1/8 Doping Anomalies and Oxygen Vacancies in Underdoped Superconducting Cuprates

Measurements of thermal conductivity ($\kappa$) versus temperature and doping for several cuprate superconductors are discussed. Suppressed values of the normal-state $\kappa$ and the slope change in $\kappa$ at $T_c$, observed near 1/8 doping in both YBa$_2$Cu$_3$O$_{6+x}$ and Hg cuprates, are attributed to local lattice distortions and the suppression of the superconducting condensate, respectively. Both phenomena are proposed to arise from small domains of localized planar holes, presumably a manifestation of phase separation. It is suggested that the phase behavior of $\kappa$ reflects stripe dynamics and the 1/8 doping anomalies stripe pinning by oxygen-vacancy clusters.Comment: 6 pages, AIP 6"x9" format, 3 embedded postscript fig.s Proceedings of University of Miami Conference (HTS99), 7-13 Jan., 199

Numerical solution of degenerate stochastic Kawarada equations via a semi-discretized approach

The numerical solution of a highly nonlinear two-dimensional degenerate stochastic Kawarada equation is investigated. A semi-discretized approximation in space is comprised on arbitrary nonuniform grids. Exponential splitting strategies are then applied to advance solutions of the semi-discretized scheme over adaptive grids in time. It is shown that key quenching solution features including the positivity and monotonicity are well preserved under modest restrictions. The numerical stability of the underlying splitting method is also maintained without any additional restriction. Computational experiments are provided to not only illustrate our results, but also provide further insights into the global nonlinear convergence of the numerical solution.Comment: 22 pages, 9 figures, article accepted (being uploaded to arXiv to create repository of all work

Opinion: Too Many Veterans with Children are Still Homeless

Don’t ignore homeless veterans. As we pause this Veterans Day to reflect on those who have sacrificed in the service of our country, let us not neglect to address the plight of those who have returned to a civilian life with far less promise than they have every right to expect. [excerpt

An Examination of the Optical Substructure of Galaxy Clusters Hosting Radio Sources

Using radio sources from the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey, and optical counterparts in the Sloan Digital Sky Survey (SDSS), we have identified a large number of galaxy clusters. The radio sources within these clusters are driven by active galactic nuclei, and our cluster samples include clusters with bent, and straight, double-lobed radio sources. We also included a single-radio-component comparison sample. We examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. We use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. We found no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.Comment: 26 total pages, 15 figures, 8 tables. Published in Ap