Redox kinetics of benzene oxidation to maleic anhydride

Steady state kinetics of the oxidation reaction have been determined with the help of a gradientless semi-differential, fixed-bed reactor. The Mars and van Krevelen phenomenological model satisfactorily correlates the experimental data but a modification of the Langmuir-Hinshelwood model taking into account partial coverage of the catalyst surface with reaction intermediates is preferred. Transient kinetics have been studied with a new automated periodic-pulse reactor, directly connected to a gas chromatograph. The response of a catalyst (essentially V₂O₅–MoO₃) to reduction and oxidation has been investigated. The rate of bulk (lattice) oxygen utilization as well as the degree of carbon coverage are estimated by this technique. Selectivity is dependent on the oxidation state of the catalyst: high partial pressure of either benzene or oxyen and high temperatures are detrimental to selectivity.     

Ce对Fe-Cr合金高温氧化行为的影响

Fe-15Cr 和 Fe-30Cr 合金在1000至1200℃空气中氧化时,表面富铁氧化伤的发展导致保护性Cr_2O_3层衰退,氧化速率增大。添加 Ce 可延迟衰退过程的发生,从而大幅度减低氧化速率。随氧化温度和合金成份变化,Cr_2O_3层衰退的开始时间和发展特征随之改变,Ce 对氧化行为的影响因而呈现出规律性的变化。研究发现,合金中 Cr 的内氧化使 Cr_2O_3层形成小舌包卷合金并使其氧化成富铁氧化物。这是Cr_2O_3层衰退的原因之一。含 Ce 合金中 Ce 的优先内氧化则降低自氧化层进入合金的氧浓度,抑制Cr 的内氧化。氧浓度降低还能促进 Si 的内氧化物在氧化层/合金界面集聚。     

An amorphous silicon-based one-unit photovoltaic electrolyzer

A one-unit photovoltaic electrolyzer, fabricated from double-stacked amorphous silicon cells (pin-pin), is described. A solar energy conversion efficiency to hydrogen of 2.6% has been achieved, which, with recent technological developments, can be raised to 6%. A one-unit array (with storage) capable of supplying solar hydrogen to power tractors on the average farm would give rise to a cost of ca. 6.2¢/kWh, using the expected 1990 value of $1 per peak W for amorphous silicon photovoltaics. The cost of the hydrogen derived from the system is ca. two to three times that of conventional gasoline per gallon equivalent.     

Flow visualization during solid-liquid phase change heat transfer II. Melting in a rectangular cavity

The results of flow visualization in a rectangular test cell during the melting of n-octadecane are reported. The experiments provide information on buoyancy-induced fluid motion and its effect on the shape of the solid-liquid interface.     

Multistage linear estimation using partitioning

The estimation algorithm described in this note solves the linear estimation problem as a two-stage estimator consisting of two consecutive Kalman filters. The interconnections between this estimator structure and the more familiar one-stage optimal Kalman filter are discussed. Applications to decentralized estimation, bias estimation, and parameter identification are described.     

Influence des agrégats sur le rendement d'un réacteur à transport pneumatique

The evaluation of the performance of a pneumatic transport reactor operating at low gas velocity and high solid volumic concentration is presented. This reactor has a high length-diameter ratio and can be considered as a representative tube of a multitubular reactor with gas—solid suspension circulating inside the tubes. Two experimental techniques have been used: ozone adsorption or catalytic ozone decomposition on a porous solid. The agregation of the particles, which has an important effect on the hydrodynamics, does not contribute to the diffusional resistance. The design of an industrial reactor should be accordingly relatively simple.     

An effectiveness trial of a dissonance-based eating disorder prevention program for high-risk adolescent girls.

Efficacy trials indicate that an eating disorder prevention program involving dissonance-inducing activities that decrease thin-ideal internalization reduces risk for current and future eating pathology, yet it is unclear whether this program produces effects under real-world conditions. The present effectiveness trial tested whether this program produced effects when school staff recruit participants and deliver the intervention. Adolescent girls with body image concerns (N = 306; M age = 15.7, SD = 1.1) randomized to the dissonance intervention showed significantly greater decreases in thin-ideal internalization, body dissatisfaction, dieting attempts, and eating disorder symptoms from pretest to posttest than did those assigned to a psychoeducational brochure control condition, with the effects for body dissatisfaction, dieting, and eating disorder symptoms persisting through 1-year follow-up. Effects were slightly smaller than those observed in a prior efficacy trial, suggesting that this program is effective under real-world conditions, but that facilitator selection, training, and supervision could be improved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed onset of Alzheimer's disease with nonsteroidal anti-inflammatory and histamine H2 blocking drugs

Factors that modify onset of Alzheimer's disease (AD) may be revealed by comparing environmental exposures in affected and unaffected members of discordant twin pairs or sibships. Among siblings at high risk of AD, sustained use of nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with delayed onset and reduced risk of AD. After adjustment for use of NSAIDs, there was minimal effect on onset with reported history of any of three common illnesses (arthritis, diabetes, or acid-peptic disease). However, independent of exposure to NSAIDs, onset was unexpectedly delayed in those reporting extended use of histamine H2 blocking drugs. Randomized clinical trials will be needed to affirm the utility of these drugs for prevention, but the present findings may have implications for pathogenesis: because NSAIDs block the calcium-dependent postsynaptic cascade that induces excitotoxic cell death in NMDA-reactive neurons, and because histamine potentiates such events, excitotoxicity may deserve additional investigation in AD.     

Solutions approximatives pour l'absorption dans un solide poreux

The adsorption of a solute by porous solid particles can be represented with good accuracy by a simple approximate formula of the “penetration” type. The corresponding “kinetic” model makes use of average lumped concentrations of the two phases. It can be applied, by introduction of the fluid—solid slip velocity, either to the agitated vessel, or to the co- or counter-current moving bed. With the external specific area of the particle sample, the formula also represents correctly the, absorption by particles of any shape and any size distribution.     

步行车辆在坡道上行走时的稳定性分析

本文系统地分析了步行车辆在坡道上行走时的稳定性问题。利用本文的分析方法,可以方便地求解步行车辆沿纵向坡道、横向坡道以及在坡道上沿任意方向行走时的稳定性,还可以方便地求出步行车辆能够稳定行走的最大纵向坡度和最大横向坡度以及能够在坡道上沿任意方向稳定行走时坡道的最大坡度角。