厌氧反应除硫酸盐的新工艺

对目前消除硫酸盐对厌氧反应影响的几种方法进行了归纳评价 ,并提出了硫酸盐还原 微电解除硫化物 厌氧反应的新思路 ,从理论上分析了这种新工艺的特点 ,同时提出了存在的问题及对策。     

利用闲置设备生产均三甲苯的探索

介绍了利用闲置设备工业化生产均三甲苯的方法,并从理论上研究了生产的可行性。探讨了提高均三甲苯产品纯度和收率的途径。     

新一代静止图像压缩标准JPEG2000

随着多媒体应用领域的扩展,传统的图像压缩技术已无法满足人们对多媒体图像的要求,各种图像压缩格式应运而生,如JPEG、MPEG-4VTC、PNG等。其中新一代ISO/ITU-T静止图像压缩标准JPEG2000成为热点。文章重点介绍JPEG2000图像编码系统的基本思想及其特性。     

Facile optical resolution of amino acid esters via hydrolysis by an industrial enzyme in organic solvents

Racemic amino acid esters were optically resolved via hydrolysis in organic solvents by the catalysis of an industrial alkaline protease, “Alcalase”. The products which were composed mainly of L-amino acids were insoluble and easily separated by filtration. The activity of the enzyme and enantiomeric excess of the products were significantly dependent on the nature of solvent and the water content in the reaction media. Generally, high values of enantiomeric excess were obtained at low water contents. Many natural and unnatural amino acids were resolved by this method.     

Preparation of fatty acid methyl esters for gas-chromatographic analysis of lipids in biological materials

Theoretically, preparation of fatty acid methyl esters (FAMEs) deals with reversible chemical reactions in a complex system. Methodologically, there are numerous ways, generally characterized by the type of catalysts used and steps involved. Although there are more than a half dozen common catalysts, the majority fall into either acidic (HCl, H₂SO₄ and BF₃) or alkaline types (NaOCH₃, KOH and NaOH), with each having its own catalytic capability and application limitations. In terms of steps, many conventional methods, including those officially recognized, consist of drying, digestion, extraction, purification, alkaline hydrolysis, transmethylation/methylation and postreaction work-up. Although these methods are capable of providing reliable estimates if some precautions are taken, they are cumbersome, time-consuming and cost-inefficient. A new approach has been to transmethylate lipidsin situ. Due to its simplicity, high sensitivity, comparable reliability and capability to determine total fatty acids, the method of direct transmethylation is finding a unique place in lipid determination. Regardless of which method is used, quantitative methylation requires chemists to take precautions at every step involved, particularly during FAME formation and subsequent recovery steps. Evidently, there is an urgent need for more systematic studies, guided by the chemical principle of reactions involved and physicochemical properties of regents and end products, into factors affecting these steps. Hopefully, this will lead to an improved method, which measures lipid composition in biological materials not only with high accuracy but also with high efficiency and minimum costs.     

过一硫酸的合成及其在铀水冶中的应用

文章介绍了选择过一硫酸合成的最佳条件及进行生产的可行性。介绍了过一硫酸用于含铀煌斑岩、辉绿岩、花岗岩及炭板岩矿石提取铀时,与常规酸浸方法对比,有很好的经济效益和对环境的保护价值。     

由1,4-萘醌催化合成1,4-二烷氧基萘-2,3-二甲腈

研究了以 1 ,4-萘醌为原料 ,通过溴代、氰化和 O-烷基化三步合成 1 ,4-二烷氧基萘 -2 ,3 -二甲腈。在溴代反应中以溴化试剂代替液溴 ;在氰化和 O-烷基化反应中以溴化十二烷基三甲基铵 (DTMAB)和聚乙二醇(PEG)作为相转移催化剂 ,并采用正交设计法考察了相转移催化剂、固体碱、反应温度等因素对反应的影响 ,其中氰化产物收率达 88.7%。     

不同品位高钛渣对沸腾氯化工艺的影响

分别以94％品位高钛渣和90％品位高钛渣为原料，采用沸腾氯化工艺制备粗TiCl4，分析了两种品位高钛渣对沸腾氯化工艺的影响。结果表明：94％品位高钛渣由于其活性低而对沸腾氯化工艺的影响较大。     

Drying of Probiotics: Optimization of Formulation and Process to Enhance Storage Survival

This work describes how probiotic bacteria can be dried at low temperature in two steps, combining spray drying and vacuum drying, in order to enhance their survival during storage. A sufficient number of dried probiotics survived storage for more than 3 months at 30°C, if an appropriate combination of protein and carbohydrate was selected as carrier and storage conditions were maintained optimal. The use of soy protein and maltodextrin or skim milk and arabic gum resulted in the best survival rates of probiotics during storage. No evident difference was found between different spray dryer configurations, although a cocurrent flow was preferred.     

Enzymatic Browning in Apple Pulps

Enzymatic browning in Golden Delicious apple pulp was studied as related to degree of ripeness and temperature (3.5–31°C). Green apple pulp showed the highest rate of browning. This was attributable to differences in ascorbic acid (AA) content and polyphenoloxidase activity in young fruits. The rate of browning determined by CIE L* measurements followed complex temperature dependent kinetics, represented by a multiple linear effects with log time. Equal changes in L* parameter yielded straight lines in a log temperature vs log time plot. Inhibition with AA caused an initial slow rate of browning and a well defined break point associated with exhaustion of antioxidant properties of the AA. The greater the AA concentration the longer the initial period.