C-peptide fragments stimulate glucose utilization in diabetic rats

Studies of C-peptide cellular effects show that not only the full-length native peptide but also specific C-terminal fragments are biologically active in in vitro systems. In the present study, the effect of five C-peptide fragments and the native peptide on whole-body glucose turnover was studied in streptozotocin diabetic rats using the insulin clamp technique. Insulin was infused intravenously at 18 pmol kg^–1 min^–1 for 90 min and blood glucose concentration was clamped at 8 and 4 mM in diabetic and non-diabetic animals. A steady state was reached during the last 30 min of the study period. Rat C-peptide II and fragments comprising residues 27–31 and 28–31 were effective in augmenting glucose turnover in diabetic rats (+100% to 150%), while no significant effects were seen for segments 1–26, 11–19 and 11–15. The metabolic clearance rate for glucose during infusion of C-peptide or fragments 27–31 and 28–31 in diabetic rats was similar to that seen in non-diabetic animals. We conclude that C-terminal tetra- and pentapeptides, but not fragments from the middle segment of C-peptide, are as effective as the full-length peptide in stimulating whole-body glucose turnover in diabetic rats.Received 18 December 2003; received after revision 19 January 2004; accepted 21 January 2004     

基于分层着色Petri网的装备战场抢修系统建模

讨论了一种基于分层着色Petri网理论建立装备战场抢修系统模型的方法。这种方法是通过引入复杂库所和Petri子网来对原有的装备战场抢修系统模型进行改造，克服了以往用普通Petri网建模的不足之处，使模型变得直观、简单，并有利于模型分析和仿真实现。     

Controlled analogue experiments on propagation of seismic electromagnetic signals

This study presented a method of laboratory analogue experiments based on a geographical scaling model and a waveguide model to investigate the characteristics of the propagation of seismic electromagnetic signals in the crust and the atmosphere. Some controlled experiments were done to evaluate the possible influence on the experimental results from the background electromagnetic field, geographical conditions, boundary effects, the source of electromagnetic signals （position, magnitude, and frequency）, and media conductivity. The reliability and the extensibility of the above analogue experimental method were also investigated. This study indicated that such kind of analogue experimental method provided an intuitionistic way of studying the propagation of seismic electromagnetic signals, which is one of the most difficult research topics in seismo-electromagnetism.     

Crystal structure of <Emphasis Type="Italic">Enterobacter cloacae</Emphasis> 908R class C β-lactamase bound to iodo-acetamido-phenyl boronic acid,a transition-state analogue

The structures of the class C -lactamase from Enterobacter cloacae 908R alone and in complex with a boronic acid transition-state analogue were determined by X-ray crystallography at 2.1 and 2.3 Å, respectively. The structure of the enzyme resembles those of other class C -lactamases. The structure of the complex with the transition-state analogue, iodo-acetamido-phenyl boronic acid, shows that the inhibitor is covalently bound to the active-site serine (Ser64). Binding of the inhibitor within the active site is compared with previously determined structures of complexes with other class C enzymes. The structure of the boronic acid adduct indicates ways to improve the affinity of this class of inhibitors. This structure of 908R class C -lactamase in complex with a transition-state analogue provides further insights into the mechanism of action of these hydrolases.Received 16 May 2003; accepted 4 June 2003     

分布交互仿真系统支撑软件的研究

分布交互仿真是一种新兴的仿真技术,是指利用计算机网络将分布在各地区的仿真器和仿真人员联结起来,使众多仿真器在大范围内可进行综合性能测试及培训。     

流体网络拓扑分析的研究

从建模对象的系统图出发,详细探讨了流体网络的拓扑分析策略,并首次提出端口组的概念,解决了一个模块在同一个网络中可能具有多个支路或节点编号的问题,这在国内外同类软件中尚属首次。并根据以上的研究成果成功地研制了一套单相流流体网络自动建模软件,利用该软件,用户只需输入建模对象的系统图并进行实例化,即可自动产生它的流体网络仿真模型,实践证明该软件是可靠的,利用它可大大地提高建模效率和建模质量。     

支持事务重建的企业模型与建模方法

事务重建（BR）作为一种以系统观和变革观为基础的系统改造的指导,需要有与之相适应的模型工具与建模方法来支持．为此,文中在综述各种新型企业模型框架的基础上,提出一种三维企业模型体系,因其具有对企业组织因素及企业流程改造的描述能力,因此能较好地支持BR建模基于此模型体系,还进一步对支持BR的企业建模方法进行了探讨．     

平面端铣非线性切削过程模型

提出一个非线性切削过程模型，证实动态、静态切削力系数间存在联系，表明可以在切削稳定性研究中利用静态试验数据，论证了该模型的切合实际、普遍和衫性，讨论了国际切削动力学研究中的有关问题，推导了端铣平面时模型的具有表现形式。     

影响类可可脂质量的因素分析及改进措施

用石油醚作为溶剂，油温１０℃下的分提工艺会影响ＣＢＥ产品的熔点和结晶。建议改用丙酮溶解，分别在３７－３８℃和１５℃下分提结晶，试验结果表明，产品熔点可达到３６℃，油脂结晶均匀，无白粉出现。     

动态参数测量仪

动态参数测量仪是采用单片微型计算机控制的微型机系统，可对电力系统的运行参数进行动态测量、储存。接不同的传感器也适用于对其它的动态参数的测量。