Showing papers by "University of Minho published in 2002"
TL;DR: In this article, the possibilities of analysis of historic masonry structures are addressed and a set of guidelines is proposed for the analysis of masonry constructions and their experimental behavior is discussed.
Abstract: Is modelling and analysis of historical masonry structures necessary? Is the experimental behaviour of historical masonry constructions known? The answers seem to be ‘yes’, and substantial developments have occurred in recent decades in the challenging issues of conservation and restoration. A key issue is what type of analysis should be used. It seems that all methods are of interest, depending on the actual constraints of the engineering problem. In this paper, the possibilities of analysis of historic structures are addressed and a set of guidelines is proposed.
487 citations
TL;DR: The understanding of the involvement of a mitochondria-dependent apoptotic pathway in S. cerevisiae PCD process will be most useful in the further elucidation of an ancestral pathway common to PCD in metazoans.
Abstract: Evidence is presented that mitochondria are implicated in the previously described programmed cell death (PCD) process induced by acetic acid in Saccharomyces cerevisiae. In yeast cells undergoing a PCD process induced by acetic acid, translocation of cytochrome c (CytC) to the cytosol and reactive oxygen species production, two events known to be proapoptotic in mammals, were observed. Associated with these events, reduction in oxygen consumption and in mitochondrial membrane potential was found. Enzymatic assays showed that the activity of complex bc1 was normal, whereas that of cytochrome c oxidase (COX) was strongly decreased. This decrease is in accordance with the observed reduction in the amounts of COX II subunit and of cytochromes aa3. The acetic acid-induced PCD process was found to be independent of oxidative phosphorylation because it was not inhibited by oligomycin treatment. The inability of S. cerevisiae mutant strains (lacking mitochondrial DNA, heme lyase, or ATPase) to undergo acetic acid-induced PCD and in the ATPase mutant (knockout in ATP10) the absence of CytC release provides further evidence that the process is mediated by a mitochondria-dependent apoptotic pathway. The understanding of the involvement of a mitochondria-dependent apoptotic pathway in S. cerevisiae PCD process will be most useful in the further elucidation of an ancestral pathway common to PCD in metazoans.
373 citations
TL;DR: The cytotoxicity test revealed that SCA and SEVA-C composites have a similar response to the one obtained for SCA polymer, and both types of starch-based polymers exhibit a cytocompatibility that might allow for their use as biomaterials.
327 citations
TL;DR: Workplace bullying is increasingly being recognized as a serious problem in society today; it is also a problem that can be difficult to define and evaluate accurately as mentioned in this paper, which can also make it difficult to evaluate accurately.
312 citations
TL;DR: The design and preparation of novel biodegradable hydrogels developed by the free radical polymerization of acrylamide and acrylic acid, and some formulations with bis-acrylamides, in the presence of a corn starch/ethylene-co-vinyl alcohol copolymer blend (SEVA-C), is reported.
310 citations
07 Aug 2002
TL;DR: Particle swarm is an optimization paradigm for real-valued functions, based on the social dynamics of group interaction, and its application to the training of neural networks is proposed.
Abstract: Particle swarm is an optimization paradigm for real-valued functions, based on the social dynamics of group interaction. We propose its application to the training of neural networks. Comparative tests were carried out, for classification and regression tasks.
274 citations
TL;DR: Several linear programming formulations for the one-dimensional cutting stock and bin packing problems are reviewed, including the models of Kantorovich, Gilmore–Gomory, onecut models, as in the Dyckhoff–Stadtler approach, position-indexed models, and a model derived from the vehicle routing literature.
257 citations
TL;DR: This communication revises recent work developed in the laboratories with the aim of producing 3-D polymeric structures (from starch-based blends) with adequate properties to be used as scaffolds for bone tissue engineering applications.
223 citations
TL;DR: Almost-invariant ratios were common, suggesting that they represent a reliable property of the natural visual environment and a suitable foundation for visual color constancy.
Abstract: For some sets of surfaces, the spatial ratios of cone-photoreceptor excitations produced by light reflected from pairs of surfaces are almost invariant under illuminant changes. These sets include large populations of spectral reflectances, some of which represent individual natural surfaces but not their relative abundances in nature. The aim of this study was to determine whether spatial cone-excitation ratios are preserved under illuminant changes within the natural visual environment. A fast hyperspectral imaging system was used to obtain populations of 640,000 reflectance spectra from each of 30 natural scenes. The statistics of spatial cone-excitation ratios for randomly selected pairs of points in these scenes were determined for two extreme daylights. Almost-invariant ratios were common, suggesting that they represent a reliable property of the natural visual environment and a suitable foundation for visual color constancy.
222 citations
TL;DR: In this article, a micro-mechanical model based on the actual deformations of the basic cell and additional internal deformation modes, with regard to the standard two-step homogenisation procedure is presented.
206 citations
TL;DR: This study indicates that 3-D virtual environments may help students with high spatial aptitude to acquire better conceptual understandings and creates a virtual environment (Virtual Water) for studying phases of matter, phase transitions and atomic orbitals at the final year of high school and first year of university levels.
Abstract: Usually, students learn more if the method of instruction matches their learning style. Since Physics and Chemistry deal with three-dimensional (3-D) objects, the ability to visualize and mentally manipulate shapes is very helpful in their learning. In fact, much of what Physics and Chemistry students know takes the form of images. However, little attention has been given to the pedagogical effectiveness of visual stimuli in those disciplines. Computers are being increasingly used as teaching tools. The new approaches include simulations, multimedia presentations and, more recently, virtual environments. Computer-based worlds are useful to visualize physical and chemical processes allowing for better conceptual understanding. Since 3-D virtual environments need to be explored and evaluated in science education, we have created a virtual environment (Virtual Water) for studying phases of matter, phase transitions and atomic orbitals at the final year of high school and first year of university levels. Based on that work, we discuss the implications of visual learning in designing strategies to cater for differences in learning modes. Our study indicates that 3-D virtual environments may help students with high spatial aptitude to acquire better conceptual understandings. However, only some parameters (interactivity, navigation and 3-D perception) have shown to be relevant and only for some topics. On the other hand, stereoscopic visualizations do not seem to be relevant, with the exception of crystalline structures.
TL;DR: In this paper, a generalized Drazin inverse for ring elements with involution was defined and studied, and a characterization of elements a, b for which aa D = bb D was given.
Abstract: In this paper we define and study a generalized Drazin inverse x D for ring elements x, and give a characterization of elements a, b for which aa D = bb D . We apply our results to the study of EPelements of a ring with involution.
TL;DR: These conclusions, together with the fact that the biofilms were more dense and stable when formed in contact with turbulent flows, favor the design of more compact and efficient biofilm reactors operating in turbulent conditions.
Abstract: A comparison of the effects of laminar versus turbulent flow regime on the characteristics of a single-species biofilm is presented. The study was carried out by growing Pseudomonas fluorescens biofilms in a flow cell and studying the different layers of the biological matrix with a confocal laser-scanning microscope. The following conclusions were obtained: i) a higher concentration of cells was found in the upper layers of the microbial films than in their inner layers, regardless of the flow regime; ii) the fraction of cells in the overall biofilm mass decreased with time as the film grew; and iii) under laminar flow the total number of cells was higher than in biofilms formed under turbulent flow, but the latter had a higher number of cells per unit volume. Such conclusions, together with the fact that the biofilms were more dense and stable when formed in contact with turbulent flows, favor the design of more compact and efficient biofilm reactors operating in turbulent conditions.
TL;DR: It was observed that the compounds obtained from the degradation of ochratoxin A by black aspergilli and by A. ochraceus and A. wentii strains were different, and other fungi frequently isolated from grapes showed significant degradation capabilities.
Abstract: Ochratoxin A is a mycotoxin present in several food products for which levels should be reduced. Chemical, physical, and biological methods have been proposed for the detoxification of mycotoxins, biological methods being the more promising ones. In this report, filamentous fungi isolated from Portuguese grapes were assessed for ochratoxin A degradation capabilities. It was observed that 51 of the 76 tested strains, predominantly aspergillus species, were able to degrade more than 80% of ochratoxin A added to the culture medium and that the most potent species (more than 95% of initial amount) were the black aspergilli, A. clavatus, A. ochraceus, A. versicolor, and A. wentii. Other fungi frequently isolated from grapes, such as Alternaria, Botrytis, Cladosporium, and Penicillium, also showed significant degradation capabilities. It was observed that the compounds obtained from the degradation of ochratoxin A by black aspergilli and by A. ochraceus and A. wentii strains were different.
TL;DR: In this article, the authors determined the relaxation times of the cooperative conformational rearrangements of the amorphous phase in semi-crystalline poly(ethylene terephthalate) (PET) and compared them with those calculated in amorphoung PET.
TL;DR: New partially biodegradable acrylic bone cements based on corn starch/cellulose acetate blends (SCA), prepared by the free radical polymerization of methyl methacrylate and acrylic acid at low temperature are reported.
TL;DR: In this paper, a microfibrillar reinforced composites (MFC) consisting of an isotropic matrix from a lower melting polymer reinforced by micro-fibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding.
Abstract: Microfibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer-polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations, the MFC dogbone samples show impressive mechanical properties-the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short-glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers.
TL;DR: Results exclude dependence of thyroid hormone homeostasis on any major plasma carrier per se and agree with the free hormone hypothesis which states that the biologically significant fraction taken up by the tissues, is the free circulating hormone.
Abstract: Thyroid hormones are essential for normal mammalian development and for normal metabolism. Thyroxine (T4) is the principal product synthesized by the thyroid follicles, and triiodothyronine (T3), the biologically active hormone, derives mainly from tissue T4 deiodination. More than 99% of the circulating hormone is bound to plasma proteins, mainly to thyroxine-binding globulin, transthyretin and albumin in man, and to transthyretin and albumin in rodents. The role of plasma proteins in the transport of hormones to target tissues has, for a long time, been controversial. The liver and the choroid plexus are the major sites of transthyretin synthesis, tissues from which transthyretin is secreted into the blood and the cerebrospinal fluid, respectively. Transthyretin has been proposed to mediate thyroid hormone transfer into the tissues, particularly into the brain across the choroid-plexus-cerebrospinal fluid barrier. Studies in a transthyretin-null mice strain have shown conclusively that transthyretin is not indespensable for thyroid hormones' entry into the brain and other tissues, nor for the maintenance of an euthyroid status. An euthyroid status is also observed in man totally deprived of thyroxine-binding globulin and in rats without albumin. Taken together, these results exclude dependence of thyroid hormone homeostasis on any major plasma carrier per se. This evidence agrees with the free hormone hypothesis which states that the biologically significant fraction, that is taken up by the tissues, is the free circulating hormone.
TL;DR: The immobilization technique provided repeated application of the enzyme even in low concentration, and the hydrogen peroxide generated in the enzymatic reaction was successively used for textile bleaching.
TL;DR: In this article, the authors focus on the prosodic word in European Portuguese (EP) and the relationship between grammar and phonology, its interface with morphology and syntax, and the nature of phonological representations.
Abstract: The subject matter of the dissertation is the prosodic word. It bears on the organization of grammar and phonology, its interface with morphology and syntax, and the nature of phonological representations. Despite the reference to various other languages, it primarily focuses on European Portuguese (EP).
TL;DR: The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors fed with increasing oleic acid concentrations between 2 and 8 gCOD/l.
TL;DR: In this article, an experimental program has been carried out to evaluate the performance of plain concrete and fiber-reinforced concrete under compressive fatigue loading, and the correlation between the secondary creep rate and the fatigue life was investigated.
Abstract: An experimental program has been carried out to evaluate the performance of plain concrete and fiber-reinforced concrete under compressive fatigue loading. Two types of hooked-end steel fibers (30 mm length and 60 mm length) have been tested and their performance compared. The displacements and the acting load were measured during the tests so that several material parameters could be identified and assessed. Wohler diagrams were determined, cyclic creep curves were plotted and the evolution of the secant stiffness was also appraised for the tested materials. The correlation between the secondary creep rate and the fatigue life was investigated. The monotonic stress–strain envelope was compared with fatigue deformations at failure and a good agreement was found between them.
TL;DR: In this article, the authors extend the Altonji and Card framework for analysing the impact of immigrants on natives' wages from two to three labour types and estimate reduced form wage equations for The Netherlands, United Kingdom and Norway.
Abstract: We extend the Altonji and Card (1991) framework for analysing the impact of immigrants on natives' wages from two to three labour types and estimate reduced form wage equations for The Netherlands, United Kingdom and Norway. We find very small effects on natives' wages and no dominant robust patterns of substitution and complementarity. Effects on wages of earlier immigrants are larger but less reliable. Further work should focus on these own effects.
TL;DR: In this paper, the authors argue that real nature conservation can only be attained if geology is integrated into protected area management at the same level of importance as biology and all natural processes are considered together.
Abstract: IntroductionIn most countries, protected area managers are primarily interested in biology (McNeely & Miller 1984; Nelson & Serafin 1997). This perspective is not suitable for effective nature conservation because there is no real separation between geological and biological processes. Geology is important in all kinds of planning projects because geology is part of all natural systems. Understanding of climate, landforms and biodiversity depends on geological studies. Even human habitation and cultural heritage depend on geology. During the last 30 years, numerous studies have shown that biological conservation is essential to the welfare of all human beings. Nevertheless, the concept of geoconservation and preservation of the geological heritage has appeared only recently (Wilson 1994; Sharples 1998; Barettino et al. 1999, 2000; Osborne 2000).I argue that real nature conservation can only be attained if geology is integrated into protected area management at the same level of importance as biology and all natural processes are considered together.
TL;DR: In vitro shoots of sage were established under four different cytokinin supplementations by culturing nodal segments excised from aseptically germinated seedlings, and the highest rates of shoot proliferation and linear shoot growth occurred with the supplementation of 1.5mg/l benzyladenine and 0.05 mg/l dichlorophenoxyacetic acid, while the specific production of total antioxidant phenolics was the lowest.
TL;DR: Six different compounds capable of mediating laccase-catalysed reactions have been tested by cyclic voltammetry and this trend fitted Michaelis-Menten kinetics, which allowed us to give an estimation of the affinity of the fungal laccases for the different mediators.
TL;DR: In this paper, a new technique based on extrusion by using blowing agents in combination with a 50:50 blend of starch/cellulose acetate (SCA) was studied.
TL;DR: In this article, the authors characterized the weathering products of the two-mica Oporto granite in terms of its mineralogical, chemical, geotechnical and physical properties.
Abstract: This paper characterizes the weathering products of the two-mica Oporto granite in terms of its mineralogical, chemical, geotechnical and physical properties. This information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties. In outcrop, the Oporto granite is always weathered and weathering profiles frequently exceed 20 m. Within these profiles, granitic saprolites are composed of quartz, feldspars and some mica with kaolinite and gibbsite as final weathering products. The average percentage of secondary minerals determined by bulk X-ray diffraction (XRD) is low in both weathered rock (2.4%) and saprolite (8.7%). Geotechnically, the saprolites exhibit no or low plasticity (plasticity index, PI≤12%). The skeleton character of the saprolites is reflected in the significant proportion of fines (29.5%
TL;DR: In this article, the authors used X-ray diffraction of granitic saprolites from granitoid rocks of Portugal to study their clay fraction and observations of polished thin sections combined with transmission electron microscopy with energy dispersive spectrometer (SEM-EDS) microanalyses.
Abstract: Saprolites or in situ weathering products from granitoid rocks of Northwest Portugal were studied by means of X-ray diffraction (XRD) of their clay fraction and observations of polished thin sections combined with transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive spectrometer (SEM-EDS) microanalyses. Their principal features are: (1) depths of more than 10 m; (2) mean material loss of 40% as calculated by an isovolumetric method; (3) low clay content (mean value of 7%) and a high degree of mineralogical evolution. The clay fraction is characterized by a predominance of kaolinite and gibbsite, with subordinate 2:1 minerals (illite, chlorite, vermiculitic mixed layers, vermiculite). The significance of the secondary minerals in granitic saprolites from Northwest Portugal is compared to published data from Atlantic Europe. This allows the definition of a climatic zonality for weathering products and identifies ‘arenization’ as an important weathering process.
TL;DR: In this article, the transmission, absorption, spectral and diffuse reflection of indium-tin-oxide (ITO) thin films were measured in some ranges of UV-Vis-NIR.