期刊文献+
共找到3篇文章
< 1 >
每页显示 20 50 100
反胶束萃取α-淀粉酶动力学分析
1
作者 张建国 陈晓明 +1 位作者 熊双丽 钱会芳 《食品工业科技》 CAS CSCD 北大核心 2012年第22期105-108,112,共5页
利用恒界面池,在双膜理论基础上建立了CTAB-异辛烷-正丁醇反胶团体系萃取α-淀粉酶的动力学模型。考察了不同起始酶活浓度、搅拌转速、pH、液相离子强度以及表面活性剂和助表面活性剂浓度对α-淀粉酶萃取表观传质系数kL的影响并对利用... 利用恒界面池,在双膜理论基础上建立了CTAB-异辛烷-正丁醇反胶团体系萃取α-淀粉酶的动力学模型。考察了不同起始酶活浓度、搅拌转速、pH、液相离子强度以及表面活性剂和助表面活性剂浓度对α-淀粉酶萃取表观传质系数kL的影响并对利用改变恒界面大小在判断传质控制机理方面进行了探讨。结果表明,起始酶活浓度在1105U.L-1到4420U.L-1条件下,残酶浓度对萃取时间常用对数曲线为一直线且斜率恒定,表明该动力学方程能够较好地描述α-淀粉酶萃取过程且与初始酶活浓度在无关;搅拌转速、水相pH、水相离子强度、表面活性剂和助表面活性剂浓度对萃取过程中α-淀粉酶表观传质系数kL都有影响,从而改变传质的机制。在规定的条件下,萃取速率对恒界面相对斜率随着pH增加而减小,当pH为9.9、10.8、11.9时,萃取过程分别以界面控制、混合控制、扩算控制为主,由此可见传质速率对恒界面大小变化相对斜率可以表征界面控制的影响程度。 展开更多
关键词 Α-淀粉酶 反胶束萃取 动力学 表观传递系数(kl)
下载PDF
硫酸镍体系中电解铜箔镀镍的动力学研究
2
作者 赵为上 《湖南有色金属》 CAS 2007年第4期12-13,58,共3页
通过电化学测试方法,初步探讨了硫酸镍体系中电解铜箔镀镍的某些动力学问题。结果表明,镍阴极电沉积的Tafel斜率为0.106 V,表观传递系数为0.58,交换电流密度为1.14×10-7A/cm2,电极反应表观活化能为61.1 kJ/mol。在0.5~0.6 V的电... 通过电化学测试方法,初步探讨了硫酸镍体系中电解铜箔镀镍的某些动力学问题。结果表明,镍阴极电沉积的Tafel斜率为0.106 V,表观传递系数为0.58,交换电流密度为1.14×10-7A/cm2,电极反应表观活化能为61.1 kJ/mol。在0.5~0.6 V的电位范围内,第一电子传递反应为电极反应的速度步骤控制,而在较高的阴极极化电位下,镍电沉积是混合步骤控制。 展开更多
关键词 硫酸镍体系 Tafel斜率 表观传递系数 交换电流密度 表观活化能
下载PDF
HIV相关认知功能障碍的疾病负担:全脑成像测定研究
3
作者 Ragin A.B. Storey P. +1 位作者 Cohen B.A. 李宏建 《世界核心医学期刊文摘(神经病学分册)》 2005年第5期40-41,共2页
Objective: To study whole-brain MR measures derived from diffusion tensor i maging and magnetization transfer imaging(MTI) for the in vivo assessment of cum ulative neuropathologic changes in HIV and to evaluate the q... Objective: To study whole-brain MR measures derived from diffusion tensor i maging and magnetization transfer imaging(MTI) for the in vivo assessment of cum ulative neuropathologic changes in HIV and to evaluate the quantitative imaging strategies with respect to cognitive status measures including the severity of d ementia and the degree of impairment in specific cognitive domains including att ention, memory, constructional abilities, and motor speed. Methods: Quantitative whole-brain measurements, including fractional anisotropy (FA), apparent diff usion coefficient (ADC), and magnetization transfer ratio (MTR), were derived fr om histograms and compared in HIV and control participants. Relationships betwee n the MR and cognitive status measures were examined. Results: Wholebrain FA and MTR were reduced in patients with HIV and correlated with dementia severity. Wh ole-brain MTR and ADC were correlated with psychomotor deficits. Evaluation of relationships between the studied MR measures indicated a correlation between A DC and MTR; FA was not correlated with either ADC or MTR. Conclusions: Findings from this investigation support the use of quantitative whole-brain MR measure s for evaluation of disease burden in HIV. Reductions in whole-brain fractiona l anisotropy and magnetization transfer ratio (MTR) distinguished HIV and contro l subjects, and these measures were associated with dementia severity. Relations hips were identified between whole-brain MTR and apparent diffusion coefficien t and psychomotor deficits. Combining these quantitative strategies in neuroimag ing examinations may provide more comprehensive information concerning ongoing c hanges in the brains of HIV patients. 展开更多
关键词 HIV相关 脑成像 磁化转移率 磁化传递成像 精神运动性 神经病理学 构建能力 表观弥散系数 弥散张量成像 认知范围
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部