Search

Flux flow was studied over an entire temperature range down to T{approx}2% of T{sub c} by using intense pulsed current densities to overcome flux-vortex pinning. The resistivity at high vortex velocities is proportional to B and roughly follows {rho}{approx}{rho}{sub n}B/H{sub c2} , with a prefactor of order unity. Contrary to some speculation, {rho}{sub n} saturates to a finite residual value as T{yields}0 , indicating a metallic ({rho}{yields}finite ) rather than insulating ({rho}{yields}{infinity}) normal state, and the vortex dissipation continues to be conventional as T{yields}0 . (c) 2000 The American Physical Society.

In a supersymmetry scenario with a mass hierarchy m/sub g/roughly-equalm/sub q/>m/sub omega-tilde/>m/sub l/ , gluino-scalar quark pair production followed by the decay chain g..-->..q q-bar(qq), q..-->..omega-tildeq, omega-tilde..-->..mu-tilde..nu..(..mu..nu-tilde), mu-tilde..--> mu..gamma-tilde leads to like-sign and unlike-sign dimuons with comparable rates and possibly little accompanying hadronic activity; such events will often contain strange particles. Predictions are made for the dimuon distributions. The possible relevance to dimuon observations by Arnison et al. is addressed.

A simple model is proposed for the static electronic dielectric constants of zinc-blende and wurtzite crystals in terms of the dielectric constants of diamond-type crystals. The model suggests a natural definition of electronegativity in ($s{p}^{3}$)-hybridized valence states.

Magnetic susceptibility and Moessbauer-effect measurements on a series of dilute alloys of Eu in Mg have been performed. In strain-free samples the Eu ions are divalent, but in cold-worked samples a large fraction are converted to the trivalent state. Isochronal annealing studies suggest that this is related to the trapping of dislocation on impurity clusters with the valence change occurring because of the strain field of the dislocation.

The self-consistent charge distribution in covalently bonded crystals and molecules is divided into two components, an atomic and a bonding part. Both can be calculated in elemental crystals from macroscopic dielectric properties. The theory is easily generalized to treat heteropolar and anisotropic effects, lattice vibrations, dipole and quadrupole moments, and bond lengths in large molecules.

The larger cross section for pp than pp is associated with a narrower diffraction peak. A Regge-pole model for high-energy scattering is used to resolve this. (R.E.U.)

There is current interest in possible means of producing and analyzing deuteron polarization. Studies of d- alpha scattering on the 1.07-Mev resonance and the T(d,n)He/sup 4/ reaction show that d- alpha scattering can be a useful producer (and analyzer) of deuteron polarization at energies between resonances, where the weak energy dependence may be an advantage. The phase shifts of Galonsky and McEllistrem, deduced from differential cross sections with the help of dispersion theory, were used to calculate dispersion parameters in the interval between the resonances at 1.07 and 4.6 Mev. (A.C.)