Modified system of high-resolution Bragg reflection was used to observe both the spatial and temporal sound waves simultaneously in the relaxation region of liquid furan (${\mathrm{C}}_4$${\mathrm{H}}_4$O). The spatial phase velocity at 100 MHz was shown to be higher than the temporal velocity by 7 m/s at 20°C. The result is in good agreement with the theoretical prediction, providing an experimental evidence of the difference between them.

The effect of fluctuations on the transition to turbulence is examined by introducing large-amplitude noise into the boundary temperature of a Rayleigh-Bénard system. The response can be largely described in terms of variables whose induced fluctuations are much slower than either the natural oscillations or the external noise. However, the sequence of transitional regimes and the statistical properties of the turbulent state are not dramatically affected.

It is usually assumed in both optical and acoustical holography that the resolution of a reconstructed image is limited by the wavelength of the radiation. In this paper it is demonstrated that this is not necessarily true in acoustical holography. A technique which images the source vector intensity as well as the sound pressure amplitude with a resolution independent of the wavelength is presented. Application to electromagnetic radiation may be possible.

A probability distribution $W\left(t\right)\mathrm{}$ for the delay time $t$ of superfluorescent pulses is defined in terms of a functional integral, which is evaluated exactly. Although the linearized early-stage dynamics is used, full agreement is obtained with previous numerical and experimental results for the variance of $t$ and, more generally, for the shape of $W\left(t\right)\mathrm{}$. The effect of inhomogeneous broadening of the atomic levels, showing that decrease of the dephasing time ${T_2}^{*}$ leads to substantial increase of the mean and variance of $t$, is also analyzed.

In this Letter, a model is described in which spatially stochastic magnetic field and current fluctuations in a plasma with sheared average magnetic field are treated consistently with Ampere's Law.

An exact stochastic simulation of the Schroedinger equation for charged bosons and fermions has been used to calculate the correlation energies, to locate the transitions to their respective crystal phases at zero temperature within 10%, and to establish the stability at intermediate densities of a ferromagnetic fluid of electrons.

Polystyrene spheres (2450 Å in diameter) are trapped in a surface energy well at water/air interface. Because of asymmetry of charge distribution, electrical dipoles are associated with each interfacial particle. The dipole-dipole repulsive interactions organize the polystyrene spheres into a two-dimensional triangular lattice. The direct microscopic observations of such an interfacial colloidal crystal are reported for the first time.

The first Monte Carlo calculations explicitly employing triplet correlations in the variational wave function for the ground state of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are presented. A significant lowering of energy is obtained, accounting for 75% of the discrepancy between previous Jastrow variational calculations and the known exact numerical results. An improved density dependence of the energy is obtained and the pair correlation function is sharpened leading to much better agreement with the exact ground state.

High-resolution x-ray scattering studies show a new charge-density wave (CDW) structure on warming through the commensurate-incommensurate transition in $2H$-Ta${\mathrm{Se}}_2$ at 93 K. In contrast to the fully incommensurate CDW structure seen on cooling, hexagonal symmetry is broken in the new phase and the triple-$\overrightarrow{\mathrm{q}}$ CDW has one commensurate and two incommensurate wave vectors. At 112 K (warming) the CDW transforms to the fully incommensurate structure.

The ionization probability of an atomic particle sputtered from a simple substrate system has been analyzed with use of a computer simulation of the sputtering process. The ionization probability was found to have a Boltzmann-like functional form and a quantity called "the effective temperature" $T_e$ could be defined. The value of $T_e$ was found to be in the range of 2000-3500 K. The dependence of $T_e$ on the microscopic parameters of the system has been investigated.

The zero-field spin relaxation of positive muon is measured in spin-glasses $\mathrm{Au}\mathrm{Fe}$ and $\mathrm{Cu}\mathrm{Mn}$. A stochastic theory of muon spin relaxation in a random dilute spin system is formulated to deduce the correlation time of Fe (or Mn) moments. The observed correlation time increases rapidly from ${10}^{-10\mathrm{}}$ sec (at $T\sim 1.2T_g$) to ${10}^{-5\mathrm{}}$ sec (at $T\sim 0.5T_g$), showing a sharp slowing down of spin fluctuation around $T_g$.

Very-low-angle Brillouin light-scattering experiments have been performed in liquid water subjected to a temperature gradient. The line intensities are unequal, and both the sign and the order of magnitude of this effect agree with recent theoretical calculations for nonequilibrium systems.

An exact coherent-state representation is given for fermion systems which avoids the Gaussian overlap approximation in the reduction of the Hill-Wheeler-Griffin integral equation to a differential equation. An application shows that the random-phase-approximation ground-state correlation energy, derived with use of the Gaussian overlap approximation, is a factor of 2 too large.

Coupling constant renormalization for $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ lattice gauge theories is studied with Hamiltonian methods. Expansions to $O\left(g^{-16\mathrm{}}\right)$ suggest that the crossover from weak to strong coupling occurs progressively more abruptly in the variable ${\lambda }^2=g^{2}N$ as $N$ increases. The constants relating the string tension to the scale-breaking parameter $\Lambda$ are estimated for all $N$. It is suggested that the Callan-Symanzik $\beta$ function develops a kink in the $N\to \infty$ limit at a nonzero value of ${\lambda }^2$.

Unification of strong and electroweak forces implies that protons (and bound neutrons) decay. Modes like $\overline{\nu }\pi$, $e^{+}\pi$, and ${\mu }^{+}{K}^0$ are expected, while modes like ${\mu }^{+}\pi$ and $e^{+}{K}^0$ are "Cabibbo" suppressed. Branching ratios can reveal much about the nature of the unifying group and the origin of fermion masses. Plausible models of unification and flavor mixing give surprisingly different predictions for two-body branching ratios.

Consideration of both the effect of the one-pion and $\rho$-meson exchange potentials in the particle-hole interaction and the inclusion of 2p-2h configurations explains why the magnetic high-spin states discovered recently in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are close to the shell-model energies although the cross sections are only 50% of the single-particle estimate.

Transitions to ($4^{-}$,$T=0\mathrm{}$) states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at 17.79 and 19.80 MeV are found to be strongly asymmetric in ${\pi }^{+}$ vs ${\pi }^{-}$ inelastic scattering; in contrast, the ${\pi }^{+}$ and ${\pi }^{-}$ cross sections for the ($4^{-}$, $T=1\mathrm{}$) state at 18.99 MeV are equal. Three-state isospin mixing is proposed as an explanation. Off-diagonal charge-dependent mixing matrix elements of - 147±25 and - 99±17 keV are obtained.

Alpha-gamma coincidence measurements have been made with reactions of 142-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{146}{}_{}{}^{}\mathrm{Nd}$ leading to the noncollective nuclei ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Dy}$. The side-feeding pattern in coincidence with forward energetic alpha particles peaks at $J=30\mathrm{}$ with full width at half maximum ∼10, indicating that central collisions do not participate, while that for backward alpha particles extends down to $J=0\mathrm{}$. The data are consistent with the generalized critical-angular-momentum model of incomplete fusion.

Combining certain well-known facts from low-energy scattering theory leads to the accurate determination of the ground-state level ($0^{+}$, $T=1\mathrm{}$) of the ${}_{}{}^2{}_{}{}^{}\mathrm{He}$ nucleus at energy $E=-140-i467\mathrm{}$ keV.

A scheme is proposed for laser-selective photodamage of biological molecules, based on time-delayed two-step photoionization of a dye molecule bound to the biomolecule. The validity of the scheme is experimentally demonstrated in the case of the dye Proflavine, bound to synthetic polynucleotides.