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Coimbra, Portugal

The University of Coimbra dɨ kuˈĩbɾɐ]) is a Portuguese public university in Coimbra, Portugal. Established in 1290, it is one of the oldest universities in continuous operation in the world, the oldest university of Portugal, and one of its largest higher education and research institutions. It is organized into eight different faculties according to a wide range of fields, granting academic bachelor's , master's and doctorate degrees in arts, engineerings, humanities, mathematics, natural science, social science, sports and technologies. It is a founding member of the Coimbra Group, a group of leading European research universities, whose inaugural meeting it hosted. The University of Coimbra has approximately 20,000 students, and hosts one of the largest communities of international students in Portugal, being the most cosmopolitan Portuguese university.On 22 June 2013, UNESCO added the university to its World Heritage List. Wikipedia.

Silveirinha M.G.,University of Pennsylvania | Silveirinha M.G.,University of Coimbra | Engheta N.,University of Pennsylvania
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The speed of integrated circuits is ultimately limited by the mobility of electrons or holes, which depend on the effective mass in a semiconductor. Here, building on an analogy with electromagnetic metamaterials and transformation optics, we describe a transport regime in a semiconductor superlattice characterized by extreme anisotropy of the effective mass and a low intrinsic resistance to movement-with zero effective mass-along some preferred direction of electron motion. We theoretically demonstrate that such a regime may permit an ultrafast, extremely strong electron response, and significantly high conductivity, which, notably, may be weakly dependent on the temperature at low temperatures. These ideas may pave the way for faster electronic devices and detectors and functional materials with a strong electrical response in the infrared regime. © 2012 American Physical Society.

Marinopoulos A.G.,University of Coimbra
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Hydrogen is a common impurity in oxides and is known to exhibit dual behavior: It can act either as a dopant or alternatively as a compensating impurity, depending on whether its transition (pinning) level, E(+/-), intersects the conduction band or lies deep in the energy gap. In the present work the incorporation of isolated hydrogen in 10.3 mol% yttria-stabilized zirconia was studied by ab initio calculations employing a semilocal exchange-correlation density functional and a hybrid-functional approach. Equilibrium sites and formation energies were determined for the different charged states of hydrogen and the role of intrinsic oxygen vacancies needed to stabilize the cubic phase of the oxide was particularly examined. Hydrogen was found to be an amphoteric impurity with the equilibrium charge-transition levels, E(q,q ′), lying deep inside the gap. Whereas, in its positively charged state, H +, hydrogen was found exclusively to form a dative-type bond with the lattice oxygens, the negatively charged and neutral states also adopt interstitial configurations provided by the empty cubes and the intrinsic structural vacancies of the anion sublattice. Two distinct paramagnetic configurations of hydrogen, H0, are predicted and both of them induce deep localized levels in the band gap. The first configuration is higher-energy compact atomlike with the hydrogen at the interstitial sites, whereas the second one is a bond-type deep donor configuration with the unpaired 4d electron localized predominantly at an undercoordinated Zr cation in the vicinity of the impurity. Minimum-energy paths and corresponding classical barriers of migration were also determined for H0 with the aid of the nudged elastic-band method providing insight on the feasibility of site interplay of H0 and interconversion among its interstitial and donor configurations. Oxygen vacancies and lattice relaxation were found to have a major effect on the energy profiles of the paths, the position of the transition states, and the magnitude of the migration barriers. © 2012 American Physical Society.

A new method of analyzing the internal shell morphology (including the complete brachidium of internal molds) of articulated brachiopod shells through the use of serial sections and digital three-dimensional reconstruction is presented. The method introduced is essential for the study of internal shell structures such as brachidia, or cardinalia, if computed tomography (CT) is not suitable or if a CT scanner is not available. A new species of Athyris from Givetian beds of Northwest Africa was selected to exemplify this method. To compare this species with figured serial sections in the literature, two-dimensional drawings of grinding surfaces are provided. Athyris africana n. sp. is only preserved as internal molds of articulated specimens. The new species is included in the evolutionary lineage of the group around Athyris concentrica. The faunal assemblage of A. africana n. sp. shows affinities to Western European and North American brachiopod faunas. Copyright © 2014, The Paleontological Society.

Odd-hydrogen (any hydrogen-oxygen radical containing but a single hydrogen atom) plays a key role in atmospheric chemistry, particularly in the chemistry of ozone. Notable is also the role played by water in atmospheric and environmental chemistry. Without attempting a broad coverage, the present survey focuses on the electronic structure and dynamics of odd-hydrogen and related water-mediated complexes with impact in atmospheric chemistry, with emphasis on systems studied at the author's laboratory. Review oriented, it contains some ab initio results for HO3 and insights on hydrogen bonding and the role of water in mediating HOx reactions with ozone that have not appeared elsewhere. While providing an account on the status of the title topical issues, it is hoped that it may encourage new research directions. © 2013 Wiley Periodicals, Inc. Odd-hydrogen, the family of hydrogen-oxygen radicals with a single H-atom, plays a crucial role in the atmosphere but this may be affected by the presence of water, another key atmospheric constituent. Despite their small sizes, an accurate description of their electronic, thermochemical and kinetic properties is challenging. While introducing a new accurate ab initio scheme for the study of odd-hydrogen with up to three O atoms, a systematic cost-effective approach is undertaken for larger species, naked or water-dressed. © 2013 Wiley Periodicals, Inc.

Fiolhais M.C.N.,University of Coimbra | Kleinert H.,Free University of Berlin
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The tricritical point, which separates first and second order phase transitions in three-dimensional superconductors, is studied in the four-dimensional Coleman-Weinberg model, and the similarities as well as the differences with respect to the three-dimensional result are exhibited. The position of the tricritical point in the Coleman-Weinberg model is derived and found to be in agreement with the Thomas-Fermi approximation in the three-dimensional Ginzburg-Landau theory. From this we deduce a special role of the tricritical point for the Standard Model Higgs sector in the scope of the latest experimental results, which suggests the unexpected relevance of tricritical behavior in the electroweak interactions. © 2013 Elsevier B.V. All rights reserved.

Machado P.,University of Coimbra
Acta Reumatologica Portuguesa | Year: 2012

Objective: To develop recommendations for the treat -ment of psoriatic arthritis (PsA) with biological therapies, endorsed by the Portuguese Society of Rheumatology. Methods: These treatment recommendations were formulated by Portuguese rheumatologists based on literature evidence and consensus opinion. A draft of the recommendations was first circulated to all Portuguese rheumatologists and their suggestions were incorporated in the draft. At a national meeting the recommendations were discussed and all attending rheumatologists voted on the level of agreement for each recommendation. A second draft was again circulated before publication. Results: A consensus was achieved regarding the initiation, assessment of response and switching biological therapies in patients with PsA. Specific recommendations were developed for several disease domains: peripheral arthritis, axial disease, enthesitis and dactylitis. Conclusion: These recommendations may be used for guidance in deciding which patients with PsA should be treated with biological therapies. They cover a rapidly evolving area of therapeutic intervention. As more evidence becomes available and more biological therapies are licensed, these recommendations will have to be updated.

Valente A.J.M.,University of Coimbra | Soderman O.,Lund University
Advances in Colloid and Interface Science | Year: 2014

Cyclodextrins are able to act as host molecules in supramolecular chemistry with applications ranging from pharmaceutics to detergency. Among guest molecules surfactants play an important role with both fundamental and practical applications. The formation of cyclodextrin/surfactant host-guest compounds leads to an increase in the critical micelle concentration and in the solubility of surfactants. The possibility of changing the balance between several intermolecular forces, and thus allowing the study of, e.g., dehydration and steric hindrance effects upon association, makes surfactants ideal guest molecules for fundamental studies. Therefore, these systems allow for obtaining a deep insight into the host-guest association mechanism. In this paper, we review the influence on the thermodynamic properties of CD-surfactant association by highlighting the effect of different surfactant architectures (single tail, double-tailed, gemini and bolaform), with special emphasis on cationic surfactants. This is complemented with an assessment of the most common analytical techniques used to follow the association process. The applied methods for computation of the association stoichiometry and stability constants are also reviewed and discussed; this is an important point since there are significant discrepancies and scattered data for similar systems in the literature. In general, the surfactant-cyclodextrin association is treated without reference to the kinetics of the process. However, there are several examples where the kinetics of the process can be investigated, in particular those where volumes of the CD cavity and surfactant (either the tail or in special cases the head group) are similar in magnitude. This will also be critically reviewed. © 2013 Elsevier B.V.

Pinho E Melo T.M.V.D.,University of Coimbra
Monatshefte fur Chemie | Year: 2011

Allenes have a unique structural feature characterized by having two cumulated double bonds. The inherent instability associated with these 1,2-dienes has been widely exploited for various synthetic purposes. Allenes have thus become important and versatile building blocks in organic chemistry. In this paper some illustrative examples of the chemistry of these building blocks in the synthesis of heterocyclic compounds are presented. © Springer-Verlag 2011.

Khan E.,University Paris - Sud | Margueron J.,University Paris - Sud | Vidana I.,University of Coimbra
Physical Review Letters | Year: 2012

Only one-third of the nucleons in Pb208 occupy the saturation density area. Consequently, nuclear observables related to the average properties of nuclei, such as masses or radii, constrain the equation of state not at the saturation density but rather around the so-called crossing density, localized close to the mean value of the density of nuclei: ρ0.11fm -3. This provides an explanation for the empirical fact that several equation of state quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy per unit of volume at the crossing density is constrained by the giant monopole resonance measurements in an isotopic chain rather than the incompressibility at saturation density. The giant monopole resonance measurements provide M=1100±70MeV (6% uncertainty), whose extrapolation gives K ∞=230±40MeV (17% uncertainty). © 2012 American Physical Society.

Pearson J.M.,University of Montreal | Chamel N.,Free University of Colombia | Goriely S.,Free University of Colombia | Ducoin C.,University of Coimbra | Ducoin C.,University Claude Bernard Lyon 1
Physical Review C - Nuclear Physics | Year: 2012

The equation of state and composition of the inner crust of neutron stars at zero temperature are calculated, using the T = 0 version of the temperature-dependent extended Thomas-Fermi plus Strutinsky integral method, for each of a family of three functionals based on Skyrme-type forces BSk19, BSk20, and BSk21, which are characterized by different degrees of symmetry-energy stiffness, and also for the SLy4 functional. We also solve the Tolman-Oppenheimer-Volkoff equations to calculate the distribution of mass within the inner crust. Qualitatively similar results are found for all four functionals, and in particular the number of protons per Wigner-Seitz cell is in all cases equal to 40 throughout the inner crust. © 2012 American Physical Society.

Callisto M.,Federal University of Minas Gerais | Graca M.A.S.,University of Coimbra
International Review of Hydrobiology | Year: 2013

Fine particulate organic matter (FPOM) is abundant in rivers, but the quality and quantity of FPOM in low-order streams have been investigated less frequently than the dynamics of coarse particulate organic matter (CPOM). We (i) assessed the quantity and quality of FPOM in several low-order mountain streams and the relationship between the quantity of FPOM and invertebrate abundance and (ii) evaluated the importance of microbial colonization to the growth of the FPOM consumer Chironomus riparius. FPOM availability ranged from 0.3 to 25.9g ash-free dry mass (AFDM)/m2 and was significantly higher during summer than during autumn. The density of invertebrates (10-13,500 individuals/m2) and FPOM were correlated (R=0.74). Chironomids were the most abundant organisms in the depositional zones where FPOM accumulated. Typically, FPOM nitrogen content was <1%, C:N ranged from 21 to 30%, and lignin ranged from 44 to 66%. Nitrogen content was generally lower during the autumn than summer. The ergosterol content of the FPOM was significantly lower (18μg/g AFDM) than that determined for leaves, from either water or soil. Chironomids fed with FPOM obtained from milled oak leaves, natural FPOM and sterile FPOM had 80, 45, and 0% emergence, respectively. We concluded that FPOM varies seasonally in quantity and quality in low-order streams and is a poor food resource relative to CPOM. Microbial colonization of FPOM could be important for the trophic ecology of collector species in low-order streams. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Objective: To develop recommendations for the treatment of axial spondyloarthritis with biological therapies, endorsed by the Portuguese Society of Rheumatology. Methods: These treatment recommendations were formulated by Portuguese rheumatologists based on literature evidence and consensus opinion. A draft of the recommendations and supporting evidence was first circulated to all Portuguese rheumatologists and their suggestions were incorporated in the draft. Secondly, at a national meeting the recommendations were presented, discussed and revised. Finally, the document resulting from this meeting was again circulated to all Portuguese rheumatologists, who anonymously voted online on the level of agreement with the recommendations. Results: A consensus was achieved regarding the initiation, assessment of response and switching biological therapies in patients with axial spondyloarthritis. Conclusion: These recommendations may be used for guidance in deciding which patients with axial spondyloarthritis should be treated with biological therapies. They cover a rapidly evolving area of therapeutic intervention. As more evidence becomes available and more biological therapies are licensed, these recommendations will have to be updated.

Soares Jr. D.,Federal University of Juiz de fora | Godinho L.,University of Coimbra
Computers and Structures | Year: 2012

In this work, a coupled BEM-FEM strategy for the analysis of fluid-solid interaction problems in the frequency domain is presented. Here, acoustic fluids are modelled by the BEM, whereas elastodynamic solids are discretized by the FEM. The fluid-solid coupling is carried out by an optimized iterative procedure. This coupling technique allows independent discretizations to be efficiently employed for both Boundary and Finite Element Methods, without any requirement of matching nodes at the fluid/solid common interfaces. Optimal relaxation parameters are computed, in order to ensure the convergence of the iterative procedure, properly dealing with the frequency domain wave propagation ill-posed problem. © 2012 Elsevier Ltd. All rights reserved.

Gomes L.C.,Venetian Institute of Molecular Medicine | Gomes L.C.,University of Coimbra | Scorrano L.,Venetian Institute of Molecular Medicine | Scorrano L.,University of Geneva
Autophagy | Year: 2011

Mitochondrial morphological and structural changes play a role in several cellular processes, including apoptosis. We recently reported that mitochondrial elongation is also critical to sustain cell viability during macroautophagy. During macroautophagy unopposed mitochondrial fusion leads to organelle elongation both in vitro and in vivo. Longer mitochondria are protected from being degraded and possess more cristae where activity of the ATP synthase is increased, optimizing ATP production in times of nutrient restriction. © 2011 Landes Bioscience.

Van Beveren E.,University of Coimbra | Rupp G.,University of Lisbon | Segovia J.,University of Salamanca
Physical Review Letters | Year: 2010

We argue that the X(4260) enhancement contains a wealth of information on 1- cc̄ spectroscopy. We discuss the shape of the X(4260) observed in the Okubo-Zweig-Iizuka-forbidden process e+e -→π+π-J/ψ, in particular, at and near vector charmonium resonances as well as open-charm threshold enhancements. The resulting very broad X(4260) structure does not seem to classify itself as a 1- cc̄ resonance, but its detailed shape allows us to identify new vector charmonium states with higher statistics than in open-charm decay. Here, we estimate the resonance parameters of the ψ(3D). Our approach also provides an explanation for the odd dip in the π+π -J/ψ data precisely at the ψ(4415) resonance. © 2010 The American Physical Society.

Schemm-Gregory M.,University of Coimbra
Rivista Italiana di Paleontologia e Stratigrafia | Year: 2011

A new species of Cyrtospirifer is described from the Middle to Upper Givetian of the Western Sahara (Northwest Africa). Cyrtospirifer tindoufensis n. sp. differs in its smaller number and coarser medial and flank plications and equibiconvex shell profile from the other Givetian species of Cyrtospirifer that all occur in Europe and to which the new species probably gives rise. The new implications of the proposed phylogeny of the earliest cyrtospiriferids and their origin from the Western Sahara are discussed. The palaeogeographic distribution of the cyrtospiriferids during the Givetian and Frasnian is shown and its migration ways are described considering the global transgression and regression cycles.

Santos A.,University of Amsterdam | Santos A.,University of Coimbra | Van Ree R.,University of Amsterdam
International Archives of Allergy and Immunology | Year: 2011

Profilins are ubiquitous proteins, present in all eukaryotic cells and identified as allergens in pollen, latex and plant foods. The highly conserved structure justifies the cross-reactive nature of IgE antibodies against plant profilins and their designation as pan-allergens. Primary sensitization to profilin seems to arise from pollen sensitization with later development of cross-reactive IgE antibodies against plant food (and possibly latex) profilins. The role of profilin in inducing allergic symptoms needs to be evaluated and raises important issues in allergy diagnosis due to cross-reactivity. IgE cross-reactivity among profilins is associated with multiple pollen sensitization and with various pollen-food syndromes. In respiratory allergy, sensitization to pollen to which the patient has virtually no environmental exposure has been identified as a manifestation of profilin sensitization. As a food allergen, profilin usually elicits mild reactions, such as oral allergy syndrome, is not modified by processing and is especially important in allergy to some fruits, such as melon, watermelon, banana, tomato, citrus fruit and persimmon. Purified natural and recombinant profilins for in vitro and in vivo allergy tests are helpful in the diagnostic work-up. Herein we review the current state of knowledge about the allergen profilin and its implications in the diagnosis and treatment of allergic diseases. We conclude that, although its role in triggering allergic symptoms is still controversial, profilin is undoubtedly a relevant allergen. As a pan-allergen, profilin is associated with multiple pollen sensitization and pollen-food-latex syndromes that the allergist has to be aware of in order to accomplish an accurate diagnosis and successful treatment of allergic diseases. Copyright © 2011 S. Karger AG.

A new genus and species of delthyridoid spirifer brachiopods, Lusitanispirifer lusitanensis, is established in the present study. The taxon is described from the Dornes Formation within the Dornes Syncline (Central Portugal) and based on the associated fauna a Siegenian to Emsian (middle to late Early Devonian) age is indicated. [Remark: Neritic Gedinnian strata represent the pelagic Lochkovian strata, neritic Siegenian strata represent approximately pelagic Pragian strata]. Due to its capillate micro-ornamentation the new genus is attributed to the northern Gondwana delthyridoid spirifer fauna, however, it also shows similarities to the genus Australospirifer from the Malvinokaffric Realm. The relationship of Lusitanispirifer with the other genera within the capillate family Filispiriferidae to which it has been assigned, and Australospirifer is discussed. Implications derived from this study are put forward regarding the palaeogeographic position of the Dornes Syncline area during the Early Devonian.

Robalo J.R.,University of Evora | Ramalho J.P.P.,University of Evora | Loura L.M.S.,University of Coimbra
Journal of Physical Chemistry B | Year: 2013

Nitrobenzoxadiazole (NBD)-labeled sterols are commonly used as fluorescent cholesterol analogues in membrane biophysics. However, some experimental reports have questioned their ability to emulate the behavior of cholesterol in phospholipid bilayers. For the purpose of a detailed clarification of this matter, atomistic molecular dynamics simulations of 1-palmitoyl-2-oleoyl-sn- glycero-3-phosphocholine (POPC) bilayers, containing either cholesterol or one of two fluorescent cholesterol analogues, 22-NBD-cholesterol or 25-NBD-cholesterol, were carried out. It is found that these sterol probes tend to adopt conformations in which their tail-labeled fluorophore is oriented toward the lipid/water interface, with a location similar to that observed in molecular dynamics simulations of other NBD probes. This implies that in these molecules the long sterol axis is no longer aligned with the membrane normal, and preferentially adopts orientations approximately parallel to the bilayer plane. In turn, these stretched conformations, together with NBD-POPC atomic interactions, lead to slowed-down lateral diffusion of both fluorescent sterols, compared to cholesterol. From computation of the deuterium order parameter and acyl chain tilts of POPC chains for varying POPC-sterol distance, it is observed that the local ordering effect of sterol is altered in both fluorescent derivatives. In agreement with reported experimental data, both fluorescent sterols are able to increase the order of POPC at 20 mol % concentration (as some molecules adopt an upright conformation, possibly related to formation of transbilayer aggregates), albeit to a smaller extent to that of cholesterol. Altogether, this study indicates that both 22- and 25-NBD-cholesterol are unable to mimic the most important features of cholesterol's behavior in lipid bilayers. © 2013 American Chemical Society.

Feio M.J.,University of Coimbra | Poquet J.M.,University of Granada
International Review of Hydrobiology | Year: 2011

In the last three decades, predictive models have been developed and applied worldwide for freshwater bioassessment. They consist of statistical tools that follow the concept of the Reference Condition Approach. Composed of several sequential steps, these assessment tools assess the deviation of given site assemblages from the expected biological condition in the absence of human disturbance. The most common approaches (RIVPACS/AUSRIVAS and BEAST) are based on a posteriori classifications that use the biological composition of a community to classify reference sites in groups, and afterwards to establish which environmental features best discriminate the biological groups obtained. Here, we review the predictive modeling procedures used in freshwaters bioassessment (RIVPACS/AUSRIVAS, BEAST, ANNA, Artificial Neural Networks, Bayesian Belief Networks and others) as well as the biological elements to which they have been applied. We also review the Spanish and Portuguese experiences in the development and application of predictive models, with particular attention to regional environmental conditions, the different modeling approaches, and the available implementation tools. Moreover, and considering the natural continuity within the Iberian Peninsula (which include several transnational rivers), we discuss the possibilities of the development of common predictive models across the region, considering all factors that may influence their performance, such as the target scale used to develop the models (regional or peninsular); common reference criteria; sampling and sorting procedures; the taxonomic resolution used in the models; the temporal variability (mainly in the Iberian Mediterranean region); and the biological elements to consider. We concluded that there are good technical conditions for the implementations of a common predictive approach throughout the Iberian Peninsula, which should allow a global biological assessment of streams with different biological elements and seasons that could be used by water managers in the context of the Water Framework Directive. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pena R.C.,University of Sao Paulo | Bertotti M.,University of Sao Paulo | Brett C.M.A.,University of Coimbra
Electroanalysis | Year: 2011

A novel amperometric sensor based on the incorporation of multiwalled carbon nanotubes (MWCNT) into a poly(methylene blue) (PMB) film immobilized on carbon composite electrodes is described. Cyclic voltammetry indicated that at a surface covered by a MWCNT/PMB layer the cathodic reduction of hydrogen peroxide is facilitated and occurs already at 0.0V versus SCE. The effect of the order of deposition of PMB and MWCNT, as well as its loading, on electrochemical behaviour was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The influence of the various immobilised platforms on the electrocatalytic performance towards hydrogen peroxide was also examined. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Milne B.F.,University of Coimbra
Dalton Transactions | Year: 2014

The optical absorption spectra and quadratic hyperpolarisabilities of 1,3,5,7-tetra-substituted cubane derivatives containing group 15 atoms have been investigated computationally using Coulomb-attenuated time-dependent density functional theory. The non-linear optical responses of these octupolar systems are shown to be highly dependent on the group 15 heteroatom with the bismuth-containing derivative displaying large enhancement of its quadratic hyperpolarisability, β, relative to 1,3,5,7-tetraazacubane in vacuo and with acetonitrile solvation. Spin-orbit coupling and scalar relativistic corrections play an important part in determining the value of β for compounds containing As, Sb and Bi. This journal is © the Partner Organisations 2014.

Teixeira V.,University of Coimbra
Dermatology online journal | Year: 2012

Verruciform xanthoma (VX) is an uncommon benign condition of unknown etiology, which frequently affects the oral mucosa in adults. Other less common locations include the anogenital region and the skin. VX typically presents as an asymptomatic plaque showing a verrucous appearance. Histological examination is essential for the diagnosis and shows verrucous hyperplasia of the epidermis and xanthoma cells limited to the dermal papillae. We present herein two cases of VX and discuss the histopathological findings and possible correlation with a postulated etio-pathogenesis.

Marinopoulos A.G.,University of Coimbra
Journal of Physics Condensed Matter | Year: 2014

Hydrogen is a common impurity in oxides and has been studied extensively by first-principles electronic structure methods. From the calculated charge-transition levels and their position with respect to the conduction-band edge, definitive conclusions can be drawn concerning the electrical activity of hydrogen either as an isolated defect or as part of a defect complex with intrinsic defects of the host lattice. For those oxides such as yttria-stabilized zirconia, which in many cases are used in polycrystalline or nanocrystalline forms, the interaction of hydrogen with grain boundaries needs to be better understood. Using both density-functional theory in the generalized-gradient approximation and a hybrid-functional approach, the present study reports on the types of isolated hydrogen configuration that can be stabilized at the core of the Σ5(310) tilt grain boundary, an interface whose atomistic structure has been determined in good detail by Z-contrast transmission electron microscopy. Initially, the present calculations elucidated the major relaxation modes that lead to low-energy structures for this boundary. Hydrogen exhibited dual behavior by binding to oxygen ions in bond-type OH- configurations in its positively charged state, H +, whereas the negative H- species occupied preferably interstitial positions in the available empty space of the grain-boundary core regions. The neutral paramagnetic state, H0, detected recently in muonium-based spectroscopic studies, was found to be stable in two different configurations: a deep-donor bond-type and a higher-energy quasiatomic interstitial. These configurations are characterized in terms of the trapping character of their excess electron, the spatial localization of the spin density and the resulting hyperfine parameters. © 2014 IOP Publishing Ltd.

Andrade A.I.A.S.S.,University of Coimbra | Stigter T.Y.,University of Lisbon
Science of the Total Environment | Year: 2013

In this study multivariate and geostatistical methods are jointly applied to model the spatial and temporal distribution of arsenic (As) concentrations in shallow groundwater as a function of physicochemical, hydrogeological and land use parameters, as well as to assess the related uncertainty. The study site is located in the Mondego River alluvial body in Central Portugal, where maize, rice and some vegetable crops dominate. In a first analysis scatter plots are used, followed by the application of principal component analysis to two different data matrices, of 112 and 200 samples, with the aim of detecting associations between As levels and other quantitative parameters. In the following phase explanatory models of As are created through factorial regression based on correspondence analysis, integrating both quantitative and qualitative parameters. Finally, these are combined with indicator-geostatistical techniques to create maps indicating the predicted probability of As concentrations in groundwater exceeding the current global drinking water guideline of 10 μg/l. These maps further allow assessing the uncertainty and representativeness of the monitoring network. A clear effect of the redox state on the presence of As is observed, and together with significant correlations with dissolved oxygen, nitrate, sulfate, iron, manganese and alkalinity, points towards the reductive dissolution of Fe (hydr)oxides as the essential mechanism of As release. The association of high As values with rice crop, known to promote reduced environments due to ponding, further corroborates this hypothesis. An additional source of As from fertilizers cannot be excluded, as the correlation with As is higher where rice is associated with vegetables, normally associated with higher fertilization rates. The best explanatory model of As occurrence integrates the parameters season, crop type, well and water depth, nitrate and Eh, though a model without the last two parameters also gives quite satisfactory results. © 2013 Elsevier B.V.

Souza-Alonso P.,University of Vigo | Gonzalez L.,University of Vigo | Cavaleiro C.,University of Coimbra
Journal of Chemical Ecology | Year: 2014

Acacia dealbata Link is a widespread invader in Mediterranean type ecosystems, and traits promoting its invasiveness are currently under investigation. Due to the dense atmosphere below its canopy, we hypothesized that volatile organic compounds (VOCs) released from flowers, leaves, litter, or a mixture of treatments exert inhibitory effects on the natives Trifolium subterraneum, Lolium multiflorum, Medicago sativa, and also on its own seeds. We reported that VOCs from flowers significantly reduced germination in L. multiflorum and A. dealbata; moreover, root length, stem length, aboveground and belowground biomass were also reduced in all species studied. Volatile organic compounds from flowers and the mixture also increased significantly malondialdehyde content in T. subterraneum and L. multiflorum. The effects of VOCs on antioxidant enzymatic activities were species dependent. Flowers enhanced peroxidase but decreased superoxide dismutase activity in T. subterraneum. In contrast, VOCs released from leaves increased the activity of superoxide dismutase in L. multiflorum. GC/MS analyses revealed 27 VOCs in the volatile fraction from flowers, 12 of which were exclusive to this fraction. Within them, heptadecadiene, n-nonadecane, ntricosane, and octadecene represent 62% of the fraction. We present evidence that the VOCs released from A. dealbata flowers strongly inhibited germination and seedling growth of selected species, and mainly on its own seedlings. As far as we know, this is the first evidence of phytotoxicity induced by VOCs in invasive species belonging to the Acacia genus. © Springer Science+Business Media New York 2014.

Oueslati I.,University of Coimbra
Materials Today: Proceedings | Year: 2015

Two calix[4]azacrowns 1 and 2 show luminescence upon aggregation or in the solid state described as aggregation-induced emission (AIE). The shift of the self-assembly of 1 from nanoporous to helical framework in the crystal is associated with a remarkable blue-shift and 33-fold increase in the fluorescence intensity. The blue light emission is highly efficient (ΦF ~ 60%) and is switched to thermally-activated yellow emission as a stimuli-responsive behavior of the helical assembly. In solution, 2 aggregate into luminescent nanoparticles producing violet emission. Drop-casting of the aggregates gives highly ordered films showing selective emission response to volatile tetrahydrofuran. © 2015 Elsevier Ltd.

Baldo M.,University of Catania | Ducoin C.,University of Coimbra
Physical Review C - Nuclear Physics | Year: 2011

The thermal evolution of neutron stars depends on the elementary excitations affecting the stellar matter. In particular, the low-energy excitations, whose energy is proportional to the transferred momentum, can play a major role in the emission and propagation of neutrinos. In this paper, we focus on the density modes associated with the proton component in the homogeneous matter of the outer core of neutron stars (at density between one and three times the nuclear saturation density, where the baryonic constituents are expected to be neutrons and protons). In this region, it is predicted that the protons are superconducting. We study the respective roles of the proton pairing and Coulomb interaction in determining the properties of the modes associated with the proton component. This study is performed in the framework of the random phase approximation, generalized in order to describe the response of a superfluid system. The formalism we use ensures that the generalized Ward's identities are satisfied. An important conclusion of this work is the presence of a pseudo-Goldstone mode associated with the superconducting protons in neutron-star matter. Indeed, the Goldstone mode, which characterizes a pure superfluid, is suppressed in usual superconductors because of the long-range Coulomb interaction, which allows a plasmon mode. However, for the proton component of stellar matter, the Coulomb field is screened by the electrons and a pseudo-Goldstone mode occurs, with a velocity increased by the Coulomb interaction. © 2011 American Physical Society.

Duarte B.,University of Lisbon | Santos D.,University of Lisbon | Marques J.C.,University of Coimbra | Cacador I.,University of Lisbon
Plant Physiology and Biochemistry | Year: 2013

Halimione portulacoides and Sarcocornia fruticosa commonly exhibit a reddish coloration especially in high evaporation periods, due to betacyanin production in response to stress. Although sharing the same area in salt marshes, they present different strategies to overcome salinity stress. While S.fruticosa present a dilution strategy, increasing succulence, H.portulacoides appears to have developed an ionic compartmentalization strategy. Nevertheless, there's still a decrease in the photosynthetic activity in different extents. While in S.fruticosa, the impairment of photosynthetic activity is due to a decrease in the flow from the electron transport chain to the quinone pool; in H.portulacoides the process is affected far more early, with high amounts of energy dissipated at the PSII light harvesting centers. This photosynthetic impairment leads to energy accumulation and consequently to the production of reactive oxygen species (ROS). SOD was particularly active in stressed individuals, although this increment is rather more significant in S.fruticosa than in H.portulacoides suggesting that H.portulacoides may have a maximum salt concentration at which can sustain cellular balance between ROS production and scavenging. These different ecophysiological responses have great importance while evaluating the impacts climate change driven increase of sediment salinity on halophyte physiology and on the marsh community and ecosystem services. © 2013 Elsevier Masson SAS.

Viegas D.X.,University of Coimbra | Simeoni A.,Worcester Polytechnic Institute
Fire Technology | Year: 2011

A critical review of the mechanisms that are described in the literature to explain the onset and development of eruption or blow up in forest fires is presented, given their great relevance for fire safety, particularly in canyons. The various processes described in the literature that are considered as potential causes of fire eruption are discussed. Some of them seem more likely to cause the phenomenon and the others seem to have a complementary role in some conditions. The current review highlights that more research is required to create a classification of Fire Eruption types and to allow the development of specific Fire Safety procedures for fire fighters to minimize accidents. © 2010 Springer Science+Business Media, LLC.

Heleno R.H.,University of Coimbra | Vargas P.,Real Jardin Botanico de Madrid CSIC RJB
Global Ecology and Biogeography | Year: 2015

Aim: Four long-distance dispersal (LDD) modes have generally been considered to play central roles in the colonization of islands by plants: anemochory (dispersal by wind), thalassochory (dispersal by oceanic currents), endozoochory (internal dispersal by animals) and epizoochory (external dispersal by animals). However, seeds can also be transported by vectors different from those to which they are best suited (non-standard dispersal), meaning that the actual vector of colonization cannot be inferred based on diaspore traits alone. We propose an alternative approach to explore the relative contribution of LDD syndromes to island colonization. Location: Europe and the Azores. Methods: We scored the presence of syndromes relevant for LDD in the native flora of Europe (c. 10,000 species) and the Azores (148 species). We then contrasted the importance of each syndrome in the recipient flora (Azores) and the source floras (Europe and mainland Portugal) to estimate which, if any, syndrome was particularly successful for overseas colonization. We further investigated whether particular LDD syndromes increased plant distribution within the Azores archipelago. Results: Most native species in Europe (63%), mainland Portugal (67%) and the Azores (63%) produce unspecialized diaspores. Only species adapted to sea dispersal were overrepresented in the Azores, while those adapted to wind dispersal were underrepresented. The presence of LDD syndromes did not significantly improve the distribution of plant species across the archipelago, except for the moderate advantage of endozoochorous diaspores. Differences in the importance of LDD syndromes across plant families at least partially explain the floristic disharmony of the Azorean flora. Main conclusions: Only thalassochory appeared to have significantly favoured the colonization of the Azores. The high proportion of unspecialized diaspores, the unexceptional representation of most specialized LDD syndromes and the dissociation between syndromes and inter-island plant distribution in the Azores suggest that non-standard events are more common than previously believed in the colonization of islands by plants. © 2014 John Wiley & Sons Ltd.

Prasath V.,University of Coimbra
International Journal of Applied Mathematics and Computer Science | Year: 2011

We propose an edge adaptive digital image denoising and restoration scheme based on space dependent regularization. Traditional gradient based schemes use an edge map computed from gradients alone to drive the regularization. This may lead to the oversmoothing of the input image, and noise along edges can be amplified. To avoid these drawbacks, we make use of a multiscale descriptor given by a contextual edge detector obtained from local variances. Using a smooth transition from the computed edges, the proposed scheme removes noise in flat regions and preserves edges without oscillations. By incorporating a space dependent adaptive regularization parameter, image smoothing is driven along probable edges and not across them. The well-posedness of the corresponding minimization problem is proved in the space of functions of bounded variation. The corresponding gradient descent scheme is implemented and further numerical results illustrate the advantages of using the adaptive parameter in the regularization scheme. Compared with similar edge preserving regularization schemes, the proposed adaptive weight based scheme provides a better multiscale edge map, which in turn produces better restoration.

Moreira P.I.,University of Coimbra
European Neurological Review | Year: 2010

Oxidative stress and mitochondrial dysfunction are important issues in understanding the pathogenesis of Alzheimer's disease (AD). Mitochondria are pivotal in controlling cell life and death not only by producing adenosine triphosphate and sequestering calcium but also by generating reactive oxidative species and serving as repositories for proteins that regulate the intrinsic apoptotic pathway. Perturbations in the physiological function of mitochondria inevitably disturb cell function, sensitise cells to neurotoxic insults and may initiate cell death, all significant phenomena in the pathogenesis of AD. This article discusses evidence supporting the notion that mitochondrial dysfunction and oxidative stress are intimately involved in AD pathophysiology. © TOUCH BRIEFINGS 2009.

Radzisheuskaya A.,University of Cambridge | Le Bin Chia G.,University of Cambridge | Dos Santos R.L.,University of Cambridge | Dos Santos R.L.,University of Coimbra | And 5 more authors.
Nature Cell Biology | Year: 2013

Oct4 is considered a master transcription factor for pluripotent cell self-renewal, but its biology remains poorly understood. Here, we investigated the role of Oct4 using the process of induced pluripotency. We found that a defined embryonic stem cell (ESC) level of Oct4 is required for pluripotency entry. However, once pluripotency is established, the Oct4 level can be decreased up to sevenfold without loss of self-renewal. Unexpectedly, cells constitutively expressing Oct4 at an ESC level robustly differentiated into all embryonic lineages and germline. In contrast, cells with low Oct4 levels were deficient in differentiation, exhibiting expression of naive pluripotency genes in the absence of pluripotency culture requisites. The restoration of Oct4 expression to an ESC level rescued the ability of these to restrict naive pluripotent gene expression and to differentiate. In conclusion, a defined Oct4 level controls the establishment of naive pluripotency as well as commitment to all embryonic lineages. © 2013 Macmillan Publishers Limited. All rights reserved.

Quaresma P.,University of Coimbra
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Thousands of Geometric problems for geometric Theorem Provers (TGTP) is a Web-based library of problems in geometry. The principal motivation in building TGTP is to create an appropriate context for testing and evaluating geometric automated theorem proving systems (GATP). For that purpose TGTP provides a centralised common library of geometric problems with an already significant size but aiming to became large enough to ensure meaningful system evaluations and comparisons. TGTP provides also a workbench were it is possible to test any given geometric conjecture. TGTP is independent of any given GATP. For each problem the code for each GATP (whenever available) is kept in the library. A common format for geometric conjectures, extending the i2g format, is being developed. This common format, plus a list of converters, one for each GATP, will allow to test all the GATPs with all the problems in the library. TGTP is well structured, documented and with a powerful querying mechanism, allowing an easy access to the information. All information in the library, and also the supporting formats and tools are freely available. TGTP aims, in a similar spirit of TPTP and other libraries, to provide the automated reasoning in geometry community with a comprehensive and easily accessible library of GATP test problems. The development of TGTP problem library is an ongoing project. © 2011 Springer-Verlag.

Antunes do Carmo J.S.,University of Coimbra
Advances in Engineering Software | Year: 2010

In shallow water conditions, current and wave propagation cannot be simulated separately and then superposed linearly. In these conditions, in fact, the fluid dynamics of the wave and current motions and, as a consequence, the responses of the movable bed are significantly different from those expected for a linear superposition of a current with a sinusoidal wave. Thus, wave nonlinearity and the wave-current interaction effects become important factors that need to be considered. A model should be also able to reproduce the fluid dynamics under shallow water conditions over significant slopes and time-bed-level changes. This paper presents a 1DH mathematical formulation of a hydrodynamic model and its numerical solution. The model is able to reproduce all characteristic shallow water phenomena, including: (i) wave-wave and wave-current interaction effects; (ii) important ratios between the current and wave velocities; (iii) significant bed slopes and sudden time-bed-level changes, and (iv) friction stresses at the bottom and at the free surface. Different orders of mathematical approximations and appropriate application examples are also presented. © 2009 Elsevier Ltd. All rights reserved.

This paper aims to answer the following question that arouse during fieldwork: why some people with hanseniasis and treated with multidrug therapy (MDT) feel healed and others don’t? From a multi-sited ethnography in the transnational (global program for hanseniasis from the World Health Organization), national (Portuguese and Brazilian moral landscapes and biopolitical paradigms), local (clinical practice and incorporated experience of people with hanseniasis in both countries) scales, it examines how the uncertainty documented in the clinic and the gap experienced by some people between the bacteriological cure and the feeling of being healed, opens for a controversy on the main postulates that sustain the use of MDT as an autonomous entity and diffract the contemporaneous framing of hanseniasis and the institutional responses to it. Finally, it concludes on the need for including an incorporated choice that might widen hanseniasis’ ontological politics and rebuild a new participatory paradigm of care. © 2016, All rights reserved.

Bernardo F.P.,University of Coimbra
Computers and Chemical Engineering | Year: 2016

Model analysis and optimization under uncertainty needs efficient n-dimensional integration techniques, particularly when n (number of uncertain parameters) is large and the numerical model heavy. New thinned cubature formulae, recently tested by us and still practically unknown in engineering areas, have significantly changed the status of cubatures vs. quasi-Monte Carlo integration, for moderately high values of n. This paper presents these new cubatures (based on orthogonal arrays) from a practitioner's point of view and illustrates their remarkable efficiency in solving process systems engineering problems, namely those under the classes of simulation under uncertainty, variance-based global sensitivity analysis and optimization under uncertainty. Thinned cubatures allow efficient solution of these problems up to dimension n around 20, producing very reasonable estimates with only a few hundred or thousand of integration points. Three practical applications are provided: (i) analysis of a large-scale mass transfer model, (ii) optimal planning of a production network, (iii) preliminary design of a batch process under high levels of uncertainty and from different sources. © 2016 Elsevier Ltd.

Viegas D.,University of Coimbra
Fire Safety Science | Year: 2011

Forest fires are one of the major threats to natural and human built environments and have shown a tendency to increase in recent years. They are the result of several combined natural and social factors making their study and management particularly difficult and requiring the intervention of several scientific fields. One of the major issues of forest fires is associated with the combustion and propagation processes. An overview of physical processes linked to fire propagation, especially under extreme conditions will be presented. Emphasis will be given to fire safety and to the protection of human life during fire spread. Case studies and the results of the research program carried out by the author are presented to illustrate some of the topics dealt with in the presentation. © 2011 INTERNATIONAL ASSOCIATION FOR FIRE SAFETY SCIENCE.

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.

Montesinos D.,CIDE CSIC UV GV | Montesinos D.,University of Coimbra | Villar-Salvador P.,University of Alcala | Garcia-Fayos P.,CIDE CSIC UV GV | Verdu M.,CIDE CSIC UV GV
New Phytologist | Year: 2012

• Differences in reproductive investment can trigger asymmetric, context-dependent, functional strategies between genders in dioecious species. However, little is known about the gender responses of dioecious species to nutrient availability. • We experimentally fertirrigated a set of male and female Juniperus thurifera trees monthly for 2yr. Water potential, photosynthesis rate and stomatal conductance were measured monthly for 2yr, while shoot nitrogen (N) concentration, carbon isotopic composition (δ 13C), branch growth, trunk radial growth and reproductive investment per branch were measured yearly. • Control males had lower gas exchange rates and radial growth but greater reproductive investment and higher water use efficiency (WUE; as inferred from more positive δ 13C values) than females. Fertirrigation did not affect water potential or WUE but genders responded differently to increased nutrient availability. The two genders similarly increased shoot N concentration when fertilized. The increase in shoot N was associated with increased photosynthesis in males but not in females, which presented consistently high photosynthetic rates across treatments. • Our results suggest that genders invest N surplus in different functions, with females presenting a long-term strategy by increasing N storage to compensate for massive reproductive masting events, while males seem to be more reactive to current nutrient availability, promoting gas-exchange capacity. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Cruz M.G.,CSIRO | Butler B.W.,Rocky Research | Viegas D.X.,University of Coimbra | Palheiro P.,Autoridade Florestal Nacional
Combustion and Flame | Year: 2011

The present study is aimed at quantifying the flame radiosity vertical profile and gas temperature in moderate to high intensity spreading fires in shrubland fuels. We report on the results from 11 experimental fires conducted over a range of fire rate of spread and frontal fire intensity varying respectively between 0.04-0.35ms-1 and 468-14,973kWm-1. Flame radiosity, or radiant emissive power, and gas temperatures were measured with narrow angle radiometers and fine wire thermocouples located at three different heights in the flames, 0.6, 1.1 and 1.6m above ground. Measured peak radiosity within the visual flame region (reaction zone and free flame) varied between 41 and 176kWm-2. Measurements within the intermittent flame region above the visually estimated average flame height varied between 10 and 30kWm-2. The flame vertical radiometric profile was characterized by a uniform area within the reaction zone and lower free flame, and a decrease in radiosity with height as the measurements approach the flame tip. © 2011.

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.

Lobo J.,University of Coimbra
International Journal of Online Engineering | Year: 2012

In this interactive demonstration we show the usage of a remote reconfigurable logic laboratory for digital design students, presented in a full paper submitted to the conference. A very simple web based approach is used to enable the remote access to a FPGA (Field Programmable Gate Array) development and educational board. The board switches and keys are virtualised with an online web form, and a webcam is used to provide feedback to the user.

Abreu J.M.,University of Lisbon | Camara Pereira F.,University of Coimbra | Ferrao P.,University of Lisbon
Energy and Buildings | Year: 2012

Recognizing habitual behavior and providing feedback in context are key to empower individuals to take control over residential electricity consumption. Yet, it is a challenge to change habitual behavior, embedded in everyday routines. This paper intends to discover whether habitual behavior can be identified by pattern recognition techniques. The data source is an experiment similar to a utility led advanced metering infrastructure implementation. The analysis discovers: (1) persistent daily routines and (2) patterns of consumption or baselines typical of specific weather and daily conditions. Approximately 80% of household electricity use can be explained within these two patterns, with several applicable "profiles" for this population, including: unoccupied baseline, hot working days, temperate working days, cold working days, and cold weekend days. The proposed methodology demonstrates that it is possible to use pattern recognition methodologies to recognize habitual electricity consumption behavior given the intrinsic characteristics of the family. This approach could be useful to improve small scale forecast, and as a mechanism to enable the provision of tailor-made information to the families. © 2012 Elsevier B.V. All rights reserved.

Silva T.,University of Aveiro | Vicente R.,University of Aveiro | Soares N.,University of Coimbra | Ferreira V.,University of Aveiro
Energy and Buildings | Year: 2012

Presently the essential research trend for sustainable buildings is the use of renewable energy sources and the development of new techniques of energy storage. Phase change materials (PCMs) may store latent heat energy in addition to the typical sensible energy capacity of current building materials, allowing to store significantly more energy during the phase change process (solid to liquid and vice versa). The incorporation of PCMs into building envelope solutions takes advantage of solar energy, contributing to the overall reduction of energy consumption associated to use of the air conditioning systems. This paper presents and discusses research developed in two main components: experimental testing and numerical simulation of a building component with PCM incorporation. The main goal of the experimental testing carried out was to evaluate the effect of the incorporation of PCM macro encapsulated into a typical Portuguese clay brick masonry enclosure wall. It is evaluated the influence of the phase change process of the PCM over the attenuation and time delay of the temperature fluctuations for indoor spaces. The experimental results allowed the calibration and validation of the numerical model, enabling to carry out parametric studies with different PCMs quantity analysing consequent temperature damping and time delay. © 2012 Elsevier B.V. All rights reserved.

Ferreira A.J.L.,University of Coimbra
Proceedings of the Institution of Civil Engineers: Municipal Engineer | Year: 2012

This briefing describes recent developments in pavement energy harvest systems and a research project, currently being undertaken by the University of Coimbra in Portugal, in which the aim is to test different systems for harvesting energy from pavements.

Goncalo Oliveira H.,University of Coimbra
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

There are several lexical resources available for the computational processing of Portuguese, organised differently and created by different people with different approaches and limitations. This paper presents the first experiments towards the exploitation of seven of those resources in the automatic creation of a large wordnet, where numerical scores are assigned to the inclusion of words in synsets and to the connection of synsets by semantic relations. Experiments confirm that a large wordnet can indeed be created and, to some extent, computed scores can be used as a confidence measure, which will enable the users to select only a portion of the resource, depending on the needs of their application on quantity and quality of lexical-semantic knowledge. © Springer International Publishing Switzerland 2016.

Chebykin A.V.,National Research University of Information Technologies | Orlov A.A.,National Research University of Information Technologies | Vozianova A.V.,National Research University of Information Technologies | Maslovski S.I.,University of Coimbra | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study layered metal-dielectric structures, which can be considered as a simple example of nanostructured metamaterials. We analyze the dispersion properties of such structures and demonstrate that they show strong optical nonlocality due to excitation of surface plasmon polaritons. We derive a model of a nonlocal effective medium for describing the effects of strong spatial dispersion in the multilayered metal-dielectric metamaterials. We obtain analytical expressions for the components of the effective permittivity tensor which depend on the wave vector and reveal that spatial dispersion effects exist in both directions across and along the layers. © 2011 American Physical Society.

Neiva A.M.R.,University of Coimbra | Ramos J.M.F.,National Laboratory of Energy and Geology
European Journal of Mineralogy | Year: 2010

Granitic amblygonite-subtype and lepidolite-subtype, aplite-pegmatite sills intruded a biotite>muscovite granite (G1). Two other biotite>muscovite granites (G2 and G3) and a muscovite>biotite granite (G4) crop out in the area. Variation diagrams for major and trace elements of the Variscan rocks show fractionation trends for a) G1 and G4; b) G2, G3 and aplite-pegmatite sills. The two series are confirmed by the two trends defined by major elements of primary muscovite. The sills also contain Li-bearing muscovite, which has higher Mn, Li, F and paragonite contents and lower Al VI content than primary muscovite from G2, G3 and sills. All sills have pure albite and P 2O 5 content of K-feldspar and plagioclase increases in the series G2, G3 and sills. Beryl occurs in all sills, but lepidolite and a nearly pure petalite only occur in lepidolite-subtype sills, which are the most evolved sills. Primary topaz and amblygonite have a similar composition in all sills. Aplite-pegmatite sills contain cassiterite, which shows sequences of alternating darker and lighter zones. The former are richer in (Nb + Ta + Fe + Mn) than the latter. Manganocolumbite is common in all sills, but ferrocolumbite only appears in amblygonite-subtype sills and manganotantalite in lepidolite-subtype sills. The sills richest in Li contain reversely-zoned crystals with a homogeneous microlite core and a heterogeneous uranmicrolite rim. Least squares analysis of major elements shows that granite G3 and amblygonite-subtype and lepidolite-subtype aplite-pegmatite sills can be derived from granite G2 magma by fractional crystallization of quartz, plagioclase, K-feldspar, biotite and ilmenite. Modelling of trace elements shows good results for Sr, but magmatic fluids controlled the Rb and Ba contents of the aplite-pegmatite sills and probably also their Li, F, Sn and Ta contents and crystallization of lepidolite, cassiterite and Nb-Ta oxide mineral assemblage. Schorl from the lepidolitesubtype sills that cut granite Gl has higher Mg/(Mg + Fe) than schorl from metasomatised granite at sill walls and resulted from the mixing of magmatic fluids carrying B and some Fe with a meteoric fluid that has interacted with the host granite G1 and carried Fe and Mg. Schorl and dravite, respectively from metasomatised granite and micaschist at sill walls, were also formed from the mixing processes. © 2010 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

Seena S.,University of Coimbra | Seena S.,University of Minho | Monroy S.,University of the Basque Country
Fungal Ecology | Year: 2016

Aquatic hyphomycetes play a key role in leaf litter decomposition and are mediators of organic matter turnover in streams. Molecular studies have shown that some aquatic fungi are also plant endophytes, however, more evidence is needed to evaluate their multiple ecological abilities. To date, little information is available on fungal lineages that might have undergone convergent evolution to adapt to multiple ecological modes. We examined the phylogenetic relationships and evolutionary divergences of aquatic hyphomycetes, endophytic aquatic hyphomycetes and other fungal endophytes of riparian/terrestrial plants by analyzing ITS1-5.8S-ITS2 sequences retrieved from the National Center for Biotechnology Information (NCBI). Sequences with close phylogenetic affinity to aquatic fungi can occur as endophytes of terrestrial plants or in soil far from streams. To fully understand the ecological impact of aquatic hyphomycetes, we need to document and interpret their niches more broadly. © 2015 Elsevier Ltd and The British Mycological Society.

Coito S.,University of Lisbon | Rupp G.,University of Lisbon | van Beveren E.,University of Coimbra
European Physical Journal C | Year: 2011

The nature of the X(3872) enhancement is analyzed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular JPC=1++ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo-Zweig-Iizuka-forbidden ρ0J/ψ and ωJ/ψ channels are coupled as well, but effectively smeared out by using complex ρ0 and ω masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A very delicate interplay between the D0 D*0, ρ0 J/ψ, and ωJ/ψ channels is observed. The data clearly suggest that the X(3872) is a very narrow axial-vector cc̄ resonance, with a pole at or slightly below the D0 D*0 threshold. © 2011 Springer-Verlag / Società Italiana di Fisica.

Bernardo L.F.A.,University of Beira Interior | Andrade J.M.A.,University of Beira Interior | Lopes S.M.R.,University of Coimbra
Engineering Structures | Year: 2012

A computing procedure is presented to predict the ultimate behavior of Normal-Strength Concrete (NSC) and High-Strength Concrete (HSC) beams under torsion. Both plain and hollow beams are considered. In order to model the non-linear behavior of the compressed concrete in the struts and of the tensioned steel reinforcement several proposals for the stress (σ)-strain (ε) relationships were tested. The theoretical predictions of the maximum torque and corresponding twist were compared with results from reported tests and with the predictions obtained from Codes. One of the tested theoretical models was found to give excellent predictions for the maximum torque when compared with those obtained from some codes of practice and with experimental values of NSC and HSC beams (plain and hollow). © 2012 Elsevier Ltd.

Morais M.C.,University of Coimbra | Pereira H.,University of Lisbon
Wood Science and Technology | Year: 2012

The variation in extractives content in sapwood and heartwood was investigated among 12 trees in each of four commercial plantations of Eucalyptus globulus in central Portugal. The study was carried out at the 15% height level and extractions used successively dichloromethane, ethanol and water. At all sites, heartwood had significantly more extractives than sapwood, on average 3.8 and 2.4%, respectively. Most extractives consisted of ethanol soluble material (on average 52% of total extractives). Among the sites, there was a statistically significant difference in the content of extractives but the most important source of variation was the within-tree variation between sapwood and heartwood. Differences in the content of extractives were also observed among trees. A strong relation between extractives content and heartwood proportion was found. The potential loss of pulp yield and problems associated with accumulation of extractives are directly related to the heartwood proportion in the eucalypt stems. Forest management should take into account heartwood development and selection for minimising heartwood extractives. © Springer-Verlag 2011.

Alu A.,University of Texas at Austin | Maslovski S.,University of Coimbra
IEEE Transactions on Antennas and Propagation | Year: 2010

The main objective of this paper is to provide a self-consistent analytical model for the approximate current distribution induced on an arbitrarily loaded wire antenna of moderate length operating in its receiving mode. The results of our analysis shed light on a debated issue regarding the circuit model of a receiving antenna and show that currently available simplified analytical models for receiving dipoles fail to satisfy basic power conservation requirements. These general findings are applied to the proper homogenization of composite materials and surfaces, and to minimum-scattering receivers and absorbers. © 2006 IEEE.

Ramalho A.,University of Coimbra
Wear | Year: 2010

Tribology experimental research has been a considerable improvement during the last years, leading to a significant amount of results and consequently an increasing number of papers appear every month. Unfortunately, in spite of this development, the obtained results usually are characterized by big scatter and significant discrepancies can be founded for the same materials if tested by different research teams. The scatter found in the data has been frequently attributed to many variables involved in the experiments, namely: environment (especially humidity), contaminant layers, differences on test conditions, uncertainty on the results evaluation and rarely on the experimental equipment response.The control of the test variables, the atmosphere and also the test procedure can play an important role on the results reliability but accurate equipments and careful laboratory practices certainly could improve the quality of the results.However, the basic problem remains and even taking into account all that statements, the results could have significant scatter. This work aims to discuss several sources of imprecision which lead to scatter of the experimental tribology results. The usual experimental procedure used to calculate performance parameters, namely wear and friction coefficients will be compared to other solutions, including energy approaches. A reliability method will be proposed to characterize friction and wear data. Experimental results obtained by unidirectional sliding and by micro-abrasion will be used to support the discussion. © 2010 Elsevier B.V.

Rodriguez-Echeverria S.,University of Coimbra
Journal of Biogeography | Year: 2010

Aim: This study analysed the diversity and identity of the rhizobial symbionts of co-existing exotic and native legumes in a coastal dune ecosystem invaded by Acacia longifolia. Location: An invaded coastal dune ecosystem in Portugal and reference bradyrhizobial strains from the Iberian Peninsula and other locations. Methods: Symbiotic nitrogen-fixing bacteria were isolated from root nodules of plants of the Australian invasive Acacia longifolia and the European natives Cytisus grandiflorus, Cytisus scoparius and Ulex europaeus. Total DNA of each isolate was amplified by polymerase chain reaction (PCR) with the primer BOX A1R. Subsequent PCR-sequencing and phylogenetic analyses of the internal transcribed spacer region and the nifD and nodA genes were performed for all different strains. Results: The four plant species analysed were nodulated by bacteria from three different Bradyrhizobium lineages, although most of the isolates belonged to the Bradyrhizobium japonicum lineage sensu lato. Ninety-five per cent of the bradyrhizobia isolated from A. longifolia, C. grandiflorus and U. europaeus in the invaded ecosystem had nifD and nodA genes of Australian origin. Seven isolates obtained in this study define a new distinctive nifD group of Bradyrhizobium from western and Mediterranean Europe. Main conclusions: These results reveal the introduction of exotic bacteria with the invasive plant species, their persistence in the new geographical area and the nodulation of native legumes by rhizobia containing exotic symbiotic genes. The disruption of native mutualisms and the mutual facilitation of the invasive spread of the introduced plant and bradyrhizobia could constitute the first report of an invasional meltdown documented for a plant-bacteria mutualism. © 2010 Blackwell Publishing Ltd.

Tahri O.,University of Coimbra | Mezouar Y.,University Blaise Pascal
Robotics and Autonomous Systems | Year: 2010

This paper deals with the Efficient Second order Minimization (ESM) and the image-based visual servoing schemes. In other words, it deals with the minimization based on the pseudo-inverse of the mean of the Jacobians or on the mean of Jacobian Pseudo-inverses. Chronologically, it has been noticed in Tahri and Chaumette (2003) [22] that ESM generally improves the system behavior when compared with the system in which only the simple Jacobian Pseudo-inverses are used. Subsequently, a mathematical explanation has been given in Malis (2004) [12]. In this paper, the proofs given by Malis are discussed and it will be shown that there is a limitation to the validity of the ESM. We will also show that the use of ESM does not necessarily ensure a better system behavior, especially in the situations where large rotational motions are involved. Further, a new appropriate formula of the ESM is proposed and validated using several kinds of features. © 2009 Elsevier B.V. All rights reserved.

Background: Bullying has been considered as a traumatic experience that can lead to paranoid ideation in students (Campbell and Morrison, 2007). This study aimed to explore differences concerning experiences of childhood trauma, the display of social anxiety behaviours, paranoid ideation, and aggressive traits and behaviour in a mixed clinical population with and without persecutory delusions, between individuals who reported being victims of bullying versus those who did not. Method: A total of 61 individuals with diagnoses of paranoid schizophrenia and social anxiety disorder were given a battery of questionnaires that measured bullying experiences, childhood abuse and experiences of threat and subordination, paranoid ideation, social anxiety behaviours, shame, and aggressive traits and behaviours. Results: Data on the differences between the victims of bullying and non-victims, in terms of recalling being bullied, showed higher scores on childhood abuse, experiences of threat and subordination within the family, aggressive traits and higher display of persecutory symptoms and less social anxiety behaviours. Conclusion: Bullying is a traumatic phenomenon that is reported by people who suffer from persecutory delusions to a higher degree than those who do not. This study, thus, gives support to the idea that childhood abuse within the family is associated with bullying experiences and that a traumatic infancy may lead to the use of aggressive traits and behaviours to deal with a threatening environment (Bentall and Fernyhough,). This argument raises clinical issues regarding anger management and addressing bullying experiences in individuals with persecutory ideation. © 2011 John Wiley & Sons, Ltd.

Avancini S.S.,Federal University of Santa Catarina | Menezes D.P.,Federal University of Santa Catarina | Providencia C.,University of Coimbra
Physical Review C - Nuclear Physics | Year: 2011

In this paper, we use the mean-field approximation to investigate quark matter described by both SU(2) and SU(3) versions of the Nambu-Jona-Lasinio model at temperatures below 150 MeV and subject to a strong magnetic field. This kind of matter is possibly present in the early stages of heavy-ion collisions and in the interior of protoneutron stars. We have studied symmetric and asymmetric quark matter. The effect of the magnetic field on the effective quark masses and chemical potentials is only felt for quite strong magnetic fields, above 5×1018 G, with larger effects for the lower densities. Spin polarizations are more sensitive to weaker magnetic fields and are larger for lower temperatures and lower densities. Temperature tends to wash out the magnetic field effects. © 2011 American Physical Society.

Adhikari S.,Indian Association for The Cultivation of Science | Varandas A.J.C.,University of Coimbra
Computer Physics Communications | Year: 2013

We have implemented the coupled three-dimensional wave packet approach in hyperspherical coordinates for time-dependent reactive scattering calculations of triatomic systems. The coupling of these wave packets arises through the rotation of the three particle plane by the Euler angles. The necessary transformation from Jacobi to hyperspherical coordinates for the initialization and the reverse transformation for the projection of the wave packet by the asymptotic state(s), and the coupled equation of motion are presented briefly. We demonstrate the workability and convergence profiles of the approach on the D+H 2 system for total angular momentum equal to zero and non-zero situations. © 2012 Elsevier B.V. All rights reserved.

Sousa E.,University of Coimbra
International Journal of Bifurcation and Chaos | Year: 2012

The fractional derivative of order , with 1 < ≤ 2 appears in several diffusion problems used in physical and engineering applications. Therefore to obtain highly accurate approximations for this derivative is of great importance. Here, we describe and compare different numerical approximations for the fractional derivative of order 1 < ≤ 2. These approximations arise mainly from the Grünwald-Letnikov definition and the Caputo definition and they are consistent of order one and two. In the end some numerical examples are given, to compare their performance. © 2012 World Scientific Publishing Company.

Dias D.,University of Aveiro | Tchepel O.,University of Coimbra
Environmental Science and Pollution Research | Year: 2014

The main objective of this work was the development of a new modelling tool for quantification of human exposure to traffic-related air pollution within distinct microenvironments by using a novel approach for trajectory analysis of the individuals. For this purpose, mobile phones with Global Positioning System technology have been used to collect daily trajectories of the individuals with higher temporal resolution and a trajectory data mining, and geo-spatial analysis algorithm was developed and implemented within a Geographical Information System to obtain time-activity patterns. These data were combined with air pollutant concentrations estimated for several microenvironments. In addition to outdoor, pollutant concentrations in distinct indoor microenvironments are characterised using a probabilistic approach. An example of the application for PM2.5 is presented and discussed. The results obtained for daily average individual exposure correspond to a mean value of 10.6 and 6.0-16.4 μg m-3 in terms of 5th-95th percentiles. Analysis of the results shows that the use of point air quality measurements for exposure assessment will not explain the intra- and inter-variability of individuals' exposure levels. The methodology developed and implemented in this work provides time-sequence of the exposure events thus making possible association of the exposure with the individual activities and delivers main statistics on individual's air pollution exposure with high spatio-temporal resolution. © 2013 Springer-Verlag Berlin Heidelberg.

The purpose of this paper was to analyze the evolution and regional distribution of both forest fire ignitions and burnt areas in mainland Portugal and to identify the relationship between biophysical and human variables and the incidence of forest fires at the district level over the last 3 decades (1980-2009). A positive trend can be observed in the number of fires and in the areas burnt by forest fires since 1980. An interesting regional distribution of forest fire ignitions and burned areas was detected, highlighting some districts especially vulnerable to the outbreak of fires and others particularly susceptible to the spread of fire. A stepwise multiple regression methodology was applied to determine the relative importance of each variable in explaining the regional distribution of ignitions and burned area fractions and to address hypotheses regarding human and biophysical influences on the drivers of forest fires.Population density was the primary determining variable in the outbreak of fires at the district level (this factor alone explained 65% of the inter-district variation in the density of fire ignitions), whereas burn areas were influenced by the synergistic effects of topography, changes in land use, and vegetation.The topographic roughness index emerged as the most important variable causing the regional variations observed in the percentage of the district area burnt over the last 30 years, explaining 70% of the observed variance. Variables associated with changes in land use and cover during the second half of the last century explained an additional 17% of the variance. Multiple regression analysis also suggested a positive relationship between the total area burnt and the total uncultivated area, explaining 57% of the variance at the district level. In general, the greatest pressures from fire occur in the districts north of the Tejo River, which are more mountainous, have lower annual temperatures and more rainfall, and produce the most biomass under pressure from agriculture and grazing. In these districts, the decline of traditional agriculture has resulted in important transformations to the landscape characterized by the spread of natural vegetation. © 2012 Elsevier Ltd.

Rodrigues L.,University of Coimbra
Journal of physiology and biochemistry | Year: 2011

Type 2 diabetes is a heterogeneous metabolic disease characterized by insulin resistance and β-cell dysfunction leading to hyperglycaemia and dyslipidaemia. Dietary intervention seems to improve some of these cellular complications, namely insulin resistance. Our aim was to evaluate the effects of dietary restriction on systemic and skeletal muscle oxidative stress and insulin resistance in normal Wistar rats and Goto-Kakizaki (GK) rats, a non-obese type 2 diabetic animal model. Four-month-old normal and diabetic rats were separated in four groups. One group of each strain was maintained with ad libitum standard diet, and the other group was submitted to a dietary restriction (50% of control animals daily food intake), during 2 months. Metabolic profile, insulin resistance indexes and muscle lipids were determined. Oxidative stress parameters were also measured at systemic and muscle levels: protein carbonyl, 8-hydroxy-2'-deoxyguanosine and free 8-isoprostane. Dietary restriction improved lipid profile in both strains and urinary free 8-isoprostane and plasma carbonyl compounds in diabetic rats. An improvement of muscle triglycerides accumulation and 8-isoprostane concentration and a reduction of insulin resistance were also observed in GK rats. Our data show that dietary restriction ameliorates systemic and skeletal muscle oxidative stress state in type 2 diabetes, which is associated with improved insulin resistance.

Grill F.,University of Milan | Grill F.,University of Coimbra | Margueron J.,University Paris - Sud | Sandulescu N.,Horia Hulubei National Institute of Physics and Nuclear Engineering
Physical Review C - Nuclear Physics | Year: 2011

We analyze how the structure of the inner crust is influenced by the pairing correlations. The inner crust matter, formed by nuclear clusters immersed in a superfluid neutron gas and ultrarelativistic electrons, is treated in the Wigner-Seitz approximation. The properties of the Wigner-Seitz cells, i.e., their neutron-to-proton ratio and their radius at a given baryonic density, are obtained from the energy minimization at beta equilibrium. To obtain the binding energy of baryonic matter we perform Skyrme-Hartree-Fock- Bogoliubov (HFB) calculations with zero-range density-dependent pairing forces of various intensities. The most important effect of pairing is to smooth the dependence of Hartree-Fock (HF) energy on proton number. For some cells pairing can change significantly the proton number of the HF configurations. However, these changes are not so relevant because the energy difference between the absolute HFB minima and the energies corresponding to HF minima is very small. In the high-density cells, well-defined absolute minima are not found since the binding energies decrease continuously for small proton numbers. We show that the structure of these cells can be eventually determined by taking into account the underestimation of the binding energy due to the discretization of the energy spectrum of the nonlocalized neutrons induced by the boundary conditions at the border of the cells. © 2011 American Physical Society.

Cunha M.D.C.,University of Coimbra | Sousa J.J.D.O.,Polytechnic Institute of Coimbra
Journal of Water Resources Planning and Management | Year: 2010

In the last three decades the optimal design of water distribution systems problem has been studied by a great many researchers, and this has resulted in the development of a large number of models and the application of optimization techniques. The design of these infrastructures is based on future predefined and perfectly known working conditions for the water distribution networks, a premise that may direct the optimization process to solutions which, although optimal for the imposed scenario, may perform badly if reality turns out to be significantly different. In fact the working conditions can be disrupted by accidents such as broken pipes or reservoirs, technical failures, change in demand, etc. In the context of a proactive attitude toward risk, it is important to consider these aspects at the design phase. This paper presents a robust optimization-based approach for designing a water distribution network aimed at obtaining solutions that can cope with the uncertainty of the network's working conditions. Robust optimization is a scenario based technique, and in the present case its goal is to provide significant savings in comparison with the worst case scenario solution, while incurring only minor suboptimality for the rest of the scenarios, and being almost feasible for all the scenarios. The solution of the robust optimization problem is obtained with a methodology that uses the link between a simulated annealing algorithm, the optimizer, and a hydraulic simulator, here used to solve the problem's hydraulic constraints. The application of the proposed methodology is illustrated with an example of a water distribution network. © 2010 ASCE.

Ghamisi P.,University of Iceland | Couceiro M.S.,University of Coimbra | Couceiro M.S.,Polytechnic Institute of Coimbra | Martins F.M.L.,Polytechnic Institute of Coimbra | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

Hyperspectral remote sensing images contain hundreds of data channels. Due to the high dimensionality of the hyperspectral data, it is difficult to design accurate and efficient image segmentation algorithms for such imagery. In this paper, a new multilevel thresholding method is introduced for the segmentation of hyperspectral and multispectral images. The new method is based on fractional-order Darwinian particle swarm optimization (FODPSO) which exploits the many swarms of test solutions that may exist at any time. In addition, the concept of fractional derivative is used to control the convergence rate of particles. In this paper, the so-called Otsu problem is solved for each channel of the multispectral and hyperspectral data. Therefore, the problem of n-level thresholding is reduced to an optimization problem in order to search for the thresholds that maximize the between-class variance. Experimental results are favorable for the FODPSO when compared to other bioinspired methods for multilevel segmentation of multispectral and hyperspectral images. The FODPSO presents a statistically significant improvement in terms of both CPU time and fitness value, i.e., the approach is able to find the optimal set of thresholds with a larger between-class variance in less computational time than the other approaches. In addition, a new classification approach based on support vector machine (SVM) and FODPSO is introduced in this paper. Results confirm that the new segmentation method is able to improve upon results obtained with the standard SVM in terms of classification accuracies. © 1980-2012 IEEE.

Cardoso J.M.,University of Coimbra
Genetics and molecular research : GMR | Year: 2012

The sequence variation of internal transcribed spacer (ITS) regions of ribosomal DNA has been routinely used for species identification and species-level phylogeny of the pinewood nematode, Bursaphelenchus xylophilus. In this study, the intraspecies ITS genetic diversity of B. xylophilus was evaluated. Three pinewood nematode isolates from the United States, Japan, and Portugal were used for polymerase chain reaction (PCR) ITS region amplification and sequencing. Multiple peaks were observed in sequencing chromatograms from ITS regions of American and Japanese isolates, suggesting the presence of more than one ribosomal sequence for each isolate. PCR products were further cloned and 10 clones of each isolate were subsequently sequenced. Additionally, the ITS regions of individual nematodes from each isolate were amplified, cloned and sequenced. Among the 3 B. xylophilus isolates analyzed, an intraspecific and intra-isolate molecular variability was found. The intra-isolate ITS molecular diversity in the American isolate was higher than that in the Japanese and Portuguese isolates. However, the level of sequence variation observed within isolates was about the same as that described among ITS repeats within individuals.

Fernandes D.M.,University of Aveiro | Brett C.M.A.,University of Coimbra | Cavaleiro A.M.V.,University of Aveiro
Journal of Solid State Electrochemistry | Year: 2011

Hybrid multilayer films composed of poly(ethylenimine) and the Keggin-type polyoxometalates {SiW 11O 39} 8- {SiW 11} [SiW 11Co II (H 2O) O 39} 6- (SiW 11Co) were prepared on glassy carbon electrodes by layer-by-layer self-assembly, and were characterized by cyclic voltammetry and scanning electron microscopy. UV-vis absorption spectroscopy of films deposited on quartz slides was used to monitor film growth, showing that the absorbance values at characteristic wavelengths of the multilayer films increase almost linearly with the number of bilayers. Cyclic voltammetry indicates that the electrochemical properties of the polyoxometalates are maintained in the multilayer films, and that the first tungsten reduction process for immobilized SiW 11 and SiW 11Co is a surface-confined process. Electron transfer to [FeCN 6} 3-/4- and [Ru(NH 3) 6] 3+2+ as electrochemical probes was also investigated by cyclic voltammetry. The (PEI/SiW 11Co) n multilayer films showed excellent electrocatalytic reduction properties towards nitrite, bromate and iodate. © 2010 Springer-Verlag.

Varandas A.J.C.,University of Coimbra
Physical Chemistry Chemical Physics | Year: 2011

The dissociation of HO3 into OH + O2 has been studied in a systematic and consistent way using the multireference configuration interaction method. Upon extrapolation of the calculated raw energies to the complete basis set limit and using jointly with a recent realistic estimate of the zero-point vibrational energy, the energy for OO-OH bond-breaking in the trans isomer is predicted to be of D0 = (2.4 ± 0.1) kcal mol-1, where the uncertainty reflects only the one inherent to the extrapolation. The average value so obtained falls short of the commonly accepted experimental counterpart by 0.5 kcal mol-1. Reasons for the deviation are advanced, as well as an estimate of the binding energy for the cis-HO3 isomer which is predicted to have a somewhat smaller binding energy than trans-HO3, but likewise the latter dissociates without a barrier to the same products. This journal is © the Owner Societies.

Goncalves N.,University of Coimbra
Optics Letters | Year: 2010

We address the problem of determining the reflection point on a specular surface where a light ray that travels from a source to a target is reflected. The specular surfaces considered are those expressed by a quadratic equation. So far, there is no closed form explicit equation for the general solution of this determination of the reflection point, and the usual approach is to use the Snell law or the Fermat principle whose equations are derived in multidimensional nonlinear minimizations. We prove in this Letter that one can impose a set of three restrictions to the reflection point that can impose a set of three restrictions that culminates in a very elegant formalism of searching the reflection point in a unidimensional curve in space. This curve is the intersection of two quadratic equations. Some applications of this framework are also discussed. © 2010 Optical Society of America.

Freire N.M.A.,University of Coimbra | Cardoso A.J.M.,University of Beira Interior
IEEE Transactions on Industry Applications | Year: 2014

Fault-tolerant permanent magnet synchronous generator (PMSG) drives for wind turbine applications play a major role in improving reliability and availability levels, since power converters are very prone to fail. In this paper, a fault-tolerant converter with the ability to handle power switch open-circuit faults is addressed. The main concern of the proposed converter topology is the minimization of the hardware requirements, leading to a low increase of the system cost. First, the employed fault diagnostic technique does not require additional measurements, nor high computational effort. Secondly, the circuit topology reconfiguration implies a minimum number of extra components as well as minimal oversizing of the standard ones. Accordingly, a four-switch three-phase converter with the dc bus midpoint connected to the transformer neutral point and a three-switch three-phase rectifier are adopted for post-fault operation of the grid- and PMSG-side converters, respectively. Vector control strategies are proposed for both converters under analysis, focusing the issues of capacitor voltages balancing and torque ripple minimization. The performance of the proposed fault-tolerant PMSG drive is analyzed by means of experimental results. © 2014 IEEE.

Freire N.M.A.,University of Coimbra | Estima J.O.,University of Beira Interior | Cardoso A.J.M.,University of Beira Interior
IEEE Transactions on Industry Applications | Year: 2014

Fault diagnosis is a mandatory feature in fault-tolerant systems, since it provides the information necessary for the fault isolation and system reconfiguration. Recently, permanent-magnet synchronous generator (PMSG) drives have achieved prominence in wind energy conversion systems (WECSs), due to their reliability and availability. In this paper, a new approach is proposed for current sensor fault diagnosis in PMSG drives for WECSs. As opposed to the conventional state-observer-based methods for current sensor faults, which require a system model and the respective parameters, the proposed diagnostic method uses the measured phase currents only. Thus, its main merits are simplicity and reliability in the diagnosis, making it suitable for real-time implementation and to trigger remedial procedures. In addition, current sensor and open-circuit faults can be distinguished, and the affected phase is effectively identified in both cases. The proposed diagnostic technique is applied to the two power converters of a conventional back-to-back topology, and its performance is analyzed by means of several experimental results. © 1972-2012 IEEE.

The predicted increase in atmospheric CO 2 concentration for this century is expected to lead to increases in temperature and changes in litter quality that can affect small woodland streams, where water temperature is usually low and allochthonous organic matter constitutes the basis of the food web. We have assessed the individual and interactive effect of water temperature (5 and 10°C) and alder litter quality produced under ambient CO 2 levels (ambient litter) or under CO 2 concentrations predicted for 2050 (elevated litter) on litter decomposition and on fungal activity and assemblage structure. Litter decomposition rates and fungal respiration rates were significantly faster at 10 than at 5°C, but they were not affected by litter quality. Litter quality affected mycelial biomass accrual at 5 but not at 10°C, while increases in temperature stimulated biomass accrual on ambient but not on elevated litter. A similar pattern was observed for conidial production. All variables were stimulated on elevated litter at 10°C (future scenario) compared with ambient litter at 5°C (present scenario), but interactions between temperature and litter quality were additive. Temperature was the factor that most strongly affected the structure of aquatic hyphomycete assemblages. Our results indicate that if future increases in atmospheric CO 2 lead to only slight modifications in litter quality, the litter decomposition and fungal activities and community structure will be strongly controlled by increased water temperature. This may have serious consequences for aquatic systems as faster litter decomposition may lead to food depletion for higher trophic levels. © 2011 Springer-Verlag.

Bandeira A.S.,Princeton University | Scheinberg K.,Lehigh University | Vicente L.N.,University of Coimbra
Mathematical Programming | Year: 2012

Interpolation-based trust-region methods are an important class of algorithms forDerivative-Free Optimizationwhich rely on locally approximating an objective function by quadratic polynomial interpolation models, frequently built from less points than there are basis components. Often, in practical applications, the contribution of the problem variables to the objective function is such that many pairwise correlations between variables are negligible, implying, in the smooth case, a sparse structure in the Hessian matrix. To be able to exploit Hessian sparsity, existing optimization approaches require the knowledge of the sparsity structure. The goal of this paper is to develop and analyze a method where the sparse models are constructed automatically. The sparse recovery theory developed recently in the field of compressed sensing characterizes conditions under which a sparse vector can be accurately recovered from few random measurements. Such a recovery is achieved by minimizing the l1-norm of a vector subject to the measurements constraints. We suggest an approach for building sparse quadratic polynomial interpolationmodels byminimizing the l1-norm of the entries of themodel Hessian subject to the interpolation conditions. We show that this procedure recovers accurate models when the function Hessian is sparse, using relatively few randomly selected sample points. Motivated by this result, we developed a practical interpolation-based trust-region method using deterministic sample sets and minimum l1-norm quadratic models. Our computational results show that the new approach exhibits a promising numerical performance both in the general case and in the sparse one. © Springer and Mathematical Optimization Society 2012.

Silveirinha M.G.,University of Coimbra
Physical Review X | Year: 2014

One of the most extraordinary manifestations of the coupling of the electromagnetic field and matter is the emission of light by charged particles passing through a dielectric medium: the Vavilov-Cherenkov effect. Here, we theoretically predict that a related phenomenon may be observed when neutral fast polarizable particles travel near a metal surface supporting surface plasmon polaritons. Based on a classical formalism, we find that at some critical velocity, even if the initial optical field is vanishingly small, the system may become unstable and may start spontaneously emitting light such that in some initial time window the electromagnetic field grows exponentially with time.

Ramalho A.,University of Coimbra
Wear | Year: 2015

In rail-wheel transports the maintenance interval for both wheels and rails has become a major issue in reducing costs and increasing safety and has encouraged the development of new numeric procedures for predicting the evolution of wear in order to establish a convenient maintenance schedule. These new tools require the synergy of dynamic analysis and the development of accurate and easy to use wear models. Rail/wheel wear depends on the material properties resulting from contact fatigue and sliding wear. Therefore, all the contact conditions affecting the contact stress distribution will determine the wear behaviour and the contact profiles of wheel and rails. The current research paper investigates the effect of contact conditions on friction and wear behaviour of EN 260 rail steel and R7 wheel steel. Laboratory simulation used twin-disc rolling-sliding tests to study the effect of the creep ratio, contact pressure and tangential speed on the resulting traction coefficient and amount of wear. The volume loss was estimated by weighing both specimens before and after the tests. Wear volumes were used to develop a wear equation based on Archard's model and considering weighting factors to estimate the influence of creep ratio, contact pressure and tangential speed on the specific wear rate. The predicted results were compared with the results of tests performed in the laboratory. Quite small differences between previsions and laboratory tests confirm the reliability of the forecast method. Wear mechanisms were discussed and compared to real rail-wheels sets analysing the fatigue cracks and the strain hardening effects beneath the contact surfaces. © 2015 Elsevier B.V.

Carvalho A.D.,Polytechnic Institute of Coimbra | Mendrinos D.,Center for Renewable Energy Sources CRES | De Almeida A.T.,University of Coimbra
Renewable and Sustainable Energy Reviews | Year: 2015

The main purpose of this study is to assess the impacts in the European Union (EU) of a fuel switching strategy focused on the replacement of Natural Gas (NG) boilers by high efficiency Heat Pumps (HPs) supplied by electricity with a fast decreasing carbon content. Additionally, to illustrate the high performance of heat pumps, the experimental results of an advanced Ground Source Heat Pump (GSHP) system installed in a service building in Portugal are presented. Based on the analysis carried out, it was found that the large scale use of heat pumps for space heating in buildings can contribute to significant primary energy and CO2 emissions savings, when compared to NG boilers. In Europe, in 2050, through the replacement NG space heating in buildings by high efficiency heat pumps, around 60% of the primary energy required and 90% of the associated CO2 emissions can be saved. At global EU level, in 2050 the European NG dependency on external suppliers can be decreased to 50% and an additional contribution of 5.6% for Renewable Energy Sources (RES) share in the total final energy consumption can be achieved. Furthermore, HPs can also play an important role towards exploiting the increasing penetration of renewable electricity generation, effectively contributing to the replacement of fossil fuels and in particular to decrease the growing natural gas dependency of Europe from risky and unstable countries. © 2015 Elsevier Ltd. All rights reserved.

de Lemos E.T.,University of Coimbra
Oxidative medicine and cellular longevity | Year: 2012

Over the last 30 years the combination of both a sedentary lifestyle and excessive food availability has led to a significant increase in the prevalence of obesity and aggravation of rates of metabolic syndrome and type 2 diabetes mellitus (T2DM). Several lines of scientific evidence have been demonstrating that a low level of physical activity and decreased daily energy expenditure leads to the accumulation of visceral fat and, consequently, the activation of the oxidative stress/inflammation cascade, which underlies the development of insulin resistant T2DM and evolution of micro, and macrovascular complications. This paper focuses on the pathophysiological pathways associated with the involvement of oxidative stress and inflammation in the development of T2DM and the impact of regular physical exercise (training) as a natural antioxidant and anti-inflammatory strategy to prevent evolution of T2DM and its serious complications.

Rajkumar M.,Indian National Environmental Engineering Research Institute | Sandhya S.,Indian National Environmental Engineering Research Institute | Prasad M.N.V.,University of Hyderabad | Freitas H.,University of Coimbra
Biotechnology Advances | Year: 2012

"Phytoremediation" know-how to do-how is rapidly expanding and is being commercialized by harnessing the phyto-microbial diversity. This technology employs biodiversity to remove/contain pollutants from the air, soil and water. In recent years, there has been a considerable knowledge explosion in understanding plant-microbes-heavy metals interactions. Novel applications of plant-associated microbes have opened up promising areas of research in the field of phytoremediation technology. Various metabolites (e.g., 1-aminocyclopropane-1-carboxylic acid deaminase, indole-3-acetic acid, siderophores, organic acids, etc.) produced by plant-associated microbes (e.g., plant growth promoting bacteria, mycorrhizae) have been proposed to be involved in many biogeochemical processes operating in the rhizosphere. The salient functions include nutrient acquisition, cell elongation, metal detoxification and alleviation of biotic/abiotic stress in plants. Rhizosphere microbes accelerate metal mobility, or immobilization. Plants and associated microbes release inorganic and organic compounds possessing acidifying, chelating and/or reductive power. These functions are implicated to play an essential role in plant metal uptake. Overall the plant-associated beneficial microbes enhance the efficiency of phytoremediation process directly by altering the metal accumulation in plant tissues and indirectly by promoting the shoot and root biomass production. The present work aims to provide a comprehensive review of some of the promising processes mediated by plant-associated microbes and to illustrate how such processes influence heavy metal uptake through various biogeochemical processes including translocation, transformation, chelation, immobilization, solubilization, precipitation, volatilization and complexation of heavy metals ultimately facilitating phytoremediation. © 2012 Elsevier Inc.

Hankel M.,University of Queensland | Smith S.C.,University of Queensland | Varandas A.J.C.,University of Coimbra
Physical Chemistry Chemical Physics | Year: 2011

We present exact quantum integral and differential cross sections for the title reaction from a time-dependent wavepacket method which takes account of all Coriolis couplings. We employ two new potential energy surfaces fitted using the double many-body expansion (DMBE) method. The difference between the two surfaces is that for the first the data was extrapolated to the complete basis set limit (CBS) and for the second the data was corrected semi-empirically (SEC). While the DMBE/CBS surface is, on first impressions, regarded as the most accurate, our results show that this surface gives consistent smaller cross section when compared to previous results employing an earlier surface, named Ho after its first author. We also find that the DMBE/CBS surface features an unphysical barrier for contracted H2 distances which explains the smaller results. The DMBE/SEC surface, which is based on the same data, does not show the same barrier and the results compare much better to previous theoretical results as well as those from experiment. While we find that overall the differential cross sections from the DMBE/SEC surface are forward scattered, which is in line with experiment, the cross sections do not rise steeply enough with decreasing energy showing that this surface is not sufficiently attractive at low energies. We find this is due to a shallow van der Waals well present for the Ho surface but not on the DMBE surfaces. © the Owner Societies 2011.

Najafi M.,University of Tehran | Abbasi A.,University of Tehran | Masteri-Farahani M.,Kharazmi University | Rodrigues V.H.,University of Coimbra
Inorganic Chemistry Communications | Year: 2014

A new Co2 +-centered heteropolyoxomolybdate nanocluster containing the bipy ligand (4,4′-bipy = 4,4′-bipyridine), with formula [4,4′-H2bipy][Co0.23Mo6O 20]·2H2O (1), has been hydrothermally synthesized and structurally characterized by means of FT-IR, atomic absorption spectroscopy, single-crystal and powder X-ray diffraction (XRD). The catalytic investigations disclosed that 1 displayed both good activity and stability in the epoxidation of cyclooctene. It can also be recovered easily and reused in the reaction without significant loss of activity or selectivity. Furthermore, the effect of the type of oxidant and solvent on the conversion of the reaction was investigated. © 2014 Elsevier B.V.

Gregorio S.,University of Coimbra
The Spanish journal of psychology | Year: 2013

The growing interest in mindfulness from the scientific community has originated several self-report measures of this psychological construct. The Mindful Attention and Awareness Scale (MAAS) is a self-report measure of mindfulness at a trait-level. This paper aims at exploring MAAS psychometric characteristics and validating it for the Portuguese population. The first two studies replicate some of the original author's statistical procedures in two different samples from the Portuguese general community population, in particular confirmatory factor analyses. Results from both analyses confirmed the scale single-factor structure and indicated a very good reliability. Moreover, cross-validation statistics showed that this single-factor structure is valid for different respondents from the general community population. In the third study the Portuguese version of the MAAS was found to have good convergent and discriminant validities. Overall the findings support the psychometric validity of the Portuguese version of MAAS and suggest this is a reliable self-report measure of trait-mindfulness, a central construct in Clinical Psychology research and intervention fields.

Cunha L.,University of Coimbra
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: 2012

In the last years the incidence of thromboembolic stroke has increased. Better control of other cardiovascular risk factors and the ageing of the population with the consequent augmentation of the prevalence of non valvular atrial fibrillation (NVAF) justify that increase. Although anticoagulation therapy has remarkable efficacy, from the perspective of the neurologist it seems to be underestimated. To support that perspective we present the casuistic of admissions in the Neurology Department of Hospitais da Universidade de Coimbra (HUC) during the first trimester of 2011 and the follow up from one to two years of all the patients that were admitted in the Stroke Unit of the HUC during 2010. We conclude that the introduction in the clinical practice of the new oral anticoagulants will allow a simplification of the proceedings in the patients with NVAF promoting, in the majority of the cases, a more marked reduction of thromboembolic events and also a reduction of their most feared complication, intracranial bleeding. Copyright © 2012 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

Reis M.S.,University of Coimbra
Chemometrics and Intelligent Laboratory Systems | Year: 2015

We present an integrated approach for conducting on-line and off-line image-based monitoring of processes whose products (raw materials, intermediate or final) consist of colour random textures. The methodology combines the principles underlying wavelet texture analysis and multivariate image analysis into a single framework, able to detect both abnormal changes in texture and colour. By taking into account a scale-dependent description of colour, it can detect subtle changes on how colour interacts with texture across the several length-scales considered. The proposed methodology was studied and characterized following best practice procedures for developing statistical process control methods, where controlled simulated test scenarios are employed to generate normal operation condition (NOC) data, as well as faults of different types and magnitudes. By simulating normal operation and faulty images in this way, it is possible to assess the monitoring potential of the proposed methodology to detect abnormal situations under a diversity of monotonically increasing faulty conditions. Results show that the proposed methodology is able to effectively detect changes in both colour and texture characteristics and one type of monitoring statistics in particular leads the performance in most of the tested scenarios: the PCA statistics for monitoring multiscale textural features. For this reason and for encompassing less computational and programming effort, its adoption is particularly recommended. © 2015.

Silveirinha M.G.,University of Pennsylvania | Silveirinha M.G.,University of Coimbra | Engheta N.,University of Pennsylvania
Physical Review Letters | Year: 2013

It is theoretically demonstrated that electron states in semiconductors or graphene can be perfectly transmitted through a complementary material with dual properties, independent of the angle of incidence. It is shown that such complementary material may also provide a strong spatial delocalization of bounded electronic states, changing dramatically the confinement of the wave function, and acting effectively as a lens for the probability wave. The results are the electron analogue of a perfect lens for electromagnetic waves proposed in an earlier work. © 2013 American Physical Society.

Pereira L.,University of Coimbra | Van De Velde F.,TI Food and Nutrition | Van De Velde F.,NIZO food research
Carbohydrate Polymers | Year: 2011

Eight carrageenophytes from the Centre and North coast of Portugal, representing seven genera and three families of Gigartinales, were studied in 15 different coastal stations in a geographic study, from Baleal (Peniche), in the central zone, to Moledo, in the northern zone. In order to characterize the different carrageenan types, 1H NMR spectroscopy was used to identify and quantify the different carrageenan fractions in the extracted phycocolloids (both water and alkali extractions). Thereby, detailed information concerning the properties and structure of these polysaccharides at molecular level was revealed. Based on the results of the analysis of the carrageenan types, the following conclusions were made: female gametophytes and non-fertile thalli of Chondrus crispus, Mastocarpus stellatus, Chondracanthus teedei var. lusitanicus, Gigartina pistillata, Chondracanthus acicularis and Gymnogongrus crenulatus, presented a varying degrees of kappa-iota hybrid carrageenan (co-polymers of kappa-iota carrageenan). The kappa/iota ratio ranged from 0 to 2.2. The carrageenans extracted from Ahnfeltiopsis devoniensis were mainly iota-carrageenan, but some geographic variations in the composition of carrageenans were found. Calliblepharis jubata contained carrageenans of iota-type in all reproductive stages. Lambda-family carrageenans were found in tetrasporophytes of C. cripus (lambda), M. stellatus (lambda), C. teedei var. lusitanicus (hybrid xi-theta), C. acicularis (hybrid xi-theta) and G. pistillata (hybrid xi-lambda). © 2010 Elsevier Ltd. All rights reserved.

Dabestani S.,Skane University Hospital | Marconi L.,University of Coimbra | Hofmann F.,Sunderby Hospital | Stewart F.,University of Aberdeen | And 6 more authors.
The Lancet Oncology | Year: 2014

Local treatment of metastases such as metastasectomy or radiotherapy remains controversial in the treatment of metastatic renal cell carcinoma. To investigate the benefits and harms of various local treatments, we did a systematic review of all types of comparative studies on local treatment of metastases from renal cell carcinoma in any organ. Interventions included metastasectomy, radiotherapy modalities, and no local treatment. The results suggest that patients treated with complete metastasectomy have better survival and symptom control (including pain relief in bone metastases) than those treated with either incomplete or no metastasectomy. Nevertheless, the available evidence was marred by high risks of bias and confounding across all studies. Although the findings presented here should be interpreted with caution, they and the identified gaps in knowledge should provide guidance for clinicians and researchers, and directions for further research. © 2014 Elsevier Ltd.

Fonseca J.,University of Coimbra
Compendium of continuing education in dentistry (Jamesburg, N.J. : 1995) | Year: 2011

Prolonged tooth maintenance by a more aged population considerably increases the probability of dentists having to treat patients with high levels of tooth wear. Pathological tooth wear, caused primarily by parafunction, seems to be a growing problem that affects a large number of adult patients. The clinical report presents a case of a partially edentulous patient with an elevated degree of wear in the upper jaw caused by attrition and erosion, rehabilitated with a maxillary overlay removable partial denture (ORPD) consisting of a chrome-cobalt (Cr-Co) framework with anterior acrylic resin veneers, posterior cast overlays, and acrylic resin denture bases. Removable partial prosthesis is a treatment alternative when teeth are found to be severely worn or when the patient needs a simple and economical option. Because economics is a conditional factor of the treatment, the clinician should present different treatment alternatives to the patient, in which the overlay prosthesis can be considered.

Microevolution due to pollution can occur mainly through genetic drift bottlenecks, especially of small sized populations facing intense lethal pulses of contaminants, through mutations, increasing allelic diversity, and through natural selection, with the disappearance of the most sensitive genotypes. This loss of genotypes can lead to serious effects if coupled to specific hypothetical scenarios. These may be categorized as leading, first, to the loss of alleles - the recessive tolerance inheritance hypothesis. Second, leading to a reduction of the population growth rate - the mutational load and fitness costs hypotheses. Third, leading to an increased susceptibility of further genetic erosion both at future inputs of the same contaminant - differential physiological recovery, endpoints (dis)association, and differential phenotypic plasticity hypotheses - and at sequential or simultaneous inputs of other contaminants - the multiple stressors differential tolerance hypothesis. Species in narrowly fluctuating environments (tropics and deep sea) may have a particularly high susceptibility to genetic erosion - the Plus ça change (plus c'est la meme chose) hypothesis. A discussion on the consequences of these hypotheses is what this essay aimed at. © 2013 The Author(s).

At the Paris Colloquium held forty years ago, and which this paper celebrates, the issue of psychosurgery had not been tackled yet. At that time psychosurgery was tainted by the controversial history of lobotomy and leucotomy. Supporters of psychosurgery at the time of the Colloquium were preparing their fourth International Conference, which was held in Madrid the following year. This represented a key characteristic of the collective, institutional and symbolic action of psychosurgery practitioners. At the end of the seventies, their strategy changed as noted below. Furthermore, we focus on the special importance of the results presented and commented on by psychosurgery supporters, including its conception and classification throughout the rhetoric historically involved (its supposed ventriloquism, its persuasive strength). Based on this view, we suggest a critical reflection encompassing old and new psychosurgery, while questioning the value of new rhetorical devices for the assessment and presentation of psychosurgery results after the surge of Deep Brain Stimulation. © 2015 Academie des science.

Oertel M.,University Paris Diderot | Providencia C.,University of Coimbra | Gulminelli F.,University of Caen Lower Normandy | Raduta Ad.R.,IFIN HH
Journal of Physics G: Nuclear and Particle Physics | Year: 2015

Since the discovery of neutron stars with masses around 2 M the composition of matter in the central part of these massive stars has been intensively discussed. Within this paper we will (re)investigate the question of the appearance of hyperons. To that end we will perform an extensive parameter study within relativistic mean field models. We will show that it is possible to obtain high mass neutron stars with (i) a substantial amount of hyperons, (ii) radii of 12-13 km for the canonical mass of 1.4 M, and (iii) a spinodal instability at the onset of hyperons. The results depend strongly on the interaction in the hyperon-hyperon channels, on which only very little information is available from terrestrial experiments up to now. © 2015 IOP Publishing Ltd.

Prasad B.,University of Hyderabad | Sreenivas B.Y.,University of Hyderabad | Krishna G.R.,Indian Institute of Science | Kapavarapu R.,University of Coimbra | Pal M.,University of Hyderabad
Chemical Communications | Year: 2013

Unprecedented synthesis of functionalized indoles of potential pharmacological interest has been developed via a Pd-mediated cascade reaction involving an intramolecular Heck coupling followed by the construction of a fused cyclopentane ring in a single pot. © 2013 The Royal Society of Chemistry.

Costa J.,University of Porto | Mafra I.,University of Porto | Carrapatoso I.,University of Coimbra | Oliveira M.B.P.P.,University of Porto
Journal of Agricultural and Food Chemistry | Year: 2012

Almond (Prunus dulcis) has been widely used in all sorts of food products (bakery, pastry, snacks), mostly due to its pleasant flavor and health benefits. However, it is also classified as a potential allergenic seed known to be responsible for triggering several mild to life-threatening immune reactions in sensitized and allergic individuals. Presently, eight groups of allergenic proteins have been identified and characterized in almond, namely, PR-10 (Pru du 1), TLP (Pru du 2), prolamins (Pru du 2S albumin, Pru du 3), profilins (Pru du 4), 60sRP (Pru du 5), and cupin (Pru du 6, Pru du γ-conglutin), although only a few of them have been tested for reactivity with almond-allergic sera. To protect sensitized individuals, labeling regulations have been implemented for foods containing potential allergenic ingredients, impelling the development of adequate analytical methods. This work aims to present an updated and critical overview of the molecular characterization and clinical relevance of almond allergens, as well as review the main methodologies used to detect and quantitate food allergens with special emphasis on almond. © 2012 American Chemical Society.

Guerreiro R.J.,U.S. National Institutes of Health | Guerreiro R.J.,University of Coimbra | Gustafson D.R.,Gothenburg University | Gustafson D.R.,SUNY Downstate Medical Center | Hardy J.,University College London
Neurobiology of Aging | Year: 2012

Alzheimer's disease (AD) is a complex disorder with a clear genetic component. Three genes have been identified as the cause of early onset familial AD (EOAD). The most common form of the disease, late onset Alzheimer's disease (LOAD), is, however, a sporadic one presenting itself in later stages of life. The genetic component of this late onset form of AD has been the target of a large number of studies, because only one genetic risk factor (APOE4) has been consistently associated with the disease. However, technological advances allow new approaches in the study of complex disorders. In this review, we discuss the new results produced by genome wide association studies, in light of the current knowledge of the complexity of AD genetics. © 2012.

Gameiro S.,University of Coimbra | Gameiro S.,University of Cardiff | Verhaak C.M.,Radboud University Nijmegen | Kremer J.A.M.,Radboud University Nijmegen | Boivin J.,University of Cardiff
Human Reproduction Update | Year: 2013

background: The goal of this systematic review and meta-analysis was to estimate the rate of compliance with assisted reproductive technologies (ART) and examine its relationship with treatment success rates. methods: Six databases were systematically searched from 1978 to December 2011. Studies were included if they reported data on patient progression through three consecutive standard ART cycles. Compliance was estimated for the first three ART cycles (typical ART Regimen Compliance, TARC) and after the first and the second failed cycles (CAF1, CAF2). Treatment success rates for all patients who started ART and for those who fully complied with the three ART cycles were estimated. results: Ten studies with data for 14 810 patients were included. TARC was 78.2% [95% confidence interval (CI) 68.8-85.3%], CAF1 was 81.8% (73.3-88.1%) and CAF2 was 75.3% (68.2-81.2%). The overall success rate was 42.7% (32.6-53.6%) for all patients starting ART and 57.9% (49.4-65.9%) for those who complied with three ART cycles. Compliance rates did not vary according to study quality, but TARC was higher for studies that reported data on doctor-censored patients versus those that did not (84.2% 95% CI 75.5-90.2 versus 70.6% 95% CI 58.3-80.5, P = 0.043). Analysis of funnel plots and the Egger test indicated publication bias for CAF1. conclusions: Findings from this meta-analysis should reassure clinics and patients that most patients are able to comply with three cycles of ART. Compliers could increase their chances of success by as much as 15%. A more detailed assessment of compliance requires monitoring long-term treatment trajectories through the creation of national registries. © The Author 2012. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.

Barros F.J.,University of Coimbra
Software - Practice and Experience | Year: 2015

The support for software reuse has been a major goal in the design of programming languages. This goal, however, has proven difficult to reach, being only partially enabled by current software tools. In particular, reuse is not fully supported by object-oriented programming (OOP). Aspect-oriented programming (AOP) has introduced new operators that extend OOP, enabling a superior support for reusability. However, AOP operators exhibit limitations in supporting software reuse and more powerful constructs are still required. We consider the ability to define software in an independent manner as the key construct to enable systematic software reuse. To bridge the gap between independence and practical software tools, we have developed the concept of Independent and Pluggable Software Unit (PU), a construct that supports the definition of software topologies. In this paper, we compare PUs with AOP in their support for reusable software. To enable comparison, we employ some well described problems addressed by Software Design Patterns (SDPs). We provide PU and AOP versions of several SDPs, including, Observer, Composite, Command, Chain of Responsibility, and Proxy. In particular, we show that, whereas PUs provide a unified representation of design patterns, AOP representations do not achieve this unification. We also show that AOP solutions do not promote independent and reusable software. Copyright © 2013 John Wiley & Sons, Ltd.

Rodriguez-Echeverria S.,University of Coimbra | Lozano Y.M.,CSIC - Estacion Experimental De Zonas Aridas | Bardgett R.D.,University of Manchester
Functional Ecology | Year: 2016

Facilitation by nurse plants is a key process involved in the organization of plant communities and maintenance of biodiversity, particularly in harsh environments. Nurse plants increase plant diversity and productivity in these ecosystems, but our knowledge on the mechanisms through which such facilitation operates is still expanding. Despite growing evidence that soil microbiota impact plant fitness and community dynamics, their role in plant facilitation has been little explored. Here, we synthesize available evidence on the effect of nurse plants on the abundance, composition and activity of soil microbial communities, and the effect of these soil communities on beneficiary plant species. Studies conducted mostly in arid and semi-arid systems show that nurse plants promote the development of differentiated soil microbial communities characterized by a higher microbial abundance and activity, the dominance of competitive bacteria and larger mycorrhizal networks, compared to gaps and to coexisting non-nurses. There is also evidence that differentiated soil microbiota associated with nurse plants has positive effects on the establishment, growth and fitness of beneficiary plant species, although the mechanisms involved remain unclear. We suggest that they include increased nutrient availability for plants, a better use of resources through functional complementarity in the microbial community, soil stabilization and also direct molecular signalling between soil microbes and plants that affect plant defence and plant interactions. Evidence for the role of soil microbiota as mediators of facilitation by nurse plants is growing, but there are still too few studies on which to draw generalizable conclusions. Future studies are needed to assess the effect of plant ontogeny and environmental conditions on soil microbial communities under nurse plants and other coexisting species, and to determine the microbial groups and specific mechanisms involved in facilitation by nurse plants. © 2016 British Ecological Society.

Valero R.,University of Coimbra | Andersson S.,Sintef
Physical Chemistry Chemical Physics | Year: 2012

The OH + CO → H + CO 2 reaction is important in combustion, atmospheric, and interstellar chemistry. Whereas the direct reaction has been extensively studied both experimentally and theoretically, the reverse reaction has received relatively less attention. Here we carry out a quasiclassical trajectory study of the hyperthermal H + CO 2 → OH + CO reaction on a new interpolated potential energy surface based on the M06-2X density functional. The results reveal for the first time quantitative agreement with experiment for the reaction cross sections in the range of relative translational energies 1.2-2.5 eV. We attribute this excellent agreement to both the quality of the M06-2X energies, which closely reproduce CCSD(T) energies, and to the potential surface construction strategy that emphasizes both the direct and reverse reactions. © 2012 the Owner Societies.

Puig L.,University of Zaragoza | Bastanlar Y.,Middle East Technical University | Sturm P.,French Institute for Research in Computer Science and Automation | Guerrero J.J.,University of Zaragoza | Barreto J.,University of Coimbra
International Journal of Computer Vision | Year: 2011

In this study, we present a calibration technique that is valid for all single-viewpoint catadioptric cameras. We are able to represent the projection of 3D points on a catadioptric image linearly with a 6×10 projection matrix, which uses lifted coordinates for image and 3D points. This projection matrix can be computed from 3D-2D correspondences (minimum 20 points distributed in three different planes). We show how to decompose it to obtain intrinsic and extrinsic parameters. Moreover, we use this parameter estimation followed by a non-linear optimization to calibrate various types of cameras. Our results are based on the sphere camera model which considers that every central catadioptric system can be modeled using two projections, one from 3D points to a unitary sphere and then a perspective projection from the sphere to the image plane. We test our method both with simulations and real images, and we analyze the results performing a 3D reconstruction from two omnidirectional images. © 2010 Springer Science+Business Media, LLC.

Calvete M.J.F.,University of Coimbra
International Reviews in Physical Chemistry | Year: 2012

This review gives an overview of the nonlinear transmission (NLT) properties of near-infrared absorbing materials such as naphthalocyanines, extended porphyrins, conjugated polyenes, polymethines and other chromophores. Special attention is given to the mechanism of the NLT effect, discussing the several types mechanisms encountered. It focuses on the most important contributions about materials modulation through organic synthesis versatility, permitting the variation of the different physico-chemical features, and consequently aiming the achievement of effective systems in terms of NLT performance. © 2012 Taylor & Francis.

Bilalov A.,Lund University | Olsson U.,Lund University | Lindman B.,Lund University | Lindman B.,University of Coimbra
Soft Matter | Year: 2012

The interaction between DNA and various cationic species, e.g. cationic surfactant (CS), has a broad biological and biotechnological significance. In the cell nucleus as well as in transfection formulations, other species, mainly zwitterionic lipids, are also present but their exact role needs elucidation. A closer investigation of the stability of structures formed as well as the molecular arrangements is hampered by the complexity of the systems with respect to the number of components. A powerful way for reducing the number of components is to base studies on the stoichiometric (1:1) compound CSDNA, where the simple (sodium) counterions have been ion-exchanged by a cationic amphiphile ion. CSDNA is typically insoluble in water but is able to form liquid crystalline phases in aqueous mixtures with many additives capable of associating with the amphiphilic counterions (alcohols, non-ionic surfactants, lipids, cyclodextrins, etc.). Mixtures of CSDNA with a number of components have been investigated in detail with respect to phase behavior. The phase diagrams demonstrate a rich liquid crystallinity. The organization of DNA and the surfactant-lipid self-assemblies is controlled by different factors for different cases, mainly (i) the lipophilic characteristics of the components, (ii) the [CSDNA]/[amphiphile] ratio and (iii) DNA packing constraints, due to the large persistence length. A summary of phase diagrams is presented together with structural investigations based mainly on small-angle X-ray scattering. The role of DNA rigidity is illustrated in a comparison with analogous systems based on flexible polyanions. © 2012 The Royal Society of Chemistry.

Marinopoulos A.G.,University of Coimbra
Journal of Physics Condensed Matter | Year: 2011

While yttrium and impurity segregation at interfaces of yttria-stabilized zirconia (YSZ) has been intensively studied experimentally, the mechanisms governing the propensity for segregation are still not fully understood. The segregation energetics of yttrium and aluminum, another common segregant at interfaces of YSZ, were studied by means of first principles calculations based on density functional theory. Site-dependent formation energies were calculated following the substitutional incorporation of yttrium and aluminum in the near-interface region of the σ5(310) grain boundary in cubic zirconia, for which recent experimental data revealed strong yttrium enrichment. Aluminum segregation was found to be strongly favored, accompanied by extensive changes in its local environment and coordination. Yttrium displayed a segregation propensity dependent on the site of substitution that correlated with the ability of its surrounding environment to accommodate the misfit strain by a breathing-type relaxation and increase of the nearest-neighbor yttrium-oxygen distances. Formation energies of oxygen vacancies were also determined near the interface, both as isolated defects and also by considering cosegregation with yttrium; the ensuing defect association led to stable yttrium-vacancy complexes and increased the energy gain from yttrium incorporation at the core of the grain boundary. © 2011 IOP Publishing Ltd.

Coutinho J.A.P.,University of Aveiro | Carvalho P.J.,University of Aveiro | Oliveira N.M.C.,University of Coimbra
RSC Advances | Year: 2012

While the design of products and processes involving ionic liquids (ILs) requires knowledge of the thermophysical properties for these compounds, the massive number of possible distinct ILs precludes their detailed experimental characterization. To overcome this limitation, chemists and engineers must rely on predictive models that are able to generate reliable values for these properties, from the knowledge of the structure of the IL. A large body of literature was developed in the last decade for this purpose, aiming at developing predictive models for thermophysical and transport properties of ILs. A critical review of those models is reported here. The modelling approaches are discussed and suggestions relative to the current best methodologies for the prediction of each property are presented. Since most of the these works date from the last 5 years, this field can still be considered to be in its infancy. Consequently, this work also aims at highlighting major gaps in both existing data and modelling approaches, identifying unbeaten tracks and promising paths for further development in this area. This journal is © The Royal Society of Chemistry 2012.

Alves M.,University of Algarve | Goncalves T.,University of Coimbra | Quintas C.,University of Algarve
Food Control | Year: 2012

Cracked green table olives, from the Manzanilla variety, are a fermented food produced and consumed in Portugal. The objective of the present work was to study the microbiological characteristics and yeast population evolution during the fermentation of cracked green olives. The predominant microorganisms were yeasts while lactic acid bacteria were not detected and a clear decrease of the mould population was observed. At the end of the fermentations, no viable counts of Enterobacteriaceae were found. Yeast isolates were identified by the 5.8S rRNA-ITS region restriction analysis and by sequencing the D1/D2 region of the 26S rRNA gene. During the initial phases of the fermentations a great diversity of yeasts was observed. However, as the processes evolved the biodiversity decreased with the fermentative yeasts Citeromyces matritensis, Zygotorulaspora mrakii and Saccharomyces cerevisiae becoming the dominant species. The presence of these fermentative yeasts at the end of the production process is associated to a risk of spoilage. The results obtained represent a first attempt towards the comprehension of the microbiota of this type of " Natural olives" that constitute an important component of the Mediterranean diet. © 2011 Elsevier Ltd.

Lemos J.,University of Coimbra | Eggenberger E.,Michigan State University
Current Opinion in Ophthalmology | Year: 2014

Purpose of review This work reviews supranuclear ocular motor disorders, highlighting new data published during the past year. Recent findings Perceptional adaptative mechanisms may explain recent research concerning the discrepancy between objective measurement of saccade abnormalities and their putative functional visual impairment. Eye movement classes seem to be selectively disrupted by different neurodegenerative disorders. Deep brain stimulation in Parkinson's disease patients may improve pursuit deficits, highlighting the role of basal ganglia in the control of smooth pursuit. Subcortical optokinetic pathways seem to play an important role in maintaining the monocular nasotemporal optokinetic asymmetry seen in patients with infantile esotropia. Vergence-vestibular interaction has been further delineated in patients with idiopathic bilateral vestibular failure. Pharmacological treatment of central vestibular disorders with 4-aminopyridine has been extended to patients with ataxia-telangiectasia in whom it seems to reduce slow-phase velocity of nystagmus. Summary Recent data derived from anatomic and functional imaging studies are providing new insights into supranuclear ocular motor circuitry. Novel pharmacological and surgical therapies may have future implications in visual and vestibular rehabilitation of patients with supranuclear eye movement disorders. © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Laporte G.,Interuniversity Research Center on Enterprise Networks | Pascoal M.M.B.,University of Coimbra | Pascoal M.M.B.,Polytechnic Institute of Coimbra
Computers and Operations Research | Year: 2010

The minimum cost path problem with relays (MCPPR) consists of finding a minimum cost path from a source to a destination, along which relay nodes are located at a certain cost, subject to a weight constraint. This paper first models the MCPPR as a particular bicriteria path problem involving an aggregated function of the path and relay costs, as well as a weight function. A variant of this problem which takes into account all three functions separately is then considered. Formulating the MCPPR as a part of a bicriteria path problem allows the development of labeling algorithms in which the bound on the weight of paths controls the number of node labels. The algorithm for this constrained single objective function version of the problem has a time complexity of O(WmWnlog(maxW,n)), where n is the number of nodes, m is the number of arcs and W is the weight upper bound. Computational results on random instances with up to 10 000 nodes and 100 000 arcs, are reported. © 2010 Elsevier Ltd. All rights reserved.

Reva I.,University of Coimbra
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

In a recently published paper [Spectrochim. Acta A: Mol. Biomol. Spect. 138 (2015) 711-722], Prabhaharan, Prabakaran, Srinivasan, and Gunasekaran presented a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of cyanuric acid, and explain their findings using the tri-hydroxy tautomeric form of the compound. In reality, the compound adopts the tri-oxo tautomeric form, which is by over 100 kJ mol-1 more stable comparatively to the tri-hydroxy tautomer discussed and characterized by Prabhaharan et al. © 2015 Elsevier B.V. All rights reserved.

Alberto P.,University of Coimbra | De Castro A.S.,Sao Paulo State University | Malheiro M.,Brazilian Technological Institute of Aeronautics
Physical Review C - Nuclear Physics | Year: 2013

We derive the node structure of the radial functions which are solutions of the Dirac equation with scalar S and vector V confining central potentials, in the conditions of exact spin or pseudospin symmetry, i.e., when one has V=±S+C, where C is a constant. We show that the node structure for exact spin symmetry is the same as the one for central potentials which go to zero at infinity but for exact pseudospin symmetry the structure is reversed. We obtain the important result that it is possible to have positive energy bound solutions in exact pseudospin symmetry conditions for confining potentials of any shape, including naturally those used in hadron physics, from nuclear to quark models. Since this does not occur for potentials going to zero at large distances, which are used in nuclear relativistic mean-field potentials or in the atomic nucleus, this shows the decisive importance of the asymptotic behavior of the scalar and vector central potentials on the onset of pseudospin symmetry and on the node structure of the radial functions. Finally, we show that these results are still valid for negative energy bound solutions for antifermions. © 2013 American Physical Society.

The Combined-Hyperbolic-Inverse-Power-Representation method, which treats evenly both short- and long-range interactions, is used to fit an extensive set of ab initio points for HO2 previously utilized [Xu, J. Chem. Phys. 122, 244305 (2005)10.1063/1.1944290] to develop a spline interpolant. The novel form is shown to perform accurately when compared with others, while quasiclassical trajectory calculations of the O + OH reaction clearly pinpoint the role of long-range forces at low temperatures. © 2013 American Institute of Physics.

Cardoso J.,University of Coimbra
Lecture Notes in Business Information Processing | Year: 2013

The last decade has seen an increased interest in the study of networks in many fields of science. Examples are numerous, from sociology to biology, and to physical systems such as power grids. Nonetheless, the field of service networks has received less attention. Previous research has mainly tackled the modeling of single service systems and service compositions, often focusing only on studying temporal relationships between services. The objective of this paper is to propose a computational model to represent the various types of relationships which can be established between services systems to model service networks. This work acquires a particular importance since the study of service networks can bring new scientific discoveries on how service-based economies operate at a global scale. © 2013 Springer-Verlag.

In the so-called democratic societies citizens' participation has become a central issue to the analysis of decision making processes. However, in this scope the major difficulty is related to a broad definition of what can be considered as participatory modalities. In this paper protest actions are assumed as legitimate forms of participation in public decision making processes. Accordingly, this work describes and analyses the maternity wards closure in Portugal, one of the measures of the recent restructuring of the maternal and child health services that was implemented between May 2006 and December 2007, and the consequent protest actions developed by the local populations affected by the measure. It is also evaluated how a non-informed and communicated measure based on criteria such as security and quality of the provided health care can trigger protest movements, particularly as a strategy of citizens to participate in a public policy (re)formulation.

Maudet C.,University of Wurzburg | Mano M.,International Center for Genetic Engineering and Biotechnology | Mano M.,University of Coimbra | Eulalio A.,University of Wurzburg
FEBS Letters | Year: 2014

MicroRNAs (miRNAs) are small non-coding RNAs with a central role in the post-transcriptional control of gene expression, that have been implicated in a wide-range of biological processes. Regulation of miRNA expression is increasingly recognized as a crucial part of the host response to infection by bacterial pathogens, as well as a novel molecular strategy exploited by bacteria to manipulate host cell pathways. Here, we review the current knowledge of bacterial pathogens that modulate host miRNA expression, focusing on mammalian host cells, and the implications of miRNA regulation on the outcome of infection. The emerging role of commensal bacteria, as part of the gut microbiota, on host miRNA expression in the presence or absence of bacterial pathogens is also discussed. © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Dias A.M.P.G.,University of Coimbra
Journal of Structural Engineering (United States) | Year: 2012

This paper discusses the nonlinear mechanical behavior of timber-concrete structures, mainly when dowel-type fasteners are used in the connections. These nonlinear phenomena result from the nonlinear mechanical behavior of the materials and connections. This paper deals with the connection aspect of the nonlinearity and goes on to present and discuss the causes of such phenomena as well as the approaches available to address them. Since these analyses require an adequate definition of the load-slip behavior of the connection, a numerical model is proposed to derive it, based on either results from experimental tests or numerical models. A calculation example is used to assess the influence of the nonlinear phenomena on the design of this type of structure. From the analysis undertaken, it is concluded that the nonlinear mechanical behavior of the connections may have a significant influence on the mechanical behavior of the composite structures. Moreover, the model proposed to describe the load-slip behavior of the connection is shown to be accurate and effective. © 2012 American Society of Civil Engineers.

Lopes S.,University of Coimbra | Jorge L.,Polytechnic Institute of Castelo Branco | Cruz H.,National Laboratory for Civil Engineering
Materials and Structures/Materiaux et Constructions | Year: 2012

This article describes a numerical model that was developed for the analysis of composite timber-concrete beams. This model presents a simplified methodology for determining the effective bending stiffness of the timber-concrete composite structure. It is based on previous work done usually referred to in some non-normative literature by γ-method. The implemented methodology assumes some simplifications, as for instance, linear elastic behavior of all components, constant stiffness of the connection and sinusoidal loading. For comparison purposes, the work benefits from an experimental program in which full-scale beams were tested in bending and timber-concrete connections were tested in shear. The FE model has shown the ability to overcome the simplifications of the Eurocode, namely the variation of shear force along the beam axis. The numerical model is capable of detecting and quantifying the influence of the non-linear behavior of the connections on the composite structure. Different parameters are analyzed and, for instance, the ductility behavior of the timber-concrete connection could be more important than the maximumstrength,which is an interesting result. By comparing theoretical predictions with test results, it is clear that the numerical model used in this work is a very interesting method when compared with the usual design models, such as that of Annex B of Eurocode 5 (EN 1995-1-1). The influence of the connections behavior on the ultimate load of the composite structure is very important and the described approach proved to give good predictions. © RILEM 2011.

Simovski C.,Aalto University | Maslovski S.,University of Coimbra | Nefedov I.,Aalto University | Tretyakov S.,Aalto University
Optics Express | Year: 2013

Using our recently developed method we analyze the radiative heat transfer in micron-thick multilayer stacks of metamaterials with hyperbolic dispersion. The metamaterials are especially designed for prospective thermophotovoltaic systems.We show that the huge transfer of near-infrared thermal radiation across micron layers of metamaterials is achievable and can be optimized. We suggest an approach to the optimal design of such metamaterials taking into account high temperatures of the emitting medium and the heating of the photovoltaic medium by the low-frequency part of the radiation spectrum.We show that both huge values and frequency selectivity are achievable for the radiative heat transfer in hyperbolic multilayer stacks. © 2013 Optical Society of America.

Schaeffer N.,Joseph Fourier University | Pais M.A.,University of Coimbra
Geophysical Research Letters | Year: 2011

Quasi-geostrophic (QG) flows are a recently developed and very promising paradigm for modeling decadal secular variation (SV). Here we examine the effects of allowing anisotropy and departures of the flow from quasigeostrophy. We perform dedicated numerical experiments of the flow dynamics and magnetic induction inside the Earth's liquid core at time scales characteristic of secular variation of the geomagnetic field. Obtained results motivate new flow inversion regularization featuring an equatorially anti-symmetric component superimposed to quasi-geostrophic columns, and stronger latitudinal than longitudinal flow gradients. Applying these constraints allows to explain the observed SV for the whole period 1840-2010, and most significantly, provides a clearly improvement in prediction for decadal length-of-day variations for the period 1980-2000. Furthermore, the trace of the inner-core appears clearly without any assumption for the 1997-2010 period covered by satellite geomagnetic data. Our results support QG being the appropriate description of the force balance within the core on decadal time scales and large spatial scales. Copyright 2011 by the American Geophysical Union.

Dabrowski J.M.,Jagiellonian University | Arnaut L.G.,University of Coimbra | Arnaut L.G.,Luzitin SA
Photochemical and Photobiological Sciences | Year: 2015

Photodynamic therapy (PDT) requires a medical device, a photosensitizing drug and adequate use of both to trigger biological mechanisms that can rapidly destroy the primary tumour and provide long-lasting protection against metastasis. We present a multidisciplinary view of the issues raised by the development of PDT. We show how spectroscopy, photophysics, photochemistry and pharmacokinetics of photosensitizers determine the mechanism of cell death and clinical protocols. Various examples of combinations with chemotherapies and immunotherapies illustrate the opportunities to potentiate the outcome of PDT. Particular emphasis is given to the mechanisms that can be exploited to establish PDT as a systemic treatment of solid tumours and metastatic disease. © The Royal Society of Chemistry and Owner Societies 2015.

Ljungberg B.,Umea University | Bensalah K.,University of Rennes 1 | Canfield S.,University of Houston | Dabestani S.,Skane University Hospital | And 11 more authors.
European Urology | Year: 2015

Context The European Association of Urology Guideline Panel for Renal Cell Carcinoma (RCC) has prepared evidence-based guidelines and recommendations for RCC management. Objectives To provide an update of the 2010 RCC guideline based on a standardised methodology that is robust, transparent, reproducible, and reliable. Evidence acquisition For the 2014 update, the panel prioritised the following topics: percutaneous biopsy of renal masses, treatment of localised RCC (including surgical and nonsurgical management), lymph node dissection, management of venous thrombus, systemic therapy, and local treatment of metastases, for which evidence synthesis was undertaken based on systematic reviews adhering to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Relevant databases (Medline, Cochrane Library, trial registries, conference proceedings) were searched (January 2000 to November 2013) including randomised controlled trials (RCTs) and retrospective or controlled studies with a comparator arm. Risk of bias (RoB) assessment and qualitative and quantitative synthesis of the evidence were performed. The remaining sections of the document were updated following a structured literature assessment. Evidence synthesis All chapters of the RCC guideline were updated. For the various systematic reviews, the search identified a total of 10 862 articles. A total of 151 studies reporting on 78 792 patients were eligible for inclusion; where applicable, data from RCTs were included and meta-analyses were performed. For RCTs, there was low RoB across studies; however, clinical and methodological heterogeneity prevented data pooling for most studies. The majority of studies included were retrospective with matched or unmatched cohorts based on single or multi-institutional data or national registries. The exception was for systemic treatment of metastatic RCC, in which several RCTs have been performed, resulting in recommendations based on higher levels of evidence. Conclusions The 2014 guideline has been updated by a multidisciplinary panel using the highest methodological standards, and provides the best and most reliable contemporary evidence base for RCC management. Patient summary The European Association of Urology Guideline Panel for Renal Cell Carcinoma has thoroughly evaluated available research data on kidney cancer to establish international standards for the care of kidney cancer patients. © 2015 European Association of Urology.

MacHado P.,University of Coimbra | MacHado P.,Leiden University | Landewe R.,Maastricht University | Lie E.,Diakonhjemmet Hospital | And 4 more authors.
Annals of the Rheumatic Diseases | Year: 2011

Background: The Ankylosing Spondylitis Disease Activity Score (ASDAS) is a new composite index to assess disease activity in ankylosing spondylitis (AS). It fulfi ls important aspects of truth, feasibility and discrimination. Criteria for disease activity states and improvement scores are important for use in clinical practice, observational studies and clinical trials and so far have not been developed for the ASDAS. Objective: To determine clinically relevant cut-off values for disease activity states and improvement scores using the ASDAS. Methods: For the selection of cut-offs data from the Norwegian disease modifying antirheumatic drug (NORDMARD) registry, a cohort of patients with AS starting conventional or biological DMARDs, were used. Receiver operating characteristic analysis against several external criteria was performed and several approaches to determine the optimal cut-offs used. The fi nal choice was made on clinical and statistical grounds, after debate and voting by Assessment of SpondyloArthritis international Society members. Crossvalidation was performed in NOR-DMARD and in Ankylosing Spondylitis Study for the Evaluation of Recombinant Infl iximab Therapy, a database of patients with AS participating in a randomised placebo-controlled trial with a tumour necrosis factor blocker. Results: Four disease activity states were chosen by consensus: inactive disease, moderate, high and very high disease activity. The three cut-offs selected to separate these states were: 1.3, 2.1 and 3.5 units. Selected cut-offs for improvement were: change ≥1.1 units for clinically important improvement and change ≥2.0 units for major improvement. Results: of the crossvalidation strongly supported the cut-offs. Conclusions: Cut-off values for disease activity states and improvement using the ASDAS have been developed. They proved to have external validity and a good performance compared to existing criteria.

Guemez J.,University of Cantabria | Fiolhais M.,University of Coimbra
European Journal of Physics | Year: 2014

We analyze, from the thermodynamical point of view, mechanical systems in which there is the production of mechanical energy due to an internal source of energy, and compare that analysis with a similar one for the 'symmetric' motion that occurs with energy dissipation. The analysis of the energetic asymmetries is instructive to put in evidence the role of thermodynamics even in the discussion of mechanical aspects. We illustrate the discussion with the well-known example of a person on a rotating platform outstretching and contracting his or her arms, and also with other common situations such as jumping and walking. © 2014 IOP Publishing Ltd.

Guemez J.,University of Cantabria | Fiolhais M.,University of Coimbra
European Journal of Physics | Year: 2014

We solve a set of selected exercises on rotational motion requiring a mechanical and thermodynamical analysis. When non-conservative forces or thermal effects are present, a complete study must use the first law of thermodynamics together with Newton's second law. The latter is here better expressed in terms of an 'angular' impulse-momentum equation (Poinsot-Euler equation), or, equivalently, in terms of a 'rotational' pseudo-work-energy equation. Thermodynamical aspects in rotational systems, when e.g. frictional forces are present or when there is a variation of the rotational kinetic energy due to internal sources of energy, are discussed. © 2014 IOP Publishing Ltd.

The spin-component-scaling second-order Møller-Plesset theory proposed by Grimme, the scaled opposite-spin variant of Head-Gordon and co-workers, and other variants of the theory to treat the electron correlation energy are examined. A refinement of scaled opposite-spin theory for strong chemical interactions is suggested where the scaled correlation contribution is chosen such as to mimic closely the one obtained by more sophisticated methods of the coupled cluster type. With the scaling factor chosen to vary in a simple statistical manner with the number of opposite-spin electron pairs of the system, the parameters have been calibrated from standard coupled cluster type calculations for a chosen ab initio test data set. The new approach, termed as variable-scaling opposite spin, aims to be applicable at any regions of the molecule configuration space where second-order Møller-Plesset perturbation theory converges. It thus benefits of all advantages inherent to the original theory, which makes it an attractive approach on a computational cost basis. Because the method in one of its formats fails size-extensivity, the consequences and remedies of this are analyzed. Illustrations are presented for many molecules utilizing Dunning-type basis sets, in particular, for a detailed analysis of N3 in its lowest quartet state, which does not belong to the test set. Extrapolations of the calculated raw energies to the complete one-electron basis set limit are also reported, giving the most reliable estimates available thus far of the energetics for the N (S4) + N2 exchange reaction. All spin-component-scaling schemes are known to show difficulties in dealing with weak interactions of the van der Waals type, which has justified the design of specific variants of the theory according to the property and regime of interactions. Several variants of the theory are then examined using a second test set of molecules, and shown to be linked via a coordinate that evolves gradually between two known extreme regimes. It is further shown that such a coordinate can be specified via a constrained Feenberg-type scaling approach, a theory whose merits are also explored. © 2010 American Institute of Physics.

The physicochemical surface properties of cellulose and lignocellulosic materials are of major importance in the context of the production of composites, in papermaking, and textile area. These properties can be evaluated by using inverse gas chromatography (IGC), a particularly suitable technique for the characterization of the surface properties of fibrous materials and powders. At infinite dilution conditions of appropriate gas probes, IGC may provide important parameters including the dispersive component of the surface energy of the material under analysis, thermodynamic data on the adsorption of specific probes, and Lewis acid-base interaction parameters between the matrix and the filler of composite materials. This paper critically reviews the most relevant results available in the literature concerning the characterization of cellulose and lignocellulosic materials using IGC. Emphasis will be put into the cellulose and nanocellulose surface properties, changes in the surface properties of cellulose and lignocellulosic materials after chemical and physical modifications, and in the compatibility of cellulose-based materials with polymeric matrices. The surface properties of non-woody fibers will also be considered. Before discussing the results available in the literature, the theoretical background and the main approaches used for the calculation of parameters accessed by IGC will be given. It is expected that this review can contribute to a better knowledge of the physicochemical surface properties of cellulosics. © 2013 Springer Science+Business Media Dordrecht.

Aguilar-Saavedra J.A.,University of Granada | Aguilar-Saavedra J.A.,University of Coimbra | Aguilar-Saavedra J.A.,Institute Fisica Of Cantabria Csic Uc | Benbrik R.,Institute Fisica Of Cantabria Csic Uc | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We obtain constraints on the mixing of vectorlike quarks coupling predominantly to the third generation. We consider all (seven) relevant types of vectorlike quarks, individually. The constraints are derived from oblique corrections and Z→bb̄ measurements at the Large Electron-Positron (LEP) Collider and the Stanford Linear Collider. We investigate the implications of these constraints on LHC phenomenology, concerning the decays of the heavy quarks and their single production. We also explore indirect effects of heavy quark mixing in top and bottom couplings. A remarkable effect is the possibility of explaining the anomalous forward-backward asymmetry in Z→bb̄ at the LEP with a hypercharge -5/6 doublet. We also study the impact of the new quarks on single Higgs production at the LHC and Higgs decay. © 2013 American Physical Society.

Lobo C.,University of Coimbra
Ophthalmologica | Year: 2012

Cataract surgery is an efficient procedure, and is generally associated with good visual results. Nevertheless, cystoid macular edema (CME) may develop, and this can result in suboptimal postoperative vision. Many factors are considered to contribute to its development, and although the treatment options depend upon the underlying cause of CME, the usual therapeutic approach for prophylaxis and treatment of CME is directed towards blocking the inflammatory mediators. This article provides a review of possible risk factors, pathogeneses, incidence rates, and methods of diagnosis, as well as the current guidelines for managing CME. Copyright © 2011 S. Karger AG, Basel.

Vorotnikov D.,University of Coimbra
Journal of Mathematical Biology | Year: 2014

The muscle contraction, operation of ATP synthase, maintaining the shape of a cell are believed to be secured by motor proteins, which can be modelled using the Brownian ratchet mechanism. We consider the randomly flashing ratchet model of a Brownian motor, where the particles can be in two states, only one of which is sensitive the applied spatially periodic potential (the mathematical setting is a pair of weakly coupled reaction-diffusion and Fokker-Planck equations). We prove that this mechanism indeed generates unidirectional transport by showing that the amount of mass in the wells of the potential decreases/increases from left to right. The direction of transport is unambiguously determined by the location of each minimum of the potential with respect to the so-called diffusive mean of its adjacent maxima. The transport can be generated not only by an asymmetric potential, but also by a symmetric potential and asymmetric transition rates, and as a consequence of the general result we derive explicit conditions when the latter happens. When the transitions are localized on narrow active sites in the protein conformation space, we find a more explicit characterization of the bulk transport direction, and infer that some common preconditions of the motor effect are redundant. © 2013 Springer-Verlag Berlin Heidelberg.

Maslovski S.I.,University of Coimbra
Optics Communications | Year: 2012

Here, I briefly review the key principles of subwavelength imaging in dense arrays of resonant scatterers, with an emphasis on resonant plasmonic structures at optical frequencies. © 2012 Elsevier B.V. All rights reserved.

Tuberculosis (TB) may be an acute or chronic infection of bone and/or soft tissues. Nevertheless, human skeletons only registered a small percentage of those cases. This work aims to explore data from morbidity and mortality of individuals who contracted or died of TB after Koch bacillus discovery and before the development of antibiotics, using this information to interpret the scarcity of evidences detectable by paleopathological studies. To fulfill these goals, the Coimbra University Hospital and Coimbra Municipality Cemetery records from 1919 to 1928 were analyzed. As expected, pulmonary TB was the most common form of the diseases, both at hospital admission (43.7%, n = 904) and as cause of death of the individuals inhumed, especially after the age of 10 years. In children under 10 years, meningeal TB was the more common form. Pott's diseases represented only 4.7% (n = 98) of the hospital admission due to TB and 0.7% (n = 8) of the TB deaths at the cemetery. However, in paleopathology the macroscopic evidence of TB comes mainly from Pott's disease. Documented skeletons shows that new bone on visceral surfaces of ribs can occurs in other diseases besides pulmonary TB but its presence can be also use as an indicative of possible TB infection. © 2015 Elsevier Ltd. All rights reserved.

Cascao R.,Institute Medicina Molecular | Rosario H.S.,Institute Medicina Molecular | Souto-Carneiro M.M.,University of Coimbra | Fonseca J.E.,Institute Medicina Molecular
Autoimmunity Reviews | Year: 2010

Rheumatoid arthritis is the most common inflammatory joint disease. The etiopathogenesis of this condition has been classically explained by a T cell-driven process. However, recent studies have highlighted the possible contribution of neutrophils for the early phases of RA physiopathology. These cells are phagocytic leukocytes that play crucial roles in the acute defense against pathogens while modulating the function of other immune cells and contributing to the perpetuation of an initial inflammatory response. The herein article reviews recent progresses in the understanding of the immunopathology of RA with a special emphasis on the role of neutrophils. © 2010 Elsevier B.V. All rights reserved.

Freitas A.,Laboratorio Nacional Of Investigacao Veterinaria | Barbosa J.,Laboratorio Nacional Of Investigacao Veterinaria | Ramos F.,University of Coimbra
Meat Science | Year: 2014

A multi-residue quantitative screening method covering 41 antibiotics from 7 different families, by ultra-high-performance-liquid-chromatography tandem mass spectrometry (UHPLC-MS/MS), is described. Sulfonamides, trimethoprim, tetracyclines, macrolides, quinolones, penicillins and chloramphenicol are simultaneously detected after a simple sample preparation of bovine muscle optimized to achieve the best recovery for all compounds. A simple sample treatment was developed consisting in an extraction with a mixture of acetonitrile and ethylenediaminetetraacetic acid (EDTA), followed by a defatting step with n-hexane. The methodology was validated, in accordance with Decision 2002/657/EC by evaluating the required parameters: decision limit (CCα), detection capability (CCβ), specificity, repeatability and reproducibility. Precision in terms of relative standard deviation was under 20% for all compounds and the recoveries between 91% and 119%. CCα and CCβ were determined according the maximum residue limit (MRL) or the minimum required performance limit (MRPL), when required. © 2014 Elsevier Ltd.

Lopes A.C.,University of Coimbra
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2010

This paper presents a shared-control approach for Assistive Mobile Robots (AMR), which depends on the user's ability to navigate a semi-autonomous powered wheelchair, using a sparse and discrete human-machine interface (HMI). This system is primarily intended to help users with severe motor disabilities that prevent them to use standard human-machine interfaces. Scanning interfaces and Brain Computer Interfaces (BCI), characterized to provide a small set of commands issued sparsely, are possible HMIs. This shared-control approach is intended to be applied in an Assisted Navigation Training Framework (ANTF) that is used to train users' ability in steering a powered wheelchair in an appropriate manner, given the restrictions imposed by their limited motor capabilities. A shared-controller based on user characterization, is proposed. This controller is able to share the information provided by the local motion planning level with the commands issued sparsely by the user. Simulation results of the proposed shared-control method, are presented.

Proenca J.,University of Coimbra
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2010

The Pulse Transit Time (PTT) is generally assumed to be a good surrogate measure to comfortably track blood pressure (BP) and blood pressure changes. This paper investigates PTT variations for healthy young subjects during a sequence of short-term physical exercises. PTT was measured by two different methodologies having different measurement accuracies as well as underlying assumptions: the total PTT from heart to fingertip and the difference of fingertip and earlobe PTTs. Small non consistent changes and very low correlation of both PTTs with systolic blood pressure (SBP) have been observed for the study population (-0.19 ± 0.45 and 0.22 ± 0.46). In conclusion, there might be a need for an improved measurement accuracy of the sensors and data processing techniques in use. The applicability of the Moens-Korteweg equation is also questionable for young people having flexible arteries. In this case, significant radius changes do occur in the large arteries during exercise, which might counteract a PTT decrease with the BP elevation. These radius effects are excluded from the Moens-Korteweg model.

Oueslati I.,University of Coimbra
Current Organic Chemistry | Year: 2015

Besides cyclodextrins and crown ethers, calixarenes are the most commonly studied macrocyclic compounds. Although their chemistry is well documented, sub-categorizing of azacrown conjugates of calixarenes still stands as a mystery. This review, mustered with 104 references, offers the readers of various disciplines an overview of the up to date knowledge of calixazacrowns apropos to their recognition behavior in solution and at the surface, and assesses the state of the art achievements in their self-assembly and application in nanomaterial chemistry, sensing, light-emitting, electronics and biology. The progress of calixazacrowns in the nanoworld is anticipated to emerge as a rich research area in near future. © 2015 Bentham Science Publishers.

Bruze M.,Skane University Hospital | Engfeldt M.,Skane University Hospital | Goncalo M.,University of Coimbra | Goossens A.,Catholic University of Leuven
Contact Dermatitis | Year: 2013

Background Methylisothiazolinone (MI) is used as a preservative in occupational and household products, and cosmetics. It is a part of the preparation of methylchloroisothiazolinone (MCI)/MI, which is patch tested in water in the European baseline series. However, this preparation fails to detect a significant percentage of allergic contact reactions to MI. Objectives To investigate whether a separate test preparation with MI should be included in the European baseline series. Methods Literature survey. Results In consecutively tested dermatitis patients, the contact allergy rate for MI varies between 0.6% and 6%, with a marked increase in recent years. The contact allergy rate for MI alone, not detected with MCI/MI, varies between 0% and 1.6%. Most cases are relevant, as shown by repeated open application test studies, and are mainly related to exposure from cosmetic products. Conclusions Owing to the increase in contact allergy to MI not detected with MCI/MI, it is recommended that MI in water at 2000 ppm be included in the European baseline series. With the Finn Chamber® (diameter, 8 mm) technique, a volume of 15 μl should be applied, giving a dose of 60 μg/cm2. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Brito M.,University of Coimbra
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2010

In this paper, the architecture of a modular, service-oriented, Sensor Middleware for data acquisition and processing is presented. The described solution was developed with the purpose of solving two increasingly relevant problems in the context of modern pHealth systems: i) to aggregate a number of heterogeneous, off-the-shelf, devices from which clinical measurements can be acquired and ii) to provide access and integration with an 802.15.4 network of wearable sensors. The modular nature of the Middleware provides the means to easily integrate pre-processing algorithms into processing pipelines, as well as new drivers for adding support for new sensor devices or communication technologies. Tests performed with both real and artificially generated data streams show that the presented solution is suitable for use both in a Windows PC or a Windows Mobile PDA with minimal overhead.

Freire N.M.A.,University of Coimbra | Estima J.O.,University of Beira Interior | Cardoso A.J.M.,University of Beira Interior
IEEE Transactions on Industrial Electronics | Year: 2014

The widespread use of electric drives has led to an increasing interest in their condition monitoring and fault diagnostics. With respect to power-switch open-circuit fault diagnosis, the majority of the proposed voltage-based approaches require additional hardware, increasing the system cost. As a result, industry acceptance may be low. This paper proposes a new voltage-based approach - without additional sensors - for open-circuit fault diagnosis in closed-loop controlled pulsewidth-modulation (PWM) ac voltage source converters, by using the information contained in the reference voltages available from the control system. The robustness against false alarms of the proposed technique is improved by employing a voltage observer, in order to estimate the actual converter voltages. It has been proven that the algorithm is insensitive to parameter errors; thus, its effectiveness is not compromised. In order to assess the applicability of the diagnostic technique, it is integrated into the control system of a permanent-magnet-synchronous-machine drive, with regenerative capabilities, together with three of the most widely used PWM control strategies: hysteresis current control, direct torque control, and space vector modulation. The technique performance is analyzed in detail by means of several experimental results. © 1982-2012 IEEE.

Neves M.,University of Coimbra
Transplantation proceedings | Year: 2012

Accumulation of C4d along peritubular capillaries (PTC) of renal allografts is normally attributed to antibody-mediated rejection. The prognostic implication of these deposits associated with "cell-mediated" rejection on graft survival remains uncertain. Our study aims to evaluate the impact of C4d deposits along PTC of patients with acute cell- mediated rejection on graft function and survival. We retrospectively analyzed patients transplanted between 2005 and 2010 with histopathologic diagnosis of acute rejection (AR). Eleven patients with "pure" antibody-mediated rejection were excluded. The remaining 79 patients were divided into two groups according to type of AR by Banff 2003 criteria: type I (69.6%) versus type II (30.4%). In each group, comparisons were made between C4d-negative (-) and C4d-positive (+) biopsies. Fifty-five patients presented with type I AR: 35 (63.6%) C4d- and 20 (36.4%) C4d+. Twenty-four patients presented with type II AR: 13 (54.2%) C4d- and 11 (45.8%) C4d+. In the type I AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (94% and 91% versus 75% and 75%, respectively, log-rank P = .26). No differences were encountered in estimated glomerular filtration rate (eGFR) between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 14.7% of C4d- patients versus 25% in C4d+ patients (P = NS). In the type II AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (85% and 85% versus 72% and 61%, respectively, log-rank P = .50). No differences were encountered in eGFR between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 30.8% of C4d- patients versus 45.5% in C4d+ patients (P = NS). Our results suggest that detection of C4d staining in acute "cell-mediated" rejection does not imply a worse renal prognosis. Copyright © 2012 Elsevier Inc. All rights reserved.

Freire N.M.A.,University of Coimbra | Freire N.M.A.,Institute Telecomunicaes | Cardoso A.J.M.,Institute Telecomunicaes | Cardoso A.J.M.,University of Beira Interior
IEEE Transactions on Industrial Electronics | Year: 2014

Reliability and availability levels are crucial aspects for assessing the economic viability of wind energy conversion systems. Therefore, fault-tolerant systems can make a valuable contribution. This paper presents a fault-tolerant permanent-magnet synchronous generator (PMSG) drive employing new direct control techniques. For postfault operation, a direct power control (DPC) of a four-switch three-phase converter and a direct torque control of a three-switch three-phase rectifier are proposed. Switching tables are theoretically formulated for both control techniques. Two alternative tables are obtained for the DPC of the grid-side converter, permitting the choice between implementation simplicity and enhanced performance. All necessary reconfigurations to handle open-circuit faults are triggered by a reliable fault diagnostic method, which has a low computational demand, without requiring additional measurements. Experimental results are presented, demonstrating the feasibility of the proposed fault-tolerant PMSG drive. © 1982-2012 IEEE.

Chung H.Y.,Leiden University | Chung H.Y.,University of Hong Kong | Machado P.,Leiden University | Machado P.,University of Coimbra | And 3 more authors.
Annals of the Rheumatic Diseases | Year: 2012

Objectives: To investigate the association of smoking with various clinical, functional and imaging outcomes in patients with early axial spondyloarthritis (SpA). Methods: 647 patients with early inflammatory back pain (IBP) fulfilling at least one of the internationally accepted SpA criteria and with available smoking data were included in the analyses. Clinical, demographic and imaging parameters were compared between smokers and non-smokers at a cross-sectional level. Variables with significant differences in univariate analyses were used as dependent variables in multivariate linear and logistic regression models adjusted for potential confounding/contributing factors. Results: Multivariate analysis showed that smoking was associated with an earlier onset of IBP (regression coefficient (B)=(-1.46), p=0.04), higher disease activity (ankylosing spondylitis disease activity score B=0.20, p=0.03; Bath ankylosing spondylitis disease activity index B=0.50, p=0.003), worse functional status (Bath ankylosing spondylitis functional index B=0.38, p=0.02), more frequent MRI inflammation of the sacroiliac joints (OR 1.57, p=0.02) and the spine (OR 2.33, p<0.001), more frequent MRI structural lesions of the sacroiliac joints (OR 1.54, p=0.03) and the spine (OR 2.02, p=0.01), and higher modified Stoke ankylosing spondylitis spine score (B=0.54, p=0.03) reflecting radiographic structural damage of the spine. Smoking was also associated with poorer quality of life (Euroquality of life questionnaire B=1.38, p<0.001, short form 36 physical B=(-4.89), p<0.001, and mental component score B=(-5.90), p<0.001). Conclusion: In early axial SpA patients, smoking was independently associated with earlier onset of IBP, higher disease activity, increased axial inflammation on MRI, increased axial structural damage on MRI and radiographs, poorer functional status and poorer quality of life.

Nagia L.,University of Alabama at Birmingham | Lemos J.,University of Coimbra | Abusamra K.,Michigan State University | Cornblath W.T.,University of Michigan | Eggenberger E.R.,Michigan State University
Ophthalmology | Year: 2015

Purpose To calculate the rate and timing of conversion from ocular myasthenia gravis to generalized myasthenia gravis. Design Retrospective multicenter analysis. Subjects Patients included in the study were diagnosed with ocular myasthenia gravis without the presence of generalized disease at onset. Methods We conducted a retrospective multicenter analysis. We reviewed charts of 158 patients who met diagnostic criteria for ocular myasthenia gravis. Patients were divided into 2 subgroups: an immunosuppressant treatment group and a nonimmunosuppressant treatment group. Timing of conversion to generalized disease and duration of follow-up also was evaluated. Additional data such as clinical symptoms at presentation, laboratory test results, and chest imaging results also were recorded. Main Outcome Measures Conversion rates to generalized myasthenia at 2 years, effect of immunosuppression on conversion, and timing of conversion. Results The 158-patient cohort included 76 patients who received immunosuppressant therapy; the remaining 82 patients did not. The overall conversion rate to generalized disease was 20.9%. At 2 years, generalized myasthenia developed in 8 of 76 patients in the treated group and in 15 of 82 patients in the nonimmunotherapy group (odds ratio, 0.52; 95% confidence interval, 0.20-1.32). Median time for conversion to generalized disease was 20 months in the nonimmunosuppressant group and 24 months in the immunosuppressant group. Conversion occurred after 2 years of symptom onset in 30% of patients. Conclusions Conversion rates from ocular to generalized myasthenia gravis may be lower than previously reported both in immunosuppressed and nonimmunosuppressed patients. A subset of patients may continue to convert to generalized disease beyond 2 years from onset of symptoms, and close monitoring should be continued. © 2015 American Academy of Ophthalmology.

To evaluate the effect of gender and menopause in cardiovascular risk (CVR) in a healthy population based on both classical and nontraditional markers. 56 men and 68 women (48 pre- and 20 postmenopause) were enrolled in the study. The following markers were analyzed: blood pressure (BP), body mass index (BMI), waist circumference (WC), glucose, total cholesterol (total-c), triglycerides (TGs), low-density lipoprotein cholesterol (LDL-c), oxidized-LDL (Ox-LDL), HDL-c and subpopulations, paraoxonase-1 activity, hsCRP, uric acid, tumor necrosis factor alpha (TNF- α ), adiponectin, vascular endothelial growth factor (VEGF), and intercellular adhesion molecular 1 (ICAM1). Relative to the women, men present significantly increased BMI, WC, BP, glucose, total-c, TGs, LDL-c, Ox-LDL, uric acid, and TNF- α and reduced adiponectin and total and large HDL-c. The protective profile of women is lost after menopause with a significantly increased BMI, WC, BP, glucose, LDL-c, Ox-LDL, hsCRP, and VEGF and decreased total and large HDL-c. Significant correlations were found in women population and in postmenopausal women between Ox-LDL and total, large, and small HDL-c and between TNF- α and total, large, and small HDL-c, LDL-c, and Ox-LDL. Men present higher CVR than women who lost protection after menopause, evidenced by nontraditional markers, including Ox-LDL and HDL subpopulations.

Prasath V.B.S.,University of Missouri | Vorotnikov D.,University of Coimbra
Journal of Mathematical Imaging and Vision | Year: 2014

In this paper, we consider a coupled system of partial differential equations (PDEs) based model for image restoration. Both the image and the edge variables are incorporated by coupling them into two different PDEs. It is shown that the initial-boundary value problem has global in time dissipative solutions (in a sense going back to P.-L. Lions), and several properties of these solutions are established. Some numerical examples are given to highlight the denoising nature of the proposed model along with some comparison results. © 2012 Springer Science+Business Media New York.

Marques Da Silva P.,Nucleo de Investigacao Arterial e da Consulta de Hipertensao e Dislipidemias do Servico de Medicina | Cardoso S.M.,University of Coimbra
Revista Portuguesa de Cardiologia | Year: 2011

Introduction: Cardiovascular disease (CVD) is the leading cause of death and one of the most important causes of morbidity in Western societies. Dyslipidemia is an important risk factor for CVD and effective treatment significantly reduces cardiovascular risk. Objective: To evaluate the prevalence and type of persistent lipid abnormalities in patients treated with statins. Methods: The Dyslipidemia International Study (DYSIS) was a multicenter, epidemiologic cross-sectional study conducted in 12 European countries and Canada. Patients ≥45 years old, treated with statins for at least three months during the enrolment period from April 2008 to February 2009, were sequentially enrolled. This study presents the results for the Portuguese population. Results: In Portugal, 916 patients were recruited in 125 centers; mean age was 64.1±9.9 years and 47.1% were women. Most patients (66.7%) presented high cardiovascular risk. The most frequently used statin was simvastatin (55.9%; dose 21.3±6.2 mg/day) and only 15.3% of the patients were simultaneously taking other lipid-lowering agents. In most patients, LDL (62.9%; n=883) and total cholesterol (68%; n=883) were not at the target levels recommended by the European Society of Cardiology (ESC). It was also found that 22% of patients presented lower HDL values than those recommended and that 39% presented high triglyceride levels. LDL outside the target range was the most common abnormality, both when assessed separately and when combined with low HDL and high triglycerides. Conclusion: The number of patients with lipid abnormalities was very significant, especially for LDL, considering that all were under statin therapy.

Basile P.G.,University of Coimbra
Applied Categorical Structures | Year: 2015

A characterization of effective étale-descent morphisms in the category M-Ord of M-ordered sets, for a given monoid M, is obtained using the corresponding characterization in the category Cat of small categories. © 2015 Springer Science+Business Media Dordrecht

Nepomuceno M.,University of Beira Interior | Oliveira L.,University of Beira Interior | Lopes S.M.R.,University of Coimbra
Construction and Building Materials | Year: 2012

This paper details a comparative analysis of the results obtained in tests on mortars suitable for self-compacting concrete (SCC). The binary and ternary blends of powder materials used were combinations of two cements with four additions in different percentages: limestone powder, fly ash, granite filler and microsilica. The correlations between the mix design parameters of the mortar phase and the flow properties and compressive strength were evaluated. As a result of this evaluation, a simple methodology was proposed for the mix design of the mortar phase in binary blends of powder with the aim of simultaneously obtaining both adequate flow properties and the necessary compressive strength of the mortar. © 2011 Elsevier Ltd. All rights reserved.

Gomes C.M.F.,University of Coimbra
Current Radiopharmaceuticals | Year: 2012

The multidrug resistance (MDR) phenotype is frequently associated with the overexpression of transmembrane drug proteins such as the P-glycoprotein (Pgp) and/or multidrug resistance related protein-1 (MRP1). These proteins belong to the superfamily of the so-called ATP-binding cassette superfamily and act as drug efflux pumps of a broad range of chemotherapeutic agents commonly used in the treatment of malignancies. These proteins have been found to be overexpressed in both haematological and solid tumours and are considered as adverse prognostic factors. The ability to obtain in vivo and non-invasively information regarding the functional activity of MDR-related transporters, using probes that mimic the antineoplastic agents, provide a very useful tool in the clinical setting by determining the individual tumour susceptibility to chemotherapy. This previous knowledge could serve as a critical tool for optimizing chemotherapeutic protocols on a patient-specific basis. The emergence of non-invasive molecular imaging techniques using radiolabelled probes provides an interesting approach for functional assessment of the classical mechanism of MDR in cancer patients. Toward this objective, the clinically approved 99mTc-labelled cationic lipophilic complexes (sestamibi and tetrofosmin) have been characterized as transport substrates of Pgp and MRP1 and proposed as surrogate markers of chemotherapeutic agents for functional evaluation of MDR by single-photon emission tomography (SPECT). Here we review the potential applications of these agents in identifying drug resistance mechanisms based on functional assays and their potential as a tool for evaluating the efficacy of MDR inhibitors, using cellular and animal models of chemoresistance. © 2012 Bentham Science Publishers.

Couceiro L.,Office of the High Commissioner for Health | Santana P.,University of Coimbra | Nunes C.,New University of Lisbon
International Journal of Tuberculosis and Lung Disease | Year: 2011

Tuberculosis (TB) is a multidimensional disease, and interactions between individuals and groups are of extreme importance in its development. The aim of this study was to estimate the occurrence of pulmonary TB (PTB) to identify potential risk factors and to define high-risk areas in Portugal (2004-2006). The relevance of the common risk factors identified was evaluated at the national and local levels. Considering local public health at the municipality level, the main objective of this study was the support of local interventions, identifying local high-risk areas and the corresponding local risk factors. A complex statistical methodology based on correlation analysis, spatial clustering, risk maps and multivariate regression models was developed. The results showed that some areas were at higher risk of PTB than others due to high incidence of HIV/AIDS, incarceration, nonstandard (abnormal) and/or crowded accommodation, unemployment and immigrant populations. The majority of these areas showed increased TB incidence rates. © 2011 The Union.

Silveirinha M.G.,University of Coimbra
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

In open resonators the energy associated with a localized photonic excitation is lost in the form of a radiated wave, in the same manner that a classical charged particle in a curved orbit loses energy in the form of electromagnetic radiation. As a consequence, photonic modes in conventional spatially bounded open resonators have finite decay times. Here, we theoretically show that, surprisingly, in the limit of vanishing material loss, plasmons give the opportunity to have light localization in open spatially bounded systems with infinitely large lifetimes. © 2014 American Physical Society.

Ferreira F.,University of Porto | Simoes L.,University of Coimbra
Computers and Structures | Year: 2012

Traditionally, structures and control devices are designed separately. Here an integrated approach is proposed and applied to find the least cost solution of a passive and active cable stayed footbridge. The optimization process reduces simultaneously cost, stress, acceleration and displacement. By using an entropy-based procedure a Pareto solution is obtained by unconstrained scalar function minimization and an efficient polynomial convergence algorithm is employed. The designed controller is compared with an active linear quadratic regulator (LQR). Numerical simulations show that both passive and active optimum designs are efficient, with different geometry, mass distribution and cost (22% higher in the passive design). © 2012 Elsevier Ltd. All rights reserved.

Li Y.Q.,Liaoning University | Varandas A.J.C.,University of Coimbra
International Journal of Quantum Chemistry | Year: 2012

An accurate single-sheeted double many-body expansion potential energy surface (PES) is reported for the title system, which is suitable for dynamics and kinetics studies of the reactions N( 2D) + H 2(X 1 ∑ g +) ⇌ NH(b 1 ∑ +) + H( 2S) and their isotopomeric variants. It is obtained using the aug-cc-pVTZ and aug-cc-pVQZ basis sets with extrapolation of the electron correlation energy to the complete basis set limit, plus extrapolation to the complete basis set limit of the complete-active-space self-consistent field energy. A switching function formalism has been used to ensure the correct behavior at the NH(A 3 ∝) + H( 2S) and NH(b 1 ∑ +) + H( 2S) dissociation limits. The topographical features of the new global PES are examined in detail, and found to be in general good agreement with those calculated directly from the raw ab initio energies, as well as previous calculations from the literature. © 2012 Wiley Periodicals, Inc. A global double-many-body expansion potential energy surface is reported for the second excited state of NH2 (2 2A') from accurate ab initio electronic structure calculations. The form here reported, jointly with similar ones published elsewhere by the authors for the ground and first excited doublet electronic states, are expected to have an important role in the dynamics and kinetics of the N + H2 reaction being, therefore, recommended for such purposes. Copyright © 2012 Wiley Periodicals, Inc.

Silveirinha M.G.,University of Coimbra
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

Optical instabilities in moving media are linked to a spontaneous parity-time-symmetry breaking of the system. It is shown that in general the time evolution of the electromagnetic waves in moving media is determined by a non-Hermitian parity-time-symmetric operator. For lossless systems the frequency spectrum of the time evolution operator may be complex valued, and has a mirror symmetry with respect to the real-frequency axis. The possibility of optical amplification of a light pulse in the broken parity-time-symmetry regime is demonstrated. © 2014 American Physical Society.

Gomes C.M.F.,University of Coimbra
Stem Cell Research and Therapy | Year: 2013

Mesenchymal stem cells (MSCs) have attracted increasing interest in the field of oncology because of their inherent capacity to migrate and home tumor tissues. The remarkable tropism of MSCs for tumor microenvironments has been exploited in order to use these cells as cellular vehicles to deliver gene therapies or anticancer agents. At functional levels, these cells display chemotactic properties similar to those of immune cells in response to tissue insult and inflammation and secrete a broad range of bioactive biomolecules with an impact on tumor development and a progression through direct actions on tumor cells and the stromal microenvironment. However, the exact contribution of such interactions in tumor progression has not yet been fully clarified, and some concerns remain regarding whether MSCs exert a tumor-suppressive effect or, on the contrary, favor tumor growth. The article by Keramidas and colleagues in this issue of Stem Cell Research & Therapy provides an interesting contribution to this hot topic. © 2013 BioMed Central Ltd.

Shadrivov I.V.,Australian National University | Kapitanova P.V.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Maslovski S.I.,University of Coimbra | Kivshar Y.S.,Australian National University | Kivshar Y.S.,Saint Petersburg State University of Information Technologies, Mechanics and Optics
Physical Review Letters | Year: 2012

We suggest and verify experimentally the concept of functional metamaterials whose properties are remotely controlled by illuminating the metamaterial with a pattern of visible light. In such metamaterials arbitrary gradients of the effective material parameters can be achieved simply by adjusting the profile of illumination. We fabricate such light-tunable microwave metamaterials and demonstrate their unique functionalities for reflection, shaping, and focusing of electromagnetic waves. © 2012 American Physical Society.

Vidana I.,University of Coimbra
Nuclear Physics A | Year: 2013

In this work we briefly review some of the effects of hyperons on neutron and proto-neutron star properties. We revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, due to the presence of hyperons, a puzzle which has become more intriguing due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1614-2230 (1.97 ± 0.04M ⊙) and PSR J1903+0327 (1.667 ± 0.021M ⊙). We examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability. © 2013 Elsevier B.V.

Silveirinha M.G.,University of Coimbra
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We derive an effective medium model to characterize the macroscopic electromagnetic response of metallic nanowire arrays embedded in a host dielectric with a Kerr-type nonlinear permittivity function. It is shown that the macroscopic electromagnetic fields are coupled to the conduction current in the nanowires and to an additional quasistatic potential through a system of nonlinear equations. We prove that a weak nonlinearity leads to an electromagnetic response closer to that of an indefinite medium, and to isofrequency contours with increased hyperbolicity. For high field intensities the negative refraction of electromagnetic waves at an air-nanowire material interface is enhanced when the nanowires are embedded in a self-focusing Kerr medium. © 2013 American Physical Society.

Gomes L.C.,Venetian Institute of Molecular Medicine | Gomes L.C.,University of Coimbra | Scorrano L.,Venetian Institute of Molecular Medicine | Scorrano L.,University of Geneva
Biochimica et Biophysica Acta - Molecular Cell Research | Year: 2013

Mitochondria are critical organelles in energy conversion, metabolism and amplification of signalling. They are however also major sources of reactive oxygen species and when dysfunctional they consume cytosolic ATP. Maintenance of a cohort of healthy mitochondria is therefore crucial for the overall cell fitness. Superfluous or damaged organelles are mainly degraded by mitophagy, a selective process of autophagy. In response to the triggers of mitophagy, mitochondria fragment: this morphological change accompanies the exposure of "eat-me" signals, resulting in the engulfment of the organelle by the autophagosomes. Conversely, during macroautophagy mitochondria fuse to be spared from degradation and to sustain ATP production in times of limited nutrient availability. Thus, mitochondrial shape defines different types of autophagy, highlighting the interplay between morphology of the organelle and complex cellular responses. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology. © 2012 Elsevier B.V.

Fonte P.,University of Coimbra | Fonte P.,Polytechnic Institute of Coimbra
Journal of Instrumentation | Year: 2013

Apparently simple detectors, Resistive Plate Chambers actually incorporate a range of physical situations somewhat more complex than those found in most other gaseous detectors. These include the interplay between materials with different electrical characteristics, space-charge dominated avalanches evolving in very high electric fields and the propagation of fast signals on heterogeneous multiconductor transmission lines. In this article the state-of-the-art of physical modelling of many of these aspects is reviewed and sometimes expanded, while aspects still requiring further work are highlighted.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

Sousa E.,University of Coimbra
Computers and Mathematics with Applications | Year: 2012

We develop a numerical method for fractional advection diffusion problems with source terms in domains with homogeneous boundary conditions. The numerical method is derived by using a Lax-Wendroff-type time discretization procedure, it is explicit and second order accurate. The convergence of the numerical method is studied and numerical results are presented. © 2011 Elsevier Ltd. All rights reserved.

Fiolhais M.C.N.,University of Coimbra | Essen H.,KTH Royal Institute of Technology
International Journal of Theoretical Physics | Year: 2013

The most general electrodynamic equations of a perfect conducting state are obtained using a variational principle in a classical framework, following an approach by Pierre-Gilles de Gennes. London equations are derived as the time-independent case of these equations, corresponding to the magnetostatic minimal energy state of the perfect conducting system. For further confirmation, the same equations are also derived in the classical limit of the Coleman-Weinberg model, the most successful quantum macroscopic theory of superconductivity. The magnetic field expulsion is, therefore, a direct consequence of zero resistivity and not an exclusive property of superconductors. © 2013 Springer Science+Business Media New York.

Martins-Ferreira N.,Polytechnic Institute of Leiria | Van Der Linden T.,University of Coimbra
Applied Categorical Structures | Year: 2012

We show that two known conditions which arose naturally in commutator theory and in the theory of internal crossed modules coincide: every starmultiplicative graph is multiplicative if and only if every two ef fective equivalence relations commute as soon as their normalisations do. This answers a question asked by George Janelidze. © 2010 Springer Science+Business Media B.V.

Vicente L.N.,University of Coimbra | Custodio A.L.,New University of Lisbon
Mathematical Programming | Year: 2012

It is known that the Clarke generalized directional derivative is nonnegative along the limit directions generated by directional direct-search methods at a limit point of certain subsequences of unsuccessful iterates, if the function being minimized is Lipschitz continuous near the limit point. In this paper we generalize this result for discontinuous functions using Rockafellar generalized directional derivatives (upper subderivatives). We show that Rockafellar derivatives are also nonnegative along the limit directions of those subsequences of unsuccessful iterates when the function values converge to the function value at the limit point. This result is obtained assuming that the function is directionally Lipschitz with respect to the limit direction. It is also possible under appropriate conditions to establish more insightful results by showing that the sequence of points generated by these methods eventually approaches the limit point along the locally best branch or step function (when the number of steps is equal to two). The results of this paper are presented for constrained optimization and illustrated numerically. © 2010 Springer and Mathematical Optimization Society.

Galvao B.R.L.,Federal University of Minas Gerais | Varandas A.J.C.,University of Coimbra | Braga J.P.,Federal University of Minas Gerais | Belchior J.C.,Federal University of Minas Gerais
Journal of Physical Chemistry Letters | Year: 2013

Rate constants for the electronic quenching reaction N(2D) + N2 → N(4S) + N2 are calculated for temperatures over the range of 240 ≤ T/K ≤ 1000 using an accurate set of three global electronic potential energy surfaces for the N3 system (4A″,2A′, and 2A″). The nuclear motion is treated by running quasiclassical trajectories, incorporating spin-forbidden transitions with the trajectory surface hopping method. The exclusively theoretical results are compared with available experimental data for the reaction and contribute to clarify the discrepancies among them. The rate constants at higher temperatures achieved in the atmosphere, for which no experiments have been performed, are presented for the first time. The impact of the results in atmospheric modeling is analyzed, predicting at what altitudes this reaction will play an important role. © 2013 American Chemical Society.

Vieira O.V.,University of Coimbra | Jordao L.,National Institute of Health
International Journal of Cell Biology | Year: 2011

Tuberculosis is an ancient infectious disease that remains a threat for public health around the world. Although the etiological agent as well as tuberculosis pathogenesis is well known, the molecular mechanisms underlying the host defense to the bacilli remain elusive. In this paper we focus on the innate immunity of this disease reviewing well-established and consensual mechanisms like Mycobacterium tuberculosis interference with phagosome maturation, less consensual mechanism like nitric oxide production, and new mechanisms, such as mycobacteria translocation to the cytosol, autophagy, and apoptosis/necrosis proposed mainly during the last decade. Copyright © 2011 Luisa Jordao and Otilia V. Vieira.

Kraehenbuehl T.P.,Massachusetts Institute of Technology | Kraehenbuehl T.P.,Hoffmann-La Roche | Langer R.,Massachusetts Institute of Technology | Ferreira L.S.,University of Coimbra
Nature Methods | Year: 2011

The self-renewal and differentiation of human pluripotent stem cells (hPSCs) have typically been studied in flat, two-dimensional (2D) environments. In this Perspective, we argue that 3D model systems may be needed in addition, as they mimic the natural 3D tissue organization more closely. We survey methods that have used 3D biomaterials for expansion of undifferentiated hPSCs, directed differentiation of hPSCs and transplantation of differentiated hPSCs in vivo. © 2011 Nature America, Inc. All rights reserved.

Heleno R.H.,University of Coimbra
Proceedings. Biological sciences / The Royal Society | Year: 2013

Alien plants are a growing threat to the Galápagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most dispersed invaders were Lantana camara, Rubus niveus and Psidium guajava, the latter two likely benefiting from an asynchronous fruit production with most native plants, which facilitate their consumption and spread. Lava lizards dispersed the seeds of 27 species, being the most important dispersers, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien plants were dispersed via two pathways: dry-fruited plants were preferentially dispersed by finches, while fleshy fruited species were mostly dispersed by other birds and reptiles.

Sousa E.,University of Coimbra
Computers and Mathematics with Applications | Year: 2011

A one-dimensional fractional diffusion model is considered, where the usual second order derivative gives place to a fractional derivative of order α, with 1<α≤2. We consider the Caputo derivative as the space derivative, which is a form of representing the fractional derivative by an integral operator. An implicit numerical method is derived which uses a spline approximation for the Caputo derivative. The consistency and stability of the method are examined and numerical results are presented. © 2011 Elsevier Ltd. All rights reserved.

Costa P.,University of Coimbra
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2+1) Nambu-Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultrarelativistic heavy ion collisions, and β equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen. © 2016 American Physical Society.

Natella R.,University of Naples Federico II | Cotroneo D.,University of Naples Federico II | Duraes J.A.,Polytechnic Institute of Coimbra | Madeira H.S.,University of Coimbra
IEEE Transactions on Software Engineering | Year: 2013

The injection of software faults in software components to assess the impact of these faults on other components or on the system as a whole, allowing the evaluation of fault tolerance, is relatively new compared to decades of research on hardware fault injection. This paper presents an extensive experimental study (more than 3.8 million individual experiments in three real systems) to evaluate the representativeness of faults injected by a state-of-the-art approach (G-SWFIT). Results show that a significant share (up to 72 percent) of injected faults cannot be considered representative of residual software faults as they are consistently detected by regression tests, and that the representativeness of injected faults is affected by the fault location within the system, resulting in different distributions of representative/nonrepresentative faults across files and functions. Therefore, we propose a new approach to refine the faultload by removing faults that are not representative of residual software faults. This filtering is essential to assure meaningful results and to reduce the cost (in terms of number of faults) of software fault injection campaigns in complex software. The proposed approach is based on classification algorithms, is fully automatic, and can be used for improving fault representativeness of existing software fault injection approaches. © 1976-2012 IEEE.

Alves M.G.,University of Coimbra
Journal of cardiovascular pharmacology | Year: 2012

Understanding heart metabolism during preservation is crucial to develop new effective cardioplegic solutions. We aim to investigate metabolic alterations during heart preservation in the clinically used Celsior (Cs) and histidine buffer solution (HBS). We also focused in gender-specific metabolic adaptations during ischemia. We followed energy metabolism in hearts from males and females preserved during 6 hours in Cs and HBS. Hearts were subjected to cold ischemia (4°C) in Cs or HBS, and aliquots of the cardioplegic solution were collected throughout preservation for nuclear magnetic resonance analysis. HBS-preserved hearts from males consumed glucose mostly between 240 and 360 minutes, whereas HBS-preserved hearts from females consumed glucose throughout the 6 hours of ischemia. Lactate production rates followed approximately the glucose consumption rates in HBS-preserved hearts. The lactate to alanine ratio, an indicator of the redox state, was increased in HBS-preserved hearts when compared with Cs-preserved hearts. Hearts from males presented a higher redox state than those from females preserved in Cs after 300 minutes. Both Cs and HBS were capable of preventing acidification in hearts from females but not in hearts from males, which decreased the extracellular pH. HBS-preserved hearts from males and females produced 0.1 ± 0.01 and 0.15 ± 0.03 μmol·min·gdw of lactate, respectively. Those rates were significantly higher than in Cs-preserved hearts. Thus, Cs was more effective in preventing lactate production. We conclude that glycolysis and lactate production are stimulated in HBS-preserved hearts. HBS shows better overall results particularly in hearts from females, which presented less extracellular acidification and were more effective in recycling the metabolic subproducts.

De Sa Teixeira N.,University of Coimbra | Hecht H.,Johannes Gutenberg University Mainz
Attention, Perception, and Psychophysics | Year: 2014

The memory for the vanishing location of a horizontally moving target is usually displaced forward in the direction of motion (representational momentum) and downward in the direction of gravity (representational gravity). Moreover, this downward displacement has been shown to increase with time (representational trajectory). However, the degree to which different kinematic events change the temporal profile of these displacements remains to be determined. The present article attempts to fill this gap. In the first experiment, we replicate the finding that representational momentum for downward-moving targets is bigger than for upward motions, showing, moreover, that it increases rapidly during the first 300 ms, stabilizing afterward. This temporal profile, but not the increased error for descending targets, is shown to be disrupted when eye movements are not allowed. In the second experiment, we show that the downward drift with time emerges even for static targets. Finally, in the third experiment, we report an increased error for upward-moving targets, as compared with downward movements, when the display is compatible with a downward ego-motion by including vection cues. Thus, the errors in the direction of gravity are compatible with the perceived event and do not merely reflect a retinotopic bias. Overall, these results provide further evidence for an internal model of gravity in the visual representational system. © 2014 Psychonomic Society, Inc.

MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) is a mitochondrial hereditary dysfunction in which the physiopathological mechanism of cerebral lesions is not totally understood as yet. Typically, these lesions are described as having normal to increased apparent diffusion coefficient (ADC), and this has been used to distinguish stroke-like lesions from ischemic lesions. Notwithstanding this, within the last few years, there have been reports of diffusion restriction in stroke-like episodes. Analysis of the diffusion characteristics on serial magnetic resonance imaging (MRI) over a 16 month period, on a patient with MELAS and stroke-like lesions, to investigate the controversial changes of the ADC, reported in the last years. Evaluation of the proton spectroscopy changes in stroke-like lesions and apparently spared brain. We performed four serial magnetic resonance imaging (MRI), including two stroke-like episodes, in a 28-year-old man with MELAS (mitochondrial DNA mutation A3243G). Qualitative analysis of the magnetic resonance images, including the single voxel spectroscopy and ADC maps, with analysis of evolution patterns of the last ones. Both MRI that were performed during those episodes of stroke-like lesion revealed areas of diffusion restriction, coexisting areas of high ADC. During the chronic phase, there was a regression of those changes. Proton spectroscopy showed the presence of lactate and reduction of N-acetyl aspartate peak in stroke-like lesion and the presence of lactate in apparently spared brain. All alterations that were recorded strengthen the view that cytotoxic oedema can occur in stroke-like lesions. Thus, their presence should not weaken the possibility of MELAS, especially if those lesions affect the temporal, parietal and/or occipital lobes, or if they predominantly involve the cortical gray matter, spanning vascular borders and if proton spectroscopy reveals lactate peak in the apparently spared brain.

Alves M.G.,University of Beira Interior | Martins A.D.,University of Beira Interior | Rato L.,University of Beira Interior | Moreira P.I.,University of Coimbra | And 2 more authors.
Biochimica et Biophysica Acta - Molecular Basis of Disease | Year: 2013

Diabetes mellitus (DM) is one of the greatest public health threats in modern societies. Although during a few years it was suggested that DM had no significant effect in male reproductive function, this view has been challenged in recent years. The increasing incidence of DM worldwide will inevitably result in a higher prevalence of this pathology in men of reproductive age and subfertility or infertility associated with DM is expected to dramatically rise in upcoming years. From a clinical perspective, the evaluation of semen parameters, as well as spermatozoa deoxyribonucleic acid (DNA) integrity, are often studied due to their direct implications in natural and assisted conception. Nevertheless, recent studies based on the molecular mechanisms beyond glucose transport in testicular cells provide new insights in DM-induced alterations in male reproductive health. Testicular cells have their own glucose sensing machinery that react to hormonal fluctuations and have several mechanisms to counteract hyper- and hypoglycemic events. Moreover, the metabolic cooperation between testicular cells is crucial for normal spermatogenesis. Sertoli cells (SCs), which are the main components of blood-testis barrier, are not only responsible for the physical support of germ cells but also for lactate production that is then metabolized by the developing germ cells. Any alteration in this tied metabolic cooperation may have a dramatic consequence in male fertility potential. Therefore, we present an overview of the clinical significance of DM in the male reproductive health with emphasis on the molecular mechanisms beyond glucose fluctuation and transport in testicular cells. © 2013 Elsevier B.V.

Zahradnik J.,Charles University | Custodio S.,University of Coimbra
Bulletin of the Seismological Society of America | Year: 2012

We present a method to assess the uncertainty of earthquake focal mechanisms based on the standard theory of linear inverse problems. We compute the uncertainty of the moment tensor, M, then map it into uncertainties of the strike, dip, and rake. The inputs are: source and station locations, crustal model, frequency band of interest, and an estimate of data error. The output is a six-dimensional (6D) error ellipsoid, which shows the uncertainty of the individual parameters of M. We focus on the double-couple (DC) part of M. The method is applicable both with and without waveforms. The latter is particularly useful for network design. As an example we present maps of DC resolvability for earthquakes in southwest Europe, computed without waveforms. We find that the resolvability depends critically on frequency range and source depth. Shallow DC sources (10 km) are theoretically better resolved than deeper sources (40 km and 60 km). The DC resolvability of a 40-km-deep event improves considerably when the Portuguese network is supplemented by stations in Spain and Morocco. The DC resolvability can be further improved by using a few ocean bottom seismometer (OBS) stations or a dense land network. A dense land network is able to resolve M well in spite of the large azimuthal gap, which spans ∼200°. The theoretical resolution analysis also explains the success of single-station inversions when using a broad frequency range, as exemplified by an application using waveforms of a M w 6 earthquake offshore Iberia.

Ascensao A.,University of Porto | Oliveira P.J.,University of Coimbra | Magalhaes J.,University of Porto
International Journal of Cardiology | Year: 2012

One of the mostly used chemotherapeutic drugs is the highly effective anthracycline Doxorubicin. However, its clinical use is limited by the dose-related and cumulative cardiotoxicity and consequent dysfunction. It has been proposed that the etiology of this toxicity is related to mitochondrial dysfunction. The present review aimed to analyze the promising results regarding the effect of several types of physical exercise in cardiac tolerance of animals treated with acute and sub-chronic doses of Doxorubicin (DOX), highlighting the importance of cardiac mitochondrial-related mechanisms in the process. Physical exercise positively modulates some important cardiac defense systems to antagonize the toxic effects caused by DOX treatment, including antioxidant capacity, the overexpression of heat shock proteins and other anti-apoptotic proteins. An important role in this protective phenotype afforded by exercise should be attributed to mitochondrial plasticity, as related adaptations could be translated into improved cardiac function in the setting of the DOX cardiomyopathy. © 2009 Elsevier Ireland Ltd. All rights reserved.

Khadem M.,University of Madeira | Camacho R.,University of Madeira | Nobrega C.,University of Coimbra
Journal of Evolutionary Biology | Year: 2011

The X chromosome is known to exert a disproportionately large effect on characters related to post-zygotic reproductive isolation. There is also growing evidence about the important role of the chromosomal regions with reduced recombination (such as inversions) in maintaining the identity of closely related species. Using molecular markers, we examine the effect of different regions of the X chromosome on determination of hybrid traits (viability, testes size, sperm motility and morphological anomalies) in hybrid males between Drosophila madeirensis and Drosophila subobscura. The preponderant effect of a region localized inside the A2 inversion in the X chromosome in all hybrid traits is identified. Other marked regions exert a weaker influence or only influence some of the hybrid trait. Our results confirm the crucial role of sex-linked chromosomal inversion in preserving the identity of species with incomplete reproductive isolation. The specific genomic make-up of parental lines used to perform crosses has a great effect on hybrid fitness. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

Tenreiro C.,University of Coimbra
Computational Statistics and Data Analysis | Year: 2011

A multiple test procedure for assessing multivariate normality (MVN) is proposed. The new test combines a finite set of affine invariant test statistics for MVN through an improved Bonferroni method. The usefulness of such an approach is illustrated by a multiple test including the Mardia and BHEP (Baringhaus-Henze-Epps-Pulley) tests that are among the most recommended procedures for testing MVN. A simulation study carried out for a wide range of alternative distributions, in order to analyze the finite sample power behavior of the proposed multiple test procedure, indicates that the new test demonstrates a good overall performance against other highly recommended MVN tests. © 2010 Elsevier B.V. All rights reserved.

Opicapone (BIA 9-1067) is a novel catechol-O-methyltransferase inhibitor presently under clinical development as an adjuvant in the pharmacotherapy of Parkinson's disease. This report describes the development and validation of a bioanalytical assay for the simultaneous quantification of opicapone and its active metabolite (BIA 9-1079) in human plasma. The method herein reported is based on high-performance liquid chromatography coupled with diode-array detection (HPLC-DAD) and the sample preparation consists of a plasma protein precipitation step followed by liquid-liquid extraction. Chromatographic separation of the analytes (opicapone and BIA 9-1079) and the internal standard (tamoxifen) was achieved in less than 10 min on a reversed-phase C18 column at 25 °C by applying a gradient elution program using a mobile phase composed of 0.05 M monosodium phosphate solution adjusted to pH 2.45 (A) and acetonitrile (B) pumped at 0.8 mL min(-1). Opicapone and the internal standard were monitored at 271 nm while BIA 9-1079 was assessed at 257 nm. Calibration curves of both analytes were linear (r(2) ≥ 0.997) in the concentration range of 25-3000 ng mL(-1) and their limits of quantification were established to be 25 ng mL(-1). The overall precision did not exceed 13.2% and the accuracy was within ±11.1%. Several drugs potentially co-administered with opicapone were tested and they did not interfere at the retention times of the analytes (opicapone and BIA 9-1079) and internal standard. The method was then successfully applied for quantifying opicapone and its active metabolite (BIA 9-1079) in plasma samples obtained from a healthy subject enrolled in a clinical trial.

Ruivo C.R.,University of Algarve | Ruivo C.R.,University of Coimbra | Goldsworthy M.,CSIRO | Intini M.,Polytechnic of Milan
Energy | Year: 2014

The desiccant wheel is a key component of open desiccant air-conditioning systems. Development of a simplified method of assessing their dynamic performance would assist the growth of the industry. Important errors can occur when constant values of the effectiveness parameters are assumed in the effectiveness method. The present work investigates the feasibility of using different interpolation methods to predict the influence of the inlet states of the process and regeneration airflows on the global behaviour of a desiccant wheel. The procedures require a set of reference operating cases. One approach considers interpolation on a grid of known reference points, in a triangular arrangement, for each inlet state domain. The second approach is based on the radial basis function, where all points of the reference grid influence the estimated values. The reference cases are simulated by a validated numerical model. Comparison of the methods shows that the second approach requires fewer reference cases and so is more suitable for the development of a generic simplified tool that takes into account the influence of variable airflow rates and rotation speed on the performance. © 2014 Elsevier Ltd.

Coito S.,University of Lisbon | Rupp G.,University of Lisbon | van Beveren E.,University of Coimbra
European Physical Journal C | Year: 2013

A solvable coordinate-space model is employed to study the cc̄ component of the X(3872) wave function, by coupling a confined 3P1cc̄ state to the almost unbound S-wave D0D*0 channel via the 3P0 mechanism. The two-component wave function is calculated for different values of the binding energy and the transition radius a, always resulting in a significant cc̄ component. However, the long tail of the D0D*0 wave function, in the case of small binding, strongly limits the cc̄ probability, which roughly lies in the range 7-11 %, for the average experimental binding energy of 0. 16 MeV and a between 2 and 3 GeV-1. Furthermore, a reasonable value of 7. 8 fm is obtained for the X(3872) r. m. s. radius at the latter binding energy, as well as an S-wave D0D*0 scattering length of 11. 6 fm. Finally, the S-matrix pole trajectories as a function of coupling constant show that X(3872) can be generated either as a dynamical pole or as one connected to the bare cc̄ confinement spectrum, depending on details of the model. From these results we conclude that X(3872) is not a genuine meson-meson molecule, nor actually any other mesonic system with non-exotic quantum numbers, due to inevitable mixing with the corresponding quark-antiquark states. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Creutzfedt-Jakob Disease (CJD) is a rapidly progressive neurodegenerative disease caused by prions. Early diagnosis and the determination of its form are epidemiologically important, with strong impact on public health. Bilateral pulvinar hyperintensity, either alone (pulvinar sign) or in association with the dorsomedial nucleus of the thalamus (double hockey stick sign) on T2, FLAIR and diffusion weighted imaging (DWI), is a criterion for the probable diagnosis of the variant CJD (vCJD). Bilateral hyperintensity of the caudate, putamina and cortex is the usual pattern found in the sporadic CJD (sCJD). Analysis of the imaging aspects on a sCJD patient showing T2 hyperintensity of the pulvinar and dorsomedial thalamic nucleus, in order to assess the magnetic resonance imaging (MRI) accuracy in the discrimination between vCJD and sCJD, when this lesion pattern is present. We performed a MRI on a 62-year-old female with definitive diagnosis of sCJD made by anatomopathologic study of the brain tissue. Qualitative analysis of MRI, including DWI, T2 and FLAIR sequences, as well as lesional patterns found. Brain MRI showed hyperintensity of the caudate, putamina, pulvinar and dorsomedial nucleus of the thalamus, in DWI, T2 and FLAIR sequences; hypersignal of the caudate and putamina was greater than the signal intensity of the thalami. Hyperintensity of the hippocampus and frontal, temporal and parietal cortex were more obvious in FLAIR and DWI. Hyperintensity of the pulvinar and dorsomedial nucleus of the thalamus on sCJD may complicate the differential diagnosis with vCJD. True pulvinar sign and double hockey stick sign, consistent with vCJD, must only be considered if the hyperintensity is greater than signal intensity of the caudate and putamina.

Ventura S.P.M.,University of Aveiro | Goncalves A.M.M.,University of Coimbra | Goncalves F.,University of Aveiro | Coutinho J.A.P.,University of Aveiro
Aquatic Toxicology | Year: 2010

Ionic liquids (ILs) are an exciting class of neoteric solvents that are being object of great attention as a potential replacement to conventional environmental damaging solvents in industrial applications. Despite some progress concerning ILs' toxicity and their environmental impact, the information about these compounds is still scarce. In this work, biological tests were performed to establish the toxicity of 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, [C3mim][Tf2N], in five aquatic species at different trophic levels. Freshwater algal growth inhibition (Pseudokirchneriella subcapitata and Chlorella vulgaris), freshwater cladocerans' immobilization and chronic traits (Daphnia magna and Daphnia longispina) and viability of luminescent marine bacteria (Vibrio fischeri) were investigated. The sensitivity of the different species to the IL was compared in order to determine further repercussions in trophic food web. It is shown that the studied IL is moderately toxic to the studied organisms. P. subcapitata and D. magna are the most tolerant species and C. vulgaris and D. longispina the most sensitive to its presence. © 2009 Elsevier B.V. All rights reserved.

Salvador J.A.,University of Coimbra
Natural product reports | Year: 2012

This review highlights the potential of natural and semisynthetic ursane-type triterpenoids as candidates for the design of multi-target bioactive compounds, with focus on their anticancer effects. A brief illustration of the biosynthesis, sources, and general biological effects of the main classes of naturally occurring pentacyclic triterpenoids (PTs) are provided.

Costenla A.R.,University of Lisbon | Cunha R.A.,University of Coimbra | De Mendonca A.,University of Lisbon
Journal of Alzheimer's Disease | Year: 2010

Few studies to date have looked at the effects of caffeine on synaptic plasticity, and those that did used very high concentrations of caffeine, whereas the brain concentrations attained by regular coffee consumption in humans should be in the low micromolar range, where caffeine exerts pharmacological actions mainly by antagonizing adenosine receptors. Accordingly, rats drinking caffeine (1 g/L) for 3 weeks, displayed a concentration of caffeine of circa 22 μM in the hippocampus. It is known that selective adenosine A1 receptor antagonists facilitate, whereas selective adenosine A2A receptor antagonists attenuate, long term potentiation (LTP) in the hippocampus. Although caffeine is a non-selective antagonist of adenosine receptors, it attenuates frequency-induced LTP in hippocampal slices in a manner similar to selective adenosine A2A receptor antagonists. These effects of low micromolar concentration of caffeine (30 μM) are maintained in aged animals, which is important when a possible beneficial effect for caffeine in age-related cognitive decline is proposed. Future studies will still be required to confirm and detail the involvement of A1 and A2A receptors in the effects of caffeine on hippocampal synaptic plasticity, using both pharmacological and genetic approaches. © 2010 IOS Press and the authors. All rights reserved.

Given its conspicuous nature, gravity has been acknowledged by several research lines as a prime factor in structuring the spatial perception of one's environment. One such line of enquiry has focused on errors in spatial localization aimed at the vanishing location of moving objects - it has been systematically reported that humans mislocalize spatial positions forward, in the direction of motion (representational momentum) and downward in the direction of gravity (representational gravity). Moreover, spatial localization errors were found to evolve dynamically with time in a pattern congruent with an anticipated trajectory (representational trajectory). The present study attempts to ascertain the degree to which vestibular information plays a role in these phenomena. Human observers performed a spatial localization task while tilted to varying degrees and referring to the vanishing locations of targets moving along several directions. A Fourier decomposition of the obtained spatial localization errors revealed that although spatial errors were increased "downward" mainly along the body's longitudinal axis (idiotropic dominance), the degree of misalignment between the latter and physical gravity modulated the time course of the localization responses. This pattern is surmised to reflect increased uncertainty about the internal model when faced with conflicting cues regarding the perceived "downward" direction. © 2014 Elsevier Ltd.

Ascione Kenov I.,University of Lisbon | Garcia A.C.,University of Coimbra | Neves R.,University of Lisbon
Estuarine, Coastal and Shelf Science | Year: 2012

The residence time of water is widely used as an indicator of how long a substance will remain in an estuary, a harbour, or a lagoon, and it is used to enable comparisons among different water bodies. In this work, the residence time in the Mondego Estuary, Portugal, is calculated by using two methodologies: the first one is based on field data and a freshwater fraction model, and the second one is based on a Lagrangian transport model. The Lagrangian model is coupled to a two-dimensional hydrodynamic numerical model that solves the depth-averaged advection and diffusion equations. Boundary conditions are provided by the Portuguese Coastal Operational Model, downscaled by using four nested domains with increasing resolution from the large to the local scale. The spatial variation of the residence time is characterized by subdividing the Mondego Estuary into boxes. The observed average salinity for each box is applied to the freshwater fraction model. With the Lagrangian model, boxes are filled with tracers and the path of the particles passing through them is quantified. The overall results of the two methodologies are similar, with a value of the residence time varying over the year between 1 and 12 days computed with the Lagrangian transport model and 2 and 9 days with the freshwater fraction model. Several scenarios were built by applying the Lagrangian transport model to investigate the history of water renewal and the influence of freshwater inflows and geomorphologic factors on the residence time. The overall results indicate that freshwater inflow is the main factor influencing the residence time. The analysis of the history of the water renewal was carried out by calculating the water exchange among boxes inside the estuary, pointing to the river flow as the main factor contributing to the water renewal of boxes. © 2012 Elsevier Ltd.

Sant'Ovaia H.,University of Porto | Lacerda M.J.,University of Porto | Gomes C.,University of Coimbra
Atmospheric Environment | Year: 2012

In this study the magnetic properties of tree leaves were measured in order to compare their capability to accumulate particles, to establish the relationship between magnetic properties and chemical data and to assess the particle pollution in selected locations in the cities of Braga, Porto, Valongo and Trancoso-Reboleiro, northern Portugal. In Porto, Braga and Valongo, leaves from the evergreen Nerium oleander were sampled each month during a year. N. oleander and deciduous Quercus spp. and Platanus spp. samples were collected in the same site in Porto, in order to determine the ability of these different leaves to accumulate particles. The leaves of deciduous Tilia spp. were collected in Porto and in a rural area (Trancoso-Reboleiro) so that a comparison could be established between them. The results indicated a contrast between the urban and the rural areas. The highest concentration of magnetic particles was found in the sampling site of Valongo and the lowest concentration in the sampling site of Trancoso-Reboleiro. In Porto, the results have shown that the Quercus leaves possessed the highest capability to accumulate particles even though it is a deciduous species. The IRM acquisition curves and the S-300 ratios found in the samples of the urban areas indicated the presence of magnetite-like structures. SIRM/. χ ratio revealed particles whose dimensions ranged between 5 μm and 8 μm in urban areas. The chemical elements copper and iron have a significant positive correlation with χ and SIRM, which highlights the use of magnetic properties as a proxy for the concentration of these metals in atmospheric dust. The magnetic properties were interpreted taking into consideration the rainfall peaks and then compared with the PM10 concentration levels monitored in an air quality station in Porto. Our data corroborated that magnetic properties provide a fast and inexpensive tool to evaluate long-term urban pollution from anthropogenic origin, especially heavy traffic. © 2012 Elsevier Ltd.

Lopes M.A.R.,INESC Coimbra | Antunes C.H.,University of Coimbra | Antunes C.H.,INESC Coimbra | Martins N.,University of Aveiro
Renewable and Sustainable Energy Reviews | Year: 2012

Energy behaviours represent a significant untapped potential for the increase of end-use energy efficiency in buildings. Although energy behaviours are a major determinant of energy use in buildings, energy savings potential due to behaviour are usually neglected, albeit being referred to be as high as those from technological solutions. This paper presents a review of recent literature on energy behaviours in order to recognise recent trends, quantify energy behaviours potential savings, characterise energy behaviour modelling strategies and identify potential research gaps. Energy behaviour research is vast and has been essentially focused on the residential sector, striving to establish behaviour determinants and the best strategies and instruments to promote more efficient energy behaviours. Potential savings of energy behaviours are referred to reach 20%, but values differ up to 100% between experiences and additional studies to quantify behavioural savings are needed, in particular by using standard quantification techniques. Different modelling techniques have been used to model energy behaviours: qualitative approaches from the social sciences trying to interpret behaviour, here named energy behaviour frameworks; quantitative approaches from the engineering and economics that quantify energy consumption, here designated by energy models; and hybrid approaches that are considered the most relevant since they integrate multiple dimensions of energy behaviours, here referred as energy behaviour modelling. Energy behaviours have a crucial role in promoting energy efficiency, but energy behaviours characteristics and complexity create several research challenges that must be overcome so energy behaviours may be properly valorised and integrated in the energy policy context. © 2012 Elsevier Ltd. All right reserved.

Falcao G.,University of Coimbra
IEEE Potentials | Year: 2013

Parallel computers are everywhere. Over the last few years, a change of paradigm occurred in the computer industry. Mainly due to power dissipation constraints and memory access time limitations, rather than increasing the processor?s frequency of operation (the usual strategy), computer manufacturers started introducing more cores per chip. This created the potential for increasing processing performance but also posed new challenges, namely regarding the extra level of effort required for programmers to exploit these new processing machines. Furthermore, the variety of multicore and manycore architectures commercially available is now relatively high. Since most use distinct programming models and languages, the challenge becomes even more significant for a programmer that wishes to develop programs for more than a single architecture. The immediate question that I?ve had for quite a long time is: if multicore computers have gone mainstream, why are we still teaching sequential programming to our undergraduate students? Why do we tell them to use only one of an increasingly number of available cores? © 1988-2012 IEEE.

Cesarino I.,University of Sao Paulo | Cavalheiro E.T.G.,University of Sao Paulo | Brett C.M.A.,University of Coimbra
Electroanalysis | Year: 2010

A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite-polyurethane composite electrode with SBA-15 silica organofunctionalized with 2-benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at 1.1 V vs. SCE where they complex with 2- benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd2{thorn}, Pb2{thorn}, Cu2{thorn} and Hg2{thorn} in natural waters was achieved. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

Loura L.M.S.,University of Coimbra | Loura L.M.S.,Center for Chemistry Coimbra
International Journal of Molecular Sciences | Year: 2012

Because of its acute sensitivity to distance in the nanometer scale, Förster resonance energy transfer (FRET) has found a large variety of applications in many fields of chemistry, physics, and biology. One important issue regarding the correct usage of FRET is its dependence on the donor-acceptor relative orientation, expressed as the orientation factor κ2. Different donor/acceptor conformations can lead to κ2 values in the 0 ≤ κ2 ≤ 4 range. Because the characteristic distance for FRET, R0, is proportional to (κ2)1/6, uncertainties in the orientation factor are reflected in the quality of information that can be retrieved from a FRET experiment. In most cases, the average value of κ2 corresponding to the dynamic isotropic limit (<κ2> = 2/3) is used for computation of R0 and hence donor-acceptor distances and acceptor concentrations. However, this can lead to significant error in unfavorable cases. This issue is more critical in membrane systems, because of their intrinsically anisotropic nature and their reduced fluidity in comparison to most common solvents. Here, a simple numerical simulation method for estimation of the probability density function of κ2 for membrane-embedded donor and acceptor fluorophores in the dynamic regime is presented. In the simplest form, the proposed procedure uses as input the most probable orientations of the donor and acceptor transition dipoles, obtained by experimental (including linear dichroism) or theoretical (such as molecular dynamics simulation) techniques. Optionally, information about the widths of the donor and/or acceptor angular distributions may be incorporated. The methodology is illustrated for special limiting cases and common membrane FRET pairs. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

Alvarez-Ruso L.,University of Coimbra
Nuclear Physics B - Proceedings Supplements | Year: 2012

The present theoretical status of neutrino interactions in the few-GeV region is reviewed. Quasielastic scattering, pion production, photon emission and their importance for neutrino oscillation studies are discussed, making emphasis on the open questions that arise in the comparison with new experimental data. © 2012.

Maslovski S.,University of Coimbra | Tretyakov S.,Aalto University
New Journal of Physics | Year: 2012

It is theoretically known that a pair of phase-conjugating surfaces can function as a perfect lens, focusing propagating waves and enhancing evanescent waves. However, the known experimental approaches based on thin sheets of nonlinear materials cannot fully realize the required phase conjugation boundary condition. In this paper, we show that the ideal phase-conjugating surface is, in principle, physically realizable and investigate the necessary properties of nonlinear and nonreciprocal particles which can be used to build a perfect lens system. The physical principle of the lens operation is discussed in detail and directions of possible experimental realizations are outlined. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Udy A.A.,University of Queensland | Baptista J.P.,University of Coimbra | Lim N.L.,Anaesthesia and Surgical Intensive Care | Joynt G.M.,University of Queensland | And 5 more authors.
Critical Care Medicine | Year: 2014

OBJECTIVE:: To describe the prevalence and natural history of augmented renal clearance in a cohort of recently admitted critically ill patients with normal plasma creatinine concentrations. DESIGN:: Multicenter, prospective, observational study. SETTING:: Four, tertiary-level, university-Affiliated, ICUs in Australia, Singapore, Hong Kong, and Portugal. PATIENTS:: Study participants had to have an expected ICU length of stay more than 24 hours, no evidence of absolute renal impairment (admission plasma creatinine < 120 μmol/L), and no history of prior renal replacement therapy or chronic kidney disease. Convenience sampling was used at each participating site. INTERVENTIONS:: Eight-hour urinary creatinine clearances were collected daily, as the primary method of measuring renal function. Augmented renal clearance was defined by a creatinine clearance more than or equal to 130 mL/min/1.73 m. Additional demographic, physiological, therapeutic, and outcome data were recorded prospectively. MEASUREMENTS AND MAIN RESULTS:: Nine hundred thirty-two patients were admitted to the participating ICUs over the study period, and 281 of which were recruited into the study, contributing 1,660 individual creatinine clearance measures. The mean age (95% CI) was 54.4 years (52.5-56.4 yr), Acute Physiology and Chronic Health Evaluation II score was 16 (15.2-16.7), and ICU mortality was 8.5%. Overall, 65.1% manifested augmented renal clearance on at least one occasion during the first seven study days; the majority (74%) of whom did so on more than or equal to 50% of their creatinine clearance measures. Using a mixed-effects model, the presence of augmented renal clearance on study day 1 strongly predicted (p = 0.019) sustained elevation of creatinine clearance in these patients over the first week in ICU. CONCLUSIONS:: Augmented renal clearance appears to be a common finding in this patient group, with sustained elevation of creatinine clearance throughout the first week in ICU. Future studies should focus on the implications for accurate dosing of renally eliminated pharmaceuticals in patients with augmented renal clearance, in addition to the potential impact on individual clinical outcomes. Copyright © 2013 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.

Guemez J.,University of Cantabria | Fiolhais M.,University of Coimbra
European Journal of Physics | Year: 2013

We present and discuss a selection of classical mechanics and thermodynamics problems. The discussion is based on the use of the impulse-momentum equation simultaneously with the centre-of-mass (pseudo-work) equation or the first law of thermodynamics, depending on the nature of the problem. Thermodynamical aspects of classical mechanics, namely problems involving non-conservative forces or variation of mechanical energy are discussed in different reference frames, in connection with the use of one or other of the energy equations, and also compliance with the principle of relativity. © 2013 IOP Publishing Ltd.

Varandas A.J.C.,University of Coimbra
Journal of Chemical Physics | Year: 2013

The purpose is to fit an accurate smooth function of the many-body expansion type to a multidimensional large data set using a basis-set type method. By adopting a combined-hyperbolic-inverse-power-representation for the basis, the novel approach is tested in detail for the ground electronic state of tri-hydrogen and hydroperoxyl systems, assuming that their potential energy surfaces are single-sheeted representable. It is also shown that the method can be easily applicable to potential energy curves by considering as prototypes molecular oxygen and the hydroxyl radical. © 2013 American Institute of Physics.

Hogg R.E.,Institute of Clinical Science A | Silva R.,University of Coimbra | Silva R.,Association for Innovation and Biomedical Research on Light and Image | Staurenghi G.,University of Milan | And 4 more authors.
Ophthalmology | Year: 2014

Purpose To describe associations between reticular pseudodrusen, individual characteristics, and retinal function. Design Cohort study. Participants We recruited 105 patients (age range, 52-93 years) who had advanced neovascular age-related macular degeneration (AMD) in only 1 eye from 3 clinical centers in Europe. Methods Minimum follow-up was 12 months. The eye selected for study was the fellow eye without advanced disease. Clinical measures of vision were distance visual acuity, near visual acuity, and results of the Smith-Kettlewell low-luminance acuity test (SKILL). Fundus imaging included color photography, red-free imaging, blue autofluorescence imaging, fluorescein angiography, indocyanine green angiography, and optical coherence tomography using standardized protocols. These were used to detect progression to neovascular AMD in the study eye during follow-up. All imaging outputs were graded for the presence or absence of reticular pseudodrusen (RPD) using a multimodal approach. Choroidal thickness was measured at the foveal center and at 2 other equidistant locations from the fovea (1500 μm) nasally and temporally. Metrics on retinal thickness and volume were obtained from the manufacturer-supplied automated segmentation readouts. Main Outcome Measures Presence of RPD, distance visual acuity, near visual acuity, SKILL score, choroidal thickness, retinal thickness, and retinal volume. Results Reticular pseudodrusen was found in 43 participants (41%) on 1 or more imaging method. The SKILL score was significantly worse in those with reticular drusen (mean score ± standard deviation [SD, 38±12) versus those without (mean score ± SD, 33±9) (P = 0.034). Parafoveal retinal thickness, parafoveal retinal volume, and all of the choroidal thickness parameters measured were significantly lower in those with reticular drusen than in those without. The presence of RPD was associated with development of neovascular AMD when corrected for age and sex (odds ratio, 5.5; 95% confidence interval, 1.1-28.8; P = 0.042). All participants in whom geographic atrophy developed during follow-up had visible RPD at baseline. Conclusions Significant differences in retinal and choroidal anatomic features, visual function, and risk factor profile exist in unilateral neovascular AMD patients with RPD compared with those without; therefore, such patients should be monitored carefully because of the risk of developing bilateral disease. © 2014 by the American Academy of Ophthalmology.

Marques F.C.,Hebrew University of Jerusalem | Marques F.C.,University of Coimbra | Volovik Y.,Hebrew University of Jerusalem | Cohen E.,Hebrew University of Jerusalem
Annual Review of Pathology: Mechanisms of Disease | Year: 2015

Numerous disorders, including neurodegenerative diseases and certain types of cancer, manifest late in life. This common feature raises the prospect that an aging-associated decline in the activity of cellular and organismal maintenance mechanisms enables the emergence of these maladies in late life stages. Accordingly, the alteration of aging bears the promise of harnessing the mechanisms that protect the young organism to prevent illness in the elderly. The identification of aging-regulatory pathways has enabled scrutiny of this hypothesis and revealed that the alteration of aging protects invertebrates and mammals from toxic protein aggregation linked to neurodegeneration and from cancer. Here we review the current knowledge on the regulation of aging at the cellular and organismal levels, delineate the mechanistic links between aging and late-onset disorders, describe efforts to develop compounds that protect from these maladies by selectively manipulating aging, and discuss future research directions and possible therapeutic implications of this approach. © 2015 by Annual Reviews.

Ferreira Da Silva M.G.,University of Aveiro | Costa B.F.O.,University of Coimbra
Journal of Non-Crystalline Solids | Year: 2011

Glass-ceramics with the composition 2Fe 2O 3.1ZnO.1MgO. 96SiO 2 [4ZnMgFe] and 2Fe 2O 3.2ZnO.3MgO. 93SiO 2 [7ZnMgFe] (mol%) were prepared using the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron diffraction (ED) and Mössbauer spectroscopy (MS) were used to investigate the glass-ceramics structure. The samples contain ferrite nanoparticles embedded in a glass matrix. However, zinc ferrite nanoparticles seems to be the preferential crystalline phase formed. The amount of ferrite particles depends on treatment temperature and sample composition. The Mössbauer spectroscopy measurements show that ferrite nanoparticles can exhibit a ferrimagnetic behaviour combined with superparamagnetism. © 2011 Elsevier B.V. All rights reserved.

Aveleira C.A.,University of Coimbra
Nature Reviews Endocrinology | Year: 2016

Hypothalamic dysfunction has emerged as an important mechanism involved in the development of obesity and its comorbidities, as well as in the process of ageing and age-related diseases, such as type 2 diabetes mellitus, hypertension and Alzheimer disease. In both obesity and ageing, inflammatory signalling is thought to coordinate many of the cellular events that lead to hypothalamic neuronal dysfunction. This process is triggered by the activation of signalling via the toll-like receptor 4 pathway and endoplasmic reticulum stress, which in turn results in intracellular inflammatory signalling. However, the process that connects inflammation with neuronal dysfunction is complex and includes several regulatory mechanisms that ultimately control the homeostasis of intracellular proteins and organelles (also known as 'proteostasis'). This Review discusses the evidence for the key role of proteostasis in the control of hypothalamic neurons and the involvement of this process in regulating whole-body energy homeostasis and lifespan. © 2016 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.

Dudal D.,Ghent University | Oliveira O.,University of Coimbra | Rodriguez-Quintero J.,University of Huelva
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

Either by solving the ghost propagator Dyson-Schwinger equations or through a one-loop computation in the refined Gribov-Zwanziger (RGZ) formalism, we show that a nontrivial ghost-gluon vertex is required to obtain a ghost propagator prediction compatible with the available corresponding lattice data in the SU(3) case. For the necessary gluon propagator input, we present RGZ tree-level fits which account well for the gluon lattice data. Interestingly, this propagator can be rewritten in terms of a running gluon mass. A comparison of both Dyson-Schwinger equations and RGZ results for the ghost propagator is furthermore provided. We also briefly discuss the connection between the RGZ and the operator product expansion d=2 gluon condensate. © 2012 American Physical Society.

Reis M.S.,University of Coimbra | Bauer A.,Voith GmbH
Computers and Chemical Engineering | Year: 2010

The characteristics of paper surface play a central role in the overall quality of paper produced in modern paper machines. Among the surface features, paper formation, i.e., the level of homogeneity in the distribution of fibres on the surface of paper, is a key quality parameter, being currently monitored off-line, at low sampling rates relatively to the high production speeds achieved with modern paper machines. Therefore, in this paper, we address the problem of assessing the quality of paper formation, on-line, in situ, in an autonomous, efficient, objective and fast way, using features derived from images collected by a specially designed sensor, coupled with proper classification methodologies. The results obtained clearly demonstrate the potential of the proposed assessment approach either for the more complex three-class classification problem as well as for less demanding, but still important in practice, two-class " Accept" /" Reject" or " Pass" /" Fail" problem. © 2010 Elsevier Ltd.

Volovik Y.,Hebrew University of Jerusalem | Marques F.C.,Hebrew University of Jerusalem | Marques F.C.,University of Coimbra | Cohen E.,Hebrew University of Jerusalem
Methods | Year: 2014

Toxicity arising from protein misfolding and aggregation (proteotoxicity) is tightly mechanistically linked to the emergence of late-onset neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Why these maladies manifest in late stages of life and what mechanisms protect the young organism from disease are key enigmas. The nematode Caenorhabditis elegans offers key advantages that enable systematic exploration of many cell biological and functional aspects of neurodegeneration-linked proteotoxicity. Here we review the abundantly used nematode-based proteotoxicity models and delineate common techniques for the measurement of protein aggregation and rate of proteotoxicity. We also discuss the advantages offered by the worm for genetic screening, drug development and for the exploration of the links between proteotoxicity and the aging process. © 2014 Elsevier Inc.

A 69-year-old Caucasian woman with a 15-year history of refractory chronic lymphocytic B-cell leukaemia (CLL), treated with alemtuzumab in the past 10 months presented with a subacute right foot drop. Initial evaluation with a brain CT scan, lumbosacral MRI, nerve conduction studies and LP was negative. In the following months, progressive right hemibody weakness and dysarthria developed. Brain MRI showed a bilateral parasagittal frontal lesion. Alemtuzumab treatment was withdrawn. Progressive multifocal leukoencephalopathy (PML) was confirmed by PCR. Attempted antiviral therapies proved fruitless. Inexorable clinical deterioration ensued and the patient passed away 10 months after the presentation. This case report intends to call attention for PML as a potential fatal complication of severe immunosuppression, including the possible role of new monoclonal antibodies (such as alemtuzumab) in its pathogenesis.

Moreno-Pires S.,University of Coimbra | Fidelis T.,University of Aveiro
Ecological Indicators | Year: 2012

The actual use of sustainability indicators and their steering potential is constrained by the particularities of governance contexts, by institutional patterns and changes, by the different interpretations of what sustainable development means and entails, and by the tensions around the main values nurturing the positions of the most relevant actors. This paper proposes a normative conceptual framework to further explore the role of sustainability indicators in local governance contexts, and applies it to the Portuguese municipality of Palmela. It aims to contribute to a better understanding of how, why and in what circumstances the processes of developing and using indicators can be important steering mechanisms for governance for sustainability, particularly at the local level. The methods used include primary literature review and official documents and data, interviews to local public officers and qualitative analysis. Palmela provides insights on concrete government achievements through the implementation of sustainability indicators, but clearly shows how they are insufficient to foster innovative governance arrangements for sustainability. The normative framework enables the identification of successes and failures of developing and using sustainability indicators in improving local governance and ultimately in helping to achieve sustainability goals. © 2012 Elsevier Ltd. All rights reserved.

Ribeiro E.,University of Coimbra | Ribeiro E.,Telecommunications Institute of Portugal | Cardoso A.J.M.,Telecommunications Institute of Portugal | Cardoso A.J.M.,University of Beira Interior | Boccaletti C.,University of Rome La Sapienza
IEEE Transactions on Power Electronics | Year: 2013

The photovoltaic (PV) technology has a small impact on the environment and is suitable for a wide range of applications. The main barrier for a more extensive implementation has been the reliability, mainly related to the power converters. According to this consideration, this paper presents an open-circuit fault diagnosis and fault-tolerant scheme for a three-level boost converter in a PV power system using batteries as storage devices. The fault diagnosticmethod takes advantage only of the control variables used for maximum power point tracking and output dc-link capacitor voltage balance. The fault-tolerant strategy requires only a few components added to the original three-level boost converter, so that, under an open-circuit power switch fault, it can be partly reconfigured into a two-level boost converter ensuring battery energy supply. Experimental results verify the proposed fault diagnostic method and reconfiguration for fault-tolerant operation. © 2012 IEEE.

Palma D.,University of Coimbra
Eurasip Journal on Wireless Communications and Networking | Year: 2013

Infrastructure-less wireless multi-hop networks have long been proposed for natural disaster and warfare scenarios. However, the current demand of such networks has been towards social networking, gaming and ultimately, ubiquitous computing. In fact, the increasing number of users that own wireless capable devices is taking these networks to an entirely different scale. Existing routing protocols do not scale and do not consider the context wherein services operate. By presenting an alternative routing scheme that appropriately handles mobility of users among different contexts, large-scale clustered wireless networks are designed, using an efficient gateway selection with load-balancing capabilities. This approach uses a virtual hierarchy of clusters to explore the contextual-proximity of nodes, while reducing the total overhead of routing traffic even when compared with other cluster-based approaches. Moreover, it is capable of predicting gateway link disconnections, increasing the total amount of delivered data. The obtained results reveal that this routing scheme outperforms existing routing protocols regardless of the mobility pattern being used, being consistently lighter in overhead and delivering up to 50% more data traffic. These results motivate a new era of large-scale wireless multi-hop networks suitable for hand-held devices exchanging data amongst themselves. © 2013 Palma and Curado.

Alvarez-Ruso L.,University of Coimbra
AIP Conference Proceedings | Year: 2010

The recent theoretical developments in the field of neutrino-nucleus interactions in the few-GeV region are reviewed based on the presentations made at the NuInt09Workshop. The topics of electron scattering and its connections with neutrino interactions, neutrino induced quasielastic scattering and pion production (coherent and incoherent) are covered, with special emphasis on the challenges that arise in the comparison with new experimental data. © 2010 American Institute of Physics.

Maslovski S.I.,University of Coimbra | Simovski C.R.,Aalto University | Tretyakov S.A.,Aalto University
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Here, we develop a theory of radiative heat transfer based on an equivalent electrical network representation for the hot material slabs in an arbitrary multilayered environment with arbitrary distribution of temperatures and electromagnetic properties among the layers. Our approach is fully equivalent to the known theories operating with the fluctuating current density, while being significantly simpler in analysis and applications. A practical example of the near-infrared heat transfer through the micron gap filled with an indefinite metamaterial is considered using the suggested method. The giant enhancement of the transferred heat compared to the case of the empty gap is shown. © 2013 American Physical Society.

Negrao J.H.,University of Coimbra
Construction and Building Materials | Year: 2016

The possibility of improving the bending strength of timber beams through prestress is discussed. Different prestressing and anchoring procedures are investigated: (i) post-tension, with mechanical anchorage on the ends of the wood elements; (ii) pre-tension, with the anchorages being either mechanical, as in the previous system, or glued, with the force being gradually transferred through shear stresses along a certain length of the wire/wood interface. The main conclusion is that any of the procedures may be advantageously used with either small (mass-production) or long glued-laminated timber beams, as a possible alternative to CFRP reinforced beams. © 2014 Elsevier Ltd.

Baldo M.,National Institute of Nuclear Physics, Italy | Polls A.,University of Barcelona | Rios A.,University of Surrey | Schulze H.-J.,National Institute of Nuclear Physics, Italy | Vidana I.,University of Coimbra
Physical Review C - Nuclear Physics | Year: 2012

We present calculations of the energy per particle of pure neutron and symmetric nuclear matter with simplified Argonne nucleon-nucleon potentials for different many-body theories. We compare critically the Brueckner-Hartree-Fock results to other formalisms, such as the Brueckner-Bethe-Goldstone expansion up to third order, self-consistent Green's functions, auxiliary field diffusion Monte Carlo, and Fermi hypernetted chain. We evaluate the importance of spin-orbit and tensor correlations in the equation of state and find these to be important in a wide range of densities. © 2012 American Physical Society.

Serna-Chavez H.M.,VU University Amsterdam | Serna-Chavez H.M.,University of Coimbra | Serna-Chavez H.M.,University of Amsterdam | Fierer N.,University of Colorado at Boulder | Van Bodegom P.M.,VU University Amsterdam
Global Ecology and Biogeography | Year: 2013

Aim: While soil microorganisms play key roles in Earth's biogeochemical cycles, methodological constraints and sparse data have hampered our ability to describe and understand the global distribution of soil microbial biomass. Here, we present a comprehensive quantification of the environmental drivers of soil microbial biomass. Location: Global. Methods: We used a comprehensive global dataset of georeferenced soil microbial biomass estimates and high-resolution climatic and soil data. Results: We show that microbial biomass carbon (CMic) is primarily driven by moisture availability, with this single variable accounting for 34% of the global variance. For the microbial carbon-to-soil organic carbon ratio (CMic/COrg), soil nitrogen content was an equally important driver as moisture. In contrast, temperature was not a significant predictor of microbial biomass patterns at a global scale, while temperature likely has an indirect effect on microbial biomass by influencing rates of evapotranspiration and decomposition. As our models explain an unprecedented 50% of the global variance of CMic and CMic/COrg, we were able to leverage gridded environmental information to build the first spatially explicit global estimates of microbial biomass and quantified the global soil microbial carbon pool to equal 14.6 Pg C. Main Conclusions: Our unbiased models allowed us to build the first global spatially explicit predictions of microbial biomass. These patterns show that soil microbial biomass is not primarily driven by temperature, but instead, biomass is more heterogeneous through the effects of moisture availability and soil nutrients. Our global estimates provide important data for integration into large-scale carbon and nutrient models that may imply a major step forward in our ability to predict the global carbon balance, now and in a future climate. © 2013 John Wiley & Sons Ltd.

Lovejoy S.,McGill University | de Lima M.I.P.,Institute of Marine Research and Marine and Environmental science Center | de Lima M.I.P.,University of Coimbra
Chaos | Year: 2015

Over the range of time scales from about 10 days to 30-100 years, in addition to the familiar weather and climate regimes, there is an intermediate "macroweather" regime characterized by negative temporal fluctuation exponents: implying that fluctuations tend to cancel each other out so that averages tend to converge. We show theoretically and numerically that macroweather precipitation can be modeled by a stochastic weather-climate model (the Climate Extended Fractionally Integrated Flux, model, CEFIF) first proposed for macroweather temperatures and we show numerically that a four parameter space-time CEFIF model can approximately reproduce eight or so empirical space-time exponents. In spite of this success, CEFIF is theoretically and numerically difficult to manage. We therefore propose a simplified stochastic model in which the temporal behavior is modeled as a fractional Gaussian noise but the spatial behaviour as a multifractal (climate) cascade: a spatial extension of the recently introduced ScaLIng Macroweather Model, SLIMM. Both the CEFIF and this spatial SLIMM model have a property often implicitly assumed by climatologists that climate statistics can be "homogenized" by normalizing them with the standard deviation of the anomalies. Physically, it means that the spatial macroweather variability corresponds to different climate zones that multiplicatively modulate the local, temporal statistics. This simplified macroweather model provides a framework for macroweather forecasting that exploits the system's long range memory and spatial correlations; for it, the forecasting problem has been solved. We test this factorization property and the model with the help of three centennial, global scale precipitation products that we analyze jointly in space and in time. © 2015 AIP Publishing LLC.

Pinhoe Melo T.M.V.D.,University of Coimbra
European Journal of Organic Chemistry | Year: 2010

This review provides coverage of the more relevant contributions to the synthesis and reactivity of 4-isoxazolines (2,3dihydroisoxazoles). The richness of the reactivity of these heterocycles makes them interesting building blocks for the synthesis of both cyclic and acyclic compounds. © 2010 Wiley-VCH Verlag GmbH &. Co. KGaA, Weinheim.

Cordier D.,University of Franche Comte | Barnes J.W.,University of Idaho | Ferreira A.G.,University of Coimbra
Icarus | Year: 2013

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains-suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments. © 2013 Elsevier Inc.