It is shown that in (3 + 1)-dimensional space-time the recently proposed supersymmetric models of disordered systems can have finite-energy solitonlike solutions. As a a consequence, it is suggested that the lower critical dimension of a ferromagnet in a quenched random magnetic field is $d_c=3\mathrm{}$.

Fusion excitation functions for the systems ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+${}_{}{}^{112,116,122}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+${}_{}{}^{144,148,154}{}_{}{}^{}\mathrm{Sm}$ have been determined, covering cross sections ranging from several hundred millibarns down to the microbarn level. The data are interpreted with a fusion model that includes fluctuations of the barrier with an amplitude that is shown to be correlated with the collective surface properties of the nuclei. There is no need to assume an additional enhanced tunneling process.

Three different experimental groups have recently published the results of their investigations on highly interacting relativistic nuclear fragments (denoted as "anomalons"). These results are combined to form an anomalon data base, and then ${\chi }^2$ analyses are used to demonstrate that the anomalon mean free paths are $Z$ dependent. It is also demonstrated that these anomalon mean free paths lie on the boundary that delineates the "domain of nuclear forces."

The isotope dependence in the angular distribution of electron-capture cross sections for protons and deuterons with equal velocity ($E=40\mathrm{}$ keV/u) colliding with atomic hydrogen or deuterium targets is predicted theoretically and observed experimentally. A projectile-dependent effect is observed at small scattering angles. No target dependence was detected in the differential cross sections. A scaling relationship is determined which permits the prediction of differential cross sections for hydrogen-isotope projectiles.

The growth of the negative-energy $l=1\mathrm{}$ diocotron wave has been studied on a column of pure electron plasma. An external $\mathrm{RC}$ circuit connecting sectors of the bounding wall is used to induce growth of the wave, which is otherwise essentially neutrally stable. Such a circuit also causes small shifts in the real part of the wave frequency. The experimentally measured growth rates and frequency shifts are in close agreement with the predictions of theory over a wide range of experimental parameters.

With use of x-ray imaging arrays, spatially and temporally resolved measurements were made of fully ionized and total absolute Si ($Z=14\mathrm{}$) densities following injection of Si into Alcator C. The fully stripped ions were detected through x rays resulting from ground-state radiative recombination. Central ion densities were found to be close to coronal equilibrium values. In addition, radial profiles of fully ionized and H-like Si showed large fluctuations during internal disruptions.

The weakly incommensurate phase of monolayer krypton adsorbed on graphite has been investigated by employing the molecular-dynamics simulation technique for a 22212-krypton-atom system. The coverages and temperatures chosen correspond to the region of the phase diagram experimentally studied by Moncton et al. The simulation results are in very good agreement with the laboratory measurements. The atomic nature of the weakly incommensurate disordered phase may be described as a "domain-wall liquid."

It is shown that phase modulations (phasons) of the order parameters of incommensurate lattices are always diffusive at sufficiently large wavelengths $\lambda$. In general there is a crossover from diffusive behavior for $\lambda \gg \Lambda$ to propagating behavior for $\lambda \ll \Lambda$ where $\Lambda$ is a mean free path due to nonlinear interactions. The present results explain why light- and neutron-scattering experiments probe different dynamical behavior of phasons.

It is shown here that superfluids (such as ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and Bose-condensed spin-polarized hydrogen) whose order parameters transform like an angular momentum eigenstate $|j, m\ne 0〉$ will have similar superfluidity—similar Josephson and vorticity equations. In particular, if spin-polarized hydrogen condenses into the $b$ state as currently believed, it will not have a stable superflow. Nonuniform magnetic fields can also induce in it a persistent current similar to that of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$.

The experimental measurements of tortuosity of porous structures using either the acoustic index of refraction of superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ or the electrical conductivity are shown to agree with each other. This and other measured parameters are used to calculate directly the acoustic speeds of water-saturated, fused-glass-bead samples; there are no adjustable parameters and agreement with experiment is excellent. The dependence of tortuosity on pore volume fraction, $\varphi$, is discussed.

For a prescribed adsorption-desorption equilibrium maintained locally through a permeable solid, the concentration of a chemical substance is governed by the diffusionconvection equation $\frac{\partial c}{\partial t}=(D{\nabla }^2-\overrightarrow{\mathrm{v}}·\nabla )\left[\frac{c}{(1+K^{-1\mathrm{}}c)}\right]$ in which $\frac{c}{(1+K^{-1\mathrm{}}c)}$ is the free concentration of the substance. Solutions of this nonlinear equation are shown to be related analytically to solutions of the elementary linear diffusion equation. This remarkable correspondence is utilized to obtain exact solutions to the nonlinear diffusionconvection equation.

A theory of desorption of atoms and molecules from solid surfaces based on a classical stochastic diffusion formulation is presented. A simple rate expression is obtained which has the form $R=\left(\frac{{\Omega }_0}{2\pi }\right)f\left(T\right)\mathrm{}\exp (-\frac{D_e}{\mathrm{kT}})$, where ${\Omega }_0$ is the surface-adsorbate vibrational frequency, $f\left(T\right)=1\mathrm{}$ for atoms, and for molecules $f\left(T\right)\mathrm{}$ depends on the parameters for the frustrated rotations at the surface. This theory has been applied to the desorption of both atoms and molecules and excellent agreement with experiment is obtained.

A critical mixture of isobutyric acid and water was quenched from the one-phase region into the two-phase region and, after the spinodal ring was well developed, a reverse quench returned the system to the one-phase region. Light-scattering measurements for this process exhibit a clearly nondiffusive relaxation which, at least for early times after the quench reversal, is in good agreement with Ruiz's scheme for the coupling of velocity and composition fluctuations.

A theoretical study of dislocations in intercalation compounds reveals that the local deformation of the host near an intercalant island exhibits damped spatial oscillations, resulting in strong interference effects in the elastic energy of Daumas-Hérold domain walls. Explicit calculations for stage 2 predict that a large energy barrier must be overcome before two domains with matching intercalant layers can merge, while staggered domains should bind to each other. Experimental implications are discussed.

The transition in cluster growth from succesive monomer absorption to cluster coalescence has been observed for C${\mathrm{O}}_2$ condensed in a supersonic beam under high pressure. A model which considers all cluster-cluster reactions achieves good qualitative agreement with the measured size distributions of the clusters. This is the first attempt to fit an experimental cluster spectrum from a first-principles model.

Shear mechanical properties of the liquid crystal 4-$n$-pentylbenzenethio-4′-$n$-tetradecyloxybenzoate ($\overline{14}\mathrm{S}5$) have been studied in films as thin as two molecular layers. Crystalline two-layer films were found to melt directly into a liquid phase by a large first-order transition. Crystalline films of three or more layers melted in two stages both by first-order transitions. Mechanical properties of the intermediate phase indicated crystalline surface layers with an anomalously soft response for a three-layer film.

The results of a synchrotron x-ray study of the crystalline-$B$ to smectic-$A$ melting transition in 4-$n$-pentylbenzenethio-4′-$n$-tetradecyloxybenzoate ($\overline{14}\mathrm{S}5$) are presented. Samples of two, three, five, and twelve molecular layers were investigated with the freestanding thin-film technique. A single, abrupt, hysteretic transition is observed in two-layer films with temperature-independent positional correlations above the transition. All thicker films melt by two first-order phase transitions; the character of the intermediate phase depends strongly on film thickness.

The interface between crystalline and superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, when charged with negative ions, is deformed as a result of melting and crystallization processes. As long as the electric field normal to the interface is below a critical value, the deformation is stable and reversible. Above the critical field a charge-induced instability of the crystal is observed, which resembles the electrohydrodynamic instability of liquid surfaces.

Generalized grand unified big-bang models which include initial fermion degeneracies are considered, and limits are obtained on specific entropy and lepton number valid for any theory which contains SU(5). Lepton degeneracies may occur which significantly affect element production. These results affect inferences about the early universe based on the standard model.

An experiment has been performed to demonstrate a new source-independent null test of the inverse square law of gravitation. A single-axis superconducting gravity gradiometer was rotated into three orthogonal orientations to measure the Laplacian of the gravitational potential produced by a 1600-kg lead pendulum at an average distance of 2.3 m. The result is that if one assumes a potential of the form $\varphi \left(\mathcal{r}\right)=-\left(\frac{\mathrm{GM}}{\mathcal{r}}\right)[1+\alpha \exp (-\mu \mathcal{r}\left)\right]$, the value of $\alpha$ is + 0.024±0.036 at ${\mu }^{-1\mathrm{}}=1\mathrm{}$ m.