1,021 research outputs found
Agenesis of distal segment of right vertebral artery: a case report.
A case is being reported in which the basilar artery was formed only by the left vertebral artery. This was detected incidentally in a female on a non contrast magnetic resonance angiogram. The right vertebral artery arose as a direct branch of the right subclavian artery but terminated blindly at the level of second cervical vertebra. The left vertebral artery which contributed to the formation of basilar artery continued as left posterior cerebral artery while right posterior cerebral artery was seen as a continuation of right posterior communicating artery. The knowledge of variations of the vertebrobasilar arterial complex is important to Clinicians, Radiologists and Surgeons operating on the great vessels and its branches, particularly vascular surgeons dealing with vertebral artery in order to prevent a vascular catastrophe
Temperature induced shell effects in deformed nuclei
The thermal evolution of the shell correction energy is investigated for
deformed nuclei using Strutinsky prescription in a self-consistent relativistic
mean-field framework. For temperature independent single-particle states
corresponding to either spherical or deformed nuclear shapes, the shell
correction energy steadily washes out with temperature. However,
for states pertaining to the self-consistent thermally evolving shapes of
deformed nuclei, the dual role played by the single-particle occupancies in
diluting the fluctuation effects from the single-particle spectra and in
driving the system towards a smaller deformation is crucial in determining
at moderate temperatures. In rare earth nuclei, it is found that
builds up strongly around the shape transition temperature; for
lighter deformed nuclei like and , this is relatively less
prominent.Comment: 6 pages revtex file + 4 ps files for figures, Phys. Rev. C (in press
Roles of proton-neutron interactions in alpha-like four-nucleon correlations
An extended pairing plus QQ force model, which has been shown to successfully
explain the nuclear binding energy and related quantities such as the symmetry
energy, is applied to study the alpha-like four-nucleon correlations in
1f_{7/2} shell nuclei.
The double difference of binding energies, which displays a characteristic
behavior at , is interpreted in terms of the alpha-like
correlations. Important roles of proton-neutron interactions forming the
alpha-like correlated structure are discussed.Comment: 10 pages, 2 figures, RevTex, submitted to Phys. Rev.
Information entropy as a measure of the quality of a nuclear density distribution
The information entropy of a nuclear density distribution is calculated for a
number of nuclei. Various phenomenological models for the density distribution
using different geometry are employed. Nuclear densities calculated within
various microscopic mean field approaches are also employed. It turns out that
the entropy increases on going from crude phenomenological models to more
sophisticated (microscopic) ones. It is concluded that the larger the
information entropy, the better the quality of the nuclear density
distribution. An alternative approach is also examined: the net information
content i.e. the sum of information entropies in position and momentum space
. It is indicated that is a maximum, when the best
fit to experimental data of the density and momentum distributions is attained.Comment: 12 pages, LaTex, no figures, Int. J. of Mod. Phys. E in pres
Pairing and alpha-like quartet condensation in N=Z nuclei
We discuss the treatment of isovector pairing by an alpha-like quartet
condensate which conserves exactly the particle number, the spin and the
isospin. The results show that the quartet condensate describes accurately the
isovector pairing correlations in the ground state of systems with an equal
number of protons and neutronsComment: 4 pages, to appear in Journal of Physics: Conference Serie
Relativistic Mean Field Approach and the Pseudo-Spin Symmetry
Based on the Relativistic Mean Field (RMF) approach the existence of the
broken pseudo-spin symmetry is investigated. Both spherical RMF and constrained
deformed RMF calculations are carried out employing realistic Lagrangian
parameters for spherical and for deformed sample nuclei. The quasi - degenerate
pseudo-spin doublets are confirmed to exist near the fermi surface for both
spherical and deformed nuclei.Comment: 9 pages RevTex, 4 p.s figures, to appear in Phys. Rev. C as R.
Alpha decay and proton-neutron correlations
We study the influence of proton-neutron (p-n) correlations on alpha-decay
width. It is shown from the analysis of alpha Q values that the p-n
correlations increase the penetration of the alpha particle through the Coulomb
barrier in the treatment following Gamow's formalism, and enlarges the total
alpha-decay width significantly.
In particular, the isoscalar p-n interactions play an essential role in
enlarging the alpha-decay width.
The so-called "alpha-condensate" in Z > 84 isotopes are related to the strong
p-n correlations.Comment: 5 pages, 6 figures, accepted for publication in Phys. Rev. C (R.C.
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