Autolysis and the endogenous proteinases characterised in beardless barb (Anematichthys apogon) muscle

Beardless barb is a common fish species used in fermentation of fish paste Ka-pi-plaa. Autolytic profile of beardless barb muscle showed the maximum autolysis was at 50 °C, at both acidic and alkaline pH values. With augmentation concentration of NaCl, autolytic activity slightly decreased. Endogenous proteinases isolated from fish muscle in crude extract forms were also characterised. The acidic proteinases had optimum activity at pH 3.0 and 50°C, and they showed higher proteolytic activity than the alkaline proteinases which were optimally active at pH 9.0 and 50 °C. Proteinases in peak at pH 3.0 were inhibited by pepstatin A, but those in peak at pH 9.0 were highly inhibited by PMSF, TLCK and soybean trypsin inhibitor, suggesting that both aspartic and serine proteinases were existed in beardless barb muscle. The proteinases were stable in pH range of 2.0-5.0 but unstable at the temperatures higher than 40 °C. NaCl suppressed the proteolytic activity, ATP activated the proteinase activity, while CaCl₂, MgCl₂ and CoCl₂ exhibited no influence on the activity. The results implied that cathepsin D is the predominant proteinase responsible for autolysis in beardless barb. The findings were useful to improve the processing and qualities of Ka-pi-plaa product using beardless barb as raw material.     

A first-principles investigation on mechanical and metallic properties of titanium carbides under pressure

The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system.     

简体接管边缘应力区局部减薄处应力特征

参考《压力容器定期检验规则》第40条,采用有限元方法计算了筒体接管边缘应力区局部减薄处的应力分布,得到了局部减薄处凹坑的尺寸与位置对应力的影响趋势,讨论了应力集中系数随尺寸变化的规律,为筒体接管边缘应力区局部减薄处的强度评定提供了一定的计算依据。     

铌和钨对γ-TiAl基合金热稳定性的影响

采用光学显微镜(OM)，扫描电镜(SEM)，X射线衍射研究了TiAl—5Nb，TiAl—14．3Nb，TiAl—8Nb—1W，TiAl—12．3Nb-2W四种合金片层组织在1000℃的热稳定性。结果表明，TiAl—12．3Nb-2W合金热稳定性最好，但合金元素对TiAl基合金热稳定性的影响机理还有待进一步的研究。     

乌江索风营水电站地下厂房岩锚梁镜面混凝土施工技术

镜面混凝土是水电工程建设中新兴的一门施工技术,在乌江索风营水电站地下厂房岩锚梁混凝土施工中采用了镜面混凝土,这在技术上是一次大胆的尝试和创新,既满足了功能上的要求,同时也达到了美观和装饰地下厂房的效果,为今后水电工程施工中广泛采用镜面混凝土技术提供了样本和宝贵经验。     

RI/VI联用测定聚乙烯相对分子质量及其分布

150℃测试温度下，以1，2，4-三氯苯为溶剂，采用示差折光指数器，毛细管黏度计双检测器联用凝胶渗透色谱技术测定了聚乙烯的相对分子质量及其分布。与常规凝胶渗透色谱法对比，该方法不仅能直接得到聚乙烯较精确的相对分子质量和分布形态，同时可以得到聚乙烯的特性黏数分布。     

对海水进行混凝除浊预处理研究

介绍采用聚合氯化铁（PFC）为絮凝剂，对海水进行混凝除浊预处理方法。考察了原海水pH、搅拌速度、反应时间及PFC用量对海水预处理效果的影响。结果表明，在原海水pH凋至9．0，搅拌速度控制在200min^-1，反应时间选择8—10min，PFC用量0．10μg／g的最佳条件下，能使处理后的海水浊度降至0．05mol／L，而联产的酸性废水中和剂浆料中Mg（OH）2含量在25％～45％，大肠菌群的去除率大于89．3％。     

岩石圈深部温度压力条件下褐煤与水的热模拟研究

在压力高达1—3GPa、温度为400—700℃的条件下，在密闭体系中进行了褐煤加水的模拟实验。分析了实验产物中液态烃的变化规律，并讨论了压力、温度及恒温时间对有机质演化的影响。实验结果表明，热模拟液态产物氯仿沥青“A”的有机碳含量为0．91％-2．55％，2GPa条件下其高峰值后移至700℃，说明高压抑制了液态烃的生成，同时压力升高有利于有机质降解产物的环化、聚合和芳构化。在400—600℃条件下，温度升高或恒温时间增长，OEP和Pr／Ph值均减小；而在700℃的恒温条件下，压力增高，OEP和Pr／Ph值均增大。说明有机质的成熟度与温度和加热时间成正相关，而压力增加抑制了有机质的成熟演化。在高压条件下，芳烃演化的主要趋势是甲基化作用，压力升高有利于甲基化反应和甲基重排。     

关于天然气水合物钻采工艺技术进展的研究

目前全球正面临着前所未有的能源危机，天然气水合物由于储量大、能量密度高而将成为一种诱人的新型能源。天然气水合物主要存在于冻土带和海洋，在地下处于低温和高压状态，以现有的技术，钻井和开采都存在很大的困难。简要介绍了天然气水合物的性质及储量，阐述了天然气水合物钻井的六个挑战及目前国外天然气水合物的两种钻探方法；同时阐述了以热力法、降压法和化学试剂注入法为主的天然气水合物开采方法，并针对天然气水合物钻采技术现状指出了下一步的研究方向。