Universal vortex-state Hall conductivity of YBa2Cu3O7 single crystals with differing correlated disorder

The vortex-state Hall conductivity ([sigma][sub]xy) of YBa2Cu3O7 single crystals in the anomalous-sign-reversal region is found to be independent of the density and orientation of the correlated disorder. After the anisotropic-to-isotropic scaling transformation is carried out, a universal scaled Hall conductivity [sigma][bar][sub]xy is obtained as a function of the reduced temperature (T/T[sub]c) and scaled magnetic field strength (H[bar]) for five samples with different densities and orientation of controlled defects. The transport scattering times {tau], derived from applying the model given by Feigel'man et al (Feigel'man M V, Geshkenbein V B, Larkin A I and Vinokur V M 1995 Pis. Zh. Eksp. Teor. Fiz. 62 811 (Engl. Transl. 1995 JETP Lett. 62 835)) to the universal Hall conductivity [sigma bar](T/T[sub]c, H[bar]), are consistent in magnitude with those derived from other measurements for quasiparticle scattering, and are much smaller than the thermal relaxation time of vortex displacement and than the vortex–defect interaction time. Our experimental results and analyses therefore suggest that the anomalous sign reversal in the vortex-state Hall conductivity is associated with the intrinsic properties of type-II superconductors, rather than extrinsic disorder effects

Ultrapure glass optical waveguide: Development in microgravity by the sol gel process

The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths

Personal Recollections of the Museum of Art and the Department of Art at Bowdoin College

Published with the assistance of the John Sloan Memorial Foundation --T.p. versohttps://digitalcommons.bowdoin.edu/art-museum-miscellaneous-publications/1002/thumbnail.jp

Stability Analysis of Numerical Boundary Conditions and Implicit Difference Approximations for Hyperbolic Equations

Implicit noniterative finite-difference schemes have recently been developed by several authors for multidimensional systems of nonlinear hyperbolic partial differential equations. When applied to linear model equations with periodic boundary conditions those schemes are unconditionally stable (A-stable). As applied in practice the algorithms often face a severe time-step restriction. A major source of the difficulty is the treatment of the numerical boundary conditions. One conjecture has been that unconditional stability requires implicit numerical boundary conditions. An apparent counterexample was the space-time extrapolation considered by Gustafsson, Kreiss, and Sundstrom. In this paper we examine space (implicit) and space-time (explicit) extrapolation using normal mode analysis for a finite and infinite number of spatial mesh intervals. The results indicate that for unconditional stability with a finite number of spatial mesh intervals the numerical boundary conditions must be implicit