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Showing papers by "Technical University of Madrid published in 2007"


Journal ArticleDOI
TL;DR: In this paper, the mechanical behavior of polymer-matrix composites unidirectionally reinforced with carbon or glass fibers subjected to compression perpendicular to the fibers was studied using computational micromechanics using finite element analysis of a representative volume element of the microstructure idealized as a random dispersion of parallel fibers embedded in the polymeric matrix.

490 citations


Journal ArticleDOI
TL;DR: In this article, the existence of global bounded classical solutions is proved under the assumption that either the space dimension does not exceed two, or that the logistic damping effect is strong enough.
Abstract: This paper deals with a nonlinear system of two partial differential equations arising in chemotaxis, involving a source term of logistic type The existence of global bounded classical solutions is proved under the assumption that either the space dimension does not exceed two, or that the logistic damping effect is strong enough Also, the existence of global weak solutions is shown under rather mild conditions Secondly, the corresponding stationary problem is studied and some regularity properties are given It is proved that in presence of certain, sufficiently strong logistic damping there is only one nonzero equilibrium, and all solutions of the non-stationary system approach this steady state for large times On the other hand, for small logistic terms some multiplicity and bifurcation results are established

482 citations


Journal ArticleDOI
TL;DR: In this article, a framework for managing the risk of water scarcity based on preparedness rather than a crisis approach is proposed, where the importance of local management at the basin level is emphasized, but the potential benefits depend on the appropriate multi-institutional and multi-stakeholder coordination.
Abstract: The Mediterranean region is undergoing rapid local and global social and environmental changes. All indicators point to an increase in environmental and water scarcity problems with negative implications towards current and future sustainability. Water management in Mediterranean countries is challenged these pressures and needs to evolve to reach the target of increasing population with reliable access to freshwater established by the Millennium Development Goals. This paper first reviews and evaluates current and future social and environmental pressures on water resources, including climate change. The results show that pressures are not homogeneous across the region and sectors of water use. Second the paper evaluates the adaptation strategies to cope with water scarcity, including technology, use of strategic groundwater, and management. Finally, the paper proposes a framework for managing the risk of water scarcity based on preparedness rather than a crisis approach. The importance of local management at the basin level is emphasized, but the potential benefits depend on the appropriate multi-institutional and multi-stakeholder coordination.

445 citations


Journal ArticleDOI
TL;DR: Comparative transcriptomic analyses identified a set of common irx upregulated genes, including a number of abscisic acid (ABA)–responsive, defense-related genes encoding antibiotic peptides and enzymes involved in the synthesis and activation of antimicrobial secondary metabolites.
Abstract: Cellulose is synthesized by cellulose synthases (CESAs) contained in plasma membrane-localized complexes. In Arabidopsis thaliana, three types of CESA subunits (CESA4/IRREGULAR XYLEM5 [IRX5], CESA7/IRX3, and CESA8/IRX1) are required for secondary cell wall formation. We report that mutations in these proteins conferred enhanced resistance to the soil-borne bacterium Ralstonia solanacearum and the necrotrophic fungus Plectosphaerella cucumerina. By contrast, susceptibility to these pathogens was not altered in cell wall mutants of primary wall CESA subunits (CESA1, CESA3/ISOXABEN RESISTANT1 [IXR1], and CESA6/IXR2) or POWDERY MILDEW-RESISTANT5 (PMR5) and PMR6 genes. Double mutants indicated that irx-mediated resistance was independent of salicylic acid, ethylene, and jasmonate signaling. Comparative transcriptomic analyses identified a set of common irx upregulated genes, including a number of abscisic acid (ABA)-responsive, defense-related genes encoding antibiotic peptides and enzymes involved in the synthesis and activation of antimicrobial secondary metabolites. These data as well as the increased susceptibility of ABA mutants (abi1-1, abi2-1, and aba1-6) to R. solanacearum support a direct role of ABA in resistance to this pathogen. Our results also indicate that alteration of secondary cell wall integrity by inhibiting cellulose synthesis leads to specific activation of novel defense pathways that contribute to the generation of an antimicrobial-enriched environment hostile to pathogens.

380 citations


Journal ArticleDOI
TL;DR: An experimental demonstration of an integrated biochemical sensor based on a slot-waveguide microring resonator that detects a minimal refractive index variation of 2x10(-4) RIU.
Abstract: We report an experimental demonstration of an integrated biochemical sensor based on a slot-waveguide microring resonator. The microresonator is fabricated on a Si3N4-SiO2 platform and operates at a wavelength of 1.3 μm. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n=1.33 to 1.42. A linear shift of the resonant wavelength with increasing ambient refractive index of 212 nm/refractive index units (RIU) is observed. The sensor detects a minimal refractive index variation of 2×10−4 RIU.

378 citations


Journal ArticleDOI
TL;DR: In this paper, the authors addressed the uncertainties and sources of variation in projected impacts of climate change on agriculture and terrestrial ecosystems by applying different impact models at site, regional and continental scales, and by separating the variation in simulated relative changes in ecosystem performance into the different sources of uncertainty and variation using analyses of variance.
Abstract: The uncertainties and sources of variation in projected impacts of climate change on agriculture and terrestrial ecosystems depend not only on the emission scenarios and climate models used for projecting future climates, but also on the impact models used, and the local soil and climatic conditions of the managed or unmanaged ecosystems under study. We addressed these uncertainties by applying different impact models at site, regional and continental scales, and by separating the variation in simulated relative changes in ecosystem performance into the different sources of uncertainty and variation using analyses of variance. The crop and ecosystem models used output from a range of global and regional climate models (GCMs and RCMs) projecting climate change over Europe between 1961–1990 and 2071–2100 under the IPCC SRES scenarios. The projected impacts on productivity of crops and ecosystems included the direct effects of increased CO2 concentration on photosynthesis. The variation in simulated results attributed to differences between the climate models were, in all cases, smaller than the variation attributed to either emission scenarios or local conditions. The methods used for applying the climate model outputs played a larger role than the choice of the GCM or RCM. The thermal suitability for grain maize cultivation in Europe was estimated to expand by 30–50% across all SRES emissions scenarios. Strong increases in net primary productivity (NPP) (35–54%) were projected in northern European ecosystems as a result of a longer growing season and higher CO2 concentrations. Changing water balance dominated the projected responses of southern European ecosystems, with NPP declining or increasing only slightly relative to present-day conditions. Both site and continental scale models showed large increases in yield of rain-fed winter wheat for northern Europe, with smaller increases or even decreases in southern Europe. Site-based, regional and continental scale models showed large spatial variations in the response of nitrate leaching from winter wheat cultivation to projected climate change due to strong interactions with soils and climate. The variation in simulated impacts was smaller between scenarios based on RCMs nested within the same GCM than between scenarios based on different GCMs or between emission scenarios.

372 citations


Journal ArticleDOI
TL;DR: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) as discussed by the authors is the scientific camera system onboard the Rosetta spacecraft, which consists of a high resolution Narrow Angle Camera (NAC) and a wide angle Camera (WAC) units accompanied by three electronics boxes.
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 67P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250–1000 nm at an angular resolution of 18.6 μrad px−1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 μrad px−1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countries.

328 citations


Journal ArticleDOI
TL;DR: The physico-chemical factors that favour the growth of these undesirable yeasts, the techniques used to detect the presence of Brettanomyces/Dekkera species in wines, and the analytical techniques for monitoring the formation of volatile ethylphenols are described.

305 citations


Journal ArticleDOI
TL;DR: Results demonstrate that although both correction techniques considered lead to significant improvements in accounting for respiratory motion artefacts in the lung fields, the elastic-transformation-based correction leads to a more uniform improvement across the lungs for different lesion sizes and locations.
Abstract: Respiratory motion in emission tomography leads to reduced image quality. Developed correction methodology has been concentrating on the use of respiratory synchronized acquisitions leading to gated frames. Such frames, however, are of low signal-to-noise ratio as a result of containing reduced statistics. In this work, we describe the implementation of an elastic transformation within a list-mode-based reconstruction for the correction of respiratory motion over the thorax, allowing the use of all data available throughout a respiratory motion average acquisition. The developed algorithm was evaluated using datasets of the NCAT phantom generated at different points throughout the respiratory cycle. List-mode-data-based PET-simulated frames were subsequently produced by combining the NCAT datasets with Monte Carlo simulation. A non-rigid registration algorithm based on B-spline basis functions was employed to derive transformation parameters accounting for the respiratory motion using the NCAT dynamic CT images. The displacement matrices derived were subsequently applied during the image reconstruction of the original emission list mode data. Two different implementations for the incorporation of the elastic transformations within the one-pass list mode EM (OPL-EM) algorithm were developed and evaluated. The corrected images were compared with those produced using an affine transformation of list mode data prior to reconstruction, as well as with uncorrected respiratory motion average images. Results demonstrate that although both correction techniques considered lead to significant improvements in accounting for respiratory motion artefacts in the lung fields, the elastic-transformation-based correction leads to a more uniform improvement across the lungs for different lesion sizes and locations.

273 citations


Journal ArticleDOI
TL;DR: It is concluded that rice can be used successfully in broiler diets and that heat processing of the cereal does not have any beneficial effect on broiler performance, and that moderate amounts of fiber in low-fiber diets might improve chick performance at early ages by reducing gizzard pH and improving the utilization of nutrients.

257 citations


Journal ArticleDOI
TL;DR: In this paper, the transient analysis of an AlGaN/GaN high-electron mobility transistor (HEMT) device is presented, revealing clear mechanisms of current collapse and related dispersion effects.
Abstract: In this paper, the transient analysis of an AlGaN/GaN high-electron mobility transistor (HEMT) device is presented. Drain-current dispersion effects are investigated when gate or drain voltages are pulsed. Gate-lag and drain-lag turn-on measurements are analyzed, revealing clear mechanisms of current collapse and related dispersion effects. Numerical 2-D transient simulations considering surface traps effects in a physical HEMT model have also been carried out. A comparison between experimental and theoretical results is shown. The presence of donor-type traps acting as hole traps, due to their low energy level of 0.25 eV relative to the valence band, with densities >1e20 cm-3 (>5e12 cm-2), uniformly distributed at the HEMT surface, and interacting with the free holes that accumulated at the top surface due to piezoelectric fields, accounts for the experimentally observed effects. Time constants next to 10 ms are deduced. Some additional features in the measured transient currents, with faster time constants, could not be associated with surface states

Book ChapterDOI
01 Jan 2007
TL;DR: The paper deals with the possibilities of control and optimization of the technological process of aluminum anodicoxidation using neural networks and Design of Experiments in order to evaluate and monitor the influence of the input factors on the resulting AAO (Anodic aluminum oxide) film thickness.
Abstract: The paper deals with the possibilities of control andoptimization of the technological process of aluminum anodicoxidation using neural networks and Design of Experiments inorder to evaluate and monitor the influence of the input factorson the resulting AAO (Anodic aluminum oxide) film thickness. Italso compares the usage of different neural unit to define therelationship between individual inputs factors and their mutualinteractions on the resulting AAO film thickness at the monitoredcurrent density 4.00 A·dm-2, 5.00 A·dm-2 and 6.00 A·dm-2. Keywords—neural network; artificial intellience; surfacetreatment; anodizing;

Journal ArticleDOI
TL;DR: In this article, a selection of more than 20 technical documents including standards from National Standards Bodies was analysed, for the use of unstabilised earth for constructing walls, including particle size distribution, binding force, shrinkage, presence of cracks and compactibility.

Journal ArticleDOI
TL;DR: In this article, the average value of the strain energy density over a well-defined volume is used to predict the static strength of U-notched specimens under mixed-mode conditions due to combined bending and shear loads.
Abstract: The averaged value of the strain energy density over a well-defined volume is used to predict the static strength of U-notched specimens under mixed-mode conditions due to combined bending and shear loads. The volume is centered in relation to the maximum principal stress present on the notch edge, by rigidly rotating the crescent-shaped volume already used in the literature to analyse U- and V-shaped notches subject to mode I loading. The volume size depends on the ultimate tensile strength σu and the fracture toughness KIC of the material. In parallel, an experimental programme was performed. All specimens are made of polymethyl-metacrylate (PMMA), a material which exhibits quasi-brittle behaviour at -60°C. Good agreement is found between experimental data for the critical loads to failure and theoretical predictions based on the constancy of the mean strain energy density over the control volume.

Book ChapterDOI
24 Mar 2007
TL;DR: This paper develops a generic framework for the automatic cost analysis of sequential Java bytecode and generates cost relations which define at compile-time the cost of programs as a function of their input data size.
Abstract: Cost analysis of Java bytecode is complicated by its unstructured control flow, the use of an operand stack and its object-oriented programming features (like dynamic dispatching) This paper addresses these problems and develops a generic framework for the automatic cost analysis of sequential Java bytecode Our method generates cost relations which define at compile-time the cost of programs as a function of their input data size To the best of our knowledge, this is the first approach to the automatic cost analysis of Java bytecode

Journal ArticleDOI
TL;DR: In this paper, the authors deal with the normalisation of the modules data by considering a base that allows for obtaining a "per unit" representation, and show the influence of these resistances in the module behaviour.

Journal ArticleDOI
TL;DR: Overexpression of VvFT in transgenic Arabidopsis plants generates early flowering phenotypes similar to those produced by FT supporting a role for this gene in flowering promotion, which is consistent with the biological roles assigned to similar genes in other species.
Abstract: The FT/TFL1 gene family encodes proteins with similarity to phosphatidylethanolamine binding proteins which function as flowering promoters and repressors. We show here that the FT/TFL1 gene family in Vitis vinifera is composed of at least five genes. Sequence comparisons with homologous genes identified in other dicot species group them in three major clades, the FT, MFT and TFL1 subfamilies, the latter including three of the Vitis sequences. Gene expression patterns are in agreement with a role of VvFT and VvMFT as flowering promoters; while VvTFL1A, VvTFL1B and VvTFL1C could be associated with vegetative development and maintenance of meristem indetermination. Overexpression of VvFT in transgenic Arabidopsis plants generates early flowering phenotypes similar to those produced by FT supporting a role for this gene in flowering promotion. Overexpression of VvTFL1A does not affect flowering time but the determination of flower meristems, strongly altering inflorescence structure, which is consistent with the biological roles assigned to similar genes in other species.

Journal ArticleDOI
TL;DR: In this article, the authors present a numerical implementation of cohesive crack model for the analysis of concrete fracture based on the strong discontinuity approach, where a simple central force model is used for the stress vs. crack opening law.

Journal ArticleDOI
TL;DR: No relationship was found between the level of physical activity and lipid‐metabolic index in either sex, but there was an inverse relationship between the lipid‐ Metabolic index and aerobic capacity in males and females, and in females, a favorable lipid‐ metabolic index was associated with greater muscle strength.
Abstract: Introduction and objectives. To determine whether the level of physical activity or physical fitness (i.e., aerobic capacity and muscle strength) in Spanish adolescents influences lipid and metabolic profiles. Methods. From a total of 2859 Spanish adolescents (age 13.0-18.5 years) taking part in the Diet and Appraisal of Nutrition State in Adolescents 460 (248 male, 212 female) were randomly selected for blood analysis. Their level of physical activity was determined by questionnaire. Aerobic capacity was assessed using the Course-Navette test. Muscle strength was evaluated using flexed arm. A lipidmetabolic cardiovascular risk index was derived from the levels of triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and glucose. Results. No relationship was found between the level of physical activity and lipid‐metabolic index in either sex. In contrast, there was an inverse relationship between the lipid‐metabolic index and aerobic capacity in males (P=.003) after adjustment for physical activity level and muscle strength. In females, a favorable lipid‐metabolic index was associated with greater muscle strength (P=.048) after adjustment for aerobic capacity.

Journal ArticleDOI
TL;DR: In this article, a two-stage clustering methodology was developed and applied to back trajectories arriving in three European cities: Athens, Madrid and Birmingham, which experience large, moderate and small numbers of daily PM10 episodes, respectively.


Journal ArticleDOI
TL;DR: In this paper, two fracture criteria are proposed and applied to blunt-notched components made of brittle materials loaded under mixed mode; the former is based on the averaged strain energy density over a given control volume, the latter on the cohesive crack zone model.
Abstract: Two fracture criteria are proposed and applied to blunt-notched components made of brittle materials loaded under mixed mode; the former is based on the averaged strain energy density over a given control volume, the latter on the cohesive crack zone model. In both instances use of the equivalent local mode I hypothesis is made. Only two material properties are needed: the ultimate tensile strength and the fracture toughness. Numerical predictions of rupture loads from the two criteria are compared with experimental measurements from more than 160 static tests with notched beams. The samples are made of PMMA and tested at − 60°C to assure a bulk behaviour almost linear elastic up to rupture. Notch root radii range from 0.2 to 4.0 mm and load mixicity varies from pure mode I to a prevailing mode II. The good agreement between theory and experimental results adds further confidence to the proposed fracture criteria.

Journal ArticleDOI
TL;DR: In this paper, the seismic wave energy, the kinetic energy and the fracture energy, respectively, transferred in the blasting process were calculated from ten production blasts and one single-hole confined blast in two quarries.

Journal ArticleDOI
TL;DR: A phylogenetic analysis of those DOF sequences identified from a variety of representative organisms from different taxonomic groups suggests duplications of an ancestral DOF, probably formed in the photosynthetic eukaryotic ancestor, followed by subsequent neo-, sub-functionalization and pseudogenization processes would have triggered the expansion of the DOF family.
Abstract: This article deals with the origin and evolution of the DOF transcription factor family through a phylogenetic analysis of those DOF sequences identified from a variety of representative organisms from different taxonomic groups: the green unicellular alga Chlamydomonas reinhardtii, the moss Physcomitrella patens, the fern Selaginella moellendorffii, the gymnosperm Pinus taeda, the dicotyledoneous Arabidopsis thaliana and the monocotyledoneous angiosperms Oryza sativa and Hordeum vulgare. In barley, we have identified 26 different DOF genes by sequence analyses of clones isolated from the screening of genomic libraries and of ESTs, whereas a single DOF gene was identified by bioinformatics searches in the Chlamydomonas genome. The phylogenetic analysis groups all these genes into six major clusters of orthologs originated from a primary basal grade. Our results suggest that duplications of an ancestral DOF, probably formed in the photosynthetic eukaryotic ancestor, followed by subsequent neo-, sub-functionalization and pseudogenization processes would have triggered the expansion of the DOF family. Loss, acquisition and shuffling of conserved motifs among the new DOFs likely underlie the mechanism of formation of the distinct subfamilies.

Journal ArticleDOI
TL;DR: Assessment of flowering phenology on the reproductive success of Silene ciliata, a Mediterranean high-mountain plant, across an altitudinal gradient during two climatically contrasting years indicates that water deficit in dry years could threaten the lowland populations of this mountainous species, while high-altitude environments are more stable over time.
Abstract: Summary • Mountain plants are particularly sensitive to climate warming because snowmelt timing exerts a direct control on their reproduction. Current warming is leading to earlier snowmelt dates and longer snow-free periods. Our hypothesis is that high-mountain Mediterranean plants are not able to take advantage of a lengthened snow-free period because this leads to longer drought that truncates the growing season. However, reproductive timing may somewhat mitigate these negative effects through temporal shifts. • We assessed the effects of flowering phenology on the reproductive success of Silene ciliata, a Mediterranean high-mountain plant, across an altitudinal gradient during two climatically contrasting years. • The species showed a late-flowering pattern hampering the use of snowmelt water. Plant fitness was largely explained by the elapsed time from snowmelt to onset of flowering, suggesting a selective pressure towards early flowering caused by soil moisture depletion. The proportion of flowering plants decreased at the lowest population, especially in the drier year. Plants produced more flowers, fruits and seeds at the highest population and in the mild year. • Our results indicate that water deficit in dry years could threaten the lowland populations of this mountainous species, while high-altitude environments are more stable over time.


Journal ArticleDOI
TL;DR: In this article, the effective mechanical behavior of an elasto-plastic matrix reinforced with a random and homogeneous distribution of aligned elastic ellipsoids was obtained by the finite element simulation of a representative volume element (RVE) of the microstructure and by homogenization methods.

Journal ArticleDOI
TL;DR: In this article, a new and very easy method to compute accurate forecasts for electricity prices using mixed models is proposed, combining several prediction methods for which forecasting performance has been checked and compared for a span of several years.
Abstract: Short-run forecasting of electricity prices has become necessary for power generation unit schedule, since it is the basis of every profit maximization strategy. In this article a new and very easy method to compute accurate forecasts for electricity prices using mixed models is proposed. The main idea is to develop an efficient tool for one-step-ahead forecasting in the future, combining several prediction methods for which forecasting performance has been checked and compared for a span of several years. Also as a novelty, the 24 hourly time series has been modelled separately, instead of the complete time series of the prices. This allows one to take advantage of the homogeneity of these 24 time series. The purpose of this paper is to select the model that leads to smaller prediction errors and to obtain the appropriate length of time to use for forecasting. These results have been obtained by means of a computational experiment. A mixed model which combines the advantages of the two new models discussed is proposed. Some numerical results for the Spanish market are shown, but this new methodology can be applied to other electricity markets as well

Journal ArticleDOI
TL;DR: It has been proposed that suboptimal vitamin B6 status is associated with certain diseases that particularly afflict the elderly population: impaired cognitive function, Alzheimer's disease, cardiovascular disease, and different types of cancer.
Abstract: Background: Vitamin B 6 is thought to be a most versatile coenzyme that participates in more than 100 biochemical reactions. It is involved in amino acid and homocysteine metabolism, glucose and lipid metabolism, neurotransmitter production and DNA/RNA synthesis. Vitamin B 6 can also be a modulator of gene expression. Nowadays, clinically evident vitamin B 6 deficiency is not a common disorder, at least in the general population. Nevertheless, a subclinical, undiagnosed deficiency may be present in some subjects, particularly in the elderly. Objective: This review gives a complete overview over the metabolism and interactions of vitamin B 6 . Further, we show which complications and deficiency symptoms can occur due to a lack of vitamin B 6 and possibilities for public health and supplemental interventions. Methods: The database Medline (www.ncvi.nlm.nih.gov) was searched for terms like “vitamin B 6 ”, “pyridoxal”, “cancer”, “homocysteine”, etc. For a complete understanding, we included studies with early findings from the forties as well as recent results from 2006. These studies were summarised and compared in different chapters. Results and conclusion: In fact, it has been proposed that suboptimal vitamin B 6 status is associated with certain diseases that particularly afflict the elderly population: impaired cognitive function, Alzheimer’s disease, cardiovascular disease, and different types of cancer. Some of these problems may be related to the elevated homocysteine concentrations associated to vitamin B 6 deficiency, but there is also evidence for other mechanisms independent of homocysteine by which a suboptimal vitamin B 6 status could increase the risk for these chronic diseases. (Nutr Hosp. 2007;22:7-24)

Journal ArticleDOI
TL;DR: In this paper, the micromechanics of elasto-viscoplastic composites made up of a random and homogeneous dispersion of spherical inclusions in a continuous matrix were studied with two methods.