30 research outputs found
Local energy-density functional approach to many-body nuclear systems with s-wave pairing
The ground-state properties of superfluid nuclear systems with ^1S_0 pairing
are studied within a local energy-density functional (LEDF) approach. A new
form of the LEDF is proposed with a volume part which fits the Friedman-
Pandharipande and Wiringa-Fiks-Fabrocini equation of state at low and moderate
densities and allows an extrapolation to higher densities preserving causality.
For inhomogeneous systems, a surface term with two free parameters is added. In
addition to the Coulomb direct and exchange interaction energy, an effective
density-dependent Coulomb-nuclear correlation term is included with one more
free parameter, giving a contribution of the same order of magnitude as the
Nolen-Schiffer anomaly in Coulomb displacement energy. The root-mean-square
deviations from experimental masses and radii with the proposed LEDF come out
about a factor of two smaller than those obtained with the conventional
functionals based on the Skyrme or finite-range Gogny force, or on the
relativistic mean-field theory. The generalized variational principle is
formulated leading to the self-consistent Gor'kov equations which are solved
exactly, with physical boundary conditions both for the bound and scattering
states. With a zero-range density-dependent cutoff pairing interaction
incorporating a density-gradient term, the evolution of differential
observables such as odd-even mass differences and staggering in charge radii,
is reproduced reasonably well, including kinks at magic neutron numbers. An
extrapolation to infinite nuclear matter is discussed. We study also the dilute
limit in both the weak and strong coupling regime.Comment: 19 pages, 8 figures. LaTeX, with modified cls file supplied. To be
published in vol. 3 of the series "Advances in Quantum Many-Body Theory",
World Scientific (Proceedings of the MBX Conference, Seattle, September
10-15, 1999
Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes
A chromosphere is a universal attribute of stars of spectral type later than
~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae
binaries) show extended and highly turbulent chromospheres, which develop into
slow massive winds. The associated continuous mass loss has a significant
impact on stellar evolution, and thence on the chemical evolution of galaxies.
Yet despite the fundamental importance of those winds in astrophysics, the
question of their origin(s) remains unsolved. What sources heat a chromosphere?
What is the role of the chromosphere in the formation of stellar winds? This
chapter provides a review of the observational requirements and theoretical
approaches for modeling chromospheric heating and the acceleration of winds in
single cool, evolved stars and in eclipsing binary stars, including physical
models that have recently been proposed. It describes the successes that have
been achieved so far by invoking acoustic and MHD waves to provide a physical
description of plasma heating and wind acceleration, and discusses the
challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript;
accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake
(Berlin: Springer
Polarized Neutron Reflectometry of Nickel Corrosion Inhibitors.
Polarized neutron reflectometry has been used to investigate the detailed adsorption behavior and corrosion inhibition mechanism of two surfactants on a nickel surface under acidic conditions. Both the corrosion of the nickel surface and the structure of the adsorbed surfactant layer could be monitored in situ by the use of different solvent contrasts. Layer thicknesses and roughnesses were evaluated over a range of pH values, showing distinctly the superior corrosion inhibition of one negatively charged surfactant (sodium dodecyl sulfate) compared to a positively charged example (dodecyl trimethylammonium bromide) due to its stronger binding interaction with the surface. It was found that adequate corrosion inhibition occurs at significantly less than full surface coverage.X-ray photoelectron spectra were obtained at the National Engineering and Physical Sciences Research Council (EPSRC) XPS User’s Service (NEXUS) at Newcastle University, an EPSRC midrange facility. NR data were obtained on the D17 instrument, and samples were treated in the laboratories of the Partnership for Soft Condensed Matter (PSCM) at the Institut Laue-Langevin. M.H.W. is grateful for funding from the Oppenheimer Trust.This is the final version of the article. It first appeared from the American Chemical Society via http://dx.doi.org/10.1021/acs.langmuir.5b0171