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Aveiro, Portugal

The University of Aveiro is a Portuguese public university, headquartered in Aveiro since its 1973 creation. It also provides polytechnic education.Administratively, the teaching and research activities are distributed by Departments and Autonomous Sections, both with specialized faculties.The University has more than 12,500 students distributed across 58 graduate courses, over 40 MSc courses and 25 PhD programs.Its main campus is near the centre of Aveiro, including a nearby Administration and Accounting Institute. The university also has external regional campuses in Águeda, Higher Education Technological and Management School of Águeda, and Oliveira de Azeméis Higher Education School of North Aveiro.It is an R&D university, having a research units developing programmes in fundamental and applied mathematics, physics, chemistry, telecommunications, robotics, bioinformatics, sea science, materials, design, business administration and industrial engineering. Wikipedia.

Monaghan K.A.,University of Aveiro
Hydrobiologia | Year: 2015

Legislation obliging the maintenance of ecologically defined quality standards has focused attention on the accuracy of bioassessment metrics. Describing the statistical distribution of ecological indicators, Taylor’s Law (TL) has important relevance to the design and interpretation of bioassessment protocols. Analyzing a detailed UK dataset revealed that most macroinvertebrate indicators were characterized by similar geometric distributions, providing a theoretical imperative to log-transform indicator abundance prior to metric derivation. Evaluating a range of bioassessment metrics revealed a 2–4 fold increase in precision and up to 50% improvement in fidelity compared to standard assessment metrics, based on raw-abundance data. Similar improvement in metric fidelity for North American rivers (up to 60%) indicates the broad biogeographic relevance of this analytical modification. Reducing the risk of misclassifying biological quality for a suite of environmentally contrasting rivers from 80% to 4% emphasizes the benefit that this application of TL could deliver to river management. Requiring no increase in costs and with the potential for retrospective application to historical data, this simple modification is entirely compatible with contemporary assessment practice. © 2015, Springer International Publishing Switzerland. Source

Nunes F.M.,University of Tras os Montes e Alto Douro | Cruz A.C.S.,University of Tras os Montes e Alto Douro | Coimbra M.A.,University of Aveiro
Journal of Agricultural and Food Chemistry | Year: 2012

To study the mechanism of coffee melanoidin formation, green coffee beans were prepared by (1) removal of the hot water extractable components (WECoffee); (2) direct incorporation of sucrose (SucCoffee); and (3) direct incorporation of type II arabinogalactan-proteins (AGPCoffee). As a control of sucrose and AGP incorporation, lyophilized green coffee beans were also immersed in water (control). The original coffee and the four modified "in bean" coffee models were roasted and their chemical characteristics compared. The formation of material not identified as carbohydrates or protein, usually referred to as "unknown material" and related to melanoidins, and the development of the brown color during coffee roasting have distinct origins. Therefore, a new parameter for coffee melanoidin evaluation, named the "melanoidin browning index" (MBI), was introduced to handle simultaneously the two concepts. Sucrose is important for the formation of colored structures but not to the formation of "unknown material". Type II AGPs also increase the brown color of the melanoidins, but did not increase the amount of "unknown material". The green coffee hot water extractable components are essential for coffee melanoidin formation during roasting. The cell wall material was able to generate a large amount of "unknown material". The galactomannans modified by the roasting and the melanoidin populations enriched in galactomannans accounted for 47% of the high molecular weight brown color material, showing that these polysaccharides are very relevant for coffee melanoidin formation. © 2012 American Chemical Society. Source

Silvestre-Blanes J.,Polytechnic University of Valencia | Almeida L.,University of Porto | Marau R.,University of Porto | Pedreiras P.,University of Aveiro
IEEE Transactions on Industrial Electronics | Year: 2011

A growing number of industrial applications incorporate multimedia information processing. These multimedia applications are commonly distributed and subject to time constraints that must be met across networks without creating intolerable interference over typical control flows. However, multimedia traffic, in general, and video streaming, in particular, have specific characteristics that conflict with the operational framework of conventional real-time protocols. In particular, video compressors generate highly variable bit-rate streams that mismatch the constant-bit-rate channels typically provided by real-time protocols, severely reducing the efficiency of network utilization. This paper focuses on low-latency multimedia transmission over Ethernet with dynamic quality-of-service (QoS) management. We propose a multidimensional mechanism that controls, in an integrated way, both the compression parameters and the network bandwidth allocated to each stream. The goal is to provide the best possible QoS to each stream, recomputing the compression levels and network bandwidth whenever significant events, such as channel setup/teardown, or structural changes happen. This paper also presents novel QoS metrics based both on the image quality and network parameters. Several experiments with prerecorded video streams illustrate the advantages of the proposed approach and the convenience of the metrics. © 2010 IEEE. Source

Barranco M.,University of the Balearic Islands | Proenza J.,University of the Balearic Islands | Almeida L.,University of Porto | Almeida L.,University of Aveiro
IEEE Transactions on Industrial Electronics | Year: 2011

There has been an increasing interest in using star topologies in field-bus communications, e.g., in Time Triggered Protocol for SAE classC applications (TTP/C), FlexRay, or controller area network (CAN), due to increased fault resilience and potential error-containment advantages. In this context, an innovative CAN-compliant star topology, CANcentrate, has been developed, whose hub includes enhanced fault-treatment mechanisms. However, despite this interest toward stars, it is still necessary to quantify their real dependability benefits. For this purpose and for the particular case of CAN, this paper presents models for the dependability features of CAN and CANcentrate using Stochastic Activity Networks (SANs). It quantitatively compares their reliability and error-containment capabilities under permanent hardware faults. These models rely on assumptions that ensure that results are not biased toward CANcentrate, which, in some cases, is too detrimental for it. Thus, despite not reflecting the full CANcentrate potential, results quantitatively confirm the improvement of error-containment it achieves over CAN. Additionally, the way in which the nodes' ability to contain their own errors affects the relevance of using a star topology has been quantified. Although this paper refers to the case of CAN, conclusions regarding the justification of using a star topology depending on this ability can be extrapolated to other field-bus technologies. © 2009 IEEE. Source

Carvalho T.M.,Agencia Portuguesa do Ambiente | Fidelis T.,University of Aveiro
Land Use Policy | Year: 2013

The latest theories on the governance of water resources point to the need to adopt integrated approaches, allowing the mediation of conflict between public and private interests by building consensus to include the participation of stakeholders and civil society in formulating and implementing policies, thereby ensuring their legitimacy. Models of governance have particular relevance in the context of estuaries, because of the complexity associated with them. Estuaries are areas where valuable, highly sensitive and diverse natural systems coexist, which are frequently threatened by the numerous human activities concentrated there. They are also areas where several organizations overlap, with their own jurisdictions and management instruments and where there is a wide range of users with distinct interests. At a time when the Planos de Ordenamento de Estuários (POE) (Estuary Land Use and Management Plan), a new tool for water resource management and planning, are being drawn up in Portugal, this paper discusses the specificities of the new Portuguese estuary plans, as well as associated potentials and constraints to further understand how water resources and land use policies may effectively be integrated in estuary contexts. It critically analyses the Portuguese legal framework established for these plans, arguing that, in spite of the novelty of the newly defined legal measures to better plan and manage estuaries, implementation of its ambitious objectives requires a robust governance model for plan preparation and implementation. Taking into account the main institutional features of complex estuaries with various agencies, stakeholders and users, as well as relevant governance principles, this paper proposes a governance model capable of enriching the implementation of estuary plans by contributing to a stronger involvement of all stakeholders and users in the construction of the plan, allowing conciliation of interests and participation in decision-making, within a framework of collaborative governance. Whilst the paper focuses on the Portuguese Law, the approach adopted is also of interest to other countries to assessing estuary planning regulations and associated collaborative measures. © 2013 Elsevier Ltd. Source

Nabovati A.,University of New Brunswick | Llewellin E.W.,Durham University | Sousa A.C.M.,University of New Brunswick | Sousa A.C.M.,University of Aveiro
Composites Part A: Applied Science and Manufacturing | Year: 2010

The lattice Boltzmann method (LBM) is used to investigate the dual-scale problem of fluid flow through three-dimensional multifilament woven fabrics. Such fabrics are characterized by two distinct length scales: the thickness of a single filament and the thickness of a bundle of filaments, known as yarn. The yarn's thickness is typically two orders of magnitude greater than that of a single filament. The inter-yarn and intra-yarn spaces, through which fluid may flow, are also of two distinct length scales. The direct simulation of fluid flow in multifilament woven fabrics involves the simultaneous resolution of the flow field in the inter-yarn and intra-yarn pores; the LBM is well-suited to modelling such geometrically-complex fluid flow. The methodology is first validated against published analytical results for two-dimensional transverse fluid flow through hexagonal arrays of cylinders; the agreement is excellent. Fluid flow in two-dimensional representations of multifilament woven fabrics is also simulated, and the results are compared against those obtained following Papathanasiou's approach (2001, Int. J. Multiphase Flow, 27: 1451-1461); the agreement is very good. The model is then used to determine the through-thickness permeability of three-dimensional woven fabrics by direct simulation of the fluid flow. The geometry used for the three-dimensional simulations resembles bi-axial, plain woven fabrics. The inter-yarn porosity ('weave porosity', φ{symbol}w) and the intra-yarn porosity ('yarn porosity', φ{symbol}y) are systematically varied in the range 0.3 ≤ φ{symbol}w ≤ 0.65 and 0 ≤ φ{symbol}y ≤ 0.80, respectively. These parameters control the weave and yarn permeabilities (Kw and Ky). The influence of these parameters on the effective permeability of the fabric, Kp, is quantified and discussed in terms of the fabric structure. Our results are analyzed following the approach developed by Papathanasiou (2001, Int. J. Multiphase Flow, 27: 1451-1461) for two-dimensional structures. The semi-empirical relationship between the fabric permeability and the weave and yarn permeabilities proposed in that study provides an excellent fit to the data produced by our three-dimensional simulations, with only minor adjustment to the fitting parameters. The parameterized relationship we obtain allows the through-thickness permeability of a three-dimensional woven fabric to be predicted if the weave and yarn permeabilities are known. © 2009 Elsevier Ltd. All rights reserved. Source

Vines F.,University of Barcelona | Gomes J.R.B.,University of Aveiro | Illas F.,University of Barcelona
Chemical Society Reviews | Year: 2014

Metallic nanoparticles (NPs) constitute a new class of chemical objects which are used in different fields as diverse as plasmonics, optics, catalysis, or biochemistry. The atomic structure of the NP and its size usually determine the chemical reactivity but this is often masked by the presence of capping agents, solvents, or supports. The knowledge of the structure and reactivity of isolated NPs is a requirement when aiming at designing NPs with a well-defined chemistry. Theoretical models together with efficient computational chemistry algorithms and parallel computer codes offer the opportunity to explore the chemistry of these interesting objects and to understand the effects of parameters such as size, shape and composition allowing one to derive some general trends. This journal is © the Partner Organisations 2014. Source

Rocha-Santos T.A.P.,University of Aveiro | Rocha-Santos T.A.P.,Piaget Institute
TrAC - Trends in Analytical Chemistry | Year: 2014

Magnetic nanoparticles (MNPs) have attracted a growing interest in the development and fabrication of sensors and biosensors for several applications. MNPs can be integrated into the transducer materials and/or be dispersed in the sample followed by their attraction by an external magnetic field onto the active detection surface of the (bio)sensor. This review describes and discusses the recent applications of MNPs in sensors and biosensors, taking into consideration their analytical figures of merit. This work also addresses the future trends and perspectives of sensors and biosensors based on MNPs. © 2014 Elsevier B.V. Source

Pereira R.N.,University of Aveiro | Rowe D.J.,University of Minnesota | Anthony R.J.,University of Minnesota | Kortshagen U.,University of Minnesota
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The future exploitation of the exceptional properties of freestanding silicon nanocrystals (Si NCs) in marketable applications relies upon our ability to produce large amounts of defect-free Si NCs by means of a low-cost method. Here, we demonstrate that Si NCs fabricated by scalable rf plasma-assisted decomposition of silane with additional hydrogen gas injected into the afterglow region of the plasma exhibit immediately after synthesis the lowest reported defect density, corresponding to a value of only about 0.002-0.005 defects per NC for Si NCs of 4 nm size. In addition, the virtually perfect hydrogen termination of these Si NCs yields an enhanced resistance against natural oxidation in comparison to Si NCs with nearly one order of magnitude larger initial defect density. © 2012 American Physical Society. Source

Morais J.,University of Aveiro | Kou K.I.,Macau University of Science and Technology | Sprossig W.,TU Bergakademie Freiberg
Computers and Mathematics with Applications | Year: 2013

Monogenic orthogonal polynomials over 3D prolate spheroids were previously introduced and shown to have some remarkable properties. In particular, the underlying functions take values in the quaternions (identified with R4), and are generally assumed to be nullsolutions of the well known Moisil-Théodoresco system. In this paper, we show that these polynomial functions play an important role in defining the Szegö kernel function over the surface of 3D (prolate) spheroids. As a concrete application, we prove an explicit expression of the monogenic Szegö kernel function over 3D (prolate) spheroids and present two numerical examples. © 2012 Elsevier B.V. All rights reserved. Source

Gandini A.,University of Aveiro
Green Chemistry | Year: 2011

The last few decades have witnessed a spiralling growth of interest in polymers from renewable resources within both the scientific and industrial communities. This review attempts to illustrate this state of affairs through a panoramic overview of recent progress in the most relevant areas related to such materials, including the polymerisation of natural monomers and their derivatives, the exploitation of biopolymers, as such, or after appropriate modifications, as well as the preparation of composites and blends. Because of the sheer size and depth of the field, no attempt has been made here to provide a comprehensive coverage, emphasis being placed instead on conveying the extent and originality of contributions reported in the last few years in important domains like sugars and polysaccharides, vegetable oils, lignin, pine resin derivatives, furans, and a series of other monomers. © 2011 The Royal Society of Chemistry. Source

Henriques J.,University of Lisbon | Costa P.J.,University of Aveiro | Calhorda M.J.,University of Lisbon | MacHuqueiro M.,University of Lisbon
Journal of Physical Chemistry B | Year: 2013

We studied the effect of using different heme group charge parametrization methods and schemes (Merz-Kollman, CHELPG, and single- and multiconformational RESP) on the quality of the results produced by the constant-(pH,E) MD method, applied to the redox titration of Desulfovibrio vulgaris Hildenborough cytochrome c3. These new and more accurate charge sets enabled us to overcome the previously reported dependence of the method's performance on the dielectric constant, ε, assigned to the protein region. In particular, we found a systematic, clear shift of the Emod toward more negative values than those previously reported, in agreement with an electrostatics based reasoning. The simulations showed strong coupling between protonating/redox sites. We were also able to capture significant direct and, especially, indirect interactions between hemes, such as those mediated by histidine 67. Our results highlight the importance of having a good quantum description of the system before deriving atomic partial charges for classic force fields. © 2012 American Chemical Society. Source

Correia A.C.M.,University of Aveiro | Correia A.C.M.,University Pierre and Marie Curie | Laskar J.,University Pierre and Marie Curie
Astrophysical Journal Letters | Year: 2012

Impact basins identified by Mariner 10 and Messenger flyby images provide us with a fossilized record of the impactor flux of asteroids on Mercury during the last stages of the early solar system. The distribution of these basins is not uniform across the surface and is consistent with a primordial synchronous rotation. By analyzing the size of the impacts, we derive a simple collisional model coherent with the observations. When combining it with the secular evolution of the spin of Mercury, we are able to reproduce the present 3/2 spin-orbit resonance (50% of chances), as well as a primordial synchronous rotation. This result is robust with respect to variations in the dissipation and collisional models, or in the initial spin state of the planet. © 2012. The American Astronomical Society. All rights reserved.. Source

Herdeiro C.,University of Aveiro | Hirano S.,Nagoya University
Journal of Cosmology and Astroparticle Physics | Year: 2012

We propose a 3+1 dimensional model of gravity which results in inflation at early times, followed by radiation- and matter-dominated epochs and a subsequent acceleration at late times. Both the inflation and late time acceleration are nearly de Sitter with a large hierarchy between the effective cosmological constants. There is no scalar field agent of inflation, and the transition from the inflation to the radiation-dominated period is smooth. This model is designed so that it yields, at the cost of giving up on Lorentz invariance in the gravitational sector, the Dirac-Born-Infeld type conformal scalar theory when the universe is conformally flat. It, however, resembles Einstein's gravity with the Gibbons-Hawking-York boundary term in weakly curved space-times. © 2012 IOP Publishing Ltd and Sissa Medialab srl. Source

Monaghan K.A.,University of Aveiro
PLoS ONE | Year: 2016

Natural ecological variability and analytical design can bias the derived value of a biotic index through the variable influence of indicator body-size, abundance, richness, and ascribed tolerance scores. Descriptive statistics highlight this risk for 26 aquatic indicator systems; detailed analysis is provided for contrasting weighted-average indices applying the example of the BMWP, which has the best supporting data. Differences in body size between taxa from respective tolerance classes is a common feature of indicator systems; in some it represents a trend ranging from comparatively small pollution tolerant to larger intolerant organisms. Under this scenario, the propensity to collect a greater proportion of smaller organisms is associated with negative bias however, positive bias may occur when equipment (e.g. mesh-size) selectively samples larger organisms. Biotic indices are often derived from systems where indicator taxa are unevenly distributed along the gradient of tolerance classes. Such skews in indicator richness can distort index values in the direction of taxonomically rich indicator classes with the subsequent degree of bias related to the treatment of abundance data. The misclassification of indicator taxa causes bias that varies with the magnitude of the misclassification, the relative abundance of misclassified taxa and the treatment of abundance data. These artifacts of assessment design can compromise the ability to monitor biological quality. The statistical treatment of abundance data and the manipulation of indicator assignment and class richness can be used to improve index accuracy. While advances in methods of data collection (i.e. DNA barcoding) may facilitate improvement, the scope to reduce systematic bias is ultimately limited to a strategy of optimal compromise. The shortfall in accuracy must be addressed by statistical pragmatism. At any particular site, the net bias is a probabilistic function of the sample data, resulting in an error variance around an average deviation. Following standardized protocols and assigning precise reference conditions, the error variance of their comparative ratio (test-site:reference) can be measured and used to estimate the accuracy of the resultant assessment. © 2016 Kieran A. Monaghan. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Baxter G.J.,University of Aveiro
Journal of Statistical Mechanics: Theory and Experiment | Year: 2011

We introduce time variation in the flip rates of the voter model. This type of generalization may be applied to other diffusion-like models in which interaction rates at the microscopic level may change with time, for example in models of language change, allowing the representation of changes in speakers' learning rates over their lifetime. The mean time taken to reach consensus varies in a nontrivial way with the rate of change of the flip rates, varying between bounds given by the mean consensus times for static homogeneous (the original voter model) and static heterogeneous flip rates. By considering the mean time between interactions for each agent, we derive excellent estimates of the mean consensus times and exit probabilities for any timescale of flip rate variation. The scaling of consensus times with population size on complex networks is correctly predicted, and is as would be expected for the ordinary voter model. Heterogeneity in the initial distribution of opinions has a strong effect, considerably reducing the mean time to consensus, while increasing the probability of survival of the opinion which initially occupies the most slowly changing agents. The mean times taken to reach consensus for different states are very different. An opinion originally held by the fastest changing agents has a smaller chance of succeeding, and takes much longer to do so than an evenly distributed opinion. © IOP Publishing Ltd. Source

Da Silva M.G.F.,University of Aveiro
Journal of Non-Crystalline Solids | Year: 2016

Glass and glass-ceramics with the compositions 1Fe2O3-99SiO2 (1Fe), 2Fe2O3-98SiO2 (2Fe), 1MnO-99SiO2 (1Mn), 2MnO-98SiO2 (2Mn), 1MnO-1Fe2O3-98SiO2 (2MnFe), 2MnO-2Fe2O3-96SiO2 (4MnFe) (mol%) were prepared using the sol-gel method. The gel samples were heat treated between 120 and 1000 °C. Thermogravimetric and differential thermal analysis (TG-DTA), ultraviolet, visible and near infrared spectrophotometry (UV-Vis-NIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (SEM-EDS) were used to study the structural changes that occur during the gel to glass and glass-ceramic conversions. Many of the prepared glass and glass-ceramics present brown or black colorations. These dark colorations are due to the presence in the samples of maghemite-C, magnetite, hematite, Mn3O4 (bixbyite) and Mn2 +(Mn3 +)14SiO24 (braunite) or simultaneously more than one of these crystalline phases. These nanoparticles give to the samples very interesting magnetic and optical properties of great importance in several medical fields. Furthermore, the study contributed to understanding the formation mechanism of some MnO and/or Fe2O3-containing silicate glasses and glass-ceramics prepared by the sol-gel method. © 2016 Elsevier B.V. Source

Melo-Pfeifer S.,University of Aveiro
Computer Assisted Language Learning | Year: 2015

Focusing on the topic of the development of the plurilingual and intercultural competence through the integration of electronic communicative practices both in foreign language classrooms and non-formal contexts, this work aims at defining and characterizing, in view of a co-actional perspective, a “pedagogical blog”, by considering it from three different axes: a personal and social dimension, a collaborative and co-actional dimension and the management of linguistic and cultural repertoires dimension. In order to do so, this contribution presents and describes a case study which will highlight how blogs can be used in order to develop plurilingual and intercultural competences: we will present the classroom dynamics developed by the blog “Falar pelos cotovelos”, a year-long project created within the scope of the teaching and learning of Portuguese as a foreign language, in a non-formal setting (non-scholar public). Throughout the discussion of this purposeful sampling, our analysis will allow us to consider pedagogical blogs as means of socialization, as instruments at the service of exolingual interaction and as time-spaces for languages and cultures. © 2013, Taylor & Francis. Source

Ahmad N.,Patna University | Sharma S.,Magadh University | Rai R.,University of Aveiro
Advanced Materials Letters | Year: 2012

We present a simple and eco-friendly biosynthesis of silver nanoparticles using Pomegranate peel extract as the reducing agent. Peel extract of Pomegranate was challenged with silver nitrate (AgNO3) and chloroauric acid (HAuCl4) solution for the production of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), respectively. The reaction process was simple for the formation of highly stable silver and gold nanoparticles at room temperature by using the biowaste of the fruit. The morphology and crystalline phase of the NPs were determined from UV-Vis spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. TEM studies showed that the average particle size of silver nanoparticles were 5 ±1.5 nm whereas the gold nanoparticles were found to be 10 ±1.5 nm. An effort has been also been made to understand the possible involved mechanism for the biosynthesis of the NPs. Presumably biosynthetic products or reduced cofactors play an important role in the reduction of respective salts to nanoparticles. © 2012 VBRI Press. Source

Teles F.,University of Aveiro
European Urban and Regional Studies | Year: 2016

Portugal is working on the reform of its local government. Although amalgamation was one of the recommended strategies, as a consequence of the European Union/International Monetary Fund bailout process, an alternative approach has been suggested. This reform is mostly a development of inter-municipal cooperation mechanisms combined with partial devolution strategies. However, as the bailout agreement was its main catalyst, the urgency to cut public administration costs required in the memorandum and the imposed deadlines gave a perverse incentive for central government to produce ad hoc and fragmented modifications. I argue that these political and economical demands, which sanctioned the argument for rushed measures, together with the country’s strong local identities, historical municipalism, political centralism and the political costs of significant territorial changes, can explain the absence of a comprehensible reform strategy and the singularities of its policies. This article explores the framework that justifies the reform and assesses the impacts of the bailout agreement. © The Author(s) 2014. Source

Dornelas M.,James Cook University | Dornelas M.,University of Aveiro
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

Understanding how disturbance affects biodiversity is important for both fundamental and applied reasons. Here, I investigate how disturbances with different ecological effects change biodiversity metrics. I define three main types of disturbance effects: D disturbance (shifts in mortality rate), B disturbance (shifts in reproductive rates) and K disturbance (shifts in carrying capacity). Numerous composite disturbances can be defined including any combination of these three types of ecological effects. The consequences of D, B and K disturbances, as well as of composite DBK disturbances are examined by comparing metrics before and after a disturbance, in disturbed and undisturbed communities. I use simulations of neutral communities and examine species richness, total abundance and species abundance distributions. The patterns of change in biodiversity metrics are consistent among different types of disturbance. K disturbance has the most severe effects, followed by D disturbance, and B disturbance has nearly negligible effects. Consequences of composite DBK disturbances are more complex than any of the three types of disturbance, with unimodal relationships along a disturbance gradient arising when D, B and K are negatively correlated. Importantly, regardless of disturbance type, community isolation enhances the negative consequences and hinders the positive effects of disturbances. This journal is © 2010 The Royal Society. Source

Shafaii Moghadam H.,Damghan University | Khademi M.,Damghan University | Hu Z.,Wuhan University | Stern R.J.,University of Texas at Dallas | And 2 more authors.
Gondwana Research | Year: 2015

The ChahJam-Biarjmand complex (CJBC), flanked by the Alborz Mountains in the north and the Lut-Tabas block to the south, is part of Central Iranian block, where the oldest continental crust of Iran is found. This complex contains granitic to tonalitic orthogneissic rocks (old plutons) and associated metasediments, amphibolites and paragneisses. Metamorphosed granitic and granodioritic dikes intrude orthogneisses as well as metasediments and are abundant close to the plutons (orthogneissic rocks). Based on the results of bulk rock trace and rare earth elements, the orthogneissic rocks are inferred to have crystallized from subduction-related melts. Amphibolites also have subduction-related signatures and are inferred to have formed both as metamorphosed volcanoclastic sediments and as attenuated basic dikes. The presence of para-amphibolites associated with paragneisses and metasediments (mica schists) could represent a sedimentary basin filled with magmatic arc erosional products. U-Pb zircon dating of the ChahJam-Biarjmand rocks yielded 238U/206Pb crystallization ages of ca. 550 to 530Ma (Ediacaran-early Cambrian). Sr-Nd isotope systematics on whole rocks (εNd(t)=-2.2 to -5.5) and zircon Hf isotope results indicate that CJBC Cadomian granitic rocks contain older, possible Mesoproterozoic, continental crust in their source. The ChahJam-Biarjmand granitic-tonalitic gneissic rocks are coeval with other similar-aged metagranites and gneisses within Iranian basement exposed in Central Iran, the Sanandaj-Sirjan Zone and the Alborz Mountains, as well as in the Tauride-Anatolide platform in western Anatolia and in NW Turkey. All these dispersed Cadomian basement rocks are interpreted to show fragments of Neoproterozoic-early Cambrian continental arcs bordering the northern active margin of Gondwana. © 2013 International Association for Gondwana Research. Source

Nunes T.,BIAL Portela and C a S.A | Rocha J.F.,BIAL Portela and C a S.A | Falcao A.,Health Consulting Ltd | Falcao A.,University of Coimbra | And 3 more authors.
Epilepsia | Year: 2013

Purpose: To evaluate the pharmacokinetics and tolerability of once-daily eslicarbazepine acetate (ESL) and twice-daily oxcarbazepine (OXC) and their metabolites in cerebrospinal fluid (CSF) and plasma following repeated oral administration. Methods: Single-center, open-label, randomized, parallel-group study in healthy volunteers. Volunteers in ESL group (n = 7) received 600 mg on days 1-3 and 1,200 mg on days 4-9, once daily. Volunteers in the OXC group (n = 7) received 300 mg on days 1-3 and 600 mg on days 4-9, twice daily. Plasma and CSF sampling was performed following the last dose. Key Findings: Eslicarbazepine was the major drug entity in plasma and CSF, accounting for, respectively, 93.84% and 91.96% of total exposure in the ESL group and 78.06% and 76.42% in the OXC group. The extent of exposure to drug entities R-licarbazepine and oxcarbazepine was approximately four-fold higher with OXC as compared with ESL. There was relatively little fluctuation from peak-to-trough (ratio) in the CSF for both eslicarbazepine (ESL = 1.5; OXC = 1.2) and R-licarbazepine (ESL = 1.2; OXC = 1.2). In contrast, oxcarbazepine showed larger differences between peak and trough (ESL = 3.1; OXC = 6.4). A total of 84 and 24 treatment-emergent adverse events (TEAEs) were reported with OXC and ESL, respectively. Significance: In comparison to OXC, administration of ESL resulted in more eslicarbazepine, less R-licarbazepine, and less oxcarbazepine in plasma and CSF, which may correlate with the tolerability profile reported with ESL. The smaller peak-to-trough fluctuation of eslicarbazepine in CSF (a measure of sustained delivery to the brain) than in plasma supports once-daily dosing of ESL. © 2012 International League Against Epilepsy. Source

Lindberg K.,Karolinska Institutet | Helguero L.A.,University of Aveiro | Omoto Y.,Karolinska Institutet | Gustafsson J.-A.,Karolinska Institutet | And 2 more authors.
Breast Cancer Research | Year: 2011

Introduction: The inhibition of estrogen receptor (ER) α action with the ER antagonist tamoxifen is an established treatment in the majority of breast cancers. De novo or acquired resistance to this therapy is common. Expression of ERβ in breast tumors has been implicated as an indicator of tamoxifen sensitivity. The mechanisms behind this observation remain largely uncharacterized. In the present study, we investigated whether ERβ can modulate pathways implicated in endocrine resistance development.Methods: T47-D and MCF-7 ERα-expressing breast cancer cells with tetracycline-regulated expression of ERβ were used as a model system. Expression levels and activity of known regulators of endocrine resistance were analyzed by performing quantitative polymerase chain reaction assays, Western blot analysis and immunostaining, and sensitivity to tamoxifen was investigated by using a cell proliferation kit.Results: Expression of ERβ in ERα-positive T47-D and MCF-7 human breast cancer cells resulted in a decrease in Akt signaling. The active form of an upstream regulator of Akt, proto-oncogene c-ErbB-2/receptor tyrosine kinase erbB-3 (HER2/HER3) receptor dimer, was also downregulated by ERβ. Furthermore, ERβ increased expression of the important inhibitor of Akt, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). Importantly, ERβ expression increased the sensitivity of these breast cancer cells to tamoxifen.Conclusions: Our results suggest a link between expression of ERβ and endocrine sensitivity by increasing PTEN levels and decreasing HER2/HER3 signaling, thereby reducing Akt signaling with subsequent effects on proliferation, survival and tamoxifen sensitivity of breast cancer cells. This study supports initiatives to further investigate whether ERβ presence in breast cancer samples is an indicator for endocrine response. Current therapies in ERα-positive breast cancers aim to impair ERα activity with antagonists or by removal of endogenous estrogens with aromatase inhibitors. Data from this study could be taken as indicative for also using ERβ as a target in selected groups of breast cancer. © 2011 Lindberg et al.; licensee BioMed Central Ltd. Source

Santinha G.,University of Aveiro
Saude e Sociedade | Year: 2016

This study focuses on the role that the territory plays in health policy-making. It is argued that the territorial context enables the decision making processes concerning the improvement of health and the equity/efficiency trade-off, hence the importance of increasing collaboration between health policies and spatial planning. In reality, however, few things are known about how and in which circumstances the territory dimensions are taken into account in decision-making processes. Focused on the Portuguese case, this study debates this issue by listening to those who are or have been involved in health policy-making. A set of 23 interviews was conducted with actors who work in the health area, whose line of thought allowed the understanding of how health policies are developed and which institutional collaborations are established during the process. In addition, programmatic instruments of health policies were analysed to improve qualitative evidence about the spatial dimension of health policies. Findings show that there is still a long path ahead to integrate in a comprehensive manner the spatial dimension in health policy-making processes. © 2016, UNIV SAOPAULO. All rights reserved. Source

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. Source

Mozyrska D.,Biaystok University of Technology | Torres D.F.M.,University of Aveiro
Signal Processing | Year: 2011

Fractional systems with RiemannLiouville derivatives are considered. The initial memory value problem is posed and studied. We obtain explicit steering laws with respect to the values of the fractional integrals of the state variables. The Gramian is generalized and steering functions between memory values are characterized. © 2010 Elsevier B.V. All rights reserved. Source

Bastos N.R.O.,Polytechnic Institute of Viseu | Ferreira R.A.C.,Lusophone University of Humanities and Technologies | Torres D.F.M.,University of Aveiro
Signal Processing | Year: 2011

We introduce a discrete-time fractional calculus of variations on the time scale (hℤ)a,a∈ℝ,h>0. First and second order necessary optimality conditions are established. Examples illustrating the use of the new Euler-Lagrange and Legendre type conditions are given. They show that solutions to the considered fractional problems become the classical discrete-time solutions when the fractional order of the discrete-derivatives are integer values, and that they converge to the fractional continuous-time solutions when h tends to zero. Our Legendre type condition is useful to eliminate false candidates identified via the Euler-Lagrange fractional equation. © 2010 Elsevier B.V. All rights reserved. Source

Freitas V.L.S.,University of Porto | Gomes J.R.B.,University of Aveiro | Ribeiro Da Silva M.D.M.C.,University of Porto
Journal of Chemical Thermodynamics | Year: 2012

In the present work, the standard (p°= 0.1 MPa) molar enthalpies of formation of xanthydrol, 9-xanthenecarboxylic acid and 9-xanthenecarboxamide, in the gaseous state, at T = 298.15 K, were determined by experimental and computational studies. The experimental techniques used were the static-bomb combustion calorimetry, which enabled the determination of the standard molar enthalpy of formation, in the crystalline state, and the vacuum drop microcalorimetric and the Knudsen effusion techniques used to derive the enthalpy of sublimation. For comparison purposes, we performed standard ab initio molecular orbital calculations, using the G3(MP2)//B3LYP composite procedure, of the enthalpies of several homodesmotic reactions, allowing to extract the standard molar enthalpies of formation, in the gaseous state, of the three xanthene derivatives considered in this work. The calculated results are in good agreement with the experimental data. © 2012 Elsevier Ltd. All rights reserved. Source

Serodio J.,University of Aveiro | Lavaud J.,University of La Rochelle
Photosynthesis Research | Year: 2011

The operation of photosynthetic energy-dissipating processes is commonly characterized by measuring the light response of the nonphotochemical quenching (NPQ) of chlorophyll fluorescence, or NPQ versus E curves. This study proposes a mathematical model for the quantitative description of the generic NPQ versus E curve. The model is an adaptation of the Hill equation and is based on the close dependence of NPQ on the xanthophyll cycle (XC). The model was tested on NPQ versus E curves measured in the plant Arabidopsis thaliana and the diatom Nitzschia palea, representing the two main types of XC, the violaxanthin- antheraxanthin-zeaxanthin (VAZ) type and the diadinoxanthin-diatoxanthin (DD-DT) type, respectively. The model was also fitted to a large number of published light curves, covering the widest possible range of XC types, taxa, growth conditions, and experimental protocol of curve generation. The model provided a very good fit to experimental and published data, coping with the large variability in curve characteristics. The model was further used to quantitatively compare the light responses of NPQ and of PSII electron transport rate, ETR, through the use of indices combining parameters of the models describing the two types of light-response curves. Their application to experimental and published data showed a systematic large delay of the buildup of NPQ relatively to the saturation of photochemistry. It was found that when ETR reaches saturation, NPQ is on average still below one fifth of its maximum attainable level, which is only reached at irradiances about three times higher. It was also found that organisms having the DD-DT type of XC appeared to be able to start operating the XC at lower irradiances than those of the VAZ type. © 2011 Springer Science+Business Media B.V. Source

Costa A.A.,University of Porto | Arede A.,University of Porto | Costa A.,University of Aveiro | Oliveira C.S.,University of Lisbon
Earthquake Engineering and Structural Dynamics | Year: 2011

The present work reports on an in situ experimental test campaign carried out on abandoned traditional masonry houses after the 9th July 1998 earthquake that seriously hit the Faial island of Azores. For the testing purposes, an experimental test setup was developed based on a self-equilibrated scheme, which is herein described reporting on the advantages and drawbacks of this in situ test setup. Five specimens were tested aiming at characterizing the out-of-plane behavior of stone masonry walls and strengthening solutions recommended for post-earthquake interventions. A detailed comparison between solutions' efficiency is presented including a cost vs benefit analysis. In order to assess the efficiency of the developed test setup for other applications on stone masonry walls, an in-plane test on an existing URM panel is also presented. Several related issues are discussed, namely the advantages of dealing with the real boundary conditions and the capacity of providing valuable information of the response, as well as a detailed analysis of the obtained results. The authors believe that this work provides an increase in knowledge on the seismic behavior of the existing masonry constructions, resulting from the development of an in situ test setup and the efficiency quantification of strengthening solutions. Therefore, the work is thought to positively contribute for the preservation of architectural heritage and for its seismic vulnerability reduction. © 2010 John Wiley & Sons, Ltd. Source

Dixit U.S.,Indian Institute of Technology Guwahati | Joshi S.N.,Indian Institute of Technology Guwahati | Davim J.P.,University of Aveiro
Materials and Design | Year: 2011

Manufacturing process modeling is gaining importance in view of stiff global competition to produce the goods of specified design in an optimal way. In particular, metal forming and machining (both traditional and non-traditional) have been extensively modeled using numerical techniques. Three basic steps of modeling of manufacturing processes are analytical representation of working principle of the process, modeling of material behavior and method of solution. In this paper, a comprehensive review of various approaches of material behavior modeling has been presented. The material behavior modeling has great influence on the design of process, tools and the final product. This aspect is highlighted in the present review. Metal forming processes, traditional machining processes and non-traditional machining processes are considered for the study. Different material models are compared with respect to their suitability for the design of process, tooling and product. Finally, the paper suggests the directions for further research in this area. © 2011 Elsevier Ltd. Source

Magurran A.E.,University of St. Andrews | Dornelas M.,University of Aveiro | Dornelas M.,James Cook University
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

From the pioneering explorations of Joseph Banks (later a President of the Royal Society), to the present day, a great deal has been learnt about the extent, distribution and stability of biological diversity in the world. We now know that diverse life can be found even in the most inhospitable places. We have also learned that biological diversity changes through time over both large and small temporal scales. These natural changes track environmental conditions, and reflect ecological and evolutionary processes. However, anthropogenic activities, including overexploitation, habitat loss and climate change, are currently causing profound transformations in ecosystems and unprecedented loss of biological diversity. This series of papers considers temporal variation in biological diversity, examines the extent of human-related change relative to underlying natural change and builds on these insights to develop tools and policies to help guide us towards a sustainable future. This journal is © 2010 The Royal Society. Source

Ceriani R.,University of Campinas | Goncalves C.B.,University of Sao Paulo | Coutinho J.A.P.,University of Aveiro
Energy and Fuels | Year: 2011

In the present work, a group contribution method is proposed for the estimation of viscosity of fatty compounds and biodiesel esters as a function of the temperature. The databank used for regression of the group contribution parameters (1070 values for 65 types of substances) included fatty compounds, such as fatty acids, methyl and ethyl esters and alcohols, tri- and diacylglycerols, and glycerol. The inclusion of new experimental data for fatty esters, a partial acylglycerol, and glycerol allowed for a further refinement in the performance of this methodology in comparison to a prior group contribution equation (Ceriani, R.; Gonçalves, C. B.; Rabelo, J.; Caruso, M.; Cunha, A. C. C.; Cavaleri, F. W.; Batista, E. A. C.; Meirelles, A. J. A.Group contribution model for predicting viscosity of fatty compounds. J. Chem. Eng. Data 2007, 52, 965-972) for all classes of fatty compounds. Besides, the influence of small concentrations of partial acylglycerols, intermediate compounds in the transesterification reaction, in the viscosity of biodiesels was also investigated. © 2011 American Chemical Society. Source

Figueiredo D.,University of Aveiro
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

When studying a biological regulatory network, it is usual to use boolean network models. In these models, boolean variables represent the behavior of each component of the biological system. Taking in account that the size of these state transition models grows exponentially along with the number of components considered, it becomes important to have tools to minimize such models. In this paper, we relate bisimulations, which are relations used in the study of automata (general state transition models) with attractors, which are an important feature of biological boolean models. Hence, we support the idea that bisimulations can be important tools in the study some main features of boolean network models. We also discuss the differences between using this approach and other well-known methodologies to study this kind of systems and we illustrate it with some examples. © Springer International Publishing Switzerland 2016. Source

Bras I.,University of Aveiro | Carapito A.C.,University of Beira Interior | Rocha P.,University of Porto
IEEE Transactions on Automatic Control | Year: 2013

In this note, we consider switched systems and switched systems with state reset. In particular we focus on the case of partial reset, i.e., where only some state components may undergo the action of a reset. First we consider switched systems with pre-specified (partial) reset and investigate under which conditions such systems are stable. In a second stage we consider the problem of stabilization by (partial) reset, which consists in finding a suitable (partial) reset for a given switched system that makes this system stable under arbitrary switching. © 1963-2012 IEEE. Source

Enghoff H.,Copenhagen University | Reboleira A.S.P.S.,University of Aveiro
Zootaxa | Year: 2013

A new cave-dwelling species of the genus Scutogona Ribuat, 1913, S. minor n. sp., is described from caves of Sicó karst in central Portugal. The classification and delimitation of Scutogona vis-à-vis related genera, in particular Meinerteuma Mauriès, 1982, is discussed. Copyright © 2013 Magnolia Press. Source

Otero M.,University of Aveiro | Sanchez M.E.,University of Leon | Gomez X.,University of Leon
Bioresource Technology | Year: 2011

Manure is a rich organic waste which, apart from its traditional use as a fertilizer, could be used as a bioenergy feedstock. In this sense, its utilization as a sole fuel or its co-combustion together with coal would be a choice for the management of this sort of biowaste. However, little is known about the behavior of this biowaste when submitted to high-temperature energy-conversion processes. Thus, the separate combustion of swine manure and coal and their co-combustion (10% dried weight of manure) were studied by simultaneous TG/MS dynamic runs. TG-MS analysis was successfully used as an easy rapid tool to assess the combustion of manure, alone or together with coal. Furthermore, non-isothermal kinetic analysis showed that the Arrhenius activation energy corresponding to the combustion of the blend (125.8-138.9. kJ/mol) was only slightly higher than that of manure (106.4-114.4. kJ/mol) or coal (107.0-119.6 kJ/mol). © 2011 Elsevier Ltd. Source

Rocha A.,University of Aveiro
Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012 | Year: 2012

Channel depolarization in Earth-Satellite links needs more experimental data for models validation and requires a physical oriented approach mainly to characterize the ice clouds contribution. An exploration of the variability of the complex crosspolar discrimination (XPD) is given by revisiting the physical properties of the propagation medium from rain to ice occurrence. Some measured events will be explored and detailed as examples of this complexity. The variability from year of the XPD is linked not only to rain rate distribution through rain contribution but also due to ice that usually is associated with rain showery weather. The ITU model for XPD is tested on the full database and is shown to be exceptionally accurate mainly for better XPDs. © 2012 IEEE. Source

Bordeira-Carrico R.,University of Porto | Pego A.P.,University of Porto | Santos M.,University of Aveiro | Oliveira C.,University of Porto
Trends in Molecular Medicine | Year: 2012

Several hereditary cancer syndromes are associated with nonsense mutations that create premature termination codons (PTC). Therapeutic strategies involving readthrough induction partially restore expression of proteins with normal function from nonsense-mutated genes, and small molecules such as aminoglycosides and PTC124 have exhibited promising results for treating patients with cystic fibrosis and Duchenne muscular dystrophy. Transgenic expression of suppressor-tRNAs and depleting translation termination factors are, among others, potential strategies for treating PTC-associated diseases. In this review, the potential of using readthrough strategies as a therapy for cancer syndromes is discussed, and we consider the effect of nonsense-mediated decay and other factors on readthrough efficiency. © 2012 Elsevier Ltd. Source

De Morais A.B.,University of Aveiro
Polymer Composites | Year: 2013

A simplified Cohesive Zone Model (CZM) was developed for the analysis of mixed-mode I-II delamination in composite beams. The present model applies to unidirectional laminates with half-thickness delaminations. Besides its beam theory basis, the present CZM differs from the common formulation in the piecewise linear softening and in the definition of dissipated energy adopted. Moreover, the consistency condition needed to ensure accurate results is embedded in the model developed. In this article, the analysis focused on the Moment-Loaded Cantilever Beam (MLCB) specimen for which an exact J-integral based analytical solution exists. The present results agreed with the latter solution despite some features that have been recently reported to compromise the accuracy of CZM, that is, nonlinearity of the whole softening process, local mode-mix variations along the cohesive zone and large cohesive zones. POLYM. COMPOS., 34:1901-1911, 2013. © 2013 Society of Plastics Engineers © 2013 Society of Plastics Engineers. Source

Rolo A.P.,University of Coimbra | Rolo A.P.,University of Aveiro | Teodoro J.S.,University of Coimbra | Palmeira C.M.,University of Coimbra
Free Radical Biology and Medicine | Year: 2012

The worldwide rising prevalence of obesity and insulin resistance is associated with a parallel increase in nonalcoholic fatty liver disease (NAFLD). NAFLD is characterized by excess accumulation of triglyceride in the hepatocyte due to increased inflow of free fatty acids and/or de novo lipogenesis caused by various drugs and multiple defects in energy metabolism. Accumulation of lipids in the hepatocyte impairs the oxidative capacity of the mitochondria, increasing the reduced state of the electron transport chain (ETC) complexes and stimulating peroxisomal and microsomal pathways of fat oxidation. The consequent increased generation of reactive oxygen species (ROS) and reactive aldehydic derivatives causes oxidative stress and cell death, via ATP, NAD, and glutathione depletion and DNA, lipid, and protein damage. Oxidative stress also triggers production of inflammatory cytokines, causing inflammation and a fibrogenic response. This ultimately results in the development of nonalcoholic steatohepatitis (NASH), which can result in end-stage liver disease. The current therapeutic strategies for NASH treatment are mostly directed toward correction of the risk factors. Stimulation of mitochondrial function may also prevent NASH development, protecting the cell against the increased flux of reduced substrates to the ETC and ROS generation. © 2011 Elsevier Inc. Source

Perez-Coll D.,CSIC - Institute of Ceramics and Glass | Nunez P.,University of La Laguna | Frade J.R.,University of Aveiro
Journal of Power Sources | Year: 2011

The solid solution Ce0.8Sm0.2O2-δ (20CSO) was synthesized by freeze-drying precursor procedure. Well-crystallized powders with nanometric grain sizes were obtained after calcining the precursor at 375 °C for 4 h. The effect of SiO2-addition and sintering temperature on the properties of the bulk and grain boundary processes were studied. For this purpose, 20CSO-SiO2 samples were prepared by the addition of 0.05 or 0.5 mol% SiO2 to Ce0.8Sm 0.2O2-δ, in the form of tetraethyl orthosilicate (TEOS). Also, 2 mol% Co was added to some of the precalcined compositions with and without silica-addition. Cobalt free samples were sintered at 1400, 1500 and 1600 °C and cobalt-added samples were sintered 1150 °C, for 10 h to obtain dense pellets. The electrical behaviour of the bulk was revealed to be nearly independent on sintering temperature and/or on the addition of impurities of SiO2 and Co to the grain boundaries. This was explained by the low solubility of impurities in the grain fluorite structure. However, the grain boundary resistance showed important differences as function of sintering temperature and with the presence of impurities. The analysis of grain boundary properties suggests that segregated impurities affect the microstructure and also segregation of Sm at the space charge layer, thus changing both the specific grain boundary conductivity and microstructural parameters. © 2011 Elsevier B.V. All rights reserved. Source

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

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

Marti J.G.,National University of Cordoba | Giuppone C.A.,National University of Cordoba | Giuppone C.A.,University of Aveiro | Beauge C.,National University of Cordoba
Monthly Notices of the Royal Astronomical Society | Year: 2013

The number of multiple-planet systems known to be involved in mean motion conmensurabilities has increased significantly since the Kepler mission. Although most correspond to two-planet resonances, multiple resonances have also been found. The Laplace resonance is a particular case of a three-body resonance in which the period ratio between consecutive pairs is n1/n2 ~ n2/n3 ~ 2/1. It is not clear how this triple resonance acts to stabilize (or not) the system. The most reliable extrasolar system located in a Laplace resonance is GJ 876, because it has two independent confirmations. However, best-fit parameters were obtained without previous knowledge of resonance structure, and not all possible stable solutions for the system have been explored. In the present work we explore the various configurations allowed by the Laplace resonance in the GJ 876 system by varying the planetary parameters of the third outer planet. We find that in this case the Laplace resonance is a stabilizationmechanism in itself, defined by a tiny island of regular motion surrounded by (unstable) highly chaotic orbits. Low-eccentricity orbits and mutual inclinations from -20° to 20° are compatible with observations. A definite range of mass ratio must be assumed to maintain orbital stability. Finally, we provide constraints on the argument of pericentres and mean anomalies to ensure stability for this kind of system. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Dias G.P.,University of Aveiro
Proceedings of the 5th Iberian Conference on Information Systems and Technologies, CISTI 2010 | Year: 2010

In this artic le we present an analysis of the potential for organizational interoperability in a cluster of local government in Portugal consisting of the City Council, the Land Registry Office and the Tax Office of Portalegre. Based on an exhaustive survey of procedures we identified the direct and indirect interactions between these three agencies and measured the rate of organizational interoperability and the potential for improving organizational interoperability. These two quantities were defined within the scope of the research work that is described in the article. We also present a set of proposals that will, in the short and medium term, significantly improve organizational interoperability in the cluster. The results obtained allow affirming the relevance of organizational interoperability in the context of e-government initiatives. Source

Carvalho J.,University of Porto | Verissimo A.,University of Aveiro | Nobre P.J.,University of Porto
Journal of Sexual Medicine | Year: 2013

Nunes B.,Fernando Pessoa University | Nunes B.,University of Aveiro
Reviews of Environmental Contamination and Toxicology | Year: 2011

Cholinesterase (ChE) is one of the most employed biomarkers in environmental analysis. Among ChEs, potentially the most significant in environmental terms is acetylcholinesterase (AChE), an enzymatic form that terminates the nerve impulse. Because of its physiological role, AChE has long been considered a highly specific biomarker for organisms exposed to anticholinesterasic agents, primarily agrochemicals (organophosphate and carbamate pesticides). The effects of these pesticides depend upon their selective inhibition of AChE. Because large amounts of such pesticides are employed, it is plausible that they exert neurotoxic effects on some non-target species. Therefore, AChE is among the most valuable of diagnostic tools that can be used to verify exposure to such chemical agents. It is well known that assays are available for use in quantifying AChE in multiple tissues of several test organisms. Enzymes other than AChE (e.g., butyrylcholinesterase and carboxylesterases) have also been used as putative markers for detecting the environmental presence of contaminating compounds. Researchers must use a step-bystep approach to identify the most prominent cholinesterasic form present in a given species, so that this form can be distinguished from others that may interfere with its use. Such fundamental work must be completed prior to using ChEs for any monitoring to assess for anticholinesterasic effects. © 2011 Springer Science+Business Media, LLC. Source

Curado Teixeira F.,University of Aveiro | Pedro Aguiar A.,University of Lisbon | Pascoal A.,University of Lisbon
Ocean Engineering | Year: 2010

This paper addresses the problem of simultaneous depth tracking and attitude control of an underwater towed vehicle. The system proposed uses a two-stage towing arrangement that includes a long primary cable, a gravitic depressor, and a secondary cable. The towfish motion induced by wave driven disturbances in both the vertical and horizontal planes is described using an empirical model of the depressor motion and a spring-damper model of the secondary cable. A nonlinear, Lyapunov-based, adaptive output feedback control law is designed and shown to regulate pitch, yaw, and depth tracking errors to zero. The controller is designed to operate in the presence of plant parameter uncertainty. When subjected to bounded external disturbances, the tracking errors converge to a neighbourhood of the origin that can be made arbitrarily small. In the implementation proposed, a nonlinear observer is used to estimate the linear velocities used by the controller thus dispensing with the need for costly sensor suites. The results obtained with computer simulations show that the controlled system exhibits good performance about different operating conditions when subjected to sea-wave driven disturbances and in the presence of sensor noise. The system holds promise for application in oceanographic missions that require depth tracking or bottom-following combined with precise vehicle attitude control. © 2010 Elsevier Ltd. All rights reserved. Source

Tsipis E.V.,Technological and Nuclear Institute of Portugal | Kharton V.V.,University of Aveiro
Journal of Solid State Electrochemistry | Year: 2011

Continuing previous reviews on mixed-conducting electrodes for intermediate-temperature solid oxide fuel cells (IT SOFCs), this work presents a short overview of novel cathode and anode materials, their electrochemical performance in contact with oxygen anion- and proton-conducting solid electrolytes, and specific features determining possible applications. Priority was given mainly to recent research reports published during the last 2-5 years. Particular emphasis is focused on the relevant methodological aspects, potential limitations and drawbacks, and factors affecting electrode polarization and durability. Typical ranges of the polarization resistances, overpotentials, power densities in the cells with various current collectors, and the electrode materials total conductivity and thermal expansion are compared. The electrode compositions appraised in single-chamber and micro-SOFCs, hydrocarbon- and carbon-fueled cells, high-temperature electrolyzers, and other solid-electrolyte appliances are briefly covered in light of their similarity to the common SOFC materials discussed in the previous parts. © 2011 Springer-Verlag. Source

Foreman I.,University of Aveiro
Organised Sound | Year: 2011

Drawing on field research carried out in the abandoned villages of the Ara Valley, this article seeks to readdress notions of acoustic community and communication in terms of a 'haptic aurality' in which listening, as a mode of touch, approximates a figure of spacing, fragmentation and withdrawal in contrast to more conventional communicational models of intimacy, presence and exchange. Arguing that soundscape compositions present an 'acoustic ontology', the article explores a form of belonging and being that is, following Jean-Luc Nancy, singular plural in which sound signals 'unwork' collectivities through the processes of 'sharing' and 'splitting' (partage) characteristic of listening and recording. Referring to the work of writer W.G. Sebald (1944-2001), whose hybrid 'literary ethnography' was the impetus for my own soundwalks and fieldwork, and considering the role of soundscape composition within the discipline of Trauma Studies, the article scopes out to consider the possibilities of soundscape composition as a form of testimony in light of Agamben's (1999) insistence that testimony is necessarily incomplete. As a form of 'myopic witnessing' (Jenckes 2010), the sonic memories of ruined soundscapes are presented as spacings and absences, fragments and lacunae, that are themselves characteristic of both the ontology of ruins and those of testimony. © 2011 Cambridge University Press. Source

Calvo L.F.,University of Leon | Gil M.V.,University of Leon | Otero M.,University of Aveiro | Moran A.,University of Leon | Garcia A.I.,University of Leon
Bioresource Technology | Year: 2012

The feasibility and operation performance of the gasification of rice straw in an atmospheric fluidized-bed gasifier was studied. The gasification was carried out between 700 and 850°C. The stoichiometric air-fuel ratio (A/F) for rice straw was 4.28 and air supplied was 7-25% of that necessary for stoichiometric combustion. Mass and power balances, tar concentration, produced gas composition, gas phase ammonia, chloride and potassium concentrations, agglomeration tendencies and gas efficiencies were assessed. Agglomeration was avoided by replacing the normal alumina-silicate bed by a mixture of alumina-silicate sand and MgO. It was shown that it is possible to produce high quality syngas from the gasification of rice straw. Under the experimental conditions used, the higher heating value (HHV) of the produced gas reached 5.1MJNm -3, the hot gas efficiency 61% and the cold gas efficiency 52%. The obtained results prove that rice straw may be used as fuel for close-coupled boiler-gasifier systems. © 2012 Elsevier Ltd. Source

Oliveira J.R.,University of Porto | Martins M.C.L.,University of Porto | Mafra L.,University of Aveiro | Gomes P.,University of Porto
Carbohydrate Polymers | Year: 2012

N-Phthaloyl-chitosan O-prop-2-ynyl carbamate was prepared as a biopolymer amenable to undergo chemoselective conjugation by azide-alkyne coupling, while allowing upturn of chitosan's amines after dephthaloylation. N-phthaloylchitosan was prepared according to previously described methods and, due to its low solubility in current organic media, subsequent modifications were run in heterogeneous conditions. Activation of hydroxyls with carbonyl-1,1′- diimidazole and coupling to propargylamine yielded N-phthaloyl-chitosan O-prop-2-ynyl carbamate, then coupled to a model PEG-like azide by azide-alkyne coupling, giving the expected triazolyl conjugate. N-Dephthaloylation allowed recovery of the free amines, responsible for chitosan's bioadhesion and tissue-regeneration properties. The structures of all polymers were confirmed by Fourier-transformed infra-red (FT-IR) and X-ray photoelectron (XPS) spectroscopies, as well as by solid-state nuclear magnetic resonance (SSNMR). All chitosan derivatives were poorly soluble in both aqueous and organic media, which makes them suitable for topical applications or for removal of toxic substances from either the gastric intestinal tract or environmental sources. © 2011 Elsevier Ltd. All Rights Reserved. Source

Lamy E.,University of Evora | Lamy E.,Higher School of Tourism and Hospitality Studies, Estoril | Lamy E.,University of Aveiro | Mau M.,Kings College London
Journal of Proteomics | Year: 2012

Saliva is an extraordinary fluid in terms of research and diagnostic possibilities. Its composition in electrolytes, hormones and especially its proteome contains information about feeding status, nutritional requirements and adaptations to diet and environment, and also about health status of animals. It is easy to collect on a non-invasive and routine basis without any need for special training. Therefore, the analysis of salivary proteomes is going to emerge into a field of high interest with the future goal to maintain and improve livestock productivity and welfare. Moreover, the comprehensive analysis and identification of salivary proteins and peptides in whole and glandular saliva is a necessary pre-requisite to identify animal disease biomarkers and a powerful tool to better understand animal physiology. This review focuses on the different approaches used to study the salivary proteomes of farm animals, in respect to the physiology of nutrition and food perception in relation to food choices. The potential of animal saliva as a source of disease biomarkers will also be pointed out. Special emphasis is laid on the 'ruminating triad' - cattle, goat and sheep - as well as swine as major species of animal production in Western and Southern Europe. This article is part of a Special Issue entitled: Farm animal proteomics. © 2012 Elsevier B.V. Source

Sundberg J.,Voice Research Center | La F.M.B.,University of Aveiro | Gill B.P.,New York University
Journal of Voice | Year: 2013

The term "formant tuning" is generally used for the case that one of the lowest formant frequencies coincides with the frequency of a source spectrum partial. Some authors claim that such coincidence is favorable and belongs to the goals of classical opera voice training, whereas other authors have found evidence for advising against it. This investigation analyzes the relationships between formant frequencies and partials in professional singers, who sang scales on the vowels /a/, /u/, /i/, and /ae/ in a pitch range including the passaggio, that is, the fundamental frequency range of approximately 300-400 Hz, applying either of the two singing strategies that are typically used (1) in classical and (2) in nonclassical singing, respectively. Formant frequencies of each note in the scales were measured by inverse-filtering the acoustic signal. In the classical style, the first formant tended to be lower than in the nonclassical style. Neither the first nor the second formant tended to change systematically between scale tones, such that on some scale tones either or both formants was just below, just above, or right on a spectrum partial. In many cases, singers produced similar spectrum characteristics of the top tones of the scales with different first and second formant frequencies. Regardless of whether the first formant was slightly lower, slightly higher, or right on a partial, the properties of the voice source did not seem to be affected. © 2013 The Voice Foundation. Source

Coutinho J.,University of Aveiro
Lecture Notes in Physics | Year: 2015

This is a contribution targeted for early scientists, from both academia and industry, providing the grounds for defect modeling in silicon materials using density functional methods. It starts with a revision of the theoretical framework and tools, including relevant approximations such as the treatment of the exchange correlation interactions and the use of pseudopotentials. It then describes how to step up from total energies, electron densities and Kohn-Sham states to the actual defect observables. Particular emphasis is given to the calculation of spectroscopic observables such as electrical levels, local vibrational modes, spin densities, migration barriers, and defect response to uniaxial stress. Each of these techniques is accompanied by examples of defect calculations. It is shown how these results can be crucial in unraveling a detailed picture of many complexes, including substitutional and interstitial impurities, dopants, transition metals, carbon, oxygen or hydrogen. In the last section we take a look at some developments in modeling defects in silicon nanostructures. While holding promising optical and magnetic properties, nano-silicon presents many challenges, particularly with regard to defect control, doping and electrical transport. © Springer Japan 2015. Source

Rocha M.A.A.,University of Porto | Coutinho J.A.P.,University of Aveiro | Santos L.M.N.B.F.,University of Porto
Journal of Physical Chemistry B | Year: 2012

This work reports the first data for the vapor pressures at several temperatures of the ionic liquids, [CN/2CN/2im][NTf 2] (N = 4, 6, 8, 10, 12) measured using a Knudsen effusion apparatus combined with a quartz crystal microbalance. The morphology and the thermodynamic parameters of vaporization derived from the vapor pressures, are compared with those for the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide series, [CN-1C1im] [NTf2] (N = 3 - 9, 11, and 13). It was found that the volatility of [CN/2CN/2im][NTf2] series is significantly higher than the asymmetric cation ILs with the same total number of carbons in the alkyl side chains, [CN-1C1im][NTf2]. The observed higher volatility is related with the lower enthalpy of vaporization. The symmetric cation, [CN/2CN/2im][NTf2], presents lower entropies of vaporization compared with the asymmetric [C N-1C1im][NTf2], indicating an increase of the absolute liquid entropy in the symmetric cation ILs, being a reflection of a change of the ion dynamics in the IL liquid phase. Moreover both the enthalpy and entropy of vaporization of the [CN/2CN/2im][NTf 2] ILs, present a clear odd-even effect with higher enthalpies/entropies of vaporization for the odd number of carbons in each alkyl chain ([C3C3im][NTf2] and [C5C 5im][NTf2]). © 2012 American Chemical Society. Source

Loureiro P.E.G.,University of Coimbra | Evtuguin D.V.,University of Aveiro | Carvalho M.G.V.S.,University of Coimbra
Journal of Chemical Technology and Biotechnology | Year: 2011

BACKGROUND: The process of chemical pulp bleaching is based for the most part in chlorine dioxide within elemental chlorine free (ECF) technologies. The use of greener alternatives such as bleaching with hydrogen peroxide (P stage) is not widely used owing to selectivity concerns related to transition metal-catalyzed decomposition reactions. Even at the final stage where peroxide is recognized to boost brightness and improve the brightness stability of the bleached pulp, cellulose degradation often overcomes these advantages. This paper presents the results of studies intended to optimize final peroxide bleaching performance considering two standard ECF industrial bleaching sequences: the conventional DED and the ECF-light OQ(PO)D (stages name: D-chlorine dioxide; E-alkaline extraction; O-oxygen; Q-chelation, (PO)-hydrogen peroxide pressurized with oxygen). RESULTS: The addition of sodium diethylenetriaminepentaacetate (DTPA) was the most effective option in terms of DED pulp bleachability and selectivity with hydrogen peroxide, as well as in terms of brightness reversion. As regards the OQ(PO)D pulp, a blend of DTPA and magnesium was the most beneficial in those properties. CONCLUSIONS: The choice of the best hydrogen peroxide stabilizer, among the different tested combinations of magnesium and chelants (EDTA and DTPA) studied, in terms of pulp bleachability, bleaching selectivity and brightness reversion is dependent on the impact of the previous bleaching stages on metallic nature and content. The pulp Mg/(Fe + Cu) ratio was highlighted as a process parameter controlling cellulose degradation in peroxide bleaching. © 2010 Society of Chemical Industry. Source

Costa V.A.F.,University of Aveiro
International Journal of Heat and Mass Transfer | Year: 2012

Transient natural convection combined heat and mass transfer in enclosures filled with humid air, including evaporation from or condensation to the walls, which are subjected to time varying prescribed temperatures, is studied numerically. Emphasis is given to the two-dimensional enclosures of circular cross-section, emulating horizontal containers or ducts filled with humid air. Starting from uniform temperature and concentration distributions, wall temperature decrease with time leads to some water condensation at the walls, and wall temperature increase with time leads to evaporation of some liquid water from the walls if it exists there. During the final period of both situations temperature ceases changing, and a final steady-state regime is reached. Situation of prescribed time-periodic wall temperature is also considered, and a periodic solution is obtained after some few periods of operation. Results reveal the flow structure and also the temperature and concentration time evolutions in the enclosure. Special attention is given to the time evolution of the overall Nusselt and Sherwood numbers over the walls, and also to the time and space evolutions of the condensate layer over the walls. © 2012 Elsevier Ltd. All rights reserved. Source

Costa V.A.F.,University of Aveiro
International Journal of Heat and Mass Transfer | Year: 2012

Natural convection in partitioned square enclosures filled with air is numerically studied, trying to characterize these enclosures mainly in what concerns its overall heat transfer performance. Two partitions of finite thickness are considered, placed in the enclosure following an ordered arrangement, which position, length and thermal conductivity are varied for some values of Rayleigh number and for different thermal boundary conditions. Study starts considering the simplest enclosures with two adiabatic partitions, after the more realistic enclosures of heat conductive walls and partitions are considered, and finally the even more realistic situation of enclosures with heat conductive partitions and walls subjected to cyclic thermal boundary conditions in the vertical direction is also considered. Position and length of the enclosures' effects depend on the thermal boundary conditions prescribed for the enclosure, and different thermal boundary conditions (corresponding to the heating or cooling operations or seasons) are considered to capture this effect. Fluid flow field, thermal field and heat transfer are analyzed for some particular situations through the streamlines, isotherms, and heatlines. The overall thermal performance of the enclosure is analyzed through the overall Nusselt number, and many data are compactly presented for different placements and lengths of the partitions, for different thermal conductivity of the walls and partitions of the enclosure, for different Rayleigh numbers and for different thermal boundary conditions imposed to the enclosure. Considered boundary conditions and the enclosure walls and partitions of finite thickness and finite thermal conductivity are much more realistic conditions than simply the single cavity without walls and with perfectly adiabatic partitions usually considered in many studies of this kind. © 2012 Elsevier Ltd. All rights reserved. Source

Romao X.,University of Porto | Delgado R.,University of Porto | Costa A.,University of Aveiro
Earthquake Engineering and Structural Dynamics | Year: 2010

The structural safety assessment procedures proposed in Part 3 of Eurocode 8 (EC8-3) for the case of reinforced concrete structures are addressed. The practical evaluation of the member chord rotation demand according to EC8-3 is examined in detail along with several alternative formulations. The need for these formulations is demonstrated by presenting example situations where the EC8-3 proposal is difficult to apply. The effectiveness of the proposed approaches is assessed through an example application and recommendations for their practical use are defined. Given the importance of the shear span in this context, a sensitivity analysis of the EC8-3 capacity models with respect to this parameter is carried out and discussed in a later section. This analysis aims to assess the validity of the simplifications proposed by a previous research study for the quantification of the EC8-3 capacity values. Copyright © 2009 John Wiley & Sons, Ltd. Source

Castanheira J.M.,University of Aveiro | Barriopedro D.,University of Lisbon
Geophysical Research Letters | Year: 2010

The dynamical connection between Northern Hemisphere blocking events and the variability of the stratospheric polar vortex strength is studied. The analysis is based on the composite time evolution of the energy of baroclinic planetary waves during regional blocking occurrence. During Euro-Atlantic blocking events, an in phase forcing of stationary zonal wavenumber 1 occurs. The enhanced wave amplitude is associated with a stratospheric polar vortex deceleration, which may result, at times, in Sudden Stratospheric Warming (SSW) events of displacement type. Pacific blocking composites reveal an in phase forcing of stationary zonal wavenumber 2. In most cases, the amplification of the wavenumber 2 does not reduce the vortex strength, being even accompanied by a mean vortex acceleration. However, if the amplification of wavenumber 2 is preceded by an amplification of wavenumber 1, the initial vortex deceleration forced by wavenumber 1 may be continued by wavenumber 2, and a SSW event of splitting type may occur. © 2010 by the American Geophysical Union. Source

Correia A.C.M.,University of Aveiro | Correia A.C.M.,French National Center for Scientific Research
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2016

Cassini states correspond to the equilibria of the spin axis of a body when its orbit is perturbed. They were initially described for planetary satellites, but the spin axes of black hole binaries also present this kind of equilibria. In previous works, Cassini states were reported as spinorbit resonances, but actually the spin of black hole binaries is in circulation and there is no resonant motion. Here we provide a general description of the spin dynamics of black hole binary systems based on a Hamiltonian formalism. In absence of dissipation, the problem is integrable and it is easy to identify all possible trajectories for the spin for a given value of the total angular momentum. As the system collapses due to radiation reaction, the Cassini states are shifted to different positions, which modifies the dynamics around them. This is why the final spin distribution may differ from the initial one. Our method provides a simple way of predicting the distribution of the spin of black hole binaries at the end of the inspiral phase. © 2016 The Authors. Source

Lakshtanov E.,University of Aveiro | Vainberg B.,University of North Carolina at Charlotte
Inverse Problems | Year: 2012

This paper contains lower bounds on the counting function of the positive eigenvalues of the interior transmission problem when the latter is elliptic. In particular, these bounds justify the existence of an infinite set of interior transmission eigenvalues and provide asymptotic estimates from above on the counting function for the large values of the wave number. They also lead to certain important upper estimates on the first few interior transmission eigenvalues. We consider the classical transmission problem as well as the case when the inhomogeneous medium contains an obstacle. © 2012 IOP Publishing Ltd. Source

Bartrum S.,University of Edinburgh | Bastero-Gil M.,University of Granada | Berera A.,University of Edinburgh | Cerezo R.,University of Granada | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

The amplitude of primordial curvature perturbations is enhanced when a radiation bath at a temperature T > H is sustained during inflation by dissipative particle production, which is particularly significant when a non-trivial statistical ensemble of inflaton fluctuations is also maintained. Since gravitational modes are oblivious to dissipative dynamics, this generically lowers the tensor-to-scalar ratio and yields a modified consistency relation for warm inflation, as well as changing the tilt of the scalar spectrum. We show that this alters the landscape of observationally allowed inflationary models, with for example the quartic chaotic potential being in very good agreement with the Planck results for nearly-thermal inflaton fluctuations, whilst essentially ruled out for an underlying vacuum state. We also discuss other simple models that are in agreement with the Planck data within a renormalizable model of warm inflation. © 2014 The Authors. Source

Silva C.,University of Aveiro | Trlat E.,University dOrlans
Systems and Control Letters | Year: 2010

We focus on the minimal time control problem for single-input control-affine systems x=X(x)+u1Y1(x) in Rn with fixed initial and final time conditions x(0)=x̂0, x(tf)=x̂1, and where the scalar control u1 satisfies the constraint |u1(·)|1. For these systems a concept of conjugate time tc has been defined in e.g. Agrachev et al. (2002) [23], Maurer and Osmolovskii (2004) [21], and Noble and Schttler (2002) [28] in the bangbang case. Besides, theoretical and practical issues for conjugate time theory are well known in the smooth case (see e.g. Agrachev and Sachkov (2004) [43] and Milyutin and Osmolovskii (1998) [15]), and efficient implementation tools are available (see Bonnard et al. (2007) [35]). The first conjugate time along an extremal is the time at which the extremal loses its local optimality. In this work, we use the asymptotic approach developed in Silva and Trlat (in press) [36] and investigate the convergence properties of conjugate times. More precisely, for ε>0 small and arbitrary vector fields Y1,...,Ym, we consider the minimal time problem for the control system xε=X(xε) +u1εY1(xε)+ε∑i=2muiεYi(xε), under the constraint ∑i=1m(uiε)21, with the fixed boundary conditions xε(0)=x̂0, xε(tf)=x̂1 of the initial problem. Under appropriate assumptions, the optimal controls of the latter regularized optimal control problem are smooth, and the computation of associated conjugate times tcε falls into the standard theory; our main result asserts the convergence, as ε tends to 0, of tcε towards the conjugate time tc of the initial bangbang optimal control problem, as well as the convergence of the associated extremals. As a byproduct, we obtain an efficient algorithmic way to compute conjugate times in the bangbang case. © 2010 Elsevier B.V. All rights reserved. Source

Morais J.,University of Aveiro
Annals of Physics | Year: 2014

Over the past few years considerable attention has been given to the role played by the Hydrogen Continuum Wave Functions (HCWFs) in quantum theory. The HCWFs arise via the method of separation of variables for the time-independent Schrödinger equation in spherical coordinates. The HCWFs are composed of products of a radial part involving associated Laguerre polynomials multiplied by exponential factors and an angular part that is the spherical harmonics. In the present paper we introduce the continuum wave functions for hydrogen within quaternionic analysis ((R)QHCWFs), a result which is not available in the existing literature. In particular, the underlying functions are of three real variables and take on either values in the reduced and full quaternions (identified, respectively, with R3 and R4). We prove that the (R)QHCWFs are orthonormal to one another. The representation of these functions in terms of the HCWFs are explicitly given, from which several recurrence formulae for fast computer implementations can be derived. A summary of fundamental properties and further computation of the hydrogen-like atom transforms of the (R)QHCWFs are also discussed. We address all the above and explore some basic facts of the arising quaternionic function theory. As an application, we provide the reader with plot simulations that demonstrate the effectiveness of our approach.(R)QHCWFs are new in the literature and have some consequences that are now under investigation. © 2014 Elsevier Inc. Source

Castro L.P.,University of Aveiro | Kapanadze D.,Tbilisi State University
Mathematical Methods in the Applied Sciences | Year: 2014

The paper is devoted to the analysis of wave diffraction problems modeled by classes of mixed boundary conditions and the Helmholtz equation, within a half-plane with a crack. Potential theory together with Fredholm theory, and explicit operator relations, are conveniently implemented to perform the analysis of the problems. In particular, an interplay between Wiener-Hopf plus/minus Hankel operators and Wiener-Hopf operators assumes a relevant preponderance in the final results. As main conclusions, this study reveals conditions for the well-posedness of the corresponding boundary value problems in certain Sobolev spaces and equivalent reduction to systems of Wiener-Hopf equations. Copyright © 2013 John Wiley & Sons, Ltd. Source

Rai R.,University of Aveiro
Journal of Alloys and Compounds | Year: 2011

Polycrystalline samples of BaFe0.5Nb0.5O3 and (1 - x)Ba(Fe0.5Nb0.5)O3-xSrTiO3 [referred as BFN and BFN-ST respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The XRD patterns of the BFN and BFN-ST at room temperature show a monoclinic phase. The microstructure of the ceramics was examined by the scanning electron microscopy (SEM) and shows the polycrystalline nature of the samples with different grain sizes, which are inhomogeneously distributed through the sample surface. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz-5 MHz) and temperatures (30-270 °C) showed that properties are strongly temperature and frequency dependent. Complex Argand plane plot of ε″ against ε′, usually called Cole-Cole plots is used to check the polydispersive nature of relaxation phenomena in above mentioned compounds. Relaxation phenomena of non-Debye type have been observed in the BFN and BFN-ST ceramics, as confirmed by the Cole-Cole plots. © 2010 Elsevier B.V. All rights reserved. Source

Rodrigues C.F.,University Pierre and Marie Curie | Rodrigues C.F.,University of Aveiro | Duperron S.,University Pierre and Marie Curie
Naturwissenschaften | Year: 2011

Thyasiridae are one of the less studied groups of chemosymbiotic bivalves. Here, we investigated symbioses in three different thyasirid species collected at three cold seeps from the Atlantic and Mediterranean. Phylogenetic analysis of bacterial 16S ribosomal RNA gene sequences demonstrated that each thyasirid species harbours a single phylotype of symbiont that belongs to a distinct lineage of putative sulphur-oxidizing Gammaproteobacteria. This result is confirmed by other marker genes (encoding 23S rRNA and APS reductase) and fluorescence in situ hybridization. This work highlights the diversity of bacteria involved in symbiosis with thyasirids and underlines the relevance of this group as a target for future symbiosis studies. © 2011 Springer-Verlag. Source

Schwaiger M.,Center for Organismal Systems Biology | Schonauer A.,Oxford Brookes University | Rendeiro A.F.,University of Aveiro | Pribitzer C.,Center for Organismal Systems Biology | And 6 more authors.
Genome Research | Year: 2014

Despite considerable differences in morphology and complexity of body plans among animals, a great part of the gene set is shared among Bilateria and their basally branching sister group, the Cnidaria. This suggests that the common ancestor of eumetazoans already had a highly complex gene repertoire. At present it is therefore unclear how morphological diversification is encoded in the genome. Here we address the possibility that differences in gene regulation could contribute to the large morphological divergence between cnidarians and bilaterians. To this end, we generated the first genome-wide map of gene regulatory elements in a nonbilaterian animal, the sea anemone Nematostella vectensis. Using chromatin immunoprecipitation followed by deep sequencing of five chromatin modifications and a transcriptional cofactor, we identified over 5000 enhancers in the Nematostella genome and could validate 75% of the tested enhancers in vivo. We found that in Nematostella, but not in yeast, enhancers are characterized by the same combination of histone modifications as in bilaterians, and these enhancers preferentially target developmental regulatory genes. Surprisingly, the distribution and abundance of gene regulatory elements relative to these genes are shared between Nematostella and bilaterian model organisms. Our results suggest that complex gene regulation originated at least 600 million yr ago, predating the common ancestor of eumetazoans. © 2014 Schwaiger et al. Source

Sidali K.L.,University of Gottingen | Kastenholz E.,University of Aveiro | Bianchi R.,University of Bari
Journal of Sustainable Tourism | Year: 2015

The countryside hosts an increasing number of alternative food networks: rural tourists can play an important role in acting as both consumer and “cultural broker” between these networks. This paper provides a theoretical framework for niche marketing food specialties in rural tourism by combining two different consumer behavioural theories, the “experience economy” and the “intimacy” model, representing a reorientation from classical marketing thinking. It explores the meaning of local food, including the pursuit of reconnection with nature, resilience to globalisation, the role of local food in reinforcing personal identity, the search for freshness, taste and authenticity, support for local producers, and environmental concerns. It considers the challenges for rural entrepreneurs and policy makers in marketing food specialties and rural regions to the post-modern consumer. Using examples derived mostly from secondary literature it identifies seven dimensions that elevate food products to an appealing culinary niche, namely, coherence, anti-capitalistic attitude, struggle against extinction, personal signature, mutual-disclosure, rituals of spatial and physical proximity, and sustainability-related practices. Food providers may use these features to signal food distinctiveness to rural tourists; policy makers can include them in their regional development models to enhance rural tourism without altering historically, socially, and environmentally layered culinary traditions. © 2015 Taylor & Francis. Source

Ait Rami M.,University of Picardie Jules Verne | Napp D.,University of Aveiro
IEEE Transactions on Automatic Control | Year: 2016

The aim of this technical note is to provide an efficient control design technique for discrete-time positive periodic systems. In particular, stability, positivity and periodic invariance of such systems are studied. Moreover, the concept of periodic invariance with respect to a collection of boxes is introduced and investigated with connection to stability. It is shown how such concept can be used for deriving a stabilizing state-feedback control that maintains the positivity of the closed-loop system and respects states and control signals constraints. In addition, all the proposed results can be efficiently solved in terms of linear programming. © 1963-2012 IEEE. Source

Ribeiro D.V.,Federal University of Bahia | Labrincha J.A.,University of Aveiro | Morelli M.R.,Federal University of Sao Carlos
Cement and Concrete Research | Year: 2012

Red mud, the main waste generated in aluminum and alumina production by the Bayer process, is considered "hazardous" due to its high pH. The characteristic of high alkalinity associated with the presence of aluminosilicates facilitates the assimilation and formation of compounds by reaction with chloride ions. The high pH also provides greater protection of rebars, which is reflected in the low corrosion potential and high electrical resistivity (filler effect) of concrete. In this study, the chloride concentration was monitored by measuring the conductivity of the anolyte. Red mud proved to be a promising additive for concrete to inhibit the corrosion process. The corrosion potential was monitored by electrochemical measurements and the electrical resistivity was evaluated using sensors embedded in concrete test specimens. The results showed that the addition of red mud is beneficial to concrete, reducing its chloride migration rate (diffusion coefficients) and corrosion potential and increasing its electrical resistivity. © 2011 Elsevier Ltd. All rights reserved. Source

Yoon J.W.,Swinburne University of Technology | Yoon J.W.,University of Aveiro | Dick R.E.,Alcoa | Barlat F.,Pohang University of Science and Technology
International Journal of Plasticity | Year: 2011

Commercial canmaking processes include drawing, redrawing and several ironing operations. It is experimentally observed that during the drawing and redrawing processes earing develops, but during the ironing processes earing is reduced. It is essential to understand the earing mechanism during drawing and ironing for an advanced material modeling. A new analytical approach that relates the earing profile to r-value and yield stress directionalities is presented in this work. The analytical formula is based on the exact integration of the logarithmic strain. The derivation is for a cylindrical cup under the plane stress condition based on rigid perfect plasticity while force equilibrium is not considered. The earing profile is obtained solely from anisotropic plastic properties in simple tension. The earing mechanism is explained from the present theory with explicit formulae. It has been proved that earing is the combination of the contributions from r-value and yield stress directionalities. From a directionality (y-axis) vs. angle from the rolling (x-axis) plot, the earing profile is generated to be a scaled mirror image of the r-value directionality with respect to 90° (x = 90) and also a scaled mirror image of the yield stress directionality with respect to the reference yield stress (y = 1). Three different materials (Al-5% Mg alloy, AA 2090-T3 and AA 3104 RPDT control coil) are considered for verification purposes. This approach provides a fundamental basis for understanding the earing mechanism. In practice, the present theory is also very useful for the prediction of the earing profile of a drawn and iron cup and its related convolute cut-edge design for an earless cup. © 2011 Elsevier Ltd. All rights reserved. Source

Benali A.,New University of Lisbon | Benali A.,University of Lisbon | Carvalho A.C.,New University of Lisbon | Nunes J.P.,University of Aveiro | And 3 more authors.
Remote Sensing of Environment | Year: 2012

Air surface temperature (T air) is an important parameter for a wide range of applications such as vector-borne disease bionomics, hydrology and climate change studies. Air temperature data is usually obtained from measurements made in meteorological stations, providing only limited information about spatial patterns over wide areas. The use of remote sensing data can help overcome this problem, particularly in areas with low station density, having the potential to improve the estimation of T air at both regional and global scales. Some studies have tried to derive maximum (T max), minimum (T min) and average air temperature (T avg) using different methods, with variable estimation accuracy; errors generally fall in the 2-3°C range while the level of precision generally considered as accurate is 1-2°C. The main objective of this study was to accurately estimate T max, T min and T avg for a 10year period based on remote sensing-Land Surface Temperature (LST) data obtained from MODIS-and auxiliary data using a statistical approach. An optimization procedure with a mixed bootstrap and jackknife resampling was employed. The statistical models estimated Tavg with a MEF (Model Efficiency Index) of 0.941 and a RMSE of 1.33°C. Regarding T max and T min, the best MEF achieved was 0.919 and 0.871, respectively, with a 1.83 and 1.74°C RMSE. The developed datasets provided weekly 1km estimations and accurately described both the intra and inter annual temporal and spatial patterns of T air. Potential sources of uncertainty and error were also analyzed and identified. The most promising developments were proposed with the aim of developing accurate T air estimations at a larger scale in the future. © 2012 Elsevier Inc. Source

Sousa C.S.,University of Aveiro
Revista da Escola de Enfermagem da U S P | Year: 2013

The present study aimed to understand the care provided to patients with HIV/AIDS in Portugal according to the healthcare providers' perspective. Thompson's method of oral history was used in the study, which included 22 healthcare providers. The data were collected by means of semi-structured interviews and were analyzed from the narrative compilation perspective formulated by the author using QSR Nvivo software. The study complied with the ethical precepts for research. Care was analyzed according to three dimensions: cognitive, affective-relational, and technical-instrumental. The participants attributed particular relevance to the cognitive dimension in association with the moment when the diagnosis of HIV/AIDS was established, as well as throughout the course of disease. The affective-relational dimension was cross-sectional and considered to be valuable throughout the course of the disease from its diagnosis to the death of the patients with HIV/AIDS. The technical-instrumental dimension was more expressive in the advanced stages of the disease, in patients suffering from addiction and in terminal illness. As a function of the results, we can conclude that the three investigated dimensions are highly relevant for the care of patients with HIV/AIDS. Source

Costa J.D.,University of Coimbra | Ferreira J.A.M.,University of Coimbra | Borrego L.P.,Polytechnic Institute of Coimbra | Abreu L.P.,University of Aveiro
International Journal of Fatigue | Year: 2012

Razminia A.,Persian Gulf University | Torres D.F.M.,University of Aveiro
Mechatronics | Year: 2013

We consider a new fractional order chaotic system displaying an interesting behavior. A necessary condition for the system to remain chaotic is derived. It is found that chaos exists in the system with order less than three. Using the Routh-Hurwitz and the Matignon stability criteria, we analyze the novel chaotic fractional order system and propose a control methodology that is better than the nonlinear counterparts available in the literature, in the sense of simplicity of implementation and analysis. A scalar control input that excites only one of the states is proposed, and sufficient conditions for the controller gain to stabilize the unstable equilibrium points derived. Numerical simulations confirm the theoretical analysis. © 2013 Elsevier Ltd. All rights reserved. Source

Morais M.H.M.,University of Aveiro | Namouni F.,French National Center for Scientific Research
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2013

We identify a set of asteroids among Centaurs and Damocloids, which orbit contrary to the common direction of motion in the Solar system and which enter into resonance with Jupiter and Saturn. Their orbits have inclinations I ≳ 140° and semimajor axes a<15 au. Two objects are currently in retrograde resonance with Jupiter: 2006 BZ8 in the 2/-5 resonance and 2008 SO218 in the 1/-2 resonance. One object, 2009 QY6, is currently in the 2/-3 retrograde resonance with Saturn. These are the first examples of Solar system objects in retrograde resonance. The present resonant configurations last for several thousand years. Brief captures in retrograde resonance with Saturn are also possible during the 20 000 yr integration timespan, particularly in the 1/-1 resonance (2006 BZ8) and the 9/-7 resonance (1999 LE31). © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Zuniga J.C.,InterDigital | Bernardos C.J.,Charles III University of Madrid | De La Oliva A.,Charles III University of Madrid | Melia T.,Polytechnic University of Turin | And 2 more authors.
IEEE Communications Magazine | Year: 2013

In this article, we introduce distributed mobility management (DMM) - a new architectural paradigm for evolving mobile IP networks. We discuss the technology trends that are driving a move toward DMM and what the relevant standards development organizations (IETF and 3GPP) are doing to address these new needs. We conclude with a discussion of how 3GPP's evolved packet core can evolve toward a DMM-based architecture. © 1979-2012 IEEE. Source

Duarte I.,University of Aveiro | Krstulovic-Opara L.,University of Split | Vesenjak M.,University of Maribor
Composite Structures | Year: 2015

Novel ex-situ foam-filled tubes (FFTs) were prepared by inserting an integral-skin foam filler into an empty aluminium alloy tube. The aluminium alloy foam filler is prepared by powder compact foaming technique allowing to combine the Al-alloy integral-skin filler with an Al-alloy tube which has not been studied yet. Axial compressive crush performance of the individual components (empty tubes and integral-skin foams) and FFTs was studied and evaluated using uniaxial compression tests, exploring their deformation and failure mechanisms. The FFTs deform by axisymmetric axial crushing mode (concertina mode) with the formation of a single visible concertina fold, but with the formation and propagation of longitudinal cracks. The results confirm an improved crush performance under axial compressive loads by introducing the integral-skin foam as a filler in empty tubes. © 2014 Elsevier Ltd. Source

Sampaio M.O.P.,University of Aveiro
International Journal of Modern Physics A | Year: 2013

We present a pedagogical introduction to the problem of evolving a head on collision of two Aichelburg-Sexl gravitational shock waves in D-dimensions, using perturbative techniques. We follow a constructive approach with examples, going in some detail through: the set up of the exact initial conditions and their properties; perturbative methods in flat space-time with Green function solutions; and numerical strategies to evaluate the integral solutions. We also discuss, briefly, radiation extraction methods adapted to this problem, together with some of the results for this system. © 2013 World Scientific Publishing Company. Source

Malonek H.R.,University of Aveiro | Falcao M.I.,University of Minho
Mathematical Methods in the Applied Sciences | Year: 2010

We consider quasi-conformal 3D-mappings realized by hypercomplex differentiable (monogenic) functions and their polynomial approximation. Main tools are the series development of monogenic functions in terms of hypercomplex variables and the generalization of Kantorovich's approach for approximating conformal mappings by powers of a small parameter. Copyright © 2009 John Wiley & Sons, Ltd. Source

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. Source

Crustaceana | Year: 2012

The present study demonstrates that specimens of the grapsoid crab Percnon gibbesi invading the Mediterranean can replace those being collected in the species home range to supply the European marine aquarium trade. Although P. gibbesi is currently ranked among the "100 worst" invasive alien species in Europe, thousands of specimens of this crab are still collected every year from the western Atlantic and shipped to Europe as "reef janitors" for marine aquariums. This work analysed the acceptance of Mediterranean P. gibbesi by European marine aquarium retailers, which, as expected, were unable to distinguish western Atlantic from alien P. gibbesi. Hobbyists claimed to prefer alien specimens, but only if these displayed an identical (or lower) retail value than those of the western Atlantic. Although a selective fishery on young recruits and female P. gibbesi will not eradicate or even stop the dispersal of this highly successful invader, it will certainly generate a new income source for local fishermen and probably help to alleviate the fishing pressure on potentially over-harvested stocks of P. gibbesi in its home range. © Koninklijke Brill NV, Leiden, The Netherlands 2012. Source

Krishnamoorthy A.,Sathyabama University | Rajendra Boopathy S.,Anna University | Palanikumar K.,Sri Sairam Institute of Technology | Paulo Davim J.,University of Aveiro
Measurement: Journal of the International Measurement Confederation | Year: 2012

Carbon Fibre Reinforced Plastic (CFRP) composite materials have potential applications in various domains. In machining, drilling is essentially required to join different structures. But CFRP drilling poses many problems that decrease the quality of holes. In this paper, Taguchi's L 27 orthogonal array is used to perform drilling of CFRP composite plates. To improve the quality of the holes drilled, the optimal combination of drilling parameters is chosen using grey relational analysis. Grey fuzzy optimization of drilling parameters is based on five different output performance characteristics, namely, thrust force, torque, entry delamination, exit delamination and eccentricity of the holes. Analysis of variance (ANOVA) is used to find the percentage contribution of the drilling parameters and found that feed rate is the most influential factor in drilling of CFRP composites. © 2012 Elsevier Ltd. All rights reserved. Source

Al-Rawi M.S.,University of Aveiro
Journal of Real-Time Image Processing | Year: 2010

A fast and numerically stable method to compute pseudo Zernike moments is proposed in this paper. Several pseudo Zernike moment computation architectures are also implemented and some have overflow problems when high orders are computed. In addition, a correction to a previous two stage p-recursive pseudo Zernike radial polynomial algorithm is introduced. The newly proposed method that is based on computing pseudo Zernike radial polynomials through their relation to Zernike radial polynomials is found to be one and half times faster than the best algorithm reported up to date. © 2009 Springer-Verlag. Source

Bystrov V.S.,University of Aveiro
Ferroelectrics | Year: 2015

The results are based on the first principle modeling and calculations of hydroxyapatite (HAP) nanostructures, especially, in ordered monoclinic phase. HAP structures were studied using local density approximation (LDA) method with calculations of density of states (DOS) in combination with molecular modeling by HyperChem. Computed data show that monoclinic and hexagonal phases can co-exist, especially in their ordered (along OH groups) states. Calculated piezoelectric coefficient dyy ∼ d33 ∼ 15.7 pm/V is consistent with recently obtained experimental data (effective longitudinal piezoelectric coefficient d33eff about 8 pm/V), which vary significantly from grain to grain and may correspond to coexisting phases. Copyright © Taylor & Francis Group, LLC. Source

Correia A.C.M.,University of Aveiro | Correia A.C.M.,University Pierre and Marie Curie | Rodriguez A.,University of Sao Paulo
Astrophysical Journal | Year: 2013

Many exoplanets have been observed close to their parent stars with orbital periods of a few days. As for the major satellites of the Jovian planets, the figure of these planets is expected to be strongly shaped by tidal forces. However, contrary to solar system satellites, exoplanets may present high values for the obliquity and eccentricity due to planetary perturbations, and may also be captured in spin-orbit resonances different from the synchronous one. Here we give a general formulation of the equilibrium figure of those bodies that makes no particular assumption on the spin and/or orbital configurations. The gravity field coefficients computed here are well suited for describing the figure evolution of a body whose spin and orbit undergo substantial variations in time. © 2013. The American Astronomical Society. All rights reserved. Source

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

Pertsev N.A.,Saint Petersburg State Polytechnic University | Kholkin A.L.,University of Aveiro
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Ferroelectric nanodomains can be created by the application of a bias voltage to the sharp conducting tip of a scanning force microscope (SFM) contacting the sample surface. Since an inhomogeneous electric field created by an SFM tip has maximum intensity along the surface normal, in multiaxial ferroelectrics the polarization inside these domains also tends to orient perpendicularly to the surface. Here we show theoretically that unusual domains can be created in uniaxial ferroelectrics when the SFM tip is applied to the crystal surface parallel to the polar axis. These 180 nanodomains have polarization directed along the surface and should appear in LiNbO3 and LiTaO3 crystals at moderate tip voltages well below 100 V. Calculations of equilibrium domain dimensions demonstrate that subsurface domains have the shape of a needle oriented along the polar axis. © 2013 American Physical Society. Source

La F.M.B.,University of Aveiro | Sundberg J.,KTH Royal Institute of Technology
Journal of Voice | Year: 2012

Objectives: Significant changes in body tissues occur during pregnancy; however, literature concerning the effects of pregnancy on the voice is sparse, especially concerning the professional classically trained voice. Hypotheses: Hormonal variations and associated bodily changes during pregnancy affect phonatory conditions, such as vocal fold motility and glottal adduction. Design: Longitudinal case study with a semiprofessional classically trained singer. Methods: Audio, electrolaryngograph, oral pressure, and air flow signals were recorded once a week during the last 12 weeks of pregnancy, 48 hours after birth and during the following consecutive 11 weeks. Vocal tasks included diminuendo sequences of the syllable /pae/ sung at various pitches, and performing a Lied. Phonation threshold pressures (PTPs) and collision threshold pressures (CTPs), normalized amplitude quotient (NAQ), alpha ratio, and the dominance of the voice source fundamental were determined. Concentrations of sex female steroid hormones were measured on three occasions. A listening test of timbral brightness and vocal fatigue was carried out. Results: Results demonstrated significantly elevated concentrations of estrogen and progesterone during pregnancy, which were considerably reduced after birth. During pregnancy, CTPs and PTPs were high; and NAQ, alpha ratio, and dominance of the voice source fundamental suggested elevated glottal adduction. In addition, a perceptible decrease of vocal brightness was noted. Conclusions: The elevated CTPs and PTPs during pregnancy suggest reduced vocal fold motility and increased glottal adduction. These changes are compatible with expected effects of elevated concentrations of estrogen and progesterone on tissue viscosity and water retention. © 2012 The Voice Foundation. Source

Resende D.N.,University of Aveiro | Gibson D.,University of Texas at Austin | Jarrett J.,University of Texas at Austin
Technovation | Year: 2013

The objective of this article is to present a qualitative analysis tool which technology transfer offices (TTOs) can utilize to improve their efficiency and effectiveness. Such qualitative tool is one of the novelties presented. The other is information that advances understanding of the processes, procedures and structures required to transfer technology, as a set of best practices. From December 2008 to September 2010 a variety of methodologies (document analysis, participative observation, interviews and surveys) generated data which led to development of a theoretical framework. The theoretical framework, called Master Plan for Technology Transfer (TT), is a reference schema for best practices. The Master Plan contains 271 rules (good practices) referring to 43 facilitators distributed in seven groups. The facilitators and rules were selected from a coding process based on grounded theory, where facilitators are the categories and rules are their properties. Based on the methodologies and development of the Master Plan, we constructed a tool called Best Transfer Practices (BTP) which is a qualitative tool to assess and study TTOs and their host R&D institutions. The collection of rules and facilitators are the soul of our BTP. It is our contribution to the knowledge of actual practices in TT. © 2012 Elsevier Ltd. Source

Pacheco-Torgal F.,University of Minho | Labrincha J.A.,University of Aveiro
Construction and Building Materials | Year: 2013

The deterioration of reinforced concrete structures is a very common problem due to the fact that this material has a high permeability which allows water and other aggressive media to enter, thus leading to corrosion problems. The use of sealers is a common way of contributing to concrete durability. However, the most common ones are based on organic polymers which have some degree of toxicity. The Regulation (EU) 305/2011 related to the Construction Products Regulation emphasizes the need to reduce hazardous substances. Therefore, new low toxicity forms to increase concrete durability are needed. Recent investigations in the field of biotechnology show the potential of bioinspired materials in the development of low toxic solutions. This paper reviews current knowledge on the use of bacteria for concrete with enhanced durability. It covers the use of bacteria in concrete mix and also biomineralization in concrete surface treatments. Investigation gaps are described. Results from practical applications in which there is exposure to environmental conditions are still needed in order to confirm the importance of this new approach. © 2012 Elsevier Ltd. All rights reserved. Source

Fernandes M.,University of Tras os Montes e Alto Douro | Almeida Paz F.A.,University of Aveiro | De Zea Bermudez V.,University of Tras os Montes e Alto Douro
European Journal of Inorganic Chemistry | Year: 2012

The influence of 1-ethyl-3-methylimidazolium chloride, 1-butyl-3- methylimidazolium chloride, 1-butyl-1-methylpyrrolidinium chloride, 1-ethyl-3-methylimidazolium tetrafluoroborate and 3-(2-hydroxyethyl)-1- methylimidazolium tetrafluoroborate ionic liquids (ILs) on the morphology and structure of CaCO 3 has been investigated in an ethanolic medium by using calcium chloride and ammonium carbonate as the calcium and carbon sources, respectively. Syntheses were carried out at 9 °C and room temp. at different IL concentrations and CO 3 2-/Ca 2+ molar ratios. No polymorph selectivity was detected, and calcite was the sole crystalline form obtained under all the considered reactions conditions. In the case of the BF 4 --based ILs, anion decomposition occurred, which led to the formation of fluorite. Low temperature reduced the precipitation rate. With the ILs employed, the morphology of CaCO 3 has been finely tailored: calcite microcubes, microframes and microboxes with potential application in drug delivery, as well as nanocubes and nanocorn-like objects were produced with Cl --based ILs; with BF 4 --based ILs, hierarchically structured materials, in which calcite coexists with fluorite, and complex and intricate shapes were produced, such as nanostructured microspheres, nanostructured calla-lily-like and ice-cream-ball-like micro-objects. CaCO 3 was precipitated in ethanol byusing calcium chloride, ammonium carbonate and an ionic liquid (IL). With Cl --based ILs, calcite microcubes, microframes, microboxes, nanocubes and nanocorn-like objects were obtained. With BF 4 --based ILs, calcite and fluorite nanostructured microspheres, nanostructured calla-lily-like and ice-cream-ball-like micro-objects were produced. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

De Morais A.B.,University of Aveiro
Engineering Fracture Mechanics | Year: 2013

A cohesive zone model was developed for mode I delamination in composite beams. The present model is an extension of a beam on elastic foundation analysis similar to the one that led to the well-known corrected beam theory data reduction scheme. In particular, it is demonstrated that the shear foundation considered in most formulations can actually be discarded, thereby allowing a much simpler model implementation. The present model agrees very well with finite element analyses of double cantilever beam and moment-loaded double cantilever beam specimens with a wide range of properties. © 2013 Elsevier Ltd. Source

Sobolev N.A.,University of Aveiro
Semiconductors | Year: 2013

The article is dedicated to the review and analysis of the effects and processes occurring in Si-Ge quantum size semiconductor structures upon particle irradiation including ion implantation. Comparisons to bulk materials are drawn. The reasons of the enhanced radiation hardness of superlattices and quantum dots are elucidated. Some technological applications of the radiation treatment are reviewed. © 2013 Pleiades Publishing, Ltd. Source

Sher B.R.,Polytechnic Institute of Lisbon | Moreira R.A.S.,University of Aveiro
Composite Structures | Year: 2013

One of the most effective ways of controlling vibrations in plate or beam structures is by means of constrained viscoelastic damping treatments. Contrary to the unconstrained configuration, the design of constrained and integrated layer damping treatments is multifaceted because the thickness of the viscoelastic layer acts distinctly on the two main counterparts of the strain energy - the volume of viscoelastic material and the shear strain field. In this work, a parametric study is performed exploring the effect that the design parameters, namely the thickness/length ratio, constraining layer thickness, material modulus, natural mode and boundary conditions have on these two counterparts and subsequently, on the treatment efficiency. This paper presents five parametric studies, namely, the thickness/length ratio, the constraining layer thickness, material properties, natural mode and boundary conditions. The results obtained evidence an interesting effect when dealing with very thin viscoelastic layers that contradicts the standard treatment efficiency vs. layer thickness relation; hence, the potential optimisation of constrained and integrated viscoelastic treatments through the use of properly designed thin multilayer configurations is justified. This work presents a dimensionless analysis and provides useful general guidelines for the efficient design of constrained and integrated damping treatments based on single or multi-layer configurations. © 2012 Elsevier Ltd. Source

Larsson A.,Chalmers University of Technology | Seemann M.,Chalmers University of Technology | Neves D.,University of Aveiro | Thunman H.,Chalmers University of Technology
Energy and Fuels | Year: 2013

A general approach to evaluating the performance of industrial-scale dual fluidized bed (DFB) gasifiers was developed in this work. The approach is intended to simplify comprehensive evaluation of DFB gasifiers and to highlight important parameters, some of which are often missed or omitted in the literature. By applying this procedure, experimental results can be generalized, which is verified in this work using the Chalmers 2-4-MWth DFB gasifier. In a DFB gasifier, some of the fuel is converted to the desired calorific gas, while the remaining portion is combusted to meet the heat demands of the process. As shown here, the total heat demands limit the amount of chemical energy that can be restored from the fuel into the produced gas, whereby the main heat demands are from the drying and heating of the fuel, in addition to heating the combustion air and steam. By establishing a heat balance across the system, the chemical efficiency can be estimated. With lower heat demands, higher chemical efficiency is achievable, whereas with higher heat demands, more of the fuel must be burned and a lower chemical efficiency is achieved. It is experimentally complicated to quantify the level of fuel conversion and heat demands of a DFB gasification system. In this work, an experimental procedure is presented and implemented using the Chalmers gasifier to quantify the fuel conversion and heat demands. Furthermore, it was investigated how a variation in the amount of steam used for fluidization of the gasifier affects fuel conversion and other important parameters. To establish a reference case, silica sand was used as bed material and wood pellets was used as fuel to minimize the effects of ash and the bed material. By increasing the level of fluidization steam, the average residence time of the gas was decreased and the gas temperature, gas velocity, and steam-to-fuel ratio were increased, which resulted in increased conversion (up to 36%) of organic compounds (OC). However, limited char conversion was achieved (0%-4%), and the chemical efficiency remained unaffected by the amount of steam added to the process. The chemical efficiency of the Chalmers gasifier was determined to be 74% when using wood pellets as fuel. This is comparable to results from thermo-economic modeling of second-generation biofuels production processes, which, based on the heat demand, report the chemical efficiency of the DFB gasifier as being in the range of 74%-77% to maximize the overall efficiency. This shows that the required chemical efficiency is achieved, even with low char conversion, when using a fuel with a high content of volatiles, such as wood pellets. © 2013 American Chemical Society. Source

Carvalho T.,University of Aveiro
Journal of Health, Organisation and Management | Year: 2012

Purpose: There have been profound changes in the Portuguese national health system (NHS), instigated under the influence of managerialism and the new public management (NPM) "philosophy". These changes have been in line with what has happened in other developed countries. At the beginning of the new century, important reforms that emphasised the efficient use of scarce resources were implemented. The objective of this study is to understand how nurses are adapting to a more managerial environment, one in which economic rationalism and market-driven initiatives are the key principles behind the health reforms. Design/methodology/approach: A qualitative study was developed, based on semi-structured interviews with 83 nurses with managerial duties in ten hospitals in Portugal. All interviews were tape-recorded and each interviewee's discourses were subjected to content analysis. Findings: Data analysis led to the conclusion that under the new logic of the market and managerialism, these professionals have tried to (re)define their professionalisation route by emphasising the importance of care but also by trying to incorporate management as their dominant role in the social division of work. In reconfiguring their notion of professionalism, nurses were incorporating new practices in their day-to-day activities. This empirical study confirms that professionalism can also be conceptualised as a technology of self-control being able to discipline professionals at the micro level. Originality/value: This research is an empirical study based on the effects of managerialism on nurses with managerial duties in Portugal. This study contributes to a better understanding of the complex process of the professionalisation of nurses in a context of institutional change. © Emerald Group Publishing Limited. Source

Jongen M.,University of Lisbon | Pereira J.S.,University of Lisbon | Aires L.M.I.,Polytechnic Institute of Leiria | Pio C.A.,University of Aveiro
Agricultural and Forest Meteorology | Year: 2011

We studied the seasonal and inter-annual variation in carbon, water and energy fluxes over a Mediterranean grassland ecosystem in Portugal, dominated by annual species, using the eddy-covariance technique. The study period, from 2004 to 2008, was characterised by high intra- and inter-annual precipitation variation: the hydrological years 2004-2005 and 2007-2008 had precipitation below average ('dry' years) whereas the other two hydrological years had precipitation above average ('wet' years).The variation in energy partitioning into sensible heat (H) and latent heat (λE) fluxes was associated with changes in soil water content, coinciding with plant emergence and senescence. The ecosystem was λE-dominated in those periods with soil water content above 15%, and became H-dominated when soil water content fell below 15%.Annually integrated net ecosystem carbon exchange (NEE) was highly sensitive to drought, varying from a carbon sink in 'wet' years (e.g., 2005-2006, -190gCm-2y-1), to a carbon source in 'dry' years (e.g., 2004-2005, +49gCm-2y-1). There was a negative correlation between annually integrated NEE and annual precipitation (r2=0.78). However, timing of precipitation influenced NEE, with individual rain events in the dry season resulting in large pulses of ecosystem respiration (Reco). Low precipitation at the peak of the growing season, as in the spring of 2007, decreased carbon sequestration. The best descriptor for inter-annual variation in NEE was leaf area duration (LAD), which explained 96% of the variance.Average radiation-use efficiency (RUE) was 1.59gMJ-1 and inherent water-use efficiency (IWUE) was 24.6gChPakg-1 H2O. RUE and IWUE had similar trends in inter-annual variation, reflecting differences in productivity and timing of precipitation.Our study showed that carbon and energy fluxes in this Mediterranean environment depended strongly upon water availability. © 2011 Elsevier B.V. Source

Costa L.F.,University of Porto | Herdeiro C.,University of Aveiro | Natario J.,University of Lisbon | Zilhao M.,University of Porto
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

It has been asserted in the literature that Mathisson's helical motions are unphysical, with the argument that their radius can be arbitrarily large. We revisit Mathisson's helical motions of a free spinning particle, and observe that such statement is unfounded. Their radius is finite and confined to the disk of centroids. We argue that the helical motions are perfectly valid and physically equivalent descriptions of the motion of a spinning body, the difference between them being the choice of the representative point of the particle, thus a gauge choice. We discuss the kinematical explanation of these motions, and we dynamically interpret them through the concept of hidden momentum. We also show that, contrary to previous claims, the frequency of the helical motions coincides, even in the relativistic limit, with the zitterbewegung frequency of the Dirac equation for the electron. © 2012 American Physical Society. Source

Agra A.,University of Aveiro | Andersson H.,Norwegian University of Science and Technology | Christiansen M.,Norwegian University of Science and Technology | Wolsey L.,Catholic University of Leuven
Networks | Year: 2013

A single-product maritime inventory routing problem (MIRP) is studied in which the production and consumption rates vary over the planning horizon. The problem involves a heterogeneous fleet and multiple production and consumption ports with limited storage capacity. Two discrete time formulations are developed: an original model and a reformulated model that is a pure fixed charge network flow (FCNF) model with side constraints. Mixed integer sets arising from the decomposition of the formulations are identified. In particular, several lot-sizing relaxations are derived for the formulations and used to establish valid inequalities to strengthen the proposed formulations. Until now, the derivation of models and valid inequalities for MIRPs has mainly been inspired by the developments in the routing community. Here, we have developed a new model leading to new valid inequalities for MIRPs obtained by generalizing valid inequalities from the recent lot-sizing literature. Considering a set of instances based on real data, a computational study is conducted to test the formulations and the effectiveness of the valid inequalities. The FCNF formulation is generally much stronger than the original formulation. The developed valid inequalities reduce the integrality gap significantly for both formulations. By using a branch-and-bound scheme based on the strengthened FCNF formulation, most of our test instances are solved to optimality. © 2013 Wiley Periodicals, Inc. NETWORKS, Vol. 62(4), 297-314 2013 Copyright © 2013 Wiley Periodicals, Inc. Source

Dias G.P.,University of Aveiro
RISTI - Revista Iberica de Sistemas e Tecnologias de Informacao | Year: 2011

In this article we present and discuss the Q-Model - a two-dimensional maturity model for e-government. Although it is the result of a synthesis effort on previously proposed maturity models, it innovates by using two dimensions of analysis: interaction in service delivery; and integration of the service delivery from the client's perspective. This approach allows the classification of a broader spectrum of e-government initiatives and suggests that multiple maturity paths can be followed from traditional face-to-face non-integrated government environments to fully multi-channel and trannsversally integrated e-government scenarios. We argue that the Q-Model contributes to shift the focus from interaction driven e-government development to a development approach that balances interaction with integration concerns. This is especially relevant since governments tend to postpone integration objectives because they are harder to achieve and have less immediate visibility. Source

Araujo A.,University Lusiada Of Vila Nova Of Famalicao | Martins N.,University of Aveiro
Measurement Science and Technology | Year: 2015

The Monte Carlo technique for uncertainty propagation was used to estimate the uncertainty of ambient temperature measurements, obtained by dual-band pyrometry, of assumed grey surfaces. A large number of simulations were performed for a wide range of values from the following parameters: uncertainty of the detectors, emissivity of the target surface, background temperature of the surrounding surfaces, and spectral characteristics of the detectors (bandwidth, location of the bands, and distance between bands). Temperature measurement uncertainties from single-band pyrometry were also simulated for evaluation against dual-band uncertainties. It is concluded that the following parameters minimize dual-band temperature uncertainty: narrow wavelength bands, far apart from each other, positioned towards low wavelengths; low surface emissivity; high or low background temperature with respect to the target surface temperature (uncertainty grows very fast as the background and target temperatures converge, and tends to a constant minimum value as the background and target temperatures diverge). © 2015 IOP Publishing Ltd. Source

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. Source

Sklyarov V.,University of Aveiro
BEC 2010 - 2010 12th Biennial Baltic Electronics Conference, Proceedings of the 12th Biennial Baltic Electronics Conference | Year: 2010

The paper integrates the results of the previous work and presents the complete methodology for synthesis of digital circuits and systems from hierarchical and parallel specifications expressed in the form of hierarchical graph-schemes. Such specifications provide support for design reuse, parallelization and other important features highlighted in the paper. The synthesis is based on the model of a hierarchical finite state machine (HFSM) and the proposed design templates. Two different types of HFSM (with explicit and implicit modules) are discussed. Practicability and advantages of the proposed technique are demonstrated on numerous examples, such as data sorting, priority buffering and embedded controllers. ©2010 IEEE. Source

Carvalho J.,University of Tras os Montes e Alto Douro | Nobre P.,University of Aveiro
Journal of Sexual Medicine | Year: 2010

Introduction. Sexual desire depends on the balance between biologic, psychological, and cultural values. Therefore, conceptualizations of female sexual desire difficulties should consider the interrelated role of those factors. Aim.: The aim of this study was to test a conceptual model regarding factors often implicated on female sexual desire, in order to understand the way those factors interact in sexual interest. Moreover, we intended to evaluate the mediation role of cognitive-emotional factors between sexual desire and other dimensions such as age, medical problems, psychopathology, or dyadic adjustment. Methods.: Two hundred and thirty-seven women from the general population participated in the study. We evaluated psychopathology, dysfunctional sexual beliefs, automatic thoughts and emotions during sexual activity, dyadic adjustment, and presence of medical problems. Main Outcome Measures.: Psychopathology measured by the Brief Symptom Inventory, dysfunctional sexual beliefs measured by the Sexual Dysfunctional Beliefs Questionnaire, thoughts and emotions in sexual context measured by the Sexual Modes Questionnaire, dyadic adjustment measured by the Dyadic Adjustment Scale, medical condition measured by the Medical History Formulation, and sexual desire measured by the Sexual Desire subscale of the Female Sexual Function Index. Results.: Results from the proposed conceptual model suggest that cognitive factors (mainly automatic thoughts during sexual activity) were the best predictors of sexual desire. In a more specific way, age, failure/disengagement thoughts, and lack of erotic thoughts during sexual activity, showed a significant direct effect on reduced sexual desire. Furthermore, sexual conservatism beliefs, and medical factors showed indirect effects, acting on sexual desire via the presence of lack of erotic thoughts, and failure/disengagement sexual thoughts, respectively. Conclusions.: Results from this integrative approach support the need to include cognitive dimensions in the assessment and treatment of sexual desire problems, considering their implication as vulnerability or resilient factors regarding deficient sexual interest in women. © 2010 International Society for Sexual Medicine. Source

Wieczorek M.A.,CNRS Paris Institute of Global Physics | Correia A.C.M.,University of Aveiro | Correia A.C.M.,University Pierre and Marie Curie | Le Feuvre M.,University of Nantes | And 2 more authors.
Nature Geoscience | Year: 2012

The planet Mercury rotates three times about its spin axis for every two orbits about the Sun, in a 3/2 spin- orbit resonance. This unique state has been explained by an initial rapid prograde rotation, which was then decelerated by tidal torques to the present resonance. When friction at the core- mantle boundary is accounted for, capture into the 3/2 resonance occurs with a probability of only 26%, whereas the most likely outcome is capture into one of the higher-order resonances. Here we use a numerical model of Mercury's rotational evolution to investigate the consequences of an initial retrograde rotation of Mercury. We find that in this case, the planet would be captured into synchronous rotation, with one hemisphere always facing the Sun, with a probability of 68%. Strong lateral variations in the impact cratering rate would have existed, consistent with the observed distribution of large impact basins. Escape from this highly stable resonance can be initiated by the momentum imparted by large, basin-forming impact events 8-10, and subsequent capture into the 3/2 resonance is likely. During synchronous rotation, substantial quantities of volatile deposits would have accumulated on the hemisphere facing away from the Sun, potentially explaining the existence of sublimation hollows on Mercury's surface 11. Source

Oliveira P.C.,Polytechnic Institute of Porto | Oliveira C.G.,University of Aveiro
European Journal of Engineering Education | Year: 2013

In the last years, science courses in higher education (HE) have been facing some problems, namely the lack of students' motivation, the number of students' failures and drop outs, particular in physics courses. The most probable reason, which has been mentioned in current science education research in HE, is that the level of interaction between teachers and learners in formal instructional settings is very low. In this paper, we describe changes that were introduced in lectures towards the promotion of active learning and analyse its effects in the classroom environment. The introduction of conceptual questions and peer instruction seems to motivate students in the class and help them engage in the learning process. These strategies have been used in the first year of an introductory physics course for engineering students in two different Portuguese HE institutions. The data were collected through questionnaires and student interviews. © 2013 Copyright SEFI. Source

Quinta Gomes A.L.,University of Tras os Montes e Alto Douro | Nobre P.,University of Aveiro
Journal of Sexual Medicine | Year: 2011

Introduction. The importance of the role played by personality variables in the etiology, development, and maintenance of most emotional disorders is strongly supported by empirical data. However, there is a lack of studies concerning the implication of these variables on sexual difficulties. Aim. The purpose of the present study was to investigate the role played by personality dimensions and psychopathology on male sexual functioning as well as to clarify the way these variables discriminate men with and without sexual dysfunction. Methods. A total of 229 men participated in the study (a community sample composed by 205 men and a clinical sample by 24 men with a DSM-IV diagnosis of sexual dysfunction). The community sample was subdivided into a control group (n=152) and a subclinical group (n=53), according to the cutoff scores of the International Index of Erectile Dysfunction. After giving informed consent, participants completed a set of clinical instruments. Partial correlations, regression analyses, and multivariate analyses of covariance were conducted. Main Outcomes Measures. All participants completed a set of measures assessing personality dimensions, psychopathological symptoms, and sexual functioning. Results. After controlling for psychopathology, men with sexual dysfunction presented significantly higher levels of neuroticism when compared to sexually healthy men. Moreover, regression analysis indicated neuroticism as the best predictor of sexual functioning (β=-0.24, P<0.01). Regarding psychopathology, men with sexual problems presented significantly higher levels of depressive symptoms than the controls. Additionally, depressive symptoms were a significant predictor of sexual functioning (β=-0.41, P<0.001). Conclusion. Personality dimensions and psychopathology play an important role on male sexual functioning. The results may have important clinical implications. © 2010 International Society for Sexual Medicine. Source

Vieira N.,University of Aveiro
Complex Analysis and Operator Theory | Year: 2015

In this paper, we establish the fractional Cauchy–Kovalevskaya extension ($$\textit{FCK}$$FCK-extension) theorem for fractional monogenic functions defined on $$\mathbb {R}^d$$Rd. Based on this extension principle, fractional Fueter polynomials, forming a basis of the space of fractional spherical monogenics, i.e. fractional homogeneous polynomials, are introduced. We studied the connection between the $$\textit{FCK}$$FCK-extension of functions of the form $$x^\alpha P_l$$xαPl and the classical Gegenbauer polynomials. Finally we present two examples of $$\textit{FCK}$$FCK-extension. © 2014, Springer Basel. Source

Mateus M.,University of Lisbon | Vaz N.,University of Aveiro | Neves R.,University of Lisbon
Journal of Marine Systems | Year: 2012

The main goal of this study is to use an integrated ecosystem model to study the role of physical, chemical and environmental parameters on the biogeochemistry of the Tagus estuary, the main estuarine system in Portugal. This work was developed as part of EU-funded INSEA project and tried to accomplish two major aims: (1) the development and implementation of a coupled modeling system capable of reproducing all the major characteristics both in physical and biological environments, and (2) to create a coastal management system based on the efficient integration of observations and biophysical models. Our results suggest that both aims were met. In this study we have used a 2D hydrodynamic application coupled to a complex ecological model presented in a companion paper which captures the state of the art of marine ecological models, and also developed during the project. Special emphasis is given to the processes governing temporal and spatial patterns of both phytoplankton and bulk properties, and the physical-biological interactions shaping their variability. The results shown in this paper are indicative of a reasonable performance of the model. It captures the complexity of the Tagus estuary and provides reasonable estimates of the biomass trends of a highly dynamic and interactive community. © 2011 Elsevier B.V. Source

Martins H.,University of Aveiro
Atmospheric Environment | Year: 2012

Urban sprawl is altering the landscape, with current trends pointing to further changes in land use that will, in turn, lead to changes in population, energy consumption, atmospheric emissions and air quality. Urban planners have debated on the most sustainable urban structure, with arguments in favour and against urban compaction and dispersion. However, it is clear that other areas of expertise have to be involved. Urban air quality and human exposure to atmospheric pollutants as indicators of urban sustainability can contribute to the discussion, namely through the study of the relation between urban structure and air quality. This paper addresses the issue by analysing the impacts of alternative urban growth patterns on the air quality of Porto urban region in Portugal, through a 1-year simulation with the MM5-CAMx modelling system. This region has been experiencing one of the highest European rates of urban sprawl, and at the same time presents a poor air quality. As part of the modelling system setup, a sensitivity study was conducted regarding different land use datasets and spatial distribution of emissions. Two urban development scenarios were defined, SPRAWL and COMPACT, together with their new land use and emission datasets; then meteorological and air quality simulations were performed. Results reveal that SPRAWL land use changes resulted in an average temperature increase of 0.4 °C, with local increases reaching as high as 1.5 °C. SPRAWL results also show an aggravation of PM10 annual average values and an increase in the exceedances to the daily limit value. For ozone, differences between scenarios were smaller, with SPRAWL presenting larger concentration differences than COMPACT. Finally, despite the higher concentrations found in SPRAWL, population exposure to the pollutants is higher for COMPACT because more inhabitants are found in areas of highest concentration levels. © 2012 Elsevier Ltd. Source

Malinowska A.B.,University of Bialystok | Torres D.F.M.,University of Aveiro
Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences | Year: 2011

We establish necessary optimality conditions for variational problems with an action depending on the free endpoints. New transversality conditions are also obtained. The results are formulated and proved using the recent and general theory of time scales via the backward nabla differential operator. © 2011 Verlag der Zeitschrift für Naturforschung, Tübingen. Source

Sudheendran K.,University of Aveiro | James Raju K.C.,University of Hyderabad
Journal of Materials Science: Materials in Electronics | Year: 2011

Metal Insulator Semiconductor (MIS) capacitors with monoclinic bismuth zinc niobate pyrocholre having the composition Bi2Zn2 /3Nb 4/3O 7 (m-BZN) dielectric layer were fabricated and characterized. Capacitance voltage (C-V) and current voltage measurements were utilized to obtain the dielectric properties, leakage current density and interface quality. The results shows that the obtained m-BZN thin films presents a high dielectric constant in between 30 and 70, a good interface quality with silicon and a leakage current density of 10 μA/cm 2 for a field strength of 100 kV/cm which is acceptable for high performance logic circuits. The equilent oxide thickness for the films annealed at 200 °C was 10 nm. These results suggest that m-BZN thin films can be potentially integrated as gate dielectric materials in CMOS technology. © 2010 Springer Science+Business Media, LLC. Source

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

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

Fajin J.L.C.,University of Porto | Cordeiro M.N.D.S.,University of Porto | Illas F.,University of Barcelona | Gomes J.R.B.,University of Aveiro
Journal of Catalysis | Year: 2014

Periodic density functional theory (DFT) based calculations were used to explore the relationship between the activation energy corresponding to RO-H bond cleavage of organic compounds on catalytically active transition metal surfaces and other simpler quantities which can be used as descriptors. Taking data for methanol on various surfaces, several Brønsted-Evans-Polanyi (BEP)-like relationships linking the activation energy barrier to the reaction energy, the adsorption energy of the reaction products or to the adsorption energy of an oxygen atom were explored. The general validity of these relationships has been explored by considering cases not included in the database used to extract the BEP relationships. For the more promising BEP relationship, the database for methanol was combined with results corresponding to O-H bond breaking of ethanol, formic acid and water on a sufficiently broad number of transition metal surfaces. This extended database provided a more general and statistically meaningful general BEP type relationship connecting the activation energy for the O-H bond breakage of general RO-H compounds on catalytic transition metal systems to the adsorption energy of the reaction products. Finally, a protocol is presented that allows one to determine good candidates for bond breakage of general RO-H compounds on metallic and bimetallic surfaces limiting the explicit calculation of the activation energy barriers to a few, previously detected, interesting cases only. © 2014 Elsevier Inc. All rights reserved. Source

Sendra A.,Asociacion para el Estudio del Medio Subterraneo | Reboleira A.S.S.,University of Aveiro | Reboleira A.S.S.,University of La Laguna
International Journal of Speleology | Year: 2012

Subsurface biota extends over a wide variety of habitats that can be spatially interconnected. The largest communities of this subsurface biota inhabit cavities and are well known mainly in caves where biologists are able to have access. Data about deep subterranean communities and arthropods living under one thousand meters was unknown. An expedition to world's deepest cave, Krubera-Voronja in Western Caucasus, revealed an interesting subterranean community, living below 2000 meters and represented by more than 12 species of arthropods, including several new species for science. This deep cave biota is composed of troglobionts and also epigean species, that can penetrate until -2140 m. Deep subterranean ecosystems should not be seen only as an evolutionary dead end towards the troglomorphic syndrome, but also as a shelter for epigean species populations, especially during long periods of time when surface conditions are severe for their survival. Most of the subsurface biota depends on allochthonous sources of organic carbon coming from: water percolating from the surface, sinking streams that enter caves, and activities of animals moving in and out of caves. The biocoenosis and the vertical distribution of invertebrate fauna of Krubera-Voronja are provided, from its entrance to the remarkable depth of 2140 meters, including the discovery of world's deepest dwelling arthropod. Source

Serodio J.,University of Aveiro
Philosophical transactions of the Royal Society of London. Series B, Biological sciences | Year: 2014

Kleptoplasty is a remarkable type of photosynthetic association, resulting from the maintenance of functional chloroplasts--the 'kleptoplasts'--in the tissues of a non-photosynthetic host. It represents a biologically unique condition for chloroplast and photosynthesis functioning, occurring in different phylogenetic lineages, namely dinoflagellates, ciliates, foraminiferans and, most interestingly, a single taxon of metazoans, the sacoglossan sea slugs. In the case of sea slugs, chloroplasts from macroalgae are often maintained as intracellular organelles in cells of these marine gastropods, structurally intact and photosynthetically competent for extended periods of time. Kleptoplasty has long attracted interest owing to the longevity of functional kleptoplasts in the absence of the original algal nucleus and the limited number of proteins encoded by the chloroplast genome. This review updates the state-of-the-art on kleptoplast photophysiology, focusing on the comparative analysis of the responses to light of the chloroplasts when in their original, macroalgal cells, and when sequestered in animal cells and functioning as kleptoplasts. It covers fundamental but ecologically relevant aspects of kleptoplast light responses, such as the occurrence of photoacclimation in hospite, operation of photoprotective processes and susceptibility to photoinhibition. Emphasis is given to host-mediated processes unique to kleptoplastic associations, reviewing current hypotheses on behavioural photoprotection and host-mediated enhancement of photosynthetic performance, and identifying current gaps in sacoglossan kleptoplast photophysiology research. Source

Bartrum S.,University of Edinburgh | Berera A.,University of Edinburgh | Rosa J.G.,University of Aveiro
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within the standard model and some of its most widely considered extensions, in different parametric regimes. We describe the generic consequences of fluctuation-dissipation dynamics in the postinflationary universe, focusing in particular on friction and particle production, and analyze in detail two important effects. First, we show that dissipative friction delays the process of spontaneous symmetry breaking and may even damp the motion of a Higgs field sufficiently to induce a late period of warm inflation. Along with dissipative entropy production, this may parametrically dilute the abundance of dangerous thermal relics. Second, we show that dissipation can generate the observed baryon asymmetry without symmetry restoration, and we develop in detail a model of dissipative leptogenesis. We further show that this generically leads to characteristic baryon isocurvature perturbations that can be tested with cosmic microwave background observations. This work provides a fundamental framework to go beyond the leading thermal equilibrium semiclassical approximation in addressing fundamental problems in modern cosmology. © 2015 American Physical Society. Source

Phycologia | Year: 2011

Within the context of the preparation of a flora for the identification of freshwater dinoflagellates, the identity ofGlenodinium edax and the affinities of a group of phagotrophic species with a conspicuous eyespot not associated withplastids (eyespot type C) currently classified in Katodinium were re-evaluated. The original description and illustrationsof the phagotrophic G. edax suggest affinity with the Pfiesteriaceae. Whereas the tabulation currently associated with G.edax is based on a probable misidentification, the similarity to Tyrannodinium berolinense suggests that the two namescan be regarded as synonyms and T. edax comb. nov. is proposed. As presented in modern floras, Katodinium isartificially defined on the basis of the position of the cingulum at or below the posterior third of the cell, and includeswidely different forms. The presence of an eyespot of type C in the phagotrophic Katodinium vorticella and relatedspecies combines with a general cell morphology reminiscent of Esoptrodinium gemma and the formation of Tovellia-likecysts to mark this group of species as belonging to the Tovelliaceae. The type species of Katodinium, K. nieuportense, ismorphologically quite different from these species and does not display tovelliacean characters. None of the knowngenera of Tovelliaceae matches the characters of K. vorticella and its close relatives. Opisthoaulax gen. nov. is described and new combinations are proposed for K. vorticella and six other species. Source

Costa V.A.F.,University of Aveiro
Energy and Buildings | Year: 2014

A numerical study is conducted to improve the thermal performance of red clay holed bricks, considering protuberances to inhibit natural convection and radiation heat transfer inside the brick holes. Protuberances are made of the same red clay and have the same thickness as the remaining elements of the bricks, the best solution leading to the lowest overall heat transfer rate with shorter protuberances. Protuberances increase conduction heat transfer but decrease natural convection and radiation heat transfer, and a minimum overall heat transfer exists. Protuberances allow an overall heat transfer reduction which increases as increases the Rayleigh number. For fixed solid material (red clay) and fluid (air), the Rayleigh number depends mainly on the temperature difference between the opposite faces of the brick. For increasing temperature differences, when the thermal performance of the buildings' walls is more important, protuberances increasingly improve the thermal performance of the bricks, giving to the bricks a smart character. Relevant information is obtained, helping holed bricks makers to obtain better bricks for energy savings and energy consumption reductions in buildings, the obtained results leading to overall heat transfer reductions up to 23%. Some comparisons are made with experimental results for common and commercially available red clay holed bricks without protuberances. © 2013 Elsevier B.V. All rights reserved. Source

Almeida I.,University of Coimbra | Soares S.C.,University of Coimbra | Soares S.C.,University of Aveiro | Castelo-Branco M.,University of Coimbra
PLoS ONE | Year: 2015

Introduction: Visual processing of ecologically relevant stimuli involves a central bias for stimuli demanding detailed processing (e.g., faces), whereas peripheral object processing is based on coarse identification. Fast detection of animal shapes holding a significant phylogenetic value, such as snakes, may benefit from peripheral vision. The amygdala together with the pulvinar and the superior colliculus are implicated in an ongoing debate regarding their role in automatic and deliberate spatial processing of threat signals. Methods: Here we tested twenty healthy participants in an fMRI task, and investigated the role of spatial demands (the main effect of central vs. peripheral vision) in the processing of fear-relevant ecological features. We controlled for stimulus dependence using true or false snakes; snake shapes or snake faces and for task constraints (implicit or explicit). The main idea justifying this double task is that amygdala and superior colliculus are involved in both automatic and controlled processes. Moreover the explicit/implicit instruction in the task with respect to emotion is not necessarily equivalent to explicit vs. implicit in the sense of endogenous vs. exogenous attention, or controlled vs. automatic processes. Results: We found that stimulus-driven processing led to increased amygdala responses specifically to true snake shapes presented in the centre or in the peripheral left hemifield (right hemisphere). Importantly, the superior colliculus showed significantly biased and explicit central responses to snake-related stimuli. Moreover, the pulvinar, which also contains foveal representations, also showed strong central responses, extending the results of a recent single cell pulvinar study in monkeys. Similar hemispheric specialization was found across structures: increased amygdala responses occurred to true snake shapes presented to the right hemisphere, with this pattern being closely followed by the superior colliculus and the pulvinar. Conclusion: These results show that subcortical structures containing foveal representations such as the amygdala, pulvinar and superior colliculus play distinct roles in the central and peripheral processing of snake shapes. Our findings suggest multiple phylogenetic fingerprints in the responses of subcortical structures to fear-relevant stimuli. © 2015 Almeida et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Ribeiro R.,University of Coimbra | Lopes I.,University of Aveiro
Ecotoxicology | Year: 2013

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). Source

Rodriguez-Solla H.,University of Oviedo | Alvaredo N.,University of Oviedo | Soengas R.,University of Aveiro
Synlett | Year: 2012

We present herein an improved synthesis of nitro sugars, consisting of a Henry-type reaction of bromonitromethane and sugar aldehydes. The reaction can be promoted by either SmI 2 or indium metal, yielding in both cases high yields and good diastereoisomeric ratios. However, while the SmI 2-promoted reaction is very sensitive to steric factors and only gives satisfactory results with bromonitromethane, the indium-mediated reaction is not subjected to this limitation, giving excellent results with bromonitromethane as well as more hindered bromonitroalkanes. © Georg Thieme Verlag Stuttgart New York. Source

Pacheco-Torgal F.,University of Minho | Labrincha J.A.,University of Aveiro
Construction and Building Materials | Year: 2013

Although the unsustainability of the human civilization has been recognized long ago, little has ever been done to change it. During the last century, materials use increased 8-fold and as a result Humanity currently uses almost 60 billion tons (Gt) of materials per year. The construction industry alone consumes more raw materials than any other economic activity. However, research on construction materials still is excessively focused on their mechanical properties with minor concerns regarding environmental considerations. In September of 2000 189 UN member states signed the Millennium Development Goals (MDGs), in which the seventh goal is related to environmental sustainability. This is a cornerstone event of paramount significance. However, research in the field of the built environment especially on the field of construction materials still seems unable to recognize its importance. This paper provides some insights on future construction materials research priorities in the context of the seventh MDG. It reviews publication patterns on the field of construction materials highlighting investigations gaps and misdirected research lines. It addresses the importance of nano and biotech hot areas and briefly analyzes the gap between research and market use. © 2012 Elsevier Ltd. All rights reserved. Source

Magalhaes Da Silva S.P.,National Laboratory of Energy and Geology | Magalhaes Da Silva S.P.,University of Aveiro | Da Costa Lopes A.M.,National Laboratory of Energy and Geology | Roseiro L.B.,National Laboratory of Energy and Geology | Bogel-Lukasik R.,National Laboratory of Energy and Geology

An efficient lignocellulosic biomass pre-treatment is a crucial step for the valorization of these kind of raw materials. Lignocellulosic biomass is a potentially valuable resource for transformation into biofuels and bio-based products. The use of ionic liquids as media for the biomass pre-treatment is an alternative method that follows the green chemistry concept. This work proposes a new methodology for wheat straw pre-treatment with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][OAc]), which allowed the production of cellulose, hemicellulose and lignin-rich fractions in a rapid and simple three-step fractionation process. Various temperatures (80-140 °C) and processing times (2-18 h) of the pre-treatment were studied. The quantitative and qualitative analysis of each lignocellulosic biomass fraction was determined by FTIR measurements. The glucan content in recovered cellulose-rich fractions was investigated by enzymatic hydrolysis. The cellulose recovery dependence on the pre-treatment conditions was ascertained through regression analysis. The optimal result for the recovery of the cellulose-rich fraction was obtained at 140 °C during 6 h achieving 37.1% (w/w) of the initial biomass loading. For the same conditions, optimal results were also produced regarding the amount of glucan present (81.1% w/wbiomass) in cellulose-rich fractions, the carbohydrate enrichment in the hemicellulose fraction (96% wt) and the purity of lignin (97% wt). The recovery of IL was performed after each pre-treatment and the obtained yields were up to 86% (w/w). The recovered ILs were analyzed by 13C and 1H NMR. The presence of value-added phenolic compounds in the recovered ILs was analyzed by capillary electrophoresis. Vanillin and its derivatives, as well as other lignin-based products, were identified. © 2013 The Royal Society of Chemistry. Source

Quinta Gomes A.L.,University of Tras os Montes e Alto Douro | Nobre P.,University of Aveiro
Journal of Sexual Medicine | Year: 2012

Introduction. The International Index of Erectile Function (IIEF) is a brief, reliable, and multidimensional scale for assessing sexual function in men in both research and clinical trials. Aim. The objective of the present study was to determine the psychometric properties of the Portuguese version of the IIEF. Methods. A total of 1,363 Portuguese men participated in this study (a clinical sample of 37 men and a community sample of 1,326 men). Main Outcome Measures. All participants completed a questionnaire regarding demographic information and the IIEF. Results. Principal component analysis using varimax rotation indicated a two-factor structure explaining approximately 55% of the total variance (one factor encompassing erection and orgasmic function domains of the original IIEF, and a second factor corresponding to sexual desire, intercourse, and overall satisfaction). The differentiated factor structure with five separate domains of sexual function was not replicated in the Portuguese version. The two-factor model and the original five-factor model of male sexual function were assessed with confirmatory factor analysis (CFA), and overall acceptable fits were demonstrated for both models. However, despite a non-optimal performance, CFA provided a better support for the five-factor solution as the model that best fitted the data. An important lack of discriminant validity evidenced by high intercorrelations among dimensions was detected in both models, suggesting a substantial overlap among factors. Reliability studies showed good internal consistency for the five subscales, and test-retest reliability analysis supported the stability of the measure over time. Discriminant validity confirmed the ability of both subscales to differentiate men with erectile dysfunction from matched controls. Conclusions. Results suggested that the Portuguese version of the IIEF has adequate psychometric properties, and its use is recommended for clinical and research purposes. Further studies are needed in order to elucidate the association among dimensions of male sexual function and, ultimately, to offer a clearer conceptualization of male's sexual response. © 2011 International Society for Sexual Medicine. Source

Nairne J.S.,Purdue University | Pandeirada J.N.S.,University of Aveiro
Cognitive Psychology | Year: 2010

Evolutionary psychologists often propose that humans carry around "stone-age" brains, along with a toolkit of cognitive adaptations designed originally to solve hunter-gatherer problems. This perspective predicts that optimal cognitive performance might sometimes be induced by ancestrally-based problems, those present in ancestral environments, rather than by adaptive problems faced more commonly in modern environments. This prediction was examined in four experiments using the survival processing paradigm, in which retention is tested after participants process information in terms of its relevance to fitness-based scenarios. In each of the experiments, participants remembered information better after processing its relevance in an ancestral environment (the grasslands), compared to a modern urban environment (a city), despite the fact that all scenarios described similar fitness-relevant problems. These data suggest that our memory systems may be tuned to ancestral priorities. © 2010 Elsevier Inc. All rights reserved. Source

Rodriguez-Alleres M.,University of Vigo | Varela M.E.,University of Vigo | Varela M.E.,University of Aveiro | Benito E.,University of Vigo
Geoderma | Year: 2012

Soil water repellency is a widespread property of Pinus pinaster forest soils in Galicia (NW Spain) that can be intensified by soil heating during fires. Fire-induced or -enhanced soil water repellency, in combination with reduced vegetation and litter cover, is widely considered to be one of the main causes of increased overland flow and accelerated soil erosion on recently burnt hill slopes.In this work, we assessed the natural severity of water repellency in forest soils of different texture under P. pinaster in Galicia (NW Spain) and we examined the specific effect of a forest fire in an area under granite substrate and P. pinaster plantation on the severity and persistence of soil water repellency. Because the burnt area included zones that were affected to a different extent by the fire, we focused on the effect of its severity on soil water repellency from surface level down to a depth of 40. cm immediately after the fire and 15. months later. Persistency in the soil water repellency was assessed with the water drop penetration time test (WDPT).Water repellency in the sampled soils was found to be extremely persistent in the surface layer (0-5. cm). Also, the soils of a coarser texture, exhibit more persistence repellency and at greater depths than those of a finer texture.Fire severity was found to influence the persistence of water repellency and the thickness of the hydrophobic layer in the burnt zones. Such persistence in the soil affected by low-severity fire not differed significantly from that in unburnt soil; also, repellency remained severe to extreme down to 10. cm. On the other hand, soil water repellency in areas subject to fire of medium-high severity was completely suppressed within the top 2. cm of soil, but increased with depth (extreme water repellency between 2 and 20. cm). Fifteen months after the fire, both burnt and unburnt zones exhibited water repellency throughout the sampled profile (0-40. cm); however, the burnt zone affected by fire of medium-high severity exhibited decreased water repellency in the surface layer but increased at depths of 2-40. cm than it was both in the unburnt zone and in the zone burnt by low-severity fire. © 2012 Elsevier B.V. Source

Azevedo Alves A.,University of Aveiro
Economic Affairs | Year: 2011

The analysis of the structural causes of the Portuguese crisis points to a mix of internal and external factors that reinforced each other. Among the external factors were the perverse incentives posed by the current institutional setting in the EU and the single currency. These have wider implications for the eurozone in that the long-term sustainability of the eurozone will require more effective operation of internal adjustment mechanisms. Additionally, the implementation of monetary competition in the eurozone is suggested as an alternative to the current path towards greater centralisation. © 2011 Institute of Economic Affairs. Published by Blackwell Publishing, Oxford. Source

Fajin J.L.C.,University of Porto | Cordeiro M.N.D.S.,University of Porto | Gomes J.R.B.,University of Aveiro
Journal of Physical Chemistry C | Year: 2012

General trends for the reaction of water dissociation on some selected transition metal (TM) bimetallic surfaces of the type TM 1@TM 2(111) or TM 1@TM 2(110), with TM 1 = Ag, Ni, Rh, or Ir and TM 2 = Cu, Au, Ni, or Ir, are interpreted from periodic density functional theory calculations. It was found that the water dissociation on bimetallic surfaces follows relationships that link the activation energy barrier with the reaction energy or with the adsorption energy of the reaction products. Furthermore, it was also found that the doping of metallic surfaces with atoms of other metals leads to a stabilizing cooperative effect of both in the adsorption of water, its dissociation products, and transition state configuration. Importantly, the catalytic activity of the bimetallic systems is found to increase visibly when compared with the reactivity of the pure parent surfaces. In fact, the activation barriers calculated for water dissociation on some bimetallic surfaces are significantly lowered when compared with the activation energies for the reaction of water dissociation on pure surfaces of the parent metals. © 2012 American Chemical Society. Source

Pages O.,University of Lorraine | Souhabi J.,University of Lorraine | Torres V.J.B.,University of Aveiro | Postnikov A.V.,University of Lorraine | Rustagi K.C.,Indian Institute of Technology Bombay
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We report on the detailed assignment of various features observed in the Raman spectra of SiGe alloys along the linear chain approximation (LCA), as achieved based on remarkable intensity interplays with composition between such neighboring features known from the literature but which so far have not been fully exploited. Such an assignment is independently supported by ab initio calculation of the frequencies of bond-stretching modes taking place in different local environments, which we define at one dimension (1D) for consistency with the LCA. Fair contour modeling of the SiGe Raman spectra is eventually obtained via a so-called 1D-cluster version of the phenomenological (LCA-based) percolation scheme, as originally developed for zincblende alloys, after ab initio calibration of the intrinsic Si-Si, Si-Ge, and Ge-Ge Raman efficiencies. The 1D-cluster scheme introduces a seven-oscillator [1 × (Ge-Ge), 4 × (Si-Ge), 2 × (Si-Si)] Raman behavior for SiGe, which considerably deviates from the currently accepted six-oscillator [1× (Ge-Ge), 1× (Si-Ge), 4 × (Si-Si)] behavior. Different numbers of Raman modes per bond are interpreted as different sensitivities to the local environment of Ge-Ge (insensitive), Si-Si (sensitive to first neighbors), and Si-Ge (sensitive to second neighbors) bond stretching. The as-obtained SiGe 1D-cluster/percolation scheme is also compared with the current version for zincblende alloys, using GaAsP as a natural reference. A marked deviation is concerned with an inversion of the like phonon branches in each multiplet. This is attributed either to the considerable Si and Ge phonon dispersions (Si-Si doublet) or to a basic difference in the lattice relaxations of diamond and zincblende alloys (Si-Ge multiplet). The SiGe vs GaAsP comparison is supported by ab initio calculation of the local lattice relaxation/dynamics related to prototype impurity motifs that are directly transposable to the two crystal structures. © 2012 American Physical Society. Source

Luis A.M.,University of Lisbon | Neves M.C.,University of Aveiro | Mendonca M.H.,University of Lisbon | Monteiro O.C.,University of Lisbon
Materials Chemistry and Physics | Year: 2011

Nanocrystalline titanium dioxide (TiO2) powders with different crystal phase composition were obtained by controlled hydrolysis and post-thermal treatments. The physicochemical properties of the powders were investigated by XRD, TEM/EDS, N2 physic adsorption and DRS. The results obtained show that the particle size and crystalline structure are parameters strongly dependent on the calcination conditions, mainly temperature and heating rate. The influence of the TiO2 phase composition on its photocatalytic activity, concerning the methylene blue photodegradation was studied. It was found that higher TiO2 photocatalytic activity is related with the co-existence of the three TiO2 polymorphs: anatase, brookite and rutile. © 2010 Elsevier B.V. All rights reserved. Source

Rodrigues M.M.,University of Aveiro
Proceedings of the World Congress on Engineering 2011, WCE 2011 | Year: 2011

In this paper, we determine the invariants of scaling transformations for a nonlinear partial differential equation of fractional order. For its invariant solutions an ordinary differential equation of fractional order with the new independent variable η = xt -α/β is derived. Using Banach fixed point theorem, the existence and uniqueness of solutions is studied for this kind of fractional differential equations. Source

Dos Santos M.F.N.,Sao Paulo State University | Battistelle R.A.G.,Sao Paulo State University | Bezerra B.S.,Sao Paulo State University | Varum H.S.A.,University of Aveiro
Journal of Cleaner Production | Year: 2014

This paper presents a research on the environmental impacts of particleboards produced from wastes, based on a comparative Life Cycle Assessment study. The particleboards were manufactured in laboratorial scale from the following residues: sugarcane bagasse (Saccharum spp.) and pine wood shavings (Pinus elliottii). The study was developed following the methodological guidelines of ISO 14040. The functional unit adopted was the m2 of the particleboards produced and the impacts were evaluated by the Environmental Development of Industrial Products method. The results indicated that pine particleboard present the highest environmental impact potential. Our findings suggested that the factors that mostly aggravated the environmental impacts were: the distance between the raw materials and the production site, and formaldehyde emissions (FE). The first is related to the combustion of fossil fuel during the acquisition of raw material, which achieved the values of 2185.94 g/m2 for consumption of non-renewable resources for pine particleboard and 893.53 g/m2 for bagasse particleboard. The second is related to the use of urea-formaldehyde resin, responsible for the FE into the air during production. The FE is accountable for the contamination of approximately 7,800,000.00 m3 of air per m2 of particleboard produced, and was the factor with the greatest impact in human toxicity potential. © 2013 Elsevier Ltd. All rights reserved. Source

Silva S.,University of Aveiro
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

Multiple detector row computed tomography (MDCT) cardiac angiography provides a large amount of data concerning multiple cardiac phases which are not often considered. Segmentation is a first step towards exploring how this additional data can be used to perform left ventricle functional analysis or myocardial perfusion assessment. We present preliminary results regarding the assessment of inter-observer variability for a semi-automatic (multi-phase) segmentation tool for the left-ventricle. Source

Reis A.,Aston University | Rudnitskaya A.,University of Aveiro | Blackburn G.J.,University of Strathclyde | Fauzi N.M.,National University of Malaysia | And 2 more authors.
Journal of Lipid Research | Year: 2013

Lipidome profile of fluids and tissues is a growing field as the role of lipids as signaling molecules is increasingly understood, relying on an effective and representative extraction of the lipids present. A number of solvent systems suitable for lipid extraction are commonly in use, though no comprehensive investigation of their effectiveness across multiple lipid classes has been carried out. To address this, human LDL from normolipidemic volunteers was used to evaluate five different solvent extraction protocols [Folch, Bligh and Dyer, acidified Bligh and Dyer, methanol (MeOH)-tert-butyl methyl ether (TBME), and hexane-isopropanol] and the extracted lipids were analyzed by LC-MS in a high-resolution instrument equipped with polarity switching. Overall, more than 350 different lipid species from 19 lipid subclasses were identified. Solvent composition had a small effect on the extraction of predominant lipid classes (triacylglycerides, cholesterol esters, and phosphatidylcholines). In contrast, extraction of less abundant lipids (phosphatidylinositols, lyso-lipids, ceramides, and cholesterol sulfates) was greatly influenced by the solvent system used. Overall, the Folch method was most effective for the extraction of a broad range of lipid classes in LDL, although the hexane-isopropanol method was best for apolar lipids and the MeOH-TBME method was suitable for lactosyl ceramides. Copyright © 2013 by the American Society for Biochemistry and Molecular Biology, Inc. Source

Ameloot N.,Ghent University | Graber E.R.,Institute of Soil, Water and Environmental Sciences | Verheijen F.G.A.,University of Aveiro | De Neve S.,Ghent University
European Journal of Soil Science | Year: 2013

The stability of biochar in soils is the cornerstone of the burgeoning worldwide interest in the potential of the pyrolysis/biochar platform for carbon (C) sequestration. While biochar is more recalcitrant in soil than the original organic feedstock, an increasing number of studies report greater C-mineralization in soils amended with biochar than in unamended soils. Soil organisms are believed to play a central role in this process. In this review, the variety of interactions that occur between soil micro-, meso- and macroorganisms and biochar stability are assessed. In addition, different factors reported to influence biochar stability, such as biochar physico-chemical characteristics, soil type, soil organic carbon (SOC) content and agricultural management practices are evaluated. A meta-analysis of data in the literature revealed that biochar-C mineralization rates decreased with increasing pyrolysis temperature, biochar-C content and time. Enhanced release of CO2 after biochar addition to soil may result from (i) priming of native SOC pools, (ii) biodegradation of biochar components from direct or indirect stimulation of soil organisms by biochar or (iii) abiotic release of biochar-C (from carbonates or chemi-sorbed CO2). Observed biphasic mineralization rates suggest rapid mineralization of labile biochar compounds by microorganisms, with stable aromatic components decomposed at a slower rate. Comparatively little information is available on the impact of soil fauna on biochar stability in soil, although they may decrease biochar particle size and enhance its dispersion in the soil. Elucidating the impacts of soil fauna directly and indirectly on biochar stability is a top research priority. © 2013 The Authors. Journal compilation © 2013 The Authors. Journal compilation © 2013 British Society of Soil Science. Source

Lakshtanov E.L.,University of Aveiro
Journal of Physics A: Mathematical and Theoretical | Year: 2010

We prove that the Dirichlet-to-Neumann operator (DtN) has no spectrum in the lower half of the complex plane. We find several applications of this fact in scattering by obstacles with impedance boundary conditions. In particular, we find an upper bound for the gradient of the scattering amplitude and for the total cross section. We justify numerical approximations by providing bounds for the difference between theoretical and approximated solutions without using any a priori unknown constants. © 2010 IOP Publishing Ltd. Source

Ramos A.,University of Aveiro | Mesnard M.,French National Center for Scientific Research
Journal of Cranio-Maxillofacial Surgery | Year: 2014

This study analyses load transfer in the fossa component based on two numerical models of total temporomandibular joint (TMJ) implants for two mouth openings. The TMJ articulation is a very complex system with muscles, ligaments and cartilage. Until now, studies of TMJ implants have analysed only condylar behaviour. The finite element models were constructed based on CT scans of a cadaveric mandible and cranium, considering the bone geometry and position. The influence of five principal muscle actions was simulated for two mouth positions, 5 mm and 15 mm openings at the incisive tooth support. Strain distributions into the surrounding bone tissue were analysed in both models in the condyle and fossa components. The results demonstrate that in Christensen® TJR of the temporomandibular joint the fossa component is the more critical part, presenting more stress near the screw holes and contact regions with the cranium. The most critical region is around the first two screws and the least critical is in the condyle component. For the mandible condyle reconstructed with a Christensen® prosthesis, the 15 mm mouth opening was more critical, as compression was increased, but for the fossa component the most critical situation occurred with the 5 mm opening. The micromovements observed suggest that the number of screws could be reduced to increase osteointegration of screws in the mandible condyle. © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. Source

Veiga C.,Polytechnic Institute of Coimbra | Davim J.P.,University of Aveiro | Loureiro A.J.R.,University of Coimbra
Reviews on Advanced Materials Science | Year: 2012

This paper presents a brief review on titanium alloys, giving especial attention to Ti-6Al-4V. The mechanical and the thermal properties were highlighted, while with regard to application the emphasis was placed to the aerospace, automotive and biomedical fields. The tensile strength of the alloys under concern varies from about 200 to 1400 MPa, but for Ti-6Al-4V the range is from about 900 to 1200 MPa. Generally, the thermal conductivity varies from about 5.5 o 25 WmK when temperature vares fom near oom o 200 °C, while for Ti-6AI-4V he values are about 6.6-6.8 WmK at near oom emperature, and about 16.0-19.0 WmK at 800 °C. Aerospace has been the major field of application of titanium materials, being one of the major challenges the development of new alloys with improved strength and higher service temperature. In automotive parts, such alloys are used especially for weight saving, but new alloys with higher service temperature, and new surface treatment to improve wear resistance are needed. New alloys without toxic elements and with elastic modulus similar to the bone need to be developed for biomedical applications. © 2012 Advanced Study Center Co. Ltd. Source

Naik M.T.,Center for Energy Studies | Sundar L.S.,University of Aveiro
International Communications in Heat and Mass Transfer | Year: 2013

Convective heat transfer and friction factor characteristics of water/propylene glycol (70:30% by volume) based CuO nanofluids flowing in a plain tube are investigated experimentally under constant heat flux boundary condition. Glycols are normally used as an anti-freezing heat transfer fluids in cold climatic regions. Nanofluids are prepared by dispersing 50. nm diameter of CuO nanoparticles in the base fluid. Experiments are conducted using CuO nanofluids with 0.025%, 0.1% and 0.5% volume concentration in the Reynolds numbers ranging from 1000 < Re < 10000 and considerable heat transfer enhancement in CuO nanofluids is observed. The effect of twisted tape inserts with twist ratios in the range of 0 < H/D < 15 on nanofluids is studied and further heat transfer augmentation is noticed. The increment in the pressure drop in the CuO nanofluids over the base fluid is negligible but the experimental results have shown a significant increment in the convective heat transfer coefficient of CuO nanofluids. The convective heat transfer coefficient increased up to 27.95% in the 0.5% CuO nanofluid in plain tube and with a twisted tape insert of H/D = 5 it is further increased to 76.06% over the base fluid at a particular Reynolds number. The friction factor enhancement of 10.08% is noticed and increased to 26.57% with the same twisted tape, when compared with the base fluid friction factor at the same Reynolds number. Based on the experimental data obtained, generalized regression equations are developed to predict Nusselt number and friction factor. © 2013 Elsevier Ltd. Source

Calhorda M.J.,University of Lisbon | Costa P.J.,University of Aveiro
Current Organic Chemistry | Year: 2012

Mo(VI) complexes MoO 2X 2L 2 (X=halide or Me, L neutral ligand) behave as catalysts for olefin epoxidation in the presence of t-butylhydroperoxide (TBHP). The active species results from OH activation of TBHP, which protonates one oxo group and leads to a seven coordinate complex, with a new OOR ligand. It was found that several Mo(II) complexes Cp'Mo(CO) 3X (Cp'=C 5R 5, Cp* or C 5H 5, Cp) acted as precursors for the same reactions and the resulting Cp'MoO 2X could also oxidize sulfides and sulfoxides, both with TBHP and H 2O 2 as oxidants. A review of the reaction mechanisms proposed for these reactions, by us and some other authors, and based on computational studies is given in this work. More than one active species can be found for the CpMoO(OH)(η 1-OOR)X intermediate, opening several competitive pathways. They differ by the O-H···O hydrogen bond formed between OH and one oxygen of the OOR ligand. This complex can also further react with oxidant to afford a peroxide complex CpMoO(η 2-O 2)X, which can also promote oxidation reactions. The activation energies depend on hydrogen bond assistance, so that the Cl and Me derivatives of CpMoO 2X behave differently (the peroxide complex has only been found active with Me), and on the steric constraints, more obvious when comparing Cp with Cp*. The preferred mechanism will thus depend on the specific infstituents, but energy barriers are comparable. © 2012 Bentham Science Publishers. Source

Marques F.M.B.,University of Aveiro
Electrochimica Acta | Year: 2013

Ceria-based composite electrolytes (50 and 70 vol%) including one mixture of Li and Na carbonates (1:1molar ratio) were prepared using either pure CeO2(modest conductor) or Gd-doped ceria (excellentoxide-ion conductor) as ceramic matrix. The composite electrolytes and their phase constituents weretested under pure CO2, air, and H2diluted in N 2, at temperatures ranging from 300 to 580°C, to studytheir electrical performance. Impedance spectroscopy measurements performed under these workingconditions were complemented by microstructural characterization. Low temperature (below melting)impedance shows in a clear manner the relevance of the matrix functionality on the performance of thesecomposites, but also reveals additional microstructural and even unusual composite effects. These datawere used to test equivalent circuit models derived from the composite constituent properties, and toassess their potential to design composites for target functionalities at higher temperature. © 2013 Elsevier Ltd. All rights reserved. Source

Gouveia L.,University of Lisbon | Moura P.,University of Lisbon | De Sousa A.,University of Aveiro
Computers and Operations Research | Year: 2010

We discuss a variant of the prize-collecting Steiner tree problem with node degree dependent costs using a telecommunications setting to motivate these costs. We present and test models which are tailored for this variant of the problem. Results taken from instances with up to 100 nodes are used to evaluate the quality of the proposed models for solving the problem, as well as, in terms of the correspondent linear programming relaxation. © 2010 Elsevier Ltd. All rights reserved. Source

Bendicho C.,University of Vigo | Lavilla I.,University of Vigo | Pena-Pereira F.,University of Vigo | Pena-Pereira F.,University of Aveiro | Romero V.,University of Vigo
Journal of Analytical Atomic Spectrometry | Year: 2012

As a result of the greater consciousness within the analytical community on the impact of chemicals on human health and environment, green issues are increasingly taken into account when choosing an established analytical method or developing a new one. Apart from typical analytical characteristics (e.g., sensitivity, limit of detection, repeatability, etc.), other features such as the amount of sample/reagents, operation time, use of energy-effective apparatus, waste production, etc. should be highlighted in order to meet the principles of Green Chemistry. Although conventional approaches for trace element analysis by atomic spectrometry usually involve well-established sample pre-treatments based on 'wet chemistry', and high consumption of gases, reagents, etc. is inherent to many techniques in this group, there are still many avenues where green issues can be implemented. For greening atomic spectrometry, green chemistry principles should be applied to every step of the analytical process, i.e., from sampling and sample pre-treatment to data processing. In this review, main pathways for greening atomic spectrometry such as downsizing of instrumentation, use of portable instruments, solid sampling, application of clean energies (ultrasound, microwaves, etc.) for sample pre-treatment, development of on-site, on-line and at-line approaches vs. typical off-line methods, application of modern extraction techniques (e.g., solid- and liquid-phase microextraction), green solvents and derivatization agents and use of chemometric tools for method optimization, signal processing, etc. are discussed in a critical way. © 2012 The Royal Society of Chemistry. Source

Lopes S.I.C.,Wageningen University | Capela M.I.,University of Aveiro | Lens P.N.L.,Wageningen University
Bioresource Technology | Year: 2010

This work studied the effect of the sulfide concentration and COD/SO4 2 - ratios (4 and 1) on sulfate reduction and acidification in a thermophilic (55 °C) UASB reactor fed with sucrose (4 g COD (lreactor d)-1) operated at a reactor mixed liquor pH controlled at 5 for a period of 301 days. When implementing N2 stripping, sulfate reduction efficiencies up to 95%, corresponding to volumetric sulfate reduction rates of 0.87 and 4.2 g (lreactor d)-1 at the COD/SO4 2 - ratios of 4 and 1, respectively, were achieved. Sulfide was toxic to sulfate reduction at a total dissolved sulfide concentration of 100 mg l-1. Acidification was always complete and acetate was the only form of substrate in the effluent at a COD/SO4 2 - ratio of 1. The sludge was well retained in the reactor and kept its granular shape throughout the reactor run. © 2010 Elsevier Ltd. All rights reserved. Source

Silva A.R.,University of Aveiro | Budarin V.,University of York | Clark J.H.,University of York
ChemCatChem | Year: 2013

An anchor into the microwaves: A directing effect on the orientation of the manganese(III) salen complexes towards the activated carbon surface was activated by using microwave-assisted anchoring. The immobilization procedure is simple, energy efficient, and fast. The resulting materials are unusually active and selective heterogeneous catalysts for the epoxidation of styrene. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Santinha G.,University of Aveiro
Saude e Sociedade | Year: 2013

Prominent economic, social and political changes, mainly over the past decade, which had broad impacts on healthcare services, justify reimagining healthcare decision-making processes. This set of changes puts into debate the competing values of equity and efficiency in articulation with territorial dynamics, impelling the readjustment of both prevailing theoretical viewpoints and strategic actions usually adopted in this field. This paper seeks to clear out the relationship between healthcare and territory according to two issues: the geographical nature of healthcare accessibility, bearing in mind both the urban/rural dichotomy and the recent trends concerning the reorganization of healthcare systems based on a centralization and cost-efficiency perspective, and the consequences on how healthcare services are spatially organised and relate, not only with other healthcare services, but also with the spatial structure of urban systems. Accordingly, this paper aims to ponder on these conspicuous challenges faced by decision-making processes in healthcare and, thus, discuss possible strategic, integrated and more spatially focused paths. Source

Brites C.D.S.,University of Aveiro
Nature Nanotechnology | Year: 2016

Brownian motion is one of the most fascinating phenomena in nature. Its conceptual implications have a profound impact in almost every field of science and even economics, from dissipative processes in thermodynamic systems, gene therapy in biomedical research, artificial motors and galaxy formation to the behaviour of stock prices. However, despite extensive experimental investigations, the basic microscopic knowledge of prototypical systems such as colloidal particles in a fluid is still far from being complete. This is particularly the case for the measurement of the particles' instantaneous velocities, elusive due to the rapid random movements on extremely short timescales. Here, we report the measurement of the instantaneous ballistic velocity of Brownian nanocrystals suspended in both aqueous and organic solvents. To achieve this, we develop a technique based on upconversion nanothermometry. We find that the population of excited electronic states in NaYF4:Yb/Er nanocrystals at thermal equilibrium can be used for temperature mapping of the nanofluid with great thermal sensitivity (1.15% K-1 at 296 K) and a high spatial resolution (<1 μm). A distinct correlation between the heat flux in the nanofluid and the temporal evolution of Er3+ emission allows us to measure the instantaneous velocity of nanocrystals with different sizes and shapes. © 2016 Nature Publishing Group Source

Amorim M.J.B.,University of Aveiro | Scott-Fordsmand J.J.,University of Aarhus
Environmental Pollution | Year: 2012

Environmental effects of copper nanoparticles are little studied in terrestrial ecosystems. In the present article, the toxicity of copper nanoparticles (Cu-NP) on the enchytraeid Enchytraeus albidus is compared to the toxicity of a copper-salt (CuCl 2). The effect parameters studied were survival, reproductive output and avoidance behaviour. The results show that Cu-NP were more toxic to E. albidus than the same concentrations of the CuCl 2-salt. The physic-chemical analysis of the particles indicated that only a small fraction was released as ions. Hence, the results indicated a nanoparticle-specific effect - lower reproductive output and higher avoidance. This was observed as 2-8 fold (significant) lower ECx values for Cu-NP (EC 50-reprod = 95 mg Cu/kg; EC 50-avoid = 241 mg Cu/kg) exposed organisms compared to CuCl 2 (EC 50- reprod = 251 mg Cu/kg; EC 50-avoid = 475 mg Cu/kg) exposed organisms. These results corroborate with a nanoparticle-specific effect. © 2012 Elsevier Ltd. All rights reserved. Source

Rodrigues E.T.,University of Coimbra | Lopes I.,University of Aveiro | Pardal M.T.,University of Coimbra
Environment International | Year: 2013

The use of pesticides for crop protection may result in the presence of toxic residues in environmental matrices. In the aquatic environment, pesticides might freely dissolve in the water or bind to suspended matter and to the sediments, and might be transferred to the organisms' tissues during bioaccumulation processes, resulting in adverse consequences to non-target species. One such group of synthetic organic pesticides widely used worldwide to combat pathogenic fungi affecting plants is the strobilurin chemical group. Whereas they are designed to control fungal pathogens, their general modes of action are not specific to fungi. Consequently, they can be potentially toxic to a wide range of non-target organisms. The present work had the intent to conduct an extensive literature review to find relevant research on the occurrence, fate and effects of azoxystrobin, the first patent of the strobilurin compounds, in aquatic ecosystems in order to identify strengths and gaps in the scientific database. Analytical procedures and existing legislation and regulations were also assessed. Data gathered in the present review revealed that analytical reference standards for the most relevant environmental metabolites of azoxystrobin are needed. Validated confirmatory methods for complex matrices, like sediment and aquatic organisms' tissues, are very limited. Important knowledge of base-line values of azoxystrobin and its metabolites in natural tropical and estuarine/marine ecosystems is lacking. Moreover, some environmental concentrations of azoxystrobin found in the present review are above the Regulatory Acceptable Concentration (RAC) in what concerns risk to aquatic invertebrates and the No Observed Ecologically Adverse Effect Concentration (NOEAEC) reported for freshwater communities. The present review also showed that there are very few data on azoxystrobin toxicity to different aquatic organisms, especially in what concerns estuarine/marine organisms. Besides, toxicity studies mostly address azoxystrobin and usually neglect the more relevant environmental metabolites. Further work is also required in what concerns effects of exposure to multi-stressors, e.g. pesticide mixtures. Even though Log Kow for azoxystrobin and R234886, the main metabolite of azoxystrobin in water, are below 3, the bio-concentration factor and the bioaccumulation potential for azoxystrobin are absent in the literature. Moreover, no single study on bioaccumulation and biomagnification processes was found in the present review. © 2012 Elsevier Ltd. Source

Perez-Sanchez G.,University of Porto | Gomes J.R.B.,University of Aveiro | Jorge M.,University of Porto | Jorge M.,University of Strathclyde
Langmuir | Year: 2013

A novel coarse-grained (CG) model to study the self-assembly of silica/surfactant mesostructures during the synthesis of periodic mesoporous silica is reported. Molecular dynamics simulations of hexadecyltrimethylammonium bromide (also called cetyltrimethylammonium bromide, or CTAB) surfactants in water and in aqueous silicate solutions have been performed to understand micelle formation, micelle growth, and their size evolution during the synthesis of surfactant-templated mesoporous materials. Direct comparison of density profiles obtained for preassembled micelles employing an all-atom description, AA, with those calculated with the CG model has been carried out for checking the validity of the latter model. Good agreement between AA and CG approaches was found, demonstrating the potential of the CG approximation for modeling these highly complex systems. The micelle formation and micelle fusion/fission processes were analyzed after performing long CG simulations for surfactant and ionized silica-surfactant aqueous solutions. We observed the formation of rodlike micelles in the case of silica-surfactant solutions, while spherical micelles were stable under the same conditions for the CTAB+H2O system. This demonstrates that the interaction of anionic silicates with cationic surfactants promotes a sphere-to-rod transition in surfactant solutions, a key step in the synthesis of nanoporous silica materials. © 2013 American Chemical Society. Source

Mirnaghi F.S.,University of Waterloo | Mousavi F.,University of Waterloo | Rocha S.M.,University of Aveiro | Pawliszyn J.,University of Waterloo
Journal of Chromatography A | Year: 2013

An automated 96-thin-film solid phase microextraction system was optimized for high throughput analysis of phenolic compounds in wine, berry, and grape samples. Liquid chromatography and tandem mass spectrometry methods were optimized and applied for separation and detection of compounds. Evaluation of five different stationary phases showed that polystyrene-divinylbenzene-polyacrylonitrile (PS-DVB-PAN) is the optimum extraction phase for the extraction of phenolic compounds under study. The thin-film PS-DVB-PAN SPME coating provided almost exhaustive extraction recovery for all phenolics compounds under study, except for naringenin with 80% recovery. Extraction efficiency, inter- and intra-day reproducibility, sensitivity, linearity, limit of detection and quantitation, and matrix effect were evaluated. Intra-day and inter-day reproducibility were in the respective range of 4-8 and 7-13% relative standard deviation (RSD) for all eight phenolic compounds. Limits of detection and quantitation of the proposed SPME-LC-MS/MS system for the analysis of analytes under study were found in the range of 0.2-3 and 0.5-10. ng/mL, respectively. Standard addition calibration was applied for the quantitative determination of unknown phenolic compounds from wine, berry, and grape samples. The assessment of matrix effect showed significant reduction of ion suppression/enhancement using SPME method in comparison with that of solvent extraction technique. © 2012 Elsevier B.V. Source

Kichakova O.,University of Oldenburg | Kunz J.,University of Oldenburg | Radu E.,University of Aveiro | Shnir Y.,University of Oldenburg | Shnir Y.,Tomsk State Pedagogical University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We investigate the thermodynamics of spherically symmetric black hole solutions in a four-dimensional Einstein-Yang-Mills-SU(2) theory with a negative cosmological constant. Special attention is paid to configurations with a unit magnetic charge. We find that a set of Reissner-Nordström-Anti-de Sitter black holes can become unstable to forming non-Abelian hair. However, the hairy black holes are never thermodynamically favoured over the full set of abelian monopole solutions. The thermodynamics of the generic configurations possessing a noninteger magnetic charge is also discussed. © 2015 The Authors. Source

Fajin J.L.C.,University of Porto | Cordeiro M.N.D.S.,University of Porto | Illas F.,University of Barcelona | Gomes J.R.B.,University of Aveiro
Journal of Catalysis | Year: 2010

Periodic density functional theory (DFT) calculations have been used to unravel the existence of Brønsted-Evans-Polanyi (BEP) relationships for water dissociation on metallic surfaces which constitutes the rate determining step for the technologically important water gas shift reaction. In addition, it is predicted that nickel surfaces possessing low coordinated atoms could be effective for catalyzing water dissociation. Finally, it is shown that the adsorption energy of atomic oxygen on a given metallic surface provides an excellent descriptor of the activation energy for water dissociation on that surface, thus allowing the screening of large number of metallic and bimetallic systems in a simple way. © 2010 Elsevier Inc. All rights reserved. Source

Pullar R.C.,University of Aveiro
Solid State Phenomena | Year: 2016

Hexagonal ferrites, or hexaferrites, are hugely important materials commercially and technologically, with common applications as permanent magnets, magnetic recording and data storage media, components in electrical devices operating at wireless frequencies, and as GHz electromagnetic wave absorbers for EMC, RAM and stealth technologies. Hexaferrites are all ferrimagnetic materials, and their magnetic properties are intrinsically linked to their crystalline structures, all having a strong magnetocrystalline anisotropy; that is the induced magnetisation has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetisation (known as uniaxial), the hard hexaferrites, and those with an easy plane (or cone) of magnetisation (known as ferroxplana or hexaplana), soft ferrites. The common hexaferrite members are: • M-type ferrites, such as BaFe12O19 and SrFe12O19• Z-type ferrites (Ba3Me2Fe24O41) • Y-type ferrites (Ba2Me2Fe12O22) • W-type ferrites (BaMe2Fe16O27) • X-type ferrites (Ba2Me2Fe28O46) • U-type ferrites (Ba4Me2Fe36O60) where Me = a small 2+ ion such as cobalt, nickel or zinc, and Ba can be fully substituted by Sr. Generally, the M ferrites are hard, the Y, Z and U ferrites are soft, and the W and X ferrites can very between these two extremes, but all have large magnetisation (M) values. There is currently increasing interest in composite materials containing hexaferrite fibres. It had been predicted that properties such as thermal and electrical conductivity, and magnetic, electrical and optical behaviour will be enhanced in material in fibrous form. This is because a continuous fine fibre can be considered as effectively one-dimensional, and it does not behave as a homogeneously distributed solid. Although the intrinsic magnetisation of the material is unaffected, the effective magnetisation of an aligned fibre sample should be greater when a field is applied parallel with fibre alignment compared to when applied perpendicularly to fibre alignment. This feature was first demonstrated by the author for aligned hexaferrite fibres in 2006. This chapter will deal with progress in the manufacture and properties of hexaferrite fibres, from the first syntheses of BaM, SrM, Co2Y, Co2Z, Co2W, Co2X and Co2U micron-scale fibres by the author 12-15 years ago, to recent developments in M ferrite hollow fibres and nanofibres, and hexaferrite-coated CNTs (carbon nanotubes).The relative properties of all reported hexaferrite fibres are compared and summarised at the end of this chapter. © (2016) Trans Tech Publications, Switzerland. Source

Pullar R.C.,University of Aveiro
Progress in Materials Science | Year: 2012

Since their discovery in the 1950s there has been an increasing degree of interest in the hexagonal ferrites, also know as hexaferrites, which is still growing exponentially today. These have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. As well as their use as permanent magnets, common applications are as magnetic recording and data storage materials, and as components in electrical devices, particularly those operating at microwave/GHz frequencies. The important members of the hexaferrite family are shown below, where Me = a small 2+ ion such as cobalt, nickel or zinc, and Ba can be substituted by Sr: M-type ferrites, such as BaFe 12O 19 (BaM or barium ferrite), SrFe 12O 19 (SrM or strontium ferrite), and cobalt-titanium substituted M ferrite, Sr- or BaFe 12-2xCo xTi xO 19 (CoTiM).Z-type ferrites (Ba 3Me 2Fe 24O 41) such as Ba 3Co 2Fe 24O 41, or Co 2Z.Y-type ferrites (Ba 2Me 2Fe 12O 22), such as Ba 2Co 2Fe 12O 22, or Co 2Y.W-type ferrites (BaMe 2Fe 16O 27), such as BaCo 2Fe 16O 27, or Co 2W.X-type ferrites (Ba 2Me 2Fe 28O 46), such as Ba 2Co 2Fe 28O 46, or Co 2X.U-type ferrites (Ba 4Me 2Fe 36O 60), such as Ba 4Co 2Fe 36O 60, or Co 2U. The best known hexagonal ferrites are those containing barium and cobalt as divalent cations, but many variations of these and hexaferrites containing other cations (substituted or doped) will also be discussed, especially M, W, Z and Y ferrites containing strontium, zinc, nickel and magnesium. The hexagonal ferrites are all ferrimagnetic materials, and their magnetic properties are intrinsically linked to their crystalline structures. They all have a magnetocrystalline anisotropy (MCA), that is the induced magnetisation has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetisation, the uniaxial hexaferrites, and those with an easy plane (or cone) of magnetisation, known as the ferroxplana or hexaplana ferrites. The structure, synthesis, solid state chemistry and magnetic properties of the ferrites shall be discussed here. This review will focus on the synthesis and properties of bulk ceramic ferrites. This is because the depth of research into thin film hexaferrites is enough for a review of its own. There has been an explosion of interest in hexaferrites in the last decade for more exotic applications. This is particularly true as electronic components for mobile and wireless communications at microwave/GHz frequencies, electromagnetic wave absorbers for EMC, RAM and stealth technologies (especially the X and U ferrites), and as composite materials. There is also a clear recent interest in nanotechnology, the development of nanofibres and fibre orientation and alignment effects in hexaferrite fibres, and composites with carbon nanotubes (CNT). One of the most exciting developments has been the discovery of single phase magnetoelectric/multiferroic hexaferrites, firstly Ba 2Mg 2Fe 12O 22 Y ferrite at cryogenic temperatures, and now Sr 3Co 2Fe 24O 41 Z ferrite at room temperature. Several M, Y, Z and U ferrites have now been characterised as room temperature multiferroics, and are discussed here. Current developments in all these key areas will be discussed in detail in Sections 7-11 of this review, and for this reason now is the appropriate time for a fresh and critical appraisal of the synthesis, properties and applications of hexagonal ferrites. © 2012 Elsevier Ltd. All rights reserved. Source

Cardoso D.,University of Aveiro | Teixeira-Dias F.,University of Edinburgh
International Journal of Impact Engineering | Year: 2016

The number of victims of attacks from improvised explosive devices (IED), especially from roadside bombs where explosively formed projectiles (EFP) are frequently used, has steeply increased until 2011. Understanding these threats, how they are built and predicting how they interact with targets is of utmost importance. For this purpose it is first necessary to understand how EFPs are formed and what parameters influence their behaviour and performance. The work in this paper proposes and describes a numerical simulation methodology that allows to reproduce the conditions of formation and ballistic capabilities of explosively formed projectiles. Different EFP configurations, materials and detonation conditions are evaluated and assessed against the performance (e.g. stable flight velocity) of the resulting projectile. The model proposed is based on a generic EFP with an aspect ratio of approximately 1 and a case/base thickness of 5 mm. The dynamic interactions between the various components of the EFP are established through specific contact algorithms that allow to interpolate the resulting pressure from detonation to the remaining components, resulting in their acceleration and consequent deformation. The model is validated against experimental observations and afterwards used to assess the influence of the liner materials and thickness, high-explosive, number and off-centre distance of detonators. The performance of the EFPs is quantified from their configuration and a set of non-dimensional geometrical parameters. It is shown that the thickness (and thickness variability) of the liner is one of the most important factors, along with the off-centre distance of the detonator(s). Within the materials and range of parameters tested, the most performant and aggressive EFP has a liner with thickness between 4 and 7% of its diameter, a copper liner and dynamite high-explosive (HE). © 2016 Elsevier Ltd. All rights reserved. Source

Kichakova O.,University of Oldenburg | Kunz J.,University of Oldenburg | Radu E.,University of Aveiro | Shnir Y.,University of Oldenburg
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We construct new finite-energy regular solutions in Einstein-Yang-Mills-SU(2) theory. They are static, axially symmetric and approach at infinity the anti-de Sitter spacetime background. These configurations are characterized by a pair of integers (m,n), where m is related to the polar angle and n to the azimuthal angle, being related to the known flat-space monopole-antimonopole chains and vortex rings. Generically, they describe composite configurations with several individual components, possessing a nonzero magnetic charge, even in the absence of a Higgs field. Such Yang-Mills configurations exist already in the probe limit, with the AdS geometry supplying the attractive force needed to balance the repulsive force of Yang-Mills gauge interactions. The gravitating solutions are constructed by numerically solving the elliptic Einstein-DeTurck-Yang-Mills equations. The variation of the gravitational coupling constant α reveals the existence of two branches of gravitating solutions which bifurcate at some critical value of α. The lower-energy branch connects to the solutions in the global AdS spacetime, while the upper branch is linked to the generalized Bartnik-McKinnon solutions in asymptotically flat spacetime. Also, a spherically symmetric, closed-form solution is found as a perturbation around the globally anti-de Sitter vacuum state. © 2014 American Physical Society. Source

Mishra S.K.,Pondicherry University | Ferreira J.M.F.,University of Aveiro | Kannan S.,Pondicherry University
Carbohydrate Polymers | Year: 2015

Bionanocomposite coatings with antimicrobial activity comprising polyvinyl alcohol (PVA)-capped silver nanoparticles embedded in chitosan (CS) matrix were developed by a green soft chemistry synthesis route. Colloidal sols of PVA-capped silver nanoparticles (AgNPs) were synthesized by microwave irradiating an aqueous solution comprising silver nitrate and PVA. The bionanocomposites were prepared by adding an aqueous solution of chitosan to the synthesized PVA-capped AgNPs sols in appropriate ratios. Uniform bionanocomposite coatings with different contents of PVA-capped AgNPs were deposited onto titanium substrates by "spread casting" followed by solvent evaporation. Nanoindentation and antimicrobial activity tests performed on CS and bionanocomposites revealed that the incorporation of PVA-capped AgNPs enhanced the overall functional properties of the coatings, namely their mechanical stability and bactericidal activity against Escherichia coli and Staphylococcus aureus. The coated specimens maintained their antimicrobial activity for 8 h due to the slow sustained release of silver ions. The overall benefits for the relevant functional properties of the coatings were shown increase with increasing contents of PVA-capped AgNPs in the bionanocomposites. © 2015 Elsevier Ltd. All rights reserved. Source

Fernandes F.A.,University of Aveiro
Accident; analysis and prevention | Year: 2013

This paper tries to make an overview of the work carried out by scientific community in the area of road helmets safety. In an area that is constantly being pushed forward by market competition, self-awareness of danger and tighter standards, several research groups around the world have contributed to safety gear improvement. In this work concepts related to head impact protection and energy absorption are explained. It also makes reference to the theories related to the development of helmets, as well as to the different existing types nowadays. The materials that are typically used in impact situations and new design concepts are also approached. In addition, it is presented a literature review of current--and most commonly used--helmet test standards, along with new tests and helmet concepts to assess the effects of rotational motion. In a non-restrictive, and never up-to-date report, a state-of-art review on road helmets safety is done, with a special insight into brain injury, helmet design and standards. Copyright © 2013 Elsevier Ltd. All rights reserved. Source

Granadeiro J.P.,University of Aveiro | Brickle P.,South Atlantic Environmental Research Institute | Catry P.,Eco ethology Research Unit
Animal Conservation | Year: 2014

Fisheries can have profound impacts on the structure and functioning of marine ecosystems and affect seabird populations. For seabirds, impacts can include direct mortality in fishing gear, but fisheries also represent an abundant source of food that may otherwise be inaccessible. Previous studies with seabirds have revealed the occurrence of individual foraging specializations, and therefore in scavenging species some individuals may have a higher propensity to feed on fisheries discharges than the rest of the population. Here we used recently developed techniques (spatio-temporal match of positions) to detect interactions between black-browed albatrosses Thalassarche melanophris and fishing vessels, and also stable isotope analysis of tissues with different turnovers, to investigate long-term individual specialization in fishery waste products. We combined global positioning system tracking data from 89 birds with vessel monitoring system data from the entire fleet operating around the Falklands Islands, in 2009 and 2011. Interactions with vessels (freezer/factory bottom trawlers) occurred in 15 out of 89 independent albatross trips. Among individuals tracked in both years, those that associated with fisheries in 2009 were not more likely to do so again in 2011. Carbon and nitrogen isotopic signatures in whole blood and feathers of albatrosses that interacted with trawlers were similar to those of individuals that did not. Also, we found no correlation between feather and blood isotopic ratios of carbon or nitrogen, indicating no long-term consistency in the isotopic niche of study birds. These results suggest no specialization of individual albatrosses with regard to fisheries. Studies of other albatrosses have also failed to show long-term trophic consistency, which may indicate that scavenging albatrosses, a group particularly threatened by fisheries activity, do not specialize in discards. Therefore, any management actions leading to a reduction of discards will be beneficial, decreasing the numbers of birds behind vessels and consequently the likelihood of incidental mortality. © 2013 The Zoological Society of London. Source

Jin Z.,Max Planck Institute for Polymer Research | Tkach A.,Johannes Gutenberg University Mainz | Tkach A.,University of Aveiro | Casper F.,Johannes Gutenberg University Mainz | And 8 more authors.
Nature Physics | Year: 2015

Spin-dependent conduction in metals underlies all modern magnetic memory technologies, such as giant magnetoresistance (GMR). The charge current in ferromagnetic transition metals is carried by two non-mixing populations of sp-band Fermi-level electrons: one of majority-spin and one of minority-spin. These electrons experience spin-dependent momentum scattering with localized electrons, which originate from the spin-split d-band. The direct observation of magnetotransport under such fundamental conditions, however, requires magnetotransport measurements on the same timescale as the electron momentum scattering, which takes place in the sub-100 fs regime. Using terahertz electromagnetic probes, we directly observe the magnetotransport in a metallic system under the fundamental conditions, and determine the spin-dependent densities and momentum scattering times of conduction electrons. We show that traditional measurements significantly underestimate the spin asymmetry in electron scattering, a key parameter responsible for effects such as GMR. Furthermore, we demonstrate the possibility of magnetic modulation of terahertz waves, along with heat- and contact-free GMR readout using ultrafast terahertz signals. © 2015 Macmillan Publishers Limited. All rights reserved. Source

Da Silva S.P.M.,National Laboratory of Energy and Geology | Da Silva S.P.M.,University of Aveiro | Morais A.R.C.,National Laboratory of Energy and Geology | Bogel-Lukasik R.,National Laboratory of Energy and Geology
Green Chemistry | Year: 2014

The CO2-assisted autohydrolysis was used for wheat straw treatments at temperatures ranging from 180 to 210 °C and an initial CO 2 pressure of 60 bar. The study was performed using three different mixture loadings, such as 250 g of H2O/25 g of wheat straw, 150 g of H2O/15 g of wheat straw and 75 g of H2O/7.5 g of wheat straw. The in situ formed carbonic acid was found to result in a higher dissolution of xylose as well as XOS (xylo-oligosaccharides) in comparison to CO2-free pre-treatments under the same conditions (temperature and LSR). The effect of CO2 concentration was also investigated to address the issue of CO2 involved in the reaction that allows to significantly increase the XOS content. At 210 °C with a mixture loading of 75 g of H2O/7.5 g of wheat straw, XOS were present in the liquor at a concentration of 15.75 g L-1. However, with more severe conditions more degradation products (mainly furfural) were detected (in the liquor and the recovered gas phase from depressurization after the reaction). Glucan was mainly retained in the solid phase (containing up to 64%) together with Klason lignin (maximum dissolution of 18%). The dissolved XOS in the liquid phase are proposed to be used in other applications, either directly, such as prebiotic ingredients, or indirectly, after post-hydrolysis to biofuel production through C5 sugars' fermentation. © 2014 The Royal Society of Chemistry. Source

Perez-Coll D.,CSIC - Institute of Ceramics and Glass | Nunez P.,University of La Laguna | Frade J.R.,University of Aveiro
Journal of Power Sources | Year: 2013

Ce1-xSmxO2-δ powders (x = 0.1, 0.2, 0.3) were prepared by a freeze-drying method, preserving monophasic fluorites when precursors were annealed between 375 and 1600 °C. Dried precursor powders were calcined at 375 °C for 4 h and sintered at 1600 °C for 10 h yielding gas-tight ceramics with densifications >95%. The oxygen-electrochemical permeability measurements were employed to study the oxygen flux under moderate oxidizing conditions which was directly related to the onset of residual electronic conductivity. In the experimental process the charge transport through the membrane was due to the ambipolar conductivity, which was controlled by the minor electronic conductivity in Ce 1-xSmxO2-δ. The electronic properties of the pellets were analysed between pO2 ≈ 10-3-0.21 atm in the range 750-900 °C. The estimated ionic transport number, obtained by combination of the electronic conductivity by oxygen permeability and total conductivity by impedance spectroscopy, remained higher than 0.99 in the studied conditions. The electronic conductivity was found dominated by p-type carriers and dependent on the content of Sm in the ceria lattice. Although the overall electrical conductivity under oxidizing conditions is governed by the ionic behaviour, an increased Sm-doping improved the p-type conductivity. © 2012 Elsevier B.V. All rights reserved. Source

Costa L.C.,University of Aveiro | Henry F.,French National Center for Scientific Research
Journal of Non-Crystalline Solids | Year: 2011

The understanding of the charge transport mechanism of the conducting polymers and their composites is important for the successful fabrication of semiconductor devices. In this work, the DC electrical conductivity of carbon black particles in a polystyrene matrix, in the temperature range of 80 to 250 K is examined, for concentrations below the critical percolation concentration. We show that three-dimensional variable range hopping is observed, that is, the temperature behavior of the DC conductivity can be expressed by σ= σ0exp- (T0/T)1/4. From the hopping parameter we obtained the mean hopping distance, the density of active centers and the energy associated with it. © 2011 Elsevier B.V. All rights reserved. Source

Langmuir | Year: 2013

An ecofriendly solid catalyst has been synthesized by anchoring palladium(II) into post synthetically modified metal organic framework IRMOF-3. The pore of IRMOF-3 was first modified with pyridine-2-aldehyde. The amine group of IRMOF-3 upon condensation with pyridine-2-aldehyde afforded a bidentate Schiff base moiety in the porous matrix. The Schiff base moieties were used to anchor palladium(II) ions. The prepared catalyst has been characterized by UV-vis, IR spectroscopy, X-ray powder diffraction, and nitrogen sorption measurements. Framework structure of the catalyst is not being destroyed in the multistep synthesis procedure as evidenced in X-ray powder diffraction studies. The catalyst has shown high activity toward the Suzuki and Stille cross-coupling reaction in 20% H2O/EtOH and EtOH medium, respectively, at 80 C. The immobilized complex did not leach or decompose during the catalytic reactions, showing practical advantages over the homogeneous catalysis. © 2013 American Chemical Society. Source

Dias A.C.,University of Aveiro
International Journal of Life Cycle Assessment | Year: 2014

Purpose: Forest residues are becoming an increasingly important bioenergy feedstock. This study evaluates the environmental impacts associated with the production of fuel chips from eucalypt logging residues in Portugal, in order to identify the supply chains and machinery that bring the best environmental performance. Besides, the stages and operations with the largest environmental impact are identified. Methods: Life cycle assessment methodology is used starting with forest management up to delivery of chips to power plant. Three different configurations for logging residue processing were simulated as follows: roadside chipping of loose residues, terminal chipping of loose residues, and terminal chipping of bundled residues. In addition, the use of different equipment for tree felling and extraction of logging residue was considered the default impact assessment methodology was the CML. In a sensitivity analysis, calculations were performed using characterization factors recommended by the International Reference Life Cycle Data System (ILCD). Different allocation criteria were tested for partitioning the environmental burdens between wood and forest residues produced during the stage of forest management. Results and discussion: Roadside chipping of loose residues seems to have less impacts regardless of the equipment used in tree felling and residue forwarding. However, for photochemical oxidant formation, this is not the case when trees are felled with a chainsaw when the CML methodology is applied. For the systems with terminal chipping, the better option will depend both on type of machinery used and distances traveled between the forest site and the power plant the forest management stage has a relevant contribution to all the supply chains analyzed. Chipping and bundling have also important impacts, as well as forwarding when this operation is accomplished with a modified farm tractor. Moreover, transports have a significant impact when loose residues are chipped in a terminal. Conclusions: The choice of the allocation method between wood and residues affects significantly the absolute results, but it is irrelevant when the objective is to select the best supply chain configuration the results obtained are valid for the input data considered, which rely on average values representative of the current most typical practices in Portugal. However, this methodology can also be applied as a decision supporting tool to select the supply chain with the best environmental performance on a case by case basis, using site-specific data. © 2013 Springer-Verlag Berlin Heidelberg. Source

Garcia de Maria J.M.,Technical University of Madrid | Bairi A.,GTE | Costa V.A.F.,University of Aveiro
International Journal of Heat and Mass Transfer | Year: 2010

New Nu-Ra correlations are proposed to evaluate the steady-state natural convection heat transfer taking place in air-filled enclosures of parallelogrammic section. The thermal conditions and dimensions of the cavities treated in the present work lead to high values of the Rayleigh number, reaching 3×109. The cavities considered are formed by two vertical active walls connected by a closing adiabatic channel. The cold wall is maintained isotherm at temperature Tc while the hot one consists of 5 bands, alternately isotherm at temperature Th and adiabatic. The upper and lower walls of the channel are inclined at an angle α with respect to the horizontal. This angle is either positive (hot wall below the level of the cold one) or negative, giving rise respectively to a conducting or insulating cavity in the convective sense of the term. A detailed steady-state 2D numerical study is carried out with the finite volume method and is accompanied with surface temperature experimental measurements. A good agreement between the experimental and numerical results is found in terms of the global heat exchanges and hence of the convective transfer. The dependence of the mean Nusselt number is presented as a function of the inclination angle α and of the Rayleigh number Ra and confirm the convective diode effect taking place. Correlations of the type Nu{combining low line}{combining low line}α=k(α)Ran, suitable for -60°≤α≤+60°, are proposed for the range 5×103≤Ra≤3×109 corresponding to diverse engineering applications. © 2010 Elsevier Ltd. Source

Bonekamp N.A.,University of Aveiro
Methods in molecular biology (Clifton, N.J.) | Year: 2013

Peroxisomes and mitochondria are essential subcellular organelles in mammals. Interestingly, recent studies have elucidated that these highly dynamic and plastic organelles exhibit a much closer interrelationship than previously assumed. Peroxisomes and mitochondria are metabolically linked organelles, which are cooperating and cross-talking. They share key components of their division machinery and cooperate in antiviral signaling and defense. As peroxisomal alterations in metabolism, biogenesis, dynamics, and proliferation have the potential to influence mitochondrial morphology and functions (and vice versa), there is currently great interest in the detection of both organelles under different experimental conditions. Here, we present protocols used successfully in our laboratory for the dual detection of peroxisomes and mitochondria in cultured mammalian cells. We address double immunofluorescence and fluorescence-based techniques as well as reagents to investigate organelle dynamics, morphological alterations, and organelle-specific targeting of proteins. In addition, we describe the application of diaminobenzidine cytochemistry on cultured cells to specifically label peroxisomes in ultrastructural studies. Source

Arjmandzadeh R.,Payame Noor University | Santos J.F.,University of Aveiro
International Journal of Earth Sciences | Year: 2014

The Dehsalm Cu-Mo-bearing porphyritic granitoids belong to the Lut Block volcanic-plutonic belt (central eastern Iran). These rocks range in composition from gabbro-diorite to granite, with dominance of monzonites and quartz monzonites, and have geochemical features of high-K calc-alkaline to shoshonitic volcanic arc suites. Primitive mantle-normalized trace element spider diagrams display strong enrichment in large-ion lithophile elements such as Rb, Ba and Cs and depletions in some high-field strength elements, e.g., Nb, Ti, Y and HREE. Chondrite-normalized plots display significant LREE enrichments, high LaN/YbN and a lack of Eu anomaly. High Sr/Y and La/Yb ratios of Dehsalm intrusives reveal that, despite their K-rich composition, these granitoids show some resemblances with adakitic rocks. A Rb-Sr whole rock-feldspar-biotite age of 33 ± 1 Ma was obtained in a quartz monzonite sample and coincides, within error, with a previous geochronological result in Chah-Shaljami granitoids, further northwest within the Lut Block. (87Sr/86Sr)i and εNdi isotopic ratios range from 0.70481 to 0.70508 and from +1.5 to +2.5, respectively, which fits into a supra-subduction mantle wedge source for the parental melts and indicates that crustal contribution for magma diversification was of limited importance. Sr and Nd isotopic compositions together with major and trace element geochemistry point to an origin of the parental magmas by melting of a metasomatized mantle source, with phlogopite breakdown playing a significant role in the geochemical fingerprints of the parental magmas; small amounts of residual garnet in the mantle source also help to explain some trace element patterns. Geochemical features of Dehsalm porphyries and its association with Cu-Mo mineralization agree with a mature continental arc setting related to the convergence of Afghan and Lut plates during Oligocene. © 2013 The Author(s). Source

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

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

Marichy C.,University of Aveiro | Pinna N.,Humboldt University of Berlin
Coordination Chemistry Reviews | Year: 2013

Carbon-based nanomaterials demonstrated to be highly suitable as support for the elaboration of heterostructures. Atomic layer deposition (ALD) proved to be a technique of choice for the coating of nanostructured carbon materials. These heterostructures find applications in various areas such as electronics, sensors and energy storage and conversion. Because the chemical inertness of the graphitic carbon inhibits the initiation of ALD film growth, numerous surface functionalization approaches have been investigated in order to provide the required nucleation sites. The different strategies employed for the ALD onto carbon nanotubes, graphene, graphite and other nanostructured carbon materials (e.g. carbon black, fibers) are reviewed. The peculiarity of ALD for tailoring the chemical, structural and morphological properties of the deposited material are discussed. Finally, in order to highlight the importance of this class of materials, possible applications in catalysis and gas sensing devices are also reviewed. © 2013 Elsevier B.V. Source

Shvartsman V.V.,University of Duisburg - Essen | Dkhil B.,Ecole Centrale Paris | Kholkin A.L.,University of Aveiro
Annual Review of Materials Research | Year: 2013

Ferroelectric relaxors continue to be one of the most mysterious solid-state materials. Since their discovery by Smolenskii and coworkers, there have been many attempts to understand the properties of these materials, which are exotic, yet useful for applications. On the basis of the numerous experimental data, several theories have been established, but none of them can explain all the properties of relaxors. The recent advent of piezoresponse force microscopy (PFM) has allowed for polarization mapping on the surface of relaxors with subnanometer resolution. This development thus leads to the question of whether the polar nanoregions that contribute to diffuse X-ray scattering and a range of macroscopic properties can be visualized. This review summarizes recent advancements in the application of PFM to a number of ferroelectric relaxors and provides a tentative explanation of the peculiar polarization distributions related to the intriguing physical phenomena in these materials. © Copyright © 2013 by Annual Reviews. All rights reserved. Source

Fajin J.L.C.,University of Porto | Gomes J.R.B.,University of Aveiro | Cordeiro M.N.D.S.,University of Porto
Langmuir | Year: 2013

Sampaio M.O.P.,University of Aveiro
Journal of High Energy Physics | Year: 2012

We perform a parton level study of angular correlations, in higher dimensional black hole scenarios at the LHC. We start by discussing some features of the angular spectrum in the high energy limit using the geometrical optics approximation. This allows us to recover the high energy limit of the Hawking fluxes. Then we use the full Hawking angular fluxes on the brane, for a singly rotating Myers-Perry black hole, to motivate the construction of various angular observables as to maximise the angular asymmetries due to rotation. This is finally adapted to a parton level simulation using the CHARYBDIS2 generator. We explore two types of variables based on: axis reconstruction and two-particle angular correlators. We find energy cuts which have the potential to help identify the effects of rotation in semi-classical rotating black hole events at the LHC during the 14 TeV run, especially for spin-1 particles. © 2012 SISSA. Source

Barros D.,University of Aveiro | Barbieri E.,Institute Pesca
Mundo da Saude | Year: 2012

The objective of this study was to evaluate the concentrations of trace elements, such as cadmium, lead, copper, zinc and nickel in sediments and oysters of the species Crassostrea brasiliana (bivalve quite abundant and of great economic value to the region) and taking into account that the choice of these nature may reflect specific environmental conditions and, from then on, diagnose quality for cultivation in this region, in particular in relation to food security and still provide for long and medium-term effects of disturbances. The Pb, relative to other metals analyzed, 75% of the sampled points predominated and their surface distribution 0.137 ± 0.015; 0.127 ± 0.006; 0.127 ± 0.015 and 0.030 ± 0.052 ppm, for order of points sampled. Already the concentration in oysters followed in the order Zn > Cu > Pb > Ni and Cd missing in all the samples collected. Source

Ramalho J.P.P.,University of Evora | Gomes J.R.B.,University of Aveiro | Illas F.,University of Barcelona

This article reviews the different density functional theory (DFT) methods available in the literature for dealing with dispersion interactions and recent applications of DFT approaches including van der Waals corrections in the study of the interaction of atoms and molecules with several different surfaces. Focus is given to the interaction of atoms and molecules with metal, metal oxide and graphite surfaces or more complex systems. It will be shown that DFT approaches including van der Waals corrections present significant advances over standard exchange-correlation functionals for treating systems dominated by weak interactions. © 2013 The Royal Society of Chemistry. Source

Ribas de Pouplana L.,Barcelona Institute for Research in Biomedicine | Ribas de Pouplana L.,Catalan Institution for Research and Advanced Studies | Santos M.A.S.,University of Aveiro | Zhu J.-H.,Tsinghua University | And 3 more authors.
Trends in Biochemical Sciences | Year: 2014

The translation of genes into functional proteins involves error. Mistranslation is a known cause of disease, but, surprisingly, recent studies suggest that certain organisms from all domains of life have evolved diverse pathways that increase their tolerance of translational error. Although the reason for these high error rates are not yet clear, evidence suggests that increased mistranslation may have a role in the generation of diversity within the proteome and other adaptive functions. Error rates are regulated, and there appears to be an optimal mistranslation rate that varies by organism and environmental condition. Advances in unbiased interrogation of error types and experiments involving wild organisms may help our understanding of the potentially adaptive roles for protein translation errors. © 2014 Elsevier Ltd. Source

Cancelo-Gonzalez J.,University of Santiago de Compostela | Rial-Rivas M.E.,University of Aveiro | Diaz-Fierros F.,University of Santiago de Compostela
International Journal of Wildland Fire | Year: 2013

Laboratory experiments were carried out to explore the effect of thermal shocks (as occur during fire) and simulated rainfall events on cation leaching dynamics in an organic rich Leptic Umbrisol soil. The soil samples were collected in the field using specially designed lysimeter boxes that allow sampling and application of thermal shock treatments and simulated rainfall while keeping the soil structure unaltered. The soil temperature during the thermal shocks and degree-hours of accumulated heat were determined, and cation (Na+, K+, Ca2+ and Mg2+) leaching was measured in surface runoff (0-cm depth) and subsurface flow (12-cm depth) samples collected from the lysimeter boxes. Important differences were found in cation leaching in relation to thermal shock: monovalent cation leaching from the soil above 200°C (68 degree-hours) and divalent cations leaching above 220°C (195 degree-hours) was higher than that seen in other treatments. In general, the amount of cations leached increased with the severity of the thermal shock; however, under moderate conditions, there was a decrease in cation leaching, mainly of monovalent ions. The exchangeable cation losses by leaching in the intense heat treatments were ∼80%. © IAWF 2013. Source

Fernandes M.E.,University of Aveiro | Leemans D.,Free University of Colombia | Mixer M.,Free University of Colombia
Journal of Combinatorial Theory. Series A | Year: 2012

There is a well-known correspondence between abstract regular polytopes and string C-groups. In this paper, for each d≥. 3, a string C-group with d generators, isomorphic to an alternating group of degree n is constructed (for some n≥. 9), or equivalently an abstract regular d-polytope, is produced with automorphism group Alt(n). A method that extends the CPR graph of a polytope to a different CPR graph of a larger (or possibly isomorphic) polytope is used to prove that various groups are themselves string C-groups. © 2011 Elsevier Inc. Source

Odziehjewicz T.,University of Aveiro
Lecture Notes in Electrical Engineering | Year: 2013

In this work we study three types of partial variable order fractional operators. Using integration by parts formulas for variable order fractional integrals, we prove necessary optimality condition of Euler-Lagrange type for multi-dimensional isoperimteric problem. © 2013 Springer International Publishing Switzerland. Source

Costa V.A.F.,University of Aveiro | Raimundo A.M.,University of Coimbra
International Journal of Heat and Mass Transfer | Year: 2010

Mixed convection in a square enclosure with a rotating cylinder centered within it is numerically studied. Depending on the rotation of the cylinder, the natural and forced convection effects can be combined or opposite. However, due to the complex flow structure assumed by the flow, in some conditions the combined effects do not lead to the maximum overall heat transfer crossing the enclosure. The rotating cylinder participates on both the conductive and convective heat transfer processes, and exchanges heat with the fluid naturally, without imposition of a thermal condition at its surface. It is explored the influence of the cylinder through its radius, rotating velocity, thermal conductivity and thermal capacity on the resulting mixed convection problem. Thermal field is visualized using the isotherms, the flow structure is visualized through the streamlines, and the heat transfer process is visualized through the heatlines. For the first time, these visualization tools are applied to a moving solid. The overall thermal performance of the enclosure is analyzed through the overall Nusselt number. For a better understanding of the participation of the cylinder on the heat transfer process, the local heat exchanged between the cylinder surface and the fluid is also analyzed. Results clearly show how the rotating cylinder affects the thermal performance of the enclosure, and how the thermophysical properties of the cylinder are important on the overall heat transfer process across the enclosure. © 2009 Elsevier Ltd. All rights reserved. Source

Fajin J.L.C.,University of Porto | Cordeiro M.N.D.S.,University of Porto | Gomes J.R.B.,University of Aveiro
Chemical Communications | Year: 2011

Several pure and Ag-doped gold surfaces were used as models of nanoporous gold catalysts where O2 was suggested to be activated. Density functional theory (DFT) calculations show that residual Ag on Au is able to promote adsorption and to dissociate thermodynamically favorable O2 with high rate constants. © 2011 The Royal Society of Chemistry. Source

Fischer M.,University of Hamburg | Fischer M.,University College London | Gomes J.R.B.,University of Aveiro | Froba M.,University of Hamburg | Jorge M.,University of Porto
Langmuir | Year: 2012

We present a new approach for modeling adsorption in metal-organic frameworks (MOFs) with unsaturated metal centers and apply it to the challenging propane/propylene separation in copper(II) benzene-1,3,5-tricarboxylate (CuBTC). We obtain information about the specific interactions between olefins and the open metal sites of the MOF using quantum mechanical density functional theory. A proper consideration of all the relevant contributions to the adsorption energy enables us to extract the component that is due to specific attractive interactions between the π-orbitals of the alkene and the coordinatively unsaturated metal. This component is fitted using a combination of a Morse potential and a power law function and is then included into classical grand canonical Monte Carlo simulations of adsorption. Using this modified potential model, together with a standard Lennard-Jones model, we are able to predict the adsorption of not only propane (where no specific interactions are present), but also of propylene (where specific interactions are dominant). Binary adsorption isotherms for this mixture are in reasonable agreement with ideal adsorbed solution theory predictions. We compare our approach with previous attempts to predict adsorption in MOFs with open metal sites and suggest possible future routes for improving our model. © 2012 American Chemical Society. Source

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. Source

Simao J.E.,University of Aveiro
Portugaliae Electrochimica Acta | Year: 2015

Communication by Prof. Dr. João Evangelista Simão when receiving the SPE Award for his outstanding scientific career and for his contribution to the Portuguese Electrochemical Society at the XIX Meeting of the Portuguese Electrochemical Society and XVI Iberic Meeting of Electrochemistry. © 2016, Portugaliae Electrochimica Acta. All Rights Reserved. Source

Gandini A.,University of Aveiro | Pasquini D.,Federal University of Uberlandia
Industrial Crops and Products | Year: 2012

This review covers both physical and chemical modifications of cellulose fibre surface and their impact on the properties of the ensuing papers. It is not restricted to actual industrial operations, but also deals instead with ongoing research in this area, which appears promising in terms of possible applications to papermaking. © 2011 Elsevier B.V. Source

Polonia A.R.,University of Aveiro
Microbial ecology | Year: 2014

Coral reefs are among the most diverse and productive ecosystems in the world. Most research has, however, focused on eukaryotes such as corals and fishes. Recently, there has been increasing interest in the composition of prokaryotes, particularly those inhabiting corals and sponges, but these have mainly focused on bacteria. There have been very few studies of coral reef Archaea, despite the fact that Archaea have been shown to play crucial roles in nutrient dynamics, including nitrification and methanogenesis, of oligotrophic environments such as coral reefs. Here, we present the first study to assess Archaea in four different coral reef biotopes (seawater, sediment, and two sponge species, Stylissa massa and Xestospongia testudinaria). The archaeal community of both sponge species and sediment was dominated by Crenarchaeota, while the seawater community was dominated by Euryarchaeota. The biotope explained more than 72% of the variation in archaeal composition. The number of operational taxonomic units (OTUs) was highest in sediment and seawater biotopes and substantially lower in both sponge hosts. No "sponge-specific" archaeal OTUs were found, i.e., OTUs found in both sponge species but absent from nonhost biotopes. Despite both sponge species hosting phylogenetically distinct microbial assemblages, there were only minor differences in Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathways. In contrast, most functional pathways differed significantly between microbiomes from sponges and nonhost biotopes including all energy metabolic pathways. With the exception of the methane and nitrogen metabolic pathway, all energy metabolic pathways were enriched in sponges when compared to nonhost biotopes. Source

Bystrov V.S.,University of Aveiro | Bystrov V.S.,Russian Academy of Sciences
Physica B: Condensed Matter | Year: 2014

The molecular modeling and molecular dynamics of polarization switching for the ferroelectric films model of polyvinylidene fluoride (PVDF) are investigated at the nanoscale. We consider a molecular model of PVDF film, consisting of two and four a chains [-CH2-CF2-]n limited by n=6 elementary units. The first-principle approach is applied to the switching and kinetics of these models. Two types of behavior were established for PVDF chains: simultaneous and sequential rotation in high and low electric fields. Kinetics of sequential polarization switching shows a homogeneous critical behavior in the low electric field with a critical point at Landau-Ginzburg- Devonshire (LGD) coercive field E=EC. This type of kinetics demonstrates a kink-like behavior for polarization solitary wave propagation. The simultaneous type of kinetics demonstrates the total domain-like polarization switching, corresponding to exponential behavior of switching time in high electric field as for bulk samples. Corresponding LGD intrinsic coercive field for a two-chain and four-chains model is EC∼2.0 GV/m with revealing size effect. Obtained results show common quantum nature of PVDF chains switching phenomena - the quantum interaction of the PVDF molecular orbitals under applied electric field at the nanoscale level. The results obtained are compared with experimental data. © 2013 Elsevier B.V. All rights reserved. Source

Chieng S.,National University of Malaysia | Carreto L.,University of Aveiro | Nathan S.,National University of Malaysia
BMC Genomics | Year: 2012

Background: Burkholderia pseudomallei is a facultative intracellular pathogen of phagocytic and non-phagocytic cells. How the bacterium interacts with host macrophage cells is still not well understood and is critical to appreciate the strategies used by this bacterium to survive and how intracellular survival leads to disease manifestation.Results: Here we report the expression profile of intracellular B. pseudomallei following infection of human macrophage-like U937 cells. During intracellular growth over the 6 h infection period, approximately 22 % of the B. pseudomallei genome showed significant transcriptional adaptation. B. pseudomallei adapted rapidly to the intracellular environment by down-regulating numerous genes involved in metabolism, cell envelope, motility, replication, amino acid and ion transport system and regulatory function pathways. Reduced expression in catabolic and housekeeping genes suggested lower energy requirement and growth arrest during macrophage infection, while expression of genes encoding anaerobic metabolism functions were up regulated. However, whilst the type VI secretion system was up regulated, expression of many known virulence factors was not significantly modulated over the 6hours of infection.Conclusions: The transcriptome profile described here provides the first comprehensive view of how B. pseudomallei survives within host cells and will help identify potential virulence factors and proteins that are important for the survival and growth of B. pseudomallei within human cells. © 2012 Chieng et al.; licensee BioMed Central Ltd. Source

Asgher M.,Aligarh Muslim University | Khan M.I.R.,Aligarh Muslim University | Anjum N.A.,Aligarh Muslim University | Anjum N.A.,University of Aveiro | Khan N.A.,Aligarh Muslim University
Protoplasma | Year: 2015

A range of man-made activities promote the enrichment of world-wide agricultural soils with a myriad of chemical pollutants including cadmium (Cd). Owing to its significant toxic consequences in plants, Cd has been one of extensively studied metals. However, sustainable strategies for minimising Cd impacts in plants have been little explored. Plant growth regulators (PGRs) are known for their role in the regulation of numerous developmental processes. Among major PGRs, plant hormones (such as auxins, gibberellins, cytokinins, abscisic acid, jasmonic acid, ethylene and salicylic acid), nitric oxide (a gaseous signalling molecule), brassinosteroids (steroidal phytohormones) and polyamines (group of phytohormone-like aliphatic amine natural compounds with aliphatic nitrogen structure) have gained attention by agronomist and physiologist as a sustainable media to induce tolerance in abiotic-stressed plants. Considering recent literature, this paper: (a) overviews Cd status in soil and its toxicity in plants, (b) introduces major PGRs and overviews their signalling in Cd-exposed plants, (c) appraises mechanisms potentially involved in PGR-mediated enhanced plant tolerance to Cd and (d) highlights key aspects so far unexplored in the subject area. © 2014, Springer-Verlag Wien. Source

Hausser F.,University of Applied Sciences, Berlin | Lakshtanov E.,University of Aveiro
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

Within the framework of the Lifshitz-Slyozov-Wagner theory of Ostwald ripening, the amount of volume of the second (solid) phase in a liquid solution that is newly formed by recrystallization is investigated. It is shown that in the late stage, the portion of the newly generated volume formed within an interval from time t0 to t is a certain function of t/t0 and an explicit expression of this volume is given. To achieve this, we introduce the notion of the return radius r(t,t0), which is the unique radius of a particle at time t0 such that this particle has - after growing and shrinking - the same radius at time t. We derive a formula for the return radius, which later on is used to obtain the newly formed volume. Moreover, formulas for the growth rate of the return radius and the recrystallized material at time t0 are derived. © 2012 American Physical Society. Source