screened using gas chromatography mass spectrometry (GC-MS). The results of the monitoring study, showed the occurrence of all target compounds in the wastewater samples. Concentrations in the municipal WWTP ranged between 0.3 and 164.4μg/L in the influent and between 0.5 and 13.9μg/L in the effluent. In the hospital WWTP concentrations ranged between 0.6 and 70.1μg/L in the influent and between 0.5 and 14.6μg/L in the effluent. Mean removal efficiencies ranged between 13% and 97% and between 9% and 87% for municipal and hospital WWTPs, respectively. Removal efficiencies were higher in the municipal WWTP than in the hospital WWTP. © 2010 Elsevier B.V.

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

The case of the planar circular restricted three-body problem is used as a test field in order to determine the character of the orbits of a small body which moves under the gravitational influence of the two heavy primary bodies. We conduct a thorough numerical analysis on the phase space mixing by classifying initial conditions of orbits and distinguishing between three types of motion: (1) bounded, (2) escape and (3) collisional. The presented outcomes reveal the high complexity of this dynamical system. Furthermore, our numerical analysis shows a remarkable presence of fractal basin boundaries along all the escape regimes. Interpreting the collisional motion as leaking in the phase space, we related our results to both chaotic scattering and the theory of leaking Hamiltonian systems. We also determined the escape and collisional basins and computed the corresponding escape/collisional times. We hope our contribution to be useful for a further understanding of the escape and collisional mechanism of orbits in the restricted three-body problem. © 2015 Springer Science+Business Media Dordrecht

Ferraldeschi R.,Molecular Therapeutics | Pezaro C.,Institute of Cancer Research | Karavasilis V.,Aristotle University of Thessaloniki | De Bono J.,Institute of Cancer Research
Annual Review of Medicine | Year: 2013

Suppression of gonadal androgens by medical or surgical castration remains the mainstay of treatment for patients with advanced prostate cancer. However, the response to treatment is not durable, and transition to a "castration-resistant" state is invariable. Recent advances in our understanding of the androgen receptor signaling pathway have led to the development of therapeutic strategies to overcome castration resistance. This article reviews current concepts and challenges behind targeting continued androgen receptor signaling in castration-resistant prostate cancer and provides an overview of recently completed and ongoing clinical trials of novel hormonal agents, with a focus on abiraterone acetate and enzalutamide (MDV3100). Copyright © 2013 by Annual Reviews.

Gounaris G.J.,Aristotle University of Thessaloniki | Renard F.M.,Montpellier University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Studying e-e+→W-W+ at the one-loop electroweak order, we derive very accurate and simple expressions for the four helicity conserving amplitudes which dominate this process at high energies. The calculations are done in both the standard model and minimal supersymmetric standard model frameworks. Such expressions, called supersimple, nicely emphasize the dynamical contents of each framework. Numerical illustrations are presented, which show the accuracy of this description, and how it can be used for identifying possible additional new physics contributions, like, e.g., anomalous gauge couplings or a new Z ′ vector boson exchange. The procedure is useful even if only the standard model is visible at the future linear collider energies. © 2013 American Physical Society.

Griesinger G.,University of Lubeck | Kolibianakis E.M.,Aristotle University of Thessaloniki
Reproductive BioMedicine Online | Year: 2012

Scheduling the initiation of ovarian stimulation in a gonadotrophin- releasing hormone (GnRH)-antagonist protocol by sex steroid pretreatment has been suggested as a means to reduce the incidence of oocyte retrievals during weekends. The rationale is that by manipulating the initiation of gonadotrophin stimulation, Thursday or Friday will be avoided as days on which triggering of final oocyte maturation will be performed and thus weekend oocyte retrievals will not occur. Apparently, the assumption behind such an approach is that duration of stimulation is homogenous enough to serve this purpose reliably. However, existing data suggest that large inter-individual variation exists in the duration of gonadotrophin stimulation required to reach predefined criteria for triggering final oocyte maturation, regardless of whether stimulation was initiated with spontaneous menstruation or after pretreatment with sex-steroids. Therefore, it is highly unlikely that any type of pretreatment aiming to allow initiation of stimulation on a certain day will result in avoidance of weekend oocyte retrievals, when predefined criteria for triggering final oocyte maturation are used. © 2012, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Moustakidis C.C.,Aristotle University of Thessaloniki | Moustakidis C.C.,University of Tubingen
Physical Review C - Nuclear Physics | Year: 2012

The symmetry energy effects on the location of the inner edge of neutron star crusts are studied. Three phenomenological models are employed in order to check the accuracy of the well known parabolic approximation of the equation of state for asymmetric nuclear matter in the determination of the transition density n t and transition pressure P t. The results corroborate the statement that the error due to the assumption that a priori the equation of state is parabolic may introduce a large error in the determination of related properties of a neutron star as the crustal fraction of the moment of inertia and the critical frequency of rotating neutron stars. © 2012 American Physical Society.

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

Colonic diverticular disease is extremely common in developed countries. Although the majority of patients with diverticulosis remain asymptomatic, about one-third of the patients manifest the disease with either hemorrhage or inflammation. Diverticulitis may be uncomplicated or complicated by abscess formation, perforation with peritonitis, fistula, intestinal obstruction, or stricture. Controversy exists regarding the aggressiveness of diverticulitis during recurrent attacks of the disease as well as in special groups of patients including immunocompromised patients, young patients, and patients with right-sided disease. Clinical characteristics of symptomatic uncomplicated disease can be similar to irritable bowel syndrome, while acute diverticulitis is sometimes difficult to distinguish from segmental colitis associated with diverticulosis. The considerable clinical overlap between those entities with diverticular disease demonstrates that there are still areas of uncertainty in their physiopathology.

Karavelidis V.,Aristotle University of Thessaloniki
International journal of nanomedicine | Year: 2011

Four new polyesters based on 1,3-propanediol and different aliphatic dicarboxylic acids were used to prepare ropinirole HCl-loaded nanoparticles. The novelty of this study lies in the use of polyesters with similar melting points but different degrees of crystallinity, varying from 29.8% to 67.5%, as drug nanocarriers. Based on their toxicity to human umbilical vein endothelial cells, these aliphatic polyesters were found to have cytotoxicity similar to that of polylactic acid and so may be considered as prominent drug nanocarriers. Drug encapsulation in polyesters was performed via an emulsification/solvent evaporation method. The mean particle size of drug-loaded nanoparticles was 164-228 nm, and the drug loading content was 16%-23%. Wide angle X-ray diffraction patterns showed that ropinirole HCl existed in an amorphous state within the nanoparticle polymer matrices. Drug release diagrams revealed a burst effect for ropinirole HCl in the first 6 hours, probably due to release of drug located on the nanoparticle surface, followed by slower release. The degree of crystallinity of the host polymer matrix seemed to be an important parameter, because higher drug release rates were observed in polyesters with a low degree of crystallinity.

Karatzia M.A.,Aristotle University of Thessaloniki
Livestock Science | Year: 2010

This study investigated the effect of the dietary inclusion of clinoptilolite, either alone or in combination, with intramuscular administration of Se, on antibody production by dairy cows vaccinated in late pregnancy against enterotoxigenic strains of Escherichia coli. Thirty-four clinically healthy pregnant Holstein heifers were randomly assigned to 1 of 4 treatments and vaccinated (days 210 and 240 of gestation) against E. coli with a multivalent vaccine. Treatment A (n = 8) was offered the basal ration supplemented with 200 g clinoptilolite/day and was injected with 0.1 mg/kg selenium (sodium selenite 0.5%) on the days of vaccination; treatment B (n = 9) was fed the basal ration supplemented with 200 g clinoptilolite/day; treatment C (n = 8) was injected with 0.1 mg/kg selenium on the days of vaccination and treatment D (n = 9) served as controls. The calves born were consuming the colostrum of their dams. Specific antibody titres against E. coli were determined with ELISA in blood serum samples of the heifers (210 and 240 of gestation and immediately after calving) and their calves (at birth, 12, 24 and 48 h after calving) and in composite colostrum samples (0, 12, 24 and 36 h post calving). During the first week of age all calves were monitored for the incidence of diarrhea. The administration of clinoptilolite alone and particularly in combination with selenium significantly increased the antibody titres against E. coli in blood serum of heifers and calves and in the colostrum of heifers. The incidence of diarrhea in calves was not significantly different among treatments. In the context of this experiment clinoptilolite administration, either alone or in combination with selenium appeared to improve the immune response of heifers vaccinated against E. coli and to provide enhanced protection to their calves. © 2009 Elsevier B.V. All rights reserved.

Pozoukidou G.,Aristotle University of Thessaloniki
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Spatial allocation of households and regional employment are the most significant data inputs in land use forecasting development and transportation modeling. Therefore obtaining and validating socioeconomic data and forecasts are becoming crucial tasks for any planning organization that wants to utilize land use forecasting models as planning analysis tool. This paper presents the results of an ongoing research investigating the application of an integrated transport land use model in small and medium sized metropolitan planning organizations. To this purpose it uses FHWA's freely available Transportation Economic Land Use Model for Ada and Canyon counties of Boise, ID. The paper concludes with the strengths and limitations of the model in the context of data requirements and calibration process. © 2014 Springer International Publishing.

Pramateftakis M.G.,Aristotle University of Thessaloniki
Techniques in Coloproctology | Year: 2010

Introduction: Hemorrhoidopathy is a very common benign surgical pathology. Hemorrhoids are divided into 4 stages, depending on symptoms and degree of prolapse. Hemorrhoidopexy is a technique developed for the treatment of 3rd degree hemorrhoids, but its application has been extended to the treatment of 4th degree hemorrhoids as well. Nevertheless, recent studies identify weaknesses of the PPH in the treatment of 4th degree hemorrhoids. Patients: One hundred and twenty-six consecutive patients with 3rd degree hemorrhoids underwent stapled hemorrhoidopexy. All procedures were performed under general anesthesia with the patient in lithotomy position. A phosphate enema was given to the patient 2 h before the procedure, and cephalosporine and metronidazole were administered at anesthesia induction. Most patients were discharged the day after the operation. All patients were reassessed at 1, 6 weeks, 6 and 12 months after the procedure. Results: The mean operating time was 16.3 min. Of all patients, 5.8% complained of mild rectal pain for a postoperative period of 5-12 days, 5.8% developed post-operative urinary retention, managed with catheterization, 13.3% experienced fecal urgency while 5.8% experienced gas incontinence, which subsided 2-8 weeks from surgery. The mean hospital stay was 1.2 days. Most patients returned to daily activities within 2-5 days. Ninety-five percent of patients returned for their follow-up visits. Recurrence of the disease occurred in 8 patients (6.6%). It was managed conservatively in 2 patients, 3 underwent redo hemorrhoidopexy and 3 underwent classic hemorrhoidectomy. Conclusion: According to our results, stapled hemorrhoidopexy seems to be a safe, pain-free and, in the longterm, effective technique for the treatment of 3rd degree hemorrhoids. © Springer-Verlag 2010.

Feidas H.,Aristotle University of Thessaloniki
Theoretical and Applied Climatology | Year: 2016

Summary: In this paper, the surface and lower tropospheric temperature trends in Greece and their relationship to the atmospheric circulation for the period 1955–2013 were examined, updating the study of Feidas et al. (Theor Appl Climatol 79:185–208, 2004) for data observed during the 12-year period 2002–2013. The trend analysis is based on a combination of three statistical tests. The trends are now examined for all the seasonal time series, new atmospheric circulation indices were added in the analysis, and maps with the spatial distribution of correlation between air temperature and atmospheric circulation were constructed and analysed. The series updated to 2013 for 18 stations reveal a clearer positive trend than that found for the period 1955–2001 on both the annual and the seasonal timescales. The warming signal detected only in summer in the study of Feidas et al. (Theor Appl Climatol 79:185–208, 2004) has now intensified and spread in other seasons. This warming appears to be mainly caused by the very high temperatures in the last decade (after 2004) of the record. At the national scale, there is now a match between surface temperature trends in Greece and Northern Hemisphere (NH) but only for summer, spring and annual time series, which are the only time series presenting a statistically significant warming trend in Greece. Satellite-induced lower tropospheric temperatures now show a statistically significant tropospheric temperature warming trend for the period 1979–2013, for both areas (Greece and NH). Lower tropospheric and surface air temperatures for the same period (1979–2013) show a very good agreement, with differences only in winter and summer for Greece. The influence of atmospheric circulation on the temperature variability in Greece was also examined using two more circulation indices: the Eastern Mediterranean Pattern Index (EMPI) and the North-Sea Caspian Pattern Index (NCPI). EMPI and especially NCPI explain better now the temperature variance in Greece, principally in winter. This connection, however, is not only developed during winter, as expected, but is also present for annual and other seasonal temperatures. © 2016 Springer-Verlag Wien

Pegklidou K.,Aristotle University of Thessaloniki
Current diabetes reviews | Year: 2010

Diabetes mellitus is an increasing world health problem; particularly the prevalence of type 2 diabetes has assumed epidemic dimensions in Western industrialized societies. It is mainly the environmental, dietary and lifestyle behavioral factors that are the control keys in the progress of this disease. Several epidemiological studies have linked over nutrition and lack of physical activity with type 2 diabetes. Indeed, the excessive consumption of energy dense foods as source of carbohydrates and fats along with ineffective medical management has negative impact on controlling blood glucose levels and on insulin response. This usually leads to a hyperglycemic state, which is associated with the development of the devastating secondary complications. Dietary guidelines have always been important for people with diabetes mellitus. Nutrition management aims to improve health quality maintaining blood glucose levels in normal range so as to reduce the risk for diabetes complications. A well-balanced diet that provides the essential macro- and micro-nutrients is always an impaired need for a patient with diabetes. In this article nutrition recommendations will be displayed for the management of diabetes type 2 and the prevention of its complications. Particular emphasis will be given to the important role of micronutrients such as trace elements and vitamins as well as to the potentiality of some dietary agents to inhibit aldose reductase enzyme, implicated in the etiology of diabetes complications.

Oikonomou V.K.,Aristotle University of Thessaloniki | Oikonomou V.K.,Tomsk State University of Control Systems and Radioelectronics
General Relativity and Gravitation | Year: 2015

Using the reconstruction technique with an auxiliary field, we investigate which F(R) gravities can produce the matter bounce cosmological solutions. Owing to the specific functional form of the matter bounce Hubble parameter, the reconstruction technique leads, after some simplifications, to the same Hubble parameter as in the matter bounce scenario. Focusing the study to the large and small cosmic time t limits, we were able to find which F(R) gravities can generate the matter bounce Hubble parameter. In the case of small cosmic time limit, which corresponds to large curvature values, the F(R) gravity is F(R)∼R+αR2, which is an inflation generating gravity, and at small curvature, or equivalently, large cosmic time, the F(R) gravity generating the corresponding limit of the matter bounce Hubble parameter, is F(R)∼1R, a gravity known to produce late-time acceleration. Thus we have the physically appealing picture in which a Jordan frame F(R) gravity that imitates the matter bounce solution at large and small curvatures, can generate Starobinsky inflation and late-time acceleration. Moreover, the scale factor corresponding to the reconstruction technique coincides almost completely to the matter bounce scenario scale factor, when considered in the aforementioned limiting curvature cases. This is scrutinized in detail, in order to examine the validity of the reconstruction method in these limiting cases, and according to our analysis, exact agreement is achieved. © 2015, Springer Science+Business Media New York.

Mademli L.,Aristotle University of Thessaloniki | Arampatzis A.,Humboldt University of Berlin
Age | Year: 2014

Older adults are more prone to falls during walking than young adults, although they walk more slowly and demonstrate higher stability state. This paradox of higher stability state but less safe locomotion let us hypothesize that older people may move closer to their dynamic stability limits. In order to investigate this hypothesis, the present study examined the safety factor of dynamic stability in old and young individuals when walking at their preferred velocity. Twelve older and 12 young male participants walked at their (a) walk-to-run transition velocity (WRV, i.e., maximum capacity) and (b) preferred walking velocity (PWV, i.e., actual applied load). Whole body kinematic data and ground reaction forces were captured. Dynamic stability was assessed using the "margin of stability (MoS)" as a criterion for the stability state of the body (extrapolated center of mass concept). The safety factor was calculated as the ratio between MoS at WRV and MoS at PWV. We found that, although older participants walked slower and provided a higher stability state compared to young ones, they showed a significantly reduced safety factor during preferred walking. This confirmed our hypothesis. Old adults do not walk slowly enough in relation to their maximum walking velocity, resulting to a lower safety factor during normal locomotion. Apparently, the age-related muscle degeneration affects WRV more than PWV. The resulting lower safety factor for the older participants may partly explain the increased risk of falls in their daily life, in spite of slower locomotion. © 2014 American Aging Association.

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.

Papadopoulos K.G.,ABB | Margaris N.I.,Aristotle University of Thessaloniki
Journal of Process Control | Year: 2012

An extension of the Symmetrical Optimum criterion for the design of PID type-p closed- loop control systems is proposed. Type-p control loops are characterized by the presence of p integrators in the open-loop transfer function. For designing a PID type-p control loop there should exist an PI pD, or PI (p-1)D, or PID and so on, if the controlled process is of type-0 or type-1 or type-(p - 1) respectively. A type-II control loop achieves zero steady state position and velocity error, a type-III control loop achieves zero steady state position, velocity and acceleration error and therefore a type-p control loop is expected to track both faster reference signals and eliminate higher order errors at steady state. For deriving the proposed control law, a transfer function containing dominant time constants and the plant's unmodelled dynamics has been considered in the frequency domain. The final control law consists of analytical expressions that involve both dominant dynamics and model uncertainty of the controlled process. For justifying the potential of the proposed theory, simulation results for representative processes met in many industry applications are presented. © 2011 Elsevier Ltd. All Rights Reserved.

Karampetakis N.P.,Aristotle University of Thessaloniki
Asian Journal of Control | Year: 2010

A new family of companion forms for polynomials and polynomial matrices has recently been developed in (Lin. Algebra Appl. 2003; 372: 325-331; Electron. J. Lin. Algebra 2004; 11:78-87) respectively. The application of these new companion forms to polynomial matrices with symmetries has been examined in (Electron. J. Lin. Algebra 2006; 15:107-114). In this work we extend the results presented in (Electron. J. Lin. Algebra 2006; 15:107-114) to the case of 2-D polynomial matrices. Thus, we provide a new matrix pencil that preserves both the symmetric structure and the structural invariants, of the original 2-D polynomial matrix. The results are also extended to the polynomial system matrix case. © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.

Tsonos A.-D.G.,Aristotle University of Thessaloniki
Engineering Structures | Year: 2010

This paper investigates the effectiveness and suitability of shotcrete and cast-in-place concrete as means of retrofitting columns and beam-column joints in reinforced concrete frame structures, so as to improve their shear and/or flexural performance. Thus, the use of four-sided and two-sided reinforced shotcrete or cast-in-place concrete jackets has been investigated experimentally for the case of pre-earthquake retrofitting of columns and beam-column joints. Focus has been placed on studying their lateral performance and on comparing the effectiveness of the reinforced shotcrete jackets with reference to the corresponding cast-in-place ones, as well as that of the two-sided jackets with reference to the corresponding four-sided ones. All types of concrete jackets examined were found to be equally satisfactory in their ability to strengthen existing old frame structures. © 2009 Elsevier Ltd. All rights reserved.

Roubos K.,Aristotle University of Thessaloniki
Genetics and molecular research : GMR | Year: 2010

Olea europaea is one of the oldest species of domesticated trees. We used microsatellite markers for fingerprinting and for evaluation of genetic similarity and structure of 26 Greek olive cultivars, which cover most of the olive cultivation regions of Greece, including previously undescribed denominations from northern Greece. Eighty-one alleles were revealed with six SSR loci that were selected as most informative of 10 SSR primers that were initially investigated. The number of alleles per locus varied from 7 to 20 (mean, 13.5). Heterozygosity ranged from 0.240 at locus DCA-3 to 0.826 at locus UDO99-9, with a mean value of 0.600. Analysis of 104 trees representing 26 denominations (four trees per denomination) revealed 26 distinct SSR profiles, indicating 26 olive cultivars; no intracultivar variability was observed. Genetic and geographic distances were not significantly correlated, based on the Mantel test. These SSR loci allowed unequivocal identification of all the cultivars and will be useful for future breeding and olive germplasm management efforts.

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.

Boboridis K.G.,Aristotle University of Thessaloniki
Cochrane database of systematic reviews (Online) | Year: 2011

Orbital decompression is an established procedure for the management of exophthalmos and visual rehabilitation from optic neuropathy in cases of thyroid eye disease. Numerous procedures for removal of orbital bony wall, fat or a combination of these for a variety of indications in different stages of the disease have been well reported in the medical literature. However, the relative effectiveness and safety of these procedures in relation to the various indications remains unclear. To review current published evidence for the effectiveness of surgical orbital decompression for disfiguring proptosis in adult thyroid eye disease and summa rise information on possible complications and the quality of life from the studies identified. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 10), MEDLINE (January 1950 to October 2011), EMBASE (January 1980 to October 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (http://clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 6 October 2011. We searched oculoplastic textbooks, conference proceedings from the European and American Society of Ophthalmic Plastic and Reconstructive Surgery (ESOPRS, ASOPRS), European Ophthalmological Society (SOE), the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) for the years 2000 to 2009 to identify relevant data. We attempted to contact researchers who are active in this field for information about further published or unpublished studies. We included randomised controlled trials (RCTs) with no restriction on date or language comparing two or more surgical methods for orbital decompression with removal of bony wall, orbital fat or a combination of both for disfiguring proptosis or comparison of surgical techniques with any form of medical decompression. Each review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained according to the inclusion criteria. Disagreements between the authors were resolved by discussion. We identified two randomised trials eligible for inclusion in the review. There was significant variability between the trials for interventions, methodology and outcome measures and therefore meta-analysis was not performed. One study suggested that the transantral approach and endoscopic transnasal technique had similar effects in reducing exophthalmos but that the endoscopic approach may be safer, relating to fewer complications. This study had short-term follow-up and lacked information on our primary outcome (success or failure of treatment). The second study provided evidence that intravenous steroids may be superior to primary surgical decompression in the management of compressive optic neuropathy requiring less secondary surgical procedures, although it relates more frequently to transient side effects. This study was weakened by a small sample size. Until more credible evidence is available recommendations as to best treatment cannot be reliably made. A single study showed that the transantral approach for orbital decompression was related to more complications than the endoscopic transnasal technique which is preferred by Ear, Nose and Throat (ENT) surgeons, usually as an adjunctive procedure. Intravenous steroids were reported in a single trial to be the most efficient intervention for dysthyroid optic neuropathy. The majority of published literature on orbital decompression for thyroid eye disease consists of retrospective, cohort, or case series studies. Although these provide useful descriptive information, clarification is required to show the relative effectiveness of each intervention for various indications.The two RCTs reviewed are not robust enough to provide credible evidence to our understanding of current decompressive surgery and to support recommendations for clinical practice. There is evidence from currently available uncontrolled studies that removal of the medial and lateral wall (balanced decompression) with or without fat removal may be the most effective surgical method related to only a few complications.There is a clear need for randomised studies evaluating the balanced two-wall, three-wall and orbital fat decompression techniques. Comparison with other surgical techniques for orbital decompression or with immunosuppression in cases of compressive optic neuropathy would also be important. These studies should primarily address the reduction of exophthalmos, disease severity, complication rates, quality of life and cost of the intervention.

Panayiotou C.,Aristotle University of Thessaloniki
Polymer (United Kingdom) | Year: 2013

The novel predictive approach of Partial Solvation Parameters (PSP) is extended and applied to polymer mixtures. Quantum mechanics and statistical thermodynamics are used in order to extract information on the molecular descriptors of each compound and develop simple analytical expressions for all basic thermodynamic quantities of mixtures. Emphasis is given on hydrogen-bonded polymer mixtures. Apart from polymer-polymer miscibility, the PSP approach is used for the prediction of melting point depression, fraction of hydrogen-bonded groups, critical composition of a copolymer for miscibility with another polymer, and the Flory-Huggins χ1,23 interaction parameter of a solute-probe (1) at infinite dilution in a mixture of polymers (2,3) which is obtained from inverse gas chromatography (IGC) experiments. The predictions are compared with experimental data and the agreement is critically discussed. The predictions of polymer-polymer miscibility on the basis of spinodal lines are compared with the corresponding predictions on the basis of χ interaction parameters. The strength and weakness of the approach are also critically discussed in relation with its capacity and reliability to act as a designing tool of new compatible polymer blends. The perspectives of this unified approach to solution thermodynamics are discussed. © 2013 Elsevier Ltd. All rights reserved.

Aravanopoulos F.A.,Aristotle University of Thessaloniki
Biomass and Bioenergy | Year: 2010

The purpose of this review is to provide a critical analysis of the literature regarding the breeding of fast growing forest tree species dedicated to biomass production in Greece and to identify future goals. The main genera employed in pertinent research which show the most promising results for operational plantations belong to Populus spp. and Platanus spp. The best poplar clone (P. x euramericana I-455) produced 16.54 t ha-1 y-1 dry weight averaged over different experimental plantations and rotation periods, while the best clone derived from the Greek breeding program (Populus deltoides var. missouriensis × Populus nigra var. pubescens He-X/3) produced 14.23 t ha-1 y-1 respectively. The best results of Platanus species and hybrids were at the vicinity of 10 t ha-1 y-1. Clones selected under a combination of higher temperature and drier condition regimes reflecting the Mediterranean field conditions will be valuable in future breeding under a changing climate and increased energy needs. The high genetic diversity of the virtually unattached local genetic reserve can provide even from the initial breeding cycles great opportunities for genetic improvement and significant genetic gains. © 2010 Elsevier Ltd.

Panidis D.,Aristotle University of Thessaloniki
European journal of endocrinology / European Federation of Endocrine Societies | Year: 2013

Insulin resistance (IR) is frequent in polycystic ovary syndrome (PCOS) and contributes to the increased risk for type 2 diabetes mellitus and cardiovascular disease of this population. Several markers of IR are used but most are expensive or have limited sensitivity and specificity. Preliminary data suggest that the menstrual cycle pattern correlates with IR in PCOS but existing studies are small. We aimed to assess the relationship between the type of menstrual cycle irregularities and IR in PCOS. Prospective study. We studied 1285 women with PCOS, divided according to the menstrual cycle pattern. Patients with isolated secondary amenorrhea and those with secondary amenorrhea alternating with regular menstrual cycles were more insulin resistant than patients with regular cycles (Group D). Patients with isolated oligomenorrhea were also more insulin resistant than Group D. However, patients with oligomenorrhea alternating with regular cycles, secondary amenorrhea, or polymenorrhea had comparable levels of markers of IR with Group D. Moreover, patients with oligomenorrhea alternating with regular cycles were less insulin resistant than patients with secondary amenorrhea alternating with regular cycles. Finally, patients with isolated polymenorrhea and those with polymenorrhea alternating with regular cycles had comparable levels of markers of IR with Group D. Amenorrhea is associated with more pronounced IR in PCOS, and oligomenorrhea portends a less excessive risk for IR than amenorrhea whereas polymenorrhea appears to be even more benign metabolically. Therefore, the type of menstrual cycle abnormality appears to represent a useful tool for identifying a more adverse metabolic profile in PCOS.

Petsatodis G.,Aristotle University of Thessaloniki
Journal of orthopaedic surgery (Hong Kong) | Year: 2011

Pigmented villonodular synovitis is a reactive condition characterised by exuberant proliferation of synovial villi and nodules. It may be localised or diffuse and can cause severe articular damage. This report is of 2 patients with pigmented villonodular synovitis of the shoulder causing extensive arthritic changes. Both patients underwent shoulder hemiarthroplasty and total synovectomy and achieved satisfactory painless range of motion, with no signs of local recurrence or loosening of the prosthesis after 4 to 5 years of follow-up.

Charalambakis N.,Aristotle University of Thessaloniki
Applied Mechanics Reviews | Year: 2010

In this paper, we present a critical survey on homogenization theory and related techniques applied to micromechanics. The validation of homogenization results, the characterization of composite materials and the optimal design of complex structures are issues of gre-technological importance and are viewed here as a combination of mathematical and mechanical homogenization. The mathematical tools for modeling sequentially layered composites are explained. The influence of initial and boundary conditions on the effective properties in nonlinear problems is clarified and the notion of stability by homogenization is analyzed. Multiscale micromechanics methods are outlined and the classical as well as the emerging analytical and computational techniques are presented. Computation of effective static and dynamical properties of materials with linear or nonlinear constitutive equations is closely related to the development of generalized theories such as the strain-gradient mechanics. Selected applications of these techniques are outlined. Moreover, the extension of kinetic techniques in homogenization and the related inverse imaging problem are presented. © 2010 by ASME.

Basdanis G.,Aristotle University of Thessaloniki
Techniques in coloproctology | Year: 2011

Colorectal cancer (CRC) is a major cause of death in the western world and a leading cause of cancer-related death. It is one of the most common human malignancies with >300,000 cases both in the United States and in the European Union each year. The present study was conducted to assess differences in various variables of CRC, such as location of the tumor, differentiation, Dukes classification, 5-year survival and possible changes in these patterns during the examined period. We collected data on 2000 patients with colorectal cancer, diagnosed and treated from 1960 to 2008 in 1st Propedeutic Surgical Clinic of Aristotle's University, Thessaloniki. Of 2000 cases reviewed, cancer was almost equal presented to both sexes, for all groups. Rectum was the most common tumor location in all analyzed groups (40.1%). The most common tumor differentiation was the moderate one (68.5%). Concerning tumor staging, Dukes' B tumors were most common (42.5%), and the cancer-related 5-year survival was increased by the time from 42 to 71%. In the past 20 years, considerable improvements have been made in colorectal cancer therapy, and patients had received more sophisticated and multidisciplinary treatments, resulting in a better 5-year survival rate.

Dimitrakopoulos E.G.,Aristotle University of Thessaloniki
Nonlinear Dynamics | Year: 2010

The oblique contact/impact of skew bridges triggers a unique rotational mechanism which earthquake reconnaissance reports correlate with deck unseating of such bridges. Building on the work of other researchers, the present study adopts a fully non-smooth rigid body approach and set-valued force laws, in order to analyze in depth this oblique multi-impact phenomenon. A linear complementarity formulation is proposed which yields a great variety of (multi-) impact states, depending on the initial (pre-impact) conditions, such as "slip" or "stick" at one corner (single-impact) or two corners (double-impact) of the body. The pertinent existential conditions of those impact states reveal a complex dynamic behavior. With respect to the rotational mechanism associated with double-impact, the physically feasible impact states as well as, counter-intuitive exceptions are recognized. The study proves that double oblique impact, both frictionless and frictional, may or may not produce rotation of the body and proposes criteria that distinguish each case. Most importantly, it is shown that the tendency of skew bridges to rotate (and hence unseat) after deck-abutment collisions is not a factor of the skew angle alone, but rather of the overall geometry in-plan, plus the impact parameters (coefficient of restitution and coefficient of friction). The study also provides a theoretical justification of the observed tendency of skew bridges to jam at the obtuse corner and rotate in such a way that the skew angle increases. Finally, counter-intuitive trends hidden in the response are unveiled which indicate that, due to friction, a skew bridge may also rotate so that the skew angle decreases. © 2009 Springer Science+Business Media B.V.

Bikiaris D.,Aristotle University of Thessaloniki
Materials | Year: 2010

In the last few years, great attention has been paid to the preparation of polypropylene (PP) nanocomposites using carbon nanotubes (CNTs) due to the tremendous enhancement of the mechanical, thermal, electrical, optical and structural properties of the pristine material. This is due to the unique combination of structural, mechanical, electrical, and thermal transport properties of CNTs. However, it is well-known that the properties of polymer-based nanocomposites strongly depend on the dispersion of nanofillers and almost all the discussed properties of PP/CNTs nanocomposites are strongly related to their microstructure. PP/CNTs nanocomposites were, mainly, prepared by melt mixing and in situ polymerization. Young's modulus, tensile strength and storage modulus of the PP/CNTs nanocomposites can be increased with increasing CNTs content due to the reinforcement effect of CNTs inside the polymer matrix. However, above a certain CNTs content the mechanical properties are reduced due to the CNTs agglomeration. The microstructure of nanocomposites has been studied mainly by SEM and TEM techniques. Furthermore, it was found that CNTs can act as nucleating agents promoting the crystallization rates of PP and the addition of CNTs enhances all other physical properties of PP. The aim of this paper is to provide a comprehensive review of the existing literature related to PP/CNTs nanocomposite preparation methods and properties studies. © 2010 by the authors.

Roukas T.,Aristotle University of Thessaloniki
Critical Reviews in Biotechnology | Year: 2016

In aerobic metabolism, reactive oxygen species (ROS) are formed during the fermentation that can cause oxidative stress in microorganisms. Microbial cells possess both enzymatic and non-enzymatic defensive systems that may protect cells from oxidative damage. The antioxidant enzymes superoxide dismutase and catalase are the two key defensive enzymes to oxidative stress. The factors that induce oxidative stress in microorganisms include butylated hydroxytoluene (BHT), hydrogen peroxide, metal ions, dissolved oxygen tension, elevated temperature, menadione, junglone, paraquat, liquid paraffin, introduction to bioreactors of shake flask inocula and synthetic medium sterilized at initial pH 11.0. Carotenes are highly unsaturated isoprene derivatives. They are used as antioxidants and as coloring agents for food products. In fungi, carotenes are derived via the mevalonate biosynthesis pathway. The key genes in carotene biosynthesis are hmgR, ipi, isoA, carG, carRA and carB. Among microorganisms, Βlakeslea trispora is the main microorganism used for the production of carotenes on the industrial scale. Currently, the synthetic medium is considered the superior substrate for the production of carotenes in a pilot plant scale. The fermentation systems used for the production of carotenes include shake flasks, stirred tank fermentor, bubble column reactor and flat panel photobioreactor. This review summarizes the oxidative stresses in microorganisms and it is focused on the current status of carotene production by B. trispora including oxidative stress induced by BHT, enhanced dissolved oxygen levels, iron ions, liquid paraffin and synthetic medium sterilized at an initial pH 11.0. The oxidative stress induced by the above factors increases significantly the production of carotenes. However, to further reduce the cost of carotene production, new biotechnological methods with higher productivity still need to be explored. © 2015 Informa Healthcare USA, Inc.

Papamichos E.,Aristotle University of Thessaloniki
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2010

Borehole failure under anisotropic stresses in a sandstone is analyzed numerically for various borehole sizes using a nonlinear elastic-plastic constitutive model for a Cosserat continuum. Borehole failure is identified as macroscopic failure of the borehole through the development of shear bands and breakouts. The results compare well both qualitatively and quantitatively with experimental results from polyaxial tests on Red Wildmoor sandstone. They show that the hole size effect of the borehole failure strength is independent of the far-field stress anisotropy and follows a 2/5 power law of the hole size. A similar scale effect equation with a 4/5 power law is proposed for the scale effect of the maximum plastic shear strain at failure. This equation can be useful for better predicting hole-size-dependent failure with standard codes based on classical continua. The effect of stress anisotropy on the borehole failure stress is found to be independent of the hole size. The failure stress decreases linearly to 40% as the stress anisotropy increases. However, the maximum plastic shear strain at failure is stress anisotropy independent and therefore the critical plastic shear strain for failure is only hole-size dependent. © 2009 John Wiley & Sons, Ltd.

Sidiropoulos E.,Aristotle University of Thessaloniki
Journal of Physics: Conference Series | Year: 2014

A new treatment is presented for land use planning problems by means of extremal optimization in conjunction to cell-based neighborhood local search. Extremal optimization, inspired by self-organized critical models of evolution has been applied mainly to the solution of classical combinatorial optimization problems. Cell-based local search has been employed by the author elsewhere in problems of spatial resource allocation in combination with genetic algorithms and simulated annealing. In this paper it complements extremal optimization in order to enhance its capacity for a spatial optimization problem. The hybrid method thus formed is compared to methods of the literature on a specific characteristic problem. It yields better results both in terms of objective function values and in terms of compactness. The latter is an important quantity for spatial planning. The present treatment yields significant compactness values as emergent results. © Published under licence by IOP Publishing Ltd.

Current Opinion in Allergy and Clinical Immunology | Year: 2010

PURPOSE OF REVIEW: The purpose of the present review is to outline the clinical aspects and management of the upper airway involvement in the patients suffering from hereditary angioedema. RECENT FINDINGS: Molecular mechanisms of hereditary angioedema reviewed in the literature conclude that it is an autosomal dominant disorder, characterized by the deficiency of C1 inhibitor due to mutations of its gene (SERPING). Hereditary angioedema manifests as episodes of localized swelling in any site of the body from skin, gastrointestinal tract to the upper airway, where it is severe and life-threatening. The age of onset, frequency of attacks and the factors triggering upper airway swelling in hereditary angioedema are variable among different patients. Acute laryngeal edema should be managed in emergency with monitoring of airway patency. To avoid airway obstruction, therapy should begin early either with current treatment (C1 inhibitor concentrate) or with new drugs developed recently. In patients with recurrent upper airway swelling attacks, long-term prophylaxis is recommended. CONCLUSION: The use of old and new treatment in acute attacks as well as in prophylaxis (long and short-term) has changed the outcome of patients with hereditary angioedema who present upper airway swelling. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Tamiolakis I.,University of Crete | Lykakis I.N.,Aristotle University of Thessaloniki | Katsoulidis A.P.,Northwestern University | Armatas G.S.,University of Crete
Chemical Communications | Year: 2012

We report an unprecedented formation of mesoporous titania via a surfactant-assisted aggregating assembly of TiO 2 nanoparticles. These mesostructures possess a highly crystalline anatase phase, large and accessible pore surface area, and exhibit superior photocatalytic performance. © 2012 The Royal Society of Chemistry.

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.

Papanikolaou V.K.,Aristotle University of Thessaloniki
Computers and Structures | Year: 2012

A new methodology is presented for the ultimate strength and moment-curvature analysis of arbitrary composite sections under biaxial bending and axial load. The definition of section geometry and material properties can be unconditionally complex, based on an object-oriented implementation. Stress integration is performed using a Green path integral, with an adaptive strain-mapped Gaussian sampling. Derivative-free solution strategies for the calculation of incremental and ultimate response are applied. Results are presented in the form of moment-curvature curves, ultimate strength interaction curves and 3D failure surfaces. The performance of the methodology is demonstrated through various case studies, comparisons and benchmarks. © 2012 Elsevier Ltd. All rights reserved.

Grigoriadis N.,Aristotle University of Thessaloniki | van Pesch V.,Cliniques Universitaires St Luc
European Journal of Neurology | Year: 2015

Multiple sclerosis (MS) is a multi-component disease characterized by inflammation, neurodegeneration and failure of central nervous system (CNS) repair mechanisms. Immune dysregulation appears to originate with dendritic cells (antigen-presenting cells) which have an activated phenotype in individuals with MS. Dendritic cells migrate across the blood-brain barrier and induce differentiation of memory T cells into pro-inflammatory T helper 1 (Th1) and Th17 lymphocytes. In turn, induction of macrophage and microglial activation produces other pro-inflammatory cytokines and oxygen and nitric oxide radicals responsible for the demyelination and axonal loss. Other known mediators of MS pathology include CD8+ T cells and memory B cells within the CNS. Some pathological hallmarks of MS are early axonal degeneration and progressive decline of brain volume in patients with clinically isolated syndromes who progress to clinically definite MS. Many new options to interfere with the course of MS have become available in recent years. To limit inflammatory demyelinating processes and delay disease progression, intervention to control inflammation must begin as early as possible. Each distinct type of immunotherapy (immunomodulation, immunosuppression and immune-selective intervention - blockade type, sequestering type or depleting type) corresponds to a specific underlying immunopathology of MS. © 2015 European Academy of Neurology.

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.

Apostolidis A.,Aristotle University of Thessaloniki
Expert Opinion on Pharmacotherapy | Year: 2011

Introduction: Considered by many a 'revolution' in the treatment of intractable overactive bladder (OAB) and with an increasing number of centers including it in their practice worldwide, botulinum neurotoxin A (BoNT/A) injected into the bladder wall is a treatment of significant potential. In anticipation of the results of multicenter, placebo-controlled, dose-ranging studies, this is a critical review of the available literature on the use of botulinum toxins in the treatment of either neurogenic or idiopathic OAB. Areas covered: The review is based on the English-language literature published by Medline on the use of botulinum toxins in neurogenic or idiopathic detrusor overactivity/OAB since the seminal publication in 2000. The reader is exposed to the cumulative data as well as to a more critical insight on the clinical efficacy of single and repeat injections of the most widely used formulations, the injection techniques, including different doses, dilutions and injection sites, the mechanism of action, the side effects and the cost-effectiveness of the treatment. Expert opinion: Despite the markedly heterogeneous methodologies, published studies suggest that BoNT/A is effective when a number of outcomes are considered, and is considered safe. As results of large registration studies are awaited, additional research on the optimization of clinical practice parameters such as benefit-risk ratio, injection technique, predictors of response and long-term safety, as well as on the mechanism of action and the cost-effectiveness of the treatment, would be welcome. © 2011 Informa UK, Ltd.

Mataftsi A.,Aristotle University of Thessaloniki
Developments in Ophthalmology | Year: 2016

Postoperative glaucoma is perhaps the most feared complication after paediatric cataract surgery, as it is difficult to control. Paediatric glaucoma is also challenging to diagnose, and different definitions of glaucoma have led to a rather big range of reported incidences of this disease. It can occur soon after surgery, in which case it is usually closed-angle glaucoma, or it can have a late onset, even more than a decade after surgery, and its aetiopathogenesis remains unclear to this day. There is significant controversy as to what the risk factors are for developing it, especially regarding intraocular lens implantation. The vast majority of studies show that an earlier age at surgery confers a higher risk. Medical and surgical treatment of aphakic/pseudophakic glaucoma can be successful; however, management often requires repeated procedures with or without multiple medications, and the prognosis is guarded. The visual outcome depends on sufficient intraocular pressure control and management of concurrent amblyopia. © 2016 S. Karger AG, Basel.

Kiratzi A.,Aristotle University of Thessaloniki
Tectonophysics | Year: 2010

On 24 May 2009 (GMT 16:17) a moderate size (Mw5.2) earthquake sequence burst north of Lake Doirani along the Greek-FYROM borders and ruptured a N282°E striking normal fault of ~6. km in length dipping at an angle of ~60° to the north. The focal mechanisms for 25 of the stronger events, obtained through time-domain moment tensor inversion, reveal the prevalence of normal faulting along ~WNW-ESE striking planes, sometimes dip slip motions are combined with a considerable strike-slip component. Broad band waveforms from the Hellenic Unified Seismological Network (HUSN) and neighbouring networks were used to invert source time functions (STFs) and calculate the slip model for the strongest event (GMT 16:17). STFs were obtained through an empirical Green's function approach. No directivity could be clearly identified for this moderate magnitude event. Slip was released in a single patch of dimensions 6. km × 8 km, maximum slip is estimated at 15. cm, while average slip on the ruptured area (area of subfaults of non-zero slip) was 3. cm. One characteristic of the slip model was the large rise time, for a moderate size event, which was estimated to be 1.0. s, implying a slow slip-rate function. Brune's static stress drop is calculated ~5 bars. It must be noted that the north dipping plane is identified as the fault plane, (slip vector trending N332°E) based on the model variance of the STFs inversion. © 2010 Elsevier B.V.

Mavromatis T.,Aristotle University of Thessaloniki
International Journal of Climatology | Year: 2010

This paper presents a framework for making use of drought indices in climate change impact assessment studies. To achieve this goal: (1) linear relationships between drought indices and satellite soil moisture information, derived from the ERS scatterometer [Soil Water Index, (SWI)] for the years 1992-2000, are developed by employing [analysis of covariance (ANCOVA)] and (2) the vulnerability of soil water content to climate change is assessed using regional climate model (RCM) projections. Several drought indices are evaluated for their abilities to monitor SWI, on a monthly basis, at nine locations in Greece. The original Palmer Drought Severity Index (Orig-PDSI) and its self-calibrated version (SC-PDSI) correlated best with SWI in three stations each and precipitation in two. The degree of agreement, however, varies substantially among the sites. Seasonality has a significant effect on the relationship between the SWI and the two aforementioned drought indices (Orig-PDSI, SC-PDSI), presenting a bimodal pattern that fluctuates markedly during the year. ANCOVA has proved to be a useful method for measuring the agreement between SWI and the drought indices (r2 ranged from 46.2% to 79.9%), implying that drought indices can be an important information source for detecting and monitoring drought. 11 different RCM runs are compared for their abilities to reproduce present climate mean and variability of temperature and precipitation. Orig-PDSI is not sensitive to the much warmer future climate change scenarios constructed and, therefore, is not suggested for climate change impacts assessment studies. SC-PDSI, on the other hand, has the potential to be used; however, its responses depend on the time period on which the climate characteristics and duration factors are computed from. © 2009 Royal Meteorological Society.

Asvesta A.,Technological Educational Institute of West Macedonia | Dimitriadis S.,Aristotle University of Thessaloniki
Journal of Volcanology and Geothermal Research | Year: 2010

In northern Greece, along the western edge of the Paleozoic Vertiscos terrane (Serbomacedonian massif) and within the Peonias subzone - the eastern part of the Vardar (Axios) Zone - a Silicic Volcano-Sedimentary (SVS) succession of Permo(?)-Skythian to Mid Triassic age records the development of a faulted continental margin and the formation of rhyolitic volcanoes along a continental shelf fringed by neritic carbonate accumulations. It represents the early rifting extensional stages that eventually led to the opening of the main oceanic basin in the western part of the Vardar (Axios) Zone (the Almopias Oceanic Basin). Even though the SVS succession is deformed, altered, extensively silicified and metamorphosed in the low greenschist facies, primary textures, original contacts and facies relationships are recognized in some places allowing clues for the facies architecture and the depositional environment.Volcanic and sedimentary facies analysis has been carried out at Nea Santa and Kolchida rhyolitic volcanic centres. Pyroclastic facies, mostly composed of gas-supported lapilli tuffs and locally intercalated accretionary lapilli tuffs, built the early cones which were then overridden by rhyolitic aphyric and minor K-feldspar-phyric lava flows. The characteristics of facies, especially the presence of accretionary lapilli, imply subaerial to coastal emplacement at this early stage. The mature and final stages of volcanism are mostly represented by quartz-feldspar porphyry intrusions that probably occupied the vents. At Nea Santa area, the presence of resedimented hyaloclastite facies indicates subaqueous emplacement of rhyolitic lavas and/or lobes. Moreover, quartz-feldspar-phyric sills and a partly extrusive dome featuring peperites at their margins are inferred to have intruded unconsolidated, wet carbonate sediments of the overlying Triassic Neritic Carbonate Formation, in a shallow submarine environment. The dome had probably reached above wave-base as is indicated by the presence of reworked rhyolitic clasts in the younger mixed rhyolite-carbonate epiclastic sedimentary facies. This facies is interpreted as mass- and debris-flow of mixed provenance, deposited below wave-base.The facies architecture of the SVS succession records a change in volcanic activity from explosive to effusive and then to intrusive. The depositional environment changed from subaerial-coastal to shallow submarine as the silicic volcanism evolved and carbonate sedimentation was progressively taking over, probably compensating for the gradual subsidence of the corresponding basin. Silicic magmatism and carbonate sedimentation were contemporaneous and spatially related.The timing of the rifting, the continental crustal elements involved and the accompanying tectonic, magmatic and sedimentary processes are features of the spatially and temporally evolving western peri-Tethyan region. © 2010 Elsevier B.V.

Panayiotou C.,Aristotle University of Thessaloniki
Journal of Chemical and Engineering Data | Year: 2010

The central theme in this series of papers is the development of a coherent and consistent equation-of-state model of fluids in the frame of solvation thermodynamics. Two main ingredients will be used for this purpose: the first will be the successful conductor-like screening model (COSMO) type group-contribution models with their quantum-mechanical description of fluids, and the second, our recent nonrandom hydrogen-bonding (NRHB) equation-of-state framework. The bridge between the two is the quasi-chemical treatment of the nonrandom distribution of molecular entities in the system, a treatment used by Henry Kehiaian in his DISQUAC group-contribution model. In this first part we develop the solvation formalism of NRHB and propose a first approach for turning the COSMO model into an equation-of-state model in a straightforward and consistent manner. Although the formalism is general, the focus is on the self-solvation of fluids. This development permits the calculation of the various components of solvation Gibbs energy, such as the cavitation and charging components or the enthalpic and the entropic ones. It permits, in particular, their study over a broad range of external conditions. The strength of the intermolecular forces and its role on the variation of these components, as well as their interdependence, are critically discussed. © 2010 American Chemical Society.

Petridis H.P.,Aristotle University of Thessaloniki
The European journal of prosthodontics and restorative dentistry | Year: 2010

The purpose of this study was to study the stability of teeth adjacent to posterior edentulous spaces and correlate it with patient age and time lapse since tooth loss. Dental casts, panoramic radiographs, and questionnaires of patients treated in a University setting were employed. Teeth adjacent and opposing posterior edentulous spaces were examined for the following parameters: Supraeruption, rotation, space closure, and axial inclination. One hundred twenty three patients with 229 edentulous spaces were analyzed. Statistical analysis showed that the effects of "jaw", "gender", and "age group at the time of tooth loss" were not significant for any of the variables tested. The effect of time lapse since tooth loss was significant regarding the "amount of distal tooth inclination" (P<0.001), the "amount of distal tooth rotation" (P=0.004), and "space closure" (P=0.038). Post-hoc analysis of the "amount of distal tooth inclination" revealed a marked increase in inclination 5 years after tooth loss. Within the limitations of this study, it was concluded that in the group of patients studied, minor positional changes in teeth opposing or adjacent to posterior edentulous spaces had occurred. The greatest changes in position were recorded for mandibular teeth distal to edentulous spaces.

Pozoukidou G.,Aristotle University of Thessaloniki
Spatium | Year: 2014

Land use patterns and transport system are considered to be the two basic components of the urban development process, and as such they have been in the core of spatial planning policies for the last 4 decades. Land use transport interaction models are computer tools that could help us understand land use changes and organization of human activities in relation to existing or planned transport infrastructure. In this context this paper examines the perspectives of applying a land use transport interaction model for the city of Thessaloniki. Obtaining, preparing and validating socioeconomic data is a crucial part of the modeling process, therefore an extensive search of the required data was performed. The quest for appropriate and suitable data concluded with a detailed recording of emerged problems. In response to the inability of finding suitable data to perform the first step of the modeling process i.e. calibration, the paper concludes with some thoughts related to data availability, organization and standardization issues. Last but not least, the paper stresses out the significance of data availability for utilization of land use transport models, so as not to remain purely academic products but tools with practical value in planning.

Pantelidis L.,Aristotle University of Thessaloniki
Bulletin of Engineering Geology and the Environment | Year: 2010

A system for the quantification of the failure hazard of rock cuttings structured in the form of rating tables is proposed. Rock cuttings are classified according to their failure hazard taking into account both their drained condition and the influence that climatic conditions have on stability; the latter being the most common landslide-triggering factor. The system deals with seven types of failure including slides, topples and falls. Where possible and convenient, parameters are amalgamated using well-established expressions of safety factor increasing the objectivity of the system. In addition to triggering mechanisms, site-specific parameters related to the mean and critical precipitation height, as well as the potential for the development of adverse, water-related conditions are taken into account to arrive at a Hazard Index value. © 2009 Springer-Verlag.

Computers and Geotechnics | Year: 2010

The effect of inclined loading on the bearing capacity of foundations on horizontal ground surface is well established and both the exact solution and simpler empirical equations are available for the calculation of the failure loads. However, for footings on or near slopes complete solutions are available only for vertical loading. This paper investigates the influence of inclined loading on the horizontal and vertical failure loads. The finite element, upper bound plasticity and stress field methods are used to examine a wide range of geometries and soil properties. The methods are first validated against known solutions for two special cases and are subsequently employed to investigate the effect of the geometrical and material properties on the failure loads and the bearing capacity load interaction diagram. Based on this investigation an empirical equation is proposed for the load interaction diagram for undrained inclined loading of footings on or near slopes. © 2009 Elsevier Ltd. All rights reserved.

Tsipis C.A.,Aristotle University of Thessaloniki
Structure and Bonding | Year: 2010

During the last decade, the aromaticity/antiaromaticity of "bare" and "ligand-stabilized" rings of metal atoms has flourished reaching a high level of sophistication. Compared to the aromaticity/antiaromaticity encountered in organic rings, primarily being of the traditional π-type, "bare" and "ligand-stabilized" rings of metal atoms can exhibit a multifold aromaticity/antiaromaticity and conflicting aromaticity, arising from the electron delocalization of s, p, d, and even f orbitals of the ring atoms. In this context we can speak for σ-, π-, δ-, and φ-aromaticity/antiaromaticity as well as for double (σ + π) and even triple (σ +π + δ) aromaticity (possible in rings of transition metal atoms) and any possible combination of the σ-,π-, δ-, and σ-types of aromaticity/antiaromaticity. The f-orbital and possibly φ-aromaticity can exist only in rings of lanthanide and actinide metal atoms. In view of these facts, in this review we have provided an overview and updated information about aromaticity/antiaromaticity of rings of metal atoms covering the most significant developments in this new emerging field. © Springer-Verlag Berlin Heidelberg 2010.

Stamovlasis D.,Aristotle University of Thessaloniki
Chemistry Education Research and Practice | Year: 2010

The aim of the present paper is two-fold. First, it attempts to support previous findings on the role of some psychometric variables, such as, M-capacity, the degree of field dependence-independence, logical thinking and the mobility-fixity dimension, on students' achievement in chemistry problem solving. Second, the paper aims to raise some methodological and epistemological issues concerning the implementation of the general linear model (GLM) in this type of research. Multiple regression analysis was used to analyze the data, which were taken from students (N =86) in tenth grade of high school taking a compulsory course in chemistry. Three different techniques were implemented in order to support a linear model: The Added Variable Plots, the Stepwise Regression and the Best Subsets Regression. Residual analysis and collinearity diagnosis were also performed in order to test the robustness of inferential statistics. The GLM explained 39% of the variance and suggested that only M-capacity and logical thinking were the significant predictors, even though all the correlation coefficients with achievement were statistically significant. The extensive analysis of the linear regression procedures revealed their advantages and also their limitations in terms of statistical robustness. Moreover, a discussion is initiated concerning the explanatory power of linear models and suggests rethinking variance explained under a different philosophical perspective. It is argued that the weakness of the GLM in studying complex dynamical processes, such as problem solving, is rooted not merely in the statistical assumptions that do not hold, or in the variables that are ignored, but substantially it is deeply epistemological. © The Royal Society of Chemistry 2010.

Baltzis K.B.,Aristotle University of Thessaloniki
Recent Patents on Electrical Engineering | Year: 2012

In order to enhance the performance of wireless communication systems, we usually employ diversity combining techniques. Rake reception is a diversity method that gained popularity mainly due to its use in second and third generation mobile systems. This paper reviews important and recent advances in rake diversity and its applications in wireless communications. First, we provide some theoretical background of rake reception focusing on the initial idea proposed in the late 50's. Next, we present selected patent and scientific literature on rake receiver design. Recent patents, patent applications and scientific articles on the application of rake diversity in code division multiple access systems, ultrawideband communications and channel estimation are then discussed. Some more general applications of rake reception in wireless communications are also examined. Future perspectives of rake diversity are finally explored. © 2012 Bentham Science Publishers.

Sotiriadis A.,Aristotle University of Thessaloniki | Papatheodorou S.,University of Ioannina | Makrydimas G.,University of Ioannina
Ultrasound in Obstetrics and Gynecology | Year: 2012

Objective To quantify the effect on perinatal outcome in women treated with progesterone for the prevention of preterm birth. Methods MEDLINE and SCOPUS searches, including references of the retrieved articles and additional automated search using the 'search for related articles' PubMed function, were used. Randomized controlled trials assigning women at risk for preterm birth to progesterone or placebo were included (both singleton and multiple pregnancies). Outcomes were neonatal and perinatal death, respiratory distress syndrome (RDS), retinopathy, necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH) Grade 3-4, sepsis, admission to the neonatal intensive care unit (NICU) and composite adverse outcome. Results Sixteen studies (singletons, n = 7; twins, n = 7; triplets, n = 2) were included in the meta-analysis. For singleton pregnancies, progesterone reduced the rates of neonatal death (risk ratio (RR) 0.487 (95% CI, 0.290-0.818)), RDS (RR 0.677 (95% CI, 0.490-0.935)), NICU admission (RR 0.410 (95% CI, 0.204-0.823)) and composite adverse outcome (RR 0.576 (95% CI, 0.373-0.891)). No favorable effect was observed in twins; in fact, progesterone was associated with increased rates of perinatal death (RR 1.551 (95% CI, 1.014-2.372)), RDS (RR 1.218 (95% CI, 1.038-1.428)) and composite adverse outcome (RR 1.211 (95% CI, 1.029-1.425)). No significant effect was observed in triplet pregnancies. Conclusion Progesterone administration in singleton pregnancies at risk for preterm birth improves perinatal outcomes, but may actually have adverse effects in multiple pregnancies. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

Gialamas E.,Aristotle University of Thessaloniki
Türkiye parazitolojii dergisi / Türkiye Parazitoloji Derneǧi = Acta parasitologica Turcica / Turkish Society for Parasitology | Year: 2012

Although appendicitis is one of the most common causes of emergency surgery, parasites are rarely found associated with inflammation of the appendix. The aim of this study is to establish the prevalence of Enterobius vermicularis in surgically removed appendices, as well as to determine its possible role in the pathogenesis of appendicitis. A retrospective analysis of all the appendices removed during the last 20 years at a tertiary university hospital. Appendices removed during the course of another intra-abdominal procedure were excluded from the study. All 1085 surgical specimens removed from patients with clinical appendicitis were evaluated. Enterobius vermicularis was found in seven appendices (0.65%) with clinical symptoms of appendicitis. The parasite was most frequently identified in appendices without pathological changes (6/117). There was no case of chronic appendicitis presenting E. vermicularis infestation, while the parasite was rarely related to histological changes of acute appendicitis (1/901). The results suggest that the presence of E. vermicularis in the appendix might cause appendiceal pain (colic), but can rarely be associated with pathologic findings of acute appendicitis.

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

We investigate in detail the escape dynamics in an analytical gravitational model, which describes the motion of stars in a quasar galaxy with a disk and a massive nucleus. 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 ALignment Index method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $$L_1$$L1 and $$L_2$$L2 and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the configuration (x, y) and in the phase $$(x,\dot{x})$$(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 a remarkable presence of fractal basin boundaries along all the escape regimes. We hope our outcomes to be useful for a further understanding of the escape mechanism in active galaxy models. © 2015, Springer Science+Business Media Dordrecht.

Lazaridis N.K.,Aristotle University of Thessaloniki | Keenan H.,University of Strathclyde
Journal of Hazardous Materials | Year: 2010

The development of chitosan-based materials as useful adsorbent polymeric matrices is an expanding field in the area of adsorption science. Although chitosan has been successfully used for the removal of dyes from aqueous solutions, no consideration is given to the removal of dyes from contaminated soils. Therefore this study focuses on the potential use of chitosan as an in situ remediation technology. The chitosan beads were used as barriers to the transport of a reactive dye (Reactive Black 5, RB5) in soil column experiments. Batch sorption experiments, kinetic and equilibrium, were performed to estimate the sorption behavior of both chitosan and soil. The chitosan beads were prepared in accordance with published literature and a synthetic soil was prepared by mixing quantities of sand, silt and clay. The synthetic soil was classified according to British Standards. Calcium chloride was used as tracer to define transport rates and other physical experimental parameters. Dye transport reaction parameters were determined by fitting dye breakthrough curves (BTCs) to the HYDRUS-1D version 4.xx software. Fourier Transform-Infra Red (FT-IR) spectroscopy was used to reveal the sorption mechanism. The study showed that chitosan exhibited a high sorption capacity (Smax = 238 mg/g) and pseudo-first sorption rate (k1 = 1.02 h-1) coupled with low swelling and increased retardation for the azo dye tested. Thus it has potential as a Permeable Reactive Barrier (PRB) for containment and remediation of contaminated sites. © 2009 Elsevier B.V. All rights reserved.

Zotos E.E.,Aristotle University of Thessaloniki
Baltic Astronomy | Year: 2014

The main objective of this work is to determine the character of orbits of stars moving in the meridional (R, z) plane of an axially symmetric time-independent disk galaxy model with a central massive nucleus and an additional spherical dark matter halo component. In particular, we try to reveal the influence of the scale length of the dark matter halo on the different families of orbits of stars, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when this parameter varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish safely bet ween ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Our numerical computations reveal that when the dark matter halo is highly concentrated, that is when the scale length has low values the vast majority of star orbits move in regular orbits, while on the oth er hand in less concentrated dark matter haloes the percentage of chaos increases significantly. We also compared our results with early related work.

Zotou A.,Aristotle University of Thessaloniki
Central European Journal of Chemistry | Year: 2012

This review highlights the fundamentals and the most prominent advances in the field of HPLC instrumentation over the last decades. Fundamental aspects and practical considerations of column switching, conventional (heart-cut) and comprehensive two-dimensional LC are presented. Different aspects of microcolumn- and nanoliquid- chromatography are reviewed. Recent progress in column technology and the demands and developments in instrumentation and accessories for miniaturized LC are also discussed. In the field of miniaturization, particularly in chip-based nano-LC systems, some aspects on micro-fluidic chip fabrication, using particle-packed HPLC microchips or polymer-based monoliths, are addressed. An introduction to ultra performance LC (UPLC) is also presented. © Versita Sp. z o.o.

Sarigiannis D.A.,European Commission | Sarigiannis D.A.,Aristotle University of Thessaloniki | Hansen U.,European Commission
Environmental Health: A Global Access Science Source | Year: 2012

Background: The current paradigm for the assessment of the health risk of chemical substances focuses primarily on the effects of individual substances for determining the doses of toxicological concern in order to inform appropriately the regulatory process. These policy instruments place varying requirements on health and safety data of chemicals in the environment. REACH focuses on safety of individual substances; yet all the other facets of public health policy that relate to chemical stressors put emphasis on the effects of combined exposure to mixtures of chemical and physical agents. This emphasis brings about methodological problems linked to the complexity of the respective exposure pathways; the effect (more complex than simple additivity) of mixtures (the so-called 'cocktail effect'); dose extrapolation, i.e. the extrapolation of the validity of dose-response data to dose ranges that extend beyond the levels used for the derivation of the original dose-response relationship; the integrated use of toxicity data across species (including human clinical, epidemiological and biomonitoring data); and variation in inter-individual susceptibility associated with both genetic and environmental factors. Methods. In this paper we give an overview of the main methodologies available today to estimate the human health risk of environmental chemical mixtures, ranging from dose addition to independent action, and from ignoring interactions among the mixture constituents to modelling their biological fate taking into account the biochemical interactions affecting both internal exposure and the toxic potency of the mixture. Results: We discuss their applicability, possible options available to policy makers and the difficulties and potential pitfalls in implementing these methodologies in the frame of the currently existing policy framework in the European Union. Finally, we suggest a pragmatic solution for policy/regulatory action that would facilitate the evaluation of the health effects of chemical mixtures in the environment and consumer products. Conclusions: One universally applicable methodology does not yet exist. Therefore, a pragmatic, tiered approach to regulatory risk assessment of chemical mixtures is suggested, encompassing (a) the use of dose addition to calculate a hazard index that takes into account interactions among mixture components; and (b) the use of the connectivity approach in data-rich situations to integrate mechanistic knowledge at different scales of biological organization. © 2012 Sarigiannis and Hansen; licensee BioMed Central Ltd.

Tsagas C.G.,Aristotle University of Thessaloniki
Monthly Notices of the Royal Astronomical Society | Year: 2010

Recent surveys seem to support bulk peculiar velocities well in excess of those anticipated by the standard cosmological model. In view of these results, we consider here some of the theoretical implications of large-scale drift motions. We find that observers with small, but finite, peculiar velocities have generally different expansion rates from the smooth Hubble flow. In particular, it is possible for observers with larger than the average volume expansion at their location, to experience apparently accelerated expansion when the Universe is actually decelerating. Analogous results have been reported in studies of inhomogeneous (non-linear) cosmologies and within the context of the Lemaitre-Tolman-Bondi models. Here, they are obtained within the linear regime of a perturbed, dust-dominated Friedmann-Robertson-Walker cosmology. © 2010 The Author. Journal compilation © 2010 RAS.

Casale P.,University of Rome La Sapienza | Mazaris A.D.,Aristotle University of Thessaloniki | Freggi D.,Sea Turtle Rescue Center Italy
Endangered Species Research | Year: 2011

It is widely accepted that the age at sexual maturity of sea turtles is a critical parameter for studying population dynamics and persistence. Estimates of the age at maturity for such longlived species are derived using somatic growth models, which are still lacking for several regions of the world. In the present study, the growth rate of the loggerhead sea turtle Caretta caretta in the Mediterranean was investigated using a length-frequency analysis of a dataset collected over a 19 yr period (1990 to 2008). A total of 2255 individuals were measured in the central Mediterranean, with turtle size ranging from 16.8 to 97.5 cm curved carapace length (CCL). Monthly length-frequency histograms were constructed, and strong size modes were identified, assumed to represent individual cohorts. Growth rates were calculated by tracking the progression of the modes, by means of a modal progression analysis. Annual growth rates ranged from 0.37 to 6.5 cm yr -1. A von Bertalanffy growth function was used to estimate the time required by turtles to grow within the observed size range. The results indicate that turtles would take from 23.5 to 29.3 yr to reach 80 cm CCL, considered an approximation of the size at maturity. This estimation integrates and confirms a previous estimate obtained using a different method. It provides information vital to understanding the population dynamics of loggerhead turtles in the Mediterranean, and highlights the value of datasets of longterm series when investigating critical demographic parameters. © Inter-Research 2011.

Maria S.,Aristotle University of Thessaloniki
Angiology | Year: 2010

We assessed the effect of leptin on human monocytes. Monocytes were isolated from 16 healthy obese and 10 lean healthy participants. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp. Obese participants were subdivided into 2 subgroups, insulin sensitive (IS) and insulin resistant (IR). Monocyte properties (attachment to laminin 1, migration through laminin 1, surface expression of CD36, oxidized low-density lipoprotein [oxLDL] phagocytosis) were assessed pre- and poststimulation in vitro with leptin. Experiments were repeated after incubation with rosiglitazone and a Na(+)/H(+) exchanger-1 inhibitor (cariporide). We found a significant correlation between insulin resistance and monocyte attachment to laminin and oxLDL phagocytosis. Leptin increased the atherosclerosis-related properties of monocytes in all groups, apart from surface expression of CD36 in IS obese participants. Incubation with rosiglitazone or cariporide attenuated the observed effects. Leptin induces monocyte dysfunction which may be atherogenic. Correlation with insulin resistance suggests that atherosclerosis might be accelerated before the onset of diabetes.

Zografopoulos D.C.,CNR Institute for Microelectronics and Microsystems | Kriezis E.E.,Aristotle University of Thessaloniki
Optics Letters | Year: 2014

Switchable beam steerers based on zenithal bistable liquid crystal (LC) gratings are designed and theoretically investigated. The nematic orientation profiles and the optical transmittance properties of the gratings are rigorously calculated, respectively, via a tensorial formulation of the Landau-de Gennes theory and the full-wave finite-element-method. By proper design of the grating geometry, beam steering with high diffraction efficiency is demonstrated between the two stable LC states. The tolerance of the device performance with respect to material parameters is assessed, evidencing spectral operation windows of more than 50 nm in the visible for a beam steering efficiency higher than 90%. © 2014 Optical Society of America

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.

Oikonomou V.K.,Aristotle University of Thessaloniki
International Journal of Geometric Methods in Modern Physics | Year: 2015

In view of the many quantum field theoretical descriptions of graphene in 2 + 1 dimensions, we present another field theoretical feature of graphene, in the presence of defects. Particularly, we shall be interested in gapped graphene in the presence of a domain wall and also for superconducting graphene in the presence of a vortex. As we explicitly demonstrate, the gapped graphene electrons that are localized on the domain wall are associated with four N = 2 one-dimensional supersymmetries, with each pair combining to form an extended N = 4 supersymmetry with non-Trivial topological charges. The case of superconducting graphene is more involved, with the electrons localized on the vortex being associated with n one-dimensional supersymmetries, which in turn combine to form an N = 2n extended supersymmetry with non-Trivial topological charges. As we shall prove, all supersymmetries are unbroken, a feature closely related to the number of the localized fermions and also to the exact form of the associated operators. In addition, the corresponding Witten index is invariant under compact and odd perturbations. © 2015 World Scientific Publishing Company.

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.

Heracleous E.,Center for Research and Technology Hellas | Heracleous E.,Aristotle University of Thessaloniki
International Journal of Hydrogen Energy | Year: 2011

The environmental profile of hydrogen depends greatly on the nature of the feedstock and the production process. In this Well-to-Wheels (WTW) study, the environmental impacts of hydrogen production from lignocellulosic biomass via pyrolysis and subsequent steam reforming of bio-oil were evaluated and compared to the conventional production of hydrogen from natural gas steam reforming. Hydrogen was assumed to be used as transportation fuel in an internal combustion engine vehicle. Two scenarios for the provision of lignocellulosic biomass were considered: wood waste and dedicated willow cultivation. The WTW analysis showed that the production of bio-hydrogen consumes less fossil energy in the total lifecycle, mainly due to the renewable nature of the fuel that results in zero energy consumption in the combustion step. The total (fossil and renewable) energy demand is however higher compared to fossil hydrogen, due to the higher process energy demands and methanol used to stabilize bio-oil. Improvements could occur if these are sourced from renewable energy sources. The overall benefit of using a CO2 neutral renewable feedstock for the production of hydrogen is unquestionable. In terms of global warming, production of hydrogen from biomass through pyrolysis and reforming results in major GHG emissions, ranging from 40% to 50%, depending on the biomass source. The use of cultivated biomass aggravates the GHG emissions balance, mainly due to the N2O emissions at the cultivation step. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Tranos M.D.,Aristotle University of Thessaloniki | Lacombe O.,CNRS Paris Institute of Earth Sciences
Journal of Geodynamics | Year: 2014

We investigate the geometry and kinematics of the faults exposed in basement rocks along the Strouma River in SW Bulgaria as well as the sequence of faulting events in order to place constraints on the Cenozoic kinematic evolution of this structurally complex domain. In order to decipher the successive stress fields that prevailed during the tectonic history, we additionally carried out an analysis of mesoscale striated faults in terms of paleostress with a novel approach. This approach is based on the P-T axes distribution of the fault-slip data, and separates the fault-slip data into different groups which are characterized by kinematic compatibility, i.e., their P and T axes have similar orientations. From these fault groups, stress tensors are resolved and in case these stress tensors define similar stress regimes (i.e., the orientations of the stress axes and the stress shape ratios are similar) then the fault groups are further unified. The merged fault groups after being filled out with those fault-slip data that have not been incorporated into the above described grouping, but which present similar geometric and kinematic features are used for defining the final stress regimes. In addition, the sequence of faulting events was constrained by available tectonostratigraphic data.Five faulting events named D1, D2, D3, D4 and D5 are distinguished since the Late Oligocene. D1 is a pure compression stress regime with σ1 stress axis trending NNE-SSW that mainly activated the WNW-ESE to ENE-WSW faults as reverse to oblique reverse and the NNW-SSE striking as right-lateral oblique contractional faults during the Latest Oligocene-Earliest Miocene. D2 is a strike-slip - transpression stress regime with σ1 stress axis trending NNE-SSW that mainly activated the NNW-SSE to N-S striking as right-lateral strike-slip faults and the ENE-WSW striking faults as left-lateral strike-slip ones during the Early-Middle Miocene. D3 extensional event is associated with a NW-SE to WNW-ESE extension causing the activation of mainly low-angle normal faults of NE-SW strike and NNE-SSW to NNW-SSE striking high-angle normal faults. D4 is an extensional event dated from Late Miocene to Late Pliocene. It activated NNW-SSE to NW-SE faults as normal faults and E-W to WNW-ESE faults as right-lateral oblique extensional faults. The latest D5 event is an N-S extensional stress regime that dominates the wider area of SW Bulgaria in Quaternary times. It mainly activated faults that generally strike E-W (ENE-WSW and WNW-ESE) normal faults, along which fault-bounded basins developed. The D1 and D2 events are interpreted as two progressive stages of transpressional tectonics related to the late stages of collision between Apulia and Eurasia plates. These processes gave rise to the lateral extrusion of the Rhodope and Balkan regions toward the SE along the Strouma Lineament. The D3 event is attributed to the latest stage of this collision, and represents the relaxation of the overthickened crust along the direction of the lateral extrusion. The D4 and D5 events are interpreted as post-orogenic extensional events related to the retreat of the Hellenic subduction zone since the Late Miocene and to the widespread back-arc Aegean extension still prevailing today. © 2013 Elsevier Ltd.

Mikhailidis D.P.,University College London | Athyros V.G.,Aristotle University of Thessaloniki
Nature Reviews Cardiology | Year: 2014

The new ACC/AHA guidelines on treatment of blood cholesterol focus on intensity of statin therapy rather than target levels of lipids. Early studies show substantial reductions in LDL-cholesterol level with antibodies against PCSK9. MicroRNA silencing and gene-repair techniques to treat dyslipidaemia are promising strategies under development. © 2014 Macmillan Publishers Limited. All rights reserved.

Lambropoulou D.A.,Aristotle University of Thessaloniki
Current Organic Chemistry | Year: 2010

Sample preparation is a very important and essential step in environmental analysis. A brief overview of modern sample preparation such as solvent based methods, sorptive, membrane - assisted and instrumental methods which have been recently applied to extract and preconcentrate organic analytes from different environmental matrices, is presented. The different requirements of each methodology (and its modes of implementation), especially the extraction phase, are discussed. Instead of a comprehensive list of applications, the implementation of these techniques with selected examples covering mainly research published the last three years is highlighted. © 2010 Bentham Science Publishers Ltd.

Karakiulakis G.,Aristotle University of Thessaloniki | Roth M.,University of Basel
Mediators of Inflammation | Year: 2012

Muscarinic receptors are expressed by most cell types and mediate cellular signaling of their natural ligand acetylcholine. Thereby, they control numerous central and peripheral physiological organ responses to neuronal activity. In the human lung, muscarinic receptors are predominantly expressed by smooth muscle cells, epithelial cells, and fibroblasts. Antimuscarinic agents are used for the treatment of chronic obstructive pulmonary disease and to a lesser extent for asthma. They are primarily used as bronchodilators, but it is now accepted that they are also associated with anti-inflammatory, antiproliferative, and antiremodeling effects. Remodeling of the small airways is a major pathology in COPD and impairs lung function through changes of the extracellular matrix. Glycosaminoglycans, particularly hyaluronic acid, and matrix metalloproteases are among extracellular matrix molecules that have been associated with tissue inflammation and remodeling in lung diseases, including chronic obstructive pulmonary disease and asthma. Since muscarinic receptors have been shown to influence the homeostasis of glycosaminoglycans and matrix metalloproteases, these molecules may be proved valuable endpoint targets in clinical studies for the pharmacological exploitation of the anti-inflammatory and antiremodeling effects of muscarinic inhibitors in the treatment of chronic obstructive pulmonary disease and asthma. © 2012 George Karakiulakis and Michael Roth.

Papadopoulos A.I.,Aristotle University of Thessaloniki | Papadopoulos A.I.,Center for Research and Technology Hellas | Stijepovic M.,Texas A&M University at Qatar | Linke P.,Texas A&M University at Qatar
Applied Thermal Engineering | Year: 2010

This work presents the first approach to the systematic design and selection of optimal working fluids for Organic Rankine Cycles (ORCs) based on computer aided molecular design (CAMD) and process optimization techniques. The resulting methodology utilizes group contribution methods in combination with multi-objective optimization technology for the generation of optimum working fluid candidates. Optimum designs of the corresponding ORC processes are then developed for the comprehensive set of molecules obtained at the CAMD stage, in order to identify working fluids that exhibit optimum performance in ORCs with respect to important economic, operating, safety and environmental indicators. The proposed approach is illustrated with a case study in the design of working fluids for a low-temperature ORC system. Particular attention is paid to safety and environmental characteristics such as flammability, toxicity, ozone depletion and global warming potential. The methodology systematically identified both novel and conventional molecular structures that enable optimum ORC process performance.

Gounaris G.J.,Aristotle University of Thessaloniki | Renard F.M.,Montpellier University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We study the process e-e+→γH, where H represents HSM, h0, or H0. This process occurs at the one loop level in the standard model or in the minimal supersymmetric standard model (MSSM). We establish supersimple (sim) high energy expressions for all helicity amplitudes of this process, and we identify their level of accuracy for describing the various polarized and unpolarized observables, and for distinguishing SM from MSSM or another beyond the standard model. We pay special attention to transverse e± polarization and azimuthal dependencies induced by the imaginary parts of the amplitudes, which are relatively important in this process. © 2015 American Physical 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.

Arabelos D.N.,Aristotle University of Thessaloniki | Tscherning C.C.,Copenhagen University
Journal of Geodesy | Year: 2010

Since the publication of the Earth gravitational model (EGM)96 considerable improvements in the observation techniques resulted in the development of new improved models. The improvements are due to the availability of data from dedicated gravity mapping missions (CHAMP, GRACE) and to the use of 5′ × 5′ terrestrial and altimetry derived gravity anomalies. It is expected that the use of new EGMs will further contribute to the improvement of the resolution and accuracy of the gravity and geoid modeling in continental and regional scale. To prove this numerically, three representative Earth gravitational models are used for the reduction of several kinds of data related to the gravity field in different places of the Earth. The results of the reduction are discussed regarding the corresponding covariance functions which might be used for modeling using the least squares collocation method. The contribution of the EIGEN-GL04C model in most cases is comparable to that of EGM96. However, the big difference is shown in the case of EGM2008, due not only to its quality but obviously to its high degree of expansion. Almost in all cases the variance and the correlation length of the covariance functions of data reduced to this model up to its maximum degree are only a few percentages of corresponding quantities of the same data reduced up to degree 360. Furthermore, the mean value and the standard deviation of the reduced gravity anomalies in extended areas of the Earth such as Australia, Arctic region, Scandinavia or the Canadian plains, vary between -1 and +1 and between 5 and 10 × 10-5 ms-2, respectively, reflecting the homogenization of the gravity field on a regional scale. This is very important in using least squares collocation for regional applications. However, the distance to the first zero-value was in several cases much longer than warranted by the high degree of the expansion. This is attributed to errors of medium wavelengths stemming from the lack of, e. g., high-quality data in some area. © 2010 Springer-Verlag.

Geotechnique | Year: 2010

An analytical upper-bound plasticity solution is presented for the calculation of the undrained bearing capacity of strip footings on or near slopes. Typical results, presented in terms of the undrained bearing capacity factor, are shown to be in excellent agreement with finite-element analysis results and generally more conservative than those obtained from other available solutions. The proposed upper-bound solution is used to investigate the influence of the slope angle, the distance of the footing from the slope, the footing width and the soil properties on the undrained bearing capacity.

Feidas H.,Aristotle University of Thessaloniki
Theoretical and Applied Climatology | Year: 2010

Six widely available satellite precipitation products were extensively validated and intercompared on monthly-to-seasonal timescales and various spatial scales, for the period 1998-2006, using a dense station network over Greece. Satellite products were divided into three groups according to their spatial resolution. The first group had high spatial (0.5°) resolution and consists only of Tropical Rainfall Measuring Mission (TRMM) products: the TRMM Microwave Imager (TMI) precipitation product (3A12) and the TRMM multisatellite precipitation analysis products (3B42 and 3B43). The second group comprised products with medium spatial (1°) resolution. These products included the TRMM 3B42 and 3B43 estimates (remapped to 1° resolution) and the Global Precipitation Climatology Project one-degree daily (GPCP-1DD) analysis. The third group consisted of low spatial (2.5°) resolution products and included the 3B43 product (remapped to 2.5° resolution), the GPCP Satellite and Gauge (GPCP-SG) product, and the National Oceanographic and Atmospheric Administration Cimate Prediction Center (NOAA-CPC) Merged Analysis (CMAP). Rain gauge data were first gridded and then compared with monthly and seasonal precipitation totals as well as with long-term averages of the six satellite products at different spatial resolutions (2.5°, 1°, and 0.5°). The results demonstrated the excellent performance of the 3B43 product over Greece in all three spatial scales. 3B42 from the first and second group and CMAP from the third exhibited a reasonable skill. © 2009 Springer-Verlag.

Oikonomou V.K.,Technological Educational Institute of Piraeus | Oikonomou V.K.,Aristotle University of Thessaloniki
Nuclear Physics B | Year: 2011

We connect the fermionic fields, localized on the intersection curve ς of two D7-branes with zero background flux, to a N=2 supersymmetric quantum mechanics algebra, within the theoretical framework of F-theory. © 2011 Elsevier B.V.

Papaioannou S.,NHS England | Tzafettas J.,Aristotle University of Thessaloniki
Best Practice and Research: Clinical Obstetrics and Gynaecology | Year: 2010

The relationship of infertility, endocrinology and cancer has become clearer in recent years. Polycystic ovaries (PCO) increase the risk of endometrial cancer. Prolonged amenorrhoea, therefore, should be prevented in such cases with the use of cyclical progestogens, in order for regular withdrawal bleeds to be induced and the endometrium protected from long-term unopposed oestrogen stimulation. There is no secure evidence base on which a relationship between PCO and breast cancer can be based. No specific breast screening for women with PCO is, therefore, recommended. Hyperandrogenaemia and hyperinsulinaemia are conditions whose significance in terms of increasing both endometrial and breast cancer risks is increasingly recognised. The exact mechanism with which they influence carcinogenesis is still far from clear. Whether they act in isolation or as expressions of the common background of the metabolic syndrome - in interaction with other components of this syndrome - is still the subject of research. © 2009 Elsevier Ltd. All rights reserved.

Papagianni M.,Aristotle University of Thessaloniki | Papamichael E.M.,University of Ioannina
Bioresource Technology | Year: 2011

Weissella paramesenteroides DX has been shown to produce a 4450-Da class IIa bacteriocin, weissellin A, composed of 43 amino acids with the sequence KNYGNGVYCNKHKCSVDWATFSANIANNSVAMAGLTGGNAGN. The bacteriocin shares 68% similarity with leucocin C from Leuconostoc mesenteroides. Computational analyses predict that the bacteriocin is a hydrophobic molecule with a beta-sheet type conformation. Weissellin A exhibited various levels of activity against all gram-positive bacteria tested, but was not active against Salmonella enterica Enteritidis. The antimicrobial activity was not associated with target-cell lysis. The bacteriocin retained activity after exposure to 121 °C for 60. min or to -20 °C for 6. months, and to pH 2.0-10.0. It was not sensitive to trypsin, α-chymotrypsin, pepsin and papain, but was inactivated by proteinase K. At a dissolved oxygen concentration of 50%, weissellin A was produced with growth-associated kinetics. The properties of weissellin A make this bacteriocin a potentially suitable agent for food and feed preservation. © 2011 Elsevier Ltd.

Grimbizis G.F.,Aristotle University of Thessaloniki | Campo R.,Surgery Academy
Fertility and Sterility | Year: 2010

Current proposals for classifying female genital anomalies seem to be associated with limitations in effective categorization, creating the need for a new classification system that is as simple as possible, clear and accurate in its definitions, comprehensive, and correlated with patients' clinical presentation, prognosis, and treatment on an evidence-based foundation. Although creating a new classification system is not an easy task, it is feasible when taking into account the experience gained from applying the existing classification systems, mainly that of the American Fertility Society. © 2010 American Society for Reproductive Medicine.

Hatzikraniotis E.,Aristotle University of Thessaloniki
Acta Physica Polonica A | Year: 2012

In this work TlBiTe 2 were grown by a modified Bridgman technique and examined samples had different lateral dimensions of twins, ranging from 0.1 μm to 1 μm. The average lateral size of the twins seems to affect free carrier concentration and plasma frequency. Infrared spectra were analyzed by two models, the extended Drude model and a generalized empirical model of frequency-dependent damping factor. Increase in size of twins affects the electronic properties and hence plasma reflectivity and free carrier concentration of TlBiTe 2.

Mavromatis T.,Aristotle University of Thessaloniki
Climatic Change | Year: 2012

The aim of the present study is, primarily, to compare the frequencies of exceptional hydrological and meteorological weekly events, employing the self-calibrated versions of Palmer's drought indices (PDSI and PHDI, respectively), from 17 stations across Greece in the decade 1997-2006 with these of 1961-1990; on second level, to identify the trends and define the time lags between these two indices for the study period 1961-2006. The changes in the spatial distribution of exceptional weekly event frequencies between the most recent decade and the baseline period were similar for both drought indices. When 1997-2006 was compared with 1961-1990, the number of stations with a frequency of exceptionally dry weekly events >93rd percentile, increased by seven stations (41%) for PDSI and nine (53%) for PHDI, at the expense of exceptionally moist weekly spells. PDSI was found to lead PHDI by three to 20 weeks. If exceptional weekly events continue to be more frequent in the future, major implications for natural water resources are expected. © 2011 Springer Science+Business Media B.V.

Hatzistilianou M.,Aristotle University of Thessaloniki
TheScientificWorldJournal | Year: 2010

Despite several consensus conferences, the criteria for the definition of sepsis are still considered too sensitive and insufficiently specific. The traditional clinical signs of infection and routine laboratory tests used to diagnose bacterial infection and sepsis lack diagnostic accuracy and can be misleading, particularly in patients with immunodeficiencies. The problems with sepsis definitions and diagnoses are indications of the need to focus on biochemical mediators capable not only of distinguishing the inflammatory response to infection from other types of inflammation, but also of indicating the severity and prognosis of the disease. Thus, physicians need an early and rapid marker for detecting bacterial infection and distinguishing it from viral infection. Several studies revealed that elevated procalcitonin (PCT) levels in human blood could be detected in cases of sepsis and bacterial infection. PCT is a protein that can act as a hormone and a cytokine. It can be produced by several cell types and many organs in response to proinflammatory stimuli, particularly bacterial infection. It provides a rapid diagnostic test, available at the patient's bedside, and its half-life is suitable for daily monitoring of the disease progress. ©2010 with author.

Mitri G.H.,University of Balamand | Gitas I.Z.,Aristotle University of Thessaloniki
International Journal of Applied Earth Observation and Geoinformation | Year: 2012

Careful evaluation of forest regeneration and vegetation recovery after a fire event provides vital information useful in land management. The use of remotely sensed data is considered to be especially suitable for monitoring ecosystem dynamics after fire. The aim of this work was to map post-fire forest regeneration and vegetation recovery on the Mediterranean island of Thasos by using a combination of very high spatial (VHS) resolution (QuickBird) and hyperspectral (EO-1 Hyperion) imagery and by employing object-based image analysis. More specifically, the work focused on (1) the separation and mapping of three major post-fire classes (forest regeneration, other vegetation recovery, unburned vegetation) existing within the fire perimeter, and (2) the differentiation and mapping of the two main forest regeneration classes, namely, Pinus brutia regeneration, and Pinus nigra regeneration. The data used in this study consisted of satellite images and field observations of homogeneous regenerated and revegetated areas. The methodology followed two main steps: a three-level image segmentation, and, a classification of the segmented images. The process resulted in the separation of classes related to the aforementioned objectives. The overall accuracy assessment revealed very promising results (approximately 83.7% overall accuracy, with a Kappa Index of Agreement of 0.79). The achieved accuracy was 8% higher when compared to the results reported in a previous work in which only the EO-1 Hyperion image was employed in order to map the same classes. Some classification confusions involving the classes of P. brutia regeneration and P. nigra regeneration were observed. This could be attributed to the absence of large and dense homogeneous areas of regenerated pine trees in the study area. © 2011 Elsevier B.V.

Paramythiotis D.,Aristotle University of Thessaloniki
Techniques in coloproctology | Year: 2011

The term "gossypiboma" is used to describe any mass of non-absorbable surgical material. It is estimated that this complication appears every 1.000-10.000 procedures. It may lead to peritonitis, acute abdominal pain, intraperitoneal abscess, bowel obstruction, or perforation. REPORT OF A CASE: We present the case of an 80-year-old female patient admitted for chronic abdominal pain and fever. A CT scan and MRI were performed with a probable diagnosis of carcinoma or pelvic abscess. A surgical history of hysterectomy and repair of abdominal wall hernia with a mesh were mentioned. Exploratory laparotomy revealed the presence of an irregular, soft mass with characteristics of an abscess located into the mesosigmoid. Hartman's sigmoidectomy was performed, and the patient's postoperative course was uneventful. The histopathological examination confirmed the diagnosis of gossypiboma. Retained foreign intraperitoneal materials often represent diagnostic dilemmas, since symptomatology is no specific and the time elapsed from surgery is long. The policy of prevention's importance is highly appreciated.

Kotzekidou P.,Aristotle University of Thessaloniki
Food Microbiology | Year: 2013

During a 10-year inspection survey (2001-2010), a microbiological study of ready-to-eat (RTE) foods and ready-to-bake frozen pastries from 15 canteens of the university campus was undertaken to determine their microbiological quality. The cumulative study revealed that the aerobic colony counts for the RTE product groups were as follows: from 106 to 108 CFU/g for 50% of sandwiches; under the detection limit (<10 CFU/g) for 88.6% of oven baked pastries; <105 CFU/g for 86.5% of desserts oven baked; from 103 to 109 CFU/g for desserts with dairy cream. The highest mean Enterobacteriaceae counts were recorded for desserts with dairy cream. The highest percentages of foodborne pathogens were: 20% Listeria monocytogenes and 12.5% Staphylococcus aureus in desserts with dairy cream; 17.5% Salmonella spp. and 8.5% presumptive Escherichia coli O157 in sandwiches; 14.6% Bacillus cereus in oven baked pastries. Aerobic colony counts were in the range 107-108 CFU/g for 48.8% of frozen pastries; whereas Enterobacteriaceae counts between 103 and 104 CFU/g were detected in 35.3%. Foodborne pathogens prevalences for frozen pastries were as follows: B. cereus, 31.8%; Salmonella spp., 28.6%; presumptive E. coli O157, 25%; S. aureus, 8.7%; L. monocytogenes, 8.7%. Improved sanitary conditions in the processing plants and precautionary measures are necessary for consumer protection. © 2013 Elsevier Ltd.

Sidiropoulos E.,Aristotle University of Thessaloniki
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

The role of cellular automata in optimization is a current area of research. This paper presents a multi-objective approach to cellular optimization. A typical nonlinear problem of spatial resource allocation is treated by two alternative methods. The first one is based on a specially designed operative genetic algorithm and the second one on a hybrid annealing - genetic procedure. Pareto front approximations are computed by the two methods and also by a non-cellular version of the second approach. The better performance of the cellular methods is demonstrated and questions for further research are discussed. © 2012 Springer-Verlag Berlin Heidelberg.

Mandrali E.,Aristotle University of Thessaloniki
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

We introduce a weighted linear temporal logic over infinite words with weights and discounting parameters over ℝ max. We translate the formulas of a syntactically defined fragment of our logic to weighted Büchi automata with discounting. We prove that every ω-recognizable series with discounting is the image of a series definable by a formula of this syntactic fragment through a strict alphabetic epimorphism. © 2012 Springer-Verlag.

Gaertig E.,University of Tubingen | Kokkotas K.D.,University of Tubingen | Kokkotas K.D.,Aristotle University of Thessaloniki
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We investigate damping and growth times of the quadrupolar f mode for rapidly rotating stars and a variety of different polytropic equations of state in the Cowling approximation. This is the first study of the damping/growth time of these types of oscillations for fast-rotating neutron stars in a relativistic treatment where the spacetime degrees of freedom of the perturbations are neglected. We use these frequencies and damping/growth times to create robust empirical formulae which can be used for gravitational-wave asteroseismology. The estimation of the damping/growth time is based on the quadrupole formula and our results agree very well with Newtonian ones in the appropriate limit. © 2011 American Physical Society.

Oikonomou V.K.,Technological Educational Institute of Piraeus | Oikonomou V.K.,Aristotle University of Thessaloniki
Nuclear Physics B | Year: 2012

The localized fermions on the intersection curve σ of D7-branes, are connected to a N=2 supersymmetric quantum mechanics algebra. Due to this algebra the fields obey a global U(1) symmetry. This symmetry restricts the proton decay operators and the neutrino mass terms. Particularly, we find that several proton decay operators are forbidden and the Majorana mass term is the only one allowed in the theory. A special SUSY QM algebra is studied at the end of the paper. In addition we study the impact of a non-trivial holomorphic metric perturbation on the localized solutions along each matter curve. Moreover, we study the connection of the localized solutions to an N=2 supersymmetric quantum mechanics algebra when background fluxes are turned on. © 2011 Elsevier B.V.

Dionysopoulos D.,Aristotle University of Thessaloniki
Strahlentherapie und Onkologie : Organ der Deutschen Röntgengesellschaft ... [et al] | Year: 2013

EGFR (epidermal growth factor receptor), cyclin D1 and Akt/mTOR pathways are active in head and neck cancer. The aim of this study was to explore biomarker expression, their correlations with clinicopathological parameters and their prognostic utility in a cohort of patients with localized squamous laryngeal carcinoma. We assessed relative messenger RNA expression of EGFR, Akt1, 2, and 3, mTOR and CCND1, copy number variants of the EGFR and CCND1 genes and immunohistochemical protein expression of EGFR, p-Akt308, p-Akt473, pmTOR, PTEN, p53 and cyclin D1 in paraffin-embedded tissue samples of localized laryngeal carcinomas. In 289 patients with T3-4 (77.8%), node-negative (84.1%) tumors of the larynx, high EGFR and CCND1 mRNA correlated with no or ex-smoking, (p = 0.003 and p = 0.029, respectively), while low Akt3 mRNA correlated with alcohol abuse, N0 stage, total laryngectomy, and absence of neck dissection. At a median follow-up of 74.5 months, high mTOR mRNA expression was marginally associated with shorter disease-free survival (hazard ratio [HR] = 1.54; p = 0.093) and high Akt3 mRNA with shorter overall survival (HR = 1.49; p = 0.0786), in univariate analysis. In multivariate analysis, node-positive status, subglottic-transglottic location, surgery other than total laryngectomy and mTOR/CCND1 mRNA interaction with a hazard ratio of 2.16 (p value for interaction: 0.0010) were independent predictors of relapse, while node-positive status and subglottic-transglottic location were associated with higher risk for death. In localized laryngeal cancer, clinicopathological parameters and an interaction of high mTOR and CCND1 mRNA expression were found to be associated with poor patient outcome.

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.

Pouliasis S.,Aristotle University of Thessaloniki
Computational Methods and Function Theory | Year: 2011

It is well known that meromorphic functions decrease the capacity of a condenser. We prove an equality statement for the condenser capacity inequality under meromorphic functions. © 2011 Heldermann Verlag.

Lazarides G.,Aristotle University of Thessaloniki | Shafi Q.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

Inspired by the 750 GeV diphoton state recently reported by ATLAS and CMS, we propose a U(1)B-L extension of the MSSM which predicts the existence of four spin zero resonance states that are degenerate in mass in the supersymmetric limit. Vectorlike fields, a gauge singlet field, as well as the MSSM Higgsinos are prevented from acquiring arbitrary large masses by a U(1) R symmetry. Indeed, these masses can be considerably lighter than the Z′ gauge boson mass. Depending on kinematics, the resonance states could decay into right-handed neutrinos and sneutrinos, and/or MSSM Higgs fields and Higgsinos with total decay widths in the multi-GeV range. © 2016 American Physical Society.

Nizetic S.,University of Split | Tolj I.,University of Split | Papadopoulos A.M.,Aristotle University of Thessaloniki
Energy Conversion and Management | Year: 2015

In this paper, a specific hybrid energy system was proposed for household applications. The hybrid energy system was assembled from a HT-PEM fuel cell stack supplied by hydrogen via a steam reformer, where finally the majority of produced electricity is used to drive a modified split heat pump system with heat recovery (that is enabled via standard modified accumulation boilers). The system is able to produce both high and low temperature heat output (in the form of hot water), cooling thermal output and electricity. Performance analysis was conducted and the specific hybrid energy system showed high value for overall energy efficiency, for the specific case examined it reached 250%. Levelized Cost of Energy (LCOE) analysis was also carried out and the proposed hybrid energy system's cost is expected to be between 0.09 €/kW h and 0.16 €/kW h, which is certainly competitive with the current retail electricity price for households on the EU market. Additionally, the system also has environmental benefits in relation to reduced CO2 emissions, as estimated CO2 emissions from the proposed hybrid energy system are expected to be at around 9.0 gCO2/kW h or 2.6 times less than the emissions released from the utilization of grid electricity. © 2015 Elsevier Ltd.All rihts reserved.

Tsagas C.G.,Aristotle University of Thessaloniki
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

The post-inflationary evolution of inflation-produced magnetic fields, conventional or not, can change dramatically when two fundamental issues are accounted for. The first is causality, which demands that local physical processes can never affect superhorizon perturbations. The second is the nature of the transition from inflation to reheating and then to the radiation era, which determine the initial conditions at the start of these epochs. Causality implies that inflationary magnetic fields do not freeze into the matter until they have re-entered the causal horizon. The nature of the cosmological transitions and the associated initial conditions, on the other hand, determine the large-scale magnetic evolution after inflation. Put together, the two can slow down the adiabatic magnetic decay on superhorizon scales throughout the Universe's post-inflationary evolution and thus lead to considerably stronger residual magnetic fields. This is "good news" for both the conventional and the nonconventional scenarios of cosmic magnetogenesis. Mechanisms operating outside standard electromagnetism, in particular, do not need to enhance their fields too much during inflation in order to produce seeds that can feed the galactic dynamo today. In fact, even conventionally produced inflationary magnetic fields might be able to sustain the dynamo. © 2016 American Physical Society.