Using a light-beating spectrometer, we have observed in the smectic-$A$ phase of $p$-cyanobenzilidene-$p$-octyloxyaniline the thermally excited undulations of layers predicted by de Gennes. From the wave-vector dependence of their damping time we determined the diffusivity of the angular orientation, $\frac{K_1}{\eta }=(2.0\mathrm{}\pm 0.2)\times {10}^{-6\mathrm{}}$ cgs. From the thickness dependence of the boundary quenching, we determined the penetration length, $\lambda =14\mathrm{}\pm 1$ Å at 75°C.

The magnetic field dependence of the structural transformation temperature of a single crystal of ${\mathrm{V}}_3$Si has been measured up to 156 kOe. Quantitative agreement with the Weger-Labbé-Friedel model is obtained with appropriate band parameters and a density of states that accounts for finite lifetimes of the $d$ electrons.

An ab initio analytic Hartree-Fock procedure is introduced which yields directly eigenvalues and eigenvectors of an $R$ matrix to be matched with data extracted from different spectroscopic experiments. Results of a pilot calculation are presented.

The entire spectrum of hydrogen in combined static and periodic electric and magnetic fields is derived by using O(4) algebra, and related to the corresponding simpler Lyman-$\alpha$ spectrum by a scaling relation. This time-dependent generalization of the Stark-Zeeman effects provides the necessary basis for the proper analysis of hydrogenic spectra for plasma diagnostic purposes.

The Kapitza thermal boundary resistance at temperatures near 1 K is anomalously small to solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ or solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ just as it is to liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ or liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

We find evidence that the $E_2$ optical peak in Ge arises from transitions in a well-defined, limited region inside the Brillouin zone. This conclusion is compatible with the recent experimental results of Aspnes. The region of interest is not on symmetry lines, but it is close to the ($\frac{3}{4}$, ¼,¼) special point determined by Chadi and Cohen. The calculated modulated reflectivity, density of states, and interband masses are in good agreement with experiment.

Inelastic neutron-scattering measurements of acoustic magnons are reported for ferromagnetic Tb${\mathrm{Al}}_2$ between 4.2 and 80 K for wave-vector transfers of 0.00 and 0.10 ${\mathrm{\AA }}^{-1\mathrm{}}$. Above 35 K we observe a double-peak structure in the scattered neutron intensity which is theoretically interpreted in terms of an interaction between the magnon and a magnetic exciton excited from an almost unpopulated state. This is the first observation of an interaction of this kind.

It is shown that the surface magnetic ordered state implied by mean field calculations in the paramagnetic temperature region does not lead to a physically inconsistent spinwave spectrum below the surface ordering temperature, contrary to what would be expected if surface ordering were a purely two-dimensional phenomenon.

The orbit of the comet Kohoutek is probably parabolic, so the conjecture that some comets consist of antimatter may apply to it. Cosmic-ray observations are suggested to test this possibility, unlikely as it is.

We propose experiments for observing double-quantum transitions between the $s$ levels in atomic hydrogen. The inherent resolution is considerably higher than in the single-quantum transitions normally used for optical measurements in hydrogen. We present simplified calculations of relevant double-quantum processes, and show how they might be observed in a double-resonance extension of present techniques of precision laser spectroscopy.

New computer-simulation results reveal the source of a previously found difference between analytical and simulation calculations of channeling minimum yield. The difference stems from a focusing effect on ion trajectories in the simulation method which cannot be present if statistical equilibrium exists as is assumed in the analytical method. It is concluded that statistical equilibrium is generally an unsound basis for channeling calculations.

The electron-cyclotron drift instability is observed to develop an absolute instability in the laboratory frame of stationary electrons. We investigate the threshold, temporal and spatial growth, and the saturation mechanism.

A convectively unstable beam-plasma wave is excited and observed to grow and saturate. In the saturation region, the beam wave excites by parametric interaction an ion-acoustic wave and a backward-propagating Trivelpiece-Gould mode. Significant energy is deposited into these modes, and this suggests that pump depletion may play a role in the saturation process.

Raman-scattering techniques have been used to obtain a new quantitative measure of orientational statistics of individual molecules in a nematic liquid crystal. A marked discrepancy is observed between these measurements and the predictions of existing theories of nematic ordering.

Recent remarks on the possibility of negative-pion condensation in superdense nuclear matter are shown to be based on an incorrect formalism. The possibilities of ${\pi }^{-}$ and ${\pi }^0$ condensation are compared and some problems are enumerated which must be solved before it is known which, if either, of the phenomena can occur.

We have calculated vacuum-polarization charge densities to all orders ${\left(Z\alpha \right)}^n\alpha$ for realistic nuclei of finite extent. In muonic Pb, orders $n>~3$ contribute -34 ± 2 eV to the $5g\to 4f$ transitions, compared with the point nucleus value of -50 eV. This increases the discrepancy (first reported by Dixit et al.) to $E\left(\mathrm{theor}\right)-E\left(\mathrm{expt}\right)=57\mathrm{}\pm 18 \mathrm{eV} (5\mathrm{}{g}_{\frac{9}{2}}\to 4f_{\frac{7}{2}}) \mathrm{and} 72\pm 21 \mathrm{eV} (5\mathrm{}{g}_{\frac{7}{2}}\to 4f_{\frac{5}{2}})$. Contributions to low-lying states show nearly an order-of magnitude reduction.

We have measured the total inelastic cross section (${\sigma }_{\mathrm{inel}}$) and charged-particle multiplicities obtained in $\mathrm{pp}$ collisions at 405 GeV/c. The data are from a preliminary 12 000-picture bubble-chamber exposure. We find ${\sigma }_{\mathrm{inel}}=32.8\mathrm{}\pm 1.0$ mb; the low moments of the multiplicity distribution for negative particles are $〈n_{-}〉=3.50\mathrm{}\pm 0.07$, $D_{-}=2.37\mathrm{}\pm 0.05$, ${f_2}^{-}=2.1\mathrm{}\pm 0.2$, and ${f_3}^{-}=0.1\mathrm{}\pm 0.9$. We also present updated results at 102 GeV/c.

Conflicting inclusive data from the CERN intersecting storage rings, treated with Landau's original hydrodynamical differential equations for an arbitrary equation of state ($p=H\epsilon$) describing the created hadronic matter fluid, lead to two different physical pictures. A recent Pisa-Stony Brook experiment suggests $p=0.3\mathrm{}\epsilon$; $p=\frac{\epsilon }{3}$ implies scale invariance, suggesting we are near an asymptotic region governed by scaling. However, earlier experiments imply that the dynamics may be quite different ($p\approx \frac{1}{2}\epsilon$,), with viscous hadronic "fluid" being produced.

A new generalized thermodynamic potential is presented which governs the stability, the dynamics, and the fluctuations of a liquid fluid layer near the Benard point, even in the nonlinear domain. By analogy, a large number of results obtained for other systems are shown to be applicable to the Benard problem.

Strong Langmuir turbulence is described in terms of a random set of blobs of selftrapped plasma waves. The interaction of these blobs leads to the generation of power spectra $〈{\left|E_k\right|}^2〉\propto k^{-2\mathrm{}}$ that agree with the results of one-dimensional computer simulation.