Showing papers by "Technical University of Madrid published in 1996"

The SAL1 gene of arabidopsis, encoding an enzyme with 3'(2'),5'-bisphosphate nucleotidase and inositol polyphosphate 1-phosphatase activities, increases salt tolerance in yeast

Abstract: A cDNA library in a yeast expression vector was prepared from roots of Arabidopsis exposed to salt and was used to select Li(+)-tolerant yeast transformants. The cDNA SAL1 isolated from one of these transformants encodes a polypeptide of 353 amino acid residues. This protein is homologous to the HAL2 and CysQ phosphatases of yeast and Escherichia coli, respectively. Partial cDNA sequences in the data bases indicate that rice produces a phosphatase highly homologous to SAL1 and that a second gene homologous to SAL1 exists in Arabidopsis. The SAL1 protein expressed in E. coli showed 39(29),59-bisphosphate nucleotidase and inositol polyphosphate 1-phosphatase activities. In yeast, SAL1 restored the ability of a hal2/met22 mutant to grow on sulfate as a sole sulfur source, increased the intracellular Li+ tolerance, and modified Na+ and Li+ effluxes. We propose that the product of SAL1 participates in the sulfur assimilation pathway as well as in the phosphoinositide signaling pathway and that changes in the latter may affect Na+ and Li+ fluxes.

Towards a Method to Conceptualize Domain Ontologies

Abstract: This paper presents the suite of principles, designs criteria and verification process used in the knowledge conceptualization process of a consensuated domain ontology in the domain of chemicals. To achieve agreement between different development teams we propose the use of a common and shared conceptual model as starting point. To capture domain knowledge of a given domain and organize it in a shared and consensuated conceptual model, we recommend an approach that integrates the following intermediate representation techniques: Data Dictionary, Concepts Classification Trees, Tables of Instance Attributes, Table of Class Attributes, Table of Constants, Tables of Formulas, Attributes Classification Trees, and Tables of Instances. We also provide a set of guidelines to verify the knowledge gathered inside each intermediate representations and between intermediate representations.

Towards a framework to verify knowledge sharing technology

Abstract: Based on the empirical verification of bibliographic-data and other Ontolingua ontologies, this paper provides an initial framework for verifying Knowledge Sharing Technology (KST). Verification of KST refers to the engineering activity that guarantees the correctness of the definitions in an ontology, its associated software environments and documentation with respect to a frame of reference during each phase and between phases of its life cycle. Verification of the ontologies refers to building the correct ontology, and it verifies that (1) the architecture of the ontology is sound, (2) the lexicon and the syntax of the definitions are correct and (3) the content of the ontologies and their definitions are internally and metaphysically consistent, complete, concise, expandable and sensitive.

Distributed strain measurement based on a fiber Bragg grating and its reflection spectrum analysis

Abstract: A method of extracting the strain profile along a fiber Bragg grating from the intensity reflection spectrum is described The procedure is based on a filter synthesis theory that relates the aperiodicity of a grating with its reflection spectrum To illustrate the approach, we measured the strain profile near a hole in a plate and obtained a strain resolution of 80 μ∊ The spatial resolution depends on the strain gradient; ie, the higher the gradient, the better the resolution A resolution of 08 mm was achieved for a 5-mm grating with a gradient of 250 μ∊/mm

Portfolio Selection: A Compromise Programming Solution

Abstract: A surrogate for an investor's bi-criteria utility function (profitability, safety) is proposed as an alternative methodology for selecting portfolios. The optimum is approximated by resorting to a recent utility theorem expounded in multi-criteria analysis. This method is developed for an 'average' investor and could be used as a routine procedure by investment consultants with incomplete information of the client's utility function.

Telemedicine for diabetes care: The DIABTel approach towards diabetes telecare

Abstract: Telemedicine is modifying classical health care by providing effective solutions to an increasing number of new situations. This article summarizes the potential benefits made available by this technology in diabetes care, and describes in detail how the new DIABTel Telemedicine Service complements the daily care of diabetic patients. The basic functions of the telemedicine system include telemonitoring of patient's blood glucose data and self-management actions, and remote care from doctors to diabetic patients. The system's architecture comprises two main components: the Medical Workstation, a PC-based system to be used by physicians and nurses in Diabetes Day Centre units in hospitals, and the Patient Unit, a palmtop-computer to be used by patients in their day to day activities. Both components, in an integrated approach, offer tools to doctors and patients for data collection and management, viewing and interpretation modules, data/message exchange services and an interactive glucose/insulin simulator for educational purposes. The DIABTel telemedicine diabetes care procedure aims: (1) to improve communication of the patient with the hospital-based diabetologist, in between the patient's visits to the clinic; (2) to allow doctors to assess the patient's condition on a frequent basis (every week); (3) to help patients with management in the daily care of diabetes, and (4) to provide patients with a service of 'supervised autonomy', to increase patient's independence without decreasing the necessary continual support and supervision from the doctor. Finally, we discuss the practical problems, limitations and vital issues regarding implementation of the telemedicine service.

A methodology for granularity-based control of parallelism in logic programs

Abstract: Several types of parallelism can be exploited in logic programs while preserving correctness and efficiency, i.e. ensuring that the parallel execution obtains the same results as the sequential one and the amount of work performed is not greater. However, such results do not take into account a number of overheads which appear in practice, such as process creation and scheduling, which can induce a slow-down, or, at least, limit speedup, if they are not controlled in some way. This paper describes a methodology whereby the granularity of parallel tasks, i.e. the work available under them, is efficiently estimated and used to limit parallelism so that the effect of such overheads is controlled. The run-time overhead associated with the approach is usually quite small, since as much work is done at compile time as possible. Also, a number of run-time optimizations are proposed. Moreover, a static analysis of the overhead associated with the granularity control process is performed in order to decide its convenience. The performance improvements resulting from the incorporation of grain size control are shown to be quite good, specially for systems with medium to large parallel execution overheads.

The instability and breakdown of tall columnar vortices in a quasi-geostrophic fluid

Abstract: We examine the linear stability of elliptical columns of uniform potential vorticity subject to two-dimensional (horizontal) straining within a rapidly rotating, stratified (quasi-geostrophic) fluid. We find that horizontal straining can promote the exponential growth of three-dimensional disturbances when the vortex height-to-width aspect ratio exceeds, qualitatively, three times the ratio of the Coriolis parameter to the buoyancy frequency. This instability is not related to the usual baroclinic instability which operates on shallow vortex columns whose potential vorticity changes sign with height. The nonlinear development of these instabilities is investigated numerically using a high-resolution contour surgery algorithm. Simulations are conducted for both a Boussinesq (ocean-like) fluid and a compressible (atmospheric-like) fluid having exponentially decreasing density with height. The simulations reveal a generic nonlinear development that results in a semi-ellipsoidal baroclinic vortex dome at the lower surface and, in the case of a Boussinesq fluid, another such dome at the upper surface.The related problem of two interacting vortex columns is also examined. A generic three-dimensional instability and nonlinear development occurs no matter how great the distance between the vortex columns, provided that they are sufficiently tall.Our results may bear upon the observed structure of many atmospheric and oceanic vortices, whose height-to-width aspect ratios are consistent with our findings. Remarkably, even strongly ageostrophic vortices, such as tropical cyclones, fit the pattern. Our results furthermore re-open questions about the long-time nature of freely decaying quasi-geostrophic turbulence, for which recent simulations indicate a progressive two-dimensionalization by vortex alignment, while earlier simulations have indicated long-lived baroclinic vortices, not unlike what we find here.

Use of Kraft Pine Lignin in Controlled-Release Fertilizer Formulations

Abstract: Lignin was used as a majority component in a controlled-release fertilizer coating, since this waste product displays properties that make it an ideal substance for application in soil together with conventional mineral fertilizers. Pine lignin marketed under the name of Indulin AT and obtained by the Kraft process was used. Insoluble in water for all pH values that may occur in soil, this product was employed for coating pelleted urea. Seven series of fertilizer were obtained, which also contained various types of rosins and in some cases linseed oil as additives. The physical−chemical evaluation of these fertilizers showed that the most efficient are those whose coating embodies a mixture of dimerized, esterified, and natural rosins, as well as lignin. It was also demonstrated that the efficiency of the products noticeably increases by adding linseed oil as a sealing agent.

A comparison between seasonal changes in soil water storage and penetration resistance under conventional and conservation tillage systems in Aragón

Abstract: Low and extremely variable precipitations limit dryland crop production in the semi-arid areas of Aragon (NE Spain). These areas are also affected by high annual rates of topsoil losses by both wind and water erosion. A long-term experiment to determine the feasibility of conservation tillage in the main winter barley production areas of Aragon was initiated in 1989 at four locations, three on loam to silt loam soils (Xerollic Calciorthid) and one on a silty clay loam (Fluventic Ustochrept), receiving between 300 and 600 mm of average annual rainfall. In this study, we compared, under both continuous cropping and cereal-fallow rotation, the effects of conventional tillage (mouldboard plough) and two conservation tillage systems, reduced tillage (chisel plough) and no-tillage, on soil water content and penetration resistance during the first two growing seasons. Whereas reduced and conventionally tilled treatments generally had similar soil water content during the experimental period, the effects of no-tillage were inconsistent. No-tilled plots had from 26% less to 17% more stored soil water (0–80 cm) than conventional tilled plots at the beginning of the growing season. In contrast to the conventional and reduced tillage treatments, penetration resistances were between 2 and 4 MPa after sowing in most of the plough layer (0–40 cm) under no-tillage at all sites. Fallow efficiencies in moisture storage in the cereal-fallow rotation, when compared with the continuous cropping system, ranged from −8.7 to 12%. The highest efficiencies were recorded when the rainfall in the months close to primary tillage exceeded 100 mm. Since this event is very unlikely, long fallowing (9–10 months) appears to be an inefficient practice for water conservation under both conventional and conservation management. Our results suggest that, up to now, only reduced tillage could replace conventional tillage without adverse effects on soil water content and penetration resistance in the dryland cereal-growing areas of Aragon.

Optimized Algorithms for Incremental Analysis of Logic Programs

Abstract: Global analysis of logic programs can be performed effectively by the use of one of several existing efficient algorithms. However, the traditional global analysis scheme in which all the program code is known in advance and no previous analysis information is available is unsatisfactory in many situations. Incremental analysis of logic programs has been shown to be feasible and much more efficient in certain contexts than traditional (non-incremental) global analysis. However, incremental analysis poses additional requirements on the fixpoint algorithm used. In this work we identify these requirements, present an important class of strategies meeting the requirements, present sufficient a priori conditions for such strategies, and propose, implement, and evaluate experimentally a novel algorithm for incremental analysis based on these ideas. The experimental results show that the proposed algorithm performs very efficiently in the incremental case while being comparable to (and, in some cases, considerably better than) other state-of-the-art analysis algorithms even for the non-incremental case. We argue that our discussions, results, and experiments also shed light on some of the many tradeoffs involved in the design of algorithms for logic program analysis.

High strain rate properties of aramid and polyethylene woven fabric composites

Abstract: In this paper, the influence of the strain rate on the mechanical properties of aramid and polyethylene woven fabric composites is studied from tensile measurements provided by a Hopkinson bar and conventional testing machines. A detailed description of the experimental technique includes a critical discussion of the points related to the reliability and confidence of the data obtained. On the other hand, the experimental results indicate that strain rate influences significantly the values of the longitudinal tensile strength and failure strain of the composites tested. Some differences are also observed between the static and dynamic stress-strain curves.

Global Analysis of Standard Prolog Programs

Abstract: interpretation-based data-flow analysis of logic programs is, at this point, relatively well understood from the point of view of general frameworks and abstract domains. On the other hand, comparatively little attention has been given to the problems which arise when analysis of a full, practical dialect of the Prolog language is attempted, and only few solutions to these problems have been proposed to date. Existing proposals generally restrict in one way or another the classes of programs which can be analyzed. This paper attempts to fill this gap by considering a full dialect of Prolog, essentially the recent ISO standard, pointing out the problems that may arise in the analysis of such a dialect, and proposing a combination of known and novel solutions that together allow the correct analysis of arbitrary programs which use the full power of the language.

Weakly nonlinear oscillations of nearly inviscid axisymmetric liquid bridges

Abstract: A weakly nonlinear analysis is presented of the small oscillations of nearly inviscid liquid bridges subjected to almost resonant axial vibrations of the disks. An amplitude equation is derived for the evolution of the complex amplitude of the oscillations that exhibits hysteresis and period doublings. We also analyse the steady streaming in the bulk forced by the oscillatory boundary layers near the disks; the boundary layer near the free surface produces no forcing terms. In particular some experimentally observed patterns are explained, and some new, non-observed ones are predicted. We conclude that the structure of this steady flow is not the appropriate one to counterbalance steady thermocapillary convection, but our results indicate how to get the desired counterbalancing effect.

Optimizing the winding strategy of the transformer in a flyback converter

Abstract: This work presents a study of the influence of the winding strategy in the parameters of the flyback transformer. A frequency and geometry dependent model generated from FEM simulations has been employed in order to study the influence of the position of the windings on the leakage energy and AC resistance. A study of the interleaving technique in the flyback transformer has also been developed using the FEM solver. Conclusions of the advantages of the interleaving technique in the flyback transformer compared with its application in common transformers have been extracted. The influence of the leakage inductance in primary and secondary windings has been studied by means of SPICE simulations. The final goal of this paper is to obtain winding strategy design rules to minimize the leakage inductance and AC resistance in order to optimize power converter performance.

The hydrogenase gene cluster ofRhizobium leguminosarum bv.viciae contains an additional gene (hypX), which encodes a protein with sequence similarity to the N10-formyltetrahydrofolate-dependent enzyme family and is required for nickel-dependent hydrogenase processing and activity

Abstract: Plasmid pAL618 contains the genetic determinants for H2 uptake (hup) fromRhizobium leguminosarum bv.viciae, including a cluster of 17 genes namedhupSLCDEFGHIJK-hypABFCDE. A 1.7-kb segment of insert DNA located downstream ofhypE has now been sequenced, thus completing the sequence of the 20 441-bp insert DNA in plasmid pAL618. An open reading frame (designatedhypX) encoding a protein with a calculated Mr of 62 300 that exhibits extensive sequence similarity with HoxX fromAlcaligenes eutrophus (52% identity) andBradyrhizobium japonicum (57% identity) was identified 10 bp downstream ofhypE. Nodule bacteroids produced byhypX mutants in pea (Pisum sativum L.) plants grown at optimal nickel concentrations (100 µM) for hydrogenase expression, exhibited less than 5% of the wild-type levels of hydrogenase activity. These bacteroids contained wild-type levels of mRNA from hydrogenase structural genes (hupSL) but accumulated large amounts of the immature form of HupL protein. The Hup-deficient mutants were complemented for normal hydrogenase activity and nickel-dependent maturation of HupL by ahypX gene provided in trans. From expression analysis ofhypX-lacZ fusion genes, it appears thathypX gene is transcribed from the FnrN-dependenthyp promoter, thus placinghypX in thehyp operon (hypBFCDEX). Comparisons of the HypX/HoxX sequences with those in databases provided unexpected insights into their function in hydrogenase synthesis. Similarities were restricted to two distinct regions in the HypX/HoxX sequences. Region I, corresponding to a sequence conserved in N10-formyltetrahydrofolate-dependent enzymes involved in transferring one-carbon units (C1), was located in the N-terminal half of the protein, whereas region II, corresponding to a sequence conserved in enzymes of the enoyl-CoA hydratase/isomerase-family, was located in the C-terminal half. These similarities strongly suggest that HypX/HoxX have dual functions: binding of the C1 donor N10-formyl-tetrahydrofolate and transfer of the C1 to an unknown substrate, and catalysis of a reaction involving polarization of the C=O bond of an X-CO-SCoA substrate. These results also suggest the involvement of a small organic molecule, possibly synthesized with the participation of an X-CO-SCoA precursor and of formyl groups, in the synthesis of the metal-containing active centre of hydrogenase.

Fracture toughness and fracture mechanisms of Al-Al2O3 composites at cryogenic and elevated temperatures

Abstract: The fracture toughness of two Al alloys (2014 and 6061) reinforced with 15 vol.% Al2O3 particulates was measured in the temperature range from −150 °C to 300 °C. Both composites maintained acceptable levels of toughness (over 20 MPa m 1 2 ) up to 200 °C, but the fracture toughness dropped very quickly above this temperature. Fracture always took place by a ductile mechanism involving the nucleation of voids from the ceramic particulates, the progressive growth of these voids, and the final coalescence through the matrix. Quantitative microscopy analyses demonstrated that voids were initiated from reinforcement fracture at low temperatures and by failure at the interface or in the matrix near the interface at elevated temperatures. Regardless of these differences, the changes in toughness could be explained by the deterioration in the mechanical properties with temperature rather than by the microstructural changes induced by the exposure to elevated temperatures.

Self-consistent analytical model of the Rayleigh-Taylor instability in inertial confinement fusion

Abstract: The model presented overcomes past inconsistencies by applying matching asymptotic techniques. The obtained growth rate, {gamma}{approx_equal}{alpha}({ital k}){radical}{ital kg}{minus}2{ital k}{nu}{sub {ital a}} (where {nu}{sub {ital a}} is the ablation velocity), could reproduce numerical simulations and experiments in a more complete way than the so-called Takabe formula {gamma}=0.9{radical}{ital kg}{minus}3{ital k}{nu}{sub {ital a}}. Here {alpha}({ital k}){equivalent_to}[1{minus}({ital k}/{ital k}{sub {ital c}}){sup {ital r}}]{sup 1/2}, represents the stabilization heat conduction effect and the cutoff wave number {ital k}{sub {ital c}} is much smaller than the inverse of the density scale length at the ablation front. Such a rigorously derived stabilization mechanism is the correct interpretation which underlies many of the numerical, analytical and simulation results found in the literature. {copyright} {ital 1996 The American Physical Society.}

Community patterns on exposed cliffs in a Mediterranean calcareous mountain

Abstract: The main focus of this paper is to establish the community diversity pattern of vegetation in exposed-cliffs in the Mediterranean region and the relative importance of some environmental factors. Consequently, a study of a calcareous mesa in C-N Spain has been carried on, based on constrained ordination — CCA. The spatial scale approach for sampling was the patch on the cliff. The total number of taxa was 117 and the average per patch was 15. It is remarkable that the highest frequency plants are not rock specialists (chasmophytes), but generalist nanophanerophytes and chamaephytes.