730 research outputs found

    Measurement of the radiative capture cross section of the s-process branching points 204Tl and 171Tm at the n-TOF facility (CERN)

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    The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,γ) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.The authors acknowledge financial support by the Spanish FPA2014-52823-C2-2-P project, by the EC Marie Curie Action “NeutAndalus” (FP7-PEOPLE-2012-CIG- 334315), by the ARGOS scholarship of the Spanish Nuclear Safety Council (CSN) and the Universitat Politècnica de Catalunya, and by the University of Sevilla via the VI PPIT-US program

    Neutron Capture on the s-Process Branching Point Tm 171 via Time-of-Flight and Activation

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    The neutron capture cross sections of several unstable nuclides acting as branching points in the s process are crucial for stellar nucleosynthesis studies. The unstable 171Tm (t1/2=1.92yr) is part of the branching around mass A∼170 but its neutron capture cross section as a function of the neutron energy is not known to date. In this work, following the production for the first time of more than 5 mg of 171Tm at the high-flux reactor Institut Laue-Langevin in France, a sample was produced at the Paul Scherrer Institute in Switzerland. Two complementary experiments were carried out at the neutron time-of-flight facility (n_TOF) at CERN in Switzerland and at the SARAF liquid lithium target facility at Soreq Nuclear Research Center in Israel by time of flight and activation, respectively. The result of the time-of-flight experiment consists of the first ever set of resonance parameters and the corresponding average resonance parameters, allowing us to make an estimation of the Maxwellian-averaged cross sections (MACS) by extrapolation. The activation measurement provides a direct and more precise measurement of the MACS at 30 keV: 384(40) mb, with which the estimation from the n_TOF data agree at the limit of 1 standard deviation. This value is 2.6 times lower than the JEFF-3.3 and ENDF/B-VIII evaluations, 25% lower than that of the Bao et al. compilation, and 1.6 times larger than the value recommended in the KADoNiS (v1) database, based on the only previous experiment. Our result affects the nucleosynthesis at the A∼170 branching, namely, the 171Yb abundance increases in the material lost by asymptotic giant branch stars, providing a better match to the available pre-solar SiC grain measurements compared to the calculations based on the current JEFF-3.3 model-based evaluation.The authors acknowledge financial support by University of Seville via the V PPIT-US programme, the Spanish Ministerio de Economía y Competitividad FPA2013-45083-P, FPA2014-53290-C2-2-P and FPA2016-77689-C2-1-R projects, the EC FP7 projects NeutAndalus (Grant No. 334315) and CHANDA (Grant No. 605203), and the n_TOF Collaboration. The SARAF-LiLiT experiment was supported by the Pazy Foundation (Israel). M. P. acknowledges support of the Israel Science Foundation (Grant No. 1387/15). The University of Edinburgh acknowledges funding from the Science and Technology Facilities Council UK (ST/M006085/1), and the European Research Council ERC-2015-STG No. 677497

    Enhancing informal learning recognition through TRAILER project

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    Conde, M. A., García-Peñalvo, F. J., Zangrando, V., García-Holgado, A., Seoane-Pardo, A. M., Alier, M., Galanis, N., Griffiths, D., Johnson, M., Janssen, J., Brouns, F., Vogten, H., Finders, A., Sloep, P. B., Marques, M. A., Viegas, M. C., Alves, G. R., Waszkiewicz, E., Mykowska, A., Minovic, M., & Milovanovic, M. (2013). Enhancing informal learning recognition through TRAILER project. In F. J. García-Peñalvo, M. Á. Conde, & D. Griffiths (Eds.), Proceedings of the Workshop on Solutions that Enhance Informal Learning Recognition (WEILER 2013) (pp. 21-30). September, 18, 2013, Paphos, Cyprus. http://ceur-ws.org/Vol-1039/The evolution of new technology and its increasing use, has for some years been making the existence of informal learning more and more transparent, especially among young and older adults in both Higher Education and workplace contexts. However, the nature of formal and non-formal, coursebased, approaches to learning has made it hard to accommodate these informal processes satisfactorily. The project aims to facilitate first the identification by the learner (as the last responsible of the learning process), and then the recognition by the institution, in dialogue with the learner, of this learning. To do so a methodology and a technological framework to support it have been implemented. This project has been tested in several contexts showing that an informal learning dialogue between learners and people in charge of the institutions is possible.Tagging, Recognition and Acknowledgment of Informal Learning ExpeRiences project (TRAILER) that is funded by the European Commission's Lifelong Learning Programme. Ref. 519141-LLP-1-2011-1-ES-KA3-KA3MP [http:// trailerproject.eu]. This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein

    The 2010 very high energy gamma-ray flare & 10 years of multi-wavelength observations of M 87

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    Abridged: The giant radio galaxy M 87 with its proximity, famous jet, and very massive black hole provides a unique opportunity to investigate the origin of very high energy (VHE; E>100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of super-massive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (~day), peak fluxes (Phi(>0.35 TeV) ~= (1-3) x 10^-11 ph cm^-2 s^-1), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken ~3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core. The long-term (2001-2010) multi-wavelength light curve of M 87, spanning from radio to VHE and including data from HST, LT, VLA and EVN, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified.Comment: 19 pages, 5 figures; Corresponding authors: M. Raue, L. Stawarz, D. Mazin, P. Colin, C. M. Hui, M. Beilicke; Fig. 1 lightcurve data available online: http://www.desy.de/~mraue/m87

    The labor market effects of technology shocks

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    We analyze the effects of neutral and investment-specific technology shocks on hours worked and unemployment. We characterize the response of unemployment in terms of job separation and job finding rates. We find that job separation rates mainly account for the impact response of unemployment while job finding rates for movements along its adjustment path. Neutral shocks increase unemployment and explain a substantial portion of unemployment and output volatilityinvestment-specific shocks expand employment and hours worked and mostly contribute to hours worked volatility. We show that this evidence is consistent with the view that neutral technological progress prompts Schumpeterian creative destruction, while investment specific technological progress has standard neoclassical feature
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