A strong accumulation layer can be produced on the surface of polycrystalline ZnO films when the samples are exposed to ions from an inert gas discharge in Ar or Kr. A combination of surface conductance and surface po...
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A strong accumulation layer can be produced on the surface of polycrystalline ZnO films when the samples are exposed to ions from an inert gas discharge in Ar or Kr. A combination of surface conductance and surface potential measurements show that an accumulation layer is induced by the adsorption of charges from the inert gas plasma which neutralizes and removes chemisorbed oxygen atoms, and this can increase the conductance by more than 6 orders of magnitude, for 500 nm thick films. Electrical neutrality in the ZnO provides the electrons for the accumulation layer, either from the ohmic contacts or the plasma. This accumulation layer can be further enhanced by illumination with UV light.
We calculate the far-infrared absorption spectrum of the endohedral fullerene He@C-70. In this molecule the He inclusion experiences a strongly anisotropic potential V(rho, z). The 2D Schrodinger equation governing it...
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We calculate the far-infrared absorption spectrum of the endohedral fullerene He@C-70. In this molecule the He inclusion experiences a strongly anisotropic potential V(rho, z). The 2D Schrodinger equation governing its rovibrational motion is solved variationally. The spectrum consists of strong P- and R-branches (Delta m = +/-1) and a much weaker Q-branch (Delta m = 0), and peaks near 100cm(-1). Despite its apparent complexity, however, the eigenvalue spectrum is essentially regular, and the system displays little evidence of chaos.
Based on the Rayleigh-Gans-Debye thin shell approximation, a fast Fourier cosine transform method was developed to retrieve vesicle size distributions directly from the light scattering measurement. The method was tes...
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Interfacial structure in the isotropic phase of a liquid-crystalline material near a wall is studied by a mean-field density-functional theory. With increasing strength of the wall anchoring potential, the theory pred...
Interfacial structure in the isotropic phase of a liquid-crystalline material near a wall is studied by a mean-field density-functional theory. With increasing strength of the wall anchoring potential, the theory predicts a first-order transition from incomplete to complete wetting by the smectic-A phase at bulk isotropic-smectic coexistence, with an associated prewetting transition occurring away from bulk coexistence. The incomplete wetting case is accompanied by a small number (between 0 and and 2) of discrete layer transitions, while an infinite number of such transitions occurs at complete wetting. An analysis of the underlying physical mechanisns for layer transitions reveals that these transitions tend to disappear as the system is moved both sufficiently close to and sufficiently far from the bulk isotropic–nematic–smectic-A triple point by varying the model coupling parameters. These results reconcile findings from previous theories and experiments.
We examine a three-dimensional vector lattice model for water, oil, and amphiphile mixtures, using the mean-field and Bethe approximations as well as Monte Carlo methods. The Monte Carlo results exhibit three-phase co...
We examine a three-dimensional vector lattice model for water, oil, and amphiphile mixtures, using the mean-field and Bethe approximations as well as Monte Carlo methods. The Monte Carlo results exhibit three-phase coexistence between water-rich, oil-rich, and microemulsion phases, where the microemulsion has low amphiphile concentration (≊15%) in agreement with experiment. Also present is a floating incommensurate lamellar phase which coexists with the microemulsion at slightly higher amphiphile concentration, similar to lamellar phases observed experimentally. These features are absent in the two mean-field-like approximations and we conclude that, in general, these types of approximations are inappropriate for describing mixtures containing efficient amphiphiles.
We present a renormalization group theory in polymer conformation space to describe randomly branched polymers in which monomers interact with each other through the excluded volume interaction. We make a perturbation...
We present a renormalization group theory in polymer conformation space to describe randomly branched polymers in which monomers interact with each other through the excluded volume interaction. We make a perturbation expansion for the mean square radius of gyration of randomly branched polymers with annealed structures and identify the appropriate scaling variable. We further perform a renormalization group analysis that results in the ε expansion for the critical exponents of the radius of gyration ν=1/4+ε/36 and of the number of configurations θ=5/2-ε/12, which are consistent with the results of an earlier theory.
The behavior of liquid crystalline polymers in the interfacial region between the isotropic and nematic phases is investigated based on an inhomogeneous free-energy functional. A mean-field approximation is used for t...
The behavior of liquid crystalline polymers in the interfacial region between the isotropic and nematic phases is investigated based on an inhomogeneous free-energy functional. A mean-field approximation is used for the system of semiflexible polymers obeying the Saito-Takahashi-Yunoki description and interacting via the Onsager-type repulsive interaction. The density distribution of the polymers crossing the interface is computed by using a spherical-harmonics expansion. The calculated interfacial tension is consistent with the results of the scaling argument which is also presented in this paper.
Randomly branched polymers with quenched branchings, in which monomers interact with each other through the excluded volume interaction, are investigated by using an approach of conformation-space renormalization grou...
Randomly branched polymers with quenched branchings, in which monomers interact with each other through the excluded volume interaction, are investigated by using an approach of conformation-space renormalization group theory combined with the replica technique. The perturbation expansion for the mean-square radius of gyration is found and the scaling variable is identified. The renormalization group analysis shows that the critical exponents of the radius of gyration (ν=1/4+ε/40) and of the total number of configurations (θ=5/2-3ε/20) no longer obey the scaling law θ-1=(D-2)ν, where ε=8-D and D is the space dimensionality, which is tenable for randomly branched polymers with annealed branchings.
Reports on the feasibility of applying neural networks to the problem of forecasting the Canada/US spot exchange rate. The inputs to the network consist of the short-term trend in the spot rate (Monday-Thursday) and t...
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Reports on the feasibility of applying neural networks to the problem of forecasting the Canada/US spot exchange rate. The inputs to the network consist of the short-term trend in the spot rate (Monday-Thursday) and the change in interest rate spread between the two countries (Wednesday-Thursday). The output is a prediction of the exchange rate on Friday. The model is able to explain 6.6% of the variance in the data between November 1991 and June 1993 (out of the sample), yielding a success rate of 59% on directional forecasts.
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