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81.
Andrea Engl Benno Kunz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):257-261
Studies took place to investigate the effects of different nutrient conditions on the biosorption ability and selectivity of heavy metals by Saccharomyces cerevisiae. After having grown in media supplemented with additional glucose, ammonium, phosphate or cysteine, the yeast was exposed to an equimolar solution of lead, cadmium, zinc and copper. Lead removal from a mixed solution was significantly higher than that of copper, followed by zinc and cadmium. Generally, yeasts from cysteine-rich media showed greatest sorption capacity whereas phosphate addition influenced zinc selectivity. In addition, glucose, fructose and sucrose as carbon sources were examined. Cultures grown in glucose had a better uptake than those cultivated with fructose at an incubation time of 30 min. 相似文献
82.
本文研究了用金属有机物热发解法制备PLT8薄膜的工艺过程和基片对薄膜结构的影响,并且给出了铁电性能的测量结果。 相似文献
83.
84.
将Willenborg的超载残余应力场模型与裂尖形变动力学、裂尖表面析氢反应电化学动力学以及裂尖材料内部氢的扩散动力学和热力学相结合,建立了氢脆腐蚀疲劳裂纹扩展(CFCG)超载效应的定量描述模型,给出了超载对裂尖表面析氢电化学反应及裂尖氢扩展影响的一系列判据和表达式.用上述模型进行的预测表明,对于超高强度钢,当两次超载周次之间裂纹扩展长度ad远小于超载塑性区尺寸rpOL与恒载塑性区尺寸rpCLA之差,即ad<<rpOL-rpCLA时,CFCG会发生比空气疲劳还强烈的超载迟滞效应.而当ad>rpOL-rpCLA时,可能会发生超载加速效应.这种预测在后文中由试验的宏观规律与断口特征得到充分验证. 相似文献
85.
Heat-shock induction of heat-shock protein genes is due to a specific promoter element (the heat-shock element, HSE). This study used lacZ under HSE control (HSE-lacZ) to characterize HSE activity in Saccharomyces cerevisiae cells of different physiological states and differing genetic backgrounds. In batch fermentations HSE-lacZ induction by heat shock was maximal in exponential growth, and showed marked decline with the approach to stationary phase. Expression in the absence of heat shock was unaffected by growth phase, indicating that the growth-dependent expression of many yeast heat-shock genes uses promoter elements in addition to the HSE. Heat-induced expression was strongly influenced by the temperature at which cultures were grown. While basal, uninduced expression was constant during growth at different temperatures to 30 degrees C, induction by transfer to 39 degrees C was reduced by increases in growth temperature as low as 18-24 degrees C. Maximal HSE-lacZ induction (30- to 50-fold) was in cultures grown at low temperatures (18-24 degrees C), then heat shocked at 39 degrees C. Ethanol was a poor inducer. Mutations having little effect on HSE-lacZ expression included a respiratory petite; ubi4 (which inactivates the poly-ubiquitin gene); also ubc4 and ubc5 (which each inactivate one of the ubiquitin ligases involved in degradation of aberrant protein). pep4-3 increased both basal and induced beta-galactosidase about two-fold, probably because of slower turnover of this enzyme in pep4-3 strains. 相似文献
86.
A series of Mo–TiC alloys were heated in vacuum at 2473 K for 36 ks. First grain growth behavior was observed using a scanning electron microscope. Then effects of TiC addition on the strengths and ductility at low temperature were discussed from the viewpoints of chemical composition and grain structure.
Materials with TiC additions of not larger than 0.1% demonstrated a single-crystalline grain structure. Both yield and maximum strengths increased by TiC addition and consequently ductility was improved. 相似文献
87.
Spherical bulb fibre optic probes, developed and applied for bubble characterization in a bubble column and a slurry bubble column at high temperature, were investigated. The principle of operation of these new optical fibre probes is based on the difference in refractive indices between the gas and the liquid phases. The interaction between the gas bubbles and the fibre optic probes in a bubble column was studied using photographic techniques. The first objective of these experiments was to study the response of the sensors upon contact with gas bubbles of various sizes. The second objective of this study was to establish, under controlled situations, the optical probe bubble detection performance and ability for local quantitative measurements of the bubble rise velocity and the gas hold-up. 相似文献
88.
The complete crystallographic orientation dependence of the growth rate for GaAs low pressure organometallic vapor phase epitaxy
(LPOMVPE) is determined using a previously described semi-empirical model. A set of LPOMVPE growth rate polar diagrams is
presented for reactor temperatures near 550°C as well as near 700°C. Also, the variation of the growth rate polar diagrams
as a function of process variables is given. The experimental data utilized in the semiempirical model was attained using
a typical horizontal reactor LPOMVPE system and typical LPOMVPE process parameters. 相似文献
89.
90.
Abdulla A. Shaikh S. M. Javaid Zaidi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,56(2):139-145
The absorption and reaction of oxygen in aqueous alkaline solutions of sodium dithionite has been experimentally investigated in a novel gas-liquid contactor. The novel gas-lift bubble column contactor was used to study the kinetics over wide ranges of reactant concentrations, temperature, and pH. The oxygen-sodium dithionite reaction was found to be first-order with respect to dithionite in the range of dithionite concentration < 0.1 M, and second-order in the range of dithionite concentration > 0.1 M. The reaction with respect to oxygen was found to be zero-order for all dithionite concentrations. These results and experimental investigations of the effect of solution alkalinity and temperature on the reaction rate are consistent with previous findings obtained in different gas-liquid contactors. The results thus confirm the feasibility of using the gas-lift bubble column for the kinetics of gas-liquid reactions. 相似文献