32,429 research outputs found
Simple function form for n+208Pb total cross section between 5 and 600 MeV
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
The proportionality between single charge-exchange reaction cross sections in
the forward direction as found, for example from and He, and
from and He) 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 Ge-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.
GeAs. 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
SeAs. 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 () interaction in connection with the Pauli principle
on the cross sections in the 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
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
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
Charged null fluid and the weak energy condition
Uses the Einstein-Maxwell field equations to derive the fundamental equation of motion for charged null fluid. This equation of motion includes a Lorentz force term. Using this equation, it is shown that charged null fluid always satisfies the weak energy condition. This result is in contrast to previous interpretations of the charged Vaidya solution (a special case of a charged null fluid), which produced violations of the weak energy condition. The errors in the previous interpretations are explained. The new interpretation is then applied explicitly to the charged Vaidya solution
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