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.     

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.     

XPDL与关系数据库之间的映射

XPDL( XML Process Definition Language)是工作流管理联盟(WFMC)制定的工作流模型标准,而关系数据库是当前很多工作流厂商存放工作流数据的首选方法.讨论了XPDL与关系数据库(RDB)之间的映射原理及映射方法,并由此建立了映射文件,从而方便了XPDL与RDB之间的双向数据转换.     

Heterochromatin links to centromeric protection by recruiting shugoshin

The centromere of a chromosome is composed mainly of two domains, a kinetochore assembling core centromere and peri-centromeric heterochromatin regions. The crucial role of centromeric heterochromatin is still unknown, because even in simpler unicellular organisms such as the fission yeast Schizosaccharomyces pombe, the heterochromatin protein Swi6 (HP1 homologue) has several functions at centromeres, including silencing gene expression and recombination, enriching cohesin, promoting kinetochore assembly, and, ultimately, preventing erroneous microtubule attachment to the kinetochores. Here we show that the requirement of heterochromatin for mitotic chromosome segregation is largely replaced by forcibly enriching cohesin at centromeres in fission yeast. However, this enrichment of cohesin is not sufficient to replace the meiotic requirement for heterochromatin. We find that the heterochromatin protein Swi6 associates directly with meiosis-specific shugoshin Sgo1, a protector of cohesin at centromeres. A point mutation of Sgo1 (V242E), which abolishes the interaction with Swi6, impairs the centromeric localization and function of Sgo1. The forced centromeric localization of Sgo1 restores proper meiotic chromosome segregation in swi6 cells. We also show that the direct link between HP1 and shugoshin is conserved in human cells. Taken together, our findings suggest that the recruitment of shugoshin is the important primary role for centromeric heterochromatin in ensuring eukaryotic chromosome segregation.     

Behavioural ecology: transient sexual mimicry leads to fertilization

Sexual mimicry among animals is widespread, but does it impart a fertilization advantage in the widely accepted 'sneak-guard' model of sperm competition? Here we describe field results in which a dramatic facultative switch in sexual phenotype by sneaker-male cuttlefish leads to immediate fertilization success, even in the presence of the consort male. These results are surprising, given the high rate at which females reject copulation attempts by males, the strong mate-guarding behaviour of consort males, and the high level of sperm competition in this complex mating system.     

Potentiation of the biological activities of daunomycin and adriamycin by ascorbic acid and dimethylsulfoxide

Summary L-Ascorbic acid (0.57 mM) and dimethylsulfoxide (14.1 mM) were found to potentiate four times the antibacterial activities of daunomycin and adriamycin in theStaphylococcus aureus test. This effect, however, could not be demonstrated against eukaryotic cells and leukemia P388 in mice. The authors thank Dr A. Maráz, Department of Microbiology, J.A. University, Szeged, and Dr Zs. Somfai, Institute of Oncology, Budapest, for collaboration in the experiments with yeast and tumor cells.     

新疆主要土壤物理性状空间分布及其气候影响分析

依据新疆33个农业气象观测站（点）2006～2007年实测的0～50em土层土壤水文物理常数资料以及各站多年平均气候资料。综合分析了各常数的空间分布特征、相互间的关系以及各常数与年平均气温、年降水量的统计关系。结果表明,在新疆区域内,1）土壤容重具有南疆〉北疆〉天山山区的分布特征,田间持水量和凋萎湿度具有南疆〈北疆〈天山山区分布格局;2）各土壤水文物理常数两两之间均具有极显著的对数型回归关系,其中,土壤容重与田间持水量、土壤容重与凋萎湿度间呈负相关关系,而田间持水量与凋萎湿度间呈正相关关系;3）各常数与年平均气温和年降水量之间也具有显著的统计关系,其中,土壤容重与气温呈正相关关系,田间持水量、凋萎湿度与气温呈负相关关系;土壤容重与年降水量呈负相关关系,但田间持水量、凋萎湿度与年降水量呈正相关关系。