1,433 research outputs found
One-neutron halo structure by the ratio method
We present a new observable to study halo nuclei. This new observable is a
particular ratio of angular distributions for elastic breakup and scattering.
For one-neutron halo nuclei, it is shown to be independent of the reaction
mechanism and to provide significant information about the structure of the
projectile, including binding energy, partial-wave configuration, and radial
wave function of the halo. This observable offers new capabilities for the
study of nuclear structure far from stability.Comment: 9 pages, 4 figure
Dynamic critical behavior of failure and plastic deformation in the random fiber bundle model
The random fiber bundle (RFB) model, with the strength of the fibers
distributed uniformly within a finite interval, is studied under the assumption
of global load sharing among all unbroken fibers of the bundle. At any fixed
value of the applied stress (load per fiber initially present in the bundle),
the fraction of fibers that remain unbroken at successive time steps is shown
to follow simple recurrence relations. The model is found to have stable fixed
point for applied stress in the range 0 and 1; beyond which total failure of
the bundle takes place discontinuously. The dynamic critical behavior near this
failure point has been studied for this model analysing the recurrence
relations. We also investigated the finite size scaling behavior. At the
critical point one finds strict power law decay (with time t) of the fraction
of unbroken fibers. The avalanche size distribution for this mean-field
dynamics of failure has been studied. The elastic response of the RFB model has
also been studied analytically for a specific probability distribution of fiber
strengths, where the bundle shows plastic behavior before complete failure,
following an initial linear response.Comment: 13 pages, 5 figures, extensively revised and accepted for publication
in Phys. Rev.
Learning from the Success of MPI
The Message Passing Interface (MPI) has been extremely successful as a
portable way to program high-performance parallel computers. This success has
occurred in spite of the view of many that message passing is difficult and
that other approaches, including automatic parallelization and directive-based
parallelism, are easier to use. This paper argues that MPI has succeeded
because it addresses all of the important issues in providing a parallel
programming model.Comment: 12 pages, 1 figur
Density of states and magnetoconductance of disordered Au point contacts
We report the first low temperature magnetotransport measurements on
electrochemically fabricated atomic scale gold nanojunctions. As , the
junctions exhibit nonperturbatively large zero bias anomalies (ZBAs) in their
differential conductance. We consider several explanations and find that the
ZBAs are consistent with a reduced local density of states (LDOS) in the
disordered metal. We suggest that this is a result of Coulomb interactions in a
granular metal with moderate intergrain coupling. Magnetoconductance of atomic
scale junctions also differs significantly from that of less geometrically
constrained devices, and supports this explanation.Comment: 5 pages, 5 figures. Accepted to PRB as Brief Repor
Vascular reactivity in hypertension: Altered effect of ouabain
Ouabain inhibits the relaxing effect of Ca 2+ (but not of Mn 2+ ) on contractile responses in tail artery strips isolated from spontaneously hypertensive and normotensive rats. The magnitude of ouabain inhibition was greater in vascular strips from hypertensive rats suggesting a significant difference in basic membrane function in hypertensive vascular smooth muscle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42713/1/18_2005_Article_BF01953743.pd
Core excitation in Coulomb breakup reactions
Within the pure Coulomb breakup mechanism, we investigate the one-neutron
removal reaction of the type A(a,b)X with Be and C
projectiles on a heavy target nucleus Pb at the beam energy of 60
MeV/nucleon. Our intention is to examine the prospective of using these
reactions to study the structure of neutron rich nuclei. Integrated partial
cross sections and momentum distributions for the ground as well as excited
bound states of core nuclei are calculated within the finite range distorted
wave Born approximation as well as within the adiabatic model of the Coulomb
breakup. Our results are compared with those obtained in the studies of the
reactions on a light target where the breakup proceeds via the pure nuclear
mechanism. We find that the transitions to excited states of the core are quite
weak in the Coulomb dominated process as compared to the pure nuclear breakup.Comment: Revtex format, five postscript figures included, to appear in Phys.
Rev.
A Simple Shell Model for Quantum Dots in a Tilted Magnetic Field
A model for quantum dots is proposed, in which the motion of a few electrons
in a three-dimensional harmonic oscillator potential under the influence of a
homogeneous magnetic field of arbitrary direction is studied. The spectrum and
the wave functions are obtained by solving the classical problem. The ground
state of the Fermi-system is obtained by minimizing the total energy with
regard to the confining frequencies. From this a dependence of the equilibrium
shape of the quantum dot on the electron number, the magnetic field parameters
and the slab thickness is found.Comment: 15 pages (Latex), 3 epsi figures, to appear in PhysRev B, 55 Nr. 20
(1997
Single-Proton Removal Reaction Study of 16B
The low-lying level structure of the unbound system B has been
investigated via single-proton removal from a 35 MeV/nucleon C beam. The
coincident detection of the beam velocity B fragment and neutron allowed
the relative energy of the in-flight decay of B to be reconstructed. The
resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is
argued that this feature corresponds to a very narrow (100 keV)
resonance, or an unresolved multiplet, with a dominant + configuration which decays by d-wave neutron
emission.Comment: 16 pages, 5 figures, 1 table, submitted to Phys. Lett.
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