Substituted glycals as probes of glycosidase mechanisms

D-Glucal and a series of substituted derivatives have been tested as substrates, inhibitors and inactivators of the Agrobacterium faecalis beta-glucosidase in order to probe structure/function relationships in this enzyme. D-Glucal is shown to be a substrate (kcat = 2.3 min-1, Km = 0.85 mM) undergoing hydration with stereospecific protonation from the alpha-face to yield 2-deoxy-beta-D-glucose. 1-Methyl-D-glucal surprisingly serves as only a poor substrate (kcat = 0.056 min-1, Km = 57 mM), also undergoing protonation from the alpha-face. 2-Fluoro-D-glucal, however is completely inert, as a result of inductive destabilisation of the oxocarbenium ion-like transition state for protonation, and functions only as a relatively weak (Ki = 24 mM) inhibitor. Similar behaviour was seen with almond beta-glucosidase and yeast alpha-glucosidase and for the interaction of 2-fluoro-D-galactal with Escherichia coli beta-galactosidase. A series of of alpha, beta-unsaturated glucal derivatives was also synthesised and tested as potential substrates, inhibitors or inactivators of A. faecalis beta-glucosidase. Of these only 1-nitro-D-glucal functioned as a time dependent, irreversible inactivator (ki = 0.011 min-1, Ki = 5.5 mM), presumably acting as a Michael acceptor. Electrospray mass spectrometric analysis revealed multiple labeling of the enzyme by this inactivator, lessening its usefulness as an affinity label. Less reactive Michael acceptor glycals which might have been more specific (1-cyano-, 2-cyano-, 1-carboxylic acid, 1-carboxylic acid methyl ester) unfortunately did not function as inactivators or substrates, only as relatively weak reversible inhibitors (Ki = 3-96 mM).     

Improvement of some pharmaceutical properties of drugs by cyclodextrin complexation. 4. Chlorpromazine hydrochloride

This study is a retrospective review of admissions, discharge records and blood culture results of neonates admitted to the Neonatal Intensive Care Unit of Korle Bu Teaching Hospital in Accra, from the first of January 1991 to the 31st of December 1992. During this two year period there were 443 positive blood cultures. Ninety percent of the blood cultures were from babies born in Korle Bu Teaching Hospital, thus making the incidence of neonatal bacteraemia 22.2 per 1000 live births. The overall mortality rate was 37.2%. Gram negative bacteria accounted for 70.9% and Gram positive bacteria for 29.1% of all neonatal bacteraemia. The most common isolates were Enterobacter species 29.6%; Streptococcus faecalis 14.4%; Staphylococcus aureus 10.8%; Acinetobacter species 9.5%; Klebsiella species 9% and Escherichia coli 8.8%. It is concluded that the incidence of neonatal bacterial sepsis is high in our hospital and is associated with a very high mortality rate. There is thus an urgent need to institute appropriate preventive and therapeutic measures.     

Reductions in self-injury produced by transcutaneous electrical nerve stimulation

Transcutaneous electrical nerve stimulation is used to reduce pain but also may be useful for self-injurious behavior (SIB). In the current investigation, a microcurrent electromedical device, classified as a transcutaneous electrical nerve stimulator (TENS), was applied with a man with Down syndrome who displayed SIB that persisted in the absence of social contingencies. Although clinically significant results were not maintained, a clear difference in the rates of SIB during active and inactive TENS was observed.     

基于安全人机学的驾驶作业疲劳评价模型研究

驾驶作业涉及人-汽车-环境,是较复杂的半自动化人机系统,驾驶作业疲劳是由多种因素造成的,对其评价存在不确定性.建立一种多因素多等级的评价模型,对驾驶作业疲劳程度进行总体评价,对致劳因素进行排序,为驾驶疲劳的评价及预防和减轻驾驶疲劳提供一种方法.     

芳纶纤维在轮胎工业中的应用

笔者主要介绍了芳纶纤维(包括长纤维和短纤维)的性能及其在轮胎工业的应用，同时简要叙述了芳纶纤维的分类和发展历史。     

Investigation of Aerosol Penetration Through Individual Protective Equipment in Elevated Wind Conditions

A methodology to characterize particle penetration characteristics of individual protective equipment (IPE) under elevated wind conditions was developed. Performance of a complete IPE system can be determined from the knowledge of the performance characteristics of the IPE subsystems, or components. Here, particle penetration characteristics of a cylindrical-shaped component, consisting of an outer fabric sleeve enclosing an inner appendage, were studied as a function of particle size and ambient wind conditions. A component particle penetration model was developed by combining a potential flow model to calculate flow through and around a component with a filtration model. The filtration model combines classical filtration theory with simple bench-top experiments to determine net particle penetration. The component model predictions of particle penetration through a cylindrical component suggest that its filtration performance is strongly dependent on particle size and ambient wind velocities. To test model predictions, wind-tunnel experiments were conducted over an ambient wind velocity range of 10–80 mph (5–40 m s^?1) and particle diameter range of 10 nm to 2 μm. The experimental results validated model predictions of particle penetration through a cylindrical component. The component model can be extended to model the integrated IPE system considering it to be composed of a combination of cylindrical components.

Copyright 2013 American Association for Aerosol Research     

芳纶橡胶输送带的接头强度研究

针对芳纶橡胶输送带接头强度保持率低的问题,本研究以国内外芳纶橡胶输送带接头方案为基础,采用指型插接方案,系统性地探究了指型长径比、贴胶厚度、织物增强层结构等因素对接头强度的影响。实验证明接头强度随长径比的增大而升高;贴胶厚度在1mm时接头强度达到最大,此后接头强度随贴胶厚度的增加而降低;织物增强层沿经向放置的接头强度提高87%,接头强度保持率达到带体强度的60%。     

节能型活性染料的发展状况

综述了开发节能型活性染料的重要性.重点介绍了适用于冷轧堆染色、小浴比染色和涤/棉一浴法染色用活性染料以及高固色率活性染料的发展状况;通过提高染料的耐碱性、溶解度、染深性以及固着率等方面来达到节能减排的目的.     

CY-61100车床尾座铸造过程仿真优化研究

对CY-61100车床尾座铸件充型及凝固过程进行了数值模拟及优化研究。根据模拟的结果及铸造缺陷预测,改进及优化了尾座浇注系统,在工厂实际浇铸生产应用中取得了良好效果。并由此建立了铸造过程CAE仿真优化技术与传统铸造工艺设计有效结合的先进铸造工艺设计模式。