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Caracterización morfológica, física, química, mineralógica y génesis de un pedón sódico alcalino ubicado en Papelón, estado Portuguesa
Guerrero-Alves,Jose P; Pla-Sentis,Ildefonso; Valera,Angel;
Agronomía Tropical , 2009,
Abstract: salt-affected soils are a major factor limiting plant growth and productivity of crop plants. out of the 831 million hectares that the fao/unesco reports worldwide as salt affected soils more than 50 % (434 million hectares) are alkaline-sodic soils. this study was conduced in order to identify factors and processes in the genesis of an alkalinesodic soil from the alluvial plains of portuguesa river. morphological, physical, chemical and mineralogical attributes were determined. results indicated exchangeable sodium percentage (esp) up to 43 %, nahco3 accumulation, high phs (>8.5), very high bulk densities (up to 2.03 mg m-3), both low hydraulic conductivity (< 0.5 mm h-1) and macroporosity values (<3.4%) in btn and cn horizons, caco3 precipitation, mixed mineralogy characterized by clorite, interstratified 10/14m, quartz and micas. it was inferred that the soil was produced, first, from materials grounded by glacial ice action in venezuelan andes during the arid phase of pleistocene. later, during the holocene humid and warmer climate, sediments were transported and deposited in plains of portuguesa river and then interacted with nahco3 rich waters in micro-depressions. alkaline sodium salts could be formed by weathering of sodic silicates in rocks from venezuelan andes or from accumulation of organic matter in a reduction environment with elimination of sulfates as h2s. the soil evolved to promote clay migration, substitution of ca-mg by sodium in soil exchange complex, caco3 precipitation, natric horizon formation, elimination of salts in deep drainage, and finally, when total salt quantities diminished to critic levels the degradation of soil structure was produced
Génesis de un suelo salino-sódico de tucupido, estado guárico-venezuela
Guerrero-Alves,José P; Pla-Sentis,Ildefonso; Camacho,Rafael G; Valera,ángel; Ferrer,Jairo;
Agronomía Tropical , 2007,
Abstract: saline-sodic soils, which are rich in salts and sodium, are degraded soils common in zones from subhumid toarid climates. this study was carried out to identifyfactors and processes related with the genesis, undernatural conditions, of a saline-sodic soil (sodic haplusterts, fine, smectitic, isohyperthermic) in tucupido(guárico-venezuela), under a semiarid climate. therewere evaluated morphological, physical, chemical andmineralogical characteristics and properties of the soil.the ph, exchangeable sodium, and electric conductivity(saturation extract) varied between 7.55-8.4; 2-32% and1.0-8.7 ds m-1 respectively. nacl was the dominantsalt (> 66% below 0.1-m depth). bulk density, macroporosity, and saturated hydraulic conductivity varied from 1.8 to 2.2 mg m-3, 4 to 5% and 3x10-7 to 1x10-5 m s-1, respectively. smectites were the dominating clays, butchlorites and hydrated micas there were present too.high quantities of ca- and mg-carbonates were alsofound precipitated in the soil (18%). the conclusionwas that these soils were probably formed by alterationof calcareous shales, formed in sedimentary environments in contact with saline waters rich in sodium, to produce saline-sodic soils during the arid phase at theend of the pleistocene period. the very low permeabilityof these soils limited salts washing during the wetterholocene period. high electric conductivities probablywould allow the collapse of interlayer space ofsmectites, and the high content of ca-carbonates the production of ca-al silicate compounds which couldbe acting as cementing agents in the interlayer space ofsmectites, and these processes probably could preventedthe increase of the exchangeable na% in the soil tovalues higher than 32%.
Inseparability and customisation degree as determinants of service firms’ internationalization
ESTHER SáNCHEZ PEINADO,JOSE PLA BARBER
Cuadernos de Gestión , 2005,
Abstract: The vast majority of theoretical approaches in internationalisation have emerged from manufacturing sector and, thus, some explanations may not be true in the whole service sector. This paper analyses the importance of sector characteristics in the entry mode choice and shows that there are different behaviours patterns not only among the service and manufacturing sectors but also among service firms.In this paper, we propose two characteristics of services, inseparability and customisation degree, as key dimensions to classify services because of their importance in the international arena. From a cluster analysis in a sample of 113 Spanish service firms, this paper identifies four groups of services and it provides evidence about the existence of some differences in the entry mode choice patterns according to the nature of the group being analysed.
Dimensiones pragmáticas
Franklin Sentis
Onomázein : Revista de Lingüística, Filología y Traducción , 1999,
Abstract: Esta indagación bibliográfica discute distintas concepciones de la pragmática en contraste permanente con la semántica. Pone de manifiesto la existencia de dos modos complementarios de entender la teorización pragmática; estas dos formas teóricas delinean dos dimensiones de los eventos pragmáticos: la comunicativo-retórica y la gramático-contextual. Estas dimensiones abarcan un mayor número de fenómenos pragmáticos, superando la concepción de la pragmática de fines de década de los setenta, sustentada en forma exclusiva en los actos de habla. (This bibliographic research discusses different notions of pragmatics in constant opposition to semantics. It reveals the existence of two complementary views of pragmatic theory: the communicative-rhetorical and the grammaticalcontextual ones. These dimensions embrace a larger spectrum of pragmatic phenomena, superseding the notion of pragmatics held during the late 70's, anchored exclusively on speech acts.)
La composicionalidad en el estudio léxico
Franklin Sentis
Onomázein : Revista de Lingüística, Filología y Traducción , 2006,
Abstract: Este trabajo hace una síntesis de diferentes estados epistemológicos del estudio léxico de un texto o de un discurso; discute distintas concepciones del análisis componencial; valida el principio de composicionalidad y sugiere algunos medios descriptivos que pueden emplearse en la indagación léxica. (This article synthesizes different epistemological stages in the lexical analysis of a text or discourse. It reviews different conceptions of componential analysis, it validates the principle of compositionality and it proposes some descriptive means that can be used in lexical analysis.)
La presuposición como categoría pragmática: un caso de confrontación epistemológica
Franklin Sentis
Onomázein : Revista de Lingüística, Filología y Traducción , 2001,
Abstract: Esta investigación bibliográfica tiene por finalidad dar a conocer y destacar las discusiones de índole epistemológica. Estas se relacionan con los hechos empíricos y con los estudios que conllevan a concebir la presuposición como categoría pragmática, y a delinear los criterios básicos de la teoría pragmática vigente. De manera específica, examina la presuposición desde la filosofía del lenguaje, la semántica generativa y el análisis del discurso. Corrobora el carácter pragmático de la presuposición a partir de su dependencia y cancelación de factores situacionales. (The purpose of the following bibliographic investigation is to announce and emphasize the discussions of epistemologic nature. These relate to the empirical facts and studies that lead to conceive the presupposition as a pragmatic category and to delineate the basic criteria of the current pragmatic theory. Specifically, it examines the presupposition from the viewpoint of the philosophy of language, the generative semantics and the discourse analysis. It corroborates the pragmatic character of the presupposition, from its dependenceand cancellation of situational aspects.)
Size distribution of particle systems analyzed with organic photodetectors
Matthias Sentis
Physics , 2015,
Abstract: As part of a consortium between academic and industry, this PhD work investigates the interest and capabilities of organic photo-sensors (OPS) for the optical characterization of suspensions and two-phase flows. The principle of new optical particle sizing instruments is proposed to characterize particle systems confined in a cylinder glass (standard configuration for Process Analytical Technologies). To evaluate and optimize the performance of these systems, a Monte-Carlo model has been specifically developed. This model accounts for the numerous parameters of the system: laser beam profile, mirrors, lenses, sample cell, particle medium properties (concentration, mean & standard deviation, refractive indices), OPS shape and positions, etc. Light scattering by particles is treated either by using Lorenz-Mie theory, Debye, or a hybrid model (that takes into account the geometrical and physical contributions). For diluted media (single scattering), particle size analysis is based on the inversion of scattering diagrams obtained over a wide angular range or near optical singularities (rainbow, critical scattering, diffraction). For dense media (multiple scattering), the solutions foreseen are based on the analysis of the backscattering spotlight characteristics.
Sous-investissement et suppression d’effectifs : vers une réduction des co？ts d’agence
Sentis, Patrick
- , 2001, DOI: https://doi.org/10.7202/602342ar
Abstract: Cet article montre que la possibilité pour une firme endettée de réduire ses effectifs permet de supprimer les situations de sous-investissement et les co？ts d’agence qui leurs sont liés. L’influence de la possibilité de réduire les effectifs sur la richesse des parties prenantes de l’entreprise est étudiée. Seuls les créanciers et les travailleurs profitent de la politique de réduction d’effectifs. La valeur des actions demeure inchangée. Enfin, dans le modèle, une structure du capital optimale existe et la valeur de l’entreprise endettée appara？t supérieure à celle de l’entreprise sans dette
Phenotypic and genetic variability of morphometrical traits in natural populations of Drosophila melanogaster and D simulans. I. Geographic variations
P Capy, E Pla, JR David
Genetics Selection Evolution , 1993, DOI: 10.1186/1297-9686-25-6-517
Abstract:
Phenotypic and genetic variability of morphometrical traits in natural populations of Drosophila melanogaster and D simulans. II. Within-population variability
P Capy, E Pla, JR David
Genetics Selection Evolution , 1994, DOI: 10.1186/1297-9686-26-1-15
Abstract:
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