Simultaneous suppression of several unstable drift wave modes in a collisionless plasma has been achieved using several independent feedback systems, each one tuned to a different mode. This is an improvement over broadband systems in which suppression of one mode has generally led to enhancement of other modes.

The predicted sheet current which connects the partial ring current and the auroral electrojet in auroral substorms is shown to be unstable against a shear perturbation (kink instability). A consequence of the instability is the deformation of the sheet current into a curtain shape as is visibly observed in auroras.

The exact behavior of a modulated cyclotron wave in a plasma is traced in a numerical model to study the self-trapping instability represented by the nonlinear Schrödinger equation with an attractive potential. The instability is found to be explosive in that the wave collapses at a much faster rate than the prediction of the perturbation solution.

We use linear response theory to calculate the elementary excitation spectrum of a dilute hard-sphere Bose gas. Our result differs by a factor $2^{-\mathrm{½}}$ from the exact result.

The critical slowing down of the diffusion in a binary liquid is calculated from the fluctuation-dissipation theorem. The fluctuating current is the product of the local fluctuations in concentration and velocity. Assuming statistical independence of these variables yields results identical to those found by Kawasaki using another method.

Uv photoemission measurements on evaporated films of Yb are reported. The results locate the spin-orbit-split $4f$ states at 1.20 and 2.50 eV below the Fermi level.

Electric conduction of cubic ZnS crystal was investigated in the field range from 2×${10}^4$ to 3×${10}^6$ V/cm. The resonant type current anomalies were observed around 4×${10}^5$, 1×${10}^6$, and 1.4×${10}^6$ V/cm. The experimental results suggest that the Stark ladder will play an important role in the high-field transport phenomena.

When surface spin pinning is included in the thin-film magnetostatic-mode eigenvalue problem, exchange must be included even when the exchange energy is negligible. The magnetization is changed drastically in general, but the intensities and frequencies are essentially the same as for the pure magnetostatic modes (exchange constant $D=0\mathrm{}$ and no explicit pinning mechanism).

Nuclear adiabatic demagnetization experiments have been carried out on the Van Vleck paramagnets Pr${\mathrm{Pt}}_5$ and Pr${\mathrm{Tl}}_3$. Starting from 60 mdeg K and 20 kOe, end temperatures of 5 and 3 mdeg K, respectively, are obtained. In Pr${\mathrm{Pt}}_5$, the end temperature seems to be limited by a residual nuclear level splitting due to the hexagonal structure. No sign of a nuclear ordering phenomenon can be detected in Pr${\mathrm{Tl}}_3$ down to 3 mdeg K. The suitability of these materials for magnetic cooling purposes is pointed out.

Detailed neutron-scattering measurements have yielded the behavior of the scattering function $S(q, \omega )$ for both the transverse and longitudinal fluctuations in the critical region of the uniaxial antiferromagnet Mn${\mathrm{F}}_2$. The static wavelength-dependent susceptibilities are measured both above and below $T_N$. The relaxation rates for the longitudinal fluctuations are found to be correctly described by dynamical scaling both above and below $T_N$. The scaling functions ${\Omega }_{\pm }\left(\frac{q}{\kappa }\right)$ applying respectively above and below $T_N$ are determined explicitly.

It has been found that low-lying states are strongly excited in nickel isotopes by $\alpha$-transfer reactions induced by 48-MeV oxygen ions on iron targets, i.e., via the fourparticle, two-hole components of the nuclear wave functions.

It is shown that the crust of pulsars can deform in a gradual plastic manner in spite of its extreme density and strength. This deformation leads to stronger damping of pulsar rotation and to higher magnetic moments and also to rarer starquakes than calculated for a rigid crust.

We deduce the interstellar electron spectrum from the nonthermal radio background. From 200 MeV to a few GeV the spectral index is 1.8 and there is evidence for residual solar modulation. Above a few GeV, the spectrum is steeper and the intensity is similar to that observed at earth. A consistent modulation for electrons and protons of the same rigidity can be obtained by using the complete diffusion-convection energy-loss theory of solar modulation.

The electron-positron mass spectrum has been studied in the process $\gamma +\mathrm{C}\to e^{+}+e^{-}+\mathrm{C}$ in the invariant-mass region between 675 and 850 MeV/${\mathit{c}}^2$. An enhancement in the region of the $\omega$ mass due to $\rho -\omega$ interference is clearly observed, and from a fit to the data we find $\frac{{{\gamma }_{\rho }}^2}{4\pi }={0.50}_{-0.10\mathrm{}}^{+0.12\mathrm{}}$ and $\frac{\gamma {\omega }^2}{4\pi }=3.5\mathrm{}\pm 1.2$. The value of the relative phase of the $\rho -\omega$ photoproduction amplitudes is found to be ${100}_{-30\mathrm{}}^{+38\mathrm{}}$ deg. The errors quoted are purely statistical.

The reaction $\gamma +\mathrm{C}\to {\pi }^{+}+{\pi }^{-}+\mathrm{C}$ has been investigated in the invariant-mass region of the $\rho$ and $\omega$ mesons and shows distinct interference effects between the $\rho$ and $\omega$ contributions to the cross section. The experiment was performed at a mean photon energy of 4.2 GeV with 140 000 events. A phenomenological analysis of the data yields the result ${\Gamma }_{\omega \to 2\pi }={0.091}_{-0.025\mathrm{}}^{+0.031\mathrm{}}$ MeV/${\mathit{c}}^2$. The relative phase of the $\rho$ and $\omega$ terms in the amplitude is obtained and discussed.

A phenomenological model of electron-proton scattering is developed which can account for the general qualitative and quantitative features of the data. Some interesting links between the elastic and inelastic form factors are discussed.

The atomic-beam magnetic-resonance technique has been used to search for a linear Stark effect, which would violate parity and time-reversal invariance, in the $6{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ ground state of thallium. The motional magnetic field effect ($\overrightarrow{\mathrm{v}}\times \frac{\overrightarrow{\mathrm{E}}}{c}$) was accounted for by comparison experiments between Tl and Na and K. The electric dipole moment of the thallium atom is $D_{\mathrm{Tl}}=\left[\right(1.3\mathrm{}\pm 2.4)\times {10}^{-21\mathrm{}} \mathrm{cm}]e$, where the error is the standard deviation.

The weakly interacting Bose gas is studied on the one hand with the independent-particle perturbation formalism of Hugenholtz and Pines, and on the other hand by a perturbation theory using a set of correlated basis functions. We find by comparison that up to fourth order in energy, a Jastrow correlated wave function sums all rings and ladders, and other diagrams in part; and the simplest correlated basis functions perturbation correction accounts for all remaining discrepancies.

We present results of the injection of a high-intensity, high-current, relativistic electron beam into a cusped magnetic field. ${10}^{14}$ electrons are passed through the cusp. Prelimary observations indicate that these electrons produce a "cloud" of relativistic electrons gyrating in a magnetic field and having a small ratio of translational to rotational energies.

We derive the imaginary part of the phonon self-energy to lowest order in frequency and temperature in terms of effective anharmonic interactions which are determined by higher order elastic constants. Since our results are derived to all orders in the bare anharmonic interactions they can be applied to quantum crystals. Comparing with renormalization theory we give a new interpretation of the "elastic-continuum model" for crystals and the "quantum-hydrodynamic model" for He II.