4,163 research outputs found

    Star Formation History and Extinction in the central kpc of M82-like Starbursts

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    We report on the star formation histories and extinction in the central kpc region of a sample of starburst galaxies that have similar far infrared (FIR), 10 micron and K-band luminosities as those of the archetype starburst M82. Our study is based on new optical spectra and previously published K-band photometric data, both sampling the same area around the nucleus. Model starburst spectra were synthesized as a combination of stellar populations of distinct ages formed over the Hubble time, and were fitted to the observed optical spectra and K-band flux. The model is able to reproduce simultaneously the equivalent widths of emission and absorption lines, the continuum fluxes between 3500-7000 Ang, the K-band and the FIR flux. We require a minimum of 3 populations -- (1) a young population of age < 8 Myr, with its corresponding nebular emission, (2) an intermediate-age population (age < 500 Myr), and (3) an old population that forms part of the underlying disk or/and bulge population. The contribution of the old population to the K-band luminosity depends on the birthrate parameter and remains above 60% in the majority of the sample galaxies. Even in the blue band, the intermediate age and old populations contribute more than 40% of the total flux in all the cases. A relatively high contribution from the old stars to the K-band nuclear flux is also apparent from the strength of the 4000 Ang break and the CaII K line. The extinction of the old population is found to be around half of that of the young population. The contribution to the continuum from the relatively old stars has the effect of diluting the emission equivalent widths below the values expected for young bursts. The mean dilution factors are found to be 5 and 3 for the Halpha and Hbeta lines respectively.Comment: 20 pages, uses emulateapj.cls. Scheduled to appear in ApJ Jan 1, 200

    Estilos de vida asociados al riesgo cardiovascular global en trabajadores universitarios del Estado de México

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    Objetivo. Evaluar la asociación del estilo de vida con el riesgo cardiovascular (RCV) en trabajadores universitarios del Estado de México. Material y métodos. Estudio de casos y controles anidado en una cohorte. Se evaluaron variables del estilo de vida, sociodemográficas, antropométricas y antecedentes familiares. El análisis estimó razones de momios pareadas crudas y ajustadas a través de regresión logística condicional. Resultados. Se estudiaron 342 casos con RCV y 684 controles. En los trabajadores con sobrepeso u obesidad, el RCV superó al de aquéllos con peso normal. Los antecedentes familiares de infarto del miocardio se asociaron directamente, y la actividad física moderada-vigorosa inversamente con el RCV, en modelos con interacciones entre género y actividad física; esta relación se mantuvo sólo en los hombres. Conclusiones. Los resultados muestran el papel preponderante de la actividad física moderada-vigorosa como factor del estilo de vida asociado con menor RCV

    The Mexican Non-toxic Jatropha curcas L., Food Resource or Biofuel?

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    Jatropha curcas L. is a promising natural resource which has been promoted globally for biodiesel production by policy makers and researchers in tropical and subtropical countries. However, both J. curcas seeds and oil have been found to be toxic to humans and domestic animals when consumed. A non-toxic genotype of J. curcas has been reported from some rural communities in southern Mexico, and is suitable for human consumption. This non-toxic germplasm has been used in traditional Totonacan cuisine in Mexico. However, increasing demand for J. curcas to be used in biofuel production is exerting pressure on the non-toxic genotype. In this work we analyze the possible origins and dispersal of non-toxic Jatropha by the Totonaca culture; the traditional uses of J. curcas seeds as a food; its status with respect to the Mexican commercial forestry regulations; and the risks associated with the demands of biofuels on this Mexican germplasm

    Evaluation of mesoscale convective systems in South America using multiple satellite products and an object‐based approach

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    In this study, an object-based verification method was used to reveal the existence of systematic errors in three satellite precipitation products: Tropical Rainfall Measurement Mission (TRMM), Climate Prediction Center Morphing Technique (CMORPH), and Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks (PERSIANN). Mesoscale convective systems (MCSs) for the austral summer 2002–2003 in the La Plata river basin, southeastern South America, were analyzed with the Contiguous Rain Area (CRA) method. Errors in storms intensity, volume, and spatial location were evaluated. A macroscale hydrological model was used to assess the impact of spatially shifted precipitation on streamflows simulations. PERSIANN underestimated the observed average rainfall rate and maximum rainfall consistent with the detection of storm areas systematically larger than observed. CMORPH overestimated the average rainfall rate while the maximum rainfall was slightly underestimated. TRMM average rainfall rate and rainfall volume correlated extremely well with ground observations whereas the maximum rainfall was systematically overestimated suggesting deficiencies in the bias correction procedure to filter noisy measurements. The preferential direction of error displacement in satellite-estimated MCSs was in the east-west direction for CMORPH and TRMM. Discrepancies in the fine structure of the storms dominated the error decomposition of all satellite products. Errors in the spatial location of the systems influenced the magnitude of simulated peaks but did not have a significant impact on the timing indicating that the system's response to precipitation was mitigating the effect of the errors.Fil: Demaria, E. M. C.. University Of Arizona; Estados UnidosFil: Rodriguez, D. A.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Ebert, E. E.. Centre for Australian Weather and Climate Research; AustraliaFil: Salio, Paola Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Su, F.. University of Washington; Estados UnidosFil: Valdes, J. B.. University Of Arizona; Estados Unido

    ANÁLISE SUSTENTÁVEL DO MODELO DE CICLO DE VIDA. SITUAÇÃO E PERSPECTIVAS DE IXTAPAN DE LA SAL, MÉXICO

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    Cuando se busca entender la evolución de un destino turístico, el análisis del ciclo de vida es una de las herramientas de gestión y planeación más utilizadas. Sin embargo, existen para su medición, variables limitadas que generalmente se basan en la cantidad de turistas y en el tiempo en que se ha desarrollado la actividad, lo cual deja en un segundo plano la sustentabilidad. En este trabajo, se formula un esquema alternativo de análisis mediante el cual se integran variables de sustentabilidad para establecer los impactos económicos, ambientales y sociales de los turistas actuales y futuros. Así también, se presenta una metodología que estima la curva de evolución de los destinos, para aquellos lugares que no cuentan con información suficiente. Finalmente se concluye que el destino de Ixtapan de la Sal, en México, hoy en día no es sustentable, y un mayor número de turistas solo pondría en riesgo su competitividad

    Draft Genome Sequence of a Multi-Metal Resistant Bacterium Pseudomonas putida ATH-43 Isolated from Greenwich Island, Antarctica

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    Indexación: Web of Science; Scopus.In this report we present the first draft genome sequence of a P. putida strain isolated from the Antarctic continent. The shotgun sequencing strategy, assembly, and subsequent annotation showed that the ATH-43 strain possesses a wide spectrum of genetic determinants involved in heavy metal and antibiotic resistance, apparently to cope with extreme oxidative stress conditions. P. putida ATH-43 genome now forms part of the 65 genomes of this species registered at the NCBI database (September, 2016) and it is highly related with the endophytic strain P. putida W619, which is also resistant to several heavy metals. Further characterization of multi-metal resistant psychrotrophic bacteria such as P. putida ATH-43 will be promising to develop novel strategies for heavy metal bioremediation in low temperature environments. All genome data has been submitted to NCBI.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01777/ful

    A 3D Automated Classification Scheme for the TAUVEX data pipeline

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    In order to develop a pipeline for automated classification of stars to be observed by the TAUVEX ultraviolet space Telescope, we employ an artificial neural network (ANN) technique for classifying stars by using synthetic spectra in the UV region from 1250\AA to 3220\AA as the training set and International Ultraviolet Explorer (IUE) low resolution spectra as the test set. Both the data sets have been pre-processed to mimic the observations of the TAUVEX ultraviolet imager. We have successfully classified 229 stars from the IUE low resolution catalog to within 3-4 spectral sub-class using two different simulated training spectra, the TAUVEX spectra of 286 spectral types and UVBLUE spectra of 277 spectral types. Further, we have also been able to obtain the colour excess (i.e. E(B-V) in magnitude units) or the interstellar reddening for those IUE spectra which have known reddening to an accuracy of better than 0.1 magnitudes. It has been shown that even with the limitation of data from just photometric bands, ANNs have not only classified the stars, but also provided satisfactory estimates for interstellar extinction. The ANN based classification scheme has been successfully tested on the simulated TAUVEX data pipeline. It is expected that the same technique can be employed for data validation in the ultraviolet from the virtual observatories. Finally, the interstellar extinction estimated by applying the ANNs on the TAUVEX data base would provide an extensive extinction map for our galaxy and which could in turn be modeled for the dust distribution in the galaxy.Comment: 8 pages, 12 figures, Accepted for publication in MNRAS; High resolution figures available from the authors on reques

    ANÃLISIS FODA Y PERSPECTIVAS DEL CULTIVO DEL NOGAL PECANERO EN CHIHUAHUA

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    Pecan production is one of the most important crops in our country. It not only has an economical capacity as a generator of foreign currency, but also for the social context in which it develops its production. Most of the pecan growers have small sized orchards, but at the same time, there are few pecan growers with large sized orchards that use modern technology. The objective of this study is to present a SWOT analysis of the pecan system and to describe the contexts in which it is produced and commercialized, as well as the main characteristics and problems that appear in pecan production, as well as the prediction of its future under current production and management conditions.WOTS-UP analysis, pecan system, production and commercialization., Agribusiness,
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