Showing papers by "University of Coimbra published in 2003"
TL;DR: The importance of biodiversity (below and above ground) is increasingly considered for the cleanup of the metal contaminated and polluted ecosystems, and plants that hyperaccumulate metals have tremendous potential for application in remediation of metals in the environment.
916 citations
TL;DR: The mitochondria have been also implicated as central executioners of cell death, and increased mitochondrial Ca2+ overload as a result of excitotoxicity has been associated with the generation of superoxide and may induce the release of proapoptotic mitochondrial proteins.
Abstract: In recent years we have witnessed a major interest in the study of the role of mitochondria, not only as ATP producers through oxidative phosphorylation but also as regulators of intracellular Ca2+ homeostasis and endogenous producers of reactive oxygen species (ROS). Interestingly, the mitochondria have been also implicated as central executioners of cell death. Increased mitochondrial Ca2+ overload as a result of excitotoxicity has been associated with the generation of superoxide and may induce the release of proapoptotic mitochondrial proteins, proceeding through DNA fragmentation/condensation and culminating in cell demise by apoptosis and/or necrosis. In addition, these processes have been implicated in the pathogenesis of many neurodegenerative diseases, which share several features of cell death: selective brain areas undergo neurodegeneration, involving mitochondrial dysfunction (mitochondrial complexes are affected), loss of intracellular Ca2+ homeostasis, excitotoxicity, and the extracellular or intracellular accumulation of insoluble protein aggregates in the brain.
445 citations
TL;DR: The FTIR and FT-RAMAN spectra of carrageenan and agar, obtained by alkaline extraction from different seaweeds, were recorded in order to identify the type of phycocolloid produced, with special emphasis given to the 500-1500 cm(-1) region, which presents several vibrational modes, sensitive to thetype of polysaccharide and to the types of glycosidic linkage.
302 citations
TL;DR: This paper presents an implementation of Yen’s algorithm, a classical algorithm for ranking the K shortest loopless paths between a pair of nodes in a network, and concludes that in practice this new implementation outperforms two other, Perko's implementation and a straightforward one.
Abstract: Yen’s algorithm is a classical algorithm for ranking the K shortest loopless paths between a pair of nodes in a network. In this paper an implementation of Yen’s algorithm is presented. Both the original algorithm and this implementation present ${\cal O}(Kn(m + n\log n))$
computational complexity order when considering a worst-case analysis. However, computational experiments are reported, which allow to conclude that in practice this new implementation outperforms two other, Perko’s implementation and a straightforward one.
301 citations
TL;DR: The mechanism of electrochemical oxidation of quercetin on a glassy carbon electrode has been studied using cyclic, differential pulse and square wave voltammetry at different pH.
Abstract: The mechanism of electrochemical oxidation of quercetin on a glassy carbon electrode has been studied using cyclic, differential pulse and square-wave voltammetry at different pH. It proceeds in a cascade mechanism, related with the two catechol hydroxyl groups and the other three hydroxyl groups which all present electroactivity, and the oxidation is pH dependent. Quercetin also adsorbs strongly on the electrode surface; and the final oxidation product is not electroactive and blocks the electrode surface. The oxidation of the catechol 3,4-dihydroxyl electron-donating groups, occurs first, at very low positive potentials, and is a two electron two proton reversible reaction. The hydroxyl group oxidized next was shown to undergo an irreversible oxidation reaction, and this hydroxyl group can form a intermolecular hydrogen bond with the neighboring oxygen. The other two hydroxyl groups also have an electron donating effect and their oxidation is reversible.
240 citations
TL;DR: The very recently observed D(*)(sJ)(2317)(+) meson is described as a quasibound scalar csmacr; state in a unitarized meson model, owing its existence to the strong 3P0 Okubo-Zweig-Iizuka-allowed coupling to the nearby S-wave DK threshold.
Abstract: The very recently observed ${D}_{sJ}^{*}(2317{)}^{+}$ meson is described as a quasibound scalar $c\overline{s}$ state in a unitarized meson model, owing its existence to the strong $^{3}P_{0}$ Okubo-Zweig-Iizuka\char21{}allowed coupling to the nearby $S$-wave $DK$ threshold. By the same mechanism, a scalar ${D}_{0}^{*}(2100\char21{}2300)$ resonance is predicted above the $D\ensuremath{\pi}$ threshold. These scalars are the charmed cousins of the light scalar nonet ${f}_{0}(600)$, ${f}_{0}(980)$, ${K}_{0}^{*}(800)$, and ${a}_{0}(980)$, reproduced by the same model. The standard $c\overline{n}$ and $c\overline{s}$ charmed scalars ${D}_{0}$ and ${D}_{s0}$, cousins of the scalar nonet ${f}_{0}(1370)$, ${f}_{0}(1500)$, ${K}_{0}^{*}(1430)$, and ${a}_{0}(1450)$, are predicted to lie at about 2.64 and 2.79 GeV, respectively, both with a width of some 200 MeV.
238 citations
TL;DR: First in vitro evidence to suggest that adenosine A2A receptors may be the molecular target responsible for the observed beneficial effects of caffeine consumption in the development of Alzheimer's disease is observed.
Abstract: Adenosine is a neuromodulator in the nervous system and it has recently been observed that pharmacological blockade or gene disruption of adenosine A2A receptors confers neuroprotection under different neurotoxic situations in the brain. We now observed that coapplication of either caffeine (1–25 μM) or the selective A2A receptor antagonist, 4-(2-[7-amino-2(2-furyl)(1,2,4)triazolo (2,3-a)(1,3,5)triazin-5-ylamino]ethyl)phenol (ZM 241385, 50 nM), but not the A receptor antagonist, 8-cyclopentyltheophylline (200 nM), prevented the neuronal cell death caused by exposure of rat cultured cerebellar granule neurons to fragment 25–35 of β-amyloid protein (25 μM for 48 h), that by itself caused a near three-fold increase of propidium iodide-labeled cells. This constitutes the first in vitro evidence to suggest that adenosine A2A receptors may be the molecular target responsible for the observed beneficial effects of caffeine consumption in the development of Alzheimer's disease.
238 citations
TL;DR: The data obtained show that the enhancement of AChE activity induced by Abeta(25-35) is mediated by oxidative stress, and that vitamin E and NOS inhibitors can have an important role in the maintenance of acetylcholine synaptic levels, thus preventing or improving cognitive and memory functions of AD patients.
228 citations
TL;DR: A framework for using inertial sensor data in vision systems is set, some results obtained, and the unit sphere projection camera model is used, providing a simple model for inertial data integration.
Abstract: This paper explores the combination of inertial sensor data with vision. Visual and inertial sensing are two sensory modalities that can be explored to give robust solutions on image segmentation and recovery of 3D structure from images, increasing the capabilities of autonomous robots and enlarging the application potential of vision systems. In biological systems, the information provided by the vestibular system is fused at a very early processing stage with vision, playing a key role on the execution of visual movements such as gaze holding and tracking, and the visual cues aid the spatial orientation and body equilibrium. In this paper, we set a framework for using inertial sensor data in vision systems, and describe some results obtained. The unit sphere projection camera model is used, providing a simple model for inertial data integration. Using the vertical reference provided by the inertial sensors, the image horizon line can be determined. Using just one vanishing point and the vertical, we can recover the camera's focal distance and provide an external bearing for the system's navigation frame of reference. Knowing the geometry of a stereo rig and its pose from the inertial sensors, the collineations of level planes can be recovered, providing enough restrictions to segment and reconstruct vertical features and leveled planar patches.
221 citations
TL;DR: To increase biomass concentration the positive effect of several factors was evident; a small air flow rate with large bubbles can be more efficient for CO(2) mass transfer (associated to reduced shearing).
217 citations
TL;DR: In this paper, the authors focus mainly on dismissals protection, distinguishing between the themes of employment and unemployment development and labor market dynamics proper, and formalize the link between analyses of levels of and changes in variables.
Abstract: Empirical investigation of the labor market consequences of employment protection has mushroomed since Lazear's (1990) pioneering study. Having sketched the theoretical background, we chart the course of the modern empirical literature. We focus mainly on dismissals protection, distinguishing between the themes of employment and unemployment development and labor market dynamics proper. Our discussion of employment and unemployment largely deals with the effect of employment protection on levels of these outcome indicators. We distinguish between overall and compositional effects (e.g., by demographic group and type of contract), between developing and industrialized nations, and identify some key control variables. Our discussion of labor market dynamics focuses on the speed of adjustment issue and on gross flows. It also formalizes the link between analyses of levels of and changes in variables. At all times potential offsets to the adverse effects of employment protection receive consideration.
TL;DR: The free radical scavenging effectiveness of a bee pollen as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC.
Abstract: Bee-collected pollen (“bee pollen”) is promoted as a health food with a wide range of nutritional and therapeutic properties. The objective of the current study is to evaluate the contribution made through the free radical scavenging capability of bee-collected floval pollens by their flavonoid/phenolics constituents, and to determine whether this capability is affected by aging. The free radical scavenging effectiveness of a bee pollen (EC50) as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC. Each pure floral pollen has been found to possess a consistent EC50 value, irrespective of its geographic origin or date of collection, and the EC50 value is determined to a large extent (ca. 50%) by the nature and the levels of the pollen's flavonoids and phenolic acids. Non-phenolic antioxidants, possibly proteins, account for the balance of the activity. Pollen aging over 3 years is demonst...
20 Jul 2003
TL;DR: The purpose is to determine the importance of several basic reduction techniques on Support Vector Machines, by comparing their relative performance improvement when applied on the standard REUTERS-21578 benchmark.
Abstract: Given a data set and a learning task such as classification, there are two prime motives for executing some kind of data set reduction. On one hand there is the possible algorithm performance improvement. On the other hand the decrease in the overall size of the data set can bring advantages in storage space used and time spent computing. Our purpose is to determine the importance of several basic reduction techniques on Support Vector Machines, by comparing their relative performance improvement when applied on the standard REUTERS-21578 benchmark.
TL;DR: This work addresses the problem of identifying subsets of constraints which, when removed, lead to a consistent system and presents two algorithms to identify such subsets using mixed integer linear programming and linear programming.
TL;DR: In this article, a new set of special functions, which have a wide range of applications from number theory to integrability of nonlinear dynamical systems, is described, and a classification of multiple orthogonal polynomials with respect to classical weights is given based on properties of the corresponding Rodrigues operators.
Abstract: A new set of special functions, which has a wide range of applications from number theory to integrability of nonlinear dynamical systems, is described. We study multiple orthogonal polynomials with respect to p > 1 weights satisfying Pearson's equation. In particular, we give a classification of multiple orthogonal polynomials with respect to classical weights, which is based on properties of the corresponding Rodrigues operators. We show that the multiple orthogonal polynomials in our classification satisfy a linear differential equation of order p + 1. We also obtain explicit formulas and recurrence relations for these polynomials.
TL;DR: The results of the present study suggest that prohibitin is one of the ubiquitinated substrates that makes the sperm mitochondria recognizable by the egg's ubiquitin-proteasome dependent proteolytic machinery after fertilization and most likely facilitates the marking of defective spermatozoa in the epididymis for degradation.
Abstract: Ubiquitination of the sperm mitochondria during spermatogenesis has been implicated in the targeted degradation of paternal mitochondria after fertilization, a mechanism proposed to promote the predominantly maternal inheritance of mitochondrial DNA in humans and animals. The identity of ubiquitinated substrates in the sperm mitochondria is not known. In the present study, we show that prohibitin, a highly conserved, 30- to 32-kDa mitochondrial membrane protein, occurs in a number of unexpected isoforms, ranging from 64 to greater than 185 kDa in the mammalian sperm mitochondria, which are the ubiquitinated substrates. These bands bind antiubiquitin antibodies, displaying a pattern consistent with polyubiquitinated "ladders." Immunoprecipitation of sperm extracts with antiprohibitin antibodies followed by probing of the resultant immunocomplexes with antiubiquitin yields a banding pattern identical to that observed by antiprohibitin Western blot analysis. In fact, the presumably nonubiquitinated 30-kDa prohibitin band shows no antiubiquitin immunoreactivity. We demonstrate that ubiquitination of prohibitin occurs in testicular spermatids and spermatozoa. Ubiquitinated prohibitin molecules also accumulate in the defective fractions of ejaculated spermatozoa, which are thought to undergo surface ubiquitination during epididymal passage. In such sperm fractions, ubiquitin also coprecipitates with tubulin and microtubule-associated proteins, presumably contributed by the axonemes of defective, ubiquitinated spermatozoa. The results of the present study suggest that prohibitin is one of the ubiquitinated substrates that makes the sperm mitochondria recognizable by the egg's ubiquitin-proteasome dependent proteolytic machinery after fertilization and most likely facilitates the marking of defective spermatozoa in the epididymis for degradation.
TL;DR: A modification of the Marching Cubes algorithm for isosurfacing is proposed, with the intent of improving the representation of the surface in the interior of each grid cell, which correctly models the topology of the trilinear interpolant within the cell and which is robust under perturbations of the data and threshold value.
Abstract: This paper proposes a modification of the Marching Cubes algorithm for isosurfacing, with the intent of improving the representation of the surface in the interior of each grid cell. Our objective is to create a representation which correctly models the topology of the trilinear interpolant within the cell and which is robust under perturbations of the data and threshold value. To achieve this, we identify a small number of key points in the cell interior that are critical to the surface definition. This allows us to efficiently represent the different topologies that can occur, including the possibility of "tunnels." The representation is robust in the sense that the surface is visually continuous as the data and threshold change in value. Each interior point lies on the isosurface. Finally, a major feature of our new approach is the systematic method of triangulating the polygon in the cell interior.
TL;DR: In this article, Fatigue crack propagation tests with single tensile peak overloads have been performed in 6082-T6 aluminium alloy at several baseline Δ K levels and stress ratios of 0.05 and 0.25.
TL;DR: In this paper, the authors integrate the available information to provide a theoretical interpretation of the recent physicochemical and biological changes in the Mondego estuarine ecosystem, which will be further used as basic framework for the development of a structurally dynamic model.
TL;DR: This work uses both model dependent and independent techniques to assess the difference between dissolution profiles in which ibuprofen, in the form of uncoated pellets, is used as a model drug.
University of Copenhagen1, Stanford University2, University of Texas at San Antonio3, Medical College of Wisconsin4, University of Cincinnati5, Detroit Medical Center6, University of Arizona7, University of Iowa8, University of Kansas9, University of Miami10, Grady Memorial Hospital11, Main Line Health12, University of Pittsburgh13, Veterans Health Administration14, Rochester General Health System15, Washington University in St. Louis16, University of Colorado Denver17, University of Pennsylvania18, University of Texas Medical Branch19, Vanderbilt University20, University of Maryland, Baltimore21, North Shore-LIJ Health System22, LSU Health Sciences Center Shreveport23, Women & Children's Hospital of Buffalo24, NorthShore University HealthSystem25, Cleveland Clinic26, University Medical Center27, Tufts University28, University of Toledo29, University of California, Davis30, Rhode Island Hospital31, University of South Alabama32, McGill University33, Foothills Medical Centre34, Université de Montréal35, Trillium Health Centre36, University of Alberta37, Laval University38, University of Western Ontario39, University of British Columbia40, Innsbruck Medical University41, University of Helsinki42, University of Eastern Finland43, Uppsala University44, University of Paris45, Lille University of Science and Technology46, Centre Hospitalier Universitaire de Nice47, Heidelberg University48, University of Cologne49, Ruhr University Bochum50, Charité51, University of Duisburg-Essen52, Ludwig Maximilian University of Munich53, University of Münster54, University of Genoa55, University of Perugia56, University of Groningen57, Erasmus University Rotterdam58, University of Lausanne59, University of Bern60, University of Zurich61, University of Dundee62, Aberdeen Royal Infirmary63, Nottingham City Hospital64, Western Infirmary65, University of Lisbon66, University of Coimbra67, University of Barcelona68, Autonomous University of Barcelona69, Complutense University of Madrid70, University of Melbourne71, Royal Melbourne Hospital72, Alfred Hospital73, North Shore Hospital74, Christchurch Hospital75, Auckland City Hospital76, Stellenbosch University77
TL;DR: The SPARCL Study is a prospective, multi-centre, double-blind, randomised, placebo-controlled trial designed to evaluate the effect of statin treatment in secondary stroke prevention.
Abstract: Evidence suggests that statin therapy reduces the risk of stroke in patients with coronary heart disease (CHD), but its benefit for patients with cerebrovascular disease and no history of CHD remains
TL;DR: CHX is effective against E faecalis in vitro and further in vivo studies are needed to confirm the value of CHX in clinical treatment.
Abstract: Objective We sought to assess the efficacy of chlorhexidine (CHX) and calcium hydroxide, Ca(OH) 2 , against Enterococcus faecalis in vitro. Study design The effect of CHX (0.2% and 2% in gel or solution) and Ca(OH) 2 (alone or with 0.2% CHX gel) was evaluated by using the agar diffusion test and an in vitro human root inoculation method, to measure zone of inhibition or bacterial growth with optical density analysis, respectively. For optical density analysis, samples from infected root canals were collected after 7 days of medication and were cultured for 24 hours in brain-heart infusion to detect viable bacteria. Results In the agar diffusion test, CHX was effective against E faecalis in a concentration-dependent fashion, but Ca(OH) 2 alone had no effect. In the root canal inoculation test, CHX was significantly more effective against E faecalis than Ca(OH) 2 was ( P Conclusions CHX is effective against E faecalis in vitro. Further in vivo studies are needed to confirm the value of CHX in clinical treatment.
TL;DR: In this review considerations are made regarding the structure-activity relationships of cationic liposome/DNA complexes and the key formulation parameters influencing the features of lipoplexes are presented and discussed in terms of their effect on biological activity.
Abstract: The use of an efficient carrier for nucleic acid-based medicines is considered to be a determinant factor for the successful application of gene therapy. The drawbacks associated with the use of viral vectors, namely those related with safety problems, have prompted investigators to develop alternative methods for gene delivery, cationic lipid-based systems being the most representative. Despite extensive research in the last decade on the use of cationic liposomes as gene transfer vectors and the development of elegant strategies to enhance their biological activity, these systems are still far from being viable alternatives to the use of viral vectors in gene therapy. In this review considerations are made regarding the structure-activity relationships of cationic liposome/DNA complexes and the key formulation parameters influencing the features of lipoplexes are presented and discussed in terms of their effect on biological activity. Particular emphasis is given to the interaction of the lipoplexes with serum components as well as to novel strategies developed to circumvent difficulties that may emerge upon iv administration of the complexes. Finally, since the ability of the lipoplexes to be stored while preserving their transfection activity is a crucial issue for the repeated use of such carriers, approaches reported on the improvement of their physical stability are also reviewed.
12 Oct 2003
TL;DR: In this paper, the authors proposed two different approaches for the diagnosis of stator faults in direct torque control (DTC) induction motor drives, based on motor current spectrum analysis and multiple reference frames theory.
Abstract: This paper addresses the subject of stator fault diagnosis in direct torque control (DTC) induction motor drives. The particularities of the behavior of a DTC drive, when in the presence of inter-turn short circuits, are exploited, thus allowing the proposal of two different approaches for the diagnosis of this type of fault. One of the proposed diagnostic techniques is the well known motor current spectrum analysis. It is demonstrated that in a DTC induction motor drive, with stator inter-turn short circuits, the action of the torque and flux controllers introduce a strong third harmonic in the motor supply currents, which can be used to detect this type of fault. The other diagnostic technique is based on the multiple reference frames theory, recently proposed by the authors for the diagnosis of stator faults in line-connected motors. Here, its use is exploited in the diagnosis of stator faults in DTC induction motor drives. Simulation and experimental results demonstrate the effectiveness of the two proposed techniques for the diagnosis of stator faults but emphasize the fact that the multiple reference frames technique is the preferred one when the residual asymmetries of the motor are not negligible.
TL;DR: A(1) receptor immunoreactivity was evident in the postsynaptic density together with NMDA receptor subunits 1, 2A and 2B and with N-and P/Q-type calcium channel immunore activity, emphasizing the importance of A( 1) receptors in the control of dendritic integration.
TL;DR: In this paper, Springtail communities (Hexapoda: Collembola) were sampled in the Morvan Nature Regional Park (Burgundy, France) in six land use units (LUUs) 1 km2 each, which had been selected in order to cover a range of increasing intensity of land use.
Abstract: Springtail communities (Hexapoda: Collembola) were sampled in the Morvan Nature Regional Park (Burgundy, France) in six land use units (LUUs) 1 km2 each, which had been selected in order to cover a range of increasing intensity of land use. Human influence increased from LUU 1 (old deciduous forest) to LUU 6 (agricultural land mainly devoted to cereal crops), passing by planted coniferous forests (LUU 2) and variegated landscapes made of cereal crops, pastures, hay meadows, conifer plantations and small relict deciduous groves in varying proportion (LUUs 3–5). Sixteen core samples were taken inside each LUU, at intersections of a regular grid. Species composition, species richness and total abundance of collembolan communities varied according to land use and landscape properties. Land use types affected these communities through changes in the degree of opening of woody landscape (woodland opposed to grassland) and changes in humus forms (measured by the Humus Index). A decrease in species richness and total abundance was observed from old deciduous forests to cereal crops. Although the regional species richness was not affected by the intensification gradient (40–50 species were recorded in every LUU), a marked decrease in local biodiversity was observed when the variety of land use types increased. In variegated landscapes the observed collapse in local species richness was not due to a different distribution of land use types, since it affected mainly woodland areas. Results indicated the detrimental influence of the rapid afforestation of previous agricultural land, which did not afford time for the development of better adapted soil animal communities.
TL;DR: The present study provides evidence that the disappearance of macrophyte beds, as a result of ongoing eutrophication, constitutes a major threat to the sustainability of the estuarine ecosystem.
Abstract: Secondary production of a macrobenthic community at an intertidal mudflat was estimated for 33 successive months. Sampling was carried out along a eutrophication gradient, including non-eutrophied Zostera meadows, an intermediate muddy area, and a strongly eutrophied sand-muddy flat, where macroalgal blooms of Enteromorpha spp. usually occur. The Zostera meadows were always the most productive habitat (145–225 g ash-free dry weight m−2 year−1). In the short term, the macroalgal bloom benefited the total estuarine production by enhancing the annual production in the eutrophied area. Nevertheless, our results show that this increase was short lived and in no way sufficient to match the production in the Zostera meadows. In the long term, the present study provides evidence that the disappearance of macrophyte beds, as a result of ongoing eutrophication, constitutes a major threat to the sustainability of the estuarine ecosystem.
TL;DR: The Sexual Dysfunctional Beliefs Questionnaire as discussed by the authors is a 40-item self-reported measure constituted by two versions (female and male) rated on a five point likert scale.
Abstract: The aim of the present article is to present a new instrument, specially developed to assess beliefs about sexuality that are supposed to be closely related with the development of sexual disorders. Using a cognitive theory perspective we hypothesized that sexual behaviour and its problems are in someway related to the way we think about sexuality, our beliefs and our expectations. Although some questionnaires of sexual attitude, information and beliefs already exist, there is, until now, no specific measure oriented to assess both male and female sexual dysfunctional beliefs related to aetiology. The Sexual Dysfunctional Beliefs Questionnaire is a 40-item self-reported measure constituted by two versions (female and male) rated on a five point likert scale. Both male and female versions present satisfactory test-retest reliability (r=0.73 and r=0.80 respectively), and internal consistency (Cronbach's alpha=0.93 for male and 0.81 for the female version). Studies of convergent validity show a relationship ...
TL;DR: In this paper, reinforced concrete jacketing of columns is assessed, considering different practical aspects: anchoring and slab crossing of the added longitudinal reinforcement, interface surface preparation, spacing of added stirrups, temporary shoring of the structure and addition of new concrete.
Abstract: Summary Strengthening and rehabilitation by reinforced concrete jacketing of columns is assessed, considering different practical aspects: anchoring and slab crossing of the added longitudinal reinforcement, interface surface preparation, spacing of added stirrups, temporary shoring of the structure and addition of new concrete. Recent research on these topics and the main recommendations to achieve good RC jacketing are presented.
TL;DR: This approach is illustrated to tackle uncertainty and imprecision associated with the coefficients of an input–output energy-economy planning model, aimed at providing decision support to decision makers in the study of the interactions between the energy system and the economy on a national level.