481 research outputs found
Onset of T=0 Pairing and Deformations in High Spin States of the N=Z Nucleus 48Cr
The yrast line of the N=Z nucleus 48Cr is studied up to high spins by means
of the cranked Hartree-Fock-Bogoliubov method including the T=0 and T=1 isospin
pairing channels. A Skyrme force is used in the mean-field channel together
with a zero-range density-dependent interaction in the pairing channels. The
extensions of the method needed to incorporate the neutron-proton pairing are
summarized. The T=0 pairing correlations are found to play a decisive role for
deformation properties and excitation energies above 16hbar which is the
maximum spin that can be obtained in the f7/2 subshell.Comment: LaTeX, 4 ps figure
The effect of the skin-core structure of injection-molded isotactic polypropylene on the stress distribution in bending tests
We examine the effect of the skin-core structure of isotactic polypropylene (iPP) in bending tests. The depth-dependent material properties are determined in tensile tests and mapped to a finite element model. This enables the examination of internal stresses during bending numerically. In a bending test, one usually expects a monotonic stress distribution across the thickness, provided that the material is homogeneous and does not strain-soften. We found that the structural gradient of injection-molded iPP easily overcompensates the monotonic stress dependence, such that the maximal equivalent von Mises stress lies well below the surface in the so called shear layer. The latter is a result of the injection molding process
Particle-drip lines from the Hartree-Fock-Bogoliubov theory with Skyrme interaction
We calculate positions of one- and two-particle, proton and neutron drip
lines within the Hartree-Fock-Bogoliubov theory using Skyrme interaction. We
also determine an approximate -process path defined as a line where the
neutron binding energy is equal to 2~MeV. A weakening of the nuclear shell
structure at drip lines is found and interpreted as resulting from a coupling
with continuum states.Comment: 10 pages REVTEX 3.0, 3 uuencoded postscript figures included,
IFT/14/9
Spin-orbit interaction in Hartree-Fock calculations
The contribution of the spin-orbit interaction in Hartree-Fock calculations
for closed shell nuclei is studied. We obtain explicit expressions for the
finite range spin-orbit force. New terms with respect to the traditional
spin-orbit expressions are found. The importance of the finite-range is
analyzed. Results obtained with spin-orbit terms taken from realistic
interactions are presented. The effect of the spin-orbit isospin dependent
terms is evaluated.Comment: To be published on Nuovo Cimento
Trouble in Paradise - A disabled person's right to the satisfaction of a self-defined need:Some conceptual and practical problems
This paper questions the usefulness of the rights-based approach to ameliorating the social situation of disabled people in Britain and advances two criticisms. First, that rights and self-de? ned needs have been under-theorised by disability theorists to the extent that they have insuf? ciently appreciated the problems that these approaches pose. The paper suggests that rights to appropriate resources to satisfy self-de? ned needs will generate vast numbers of competing rights claims and that the resulting tendency of rights to con? ict has been under-appreciated. Secondly, that there has been little consideration of how these con? icts might be reconciled. The ? rst two sections of the paper look at the concepts of ascribed and self-de? ned needs, respectively, whilst the ? nal one looks at some of the problems of the rights approach and some of the dif? culties of making self-de? ned need the basis of rights claims
Half-lives of rp-process waiting point nuclei
We give results of microscopic calculations for the half-lives of various
proton-rich nuclei in the mass region A=60-90, which are involved in the
astrophysical rp-process, and which are needed as input parameters of numerical
simulations in Nuclear Astrophysics. The microscopic formalism consists of a
deformed QRPA approach that involves a selfconsistent quasiparticle deformed
Skyrme Hartree-Fock basis and residual spin-isospin separable forces in both
the particle-hole and particle-particle channels. The strength of the
particle-hole residual interaction is chosen to be consistent with the Skyrme
effective force and mean field basis, while that of the particle-particle is
globally fixed to 0.07 MeV after a judicious choice from comparison to
experimental half-lives. We study and discuss the sensitivity of the half-lives
to deformation and residual interactions.Comment: 8 pages, 4 figures, to be published in Eur. Phys. J.
Resonant continuum in the Hartree-Fock+BCS approximation
A method for incorporating the effect of the resonant continuum into
Hartree-Fock+BCS equations is proposed. The method is applied for the case of
a neutron-rich nucleus calculated with a Skyrme-type force plus a zero-range
pairing interaction and the results are compared with
Hartree-Fock-Bogoliubov calculations. It is shown that the widths of resonant
states have an important effect on the pairing properties of nuclei close to
the drip line.Comment: 9 pages, 2 figures, comparison with HFB adde
Probing coherent charmonium photoproduction off light nuclei at medium energies
We demonstrate how the elementary amplitudes , the
amplitude of the nondiagonal transition, and
the total and cross sections can be determined from
measurements of the coherent and photoproduction off light
nuclei at moderate energies. For this purpose we provide a detailed numerical
analysis of the coherent charmonium photoproduction off silicon within the
generalized vector dominance model (GVDM) adjusted to account for the physics
of charmonium models and color transparency phenomenon.Comment: 8 pages, 5 figures (color
Single particle strength restoration and nuclear transparency in high Q^2 exclusive (e,e'p) reactions
Quenching of the single particle strength which previously precluded
unambiguous measurement of nuclear transparency in quasifree (e,e'p) reactions
at high momentum transfer is evaluated from the cross sections of measured
processes. We have demonstrated evidence of the single particle strength
restoration with increase of the momentum transfer in exclusive (e,e'p)
reactions and argue that in practically interesting cases of study the nuclear
transparency in these processes quenching is weakly depends on the probability
of short range nucleon correlations. It is shown that use of Glauber
approximation well describes NE18 and E94-139 (e,e'p) data at the momentum
transfers 1 GeV^2 < Q^2 < 3 GeV^2. This gives a further support to our
observation that the quenching of nuclear levels strongly depends on the
resolution (Q^2)and practically disappears at Q^2>1GeV^2.Comment: 15 pages, 5 figures; references added, discussion extende
Breakup of loosely bound nuclei as indirect method in nuclear astrophysics: 8B, 9C, 23Al
We discuss the use of one-nucleon breakup reactions of loosely bound nuclei
at intermediate energies as an indirect method in nuclear astrophysics. These
are peripheral processes, therefore we can extract asymptotic normalization
coefficients (ANC) from which reaction rates of astrophysical interest can be
inferred. To show the usefulness of the method, three different cases are
discussed. In the first, existing experimental data for the breakup of 8B at
energies from 30 to 1000 MeV/u and of 9C at 285 MeV/u on light through heavy
targets are analyzed. Glauber model calculations in the eikonal approximation
and in the optical limit using different effective interactions give
consistent, though slightly different results, showing the limits of the
precision of the method. The results lead to the astrophysical factor
S_17(0)=18.7+/-1.9 eVb for the key reaction for solar neutrino production
7Be(p,\gamma)8B. It is consistent with the values from other indirect methods
and most direct measurements, but one. Breakup reactions can be measured with
radioactive beams as weak as a few particles per second, and therefore can be
used for cases where no direct measurements or other indirect methods for
nuclear astrophysics can be applied. We discuss a proposed use of the breakup
of the proton drip line nucleus 23Al to obtain spectroscopic information and
the stellar reaction rate for 22Mg(p,\gamma)23Al.Comment: 6 pages, 4 figures. Presented at the conference "Nuclear Physics for
Astrophysics 2", Debrecen, Hungary, May 2005. Prepared for the Proceeding
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