5,680 research outputs found

    Pobreza y activos en Bolivia: Qué rol juega el capital social?

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    Análisis recientes de la pobreza en Bolivia muestran que, a pesar de un ligero descenso en el porcentaje de la población que vive en condiciones de pobreza a lo largo de la última década, el número absoluto de hogares pobres continúa en ascenso (Jiménez y Yañez 1997a y b; Vos et al. 1997; Banco Mundial 1996). El bajo nivel de crecimiento de los ingresos de los hogares más pobres sugiere que los esfuerzos sostenidos por mantener niveles de crecimiento económico moderados e incrementar la eficiencia en la asignación del gasto e inversión pública no han sido suficientes para revertir las condiciones de pobreza crónica que caracterizan al país. Los enfoques analíticos que sostuvieron la aplicación de políticas de crecimiento y redes de protección en la región también se encuentran en un periodo de cuestionamiento y reformulación. Perspectivas que enfatizaban la medición de la pobreza por insuficiencia de ingresos o necesidades básicas (Lipton y van der Gaag 1993; Boltvinik 1992), se encuentran interpelados por modelos alternativos que procuran analizar patrones de causalidad entre pobreza y el acceso a mercados de activos de capital humano, capital físico (público y privado) y capital social (Birdsall y Londoño 1997a y b; Moser 1998; Collier 1998). Este estudio procura contribuir al análisis de la pobreza desde la perspectiva de recursos y activos, y describir los alcances de este enfoque aplicado al caso boliviano.

    The star formation histories of galaxies in the Sloan Digital Sky Survey

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    We present the results of a MOPED analysis of ~3 x 10^5 galaxy spectra from the Sloan Digital Sky Survey Data Release Three (SDSS DR3), with a number of improvements in data, modelling and analysis compared with our previous analysis of DR1. The improvements include: modelling the galaxies with theoretical models at a higher spectral resolution of 3\AA; better calibrated data; an extended list of excluded emission lines, and a wider range of dust models. We present new estimates of the cosmic star formation rate, the evolution of stellar mass density and the stellar mass function from the fossil record. In contrast to our earlier work the results show no conclusive peak in the star formation rate out to a redshift around 2 but continue to show conclusive evidence for `downsizing' in the SDSS fossil record. The star formation history is now in good agreement with more traditional instantaneous measures. The galaxy stellar mass function is determined over five decades of mass, and an updated estimate of the current stellar mass density is presented. We also investigate the systematic effects of changes in the stellar population modelling, the spectral resolution, dust modelling, sky lines, spectral resolution and the change of data set. We find that the main changes in the results are due to the improvements in the calibration of the SDSS data, changes in the initial mass function and the theoretical models used.Comment: replaced to match accepted version in MNRA

    Interacting Energy Components and Observational H(z)H(z) Data

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    In this note, we extend our previous work [Phys. Lett. B 644, 7 (2007), astro-ph/0609597], and compare eleven interacting dark energy models with different couplings to the observational H(z)H(z) data. However, none of these models is better than the simplest Λ\LambdaCDM model. This implies that either more exotic couplings are needed in the cosmological models with interaction between dark energy and dust matter, or {\em there is no interaction at all}. We consider that this result is disadvantageous to the interacting dark energy models studied extensively in the literature.Comment: 15 pages, 5 figures, 3 tables, Latex2e; v2: references added; v3: discussions added, Phys. Lett. B in press; v4: published versio

    The thinnest, steepest, and maximum elevation Corneal locations in noncontact and contact lens wearers in keratoconus

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    PURPOSE:: To assess the relationship between the thinnest corneal location and the steepest and maximum elevation corneal locations in subjects with keratoconus and the effect of gas permeable contact lens wear on the location of these points. METHODS:: Sixty-one consecutive subjects (98 eyes) with keratoconus. Thirty-one (49 eyes) and 30 (49 eyes) subjects were gas permeable contact lens (CL-W) and non-contact lens wearers (N-CL), respectively. Thinnest, steepest, and maximum elevation corneal locations were evaluated from topographies collected with Pentacam Eye Scanner. RESULTS:: In the entire sample and in N-CL and CL-W, the thinnest location does not overlap with the steepest or maximum elevation corneal locations (all P > 0.05). The thinnest and maximum tangential curvature locations were found to be located further away from the geometric center of the cornea in CL-W versus N-CL (P < 0.05). CONCLUSION:: The thinnest corneal location does not overlap with maximum axial and tangential curvatures or with the front and back elevation locations in keratoconus subjects. Contact lens wear does not affect this lack of overlapping.Clinical & Experimental Optometry Research LabMenicon Co., Ltd.Center of Physics, University of Minho, Braga, Portuga

    A robust statistical estimation of the basic parameters of single stellar populations. I. Method

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    The colour-magnitude diagrams of resolved single stellar populations, such as open and globular clusters, have provided the best natural laboratories to test stellar evolution theory. Whilst a variety of techniques have been used to infer the basic properties of these simple populations, systematic uncertainties arise from the purely geometrical degeneracy produced by the similar shape of isochrones of different ages and metallicities. Here we present an objective and robust statistical technique which lifts this degeneracy to a great extent through the use of a key observable: the number of stars along the isochrone. Through extensive Monte Carlo simulations we show that, for instance, we can infer the four main parameters (age, metallicity, distance and reddening) in an objective way, along with robust confidence intervals and their full covariance matrix. We show that systematic uncertainties due to field contamination, unresolved binaries, initial or present-day stellar mass function are either negligible or well under control. This technique provides, for the first time, a proper way to infer with unprecedented accuracy the fundamental properties of simple stellar populations, in an easy-to-implement algorithm.Comment: 17 pages, 12 figures, MNRAS, in pres

    DNA condensation and redissolution: Interaction between overcharged DNA molecules

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    The effective DNA-DNA interaction force is calculated by computer simulations with explicit tetravalent counterions and monovalent salt. For overcharged DNA molecules, the interaction force shows a double-minimum structure. The positions and depths of these minima are regulated by the counterion density in the bulk. Using two-dimensional lattice sum and free energy perturbation theories, the coexisting phases for DNA bundles are calculated. A DNA-condensation and redissolution transition and a stable mesocrystal with an intermediate lattice constant for high counterion concentration are obtained.Comment: 26 pages, 10 figure

    Developing and evaluating a pediatric virtual simulation for nurse practitioner students in advanced pharmacology courses

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    The purpose of this study is to illustrate how virtual patient simulations can be used with nurse practitioner students to practice medication selection, dosage calculation, patient and parent education, and prescription writing with pediatric patients in advanced pharmacology courses

    The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

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    The Atacama Cosmology Telescope (ACT) is currently observing the cosmic microwave background with arcminute resolution at 148 GHz, 218 GHz, and 277 GHz. In this paper, we present ACT's first results. Data have been analyzed using a maximum-likelihood map-making method which uses B-splines to model and remove the atmospheric signal. It has been used to make high-precision beam maps from which we determine the experiment's window functions. This beam information directly impacts all subsequent analyses of the data. We also used the method to map a sample of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect, and show five clusters previously detected with X-ray or SZ observations. We provide integrated Compton-y measurements for each cluster. Of particular interest is our detection of the z = 0.44 component of A3128 and our current non-detection of the low-redshift part, providing strong evidence that the further cluster is more massive as suggested by X-ray measurements. This is a compelling example of the redshift-independent mass selection of the SZ effect.Comment: 16 pages, 10 figures. Accepted for publication in ApJS. See Marriage et al. (arXiv:1010.1065) and Menanteau et al. (arXiv:1006.5126) for additional cluster result
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