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排序方式: 共有36条查询结果,搜索用时 190 毫秒
1.
The biotransformation of oxazepam by Bifidobacterium bifidum was studied. The major metabolite was purified by chromatographic methods and found to be desmethyldiazepam using NMR, IR and other physicochemical data.  相似文献   
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Laboratory-scale ageing and poisoning procedures were performed on selected diesel catalysts. The results showed that phosphorus poisoning together with high temperature ageing has a strong effect on the catalytic activity and microstructure of platinum containing catalysts. Phosphorus poisoning contaminated the catalysts resulting in phosphate formation, e.g. CePO4 and AlPO4. Poisoning and air ageing increased platinum particle-size and washcoat grain-size.  相似文献   
4.
The effect of metal-composite debonding on low-velocity impact response, i.e. on contact force–central deflection response, deformation profiles and strains on the free surfaces was studied. We focused on type 2/1 fibre metal laminate specimens made of stainless steel and carbon fibre epoxy layers, and tested them with drop-weight impact and quasi-static indentation loadings. Local strains were measured with strain gauges and full-field strains with a 3-D digital image correlation method. In addition, finite element simulations were performed and the effects of debonding were studied by exploiting cohesive elements. Our results showed that debonding, either the initial debonding or that formed during the loading, lowers the slope of the contact force–central deflection curve during the force increase. The debonding formation during the rebound phase was shown to amplify the rebound of the impact side, i.e. to lower the ultimate post-impact deflection. The free surface strains were studied on the laminate’s lower surface at the area outside the debond damage. In terms of in-plane strains, debonding formation during impact and indentation, as well as the initial debonding, lowered the peripheral strain and resulted in a positive change in the radial strain.  相似文献   
5.
Proposes 10 models for predicting a student's final grade placement in a computer-assisted instruction curriculum from the time the student spends taking lessons. Using data from approximately 2,000 elementary students, the models are tested both for ability to predict final grade placement and for ability to describe all points observed throughout the year. Two of the simplest models, using only the most recent point and parameters estimated for the whole group, are best at prediction. The power function model with all parameters estimated individually for each student, while relatively poor at prediction, is best for describing all observed points. Several methods for predicting the amount of time a student will spend taking lessons during a year are also tested. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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Kröger  V.  Kanerva  T.  Lassi  U.  Rahkamaa-Tolonen  K.  Lepistö  T.  Keiski  R. L. 《Topics in Catalysis》2007,42(1-4):433-436
Powdered ZSM-5 and Pt/ZSM-5 catalysts were studied as fresh and after two treatments: hydrothermal ageing and phosphorus poisoning in hydrothermal conditions. The results showed that the deactivating effect of phosphorus was stronger than the effect of the hydrothermal treatment alone. Phosphorus had accumulated in the samples during the ageing. The decrease in specific surface area and increase in Pt particle size indicated the possible reasons for deactivation.  相似文献   
7.
Coeliac disease is triggered by exposure to the prolamin protein fraction of wheat, barley, or rye. The prolamin content of five lager beers and one wheat beer were analyzed by sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting and seven lager beers and three wheat beers were analyzed by enzyme‐linked immunosorbent assay (ELISA). Most of the lager beers were made from barley and some had varying amounts of rice or corn as adjuncts. One of the beers was “gluten‐free”, having been produced from corn and buckwheat without barley. The lager beer samples were gel‐filtered before ELISA or SDS‐PAGE analysis. Prolamin proteins were found in all but one beer which was made of corn, rice and barley and which was not the “gluten‐free” beer. ELISA analysis was done using a commercially available gluten assay kit. For lager beers, a barley prolamin standard for ELISA was propanol‐extracted from barley malt instead of using the prolamin standard of the gluten assay kit. As expected, the wheat beers contained much higher amounts of prolamins than the lager beers. The samples were studied by SDS‐PAGE to identify different prolamin fractions. Proteins having a relative molecular mass in the range of 8000–17,000 and 38,000 and above were detected in immunoblotting by the prolamin sensitive antibody in the lager beers.  相似文献   
8.
Use of a water-ring gas blower as a stage of the “wet removal” of dust from gases is examined. A procedure is presented for simplified analysis of the required excess pressure created by the gas blower, during which no liquid enters the gas cavity of the impeller and there is no reduction in the operating characteristics of the gas blower. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 2, pp. 28–29, February, 2007.  相似文献   
9.
Two series of titanium dioxide, TiO2, powder were prepared at a temperature of 50 °C without any catalyst. The effects of 2-propanol and water contents on the formation of crystalline powder mixture of anatase and brookite were systematically studied. The characteristics of produced powder were determined by employing X-ray diffraction, transmission electron microscopy, nitrogen adsorption test and Fourier transform infrared spectroscopy.  相似文献   
10.
The structure and the operation of the model for the brushless excitation system for a synchronous machine are presented. The nonlinear model including the excitation machine, the AC-AC converter supplying the excitation machine and the rectifier diode bridge, mounted on the rotor, is based on a state machine. The states are defined by current commutation in the power electric devices. The operation of the excitation system model is verified by measurements with a slip-ring machine imitating the excitation machine. The excitation system model is integrated and simulated as a part of a synchronous machine simulator.  相似文献   
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