31,408 research outputs found
Critique [of The Ethnic Matrix: Implications for Human Service Practitioners by Jesse M. Vazquez]
Vazquez\u27s psychosocial model for understanding ethnicity and the ethnic process in American society and how this model could be used by practitioners and researchers to further expand their own work is noble. Vazquez fulfilled his purpose. However, the underlying assumption is somewhat misleading, i.e., practitioners and researchers, generally, are not employing the ethnic matrix model. Vazquez states that the absence of ethnic content and concern with ethnic issues in professional training programs was seriously questioned
Well-posedness, energy and charge conservation for nonlinear wave equations in discrete space-time
We consider the problem of discretization for the U(1)-invariant nonlinear
wave equations in any dimension. We show that the classical finite-difference
scheme used by Strauss and Vazquez \cite{MR0503140} conserves the
positive-definite discrete analog of the energy if the grid ratio is , where and are the mesh sizes of the time and space
variables and is the spatial dimension. We also show that if the grid ratio
is , then there is the discrete analog of the charge which is
conserved.
We prove the existence and uniqueness of solutions to the discrete Cauchy
problem. We use the energy conservation to obtain the a priori bounds for
finite energy solutions, thus showing that the Strauss -- Vazquez
finite-difference scheme for the nonlinear Klein-Gordon equation with positive
nonlinear term in the Hamiltonian is conditionally stable.Comment: 10 page
Theoretical studies of the kinetics of mechanical unfolding of cross-linked polymer chains and their implications for single molecule pulling experiments
We have used kinetic Monte Carlo simulations to study the kinetics of
unfolding of cross-linked polymer chains under mechanical loading. As the ends
of a chain are pulled apart, the force transmitted by each crosslink increases
until it ruptures. The stochastic crosslink rupture process is assumed to be
governed by first order kinetics with a rate that depends exponentially on the
transmitted force. We have performed random searches to identify optimal
crosslink configurations whose unfolding requires a large applied force
(measure of strength) and/or large dissipated energy (measure of toughness). We
found that such optimal chains always involve cross-links arranged to form
parallel strands. The location of those optimal strands generally depends on
the loading rate. Optimal chains with a small number of cross-links were found
to be almost as strong and tough as optimal chains with a large number of
cross-links. Furthermore, optimality of chains with a small number of
cross-links can be easily destroyed by adding cross-links at random. The
present findings are relevant for the interpretation of single molecule force
probe spectroscopy studies of the mechanical unfolding of load-bearing
proteins, whose native topology often involves parallel strand arrangements
similar to the optimal configurations identified in the study
Cluster analysis to define distinct clinical phenotypes among septic patients with bloodstream infections
S^1-wrapped D3-branes on Conifolds
We construct a D3-brane wrapped on S^1, which is fibred over the resolved
conifold as its transverse space. Whereas a fractional D3-brane on the resolved
conifold is not supersymmetric and has a naked singularity, our solution is
supersymmetric and regular everywhere. We also consider an -wrapped
D3-brane on the resolved cone over T^{1,1}/Z_2, as well as on the deformed
conifold. In the former case, we obtain a regular supergravity dual to a
certain four-dimensional field theory whose Lorentz and conformal symmetries
are broken in the IR region and restored in the UV limit.Comment: Latex, 14 pages, minor correction
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