1,940 research outputs found

    A tomographic approach to the statistical analysis of the large-scale structure of the universe

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    Instruction scheduling in micronet-based asynchronous ILP processors

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    La Participación Ciudadana en la Obra Pública Municipal. Estudio de Caso: Los Comités Ciudadanos de Control y Vigilancia del Municipio de Toluca Estado de México, en el periodo 2009-2012

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    Se analizan y evaluan los aspectos de capacitación, operación, funcionamiento y grado de participación del ciudadano como contralor social, dentro de los Comités Ciudadanos de Control y Vigilancia (COCICOVI) en las obras públicas del municipio de Toluca, en el periodo 2009-2012

    Aplicación del método de valoración contingente al parque natural de L'Albufera

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    El trabajo que aquí se presenta pretende, por un lado, realizar un breve repaso de los fundamentos teóricos del método de valoración contingente, sin olvidar los posibles sesgos en los que se puede incurrir y, por otro lado, dada las ventajas que presenta dicho método, se centrará en la aplicación del mismo a un espacio de elevado interés ecológico como es el Parque Natural de L'Albufera tratando de obtener el valor de los servicios recreativos que proporciona a los visitantes (valor de uso) así como el valor de no uso (existencia). Por lo tanto, este trabajo se encuadra dentro de lo que McConnell (1985) denomina economía de las actividades recreativas al aire libre (Economics of outdoor recreation

    Bolivia 1991 Field Notes

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    Bolivia 1991 Catalog

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    Stochastic angular momentum slews and flips and their effect on discs in galaxy formation models

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    The angular momentum of galactic discs in semi-analytic models of galaxy formation is usually updated in time as material is accreted to the disc by adopting a constant dimensionless spin parameter and little attention is paid to the effects of accretion with misaligned angular momenta. These effects are the subject of this paper, where we adopt a Monte-Carlo simulation for the changes in the direction of the angular momentum of a galaxy disc as it accretes matter based on accurate measurements from dark-matter haloes in the Millennium II simulation. In our semi-analytic model implementation, the flips seen the dark matter haloes are assumed to be the same for the cold baryons; however, we also assume that in the latter the flip also entails a difficulty for the disc to increase its angular momentum which causes the disc to become smaller relative to a no-flip case. This makes star formation to occur faster, specially in low mass galaxies at all redshifts allowing galaxies to reach higher stellar masses faster. We adopt a new condition for the triggering of starbursts during mergers. As these produce the largest flips it is natural to adopt the disc instability criterion to evaluate the triggering of bursts in mergers instead of one based on mass ratios as in the original model. The new implementation reduces the average lifetimes of discs by a factor of 2, while still allowing old ages for the present-day discs of large spiral galaxies. It also provides a faster decline of star formation in massive galaxies and a better fit to the bright end of the luminosity function at z = 0.Comment: 15 pages, 12 figures, MNRAS in pres

    Gaussian covariance matrices for anisotropic galaxy clustering measurements

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    Measurements of the redshift-space galaxy clustering have been a prolific source of cosmological information in recent years. Accurate covariance estimates are an essential step for the validation of galaxy clustering models of the redshift-space two-point statistics. Usually, only a limited set of accurate N-body simulations is available. Thus, assessing the data covariance is not possible or only leads to a noisy estimate. Further, relying on simulated realisations of the survey data means that tests of the cosmology dependence of the covariance are expensive. With these points in mind, this work presents a simple theoretical model for the linear covariance of anisotropic galaxy clustering observations with synthetic catalogues. Considering the Legendre moments (`multipoles') of the two-point statistics and projections into wide bins of the line-of-sight parameter (`clustering wedges'), we describe the modelling of the covariance for these anisotropic clustering measurements for galaxy samples with a trivial geometry in the case of a Gaussian approximation of the clustering likelihood. As main result of this paper, we give the explicit formulae for Fourier and configuration space covariance matrices. To validate our model, we create synthetic HOD galaxy catalogues by populating the haloes of an ensemble of large-volume N-body simulations. Using linear and non-linear input power spectra, we find very good agreement between the model predictions and the measurements on the synthetic catalogues in the quasi-linear regime.Comment: 17 pages, 16 figures, 3 tables; modified to match version accepted by MNRA

    How complexity increases in development : An analysis of the spatial-temporal dynamics of Gene expression in Ciona intestinalis

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    The increase in complexity in an embryo over developmental time is perhaps one of the most intuitive processes of animal development. It is also intuitive that the embryo becomes progressively compartmentalized over time and space. In spite of this intuitiveness, there are no systematic attempts to quantify how this occurs. Here, we present a quantitative analysis of the compartmentalization and spatial complexity of Ciona intestinalis over developmental time by analyzing thousands of gene expression spatial patterns from the ANISEED database. We measure compartmentalization in two ways: as the relative volume of expression of genes and as the disparity in gene expression between body parts. We also use a measure of the curvature of each gene expression pattern in 3D space. These measures show a similar increase over time, with the most dramatic change occurring from the 112-cell stage to the early tailbud stage. Combined, these measures point to a global pattern of increase in complexity in the Ciona embryo. Finally, we cluster the different regions of the embryo depending on their gene expression similarity, within and between stages. Results from this clustering analysis, which partially correspond to known fate maps, provide a global quantitative overview about differentiation and compartmentalization between body parts at each developmental stage. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe
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