It was proposed that the mass of a particle be defined by its de Broglie frequency, measured as ${\mathit{c}}^2$/λ/γv, where λ/ is the mean de Broglie wavelength of the particle when it has mean speed v and Lorentz factor γ; the masses of systems too large to have a measurable λ/ are then to be derived by specifying the usual inertial and additive properties of mass. This avoids the use of an arbitrary macroscopic standard such as the prototype kilogram, and does not even require the choice of a specific particle as a mass standard. Suggestions are made as to how this absolute mass can be realized and measured at the macroscopic level and comments are made on the effect of the new definition on the form of the equations of physics.

Peaked electron temperature profiles are observed in the DIII-D tokamak during electron cyclotron heating despite the fact that >75% of the input power is deposited significantly off axis. Power balance analysis indicates a net inward flow of energy for electrons. An inward energy flow is not compatible with diffusive or critical gradient models. A time-dependent perturbation technique is employed to estimate the conductive loss and the nondiffusive part of the energy transport. The nondiffusive component of the transport appears only at radii smaller than that of the heating location.

A quantitative description of time-dependent intermediate shocks is formulated using the Cohen-Kulsrud-Burgers equations. In noncoplanar Riemann problems, time-dependent 2→3 intermediate shocks evolve in time as a localized self-similar structure whose strength decreases as 1/ √t , and whose width expands as √t . Time-dependent intermediate shocks offer a way of solving the noncoplanar MHD Riemann problem.

Isothermal scans of third-sound velocity as a function of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage on graphite exhibit pronounced dips integral layer periodicity. The minimum ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage on graphite needed to support third sound is nearly three layers. The heat-capacity isotherm exhibits minima at layer completion but there is no noticeable feature related to the onset of superfluidity. High-resolution adsorption isotherms below 1 K show that ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film grows layer by layer through at least seven layers.

Water droplets condensing with a nonzero contact angle on a solid substrate maintained near its melting point exhibit a very unusual behavior. Droplet growth is accompanied by rotation, translation, and hopping movements. Microscopic observations show that the substrate melts along the line of three-phase contact. An analysis of the flow rate and temperature dependence of the phenomenon indicates that droplets are set into motion by the relaxation of the substrate strain during melting.

The ordering in thin films of symmetric diblock copolymers has been studied by neutron reflectivity as a function of temperature and film thickness. Exponentially damped oscillatory variations in the concentration are shown to propagate into the specimens from both surfaces with decay lengths increasing with decreasing temperature. No distinguishable order-to-disorder transition is observed; only a transition from a partially to fully ordered state is found. The temperature of this transition is found to depend in a power-law manner on the film thickness.

Studying the dynamic structure factor of polybutadiene in the first valley of S(Q) we observed a decoupling of microscopic and macroscopic time scales about 40° above ${\mathit{T}}_{\mathit{g}}$. At higher temperatures the time scale set by the viscosity scales with the microscopic scale, while at lower T strong decoupling effects occur. We present evidence that the decoupled low-temperature relaxation is distinctly different from the high-frequency ‘‘β process.’’ The decoupling temperature coincides with the critical temperature of the mode coupling theory.

Thin polystyrene films (<100 nm) on silicon substrates undergo dewetting when annealed above the glass transition temperature. Three different stages can be distinguished: The smooth films break up by the creation of cylindrical holes. The holes then grow and form rims ahead of them which finally contact each other creating ‘‘cellular’’ structures. The rims are unstable and decay into droplets. The influence of the film thickness on this process is investigated and compared to recent theoretical predictions of spinodal decomposition of partially wetting thin films.

The temperature dependence of the nonergodicity parameter ${\mathit{f}}_{\mathit{q}}$ in the ‘‘fragile’’ glass-former propylene carbonate has been investigated using a wide-frequency-window Brillouin-scattering technique. A critical decrease of ${\mathit{f}}_{\mathit{q}}$ is revealed at temperatures well above the calorimetric glass transition in accordance with mode-coupling theories for the liquid-glass transition. The determined critical temperature (270±5 K) is, however, significantly higher than that obtained using incoherent neutron scattering (210±15 K); this does not agree with the universal ${\mathit{T}}_{\mathit{c}}$ in the mode-coupling theory.

Recent experiments [Kruger and Jeanloz, Science 249, 647 (1990)] have shown that the pressure-induced amorphous form of ${\mathrm{AlPO}}_4$ reverts to its original ‘‘single-crystal’’ form on release of pressure. Here we present the results of a Brillouin scattering study of the sister compound α-quartz, ${\mathrm{SiO}}_2$ (which can also be pressure amorphized but retains its amorphous structure on release of pressure), which shows that the recovered material is not elastically isotropic but retains a ‘‘memory’’ of its original crystallographic orientation.

The interstitial carbon-oxygen complex is one of the dominant defects produced in electron irradiated Si. In spite of much work, there is no consensus on its structure and a recent model of Trombetta and Watkins seems inconsistent with the lack of strong O-related vibrational modes expected from bond-centered O. Our ab initio cluster calculations reveal very unusual bonding of O in these complexes but yield vibrational modes and isotope shifts which are in reasonable agreement with experiment.

Relying on the recent proposed multicanonical algorithm, we present a numerical simulation of the first-order phase transition in the 2D 10-state Potts model on lattices up to sizes 100×100. It is demonstrated that the new algorithm lacks an exponentially fast increase of the tunneling time between metastable states as a function of the linear size L of the system. Instead, the tunneling time diverges approximately proportional to ${\mathit{L}}^{2.65}$. On our largest lattice we gain more than 2 orders of magnitude as compared to a standard heat-bath algorithm. As a first physical application we report a high-precision computation of the interfacial free energy per unit area.

The vibrational spectra of H on Cu(110) measured with high-resolution energy-loss spectroscopy at very low coverage strongly support the predicted ‘‘protonic’’ band structure. Localization is observed for increasing coverage. A simple model qualitatively describes the coverage dependence of the spectra.

Ordered structures formed by Na adsorption on the Al(111) surface are investigated by high-resolution core-level spectroscopy. It is shown that, contrary to the common picture of alkali adsorption, two of the structures formed at room temperature consist of intermixed Na-Al layers. The results for the (√3 × √3 )-rotated-30° structure are also consistent with intermixing although they do not provide any definite proof. For Na layers deposited at 100 K no intermixing is found.

Transmission through an opaque static barrier is greatly enhanced by an alternating potential. If a particle is activated to its lowest instantaneous eigenenergy, it is ‘‘trapped’’ and will follow the alternating potential to the top of the static barrier (‘‘elevator effect’’).

Universal amplitude relations associated with hyperscaling are obtained exactly for several integrable perturbations of two-dimensional (multi)critical points described by minimal models. The results are confirmed numerically and it is discussed how they can be verified by experiment.

We present a unified interpretation of observations of interplanetary fluctuations in terms of nearly incompressible magnetohyrodynamics. Incompressive effects explain the rapid evolution of turbulence in slow wind containing the heliospheric current sheet. The relative constancy of the spectrum of ‘‘inward propagating’’ fluctuations compared to the rapid decline in ‘‘outward’’ fluctuations results from incompressive spectral transfer combined with strong dissipation of the outward fluctuations. Secondary compressive effects account for nearly pressure-balanced structures and the density fluctuation levels.

In the perturbative domain of quantum chromodynamics, transverse electroproduction of hybrid baryons is small. Their longitudinal electroproduction has size and scaling behavior like normal baryons. Thus deep inelastic scattering has a hybrid resonance peak to background ratio that is small for the transverse structure function but normal size and constant for the longitudinal one. This signature can test if the Roper resonance is a hybrid. Related high-momentum-transfer signatures may clarify the structure of possible nonstandard states such as Λ(1405), ${\mathit{f}}_0$(975), or ${\mathit{a}}_0$(980).

We present the first direct experimental evidence of topological defects in nonlinear optics. For increasing Fresnel numbers F, the two-dimensional field is characterized by an increasing number of topological defects, from a single vortex, up to a large number of vortices with zero net topological charge. At variance with linear scattering from a fixed phase plate, here the defect pattern evolves in time according to the nonlinear dynamics. We assign the scaling exponents for the mean number of defects, their mean separation, and the charge unbalance as functions of F, as well as the correlation time of the defect pattern.

We report here the first experimental study of femtosecond time-resolved molecular multiphoton ionization. Femtosecond pump-probe techniques are combined with time-of-flight spectroscopy to measure transient ionization spectra of ${\mathrm{Na}}_2$ in a molecular-beam experiment. The wave-packet motions in different molecular potentials show that incoherent contributions from direct photoionization of a singly excited state and from excitation and autoionization of a bound doubly excited molecular state determine the observed transient ionization signal.