696 research outputs found

    On the shape of the mass-function of dense clumps in the Hi-GAL fields. II. Using Bayesian inference to study the clump mass function

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    Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin, their evolution and their detailed physical properties. In particular, the relationship between the mass distribution of these clumps (also known as the "clump mass function", or CMF) and the stellar initial mass function (IMF), is still poorly understood. Aims. In order to better understand how the CMF evolve toward the IMF, and to discern the "true" shape of the CMF, large samples of bona-fide pre- and proto-stellar clumps are required. Two such datasets obtained from the Herschel infrared GALactic Plane Survey (Hi-GAL) have been described in paper I. Robust statistical methods are needed in order to infer the parameters describing the models used to fit the CMF, and to compare the competing models themselves. Methods. In this paper we apply Bayesian inference to the analysis of the CMF of the two regions discussed in Paper I. First, we determine the Bayesian posterior probability distribution for each of the fitted parameters. Then, we carry out a quantitative comparison of the models used to fit the CMF. Results. We have compared the results from several methods implementing Bayesian inference, and we have also analyzed the impact of the choice of priors and the influence of various constraints on the statistical conclusions for the preferred values of the parameters. We find that both parameter estimation and model comparison depend on the choice of parameter priors. Conclusions. Our results confirm our earlier conclusion that the CMFs of the two Hi-GAL regions studied here have very similar shapes but different mass scales. Furthermore, the lognormal model appears to better describe the CMF measured in the two Hi-GAL regions studied here. However, this preliminary conclusion is dependent on the choice of parameters priors.Comment: Submitted for publication to A&A on November 12, 2013. This paper contains 11 pages and 7 figure

    Probing the role of point mutations in the cyp51A gene from Aspergillus fumigatus in the model yeast Saccharomyces cerevisiae

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    Azole-resistant strains of Aspergillus fumigatus have been detected and the underlying molecular mechanisms of resistance characterized. Point mutations in the cyp51A gene have been proved to be related to azole resistance in A. fumigatus clinical strains and with different resistance profiles depending on the amino acid change (G54E, G54V, G54R, G54W, M220V, M220K, M220T, M220I). The aim of this work was to express A. fumigatus cyp51A genes in the yeast Saccharomyces cerevisiae in order to better assess the contribution of each independent amino acid substitution to resistance. A tetracycline regulatable system allowing repression of the endogenous essential ERG11 gene was used. The expression of Aspergillus cyp51A alleles could efficiently restore the absence of ERG11 in S. cerevisiae. In general, S. cerevisiae clones expressing. A. fumigatus cyp51A alleles from azole-resistant isolates showed higher MICs to all azoles tested than those expressing alleles from susceptible isolates. The azole susceptibility profiles obtained in S. cerevisiae upon expression of specific cyp51A alleles recapitulated susceptibility profiles observed from their A. fumigatus origins. In conclusion this work supports the concept that characteristics of specific A. fumigatus cyp51A alleles could be investigated in the heterologous host S. cerevisia

    EVALUATION OF THE INFLUENCE OF MIXER ROTATION THROUGH COMPUTATIONAL FLUID DYNAMICS SIMULATION OF A CONTINUOUS STIRRED-TANK REACTOR FOR BIODIESEL PRODUCTION FROM EXPERIMENTAL KINETIC DATA

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     In the present work, a computer simulation was performed through computational fluid dynamics (CFD) for a Continuous Stirred-Tank Reactor, starting from experimental data on the kinetics of the transesterification reaction between soybean oil methyl acetate, using an enzyme as a catalyst, the Candida Antartica. A volume was proposed for the reactor so that the average residence time of the reaction mixture was sufficient for the expected yield, based on the data obtained by the Matlab®, was obtained at the exit of the reactor. The simulation of the reactor operation was of a continuous process with constant reagents flow rates made using commercial software ANSYS®. The impeller chosen was of the type inclined straight blades, the simulations were made by varying the rotation speed of the mixer where an increase in reaction yield was observed until the rotation of 120 RPM, above this speed, no real gain was observed in the amount of biodiesel obtained

    Estudios térmicos sobre minerales de interés metalúrgico. V. Cinética de la descomposición térmica de crisocola y brocantita, y estudio mineralógico

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    The thermal decomposition process of chrysocoUa mineral and a copper hidroxysulfate is studied in this work by TGA, DTA and powder X-ray diffraction. Several data on reaction orders and activation energies valúes, as well as X-ray data are reported.Se ha estudiado el proceso de descomposición térmica de dos oxisales de cobre, una natural, crisocola, y otra sintética, brocantita, mediante termogravimetría, análisis térmico diferencial y difracción de rayos X. Se ofrecen datos sobre los valores de orden de reacción y energía de activación correspondiente a los procesos de deshidratación, así como de difractometría de polvo

    The pH-responsive PacC transcription factor of Aspergillus fumigatus governs epithelial entry and tissue invasion during pulmonary aspergillosis

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    Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. Raw data have been deposited in the Gene Expression Omnibus (GEO) (http://www.ncbi.nlm.nih.gov/geo/) under accession number GSE54810. Funding: This work was supported in part by grants to EMB from the MRC (G0501164) and BBSRC (BB/G009619/1), to EMB and NDR from the Wellcome Trust (WT093596MA), to MB from Imperial College London (Division of Investigative Sciences PhD Studentship), to HH from the ERA-NET PathoGenoMics project TRANSPAT, Austrian Science Foundation (FWF I282-B09), to SGF from the National Institutes of Health, USA (R01AI073829). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

    The association between early-life gut microbiota and childhood respiratory diseases: a systematic review

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    Data from animal models suggest a role of early-life gut microbiota in lung immune development, and in establishing susceptibility to respiratory infections and asthma in humans. This systematic review summarises the association between infant (ages 0-12 months) gut microbiota composition measured by genomic sequencing, and childhood (ages 0-18 years) respiratory diseases (ie, respiratory infections, wheezing, or asthma). Overall, there was evidence that low α-diversity and relative abundance of particular gut-commensal bacteria genera (Bifidobacterium, Faecalibacterium, Ruminococcus, and Roseburia) are associated with childhood respiratory diseases. However, results were inconsistent and studies had important limitations, including insufficient characterisation of bacterial taxa to species level, heterogeneous outcome definitions, residual confounding, and small sample sizes. Large longitudinal studies with stool sampling during the first month of life and shotgun metagenomic approaches to improve bacterial and fungal taxa resolution are needed. Standardising follow-up times and respiratory disease definitions and optimising causal statistical approaches might identify targets for primary prevention of childhood respiratory diseases

    Respuesta al artículo: La concentración de tratamientos puede mejorar los resultados en cirugía compleja del cáncer

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    Sr. Editor: Hemos leído con gran interés la editorial de Borras y Guarga1 que creemos expresa el pensamiento de muchos cirujanos de nuestro país^, y con la que coincidimos, al mismo tiempo que quisiéramos hacer una serie de reflexiones constructivas sobre algunos aspectos que no vemos reflejados del todo en la misma. El que la concentración en determinados procedimientos disminuya la mortalidad1 3, ya es una buena razón por sí misma para plantearse la centralización, a pesar de que no todos los estudios lo demuestran4, pero no nos parece suficiente el solo hecho de que el volumen por sí mismo sea el principal criterio que defina el centro de referencia, ya que se pueden operar muchos casos, a nivel individual o de servicio, pero si los resultados no se auditan, se comparan o se hacen públicos, podemos caer en el error de que cantidad no sea igual a calidad3. Desde la Sección de Formación de la Asociación Española de Cirujanos http://www.aecirujanos.es pensamos que las unidades de un servicio que pretenda centralizar procedimientos deberían de estar certificadas al igual que sus profesionales, al mismo tiempo que disponer de tecnología puntera e innovadora que ofrezca las mejores oportunidades de tratamiento a nuestros pacientes, y esto sí que sería un requisito básico para que la centralización tuviese un sentido real, además del volumen, porque significa que los resultados de los profesionales y del centro, están auditados y se pueden ..
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