Using a novel fluorescence microscope configuration on a lipid monolayer, we demonstrate for the first time that $\rho \mathrm{H}$-dependent liquid-to-solid phase transitions can occur locally on the meniscus in a typical Langmuir-Blodgett transfer, at surface pressure substantially below the phase transition pressure on the bulk. A $\rho \mathrm{H}$ gradient is proposed, originating from acidification induced by absorption of ambient ${\mathrm{CO}}_2$ and the restricted hydroxide-ion exchange between the bulk and meniscus subphases.

A density expansion is obtained for the time dependence of the survival probability of diffusing particles in the presence of randomly distributed diffusing traps. The coefficients are expressed in terms of the exact survival probabilities in the presence of one trap, two traps, and so on. Its leading term coincides with the well-known Smoluchowski result which is shown to be exact for static particles and noninteracting mobile traps. As an application, the first correction term is calculated for a one-dimensional system and arbitrary ratios of particle and trap diffusion coefficients.

We present the wavelet transform as a mathematical microscope which is well suited for studying the local scaling properties of fractal objects. We apply this technique to probability measures on self-similar Cantor sets and to the golden-mean trajectories on two-tori at the onset of chaos.

In analogy to the proposed gravitational "fifth" force, limits can be set on the range $\lambda$ and the strength $\beta$ of an electrical fifth force. Specifically we consider the potential $V=\frac{(e^2}{r)}(1+{\beta e}^{-r\lambda })$ and show that there is a region near $\lambda =1\mathrm{}$ μm where existing experiments set relatively poor limits on $\beta$.

The classical stadium billiard, which is known to be ergodic and strongly mixing, is shown to have strongly localized quantum eigenstates which persist up to infinite energy, or alternately which survive the $\hslash \to 0$ limit. Consistent with the theorems of Schnirlman, Zelditch, and Colin de Verdiere, the states which we show are highly localized are collectively of zero measure (though there are infinitely many) as $E\to \infty$ or as $\hslash \to 0$. However, more relevant to the experimental world is the fact that such localized states make up a finite and calculable fraction of the quantum eigenstates at finite energy.

Very-high-energy $\gamma$ rays emitted by the supernova 1987A were searched for at the Black Birch Range in New Zealand during December 1987 and January 1988. Data obtained in 42 hours of observation time give an upper bound on the flux at the 95% confidence level of 6.1 × ${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ for $\gamma$ rays with energies above 3 TeV. Data obtained on 14 and 15 January are found to have excess counts, above the background level, corresponding to a flux of (1.9±0.5)×${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ and a total energy of ∼${10}^{43}$ ergs.

We study the electromagnetic structure of the pseudoscalar Goldstone bosons ($\pi ,K$) in the framework of a generalized $\mathrm{SU}{\mathrm{}\left(3\right)\mathrm{}}_f$ Nambu-Jona-Lasinio model. Including vector-meson contributions beyond the Hartree-Fock approximation the $q^2$ dependence of the electromagnetic form factors in the spacelike region is well reproduced. We also find that $〈r_K^2+〉<〈r_{\pi }^2+〉$, in agreement with the data.

We report on a search for the flavor-changing neutral-current decays $K_L^0\to {\pi }^0{e}^{+}{e}^{-}$ and $K_L^0\to e^{+}{e}^{-}$. Limits obtained for these processes are $B(K_L^0\to {\pi }^0{e}^{+}{e}^{-})<\mathrm{}3.2\mathrm{}\times {10}^{-7\mathrm{}}$ and $B(K_L^0\to e^{+}{e}^{-})<\mathrm{}1.2\mathrm{}\times {10}^{-9\mathrm{}}$.

Above-threshold ionization of Rydberg atoms by microwave intensities of 3 × ${10}^4$ W/${\mathrm{cm}}^2$ produces electrons with kinetic energies of up to 9 eV, corresponding to the absorption of up to 3 × ${10}^5$ photons. The observations can be described in terms of a classical free electron in an oscillating field, which is the low-frequency limit of more conventional treatments of the phenomenon.

We report on the observation of a light-pressure-induced dispersion of laser light interacting with a Doppler-broadened atomic medium. This novel dispersion feature displays an even symmetry with respect to the optical Doppler detuning; it is due to the small modification of the atomic velocity distribution caused by the spontaneous scattering force. Our phase-sensitive measurements were performed on the $\lambda =555.65\mathrm{}$ nm ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ transition in ytterbium vapor by the use of frequency-modulation spectroscopy. The experimental results are in good agreement with theoretical predictions.

A quantum Monte Carlo simulation method is introduced which treats core and valence electrons separately. This greatly minimizes problems associated with the very different energy and time scales present even at a moderate atomic number. The core is treated variationally by Metropolis sampling of a trial wave function, while the chemically important valence region is treated by a quantum Monte Carlo algorithm that solves the Schrödinger equation. We calculate ionization potentials and electron affinities of C, Si, and Ge, and find excellent agreement with experiment. Effective speedup over standard quantum Monte Carlo approaches is estimated to be as large as a factor of 5000.

Mode control is achieved for the first time in a highly overmoded, pulsed rf oscillator by injection of an external electromagnetic signal (priming). The drive signal power, frequency, and time of application determine the degree of mode control. The regime of parameter space over which a primed gyrotron operates in a single stable mode is increased by ∼40%. A coupled mode theory is used to model the drive power dependency of the priming effect. Priming may allow gyrotrons to operate at increased efficiency as well as stabilize other overmoded coherent radiation sources.

Ten fine-structure intervals separating $n=10\mathrm{}$, $L=4, 5, 6, \mathrm{and} 7$ Rydberg states bound to the ($\nu =0, R=1\mathrm{}$) state of ${\mathrm{H}}_2^{+}$ have been measured to a precision of ±0.6 MHz with microwave-optical double-resonance techniques with a fast ${\mathrm{H}}_2$ beam. These measurements are sufficient to completely determine the relative positions of these states. Agreement with $a$ priori calculations of the level positions, with the extended polarization model, is found if the electric quadrupole moment of the (0,1) state of ${\mathrm{H}}_2^{+}$ is taken to be 1.6432(2) $e{a}_0^2$, which is 0.04(1)% larger than the best calculated values.

In this paper the treatment of radiation in pulse-pulse collisions relevant to high-energy electron-positron colliders is extended to multiple-photon processes. The resultant multiple-photon spectrum is hard. We discuss the possibility of a photon-photon collider utilizing this radiation. The expected flux is calculated and turns out to be from 1 to 2 orders of magnitude larger than that of the conventional virtual-two-photon source, depending upon machine parameters. Photon-electron processes are also enhanced by this additional hard-photon source.

We verify experimentally for optical waves the striking memory effect predicted very recently by Feng, Kane, Lee, and Stone. We present data for both transmission and reflection, and find general agreement with the theoretical predictions for the linear scale dependence and asymptotic exponential falloff of the memory effect. The theoretical and experimental results suggest that significant information about the spatial variation of the incident waveform is preserved during passage through a highly disordered, strongly multiply scattering medium.

We discuss an alternative technique to the lattice-gas automata for the study of hydrodynamic properties, namely, we propose to model the lattice gas with a Boltzmann equation. This approach completely eliminates the statistical noise that plagues the usual lattice-gas simulations and therefore permits simulations that demand much less computer time. It is estimated to be more efficient than the lattice-gas automata for intermediate to low Reynolds number $R\lesssim 100$.

We present an experiment in which the ponderomotive filamentation instability is driven in a preformed, underdense plasma. The spatial profile of the driving beam is intentionally modulated to produce a striated intensity distribution of known periodicity. Dark-field imaging is used to observe the density perturbations produced by the instability. The observed threshold intensity for perturbation wavelengths of 42 μm is approximately 3×${10}^{13}$ W/${\mathrm{cm}}^2$ which compares favorably with homogeneous instability theory.

Short-range-order effects in the isotropic phase of a side-chain polymeric liquid crystal are studied by means of electric and acoustic birefringences and the viscosity. The static properties are comparable to those of conventional liquid crystals, but the dynamic properties show quite different behavior, characterized by a relaxation time which diverges as ${(T-T_c^{*})}^{-1.55\mathrm{}}$, rather than ${(T-T_c^{*})}^{-1\mathrm{}}$, $T_c^{*}$ being a virtual second-order transition temperature. Analysis of the results according to the de Gennes theory enabled the friction coefficients of this theory to be established.

We present a Monte Carlo study of a new lattice model describing defects and their elastic interactions, including a term that accounts for rotational stiffness over a length scale $l$. We show that, when going from small $l$ (as in most atomic crystals) to large $l$ (as in many molecular crystals), the melting process changes from a single first-order to two successive Kosterlitz-Thouless transitions.

Adsorption-isotherm and heat-capacity measurements on monolayer and multilayer ${\mathrm{H}}_2$ adsorbed on MgO are reported. We observe layer by layer growth with at least six layer steps measurable at 8.88 K. A complete first layer is solid at temperatures much higher than the bulk triple point. The second layer has a phase diagram with a liquid-vapor critical point at 10.05±0.05 K and a solid-liquid-vapor triple point at 7.20±0.05 K. The third, fourth, fifth, and sixth layers show layering critical points in the vicinity of 10 K that may point to a roughening transition in bulk crystals.