Search results for "estadística"
showing 10 items of 196 documents
InN thin film lattice dynamics by grazing incidence inelastic x-ray scattering.
2011
Achieving comprehensive information on thin film lattice dynamics so far has eluded well established spectroscopic techniques. We demonstrate here the novel application of grazing incidence inelastic x-ray scattering combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy optic phonon dispersion relations of thin wurtzite indium nitride films. Indium nitride is an especially relevant example, due to the technological interest for optoelectronic and solar cell applications in combination with other group III nitrides.
Variable Neighborhood Search for the Vertex Separation Problem
2012
The vertex separation problem belongs to a family of optimization problems in which the objective is to nd the best separator of vertices or edges in a generic graph. This optimization problem is strongly related to other well-known graph problems; such as the Path-Width, the Node Search Number or the Interval Thickness, among others. All of these optimization problems are NP-hard and have practical applications in VLSI, computer language compiler design or graph drawing. Up to know, they have been generally tackled with exact approaches, presenting polynomial-time algorithms to obtain the optimal solution for speci c types of graphs. However, in spite of their practical applications, these…
Internal Test Sets Studies in a Group of Antimalarials
2006
Topological indices have been applied to build QSAR models for a set of 20 an- timalarial cyclic peroxy cetals. In order to evalua te the reliability of the proposed linear models leave-n-out and Internal Test Sets (ITS) approaches have b een considered. The pro- posed procedure resulted in a robust and consensued prediction equation and here it is shown why it is superior to the employed standard c ross-validation algorithms involving multilinear regression models.
Objective Bayesian point and region estimation in location-scale models.
2007
Point and region estimation may both be described as specific decision problems. In point estimation, the action space is the set of possible values of the quantity on interest; in region estimation, the action space is the set of its possible credible regions. Foundations dictate that the solution to these decision problems must depend on both the utility function and the prior distribution. Estimators intended for general use should surely be invariant under one-to-one transformations, and this requires the use of an invariant loss function; moreover, an objective solution requires the use of a prior which does not introduce subjective elements. The combined use of an invariant informatio…
Sequential Monte Carlo methods in Bayesian joint models for longitudinal and time-to-event data
2017
El análisis estadístico de la información generada por el seguimiento médico de una enfermedad es un reto muy importante en el ámbito de la medicina personalizada. A medida que avanza el curso evolutivo de la enfermedad en un paciente, su seguimiento genera cada vez más información que debe ser procesada inmediatamente para revisar y actualizar su pronóstico y tratamiento. Nuestro objetivo en esta tesis se centra en dicho proceso de actualización a través de métodos de inferencia secuencial en modelos conjuntos de datos longitudinales y de supervivencia desde una perspectiva Bayesiana. En concreto, proponemos la utilización de métodos secuenciales de Monte Carlo adaptados a modelos conjunto…
Caracterización fónica de la (des)cortesía en el español hablado de Valencia. Aproximación cualitativo-cuantitativa
2023
En este artículo se presentan los resultados de un estudio de doble naturaleza cualitativo-cuantitativa basado en la exploración y el análisis de los datos pertenecientes a la base de datos Fonocortesía (www.fonocortesia.es), que recoge 278 secuencias de habla espontánea (des)corteses derivadas del proyecto Fonocortesía (FFI2009-07034-FILO), desarrollado entre 2009-2013. Tales secuencias (des)corteses, analizadas y sometidas a revisión conjunta por el equipo investigador del mencionado proyecto, han sido procesadas con la herramienta Oralstats (https://github.com/acabedo/oralstats) capaz de desarrollar el análisis estadístico inferencial y la visualización exploratoria de bases de datos. Lo…
Cognitive resource allocation determines the organization of personal networks
2018
Significance The way we organize our social relationships is key to understanding the structure of our society. We propose a quantitative theory to tackle this issue, assuming that our capacity to maintain relationships is limited and that different types of relationships require different investments. The theory accounts for well-documented empirical evidence on personal networks, such that connections are typically arranged in layers of increasing size and decreasing emotional content. More interestingly, it predicts that when the number of available relationships is small, this structure is inverted, having more close relationships than acquaintances. We provide evidence of the existence…
Immunocompromised patients with acute respiratory distress syndrome: Secondary analysis of the LUNG SAFE database
2018
Background: The aim of this study was to describe data on epidemiology, ventilatory management, and outcome of acute respiratory distress syndrome (ARDS) in immunocompromised patients. Methods: We performed a post hoc analysis on the cohort of immunocompromised patients enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) study. The LUNG SAFE study was an international, prospective study including hypoxemic patients in 459 ICUs from 50 countries across 5 continents. Results: Of 2813 patients with ARDS, 584 (20.8%) were immunocompromised, 38.9% of whom had an unspecified cause. Pneumonia, nonpulmonary sepsis, and noncardiog…
Some findings on zero-inflated and hurdle Poisson models for disease mapping
2018
Zero excess in the study of geographically referenced mortality data sets has been the focus of considerable attention in the literature, with zero-inflation being the most common procedure to handle this lack of fit. Although hurdle models have also been used in disease mapping studies, their use is more rare. We show in this paper that models using particular treatments of zero excesses are often required for achieving appropriate fits in regular mortality studies since, otherwise, geographical units with low expected counts are oversmoothed. However, as also shown, an indiscriminate treatment of zero excess may be unnecessary and has a problematic implementation. In this regard, we find …
Cancer mortality inequalities in urban areas: a Bayesian small area analysis in Spanish cities
2011
incluye "Erratum to: Cancer mortality inequalities in urban areas: a Bayesian small area analysis in Spanish cities" BACKGROUND: Intra-urban inequalities in mortality have been infrequently analysed in European contexts. The aim of the present study was to analyse patterns of cancer mortality and their relationship with socioeconomic deprivation in small areas in 11 Spanish cities. METHODS: It is a cross-sectional ecological design using mortality data (years 1996-2003). Units of analysis were the census tracts. A deprivation index was calculated for each census tract. In order to control the variability in estimating the risk of dying we used Bayesian models. We present the RR of the censu…