Heterogeneity and model uncertainty in bayesian regression models

Data heterogeneity appears when the sample comes from at least two different populations. We analyze three types of situations. The first and simplest case corresponds to the situation in which the majority of the data comes form a central model and a few isolated observations comes from a contaminating distribution. Then the data from the contaminating distribution are called outliers and they have been studied in depth in the statistical literature. The second case corresponds to the situation in which we still have a central model but the heterogeneous data may appears in clusters of outliers which mask each other. This is the multiple outlier problem which is much more difficult to handle and it has understood and analyzed in the last few years. The few Bayesian contributions to this problem are presented. The third case corresponds to the situation in which we do not have a central model but instead different groups of data have been generated by different models. When the data is multivariate normal, this problem has been analyzed by mixture models under the name of cluster analysis but a challenging area of research is to develop a general methodology to apply this multiple model approach to other statistical problems. Heterogeneity implies in general an increase in the uncertainty of predictions, and in this paper a procedure to measure this effect is proposed

Principal components for multivariate functional data

This is the author's version of a work that was accepted for publication in Computational Statistics and Data Analysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in COMPUTATIONAL STATISTICS AND DATA ANALYSIS, Vol 55, Issue 9, (2011) http://dx.doi.org/10.1016/j.csda.2011.03.01

Detection of outlier patches in autoregressive time series

This paper proposed a procedure to identify patches of outliers in an autoregressive process. The procedure is an improvement over the existing outlier detection methods via Gibbs sampling. It identifies the beginning and end of possible outlier patches using the existing Gibbs sampling, then carries out and adaptive procedure with block interpolation to handle patches of outliers. Empirical and simulated examples show that the proposed procedure is effective in handling masking and swamping effects caused by multiple outliers. The real example also shows that the standard Gibbs sampling to outlier detection may encounter severe masking and swamping effects in practice

Estudio de métodos de selección de conceptos

Ponencia presentada en el XI Congreso Internacional de Ingeniería de Proyectos celebrado en Lugo en el año 2007Best product concept selection is of prime importance to direct the marketing launching process. This selection is one of the most difficult and critical decisions for the designer, and an inappropriate concept selection can rarely be compensated on a later stage of the process, increasing the cost of redesign at the same time. Nowadays, there are several concept selection and evaluation methods that allow to reduce the failure risk. The objective of this communication is to carry an analysis of those different methods to evaluate and select concepts, with the aim of reinforcing the methodology developed by the authors on 2006.La elección del mejor concepto de producto es vital para encaminar el proceso de lanzamiento del mismo al mercado. Dicha elección es una de las cuestiones más críticas y difíciles que tiene que tomar el diseñador. Una elección inadecuada de concepto raramente puede ser compensada en posteriores fases del proceso incrementando a su vez el coste de rediseño. En la actualidad existen diferentes métodos de selección y evaluación de concepto que permiten reducir el riesgo de fracaso del proceso. El objetivo de esta comunicación es realizar un estudio de los diferentes métodos que existen en la actualidad para la evaluar y seleccionar conceptos de producto, con el fin de reforzar el método desarrollado por los autores en el año 2006

Brief intervention with music therapy stimulation in a case of dementia: neuroimaging effects

La demencia es un síndrome de prevalencia creciente a nivel mundial, que se caracteriza por deterioro cognitivo y la aparición de diversos síntomas. Del abanico de posibilidades en cuanto al abordaje para esta población se encuentran las intervenciones que provee la musicoterapia, una disciplina en pleno crecimiento dentro del área de salud. El objetivo del presente artículo es presentar el análisis de un estudio de caso clínico con diagnóstico de demencia vascular, a quien se le realizó una evaluación por neuroimagen con cámara gamma, antes y después del proceso de estimulación con musicoterapia. Los resultados evidenciaron una mejoría en el área de corteza frontoparietal izquierda, luego de la estimulación musicoterapeutica. Si bien el presente artículo es la presentación de un caso único, los datos permiten entrever las potencialidades que presentan las propuestas dentro del campo de la musicoterapia en el abordaje de pacientes con demencia.Dementia is a syndrome of increasing prevalence around the world, characterized by cognitive deterioration and the appearance of several symptoms. From the range of possibilities in terms of treating this population are the interventions provided by music therapy, a discipline that is growing within the health area. The aim of this article is to present the analysis of a clinical case study with a diagnosis of vascular dementia, to whom an evaluation of neuroimaging with a gamma camera was made, before and after the music therapy stimulation process. The results showed an improvement in the area of the left frontoparietal cortex after the music-therapy stimulation. Although, the current article is the presentation of a case report, the data allow to glimpse the great potentialities that the field of music therapy had in the approach of patients with dementia

Maritime antarctic lakes as sentinels of climate change

Remote lakes, such as lakes from the Maritime Antarctica, can be used as sentinels of climate change, because they are mostly free of direct anthropogenic pressures, and they experience climate change as a main stressor capable of modifying the ecosystem structure and function. In this paper, the content of a lecture that has been presented at the First Conference of Lake Sustainability, which has been centred in our studies on lakes from Byers Peninsula (Maritime Antarctica), are summarized. These included physical, chemical and biological studies of these lakes and other freshwater ecosystems, which highlighted the relevance of biotic interactions for these ecosystems and its sensibility to temperature variations and to biological invasions, which is of rel- evance given the acute regional warming occurring during the last decades in the area, concomitant with the enhancement of dispersion of alien species linked to the increased presence of humans

A Comparison of Marginal Likelihood Computation Methods

In a Bayesian analysis, different models can be compared on the basis of theexpected or marginal likelihood they attain. Many methods have been devised to compute themarginal likelihood, but simplicity is not the strongest point of most methods. At the sametime, the precision of methods is often questionable.In this paper several methods are presented in a common framework. The explanation of thedifferences is followed by an application, in which the precision of the methods is testedon a simple regression model where a comparison with analytical results is possible

Dos biomarcadores de la plasticidad de la expresión génica en corales Pocillopora del arrecife Carrizales, Pacífico Tropical Mexicano

Background. Gene expression (GE) plasticity is an acclimation response that allows organisms to adjust rapidly to environmental changes, providing an adaptive advantage. GE biomarkers are emerging as a valua-ble tool for linking the organism’s physiological plasticitywith the synergetic effects of large-scale climatic conditions and local impacts such as temperature and nutrients. Objectives. In this study, we investigate the GE plasticity of the 70-kDa heat shock protein (hsp70) and the carbonic anhydrase enzyme (CA) to confirm the ability of those two genes as biomarkers of the Cellular Stress Response and Cellular Homeostasis Res-ponse, respectively. Methods. Using qPCR, we evaluate the GE plasticity of coral colonies from Pocillopora capitata, Pocillopora damicornis,and Pocillopora verrucosa at the Carrizales reef (Colima coast of Mexico) naturally exposed to environmental changes in the Sea Surface Temperature (SST), productivity and nutrients using the cellular density of Symbiodiniaceae and chlorophyll content as health indices. Results. Our results clearly show GE plasticity in the hsp70 for Pocillopora verrucosa and Pocillopora damicornis related to a daily environmental change in temperature and nutrients. On the other hand, the CA gene expression shows no change in response to daily variations. However, there was a significantly high expression of CA and a lower expression of hsp70 in Pocillopora capitata. Furthermore, we found no significant differences in the health in-dices, suggesting some degree of physiological plasticity in Pocillopora corals like its extensive morphological plasticity that could reflect different adaptation capacities to low temperatures and high nutrients during the spring season in the central Mexican Pacific. Conclusions. Evaluating the phenotypic plasticity (morphology and molecular physiology) could help identify coral colonies with a more significant potential to survive en-vironmental stressors. The latter is an essential consideration for managing, conserving, and restoring coral reefs in the Mexican Pacific.Antecedentes. La plasticidad de la expresión génica (GE) es una respuesta inmediata de aclimatación al cambio ambiental que puede proporcionar una ventaja adaptativa. Los biomarcadores de GE están emer-giendo como una herramienta valiosa para vincular la plasticidad fisiológica del organismo con los efectos sinérgicos del cambio climático y el impacto local como la temperatura y nutrientes. Objetivos. Investigamos la plasticidad de la expresión de genes que codifican para la proteína de choque térmico de 70-kDa (hsp70) y la enzima anhidrasa carbónica (CA) para confirmar su utilidad como biomarcadores de la respuesta de estrés y de homeostasis celular, respectivamente. Métodos. Evaluamos la GE mediante qPCR en colonias de corales Pocilloporacapitata, Pocillopora damicornis y Pocillopora verrucosa del arrecife Carrizales (Colima, México) expuestas a un cambio natural en la temperatura de la superficie del mar (SST), productividad pri-maria y nutrientes utilizando la densidad de Symbiodiniaceae y el contenido de clorofila como indicadores de salud. Resultados. La plasticidad de la GE de hsp70 en Pocillopora damicornis y Pocillopora verrucosa se asocia con la variación diaria de temperatura y nutrientes, mientras que el gen de la CA no muestra cambios de expresión relacionada con esta variabilidad. Sin embargo, en Pocillopora capitata se encontró una expresión significativamente mayor de CA y una menor expresión de hsp70. Estos resultados reflejan un grado de plasticidad fisiológica en corales Pocillopora similar a la extensa plasticidad morfológica dentro de este género, lo que podría sugerir diferentes capacidades de adaptación a la temporada primave-ral de bajas temperaturas y alto contenido de nutrientes en la región. Conclusiones. Evaluar la plasticidad fenotípica (morfología y fisiolo-gía molecular) podría ser útil para identificar colonias de corales con un mayor potencial de sobrevivencia al estrés ambiental. Lo anterior resulta relevante para la conservación, manejo y restauración de los arrecifes de coral del Pacífico mexicano.   &nbsp

Can compact optimisation algorithms be structurally biased?

In the field of stochastic optimisation, the so-called structural bias constitutes an undesired behaviour of an algorithm that is unable to explore the search space to a uniform extent. In this paper, we investigate whether algorithms from a subclass of estimation of distribution algorithms, the compact algorithms, exhibit structural bias. Our approach, justified in our earlier publications, is based on conducting experiments on a test function whose values are uniformly distributed in its domain. For the experiment, 81 combinations of compact algorithms and strategies of dealing with infeasible solutions have been selected as test cases. We have applied two approaches for determining the presence and severity of structural bias, namely an (existing) visual and an (updated) statistical (Anderson-Darling) test. Our results suggest that compact algorithms are more immune to structural bias than their counterparts maintaining explicit populations. Both tests indicate that strong structural bias is found only in the cBFO algorithm, regardless of the choice of strategy of dealing with infeasible solutions, and cPSO with mirror strategy. For other test cases, statistical and visual tests disagree on some cases classified as having mild or strong structural bias: the former one tends to make harsher decisions, thus needing further investigation