[en] A new internal configuration bias (ICB) scheme for Monte Carlo (MC) sampling of any number of internal degrees of freedom in chain molecules with arbitrary fixed bond lengths and angles is proposed, extending recent methods restricted to lattice chains, freely jointed chains or short segments. The move is described pictorially for the case of a linear chain; the method may also be readily generalised to branched chains or networks. Its application to a 'phantom' hexadecane backbone with no interatomic potential confirms that it satisfies detail balance. Its application in a strategy for atomistic simulation of bulk polymeric systems is depicted. Unlike previous polymer MC schemes ICB is not dependent on the presence of chain ends, making it potentially highly suitable for the kinds of dense, entangled, high molecular weight and crosslinked systems relevant to applications in the polymer industry

[en] In the present note, we report on the presence of fullerenes in the laser produced carbon plasma in vacuum. The carbon clusters were characterised using infrared (IR) and UVIS absorption spectroscopic techniques. (orig.)

[en] Full text: In usual growth techniques, dopants are introduced at random locations in a semiconductor crystal. An ordered array of dopants would be an extremely interesting system in which to study 2D band structure and commensurability effects in a 2D periodic system in an applied perpendicular magnetic field. Dopant arrays are also of interest as computational cells in cellular automata and in electron and nuclear spin quantum computers. We propose a technique for creating dopant arrays using superfluid He films on a semiconductor surface. Dopant ions are introduced into the He, confined <100 Angstroms below the He surface by an applied electric field. At T≅1K for ion separations <1000 Angstroms, the ions will condense into a Wigner crystal suspended in the He film. Rapidly switching off the applied electric field should result in the transfer of the crystal onto the semiconductor surface. Growth of covering layers of the semiconductor will produce an embedded dopant array. Modeling of the He film-ion system indicates that dopant atom separations of ≥300 Angstroms are achievable, and short range fluctuations in the dopant spacing can in principle be comparable to the lattice spacing of the semiconductor crystal

[en] Models for the controlling mechanisms of anodic growth of native oxides under an anodized Al film on InP are presented. These models for constant current anodization use charge flow over and through the oxide-InP interfacial energy barrier to explain the observed oxide growth behavior. They account for changes in the interfacial barrier height due to variations in substrate doping type and concentration and for changes in illumination conditions. For anodization to proceed on low-doped n-type InP, holes must be generated by either impact ionization or illumination. With low-doped p-type, the interfacial barrier must be reduced by applying an overvoltage or creating energetic carriers with illumination. Increasing the doping concentration reduces the barrier to current flow; thus, neither illumination or increased voltage is required

[en] A process for preparing an amorphous metallic precipitate comprising the steps of forming a mixture of chemical compounds M/sub 1/X and M/sub 2/Y in a polar organic solvent, wherein M/sub 1/ is at least one transition metal having an atomic number in the range of 24-30, 45-48 and 77-80, M/sub 2/ is at least one metal selected from the group consisting of Sn, Pb, As, Sb, P, Te, Sc, S and mixtures thereof, and XY is soluble in the solvent, and forming (M/sub 1/)/sub a/(M/sub 2/)/sub b/ as the precipitate, the integers ''a'' and ''b'' providing stoichiometric balance in the precipitate

[en] The precipitation of ammonium uranyl carbonate (AUC) from UO₂F₂ solutions is investigated in this report. An intermediate product, identified as (NH₄)₃UO₂F₅ (AUF), was found preceding the formation of normal AUC precipitates. It dissolves only slowly in the ammonia carbonate solution. Methods of experimental design were adopted here to decide the relative importance of several parameters with respect to either uranium recovery or fluorine content. Our results suggest that the aging temperature is the most important parameter within the ranges of studies affecting the recovery of uranium in this precipitation process. While, on the other hand, the titration rate of (NH₂)₂CO₃ is the only parameter that affects the fluorine content independently. The inclusion of additional NH₄OH in the precipitant can improve the recovery of uranium but unfortunately it increases the fluorine contents as well. Other changes in the characteristics of the precipitate occur undoubtedly. (orig.)

[en] The advent of ceramic superplasticity has provided new opportunities for the fabrication of structural components for high-temperature application. In recent years, it has been demonstrated that ceramics may be superplastically deformed using extrusion, punch forming, closed die forming, and biaxial gas pressure forming. In this study, efforts to combine superplastic gas-pressure deformation with diffusion bonding are described. Ceramic superplasticity is observed at temperatures in the range of 1,200 C to 1,600 C -- a temperature range historically dominated by the refractory metals for structural application. At these temperatures, diffusion bonding between a refractory metal and a ceramic is achievable -- yielding a unique engineered material. Results of diffusion bonding studies between yttria-stabilized tetragonal zirconia and the refractory metals molybdenum and niobium alloy C103, conducted over the temperature range of 1,250 C--1,550 C are described. Two applications of this technology are also discussed: diffusion bonding and co-deformation of ceramic-metal sheet configurations, and superplastic expansion of a ceramic into a rigid refractory metal preform

[en] Short communication

[en] Short communication

[en] 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane as a specific epoxy resin is used together with a usual epoxy resin. A polyamine mixture and an imidazole type compound are used as a hardening agent. Further, a boron compound and an inorganic filler are added. Such a neutron shielding composition is hardened at a normal temperature without requiring heating, and mechanical strength, especially, compression strength can be kept over a wide range from low temperature to high temperature after the hardening. (T.M.)