离散事件系统结构化状态反馈控制逻辑

离散事件系统(Discrete Event System,DES)是从制造系统、通讯系统、资源管理系统和城市/空中交通系统等人工系统中抽象出来的.这种系统可认为是离散的(在时间上和状态空间内)、异步的(即是由事件驱动而不是由时钟驱动),并且一般是非确定性的,所以处理这类系统的方法与连续时间系统迥然不同.在已有的处理 DES 的方法中,Wonham 和他的学生所提出的一种概念模型方法已引起了广泛的注意.在这方法中,他们成功地将计算机科学的一些概念和方法引入到控制中,新领域的出现和新方法论的发展使控制科学产生了新的活力.     

快速退火对大直径CZSi单晶中原生微缺陷的影响

本文利用快速退火对 8″直拉硅单晶片中的流动图形缺陷(FPDs)进行了研究.首先用Secco腐蚀液腐蚀了大直径直拉硅片,利用光学显微镜观察了FPDs的宏观分布,并用原子力显微镜(AFM)对原生FPDs的微观形貌进行观察,证明了 FPDs是一种空位型原生缺陷,然后采用了高温快速热处理,分别在N2、N2/O2(3;)、Ar三种气氛中对原生直拉单晶硅片进行了处理.对比退火前后FPDs密度的变化,分析了高温快速热处理对直拉硅单晶片中FPDs的影响,实验表明1200℃快速热处理180s可以显著降低硅片表面的FPDs.     

Hypericum perforatum L. extract - novel photosensitizer against human bladder cancer cells

The polar methanolic fraction (PMF) of the Hypericum perforatum L. extract has recently been developed and tested as a novel, natural photosensitizer for use in the photodynamic therapy (PDT), and photodynamic diagnosis (PDD). PMF has been tested on HL-60 leukemic cells and cord blood hemopoietic progenitors. In the present study, the efficacy of PMF as a phototoxic agent against urinary bladder carcinoma has been studied using the T24 (high grade metastatic cancer), and RT4 (primary low grade papillary transitional cell carcinoma) human bladder cancer cells. Following cell culture incubation, PMF was excited using 630 nm laser light. The photosensitizer exhibited significant photocytotoxicity in both cell lines at a concentration of 60microg/ml, with 4-8 J/cm(2) light dose, resulting in cell destruction from 80% to 86%. At the concentration of 20microg/ml PMF was not active in either cell line. These results were compared with the results obtained in the same cell lines, under the same conditions with a clinically approved photosensitizer, Photofrin. Photofrin was used in the maximum clinically tolerable dose of 4microg/ml, and it was also excited with 630 nm laser light. In the T24 cell Photofrin exhibited slightly less photocytotocixity, compared with PMF, resulting in 77% cell death with 8J/cm(2) light dose. However, against the RT4 cells Photofrin resulted in minimal cell death (9%) with even 8J/cm(2) light dose. Finally, the type of cell death induced by PMF photoactivation was studied using flow cytometry and DNA laddering. Cell death by PMF photodynamic action in these two bladder cell lines is caused predominently by apoptosis. The reported significant photocytotoxicity, selective localization, natural abundance, easy, and inexpensive preparation, underscore that the PMF extract hold the promise of being a novel, effective PDT photosensitizer.     

幂群与它的生成群

设г是G上的幂群,即以G的非空子集为元素,在G的子集的运算之下所成的群.P_1,P_2是这样的两个性质 P_1:对任意g∈G,存g∈G,存在A∈г,使得g∈A. P_2:对任意A,B∈г,如果A≠B,则A∩B=φ. 本文得出了群G上的幂群г分别具有性质P_1或P_2的充要条件.