混合表面活性剂存在下盐酸羟胺-硫酸高铁铵法分光光度测定药品制剂中的青霉素

本文报导了青霉素在碱性条件下于72℃恒温水浴中与羟胺形成羟肟酸盐,而后酸化生成羟肟酸,利用羟肟酸在混合表面活性剂吐温——CTMAB等体积混合液的存在下与Fe(Ⅲ)形成稳定的紫红色络合物,从而借此显色反应作分光光度来测定药品制剂中青霉素的含量。紫红色络合物的最大吸收波长位于480nm处,摩尔吸光系数为8.7×10~3l·mol~(-1)·cm~(-1)。青霉素含量介于0.42～2.11mg/25ml范围内确准地遵守比尔定律。紫红色络合物的色泽能稳定4小时以上,方法灵敏、简便,准确度与精密度均较好。     

应用神经网络理论的计算机通信网迟延新算法

计算机网络最小平均迟延的求解实质上是一个联合优化问题。进一步的分析表明，它可以近似为一个二次型优化问题。我们利用一种具有全局收敛性质的神经网络模型解决了这一问题。计算结果表明，这种方法是可行而有效的。     

Biosynthesis of selenosubtilisin: A novel way to target selenium into the active site of subtilisin

Glutathione peroxidase （GPx, EC1.11.1.9）, an important anti-oxidative selenoenzyme, can catalyze the reduction of harmful hydroperoxides with concomitant glutathione, thereby protecting cells and other biological issues against oxidative damage. It captures considerable interest in redesign of its function for either the mechanism study or the pharmacological development as an antioxidant. In order to develop a general strategy for specifically targeting and operating selenium in active sites of enzymes, the catalytically essential residue selenocysteine （Sec） was first successfully bioincorporated into the catalytic center of subtilisin by using an auxotrophic expression system. The studies of the catalytic activity and the steady-state kinetics demonstrated that selenosubtilisin is an excellent GPx-like biocatalyst. In comparison with the chemically modified method, biosynthesis exhibits obvious advantages： Sec could be site-directly incorporated into active sites of enzymes to overcome the non-specificity generated by chemical modification. This study provides an important strategy for specifically targeting and operating selenium in the active site of an enzyme.     

INTERFACE SPIN-WAVE OF COUPLED SEMI-INFINITE MAGNETIC SUPERLATTICE

The interface spin-wave (ISW) modes or coupled semi-in-finitemagnetic superlattices separated by a nonmagnetic layer have been studied, by use of the magnetostatic method. A general expression of the ISW dispersion relation is obtained. Detailed calculations are performed in the special case where the ttwo semi-infinite superlattices is considered to be identical and the external magnetic field, is parallel or perpendicular to the surface of the. layers. Some results about ISW modes are discussed.     

气相色谱法测定工业甘油含量

本文使用Ｃｈｒｏｍｏｓｏｒｂ—１０１固定相作为柱填料，采用气相色谱法测定水溶液中甘油。操作过程简便，测定结果准确。实验选择了最佳汽化温度、柱温和载气流速。     

宽V带无级变速器的设计功率的确定

阐明了恒功率调速与恒扭矩调速时设计宽V带无级变速器所应采用的设计功率。并介绍了研制的螺旋副式双向调节调速机构。     

集值锥映象不动点指数的若干结论及应用

本文利用实Banach空间中锥的拟正规性(见[1])给出了集值锥映象不动点指数的若干结论及不动点定理,这些结果是[2]中相应结果的改进。     

电位滴定在憎液胶体表面电荷密度研究中的应用

首先讨论了进行电位滴定实验的时候,逐次加入的滴定剂中决定电位离子的数量与被分析憎液胶体分散相粒子表面电荷密度之间的定量关系式,比较了文献中几种不同的零电点的测定方法,进而肯定了其中盐滴定法的可行性.然后,文章介绍了滴定过程中,不溶于水的氧化物或含氧氢氧化物胶体分散相与电解质溶液之间的慢速质子迁移现象,介绍了这一过程的机理以及它对从电位滴定得到的表面电荷密度σ_0值的影响,提出防止这一影响,区分慢速质子迁移与表面电离、表面络合反应对表面电荷的贡献,研究表面吸附机理的实验方法.