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Search Results: 1 - 10 of 484685 matches for " Sánchez C. "
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Consideraciones sobre la capa de ozono y su relación con el cáncer de piel
Sánchez C,Francisca;
Revista médica de Chile , 2006, DOI: 10.4067/S0034-98872006000900015
Abstract: in the recent decades, a sustained increase in the worldwide incidence of skin cancer has been observed and chile is not the exception. the most important risk factor is the exaggerated and repeated exposure to ultraviolet radiation coming from the sun. the ozone layer restricts the transmission of type b and c ultraviolet light. since 1980, a sustained depletion of stratospheric ozone levels is occurring, specially in middle latitudes (-30 to -60). along with this depletion, the amount of ultraviolet light that reaches the earth surface is increasing. this article reviews some basic concepts about the ozone layer and the association between its depletion and skin cancer. the general population should be informed about the risks of inadequate and exaggerated exposure to sunlight
Rese a de "Negocios internacionales: ambientes y operaciones" de John D. Daniels, Lee H. Radebaugh y Daniel P. Sullivan
Patricio Sánchez C.
Panorama Socioeconómico , 2005,
Abstract:
Consideraciones sobre la capa de ozono y su relación con el cáncer de piel The relationship between the ozone layer and skin cancer
Francisca Sánchez C
Revista médica de Chile , 2006,
Abstract: In the recent decades, a sustained increase in the worldwide incidence of skin cancer has been observed and Chile is not the exception. The most important risk factor is the exaggerated and repeated exposure to ultraviolet radiation coming from the sun. The ozone layer restricts the transmission of type B and C ultraviolet light. Since 1980, a sustained depletion of stratospheric ozone levels is occurring, specially in middle latitudes (-30 to -60). Along with this depletion, the amount of ultraviolet light that reaches the earth surface is increasing. This article reviews some basic concepts about the ozone layer and the association between its depletion and skin cancer. The general population should be informed about the risks of inadequate and exaggerated exposure to sunlight
Parametrized Invariance for Infinite State Processes
Alejandro Sánchez,César Sánchez
Computer Science , 2013,
Abstract: We study the uniform verification problem for infinite state processes, which consists of proving that the parallel composition of an arbitrary number of processes satisfies a temporal property. Our practical motivation is to build a general framework for the temporal verification of concurrent datatypes. The contribution of this paper is a general method for the verification of safety properties of parametrized programs that manipulate complex local and global data, including mutable state in the heap. This method is based on the separation between two concerns: (1) the interaction between executing threads---handled by novel parametrized invariance rules---,and the data being manipulated---handled by specialized decision procedures. The proof rules discharge automatically a finite collection of verification conditions (VCs), the number depending only on the size of the program description and the specification, but not on the number of processes in any given instance or on the kind of data manipulated. Moreover, all VCs are quantifier free, which eases the development of decision procedures for complex data-types on top of off-the-shelf SMT solvers. We discuss the practical verification (of shape and also functional correctness properties) of a concurrent list implementation based on the method presented in this paper. Our tool also all VCs using a decision procedure for a theory of list layouts in the heap built on top of state-of-the-art SMT solvers.
A Decidable Theory of Skiplists of Unbounded Size and Arbitrary Height
César Sánchez,Alejandro Sánchez
Computer Science , 2013,
Abstract: This paper presents a theory of skiplists of arbitrary height, and shows decidability of the satisfiability problem for quantifier-free formulas. A skiplist is an imperative software data structure that implements sets by maintaining several levels of ordered singly-linked lists in memory, where each level is a sublist of its lower levels. Skiplists are widely used in practice because they offer a performance comparable to balanced binary trees, and can be implemented more efficiently. To achieve this performance, most implementations dynamically increment the height (the number of levels). Skiplists are difficult to reason about because of the dynamic size (number of nodes) and the sharing between the different layers. Furthermore, reasoning about dynamic height adds the challenge of dealing with arbitrary many levels. The first contribution of this paper is the theory TSL that allows to express the heap memory layout of a skiplist of arbitrary height. The second contribution is a decision procedure for the satisfiability prob- lem of quantifier-free TSL formulas. The last contribution is to illustrate the formal verification of a practical skiplist implementation using this decision procedure.
Perfil fisiológico de la leptina
Sánchez,Julio César;
Colombia Médica , 2005,
Abstract: introduction: leptin was discovered because of its actions in the control of feeding and metabolic expenditure, affecting hypothalamic nucleus. since that, a wide diversity of additional functions have been described for this hormone. molecule and receptor: leptin is a protein that belongs to the cytocine family and hence its receptor is similar to cytocine receptors. there are at least six isoforms, although obrb subtype is the active form. obrb is associated with jak2-stat3 system and also activates other intracellular signalling systems. functions of leptin: leptin is involved in a wide variety of processes such as regulation of body weight, regulation of feeding and metabolic expenditure, reproduction, growth, immune function, vascular tone and probably in many others to be determined. associated diseases: leptin has been associated with a number of diseases including cancer of various types, psichiatric illnesses, arterial hypertension, non-insulin-dependent diabetes mellitus, reproductive alterations, placenta insufficiency, immune defficiencies and osteoarthritis. conclusions: leptin is an hormonal regulator of many biological processes and can be involved in the pathophysiology of a wide number of diseases.
CáLCULO E INTERPRETACIóN DE LAS TRAYECTORIAS DE PUNTOS DE COMPOSICIóN CONSTANTE (PINCH) EN COLUMNAS SIMPLES DE DESTILACIóN PARA MEZCLAS AZEOTRóPICAS HOMOGéNEAS
Sánchez,César Augusto;
Revista EIA , 2011,
Abstract: a continuation method of the kind predictor-corrector is presented for completely tracking of the pinch points branches related to the products or pseudoproducts of a homogeneous azeotropic distillation column. the method easily handles the turning points allowing the localization of the tangent pinch points. the foundation of the concept is in the ideas of fidkowski, malone y doherty; however, some novelties are included, as the initiation strategy for calculations, the way to obtain the tangent vector and the set of equations on which the technique is applied. three examples are illustrated with the solutions of acetone + chloroform + benzene, acetone + chloroform + methanol and acetic acid + amyl alcohol + amyl acetate, emphasizing cases that show better separation possibilities in the finite reflux condition than with total reflux operation.
Individualismo y violencia.
César Augusto Sánchez.
Affectio Societatis , 1999,
Abstract: Tres momentos diferentes en la historia de la humanidad aportan para éste articulo algunos rasgos comunes que sirven para pensar la potencia del padre en los procesos de paz realizados por jóvenes en el espacio urbano : el padre de la horda primordial, el déspota de oriente y el Moisés egipcio conjeturado por Freud en sus elaboraciones. El padre imaginario, tal como lo asume la teoría psicoanalítica, es el eje sobre el cual gira la disertación con que se intenta comprender algo del ominoso fenómeno de la violencia y algo de las vicisitudes de los procesos de paz realizados en Colombia. De forma general, Lo escrito deja abierta la posibilidad de privilegiar alguna nueva opinión sobre el asunto dado que no se trata de una concepción acabada; y, forma particular adolece de planteamientos alrededor del padre real y simbólico, así como de otras categorías fundamentales para el análisis de éste fenómeno y éstos procesos.
STRUCTURATION HIéRARCHIQUE DU LEXIQUE VERBAL à TRAVERS LA PROPRIéTé DE TROPONYMIE
Beatriz Sánchez Cárdenas
Revista de Lingüística y Lenguas Aplicadas , 2011, DOI: 10.4995/rlyla.2011.913
Abstract: La structuration onomasiologique du lexique reste un défi à relever en lexicographie fran aise. Il serait en effet extrêmement bénéfique pour les usagers de développer de nouveaux outils qui proposent une représentation de l’organisation des unités lexicales tenant compte des liens sémantiques qui existent entre eux. Nous explorons ici la propriété de troponymie, qui détermine les liens d’inclusion sémantique verbale entre les verbes. Elle s’avère être un outil efficace pour parvenir à une structuration hiérarchique du lexique verbal. Le cas des verbes d’ingestion nous permettra d’illustrer comment cette propriété peut être mise au profit du lexicographe.
CáLCULO E INTERPRETACIóN DE LAS TRAYECTORIAS DE PUNTOS DE COMPOSICIóN CONSTANTE (PINCH) EN COLUMNAS SIMPLES DE DESTILACIóN PARA MEZCLAS AZEOTRóPICAS HOMOGéNEAS CáLCULO E INTERPRETA O DAS TRAJETóRIAS DE PONTOS DE COMPOSI O CONSTANTE (PINCH) EM COLUNAS SIMPLES DE DESTILA O PARA MISTURAS AZEOTRóPICAS HOMOGêNEAS CALCULATION AND INTERPRETATION OF THE PINCH POINTS TRAJECTORIES IN SIMPLE DISTILLATION COLUMNS FOR HOMOGENEOUS AZEOTROPIC MIXTURES
César Augusto Sánchez
Revista EIA , 2011,
Abstract: Se presenta un método de continuación del tipo predictor-corrector para trazar completamente los ramales de puntos de pinch asociados con los productos o seudoproductos de una columna de destilación azeotrópica homogénea. El método trata fácilmente con los puntos de retorno permitiendo la localización de los puntos pinch del tipo tangente. El concepto se fundamenta en las ideas de Fidkowski, Malone y Doherty, pero incluye algunas novedades, como la estrategia de iniciación de los cálculos, la forma de obtener el vector tangente y el grupo de ecuaciones sobre el cual se aplica la técnica. Se ilustran tres ejemplos con las soluciones de acetona + cloroformo + benceno, acetona + cloroformo + metanol y ácido acético + amilalcohol + amilacetato, enfatizando en casos que muestran mejores posibilidades de separación en la condición de reflujo finito que en la operación con reflujo total. Apresenta-se um método de continua o do tipo preditor-corretor para tra ar completamente os ramos de pontos de pinch associados com os produtos ou pseudoprodutos de uma coluna de destila o azeotrópica homogénea. O método trata facilmente com os pontos de retorno permitindo a localiza o dos pontos pinch do tipo tangente. O conceito fundamenta-se nas ideias de Fidkowski, Malone e Doherty, mas inclui algumas novidades, como a estratégia de inicia o dos cálculos, a forma de obter o vetor tangente e o grupo de equa es sobre o qual se aplica a técnica. Ilustram-se três exemplos com as solu es de acetona + clorofórmio + benzeno, acetona + clorofórmio + metanol e ácido acético + amilálcool+ amilacetato, enfatizando em casos que mostram melhores possibilidades de separa o na condi o de refluxo finito que na opera o com refluxo total. A continuation method of the kind predictor-corrector is presented for completely tracking of the pinch points branches related to the products or pseudoproducts of a homogeneous azeotropic distillation column. The method easily handles the turning points allowing the localization of the tangent pinch points. The foundation of the concept is in the ideas of Fidkowski, Malone y Doherty; however, some novelties are included, as the initiation strategy for calculations, the way to obtain the tangent vector and the set of equations on which the technique is applied. Three examples are illustrated with the solutions of acetone + chloroform + benzene, acetone + chloroform + methanol and acetic acid + amyl alcohol + amyl acetate, emphasizing cases that show better separation possibilities in the finite reflux condition than with total reflux operation.
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