31,792 research outputs found

    Simple function form for n+208Pb total cross section between 5 and 600 MeV

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    The total cross section for neutron scattering from 208Pb with energies between 5 and 600 MeV has been analyzed extending a previously defined simple function of three parameters to reveal a Ramsauer-like effect throughout the whole energy range. This effect can be parametrized in a simple way so that it may be anticipated that the complete function prescription will apply for total cross sections from other nuclei.Comment: 9 pages, 4 firgure

    Charge-exchange reaction cross sections and the Gamow-Teller strength for double beta decay

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    The proportionality between single charge-exchange reaction cross sections in the forward direction as found, for example from (p,n)(p,n) and (3(^3He,t)t) and from (n,p)(n,p) and (d,2(d,^2He) reactions, and the Gamow-Teller (GT) strength into the same final nuclear states has been studied and/or assumed often in the past. Using the most physically justified theory we have at our disposal and for the specific example of the 76{}^{76}Ge-76{}^{76}Se system that may undergo double beta-decay, we demonstrate that the proportionality is a relative good assumption for reactions changing a neutron into a proton, i.e. 76{}^{76}Ge(p,n)76(p,n){}^{76}As. In this channel, the main contribution to the GT strengths comes from the removal of a neutron from an occupied single-particle (SP) state and putting a proton into an unoccupied SP state having either the same state quantum numbers or those of the spin-orbit partner. In contrast to this, in the second leg of the double beta decay a single proton must be taken from an occupied SP state and a neutron placed in an unoccupied one. This second process often is Pauli forbidden in medium-heavy nuclei and only can be effected if the Fermi surface is smeared out. Such is the case for 76{}^{76}Se(n,p)76(n,p){}^{76}As. Our results suggest that one may not always assume a proportionality between the forward-angle cross sections of the charge-exchange reactions and the GT strength in any such medium-heavy nuclei. The discrepancy originates from a pronounced effect of the radial dependence of the nucleon-nucleon (NNNN) interaction in connection with the Pauli principle on the cross sections in the (n,p)(n,p) reaction channel. Such a radial dependence is completely absent in the GT transition operator.Comment: 14 p., 7 fig

    Ultrasound guided glenohumeral injections in adhesive capsulitis

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    Thesis (M.A.)--Boston UniversityObjective: The objective of this thesis was to assess outcomes of glenohumeral corticosteroid injections for adhesive capsulitis. Design: The thesis was composed of two parts. First, a systematic literature review was conducted on glenohumeral corticosteroid injections on shoulder outcomes for adhesive capsulitis. Second, an original prospective study was conducted to measure the effect of ultrasound-guided injections on pain and function for adhesive capsulitis patients. Setting: All injections for the prospective injection study were conducted at Brigham and Women’s Hospital in Boston, MA. Patients: Inclusion criteria were patients receiving an ultrasound guided injection for adhesive capsulitis. 67 patients were included, 59 patients were available at first follow up, and 40 patients were available at final follow up. Methods: The literature review was conducted using the online databases PubMed (1966-present), Embase (1947-present), Web of Science (1900– present), and the Cochrane Central Register of Controlled Trials. Study criteria were limited to clinical trials that evaluated the application of corticosteroid injections, both alone and in combination with other treatment modalities, specifically for the condition of adhesive capsulitis in the shoulder. Studies involving non-corticosteroid injections or injections for conditions not specific to adhesive capsulitis were excluded. Results were limited to papers in the English language. A data table summarizing pain, function, and range of motion outcomes of each treatment was produced. A percent change from baseline was calculated to facilitate comparisons. For the injection study, the first follow-up took place after an average of 2.0 months and patients' improvement in pain and range of motion were assessed. During a final follow-up after an average of 10.4 months, patients’ pain and shoulder function scores were assessed over telephone. [TRUNCATED

    Approximate solution to the CGHS field equations for two-dimensional evaporating black holes

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    Callan, Giddings, Harvey and Strominger (CGHS) previously introduced a two-dimensional semiclassical model of gravity coupled to a dilaton and to matter fields. Their model yields a system of field equations which may describe the formation of a black hole in gravitational collapse as well as its subsequent evaporation. Here we present an approximate analytical solution to the semiclassical CGHS field equations. This solution is constructed using the recently-introduced formalism of flux-conserving hyperbolic systems. We also explore the asymptotic behavior at the horizon of the evaporating black hole

    Social Capital, Survival Strategies, and Their Potential for Post-conflict Governance in Liberia

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    This paper investigates how people created, adapted and used social capital and conflict resolution during more than a decade of violent conflict in Liberia, and the potential of such capital to contribute to post-conflict peace building and self-governance
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