Driven depinning of strongly disordered media and anisotropic mean-field limits

Extended systems driven through strong disorder are modeled generically using coarse-grained degrees of freedom that interact elastically in the directions parallel to the drive and slip along at least one of the directions transverse to the motion. In the limit of infinite-range elastic and viscous coupling this model has a tricritical point separating a region where the depinning is continuous, in the universality class of elastic depinning, from a region where depinning is hysteretic. Many of the collective transport models discussed in the literature are special cases of the generic model.     

pH-mediated field-amplified sample stacking of pharmaceutical cations in high-ionic strength samples

Capillary electrophoretic separation of samples of physiological origin typically have both poor resolution and efficiency due to destacking. We have previously reported a stacking method for concentration of catecholamines in artificial dialysate, or Ringer's solution. However, pH-mediated sample stacking of other cations has not been investigated. In this report, pH-mediated stacking has been extended to eletripan, dofetilide, doxazosin, sildenafil, UK-103,320, UK-202,581, and CP-122,288. These compounds were chosen without prior structural screening except that they were cationic at the pH of our background electrolyte (BGE). Capillary electrophoretic behavior of samples in BGE is compared with those of samples in Ringer's solution with and without pH-mediated acid stacking. Results indicate that the peak heights and efficiencies for acid-stacked samples are increased compared to the unstacked samples in Ringer's solution or BGE. For example, the peak efficiencies for 5 s injections of eletriptan in BGE and Ringer's solution are 138,000 and 72,000 plates, respectively. In contrast, a 10 s injection of eletriptan followed by acid injection for 16 s produces a peak with 246,000 plates. Evaluation of the stacking effect was performed by comparison of the peak height at similar peak efficiencies for samples in Ringer's solution with and without stacking. Using this method, pH-mediated acid stacking provides a 10- to 27-fold sensitivity enhancement for the seven cations.     

Bistable behaviour in squeezed vacua: II. Stability analysis and chaos

Linear stability analysis and (numerical) investigation of the periodic and chaotic self-pulsing behaviour are presented for the Maxwell-Bloch equations of a bistable model in contact with a squeezed vacuum field. Effect of the squeeze phase parameter on the period doubling bifurcation that preceeds chaos is examined for the adiabatic and non-adiabatic regimes.     

Optical and photocatalytic properties of nanocrystalline TiO2 synthesised by solid-state chemical reaction

Nanoparticulate TiO₂ is of interest for a variety of technological applications, including optically transparent UV-filters and photocatalysts for the destruction of chemical waste. The successful use of nanoparticulate TiO₂ in such applications requires an understanding of how the synthesis conditions effect the optical and photocatalytic properties. In this study, we have investigated the effect of heat treatment temperature on the properties of nanoparticulate TiO₂ powders that were synthesised by solid-state chemical reaction of anhydrous TiOSO₄ with Na₂CO₃. It was found that the photocatalytic activity increased with the heat treatment temperature up to a maximum at 600 °C and thereafter declined. In contrast, the optical transparency decreased monotonically with the heat treatment temperature. These results indicate that solid-state chemical reaction can be used to prepare powders of nanoparticulate TiO₂ with properties that are optimised for use as either optically transparent UV-filters or photocatalysts.     

The effect of elevated temperature on conventional stationary phases used in SFC

Summary The effect of elevated temperatures on conventional packed bonded-phase columns used in supercritical-fluid chromatography (SFC) has been investigated. The impact of column conditioning temperature on the capacity factor, peak width, and peak asymmetry on octadecyl and propylamino columns from five commerical suppliers is reported.     

Mott–Hubbard transition in a 2D He fluid monolayer

We discuss recent observations of the heat capacity and magnetization of a fluid ³He monolayer adsorbed on graphite plated with a bilayer of HD. Approaching the density at which the monolayer solidifies into a commensurate solid, we observe an apparent divergence of the effective mass. However, the inferred values of F₀^a tend to a constant. We interpret this in terms of a Mott–Hubbard transition between a 2D Fermi liquid and a magnetically disordered solid occurring via the Brinkman–Rice–Anderson–Vollhardt scenario.     

First observation ofΩ * resonances

In a experiment at the CERN SPS charged hyperon beam using incident Ξ^?, we have obtained evidence for the production of two Ω^* resonances decaying into Ξ^?π⁺ K ^?, with the following parameters:M ₁=2251±12,Γ ₁=48±20 MeV/c², 78 ±23 events, andM ₂=2284±12,Γ ₂=26±23 MeV/c² 45±10 events. The first state is also observed as a 4.2σ effect in a subsample which contains an additionalK ⁺ orK ⁰ in the final state. Production cross sections and branching ratios to Ξ^* K ^? and Ξ^? K ^* are presented.     

A statistical model of horizontal auditory localization performance data

Horizontal localization experiments are used to evaluate the listener's ability to locate the position of a sound source, and determine how signal characteristics affect this ability. These experiments generate circular, bimodal, and repeated data that are challenging to statistically analyze. A two-part mixture of wrapped Cauchys is proposed for these data, with the effects of signal type and position on localization bias, precision, and front-back confusion modeled using regression. The model is illustrated using mid- (1.0-2.0 kHz) and high- (3.0-6.0 kHz) frequency narrow band noises localization collected among ten normal hearing listeners.