Reduced density matrix quantum approach for particle trapping and sticking on corrugated moving surfaces

A short time propagation algorithm for the reduced density matrix is derived to model the interaction of a quantum particle with a moving corrugated surface. The algorithm includes dissipative terms, which can be derived directly from the full Hamiltonian. The scattering of He from a corrugated Cu surface is examined as a function of incident energy and angle and the temperature of the substrate, with a focus on the nature of trapping. It is found that corrugation can make a significant contribution to trapping, even on a metal surface. Energy exchange with the phonons is shown to significantly modify the nature of diffraction mediated selective adsorption.     

A <Emphasis Type="Italic">q</Emphasis>-player impartial avoidance game for generating finite groups

We study a q-player variation of the impartial avoidance game introduced by Anderson and Harary, where q is a prime. The game is played by the q players taking turns selecting previously-unselected elements of a finite group. The losing player is the one who selects an element that causes the set of jointly-selected elements to be a generating set for the group, with the previous player winning. We introduce a ranking system for the other players to prevent coalitions. We describe the winning strategy for these games on cyclic, nilpotent, dihedral, and dicyclic groups.     

Global potential energy minima of C60(H2O)n clusters

Likely candidates for the global potential energy minima of C60(H2O)n clusters with n < or = 21 are found using basin-hopping global optimization. The potential energy surfaces are constructed using the TIP4P intermolecular potential for the water molecules, a Lennard-Jones water-fullerene potential, and a water-fullerene polarization potential, which depends on the first few nonvanishing C60 multipole polarizabilities. This combination produces a rather hydrophobic water-fullerene interaction. As a consequence, the water component of the lowest C60(H2O)n minima is quite closely related to low-lying minima of the corresponding TIP4P (H2O)n clusters. In most cases, the geometrical substructure of the water molecules in the C60(H2O)n global minimum coincides with that of the corresponding free water cluster. Exceptions occur when the interaction with C60 induces a change in geometry. This qualitative picture does not change significantly if we use the TIP3P model for the water-water interaction. Structures such as C60@(H2O)60, in which the water molecules surround the C60 fullerene, correspond to local minima with much higher potential energies. For such a structure to become the global minimum, the magnitude of the water-fullerene interaction must be increased to an unphysical value.     

Copolymers of (±)2-ethylhexyl acrylate and 3-[3,3,3-trimethyl-1,1-bis (trimethylsiloxy) disiloxanyl] propyl methacrylate

Statistical copolymers of (±)2-ethylhexyl acrylate and 3-[3,3,3-trimethyl- 1,1-bis (trimethylsiloxy) disiloxanyl] propyl methacrylate were synthesized and the reactivity ratios and the Q and e values were calculated. The glass transition temperatures of the copolymers were in good agreement with the predictions of Fox's equation and Wood's formula. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3571–3574, 1997     

Polymeric substitution in a pH oscillator

The iodate pH oscillator, which oscillates between pH 6.5 and 4.0, is reproducible in a semibatch reactor. pH oscillations of similar period and amplitude were observed when poly(2-acrylamido-2-methyl-1-propanesulfonic acid) was substituted for sulfuric acid. Therefore, a polymer may be used as an alternative reagent, where the polymer actively participates in the reaction instead of serving as an inert reaction medium.     

A humidity blocker approach to overcoming the humidity interference with cationic photopolymerization

A humidity blocker approach to overcoming the humidity interference with cationic photopolymerization is proposed and validated. Environmental humidity is one of the major interfering factors in cationic photopolymerization, and cationic photopolymerization is found to be inhibited by high humidity. When curing cycloaliphatic epoxide based cationic UV curable materials flexibilized by various reactive diluents under different humidity conditions, it was found that the more hydrophobic materials exhibited higher monomer conversion under higher humidity. To obtain cationic UV curable materials that are less influenced by humidity, a humidity blocker approach was proposed and monomer conversion of materials containing both hydroxy‐functional reactive diluents and epoxy‐siloxane were examined using real‐time FTIR. The hydroxy‐functional reactive diluents act as an internal hydroxyl source that enhances monomer conversion through chain transfer mechanism, and the hydrophobic epoxy‐siloxane acts as a humidity blocker, mitigating the inhibiting effects of humidity. Cationic UV curable materials with an optimized combination of these two components exhibited higher and more consistent monomer conversion under a range humidity conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4344–4351, 2008     

Dynamic exchange coupling in magnetic bilayers

A long-range dynamic interaction between ferromagnetic films separated by normal-metal spacers is reported, which is communicated by nonequilibrium spin currents. It is measured by ferromagnetic resonance and explained by an adiabatic spin-pump theory. In such a resonance the spin-pump mechanism of spatially separated magnetic moments leads to an appreciable increase in the resonant linewidth when the resonance fields are well apart, and results in a dramatic linewidth narrowing when the resonant fields approach each other.     

Theoretical support for buckyonions as carriers of the UV interstellar extinction feature

Theoretically simulated UV-visible photoabsorption spectra of the buckyonions are compared with the most recent and complete experimental data. The very good agreement found provides support for our theoretical model of the buckyonions and allows for a detailed analysis of the correspondence between these spectra and the UV interstellar extinction feature. The excellent agreement found between the theoretical and observational features and the consistency of the former with the observational data constraints gives very strong support for the buckyonion origin of the UV interstellar spectrum.     

Lowest-energy structures of (C60)nX (X=Li+,Na+,K+,Cl-) and (C60)nYCl (Y=Li,Na,K) clusters for n</=13

Basin-hopping global optimization is used to find likely candidates for the lowest minima on the potential energy surface of (C(60))(n)X (X=Li(+),Na(+),K(+),Cl(-)) and (C(60))(n)YCl (Y=Li,Na,K) clusters with n相似文献