Showing papers by "Polytechnic University of Valencia published in 1990"
TL;DR: In this article, the condensations of benzaldehyde with ethyl cyanoacetate, ethyl malonate, and ethyl acetoacetate were carried out with high activity and selectivity on lithium-, sodium-, potassium- and caesium-exchanged X and Y zeolites.
271 citations
TL;DR: The authors derive reliability functions and mean time to failure of four different memory systems subject to transient errors at exponentially distributed arrival times and derive easy-to-use expressions for MTTF of memories.
Abstract: The authors analyze the problem of transient-error recovery in fault-tolerant memory systems, using a scrubbing technique. This technique is based on single-error-correction and double-error-detection (SEC-DED) codes. When a single error is detected in a memory word, the error is corrected and the word is rewritten in its original location. Two models are discussed: (1) exponentially distributed scrubbing, where a memory word is assumed to be checked in an exponentially distributed time period, and (2) deterministic scrubbing, where a memory word is checked periodically. Reliability and mean-time-to-failure (MTTF) equations are derived and estimated. The results of the scrubbing techniques are compared with those of memory systems without redundancies and with only SEC-DED codes. A major contribution of the analysis is easy-to-use expressions for MTTF of memories. The authors derive reliability functions and mean time to failure of four different memory systems subject to transient errors at exponentially distributed arrival times. >
202 citations
TL;DR: In this article, USY samples with different silicon-to-aluminium ratios were treated with ammonium hexafluorosilicate solution to remove extra-framework aluminium (EFAL), and an IR spectroscopic study showed that all the bands related to EFAL disappear and the intensity of the bands corresponding to framework hydroxyls strongly increases.
99 citations
TL;DR: In this article, the NaGeX zeolite was used for the condensation of benzaldehyde, 2-nitrobenzaldehyde, and 2-trifluoromethylben benzaldehyde with ethyl cyanoacetate and ethyl malonate to obtain intermediates for the production of dihydropyridine derivatives.
73 citations
TL;DR: In this paper, the structural relaxation process of poly(methyl methacrylate) has been studied by differential scanning calorimetry and the enthalpy increment suffered by the sample in the isothermal stage of the thermal history (enthalpy loss due to ageing) was calculated as a function of the ageing time and temperature.
68 citations
TL;DR: In this article, it was shown that strong acid sites are active in the formation of dimethyl and cyclic ethylene acetals in the presence of HY zeolites by treatment of the corresponding carbonyl compound with trimethyl orthoformate at room temperature or with ethylene glycol using a Dean-Stark system, respectively.
62 citations
61 citations
TL;DR: In this paper, the flexor tendon of the human hand was investigated from the point of view of its nonlinear viscoelasticity and the validity of the quasilinear approach to tendon behaviour was discussed in connection with the deformation mechanism suggested by it.
52 citations
TL;DR: In this article, the most common parameters and functions used to characterize wave groups in linear seas are reviewed and interrelated in a unified manner, and the theoretical estimates used to demonstrate the relationships between the various parameters must be considered as only first-order trends to parameter estimates computed from real wave data.
45 citations
TL;DR: In this article, the crossed aldol condensation of acetophenone with benzaldehyde, in benzene at 80 °C, to give trans- and cis-chalcones was investigated.
Abstract: HY zeolites catalyze the crossed aldol condensation of acetophenone with benzaldehyde, in benzene at 80 °C, to give trans- and cis-chalcones. Together with these expected products, 3,3-diphenylpropiophenone is also produced. In the analogous basic condensation, using phase transfer catalysis, the Michael adduct was not detected, and besides chalcone a small percentage of the Cannizzaro reaction product was observed.
38 citations
TL;DR: In this paper, theoretical models are used to simulate aluminum distribution in a Y zeolite crystal when an aluminum gradient along the crystal is produced by dealumination, and the theoretical distribution of different types of acid sites is calculated.
TL;DR: The coelioscopy did not show a significant effect on litter size and birth, or on the current or the subsequent gestation, and the accuracy was very high: 91% and 98% respectively for ovulation rate and number of embryos.
Abstract: Twenty-one does were laparoscopized on d 12 of gestation and immediately killed after observation in order to estimate the ovulation rate and number of embryos. The accuracy was very high: 91% and 98% respectively, for ovulation rate and number of embryos. To measure the effect of coelioscopy on fetal survival rate 40 does were laparoscopized on d 12 of gestation. The coelioscopy did not show a significant effect on litter size and birth, or on the current or the subsequent gestation.
TL;DR: In this paper, four types of equipment (hand lances, oscillating nozzles, air assisted, and low pressure air-assisted sprayers) were compared in a Salustiana orange orchard on a randomized block with three replications.
03 Apr 1990
TL;DR: Research on continuous-speech recognition using phoneme-level hidden Markov models (HMMs) is described, and work on alternative approaches to modeling contextual effects and on improved duration modeling is described.
Abstract: Research on continuous-speech recognition using phoneme-level hidden Markov models (HMMs) is described. The aim of the project is automatic recognition of spoken airborne reconnaissance mission (ARM) reports. The evolution of the ARM system from a simple baseline system to its current configuration is described, and a considerable number of experimental results are included. Work on alternative approaches to modeling contextual effects and on improved duration modeling is described. >
TL;DR: For nonnegative n-by-n matrices with Perron eigenvectors, the authors gave simple upper and lower bounds for the ratio p(Al…Ak)/p(Al)…p(Ak), which imply that pAl/Al/Ak is approximately p(al/Ak) if the eigen vectors vary slowly.
TL;DR: It is found that not all of these models are equivalent, except certain types of hidden Markov models with observation probability distribution in the transitions, and stochastic regular grammar.
Abstract: In the literature on automatic speech recognition, the popular hidden Markov models (HMMs), left-to-right hidden Markov models (LRHMMs), Markov source models (MSMs), and stochastic regular grammars (SRGs) are often proposed as equivalent models. However, no formal relations seem to have been established among these models to date. A study of these relations within the framework of formal language theory is presented. The main conclusion is that not all of these models are equivalent, except certain types of hidden Markov models with observation probability distribution in the transitions, and stochastic regular grammar. >
TL;DR: In vivo pulse-chase experiments demonstrated that ethephon not only affected Rubisco content but that of many other (35)S-labeled proteins as well, indicating that ethylene activates a general and nonspecific mechanism of protein degradation.
Abstract: The effect of ethephon (2-chloroetylphosphonic acid) on the degradation of proteins and on the induction of Lycopersicon esculentum pathogenesis-related (PR) proteins was studied in tomato leaf discs. The rate of ribulose, -1,5-bisphosphate carboxylase/oxygenase (Rubisco) degradation was maximal in discs after 48 hours of incubation with 1 millimolar ethephon, leading to complete disappearance of Rubisco after 96 hours. This effect was correlated with an increase in PR protein synthesis and the induction of the previously reported alkaline proteolytic enzyme PR-P69 (P Vera, V Conejero [1988] Plant Physiol 87: 58-63). In vivo pulse-chase experiments demonstrated that ethephon not only affected Rubisco content but that of many other 35S-labeled proteins as well, indicating that ethylene activates a general and nonspecific mechanism of protein degradation. This effect was partially inhibited in vivo by the action of pCMB, a selective inhibitor of cysteine-proteinases such as P69. These data reinforce the hypothesis that P69 and perhaps other PR proteins are involved in the mechanism of accelerated protein degradation activated by ethylene.
TL;DR: In this article, a set of steamed ultra-stable (US) Y and acid-treated, aluminium deficient (AD) USY zeolites have been prepared and the removal of zeolite non-framework aluminium (EFAL) oxides from USY increases the micro-and meso-pore areas and the numbers of Bronsted and Lewis acid sites.
TL;DR: Two chitinases induced in tomato leaves by citrus exocortis viroid infection were purified and lend further support to the hypothesis that enhanced chit inase activity is a component of a general mechanism of response to pathogens and other stress agents.
01 Jan 1990
TL;DR: A view of viroid pathogenesis is presented in which viroid molecules are considered as pure replicating and pathogenic signals which act as elicitors of host responses which can also be activated by other afflicting agents.
Abstract: Despite the fact that viroids are the infectious agents with the lowest complexity and best known structure, our understanding of their pathogenic interaction with the host plant is still far from complete. Viroid pathogenesis poses many intriguing questions; these have to be answered without any viroid-specified protein to which to attribute a pathogenic role. Here we present a view of viroid pathogenesis in which viroid molecules are considered as pure replicating and pathogenic signals. These act as elicitors of host responses which can also be activated by other afflicting agents. A model is outlined to explain how the viroid-induced response at the cellular level becomes a developmental disease and leads to a plant which is more resistant to subsequent infections.
TL;DR: This paper considers the application of the MGGI methodology to a real problem of automatic speech recognition, thus allowing (and also requiring) the proposed problem to be properly formulated within the canonical framework of syntactic pattern recognition.
Abstract: Recently, a new methodology, referred to as “Morphic Generator Grammatical Inference” (MGGI), has been introduced as a step towards a general methodology for the inference of regular languages. In this paper we consider the application of this methodology to a real problem of automatic speech recognition, thus allowing (and also requiring) the proposed problem to be properly formulated within the canonical framework of syntactic pattern recognition. The results show both the viability and appropriateness of the application of MGGI to the problem considered.
TL;DR: In this paper an analog controller satisfying the control requirements is assumed, and some modific ations of the classical PlD algo rithms and state feedback regulators are proposed in order to keep the design specifications.
TL;DR: Two reported methods were compared with a more rapid and accurate flow injection analysis (FIA) technique, and the results with the OPA correlated well with the trinitrobenzenesulfonic acid (TNBS) but were overestimated due to reading small peptides and ammonium ions.
Abstract: Two reported methods were compared with a more rapid and accurate flow injection analysis (FIA) technique. A trinitrobenzenesulfonic acid (TNBS) method provided absolute values, was tedious, and the reagent was light-sensitive and required heating. An o-phthaldialdehyde (OPA) method was faster and less variable than the TNBS, but reaction time had to be carefully controlled. The results with the OPA correlated well with the TNBS but were overestimated due to reading small peptides and ammonium ions. The FIA method was simple and reliable, yielded values which correlated closely with amino acids and gave information about degree of proteolysis.
TL;DR: RPL(j) parameters have a high specificity for discriminating between VT and VF and may differentiate between fibrillating and nonfibrillsating rhythms, and in the first case between "course" and "fine" VF.
TL;DR: In this article, the parallel chaotic extrapolated Jacobi method is presented and sufficient conditions for the convergence of this method in function of convergence of the Jacobi matrix are given. But the convergence is not guaranteed.
TL;DR: A matrix separation of the variables method for solving initial-boundary value problems for coupled systems of second order partial differential equations and finite computable approximate solutions and upper error bounds for them in terms of data are given.
Abstract: In this paper a matrix separation of the variables method for solving initial-boundary value problems for coupled systems of second order partial differential equations is presented. Finite computable approximate solutions and upper error bounds for them in terms of data are given.
01 Jan 1990
TL;DR: Cucurbits were among the first plants used by man, and the bottle gourd may be the only plant known in both the New and Old Worlds in early prehistoric times.
Abstract: Cucurbits were among the first plants used by man, and the bottle gourd may be the only plant known in both the New and Old Worlds in early prehistoric times. Species of Cucurbita were major crops in the agriculture of the Aztec, Inca, and Mayan civilizations in Central and South America. Cucumbers have been cultivated in India for perhaps 3000 years (Esquinas-Alcazar and Gulik 1983).
TL;DR: In this article, a marked finite point process of convective cell arrivals, each point or occurrence in time representing the birth of a cell, is used to model extreme convective precipitation.
TL;DR: The dynamic behaviour of the distribution of Evans blue (EB), sodium fluorescein (SF), Lucifer yellow (LY) and horseradish peroxidase (HRP) was studied using standard light- and fluorescence microscopy following ultraviolet radiation induced brain oedema in the rat model to point out a specific selectivity of tracer distribution in oedematous brain following ultraviolet Radiation.
Abstract: The dynamic behaviour of the distribution of Evans blue (EB), sodium fluorescein (SF), Lucifer yellow (LY) and horseradish peroxidase (HRP) was studied using standard light- and fluorescence microscopy following ultraviolet radiation induced brain oedema in the rat model. The cerebral cortex was irradiated after craniotomy (2 × 2 mm) under anaesthesia. The tracers were injected (iv) 30 min prior to radiation. Animals were perfused with glutaraldehyde through the heart at different survival periods ranging from 30 min to 24 h post irradiation. The results showed a remarkable difference in distribution and spread of these tracers in the oedematous brain following radiation. The extravasation of EB was evident in ipsilateral cortex 6 h after radiation which extended to the contralateral side at the end of the 24 h survival period. The HRP reaction product was seen in the necrotic area 3 h after radiation which further extended to the underlying white matter at 24 h survival. The LY stained the ipsilateral micronecrotic area 6 h after radiation, whereas a non-specific diffuse fluorescence of SF was noted at this time period. These results point out a specific selectivity of tracer distribution in oedematous brain following ultraviolet radiation.
TL;DR: In this article, the catalytic cracking of gas oil has been investigated over ultra-stable (US) Y and aluminium deficient (AD USY zeolites, the zeolite steam treated at 760°C then mixed with silica matrix and finally the Zeolites mixed with a silica-alumina phase formed when USY was steam equilibrated, promoting catalyst activity and improving gasoline and especially diesel oil selectivities.