762 research outputs found
Non-adiabatic corrections to elastic scattering of halo nuclei
We derive the formalism for the leading order corrections to the adiabatic
approximation to the scattering of composite projectiles. Assuming a two-body
projectile of core plus loosely-bound valence particle and a model (the core
recoil model) in which the interaction of the valence particle and the target
can be neglected, we derive the non-adiabatic correction terms both exactly,
using a partial wave analysis, and using the eikonal approximation. Along with
the expected energy dependence of the corrections, there is also a strong
dependence on the valence-to-core mass ratio and on the strength of the
imaginary potential for the core-target interaction, which relates to
absorption of the core in its scattering by the target. The strength and
diffuseness of the core-target potential also determine the size of the
corrections. The first order non-adiabatic corrections were found to be smaller
than qualitative estimates would expect. The large absorption associated with
the core-target interaction in such halo nuclei as Be11 kills off most of the
non-adiabatic corrections. We give an improved estimate for the range of
validity of the adiabatic approximation when the valence-target interaction is
neglected, which includes the effect of core absorption. Some consideration was
given to the validity of the eikonal approximation in our calculations.Comment: 14 pages with 10 figures, REVTeX4, AMS-LaTeX v2.13, submitted to
Phys. Rev.
Effects of an induced three-body force in the incident channel of (d,p) reactions
A widely accepted practice for treating deuteron breakup in
reactions relies on solving a three-body Schr\"odinger equation with
pairwise -, - and - interactions. However, it was shown in
[Phys. Rev. C \textbf{89}, 024605 (2014)] that projection of the many-body
wave function into the three-body channel results in a
complicated three-body operator that cannot be reduced to a sum of pairwise
potentials. It contains explicit contributions from terms that include
interactions between the neutron and proton via excitation of the target .
Such terms are normally neglected. We estimate the first order contribution of
these induced three-body terms and show that applying the adiabatic
approximation to solving the model results in a simple modification of
the two-body nucleon optical potentials. We illustrate the role of these terms
for the case of Ca()Ca transfer reactions at incident
deuteron energies of 11.8, 20 and 56 MeV, using several parameterisations of
nonlocal optical potentials.Comment: 7 pages, 2 figures. Publication due in Phys. Rev.
Assessing Service Quality at Optical Centers in Palestine Using SERVQUAL: Measuring Ambiguity
The main purpose of this article is to employ the SERVQUAL model to assess customers’ perceptions and expectations of service quality in the optical centers in the West Bank of Palestine, and to examine the impact of this service quality on their satisfaction. A focused critical review of the service quality literature was undertaken. Data was collected from a convenient and purposeful sample of 251 customers of optical centers in the West Bank via personally administered and online questionnaires. Data was analyzed, with the aid of SPSS, using descriptive and inferential statistics, including the Mann-Whitney test, the Kruskal-Wallis test, regression analysis, and the Wilcoxon signed-rank test. The findings indicate that SERVQUAL proved to be a good tool for the purpose of assessing the gaps between customers’ expectations and perceptions of the service quality of optical centers in the Palestinian context. The findings also confirmed that customers had higher service quality expectations than perceptions in all the five dimensions of SERVQUAL. The developed regression analysis model shows that tangibles, reliability, assurance, and empathy had a significant statistical impact on customers’ satisfaction. No studies, to the best knowledge of the authors, were conducted on customers’ perceptions and expectations of service quality in the optical centers in the Palestinian context. Limitations of the study’s methodology and findings were discussed and avenues for further research suggested. The findings of this study could be valuable to interested parties including optometry regulators and managers of optical centers
Probing halo nucleus structure through intermediate energy elastic scattering
This work addresses the question of precisely what features of few body
models of halo nuclei are probed by elastic scattering on protons at high
centre-of-mass energies. Our treatment is based on a multiple scattering
expansion of the proton-projectile transition amplitude in a form which is well
adapted to the weakly bound cluster picture of halo nuclei. In the specific
case of Li scattering from protons at 800 MeV/u we show that because
core recoil effects are significant, scattering crosssections can not, in
general, be deduced from knowledge of the total matter density alone.
We advocate that the optical potential concept for the scattering of halo
nuclei on protons should be avoided and that the multiple scattering series for
the full transition amplitude should be used instead.Comment: 8 pages REVTeX, 1 eps figure, accepted for publication in Phys. Rev.
Energy Dependence of Breakup Cross Sections of Halo Nucleus 8B and Effective Interactions
We study the energy dependence of the cross sections for nucleon removal of
8B projectiles. It is shown that the Glauber model calculations with
nucleon-nucleon t-matrix reproduce well the energy dependence of the breakup
cross sections of 8B. A DWBA model for the breakup cross section is also
proposed and results are compared with those of the Glauber model. We show that
to obtain an agreement between the DWBA calculations, the Glauber formalism,
and the experimental data, it is necessary to modify the energy behavior of the
effective interaction. In particular, the breakup potential has a quite
different energy dependence than the strong absorption potential.Comment: 13 pages, 4 figure
Vector meson photoproduction studied in its radiative decay channel
We provide an analysis of vector meson photoproduction in the channel of the
vector meson decaying into a pseudoscalar meson plus a photon, i.e. . It is shown that non-trivial kinematic correlations arise from the
measurement of the angular distributions in the overall c.m. system
in comparison with those in the vector-meson-rest frame. In terms of the vector
meson density matrix elements, the implication of such kinematic correlations
in the measurement of polarization observables is discussed. For the
meson production, due to its relatively large branching ratios for
, additional events from this channel may enrich the
information about the reaction mechanism and improve the statistics of the
recent measurement of polarized beam asymmetries by the GRAAL Collaboration.
For , , and , we expect
that additional information about the spin structure of the vector meson
production vertex can be derived.Comment: Revtex, 14 pages, 2 eps figures; Version accepted by PR
Probing the Structure of Halo Nuclei
Our understanding of halo nuclei has so far relied on high-energy scattering
and reactions, but a number of uncertainties remain. I discuss in general terms
the new range of observables which will be measured by experiments around the
Coulomb barrier, and how some details of the reaction mechanisms still need to
be clarified.Comment: Proceedings of FUSION97 conference (March 1997), South Durras,
Australia. Submitted to J. Physics G: special issue `Heavy ion collisions at
near barrier energies'. No figures; uses IOPConf.sty (included
Aldosterone modulates the association between NCC and ENAC
Distal sodium transport is a final step in the regulation of blood pressure. As such, understanding how the two main sodium transport proteins, the thiazide-sensitive sodium chloride cotransporter (NCC) and the epithelial sodium channel (ENaC), are regulated is paramount. Both are expressed in the late distal nephron; however, no evidence has suggested that these two sodium transport proteins interact. Recently, we established that these two sodium transport proteins functionally interact in the second part of the distal nephron (DCT2). Given their co-localization within the DCT2, we hypothesized that NCC and ENaC interactions might be modulated by aldosterone (Aldo). Aldo treatment increased NCC and αENaC colocalization (electron microscopy) and interaction (coimmunoprecipitation). Finally, with co-expression of the Aldo-induced protein serum- and glucocorticoid-inducible kinase 1 (SGK1), NCC and αENaC interactions were increased. These data demonstrate that Aldo promotes increased interaction of NCC and ENaC, within the DCT2 revealing a novel method of regulation for distal sodium reabsorption
Sensitivity of Cross Sections for Elastic Nucleus-Nucleus Scattering to Halo Nucleus Density Distributions
In order to clear up the sensitivity of the nucleus-nucleus scattering to the
nuclear matter distributions of exotic halo nuclei, we have calculated
differential cross sections for elastic scattering of the He and Li
nuclei on several nuclear targets at the energy of 0.8 GeV/nucleon with
different assumed nuclear density distributions in He and Li.Comment: 10 pages, 7 figures. Submitted to Proceedings of the 61 International
Conference "Nucleus-2011" on the Problems of the Nuclear Spectroscopy and the
Atomic Nuclear Structure, Sarov Nijzegorodskaya district, October 10-14, 201
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