8 research outputs found

    Changes induced in relative abundance of gut bacteria species by lifestyle in women.

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    <p>(A) <i>Bifidobacterium longum</i>, <i>(</i>B) <i>Faecalibacterium prausnitzii</i>, (C) <i>Roseburia hominis</i>, (D) <i>Akkermansia muciniphila</i>. Data were log transformed and analyzed by t-test * p<0.05 **p<0.01.</p

    Differences in gut microbiota profile between women with active lifestyle and sedentary women - Fig 1

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    <p><b>Principal Coordinates Analysis (PcoA) plots of unweighted (A) and weighted (B) Unifrac distance metrics obtained from sequencing the 16s rRNA gene in fecal samples</b>. Axes represent percentage of data explained by each coordinate dimension.</p

    Analysis of dynamic common factors in the presence of autocorrelated noise-processes

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    This thesis presents a procedure to build a dynamic factor model in the presence of orthogonal stationary noise-processes. The procedure is based on the Peña-Box model (Peña & Box, 1987), in which the number of observed time series is fixed, and in the extension proposed by Peña & Poncela (2006) to non-stationary common factors, in which the common factors may be integrated processes. As a first result, an alternative for detecting the number of common factors is proposed by extending the statistical test of Peña & Poncela (2006), proposed for the Peña-Box model with a white noise process. Furthermore, in the same context, a statistical test is proposed to identify the number of non-stationary common factors. These proposals are illustrated by simulation and an application with real data, in which some empirical findings related to seasonal factors are also presented. The model is estimated by maximum likelihood, via a state-space model.Esta tesis presenta un procedimiento para construir un modelo de factores comunes dinĂĄmicos en presencia de procesos de ruido estacionarios ortogonales. El procedimiento se basa en el modelo de Peña-Box (Peña & Box, 1987), en el cual el nĂșmero de series de tiempo observadas es fijo, y en la extensiĂłn propuesta por Peña & Poncela (2006) a factores comunes no estacionarios, en la cual los factores comunes pueden ser procesos integrados. Como primer resultado, se propone una alternativa para la identificaciĂłn del nĂșmero de factores comunes extendiendo la prueba estadĂ­stica de Peña & Poncela (2006) , propuesta para el modelo Peña-Box con proceso de ruido blanco. Adicionalmente, bajo el mismo contexto, se propone una prueba estadĂ­stica para identificar el nĂșmero de factores comunes no estacionarios. Estas propuestas son ilustradas mediante simulaciĂłn y una aplicaciĂłn con datos reales, en la cual tambiĂ©n se presentan algunos hallazgos empĂ­ricos relacionados a factores estacionales. La estimaciĂłn del modelo se realiza por mĂĄxima verosimilitud, vĂ­a un modelo espacio de estados.LĂ­nea de investigaciĂłn: Series de TiempoDoctorad
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