Showing papers by "Technical University of Madrid published in 2005"

Pre- and postinvasion defenses both contribute to nonhost resistance in Arabidopsis

Abstract: Nonhost resistance describes the immunity of an entire plant species against nonadapted pathogen species. We report that Arabidopsis PEN2 restricts pathogen entry of two ascomycete powdery mildew fungi that in nature colonize grass and pea species. The PEN2 glycosyl hydrolase localizes to peroxisomes and acts as a component of an inducible preinvasion resistance mechanism. Postinvasion fungal growth is blocked by a separate resistance layer requiring the EDS1-PAD4-SAG101 signaling complex, which is known to function in basal and resistance (R) gene-triggered immunity. Concurrent impairment of pre- and postinvasion resistance renders Arabidopsis a host for both nonadapted fungi.

Spatio-temporal nonrigid registration for ultrasound cardiac motion estimation

Abstract: We propose a new spatio-temporal elastic registration algorithm for motion reconstruction from a series of images. The specific application is to estimate displacement fields from two-dimensional ultrasound sequences of the heart. The basic idea is to find a spatio-temporal deformation field that effectively compensates for the motion by minimizing a difference with respect to a reference frame. The key feature of our method is the use of a semi-local spatio-temporal parametric model for the deformation using splines, and the reformulation of the registration task as a global optimization problem. The scale of the spline model controls the smoothness of the displacement field. Our algorithm uses a multiresolution optimization strategy to obtain a higher speed and robustness. We evaluated the accuracy of our algorithm using a synthetic sequence generated with an ultrasound simulation package, together with a realistic cardiac motion model. We compared our new global multiframe approach with a previous method based on pairwise registration of consecutive frames to demonstrate the benefits of introducing temporal consistency. Finally, we applied the algorithm to the regional analysis of the left ventricle. Displacement and strain parameters were evaluated showing significant differences between the normal and pathological segments, thereby illustrating the clinical applicability of our method.

Combustion theory and modeling

Abstract: In honor of the fiftieth anniversary of the Combustion Institute, we are asked to assess accomplishments of theory in combustion over the past fifty years and prospects for the future. The title of our article is chosen to emphasize that development of theory necessarily goes hand-in-hand with specification of a model. Good conceptual models underlie successful mathematical theories. Models and theories are discussed here for deflagrations, detonations, diffusion flames, ignition, propellant combustion, and turbulent combustion. In many of these areas, the genesis of mathematical theories occurred during the past fifty years, and in all of them significant advances are anticipated in the future. Increasing interaction between theory and computation will aid this progress. We hope that, although certainly not complete in topical coverage or reference citation, the presentation may suggest useful directions for future research in combustion theory.

Tunable combline filter with continuous control of center frequency and bandwidth

Abstract: A new combline filter structure with a continuous tunability for both the center frequency and bandwidth is presented in this paper. The passband-width tunability is achieved by placing variable coupling reducers between the filter resonators. The coupling reducers, operating as bandwidth control subnetworks, are designed as detuned resonators made up of a line segment ending in a variable capacitor. The proposed filter structure is experimentally validated with the design, construction in suspended stripline technology, and characterization of a low-cost filter prototype for terrestrial digital video broadcasting receivers operating in the UHF band (470-862 MHz). Other relevant factors, such as the intermodulation distortion produced by the varactors used to control the bandwidth electronically or the power-handling performance of the constructed filter, are also discussed. The reconfigurable filter module described in this paper is very suitable for the design of flexible multifunction receiver subsystems simultaneously supporting signals with a different bandwidth.

Low level of physical fitness in Spanish adolescents. Relevance for future cardiovascular health (AVENA study)

Abstract: Introduction and objectives Several studies have demonstrated that physical fitness in childhood and adolescence is related to cardiovascular risk in adulthood. Current data on the physical fitness of Spanish adolescents are not available. Therefore, the aims of this study were: a) to assess the physical fitness of Spanish adolescents and establish reference values for use in health and educational settings as indicators of cardiovascular health, and b) to determine the percentage of Spanish adolescents below the minimum level of aerobic fitness needed to guarantee future cardiovascular health. Subjects and method The modified EUROFIT battery of tests was used to assess physical fitness in a representative sample of Spanish adolescents (n=2859; 1357 boys and 1502 girls) taking part in the AVENA (Alimentacion y Valoracion del Estado Nutricional de los Adolescentes) study. Results Standard parameters for the physical condition of Spanish adolescents are reported in this study. The 5th percentile for maximum aerobic capacity (Course Navette test) ranged from 2.0–3.3 palier in boys and from 1.4–1.9 palier in girls. The findings indicate that, on the basis of aerobic fitness, approximately 20% of Spanish adolescents have an increased risk of future cardiovascular disease. This subgroup also performed poorly in all other tests of physical fitness used. Conclusions The results reported in this study enable the level of physical fitness in adolescents to be interpreted as an indicator of future cardiovascular health. They also indicate that the physical fitness of Spanish adolescents must be improved to help protect against cardiovascular disease in adulthood. Bajo nivel de forma fisica en los adolescents espanoles. Importancia para la salud cardiovascular futura (Estudio AVENA)

Building legal ontologies with METHONTOLOGY and WebODE

Abstract: This paper presents how to build an ontology in the legal domain following the ontology development methodology METHONTOLOGY and using the ontology engineering workbench WebODE. Both of them have been widely used to develop ontologies in many other domains. The ontology used to illustrate this paper has been extracted from an existing class taxonomy proposed by Breuker, and adapted to the Spanish legal domain.

Integrated program debugging, verification, and optimization using abstract interpretation (and the Ciao system preprocessor)

Abstract: The technique of Abstract Interpretation has allowed the development of very sophisticated global program analyses which are at the same time provably correct and practical. We present in a tutorial fashion a novel program development framework which uses abstract interpretation as a fundamental tool. The framework uses modular, incremental abstract interpretation to obtain information about the program. This information is used to validate programs, to detect bugs with respect to partial specifications written using assertions (in the program itself and/or in system libraries), to generate and simplify run-time tests, and to perform high-level program transformations such as multiple abstract specialization, parallelization, and resource usage control, all in a provably correct way. In the case of validation and debugging, the assertions can refer to a variety of program points such as procedure entry, procedure exit, points within procedures, or global computations. The system can reason with much richer information than, for example, traditional types. This includes data structure shape (including pointer sharing), bounds on data structure sizes, and other operational variable instantiation properties, as well as procedure-level properties such as determinacy, termination, nonfailure, and bounds on resource consumption (time or space cost). CiaoPP, the preprocessor of the Ciao multi-paradigm programming system, which implements the described functionality, will be used to illustrate the fundamental ideas.

Bajo nivel de forma física en los adolescentes españoles. Importancia para la salud cardiovascular futura (Estudio AVENA)

Abstract: Introduccion y objetivos En diversos estudios se ha mostrado la relacion entre el nivel de forma fisica durante la infancia-adolescencia y el riesgo cardiovascular en la edad adulta. Dado que no se dispone de datos relativos al nivel de condicion fisica de los adolescentes espanoles, los objetivos de este estudio son: a) determinar el nivel de condicion fisica de los adolescentes espanoles y establecer valores de referencia que puedan ser utilizados en el medio sanitario y educativo como indicadores de salud cardiovascular, y b) conocer la proporcion de adolescentes espanoles que no alcanza valores de capacidad aerobica indicativos de salud cardiovascular futura. Sujetos y metodo Se ha utilizado la bateria EUROFIT modificada para evaluar la condicion fisica de una muestra representativa de adolescentes espanoles (n = 2.859; 1.357 varones y 1.502 mujeres) procedente del estudio AVENA (Alimentacion y Valoracion del Estado Nutricional de los Adolescentes). Resultados Se han obtenido los valores normativos de condicion fisica de la poblacion adolescente espanola. El rango del percentil 5 respecto a la capacidad aerobica maxima (test de Course Navette) es de 2,0-3,3 y 1,4-1,9 paliers para varones y mujeres, respectivamente. Casi 1 de cada 5 adolescentes presenta riesgo cardiovascular futuro sobre la base de su capacidad aerobica. Este subgrupo de adoles- centes mostro tambien una peor forma fisica que el resto de adolescentes en todas las pruebas fisicas realizadas. Conclusiones Los resultados obtenidos en el presente estudio permiten evaluar e interpretar correctamente el nivel de forma fisica de cualquier adolescente. Los resultados obtenidos indican la necesidad de mejorar el nivel de condicion fisica de los adolescentes espanoles.

MIDDLE-R: Consistent database replication at the middleware level

Abstract: The widespread use of clusters and Web farms has increased the importance of data replication. In this article, we show how to implement consistent and scalable data replication at the middleware level. We do this by combining transactional concurrency control with group communication primitives. The article presents different replication protocols, argues their correctness, describes their implementation as part of a generic middleware, Middle-R, and proves their feasibility with an extensive performance evaluation. The solution proposed is well suited for a variety of applications including Web farms and distributed object platforms.

HKT1 Mediates Sodium Uniport in Roots. Pitfalls in the Expression of HKT1 in Yeast

Abstract: The function of HKT1 in roots is controversial. We tackled this controversy by studying Na+ uptake in barley (Hordeum vulgare) roots, cloning the HvHKT1 gene, and expressing the HvHKT1 cDNA in yeast (Saccharomyces cerevisiae) cells. High-affinity Na+ uptake was not detected in plants growing at high K+ but appeared soon after exposing the plants to a K+-free medium. It was a uniport, insensitive to external K+ at the beginning of K+ starvation and inhibitable by K+ several hours later. The expression of HvHKT1 in yeast was Na+ (or K+) uniport, Na+-K+ symport, or a mix of both, depending on the construct from which the transporter was expressed. The Na+ uniport function was insensitive to external K+ and mimicked the Na+ uptake carried out by the roots at the beginning of K+ starvation. The K+ uniport function only took place in yeast cells that were completely K+ starved and disappeared when internal K+ increased, which makes it unlikely that HvHKT1 mediates K+ uptake in roots. Mutation of the first in-frame AUG codon of HvHKT1 to CUC changed the uniport function into symport. The expression of the symport from either mutants or constructs keeping the first in-frame AUG took place only in K+-starved cells, while the uniport was expressed in all conditions. We discuss here that the symport occurs only in heterologous expression. It is most likely related to the K+ inhibitable Na+ uptake process of roots that heterologous systems fail to reproduce.

Winter disruption of the circadian clock in chestnut

Abstract: Circadian clock performance during winter dormancy has been investigated in chestnut by using as marker genes CsTOC1 and CsLHY, which are homologous to essential components of the central circadian oscillator in Arabidopsis. During vegetative growth, mRNA levels of these two genes in chestnut seedlings and adult plants cycled daily, as expected. However, during winter dormancy, CsTOC1 and CsLHY mRNA levels were high and did not oscillate, indicating that the circadian clock was altered. A similar disruption was induced by chilling chestnut seedlings (to 4°C). Normal cycling resumed when endodormant or cold-treated plants were returned to 22°C. The behavior of CsTOC1 and CsLHY during a cold response reveals a relevant aspect of clock regulation not yet encountered in Arabidopsis.

The DOF protein, SAD, interacts with GAMYB in plant nuclei and activates transcription of endosperm-specific genes during barley seed development.

Abstract: The DOF protein, SAD, previously shown to be a transcriptional activator in barley aleurone cells upon seed germination, also has an important role in gene regulation during endosperm development. mRNA was detected in early (10 days after flowering) developing barley seeds where it accumulated in the starchy endosperm, aleurone cells, nucellar projection, vascular tissues and the immature embryo, as shown by RT-PCR and in situ hybridization analyses. The SAD protein, expressed in bacteria, binds to oligonucleotides containing the prolamine box, 5'-A/TAAAG-3'sequence, derived from the promoter regions of the endosperm-specific genes Hor2 and Itr1, encoding a B-hordein and trypsin-inhibitor BTI-CMe, respectively. SAD competed for the same binding sites with another endosperm-expressed DOF protein, BPBF. Transient expression experiments in co-bombarded developing endosperms demonstrated that SAD trans-activated transcription from Hor2 and Itr1 promoters through binding to the intact DOF motifs. When the two DOF factors are co-bombarded together an additive effect was observed upon the expression of the Itr1 gene. In-frame fusion of the Sad ORF to the reporter green fluorescent protein gene directs the fluorescence expression to the nucleus in transiently transformed onion epidermal layers. The visualization of fluorescence in the nucleus of onion cells, using the bimolecular fluorescent complex (BiFC) approach, has shown the in vivo interaction between SAD and the R2R3MYB protein GAMYB. The interaction in plant cells has also been documented for the DOF protein BPBF and GAMYB, but nuclear interaction could not be detected between BPBF and SAD by this procedure.

Digital channelized receiver based on time-frequency analysis for signal interception

Abstract: A digital channelized receiver is presented for the interception of a wide variety of signals of complex structure, including those with low probability of interception. The receiver is designed from the perspective of the time-frequency analysis. It uses an extended time-frequency representation based on the noncoherent integration of the short-time Fourier transform (STFT) on which the detection system and the encoder work. The encoder includes robust frequency estimation, automatic modulation recognition, and clustering, to handle broadband and simultaneous signals and to prevent out-of-channel detections (a typical phenomenon in channelized receivers). The receiver has been evaluated for a wide range of signals and shows a good performance in terms of detection, estimation, and processing of simultaneous signals. Signals collected from real-life systems and synthetic signals have been utilized.

Mechanical Properties of Melt‐Grown Alumina–Yttrium Aluminum Garnet Eutectics up to 1900 K

Abstract: Alumina/yttrium aluminum garnet (YAG) eutectic rods of 1 mm in diameter were grown by the laser-heated floating zone method at different rates to obtain microstructures with the same morphology but of very different domain size. The mechanical properties of the rods (hardness, toughness, strength) were measured at ambient temperature in the longitudinal and transverse directions and, in addition, the longitudinal flexure strength was determined up to 1900 K. The fracture resistance and the hardness of the eutectics at ambient temperature were isotropic and independent of the domain size. On the contrary, the longitudinal strength was significantly higher than the transverse one and increased linearly with the growth rate, reaching almost 2 GPa in the rods grown at 750 mm/h, which presented a submicrometer homogeneous microstructure. The critical defect size was equivalent to that of Al2O3 and YAG domains in the microstructure, and the strength was proportional to the inverse of the square root of the domain size. In addition, the strength retention of the eutectics was remarkable, and the rods with the finest microstructure withstood 1.53 GPa at 1900 K. The moderate reduction in strength at very high temperature was induced by the homogeneous coarsening of the microstructure.

Comparison of N losses (NO − 3 , N 2 O, NO) from surface applied, injected or amended (DCD) pig slurry of an irrigated soil in a Mediterranean climate

Abstract: Nitrous oxide (N 2O), nitric oxide (NO), denitrification losses and NO−3 leaching from an irrigated sward were quantified under Mediterranean conditions. The effect of injected pig slurry (IPS) with and without the nitrification inhibitor dicyandiamide (DCD) was evaluated and also compared with that of a surface pig slurry application (SPS) and a control treatment (Control) without fertiliser. After application, fluxes of NO and N 2O peaked from SPS (3.06 mg NO-N m −2 d −1 and 108 mg N 2O-N m −2 d −1) and IPS (3.50 mg NO-N m −2 d −1 and 105 mg N 2O-N m −2 d −1). However, when irrigation was applied, N 2O and NO emissions declined. The total N 2O and denitrification losses were slightly large from IPS than from SPS, although the differences were not significant (P < 0.05). Emission of NO was not affected by the method of pig slurry application. DCD inhibited nitrification during the first 20–30 days and reduced N 2O and NO emissions from pig slurry by at least 46% and 37%, respectively. Considering the 215 days following pig slurry application, the emission factor of N 2O based on N fertiliser was 1.60% (SPS), 2.95% (IPS), and 0.50% (IPS + DCD). The emission factor for NO was 0.14% (SPS), 0.12% (IPS), and 0.02% (IPS + DCD). Environmental conditions of the crop favoured the denitrification process as the most important source of N 2O during the experimental period. The differences in the denitrification rate between treatments could be explained by the pattern of water soluble carbon (WSC), that was the highest value in injected pig slurry (with and without DCD). Due to low drainage (5% of water applied), leaching losses of NO 3 − were lower than those of denitrification from the upper soil layer (0–10 cm) in all treatments and especially with IPS + DCD, where the nitrification inhibitor was very efficient in reducing leaching losses.

Modelling water markets under uncertain water supply

Abstract: This paper looks at the risk dimension of water markets under uncertain water supply. We model market participants' decisions under uncertainty and evaluate gains from trade under two different market arrangements. These differ in the confidence that irrigators can place in the water market-clearing processes, and their chances of pursuing tactical responses to deal with supply uncertainty. A two-stage stochastic model, that simulates both market arrangements, is applied to an irrigation district of Southern Spain. We show that centralised water markets, perhaps brokered by the water authority, lead to more efficient allocation and resource use than decentralised markets. The paper highlights the importance of providing a reliable market setting. Copyright 2005, Oxford University Press.

Generalized-scattering-matrix analysis of a class of finite arrays of coupled antennas by using 3-D FEM and spherical mode expansion

Abstract: A rigorous method for characterizing, in terms of a multimode scattering matrix, a finite array of antennas where each antenna can be described by means of spherical waves is presented in this paper. The procedure provides the impedance, coupling and radiating characteristics of the arrays and comprises two steps. First, the generalized scattering matrix (GSM) of each single antenna is numerically calculated over a wide band of frequencies. For this purpose we use a previously-developed methodology that combines the domain segmentation technique, the three-dimensional finite element method (3D-FEM), spherical mode expansion and a reduced order model obtained using a symmetric matrix Pade/spl acute/-Via-Lanczos (SyMPVL) algorithm. Second, the overall GSM of the finite array is calculated starting from the GSM of each antenna and using rotation and translation of spherical waves. A closed-form expression for the overall GSM is given and different examples are shown in order to validate the proposed method.

Non-destructive fruit firmness sensors: a review

Abstract: The development of sensors to measure fruit internal quality variables is one of the challenges of post-harvest technology. Several variables can currently be measured, including sugar content, acid content, firmness and internal disorders. This article reviews the state of the art of non-destructive fruit firmness sensors. These include static and on-line sensors that use different technologies for determining force-deformation relationships, impact forces, the acoustic response to vibrations or impacts, and optical properties. The rebound technique and nuclear magnetic resonance is also used. Although many techniques are under development, some companies already market instruments that determine the internal quality of fruit.