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Abstract: We have investigated the influence of molecular arrangement on the transfer rates of photoexcitations along supramolecular assemblies of hydrogen-bonded oligo-p-phenylenevinylene (OPV) molecules for two different packing geometries. For well-defined, helical stacks of monofunctional OPVs fast (≈50ps) photoluminescence depolarization and excitation transfer to dopants was observed, in agreement with semi-coherent exciton diffusion. For disordered assemblies of bifunctional OPVs incorporating a spacer to link adjacent molecules, depolarization and energy transfer dynamics occur on a longer time scale (≈nanosecond). This strongly suggests that such spacers need to be tuned carefully as they may otherwise interfere with the π-stacking thereby reducing the intermolecular electronic coupling. [Copyright &y& Elsevier]

The stability of viscous flow between concentric rotating cylinders with an axial flow due to an axial pressure gradient is considered. The governing equations with respect to three-dimensional disturbances are derived and solved by a direct numerical procedure. Results are given for the case of small-gap approximation. Three typical cases &b.mu; = -1, 0 and 0.5 are studied, where &b.mu; represents the fatio of angular velocity of the outer cylinder to that of the inner cylinder. The value of the axial Reynolds number R is up to 100. It is found that the critical disturbance is a non-axisymmetric mode when the value of R is sufficiently large, and the transition of the onset mode with R is demonstrated in detail. Results for the critical Taylor number, wave number, vortex incline angle, and relative wave velocity are also determined. The present stability analysis is found to be in agreement with previous experimental studies and particularly reveals the stability characteristics with the variation of &b.mu;. [ABSTRACT FROM AUTHOR]

Studies the long-term effectiveness of oral steroids given for 2 weeks compared with 4 weeks in patients with carpal tunnel syndrome (CTS). Prednisolone for 2 weeks versus 4 weeks for CTS at 12 months; Relative benefit reduction among patients.

Effects of various surface modifications on four-point bending property improvements of Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass (BMG) are systematically studied. Surface modifications investigated include thin-film metallic glass coating, artificial scratches and femtosecond laser patterning. After modifications, the negligible plastic strain of 3-mm-thick BMG is found to markedly enhance to ~9.2%, without sacrificing its extraordinary strength. Instead, bending yield and fracture strengths in the surface-modified samples are increased to ~2.8 GPa and ~4.0 GPa, respectively, corresponding to a rise of ~66% from those of as-cast samples. In addition, the samples with surface modifications exhibit distinct shear band morphologies. Relationships between the shear band offset, shear band spacing and plastic strain of bent BMG samples are established. Our experimental results demonstrate that BMG is able to survive plastic flow without abrupt fracture through proper designs of surface modifications, in which large numbers of shear bands are formed to distribute the strain effectively upon loading. [ABSTRACT FROM AUTHOR]

To enlarge the interaction structure to a feasible dimension and to decrease the required magnetic field to an available strength, the gyrotron devices at THz frequencies must be designed with a high-order-mode interaction, which is weaker in a beam–wave interaction and more susceptible to mode competition. Using the same interaction structure (a circular waveguide) as in the gyrotron traveling-wave amplifier (gyro-TWT), but replacing the axial magnetic field of the gyro-TWT with a tapered helical magnetic field, we found that the gyrating electrons are able to perform strong interaction with the TE11 mode in the THz region. Through an example case, we explored the behavior of the particles and wave fields as in a beam–wave interaction under a modified scheme of the gyro-TWT with a numerical simulation code. The equations required for the simulation are presented. The simulation result of the example case indicates that, through the TE11 beam–wave interaction under the presented scheme, more than one quarter of the beam energy can be converted to the wave at 612.7 GHz and to heat, dissipated on the waveguide wall, of radius 2.5 cm. [ABSTRACT FROM AUTHOR]

Abstract: Silver nanoparticles were synthesized via a reduction reaction carried out in a spinning disk reactor, to which an AgNO3 solution containing a protecting agent and an alkaline solution containing a reducing agent were added simultaneously and then recycled for a certain period. Besides starch, which has been used for producing silver particles above 10nm, two more protecting agents, i.e. polyvinyl pyrrolidone (PVP) and hydroxypropyl methyl cellulose (HPMC), were tested in order to prepare silver particles below 10nm. Then, the effects of other operating variables, such as rotation speed of disk, flow rates of reactant streams, concentration of reducing agent, and type and concentration of alkali, were investigated, aiming at a high production rate of silver nanoparticles with a size below 10nm. The produced silver particles were recovered using a centrifuge, and the size did not change after redispersion. The sintering temperature of the 10nm silver particles was greatly reduced. [Copyright &y& Elsevier]