2,335 research outputs found

    ALICE experience with GEANT4

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    Since its release in 1999, the LHC experiments have been evaluating GEANT4 in view of adopting it as a replacement for the obsolescent GEANT3 transport MonteCarlo. The ALICE collaboration has decided to perform a detailed physics validation of elementary hadronic processes against experimental data already used in international benchmarks. In one test, proton interactions on different nuclear targets have been simulated, and the distribution of outgoing particles has been compared to data. In a second test, penetration of quasi-monoenergetic low energy neutrons through a thick shielding has been simulated and again compared to experimental data. In parallel, an effort has been put on the integration of GEANT4 in the AliRoot framework. An overview of the present status of ALICE GEANT4 simulation and the remaining problems will be presented. This document will describe in detail the results of these tests, together with the improvements that the GEANT4 team has made to the program as a result of the feedback received from the ALICE collaboration. We will also describe the remaining problems that have been communicated to GEANT4 but not yet addressed.Comment: 8 pages, 12 figures, for the CHEP03 conference proceeding

    The CMS experiment workflows on StoRM based storage at Tier-1 and Tier-2 centers

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    Approaching LHC data taking, the CMS experiment is deploying, commissioning and operating the building tools of its grid-based computing infrastructure. The commissioning program includes testing, deployment and operation of various storage solutions to support the computing workflows of the experiment. Recently, some of the Tier-1 and Tier-2 centers supporting the collaboration have started to deploy StoRM based storage systems. These are POSIX-based disk storage systems on top of which StoRM implements the Storage Resource Manager (SRM) version 2 interface allowing for a standard-based access from the Grid. In this notes we briefly describe the experience so far achieved at the CNAF Tier-1 center and at the IFCA Tier-2 center

    Chemical abundances of late-type pre-main sequence stars in the σ\sigma-Orionis cluster

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    The young σ\sigma-Orionis cluster is an important location for understanding the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Its metallicity, although being a fundamental parameter, has not been well determined yet. We present the first determination of the metallicity of nine young late-type stars in σ\sigma-Orionis. Using the optical and near-infrared broadband photometry available in the literature we derive the effective temperatures for these nine cluster stars, which lie in the interval 4300--6500 K (1--3 \Msuno). These parameters are employed to compute a grid of synthetic spectra based on the code MOOG and Kurucz model atmospheres. We employ a χ2\chi^2-minimization procedure to derive the stellar surface gravity and atmospheric abundances of Al, Ca, Si, Fe, Ni and Li, using multi-object optical spectroscopy taken with WYFFOS+AF2 at at the William Herschel Telescope (λ/δλ7500\lambda/\delta\lambda\sim7500). The average metallicity of the σ\sigma-Orionis cluster is [Fe/H] =0.02±0.09±0.13 = -0.02\pm0.09\pm0.13 (random and systematic errors). The abundances of the other elements, except lithium, seem to be consistent with solar values. Lithium abundances are in agreement with the "cosmic" 7^7Li abundance, except for two stars which show a logϵ(Li)\log \epsilon(\mathrm{Li}) in the range 3.6--3.7 (although almost consistent within the error bars). There are also other two stars with logϵ(Li)2.75\log \epsilon(\mathrm{Li})\sim 2.75. We derived an average radial velocity of the σ\sigma-Orionis cluster of 28±428\pm4km/s. The σ\sigma-Orionis metallicity is roughly solar.Comment: Accepted for publication in Astronomy and Astrophysic

    Coastal macrophytes contribute to the long term geomorphological stability of Cadiz Bay

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    Charla presentada en el 2015 Aquatic Sciences Meeting. Aquatic Sciences: Global And Regional Perspectives — North Meets South (http://sgmeet.com/aslo/granada2015)In the Eastern Gulf of Cadiz, terrestrial sediments are mainly supplied by the large Guadalquivir and smaller Guadalete rivers, both of which are subject to substantial man-made interventions. These rivers are the main sediment source to Cadiz Bay; a shallow, meso-tidal bay with high subtidal macrophyte coverage and extensive salt marshes that appears to act as an effective filter, retaining fine material and ensuring accretion rates that match sea-level rise. Field observations suggest that the relative importance of the different mechanisms by which macrophyte canopies promote accretion is related to their species-specific biometric properties and zonation. Overall, we argue that the key mechanism which enhances long-term accretion in the bay is related to the reduction of erosive forces on the sediment bed cause by the interaction of plant canopies with local hydrodynamics, particularly during high wind events. Considering the importance of coastal macrophytes for long-term accretion, we briefly discuss how different local and regional management strategies in relation to IPCC climate change predictions may influence terrestrial derived-sediment dynamics.EU FP7-SPACE-2013: FAST - GA n.607131, Junta Andalucia: P07-RNM-2516, P09-RNM-4853, PR11-RNM-7722,MECD: CTM2008-00012/MAR, Schure-Beijerinck-Popping Fund: SBP/JK/2007-32), E.U. MarinERA Project MedEX: CTM2008-04036-E/MAR) y PERSEUS (FP7-287600)Charla en formato pd

    Exercise increases the dynamics of diurnal cortisol secretion and executive functionin people wiht MCI

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    Summary: Regular physical activity is protective against and beneficial for Mild Cognitive Impairment (MCI), dementia, and Alzheimer´s disease. The mechanisms underlying these benefits remain unknown although it has been suggested that exercise-induced changes in the circadian pattern of cortisol secretion may be implicated. Fitness, salivary cortisol levels (0 and 30 mins post awakening, midday, 5pm and 9pm) and cognitive function were determined in a group of amnestic MCI patients (n=39) before and after a three-month exercise program (n=19) or usual care (n=20). At base fitness measures were positively correlated with peak levels of cortisol and a greater fall in cortisol concentration from peak levels to midday. The exercise intervention successfully increased fitness and resulted in a greater fall in cortisol concentration from peak to midday, compared to the control group. The exercise intervention enhanced indices of executive function, although memory, mood, and functionality were not affected

    Fuzzy-based forest fire prevention and detection by wireless sensor networks

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    Forest fires may cause considerable damages both in ecosystems and lives. This proposal describes the application of Internet of Things and wireless sensor networks jointly with multi-hop routing through a real time and dynamic monitoring system for forest fire prevention. It is based on gathering and analyzing information related to meteorological conditions, concentrations of polluting gases and oxygen level around particular interesting forest areas. Unusual measurements of these environmental variables may help to prevent wildfire incidents and make their detection more efficient. A forest fire risk controller based on fuzzy logic has been implemented in order to activate environmental risk alerts through a Web service and a mobile application. For this purpose, security mechanisms have been proposed for ensuring integrity and confidentiality in the transmission of measured environmental information. Lamport's signature and a block cipher algorithm are used to achieve this objective

    Electron- versus neutrino-nucleus scattering

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    We illustrate the connection between electron and neutrino scattering off nuclei and show how the former process can be used to constrain the description of the latter. After reviewing some of the nuclear models commonly used to study lepton-nucleus reactions, we describe in detail the SuSAv2 model and show how its predictions compare with the available electron- and neutrino-scattering data over the kinematical range going from the quasi-elastic peak to pion-production and highly inelastic scattering.Comment: Shortened version, 71 pages, review article, 52 figure

    The nuclear and extended mid-infrared emission of Seyfert galaxies

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    We present subarcsecond resolution mid-infrared (MIR) images obtained with 8-10 m-class ground-based telescopes of a complete volume-limited (DL<40 Mpc) sample of 24 Seyfert galaxies selected from the Swift/BAT nine month catalog. We use those MIR images to study the nuclear and circumnuclear emission of the galaxies. Using different methods to classify the MIR morphologies on scales of ~400 pc, we find that the majority of the galaxies (75-83%) are extended or possibly extended and 17-25% are point-like. This extended emission is compact and it has low surface brightness compared with the nuclear emission, and it represents, on average, ~30% of the total MIR emission of the galaxies in the sample. We find that the galaxies whose circumnuclear MIR emission is dominated by star formation show more extended emission (650+-700 pc) than AGN-dominated systems (300+-100 pc). In general, the galaxies with point-like MIR morphologies are face-on or moderately inclined (b/a~0.4-1.0), and we do not find significant differences between the morphologies of Sy1 and Sy2. We used the nuclear and circumnuclear fluxes to investigate their correlation with different AGN and SF activity indicators. We find that the nuclear MIR emission (the inner ~70 pc) is strongly correlated with the X-ray emission (the harder the X-rays the better the correlation) and with the [O IV] lambda 25.89 micron emission line, indicating that it is AGN-dominated. We find the same results, although with more scatter, for the circumnuclear emission, which indicates that the AGN dominates the MIR emission in the inner ~400 pc of the galaxies, with some contribution from star formation.Comment: 27 pages, 12 figures, accepted by MNRA
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