Propuesta regulatoria para la sustituci?n del mecanismo de declaraci?n de precios de gas natural

El esquema de la Ley de Concesiones El?ctricas (LCE) consiste en un pool obligatorio bajo costos auditados. Este simula competencia, en tanto el precio spot es igual al costo variable de la ?ltima central que despacha. El DS N? 016-2000-EM estableci? una excepci?n, permitiendo las declaraciones no auditables a las Generadoras que usan GN bajo el Mecanismo de Declaraci?n de Precios (MDP). Inflexibilidades contractuales en el Suministro, Transporte y Distribuci?n de GN hacen que los costos asociados se comporten como fijos. Despachar o no despachar se convierte en una decisi?n cr?tica para la Generadora, puesto que si no despacha, sus costos comprenden la remuneraci?n a precio spot de los retiros y el pago de los insumos no consumidos. Las conclusiones principales de la tesis son: - El MDP afecta la eficiencia asignativa del Mercado de Corto Plazo (MCP). Esto incentiva, entre otros, que el CMCP sea menor y el aumento del Cargo Prima RER. - La Opci?n Regulatoria escogida es aquella donde se hace variable el costo de los insumos, y se crea una bolsa con caracteres fiduciarios que contiene los compromisos contractuales. La nominaci?n se realiza por el COES optimizando y minimizando el costo de operaci?n. Las cantidades no utilizadas (minimizadas a trav?s de declaraciones del COES) son remuneradas a trav?s de un cargo

Population mechanics: A mathematical framework to study T cell homeostasis

Unlike other cell types, T cells do not form spatially arranged tissues, but move independently throughout the body. Accordingly, the number of T cells in the organism does not depend on physical constraints imposed by the shape or size of specific organs. Instead, it is determined by competition for interleukins. From the perspective of classical population dynamics, competition for resources seems to be at odds with the observed high clone diversity, leading to the so-called diversity paradox. In this work we make use of population mechanics, a non-standard theoretical approach to T cell homeostasis that accounts for clone diversity as arising from competition for interleukins. The proposed models show that carrying capacities of T cell populations naturally emerge from the balance between interleukins production and consumption. These models also suggest remarkable functional differences in the maintenance of diversity in naïve and memory pools. In particular, the distribution of memory clones would be biased towards clones activated more recently, or responding to more aggressive pathogenic threats. In contrast, permanence of naïve T cell clones would be determined by their affinity for cognate antigens. From this viewpoint, positive and negative selection can be understood as mechanisms to maximize naïve T cell diversity

Optimising the Use of Computed Radiography in Pediatric Chest Imaging

The objective of this study was to analyze image quality of chest examinations in pediatric patients using computed radiography (CR) obtained with a wide range of doses to suggest the appropriate parameters for optimal image quality. A sample of 240 chest images in four age ranges was randomly selected from the examinations performed during 2004. Images were obtained using a CR system and were evaluated independently by three radiologists. Each image was scored using criteria proposed by the European Guidelines on Quality Criteria in Pediatrics. Mean global scoring and scoring of individual criteria more sensitive to noise were used to evaluate image quality. Agfa dose level (DL) was in the range 1.20 to 2.85. It was found that there was not significant correlation (R < 0.5) between image quality and DL for any of the age ranges for either global score or for individual criteria more related to noise. The mean value of DL was in the ranges 1.9–2.1 for the four age bands. From this study, a DL value of 1.6 is proposed for pediatric CR chest imaging. This could yield a reduction of approximately a factor of 2.5 in mean patient entrance surface doses