REFRACTIVE INDEX OF SUPERCRITICAL CO 2 -ETHANOL SOLVENTS

In-line analysis of refractive index is required for efficient design and monitoring of supercritical fluid extraction and precipitation processes. In the present work, a robust method has been developed based on measurements of laser beam deviation using an interferometer and image processing system. Data on refractive index of CO 2 -ethanol mixtures were obtained at pressures between 70 and 200 bar and temperatures between 308 and 363 K, for continuous flow of premixed solvents and, in addition, for equilibrium gas phase below the mixture critical pressure. The refractive index of a mixture is a linear function of ethanol mole fraction and can adequately describe mixing and phase behavior in the vessel. For pure CO 2 , refractive index was determined as a function of pressure and density and its Lorentz-Lorenz functions determined.     

Redox properties of molten salts for methane activation

Molten salt mixtures have been tested in a redox mode as catalysts for the activation of methane at 750 °C. It is found that after pre-treatment with dioxygen a transition metal halide/ sodium vanadate melt can convert methane selectively to C₂₊ products in the absence of molecular oxygen. The melt can be reactivated by passing dioxygen. Electron paramagnetic resonance studies of the quenched samples showed that the transition metal ions are reduced by methane and can be reoxidised by dioxygen. It is also found that higher C₂₊ selectivity, C₂₊ yield and C₂H₄/C₂H₆ ratio are promoted by added transition metal chlorides and, surprisingly, also by the corresponding metal bromides. It supports the suggestion that surface modification by halogen is more important than gas radical reactions. Comparison of the molten mixtures under redox and cofeed conditions showed that the former gave a higher C₂₊ selectivity, but no oxygenated products whereas formaldehyde was only detected in the cofeed conditions.     

Studies into the swelling of gelatine films using a scanning fluid dynamic gauge

Fluid dynamic gauging (FDG) has been developed to measure both the thickness and strength (cohesive or adhesive) of a range of fouling deposits, in situ and in real time. We report the development of a scanning FDG device (sFDG) with fully automated movement and deposit thickness measurement. Thickness-time profiles can be collected for several points on the surface over the course of a single experiment. sFDG is employed here to study the cleaning kinetics of model gelatine fouling layers when contacted with aqueous solutions at different pHs and temperatures, and with a commercial dishwasher formulation containing enzymes.Solution pH is an important parameter: above ～pH 10.6 the gelatine layers swell markedly, due to protonation of the amino acids proline and hydroxyproline, and subsequent charge repulsion within the gel. An unusual behaviour (discontinuity) is reported during swelling in the commercial formulation. It is proposed that hydration of the deposit and an extent of swelling (ratio of the final to the initial deposit thickness) of ～12 is necessary before the enzymes can promote deposit removal.     

Adaptive feedforward cancellation of sinusoidal disturbances in superconducting RF cavities

A control method, known as adaptive feedforward cancellation (AFC), is applied to damp sinusoidal disturbances due to microphonics in superconducting radio frequency (SRF) cavities. AFC provides a method for damping internal and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity for an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.     

Decision makers conceive of their choices as interventions.

Causal considerations must be relevant for those making decisions. Whether to bring an umbrella or leave it at home depends on the causal consequences of these options. However, most current decision theories do not address causal reasoning. Here, the authors propose a causal model theory of choice based on causal Bayes nets. The critical ideas are (a) that people decide using causal models of the decision situation and (b) that people conceive of their own choice as an intervention. Four corroborating experiments are reported. The first 2 experiments showed that participants chose on the basis of the causal structure underlying a choice scenario rather than the statistical relation among actions and outcomes. Experiments 3 and 4 showed that participants treated choices and interventions similarly. They also suggest that decision makers use causal models to derive inferences about expected outcomes. Boundary conditions on causal decision making and examples of faulty causal inferences in choice (e.g., self-deception) are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrochemically assisted photocatalytic degradation of methyl orange using anodized titanium dioxide nanotubes

The TiO₂ nanotubes have demonstrated potential in the photoelectrocatalytic degradation of methyl orange dye (MO). TiO₂ nanotubes were prepared using anodization of titanium foils in phosphoric acid (PA) and ethylene glycol (EG) by mechanical stirring and ultrasonic method. The TiO₂ nanotubes prepared in EG under ultrasound followed by annealing in nitrogen atmosphere showed higher activity towards dye degradation as compared to the stirring method. Dye degradation shows improved activity under an external bias compared to degradation performed in the absence of an external bias. An increase in the external bias from +0.0 to +0.1 V versus calomel electrode (SCE) is sufficient to improve the degradation rates of MO from 22% to 57% within the first 10 min. At +0.1 V, a complete degradation of 40 μM MO is observed within 30 min. The addition of oxidants such as oxygen and hydrogen peroxide demonstrate improvement in the MO degradation.     

A continuum model of the dynamics of coupled oscillator arrays forphase-shifterless beam scanning

The behavior of arrays of coupled oscillators has been previously studied by computational solution of a set of nonlinear differential equations describing the time dependence of each oscillator in the presence of signals coupled from neighboring oscillators. The equations are sufficiently complicated in that intuitive understanding of the phenomena which arise is exceedingly difficult. We propose a simplified theory of such arrays in which the relative phases of the oscillator signals are represented by a continuous function defined over the array. This function satisfies a linear partial differential equation of diffusion type, which may be solved via the Laplace transform. This theory is used to study the dynamic behavior of a linear array of oscillators, which results when the end oscillators are detuned to achieve the phase distribution required for steering a beam radiated by such an array     

用微硅层析法制作的微型硅传感器

主要介绍1种用硅的微机械加工技术研制的硅电容式传感器，采用电容层析法(ECT)技术可检测尺寸为50μm左右的微小粒子。其中的主要技术有硅材料的微机械加工技术，特厚光刻胶的匀胶曝光技术，微集成电镀技术。