Showing papers by "University of Valencia published in 1991"

Mapping burns and natural reforestation using thematic Mapper data

Abstract: Remote sensing techniques are specially suitable to detect and to map areas affected by forest fires. In this work, Landsat 5 Thematic Mapper (TM) data has been used to study a number of forest fires that occurred in the province of Valencia (Spain) and to monitor the vegetation regeneration over burnt areas. A reference area (non‐burnt forest) was established to assess the change produced by fire. The radiance in the thermal band (10.4–12.5 μm) and the normalized difference in reflectance between near 1R (0.76–0.90 μm) and middle IR (2.08–2.35 μm) were the most suitable parameters to map burnt areas. This index can also be used for monitoring vegetation regeneration in burnt areas. About a month after the fire, the burns show temperatures of 5–6 °C higher than those found in the reference area, and the vegetation index shows negative values whereas the reference area values remain positive. The differences between the burns and the reference area for the vegetation index decrease with time as ve...

Resistance to the Bacillus thuringiensis bioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor.

Abstract: The biochemical mechanism for resistance to Bacillus thuringiensis crystal proteins was studied in a field population of diamondback moths (Plutella xylostella) with a reduced susceptibility to the bioinsecticidal spray. The toxicity and binding characteristics of three crystal proteins [CryIA(b), CryIB, and CryIC] were compared between the field population and a laboratory strain. The field population proved resistant (greater than 200-fold compared with the laboratory strain) to CryIA(b), one of the crystal proteins in the insecticidal formulation. Binding studies showed that the two strains differ in a membrane receptor that recognizes CryIA(b). This crystal protein did not bind to the brush-border membrane of the midgut epithelial cells of the field population, either because of strongly reduced binding affinity or because of the complete absence of the receptor molecule. Both strains proved fully susceptible to the CryIB and CryIC crystal proteins, which were not present in the B. thuringiensis formulation used in the field. Characteristics of CryIB and CryIC binding to brush-border membranes of midgut epithelial cells were virtually identical in the laboratory and the field population.

Pneumocystis carinii pneumonia

Abstract: We present twelve cases of Pneumocystis Carinii Pneumonia (PCP) hospitalized at the Internal Medicine Service of the Hospital Clinico de Valencia between 1989 and 1990. All patients were infected by HIV-1, with ages between 25 and 32 years, with circulating CD4 lymphocytes lower than 25% or 200 cells per cubic millimeter and with positive p24 antigen. Ten of them were parenterally drug addicts and two of them, homosexuals. Diagnosis was made by fibrobronchoscopy (FB) with bronchoaspiration (BAS) and bronchoalveolar lavage (BAL), or sputum induced by physiological serum aerosol at three per cent, using in both cases blue tinction with toluidine 0 of the samples obtained. Given the foreseeable increase of this disease in our country, we stress the risk of a potential change in its clinical spectrum, affecting new population groups, mainly the elderly, as well as the development of new early diagnosis techniques and the emergence of new treatments, including corticotherapy.

GEPOL: An improved description of molecular surfaces II. Computing the molecular area and volume

Abstract: The algorithm used by the program GEPOL for a finer description of molecular surface (for a fast calculation of molecular area and volume and for an efficient selection of sampling points) is presented in detail. Different types of surfaces such as van der Waals and Richard's molecular surfaces can be computed. As we described in the first article (J.L. Pascual-Ahuir and E. Silla, J. Comp. Chem., 11, 1047(1990)), GEPOL begins by building a set of spherical surfaces which fill the space which is not solvent accessible. In this second article, a triangular tessellation approach to select the parts of these spherical surfaces which form the molecular surface is described. By using a data coded generic pentakisdodecahedron, each spherical surface is divided in triangular tesserae. A simple method is used to eliminate all triangles found at the intersection volume of the spheres. The center coordinates and the surface of the remaining triangles are used in order to calculate the molecular area and volume and as starting point of the graphic representation of scalar and vector properties. We study the behavior of the method, presenting several examples of application. Special attention is given to the accuracy, spatial invariance and computer efficiency measured by CPU time. Some models of aligned spheres whose area and volume can be found exactly allow us to do a comparative study with a well-known method, analyzing their behavior in line with their respective graining parameters. A fragment of protein is used as an example of the application of the method for characterizing biomolecular surfaces. Aqueous solubility of organic compounds is studied as an example of the experimental property that depends on the molecular area obtaining a good correlation between the logarithm of the solubility and the area calculated using GEPOL.

An Alternative Paradigm to Evaluate the Acquisition of the Van Hiele Levels.

Abstract: This article presents an alternative way of analyzing the van Hiele level of students’ geometrical reasoning. We evaluate the students’ answers, taking into account the van Hiele level they reflect and their mathematical accuracy. This gives us a description of how accomplished the students are in applying the procedures associated with each of the van Hiele levels and allows us to determine the students’ degree of acquisition of the van Hiele levels. In this way we obtain a clearer picture of the students’ geometrical reasoning than with the traditional assignment of one van Hiele level to the learners. An example of the application of this method is provided: We describe a test that evaluated students’ ability to reason in three-dimensi onal geometry, some responses of students (9 eighth-grade pupils and 41 future primary school teachers), and the classification of their responses using our method. Approximately 25 years ago, the van Hieles proposed a model of the development of geometric thinking that identified five differentiated levels of thinking, ordered so that the students moved sequentially from one level of thinking to the next as their capability increased (van Hiele, 1957, 1986; van Hiele-Geldof, 1957). In the last 10 years there has been a growing interest in the van Hieles’ model of the development of geometric thinking (Fuys, Geddes, & Tischler, 1988; Gutierrez & Jaime, 1989; Hoffer, 1983; Senk, 1985). An important focus of research has been on ways to determine students’ level of thinking. The main goal of this article is to present an alternative method to evaluate the students’ van Hiele level of reasoning, thus offering a way of identifying those students who are in transition between levels. The way the student’s level of reasoning is ascertained plays an important role in research related to the van Hiele model. Most researchers have determined a student’s van Hiele level for a topic following assessment criteria based on the number of right answers to a written test (Gutierrez & Jaime, 1987; Mayberry, 1983; Usiskin, 1982) or on the thinking level shown by the student in each activity during an interview (Burger & Shaughnessy, 1986; Fuys et al., 1988). In both cases, the respective criteria have assigned each student to one van Hiele level. Although most students show a dominant level of thinking when answering open-ended questions, a large number of them clearly reflect in their answers the presence of other levels, and there are some students whose answers show two consecutive dominant levels of reasoning simultaneously (Usiskin, 1982; Burger & Shaughnessy, 1986; Fuys et al., 1988). Burger and Shaughnessy and Fuys et al. suggested that these students were in transition between two levels, but their approaches to the problem have been different. Burger and Shaughnessy sought a consensus in the evaluators’ opinions; Fuys et al. assigned a student to Level 1-2 to indicate that the student clearly used both Levels 1 and 2 of reasoning for an activity.

Aetiology of community acquired pneumonia in Valencia, Spain: a multicentre prospective study.

Abstract: A year long multicentre prospective study was carried out in the Valencia region of Spain, to determine the cause of community acquired pneumonia. The study was based on 510 of 833 patients with pneumonia. Of these, 462 were admitted to hospital, where 31 patients died. A cause was established in only 281 cases--208 of bacterial, 60 of viral, and 13 of mixed infection. The most common microorganisms were Streptococcus pneumoniae (14.5%), Legionella sp (14%), Influenza virus (8%), and Mycoplasma pneumoniae (4%). There was a higher incidence of Legionella sp than in other studies.

The riemannian manifold of all riemannian metrics

Abstract: In this paper we study the geometry of (M, G) by using the ideas developed in [Michor, 1980]. With that differentiable structure on M it is possible to use variational principles and so we start in section 2 by computing geodesics as the curves in M minimizing the energy functional. From the geodesic equation, the covariant derivative of the Levi-Civita connection can be obtained, and that provides a direct method for computing the curvature of the manifold. Christoffel symbol and curvature turn out to be pointwise in M and so, although the mappings involved in the definition of the Ricci tensor and the scalar curvature have no trace, in our case we can define the concepts of ”Ricci like curvature” and ”scalar like curvature”. The pointwise character mentioned above allows us in section 3, to solve explicitly the geodesic equation and to obtain the domain of definition of the

Numerical relativistic hydrodynamics: Local characteristic approach.

Abstract: We extend some recent Ishock capturing methodsR designed to solve nonlinear hyperbolic systems of conservation laws and which avoid the use of artifical viscosity for treating strong discontinuities to a relativistic hydrodynamics system of equations. Some standard shock-tube problems and radial accretion onto a Schwarzschild black hole are used to calibrate our code.

Phylogeny of viroids, viroidlike satellite RNAs, and the viroidlike domain of hepatitis delta virus RNA.

Abstract: We report a phylogenetic study of viroids, some plant satellite RNAs, and the viroidlike domain of human hepatitis delta virus RNA. Our results support a monophyletic origin of these RNAs and are consistent with the hypothesis that they may be "living fossils" of a precellular RNA world. Moreover, the viroidlike domain of human hepatitis delta virus RNA appears closely related to the viroidlike satellite RNAs of plants, with which it shares some structural and functional properties. On the basis of our phylogenetic analysis, we propose a taxonomic classification of these RNAs.

Zinc-positive boutons in the cerebral cortex of lizards show glutamate immunoreactivity.

Abstract: Zinc-positive boutons, originating in the medial cortex of lizards, exhibit glutamate immunoreactivity. This finding supports the presumed homology between lizard zinc-positive boutons and the hippocampal mossy fibres of mammals, which are also glutamate-immunoreactive and zinc-positive.

Mycotoxins and mycotoxigenic moulds in nuts and sunflower seeds for human consumption.

Abstract: A survey was carried out to obtain data on the occurrence of mycotoxins and the mycotoxin-producing potential of fungi isolated from nuts (almonds, peanuts, hazelnuts, pistachio nuts) and sunflower seeds in Spain. Thin-layer chromatography was used to separate the toxins. Aflatoxins were detected in one sample of almonds (95 ppb aflatoxin B1 and 15 ppb aflaxtoxin B2) and in one sample of peanuts at a level below 10 ppb of aflatoxin B1. 100% of samples showed variable incidence of fungal contamination. The predominant fungi present in samples were Penicillium spp, Aspergillus niger, A. flavus, A. glaucus and Rhizopus spp. The results showed that isolates of different species were able to produce aflatoxins B1, B2, G1, and G2, sterigmatocystin, ochratoxin A, patulin, citrinin, penicillic acid, zearalenone, and griseofulvin.

Pharmacokinetics and bioavailability of diclofenac in the rat

Abstract: Diclofenac sodium is a widely used drug with interesting absorption and disposition features when administered to laboratory animals. The present study was undertaken to assess the pharmacokinetics of the drug after iv and gastrointestinal dosing to rats. Renal excretion of unchanged drug was negligible, but biliary excretion of the drug (unchanged and conjugated) was detected in bile duct-cannulated rats; it accounted for 27.2 and 31.2% of the total dose following iv and intraduodenal administration, respectively. Most of the drug excreted in the bile was conjugated diclofenac; unchanged drug accounted for only 4.7 and 5.4% of total diclofenac excreted in the bile after iv and intraduodenal dosing, respectively. In normal animals, intestinal absorption of the drug excreted in the bile resulted in higher drug concentrations in plasma than those obtained in bile duct-cannulated rats, but only after 60 min of dosing. When administered directly into the duodenum, diclofenac absorption was extremely fast and the maximum plasma diclofenac concentration was reached within 2 min. After oral dosing, an early peak was also observed, but it was lower than that obtained after intraduodenal dosing: 71% diclofenac hioavailability was found in bile duct-cannulated rats intraduodenally dosed, whereas in normal animals dosed by mouth a bioavailability of 79% was obtained. In normal animals intraduodenally dosed, an apparent bioavailability of 106% was observed. All of these features, particularly the influence of enterohepatic circulation on drug bioavailability, are discussed.

Characterization of cell wall proteins of yeast and hydrophobic mycelial cells of Candida albicans.

Abstract: Cell surface hydrophobicity (CSH) of blastoconidia and blastoconidia bearing germ tubes of Candida albicans ATCC 26555 was monitored by assessing attachment of polystyrene microspheres to the cell surface, and we found that mature hyphae were significantly hydrophobic. Treatment of intact cells with low concentrations of beta-glucanase (Zymolyase 20T) or proteases abolished or significantly reduced attachment of latex beads to hyphae. This effect paralleled an obvious reduction in CSH of the entire cell population, as measured by an aqueous-hydrocarbon biphasic partitioning assay. Analysis of the cell wall material released by Zymolyase and adsorbed on polystyrene microspheres indicated that germ tube-specific cell wall proteins and mannoproteins with apparent molecular masses of 20 to 67 kDa may be responsible for the hydrophobicity of hyphae. Zymolyase released from blastoconidia cell walls a different set of proteins and mannoproteins that were able to adsorb to polystyrene microbeads. Such molecular species might in turn be responsible for the CSH exhibited by blastoconidium populations as determined by the biphasic partitioning assay, although these probably hydrophobic components can be masked on the surface of blastoconidia, as the latter had no or very few latex microspheres attached to their surfaces. Treatment of cells of both C. albicans morphologies with 2-mercaptoethanol released qualitatively distinct species of polystyrene-adsorbed proteins and mannoproteins from yeast and mycelial cells. These observations suggested that hydrophobic proteins and mannoproteins that could be associated with CSH are bound to the cell wall structure through diverse types of linkages.

Afferent and efferent connections of the olfactory bulbs in the lizard Podarcis hispanica.

Abstract: The connections of the olfactory bulbs of Podarcis hispanica were studied by tract-tracing of injected horseradish peroxidase. Restricted injections into the main olfactory bulb (MOB) resulted in bilateral terminallike labeling in the medial part of the anterior olfactory nucleus (AON) and in the rostral septum, lateral cortex, nucleus of the lateral olfactory tract, and ventrolateral amygdaloid nucleus. Bilateral retrograde labeling was found in the rostral lateral cortex and in the medial and dorsolateral AON. Ipsilaterally the dorsal cortex, nucleus of the diagonal band, lateral preoptic area, and dorsolateral amygdala showed labeled cell bodies. Retrogradely labeled cells were also found in the midbrain raphe nucleus. Results from injections into the rostral lateral cortex and lateral olfactory tract indicate that the mitral cells are the origin of the centripetal projections of the MOB. Injections in the accessory olfactory bulb (AOB) produced ipsilateral terminallike labeling of the ventral AON, bed nucleus of the accessory olfactory tract, central and ventromedial amygdaloid nuclei, medial part of the bed nucleus of the stria terminalis, and nucleus sphericus. Retrograde labeling of neurons was observed ipsilaterally in the bed nucleus of the accessory olfactory tract and stria terminalis, in the central amygdaloid nucleus, dorsal cortex, and nucleus of the diagonal band. Bilateral labeling of somata was found in the ventral AON, the nucleus sphericus (hilus), and in the mesencephalic raphe nucleus and locus coeruleus. Injections into the dorsal amygdala showed that the mitral neurons are the cells of origin of the AOB centripetal projections. Reciprocal connections are present between AOB and MOB. To our knowledge, this is the first study to address the afferent connections of the olfactory bulbs in a reptile. On the basis of the available data, a discussion is provided of the similarities and differences between the reptilian and mammalian olfactory systems, as well as of the possible functional role of the main olfactory connections in reptiles.

Comparative acute toxicities of selected pesticides to Anguilla anguilla

Abstract: The acute toxicities (24, 48, 72 and 96 hr) of eight pesticides to Anguilla anguilla were determined. The organochlorine pesticide, endosulfan was the most toxic, with LC50 values in the range of 0.042 to 0.041 mg/L. Endosulfan was followed in order of decreasing toxicity by diazinon, fenitrothion, chlorpyrifos, lindane, methidathion, trichlorfon and methylparathion. When fishes were exposed to the pesticides tested they exhibited signs of restlessness, erratic swimming, convulsions and difficulty in respiration. This response was more persistent in fishes exposed to organophosphorus pesticides.

Physiological changes in glutathione metabolism in foetal and newborn rat liver.

Abstract: Glutathione metabolism was studied in isolated hepatocytes from foetal, newborn and adult rats. The GSH/GSSG ratio decreased 15-20-fold through the foetal-neonatal-adult transition. This was mainly due to an increase in GSSG. All enzyme activities involved in the glutathione redox cycle tend to increase during that transition, but the relative increases in glutathione peroxidase and glutathione S-transferase were 3-5 times those of glutathione reductase or glucose-6-phosphate dehydrogenase. GSH synthesis from methionine as a sulphur source was 6 times lower in foetal than in adult hepatocytes. However, when N-acetylcysteine was used as a sulphur donor to by-pass the cystathionine pathway, the rates of GSH synthesis were similar in foetal and adult cells. This is due to the fact that cystathionase activity in foetal cells is very low. This low activity is reflected in the blood amino acid pattern, where the concentration of cysteine rises from 8 to 52 microM from foetuses to adult rats. This supports the idea that cysteine may be an essential amino acid for the premature animal.

The action of the diffeomorphism group on the space of immersions

Abstract: We study the action of the diffeomorphism group Diff( M ) on the space ofproper immersions Imm prop ( M,N ) by composition from the right. We show that smooth transversal slices exist through each orbit, that the quotient space is Hausdorff and is stratified into smooth manifolds, one for each conjugacy class of isotropy groups.

Majority and minority influence in inductive reasoning: A preliminary study

Abstract: Ninety-three students were exposed to majority and minority influence in an inductive reasoning task. The former induced convergent thinking processes, though its effects were not reducible to mere compliance. The latter activated more divergent constructive processes, supporting the predictions of Conversion Theory.

Candida albicans mycelial wall structure: supramolecular complexes released by zymolyase, chitinase and beta-mercaptoethanol.

Abstract: Different techniques released from the wall of Candida albicans mycelial cells high molecular weight mannoprotein materials with different levels of complexity. SDS solubilized among others one protein of 180 kDa which reacted with a monoclonal antibody (MAb) specific of a O-glycosylated protein secreted by regenerating mycelial protoplasts [Elorza et al. (1989) Biochem Biophys Res Commun 162:1118-1125]. Zymolyase, chitinase and beta-mercaptoethanol, released different types of high molecular highly polydisperse mannoprotein materials (greater than 180 kDa) that also reacted with the same MAb. These materials had N-glycosidically linked sugar chains, in addition to the O-glycosidically bonded sugars, as their molecular masses were significantly reduced by Endo H digestion. Besides, the specific materials released by either zymolyase or chitinase seemed to be the same throughout the process of germ tube formation. Transmission electron microscopy of thin sections of cells and walls showed that mannoproteins and chitin are evenly distributed throughout the entire cell wall structure.

25-kW/50-kHz generator for induction heating

Abstract: The authors present the features, technology, and construction of a transistorized generator for induction heating operating over the 4-50 kHz frequency range. This type of 25 kW output-power generator allows replacement of the electronic tube generators for most of their applications. The advantages of this new generator are more energy efficiency, extended life, reduced size, separated heating station of the generator, and connection by flexible cable. In addition, the generator has incorporated a frequency automatic tracking system that allows operating without any adjustments over a wide frequency range. >

Three-dimensional electrons and two-dimensional electric subbands in the transport properties of tin-doped n-type indium selenide: Polar and homopolar phonon scattering.

Abstract: Electron-scattering mechanisms in n-type indium selenide doped with different amounts of tin are studied by means of the Hall effect (30--300 K) and photo-Hall effect (300 K). The electron mobility at room temperature is found to increase with the free-electron concentration in samples with low tin content. The same behavior is observed when the electron concentration increases due to thermal annealing or photogeneration. That is explained through the presence of two kinds of free electrons contributing to the charge transport along the layers: high-mobility three-dimensional (3D) electrons in the conduction band, and low-mobility two-dimensional electrons in the electric subbands. These 2D subbands are proposed to exist in InSe due to size-quantization effects in thin layers located between two stacking faults. In these regions electron states become higher than conduction-band states. Electrons are transferred outside these regions and are confined in 2D subbands by the resulting electric field. In regard to the electron-scattering mechanisms, it is shown that LO polar phonons play an important role in the scattering of 3D electrons, whose mobility has been calculated by an iteration method. From a comparison with experimental results, we show that the coupling constant for the 3D electron-phonon deformation-potential interaction has been overestimated in previous calculations. The relaxation time for the scattering of 2D electrons by homopolar phonons is determined by using a variational wave function, and the calculated 2D mobility decreases when the localization of the 2D subbands along the c axis increases.