282 research outputs found

    Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV

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    Intermediate mass fragments (IMF) from the interaction of 27^{27}Al, 59^{59}Co and 197^{197}Au with 200 MeV protons were measured in an angular range from 20 degree to 120 degree in the laboratory system. The fragments, ranging from isotopes of helium up to isotopes of carbon, were isotopically resolved. Double differential cross sections, energy differential cross sections and total cross sections were extracted.Comment: accepted by Phys. Rev.

    Non-equilibrium emission of complex fragments from p+Au collisions at 2.5 GeV proton beam energy

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    Energy and angular dependence of double differential cross sections d2σ^2\sigma/dΩ\OmegadE was measured for reactions induced by 2.5 GeV protons on Au target with isotopic identification of light products (H, He, Li, Be, and B) and with elemental identification of heavier intermediate mass fragments (C, N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction mechanisms give comparable contributions to the cross sections. The intranuclear cascade of nucleon-nucleon collisions followed by evaporation from an equilibrated residuum describes low energy part of the energy distributions whereas another reaction mechanism is responsible for high energy part of the spectra of composite particles. Phenomenological model description of the differential cross sections by isotropic emission from two moving sources led to a very good description of all measured data. Values of the extracted parameters of the emitting sources are compatible with the hypothesis claiming that the high energy particles emerge from pre-equilibrium processes consisting in a breakup of the target into three groups of nucleons; small, fast and hot fireball of \sim 8 nucleons, and two larger, excited prefragments, which emits the light charged particles and intermediate mass fragments. The smaller of them contains \sim 20 nucleons and moves with velocity larger than the CM velocity of the proton projectile and the target. The heavier prefragment behaves similarly as the heavy residuum of the intranuclear cascade of nucleon-nucleon collisions. %The mass and charge dependence of the total production cross %sections was extracted from the above analysis for all observed %reaction products. This dependence follows the power low behavior %(Aτ^{-\tau} or Zτ^{-\tau})

    Physicians Charged with Opioid-Analgesic Prescribing Offenses

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    Word counts: abstract = 249 , text = 4,329 ABSTRACT Objective. To provide a "big-picture" overview of the characteristics and outcomes of recent criminal and administrative cases in which physicians have been criminally prosecuted or charged by medical boards with offenses related to inappropriate prescribing of opioid analgesics. Design: We identified as many criminal and administrative cases of these types as possible that occurred between 1998 and 2006. Cases were identified using a wide variety of sources, including organizational and government-agency databases, published news accounts, and Websites. Factual characteristics of these cases and their outcomes, and of the physicians involved, then were further researched using additional sources and methods. Setting: Study findings are intended to apply to practicing U.S. patient care physicians as a whole. Patients or other participants: There were no patients or participants in this study. Outcome measures: We analyzed the numbers and types of cases and physicians involved, criminal and administrative charges brought, case outcomes and sanctions, specialties and other characteristics of the physicians involved. Results: The study identified 725 doctors, representing an estimated 0.1% of practicing patient care physicians, who were charged between 1998 and 2006 with criminal and/or administrative offenses related to prescribing opioid analgesics. A plurality of these (39.3%) were General Practice/Family Medicine physicians, compared with 3.5% who were self-identified or board-certified pain specialists. Physicians in this sample were more likely to be male, older, and not board certified (P<0.001). DEA criminal and complaint investigations averaged 658 per year (2003)(2004)(2005)(2006) and "for cause" surrenders of DEA registrations averaged 369.7 (2000-2006). Conclusions: Criminal or administrative charges and sanctions for prescribing opioid analgesics are rare. In addition, there appears to be little objective basis for concern that pain specialists have been "singled out" for prosecution or administrative sanctioning for such offenses

    Signal and System Approximation from General Measurements

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    In this paper we analyze the behavior of system approximation processes for stable linear time-invariant (LTI) systems and signals in the Paley-Wiener space PW_\pi^1. We consider approximation processes, where the input signal is not directly used to generate the system output, but instead a sequence of numbers is used that is generated from the input signal by measurement functionals. We consider classical sampling which corresponds to a pointwise evaluation of the signal, as well as several more general measurement functionals. We show that a stable system approximation is not possible for pointwise sampling, because there exist signals and systems such that the approximation process diverges. This remains true even with oversampling. However, if more general measurement functionals are considered, a stable approximation is possible if oversampling is used. Further, we show that without oversampling we have divergence for a large class of practically relevant measurement procedures.Comment: This paper will be published as part of the book "New Perspectives on Approximation and Sampling Theory - Festschrift in honor of Paul Butzer's 85th birthday" in the Applied and Numerical Harmonic Analysis Series, Birkhauser (Springer-Verlag). Parts of this work have been presented at the IEEE International Conference on Acoustics, Speech, and Signal Processing 2014 (ICASSP 2014

    Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

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    The energy and angular dependence of double differential cross sections d2sigma/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be, 10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions does almost not change whereas the absolute value of the cross sections increases by a factor about 1.7 for all ejectiles in this beam energy range. It was found that energy and angular dependencies of the cross sections cannot be reproduced by the microscopic model of intranuclear cascade with coalescence of nucleons and the statistical model for evaporation of particles from excited, equilibrated residual nuclei. The inclusion of nonequilibrium processes, described by a phenomenological model of the emission from fast and hot moving sources, resulting from break-up of the target nucleus by impinging proton, leads to very good reproduction of data. Cross sections of these processes are quite large, exhausting approximately half of the total production cross sections. Due to good reproduction of energy and angular dependencies of d2sigma/dOmega dE by model calculation it was possible to determine total production cross sections for all studied ejectiles. Results obtained in this work point to the analogous reaction mechanism for proton induced reactions on Ni target as that observed previously for Au target in the same beam energy range.Comment: 11 pages, 10 figures

    Variation of nonequilibrium processes in p+Ni system with beam energy

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    The energy and angular dependence of double differential cross sections dsigma/dOmega dE were measured for p, d, t, 3,4He, 6,7Li, 7,9Be, and 10,11B produced in collisions of 0.175 GeV protons with Ni target. The analysis of measured dfferential cross sections allowed to extract total production cross sections for ejectiles listed above. The shape of the spectra and angular distributions indicate the presence of other nonequilibrium processes besides the emission of nucleons from the intranuclear cascade, and besides the evaporation of various particles from remnants of intranuclear cascade. These nonequilibrium processes consist of coalescence of nucleons into light charged particles during the intranuclear cascade, of the fireball emission which contributes to the cross sections of protons and deuterons, and of the break-up of the target nucleus which leads to the emission of intermediate mass fragments. All such processes were found earlier at beam energies 1.2, 1.9, and 2.5 GeV for Ni as well as for Au targets, however, significant differences in properties of these processes at high and low beam energy are observed in the present study.Comment: 10 pages, 9 figure
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