On the Construction of Mohr Stress Circle and a Graphic Method in Representing the Stress Components on Different Oblique Planes

The Mohr stress circle for three-dimensional stress is usually determined by equations,which is lack of intuitionistic meanings and difficult to understand. In this paper, the construction of Mohr stress circle is illustrated directly by numerical method. The shortcoming of Mohr stress circle in representing the stress components on different oblique planes for three-dimensional stress is analyzed. A three-dimensional figure is given to describe the variation of normal and shear stress on different oblique planes at one point for the first time.     

添加剂对AN多变晶型影响研究

本文运用热分析的方法对四十余种无机、有机添加剂和几种表面活性剂及水分对硝酸铵(AN)晶型转变的影响进行了研究。结果表明这些添加剂对AN的影响应为多种因素的综合结果。     

A model for interfacial activation in lipases from the structure of a fungal lipase-inhibitor complex

Lipases are hydrolytic enzymes which break down triacylglycerides into free fatty acids and glycerols. They have been classified as serine hydrolases owing to their inhibition by diethyl p-nitrophenyl phosphate. Lipase activity is greatly increased at the lipid-water interface, a phenomenon known as interfacial activation. X-ray analysis has revealed the atomic structures of two triacylglycerol lipases, unrelated in sequence: the human pancreatic lipase (hPL)4, and an enzyme isolated from the fungus Rhizomucor (formerly Mucor) miehei (RmL). In both enzymes the active centres contain structurally analogous Asp-His-Ser triads (characteristic of serine proteinases), which are buried completely beneath a short helical segment, or 'lid'. Here we present the crystal structure (at 3 A resolution) of a complex of R. miehei lipase with n-hexylphosphonate ethyl ester in which the enzyme's active site is exposed by the movement of the helical lid. This movement also increases the nonpolarity of the surface surrounding the catalytic site. We propose that the structure of the enzyme in this complex is equivalent to the activated state generated by the oil-water interface.     

Effects of polysorbates and Cremophor EL on vascular responses in rat aorta

The effects of Tween 20, Tween 80, and Cremophor EL, surface active agents which are used for dispersion of water-insoluble substances, on vascular responsiveness were investigated using rat aortic rings. In high concentrations all these agents produced persistent contractions in aortic rings independent of the presence of endothelium. These contractions were not influenced by inhibitors of known endogenous contractile mediators. Incubation with these agents caused a concentration-dependent inhibition of the endothelium-dependent relaxant responses to acetylcholine in intact precontracted aortic rings. Endothelium-independent relaxations produced by sodium nitroprusside were not inhibited, but rather potentiated in the presence of Tween 80 (10^–1 ml/l). On the other hand, Tween 80 inhibited the contractile effects of 5-hydroxytryptamine, phenylephrine, and bradykinin significantly. The data suggests that these substances affect both endothelial cells and vascular smooth muscle.     

图书馆的人力资源建设

分析了人才资源与图书馆生存和发展的关系，指出：应从发现人才、重用人才和培养人才3个方面建立人才培养机制；同时强调只有加强领导班子建设才能充分发挥人才的作用。     

浅析城市水资源管理及利用

针对城市水环境污染严重、城市水利设施不完善、水资源管理缺乏经济学观念的状况，提出一系列强化城市水资源管理及利用的措施。     

Stamping Robust Design Method and Its Application

The application of the robust design to stamping is discussed in the paper. The regression equation of the quality index and its influencing factors can be attained by using method of central composite design. Stamping computer simulation takes the place of real stamping experiments to fulfill the special experimental conditions. The real stamping experiments prove the correctness and the feasibility of the stamping robust design method-central composite design.     

搜索引擎的智能化发展趋势

简要介绍了搜索引擎的工作机理，对传统搜索引擎与智能化搜索引擎进行了分析及综合评价，并提出了智能化搜索引擎发展的相关技术。     

The effect of calciferol,parathormone and calcitonin on the biochemical composition of kidney

Zusammenfassung Es wurde festgestellt, dass Calciferol die Stauung von Calcium, Phosphor und Zitronensäure in allen Teilen der Niere verursacht. Parathormon erhöht den Gehalt von Calcium und Zitronensäure in der Niere während einer Stunde. Nach Verabreichung von Calcitonin wurde Verminderung von Calcium in der Cortical-und Medullarzone beobachtet.