548 research outputs found

    On the driver of relativistic effects strength in Seyfert galaxies

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    Spectroscopy of X-ray emission lines emitted in accretion discs around supermassive black holes is one of the most powerful probes of the accretion flow physics and geometry, while also providing in principle observational constraints on the black hole spin.[...] We aim at determining the ultimate physical driver of the strength of this relativistic reprocessing feature. We first extend the hard X-ray flux-limited sample of Seyfert galaxies studied so far (FERO, de la Calle Perez et al. 2010) to obscured objects up to a column density N_H=6x10^23 atoms/cm/cm. We verify that none of the line properties depends on the AGN optical classification, as expected from the Seyfert unification scenarios. There is also no correlation between the accretion disc inclination, as derived from formal fits of the line profiles, and the optical type or host galaxy aspect angle, suggesting that the innermost regions of the accretion disc and the host galaxy plane are not aligned. [...]. Data are not sensitive enough to the detailed ionisation state of the line-emitting disc. However, the lack of dependency of the line EW on either the luminosity or the rest-frame centroid energy rules out that disc ionisation plays an important role on the EW dynamical range in Seyferts. The dynamical range of the relativistically broadened K-alpha iron line EW in nearby Seyferts appears to be mainly determined by the properties of the innermost accretion flow. We discuss several mechanisms (disc ionisation, disc truncation, aberration due to a mildly relativistic outflowing corona) which can explain this. [...] Observational data are still not in contradiction with scenarios invoking different mechanisms for the spectral complexity around the iron line, most notably the "partial covering" absorption scenario. (abridged).Comment: Accepted for publication on Astronomy & Astrophysics. 14 pages, 9 figure

    Integration of WiFi ToF Positioning System in the Open, Flexible and Adaptive WiSHFUL Architecture

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    We integrate a prototype WiFi Time-of-Flight (ToF) ranging and po- sitioning system in the WiSHFUL software platforms and hardware radios for experimental prototyping. Users can have access to ToF measurements as well as computed positions through uni ed pro- gramming interfaces that make possible to investigate innovative positioning and networking solutions

    Nucleation and Crystallization of PA6 Composites Prepared by T-RTM: Effects of Carbon and Glass Fiber Loading

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    Thermoplastic resin transfer molding (T-RTM) is attracting much attention due to the need for recyclable alternatives to thermoset materials. In this work, we have prepared polyamide-6 (PA6) and PA6/fiber composites by T-RTM of caprolactam. Glass and carbon fibers were employed in a fixed amount of 60 and 47 wt.%, respectively. Neat PA6 and PA6 matrices (of PA6-GF and PA6-CF) of approximately 200 kg/mol were obtained with conversion ratios exceeding 95%. Both carbon fibers (CF) and glass fibers (GF) were able to nucleate PA6, with efficiencies of 44% and 26%, respectively. The α crystal polymorph of PA6 was present in all samples. The lamellar spacing, lamellar thickness and crystallinity degree did not show significant variations in the samples with or without fibers as result of the slow cooling process applied during T-RTM. The overall isothermal crystallization rate decreased in the order: PA6-CF > PA6-GF > neat PA6, as a consequence of the different nucleation efficiencies. The overall crystallization kinetics data were successfully described by the Avrami equation. The lamellar stack morphology observed by atomic force microscopy (AFM) is consistent with 2D superstructural aggregates (n = 2) for all samples. Finally, the reinforcement effect of fibers was larger than one order of magnitude in the values of elastic modulus and tensile strength.We gratefully acknowledge the Basque Government by the funding received through the ELKARTEK 2017 Cooperative Fundamental Research project: ”Automotion Composites fabricated by RTM adapted to the 4.0 industrial philosophy (RTM4.0). The authors thank the ALBA Synchrotron Light facility for supporting the X-rays experiments at beamline BL11-NCD-SWEET and the funding by ALBA project nº 2017092338. The UPV/EHU team gratefully acknowledges the financial contribution of the Basque Government through grant IT1309-19

    Obscuring clouds playing hide-and-seek in the Active Nucleus H0557-385

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    This paper reports on two XMM-Newton observations of the Seyfert 1 Galaxy H0557-385 obtained in 2006, which show the source at an historical low flux state, more than a factor of 10 lower than a previous XMM-Newton look in 2002. The low flux spectrum presents a strong Fe Kalpha line associated to a Compton reflection continuum. An additional spectral line around 6.6 keV is required to fit Kalpha emission from Fe XXV. The spectral curvature below 6 keV implies obscuration by neutral gas with a column density of 8*10^{23}cm^{-2} partially covering the primary emission, which still contributes for a few percent of the soft X-ray emission. Absorption by ionised material on the line of sight is required to fit the deep trough below 1 keV. The comparison of the two spectral states shows that the flux transition is to be ascribed entirely to intervening line-of-sight clouds with high column density.Comment: 5 pages, accepted for publication on MNRAS Letter

    Visibilidad de los sanitarios durante la crisis del Covid-19: estudio de fuentes y temáticas en los informativos de televisión

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    Esta investigación analiza la cobertura mediática de la crisis del Covid-19 en España, y el papel que en ella ha tenido la comunicación sobre salud y sobre los profesionales sanitarios. Se estudia el tratamiento recibido por las fuentes y temas sanitarios en los informativos de Radiotelevisión Española (RTVE) emitidos entre el 31 diciembre 2019 y el 8 junio 2020. Para ello, se realiza un análisis de contenido cuantitativo de 452 noticias de 21 informativos. Los resultados muestran que los debates de política y los propios políticos ocupan más espacio como tema y fuentes, respectivamente, en los informativos analizados, por delante de la salud y de los profesionales sanitarios. El estudio confirma, por tanto, la falta de visibilidad de los profesionales de salud en la cobertura informativa televisiva en España sobre el Covid-19

    Postcopulatory sexual selection favors fertilization success of restocking hybrid quails over native Common quails (Coturnix coturnix)

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    Postcopulatory sexual selection plays an important role in the reproductive success of males in many species. Differences in fertilization success could affect rates of admixture and genetic introgression between divergent lineages. We investigated sperm precedence in matings in captivity involving Common quails (Coturnix coturnix) and farm quails of hybrid origin (C. coturnix × domestic Japanese quail, C. japonica), the last used in restocking practices to increase hunting bags. These inter-specific matings in natural conditions are claimed to represent an important threat to the conservation of native Common quail populations. Results showed that fertilization success of each male depended on (1) the time it spent with the female, (2) the presence of sperm from a previous male in the female oviduct, (3) the time that the previous partner had been copulating with the female, and, most importantly, (4) the genetic origin of the male (wild or farm). Farm hybrid males showed higher fertilization success than wild Common males, and they required less time with the female to fertilize the same proportion of eggs. The presence of sperm from another male in the female oviduct reduced the percentage of fertilized eggs by a male. However, this reduction was higher for wild males when the precedent mate was a farm male. In summary, the sperm of farm hybrid males may outcompete the sperm of native males and this could be favoring the introgression of domestic Japanese alleles into the Common quail population, thus constituting a severe conservation threat to wild Common quail populations
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