医用固体激光器脉冲式强预燃系统控制电路设计

根据激光医疗所需激光脉冲的特点,针对长脉冲Nd:YAG激光器泵浦闪光灯中脉冲式强预燃系统的控制电路展开研究,采用UCC3895芯片控制预燃电路工作状态的变化,提供所需的预燃电流,从而配合其他电路得到相应的激光脉冲。文中主要阐述以UCC3895为核心的脉冲式强预燃系统控制电路的工作原理,并且根据实验,最终验证了该套系统的可行性。     

全桥变换器中磁通不平衡的抑制

分析了开关电源在采用全桥变换器的时候磁通不平衡现象的产生原因,并提出了实现抑制磁通不平衡的措施。着重介绍了应用阻隔电容实现磁通平衡的措施,同时进行了相关器件的设计与参数的计算。     

正交试验法优选田七花总黄酮的提取工艺

用正交试验法对田七花中的总黄酮提取工艺进行优化.以田七花中的总黄酮含量为考察指标,采用正交试验L9(34)表进行实验,对提取过程中的乙醇浓度、提取时间、提取次数及料液比四个影响因素进行研究.结果显示影响田七花中的总黄酮提取工艺的显著因素是提取次数,最佳提取工艺是:12倍量的80%的乙醇提取3次,每次1 h.     

16S rRNA sequences reveal numerous uncultured microorganisms in a natural community.

Microbiologists have been constrained in their efforts to describe the compositions of natural microbial communities using traditional methods. Few microorganisms have sufficiently distinctive morphology to be recognized by microscopy. Culture-dependent methods are biased, as a microorganism can be cultivated only after its physiological niche is perceived and duplicated experimentally. It is therefore widely believed that fewer than 20% of the extant microorganisms have been discovered, and that culture methods are inadequate for studying microbial community composition. In view of the physiological and phylogenetic diversity among microorganisms, speculation that 80% or more of microbes remain undiscovered raises the question of how well we know the Earth's biota and its biochemical potential. We have performed a culture-independent analysis of the composition of a well-studied hot spring microbial community, using a common but distinctive cellular component, 16S ribosomal RNA. Our results confirm speculations about the diversity of uncultured microorganisms it contains.     

随机利率下的连续型终身增额寿险

寿险中的随机利率问题,是近来保险精算研究的热点和重点问题之一.以即时赔付的连续型终身增额寿险为对象,对随机利率采用Gauss过程建模,Gauss过程与Poisson过程联合建模,研究赔付现值的各阶矩.并在De Movie假设下,给出其简洁表达式.     

金属磁记忆检测的机理及实现

现代工业的发展,离不开各种先进的无损检测(NDT)手段.但纵观传统的NDT方法,都是在部件缺陷发展形成以后才能被发现.金属磁记忆诊断技术是目前唯一能预测部件早期损伤的新方法.本文从晶体结构出发,在理论上和实验上分析了金属磁记忆检测的机理,并建立了系统模型.     

Rapid induction of neutrophil-endothelial adhesion by endothelial complement fixation

The adhesion of neutrophils to vascular endothelium is an early event in their recruitment into acute inflammatory lesions. In evaluating potential neutrophil-endothelial adhesive mechanisms in acute inflammation, important considerations are that adhesion in vivo may occur very rapidly following injury and that the specificity of the reaction resides in altered endothelium. That is, neutrophils adhere only to altered endothelium adjacent to an inflammatory focus, rather than at random as would be expected if activation of neutrophils were the initiator of adhesion. We have explored a possible bridging role for complement in causing early neutrophil-endothelial cell adhesion. The complement system is involved in inflammatory processes, is capable of rapid amplification, and endothelial complement fixation at sites of inflammation could generate an endothelium-restricted signal for neutrophil adhesion. We have now developed a model in which this can be investigated without complicating factors such as immunoglobulin deposition, by constructing a novel molecule, a hybrid of the endothelial binding lectin Ulex europaeus I and of the complement activator cobra venom factor. This molecule has the capacity to cause fixation of complement on human umbilical vein endothelial cells. We show that complement fixation is a potent and rapid stimulus for neutrophil adhesion. Neutrophil adhesion requires only endothelial deposition of C3, and is mediated through the type 3 complement receptor.     

Rate of sister chromatid exchanges in mammalian cells differing in diploid numbers

Summary The rate of sister chromatid exchanges (SCE) under identical experimental conditions is the same in various mammalian species irrespective of their diploid chromosome numbers.Supported in part by Research grants VC-21 from American Cancer Society and DEB-76-10580 from National Science Foundation.