8,258 research outputs found
A novel consolidation-based representative volume element for granular materials and its application for the characterization of the mechanical response of sand during impact loading
Open Access funded by European Structural Integrity Society
Defense Threat Reduction Agency (DTRA), Grant No: HDTRA1-12-1-004
Probing the 6He halo structure with elastic and inelastic proton scattering
Proton elastic scattering and inelastic scattering to the first excited state
of 6He have been measured over a wide angular range using a 40.9A MeV 6He beam.
The data have been analyzed with a fully microscopic model of proton-nucleus
scattering using 6He wave functions generated from large space shell model
calculations. The inelastic scattering data show a remarkable sensitivity to
the halo structure of 6He.Comment: 9 pages, 3 figures. RevTeX. Replaced figure 3 with updated figur
Entropy maximization in the force network ensemble for granular solids
A long-standing issue in the area of granular media is the tail of the force
distribution, in particular whether this is exponential, Gaussian, or even some
other form. Here we resolve the issue for the case of the force network
ensemble in two dimensions. We demonstrate that conservation of the total area
of a reciprocal tiling, a direct consequence of local force balance, is crucial
for predicting the local stress distribution. Maximizing entropy while
conserving the tiling area and total pressure leads to a distribution of local
pressures with a generically Gaussian tail that is in excellent agreement with
numerics, both with and without friction and for two different contact
networks.Comment: 4 pages, 3 figure
Dilatancy transition in a granular model
We introduce a model of granular matter and use a stress ensemble to analyze
shearing. Monte Carlo simulation shows the model to exhibit a second order
phase transition, associated with the onset of dilatancy.Comment: Future versions can be obtained from:
http://www.ma.utexas.edu/users/radin/papers/shear2.pd
The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites
We present investigations on volume regulation and beading shape transitions
in PC12 neurites conducted using a flow-chamber technique. By disrupting the
cell cytoskeleton with specific drugs we investigate the role of its individual
components in the volume regulation response. We find that microtubule
disruption increases both swelling rate and maximum volume attained, but does
not affect the ability of the neurite to recover its initial volume. In
addition, investigation of axonal beading --also known as pearling
instability-- provides additional clues on the mechanical state of the neurite.
We conclude that the initial swelling phase is mechanically slowed down by
microtubules, while the volume recovery is driven by passive diffusion of
osmolites. Our experiments provide a framework to investigate the role of
cytoskeletal mechanics in volume homeostasis
Structure of unbound neutron-rich He studied using single-neutron transfer
The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using
the MUST2 Si-CsI array in order to shed light on the level structure of 9He.
The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was
used as a test to validate the experimental methods. The 9He missing mass
spectrum was deduced from the kinetic energies and emission angles of the
recoiling protons. Several structures were observed above the neutron-emission
threshold and the angular distributions were used to deduce the multipolarity
of the transitions. This work confirms that the ground state of 9He is located
very close to the neutron threshold of 8He and supports the occurrence of
parity inversion in 9He.Comment: Exp\'erience GANIL/SPIRAL1/MUST
Field Theory And Second Renormalization Group For Multifractals In Percolation
The field-theory for multifractals in percolation is reformulated in such a
way that multifractal exponents clearly appear as eigenvalues of a second
renormalization group. The first renormalization group describes geometrical
properties of percolation clusters, while the second-one describes electrical
properties, including noise cumulants. In this context, multifractal exponents
are associated with symmetry-breaking fields in replica space. This provides an
explanation for their observability. It is suggested that multifractal
exponents are ''dominant'' instead of ''relevant'' since there exists an
arbitrary scale factor which can change their sign from positive to negative
without changing the Physics of the problem.Comment: RevTex, 10 page
Neutrinoless Double Beta Decay and the Solar Neutrino Problem
The MSW or vacuum oscillation solution of the solar neutrino problem can be
reconciled with possible existence of the decay with a
half-life corresponding to an effective Majorana mass of the electron neutrino
eV. The phenomenological consequences of such a
possibility are analyzed and the implications for the mechanisms of neutrino
mass generation are considered.Comment: 17 pages (2 figures available upon request), LaTeX, SISSA 113/93/EP
and IC/93/360 (the word BETA inserted in the title
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