Our earlier measurements on pure KCN and ${\mathrm{}\left(\mathrm{KCN}\right)\mathrm{}}_{0.25}$ ${\mathrm{}\left(\mathrm{KBr}\right)\mathrm{}}_{0.75}$ have been extended to mixed crystals of ${\mathrm{}\left(\mathrm{KCN}\right)\mathrm{}}_{0.5}$ ${\mathrm{}\left(\mathrm{KBr}\right)\mathrm{}}_{0.5}$. From a comparison of the observed neutron scattering line shapes to those predicted by a simple extension of the theory used to describe pure KCN, it is concluded that this theory does not describe the mixed systems correctly. This Letter suggests that the current results may be indicative of the formation of a "glass" phase at low temperatures in these mixed systems.

The observation of extensive small-angle x-ray scattering from hydrogenated $a$-Si indicates that the void distribution in this material is very similar to that for evaporated $a$-Si. Thus the improved electrical properties of the hydrogenated material are not due to this material having a homogeneous structure.

The problem of superflow through a random bond network is formulated. The flow is taken to be limited by the critical velocity. This problem is solved for a two-dimensional system; a first approximation for attacking the problem in three-dimensional system is described. Possible applications are to superfluid flow through Grafoil.

The birefringence has been measured in detail near the smectic-$A$ to smectic-$B$ phase transition in N-($p$-butoxybenzylidene)-$p$-$n$-octylaniline. The birefringence undergoes a sharp discontinuity of 2.5×${10}^{-3\mathrm{}}$ within 2 mK at the transition. A pretransitional behavior in both the birefringence and the response time is found in a temperature interval of 0.3 K below the transition. The change in birefringence in the smectic-$B$ phase follows a parabolic temperature dependence.

Specific-heat measurements near the nematic-smectic-$A$ transitions of the octyloxy, nonyloxy, and decyloxy members of the 4-$n$-pentyl-phenylthiol-4′-alkoxybenzoate ($\overline{n}\mathrm{S}5$) homologous series reveal the presence of critical-tricritical crossover behavior upon increasing $\overline{n}$, with ${\overline{n}}_t\sim \overline{9}$. The results are consistent with Alben's extension of de Gennes's superfluid analogy to include superfluid-${\mathrm{He}}^3$-${\mathrm{He}}^4$-like tricritical behavior.

Velocity and angular distributions for Xe scattered from clean Pt(111) have been observed which permit the scattering process to be experimentally divided into a direct inelastic channel and a trapping-desorption channel. The trapping-desorption channel leads to Maxwellian velocity distributions at the surface temperature and a $cos\theta$ angular dependence, while the direct inelastic channel exhibits a linear relationship between exit kinetic energy and both incident kinetic energy and surface temperature.

Temperature-dependent thermoelectric-power ($S$) studies of ${(\mathrm{N}-\mathrm{m}\mathrm{e}\mathrm{t}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{p}\mathrm{h}\mathrm{e}\mathrm{n}\mathrm{a}\mathrm{z}\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{u}\mathrm{m})}_x{\left(\mathrm{phenazine}\right)}_{1-x}\left(\mathrm{tetracyanoquinodimethanide}\right)$ [${\left(\mathrm{NMP}\right)}_x{\left(\mathrm{phen}\right)}_{1-x}\left(\mathrm{TCNQ}\right)$] show that for $x=0.5\mathrm{}$, $S\left(T\right)\mathrm{}$ is indentical to that of (quinolinium)${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}_2$. $S\left(T\right)\mathrm{}$ for $0.5<x<\mathrm{}1.0\mathrm{}$ is intermediate between that of (NMP)(TCNQ) and (quinolinium)${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}_2$. Our results show strong Coulomb correlations are important in these salts and that their transport properties are determined by semiconducting gaps with disorder having only secondary importance for $T>\mathrm{}70\mathrm{}$ K.

Results of computer simulations for a dilute Ising system on the triangle and fcc lattices are reported. Though we include only a nearest-neighbor antiferromagnetic interaction $J<\mathrm{}0\mathrm{}$, these systems freeze into a spin-glass for $0.50<x<\mathrm{}1.0\mathrm{}$ for the triangle lattice and $0.18\lesssim x\lesssim 0.40\pm 0.10$ for the fcc lattice, where $x$ is the concentration of magnetic spins. The spin-glass freezing is a result of the frustration inherent in the lattice and not from competition between ferromagnetic and antiferromagnetic bonds.

Using characteristic-electron-energy-loss spectroscopy and different appearance-potential techniques, we have obtained results which suggest a new interpretation of the resonant x-ray emission in lanthanum. Identification of structures in energy-loss and x-ray-emission spectra shows that the resonant x-ray emission is mainly due to characteristic transitions and not bremsstrahlung as believed earlier.

The quadrupole interaction of copper has been measured as a function of temperature in Eu${\mathrm{Cu}}_2$${\mathrm{Si}}_2$ and Yb${\mathrm{Cu}}_2$${\mathrm{Si}}_2$. These measurements suggest that in these systems Hirst's "interconfiguration fluctuation" model provides a better description of the valence fluctuation than the localized-electron model. The observation of the influence of the valence-fluctuation phenomenon on the quadrupole interaction is reported for the first time and the importance of the NMR measurements on these materials is pointed out.

The resistivity of a composite of superconducting NbTi small particles randomly dispersed throughout a normal In matrix has been measured in fields to 6 T. The volume fraction of NbTi particles was varied from 0.01 to 0.14. For all samples the resistivity was observed to increase as a linear function of magnetic field; in strong fields the resistivity of the granular composite was greater than the resistivity of the normal metal.

A search for cosmic-ray antiprotons was recently performed with use of a balloon-borne superconducting-magnet spectrometer. A total of 46 antiproton candidates were observed in the rigidity interval from 5.6 to 12.5 GV/c. Of these events 18.3 are expected to be atmospheric and instrumentation background. The $\frac{\overline{p}}{p}$ ratio is found to be (5.2±1.5) ×${10}^{-4\mathrm{}}$. This ratio is consistent with secondary production of antiprotons in the interstellar medium.

According to the standard picture, charmed-hadron decays form a hierarchy, with increasing suppression (in powers of small mixing angles) as one goes from $\frac{\Delta C}{\Delta S}=1\mathrm{} \mathrm{to} 0 \mathrm{to} -1\mathrm{}$ processes. This Letter discusses several kinds of effects that might enhance the contributions from second-order suppressed anplitudes, namely, effects which involve their interference with leading amplitudes.

It is shown that high-transverse-momentum photons originating from the process quark+gluon→quark+photon exhibit a substantial linear polarization in perturbative quantum chromodynamics. The angular dependence of the polarization is quite sensitive to the non-Abelian structure of the interaction, and can be used to check the equality of the quark-gluon and three-gluon couplings.

We have studied inclusive photon production from ${\pi }^{+}p$ interactions at 10.5 GeV/c and found a source of centrally produced direct photons which accounts for (46±9)% of all photons detected with ${P_L}^{*}$ and $P_T$ between 0 and 20 MeV/c. The experimental data are found to be in good agreement with a calculation of hadronic inner bremsstrahlung.

We consider charge-conjugation asymmetries arising from two-gluon exchange and gluon-bremsstrahlung corrections in color-averaged quark-antiquark and quark-quark scattering. At large momentum transfers, such considerations lead to sizable predictions for forward-backward and particle-antiparticle asymmetries in hadron collisions. Jet-antijet differences are discussed and the cleanest tests involve the heavier quarks. The absence of mass singularities and the relationship to two-photon asymmetries are emphasized.

The electron energy spectrum in the process $e^{+}{e}^{-}\to {\psi }^{\prime \prime }\mathrm{}\left(3770\right)\mathrm{}\to e^{\pm }+(>\mathrm{}2\mathrm{} \mathrm{charged}\mathrm{particles})$ has been used to determine the $D(56\%D^0+44\%D^{+})$ semileptonic branching ratio. Assuming the Glashow-Iliopoulos-Maiani model, it is found that the inclusive branching ratio is $b(D\to \mathrm{Xe}\nu )=0.080\mathrm{}\pm 0.015$ and the state $X$ is dominated by $K$ and $K\pi$. The fraction of $K\pi e\nu$ is (37 ± 16)% if the $K\pi$ system is entirely $K^{*}\mathrm{}\left(890\right)\mathrm{}$, or (55 ± 21)% if the $K\pi$ system is nonresonant. Within the assumptions of the analysis, the $D$ lifetime is calculated to be (2.5 ± 1.6) × ${10}^{-13\mathrm{}}$ sec.

The excitation function for fission of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ following inelastic scattering of ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$ ions was measured by identification of internal conversion transitions in the backscattered ions. The observed fission cross section at the lowest energies is consistent with a dominant contribution from the Coulomb interaction, whereas at the highest energies one is unable to establish a predicted interference minimum between Coulomb and nuclear forces.

The masses and kinetic energies of coincident heavy fragments emitted from a ${}_{}{}^{239}{}_{}{}^{}\mathrm{U}$ target bombarded with 11.5-GeV protons were measured as a function of the angle between the fragments. Fragments with nearly equal and opposite laboratory momenta are observed with a total mass as low as ∼ ½ that of the target and higher kinetic energy than expected from fission, providing evidence for a new reaction mechanism.

The coefficients ${\alpha }_{\mp }$ in the alignment-correlation terms $\mathcal{a}{\alpha }_{\mp }E{P}_2\left(cos\theta \right)$, in ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$ decays have been determined; ${\alpha }_{-}\left({}_{}{}^{12}{}_{}{}^{}\mathrm{B}\right)=+(0.006\mathrm{}\pm 0.018)\%/\mathrm{MeV}$ and ${\alpha }_{+}\left({}_{}{}^{12}{}_{}{}^{}\mathrm{N}\right)=-(0.273\mathrm{}\pm 0.041)\%/\mathrm{MeV}$. The sign of ${\alpha }_{+}\left({}_{}{}^{12}{}_{}{}^{}\mathrm{N}\right)$ was determined for the first time, by use of an NMR method and measurements on $\beta -\gamma$ correlation in aligned ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$. The ${\alpha }_{-}-{\alpha }_{+}$ result is consistent with strong conservation of vector currents without second-class currents and the ${\alpha }_{-}+{\alpha }_{+}$ result gives unique information on the time component of the axial-vector current.