4,025 research outputs found

    Ab initio analysis of the x-ray absorption spectrum of the myoglobin-carbon monoxide complex: Structure and vibrations

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    We present a comparison between Fe K-edge x-ray absorption spectra of carbonmonoxy-myoglobin and its simulation based on density-functional theory determination of the structure and vibrations and spectral simulation with multiple-scattering theory. An excellent comparison is obtained for the main part of the molecular structure without any structural fitting parameters. The geometry of the CO ligand is reliably determined using a synergic approach to data analysis. The methodology underlying this approach is expected to be especially useful in similar situations in which high-resolution data for structure and vibrations are available.Comment: 13 pages, 3 figure

    The debris flow hazard in the Lagarelle Creek in the eastern Umbria region, central Italy

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    International audienceThis paper analyzes the Lagarelle Creek watershed, situated in the Municipality of Vallo di Nera, in the eastern Umbria region, central Italy. In this part of the Region, narrow valleys and very steep slopes characterize the morphology of the Appennine ridge. The presence of strongly-tectonized rocky masses, subdivided by several joint systems, is the main cause for the formation of sorted debris deposits, which accumulate mainly along the topographic convergences. This determines the conditions for possible events of debris flows. According to previous studies, the basin of the Lagarelle Creek, has been classified as an area prone to a high hazard of debris flows (Regione dell'Umbria ? C.N.R. I.R.P.I., 1996). For this reason, systematic studies have been carried out on the whole watershed which, in this first phase, have examined the definition of the geological and morphological features of the zone, by means of the acquisition of cartographies and of field surveys, and the elaboration of the topographical data of the basin, by means of a digital model of the terrain. Once the potential triggering areas of debris flows were identified, an assessment of the mobilizable volumes possibly involved in a debris flow event was carried out. To perform such an assessment both the geomorphologic method proposed by Hungr (Hungr et al., 1984) and the empirical relations calibrated on debris flow events of the alpine arc were applied. The results obtained were compared with those derived from information supplied by the inhabitants of the small mountain village, who have described in detail the most important events of the last century

    The Mn site in Mn-doped Ga-As nanowires: an EXAFS study

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    We present an EXAFS study of the Mn atomic environment in Mn-doped GaAs nanowires. Mn doping has been obtained either via the diffusion of the Mn used as seed for the nanowire growth or by providing Mn during the growth of Au-induced wires. As a general finding, we observe that Mn forms chemical bonds with As but is not incorporated in a substitutional site. In Mn-induced GaAs wires, Mn is mostly found bonded to As in a rather disordered environment and with a stretched bond length, reminiscent of that exhibited by MnAs phases. In Au-seeded nanowires, along with stretched Mn-As coordination we have found the presence of Mn in a Mn-Au intermetallic compound.Comment: This is an author-created, un-copyedited version of an article accepted for publication in Semiconductor Science and Technology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher-authenticated version is available online at doi:10.1088/0268-1242/27/8/08500

    The PAMELA Time-of-Flight system: status report

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    Abstract The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment, scheduled to be launched in 2003, aboard a Soyuz TM2 rocket, is designed to provide a better understanding of the antimatter component of cosmic rays. In the following we report on the features and performances of its scintillator telescope system which will provide the primary experimental trigger and time-of-flight particle identification

    The ToF and Trigger electronics of the PAMELA experiment

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    The PAMELA satellite-borne experiment, scheduled to be launched in 2004, is designed to provide a better understanding of the antimatter component of the cosmic rays. Its ToF scintillator system will provide the primary experimental trigger and time-of-flight particle identification. The time resolution requested is σ, < 120 ps. To fulfill the detector requirements the digitization electronics should have a time resolution ≤ 50 ps and provide a wide dynamic range for charge measurements. The peculiarity of the developed electronics arises from the need to obtain such a time resolution operating in a satellite environment, which implies low-power consumption, radiation hardness, redundancy and high reliability

    Multijet production in neutral current deep inelastic scattering at HERA and determination of α_{s}

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    Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson virtualities 10 5 GeV and –1 < η_{LAB}^{jet} < 2.5. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant α_{s} (M_{z}), determined from the ratio of the trijet to dijet cross sections, is α_{s} (M_{z}) = 0.1179 ± 0.0013 (stat.)_{-0.0046}^{+0.0028}(exp.)_{-0.0046}^{+0.0028}(th.)

    The Time of Flight Detector and Trigger for the Pamela Experiment in Space

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    The electronics of the Time of Flight telescope and trigger of PAMELA experiment are described. The time resolution requested by the ToF system must be less than 120 ps. The contribution of the digitization electronics is negligible if the TDC resolution is < 50 ps. The peculiarity of the developed electronics arises from the need to obtain such a time resolution associated to a wide dynamic range for charge measurements, operating in satellite environment, which implies low power consumption, radiation hardness, redundancy and high reliabilit

    Jet production in charged current deep inelastic e⁺p scatteringat HERA

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    The production rates and substructure of jets have been studied in charged current deep inelastic e⁺p scattering for Q² > 200 GeV² with the ZEUS detector at HERA using an integrated luminosity of 110.5 pb⁻¹. Inclusive jet cross sections are presented for jets with transverse energies E_{T}^{jet} > 5 GeV. Measurements of the mean subjet multiplicity, 〈n_{sbj}〉, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations are compared to the measurements. The value of α_{s} (M_{z}), determined from 〈n_{sbj}〉 at y_{cut} = 10⁻² for jets with 25 < E_{T}^{jet} < 119 GeV, is α_{s} (M_{z}) = 0.1202 ± 0.0052 (stat.)_{-0.0019}^{+0.0060} (syst.)_{-0.0053}^{+0.0065} (th.). The mean subjet multiplicity as a function of Q² is found to be consistent with that measured in NC DIS

    Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA

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    Inclusive photoproduction of D*+- mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of 37 pb^-1. Total and differential cross sections as functions of the D* transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure