The responses to shear stress of monomolecular films of fatty alcohols, ${\mathrm{C}}_n{\mathrm{H}}_{2n+1}\mathrm{OH}$, spread on water have been studied for $n=20, 21, \mathrm{and} 22$. A compression-induced melting transition has been observed for the first time.

High-resolution electron-energy-loss measurements and relevant theoretical calculations for the vibrational structure of ordered oxygen overlayers on the Ru(001) surface are presented. The vibrational spectrum of the $p(2\mathrm{}\times 2)$ overlayer shows a single dipolaractive mode above the substrate phonon band. Because of a reduction in symmetry of the threefold adsorption site, however, the vibrational spectrum of the $p(1\mathrm{}\times 2)$ overlayer is fundamentally different, showing two dipolar-active modes above the substrate phonon band.

Second-harmonic reflection from Si(100) and Si(111) surfaces exhibits a strong dependence on the angle of rotation of the sample about its surface normal. This behavior can be related directly to the structural symmetry of the crystal and of the surface. Analysis of the results shows that the surface and bulk contributions to the observed second-harmonic signals from Si are generally of the same order of magnitude.

Under heavy-ion irradiation of the metallic glass ${\mathrm{Pd}}_{80}$${\mathrm{Si}}_{20}$ the sample dimensions perpendicular to the ion beam axis grow dramatically without appreciable change in volume (no swelling) or microscopic structure. The characteristics of this growth in amorphous ${\mathrm{Pd}}_{80}$${\mathrm{Si}}_{20}$ are examined in some detail and compared with radiation growth in crystals. None of the available growth mechanisms proposed for crystalline metals is able to explain this new kind of radiation growth.

It is shown that the presence of potassium on a Ni(111) surface induces atom exchange between adsorbed CO molecules. The temperature dependence of the metastable quenching spectrum indicates that the exchange process might be concerted rather than a dissociation followed by atom recombination with CO desorption.

The cation $3s$ levels in fluorides of $3d$ transition elements have been systematically examined with use of x-ray photoelectron spectroscopy. It is shown that $3s$ line shapes are determined by the $3d$ populations (and consequent exchange splittings) associated with different core-hole screening conditions. The screening mechanisms are thus identified as major contributors to the satellite structures observed in core level photoemission. An understanding of these processes is essential for the interpretation of chemical effects in photoelectron spectra.

A class of uniformly frustrated $\mathrm{xy}$ models which describe the behavior of a Josephson-junction array in a transverse magnetic field is considered. The frustration $f$ is the fraction of flux quantum of applied field per unit cell of the lattice. The ground-state energy $E_0$ and critical current are computed for several rational $f$. The behavior for arbitrary $f$ is discussed, and it is concluded that the resistive transition temperature for $f=\frac{p}{q}$ is bounded by $k_{\mathrm{B}}{T}_c\left(\frac{p}{q}\right)\lesssim \frac{\pi \left|E_0\mathrm{}\right(f\left)\right|}{2q}$. The resistance as a function of temperature and field is determined by the sequence of $T_c$'s thus produced.

A new class of semiconductor superlattice materials consisting of alternating layers 8-1200-Å thick has been synthesized from semiconductors such as $a-\mathrm{Si}:\mathrm{H}$, $a-\mathrm{Ge}:\mathrm{H}$, $a-\mathrm{Si}{\mathrm{N}}_x:\mathrm{H}$, and $a-{\mathrm{Si}}_{1-x}{\mathrm{C}}_x:\mathrm{H}$. X-ray diffraction, photoconductivity, and photoluminescence measurements indicate that the layers are smooth on an atomic scale, and that the interfaces are essentially defect free. Changes in the optical absorption and photoluminescence as a function of layer thickness in $a-\mathrm{Si}:\mathrm{H}/a-\mathrm{Si}{\mathrm{N}}_x:\mathrm{H}$ superlattices are interpreted as quantum size effects.

Crystalline and amorphous ice were studied with monoenergetic positrons with incident energies $0<E<\mathrm{}5\mathrm{}$ keV. Positronium (Ps) forms in the ice and diffuses as a neutral particle until annihilation or escape from the surface. Measurement of the fraction of $o$-Ps leaving the surface reveals two distinct contributions to the total Ps-formation probability (both Ore- and spur-type) as well as the Ps diffusion coefficient, 0.17±0.09 ${\mathrm{cm}}^2$/sec in crystalline ice. In addition, positronium trapping is observed in sputtered (crystalline) ice and voids (≳ 17 Å diameter) in amorphous ice.

The specific heat for the asymmetric Anderson model is calculated over a physically relevant temperature range by means of the Bethe-Ansatz method. The effect of a magnetic field on the specific heat is also investigated.

A semi-infinite nearest-neighbor square Ising system whose couplings at a distance $l$ from the boundary differ from homogeneity by an amount $\delta K\sim -\frac{A}{l}$ is investigated. On the basis of the Pfaffian method we obtain the critical behavior at the surface of this system. The exponents ${\eta }_{\parallel }$, ${\nu }_{\parallel }$, ${\beta }_1$, ${\gamma }_{11}$, and ${\delta }_{11}$ display rich nonuniversal behavior as a function of the amplitude $A$. For $A$ below a critical value, there is exponent asymmetry and a spontaneous surface magnetization when the bulk ($l=\infty$) is critical.

The finite-element approach described in a previous paper approximates the operator Dirac equation on a lattice in such a way that the equal-time anticommutation relations are exactly maintained. Moreover, the approximation preserves unitarity (and chiral invariance in the massless theory) and there is no fermion doubling.

The claim that the Clauser-Horne inequality $S\left(\varphi \right)<~1$ is valid for all local theories is criticized. The criticism is based on the author's proof that this universality claim is incompatible with the conservation law of angular momentum. There exists an infinity of counterexamples to the universality claim made for $S\left(\varphi \right)<~1$. So Clauser and Horne offer no valid proof of the nonlocality of the quantum formalism; consequently experiments like Aspect's cannot be said to refute Einsteinian locality.

Upper bounds on rate differences between particle and antiparticle decays of hyperons are estimated in the standard six-quark model. For each of ${\Lambda }^0\to p{\pi }^{-}$, ${\Lambda }^0\to n{\pi }^0$, ${\Sigma }^{+}\to n{\pi }^{+}$, ${\Sigma }^{+}\to p{\pi }^0$ fractional rate differences of order ${10}^{-6\mathrm{}}$ are found whereas for ${\Sigma }^{-}\to n{\pi }^{-}$, ${\Xi }^{-}\to \Lambda {\pi }^{-}$, and ${\Xi }^0\to \Lambda {\pi }^0$ none is expected. Some other tests of $\mathrm{CP}$ conservation in hyperon decays relevant to left-right symmetric models are pointed out.

This Letter presents measurements of the nucleon structure function $F_2(x,Q^2)$ based on the deep-inelastic scattering of 215- and 93-GeV muons in the iron multimuon spectrometer at Fermilab. With use of a lowest-order QCD calculation, a value of ${\Lambda }_{\mathrm{LO}}=230\mathrm{}\pm 40(\mathrm{stat}.\mathrm{})\pm 80(\mathrm{syst}.\mathrm{})$ MeV/c is found.

For $n$-flavor lattice QCD rigorous lower bounds are derived on the masses of baryons, for even $n>~6$, and on the masses of flavor-nonsinglet mesons, for even $n>~2$. The lower bounds are proportional to the pion mass. The consequence of these inequalities for chiral-symmetry breaking is considered.

With use of a simple version of the optical background representation for the transition amplitude in the case of well nested doorways, an alternate statistical theory of multistep compound reactions is suggested, which is valid under very general conditions. Simple connections are estalished between the present approach and that of Feshbach, Kerman, and Koonin and of Agassi, Weidenmüller, and Mantzouranis.

The differential cross section for ${\pi }^{-}-d$ elastic scattering at c.m. pion angles 91°, 104°, 123°, 136°, and 155° has been measured for pion momenta between 460 and 1160 MeV/c with the finest momentum steps so far employed. A pronounced dip-bump structure around 700 MeV/c observed previously at 172° is confirmed at other angles, while the dip around 1000 MeV/c is found to degrade rapidly as the angle decreases. The angular distribution at large angles (> 90°) shows rather drastic changes at these momenta.

States in ${}_{}{}^{84}{}_{}{}^{}\mathrm{Zr}$ with angular momenta up to $34\hslash$ and rotational frequency 1.3 MeV have been studied with the techniques of discrete-line gamma-ray spectroscopy. The measurements probe the region beyond a second upbend. In this region the results are consistent with the nucleus having undergone a transition to an axially symmetric shape with $\beta =0.43\mathrm{}\pm 0.06$ and $\gamma =3\mathrm{}°\pm 6°$ which rotates with the rigidbody moment of inertia.

Intermediate-rapidity fragments with $A=1-14\mathrm{}$ emitted from 42-137-MeV/nucleon Ar + Au have been measured. Evidence is presented that these fragments arise from a common moving source. Entropy values are extracted from the mass distributions by use of quantum statistical and Hauser-Feshbach theories. The extracted entropy values of $\frac{S}{A}\approx 2-2.4$ are much smaller than the values expected from measured deuteron-to-proton ratios, but are still considerably higher than theoretically predicted values.