28,404 research outputs found
Binding of Oppositely Charged Membranes and Membrane Reorganization
We consider the electrostatic interaction between two rigid membranes, with
different surface charge densities of opposite sign, across an aqueous solution
without added salt. Exact solutions to the nonlinear Poisson-Boltzmann equation
are obtained and their physical meaning discussed. We also calculate the
electrostatic contribution to the free energy and discuss the renormalization
of the area per head group of the charged lipids arising from the Coulomb
interaction.Comment: 13 pages, 6 figures, to be published in EJP
IMEX evolution of scalar fields on curved backgrounds
Inspiral of binary black holes occurs over a time-scale of many orbits, far
longer than the dynamical time-scale of the individual black holes. Explicit
evolutions of a binary system therefore require excessively many time steps to
capture interesting dynamics. We present a strategy to overcome the
Courant-Friedrichs-Lewy condition in such evolutions, one relying on modern
implicit-explicit ODE solvers and multidomain spectral methods for elliptic
equations. Our analysis considers the model problem of a forced scalar field
propagating on a generic curved background. Nevertheless, we encounter and
address a number of issues pertinent to the binary black hole problem in full
general relativity. Specializing to the Schwarzschild geometry in Kerr-Schild
coordinates, we document the results of several numerical experiments testing
our strategy.Comment: 28 pages, uses revtex4. Revised in response to referee's report. One
numerical experiment added which incorporates perturbed initial data and
adaptive time-steppin
FIR Filter Implementation by Efficient Sharing of Horizontal and Vertical Common Sub-expressions
No abstract availabl
Family Comes First: A Family-based Resource Model for the Wife’s Pre-migration Adjustment When Couples Live Apart
NCPS-AsPh3 is a soluble polymer-supported triphenylarsine that performed equally well compared to free triphenylarsine as ligands in the Stille cross-coupling reaction of organic electrophiles and organostannanes, with the advantage that it can be conveniently and efficiently separated from the reaction by precipitation, and recycled for further use. The performance of this non-cross-linked polystyrene-supported arsine was found to be generally superior in Stille coupling reactions over the analogous polymer-supported phosphine, paralleling observations on the free ligands. Palladium-catalyzed modification of the polymer-supported arsine was possible through Pd-Ar/As-Ph exchange. Exploiting the ease of isolation of the polymer-supported reagent, the modified arsine is recycled for reuse in the Stille reaction and has led to a reduction in the yield of undesired scrambling products. © 2007 Elsevier Ltd. All rights reserved.postprin
Novel Precursors for Boron Nanotubes: The Competition of Two-Center and Three-Center Bonding in Boron Sheets
We present a new class of boron sheets, composed of triangular and hexagonal
motifs, that are more stable than structures considered to date and thus are
likely to be the precursors of boron nanotubes. We describe a simple and clear
picture of electronic bonding in boron sheets and highlight the importance of
three-center bonding and its competition with two-center bonding, which can
also explain the stability of recently discovered boron fullerenes. Our
findings call for reconsideration of the literature on boron sheets, nanotubes,
and clusters.Comment: 4 pages, 4 figures, 1 tabl
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