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Mini-bunching the AGS slow external beam
Test and modeling toward providing a continuous string of proton bursts of a few nano-seconds every 3 to 10 micro-seconds for the two second BNL AGS spill are presented
A Quantum-Mechanical Equivalent-Photon Spectrum for Heavy-Ion Physics
In a previous paper, we calculated the fully quantum-mechanical cross section
for electromagnetic excitation during peripheral heavy-ion collisions. Here, we
examine the sensitivity of that cross section to the detailed structure of the
projectile and target nuclei. At the transition energies relevant to nuclear
physics, we find the cross section to be weakly dependent on the projectile
charge radius, and to be sensitive to only the leading momentum-transfer
dependence of the target transition form factors. We exploit these facts to
derive a quantum-mechanical ``equivalent-photon spectrum'' valid in the
long-wavelength limit. This improved spectrum includes the effects of
projectile size, the finite longitudinal momentum transfer required by
kinematics, and the response of the target nucleus to the off-shell photon.Comment: 19 pages, 5 figure
Theoretical Evaluations of the Fission Cross Section of the 77 eV Isomer of 235-U
We have developed models of the fission barrier (barrier heights and
transition state spectra) that reproduce reasonably well the measured fission
cross section of U from neutron energy of 1 keV to 2 MeV. From these
models we have calculated the fission cross section of the 77 eV isomer of
U over the same energy range. We find that the ratio of the isomer
cross section to that of the ground state lies between about 0.45 and 0.55 at
low neutron energies. The cross sections become approximately equal above 1
MeV. The ratio of the neutron capture cross section to the fission cross
section for the isomer is predicted to be about a factor of 3 larger for the
isomer than for the ground state of U at keV neutron energies. We have
also calculated the cross section for the population of the isomer by inelastic
neutron scattering form the U ground state. We find that the isomer is
strongly populated, and for the cross section
leading to the population of the isomer is of the order of 0.5 barn. Thus,
neutron reaction network calculations involving the uranium isotopes in a high
neutron fluence are likely to be affected by the 77 eV isomer of U.
With these same models the fission cross sections of U and U
can be reproduced approximately using only minor adjustments to the barrier
heights. With the significant lowering of the outer barrier that is expected
for the outer barrier the general behavior of the fission cross section of
Pu can also be reproduced.Comment: 17 pages including 8 figure
Quenching of Weak Interactions in Nucleon Matter
We have calculated the one-body Fermi and Gamow-Teller charge-current, and
vector and axial-vector neutral-current nuclear matrix elements in nucleon
matter at densities of 0.08, 0.16 and 0.24 fm and proton fractions
ranging from 0.2 to 0.5. The correlated states for nucleon matter are obtained
by operating on Fermi-gas states by a symmetrized product of pair correlation
operators determined from variational calculations with the Argonne v18 and
Urbana IX two- and three-nucleon interactions. The squares of the charge
current matrix elements are found to be quenched by 20 to 25 % by the
short-range correlations in nucleon matter. Most of the quenching is due to
spin-isospin correlations induced by the pion exchange interactions which
change the isospins and spins of the nucleons. A large part of it can be
related to the probability for a spin up proton quasi-particle to be a bare
spin up/down proton/neutron. We also calculate the matrix elements of the
nuclear Hamiltonian in the same correlated basis. These provide relatively mild
effective interactions which give the variational energies in the Hartree-Fock
approximation. The calculated two-nucleon effective interaction describes the
spin-isospin susceptibilities of nuclear and neutron matter fairly accurately.
However 3-body terms are necessary to reproduce the compressibility. All
presented results use the simple 2-body cluster approximation to calculate the
correlated basis matrix elements.Comment: submitted to PR
Fear of the unknown: a pre-departure qualitative study of Turkish international students
This paper presents findings from eleven in-depth interviews with Turkish undergraduate students, who were, by the time of data collection, about to spend a semester at a European university under the Erasmus exchange scheme. The students all agreed to be interviewed about their feelings about studying in a foreign culture, and were found to be anxious prior to departure about the quality of accommodation in the new destination, their language ability and the opportunity to form friendships. Fears were expressed about possible misconceptions over Turkey as a Muslim and a developing country. Suggestions are made for HEI interventions to allay student travellersâ concerns
Social factors boost wellbeing behind bars: the importance of individual and group ties for prisoner well-being
Background
Prisoners often suffer from social isolation and higher levels of illâhealth and illâbeing. Research has demonstrated the positive health consequences that stem from social interaction, and especially group ties, amongst nonâoffender populations.
Methods
This work is based on a secondary analysis of a largeâscale dataset that includes data on prisoners residing in all prison establishments in the UK (Study 1: N = 11,880; prisons = 113), and on a questionnaire booklet that was completed by prisoners residing in one prison in the UK (Study 2: N = 157).
Results
Study 1 showed that positive prisoner interactions are associated with greater prisoner wellâbeing, due to the feelings of autonomy that these interactions provide. Study 2 showed that prisoners who reported being members of multiple groups had higher wellâbeing, an effect mediated by the satisfaction of particular psychological needs; and an effect moderated by group contact discrepancy.
Conclusions
This work provides evidence that strong prisoner ties and memberships in groups are associated with greater wellâbeing among prisoners, and identifies psychological needs and group contact as explanatory mechanisms; which progresses the field and has important policy and practical implications
Supervisors' Perceptions of the Performance of Cooperative Education Employees Working in Federal Agencies
Through cooperative education programs, many public agencies employ college students part time or intermittently and groom them for future full-time employment The combination of winnowing and nurturing that occurs in these programs is believed to produce higher performing employees This study tests this hypothesis by comparing Federal supervisors' perceptions of the performance of co-op employees with those recruited from other sources Data come from the 1992 Merit Principles Survey, US Merit Systems Protection Board The results indicate that co-op employees perform at high levels, but they do not outperform other employees as a whole Next, we compare the performance ratings of Federal workers from seven other recruitment sources to see if any source is superior Some interesting findings emerge Of course, performance ratings are an incomplete indicator of an employee's value to the organization These ratings merely reflect supervisors' perceptions, and while high performance is important, agencies may wish to promote other goals in their recruitment and retention efforts such as workforce diversityYeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Maintaining sagittal plane balance compromises frontal plane balance during reactive stepping in people post-stroke
Background. Maintaining balance in response to perturbations during walking often requires the use of corrective responses to keep the center of mass within the base of support. The relationship between the center of mass and base of support is often quantified using the margin of stability. Although people post-stroke increase the margin of stability following perturbations, control deficits may lead to asymmetries in regulation of margins of stability, which may also cause maladaptive coupling between the sagittal and frontal planes during balance-correcting responses. Methods. We assessed how paretic and non-paretic margins of stability are controlled during recovery from forward perturbations and determined how stroke-related impairments influence the coupling between the anteroposterior and mediolateral margins of stability. Twenty-one participants with post-stroke hemiparesis walked on a treadmill while receiving slip-like perturbations on both limbs at foot-strike. We assessed anteroposterior and mediolateral margins of stability before perturbations and during perturbation recovery. Findings. Participants walked with smaller anteroposterior and larger mediolateral margins of stability on the paretic versus non-paretic sides. When responding to perturbations, participants increased the anteroposterior margin of stability bilaterally by extending the base of support and reducing the excursion of the extrapolated center of mass. The anteroposterior and mediolateral margins of stability in the paretic limb negatively covaried during reactive steps such that increases in anteroposterior were associated with reductions in mediolateral margins of stability. Interpretation. Balance training interventions to reduce fall risk post-stroke may benefit from incorporating strategies to reduce maladaptive coupling of frontal and sagittal plane stability
Measurement of the Strong Coupling alpha s from Four-Jet Observables in e+e- Annihilation
Data from e+e- annihilation into hadrons at centre-of-mass energies between
91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study
the four-jet rate as a function of the Durham algorithm resolution parameter
ycut. The four-jet rate is compared to next-to-leading order calculations that
include the resummation of large logarithms. The strong coupling measured from
the four-jet rate is alphas(Mz0)=
0.1182+-0.0003(stat.)+-0.0015(exp.)+-0.0011(had.)+-0.0012(scale)+-0.0013(mass)
in agreement with the world average. Next-to-leading order fits to the
D-parameter and thrust minor event-shape observables are also performed for the
first time. We find consistent results, but with significantly larger
theoretical uncertainties.Comment: 25 pages, 15 figures, Submitted to Euro. Phys. J.
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