Cobertura de la insuficiencia renal crónica en la seguridad social nicaragüense

Estudio cuyo fin es conocer los antecedentes médicos de la Insuficiencia Renal Crónica (IRC), como enfermedad laboral además de determinar su calificación como enfermedad laboral y valorar el grado de dificultad para diagnosticarla como tal

Monte Carlo simulation of damage and amorphization induced by swift-ion irradiation in LiNbO3

This paper presents a Monte Carlo (MC) simulation tool which is applied to describe the ion beam induced damage generated by electronic excitation in LiNbO3. Based on a previously published thermal spike based analytical model, the MC technique allows for a more flexible and accurate treatment of the problem. A main advantage of this approach with respect to the analytical one is the possibility of studying the role of statistical fluctuations, relevant at low fluences. The paper recalls the main features of the physical model, describes the MC algorithm, and compares simulation results to experimental data (irradiations of LiNbO3 using silicon ions at 5 and 7.5 MeV and oxygen ions at 5 MeV). © 2006 American Institute of Physics.Peer Reviewe

Lattice preamorphization by ion irradiation: Fluence dependence of the electronic stopping power threshold for amorphization

A thermal-spike model has been applied to characterize the damage structure of the latent tracks generated by high-energy ion irradiations on LiNb O3 through electron excitation mechanisms. It applies to ions having electronic stopping powers both below and above the threshold value for lattice amorphization. The model allows to estimate the defect concentrations in the heavily damaged (preamorphized) regions that have not reached the threshold for amorphization. They include the halo and tail surrounding the core of a latent track. The existence of the preamorphized regions accounts for a synergy between successive irradiations and predicts a dependence of the amorphization threshold on previous irradiation fluence. The predicted dependence is in accordance with irradiation experiments using N (4.53 MeV), O (5.00 MeV), F (5.13 MeV), and Si (5 and 7.5 MeV). For electronic stopping powers above the threshold value the model describes the generation of homogeneous amorphous layers and predicts the propagation of the amorphization front with fluence. A theoretical expression, describing this propagation, has been obtained that is in reasonable agreement with silicon irradiation experiments at 5 and 7.5 MeV. The accordance is improved by including in a simple phenomenological way the velocity effect on the threshold. At the highest fluences (or depths) a significant discrepancy appears that may be attributed to the contribution of the nuclear collision damage. © 2005 American Institute of Physics.Peer Reviewe

Monte Carlo simulation of damage and amorphization induced by swift-ion irradiation in LiNbO3

This paper presents a Monte Carlo (MC) simulation tool which is applied to describe the ion beam induced damage generated by electronic excitation in LiNbO3. Based on a previously published thermal spike based analytical model, the MC technique allows for a more flexible and accurate treatment of the problem. A main advantage of this approach with respect to the analytical one is the possibility of studying the role of statistical fluctuations, relevant at low fluences. The paper recalls the main features of the physical model, describes the MC algorithm, and compares simulation results to experimental data (irradiations of LiNbO3 using silicon ions at 5 and 7.5 MeV and oxygen ions at 5 MeV). © 2006 American Institute of Physics.Peer Reviewe

Poder de mercado en mercados spot de generación eléctrica: metodología para su análisis

Después de analizar las experiencias internacionales relacionadas con el monitoreo y control de poder de mercado, se establece una metodología acorde a las características del pool eléctrico en Colombia, la cual permite hacer seguimiento sobre comportamientos estratégicos respecto al precio en bolsa en este mercado. Se propone un modelo exponencial para la función de oferta en el pool basado en un modelo de precios spot, explicado por los costos, las condiciones climáticas, las intervenciones de la Comisión de Regulación de Energía y Gas, la demanda diaria, las cantidades generadas y el precio histórico. Por medio de una convolución (técnica similar a la de un Filtro de Kalman) sobre los precios históricos se estiman los parámetros y elasticidades dinámicas asociadas a las cantidades que determinan el comportamiento del precio en bolsa. A su vez, estas estimaciones son utilizadas en la estructura de beneficios en un modelo de Cournot, de competencia en cantidades, que evidencia el efecto positivo, vía disminución del precio de bolsa, de mayores niveles de contratos a futuros en el pool eléctrico colombiano

On the origin of the jet-like radio/X-ray morphology of G290.1-0.8

The origin and evolution of supernova remnants of the mixed-morphology class is not well understood. Several remnants present distorted radio or X-ray shells with jet-like structures. G290.1-0.8 (MSH 11-61A) belongs to this class. We aim to investigate the nature of this supernova remnant in order to unveil the origin of its particular morphology. We based our work on the study of the X-ray emitting plasma properties and the conditions imposed by the cold interstellar medium where the remnant expanded. We use archival radio, HI line data and X-ray observations from XMM-Newton and Chandra observatories, to study G290.1-0.8 and its surrounding medium. Spatially resolved spectral analysis and mean photon energy maps are used to obtain physical and geometrical parameters of the source. Radio continuum and HI line maps give crucial information to understand the radio/X-ray morphology. The X-ray images show that the remnant presents two opposite symmetric bright spots on a symmetry axis running towards the NW-SE direction. Spectral analysis and mean photon energy maps confirm that the physical conditions of the emitting plasma are not homogeneous throughout the remnant. In fact, both bright spots have higher temperatures than the rest of the plasma and its constituents have not reached ionization equilibrium yet. HI line data reveal low density tube-like structures aligned along the same direction. This evidence supports the idea that the particular X-ray morphology observed is a direct consequence of the structure of the interstellar medium where the remnant evolved. However, the possibility that an undetected point-like object, as a neutron star, exists within the remnant and contributes to the X-ray emission cannot be discarded. Finally, we suggest that a supernova explosion due to the collapse of a high-mass star with a strong bipolar wind can explain the supernova remnant morphology.Comment: 8 pages, 6 figures. Accepted for publication in A&

Optical determination of three-dimensional nanotrack profiles generated by single swift-heavy ion impacts in lithium niobate

Three-dimensional (3D) profiles of single nanotracks generated by a low impact density of Cl ions at 46 MeV have been determined by optical methods, using an effective-medium approach. The buried location of the maximum stopping power induces a surface optical waveguiding layer even at ultralow fluences (1011-1013 at./cm2) that allows to obtain the effective refractive index profiles (from dark-mode measurements). Combining the optical information with Rutherford backscattering spectroscopy/channeling experiments, the existence of a surrounding defective halo around the amorphous track core has been ascertained. The 3D profile of the halo has also been determined. © 2006 American Institute of Physics.Peer Reviewe

Optical determination of three-dimensional nanotrack profiles generated by single swift-heavy ion impacts in lithium niobate

Three-dimensional (3D) profiles of single nanotracks generated by a low impact density of Cl ions at 46 MeV have been determined by optical methods, using an effective-medium approach. The buried location of the maximum stopping power induces a surface optical waveguiding layer even at ultralow fluences (1011-1013 at./cm2) that allows to obtain the effective refractive index profiles (from dark-mode measurements). Combining the optical information with Rutherford backscattering spectroscopy/channeling experiments, the existence of a surrounding defective halo around the amorphous track core has been ascertained. The 3D profile of the halo has also been determined. © 2006 American Institute of Physics.Peer Reviewe

Veinte años de funcionamiento del Mercado Eléctrico Mayorista en Colombia: algunas reflexiones

El objetivo de este escrito es analizar el desempeño del Mercado Eléctrico Mayorista - MEM en los veinte años de existencia. Después de describir el funcionamiento del mercado spot, el mercado de largo plazo y el cargo por confiabilidad; se analiza el efecto de variables como el fenómeno de El Niño, el nivel de embalse, la relación entre la disponibilidad real y la demanda comercial y algunos efectos de cambios regulatorios sobre el precio spot. También a través de un modelo estocástico se establecen algunas recomendaciones de cómo mejorar el funcionamiento de este mercado con la implementación de contratos estandarizados teniendo en cuenta las experiencias internacionales. A pesar del avance del mercado en estos veinte años de funcionamiento, aún quedan aspectos por resolver, como la implementación de contratos de largo plazo estandarizados, redes inteligentes y la disminución del umbral para acceder al mercado no regulado, pues estos aspectos ayudarían a disminuir el precio spot.The aim of this paper is to analyze wholesale electricity market performance in the twenty years of existence. After describing spot market operation, the market for long-term and reliability charge, we analyzed the effect of variables such as El Niño, the reservoir level, the ratio of the actual availability and market demand and some effects of regulatory changes on the spot price. Also through a stochastic model we set up some recommendations on how to improve the functioning of this market with standardized contracts implementation considering international experience. Despite the market's advance in these twenty years of operation, there are still issues to be resolved, such as contracts standardized long-term implementation, smart grids and lowering the threshold to enter the unregulated market, as these aspects would help to reduce the spot price