The trapping of negative ions by quantized vortex lines in rotating helium II is found to be strongly inhibited by a small thermal counterflow parallel to the axis of rotation.

In the trapped-electron sideband instability of a nonlinear plasma wave of potential ${\varphi }_0$, initial enhanced damping occurs for a distance $\propto {{\varphi }_0}^{-\frac{1}{2}}$, beyond which signals grow at a rate scaling nearly linearly with ${\varphi }_0$. The growth remains exponential even in cases where the main wave is significantly damped. This behavior is more consistent with a quasilinear spectral development than with the commonly cited parametric bounce-frequency instability of a stationary Bernstein-Greene-Kruskal equilibrium.

Measurements on laser-light scattering have been made of the turbulence in a normal shock. Wave-number spectrum and phase velocity were determined. The turbulence has not been identified with any instability. The predominant direction of propagation is shown not to coincide with the current vector.

We observe a second-order nematic to smectic-$A$ phase transition in $p$-nitrilebenzylidene-$p$-octyloxyaniline using the Rayleigh scattering technique. The twist elastic constant $K_{22}$ diverges at the transition, with the critical exponent $\nu =0.66\mathrm{}\pm 0.05$ in agreement with de Gennes's prediction. For large-angle scattering we observe the onset of the critical regime.

The behavior of a small test wave launched simultaneously with a large-amplitude electron plasma wave is calculated by treating the test wave as a slow modulation of the larger wave's amplitude and phase. Test-wave experiments show agreement with the calculation when the test-wave frequency is between the large wave's frequency (${\omega }_0$) and ${\omega }_0-\frac{4\pi }{T}$, where $T$ is the main wave's transit time through the experiment. When the spontaneously unstable lower sideband frequency is within this range, the sideband's slow amplitude oscillations agree with the calculation.

Recent numerical simulations have shown which nonlinear effects are important in ion-sound turbulence. These results have been used to provide the basis of a theory of ion-sound resistivity. We find a stabilizing effect of the turbulence which appears as a "virtual" increase in the ion temperature. The effective collision frequency and level of turbulent energy are calculated as functions of the relative electron-ion drift velocity and the temperature ratio $\frac{T_i}{T_e}$.

In a heat-flow experiment at zero field we have found that the phase diagram of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ below the second-order transition at $T_c$ divides into two regions. In one the heat flow is linear and enhanced by an amount predicted by a two-fluid model; the other shows nonlinearity, history dependence, and critical-velocity effects. The two are separated by a line of thermal-resistance discontinuities which extrapolates to what may be a polycritical point at the line $T_c$ and possibly to the "$B$" feature at the melting line.

Tunneling into thin superconducting films of several metals has revealed extra peaks in the voltage derivative of the tunnel current. The strength of the new structure is very thickness dependent. The peaks appear at multiples of the gap voltage above the main peak. It is suggested that the relaxation rate of tunneled electrons is promoted by stimulated emission of phonons starting at these voltages.

A classical Heisenberg Hamiltonian, to which is added single-ion anisotropy and antisymmetric Dzialoshinsky-Moriya interactions is studied with use of Wilson theory. The phase diagram is obtained; it consists of ferromagnetic, spiral, and ferromagnetic-spiral regions, with critical exponents that are Ising-like, $\mathrm{xy}$-like, and Heisenberg-like, respectively. These results lead to the conclusion that breaking of exchange symmetry does not change the nature of the phase transition. Crossover behavior is also discussed.

The effects of fluctuations on the Peierls transition in one dimension are calculated by taking a functional average over variations in the order parameter. It is found that the transition is suppressed to a temperature of approximately one quarter of the mean-field transition but remains fairly sharp. The coherence length and density of states are calculated as a function of temperature, and brief comparison is made to experimental systems.

A criticism is given of the concept put forward by Cohen and Jortner of an "inhomogeneous regime" in disordered semiconductors. It is suggested that this regime does not exist in general in disordered materials, though it may in fluids near a critical or convolution point.

A microwave-optical double-resonance technique has been used to investigate the selftrapped exciton in KBr and Cs Br. Electron and hole orbitals for triplet states are characterized on the basis of observed zero-field splittings and hyperfine parameters.

Measurements have been made of the susceptibility of ${\mathrm{Fe}}_3$Al in the temperature range $300°\mathrm{C}\lesssim T\lesssim 600°\mathrm{C}$, which encompasses both the magnetic transition ($T_c\cong 300°$C) and the order-disorder transition ($T_0\cong 530°$C.). It was found that various manifestations of the atomic ordering near $T_0$, e.g., the appearance of both long- and short-range order, are mirrored in the temperature dependence of the paramagnetic susceptibility.

From a study of stopping antiprotons in a variety of elements located in a hydrogen bubble chamber, we find evidence for the existence of a neutron fringe in heavy nuclei.

A calculation is described which contains hitherto neglected terms in the extraction of nuclear shapes from scattering data. These corrections are used in the comparison of deformations determined by measurements of distributions of nuclear potential with those of charge distributions, and serve to reduce the apparent discrepancies between those two types of measurements.

Inelastic ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ scattering at 71 MeV on twelve nuclei ranging from ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ to ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ shows an enhancement of the continuum very similar to that observed in electron and proton scattering. The effect is ascribed to a giant multipole state. The strength of the excitation indicates an $E2\mathrm{}$ character for the state.

We have investigated a new approach to deriving a diffusion equation for charged particles in a static, random magnetic field. Our method incorporates essential effects of the magnetic fluctuations in the lowest order particle orbits. Significant corrections to the usual quasilinear diffusion coefficient for cosmic rays with pitch angles near 90° are a consequence. Monte Carlo results bear out the validity of our theory.

We have studied the inclusive reaction ${\pi }^{-}+p\to {\Delta }^{++}+X^{--}$ at 15 GeV/c and have compared our data with the data from the reaction $p+p\to {\Delta }^{++}+X^0$ at 303 GeV/c. We find that the ${\Delta }^{++}$ in these reactions is a decay product of a diffractively produced higher-mass object, a main component of which is a low-mass ${\Delta }^{++}{\pi }^{-}$ system.

We draw attention to hadron collisions from cosmic-ray data showing evidence for high-transverse-momentum secondaries in substantial excess of the celebrated exponential cut-off, analogous to recent observations at the CERN intersecting storage rings. The data support a composite (parton/quark) picture of the proton in which deep inelastic proton collisions at high energy (∼${10}^3$ GeV) produce constituents, observed through hadron jets. This phenomenon is possibly connected to the rise of the total cross section observed in the same range of energy.

A class of non-Abelian gauge theories of strong interactions is described, for which parity and strangeness are automatically conserved, and for which the nonconservations of parity and strangeness produced by weak interactions are automatically of order $\frac{\alpha }{{m_W}^2}$ rather than of order $\alpha$. When such theories are "asymptotically free," the order-$\alpha$ weak corrections to natural zeroth-order symmetries may be calculated ignoring all effects of strong interactions. Speculations are offered on a possible theory of quarks.