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Porto, Portugal

The University of Porto is a Portuguese public university located in Porto, and founded on 22 March 1911. It is the largest Portuguese university by number of enrolled students and has one of the most noted research outputs in Portugal. Wikipedia.


De Moura M.F.S.F.,University of Porto | Goncalves J.P.M.,IBM
International Journal of Adhesion and Adhesives | Year: 2014

In this work a suitable cohesive zone model for high-cycle fatigue of bonded joints under mode II loading is developed. Stiffness degradation as a function of time is simulated by means of a damage parameter that accounts for static and fatigue damage. Finite element analyses of the end notched flexure test considering different coefficients of the modified Paris law and different load ratios were performed. A data reduction scheme based on the crack equivalent concept and Timoshenko Beam theory was adapted to fatigue analysis thus avoiding monitoring crack length during experiments, which is particularly cumbersome to execute in fatigue tests under mode II loading. The resulting numerical crack growth rates as a function of mode II strain energy release rate were compared with the input modified Paris laws. The verified good agreement shows the suitability of the model concerning fatigue/fracture characterization of adhesively bonded joints under high-cycle fatigue submitted to mode II loading. © 2014 Elsevier Ltd. Source


Bhatnagar A.,University of Porto | Sillanpaa M.,Lappeenranta University of Technology
Chemical Engineering Journal | Year: 2011

Nitrate, due to its high water solubility, is possibly the most widespread groundwater contaminant in the world, imposing a serious threat to human health and contributing to eutrophication. Among several treatment technologies applied for nitrate removal, adsorption has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. In this review, an extensive list of various sorbents from the literature has been compiled and their adsorption capacities for nitrate removal as available in the literature are presented along with highlighting and discussing the key advancement on the preparation of novel adsorbents tested for nitrate removal. © 2011 Elsevier B.V. Source


Araujo H.F.,University of Southern California | Araujo H.F.,University of Porto | Kaplan J.,University of Southern California | Damasio A.,University of Southern California
Frontiers in Human Neuroscience | Year: 2013

The autobiographical-self refers to a mental state derived from the retrieval and assembly of memories regarding one's biography. The process of retrieval and assembly, which can focus on biographical facts or personality traits or some combination thereof, is likely to vary according to the domain chosen for an experiment. To date, the investigation of the neural basis of this process has largely focused on the domain of personality traits using paradigms that contrasted the evaluation of one's traits (self-traits) with those of another person's (other-traits). This has led to the suggestion that cortical midline structures (CMSs) are specifically related to self states. Here, with the goal of testing this suggestion, we conducted activation-likelihood estimation (ALE) meta-analyses based on data from 28 neuroimaging studies. The ALE results show that both self-traits and other-traits engage CMSs; however, the engagement of medial prefrontal cortex is greater for self-traits than for other-traits, while the posteromedial cortex is more engaged for other-traits than for self-traits. These findings suggest that the involvement CMSs is not specific to the evaluation of one's own traits, but also occurs during the evaluation of another person's traits. © 2013 Araujo, Kaplan and Damasio. Source


Silva I.,Angiology and Vascular Surgery and Clinical Imunology Unit | Almeida J.,Centro Hospitalar Of Vila Nova Of Gaia | Vasconcelos C.,Clinical Imunology Unit | Vasconcelos C.,University of Porto
Autoimmunity Reviews | Year: 2015

Vasculopathy has a major role in the pathogenesis and tissue injury in systemic sclerosis (SSc). Raynaud's phenomenon (RP) is frequently the first clinical manifestation of SSc preceding by years other clinical manifestations. RP in SSc patients is frequent, often very severe and long lasting. The repeated bouts of RP lead to prolonged digital ischemia that may progress to digital ulceration or in extreme to critical digital ischemia with gangrene. Digital ulcers (DU) are a true burden for all patients. They are very painful, with a long and slow healing course, have high risk of infection and are extremely disabling. In adults, up to 40-50% of patients will experience at least one DU in the course of the disease and of these 31-71% will have recurrent ulcers. In order to try to identify predictive risk factors for DU in SSc patients, an extensive literature review was conducted, according to the guidelines proposed at the PRISMA statement. MEDLINE database (PubMed) and Thomson Reuters Web of Knowledge platform were searched for articles published in peer-reviewed journals since 1990 with the last search run on June 2014 and published in English language. The keyword search terms included: digital ulcer/s, systemic sclerosis, scleroderma, digital scars, ischemic complications, autoantibodies, biomarkers, endothelium dysfunction, endothelin-1, vascular endothelial growth factor (VEGF), endostatin, ADMA, endoglin, angiostatin, and capillaroscopy. The following criteria were included: (1) cohorts of SSc patients including patients with DU, (2) endothelium dysfunction and angiogenesis biomarkers compared with a healthy control group, (3) autoantibodies, capillary morphology and distribution, endothelium dysfunction and angiogenesis biomarkers compared between patients with and without digital ulcers, (4) detailed description of the statistical methods used to conclude for predictive factors, and (5) English language. Our search provided a total of 376 citations. Of these, 297 studies were discarded for not meeting the criteria proposed. © 2014 Elsevier B.V. Source


Correia A.L.,Lawrence Berkeley National Laboratory | Correia A.L.,University of Porto | Bissell M.J.,Lawrence Berkeley National Laboratory
Drug Resistance Updates | Year: 2012

The emergence of clinical drug resistance is still one of the most challenging factors in cancer treatment effectiveness. Until more recently, the assumption has been that random genetic lesions are sufficient to explain the progression of malignancy and escape from chemotherapy. Here we propose an additional perspective, one in which the tumor cells despite the malignant genome could find a microenvironment either within the tumor or as a dormant cell to remain polar and blend into an organized context. Targeting this dynamic interplay could be considered a new avenue to prevent therapeutic resistance, and may even provide a promising effective cancer treatment. © 2011 Elsevier Ltd. All rights reserved. Source


Thai C.H.,Ton Duc Thang University | Ferreira A.J.M.,University of Porto | Ferreira A.J.M.,King Abdulaziz University | Carrera E.,Polytechnic University of Turin | Nguyen-Xuan H.,Ton Duc Thang University
Composite Structures | Year: 2013

We present an isogeometric finite element formulation for static, free vibration and buckling analysis of laminated composite and sandwich plates. The idea behind this work is to associate an isogeometric analysis (IGA) with a layerwise theory [. A.J.M. Ferreira. Analyis of composite plates using a layerwise deformation theory and multiquadrics discretization. Mech Adv Mater Struct 2005;12(2):99-112]. Isogeometric analysis based on non-uniform rational B-spline (NURBS) basic functions were recently proposed to preserve exact geometries and to enhance very significantly the accuracy of the traditional finite elements. B-splines basic function (or NURBS) is used to represent for both geometric and field variable approximations, which provide a flexible way to make refinement and degree elevation. They enable us to achieve easily the smoothness with arbitrary continuity order compared with the traditional FEM. The layerwise theory assumes a first-order shear deformation theory in each layer and the imposition of displacement continuity at the layers interfaces. This permits to remove shear correction factors and improves the accuracy of transverse shear stresses. Intensive numerical studies have been conducted to show the highly efficient performance of the proposed formulation. © 2013 Elsevier Ltd. Source


Goncalves J.F.,University of Porto | Resende M.G.C.,ATandT Labs Research
Journal of Heuristics | Year: 2011

Random-key genetic algorithms were introduced by Bean (ORSA J. Comput. 6:154-160, 1994) for solving sequencing problems in combinatorial optimization. Since then, they have been extended to handle a wide class of combinatorial optimization problems. This paper presents a tutorial on the implementation and use of biased random-key genetic algorithms for solving combinatorial optimization problems. Biased random-key genetic algorithms are a variant of random-key genetic algorithms, where one of the parents used for mating is biased to be of higher fitness than the other parent. After introducing the basics of biased random-key genetic algorithms, the paper discusses in some detail implementation issues, illustrating the ease in which sequential and parallel heuristics based on biased random-key genetic algorithms can be developed. A survey of applications that have recently appeared in the literature is also given. © 2010 Springer Science+Business Media, LLC. Source


Aslani F.,University of Technology, Sydney | Maia L.,University of Porto
Magazine of Concrete Research | Year: 2013

In the present paper, a numerical and experimental study about creep and shrinkage behavior of a high strength selfcompacting concrete is performed. Two new creep and shrinkage prediction models based on the comprehensive analysis on the available models of both conventional concrete and self-compacting concrete are proposed for high strength self-compacting concrete structures. In order to evaluate the predictability of the proposed models, an experimental program was carried out. A concrete which develops 60 MPa within 24 h was used to obtain experimental results. Several specimens were loaded: (i) at different ages and (ii) with different stress-to-strength ratios. Deformation in non-loaded specimens was also measured to assess shrinkage. All specimens were kept under constant stress during at least 600 days in a climatic chamber with temperature and relative humidity of 208C and 50%, respectively. Results showed that the new models were able to predict deformations with good accuracy, although provided deformations overestimated slightly. Source


Transcription termination of RNA polymerase II between closely spaced genes is an important, though poorly understood, mechanism. This is true, in particular, in the Drosophila genome, where approximately 52% of tandem genes are separated by less than 1 kb. We show that a set of Drosophila tandem genes has a negative correlation of gene expression and display several molecular marks indicative of promoter pausing. We find that an intergenic spacing of 168 bp is sufficient for efficient transcription termination between the polo-snap tandem gene pair, by a mechanism that is independent of Pcf11 and Xrn2. In contrast, analysis of a tandem gene pair containing a longer intergenic region reveals that termination occurs farther downstream of the poly(A) signal and is, in this case, dependent on Pcf11 and Xrn2. For polo-snap, displacement of poised polymerase from the snap promoter by depletion of the initiation factor TFIIB results in an increase of polo transcriptional read-through. This suggests that poised polymerase is necessary for transcription termination. Interestingly, we observe that polo forms a TFIIB dependent gene loop between its promoter and terminator regions. Furthermore, in a plasmid containing the polo-snap locus, deletion of the polo promoter causes an increase in snap expression, as does deletion of polo poly(A) signals. Taken together, our results indicate that polo forms a gene loop and polo transcription termination occurs by an Xrn2 and Pcf11 independent mechanism that requires TFIIB. Source


Simoes M.,University of Porto
Current Medicinal Chemistry | Year: 2011

Bacteria are able to adapt to undesirable changes in nutrient availability, environmental conditions and presence of antimicrobial products, as well as to immunological defenses. One particularly important example of bacterial adaptation is the ability to grow as part of a sessile community, commonly referred to as biofilm. It is a natural tendency of microorganisms to attach to biotic or abiotic surfaces, to multiply and to embed themselves in a slimy matrix, resulting in biofilms. Biofilms are the leading example of physiological adaptation and are one of the most important sources of bacterial resistance to antimicrobials. It is now recognized that most bacterial-associated infections, including endocarditis, dental caries, middle ear infections, osteomyelitis, medical device-related infections and chronic lung infections in cystic fibrosis patients are problematic because of biofilms. Bacteria in biofilms demonstrate intrinsic resistance to antimicrobial stress more effectively than the planktonic counterparts. Antimicrobial concentrations necessary to inhibit bacterial biofilms can be up to 10-1000 times higher than those needed to inhibit the same bacteria grown planktonically. Thus, in the presence of therapeutically available antibiotic concentrations biofilms remain viable after treatment. Therefore, the identification of new antimicrobials that inhibit or destroy biofilms is needed. The aim of this review is to cover the recent advances on the studies of antimicrobial strategies effective against infectious bacterial biofilms, including the current developments in the structure-activity relationship of those effective antimicrobials. © 2011 Bentham Science Publishers Ltd. Source


Abdoos M.,Iran University of Science and Technology | Mozayani N.,Iran University of Science and Technology | Bazzan A.L.C.,University of Porto
Engineering Applications of Artificial Intelligence | Year: 2013

Agent-based technologies are rapidly growing as a powerful tool for modelling and developing large-scale distributed systems. Recently, multi-agent systems are largely used for intelligent transportation systems modelling. Traffic signals control is a challenging issue in this area, especially in a large-scale urban network. In a large traffic network, where each agent represents a traffic signals controller, there are many entities interacting with each other and hence it is a complex system. An approach to reduce the complexity of such systems is using organisation-based multi-agent system. In this paper, we use an organisation called holonic multi-agent system (HMAS) to model a large traffic network. A traffic network containing fifty intersections is partitioned into a number of regions and holons are assigned to control each region. The holons are hierarchically arranged in two levels, intersection controller holons in the first level and region controller holons in the second level. We introduce holonic Q-learning to control the signals in both levels. The inter-level interactions between the holons in the two levels contribute to the learning process. Experimental results show that the holonic Q-learning prevents the network to be over-saturated while it causes less average delay time and higher flow rate. © 2013 Elsevier Ltd. Source


Silva S.,University of Porto | Soares I.,FEP and CEFUP | Afonso O.,FEP and CEFUP
Energy Policy | Year: 2013

We build a general equilibrium model with renewable (non-polluting) and non-renewable (polluting) resources to analyze the interaction and compatibility between economic growth and a cleaner environment. The study is in two phases: (i) resource extraction/production costs are constant; (ii) resource producers invest in knowledge to reduce extraction/production costs, endogenizing technical change. With constant costs, there is a permanent trade-off between economic growth and a cleaner environment. With endogenous technical change, it is possible to harmonize more output and less emissions by replacing non-renewable resources for renewable ones. We also conduct a sensitivity analysis to explore three specific policy actions. With constant costs, the best policy action is the imposition of a higher renewable resources standard, while with endogenous technical change, under certain conditions, all policy interventions may benefit both the economy and the environment. © 2012 Elsevier Ltd. Source


Dalla Riva M.,University of Porto | Lanza de Cristoforis M.,University of Padua
Complex Analysis and Operator Theory | Year: 2011

Let Ωi and Ωo be two bounded open subsets of ℝn containing 0. Let Gi be a (nonlinear) map from ∂Ωi × ℝn to ℝn. Let ao be a map from ∂Ωo to the set Mn(ℝ) of n × n matrices with real entries. Let g be a function from ∂Ωo to ℝn. Let γ be a positive valued function defined on a right neighborhood of 0 in the real line. Let T be a map from ]1 - (2/n), +∞[×Mn (ℝ) to Mn (ℝ). Then we consider the problem, where νεΩ i and νo denote the outward unit normal to ε∂Ωi and ∂Ωo, respectively, and where ε > 0 is a small parameter. Here (ω - 1) plays the role of ratio between the first and second Lamé constants and T(ω, ·) plays the role of (a constant multiple of) the linearized Piola Kirchhoff stress tensor. Under the condition that limε → 0+ γ(ε)ε-1 (log ε)-δ 2,n = 0 and limε → 0+ εn-1 γ(ε)-1 = 0, we prove that under suitable assumptions the above problem has a family of solutions {u(ε, ·)}ε∈]0,ε′[ for ε′ sufficiently small and we analyze the behaviour of such a family as ε approaches 0 by an approach which is alternative to those of asymptotic analysis. Here δ2,n denotes the Kronecker symbol. © 2010 Springer Basel AG. Source


Sousa A.S.,University of Porto
European Journal of Clinical Nutrition | Year: 2016

Background/Objectives:This study aims to increase knowledge regarding the association of sarcopenia with hospitalization costs among a wide-ranging sample of adult hospitalized patients.Subjects/Methods:A prospective study was conducted among hospitalized adult patients. Sarcopenia was identified according to the European Working Group on Sarcopenia in Older People, as low muscle mass, assessed by bioelectrical impedance analysis and low muscle function evaluated by handgrip strength. Hospitalization cost was calculated for each patient based on discharge diagnosis-related group codes and determined on the basis of a relative weight value. Costs were defined as the percentage of deviation from the cost of a patient with a relative weight equal to one. Multivariable linear regression models were performed to identify the factors independently associated with hospitalization costs.Results:A total of 656 hospitalized patients aged ⩾18 years (24.2% sarcopenic) composed the study sample. Sarcopenia increased hospitalization costs by [euro ]1240 (95% confidence interval (CI): [euro ]596–1887) for patients aged <65 years and [euro ]721 (95% CI: [euro ]13–1429) for patients aged ⩾65 years. Sarcopenic overweight was related to an increase in hospitalization costs of [euro ]884 (95% CI: [euro ]295–1476).Conclusions:Sarcopenia is independently related to hospitalization costs. This condition is estimated to increase hospitalization costs by 58.5% for patients aged <65 years and 34% for patients aged ⩾65 years.European Journal of Clinical Nutrition advance online publication, 11 May 2016; doi:10.1038/ejcn.2016.73. © 2016 Macmillan Publishers Limited Source


Novo A.,Catholic University of Portugal | Andre S.,Agencia Portuguesa do Ambiente | Viana P.,Agencia Portuguesa do Ambiente | Nunes O.C.,University of Porto | Manaia C.M.,Catholic University of Portugal
Water Research | Year: 2013

This study was based on the hypothesis that the occurrence of antimicrobial residues and antibiotic resistant bacteria in the sewage could be correlated with the structure and composition of the bacterial community and the antibiotic resistance loads of the final effluent. Raw and treated wastewater composite samples were collected from an urban treatment plant over 14 sampling dates. Samples were characterized for the i) occurrence of tetracyclines, penicillins, sulfonamides, quinolones, triclosan, arsenic, cadmium, lead, chromium and mercury; ii) antibiotic resistance percentages for tetracycline, sulfamethoxazole, ciprofloxacin and amoxicillin and iii) 16S rRNA gene-DGGE patterns. The data of corresponding samples, taking into account the hydraulic residence time, was analyzed using multivariate analysis. Variations on the bacterial community structure of the final effluent were significantly correlated with the occurrence of tetracyclines, penicillins, sulfonamides, quinolones and triclosan in the raw inflow. Members of the class Epsilonproteobacteria presented positive correlations with those antimicrobials, whereas negative correlations were observed with Beta and Gammaproteobacteria and Firmicutes. Antibiotic resistance percentages presented different trends of variation in heterotrophs/enterobacteria and in enterococci, varied over time and after wastewater treatment. Antibiotic resistance was positively correlated with the occurrence of tetracyclines residues and high temperature. A relationship between antibiotic residues, bacterial community structure and composition and antibiotic resistance is demonstrated. Further studies, involving more wastewater treatment plants may help to elucidate this complex relationship. © 2013 Elsevier Ltd. Source


Prabhu V.U.,Carnegie Mellon University | Rodrigues M.R.D.,University of Porto
IEEE Transactions on Information Forensics and Security | Year: 2011

In this correspondence, we characterize the probability of secrecy-outage and the asymptotic high-signal-to-noise ratio (SNR) ε-outage secrecy-capacity for a single-input-single-output-multi-eavesdropper (SISOME) wireless system with eavesdroppers performing maximum ratio combining (MRC) or selection diversity combining (SDC) reception. We also consider the SISO2E case with eavesdropper antenna-correlation and finally, analyze the scenario where the eavesdropper has Rician fading links with the transmitter. © 2011 IEEE. Source


Areal H.,University of Porto
BMC evolutionary biology | Year: 2011

Toll-like receptors (TLRs) are a major class of pattern recognition receptors (PRRs) expressed in the cell surface or membrane compartments of immune and non-immune cells. TLRs are encoded by a multigene family and represent the first line of defense against pathogens by detecting foreigner microbial molecular motifs, the pathogen-associated molecular patterns (PAMPs). TLRs are also important by triggering the adaptive immunity in vertebrates. They are characterized by the presence of leucine-rich repeats (LRRs) in the ectodomain, which are associated with the PAMPs recognition. The direct recognition of different pathogens by TLRs might result in different evolutionary adaptations important to understand the dynamics of the host-pathogen interplay. Ten mammal TLR genes, viral (TLR3, 7, 8, 9) and non-viral (TLR1-6, 10), were selected to identify signatures of positive selection that might have been imposed by interacting pathogens and to clarify if viral and non-viral TLRs might display different patterns of molecular evolution. By using Maximum Likelihood approaches, evidence of positive selection was found in all the TLRs studied. The number of positively selected codons (PSC) ranged between 2-26 codons (0.25%-2.65%) with the non-viral TLR4 as the receptor with higher percentage of positively selected codons (2.65%), followed by the viral TLR8 (2.50%). The results indicated that viral and non-viral TLRs are similarly under positive selection. Almost all TLRs have at least one PSC located in the LRR ectodomain which underlies the importance of the pathogen recognition by this region. Our results are not in line with previous studies on primates and birds that identified more codons under positive selection in non-viral TLRs. This might be explained by the fact that both primates and birds are homogeneous groups probably being affected by only a restricted number of related viruses with equivalent motifs to be recognized. The analyses performed in this work encompassed a large number of species covering some of the most representative mammalian groups - Artiodactyla, Rodents, Carnivores, Lagomorphs and Primates - that are affected by different families of viruses. This might explain the role of adaptive evolution in shaping viral TLR genes. Source


Helicobacter pylori infection is the main gastric cancer determinant, which currently is an important cause of oncological morbidity and mortality in Portugal, and specially in the north of the country. In the city of Porto, unbiased estimates of the frequency of infection in different age-groups of the general population are available from the studies EPIPorto (adults, 1999-2003), EPITeen (adolescents, 13 years, 2003/2004) and Geração XXI (children, 4 years, 2010-2011). The prevalence was 73.9% in the age-group 18-30 years and higher than 88% above the age of 40. Nearly two-thirds of the adolescents and one quarter of the children were infected. In the adolescents and adults the estimated incidence rates were higher than 3/100 person-years. Understanding the frequency of the infection and its time trends, in each setting, are essential to estimate the potential impact of measures for prevention and control of infection and to predict the burden of gastric cancer. The incidence and prevalence of H. pylori infection in this setting are in accordance with the high gastric cancer mortality currently observed and will expectedly result in a high burden of morbidity and mortality due to gastric cancer in the next decades. Source


Hey J.,Rutgers University | Pinho C.,University of Porto
Evolution | Year: 2012

Species as evolutionary lineages are expected to show greater evolutionary independence from one another than are populations within species. Two measures of evolutionary independence that stem from the study of isolation-with-migration models, one reflecting the amount of gene exchange and one reflecting the time of separation, were drawn from the literature for a large number of pairs of closely related species and pairs of populations within species. Both measures, for gene flow and time, showed broadly overlapping distributions for pairs of species and for pairs of populations within species. Species on average show more time and less gene flow than populations, but the similarity of the distributions argues against there being a qualitative difference associated with species status, as compared to populations. The two measures of evolutionary independence were similarly correlated with F ST estimates, which in turn also showed similar distributions for species comparisons relative to population comparisons. The measures of gene flow and separation time were examined for the capacity to discriminate intraspecific differences from interspecific differences. If used together, the two measures could be used to develop an objective (in the sense of being repeatable) measure for species diagnosis. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution. Source


Perez-Figueroa A.,University of Vigo | Luikart G.,University of Montana | Luikart G.,University of Porto
Evolutionary Applications | Year: 2011

Early detection of population declines is essential to prevent extinctions and to ensure sustainable harvest. We evaluated the performance of two Ne estimators to detect population declines: the two-sample temporal method and a one-sample method based on linkage disequilibrium (LD). We used simulated data representing a wide range of population sizes, sample sizes and number of loci. Both methods usually detect a population decline only one generation after it occurs if Ne drops to less than approximately 100, and 40 microsatellite loci and 50 individuals are sampled. However, the LD method often out performed the temporal method by allowing earlier detection of less severe population declines (Ne approximately 200). Power for early detection increased more rapidly with the number of individuals sampled than with the number of loci genotyped, primarily for the LD method. The number of samples available is therefore an important criterion when choosing between the LD and temporal methods. We provide guidelines regarding design of studies targeted at monitoring for population declines. We also report that 40 single nucleotide polymorphism (SNP) markers give slightly lower precision than 10 microsatellite markers. Our results suggest that conservation management and monitoring strategies can reliably use genetic based methods for early detection of population declines. © 2010 Blackwell Publishing Ltd. Source


Donaire M.,University of Porto | Donaire M.,Autonomous University of Madrid
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We offer a unified approach to several phenomena related to the electromagnetic vacuum of a complex medium made of point electric dipoles. To this aim, we apply the linear response theory to the computation of the polarization field propagator and study the spectrum of vacuum fluctuations. The physical distinction among the local density of states which enter the spectra of light propagation, total dipole emission, coherent emission, total vacuum energy, and Schwinger-bulk energy is made clear. Analytical expressions for the spectrum of dipole emission and for the vacuum energy are derived. Their respective relations with the spectrum of external light and with the Schwinger-bulk energy are found. The light spectrum and the Schwinger-bulk energy are determined by the Dyson propagator. The emission spectrum and the total vacuum energy are determined by the polarization propagator. An exact relationship of proportionality between both propagators is found in terms of local field factors. A study of the nature of stimulated emission from a single dipole is carried out. Regarding coherent emission, it contains two components. A direct one which is transferred radiatively and directly from the emitter into the medium and whose spectrum is that of external light. And an indirect one which is radiated by induced dipoles. The induction is mediated by one (and only one) local field factor. Regarding the vacuum energy, we find that in addition to the Schwinger-bulk energy the vacuum energy of an effective medium contains local field contributions proportional to the resonant frequency and to the spectral line width. © 2011 American Physical Society. Source


Chaban V.V.,University of Rochester | Voroshylova I.V.,University of Porto | Kalugin O.N.,University of Kharkiv | Prezhdo O.V.,University of Rochester
Journal of Physical Chemistry B | Year: 2012

We apply a new methodology in the force field generation (Phys. Chem. Chem. Phys.2011, 13, 7910) to study binary mixtures of five imidazolium-based room-temperature ionic liquids (RTILs) with acetonitrile (ACN). Each RTIL is composed of tetrafluoroborate (BF4) anion and dialkylimidazolium (MMIM) cations. The first alkyl group of MIM is methyl, and the other group is ethyl (EMIM), butyl (BMIM), hexyl (HMIM), octyl (OMIM), and decyl (DMIM). Upon addition of ACN, the ionic conductivity of RTILs increases by more than 50 times. It significantly exceeds an impact of most known solvents. Unexpectedly, long-tailed imidazolium cations demonstrate the sharpest conductivity boost. This finding motivates us to revisit an application of RTIL/ACN binary systems as advanced electrolyte solutions. The conductivity correlates with a composition of ion aggregates simplifying its predictability. Addition of ACN exponentially increases diffusion and decreases viscosity of the RTIL/ACN mixtures. Large amounts of ACN stabilize ion pairs, although they ruin greater ion aggregates. © 2012 American Chemical Society. Source


Gama H.,University of Porto
Revista de saúde pública | Year: 2013

To assess the determinants of the lack of pharmacological treatment for hypertension. In 2005, 3,323 Mozambicans aged 25-64 years old were evaluated. Blood pressure, weight, height and smoking status were assessed following the Stepwise Approach to Chronic Disease Risk Factor Surveillance. Hypertensives (systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg and/or antihypertensive drug therapy) were evaluated for awareness of their condition, pharmacological and non-pharmacological management, as well as use of herbal or traditional remedies. Prevalence ratios (PR) were calculated, adjusted for sociodemographic characteristics, cardiovascular risk factors and non-pharmacological treatment. Most of the hypertensive subjects (92.3%), and nearly half of those aware of their condition were not treated pharmacologically. Among the aware, the prevalence of untreated hypertension was higher in men {PR = 1.61; 95% confidence interval (95%CI 1.10;2.36)} and was lower in subjects under non-pharmacological treatment (PR = 0.58; 95%CI 0.42;0.79); there was no significant association with traditional treatments (PR = 0.75; 95%CI 0.44;1.26). The lack of pharmacological treatment for hypertension was more frequent in men, and was not influenced by the presence of other cardiovascular risk factors; it could not be explained by the use of alternative treatments as herbal/traditional medicines or non-pharmacological management. It is important to understand the reasons behind the lack of management of diagnosed hypertension and to implement appropriate corrective actions to reduce the gap in the access to healthcare between developed and developing countries. Source


Soares E.V.,Polytechnic Institute of Porto | Soares E.V.,IBB Institute for Biotechnology And Bioengineering | Soares H.M.V.M.,University of Porto
Applied Microbiology and Biotechnology | Year: 2013

Heavy metal pollution is a matter of concern in industrialised countries. Contrary to organic pollutants, heavy metals are not metabolically degraded. This fact has two main consequences: its bioremediation requires another strategy and heavy metals can be indefinitely recycled. Yeast cells of Saccharomyces cerevisiae are produced at high amounts as a by-product of brewing industry constituting a cheap raw material. In the present work, the possibility of valorising this type of biomass in the bioremediation of real industrial effluents containing heavy metals is reviewed. Given the auto-aggregation capacity (flocculation) of brewing yeast cells, a fast and off-cost yeast separation is achieved after the treatment of metal-laden effluent, which reduces the costs associated with the process. This is a critical issue when we are looking for an effective, eco-friendly, and low-cost technology. The possibility of the bioremediation of industrial effluents linked with the selective recovery of metals, in a strategy of simultaneous minimisation of environmental hazard of industrial wastes with financial benefits from reselling or recycling the metals, is discussed. © 2013 Springer-Verlag Berlin Heidelberg. Source


Teixeira M.R.,Portuguese Oncology Institute | Teixeira M.R.,University of Porto | Teixeira M.R.,University of Oslo | Heim S.,University of Oslo
Advances in Cancer Research | Year: 2011

All or almost all neoplasias subjected to systematic cytogenetic scrutiny have been found to harbor acquired chromosomal aberrations. The paradigm stemming from the study of hematopoietic malignancies and sarcomas is that cancers are of monoclonal origin (i.e., they have developed from a single transformed somatic progenitor) because all the neoplastic parenchyma cells share at least one primary chromosomal abnormality, with subsequent clonal evolution along the lines of Darwinian selection occurring among the various subclones carrying secondary aberrations. When carcinomas began to be studied more extensively by cytogenetic methods, however, sometimes many cytogenetically unrelated clones were found, in seeming contradiction to the monoclonal hypothesis. Also studies of multiple samples from the same patient led to a rethinking of what the cytogenetic evidence really revealed about tumor clonality, both in its early stages and during disease development. The observed cytogenetic heterogeneity in, for example, tumors of the breast and pancreas vastly surpasses that of leukemias, lymphomas, connective tissue tumors, or even most epithelial, including uroepithelial, tumors. Theoretical reasoning as well as the available experimental data we here review show that the clonal evolution of neoplastic cell populations follows either of four principal pathways: (1) initial monoclonality is retained throughout the entire course of the disease with no additional, secondary aberrations accrued as judged by karyotypic appearance; (2) tumorigenesis is monoclonal but additional aberrations develop with time leading to secondary clonal heterogeneity (clonal divergence); (3) polyclonal tumorigenesis exists from the beginning but is followed by an overall reduction in genomic complexity with time (clonal convergence) due to selection among cytogenetically unrelated clones during tumor progression, resulting in secondary oligo- or monoclonality; or (4) polyclonal tumorigenesis with early clonal convergence is followed by later clonal divergence due to the acquisition of additional cytogenetic changes by the clone(s) that survived during the middle phases of tumor progression. Further studies of individual tumor cells are necessary to elicit precise information about the cell-to-cell variability that exists in many, especially epithelial, neoplasms and which holds the key to a more profound understanding of the complex issue of tumor clonality during all stages of cancer development. © 2011 Elsevier Inc. Source


Pinto C.M.A.,University of Porto
International Journal of Bifurcation and Chaos | Year: 2012

We study curious features appearing in three systems of two coupled rings of cells with Z 3 × Z 5 exact symmetry, and Z 3 and Z 5 interior symmetries. This study was motivated by previous work by Antoneli et al. [2008, 2010], on two rings of cells coupled through a "buffer" cell, with Z 3 × Z 5 and D 3 × D 5 exact and interior symmetry groups. There, quasi-periodic behavior was found through a sequence of Hopf bifurcations, and relaxation oscillation phenomena appearing further away from the third Hopf point seemed to be necessary for a curious dynamic feature to occur. In this paper, we analyze the dynamical behavior of three distinct networks of two coupled rings of cells, with no "buffer" cell, and find an analogous bifurcation scenario to explain the appearance of quasi-periodic motion in these systems and the curious exotic feature. We compute the relevant states numerically. © 2012 World Scientific Publishing Company. Source


Pinho C.,University of Porto
Applied Thermal Engineering | Year: 2012

An easy technique to calibrate small gas flow meters is the positive displacement method, whose application requires a simple setup and laboratory procedure. With this methodology there is an unknown gas flow coming from a given gas source that must be known by the action of a gas flow meter. The gas flow to be measured is sent to a reservoir with rigid walls and full of water. As gas enters the reservoir water flows out and the amount of water exiting the reservoir in a given time interval can be connected with the average gas flow in that same time interval. In simple terms the volume flow rate of water leaving the reservoir is equal to the gas volume flow rate entering it. The water being incompressible, the density variation is meaningless, however the same cannot be assumed for the gas. Considerations on the simple techniques to be used to minimize the importance of gas compressibility are presented in the paper. © 2011 Elsevier Ltd. All rights reserved. Source


Martins J.I.,University of Porto
Engineering Failure Analysis | Year: 2012

Tinplate steel cans were used to store contact glue for shoes. A few months after its storage, the glue displayed a change in colour to a darker brown. The visual inspection of the interior of the cans showed the presence of corrosion of steel, which was evidenced by the typical colour of the iron oxides on the sheet. SEM/EDS and FTIR tests confirmed that the anomaly was due to the following factors: (a) a bad tin coating, small thickness and lack of homogeneity; (b) a degradation of glue, hydrolysis of chloroprene, which led to its acidification. Some recommendations are made to overcome similar situations within the same use of these packages looking at the specifications of tinplate. © 2012 Elsevier Ltd. Source


Guido L.F.,University of Porto
Scientia Agricola | Year: 2016

Beer is an extremely complex mixture of more than 3,000 different compounds in an aqueous environment. Thus, it is perhaps not surprising that the maintenance of beer quality throughout its lifetime has been a considerable challenge for brewers. Whilst it is inevitable that chemical changes will occur in beer with the passage of time, it is the formation of flavor-active components which is of immediate concern to an overview of beer shelf life stability. Sulfur dioxide has long been recognized by brewers as the most important factor in delaying flavor staling, and prolonging the shelf life of beer. However, nowadays, sulfur dioxide and sulfites are considered allergens and concerns about the safety of their use as food additives have been on the increase. The present review is structured into three main parts. Firstly, the chemical properties of sulfur dioxide are presented, along with the toxic effects and maximum legal levels permitted according to U.S. and EU legislation. As the accurate determination of the free, bound and total sulfur dioxide in beer is essential to ensuring regulatory compliance, several methods have been developed for analyzing sulfur dioxide in beer. Thus, secondly, various types of methods are reported and compared with the officially recommended ones. Finally, the crucial role of sulfite in the control of flavor instability of beer is discussed in light of the current data. Two courses of action have been proposed, which are elucidated in detail relating firstly to the fact that sulfite inhibits beer oxidation during storage by acting as an antioxidant and, secondly, sulfite reacts with the carbonyl staling compounds in beer, and thereby masks stale flavors. © 2016, Scientia Agricola. All rights reserved. Source


Ruano L.,Hospital de Sao Sebastiao | Melo C.,Centro Hospitalar do Medio Ave | Silva M.C.,Abel Salazar Biomedical Sciences Institute | Coutinho P.,University of Porto
Neuroepidemiology | Year: 2014

Background: Hereditary cerebellar ataxias (HCA) and hereditary spastic paraplegias (HSP) are two groups of neurodegenerative disorders that usually present with progressive gait impairment, often leading to permanent disability. Advances in genetic research in the last decades have improved their diagnosis and brought new possibilities for prevention and future treatments. Still, there is great uncertainty regarding their global epidemiology. Summary: Our objective was to assess the global distribution and prevalence of HCA and HSP by a systematic review and meta-analysis of prevalence studies. The MEDLINE, ISI Web of Science and Scopus databases were searched (1983-2013) for studies performed in well-defined populations and geographical regions. Two independent reviewers assessed the studies and extracted data and predefined methodological parameters. Overall, 22 studies were included, reporting on 14,539 patients from 16 countries. Multisource population-based studies yielded higher prevalence values than studies based primarily on hospitals or genetic centres. The prevalence range of dominant HCA was 0.0-5.6/105, with an average of 2.7/105 (1.5-4.0/105). Spinocerebellar ataxia type 3 (SCA3)/Machado-Joseph disease was the most common dominant ataxia, followed by SCA2 and SCA6. The autosomal recessive (AR) HCA (AR-HCA) prevalence range was 0.0-7.2/105, the average being 3.3/105 (1.8-4.9/10 5). Friedreich ataxia was the most frequent AR-HCA, followed by ataxia with oculomotor apraxia or ataxia-telangiectasia. The prevalence of autosomal dominant (AD) HSP (AD-HSP) ranged from 0.5 to 5.5/105 and that of AR-HSP from 0.0 to 5.3/105, with pooled averages of 1.8/105 (95% CI: 1.0-2.7/105) and 1.8/105 (95% CI: 1.0-2.6/105), respectively. The most common AD-HSP form in every population was spastic paraplegia, autosomal dominant, type 4 (SPG4), followed by SPG3A, while SPG11 was the most frequent AR-HSP, followed by SPG15. In population-based studies, the number of families without genetic diagnosis after systematic testing ranged from 33 to 92% in the AD-HCA group, and was 40-46% in the AR-HCA, 45-67% in the AD-HSP and 71-82% in the AR-HSP groups. Key Messages: Highly variable prevalence values for HCA and HSP are reported across the world. This variation reflects the different genetic make-up of the populations, but also methodological heterogeneity. Large areas of the world remain without prevalence studies. From the available data, we estimated that around 1:10,000 people are affected by HCA or HSP. In spite of advances in genetic research, most families in population-based series remain without identified genetic mutation after extensive testing. © 2014 S. Karger AG, Basel. Source


Castro-Nallar E.,Brigham Young University | Perez-Losada M.,University of Porto | Burton G.F.,Brigham Young University | Crandall K.A.,Brigham Young University
Molecular Phylogenetics and Evolution | Year: 2012

Molecular phylogenetics has revolutionized the study of not only evolution but also disparate fields such as genomics, bioinformatics, epidemiology, ecology, microbiology, molecular biology and biochemistry. Particularly significant are its achievements in population genetics as a result of the development of coalescent theory, which have contributed to more accurate model-based parameter estimation and explicit hypothesis testing. The study of the evolution of many microorganisms, and HIV in particular, have benefited from these new methodologies. HIV is well suited for such sophisticated population analyses because of its large population sizes, short generation times, high substitution rates and relatively small genomes. All these factors make HIV an ideal and fascinating model to study molecular evolution in real time. Here we review the significant advances made in HIV evolution through the application of phylogenetic approaches. We first examine the relative roles of mutation and recombination on the molecular evolution of HIV and its adaptive response to drug therapy and tissue allocation. We then review some of the fundamental questions in HIV evolution in relation to its origin and diversification and describe some of the insights gained using phylogenies. Finally, we show how phylogenetic analysis has advanced our knowledge of HIV dynamics (i.e., phylodynamics). © 2011 Elsevier Inc. Source


Accurate chromosome segregation during cell division in metazoans relies on proper chromosome congression at the equator. Chromosome congression is achieved after bi-orientation to both spindle poles shortly after nuclear envelope breakdown, or by the coordinated action of motor proteins that slide misaligned chromosomes along pre-existing spindle microtubules. These proteins include the minus-end-directed kinetochore motor dynein, and the plus-end-directed motors CENP-E at kinetochores and chromokinesins on chromosome arms. However, how these opposite and spatially distinct activities are coordinated to drive chromosome congression remains unknown. Here we used RNAi, chemical inhibition, kinetochore tracking and laser microsurgery to uncover the functional hierarchy between kinetochore and arm-associated motors, exclusively required for congression of peripheral polar chromosomes in human cells. We show that dynein poleward force counteracts chromokinesins to prevent stabilization of immature/incorrect end-on kinetochore–microtubule attachments and random ejection of polar chromosomes. At the poles, CENP-E becomes dominant over dynein and chromokinesins to bias chromosome ejection towards the equator. Thus, dynein and CENP-E at kinetochores drive congression of peripheral polar chromosomes by preventing arm-ejection forces mediated by chromokinesins from working in the wrong direction. © 2014 Nature Publishing Group Source


Oliveira J.M.A.,University of Porto
Journal of Bioenergetics and Biomembranes | Year: 2010

Preferential striatal neurodegeneration is a hallmark of Huntington's disease (HD) pathogenesis, which has been associated with mitochondrial dysfunction. Evidence from genetic HD models suggest that mutant huntingtin (mHtt) compromises mitochondrial bioenergetics and dynamics, preventing efficient calcium handling and ATP generation in neuronal networks. Striatal neurons receive abundant glutamatergic input from the cortex, forming tripartite synapses with astrocytic partners. These are involved in bidirectional communication, play neuroprotective roles, and emerging evidence suggests that astrocyte dysfunction supports non-cell autonomous neurodegeneration. In addition to mHtt effects, inherent mitochondria vulnerability within striatal neurons and astrocytes may contribute for preferential neurodegeneration in HD. Dysfunctional astrocytic mitochondria in cortico-striatal tripartite synapses might be particularly relevant in the pathogenesis of juvenile/infantile HD, frequently associated with seizures and abnormally large mHtt polyglutamine expansions. This review discusses our work, primarily addressing in situ mitochondrial function in neurons and astrocytes, in the context of related work within the HD-mitochondria field. © 2010 Springer Science+Business Media, LLC. Source


Silva A.,Military Hospital D. Pedro V | Sampaio R.,Instituto CUF | Pinto E.,University of Porto
Knee Surgery, Sports Traumatology, Arthroscopy | Year: 2010

Tunnel enlargement after anterior cruciate ligament (ACL) reconstruction may compromise revision surgery. The cause of this tunnel enlargement is not yet fully understood, but it is thought to be multifactorial, with biomechanical and biological factors playing a role. Tunnel enlargement has been described particularly in patients who underwent ACL reconstruction with hamstring tendons with extracortical fixation devices. The purpose of our study was to evaluate prospectively with magnetic resonance imaging (MRI) the changes in femoral tunnel diameter following arthroscopic anatomic ACL reconstruction with hamstring tendons. At 3-month post-op, all tunnels had enlarged compared to the diameter of the drill and most tunnels enlarged more in the midsection than at the aperture. In the posterolateral tunnels, the entrance increased 16% in diameter and the middle of the tunnel increased 30% in diameter. In the anteromedial femoral tunnels, the tunnels enlarged 14% at the aperture and 35% in the midsection. All femoral tunnels enlarged and most of them enlarged in a fusiform manner. The biological factors explain better our findings than the mechanical theory, although mechanical factors may play a role and the cortical bone at the entrance of the tunnel may modify the way tunnels respond to mechanical stress. © 2010 Springer-Verlag. Source


Allendorf F.W.,University of Montana | Allendorf F.W.,Victoria University of Wellington | Hohenlohe P.A.,University of Oregon | Hohenlohe P.A.,Oregon State University | And 2 more authors.
Nature Reviews Genetics | Year: 2010

We will soon have complete genome sequences from thousands of species, as well as from many individuals within species. This coming explosion of information will transform our understanding of the amount, distribution and functional significance of genetic variation in natural populations. Now is a crucial time to explore the potential implications of this information revolution for conservation genetics and to recognize limitations in applying genomic tools to conservation issues. We identify and discuss those problems for which genomics will be most valuable for curbing the accelerating worldwide loss of biodiversity. We also provide guidance on which genomics tools and approaches will be most appropriate to use for different aspects of conservation. © 2010 Macmillan Publishers Limited. All rights reserved. Source


Oliveira J.M.A.,University of Porto
Journal of Neurochemistry | Year: 2010

Polyglutamine expansion mutation in huntingtin causes Huntington's disease (HD). How mutant huntingtin (mHtt) preferentially kills striatal neurons remains unknown. The link between mitochondrial dysfunction and HD pathogenesis stemmed from postmortem brain data and mitochondrial toxin models. Current evidence from genetic models, containing mHtt, supports mitochondrial dysfunction with yet uncertain nature and cause. Because mitochondria composition and function varies across tissues and cell-types, mitochondrial dysfunction in HD vulnerable striatal neurons may have distinctive features. This review focuses on mHtt and the striatum, integrating experimental evidence from patients, mice, primary cultures and striatal cell-lines. I address the nature (specific deficits) and cause (mechanisms linked to mHtt) of HD mitochondrial dysfunction, considering limitations of isolated vs. in situ mitochondria approaches, and the complications introduced by glia and glycolysis in brain and cell-culture studies. Current evidence relegates respiratory chain impairment to a late secondary event. Upstream events include defective mitochondrial calcium handling, ATP production and trafficking. Also, transcription abnormalities affecting mitochondria composition, reduced mitochondria trafficking to synapses, and direct interference with mitochondrial structures enriched in striatal neurons, are possible mechanisms by which mHtt amplifies striatal vulnerability. Insights from common neurodegenerative disorders with selective vulnerability and mitochondrial dysfunction (Alzheimer's and Parkinson's diseases) are also addressed. © 2010 International Society for Neurochemistry. Source


Zhu J.,South-Central University for Nationalities | Xiao P.,South-Central University for Nationalities | Li H.,South-Central University for Nationalities | Carabineiro S.A.C.,University of Porto
ACS Applied Materials and Interfaces | Year: 2014

Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Compared with the majority of carbon materials, it has electron-rich properties, basic surface functionalities and H-bonding motifs due to the presence of N and H atoms. It is thus regarded as a potential candidate to complement carbon in material applications. In this review, a brief introduction to g-C3N4 is given, the methods used for synthesizing this material with different textural structures and surface morphologies are described, and its physicochemical properties are referred. In addition, four aspects of the applications of g-C3N4 in catalysis are discussed: (1) as a base metal-free catalyst for NO decomposition, (2) as a reference material in differentiating oxygen activation sites for oxidation reactions over supported catalysts, (3) as a functional material to synthesize nanosized metal particles, and (4) as a metal-free catalyst for photocatalysis. The reasons for the use of g-C3N4 for such applications are also given, and we expect that this paper will inspire readers to search for further new applications for this material in catalysis and in other fields. © 2014 American Chemical Society. Source


Ayres-De-Campos D.,University of Porto
Best Practice and Research: Clinical Obstetrics and Gynaecology | Year: 2015

Caesarean section in obese patients is associated with an increased risk of surgical wound complications, including haematoma, seroma, abscess and dehiscence. This review focusses on the available strategies to decrease wound complications in this population, and on the clinical management of these situations. Appropriate dose of prophylactic antibiotics, closure of the subcutaneous tissue, and avoidance of subcutaneous drains reduce the incidence of wound complications associated with caesarean section in obese patients. For treatment of superficial wound infection associated with dehiscence, there are data from general surgery patients to suggest that the use of vacuumeassisted devices leads to faster healing and that surgical reclosure is preferable to healing by secondary intention, when there are no signs of ongoing infection. There is a need for stronger evidence regarding the prevention and management of wound complications for caesarean section in obese women. © 2014 Elsevier Ltd. All rights reserved. Source


Magro F.,University of Porto | Portela F.,University of Coimbra
BioDrugs | Year: 2010

Inflammatory bowel disease (IBD), most commonly referring to Crohn's disease and ulcerative colitis, is a chronic and disabling condition with an increasing incidence in southern Europe. The etiology of IBD remains unknown, but the characteristic disproportionate inflammatory response in the gut may develop through various mechanisms at the cellular and subcellular level. Tumor necrosis factor (TNF) alpha is one crucial mediator of this abnormal immune response, and in recent years, biological therapies targeting TNFα have significantly improved the management of IBD refractory to conventional therapies. Infliximab is the best studied anti-TNFα agent, and is currently approved in the European Union for adults and children with Crohn's disease and adults with ulcerative colitis; adalimumab is indicated for Crohn's disease in adults but not children, while certolizumab was not approved in the European Union for Crohn's disease. Infliximab has confirmed efficacy in adults with Crohn's disease (including fistulizing disease) and ulcerative colitis, with benefits observed in both clinical remission and mucosal healing, it is similarly effective in children with Crohn's disease. Evidence suggests that early treatment with infliximab may improve the natural course of the disease. Adalimumab showed efficacy in adults with Crohn's disease and more limited data suggest efficacy in children with Crohn's disease. Although certolizumab pegol has also shown promising data in adults with Crohn's disease, data in children are lacking. Anti-TNFα agents are generally well tolerated, although careful monitoring for adverse events such as infections, infusion reactions, lymphomas and demyelinating diseases is warranted. A definitive causal relationship between anti-TNFα agents and various adverse events is difficult to establish, as the underlying disease and concomitant immunosuppression also predispose patients to such events. Infliximab has not been associated with an increased incidence of serious events, and adalimumab and certolizumab are also generally well tolerated in clinical trials. Both adalimumab and certolizumab pegol are associated with lower levels of drug antibodies compared with infliximab. Reactivation of latent tuberculosis is a potential risk with any anti-TNFα agent, and identification and treatment is required before initiating therapy. Although causal relationships are difficult to establish, caution is advised with anti-TNFα compounds in patients developing neurological symptoms suggestive of demyelinating disease, or in those at high risk of malignancy. Infliximab is also generally well tolerated in children; however, data are scarce for the other compounds. No increased risks associated with pregnancy have been observed for infliximab or adalimumab, but caution in pregnancy and during breast-feeding is currently advocated. In terms of future research, more long-term data are needed for both certolizumab pegol in Crohn's disease and adalimumab in ulcerative colitis. More research on the benefits of early biological treatment on disease progression is needed. In summary, the anti-TNFα inhibitors represent a momentous advance in the treatment of Crohn's disease and ulcerative colitis refractory to conventional treatments. They offer significant benefits in quality of life and mucosal healing, and may have the potential to change the evolution of the disease when given early. © 2010 Adis Data Information BV. All rights reserved. Source


Szrek H.,University of Porto | Bundorf M.K.,Stanford University
Health Psychology | Year: 2014

Objective: To determine how choice set size affects decision quality among individuals of different levels of numeracy choosing prescription drug plans. Method: Members of an Internet-enabled panel age 65 and over were randomly assigned to sets of prescription drug plans varying in size from 2 to 16 plans from which they made a hypothetical choice. They answered questions about enrollment likelihood and the costs and benefits of their choice. The measure of decision quality was enrollment likelihood among those for whom enrollment was beneficial. Enrollment likelihood by numeracy and choice set size was calculated. A model of moderated mediation was analyzed to understand the role of numeracy as a moderator of the relationship between the number of plans and the quality of the enrollment decision and the roles of the costs and benefits in mediating that relationship. Results: More numerate adults made better decisions than less numerate adults when choosing among a small number of alternatives but not when choice sets were larger. Choice set size had little effect on decision making of less numerate adults. Differences in decision making costs between more and less numerate adults helped explain the effect of choice set size on decision quality. Conclusions: Interventions to improve decision making in the context of Medicare Part D may differentially affect lower and higher numeracy adults. The conflicting results on choice overload in the psychology literature may be explained in part by differences amongst individuals in how they respond to choice set size. © 2013 American Psychological Association. Source


Cardoso G.C.,University of Porto
Behavioral Ecology | Year: 2012

The behavioral literature contains inconsistent results on the function of sound frequency (pitch) across species, offering an unexplored opportunity to investigate evolutionary diversification of communication systems. I review those results for birds, where about half the studied species use lower than average frequency (LAF) as a relevant sexual signal, and the remaining species use higher than average frequency (HAF) for the same functions. This variation appears nonrandom with respect to putative causal factors, suggesting that advertising body size determines which species use LAF as a sexual signal. I evaluate different hypotheses to explain why the remaining species use HAF instead. Integrating tests of alternative hypotheses on focal species will be required to demonstrate the causes for this divergence in communication systems. © The Author 2011. Source


Silva M.T.,University of Porto
FEBS Letters | Year: 2010

The predominant definition of apoptosis considers that the elimination of the apoptosing cell is by heterolytic degradation following phagocytosis by an assisting scavenger (efferocytosis). However, an alternative and largely underestimated outcome of apoptosis is secondary necrosis, an autolytic process of cell disintegration with release of cell components that occurs when there is no intervention of scavengers and the full apoptotic program is completed. Secondary necrosis is the typical outcome of apoptosis in unicellular eukaryotes but, importantly, it may also occur in multicellular animals and has been implicated in the genesis of important human pathologies. Secondary necrosis is a mode of cell elimination with specific molecular and morphological features and should be considered the natural outcome of the complete apoptotic program. © 2010 Federation of European Biochemical Societies. Source


Cyclooxygenase-2 (COX-2) is known to be involved in tumour progression and has been suggested as a therapeutic target in many human and animal malignancies. A number of different pathways subjacent to cancer hallmarks are considered to be involved in COX-2-mediated tumour progression, although these are still largely undefined. Our aim is to investigate associations between COX-2 expression and angiogenesis, proliferation and the inflammatory microenvironment in canine melanocytic tumours. Understanding the involvement of COX-2 with cancer hallmarks might enable us to adapt therapeutic strategies for canine melanomas, an aggressive and often lethal malignancy with value in comparative oncology. Immunohistochemical staining of COX-2, Ki-67 (proliferation index), vascular endothelial growth factor (VEGF), factor VIII (microvessel density), CD3 (lymphocytes) and MAC387 (macrophages) was performed in 51 melanocytic tumours (31 malignant melanomas, 20 melanocytomas). Statistical associations between COX-2 and the other parameters detected were analysed. In melanocytic tumours (n=51), both COX-2 labelling extension and intensity showed a statistically significant association with angiogenesis by factor VIII, VEGF, Ki-67, CD3+ T lymphocytes and MAC387. Within malignant melanomas, COX-2 expression has shown significant associations with microvessel density (factor VIII), lymphocyte and macrophage infiltration and, considering all melanocytic tumours, COX-2 was also associated with VEGF intensity and Ki-67 cell proliferation. Our results point to a role for COX-2 in angiogenesis and in the establishment of an inflammatory microenvironment, favourable to melanoma tumour progression. Further mechanistic studies are warranted to dissect molecular pathways in which COX-2 is involved. Present evidence suggests that COX-2 inhibitors might be useful as an adjuvant treatment to hinder canine melanoma progression. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Source


Fraga H.,Autonomous University of Barcelona | Fontes R.,University of Porto
Biochimica et Biophysica Acta - General Subjects | Year: 2011

Background: Mono and dinucleoside polyphosphates (p nNs and Np nNs) exist in living organisms and induce diverse biological effects through interaction with intracellular and cytoplasmic membrane proteins. The source of these compounds is associated with secondary activities of a diverse group of enzymes. Scope of review: Here we discuss the mechanisms that can promote their synthesis at a molecular level. Although all the enzymes described in this review are able to catalyse the in vitro synthesis of Np nNs (and/or p nN), it is not clear which ones are responsible for their in vivo accumulation. Major conclusions: Despite the large amount of knowledge already available, important questions remain to be answered and a more complete understanding of p nNs and Np nNs synthesis mechanisms is required. With the possible exception of (GTP:GTP guanylyltransferase of Artemia), all enzymes able to catalyse the synthesis of p nNs and Np nNs are unspecific and the factors that can promote their synthesis relative to the canonical enzyme activities are unclear. General significance: The fact that p nNs and Np nNs syntheses are promiscuous activities of housekeeping enzymes does not reduce its physiological or pathological importance. Here we resume the current knowledge regarding their enzymatic synthesis and point the open questions on the field. © 2011 Elsevier B.V. Source


Carvalho M.I.,University of Porto | Facao M.,University of Aveiro
Optics Express | Year: 2010

New types of finite energy Airy beams are proposed. We consider two different types of beams, namely, beams that are obtained as blocked and exponentially attenuated versions of Airy functions Ai and Bi, and beams of finite width but having the Airy functions typical phase. All of them show very interesting properties, such as parabolic trajectories for longer propagation distances, profile evolution exhibiting less diffraction, or better definiteness of the main peak, when compared with other finite energy Airy beams studied before. © 2010 Optical Society of America. Source


Tilley S.D.,Ecole Polytechnique Federale de Lausanne | Schreier M.,Ecole Polytechnique Federale de Lausanne | Azevedo J.,Laboratorio Of Engineering Of Processos | Azevedo J.,University of Porto | And 2 more authors.
Advanced Functional Materials | Year: 2014

Photocathodes based on cuprous oxide (Cu2O) are promising materials for large scale and widespread solar fuel generation due to the abundance of copper, suitable bandgap, and favorable band alignments for reducing water and carbon dioxide. A protective overlayer is required to stabilize the Cu2O in aqueous media under illumination, and the interface between this overlayer and the catalyst nanoparticles was previously identified as a key source of instability. Here, the properties of the protective titanium dioxide overlayer of composite cuprous oxide photocathodes are further investigated, as well as an oxide-based hydrogen evolution catalyst, ruthenium oxide (RuO2). The RuO2-catalyzed photoelectrodes exhibit much improved stability versus platinum nanoparticles, with 94% stability after 8 h of light-chopping chronoamperometry. Faradaic efficiencies of ∼100% are obtained as determined by measurement of the evolved hydrogen gas. The sustained photocurrents of close to 5 mA cm -2 obtained with this electrode during the chronoamperometry measurement (at 0 V vs. the reversible hydrogen electrode, pH 5, and simulated 1 sun illumination) would correspond to greater than 6% solar-to-hydrogen conversion efficiency in a tandem photoelectrochemical cell, where the bias is provided by a photovoltaic device such as a dye-sensitized solar cell. Ruthenium oxide on cuprous oxide photocathodes enhanced by a built-in p-n junction yields an active catalyst for hydrogen generation from water and unprecedented 94% stability over 8 h of light chopping chronoamperometry at 0 V vs. the reversible hydrogen electrode. The photocurrents obtained would correspond to greater than 6% solar-to-hydrogen efficiency in a tandem cell configuration. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Rodrigues M.R.D.,University of Porto
IEEE International Symposium on Information Theory - Proceedings | Year: 2012

This paper characterizes the constrained capacity of multiple-antenna fading coherent channels driven by arbitrary discrete inputs in the regime of high signal-to-noise ratio (snr). In particular, we capitalize on key asymptotic expansions to unveil the effect on the constrained capacity of various channel and system parameters, such as the fading model, the number of transmit and receive antennas, antenna correlation and the characteristics of the signalling scheme. It is also shown that the effect of certain parameters on the constrained capacity is radically different from their effect on the channel capacity achieved by Gaussian inputs. © 2012 IEEE. Source


Silva S.,University of Porto | Machado H.,University of Minho
Sociology of Health and Illness | Year: 2011

This article explores the construction of meaning regarding assisted reproductive technology by legal framers, medical practitioners and would-be parents, through the concept of ecology of knowledge. It is argued that these inter-relationships between experts and lay people can be understood in terms of the formation of a social structure of ecology of knowledge, which depends on local and emotional knowledge co-produced by medical doctors, jurists and lay people in dynamic ways without compromising the autonomy of medical, legal and lay knowledge and skills. The assessment of the benefits and risks of assisted reproductive technology partially represents negotiations of knowledge between these social and professional groups, aiming to reproduce existing relations and practices, particularly the social power of medicine and technology, the dominant perceptions about women's and men's bodies and the geneticisation of genealogy. These negotiations of knowledge generate new rights, new social actors, new scientific fields and new ways of thinking and talking about individual and institutional responsibilities. Ecology of knowledge comes imbued with hope, trust, power, credibility of institutions and moralisation whereby some citizens' rights may be weakened. © 2011 The Authors. Sociology of Health & Illness © 2011 Foundation for the Sociology of Health & Illness/Blackwell Publishing Ltd. Source


Goncalves J.F.,University of Porto | Resende M.G.C.,ATandT Labs Research
Computers and Operations Research | Year: 2012

This paper presents a multi-population biased random-key genetic algorithm (BRKGA) for the single container loading problem (3D-CLP) where several rectangular boxes of different sizes are loaded into a single rectangular container. The approach uses a maximal-space representation to manage the free spaces in the container. The proposed algorithm hybridizes a novel placement procedure with a multi-population genetic algorithm based on random keys. The BRKGA is used to evolve the order in which the box types are loaded into the container and the corresponding type of layer used in the placement procedure. A heuristic is used to determine the maximal space where each box is placed. A novel procedure is developed for joining free spaces in the case where full support from below is required. The approach is extensively tested on the complete set of test problem instances of Bischoff and Ratcliff [1] and Davies and Bischoff [2] and is compared with 13 other approaches. The test set consists of 1500 instances from weakly to strongly heterogeneous cargo. The computational experiments demonstrate that not only the approach performs very well in all types of instance classes but also it obtains the best overall results when compared with other approaches published in the literature. © 2011 Elsevier Ltd. Source


Nunes J.P.L.,University of Porto
Perspectives in Biology and Medicine | Year: 2013

The field of medical therapeutics may be characterized as having suffered major scientific evolution in the last decades. The publication of landmark studies has been important enough to produce shifts in patient care. However, the scientific evolution in this field does not necessarily imply a progressively greater degree of certitude. In fact, it is not uncommon for new knowledge, when reflected in clinical practice, to weaken previous knowledge. In medical therapeutics, strict inductive reasoning implies the existence of empirical intervention data, typically clinical trial data. In many instances, however, such data does not exist-leaving room for a mixture of inductive and "pseudo-deductive" reasoning. It is often necessary to establish treatment on the basis of incomplete and inconclusive information, more so when the clinical situation is grave, but when no valid information exists, no treatment may be an option. In many instances, the rule "I wish not to impose on others" has superseded the concept "Do not impose on others what you yourself do not desire." © 2014 by Johns Hopkins University Press. Source


Vieira C.S.,University of Porto
International Journal of Civil Engineering | Year: 2014

This paper presents a simplified approach to estimate the resultant force, which should be provided by a retention system, for the equilibrium of unstable slopes. The results were obtained with a developed algorithm, based on limit equilibrium analyses, that assumes a two-part wedge failure mechanism. Design charts to obtain equivalent earth pressure coefficients are presented. Based on the results achieved with the developed computer code, an approximate equation to estimate the equivalent earth pressure coefficients is proposed. Given the slope angle, the backslope, the design friction angle, the height of the slope and the unit weight of the backfill, one can determine the resultant force for slope equilibrium. This simplified approach intends to provide an extension of the Coulomb earth pressure theory to the stability analyses of steep slopes and to broaden the available design charts for steep reinforced slopes with non-horizontal backslopes. Source


The use of a battery of three mass metrics (atomic economy - AE, reaction mass efficiency - RME, and mass intensity - MI) for systemic evaluation of the material greenness of synthesis reactions is presented. Material greenness is discussed in terms of materialization/ dematerialization of the reaction system and also according to the first two Principles of Green Chemistry, and is shown to involve two components: atomic greenness (incorporation of the atoms provided by reagents into the product, evaluated by AE and RME); and massic greenness (global mass of reagents and non-stoichiometric materials, evaluated by MI, related to the production of residues). Source


Tavares I.,University of Porto
Stem Cell Research and Therapy | Year: 2013

Injuries of the spinal cord trigger local healing but hardly restore normal function. Spinal cord injury (SCI) has been deeply studied to develop strategies for functional recovery. The study by van Gorp and colleagues uses a rat model of acute SCI to characterize the effects of intraspinal grafting of human fetal spinal cord-derived neural stem cells (HSSCs). Among the range of results obtained, several positive outcomes related to a GABA-mediated inhibition were achieved. Their interesting article is a clear step forward in elucidating the neurobiology of SCI. Some issues to consider are related to the efficacy of the cell therapy in chronic spinal lesions and to pain responses, since the latter is a common complaint of people with SCI. Furthermore, the GABA-mediated hypothesis of recovery of function upon HSSC transplant needs to be fully tested by interfering with GABA receptors and analyzing neurobiological mechanisms that may invert the inhibitory role of GABA. The future challenge for SCI work will be the translation of knowledge acquired in basic research into clinically applicable strategies. The study by van Gorp and colleagues is an important contribution to that future. © 2013 BioMed Central Ltd. Source


Abreu R.,University of Porto | Van Gemund A.J.C.,Technical University of Delft
Artificial Intelligence | Year: 2010

In fault diagnosis intermittent failure models are an important tool to adequately deal with realistic failure behavior. Current model-based diagnosis approaches account for the fact that a component cj may fail intermittently by introducing a parameter gj that expresses the probability the component exhibits correct behavior. This component parameter gj, in conjunction with a priori fault probability, is used in a Bayesian framework to compute the posterior fault candidate probabilities. Usually, information on gj is not known a priori. While proper estimation of gj can be critical to diagnostic accuracy, at present, only approximations have been proposed. We present a novel framework, coined Barinel, that computes estimations of the gj as integral part of the posterior candidate probability computation using a maximum likelihood estimation approach. Barinel's diagnostic performance is evaluated for both synthetic systems, the Siemens software diagnosis benchmark, as well as for real-world programs. Our results show that our approach is superior to reasoning approaches based on classical persistent failure models, as well as previously proposed intermittent failure models. © 2010 Elsevier B.V. Source


Costa L.F.O.,University of Porto | Costa L.F.O.,University of Lisbon | Natario J.,University of Lisbon
General Relativity and Gravitation | Year: 2014

We reexamine and further develop different gravito-electromagnetic analogies found in the literature, and clarify the connection between them. Special emphasis is placed in two exact physical analogies: the analogy based on inertial fields from the so-called “1+3 formalism”, and the analogy based on tidal tensors. Both are reformulated, extended and generalized. We write in both formalisms the Maxwell and the full exact Einstein field equations with sources, plus the algebraic Bianchi identities, which are cast as the source-free equations for the gravitational field. New results within each approach are unveiled. The well known analogy between linearized gravity and electromagnetism in Lorentz frames is obtained as a limiting case of the exact ones. The formal analogies between the Maxwell and Weyl tensors are also discussed, and, together with insight from the other approaches, used to physically interpret gravitational radiation. The precise conditions under which a similarity between gravity and electromagnetism occurs are discussed, and we conclude by summarizing the main outcome of each approach. © 2014, Springer Science+Business Media New York. Source


Rodrigues M.R.D.,University of Porto
IEEE International Symposium on Information Theory - Proceedings | Year: 2011

This paper investigates the constrained capacity of the canonical i.i.d. multi-antenna Rayleigh fading coherent channel with arbitrary equiprobable discrete inputs in a regime of high signal-to-noise ratio (SNR), in the scenario where the receiver knows the channel state but the transmitter knows only the channel distribution. By capitalizing on the relation between mutual information and minimum mean-squared error (MMSE), we provide high-SNR asymptotic expansions to the average mutual information and the average MMSE. The expansions unveil the impact of the number of transmit and receive antennas and the geometry of the multi-dimensional input constellations on the constrained capacity of the communications channel. © 2011 IEEE. Source


Covas R.,Research Center in Biodiversity and Genetic Resources | Covas R.,University of Porto | Covas R.,French National Center for Scientific Research | Covas R.,University of Edinburgh
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Island environments typically share characteristics such as impoverished biotas and less-seasonal climates, which should be conducive to specific adaptations by organisms. However, with the exception of morphological studies, broad-scale tests of patterns of adaptation on islands are rare. Here, I examine reproductive patterns in island birds worldwide. Reproductive life histories are influenced by latitude, which could affect the response to insularity; therefore, I additionally test this hypothesis. Island colonizers showed mostly bi-parental care, but there was a significant increase in cooperative breeding on islands. Additionally, I found support for previous suggestions of reduced fecundity, longer developmental periods and increased investment in young on islands. However, clutch size increased with latitude at a rate nearly five times faster on the mainland than on the islands revealing a substantially stronger effect of insularity at higher latitudes. Latitude and insularity may also interact to determine egg volume and incubation periods, but these effects were less clear. Analyses of reproductive success did not support an effect of reduced nest predation as a driver of reproductive change, but this requires further study. The effect of latitude detected here suggests that the evolutionary changes associated with insularity relate to environmental stability and improved adult survival. © 2011 The Royal Society. Source


Guedes R.M.,University of Porto
International Journal of Mechanical Sciences | Year: 2010

This paper analyzes the effect of the polymer matrix non-viscoelastic behaviour in the mechanical behaviour of thick multilayered cylinders. The original contribution of this work is to provide novel approximate analytical solutions to compute the time-dependent internal stress state through the pipe thickness within the framework of nonlinear viscoelasticity theory. The structures considered are thick, multilayered anisotropic infinitive long cylinders subjected to axisymmetric mechanical loading. Under such conditions there is an exact elastic solution which naturally satisfies equilibrium, strain-displacement, compatibility and boundary conditions for the stated constitutive equations and loading. Due to the continuous stress variations through the cylinder thickness, the proposed nonlinear viscoelastic solution assumes the averaged stress state to calculate the nonlinear elastic and viscoelastic factors in each layer. Furthermore, the solution is obtained assuming that the creep strains, within each layer, are constant through the thickness. The proposed algorithm converges to the exact solution when the number of layers is artificially increased. For the linear viscoelastic case, the proposed solution proved to match the exact known solution for isotropic viscoelastic materials. Finally several invented cases are run to illustrate the importance of the viscoelasticity phenomenon on the internal stress field in thick-laminated cylinders. © 2010 Elsevier Ltd. Source


Orosa J.A.,University of La Coruna | Oliveira A.C.,University of Porto
Renewable Energy | Year: 2011

In buildings with heating, ventilation, and air-conditioning (HVAC), the Predicted Mean Vote index (PMV) was successful at predicting comfort conditions, whereas in naturally ventilated buildings, only adaptive models provide accurate predictions. On the other hand, permeable coverings can be considered as a passive control method of indoor conditions and, consequently, have implications in the perception of indoor air quality, local thermal comfort, and energy savings. These energy savings were measured in terms of the set point temperature established in accordance with adaptive methods. Problems appear when the adaptive model suggests the same neutral temperature for ambiences with the same indoor temperature but different relative humidities. In this paper, a new design of the PMV model is described to compare the neutral temperature to real indoor conditions. Results showed that this new PMV model tends to overestimate thermal neutralities but with a lower value than Fanger's PMV index. On the other hand, this new PMV model considers indoor relative humidity, showing a clear differentiation of indoor ambiences in terms of it, unlike adaptive models. Finally, spaces with permeable coverings present indoor conditions closer to thermal neutrality, with corresponding energy savings. © 2010 Elsevier Ltd. Source


Gonzalez B.,University of Vigo | Gonzalez E.J.,University of Porto
Journal of Chemical Thermodynamics | Year: 2014

In this paper, experimental densities, speeds of sound, dynamic viscosities, refractive indices and molar isobaric heat capacities of the pure 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid, [PMpyr][NTf2], are reported as a function of temperature from T = (293.15 to 343.15) K and at atmospheric pressure. From density and refractive index data, the thermal expansion coefficient, molar refractions and molar refractions for the pure ionic liquid were calculated. Besides, a thermal analysis was carried out for the pure ionic liquid using a differential scanning calorimeter. Linear equations were used to fit the density, speed of sound, refractive index and molar isobaric heat capacity data, while the viscosity data were fitted using common equations such as Arrhenius, Vogel-Fulcher-Tamman (VFT), Litovitz, and fluidity. Furthermore, experimental density, speed of sound and refractive index data for binary mixtures with alcohols and their derived properties (excess molar volume, and excess molar isentropic compression) were determined over the whole composition range from T = (298.15, 303.15 and 308.15) K. The excess properties were satisfactorily fitted by Redlich-Kister equation. © 2013 Elsevier Ltd. All rights reserved. Source


De Moura M.F.S.F.,University of Porto | Goncalves J.P.M.,IBM | Magalhaes A.G.,Polytechnic Institute of Porto
International Journal of Adhesion and Adhesives | Year: 2012

A simple procedure to measure the cohesive laws of bonded joints under mode I loading using the double cantilever beam test is proposed. The method only requires recording the applied load-displacement data and measuring the crack opening displacement at its tip in the course of the experimental test. The strain energy release rate is obtained by a procedure involving the Timoshenko beam theory, the specimen's compliance and the crack equivalent concept. Following the proposed approach the influence of the fracture process zone is taken into account which is fundamental for an accurate estimation of the failure process details. The cohesive law is obtained by differentiation of the strain energy release rate as a function of the crack opening displacement. The model was validated numerically considering three representative cohesive laws. Numerical simulations using finite element analysis including cohesive zone modeling were performed. The good agreement between the inputted and resulting laws for all the cases considered validates the model. An experimental confirmation was also performed by comparing the numerical and experimental load-displacement curves. The numerical load-displacement curves were obtained by adjusting typical cohesive laws to the ones measured experimentally following the proposed approach and using finite element analysis including cohesive zone modeling. Once again, good agreement was obtained in the comparisons thus demonstrating the good performance of the proposed methodology. © 2012 Elsevier Ltd. Source


Massano J.,University of Porto
Acta Medica Portuguesa | Year: 2011

Parkinson's disease (PD) is a common disorder that causes a marked decrease in the quality of life of patients and implies high costs at the social, familiar and economic levels. The diagnosis is essentially achieved on clinical grounds and there is an extensive list of possible differential diagnoses, thus being fundamental to recognize the typical clinical features of PD, and then proceed to effective treatment, thus improving disability and the quality of life of patients. This review article, built on evidence-based knowledge and clinical experience, approaches pathogenesis, clinical features, the diagnostic methodology and current concepts in the treatment of PD in a pragmatic and updated manner. Source


Ferras L.L.,University of Minho | Nobrega J.M.,University of Minho | Pinho F.T.,University of Porto
Journal of Non-Newtonian Fluid Mechanics | Year: 2012

This work presents analytical solutions for both Newtonian and inelastic non-Newtonian fluids with slip boundary conditions in Couette and Poiseuille flows using the Navier linear and non-linear slip laws and the empirical asymptotic and Hatzikiriakos slip laws. The non-Newtonian constitutive equation used is the generalized Newtonian fluid model with the viscosity described by the power law, Bingham, Herschel-Bulkley, Sisko and Robertson-Stiff models. While for the linear slip model it was always possible to obtain closed form analytical solutions, for the remaining non-linear models it is always necessary to obtain the numerical solution of a transcendent equation. Solutions are included with different slip laws or different slip coefficients at different walls. © 2012 Elsevier B.V. Source


Tenreiro Machado J.A.,Polytechnic Institute of Porto | Lopes A.M.,University of Porto
Nonlinear Dynamics | Year: 2015

This paper analyzes several natural and man-made complex phenomena in the perspective of dynamical systems. Such phenomena are often characterized by the absence of a characteristic length-scale, long range correlations and persistent memory, which are features also associated to fractional order systems. For each system, the output, interpreted as a manifestation of the system dynamics, is analyzed by means of the Fourier transform. The amplitude spectrum is approximated by a power law function and the parameters are interpreted as an underlying signature of the system dynamics. The complex systems under analysis are then compared in a global perspective in order to unveil and visualize hidden relationships among them. © 2014, Springer Science+Business Media Dordrecht. Source


dos Santos C.,University of Porto | dos Santos C.,University of Santiago de Compostela | da Hora E.,Federal University of Paraiba
European Physical Journal C | Year: 2011

In this paper we study one-dimensional static self-dual non-topological solitons in an Abelian-Higgs Chern-Simons model with a non-canonical kinetic term. We choose a scalar potential with a single minimum and present an analytical soliton solution which corresponds to an electrically charged lump-like soliton without total momentum and located in a region where the scalar field gets maximum. The solitonic boundary conditions impose a discontinuity on the electric field across the soliton line where, then, there is a linear charge density. © Springer-Verlag/Società Italiana di Fisica 2011. Source


Batista S.F.A.,University of Porto | Fernandes J.,University of Coimbra
New Astronomy | Year: 2012

The main goal of this paper is to revisit the lost siblings of the Sun candidates within 100 pc. The solar siblings should have some similar characteristics as their ages, chemical compositions and kinematics properties. Considering their chemical compositions, age and kinematics properties only three potential candidates have been found in the literature: HD28676, HD83423 and HD175740. The first two stars are mentioned by Brown et al. (2010) and Bobylev et al. (2011), respectively. HD175740 is, to our knowledge, the first giant to be proposed as potential candidate. © 2012 Elsevier B.V. All rights reserved. Source


Hyaluronic acid (HA) is an important biomacromolecule, which fulfils a number of vital physiological functions (especially in the joint synovial fluid) and also has consumer and pharmaceutical applications. HA solution properties have already been quite thoroughly characterized in response to steady shear flows but are less well understood in highly deforming extensional flows. In this study, flow-induced birefringence measurements are made as a function of the strain rate in planar elongational flow at the stagnation point of a cross-slot device using HA solutions of a range of molecular weights (0.9×106 g mol-1≤Mw≤4.8×106 g mol-1) and at dilute concentrations. The results provide macromolecular relaxation times, molecular weight distributions and the extensional viscosities and Trouton ratios of the fluids. The HA relaxation time is found to vary as τ∼Mw1.8, which is consistent with a partially solvated, expanded coil. An intrinsic Trouton ratio is defined, which varies as [Tr]∼Mw2. The measurement of birefringence with strain rate is shown to be highly sensitive to the molecular weight distribution and can resolve subtle changes due to macromolecular degradation and the presence of fracture products. Mechanical degradation experiments in the cross-slots indicate midchain scission of HA macromolecules, strongly suggesting near full extension of the high-molecular weight fraction in the stagnation point extensional flow field. Taken together the results suggest a possible method for analysis of the HA in synovial fluid, and this concept is tested using synovial fluid obtained from porcine tarsal joint. Copyright © 2013 Wiley Periodicals, Inc. Source


Tome L.I.N.,University of Aveiro | Jorge M.,University of Porto | Gomes J.R.B.,University of Aveiro | Coutinho J.A.P.,University of Aveiro
Journal of Physical Chemistry B | Year: 2012

Although the understanding of the influence of ionic liquids (ILs) on the solubility behavior of biomolecules in aqueous solutions is relevant for the design and optimization of novel biotechnological processes, the underlying molecular-level mechanisms are not yet consensual or clearly elucidated. In order to contribute to the understanding of the molecular interactions established between amino acids and ILs in aqueous media, classical molecular dynamics (MD) simulations were performed for aqueous solutions of five amino acids with different structural characteristics (glycine, alanine, valine, isoleucine, and glutamic acid) in the presence of 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide. The results from MD simulations enable to relate the properties of the amino acids, namely their hydrophobicity, to the type and strength of their interactions with ILs in aqueous solutions and provide an explanation for the direction and magnitude of the solubility phenomena observed in [IL + amino acid + water] systems by a mechanism governed by a balance between competitive interactions of the IL cation, IL anion, and water with the amino acids. © 2012 American Chemical Society. Source


Castro-Lopes J.,University of Porto
Journal of Pain and Palliative Care Pharmacotherapy | Year: 2014

The results of a survey conducted by the pan-European Opioids and Pain European Network of Minds (OPENMinds) Primary Care Group (OMPC) on pain assessment, opioid therapy, and educational needs are presented. This report is adapted from paineurope 2013; Issue 4, ©Haymarket Medical Publications Ltd., and is presented with permission. paineurope is provided as a service to pain management by Mundipharma International, Ltd., and is distributed free of charge to health care professionals in Europe. Archival issues can be accessed via the Web site: http://www.paineurope.com, at which European health professionals can register online to receive copies of the quarterly publication. © 2014 Informa Healthcare USA, Inc. Source


Brazhnyi V.A.,University of Porto | Salerno M.,University of Salerno
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

The physical mechanism underlying scattering properties of matter-wave gap solitons (GSs) by linear-optical-lattice defects is investigated. The occurrence of repeated reflection, transmission, and trapping regions for increasing strengths of an optical-lattice defect are shown to be due to resonances with impurity modes inside the defect potential with chemical potentials and numbers of atoms matching corresponding quantities of the incoming GSs. For small amplitude GSs the number of these resonances coincides with the number of bound states existing in the defect potential for the given defect strength. The dependence of the positions and widths of the transmission resonant peaks on incoming velocities is investigated by means of defect-mode analysis and effective-mass theory. The comparisons with direct integrations of the Gross-Pitaevskii equation provide good agreement confirming the correctness of our approach. Multiple resonant transmissions through arrays of optical lattice defects are also investigated and the possibility of using them for very precise GS dynamical filters is also suggested. © 2011 American Physical Society. Source


Sujit P.B.,University of Porto | Saripalli S.,Arizona State University
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2013

We propose a framework for cooperative search using a combination of an unmanned aerial vehicle (UAV) and an autonomous underwater vehicle (AUV). Such a combination allows search platforms to adapt to changes in both mission objectives and environmental parameters. We propose three strategies for coordination between an UAV and AUV to maximize the area explored while minimizing the idle time of the UAV and AUV. We evaluate the efficacy of these strategies while varying the speed, communication range and the number of targets. Preliminary results suggest the feasibility of our approach to combine UAVs and AUVs for effectively searching a given area. © 2012 Springer Science+Business Media B.V. Source


Cardoso L.,University of Tras os Montes e Alto Douro | Cardoso L.,University of Porto | Mendao C.,Bayer Portugal S.A. | Madeira De Carvalho L.,The Interdisciplinary Center
Parasites and Vectors | Year: 2012

Background: Canine vector-borne diseases (CVBDs) are caused by a wide range of pathogens transmitted to dogs by arthropods including ticks and insects. Many CVBD-agents are of zoonotic concern, with dogs potentially serving as reservoirs and sentinels for human infections. The present study aimed at assessing the seroprevalence of infection with or exposure to Dirofilaria immitis, Ehrlichia canis, Borrelia burgdorferi sensu lato, Anaplasma spp. and Leishmania infantum in dogs in Portugal. Methods. Based on 120 veterinary medical centres from all the regions of mainland and insular Portugal, 557 apparently healthy and 628 CVBD-suspect dogs were sampled. Serum, plasma or whole blood was tested for qualitative detection of D. immitis antigen and antibodies to E. canis, B. burgdorferi s. l., Anaplasma spp. and L. infantum with two commercial in-clinic enzyme-linked immunosorbent assay kits. Odds ratios (OR) were calculated by logistic regression analysis to identify independent risk factors of exposure to the vector-borne agents. Results: Total positivity levels to D. immitis, E. canis, B. burgdorferi, Anaplasma spp., L. infantum, one or more agents and mixed agents were 3.6%, 4.1%, 0.2%, 4.5%, 4.3%, 14.0% and 2.0% in the healthy group, and 8.9%, 16.4%, 0.5%, 9.2%, 25.2%, 46.3% and 11.6% in the clinically suspect group, respectively. Non-use of ectoparasiticides was a risk factor for positivity to one or more agents both in the apparently healthy (OR = 2.1) and CVBD-suspect (OR = 1.5) dogs. Seropositivity to L. infantum (OR = 7.6), E. canis (OR = 4.1) and D. immitis (OR = 2.4) were identified as risk factors for the presence of clinical signs compatible with CVBDs. Positivity to mixed agents was not found to be a risk factor for disease. Conclusions: Dogs in Portugal are at risk of becoming infected with vector-borne pathogens, some of which are of zoonotic concern. CVBDs should be considered by practitioners and prophylactic measures must be put in place to protect dogs and limit the risk of transmission of vector-borne agents to humans. This study is expected to give veterinary and public health authorities an increased awareness about CVBDs in Portugal and to serve as a reference for future investigations and control actions. © 2012 Cardoso et al; licensee BioMed Central Ltd. Source


Schaller J.,Eastern Connecticut State University | Valente J.M.S.,University of Porto
Computers and Operations Research | Year: 2012

This paper considers a problem in which there is a set of jobs to be sequenced on a single machine. Each job has a weight and the objective is to sequence the jobs to minimize total weighted squared tardiness. A branch-and-bound algorithm is developed for optimally solving the problem. Several dominance conditions are presented for possible inclusion in the branch-and-bound algorithm. The dominance conditions are included in the branch-and-bound algorithm, which is tested on randomly generated problems of various numbers of jobs, due date tightness and due date ranges. The results show that the dominance conditions dramatically improve the efficiency of the branch-and-bound algorithm. © 2011 Elsevier Ltd. All rights reserved. Source


Liu B.,Beihang University | Xing Y.F.,Beihang University | Qatu M.S.,Central Michigan University | Ferreira A.J.M.,University of Porto
Composite Structures | Year: 2012

This paper presents an analytical procedure and closed-form vibration solutions with analytically determined coefficients for orthotropic circular cylindrical shells having classical boundary conditions. This analysis is based upon the Donnell-Mushtari shell theory. This is the simplest thin shell theory and its results for the lowest frequencies of a closed cylinder may not be as accurate. It is known that the exact procedure is complicated for orthotropic shells and this complexity has apparently prevented most researchers from getting results. Using the separation of variables method, the closed-form natural frequencies are successfully obtained in this work. They are found in a compact form. Moreover, the characteristics of the eigenvalues are examined. The exact solutions are validated through numerical comparisons with available solutions in literatures and the semi-analytical differential quadrature finite element method (S-DQFEM) solutions calculated by the authors. © 2011 Elsevier Ltd. Source


Carlos J.S.,University of Beira Interior | Corvacho H.,University of Porto
Renewable Energy | Year: 2014

Simulations to evaluate energy demand for heating and cooling and thermal comfort are becoming more and more common place in the building design process, at least in the most complex cases. In all detailed or simplified calculations, to analyse heat transfer to and from a building, several input parameters are needed. The inputs for the simulation of a whole building are at least the building geometry, the building envelope thermal indices (like thermal transmittance or the solar heat gain coefficient) and typical local climatic data. In a ventilated double window, the air flow through the channel between the two windows makes its thermal performance highly dynamic and dependent on the air flow characteristics. For a whole building simulation, single coefficients or easily calculated coefficients are needed for each facade system, including ventilated systems. In this paper, equivalent thermal transmittance coefficients for a ventilated double window are assessed and presented. For that, experimental measurements in the absence of solar radiation (night period) were used to identify tendencies and validate calculations. Furthermore, simulations were done in order to estimate the Uw-values of the ventilated double window under different windows configuration and different air flow rates. These values can then be used in whole building simulation programmes. © 2013 Elsevier Ltd. Source


Martins M.J.,University of Porto
Journal of Inherited Metabolic Disease | Year: 2012

Phenylketonuria represents the most prevalent inborn error of amino acid metabolism. In early diagnosed patients adequate and continued dietary treatment results in a good neurologic outcome. Natural protein and phenylalanine- restricted diet, even if rich in fruits and vegetables, represents a serious risk for nutritional deficiencies, albeit universally accepted. In the last few years, a growing number of reports have been describing oxidative stress as a concern in phenylketonuric patients. The diet itself includes good sources of dietary antioxidants (phytochemicals, some vitamins and minerals) but also a risk factor for some deficiencies (selenium, zinc, ubiquinone-10 and L-carnitine). Additionally, the extreme stringency of the diet may impose a reduced synthesis of endogenous antioxidants (like ubiquinone-10 and glutathione). Furthermore, increased phenylalanine levels, and its metabolites, may enhance the endogenous synthesis of reactive species and free radicals and/or interfere with the endogenous synthesis of enzymatic antioxidants (like glutathione peroxidase). Therefore, oxidative stress will probably increase, mainly in late diagnosed patients or in those with bad metabolic control. Considering the known association between oxidative stress, obesity and cardiovascular disease, it seems advisable to look further to the impact of oxidative stress on body macromolecules and structures (like lipoprotein oxidation), especially in phenylketonuric patients with late diagnosis or bad metabolic control, in order to prevent future increased risks. Recommendations for PKU patient's clinical follow-up improvement and educational goals are included. © SSIEM and Springer 2011. Source


Cardoso R.P.R.,University of the West of England | Cesar De Sa J.M.A.,University of Porto
Computational Mechanics | Year: 2014

IsoGeometric Analysis (IGA) is increasing its popularity as a new numerical tool for the analysis of structures. IGA provides: (i) the possibility of using higher order polynomials for the basis functions; (ii) the smoothness for contact analysis; (iii) the possibility to operate directly on CAD geometry. The major drawback of IGA is the non-interpolatory characteristic of the basis functions, which adds a difficulty in handling essential boundary conditions. Nevertheless, IGA suffers from the same problems depicted by other methods when it comes to reproduce isochoric and transverse shear strain deformations, especially for low order basis functions. In this work, projection techniques based on the moving least square (MLS) approximations are used to alleviate both the volumetric and the transverse shear lockings in IGA. The main objective is to project the isochoric and transverse shear deformations from lower order subspaces by using the MLS, alleviating in this way the volumetric and the transverse shear locking on the fully-integrated space. Because in IGA different degrees in the approximation functions can be used, different Gauss integration rules can also be employed, making the procedures for locking treatment in IGA very dependent on the degree of the approximation functions used. The blending of MLS with Non-Uniform Rational B-Splines (NURBS) basis functions is a methodology to overcome different locking pathologies in IGA which can be also used for enrichment procedures. Numerical examples for three-dimensional NURBS with only translational degrees of freedom are presented for both shell-type and plane strain structures. © 2014 Springer-Verlag Berlin Heidelberg. Source


Carabineiro S.A.C.,University of Porto
Molecules | Year: 2016

The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications. © 2016 by the author; licensee MDPI. Source


Renna F.,University of Porto | Calderbank R.,Duke University | Carin L.,Duke University | Rodrigues M.R.D.,University College London
IEEE Transactions on Signal Processing | Year: 2014

This paper determines to within a single measurement the minimum number of measurements required to successfully reconstruct a signal drawn from a Gaussian mixture model in the low-noise regime. The method is to develop upper and lower bounds that are a function of the maximum dimension of the linear subspaces spanned by the Gaussian mixture components. The method not only reveals the existence or absence of a minimum mean-squared error (MMSE) error floor (phase transition) but also provides insight into the MMSE decay via multivariate generalizations of the MMSE dimension and the MMSE power offset, which are a function of the interaction between the geometrical properties of the kernel and the Gaussian mixture. These results apply not only to standard linear random Gaussian measurements but also to linear kernels that minimize the MMSE. It is shown that optimal kernels do not change the number of measurements associated with the MMSE phase transition, rather they affect the sensed power required to achieve a target MMSE in the low-noise regime. Overall, our bounds are tighter and sharper than standard bounds on the minimum number of measurements needed to recover sparse signals associated with a union of subspaces model, as they are not asymptotic in the signal dimension or signal sparsity. © 2014 IEEE. Source


Melo S.A.,Bellvitge Biomedical Research Institute IDIBELL | Melo S.A.,University of Porto | Esteller M.,Bellvitge Biomedical Research Institute IDIBELL | Esteller M.,Catalan Institution for Research and Advanced Studies
FEBS Letters | Year: 2011

MicroRNAs [1] have emerged as key post-transcriptional regulators of gene expression, involved in various physiological and pathological processes. It was found that several miRNAs are directly involved in human cancers, including lung, breast, brain, liver, colon cancer and leukemia. In addition, some miRNAs may function as oncogenes or tumor suppressors in tumor development. Furthermore, a widespread down-regulation of miRNAs is commonly observed in human cancers and promotes cellular transformation and tumorigenesis [2-5]. More than 50% of miRNA genes are located in cancer-associated genomic regions or in fragile sites, frequently amplified or deleted in human cancer, suggesting an important role in malignant transformation. A better understanding of the miRNA regulation and misexpression in cancer may ultimately yield further insight into the molecular mechanisms of tumorigenesis and new therapeutic strategies may arise against cancer. Here, we discuss the occurrence of the deregulated expression of miRNAs in human cancers and their importance in the tumorigenic process. © 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. Source


Cardoso G.C.,University of Porto
Ethology | Year: 2013

To be evolutionarily stable, sexual signals need to convey information regarding the quality or motivation of individuals. This can be achieved through direct or indirect signal costs that guarantee honest communication or through signal designs that facilitate the assessment of quality. Here, I present the case for an alternative hypothesis: that signalling exposes informative mistakes. Signalling mistakes range from occasional to frequent and from slight distortions of typical signals to grossly atypical signals. Their occurrence may be enhanced by disease or stress, thus revealing individual quality or motivation, and receivers typically respond negatively to them. By this mechanism, honest communication is due to costs of developing resistance to mistakes. Therefore, the hypothesis can function independently of signal design costs, although it can also be enhanced by signal design costs when those increase the occurrence of mistakes. This hypothesis widens the scope of signals expected to be sexually selected and creates new approaches to research in sexual selection and animal communication. © 2013 Blackwell Verlag GmbH. Source


Pereira M.,University of Porto
Revista portuguesa de cardiologia : orgão oficial da Sociedade Portuguesa de Cardiologia = Portuguese journal of cardiology : an official journal of the Portuguese Society of Cardiology | Year: 2010

Hypertension is quantitatively the largest risk factor for cardiovascular diseases and it is highly prevalent in Portugal. It is important to understand which factors explain awareness, treatment and control of hypertension in Portugal, in order to identify barriers to prevention. This study consisted of a cross-sectional evaluation of 2310 adults (61.5% women) randomly selected from the population of Porto, Portugal, in 1999-2003. Hypertension was defined as blood pressure > or = 140/90 mmHg and/or being medicated with antihypertensive drugs. The prevalence of hypertension was 42.7% in women and 46.7% in men. The prevalence of awareness was 58.9% among women and 41.3% among men. Among aware hypertensives, 71.7% and 60.2% were treated, while 23.0% and 22.8% of treated hypertensives were controlled among women and men, respectively. Awareness of hypertension was more frequent in older subjects, those with high body mass index (BMI), diabetic women and women with high serum triglycerides, and lower among women who use private health care services, single/widowed/divorced men and among men with higher levels of alcohol consumption. In both genders, treatment was directly associated with age and BMI, while education and renal dysfunction were only directly associated among men. Physical activity was inversely associated with treatment in women. Age and BMI were associated with a lower likelihood of blood pressure control in both genders. In women, control of hypertension was observed less often among those with higher levels of alcohol consumption. Co The concurrent presence of additional cardiovascular risk factors was generally not associated with treatment and control, although the proportional contribution to this situation of patients and the health care system could not be assessed. Source


Karachalios E.F.,University of Bristol | Adams R.D.,University of Bristol | da Silva L.F.M.,University of Porto
International Journal of Adhesion and Adhesives | Year: 2013

Single lap joints in many different geometric and material configurations were analysed using finite element analysis and tested in tension. Geometric parameters, such as the overlap length and adherend thickness, together with material parameters such as the adherend and adhesive stress-strain behaviour, were all tested. The mechanisms and modes of failure were observed for different cases, and positions of damage initiation were identified. Failure patterns were related to failure mechanisms. A failure prediction methodology has been proposed and a good correlation was obtained between the experimental and finite element predictions of strength for a variety of joint configurations. The study is presented in two parts. In the first (present paper), high strength steel adherends are considered and in the second paper ductile steel adherends are studied. For high strength steel adherends and a relatively short overlap, failure is dominated by adhesive global yielding. As the overlap gets longer, however, failure is no longer due to global yielding, but due to high local shear strains. © 2013 Elsevier Ltd. All rights reserved. Source


Karachalios E.F.,University of Bristol | Adams R.D.,University of Bristol | da Silva L.F.M.,University of Porto
International Journal of Adhesion and Adhesives | Year: 2013

In the first part of this study, single lap joints in many different geometric and material configurations were tested in tension with high strength steel adherends. In the present paper, low strength steel adherends (mild steel and medium carbon steel) have been studied experimentally and numerically. Geometric parameters such as the overlap length and the adherend thickness, together with material parameters such as the adhesive stress-strain behaviour, were all tested. The mechanisms and modes of failure were observed for different cases, and positions of damage initiation were identified. Contrarily to the joints with high strength steel, it is found that the failure mechanism in this case is dictated by adherend yielding. © 2013 Elsevier Ltd. All rights reserved. Source


Katnam K.B.,University of Limerick | Da Silva L.F.M.,University of Porto | Young T.M.,University of Limerick
Progress in Aerospace Sciences | Year: 2013

Advanced composite materials have gained popularity in high-performance structural designs such as aerospace applications that require lightweight components with superior mechanical properties in order to perform in demanding service conditions as well as provide energy efficiency. However, one of the major challenges that the aerospace industry faces with advanced composites - because of their inherent complex damage behaviour - is structural repair. Composite materials are primarily damaged by mechanical loads and/or environmental conditions. If material damage is not extensive, structural repair is the only feasible solution as replacing the entire component is not cost-effective in many cases. Bonded composite repairs (e.g. scarf patches) are generally preferred as they provide enhanced stress transfer mechanisms, joint efficiencies and aerodynamic performance. With an increased usage of advanced composites in primary and secondary aerospace structural components, it is thus essential to have robust, reliable and repeatable structural bonded repair procedures to restore damaged composite components. But structural bonded repairs, especially with primary structures, pose several scientific challenges with the current existing repair technologies. In this regard, the area of structural bonded repair of composites is broadly reviewed - starting from damage assessment to automation - to identify current scientific challenges and future opportunities. © 2013 Elsevier Ltd. Source


Mokhberdoran A.,University of Porto | Ajami A.,Shahid Madani University of Azarbaijan
IEEE Transactions on Power Electronics | Year: 2014

Nowadays, use of multilevel inverters in high-power applications clearly can be seen. High quality and lower distortion of the output voltage and low blocking voltage of semiconductor switches are being presented as the major privileges of the multilevel inverter compared to the traditional voltage source inverter. In this paper, a new topology of multilevel inverter is proposed as fundamental block. The proposed topology is generalized using series connection of the fundamental blocks. The proposed multilevel inverter has been analyzed in both symmetric and asymmetric operation modes. A great perfection in voltage levels number with minimum switching devices has been obtained in both symmetric and asymmetric modes. Thereafter, a detailed study of losses and peak inverse voltage (PIV) of the proposed multilevel inverter is given. Also, in continuation, a comparison between the proposed topology and the traditional one and a recently developed topology is carried out. Finally, a computer simulation using MATLAB/Simulink is presented and a laboratory prototype implementation verifies the results. © 2014 IEEE. Source


The objective of this study was to analyze associations of cardiorespiratory fitness (CRF) with physical activity, time spent watching television and using computer, mode of commuting to school (CS), and adiposity, by gender. Participants were 1708 students (53.8% girls), aged 11 to 19 years. CRF was evaluated with a 20-meter shuttle-run test using VO2max by previously published equation. Maturation stages determined by Tanner's criteria, body mass index, and skinfolds were measured, and a questionnaire used to assess socioeconomic status, PA, television and computer time, and mode of CS. We conducted a regression analysis using CRF as the dependent variable. CRF was independent and positively associated with physical activity [β = 0.338 (95% CI = 0.119; 0.188); P < .001] and with maturation [β = -0.876 (95% CI = 0.666; 1.087); P < .001]; independent and negatively associated with television time [β = -0.003 (95% CI = -0.005; -0.002); P < .001] and adiposity [β = -0.068 (95% CI = -0.076; -0.060); P < .001]. CRF was positively associated with CS [β = 0.337; (95% CI = 0.014; 0.741); P = .014]. No associations were found for computer time. These findings suggest that increasing overall physical activity levels through interventions in different domains such as active CS, reducing sedentary activities, such as television time, might be effective strategies for improving CRF in youth. Source


Costa M.A.,University of Porto
Reproductive BioMedicine Online | Year: 2016

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest. © 2015 Reproductive Healthcare Ltd. Source


Teixeira A.A.C.,INESC Porto | Mota L.,University of Porto
Scientometrics | Year: 2012

The study of university-industry (U-I) relations has been the focus of growing interest in the literature. However, to date, a quantitative overview of the existing literature in this field has yet to be accomplished. This study intends to fill this gap through the use of bibliometric techniques. By using three different yet interrelated databases-a database containing the articles published on U-I links, which encompass 534 articles published between 1986 and 2011; a 'roots' database, which encompasses over 20,000 references to the articles published on U-I relations; and a 'influences' database which includes more than 15,000 studies that cited the articles published on U-I relations-we obtained the following results: (1) 'Academic spin offs', 'Scientific and technological policies' and (to a greater extent) 'Knowledge Transfer Channels' are topics in decline; (2) 'Characteristics of universities, firms and scientists', along with 'Regional spillovers', show remarkable growth, and 'Measures and indicators' can be considered an emergent topic; (3) clear tendency towards 'empirical' works, although 'appreciative and empirical' papers constitute the bulk of this literature; (4) the multidisciplinary nature of the intellectual roots of the U-I literature-an interesting blending of neoclassical economics (focused on licensing, knowledge transfer and high-tech entrepreneurship) and heterodox approaches (mainly related to systems of innovation) is observed in terms of intellectual roots; (5) the influence of the U-I literature is largely concentrated on the industrialized world and on the research area of innovation and technology (i. e., some 'scientific endogamy' is observed). © 2012 Akadémiai Kiadó, Budapest, Hungary. Source


Ferreira R.J.,University of Lisbon | Dos Santos D.J.,University of Porto | Ferreira M.-J.U.,University of Lisbon
Future Medicinal Chemistry | Year: 2015

Multidrug-resistance (MDR) phenomena are a worldwide health concern. ATP-binding cassette efflux pumps as P-glycoprotein have been thoroughly studied in a frantic run to develop new efflux modulators capable to reverse MDR phenotypes. The study of efflux pumps has provided some key aspects on drug extrusion, however the answers could not be found solely on ATP-binding cassette transporters. Its counterpart-the plasma membrane-is now emerging as a critical structure able to modify drug behavior and efflux pump activity. Alterations in the membrane surrounding P-glycoprotein are now known to modulate drug efflux, with membrane-related biophysical, biochemical and mechanical aspects further increasing the complexity of an already multifaceted phenomena. This review summarizes the main knowledge comprising the plasma membrane role in MDR. © 2015 Future Science Ltd. Source


Ferreira C.,Institute Investigacion en Recursos Cinegeticos IREC CSIC UCLM JCCM | Ferreira C.,University of Porto
European Journal of Wildlife Research | Year: 2012

The European rabbit (Oryctolagus cuniculus) is a high-profile prey, native from the Iberian Peninsula, the only region in the world where the two rabbit subspecies (O. cuniculus algirus and O. cuniculus cuniculus) currently co-exist in natural conditions. In this area, this important prey represents a keystone species and ecosystem engineer of Mediterranean landscapes, being also the most harvested and one of the most managed small-game species. Additionally, the species can create damage to crops in some parts of the Iberian Peninsula where it is regarded as an agricultural pest. The scientific interest towards the species is becoming increasingly apparent most likely as a repercussion of declining population trends over the last decades. The latter has been the result of the impact of habitat deterioration, viral diseases, unsustainable hunting, and predation. In this paper, I present a review of the scientific literature currently available on the European rabbit in the Iberian Peninsula. I discuss knowledge gaps and highlight priority research guidelines to suppress them, in an attempt to provide a general perspective to target research efforts more effectively. This analysis is particularly relevant due to the current vulnerability of rabbit populations in Iberia and to the recent news of cuts in scientific funding in most Mediterranean countries. © 2012 Springer-Verlag. Source


Gold nanostars of ~70 nm tip to tip distances were synthesized by a seed mediated method and covalently self-assembled on 1,5-pentanedithiol modified electrodes. Electron transfer kinetics at the AuNS/dithiol modified electrodes were studied as a function of AuNS surface density which was varied by increasing their self-assembly time from 8 h, 16 h, 24 h to 32 h. Excellent electrocatalytic properties of AuNSs were observed toward electrochemistry of [Fe(CN)6]4-/3- redox couple. The apparent heterogeneous electron transfer constant, ket, has progressively increased with the surface density of AuNSs bonded to the electrodes from 0.65 × 10-5 cm s-1 (8 h), 1.47 × 10-5 cm s-1 (16 h), 3.95 × 10-5 cm s-1 (24 h) to an excellent 85.0 × 10-5 cm s-1 (32 h). Electrochemical charging of nanostars was confirmed, for the first time, by 79 times increase of double layer capacitance, Cdl, from 0.34 μF (8 h) to 27 μF (32 h). The electrochemical charging of AuNSs had also a strong influence on the electron tunneling process through the 1,5PDT molecules being more efficient at dense layers of AuNSs. The tunneling parameter, β, has decreased from 1.13 Å-1 (16 h) to 0.50 Å-1 (32 h). The AuNSs were chemically stable toward [Fe(CN)6]4-/3- showing no change in shape after electrochemical measurements. © 2013 by the authors; licensee MDPI, Basel, Switzerland. Source


Dinis-Ribeiro M.,Portuguese Institute of Oncology | Dinis-Ribeiro M.,University of Porto | Kuipers E.J.,Erasmus University Rotterdam
Endoscopy | Year: 2015

In an aging European population, an increasing number of individuals will suffer from gastric cancer in the coming two decades. Recent research has determined the risk for gastric cancer in patients with different stages of gastric atrophy. Based on these data, it is now recommended that surveillance is offered to individuals with advanced stages of atrophic gastritis. Endoscopic biopsies of the gastric antrum and corpus are recommended in order to assess the severity and extent of gastric atrophy. This enables identification of those at highest risk of progressing to cancer. However, systematic reviews have shown that in recent years many researchers have assessed new endoscopic technologies for their accuracy in determining the severity and extent of gastric atrophy and metaplasia without the use of histology. Simple, reliable and accurate endoscopic features have been identified that can be used to either target biopsies or avoid biopsy sampling in the absence of endoscopic features of atrophy and intestinal metaplasia. This may largely simplify everyday practice. Randomized trials or large observational studies are now needed to demonstrate the accuracy of endoscopic assessment of the entire gastric mucosa and its impact on patient management. Source


de Moura M.F.S.F.,University of Porto | Goncalves J.P.M.,IBM
Engineering Fracture Mechanics | Year: 2015

A cohesive zone model to deal with high-cycle fatigue of composite bonded joints under mixed-mode I+II loading is developed. The model assumes a linear traction-relative displacements softening and uses a single parameter to simulate the cumulative damage resulting from static and fatigue loading. Finite element analyses considering the Single-Leg Bending test were conducted to verify the performance of the proposed method under different modified Paris laws and load ratios. It was verified that the model is able to capture all those effects with accuracy which proves the adequacy of the whole procedure concerning mixed-mode I+II fatigue/fracture characterization of composite bonded joints. © 2015 Elsevier Ltd. Source


Ribeiro P.,University of Porto
International Journal of Mechanical Sciences | Year: 2010

This paper intends to analyse free vibrations of beams in the geometrically non-linear regime and with plastic strains. The specific goal is to find how plastic strains combined with large displacements influence the non-linear modes of vibration, by analysing the influence of the former two factors in mode shapes and natural frequencies of vibration. The geometrical non-linearity is represented by the Von Krmn type straindisplacement relations. A stressstrain relation of the bilinear type, with isotropic strain hardening, is assumed, the Von Mises yield criterion is employed and the flow theory of plasticity applied. To obtain the time domain ordinary differential equations of motion the principle of virtual work is used and a Timoshenko p-version finite element model with hierarchical basis functions is adopted. The equations of motion are naturally different from the usual large displacement equations, due to the appearance of matrices and vectors related with plastic terms. In the cases studied, plastic strains are imposed on the beam by equally distributed static forces; the forces are then removed and a study on the free vibrations is carried out. It is assumed that, once defined, the plastic strain field does not change. The time domain equations are transformed to the frequency domain by the harmonic balance method and these frequency domain equations are solved by an arc-length continuation method. The variations of mode shapes of vibration and of natural frequencies with vibration amplitude are investigated. It is found that the plastic strain distribution defines if and how much softening spring effect occurs. Hardening spring effect always appears, but with some plastic strain fields hardening spring takes place only at large vibration amplitudes. Plastic deformations also have an important effect in the vibration shapes. © 2010 Elsevier Ltd. All rights reserved. Source


Vazquez Castro M.A.,Autonomous University of Barcelona | Vieira F.,University of Porto
IEEE Communications Magazine | Year: 2012

The second generation of the Digital Video Broadcasting standard for Satellite transmission, DVB-S2, is the evolution of the highly successful DVB-S satellite distribution technology. DVB-S2 has benefited from the latest progress in channel coding and modulation such as Low Density Parity Check Codes and higher order constellations to achieve performance that approaches Shannon¿s theoretical limit. We present a cross-layer design for Quality-of-Service (QoS) provision of interactive services, which is not specified in the standard. Our cross-layer approach exploits the satellite channel characteristics of space-time correlation via a cross-layer queueing architecture and an adaptive cross-layer scheduling policy. We show that our approach not only allows system load control but also rate adaptation to channel conditions and traffic demands on the coverage area. We also present the extension of our cross-layer design for mobile gateways focusing on the railway scenario. We illustrate the trade-off between system-wide and individual throughput by means of simulation, and that this trade-off could be a key metric in measuring the service level of DVB-S2 Broadband Service. © 2012 IEEE. Source


E-cadherin is a central molecule in the process of gastric carcinogenesis and its posttranslational modifications by N-glycosylation have been described to induce a deleterious effect on cell adhesion associated with tumor cell invasion. However, the role that site-specific glycosylation of E-cadherin has in its defective function in gastric cancer cells needs to be determined. Using transgenic mice models and human clinical samples, we demonstrated that N-acetylglucosaminyltransferase V (GnT-V)-mediated glycosylation causes an abnormal pattern of E-cadherin expression in the gastric mucosa. In vitro models further indicated that, among the four potential N-glycosylation sites of E-cadherin, Asn-554 is the key site that is selectively modified with β1,6 GlcNAc-branched N-glycans catalyzed by GnT-V. This aberrant glycan modification on this specific asparagine site of E-cadherin was demonstrated to affect its critical functions in gastric cancer cells by affecting E-cadherin cellular localization, cis-dimer formation, molecular assembly and stability of the adherens junctions and cell–cell aggregation, which was further observed in human gastric carcinomas. Interestingly, manipulating this site-specific glycosylation, by preventing Asn-554 from receiving the deleterious branched structures, either by a mutation or by silencing GnT-V, resulted in a protective effect on E-cadherin, precluding its functional dysregulation and contributing to tumor suppression.Oncogene advance online publication, 20 July 2015; doi:10.1038/onc.2015.225. © 2015 Macmillan Publishers Limited Source


Veloso F.T.,University of Porto
European Journal of Gastroenterology and Hepatology | Year: 2016

A modern approach to Crohn’s disease (CD) should be influenced by the patient’s underlying prognosis. Here, I analyse the clinical factors predicting CD course on the basis of information obtained at diagnosis and in the year following diagnosis. Perianal disease at diagnosis appears to be a strong predictor of unfavourable outcome and has been associated with a more frequent use of immunosuppressive treatment. Early age at diagnosis, ileocolonic disease and extraintestinal manifestations are characteristics of patients at risk for more complicated disease. Otherwise, patients subjected to surgery at diagnosis or during the first year of follow-up appear to have a relatively benign outcome. Disease activity in the year after diagnosis appears to be a good predictor of future disease activity as about two-third of the patients who remain in remission tend to remain unchanged thereafter, whereas those patients treated with steroids have, manifestly, an unfavourable subsequent clinical course. Moreover, there is consistent evidence that active smoking is associated with a complicated disease course. The results of the studies reviewed suggest that the combination of ‘phenotype at diagnosis’ and ‘comportment follow-up classification’ in the year following diagnosis can be potentially useful prognostic factors in clinical practice. With the development of newer therapies in CD, there is a growing need to predict disease outcome, despite the difficult challenge in anticipating the future clinical course in a given patient. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Source


Bombardelli D.,University of Porto
Journal of High Energy Physics | Year: 2014

We propose a next-to-leading Lüscher-like formula for the finite-size corrections of the excited states energies in integrable theories. We conjecture the expressions of the corrections for both the energy and the particles' rapidities by interpreting the excited states as momenta-dependent defects. We check the resulting formulas in some simple relativistic model and conjecture those for the AdS 5 /CFT 4 case. © 2014 SISSA. Source


Fontes F.,University of Porto
British journal of cancer | Year: 2013

Prostate cancer mortality has been decreasing in several high income countries and previous studies analysed the trends mostly according to geographical criteria. We aimed to identify patterns in the time trends of prostate cancer mortality across countries using a model-based approach. Model-based clustering was used to identify patterns of variation in prostate cancer mortality (1980-2010) across 37 European, five non-European high-income countries and four leading emerging economies. We characterised the patterns observed regarding the geographical distribution and gross national income of the countries, as well as the trends observed in mortality/incidence ratios. We identified three clusters of countries with similar variation in prostate cancer mortality: pattern 1 ('no mortality decline'), characterised by a continued increase throughout the whole period; patterns 2 ('later mortality decline') and 3 ('earlier mortality decline') depict mortality declines, starting in the late and early 1990s, respectively. These clusters are also homogeneous regarding the variation in the prostate cancer mortality/incidence ratios, while are heterogeneous with reference to the geographical region of the countries and distribution of the gross national income. We provide a general model for the description and interpretation of the trends in prostate cancer mortality worldwide, based on three main patterns. Source


Amorin R.,Institute Astrofisica Of Andalucia Csic | Perez-Montero E.,Institute Astrofisica Of Andalucia Csic | Vilchez J.M.,Institute Astrofisica Of Andalucia Csic | Papaderos P.,University of Porto
Astrophysical Journal | Year: 2012

We present deep broadband imaging and long-slit spectroscopy of three compact, low-mass starburst galaxies at redshift z ∼ 0.2-0.3, also referred to as Green Peas (GP). We measure physical properties of the ionized gas and derive abundances for several species with high precision. We find that the three GPs display relatively low extinction, low oxygen abundances, and remarkably high nitrogen-to-oxygen ratios. We also report on the detection of clear signatures of Wolf-Rayet (W-R) stars in these galaxies. We carry out a pilot spectral synthesis study using a combination of both population and evolutionary synthesis models. Their outputs are in qualitative agreement, strongly suggesting a formation history dominated by starbursts. In agreement with the presence of W-R stars, these models show that these GPs currently undergo a major starburst producing between ∼4% and ∼20% of their stellar mass. However, as models imply, they are old galaxies that formed most of their stellar mass several Gyr ago. The presence of old stars has been spectroscopically verified in one of the galaxies by the detection of Mg I λλ5167, 5173 absorption lines. Additionally, we perform a surface photometry study based on Hubble Space Telescope data, which indicates that the three galaxies possess an exponential low surface brightness envelope. If due to stellar emission, the latter is structurally compatible with the evolved hosts of luminous blue compact dwarf (BCD)/H II galaxies, suggesting that GPs are identifiable with major episodes in the assembly history of local BCDs. These conclusions highlight the importance of these objects as laboratories for studying galaxy evolution at late cosmic epochs. © 2012. The American Astronomical Society. All rights reserved. Source


Almeida C.,University of Porto
Journal of assisted reproduction and genetics | Year: 2013

Little is known about the apoptotic mechanisms involved in abnormal spermatogenesis. In order to describe the significance of apoptosis in azoospermia, testicular tissue from abnormal spermatogenesis was analysed. Testicular treatment biopsies were obtained from 27 men. Five presented oligozoospermia, 9 obstructive azoospermia (4 congenital bilateral absence of the vas deferens; 5 secondary azoospermia) and 13 non-obstructive azoospermia (5 hypospermatogenis; 3 maturation arrest; 5 Sertoli-cell-only syndrome). Immunohistochemical staining was performed for active caspases-3, -8 and -9. The presence of active caspases in Sertoli cells and germ cells was analyzed using stereological tools. Increased active caspase-3 was found in Sertoli-cell-only syndrome. No significant differences were found in maturation arrest. In hypospermatogenesis, primary spermatocytes were the germ cells with higher active caspases. Oligozoospermia and secondary obstruction showed significant differences among germ cells for the presence of all active caspases. In oligozoospermia, spermatogonia presented significant increased active caspase-9 in relation to active caspase-8. In primary obstruction and hypospermatogenesis, germ cells presented significant increased active caspases-3 and -9. Results suggest that increased active caspase-3 might be involved in Sertoli-cell-only syndrome etiology. In cases of hypospermatogenesis, intrinsic lesions at the meiotic stage seem to be related to the pathology. In secondary obstruction apoptosis is suggested to be initiated due to extrinsic and intrinsic lesions, whereas in primary obstruction only the intrinsic apoptotic pathway seems to be present. Finally, in oligozoospermic patients spermatogonia death by mitochondrial damage additionally to meiosis malfunctioning, might be on the origin of the decreased sperm output. Source


Cunha M.,University of Porto | Richter C.,University of Bedfordshire
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

This paper analyzes the impact of climate dynamics on vegetation growth for a rural mountainous region in northeastern Portugal. As a measure of vegetation growth, we use the normalized difference vegetation index (NDVI), which is based on the ten-day synthesis data set (S10) from Satellite Pour l'Observation de la Terre (SPOT-VEGETATION) imagery from 1998 to 2011. We test whether the dynamic growth pattern of the NDVI has changed due to climate variability, and we test the relationship of NDVI with temperature and available soil water (ASW). In order to do so, we use a time-frequency approach based on Kalman filter regressions in the time domain. The advantage of our approach is that it can be used even in the case where the sample size is relatively small. By estimating the important relationships in the time domain first and transferring them into the frequency domain, we are still able to derive a complete spectrum over all frequencies. In our example, we find a change of the cyclical pattern for the spring season and different changes if we take into account all seasons. In other words, we can distinguish between deterministic changes of the vegetation cycles and stochastic changes that only occur randomly. Deterministic changes imply that the data-generating process has changed (such as climate), whereas stochastic changes imply only temporary changes. We find that individual seasons undergo cyclical changes that are different from other seasons. Moreover, our analysis shows that temperature and ASW are the main drivers of vegetation growth. We can also recognize a shift of the relative importance away from temperature to soil water. © 2014 IEEE. Source


Humphries N.E.,Marine Biological Association of The United Kingdom | Humphries N.E.,University of Plymouth | Weimerskirch H.,CNRS Chize Center for Biological Studies | Queiroz N.,Marine Biological Association of The United Kingdom | And 4 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2012

It is an open question how animals find food in dynamic natural environments where they possess little or no knowledge of where resources are located. Foraging theory predicts that in environments with sparsely distributed target resources, where forager knowledge about resources' locations is incomplete, Lévy flight movements optimize the success of random searches. However, the putative success of Lévy foraging has been demonstrated only in model simulations. Here, we use high-temporal-resolution Global Positioning System (GPS) tracking of wandering (Diomedea exulans) and black-browed albatrosses (Thalassarche melanophrys) with simultaneous recording of prey captures, to show that both species exhibit Lévy and Brownian movement patterns. We find that total prey masses captured by wandering albatrosses during Lévy movements exceed daily energy requirements by nearly four-fold, and approached yields by Brownian movements in other habitats. These results, together with our reanalysis of previously published albatross data, overturn the notion that albatrosses do not exhibit Lévy patterns during foraging, and demonstrate that Lévy flights of predators in dynamic natural environments present a beneficial alternative strategy to simple, spatially intensive behaviors. Our findings add support to the possibility that biological Lévy flight may have naturally evolved as a search strategy in response to sparse resources and scant information. Source


Figueiredo J.L.,University of Porto
Journal of Materials Chemistry A | Year: 2013

Porous carbon materials can be used in catalysis either as catalysts or supports. The most relevant literature on this topic is reviewed, emphasizing the methods used for tuning the surface chemistry and textural properties of the carbon materials, in order to design improved catalysts. © 2013 The Royal Society of Chemistry. Source


Simoes L.C.,IBB Institute for Biotechnology And Bioengineering | Simoes M.,University of Porto | Vieira M.J.,IBB Institute for Biotechnology And Bioengineering
Applied and Environmental Microbiology | Year: 2010

Single- and multispecies biofilms formed by six drinking water-isolated bacterial species were used to assess their susceptibilities to sodium hypochlorite (SHC). In general, multispecies biofilms were more resistant to inactivation and removal than single biofilms. Total biofilm inactivation was achieved only for Acinetobacter calcoaceticus single-species biofilms and for those multispecies biofilms without A. calcoaceticus. Biofilms with all bacteria had the highest resistance to SHC, while those without A. calcoaceticus were the most susceptible. A. calcoaceticus formed single biofilmssusceptible to SHC; however, its presence in multispecies biofilms increased their resistance to disinfection. © 2010, American Society for Microbiology. Source


Cutaneous mast cell tumours (MCTs) are some of the most common canine neoplasms and their variable and often aggressive biological behaviour makes them particularly challenging for the veterinary practitioner. Over the years, scientists have accumulated a wealth of knowledge on these tumours and developed better prognostic markers and targeted therapies, mostly focused on inhibiting c-kit, a protein that plays a major role in the biopathology of MCTs. Masitinib and toceranib, targeted inhibitors of c-kit and other receptor tyrosine-kinases (RTKs), offer the promise of improving the outcome of patients with aggressive MCTs.Much of the available knowledge on MCTs is dispersed, making it difficult for practitioners to benefit when consulting a pathologist or making therapeutic decisions. This article seeks to bring together current knowledge on the biopathology of MCTs, reviewing prognostic markers and their applications, and the development of c-kit inhibitors in the context of the basic cellular, molecular and pathological features of MCTs. Future perspectives following recent biopathological data and experimental therapeutic approaches are also addressed. © 2015 Elsevier Ltd. Source


Pereira D.,University of Porto
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

Digital stethoscopes are medical devices that can collect, store and sometimes transmit acoustic auscultation signals in a digital format. These can then be replayed, sent to a colleague for a second opinion, studied in detail after an auscultation, used for training or, as we envision it, can be used as a cheap powerful tool for screening cardiac pathologies. In this work, we present the design, development and deployment of a prototype for collecting and annotating auscultation signals within real hospital environments. Our main objective is not only pave the way for future unobtrusive systems for cardiac pathology screening, but more immediately we aim to create a repository of annotated auscultation signals for biomedical signal processing and machine learning research. The presented prototype revolves around a digital stethoscope that can stream the collected audio signal to a nearby tablet PC. Interaction with this system is based on two models: a data collection model adequate for the uncontrolled hospital environments of both emergency room and primary care, and a data annotation model for offline metadata input. A specific data model was created for the repository. The prototype has been deployed and is currently being tested in two Hospitals, one in Portugal and one in Brazil. Source


Interleukin 6 (IL-6) is a class-I helical cytokine with a broad spectrum of biological activities and a gene structure conserved throughout vertebrates, with five coding exons. IL-6 from European rabbits belonging to the subspecies Oryctolagus cuniculus cuniculus was previously shown to differ from other mammals by extending an additional 27 amino acids. However, in other leporids (Sylvilagus spp and Lepus spp) that diverged from the European rabbit ~12 million years ago this mutation was not present. In this study, we extended the study of IL-6 for the Oryctolagus cuniculus algirus subspecies and five additional lagomorphs' genera (Brachylagus, Bunolagus, Pentalagus, Romerolagus, and Ochotona). We confirmed the presence of the mutated stop codon in both O. c. cuniculus and O. c. algirus. We found that the typical stop codon is present in Sylvilagus bachmani and Lepus europaeus, in agreement with previous reports, but also in Bunolagus, Brachylagus, and Ochotona. Remarkably, in Pentalagus we detected a deletion of the stop codon causing an extension of IL-6 for 17 extra residues. Our results indicate that the IL-6 extension in those species occurred by two independent events: one occurred between 2 and 8 million years ago in the ancestral of the Oryctolagus subspecies, and the other occurred in a Pentalagus ancestral at a maximum of 9 million years ago. The absence of this IL-6 extension in Bunolagus, sister genus of Oryctolagus, shows that this evolutionary event happened by convergence suggesting some functional relevance. Source


Matthiesen R.,University of Porto
Methods in Molecular Biology | Year: 2013

The frequent used bottom-up strategy for identification of proteins and their associated modifications generate nowadays typically thousands of MS/MS spectra that normally are matched automatically against a protein sequence database. Search engines that take as input MS/MS spectra and a protein sequence database are referred as database-dependent search engines. Many programs both commercial and freely available exist for database-dependent search of MS/MS spectra and most of the programs have excellent user documentation. The aim here is therefore to outline the algorithm strategy behind different search engines rather than providing software user manuals. The process of database-dependent search can be divided into search strategy, peptide scoring, protein scoring, and finally protein inference. Most efforts in the literature have been put in to comparing results from different software rather than discussing the underlining algorithms. Such practical comparisons can be cluttered by suboptimal implementation and the observed differences are frequently caused by software parameters settings which have not been set proper to allow even comparison. In other words an algorithmic idea can still be worth considering even if the software implementation has been demonstrated to be suboptimal. The aim in this chapter is therefore to split the algorithms for database-dependent searching of MS/MS data into the above steps so that the different algorithmic ideas become more transparent and comparable. Most search engines provide good implementations of the first three data analysis steps mentioned above, whereas the final step of protein inference are much less developed for most search engines and is in many cases performed by an external software. The final part of this chapter illustrates how protein inference is built into the VEMS search engine and discusses a stand-alone program SIR for protein inference that can import a Mascot search result. © Springer Science+Business Media, LLC 2013. Source


Parente M.P.,University of Porto
Obstetrics and Gynecology | Year: 2010

Objective: To estimate the influence of pelvic floor muscle activation during vaginal delivery using a three-dimensional computational finite element model. Methods: A computational finite element model of the pelvic skeletal structure, pelvic floor, and fetus was developed. The movements of the fetus during birth, in vertex position, were simulated; namely, the engagement, descent, flexion, internal rotation, and extension of the fetal head. The opposite forces against the fetal descent and the stress on the pelvic floor muscles were obtained in passive, 5%, 10%, and 15% pelvic floor muscle simulated activations. Results: The increase in pelvic floor muscle activation was associated with higher values of forces against the fetal descent. The descending fetus encountered increasing resistance in higher stations with the increase in pelvic floor muscle activation. The maximum values of stress of the pelvic floor muscles were obtained in +4 station. The increase in pelvic floor muscle activation was also followed by higher values of pelvic floor stress. Conclusion: This study demonstrates the feasibility of using a computational modeling approach to study parturition. This experimental evidence suggests that the pelvic floor muscle activation during vaginal delivery may represent an obstacle to fetal descent and increase the risk for pelvic floor injuries. © 2010 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins. Source


Doria S.,University of Porto
Epigenetics : official journal of the DNA Methylation Society | Year: 2010

Genomic imprinting is defined as an epigenetic modification that leads to parent-of-origin specific monoallelic expression. Some current research on the fetal control growth has been focused on the study of genes that display imprinted expression in utero. Four imprinted genes, two paternally expressed (IGF2 and PEG10) and two maternally expressed (PHLDA2 and CDKN1C), are well known to play a role in fetal growth and placental development. Pregnancy loss in the general reproductive population is a very common occurrence and other genetic causes beyond chromosomal abnormalities could be involved in spontaneous miscarriages or fetal deaths, such as alteration of expression in imprinted genes particularly those related to fetal or placental growth. Quantitative Real Time PCR was performed to evaluate gene expressions patterns of the four mentioned genes in spontaneous miscarriages or fetal deaths from 38 women. Expression levels of PHLDA2 gene were upregulated in the first trimester pregnancy cases and all four imprinted genes studied were upregulated in the second trimester of pregnancy cases comparing with controls. In third trimester PEG10 was downregulated in fetal samples group. This is the first study presenting data from human imprinted genes expression in spontaneous miscarriages or fetal deaths cases from the three trimesters of pregnancy. Source


The second 12 principles of Green Chemistry (Winterton, 2001) are presented and discussed to show how they press academic chemists to focus the invention of synthetic pathways more directly on industrial process development, allowing a quicker progress along the greenness chain and a softer implementation of Green Chemistry in the industrial practice of chemistry. The relationships between the two sets of principles are tentatively established and discussed to make easier their joint use. The net of connections shows the systemic nature of Green Chemistry. Source


Alberucci A.,Third University of Rome | Jisha C.P.,University of Porto | Assanto G.,Third University of Rome
Optics Letters | Year: 2014

We investigate spatial solitons in nonlocal media with a nonlinear index well modeled by a diffusive equation. We address the role of nonlocality and its interplay with boundary conditions, shedding light on the behavior of accessible solitons in real samples and discussing the accuracy of the highly nonlocal approximation. We find that symmetric solitons exist only above a power threshold, with an existence region that grows larger and larger with nonlocality in the plane width power. © 2014 Optical Society of America. Source


Sequeiros J.,University of Porto | Seneca S.,Center for Medical Genetics | Martindale J.,Sheffield Diagnostic Genetics Service
European Journal of Human Genetics | Year: 2010

Many laboratories worldwide are offering molecular genetic testing for spinocerebellar ataxias (SCAs). This is essential for differential diagnosis and adequate genetic counselling. The European Molecular Genetics Quality Network (EMQN) started an SCA external quality assessment scheme in 2004. There was a clear need for updated laboratory guidelines. EMQN and EuroGentest organized a Best Practice (BP) meeting to discuss current practices and achieve consensus. A pre-meeting survey showed that 36 laboratories (20 countries) conducted nearly 18 000 SCA tests the year before, and identified issues to discuss. Draft guidelines were produced immediately after the meeting and discussed online for several months. The final version was endorsed by EMQN, and harmonized with guidelines from other oligonucleotide repeat disorders. We present the procedures taken to organize the survey, BP meeting, as well as drafting and approval of BP guidelines. We emphasize the most important recommendations on (1) pre-test requirements, (2) appropriate methodologies and (3) interpretation and reporting, and focus on the discussion of controversial issues not included in the final document. In addition, after an extensive review of scientific literature, and responding to recommendations made, we now produce information that we hope will facilitate the activities of diagnostic laboratories and foster quality SCA testing. For the main loci, this includes (1) a list of repeat sequences, as originally published; (2) primers in use; and (3) an evidence-based description of the normal and pathogenic repeat-size ranges, including those of reduced penetrance and those in which there is still some uncertainty. This information will be maintained and updated in http://www.scabase.eu. © 2010 Macmillan Publishers Limited All rights reserved. Source


Athanasopoulos A.,University of Patras | Cruz F.,University of Porto
Expert Opinion on Pharmacotherapy | Year: 2011

Introduction: Oveactive bladder (OAB) is a common condition that affects patients' quality of life. The role of antimuscarinics and future treatments in the management of this bothersome condition is reviewed. Areas covered: The current literature on the efficacy, suitability and safety of current and future treatments is reviewed based on a search of Medline/Pubmed for relevant articles published in English between 1980 and 2010. Expert opinion: Currently, antimuscarinic drugs are the cornerstone of OAB treatment; clinically recommended doses of these agents decrease the ability of the bladder to contract during the storage phase and so increase cystometric bladder capacity. In general, these agents are safe and have mild adverse effects. There is also evidence that, despite having different tolerability profiles, available drugs are well tolerated compared with placebo. Antimuscarinic agents, as a class, have similar efficacy. They offer substantial help in the alleviation of OAB symptoms, providing significant improvement to quality of life. Investigation to provide pharmacological alternatives whenever antimuscarinic drugs do not provide symptomatic relief or cause intolerable side effects is intense. Beta-adrenergic agents may be the next pharmacologic agents for OAB. However, many other areas of research may soon provide new pharmacological agents for OAB treatment. © 2011 Informa UK, Ltd. Source


Hamilton A.J.S.,Box 440 | Avelino P.P.,University of Porto
Physics Reports | Year: 2010

If you fall into a real astronomical black hole (choosing a supermassive black hole, to make sure that the tidal forces do not get you first), then you will probably meet your fate not at a central singularity, but rather in the exponentially growing, relativistic counter-streaming instability at the inner horizon first pointed out by Poisson & Israel (1990), who called it mass inflation. The chief purpose of this paper is to present a clear exposition of the physical cause and consequence of inflation in spherical, charged black holes. Inflation acts like a particle accelerator in that it accelerates cold ingoing and outgoing streams through each other to prodigiously high energies. Inflation feeds on itself: the acceleration is powered by the gravity produced by the streaming energy. The paper: (1) uses physical arguments to develop simple approximations that follow the evolution of inflation from ignition, through inflation itself, to collapse; (2) confirms that the simple approximations capture accurately the results of fully nonlinear one- and two-fluid self-similar models; (3) demonstrates that, counter-intuitively, the smaller the accretion rate, the more rapidly inflation exponentiates; (4) shows that in single perfect fluid models, inflation occurs only if the sound speed equals the speed of light, supporting the physical idea that inflation in single fluids is driven by relativistic counter-streaming of waves; (5) shows that what happens during inflation up to the Planck curvature depends not on the distant past or future, but rather on events happening only a few hundred black hole crossing times into the past or future; (6) shows that, if quantum gravity does not intervene, then the generic end result of inflation is not a general relativistic null singularity, but rather a spacelike singularity at zero radius. © 2010 Elsevier B.V. Source


Pinto C.M.A.,University of Porto | Machado J.A.T.,INESC Porto
Nonlinear Dynamics | Year: 2010

Locomotion has been a major research issue in the last few years. Many models for the locomotion rhythms of quadrupeds, hexapods, bipeds and other animals have been proposed. This study has also been extended to the control of rhythmic movements of adaptive legged robots. In this paper, we consider a fractional version of a central pattern generator (CPG) model for locomotion in bipeds. A fractional derivative Dαf (x), with α non-integer, is a generalization of the concept of an integer derivative, where α = 1. The integer CPG model has been proposed by Golubitsky, Stewart, Buono and Collins, and studied later by Pinto and Golubitsky. It is a network of four coupled identical oscillators which has dihedral symmetry. We study parameter regions where periodic solutions, identified with legs' rhythms in bipeds, occur, for 0<α ≤ 1.We find that the amplitude and the period of the periodic solutions, identified with biped rhythms, increase as α varies from near 0 to values close to unity. © 2010 Springer Science+Business Media B.V. Source


Mena-Matos H.,University of Porto
Journal of Dynamical and Control Systems | Year: 2010

For one-parameter smooth families of pairs of control systems and profit densities on the circle, we consider the problem of maximizing the averaged profit in the infinite horizon from the singularity theory point of view. Namely, we study the generic classification of the optimal averaged profit as function of the parameter. This approach to the problem was introduced in 2002 by V. I. Arnold and all generic classifications in related problems obtained since then, assume a compact control space without boundary. The existence of a boundary in the control space is usual in real problems and so it is worthwhile to be considered. In this work, we consider the existence of a regular boundary in the control space and study the case of one-dimensional parameter. We present all generic singularities of the optimal averaged profit as function of the parameter and conclude that three new singularities appear. © 2010 Springer Science+Business Media, LLC. Source


Powers S.K.,University of Florida | Wiggs M.P.,University of Florida | Duarte J.A.,University of Porto | Murat Zergeroglu A.,Ankara University | Demirel H.A.,Hacettepe University
American Journal of Physiology - Endocrinology and Metabolism | Year: 2012

It is well established that long durations of bed rest, limb immobilization, or reduced activity in respiratory muscles during mechanical ventilation results in skeletal muscle atrophy in humans and other animals. The idea that mitochondrial damage/dysfunction contributes to disuse muscle atrophy originated over 40 years ago. These early studies were largely descriptive and did not provide unequivocal evidence that mitochondria play a primary role in disuse muscle atrophy. However, recent experiments have provided direct evidence connecting mitochondrial dysfunction to muscle atrophy. Numerous studies have described changes in mitochondria shape, number, and function in skeletal muscles exposed to prolonged periods of inactivity. Furthermore, recent evidence indicates that increased mitochondrial ROS production plays a key signaling role in both immobilization-induced limb muscle atrophy and diaphragmatic atrophy occurring during prolonged mechanical ventilation. Moreover, new evidence reveals that, during denervation-induced muscle atrophy, increased mitochondrial fragmentation due to fission is a required signaling event that activates the AMPK-FoxO3 signaling axis, which induces the expression of atrophy genes, protein breakdown, and ultimately muscle atrophy. Collectively, these findings highlight the importance of future research to better understand the mitochondrial signaling mechanisms that contribute to disuse muscle atrophy and to develop novel therapeutic interventions for prevention of inactivity-induced skeletal muscle atrophy. © 2012 the American Physiological Society. Source


Areias P.,University of Evora | Rabczuk T.,Bauhaus University Weimar | Camanho P.P.,University of Porto
Theoretical and Applied Fracture Mechanics | Year: 2014

In the context of plane fracture problems, we introduce an algorithm based on our previously proposed rotation of edges but now including the injection of continuum softening elements directly in the process region. This is an extension of the classical smeared (or regularized) approach to fracture and can be seen as an intermediate proposition between purely cohesive formulations and the smeared modeling. Characteristic lengths in softening are explicitly included as width of injected elements. For materials with process regions with macroscopic width, the proposed method is less cumbersome than the cohesive zone model. This approach is combined with smoothing of the complementarity condition of the constitutive law and the consistent updated Lagrangian method recently proposed, which simplifies the internal variable transfer. Propagation-wise, we use edge rotation around crack front nodes in surface discretizations and each rotated edge is duplicated. Modified edge positions correspond to the crack path (predicted with the Ma-Sutton method). Regularized continuum softening elements are then introduced in the purposively widened gap. The proposed solution has algorithmic and generality benefits with respect to enrichment techniques such as XFEM. The propagation algorithm is simpler and the approach is independent of the underlying element used for discretization. To illustrate the advantages of our approach, yield functions providing particular cohesive behavior are used in testing. Traditional fracture benchmarks and newly proposed verification tests are solved. Results are found to be good in terms of load/deflection behavior. © 2014 Elsevier Ltd. Source


Machado J.A.T.,Polytechnic Institute of Porto | Lopes A.M.,University of Porto
Entropy | Year: 2013

Seismic data is difficult to analyze and classical mathematical tools reveal strong limitations in exposing hidden relationships between earthquakes. In this paper, we study earthquake phenomena in the perspective of complex systems. Global seismic data, covering the period from 1962 up to 2011 is analyzed. The events, characterized by their magnitude, geographic location and time of occurrence, are divided into groups, either according to the Flinn-Engdahl (F-E) seismic regions of Earth or using a rectangular grid based in latitude and longitude coordinates. Two methods of analysis are considered and compared in this study. In a first method, the distributions of magnitudes are approximated by Gutenberg-Richter (G-R) distributions and the parameters used to reveal the relationships among regions. In the second method, the mutual information is calculated and adopted as a measure of similarity between regions. In both cases, using clustering analysis, visualization maps are generated, providing an intuitive and useful representation of the complex relationships that are present among seismic data. Such relationships might not be perceived on classical geographic maps. Therefore, the generated charts are a valid alternative to other visualization tools, for understanding the global behavior of earthquakes. © 2013 by the authors. Source


A formulation applicable to free, periodic, geometrically non-linear vibrations of thin shallow shells made of composite layers with curvilinear fibres is presented. The modes of vibration of this type of Variable Stiffness Composite Laminated (VSCL) shallow shells are examined in the non-linear regime. Due to the membrane effects and their coupling with bending, the modes of vibration of VSCL shells are more affected by alterations in the curvilinear fibre paths than what was previously found to occur in plates. Indeed, it is discovered that by changing one of the parameters that defines the fibre path - keeping all other properties of the shells unaltered - the degree of softening can be changed, hardening can become softening, the vibration displacement amplitude at which turning points occur can change and the amplitudes of harmonics vary. A significant deduction, which results from the numerical tests, is that modes of vibration that have mode shapes with more half-waves are less likely to experience softening. A geometric explanation for this behaviour, which does not apply only to VSCL shells, is given. © 2014 Elsevier Ltd. Source


Fernandes T.,University of Porto | Vale A.P.,University of Tras os Montes e Alto Douro | Martins B.,University of Tras os Montes e Alto Douro | Morais J.,Free University of Colombia | Kolinsky R.,Free University of Colombia
Developmental Science | Year: 2014

To clarify the link between anomalous letter processing and developmental dyslexia, we examined the impact of surrounding contours on letter vs. pseudo-letter processing by three groups of children - phonological dyslexics and two controls, one matched for chronological age, the other for reading level - and three groups of adults differing by schooling and literacy - unschooled illiterates and ex-illiterates, and schooled literates. For pseudo-letters, all groups showed congruence effects (CE: better performance for targets surrounded by a congruent than by an incongruent shape). In contrast, for letters, only dyslexics exhibited a CE, strongly related to their phonological recoding abilities even after partialling out working memory, whereas the reverse held true for the pseudo-letter CE. In illiterate adults, the higher letter knowledge, the smaller their letter CE; their letter processing was immune (to some extent) to inference from surrounding information. The absence of a letter CE in illiterates and the positive CE in dyslexics have their origin in different aspects of the same ability, i.e. phonological recoding. © 2013 John Wiley & Sons Ltd. Source


To determine whether the presence of Machado-Joseph disease (MJD, also spinocerebellar ataxia type 3 [SCA3]) among Australian aborigines was caused by a new mutational event or by the introduction of expanded alleles from other populations. We sequenced a region of 4 kilobases (kb), encompassing the CAG repeat within the ATXN3 gene, in 2 affected Australian aboriginal families and compared them with the Joseph and Machado lineages described before. Full-extended haplotypes (including also more distant single-nucleotide polymorphisms and flanking short tandem repeats) were assessed by segregation and allele-specific amplification. A phylogenetic tree was inferred from genetic distances, and age of the Australasian Joseph-derived lineage was estimated. The aboriginal communities of Groote Eylandt and Yirrkala, in the Northern Territories, Australia (local ethics institutional permission was granted, and both community and individual informed consent was obtained). A convenience sample of 19 patients and unaffected relatives, from 2 Australian aboriginal families affected with MJD; 40 families with MJD of multiethnic origins and 50 unrelated Asian control subjects. The 2 aboriginal families shared the same full haplotype, including 20 single-nucleotide polymorphisms:TTGATCGAGC-(CAG)(Exp)-CACCCAGCGC, that is, the Joseph lineage with a G variant in rs56268847.Among 33 families with the Joseph lineage, this derived haplotype was found only in 5 of 16 Taiwanese, all 3 Indian,and 1 of 3 Japanese families analyzed. A related-extended MJD haplotype shared by Australian aborigines and some Asian families (a Joseph-derived lineage) suggests a common ancestor for all, dating back more than 7000 years. Source


Infrared thermometers (IRT) are gaining popularity in herpetological thermal ecology due to their several advantages compared to contact thermometers (CT). To evaluate their accuracy in small lacertids, lab parallel measurements using IRT and CT are compared for a set of 52 adult lizards belonging to four different Podarcis forms, including males, pregnant and non-pregnant females, exposed to a photothermal gradient. Skin temperature was measured with an IRT and cloacal temperature with a CT at 10 time intervals, completing 520 paired measurements. Models of the relations were constructed using standardised major axis (SMA) regression. As expected, IRT and CT measurements were significantly correlated but determination coefficients were only moderate, IRT values being systematically higher. Moreover, the SMA regression lines deviated from slope 1 and intercept 0 in all cases, revealing a nonisometric bias; IRT tended to give progressively higher readings than CT for higher temperatures. Results provide methodological insights for further studies on thermal ecology of lacertids. Source


Pinto S.M.,University of Zurich | Pinto S.M.,University of Porto | Hengartner M.O.,University of Zurich
Current Opinion in Cell Biology | Year: 2012

Genetic and cell biology studies have led to the identification in Caenorhabditis elegans of a set of evolutionary conserved cellular mechanisms responsible for the clearance of apoptotic cells. Based on the phenotype of cell corpse clearance mutants, corpse clearance can be divided into three distinct, but linked steps: corpse recognition, corpse internalization, and corpse degradation. Work in recent years has led to a better understanding of the molecular pathways that mediate each of these steps. Here, we review recent developments in our understanding of in vivo cell corpse clearance in this simple but most elegant model organism. © 2012 Elsevier Ltd. Source


Martins C.J.A.P.,University of Porto
Journal of Physics: Conference Series | Year: 2014

I use a combination of state-of-the-art numerical simulations and analytic modelling to discuss the scaling properties of cosmic defect networks, including superstrings. Particular attention is given to the role of extra degrees of freedom in the evolution of these networks. Compared to the 'plain vanilla' case of Goto-Nambu strings, three such extensions play important but distinct roles in the network dynamics: the presence of charges/currents on the string worldsheet, the existence of junctions, and the possibility of a hierarchy of string tensions. I also comment on insights gained from studying simpler defect networks, including Goto-Nambu strings themselves, domain walls and semilocal strings. © Published under licence by IOP Publishing Ltd. Source


Vaz-Moreira I.,Catholic University of Portugal | Nunes O.C.,University of Porto | Manaia C.M.,Catholic University of Portugal
FEMS Microbiology Reviews | Year: 2014

Water is one of the most important bacterial habitats on Earth. As such, water represents also a major way of dissemination of bacteria between different environmental compartments. Human activities led to the creation of the so-called urban water cycle, comprising different sectors (waste, surface, drinking water), among which bacteria can hypothetically be exchanged. Therefore, bacteria can be mobilized between unclean water habitats (e.g. wastewater) and clean or pristine water environments (e.g. disinfected and spring drinking water) and eventually reach humans. In addition, bacteria can also transfer mobile genetic elements between different water types, other environments (e.g. soil) and humans. These processes may involve antibiotic resistant bacteria and antibiotic resistance genes. In this review, the hypothesis that some bacteria may share different water compartments and be also hosted by humans is discussed based on the comparison of the bacterial diversity in different types of water and with the human-associated microbiome. The role of such bacteria as potential disseminators of antibiotic resistance and the inference that currently only a small fraction of the clinically relevant antibiotic resistome may be known is discussed. © 2014 Federation of European Microbiological Societies. Source


Pinto C.M.A.,University of Porto | MacHado J.A.T.,INESC Porto
JVC/Journal of Vibration and Control | Year: 2012

In this paper we consider a complex-order forced van der Pol oscillator. The complex derivative Dα±Jβ, with α, β∈ℝ+, is a generalization of the concept of an integer derivative, where α=1, β=0. The Fourier transforms of the periodic solutions of the complex-order forced van der Pol oscillator are computed for various values of parameters such as frequency ω and amplitude b of the external forcing, the damping μ, and parameters α and β. Moreover, we consider two cases: (i) b=1, μ={1.0, 5.0, 10.0}, and ω={0.5, 2.46, 5.0, 20.0}; (ii) ω=20.0, μ={1.0, 5.0, 10.0}, and b={1.0, 5.0, 10.0}. We verified that most of the signal energy is concentrated in the fundamental harmonic ω0. We also observed that the fundamental frequency of the oscillations ω0 varies with α and μ. For the range of tested values, the numerical fitting led to logarithmic approximations for system (7) in the two cases (i) and (ii). In conclusion, we verify that by varying the parameter values α and β of the complex-order derivative in expression (7), we accomplished a very effective way of perturbing the dynamical behavior of the forced van der Pol oscillator, which is no longer limited to parameters b and ω. © The Author(s) 2011 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav. Source


Chatterjee K.,Institute of Science and Technology Austria IST Austria | Prabhu V.S.,University of Porto
IEEE Transactions on Automatic Control | Year: 2015

We introduce quantitative timed refinement and timed simulation (directed) metrics, incorporating zenoness checks, for timed systems. These metrics assign positive real numbers which quantify the timing mismatches between two timed systems, amongst non-zeno runs. We quantify timing mismatches in three ways: (1) the maximal timing mismatch that can arise, (2) the 'steady-state' maximal timing mismatches, where initial transient timing mismatches are ignored; and (3) the (long-run) average timing mismatches amongst two systems. These three kinds of mismatches constitute three important types of timing differences. Our event times are the global times, measured from the start of the system execution, not just the time durations of individual steps. We present algorithms over timed automata for computing the three quantitative simulation distances to within any desired degree of accuracy. In order to compute the values of the quantitative simulation distances, we use a game theoretic formulation. We introduce two new kinds of objectives for two player games on finite-state game graphs: (1) eventual debit-sum level objectives, and (2) average debit-sum level objectives. We present algorithms for computing the optimal values for these objectives in graph games, and then use these algorithms to compute the values of the timed simulation distances over timed automata. © 2015 IEEE. Source


Frazo J.M.,University of Porto | Adrago T.,Santa Cruz Hospital
Nephron - Clinical Practice | Year: 2012

Phosphate-binder therapy for hyperphosphataemia is key to the treatment of patients with chronic kidney disease (CKD)-mineral and bone disorder (MBD). Calcium-free phosphate binders are increasingly favoured since calcium-based agents potentially cause harmful calcium overload and vascular calcification that confound the benefits of reducing serum phosphorus. Several calcium-free phosphate binders are available, including the non-absorbed agent sevelamer and the absorbed agents, e.g. lanthanum and magnesium salts. Randomised controlled studies consistently show that sevelamer and lanthanum carbonate offer equivalent lowering of serum phosphorus and often effectively achieve phosphorus targets versus calcium salts, with sevelamer having a positive effect on bone disease, vascular calcification, and patient-level outcomes in dialysis patients in several trials. There is also evidence that lanthanum carbonate can improve bone health, but data are limited to its effects to vascular calcification or patient-level outcomes. Magnesium salts have also been shown to reduce serum phosphorus levels, but clear evidence is lacking on bone, vascular, or clinical outcomes. It also remains to be established whether long-term systemic accumulation of lanthanum and magnesium, in tissues including bone, has clinically relevant toxic effects. This review summarises the evidence of efficacy and safety for newer calcium-free phosphate binders in CKD-MBD management. Copyright © 2012 S. Karger AG, Basel. Source


Vasconcelos H.,University of Porto
International Journal of Industrial Organization | Year: 2015

Abstract This paper studies the competitive effects of exclusionary pricing in two-sided markets. While formally showing that below-cost pricing on one market side can allow an incumbent firm to exclude a potential rival which does not have a customer base yet, the proposed model does not necessarily imply that below-cost pricing in such markets should be taken as anti-competitive conduct. Instead, I find that in sufficiently asymmetric two-sided markets, exclusion is always beneficial and if anything, there is too little of it in the sense that there are cases in which there is inefficient entry. Further, prohibiting below marginal cost pricing may destroy some socially efficient exclusion and worsen the problem of excessive (or inefficient) entry. © 2015 Elsevier B.V. All rights reserved. Source


Bialer M.,Hebrew University of Jerusalem | Soares-Da-Silva P.,BIAL Portela and Co | Soares-Da-Silva P.,University of Porto
Epilepsia | Year: 2012

Eslicarbazepine acetate (ESL) is a novel once-daily antiepileptic drug (AED) approved in Europe since 2009 that was found to be efficacious and well tolerated in a phase III clinical program in adult patients with partial onset seizures previously not controlled with treatment with one to three AEDs, including carbamazepine (CBZ). ESL shares with CBZ and oxcarbazepine (OXC) the dibenzazepine nucleus bearing the 5-carboxamide substitute, but is structurally different at the 10,11 position. This molecular variation results in differences in metabolism, preventing the formation of toxic epoxide metabolites such as carbamazepine-10,11-epoxide. Unlike OXC, which is metabolized to both eslicarbazepine and (R)-licarbazepine, ESL is extensively converted to eslicarbazepine. The systemic exposure to eslicarbazepine after ESL oral administration is approximately 94% of the parent dose, with minimal exposure to (R)-licarbazepine and OXC. After ESL oral administration, the effective half-life (t 1/2,eff) of eslicarbazepine was 20-24 h, which is approximately two times longer than its terminal half-life (t 1/2). At clinically relevant doses (400-1,600 mg/day) ESL has linear pharmacokinetics (PK) with no effects of gender or moderate liver impairment. However, because eslicarbazepine is eliminated primarily (66%) by renal excretion, dose adjustment is recommended for patients with renal impairment. Eslicarbazepine clearance is induced by phenobarbital, phenytoin, and CBZ and it dose-dependently decreases plasma exposure of oral contraceptive and simvastatin. © Wiley Periodicals, Inc. © 2012 International League Against Epilepsy. Source


Costa B.J.A.,University of Beira Interior | Figueiras J.A.,University of Porto
Journal of Constructional Steel Research | Year: 2012

The old steel bridges that integrate the existing railway lines are structures built with materials that are no longer used and whose knowledge has being lost over the years, often presenting severe problems of deterioration and subjected to loading environments very different from those for which they were designed. In this context, adequate strain monitoring is a crucial tool in supporting the behavior characterization and safety assessment of these structures. This article presents and discusses the monitoring systems installed in the Trezói Bridge, within a research project aimed at developing and applying procedures for evaluation of the structural integrity of steel railway bridges. The field observations of the structural behavior were accomplished by using two different types of sensors: electric and fiber optic strain sensors. The electric monitoring system was designed and installed on the bridge to supply the experimental data for the research project, while the fiber optic monitoring system was firstly applied to evaluate the reliability of the former and to check its efficiency, and secondly to provide some redundancy of the measurements at critical locations. The obtained results are analyzed to characterize the bridge behavior and the capabilities and limitations of both types of sensors to acquire the relevant data for the bridge service condition and fatigue assessment are discussed, namely in what concerns the ability to accurately capture the static and dynamic components of the structural response and the frequency content of interest. © 2011 Elsevier Ltd. All rights reserved. Source


Correia F.P.,University of Porto
Journal of High Energy Physics | Year: 2011

We study the construction of Hermitian Yang-Mills instantons over resolutions of Calabi-Yau cones of arbitrary dimension. In particular, in d complex dimensions, we present an infinite family, parametrised by an integer k and a continuous modulus, of SU(d) instantons. A detailed study of their properties, including the computation of the instanton numbers is provided. We also explain how they can be used in the construction of heterotic non-Kähler compactifications. © SISSA 2011. Source


O'Reilly C.,University of Porto | O'Reilly C.,University of Oxford
Theoretical Criminology | Year: 2010

This article examines state-corporate organizational complexes within the transnational policing sphere. Its specific focus is upon the transnational security consultancy industry and its interaction with state security agencies. Exemplifying the proposed theoretical construct of state-corporate symbiosis, leading firms are held out as key facilitators for this ongoing close association between dominant interests. Their activities reflect how this security amalgamation imposes itself upon the agendas, discourse, methods and ideologies of the global policing environment. As well as highlighting the degree to which both behaviour and techniques traverse the state-corporate security nexus, this article also identifies core factors which have driven this convergence of interests. It concludes by suggesting that this evolution towards state-corporate symbiosis exacerbates those trends within transnational policing that prompt most concern, while undercutting those for which hope is harboured. © The Author(s), 2010. Source


Goltsev A.V.,University of Aveiro | Goltsev A.V.,RAS Ioffe Physical - Technical Institute | Dorogovtsev S.N.,University of Aveiro | Dorogovtsev S.N.,RAS Ioffe Physical - Technical Institute | And 3 more authors.
Physical Review Letters | Year: 2012

Using the susceptible-infected-susceptible model on unweighted and weighted networks, we consider the disease localization phenomenon. In contrast to the well-recognized point of view that diseases infect a finite fraction of vertices right above the epidemic threshold, we show that diseases can be localized on a finite number of vertices, where hubs and edges with large weights are centers of localization. Our results follow from the analysis of standard models of networks and empirical data for real-world networks. © 2012 American Physical Society. Source


Pace G.,University of Porto
Astronomy and Astrophysics | Year: 2013

Context. Chromospheric activity has been calibrated and widely used as an age indicator. However, it has been suggested that the viability of this age indicator is, in the best case, limited to stars younger than about 1.5 Gyr. Aims. I aim to define the age range for which chromospheric activity is a robust astrophysical clock. Methods. I collected literature measurements of the S-index in field stars, which is a measure of the strength of the H and K lines of the Ca II and a proxy for chromospheric activity, and exploited the homogeneous database of temperature and age determinations for field stars provided by the Geneva-Copenhagen survey of the solar neighbourhood. Results. Field data, inclusive data previously used to calibrate chromospheric ages, confirm the result found using open cluster data, i.e. there is no decay of chromospheric activity after about 2 Gyr. Conclusions. The only existing indication supporting the viability of chromospheric ages older than 2 Gyr is the similarity of chromospheric activity levels in the components of 35 dwarf binaries. However, even in the most optimistic scenario, uncertainty in age determination for field stars and lack of sufficient data in open clusters make any attempt of calibrating an age activity relationship for old stars premature. The hypothesis that chromospheric activity follows the Skumanich law, i.e. that it is proportional to t-1/2, should be relaxed. © 2013 ESO. Source


Cardoso J.M.P.,University of Porto | Diniz P.,University of Lisbon | Weinhardt M.,Osnabruck University of Applied Sciences
ACM Computing Surveys | Year: 2010

Reconfigurable computing platforms offer the promise of substantially accelerating computations through the concurrent nature of hardware structures and the ability of these architectures for hardware customization. Effectively programming such reconfigurable architectures, however, is an extremely cumbersome and error-prone process, as it requires programmers to assume the role of hardware designers while mastering hardware description languages, thus limiting the acceptance and dissemination of this promising technology. To address this problem, researchers have developed numerous approaches at both the programming languages as well as the compilation levels, to offer high-level programming abstractions that would allow programmers to easily map applications to reconfigurable architectures. This survey describes the major research efforts on compilation techniques for reconfigurable computing architectures. The survey focuses on efforts that map computations written in imperative programming languages to reconfigurable architectures and identifies the main compilation and synthesis techniques used in this mapping. ©2010 ACM. Source


Capelo D.,University of Lisbon | Paramos J.,University of Porto
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The bumblebee model of spontaneous Lorentz symmetry breaking is explored in a cosmological context, considering a single nonzero time component for the vector field. The relevant dynamic equations for the evolution of the Universe are derived and their properties and physical significance are studied. We conclude that a late-time de Sitter expansion of the Universe can be replicated, and attempt to constrain the parameter of the potential driving the spontaneous symmetry breaking. © 2015 American Physical Society. Source


Rosa J.G.,University of Aveiro | Rosa J.G.,University of Porto
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We show that the magnetic dipole and gravitational radiation emitted by a pulsar can undergo superradiant scattering off a spinning black hole companion. We find that the relative amount of superradiant modes in the radiation depends on the pulsar's angular position relative to the black hole's equatorial plane. In particular, when the pulsar and black hole spins are aligned, superradiant modes are dominant at large angles, leading to an amplification of the pulsar's luminosity, whereas for small angles the radiation is dominantly composed of non-superradiant modes and the signal is attenuated. This results in a characteristic orbital modulation of the pulsar's luminosity, up to the percent level within our approximations, which may potentially yield a signature of superradiant scattering in astrophysical black holes and hence an important test of general relativity. © 2015 The Author. Published by Elsevier B.V. Source


Torres I.,University of Coimbra | Freitas V.P.d.,University of Porto
Construction and Building Materials | Year: 2010

Intervention in older buildings increasingly requires extensive and objective knowledge of what one will be working with. In old buildings, rising damp in walls that are in direct contact with the ground leads to the migration of soluble salts that are responsible for many of the pathologies observed. Our research allows us to conclude that the most efficient way of treating rising damp is by ventilating the wall base [2,4]. This technique was experimentally validated to limestone walls 20 cm thick. As it experimental validation of different thicknesses and different compositions has not been possible, numerical investigation has been carried out in order to analyse their influence. In this paper we will present the results of the work developed in the Department of Civil Engineering of the University of Coimbra in collaboration with the Department of Civil Engineering in the Faculty of Engineering of the University of Porto. The main purpose is to analyse the influence of the thickness and composition of walls on the new treatment for rising damp in historic walls: the ventilation of the wall base. © 2010 Elsevier Ltd. All rights reserved. Source


Ponte P.,Perimeter Institute for Theoretical Physics | Ponte P.,University of Porto | Lee S.-S.,Perimeter Institute for Theoretical Physics | Lee S.-S.,McMaster University
New Journal of Physics | Year: 2014

We propose two possible experimental realizations of a (2 + 1)-dimensional spacetime supersymmetry at a quantum critical point on the surface of three-dimensional topological insulators. The quantum critical point between the semi-metallic state with one Dirac fermion and the s-wave superconducting state on the surface is described by a supersymmetric conformal field theory within the -expansion. We predict the exact voltage dependence of the differential conductance at the supersymmetric critical point. © 2014 IOP Publishing and Deutsche Physikalische Gesellschaft. Source


Rebelo E.M.,University of Porto
European Urban and Regional Studies | Year: 2012

The research reported in this article aims to explain the residential and work location patterns of different groups of immigrants living in a particular metropolitan area, based on the following underlying causes: socio-spatial differentiation resulting from the characteristics of urban economies, the performance of housing and labour markets, spatial and socioeconomic/professional mobility, and immigrants' own characteristics. Within this scope, census data are analysed and cartographically displayed, and classification trees are applied in order to understand the relationship between the residential and work locations of the different population groups and their respective demographic, economic and professional characteristics, on the one hand, and land occupation densities, on the other. Although this methodology is applied to the Oporto Metropolitan Area (Portugal), it can easily be used in other urban and metropolitan areas. © The Author(s) 2012. Source


Carvalho R.,University of Porto
Interactions | Year: 2013

The magical features of immersive audiovisual environments have been attracting people since long. Giovanni Battista Della Porta authored an encyclopedia called Magia Naturalis, where he explores optics, projection, and reflection. Athanasius Kircher, in 1646, published the book Ars Magna Lucis et Umbra, a compilation of the state of the art in light, lenses, mirrors, and astronomy. The book also presented detailed descriptions and illustrations about the camera obscura and lanterna magica. By the end of the 17th century, the lanterna magica became a common instrument throughout Europe. Traveling showmen would often set up magic shows with it. The computer led to endless possibilities in the creation and simulation of new worlds, manipulating images, light, sound, shapes, space, and autonomous identities. It enabled the creation of real virtual worlds that could be experienced in space and time, crossed, modified, or destroyed. Source


Ribeiro V.,University of Porto
The Canadian journal of cardiology | Year: 2013

We present a case of intravenous leiomyomatosis with intracaval and right ventricle extension that was misdiagnosed as venous thrombus. Part of the mass had split and embolized the pulmonary artery, requiring urgent surgery. Although the mass fragments were removed from the inferior vena cava, right ventricle, and pulmonary artery successfully, this case clearly shows the importance of prompt surgery. Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved. Source


Matthiesen R.,University of Porto
Methods in Molecular Biology | Year: 2013

Peak extraction from raw data is the first step in LC-MS data analysis. The quality of this procedure is important since it affects the quality and accuracy of all subsequent analysis such as database searches and peak quantitation. The most important and most accurately measured physical entity provided by mass spectrometers is m/z values which need to be extracted by state of art algorithms and scrutinized thoroughly. The aim of this chapter is to provide a discussion of peak processing methods and furthermore discuss some of the yet unresolved or neglected issues. A few novel concepts are also proposed for analysis and visualization. The final section of this chapter provides a note on possible software for spectra processing. © Springer Science+Business Media, LLC 2013. Source


Simeonova M.,University of Chemical Technology and Metallurgy of Sofia | Rangel M.,Abel Salazar Biomedical Sciences Institute | Ivanova G.,University of Porto
Physical Chemistry Chemical Physics | Year: 2013

Nuclear magnetic resonance (NMR) spectroscopy has been used for structural characterization of 5-fluorouracil (5FU) & daunorubicin (DAU) co-loaded poly(butylcyanoacrylate) nanoparticles (PBCN), prepared by an anionic polymerization of n-butylcyanoacrylate, probing two different drug loading approaches. Diffusion ordered spectroscopy, obtained through pulsed field gradient NMR experiments, has been performed to determine the overall structure of the 5FU & DAU co-loaded PBCN and to clarify the mechanisms of drug immobilization and location in the polymer matrix of PBCN. Physicochemical properties such as composition, size, surface chemistry and shape have been defined. All data obtained have been referred to the dual drug-loading procedures employed. The results show that 5FU & DAU co-loaded PBCN can be designed to exhibit different properties, composition and overall structure, depending on the method of preparation. The structural attributes relate to the drug efficacy and reactivity characteristics such as capacity for sustained drug release, targeted drug delivery, drug penetration, retention in and transport through bio-membranes. The design of nanoparticle platforms to deliver multiple drugs for combination therapy offers the opportunity for novel strategies in an effort to increase the efficacy of cancer therapy. © 2013 The Owner Societies. Source


Bertolami O.,University of Porto | Bertolami O.,University of Lisbon | Martins A.,University of Lisbon
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In this work we explore the consequences that a nonminimal coupling between geometry and matter can have on the dynamics of perfect fluids. It is argued that the presence of a static, axially symmetric pressureless fluid does not imply a Minkowski space-time like as is in general relativity. This feature can be attributed to a pressure mimicking mechanism related to the nonminimal coupling. The case of a spherically symmetric black hole surrounded by fluid matter is analyzed, and it is shown that under equilibrium conditions the total fluid mass is about twice that of the black hole. Finally, a generalization of the Newtonian potential for a fluid element is proposed and its implications are briefly discussed. © 2012 American Physical Society. Source


Jacome C.,University of Aveiro | Jacome C.,University of Porto | Marques A.,University of Aveiro
Respiratory Care | Year: 2014

BACKGROUND: Pulmonary rehabilitation (PR) is a core component of the management of patients with moderate-to-very-severe COPD. However, as impairments in quadriceps muscle strength and health-related quality of life (HRQOL) are already present in patients with mild COPD, there is a need to investigate whether PR could also be beneficial to these patients. Thus, this study assessed the impact of PR on patients with mild COPD. METHODS: A quasi-experimental study was conducted. Twenty-six participants (67.8 ± 10.3 years old; FEV1 83.8 ± 6.4% of predicted) enrolled in a 12-week PR program with exercise training and psychoeducation. Lung function was assessed by spirometry, dyspnea with the Modified Medical Research Council questionnaire, functional balance with the Timed Up and Go test, muscle strength with 10-repetition maximum testing, exercise tolerance with the 6-min walk test, emotional state with the Depression Anxiety Stress Scales, and HRQOL with the St George Respiratory Questionnaire (SGRQ). RESULTS: Significant effects were observed on participants’ dyspnea (P =.003, effect size [ES] = 0.7), functional balance (P <.001, ES = 0.8), shoulder flexor/knee extensor strength (P <.001, ES = 1.2–1.3), and exercise tolerance (P <.001, ES = 0.5). With the exception of the SGRQ impact score, the symptom (P <.001, ES = 0.6), activity (P =.02, ES = 0.4), and total (P =.005, ES = 0.3) scores improved significantly after PR. The PR program had no significant effect on participants’ lung function and emotional state. CONCLUSIONS: Patients with mild COPD benefit from PR and could therefore be routinely included in these programs. Studies with more robust designs and with long-term follow-ups are needed to inform guidelines for PR in mild COPD. © 2014 Daedalus Enterprises. Source


The formation of the highest mass stars are thought to be dominated by instabilities resulting from gravitation and radiation. Instabilities due to gravitation are commonly demonstrated by observations of fragmentation, but those due to effects of radiation have thus far not been found. Here I report on the NACO adaptive optics and mid-infrared diffraction-limited VISIR imaging data of an extemely luminous ultra-compact HII region G333.6-0.2. Two infrared sources, one bright in the near-infrared (appearing point-like) and another in the mid-infrared (resolved with an elliptical shape) are uncovered through this data, which are located at the heart of this region. These infrared sources appear to be embedded in the waist of a bipolar-shaped nebula and UCHII region, the lobes of which are separated by a dark patch. Dense filamentary features with finger/hook morphology are found; they appear to be connected to the two bright infrared sources and the sizes of these hook features are sharply limited to <5000 AU. The observed properties of this target and a large amount of previous data obtained from the literature are compared together with the results of various numerical simulations of high-mass star formation. This comparison favours the interpretation that the finger/hook-like structures likely represent radiatively driven Rayleigh-Taylor instabilities arising in the outflow cavity of a forming high-mass binary star system. © 2013 ESO. Source


Reboredo H.,University of Porto | Xavier J.,University of Lisbon | Rodrigues M.R.D.,University College London
IEEE Transactions on Signal Processing | Year: 2013

This paper considers the problem of filter design with secrecy constraints, where two legitimate parties (Alice and Bob) communicate in the presence of an eavesdropper (Eve) over a Gaussian multiple-input-multiple-output (MIMO) wiretap channel. This problem involves designing, subject to a power constraint, the transmit and the receive filters which minimize the mean-squared error (MSE) between the legitimate parties whilst assuring that the eavesdropper MSE remains above a certain threshold. We consider a general MIMO Gaussian wiretap scenario, where the legitimate receiver uses a linear zero-forcing (ZF) filter and the eavesdropper receiver uses either a ZF or an optimal linear Wiener filter. We provide a characterization of the optimal filter designs by demonstrating the convexity of the optimization problems. We also provide generalizations of the filter designs from the scenario where the channel state is known to all the parties to the scenario where there is uncertainty in the channel state. A set of numerical results illustrates the performance of the novel filter designs, including the robustness to channel modeling errors. In particular, we assess the efficacy of the designs in guaranteeing not only a certain MSE level at the eavesdropper, but also in limiting the error probability at the eavesdropper. We also assess the impact of the filter designs on the achievable secrecy rates. The penalty induced by the fact that the eavesdropper may use the optimal nonlinear receive filter rather than the optimal linear one is also explored in the paper. © 1991-2012 IEEE. Source


Lobato L.,Centro Hospitalar Do Porto Largo Prof Abel Salaza | Lobato L.,Centro Hospitalar do Porto | Lobato L.,University of Porto | Rocha A.,Centro Hospitalar Do Porto Largo Prof Abel Salaza
Clinical Journal of the American Society of Nephrology | Year: 2012

The amyloidoses are protein-misfolding disorders associated with progressive organ dysfunction. Immunoglobulin light chain is the most common, amyloid A the longest recognized, and transthyretin-associated amyloidosis (ATTR) the most frequent inherited systemic form. Although ATTR, an autosomal-dominant disease, is associated with at least 100 different transthyretin (TTR) mutations, the single amino-acid substitution of methionine for valine at position 30 is the most common mutation. Each variant has a different organ involvement, although clinical differences attributed to environmental and genetic factors exist within the same mutation. Peripheral neuropathy and cardiomyopathy are broadly described, and insights into disease reveal that kidney impairment and proteinuria are also clinical features. This review combines clinical and laboratory findings of renal involvement from the main geographic regions of disease occurrence and for different mutations of TTR. Fifteen nephropathic variants have been described, but the TTR V30M mutation is the best documented. Nephropathy affects patients with late-onset neuropathy, low penetrance in the family, and cardiac dysrhythmias. Microalbuminuria can be the disorder's first presentation, even before the onset of neuropathy. Amyloid renal deposits commonly occur, even in the absence of urinary abnormalities. The experience with renal replacement therapy is based on hemodialysis, which is associated with poor survival. Because TTR is synthesized mainly in the liver, liver transplantation has been considered an acceptable treatment; simultaneous liver-kidney transplantation is recommended to avoid recurrence of nephropathy. In addition, the kidney-safety profile of new drugs in development may soon be available. © 2012 by the American Society of Nephrology. Source


Pereira M.,University of Porto
BMC public health | Year: 2012

Cardiovascular diseases and cancer are jointly responsible for more than half all deaths in Portugal. They also share some important risk factors and act as mutual competing risks. We aimed firstly to describe time trends in death rates and years of life lost due to cardiovascular diseases and cancer in the Portuguese population from 1980 to 2010; and secondly to quantify the contribution of the variation in population and age structure, and age-independent "risk" by cardiovascular or oncological causes to the change in the corresponding number of deaths. We estimated the annual percent change in age-standardized mortality rates from cardiovascular diseases and cancer, in each sex. The specific contribution of demographic changes (due to changes in population size and in population age structure) and the variation in the age-independent "risk" of dying from the disease to the observed trends in the number of deaths was quantified using the tool RiskDiff. Years of life lost were computed using the Global Burden of Disease method. Among men, the mortality rate from all cardiovascular diseases was more than two-fold higher than cancer mortality in 1980. However, three decades later mortality from cancer surpassed cardiovascular diseases. After 2005, the years of life lost from cancer were also higher than from cardiovascular diseases. Among women, despite the decrease in death rates, cardiovascular diseases remained the leading cause of death in 2010 and their absolute burden was higher than that of cancers across the whole period, mainly due to more events in older women. In Portugal, the 20th century witnessed a dramatic decrease in the cardiovascular disease mortality and YLL, and the transition towards cancer. In more recent years, the highest burdens of disease came from cancers in men and from cardiovascular diseases in women. Source


Hinschberger Y.,University of Porto | Hervieux P.-A.,CNRS Institute of Genetics and of Molecular and Cellular Biology
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

Abstract In the domain of extreme light-matter interactions, we show that the electron-electron interaction can be modified coherently by the electric field of the light. The latter play the role of a third partner not only acting on the electrons individually but also on their mutual interaction. By using an original formalism based on the Foldy-Wouthuysen transformation and applied to the Dirac-Breit Hamiltonian in the presence of a time-dependent electromagnetic field, we obtain analytical expressions of new three-body light-matter interactions. © 2015 Elsevier B.V. Source


Alternative polyadenylation has an important function in regulating gene expression, as accumulating evidence has shown that it is related to many different biological programs such as differentiation, development and even flowering. Recently we have shown using the model organism D. melanogaster, how RNA polymerase II kinetics affects alternative polyadenylation. In six genes, which contain tandem poly(A) signals in the 3'UTR, including the cell cycle gene polo, the proximal poly(A) signal is more efficiently used in flies where a mutation in RNA polymerase II reduces its elongation rate. This finding supports the kinetic coupling model for transcription and alternative polyadenylation. polo is a key cell cycle gene encoding a protein kinase with multiple functions in cell division. To understand the physiological function of polo alternative polyadenylation, transgenic flies were constructed where the distal poly(A) signal was deleted. These individuals still produce the shorter polo mRNA, however they die with severe abdominal abnormalities. Lack of the distal poly(A) signal causes a significant decrease in Polo protein levels, which the histoblasts, the precursor cells of the abdomen, require to divide and proliferate at the onset of metamorphosis. Failure in histoblast proliferation impedes the correct development of the abdominal epidermis, causing lethality at the pupa/metamorphosis developmental stage. Polo protein was also shown to be autoregulated by alternative poly(A) site selection in a feedback loop mechanism. Our work is reviewed here and a model for integrating RNA polymerase II kinetics with alternative polyadenylation and cell cycle control is proposed. © 2011 Landes Bioscience. Source


Porto G.,University of Porto
European Journal of Human Genetics | Year: 2015

Molecular genetic testing for hereditary hemochromatosis (HH) is recognized as a reference test to confirm the diagnosis of suspected HH or to predict its risk. The vast majority (typically >90%) of patients with clinically characterized HH are homozygous for the p.C282Y variant in the HFE gene, referred to as HFE-related HH. Since 1996, HFE genotyping was implemented in diagnostic algorithms for suspected HH, allowing its early diagnosis and prevention. However, the penetrance of disease in p.C282Y homozygotes is incomplete. Hence, homozygosity for p.C282Y is not sufficient to diagnose HH. Neither is p.C282Y homozygosity required for diagnosis as other rare forms of HH exist, generally referred to as non-HFE-related HH. These pose significant challenges when defining criteria for referral, testing protocols, interpretation of test results and reporting practices. We present best practice guidelines for the molecular genetic diagnosis of HH where recommendations are classified, as far as possible, according to the level and strength of evidence. For clarification, the guidelines’ recommendations are preceded by a detailed description of the methodology and results obtained with a series of actions taken in order to achieve a wide expert consensus, namely: (i) a survey on the current practices followed by laboratories offering molecular diagnosis of HH; (ii) a systematic literature search focused on some identified controversial topics; (iii) an expert Best Practice Workshop convened to achieve consensus on the practical recommendations included in the guidelines.European Journal of Human Genetics advance online publication, 8 July 2015; doi:10.1038/ejhg.2015.128. © 2015 Macmillan Publishers Limited Source


Santos D.,University of Porto
European Journal of Human Genetics | Year: 2015

Familial amyloid polyneuropathy (FAP) ATTRV30M is a neurodegenerative disorder due to point mutations in the transthyretin gene, with V30M being the commonest. FAP ATTRV30M shows a wide variation in age at onset (AO) between clusters, families and generations. Portuguese patients also show remarkable AO differences between genders. Genes found to be associated with FAP ATTRV30M pathways may act as AO modifiers. Our aim was to further explore the role of APCS and RBP4 genes and to study for the first time the involvement of sex-linked genetic modifiers – AR and HSD17B1 genes – in AO variation in Portuguese families. We collected DNA from a sample of 318 patients, currently under follow-up. A total of 18 tagging SNPs from APCS, RBP4, AR and HSD17B1 and 5 additional SNPs from APCS and RBP4 previously studied were genotyped. To account for nonindependency of AO between members of the same family, we used generalized estimating equations (GEEs). We found that APCS and RBP4 were associated with late AO. In addition, rs11187545 of the RBP4 was associated with an early AO. For the AR, in the male group three SNPs were associated with an early AO, whereas in the female group four were associated with both an early and later AO. These results strengthened the role of APCS and RBP4 genes and revealed for the first time the contribution of AR genes as an AO modifier in both males and females. These findings may have important implications in genetic counseling and for new therapeutic strategies.European Journal of Human Genetics advance online publication, 19 August 2015; doi:10.1038/ejhg.2015.180. © 2015 Macmillan Publishers Limited Source


Gaspar D.A.,University of Porto
Biomatter | Year: 2012

Tissue engineering has emerged as a possible alternative to current treatments for bone injuries and defects. However, the common tissue engineering approach presents some obstacles to the development of functional tissues, such as insufficient nutrient and metabolite transport and non-homogenous cell distribution. Culture of bone cells in three-dimensional constructs in bioreactor systems is a solution for those problems as it improves mass transport in the culture system. For bone tissue engineering spinner flasks, rotating wall vessels and perfusion systems have been investigated, and based on these, variations that support cell seeding and mechanical stimulation have also been researched. This review aims at providing an overview of the concepts, advantages and future applications of bioreactor systems for bone tissue engineering with emphasis on the design of different perfusion systems and parameters that can be optimized. Source


Staphylococcus comprises up to two-thirds of all pathogens in orthopedic implant infections and they are the principal causative agents of two major types of infection affecting bone: septic arthritis and osteomyelitis, which involve the inflammatory destruction of joint and bone. Bacterial adhesion is the first and most important step in implant infection. It is a complex process influenced by environmental factors, bacterial properties, material surface properties and by the presence of serum or tissue proteins. Properties of the substrate, such as chemical composition of the material, surface charge, hydrophobicity, surface roughness and the presence of specific proteins at the surface, are all thought to be important in the initial cell attachment process. The biofilm mode of growth of infecting bacteria on an implant surface protects the organisms from the host immune system and antibiotic therapy. The research for novel therapeutic strategies is incited by the emergence of antibiotic-resistant bacteria. This work will provide an overview of the mechanisms and factors involved in bacterial adhesion, the techniques that are currently being used studying bacterial-material interactions as well as provide insight into future directions in the field. Source


Tran L.V.,Ton Duc Thang University | Ferreira A.J.M.,University of Porto | Ferreira A.J.M.,King Abdulaziz University | Nguyen-Xuan H.,Ton Duc Thang University
Composites Part B: Engineering | Year: 2013

This paper presents a novel and effective formulation based on isogeometric approach (IGA) and higher-order deformation plate theory (HSDT) to study the behavior of functionally graded material (FGM) plates. HSDT model using C 1 continuous element is able to improve the accuracy of solution and describe exactly the shear stress distribution without shear correction factors. IGA utilizes the non-uniform rational B-spline (NURBS) functions which allow us to achieve easily the smoothness with arbitrary continuity order. The present method hence fulfills the C1 - requirement of HSDT model. The effective material properties of the FGM plates, which property varies only through the thickness of plate, are calculated using the rule of mixture and the Mori-Tanaka homogenization technique. The static, dynamic and buckling analysis of rectangular and circular plates is investigated for different boundary conditions. Numerical results show high effectiveness of the present formulation. © 2013 Elsevier Ltd. Source


Sousa C.S.,Institute Engineering Mecanica e Gestao Industrial | Camanho P.P.,University of Porto | Suleman A.,University of Lisbon
Composite Structures | Year: 2013

This paper presents a new concept for morphing composite structures based on variable stiffness composite plates. The variable stiffness morphing laminate proposed in this paper consists in a modified version of a straight fiber laminate composed of two regions, one with symmetric and the other with unsymmetric stacking sequence. Since there is a lay-up mismatch where the two regions meet, stress concentrations are expected to occur when straight fibers are used. A solution to mitigate this effect in which the fibers are allowed to vary smoothly along the plane from one region to the other is analyzed. The particular trajectories followed by the curved fibers were designed such that the plate can be manufactured using Advanced Fiber Placement technology (AFP).A finite element analysis of the laminate is performed to predict its out-of-plane displacements for the two possible stable configurations that may be obtained after the curing process. Then, the plate may be snapped from one shape to the other with the application of a force. This snap-through behavior is analyzed and compared with the original straight fiber laminate. The concept of a bistable Variable Stiffness Panel (VSP) composed of regions of symmetric and unsymmetric lay-ups that preserve the tangential continuity of the fibers could be of great importance in morphing or shape-adaptable structures for aerospace applications, such as winglets or flaps. © 2012 Elsevier Ltd. Source


Pereira C.C.,Polytechnic Institute of Viseu | Pinho C.,University of Porto
Energy and Fuels | Year: 2013

The fluidized bed reactor is suitable for the combustion of biomass solid fuels because of its advantages in terms of pollution control. At the same time it is a useful laboratory tool to determine kinetic and diffusive combustion data in operating conditions similar to those found in industrial systems. Because of the heterogeneous nature of biomass, available information on its combustion is still limited. During the combustion of ligneous biomass, the burning of the solid carbonaceous residues formed after the initial steps of drying and volatiles release is the time-consuming step. In the present work, kinetic and diffusive data from the fluidized bed combustion of chars produced from four Portuguese wood species - Quercus ilex (holm oak), Eucalyptus globulus (eucalyptus), Pinus pinaster (maritime pine), and Quercus suber (cork oak) - were obtained in the 750-900 C temperature range. Subsequently, activation energies and pre-exponential factors were calculated from the Arrhenius plot of the kinetic data. The obtained activation energies from 38 to 121 kJ/mol are coherent with results obtained for other wood chars and demonstrate that the fluidized bed technology is a fruitful and reliable methodology to achieve a collection of results of real and industrial interest. The main goal of the present work is to widen the information on the kinetic and diffusive data of wood chars in order to better understand the mechanisms of ligneous biomass combustion, and the data now published increases the range of available kinetic data on wood char combustion. © 2013 American Chemical Society. Source


We analyse for the first time the genetic diversity within Ptyodactylus oudrii across the Maghreb. Two mitochondrial (12s rRNA and 16s rRNA) and two nuclear (C-mos and ACM4) markers are used. The results confirm the specific status of P. oudrii and show high levels of intraspecific variability, indicative of species complex. Lineages found are geographically concordant, and show similar patterns to that found in other species from the region. The study highlights once more the importance of the region as a source of genetic diversity. © 2009 Elsevier Inc. All rights reserved. Source


Monteiro M.P.,University of Porto
Human Vaccines and Immunotherapeutics | Year: 2014

Obesity is one of the largest and fastest growing public health problems in the world. Last century social changes have set an obesogenic milieu that calls for micro and macro environment interventions for disease prevention, while treatment is mandatory for individuals already obese. The cornerstone of overweight and obesity treatment is diet and physical exercise. However, many patients find lifestyle modifications difficult to comply and prone to failure in the long-term; therefore many patients consider anti-obesity drugs an important adjuvant if not a better alternative to behavioral approach or obesity surgery. Since the pharmacological options for obesity treatment remain quite limited, this is an exciting research area, with new treatment targets and strategies on the horizon. This review discusses the development of innovative therapeutic agents, focusing in energy homeostasis regulation and the use of molecular vaccines, targeting hormones such as somatostatin, GIP and ghrelin, to reduce body weight. © 2014 Landes Bioscience. Source


Carvalho M.I.,University of Porto | Facao M.,University of Aveiro
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

The effects of third-order dispersion (TOD) and intrapulse Raman scattering (IRS) on the erupting solitons of the complex cubic-quintic Ginzburg-Landau equation are investigated by direct numerical simulations and linear stability analysis. Our results indicate that positive TOD eliminates eruptions on the leading edge of the soliton, whereas negative TOD cancels them on the other side. Moreover, the combined action of TOD and IRS is in certain cases able to eliminate explosions on both sides of the soliton, at much lower IRS values than with IRS alone. The profiles of the stationary solutions are increasingly asymmetric with TOD, and their velocity varies almost linearly with IRS. © 2012 Published by Elsevier B.V. Source


Cardoso G.C.,University of Porto | Hu Y.,University of Melbourne
American Naturalist | Year: 2011

Sexual signals are often elaborate as a result of sexual selection for signals of individual quality. Contrary to expectation, however, the elaboration of signals such as birdsong is not related to the strength of sexual selection across species. With a comparative study across wood warblers (family Parulidae), we show a compromise between advertising the performance of trills (syllable repetitions) and song complexity, which can result in the evolution of simple, rather than elaborate, song. Species with higher trill performance evolved simple songs with more extensive trilled syntax. This advertises trill performance but reduces syllable diversity in songs. These two traits are commonly sexually selected in songbirds, but indexes of sexual selection were not related to either in wood warblers. This is consistent with sexual selection targeting different traits in different species, sometimes resulting in simple signals. We conclude that the evolution of sexual signals can be unpredictable when their physiology affords multiple or, as here, opposing ways of advertising individual quality. © 2011 by The University of Chicago. Source


Cardoso G.C.,University of Porto | Atwell J.W.,Indiana University
Animal Behaviour | Year: 2011

Songbirds often sing at higher frequency (pitch) in urban, noise-polluted areas, which reduces acoustic masking by low-frequency anthropogenic noise. Such frequency shifts, however, are less efficient at overcoming background noise than simply singing louder. Therefore, it was suggested that high-frequency singing might not be a functional adjustment to noise, but a physiological consequence of singing louder (also known as the Lombard effect). We tested for the first time the main tenet of this hypothesis, for birdsong whether increasing sound amplitude has a concomitant effect on song frequency, using a representative species with higher urban minimum frequency, the dark-eyed junco, Junco hyemalis. The frequency bandwidth of songs and syllables increased with amplitude, involving lower minimum frequency in louder songs and syllables. Therefore, louder singing does not explain the higher minimum frequency of urban dark-eyed juncos. Amplitude and peak frequency were weakly positively related across but not within songs, suggesting that increased frequency is not an obligatory outcome of singing louder. Instead, birds may adjust both amplitude and frequency in response to changing noise or motivation across songs. Our results suggest that adjustments in song frequency and amplitude are largely independent and, thus, can be complementary rather than alternative vocal adjustments to noise. We discuss oscine vocal physiology and details of the behaviour of urban birds, both of which we argue are consistent with the increased frequency of urban birdsong generally being a functional adjustment to noise, rather than a consequence of singing louder. © 2011 The Association for the Study of Animal Behaviour. Source


Hari Narayana Moorthy N.S.,University of Porto | Poongavanam V.,University of Southern Denmark | Pratheepa V.,CIIMAR - Interdisciplinary Center of Marine and Environmental
Mini-Reviews in Medicinal Chemistry | Year: 2014

Influenza virus is an important RNA virus causing pandemics (Spanish Flu (1918), Asian Flu (1957), Hong Kong Flu (1968) and Swine Flu (2009)) over the last decades. Due to the spontaneous mutations of these viral proteins, currently available antiviral and anti-influenza drugs quickly develop resistance. To account this, only limited anti- influenza drugs have been approved for the therapeutic use. These include amantadine and rimantadine (M2 proton channel blockers), zanamivir, oseltamivir and peramivir (neuraminidase inhibitors), favipravir (polymerase inhibitor) and laninamivir. This review provides an outline on the strategies to develop novel, potent chemotherapeutic agents against M2 proton channel. Primarily, the M2 proton channel blockers elicit pharmacological activity through destabilizing the helices by blocking the proton transport across the transmembrane. The biologically important compounds discovered using the scaffolds such as bisnoradmantane, noradamantane, triazine, spiroadamantane, isoxazole, amino alcohol, azaspiro, spirene, pinanamine, etc are reported to exhibit anti-influenza activity against wild or mutant type (S31N and V27A) of M2 proton channel protein. The reported studies explained that the adamantane based compounds (amantadine and rimantadine) strongly interact with His37 (through hydrogen bonding) and Ala30, Ile33 and Gly34 residues (hydrophobic interactions). The adamantane and the non-adamantane scaffolds fit perfectly in the active site pocket present in the wild type and the charged amino groups (ammonium) create positive electrostatic potential, which blocks the transport of protons across the pore. In the mutated proteins, larger or smaller binding pocket are created by small or large mutant residues, which do not allow the molecules fit in the active site. This causes the channel to be unblocked and the protons are allowed to transfer inside the pore. The structural analysis of the M2 proton channel blockers illustrated that the adamantane derivatives have action against both influenza A and B, but have no effect on the mutants. © 2014 Bentham Science Publishers. Source


James R.J.W.,University of Canterbury | Almada-Lobo B.,University of Porto
Computers and Operations Research | Year: 2011

We propose a general-purpose heuristic approach combining metaheuristics and mixed integer programming to find high quality solutions to the challenging single- and parallel-machine capacitated lotsizing and scheduling problem with sequence-dependent setup times and costs. Commercial solvers fail to solve even medium-sized instances of this NP-hard problem; therefore, heuristics are required to find competitive solutions. We develop construction, improvement and search heuristics all based on MIP formulations. We then compare the performance of these heuristics with those of two metaheuristics and other MIP-based heuristics that have been proposed in the literature, and to a state-of-the-art commercial solver. A comprehensive set of computational experiments shows the effectiveness and efficiency of the main approach, a stochastic MIP-based local search heuristic, in solving medium to large size problems. Our solution procedures are quite flexible and may easily be adapted to cope with model extensions or to address different optimization problems that arise in practice. © 2011 Elsevier Ltd. All rights reserved. Source


Facao M.,University of Aveiro | Carvalho M.I.,University of Porto
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

The complex cubic-quintic Ginzburg-Landau equation (CGLE) admits a special type of solutions called eruption solitons. Recently, the eruptions were shown to diminish or even disappear if a term of intrapulse Raman scattering (IRS) is added, in which case, self-similar traveling pulses exist. We perform a linear stability analysis of these pulses that shows that the unstable double eigenvalues of the erupting solutions split up under the effect of IRS and, following a different trajectory, they move on to the stable half-plane. The eigenfunctions characteristics explain some eruptions features. Nevertheless, for some CGLE parameters, the IRS cannot cancel the eruptions, since pulses do not propagate for the required IRS strength. © 2011 Elsevier B.V. All rights reserved. Source


Silva J.A.C.,Polytechnic Institute of Braganca | Schumann K.,Chemiewerk Bad Kostritz | Rodrigues A.E.,University of Porto
Microporous and Mesoporous Materials | Year: 2012

The sorption equilibrium of CO 2 and CH 4 in binderless beads of 13X zeolite has been investigated between 313 and 373 K and pressure up to 4 atm. The amount adsorbed of CO 2 and CH 4 is around 5.2 mmol/g ads and 1.2 mmol/g ads, respectively, at 313 K and 4 atm. Comparing these values with the ones in literature the value of CO 2 is 20% higher than in CECA 13X binder pellets. It is also found that isotherms are pronounced Type I for CO 2 and almost linear for CH 4. The CO 2 isotherms were modeled using a simple deviation from Langmuir isotherm that takes into account interaction between adsorbed molecules at adjacent sites (Fowler model) suggesting a moderate repulsion. Henry's constants range from 143 to 11.1 mmol/g ads.atm for CO 2 and 0.45 to 0.27 mmol/g ads.atm for CH 4 between 313 and 373 K, respectively. The heats of sorption at zero coverage are 43.1 kJ/mol for CO 2 and 9.2 kJ/mol for CH 4. The sorption kinetics has been investigated by the Zero-Length Column technique (ZLC). Recipes to analyze ZLC desorption curves in pellets of adsorbents are reviewed and it is derived a criteria which indicates that for the sorption rate be measured macroscopically the time of the experiment (that should be above a few seconds) is directly calculated with the following expression: t0.1≥7.02×10-2rc2Dc. Based on such criteria it is shown that crystal diffusivity of CO 2 in 13X can be measured macroscopically by ZLC, being the same measurement for CH 4 practically impossible. The crystal diffusivity of CO 2 measured experimentally is 5.8 × 10 -15 m 2/s and 1.3 × 10 -15 m 2/s at 373 and 313 K, respectively. These values are comparable to the ones measured by a frequency response and pulse chromatography techniques reported in literature. The ZLC desorption curves for CH 4 were measured under an equilibrium regime. © 2012 Elsevier Inc. All rights reserved. Source


De Moura M.F.S.F.,University of Porto
Journal of Adhesion | Year: 2015

Cohesive zone models can play an important role in the definition of repair strategies. These models allow the prediction of damage initiation and propagation. They are based on a softening relationship between stresses and relative displacements between crack faces, thus simulating a gradual degradation of material properties. Typically, stress-based and energetic fracture mechanics criteria are used to simulate damage initiation and growth, respectively. Those elements are placed at the planes where damage is prone to occur which, in the case of bonded repairs, is usually easy to identify a priori. Taking this into consideration, cohesive mixed-mode damage models based on interface finite elements were used with the objective of optimizing the repair efficiency. The determination of the cohesive pure mode softening laws is a key aspect of these models, and the direct method is the most accurate process to do it. The models were validated and applied to two different cases involving repairs. Several geometrical aspects influencing the single-strap repair strength were analyzed as well as the evolution of the maximum load and alteration of damage mechanism as a function of the angle used in scarf joints. It was verified that CZM are able to predict with accuracy the damage mechanisms and strength of composite bonded repairs, thus constituting a powerful tool in its design. © 2015 Taylor & Francis Group, LLC. Source


Martins C.J.A.P.,University of Porto | Martins C.J.A.P.,Institute Astrofisica e Ciencias Do Espaco | Vielzeuf P.E.,Autonomous University of Barcelona | Martinelli M.,University of Heidelberg | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We study the detailed evolution of the fine-structure constant α in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent α measurements and discuss ways to distinguish it from alternative models for varying α. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical ΛCDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT), together with more sensitive α measurements, will thus dramatically constrain these scenarios. © 2015 The Authors. Source


Amaro H.M.,CIIMAR - Interdisciplinary Center of Marine and Environmental | Macedo A.C.,Superior Institute of Maia | Malcata F.X.,CIIMAR - Interdisciplinary Center of Marine and Environmental | Malcata F.X.,University of Porto
Energy | Year: 2012

In recent decades, the world has been confronted with an energy crisis associated with irreversible depletion of traditional sources of fossil fuels, coupled with atmospheric accumulation of greenhouse gases that cause global warming. The urgent need to replace traditional fuels led to emergence of biodiesel and biohydrogen as interesting alternatives, both of which can be obtained via microalga-mediated routes.Microalgae are ubiquitous eukaryotic microorganisms, characterized by a remarkable metabolic plasticity. Their oil productivities are much higher than those of higher terrestrial plants, and they do not require high quality agricultural land. Microalgae may indeed be cultivated in brackish and wastewaters that provide suitable nutrients (e.g. NH4+,NO3-andPO43-), at the expense of only sunlight and atmospheric CO 2. On the other hand, metabolic engineering permits release of molecular hydrogen also via photosynthetic routes, which will easily be converted to electricity in fuel cells or mechanical power in explosion engines, with only water vapor as exhaust product in both cases.However, large-scale implementation of microalga-based systems to manufacture biodiesel and biohydrogen has been economically constrained by their still poor volumetric efficiencies, which imply excessively high costs when compared with current petrofuel prices. Technological improvements are accordingly critical, both on the biocatalyst and the bioreactor levels. The current bottlenecks that have apparently precluded full industrial exploitation of microalgae cells are critically discussed here, viz. those derived from the scarce knowledge on the mechanisms that control regulation of gene expression, the reduced number of species subjected to successful genetic transformation, the relatively low cell density attainable, the poor efficiency in harvesting, and the difficulties in light capture and use.Therefore, this paper provides an overview of the feasibility of microalgae for production of biofuels via synthesis of liquid endocellular metabolites (i.e. triglycerides) and gaseous extracellular ones (i.e. molecular hydrogen), and addresses technical and economic shortcomings and opportunities along the whole processing chain, at both microorganism and reactor levels. © 2012 Elsevier Ltd. Source


Lopes A.M.,University of Porto
Robotica | Year: 2010

In this paper a new approach based on the generalized momentum is used to obtain the dynamic model of a six degrees-of-freedom (dof) parallel manipulator. First, the system dynamic equations are obtained supposing the manipulator base platform is fixed. Afterwards, the dynamic model is extended to the case of a moving base platform. This could be important in a macro/micro robotic application, where a small manipulator is attached in series to a big manipulator. Simulation results of a macro/micro robotic system are presented and the contribution of the base platform motion to the total actuating forces is shown. © 2009 Cambridge University Press. Source


Povoa P.,Polyvalent Intensive Care Unit | Povoa P.,New University of Lisbon | Teixeira-Pinto A.M.,University of Porto | Carneiro A.H.,Abel Salazar Biomedical Sciences Institute
Critical Care | Year: 2011

Introduction: C-reactive protein (CRP) has been shown to be a valuable marker in the diagnosis of infection and in monitoring its response to antibiotics. Our objective was to evaluate serial CRP measurements after prescription of antibiotics to describe the clinical course of Community-Acquired Sepsis admitted to intensive care units (ICU).Methods: During a 12-month period a multi-center, prospective, observational study was conducted, segregating adults with Community-Acquired Sepsis. Patients were followed-up during the first five ICU days, day of ICU discharge or death and hospital outcome. CRP-ratio was calculated in relation to Day 1 CRP concentration. Patients were classified according to the pattern of CRP-ratio response to antibiotics: fast response if Day 5 CRP-ratio was < 0.4, slow response if Day 5 CRP-ratio was between 0.4 and 0.8, and no response if Day 5 CRP-ratio was > 0.8. Comparison between survivors and non-survivors was performed.Results: A total of 891 patients (age 60 ± 17 yrs, hospital mortality 38%) were studied. There were no significant differences between the CRP of survivors and non-survivors until Day 2 of antibiotic therapy. On the following three days, CRP of survivors was significantly lower (P < 0.001). After adjusting for the Simplified Acute Physiology Score II and severity of sepsis, the CRP course was significantly associated with mortality (ORCRP-ratio= 1.03, confidence interval 95%= (1.02, 1.04), P < 0.001). The hospital mortality of patients with fast response, slow response and no response patterns was 23%, 30% and 41%, respectively (P = 0.001). No responders had a significant increase on the odds of death (OR = 2.5, CI95%= (1.6, 4.0), P < 0.001) when compared with fast responders.Conclusions: Daily CRP measurements after antibiotic prescription were useful as early as Day 3 in identification of Community-Acquired Sepsis patients with poor outcome. The rate of CRP decline during the first five ICU days was markedly associated with prognosis. The identification of the pattern of CRP-ratio response was useful in the recognition of the individual clinical course. © 2011 Póvoa et al.; licensee BioMed Central Ltd. Source


Benkova Z.,Slovak Academy of Sciences | Benkova Z.,University of Porto | Cifra P.,Slovak Academy of Sciences
Macromolecules | Year: 2012

The constraints due to the chain closure in combination with the geometrical constraints of a DNA molecule are inevitable for many biological processes. In this work, structural properties of flexible and semiflexible cyclic chains and their linear analogues confined in cylindrical channels were studied using the coarse-grained Metropolis Monte Carlo simulations. The radius of gyration satisfactorily represents the longitudinal stretching of both chain topologies. Transition between the moderate and strong confinement regime of semiflexible cyclic chains is described for the first time. Qualitatively similar response of the chain elongation to the confinement strength variation R g(D) is obtained in the case of cyclic chains. However, the relative chain extension is stronger, the Odijk strong confinement regime is extended to larger channel diameters D, and under moderate confinement the chain extension declines less steeply for cyclic chains. All three findings are explained in terms of the strong self-avoidance of confined chains relative to their linear analogues and the last finding is consistent with the reported experimental measurements. In the Odijk regime, the relative chain extension is governed by the same analytical functions provided half of the contour length for a cyclic chain is considered at the full extension. The orientation correlations for a cyclic chain in narrow channels are characterized by a typical sharp central minimum. Upon increasing the channel cross-sectional area, the minimum is broadened, turns into a negative maximum and, ultimately, the orientation correlations merge with those for a free cycle. Confined flexible and less stiff chains resemble their linear analogues more readily. The static structure factor for tightly confined chains provides better differentiation between the chain architecture than for free chains. © 2012 American Chemical Society. Source


Neves D.,University of Porto
Free Radical Research | Year: 2013

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra-And extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation. © 2013 Informa UK, Ltd. Source


Sujit P.B.,Indraprastha Institute of Information Technology | Saripalli S.,Arizona State University | Sousa J.B.,University of Porto
IEEE Control Systems | Year: 2014

Unmanned aerial vehicles (UAVs) are mainly used by military and government organizations, but with low-cost sensors, electronics, and airframes there is significant interest in using low-cost UAVs among aircraft hobbyists, academic researchers, and industries. Applications such as mapping, search and rescue, patrol, and surveillance require the UAV to autonomously follow a predefined path at a prescribed height. The most commonly used paths are straight lines and circular orbits. Path-following algorithms ensure that the UAV will follow a predefined path in three or two dimensions at constant height. A basic requirement for these path-following algorithms is that they must be accurate and robust to wind disturbances. © 2013 IEEE. Source


Ribeiro M.C.,University of Porto
International Journal of Marine and Coastal Law | Year: 2010

The discovery of the 'Rainbow', a hydrothermal vent field located in the Portuguese continental shelf beyond 200 nautical miles, has prompted new thinking in our understanding of the law of the sea. In 2006, in the context of the OSPAR Convention, Portugal proposed the nomination of the first national marine protected area under the high seas. The subsequent acceptance of the proposal by the OSPAR Convention members makes Portugal a pioneer in the protection of marine biodiversity at an international level: first, because of the unique location of the marine protected area; second, because the nomination was accepted at a stage when the process of delineation of the outer limits of the continental shelf had not been concluded. The new juridical perspectives stimulated by these facts are addressed in this article. © 2010 Koninklijke Brill NV, Leiden. Source


Ammonium-illite (NH 4-I) is one of the alteration products present in a breccia structure in the fossil hydrothermal system from Harghita Bãi (East Carpathians), Romania. A series from smectite (S) via ordered interstratified structures to NH 4-I (40 to 5%S) was characterized by Xray diffraction (XRD), Fourier transforminfrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), and chemical analyses. Calculation of onedimensional Xray patterns was simulated with the NEWMOD code. Transition from twoto onewater smectite interlayer was identified by XRD. Selected samples were saturated with K +-, Mg 2+, and Li +-cations to differentiate lowto highcharge smectite or beidelite layers. Xray patterns of random powders of K +-saturated samples, heated at 300 °C show a transition from 1Md to cisand transvacant 1M polytype. The cell parameters of the cisvacant and transvacant 1M polytype were calculated by oblique texture electron diffraction. The vibration frequencies at 1430 cm -1 of the NH bond were identified in the samples analyzed. Scanning and transmission electron microscopy images show morphological changes from flaky to lathlike shapes. The mean shape ratio of lath crystals ranges from 6 to 5.42 nm and the mean area from 7.8 to 24 × 10 4 nm 2. The mean thickness of the NH 4-I layers ranges from 4.62 to 7.89 nm. The calculated structural formula of endmember NH 4-I (5%S) is: [(NH + 4) 0.66K + 0.10Na + 0.01Sr 2+ 0.02] 0.81(Al 3+ 1.85Fe 3+ 0.01Mg 2+ 0.15) 2.01(Si 4+ 3.30Al 3+ 0.70) 4.00O 10(OH) 2. The fixed NH + 4 content quantified ranges from 0.39 to 0.66 atoms per half unit cell [O 10(OH) 2]. Tetrahedral and octahedral substitutions took place as the %S decreases. The NH 4-I-S series formed via direct precipitation from solution at different temperatures. Source


Ahn C.,Ewha Womans University | Bombardelli D.,University of Porto
International Journal of Modern Physics A | Year: 2013

We propose exact S-matrices for the AdS3/CFT2 duality between type IIB strings on AdS3×S3×M 4 with M4 = S3×S1 or T 4 and the corresponding two-dimensional conformal field theories. We fix the two-particle S-matrices on the basis of the symmetries su(1|1) and su(1|1)×su(1|1). A crucial justification comes from the derivation of the all-loop Bethe ansatz matching exactly the recent conjecture proposed by Babichenko et al. [J. High Energy Phys. 1003, 058 (2010), arXiv:0912.1723 [hep-th]] and Ohlsson Sax and Stefanski, Jr. [J. High Energy Phys. 1108, 029 (2011), arXiv:1106.2558 [hep-th]]. © 2013 World Scientific Publishing Company. Source


Da Silva R.B.,University of Zurich | Da Silva R.B.,University of Porto | Graf C.,Johannes Gutenberg University Mainz | Munz C.,University of Zurich
Blood | Year: 2011

Human mature dendritic cells (DCs) canefficiently stimulate natural killer (NK)-cell responses without being targeted by their cytotoxicity. To understand this important regulatory crosstalk, we characterized the development of the immunologic synapse between mature DCs and resting NK cells. Conjugates between these 2 innate leukocyte populations formed rapidly, persisted for prolonged time periods and matured with DC-derived f-actin polymerization at the synapse. Polarization of IL-12 and IL-12R to the synapse coincided with f-actin polymerization, while other activating and inhibitory molecules were enriched at the interface between DCs and NK cells earlier. Functional assays revealed that inhibition of f-actin polymerization in maturesynapses led to an increase of IFN-γsecretion and cytotoxicity by NK cells. This elevated NK-cell reactivity resulted from decreased inhibitory signaling in the absence of MHC class I polarization at the interface, which was observed on inhibition of f-actin polymerization in DCs. Thus, inhibitory signaling is stabilized by f-actin at the synapse between mature DCs and resting NK cells. © 2011 by The American Society of Hematology. Source


Moutinho C.,University of Porto
Earthquake Engineering and Structural Dynamics | Year: 2012

It is well established that small tuned mass dampers (TMDs) attached to structures are very effective in reducing excessive harmonic vibrations induced by external loads but are not as interesting within the context of earthquake engineering problems. For this reason, large mass ratio TMDs have been proposed with the objective of adding a significant amount of damping to structures, thus constituting a good means of reducing structural response in these cases. This solution has other important and attractive dynamic features such as robustness to system uncertainties and reduction of the motion of the inertial mass. In this context, this paper aims to describe an alternative methodology to existing procedures used to tune these devices to earthquake loads and to present some additional considerations regarding its performance in controlling seismic vibrations. The main feature of the proposed method consists of establishing a direct proportion between the damping ratios of the structure's first two vibration modes and the adopted mass ratio. By equalizing the damping ratios of the system's main vibration modes, this proposal also facilitates the use of simplified methods, such as modal analysis based on response spectra. To demonstrate the usefulness of this alternative methodology, an application example is presented, which was also used to perform a parametric study involving other tuning methods and to estimate mass ratio values from which there is no significant advantage in increasing the TMD mass. © 2012 John Wiley & Sons, Ltd. Source


Cunha M.,University of Porto | Richter C.,University of East London
International Journal of Biometeorology | Year: 2012

This paper investigates the cyclical behaviour of the wine production in Douro region during the period 1932-2008. In general, wine production is characterised by large fluctuations which are composed of short-term and/or long-term cycles. The aim of this paper is twofold: firstly, we decompose the wine production's variance in order to find the dominating production cycles, i. e we try to explain whether wine production follows more long-term or short-term cycles. In the next step, we try to explain those cycles using a dependent variable, namely the medium spring temperature (Tm_Sp) for the period 1967-2008. We estimated a Time-Varying Autoregressive Model, which could explain 75% of the production that is characterised by 4.8- and 2.5-year cycles. We use the Short Time Fourier Transform to decompose the link between wine production and temperature. When the temperature was incorporated, the R 2 increased and the Akaike criterion value was lower. Hence, Tm_Sp causes a large amount of these cycles and the wine production variation reflects this relationship. In addition to an upward trend, there is a clearly identifiable cycle around the long-term trend in production. We also show how much of the production cycle and what cycle in particular is explained by the Tm_Sp. There is a stable but not constant link between production and the Tm_Sp. In particular, the temperature is responsible for 5.2- and 2.4-year cycles which has been happening since the 1980s. The Tm_Sp can also be used as an indicator for the 4.8- and 2.5-year cycles of production. The developed model suggests that stationarity is a questionable assumption, and this means that historical distributions of wine production are going to need dynamic updating. © 2011 ISB. Source


Perez-Cruz F.,Princeton University | Perez-Cruz F.,Charles III University of Madrid | Rodrigues M.R.D.,University of Porto | Verdu S.,Princeton University
IEEE Transactions on Information Theory | Year: 2010

In this paper, we investigate the linear precoding and power allocation policies that maximize the mutual information for general multiple- inputmultiple-output (MIMO) Gaussian channels with arbitrary input distributions, by capitalizing on the relationship between mutual information and minimum mean-square error (MMSE). The optimal linear precoder satisfies a fixed-point equation as a function of the channel and the input constellation. For non-Gaussian inputs, a nondiagonal precoding matrix in general increases the information transmission rate, even for parallel noninteracting channels. Whenever precoding is precluded, the optimal power allocation policy also satisfies a fixed-point equation; we put forth a generalization of the mercury/waterfilling algorithm, previously proposed for parallel noninterfering channels, in which the mercury level accounts not only for the non-Gaussian input distributions, but also for the interference among inputs. © 2006 IEEE. Source


Ferreira H.L.,TU Eindhoven | Garde R.,Renewable Energy National Center CENER | Fulli G.,European Commission | Kling W.,TU Eindhoven | Lopes J.P.,University of Porto
Energy | Year: 2013

In the current situation with the unprecedented deployment of clean technologies for electricity generation, it is natural to expect that storage will play an important role in electricity networks. This paper provides a qualitative methodology to select the appropriate technology or mix of technologies for different applications. The multiple comparisons according to different characteristics distinguish this paper from others about energy storage systems.Firstly, the different technologies available for energy storage, as discussed in the literature, are described and compared. The characteristics of the technologies are explained, including their current availability. In order to gain a better perspective, availability is cross-compared with maturity level. Moreover, information such as ratings, energy density, durability and costs is provided in table and graphic format for a straightforward comparison. Additionally, the different electric grid applications of energy storage technologies are described and categorised. For each of the categories, we describe the available technologies, both mature and potential. Finally, methods for connecting storage technologies are discussed. © 2013 Elsevier Ltd. Source


Monteiro C.,University of Porto | Ramirez-Rosado I.J.,University of Zaragoza | Fernandez-Jimenez L.A.,University of La Rioja
Renewable Energy | Year: 2013

This paper presents an original short-term forecasting model for hourly average electric power production of small-hydro power plants (SHPPs). The model consists of three modules: the first one gives an estimation of the " daily average" power production; the second one provides the final forecast of the hourly average power production taking into account operation strategies of the SHPPs; and the third one allows a dynamic adjustment of the first module estimation by assimilating recent historical production data. The model uses, as inputs, forecasted precipitation values from Numerical Weather Prediction tools and past recorded values of hourly electric power production in the SHPPs. The structure of the model avoids crossed-influences between the adjustments of such model due to meteorological effects and those due to the operation strategies of the SHPPs. The forecast horizon of the proposed model is seven days, which allows the use of the final forecast of the power production in Power System operations, in electricity markets, and in maintenance scheduling of SHPPs. The model has been applied in the forecasting of the aggregated hourly average power production for a real-life set of 130 SHPPs in Portugal achieving satisfactory results, maintaining the forecasting errors delimited in a narrow band with low values. © 2012 Elsevier Ltd. Source


da Silva J.C.B.,University of Porto | da Silva J.C.B.,Woods Hole Oceanographic Institution | Jeans G.,Oceanalysis
Oceanography | Year: 2012

Nonlinear internal waves are found in many parts of the world ocean. Their widespread distribution is a result of their origin in the barotropic tide and in the variety of ways they can be generated, including by lee waves, tidal beams, resonance, plumes, and the transformation of the internal tide. The differing generation mechanisms and diversity of generation locations and conditions all combine to produce waves that range in scale from a few tens of meters to kilometers, but with all properly described by solitary wave theory. The ability of oceanic nonlinear internal waves to persist for days after generation and the key role internal waves play in connecting large-scale tides to smaller-scale turbulence make them important for understanding the ocean environment. © 2012 by The Oceanography Society. Source


Santos M.,University of Porto | Santos M.,Brigham and Womens Hospital | Shah A.M.,Brigham and Womens Hospital
Current Hypertension Reports | Year: 2014

Hypertension is a powerful risk factor for cardiovascular mortality and morbidity, including heart failure with both preserved and reduced ejection fraction. Hypertensive heart disease (HHD) defines the complex and diverse perturbations of cardiac structure and function occurring secondary to hypertension. Left ventricular hypertrophy (LVH) is one of the most recognized features of HHD and is an established risk factor for adverse cardiovascular (CV) outcomes in hypertension. Beyond LVH, LV geometry provides additional information regarding the cardiac response to hypertension. Imaging studies from larger cohorts of hypertensive patients reveal wide variability in the prevalence of LVH and LV geometric patterns, with the prevalence of concentric LVH similar to that of eccentric LVH. Hypertension is also associated with concomitant impairments in LV diastolic and systolic function. It remains uncertain why patients develop different patterns of LVH, although demographics and clinical comorbidities appear to influence that response. © 2014 Springer Science+Business Media. Source


Amorim A.,University of Porto
New Genetics and Society | Year: 2012

Social impact is intrinsic to any applied branch of genetics. Since the goal of forensic genetics is to provide expertise in legal disputes, the expert should make her-or himself understood. The urgent need for measures to deepen the communication between experts and non-experts requires debunking of some myths surrounding forensic genetics, and to (re)center the discussion on the solid ground of formal genetics. Classical forensic sciences rely on the assumption of discernible uniqueness, while forensic genetics deals with types of observations. It computes expected frequency values for the observations using empirical estimates within a theoretical framework, allowing the evaluation of the probabilities of the same observation under alternative, mutually exclusive and exhaustive hypotheses. Consequently, the interpretation of DNA evidence entails fewer risks of error than classical forensic evidence. However, clear regulations and a total separation between the institutions performing criminal investigation and those acting as expert witnesses are required. © 2012 Copyright Taylor and Francis Group, LLC. Source


Yakubovich S.,University of Porto
Complex Analysis and Operator Theory | Year: 2012

We deal with an index integral involving the product of the modified Bessel functions and associated Legendre functions. It was discovered by Ferrell (Nucl Instrum Methods Phys Res B 96:483-485, 1995) while comparing solutions of the Laplace equation in different coordinate systems in his study of the so-called surface plasmons in various condensed matter samples. This integral is quite interesting from the pure mathematical point of view and it is absent in famous reference books for series and integrals. We give a rigorous proof of this formula and discuss its particular cases. We also construct a convolution operator associated with this integral, which is related to the classical Kontorovich-Lebedev and Mehler-Fock transforms. Mapping properties and the norm estimates in weighted L p-spaces, 1 ≤ p ≤ 2 are investigated. An application to a class of convolution integral equations is considered. Necessary and sufficient conditions are found for the solvability of these equations in L 2. © 2010 Springer Basel AG. Source


Ferreira C.,University of Porto
Dynamical Systems | Year: 2012

A divergence-free vector field satisfies the star property if any divergence-free vector field in some C 1-neighbourhood has all singularities and all closed orbits hyperbolic. In this article, we prove that any divergence-free vector field defined on a Riemannian manifold and satisfying the star property is Anosov. It is also shown that a C 1- structurally stable divergence-free vector field is Anosov. Moreover, we prove that any divergence-free vector field can be C 1-approximated by an Anosov divergence-free vector field, or else by a divergence-free vector field exhibiting a heterodimensional cycle. © Copyright 2012 Taylor and Francis Group, LLC. Source


Massano J.,University College London | Massano J.,University of Porto | Bhatia K.P.,University College London
Cold Spring Harbor Perspectives in Medicine | Year: 2012

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. The condition causes a heavy burden both on those affected, as well as their families. Accurate diagnosis is critical and remains founded on clinical grounds as no specific diagnostic test is available so far. The clinical picture of PD is typical in many instances; however, features distinguishing it from other disorders should be thoroughly sought. Monogenic forms of PD also have some distinctive characteristics in many cases. This text is a roadmap to accurate diagnosis in PD, as it approaches clinical features, diagnostic methodology, and leading differential diagnoses. Therapeutic issues are also briefly discussed. © 2012 Cold Spring Harbor Laboratory Press; all rights reserved. Source


Layeghi A.,Shahid Beheshti University | Latifi H.,Shahid Beheshti University | Frazao O.,University of Porto
IEEE Photonics Technology Letters | Year: 2014

A novel magnetic field sensor using a nonadiabatic tapered optical fiber (NATOF) interacting with magnetic fluid (MF) nanoparticles is proposed and experimentally demonstrated. The NATOF sensitivity when is subjected to refractive index (RI) measurement in the small range from 1.3380 to 1.3510 was 1260.17 nm/RIU as a refractometer sensor. The NATOF is surrounded by a MF whose RI changes with external magnetic field, which MF is as a cladding of tapered fiber. The output interference spectrum is shifted by the change of the applied magnetic field intensity in the range up to 44 mT with a sensitivity of - 7.17 × 10-2nm/mT, used only 0.1% of the volume concentration of MF nanoparticles. This direct manipulation of light with magnetic fields provides an approach to develop future sensors relying on electromagnetic interactions. © 2014 IEEE. Source


Bessa M.,University of Beira Interior | Rocha J.,University of Porto | Torres M.J.,CMAT
Nonlinearity | Year: 2013

We prove that a Hamiltonian system H εC2 (M,ℝ) is globally hyperbolic if any of the following statements hold: H is robustly topologically stable; H is stably shadowable; H is stably expansive; and H has the stable weak specification property. Moreover, we prove that, for a C 2-generic Hamiltonian H, the union of the partially hyperbolic regular energy hypersurfaces and the closed elliptic orbits, forms a dense subset of M. As a consequence, any robustly transitive regular energy hypersurface of a C2-Hamiltonian is partially hyperbolic. Finally, we prove that stable weakly-shadowable regular energy hypersurfaces are partially hyperbolic. © 2013 IOP Publishing Ltd & London Mathematical Society. Source


Fortes H.M.,University of Porto
Revista Brasileira de Saude Materno Infantil | Year: 2010

This article outlines the history of the various interpretations of madness. This provides an insight into the history of mental health, from initial mythical explanations to more rational modern approaches, from the tolerance of difference to its characterization as disease. The idea of treatable and possibly curable mental illnesses led to the emergence of psychiatric hospitals, which became symbols of incarceration and exclusion from society. Recurrent reports of violence and human rights abuses have, since the 1970s, fuelled calls to reform this model of psychiatric care and led to greater emphasis on care in the community, civil rights, and respect for the subjective and uniquely personal nature of mental illness. As a result, Brazilian law now recognizes the rights and duties both of the mentally ill and of the doctors who care for them, thereby ensuring respect for full human dignity, including the patient ́s right not to be subjected against his or her will to compulsory treatment. Source


Goncalves V.,University of Porto
Journal of High Energy Physics | Year: 2015

Abstract: In this short note we use the flat space limit and the relation between the 4-pt correlation function of the bottom and top components of the stress tensor multiplet to constraint its stringy corrections at strong coupling in the planar limit. Then we use this four point function to compute corrections to the anomalous dimension of double trace operators of the Lagrangian density and to compute energy-energy correlators at strong coupling. © 2015, The Author(s). Source


Costa V.S.,INESC Porto | Rocha R.,INESC Porto | Damas L.,University of Porto
Theory and Practice of Logic Programming | Year: 2012

Yet Another Prolog (YAP) is a Prolog system originally developed in the mid-eighties and that has been under almost constant development since then. This paper presents the general structure and design of the YAP system, focusing on three important contributions to the Logic Programming community. First, it describes the main techniques used in YAP to achieve an efficient Prolog engine. Second, most Logic Programming systems have a rather limited indexing algorithm. YAP contributes to this area by providing a dynamic indexing mechanism, or just-in-time indexer. Third, a important contribution of the YAP system has been the integration of both or-parallelism and tabling in a single Logic Programming system. © Copyright Cambridge University Press 2011. Source


Costa G.,Paterson Institute for Cancer Research | Costa G.,University of Porto | Kouskoff V.,Paterson Institute for Cancer Research | Lacaud G.,Paterson Institute for Cancer Research
Trends in Immunology | Year: 2012

Hematopoietic stem cells (HSCs) are capable of self-renewal and differentiation into all blood cell types. During adult life, they reside in the bone marrow in a quiescent state. By contrast, in the growing embryo hematopoiesis is sequentially found in several developmental niches. This review provides an overview of the still controversial contribution of each of these embryonic sites to the final pool of adult HSCs and discusses new insights into the cellular origin and the molecular regulation implicated in the generation of blood progenitor cells. A better understanding of HSC development during ontogeny is essential to develop new strategies to amplify HSCs or to generate them from embryonic stem cells or by somatic cell reprogramming. © 2012 Elsevier Ltd. Source


Shamarova E.,University of Porto
Infinite Dimensional Analysis, Quantum Probability and Related Topics | Year: 2014

We consider a stochastic evolution equation in a 2-smooth Banach space with a densely and continuously embedded Hilbert subspace. We prove that under Hörmander's bracket condition, the image measure of the solution law under any finite-rank bounded linear operator is absolutely continuous with respect to the Lebesgue measure. To obtain this result, we apply methods of the Malliavin calculus. © 2014 World Scientific Publishing Company. Source


Papa J.P.,Sao Paulo State University | Falcao A.X.,University of Campinas | De Albuquerque V.H.C.,University of Fortaleza | Tavares J.M.R.S.,University of Porto
Pattern Recognition | Year: 2012

Today data acquisition technologies come up with large datasets with millions of samples for statistical analysis. This creates a tremendous challenge for pattern recognition techniques, which need to be more efficient without losing their effectiveness. We have tried to circumvent the problem by reducing it into the fast computation of an optimum-path forest (OPF) in a graph derived from the training samples. In this forest, each class may be represented by multiple trees rooted at some representative samples. The forest is a classifier that assigns to a new sample the label of its most strongly connected root. The methodology has been successfully used with different graph topologies and learning techniques. In this work, we have focused on one of the supervised approaches, which has offered considerable advantages over Support Vector Machines and Artificial Neural Networks to handle large datasets. We propose (i) a new algorithm that speeds up classification and (ii) a solution to reduce the training set size with negligible effects on the accuracy of classification, therefore further increasing its efficiency. Experimental results show the improvements with respect to our previous approach and advantages over other existing methods, which make the new method a valuable contribution for large dataset analysis. © 2011 Elsevier Ltd. All rights reserved. Source


Donaire M.,University of Porto
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We study the relation between the electromagnetic vacuum energy of a random medium and its optical response. The medium is modeled by a collection of molecular electric dipoles. First, we evaluate the contribution of statistical fluctuations to the average total vacuum energy, which is made out of the integration of the variations of the Lamb shift of the individual dipoles with respect to the coupling constant. While the Lamb shift is a function of the electrical susceptibility only, the vacuum energy is generally not. Second, we compare several approximations to the computation of the vacuum energy. In particular, we make clear why the bulk energy of an effective medium does not account for the total vacuum energy of a molecular dielectric. Consequently, the Lamb shift does not derive from the effective medium bulk energy except at leading order in the molecular density. The local field factors provide natural cutoffs for the spectrum of the total vacuum energy at a wavelength of the order of the correlation length. Third, we investigate to what extent the shift of the resonant frequency of the dielectric constant may be attributed to the binding energy of a dielectric. In particular, in the effective medium approximation we have found an equivalence between the energy of longitudinal long-wavelength modes and the Lorentz-Lorenz shift. Nonetheless, we conclude that the dielectric constant resonance shift is insufficient to estimate the binding energy of molecular clusters. © 2012 American Physical Society. Source


Brazhnyi V.A.,University of Porto | Malomed B.A.,Tel Aviv University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We construct families of symmetric, antisymmetric, and asymmetric solitary modes in one-dimensional bichromatic lattices with the second-harmonic- generating (χ (2 )) nonlinearity concentrated at a pair of sites placed at distance l. The lattice can be built as an array of optical waveguides. Solutions are obtained in an implicit analytical form, which is made explicit in the case of adjacent nonlinear sites, l=1. The stability is analyzed through the computation of eigenvalues for small perturbations and verified by direct simulations. In the cascading limit, which corresponds to a large mismatch q, the system becomes tantamount to the recently studied single-component lattice with two embedded sites carrying the cubic nonlinearity. The modes undergo qualitative changes with the variation of q. In particular, at l≥2, the symmetry-breaking bifurcation, which creates asymmetric states from symmetric ones, is supercritical and subcritical for small and large values of q, respectively, while the bifurcation is always supercritical at l=1. In the experiment, the corresponding change of the phase transition between the second and first kinds may be implemented by varying the mismatch, via the wavelength of the input beam. The existence threshold (minimum total power) for the symmetric modes vanishes exactly at q=0, which suggests a possibility to create the solitary mode using low-power beams. The stability of solution families also changes with q. © 2012 American Physical Society. Source


Casana R.,Federal University of Maranhao | Ferreira M.M.,Federal University of Maranhao | Da Hora E.,Federal University of Maranhao | Dos Santos C.,University of Porto
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We have found analytical self-dual solutions within the generalized Yang-Mills-Higgs model introduced in R. Casana et al. (2012) [1]. Such solutions are magnetic monopoles satisfying Bogomol'nyi-Prasad-Sommerfield (BPS) equations and usual finite energy boundary conditions. Moreover, the new solutions are classified in two different types according to their capability of recovering (or not) the usual 't Hooft-Polyakov monopole. Finally, we compare the profiles of the solutions we found with the standard ones, from which we comment about the main features exhibited by the new configurations. © 2013 Elsevier B.V. Source


Silva P.V.,University of Porto
RAIRO - Theoretical Informatics and Applications | Year: 2012

The fixed point submonoid of an endomorphism of a free product of a free monoid and cyclic groups is proved to be rational using automata-theoretic techniques. Maslakova's result on the computability of the fixed point subgroup of a free group automorphism is generalized to endomorphisms of free products of a free monoid and a free group which are automorphisms of the maximal subgroup. © 2011 EDP Sciences. Source


Santos X.,University of Porto | Cheylan M.,EPHE Paris
Biological Conservation | Year: 2013

Wildfires are common disturbances that have a major impact on ecosystems. Recent decades have seen an increase in fire frequency and extension due to the combined effects of climate change and land-use history. We studied the taxonomic and functional response of a reptile assemblage to repeated fires in southern France to understand shifts in dominant species and diversity, as well as the mechanisms that underlie responses according to functional traits of species. In the spring of 2010, we sampled reptiles in areas with three types of fire regime: unburned, burned once (2003) and burned 4-5 times (last fire in 2003) along a fire history of 51-years period. With this field sampling design, we examined the intermediate disturbance hypothesis and the habitat accommodation model of succession as methods to predict reptile responses to natural fire regimes. We also compared habitat structure at the study area between 1944 and 2006 to certify that repeated-fire regimes have modified the habitat for reptiles. The comparison of the habitat structure between both periods demonstrated that repeated-fire regimes modified the landscape from a homogeneous sparse forest to a contrasted heterogeneous mixture of scrubland and dense forest. We found a loss of reptile diversity after one and multiple fires, a result that contradicts the intermediate disturbance hypothesis. Reptile composition differed among the three fire regimes: there was a shift in dominant species and a reduction of beta diversity related to an increase in the number of fires. We also observed a functional response to repeated fires, with an increased frequency of insectivorous reptiles, which live in open areas, are specialists in their ecological niche, and have a short lifespan. These results suggest that reptile replacement according to fire regime accounts for a habitat accommodation model following particular traits of species. Our study indicated that areas subjected to repeated fires have a more strictly Mediterranean reptile assemblage than unburned areas, due to the ability of Mediterranean species to survive thermal environments in open (burned) areas. At a regional scale, changes in dominant species between unburned and repeatedly burned areas might be an argument for maintaining a patchwork of areas burned at variable intervals. However, the increase in fire frequency and extension suggests a future scenario of extinction for species negatively impacted by fire, such as the endangered Hermann's tortoise Testudo hermanni, for which the study area is home to one of the last native populations in the western Mediterranean. © 2013 Elsevier Ltd. Source


Pereira R.A.,University of Minho | Pereira M.F.R.,University of Porto