The critical velocity has been measured at the transition from dissipationless superflow to homogeneous superfluid turbulence. The results do not agree well with the recent prediction of Schwarz based upon a topologically self-sustaining vortex tangle.

The observation of macroscopic collective behavior in a nematic liquid crystal doped with magnetic grains is reported. This behavior is manifested as a uniform molecular orientational distortion of the entire matrix upon the application of external magnetic fields as low as <1 G. The dependence of the distortion on field strength, dopant concentration, and sample thickness is presented, and a theory which quantitatively accounts for the results is given. At high field intensities, the doped nematic exhibits a heretofore unreported texture of complex cellular topology.

A new, dynamical model is presented which can explain the anomalously strong attenuation reported for ballistic phonons propagating through the (001) inversion layer of Si. The crux is an interference effect between phonon amplitudes backscattered from the two-dimensional electron gas and amplitudes specularly reflected from the Si-Si${\mathrm{O}}_2$ interface.

Holes are produced inside a thin layer of magnetic fluid with use of monodisperse polystyrene spheres with diameters in the micrometer range. With an external magnetic field an apparent magnetic dipole will be associated with each hole as a result of the displaced fluid. The apparent dipolar interactions between the spheres may be made attractive or repulsive. This Letter presents the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices.

Positive binding-energy shifts in small metallic clusters supported on poorly conducting substrates are shown to arise from the unit positive charge remaining on the cluster in the photoemission final state.

Evidence is presented that coldly deposited Ag films are highly porous and that the pores persist up to 170 K but are heated out at 250 K. Diffusion of adsorbed pyridine into the pores is negligible below 60 K but readily takes place at 130 K. Theoretical results on the classical electromagnetic enhancement of the Raman cross section within the pores as well as a survey of published surface-enhanced Raman-scattering data lead the authors to conclude that the surface-enhanced Raman-scattering active sites of coldly deposited Ag films are within the pores.

Theory and experimental evidence of a new transient polarization phenomenon, unique to sawtooth superlattices, are presented. This effect is the consequence of the lack of reflection symmetry in these structures and can be used for the implementation of a new class of high-speed, displacement current photodetectors.

A simple paramagnetic scattering function for neutrons, with Lorentzian shapes both in energy and in momentum transfer, is demonstrated to give a full explanation of the spin-wave-like peaks observed in Ni at and above $T_c$ in constant-energy scans of thermal neutron scattering. A model calculation for Ni confirms the direct connection to the critical scattering, and a comparison with EuO reveals that the spectral shape is governed by the spin-diffusion and spin-wave-stiffness constants.

The three resonantly enhanced Raman vibrations in trans-${\left(\mathrm{CH}\right)}_x$ and -${\left(\mathrm{CD}\right)}_x$ are described in terms of amplitude modes associated with the Peierls gap. The dispersion in the Raman-line profiles is explained by inhomogeneity. A narrow distribution of the effective electron-phonon coupling constant is required to account for the observed spectra in detail. The resonant Raman vibrations and the ir-active modes induced by doping or photogeneration are all described by the same form of dressed phonon propagator.

Raman scattering in Ce${\mathrm{Al}}_2$ probes the interacting phonon (${\tilde{\Gamma }}_6$) and crystalline-electric-field-split ${\tilde{\Gamma }}_7-{\tilde{\Gamma }}_8$ excitations. The observed 109-${\mathrm{cm}}^{-1\mathrm{}}$ Raman peak due to ${\tilde{\Gamma }}_6$ and the 71-${\mathrm{cm}}^{-1\mathrm{}}$ peak (at 5 K) due to ${\tilde{\Gamma }}_7\to {\tilde{\Gamma }}_{8\left(2\right)\mathrm{}}$ are in very good agreement with the recent theoretical bound-state model for Ce${\mathrm{Al}}_2$.

The Hall effect and the magnetoresistance of ${\mathrm{}\left(\mathrm{TMTSF}\right)\mathrm{}}_2$Cl${\mathrm{O}}_4$ have been measured at temperatures from 0.08 to 10 K and in magnetic fields to 22 T. The low-temperature data suggest a series of transitions induced by an orbital effect from the magnetic field which progressively reduce the carrier density. Oscillations, apparently Shubnikov-de Haas, also are observed above 10 T and at temperatures up to 10 K.

The transport dynamics of a large polaron has been studied in a one-dimensional system whose underlying vibrational spectrum is acoustic in character. Such a polaron moves as a heavy quasiparticle with transport relaxation time, $\tau$, determined mainly by collisions with thermally ambient phonons. Concrete results show that $\tau$ decreases monotonically with increasing temperature, in sharp contrast to the previously treated problem of a large polaron in a one-dimensional Einstein lattice.

The authors report on an unusual simultaneous increase in the cosmic-ray shower rate at two recording stations separated by 250 km. The event lasted for 20 s. This event was the only one of its kind detected in three years of observation. The duration and structure of this event is different from a recently reported single-station cosmic-ray burst. The simultaneity of the coincident event suggests that it was caused by a burst of cosmic gamma rays. There is a possibility that this event may be related to the largest observed glitch of the pulsar in the Crab Nebula.

A generalization of the Einstein-Green-Kubo self-diffusion coefficient is obtained for a fluid in uniform shear flow. The associated nonlinear transport coefficients do not exist, because of a nonanalytic dependence on shear rate. The relationship of this anomalous nonlinearity to the long-time tails of the velocity autocorrelation function at zero shear rate is determined from mode-coupling theory. A universal function for the crossover between frequency and shear-rate dominated limits is found.

The authors have evaluated the coefficients of the first nonanalytic logarithmic term in the density expansion for the transport properties of a gas of hard spheres, which is due to long-range dynamical correlations between molecules. Their results resolve present uncertainties about the magnitude of the effect, appear to be consistent with available information from molecular-dynamics calculations, and satisfy bounds for the logarithmic contribution deduced from experimental viscosity data for real gases.

It is shown that the "geometrical phase factor" recently found by Berry in his study of the quantum adiabatic theorem is precisely the holonomy in a Hermitian line bundle since the adiabatic theorem naturally defines a connection in such a bundle. This not only takes the mystery out of Berry's phase factor and provides calculational simple formulas, but makes a connection between Berry's work and that of Thouless et al. This connection allows the author to use Berry's ideas to interpret the integers of Thouless et al. in terms of eigenvalue degeneracies.

It is shown that a modulationally unstable pattern is selected and propagates into an initially unstable motionless state in the one-dimensional generalized Ginzburg-Landau equation. A further spatiotemporal transition occurs with a sharp interface from the selected unstable pattern to a stabilized pattern or a chaotic state. The distinct transition makes a coherent structure coexist with a chaotic state.

Renormalization-group methods are used to produce a novel Monte Carlo sampling algorithm which alleviates the problem of critical slowing down. The method is applied by means of a Kadanoff block-spin transformation to the one- and two-dimensional Ising models.

The possible importance of diquarks in high-energy physics is discussed and it is suggested that this nonperturbative phenomenon can explain the trends in high-energy data that are usually attributed to gluon processes as described by perturbative QCD. Several experimental tests are suggested for discriminating between gluon and diquark phenomena.