778 research outputs found

    Volatile contents of primitive bubble-bearing melt inclusions from Klyuchevskoy volcano, Kamchatka: Comparison of volatile contents determined by mass-balance versus experimental homogenization

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    Primitive olivine-hosted melt inclusions provide information concerning the pre-eruptive volatile contents of silicate melts, but compositional changes associated with post-entrapment processes (PEP) sometimes complicate their interpretation. In particular, crystallization of the host phase along the wall of the melt inclusion and diffusion of H+ through the host promote CO2 and potentially S or other volatiles to exsolve from the melt into a separate fluid phase. Experimental rehomogenization and analysis of MI, or a combination of Raman spectroscopy, numerical modeling, and mass balance calculations are potentially effective methods to account for PEP and restore the original volatile contents of melt inclusions. In order to compare these different approaches, we studied melt inclusions from a suite of samples from Klyuchevskoy volcano (Kamchatka Arc) for which volatile compositions have been determined using experimental rehydration, Raman spectroscopy, and numerical modeling. The maximum CO2 contents of melt inclusions are in agreement (~3600-4000 ppm), regardless of the method used to correct for CO2 in the bubble, but significantly more uncertainty is observed using mass balance calculations. This uncertainty is largely due to the lack of precision associated with the petrographic method of determining bubble volumes and may also be related to the presence of daughter minerals at the glass-bubble interface

    New neutron-rich nuclei Zr103,104 and the A100 region of deformation

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    Partial decay schemes in the neutron-rich nuclei Zr103 and Zr104 have been measured for the first time and rotational bands in Zr100 102 have been extended to spins of up to 10Latin small letter h with stroke by observing prompt rays from the spontaneous fisson of Cm248. These nuclei are among the most deformed known at low spin and excitation energy. The level structures in the odd-A nuclei show that the h11/2 intruder orbital plays an important role in stabilizing the deformation in this region

    Constraints on Dark Matter Annihilation in Clusters of Galaxies with the Fermi Large Area Telescope

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    Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from clusters in the first 11 months of observations with the Fermi Large Area Telescope. We interpret this non-detection in terms of constraints on dark matter particle properties. In particular for leptonic annihilation final states and particle masses greater than ~200 GeV, gamma-ray emission from inverse Compton scattering of CMB photons is expected to dominate the dark matter annihilation signal from clusters, and our gamma-ray limits exclude large regions of the parameter space that would give a good fit to the recent anomalous Pamela and Fermi-LAT electron-positron measurements. We also present constraints on the annihilation of more standard dark matter candidates, such as the lightest neutralino of supersymmetric models. The constraints are particularly strong when including the fact that clusters are known to contain substructure at least on galaxy scales, increasing the expected gamma-ray flux by a factor of ~5 over a smooth-halo assumption. We also explore the effect of uncertainties in cluster dark matter density profiles, finding a systematic uncertainty in the constraints of roughly a factor of two, but similar overall conclusions. In this work, we focus on deriving limits on dark matter models; a more general consideration of the Fermi-LAT data on clusters and clusters as gamma-ray sources is forthcoming.Comment: accepted to JCAP, Corresponding authors: T.E. Jeltema and S. Profumo, minor revisions to be consistent with accepted versio

    Chronic Stress, Sense of Belonging, and Depression Among Survivors of Traumatic Brain Injury

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    To test whether chronic stress, interpersonal relatedness, and cognitive burden could explain depression after traumatic brain injury (TBI). Design : A nonprobability sample of 75 mild-to-moderately injured TBI survivors and their significant others, were recruited from five TBI day-rehabilitation programs. All participants were within 2 years of the date of injury and were living in the community. Methods : During face-to-face interviews, demographic information, and estimates of brain injury severity were obtained and participants completed a cognitive battery of tests of directed attention and short-term memory, responses to the Perceived Stress Scale, Interpersonal Relatedness Inventory, Sense of Belonging Instrument, Neurobehavioral Functioning Inventory, and Center for Epidemiological Studies Depression Scale;. Findings : Chronic stress was significantly and positively related to post-TBI depression. Depression and postinjury sense of belonging were negatively related. Social support and results from the cognitive battery did not explain depression. Conclusions : Postinjury chronic stress and sense of belonging were strong predictors of post-injury depression and are variables amenable to interventions by nurses in community health, neurological centers, or rehabilitation clinics. Future studies are needed to examine how these variables change over time during the recovery process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72593/1/j.1547-5069.2002.00221.x.pd

    High-spin properties of octupole bands in 240Pu and 248Cm

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    The properties of superdeformed bands in 191,192Hg and 192,193Tl have been studied using the cranked Hartree-Fock-Bogoliubov method with the Lipkin-Nogami prescription, the Skm* interaction, and a surface-delta, density-dependent pairing force. In particular, quasiparticle excitations involving intruder orbitals are analyzed in detail. Comparisons between data and calculations are performed for J (2) moments, quadrupole moments, spins, transition energies, and alignments

    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

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    We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

    Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

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    This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

    Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

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    The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter
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