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Search Results: 1 - 10 of 54863 matches for " David; Luna "
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Desafección cívica, polarización ideológica y calidad de la democracia: una introducción al Anuario Político de América Latina
Altman,David; Luna,Juan Pablo;
Revista de ciencia política (Santiago) , 2007, DOI: 10.4067/S0718-090X2007000100001
Abstract: the year 2006 was marked by extraordinary electoral activity all over the continent. this year has also shown a higher than normal level of conflict between countries, amounting in some cases to serious diplomatic friction. in addition, there were evident domestic problems touching almost every country: enduring deficits of human development despite an economic expansion, the systematic exclusion of important social groups from the political arena, and an increasing level of political disaffection among the population as a whole. some countries were paralyzed by conflicts and stalemates between the branches of government, and in a broader sense, serious shortcomings have been observed in respect to "democratic governability". although democracy is firmly in place in most of the continent and elections are the main vehicle for selecting governments, we are now facing problems to which, years ago and for understandable reasons, political scientists did not give sufficient attention. the political reality of the region has become so fluid and the new challenges are so varied and significant, that an annual comparative chronicle on the political processes lived by each country constitutes, to our understanding, a fundamental and necessary tool for research. this article is meant to offer an introduction to this political data yearbook of latin america
Desafección cívica, polarización ideológica y calidad de la democracia: una introducción al Anuario Político de América Latina
David Altman,Juan Pablo Luna
Revista de Ciencia Política , 2007,
Abstract: El a o 2006 América Latina estuvo dominada por una inusual actividad electoral a lo largo y ancho del continente. A nivel de relaciones internacionales, este a o se caracterizó por mostrar un nivel infrecuente de conflictividad entre los países, llegando inclusive a manifestarse en roces diplomáticos serios. Al interior de cada país, también resultaron evidentes problemas transversales: déficits persistentes de desarrollo humano a contramano de la expansión económica, la exclusión casi sistemática de importantes grupos sociales del juego político, la persistencia de discriminación social y política por razones de género y/o étnicas, y la presencia de un creciente nivel de desafección política. En algunos países, además, han existido roces entre los ejecutivos y los legislativos y, en un sentido más amplio, se han observado múltiples deficiencias a nivel de "gobernabilidad democrática". Si bien la democracia ha logrado instalarse en la gran mayoría del continente y las elecciones son el principal vehículo de selección de gobiernos, hoy resultan evidentes problemas a los que en un momento de transición, y por razones entendibles, la disciplina no otorgó suficiente importancia. La realidad política de la región se ha vuelto tan dinámica y "fluida" y los nuevos desafíos de nuestras democracias son actualmente tan variados y significativos, que una crónica comparativa anual sobre los procesos políticos vividos por cada país constituye, a nuestro entender, una herramienta de investigación tan fundamental como necesaria. Este trabajo ofrece una introducción a este anuario The year 2006 was marked by extraordinary electoral activity all over the continent. This year has also shown a higher than normal level of conflict between countries, amounting in some cases to serious diplomatic friction. In addition, there were evident domestic problems touching almost every country: enduring deficits of human development despite an economic expansion, the systematic exclusion of important social groups from the political arena, and an increasing level of political disaffection among the population as a whole. Some countries were paralyzed by conflicts and stalemates between the branches of government, and in a broader sense, serious shortcomings have been observed in respect to "democratic governability". Although democracy is firmly in place in most of the continent and elections are the main vehicle for selecting governments, we are now facing problems to which, years ago and for understandable reasons, political scientists did not give sufficient attention. The politic
Diffractons: solitary waves created by diffraction in periodic media
David I. Ketcheson,Manuel Quezada de Luna
Physics , 2013,
Abstract: A new class of solitary waves arises in the solution of nonlinear wave equations with constant impedance and no dispersive terms. They depend on a balance between nonlinearity and a dispersion-like effect due to spatial variation in the sound speed of the medium. A high-order homogenized model confirms this effective dispersive behavior and its solutions agree well with those obtained by direct simulation of the variable-coefficient system. These waves are observed to be long-time stable, globally attracting solutions that arise in general as solutions to nonlinear wave problems with periodically-varying sound speed. They share some properties with known classes of solitary waves, but possess important differences as well.
Numerical simulation of cylindrical solitary waves in periodic media
Manuel Quezada de Luna David I. Ketcheson
Mathematics , 2012, DOI: 10.1007/s10915-013-9747-3
Abstract: We study the behavior of nonlinear waves in a two-dimensional medium with density and stress relation that vary periodically in space. Efficient approximate Riemann solvers are developed for the corresponding variable-coefficient first-order hyperbolic system. We present direct numerical simulations of this multiscale problem, focused on the propagation of a single localized perturbation in media with strongly varying impedance. For the conditions studied, we find little evidence of shock formation. Instead, solutions consist primarily of solitary waves. These solitary waves are observed to be stable over long times and to interact in a manner approximately like solitons. The system considered has no dispersive terms; these solitary waves arise due to the material heterogeneity, which leads to strong reflections and effective dispersion.
Two-dimensional wave propagation in layered periodic media
Manuel Quezada de Luna,David I. Ketcheson
Mathematics , 2013,
Abstract: We study two-dimensional wave propagation in materials whose properties vary periodically in one direction only. High order homogenization is carried out to derive a dispersive effective medium approximation. One-dimensional materials with constant impedance exhibit no effective dispersion. We show that a new kind of effective dispersion may arise in two dimensions, even in materials with constant impedance. This dispersion is a macroscopic effect of microscopic diffraction caused by spatial variation in the sound speed. We analyze this dispersive effect by using high-order homogenization to derive an anisotropic, dispersive effective medium. We generalize to two dimensions a homogenization approach that has been used previously for one-dimensional problems. Pseudospectral solutions of the effective medium equations agree to high accuracy with finite volume direct numerical simulations of the variable-coefficient equations.
Partidos y sistemas de partidos en América Latina: Aproximaciones desde la encuesta a expertos 2009
ALTMAN,DAVID; LUNA,JUAN PABLO; PI?EIRO,RAFAEL; TORO,SERGIO;
Revista de ciencia política (Santiago) , 2009, DOI: 10.4067/S0718-090X2009000300005
Abstract: this research note presents a classification of latin american parties and party systems, according to mainstream ideological currents and country-specific competitive patterns. this classification is based on a preliminary analysis of the results of an expert survey on latin american party systems that was carried out from 2007 to 2009. we factor-analyze parties' positions on a wide set of issues and estimate three (latent) ideological dimensions: statism, conservatism (moral, religious, nationalist), and attitudes towards democracy. based on these three ideological dimensions we perform a cluster analysis and classify the political parties of the region in ten "ideological families".
Partidos y sistemas de partidos en América Latina: Aproximaciones desde la encuesta a expertos 2009 Parties and Party Systems in Latin America: Perspectives from an Expert Survey 2009
DAVID ALTMAN,JUAN PABLO LUNA,RAFAEL PI?EIRO,SERGIO TORO
Revista de Ciencia Política , 2009,
Abstract: En base a la identificación de corrientes ideológicas y patrones de competencia nacionales, esta nota de investigación presenta una clasificación de los partidos políticos y sistemas de partido de América Latina. La clasificación que presentamos se basa en un primer análisis de los resultados de una encuesta a expertos realizada entre 2007 y 2009, para sondear las características de los partidos políticos de la región. En base a una estrategia de análisis factorial, aplicada a un conjunto amplio de preguntas incluidas en la encuesta, construimos tres dimensiones ideológicas (latentes): estatismo, conservadurismo (moral, religioso, y nacionalista), y actitudes acerca del régimen democrático. Utilizando estas tres dimensiones ideológicas como insumo para un análisis de clusters, clasificamos a los partidos políticos de la región en diez "familias ideológicas". This research note presents a classification of Latin American parties and party systems, according to mainstream ideological currents and country-specific competitive patterns. This classification is based on a preliminary analysis of the results of an expert survey on Latin American party systems that was carried out from 2007 to 2009. We factor-analyze parties' positions on a wide set of issues and estimate three (latent) ideological dimensions: statism, conservatism (moral, religious, nationalist), and attitudes towards democracy. Based on these three ideological dimensions we perform a cluster analysis and classify the political parties of the region in ten "ideological families".
Ab Initio Molecular Orbital Calculation for Optical and Electronic Properties Evaluation of Small and Medium Size Silicon Nano-Clusters Found in Silicon Rich Oxide Films  [PDF]
Néstor David Espinosa Torres, José Francisco Javier Flores Gracia, José Alberto Luna López, Juan Carlos Ramírez García, Alfredo Morales Sánchez, José Luis Sosa Sánchez, David Hernández de la Luz, Francisco Morales Morales
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.411A2001
Abstract:

In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of those found in corresponding bulk materials. Silicon agglomerates found in Silicon Rich Oxide (SRO) films have optical properties, which have reported as depended directly on nano-crystal size. Furthermore, the room temperature photoluminescence (PL) of Silicon Rich Oxides (SRO) has repeatedly generated a huge interest due to their possible applications in optoelectronic devices. However, a plausible emission mechanism has not yet widespread acceptance of the scientific community. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6 - 31G* to calculate the optical and electronic properties of small (six to ten silicon atoms) and medium size clusters of silicon (constituted of eleven to fourteen silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism experimentally found in thin SRO films.

Forecast of the Luminescent Phenomena of Silicon Rich Oxide Films off Stoichiometry by Means of the Global Reaction Model  [PDF]
Néstor David Espinosa-Torres, José álvaro David Hernández de la Luz, José Francisco Javier Flores-Gracia, José Alberto Luna-López, Javier Martínez-Juárez, Gregorio Flores-Carrasco
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.611170
Abstract: The Global Reaction Model describes a set of chemical reactions that can potentially occur during the process of obtaining silicon rich oxide (SRO) films, regardless of the technique used to grow such films which are an outside stoichiometry material. Particularly, chemical reactions that occur during the process of growing of SRO films by LPCVD technique are highlighted in this model. We suggest and evaluate either some types of molecules or resulting nanostructures and we predict theoretically, by applying the density functional theory, the contribution that they may have to the phenomenon of luminescence which is measured in SRO films. Also, we have calculated the opto-electronic properties of SRO films. The suggested model provides enough information required to identify the molecular structures resulting from the presence of defects in SRO films and also those corresponding to charged structures. It is also possible to detect the molecular structures which are modified due to the effect of heat treatment, and identify the presence of different oxidation states inclusive the formation of siloxanes.
The activity of azithromycin against Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis in the golden hamster model
Sinagra, ángel;Luna, Concepción;Abraham, David;Iannella, Maria del Carmen;Riarte, Adelina;Krolewiecki, Alejandro J.;
Revista da Sociedade Brasileira de Medicina Tropical , 2007, DOI: 10.1590/S0037-86822007000600005
Abstract: new therapeutic alternatives against leishmaniasis remain a priority. the activity of azithromycin against leishmania (leishmania) major has been previously demonstrated. different responses among species of leishmania make species-specific drug screening necessary. the activity of azithromycin against leishmania (viannia) braziliensis and leishmania (leishmania) amazonensis was evaluated in golden hamsters infected through footpad injections of metacyclic promastigotes, and compared with untreated controls and animals treated with meglumine antimoniate. footpad thickness, lesion cultures and dissemination sites were analyzed. treatment of golden hamsters with oral azithromycin at 450mg/kg had no activity against infections with leishmania (leishmania) amazonensis. for infections due to leishmania (viannia) braziliensis, azithromycin demonstrated significant activity relative to untreated controls, but inferior to meglumine antimoniate, for controlling lesion size. neither drug was able to totally eliminate parasites from the lesions. it was concluded that azithromycin has activity against leishmania (viannia) braziliensis but not against leishmania (leishmania) amazonensis in this model.
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