A realistic microscopic effective Hamiltonian ($H_{\mathrm{eff}}$) is employed with the spherical finite-temperature Hartree-Fock approximation to evaluate the thermodynamic properties of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. We scale $H_{\mathrm{eff}}$ to accommodate the $A$-dependent effects. We then adjust the Hamiltonian slightly to reproduce appropriate ground-state properties in the Hartree-Fock approximation. We find the thermal response of these nuclei to be substantially greater than that obtained with zero-range phenomenological forces.

Let $\psi$ be any normalizable energy eigenfunction for $N$ electrons in an atom having $Z$ protons in a fixed pointlike nucleus. It is shown that, for the state $\psi$, $N$ and $Z$ are rigorously related by $N<FZ+1\mathrm{}$ with $F=4\mathrm{}$. This is independent of any statistics. Evidence is presented that the result can be improved in the sense that $F=F\left(N\right)\mathrm{}\to 2$ for $N\to \infty$. A comparison is made with a recent result of Lieb.

A general class of optically bistable systems is described which operates without feedback and is based on the intrinsic response of certain nonlinear media. A detailed analysis of one such medium is presented which demonstrates that bistability may result in virtually all macroscopic optical and material parameters.

A kinetic theory of the pondermotive force on a plasma due to an electromagnetic ion cyclotron wave is developed and applied to axisymmetric mirrors. The force due to nonresonant particles is shown to modify the usual magnetohydrodynamic interchange stability criterion. Resonant-particle contributions to the force arise from the absorption of photon momentum and spin. This effect drives a radial particle flux, modifies the radial ambipolar potential profile, and couples transport and stability.

The magnetic field-line reconnection is investigated in detail by rapidly reversing the toroidal current in a torus plasma. The reconnection brings about an explosive increase in the plasma pressure in a quite narrow region where a shocklike structure is observed. A strong plasma acceleration and an anomalous resistivity due to the reconnection are estimated by the magnetohydrodynamics equations with the variables obtained from the experiment.

Neon, argon, and xenon bubbles in aluminum have been investigated by means of electron-energy-loss spectroscopy and transmission electron microscopy. The density and pressure in the bubbles were determined from the pressure shift of the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ transition of the rare gases as well as from analysis of electron-diffraction patterns. The experiments yield overpressurized bubbles, containing liquid Ne and solid Ar and Xe at room temperature. In the case of Xe, epitaxial growth of the rare gas in the Al matrix was observed.

Polymers of arbitrary fractal connectivity are considered. A Flory theory of chain swelling, with an $n$-body repulsion, gives a lower critical dimension equal to the spectral dimension, $d_s$, for any polymeric fractal with $d_s<2\mathrm{}$. The scaling form of the frequency-dependent complex viscosity of a monodisperse solution of polymeric fractals (at low or high concentration) is given in the absence of excluded-volume and entanglement effects.

dc flow of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ through a rectangular superleak exhibits two dissipative regimes and two critical currents with temperature dependence of the form $J_c=b{(1-\frac{T}{T_c})}^a$. At low pressures $a\simeq \frac{3}{2}$ and $b$ increases with pressure. Around 21.5 bars a crossover occurs to a new dissipation regime with $a\simeq 2$ and the prefactor $b$ then decreases with pressure.

Quasielastic line broadening of neutrons scattered from $\beta$-Zr alloyed with 2 at.% Co indicates that all Co atoms, not merely a small fraction, participate in fast diffusion. At 1100°C the deduced Co jump frequency is about 25 times higher than that of the Zr atoms but about 6 times lower than the Co jump frequency deduced from tracer measurements. This discrepancy and an anomalous decrease in scattering intensity above 1100°C indicate that a second Co jump frequency exists which is several hundred times higher than that of the Zr atoms.

When subjected to a compressive strain along the columns, a tubular discotic liquid crystal must present a buckling instability, where compressive elastic energy is transferred into bend energy of columns. We present the first observation of this column buckling instability in hexa-$n$-octyloxytriphenylene at $T=75\mathrm{}$°C. From the instability threshold, the curvature elastic constant is found to be 6 orders of magnitude larger than in usual liquid crystals, i.e., the correlation length extends on a quasimacroscopic range of ${10}^3$ molecules.

Small-angle neutron scattering is used to investigate the structure of single-phase AOT (sodium di-2-ethylsulfosuccinate)/${\mathrm{D}}_2$O/decane microemulsions containing equal volumes of water and oil and a variable concentration of surfactant. Each scattered-neutron spectrum exhibits a pronounced interaction peak. As the volume fraction of AOT is increased from 0.18 to 0.42, the peak position shifts to larger values of $Q$, and the peak height diminishes. The spectra are consistent with an ordered droplet phase, as opposed to a bicontinuous structure.

The adsorption of multilayers of CO on a Cu(100) surface at 10 K has been studied by LEED and infrared spectroscopy. By starting from an ordered chemisorbed CO monolayer, it was possible to grow a three-dimensional crystal with hexagonal planes parallel to the surface and with a lattice constant much larger than that of the ordinary $\alpha$-phase CO solid.

In situ x-ray photoelectron spectroscopy was used to study the oxidation of niobium films covered by some monolayers of cerium. Significant amounts of ${\mathrm{Nb}}_2$${\mathrm{O}}_5$ are formed at pressures as low as 6.6 × ${10}^{-6\mathrm{}}$ Pa, promoted by the cerium overlayer. This catalytic activity is related to the trivalent-to-tetravalent valence change of the cerium during oxidation. The kinetics of ${\mathrm{Nb}}_2$${\mathrm{O}}_5$ formation beneath the oxidized cerium shows two stages; the first is fast growth limited by ion diffusion, the second is slow growth by electron tunneling.

We present a reanalysis of the renormalization-group calculation to first order in $\epsilon =6-d$, where $d$ is the spatial dimensionality, of the exponent, $t$, which describes the behavior of the conductivity of a percolating network at the percolation threshold. If we set $t=(d-2\mathrm{})\mathrm{}{\nu }_p+\zeta$, where ${\nu }_p$ is the correlation-length exponent, then our result is $\zeta =1+\left(\frac{\epsilon }{42}\right)$. This result clarifies several previously paradoxical results concerning resistor networks and shows that the Alexander-Orbach relation breaks down at order $\epsilon$.

We relate experimental information on $\pi \pi$ scattering to tree-level effective chiral Lagrangians. The result is of a form similar to that used in Skyrme-type models of the proton, where the nucleons are described as topologically stable solitons of the chiral fields. In such models, one can express the proton mass in terms of measured scattering data, with the result $M_p=880\mathrm{}\pm 300$ MeV. We interpret this as a consistency test for the Skyrme models.

We have observed the ${\pi }^{+}{\pi }^{-}$ decay of the ${\rho }^{\prime }\mathrm{}\left(1600\right)\mathrm{}$ in the production reaction $\gamma p\to {\rho }^{\prime }p$ at 20 GeV. Using a calculation which takes into account the interference of the ${\rho }^{\prime }$ with the $\rho \mathrm{}\left(770\right)\mathrm{}$ and a Drell background, we find good evidence that this resonance is a radial excitation of the $\rho \mathrm{}\left(770\right)\mathrm{}$. The background interference strongly distorts the angular distributions predicted by a purely $s$-channel helicity-conserving production mechanism. We measure $m_0=(1.55\mathrm{}\pm 0.07)$ GeV/${\mathit{c}}^2$ and ${\Gamma }_0=\left({0.28}_{-0.08\mathrm{}}^{+0.03\mathrm{}}\right)$ GeV/${\mathit{c}}^2$.

We report measurements of differential cross sections for the reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma ,{\pi }^0){}_{}{}^4{}_{}{}^{}\mathrm{He}$ with a photon energy of 290 MeV. Use of a good-resolution ${\pi }^0$ spectrometer allowed restriction of events to those where the residual ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ nucleus was left in the ground state (the coherent process). By detecting the ${\pi }^0$ directly, we thus provide the first forward-angle data for this reaction in the $\Delta$-resonance region. Our results are in good agreement with a recent $\Delta$-hole model calculation.

The exotic nuclear decay of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ by emission of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ nuclei has been investigated by use of an intense radioactive ${}_{}{}^{227}{}_{}{}^{}\mathrm{Ac}$ source and a magnetic spectrometer with a large solid angle. After a run of 5 d, a group of eleven events was observed at the expected location of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ in a $\Delta E-E$ telescope calibrated with a ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ beam. A branching ratio of (5.5 ± 2.0) × ${10}^{-10\mathrm{}}$ was measured for the emission of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ nuclei relative to $\alpha$ particles from ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ in agreement with the previously reported ratio of (8.5 ± 2.5) × ${10}^{-10\mathrm{}}$.

Charged-particle exclusive data for Ar+Pb collisions at 0.772 GeV/u are analyzed in terms of collective variables for the event shapes in momentum space. Semicentral collisions lead to sidewards flow whereas nearly head-on collisions have spherical shapes in the c.m. frame, resulting from complete stopping of projectile motion. The hydrodynamical model predictions agree qualitatively with the data whereas the standard cascade model disagrees, lacking in stopping power and collective flow.

The branching ratio $\frac{{\Gamma }_{\gamma 0}}{{\Gamma }_{\alpha }}$ for the $d+t$ reaction has been measured between deuteron energies of 45 and 146 keV. Pair-coincidence spectrometry and pulse-shape discrimination were employed to reduce the neutron effects in the NaI(Tl) gamma-ray detector. The branching ratio is found to be constant over the energy range of the measurements with a best value $\frac{{\Gamma }_{\gamma 0}}{{\Gamma }_{\alpha }}=(5.4\mathrm{}\pm 1.3)\times {10}^{-5\mathrm{}}$. This value is significantly greater than cluster-model calculations of the branching ratio.