An analysis of earlier data on the shear viscosity of pure and binary fluids leads to the expected universal description of the critical transport properties.

An analysis is presented of data on sound absorption, specific heat, and ionic conductivity that demonstrates the existence, in the superionic conductor Rb${\mathrm{Ag}}_4$${\mathrm{I}}_5$, of internal degrees of freedom associated with the diffusing silver ions which may be characterized thermodynamically by a relaxing specific heat. It is pointed out that this simple analysis should provide useful information on ionic diffusive modes in other superionic conductors, particularly in regard to their coupling to lattice modes.

Dielectric and elastic constants of $\mathrm{K}{\mathrm{Ta}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ are presented as a function of $x$ and of the temperature. For $x=8\mathrm{}\times {10}^{-3\mathrm{}}$, the system exhibits the characteristics of a ferroelectric at the displacive limit (i.e., a "quantum ferroelectric") as evidenced by three critical indices and the temperature independence of all responses near $T=0\mathrm{}$.

The bcc phase of barium is a superconductor. $T_c$ increases steeply with pressure from 0.06 K at 37 kbar to 0.5 K at 48 kbar. A fit of McMillan's expression for $T_c$ suggests a $T_c$ already in the millikelvin range at 30 kbar. Phonon softening as inferred from the decreasing melting curve is insufficient to account for the rise of $T_c$ with pressure.

Using neutron scattering techniques, we show that the destruction of superconductivity in Er${\mathrm{Rh}}_4$${\mathrm{B}}_4$ at $T_{c2\mathrm{}}=1.0\mathrm{}$ K is accompanied by the development of long-range ferromagnetic ordering of the Er sublattice. The observed magnetic Bragg intensities indicate that the Er ion has a moment of 5.6${\mathrm{\mu }}_{\mathrm{B}}$ which is oriented in the tetragonal basal plane. The magnetic transiton appears second order, but shows anomalously strong precursor scattering.

It is argued that electronic states should be localized in any wire whose impurity resistance is greater than about 10 kΩ. At sufficiently low temperatures this will lead to a $T^{-2\mathrm{}}$ increase in resistance because one-dimensional phonons or excited electrons are needed to cause transitions between localized states. An estimate is made of the temperature needed to observe this effect.

A new emission band in AgBr is attributed to electron-hole-liquid recombination. Excitonic molecules appears only at higher excitation and temperature, corresponding to a limited region of the ($T, n$) plane called biexciton pocket.

We present rigorous perturbation results for the dynamics of the classical nearest-neighbor Heisenberg chain, using the temperature as a small parameter. The lifetime and the frequency shift of the spin waves are determined. For the antiferromagnet we find that there is a region of wave vectors close to the zone boundary where the dynamical scaling fails and we argue that this is a general property of the Heisenberg chain close to $T=0\mathrm{}$.

Recent observations of regularly pulsating x-ray sources in binary star systems are analyzed in the framework of the "emission" theory of light. Assuming that light emitted by a source moving at velocity $v$ with respect to an observer has a speed $c^{\prime }=c+kv$ in the observer's rest frame, we find that the arrival time of pulses from the binary x-ray sources implies $k<\mathrm{}2\mathrm{}\times {10}^{-9\mathrm{}}$. This appears to be the most direct and sensitive demonstration that the speed of light is independent of the velocity of the source.

We present a gauge theory of weak and electromagnetic interactions which is based on the group U(1) ⊗ SU${\mathrm{}\left(4\right)\mathrm{}}_{\mathrm{L}}$ ⊗ SU${\mathrm{}\left(4\right)\mathrm{}}_{\mathrm{R}}$ and which implements manifest left-right symmetry in a natural way. The theory is characterized by a rich lepton spectrum and is consistent with recent experimental results in atomic physics and weak trimuon production. Some novel predictions of the theory are discussed.

We observe anomalous $e\mu$ and $e$-hadron events in $e^{+}{e}^{-}$ collisions at SPEAR in an experiment that uses a lead-glass counter system to identify electrons. The anomalous events are observed in the two-charged-prong topology. Their properties are consistent with the production of a pair of heavy leptons in the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ with subsequent decays of ${\tau }^{\pm }$ into leptons and hadrons. Under the assumption that they come only from this source, we measure the branching ratios $B(\tau \to e{\nu }_e{\nu }_{\tau })=(22.4\mathrm{}\pm 5.5)\%$ and $B(\tau \to h+\mathrm{neutrals})=(45\mathrm{}\pm 19)\%$.

We have measured the circular polarization of the deexcitation $\gamma$ rays following the bombardment of natural Ag targets with 284-MeV and 303-MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions. A symmetric setup containing two polarimeters normal to the reaction plane was used. From the observed count-rate asymmetry of + 0.65%±0.15% for deep-inelastic events we conclude that the excited product nuclei are polarized in the direction of the reaction normal ${\overrightarrow{\mathrm{k}}}_i\times {\overrightarrow{\mathrm{k}}}_f$ which provides evidence for a predominance of negative classical deflection angles.

Inclusive measurements have been performed for the charge, kinetic-energy, and angular distributions of reaction products from ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at 7.42 MeV/nucleon. Fission of one or both colliding nuclei is found to dominate. For the surviving U-like fragments, more particle diffusion at a given energy dissipation is observed than in other systems. A search for the production of superheavy elements has yielded an upper cross-section limit of 2 × ${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^2$.

It is argued that the negative helium ion exists in magnetic fields. Similarly, nontrapping isoelectronic impurities in semiconductors trap with magnetic fields. Crude estimates of binding energies are given.

The two-photon transition rate for hydrogen is evaluated with the $\overrightarrow{\mathrm{E}}·\overrightarrow{\mathrm{x}}$ and the $\overrightarrow{\mathrm{A}}·\overrightarrow{\mathrm{p}}$ interactions including the continuum. We find that the $\overrightarrow{\mathrm{E}}·\overrightarrow{\mathrm{x}}$ interaction approaches the final result with a small number of intermediate states and consequently is the one to be used in any approximate calculation. Numerical values of the two-photon absorption coefficient as a function of frequency are given and the resonance enhancement is exhibited.

Stationary population inversion between the low excited states of ${\mathrm{He}}^{+}$ has been observed in a helium plasma in contact with neutral helium. The ratio of population densities as deduced from Lyman line intensities is $\frac{n_2}{g_2}:\frac{n_3}{g_3}:\frac{{\mathcal{n}}_4}{g_4}:\frac{n_5}{g_5}=1:0.6:1.1:1.2\mathrm{}$, where $\frac{n_i}{g_i}$ is the population density with the principal quantum number $i$. The mechanism leading to the population inversion is discussed.

The pure electron plasma is an excellent system in which to study transport across a strong magnetic field. We describe the basic experimental arrangement and report on measurements of transport due to an externally launched diocotron mode.

We have excited waves in a warm plasma and have observed strong absorption when $\frac{\omega }{k_{\parallel }}\lesssim 3v_e$, in agreement with the predictions of linear Landau damping. At a certain critical power level, consistent with the power required to flatten the velocity distribution, the absorption disappears. Above this level we have obtained evidence for the appearance of an enhanced electron tail, in and above the energy range where Landau damping should occur.

The electron temperature of plasma generated by 35-psec 1.06-μm laser pulses, focused onto perspex targets, has been measured as a function of laser polarization and incidence angle. These measurements demonstrate that resonance absorption contributes significantly to the total absorption of obliquely incident laser radiation. The relative magnitudes of resonance and classical absorption have been measured together with the density of "hot electrons" heated by the resonance process.

Frequency and wavelength of electrostatic ion-cyclotron waves have been measured in a mirror machine. The dominant frequency occurs near the ion-cyclotron fundamental with width $\frac{\Delta f}{f}<0.02\mathrm{}$. For most of the plasma buildup and decay the perpendicular wave numbers are consistent with an ion-diamagnetic drift wave ${{\omega }_i}^{*}=k_{\perp }\left(\frac{c{E}_i}{\mathrm{cB}}\right)\left(\frac{1}{n}\right)\frac{\mathrm{dn}}{\mathrm{dx}}$ at the ion-cyclotron frequency. With increasing wave amplitude the wave spectral properties do not change but an increase in ion energy diffusion is observed, supporting a wave-particle saturation of the mode.