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本文基于分时间片非坚持型CSMA/CD协议,提出了一种新的适合于重负载下评价CSMA/CD总线性能的数学模型.该模型合理地考虑了重载下各种新现象及影响总线性能的诸因素.实验研究结果表明,本文提出的模型较以前的评价模型更接近于实际系统. 相似文献
83.
F. K. Saunders J. Lawry D. A. Winfield J. R. Goepel B. W. Hancock R. M. Sharrard M. H. Goyns 《Cellular and molecular life sciences : CMLS》1994,50(5):493-496
2D-gel electrophoresis was used to investigate protein synthesis in leukaemic cells from a series of 15 chronic lymphocytic leukaemia (CLL) patients, and in non-malignant B-cell populations from different sources. The protein synthesis profiles of CD5+ B-cells from umbilical cord blood and from tonsil were determined, and the levels of expression of their proteins were observed to be similar to the CLL cells. The CD5-cells from cord blood resembled peripheral blood B-lymphocytes, and the protein synthesis profile of CD5-cells from tonsils was very complex. One protein was also identified which consistently appeared to be synthesised at a low level in CD5+ B-cells from tonsil but which was always more prominant in CLL cells and other non-malignant B-lymphocytes. On the basis of these data it is possible that the closest non-malignant counterpart to CLL is the CD5+ B-lymphocyte from cord blood. 相似文献
84.
加强对随书光盘的科学管理 提高其利用率 总被引:3,自引:0,他引:3
于纯良 《大庆师范学院学报》2004,24(3):91-92
本文通过实例引出目前图书馆随书光盘利用率低这一普遍存在问题 ,并提出图书馆随书光盘利用率低的根本原因是管理不善造成的 ,接着分析了当前一些图书馆的管理方法利弊并提出了作者自己设计的几种科学管理模式 ,同时呼吁质量监管部门应从用户的角度出发 ,加强对生产光盘的厂家的监管力度 ,保证光盘的质量 相似文献
85.
H. Bussey C. Boone H. Zhu T. Vernet M. Whiteway D. Y. Thomas 《Cellular and molecular life sciences : CMLS》1990,46(2):193-200
Summary The K1 killer toxin ofSaccharomyces cerevisiae is a secreted, virally-coded protein lethal to sensitive yeasts. Killer yeasts are immune to the toxin they produce. This killer system has been extensively examined from genetic and molecular perspectives. Here we review the biology of killer yeasts, and examine the synthesis and action of the protein toxin and the immunity component. We summarise the structure of the toxin precursor gene and its protein products, outline the proteolytic processing of the toxin subunits from the precursor, and their passage through the yeast secretory pathway. We then discuss the mode of action of the toxin, its lectin-like interaction with a cell wall glucan, and its probable role in forming channels in the yeast plasma membrane. In addition we describe models of how a toxin precursor species functions as the immunity component, probably by interfering with channel formation. We conclude with a review of the functional domains of the toxin structural gene as determined by site-directed mutagenesis. This work has identified regions associated with glucan binding, toxin activity, and immunity. 相似文献
86.
高校图书馆随书光盘管理方法分析 总被引:2,自引:0,他引:2
程立华 《科技情报开发与经济》2010,20(13):20-21
阐述了图书馆随书光盘的特点和类别,分析比较了常用的几种随书光盘管理模式。 相似文献
87.
D.B. Moody 《Cellular and molecular life sciences : CMLS》2001,58(10):1461-1474
T cells are well known to recognize peptide antigens presented by major histocompatibility (MHC) class I or class II molecules.
More recently, the CD1 family of antigen-presenting molecules has been shown to present both mammalian and microbial glycolipid
antigens for specific recognition by T cells. Human CD1c proteins mediate T cell recognition of polyisoprenyl glycolipids,
evolutionarily conserved phosphoglycolipids, which function in glycan synthesis pathways. This family of antigenic molecules
is particularly attractive for the study of the molecular features that control T cell recognition of self and foreign glycolipids
because natural polyisoprenols from mammals, fungi, protozoa, mycobacteria and eubacteria differ in structure. Moreover, these
naturally occurring structural differences can influence their recognition by CD1c-restricted T cells. This review of the
structural diversity and evolutionary relationships of polyisoprenoid glycolipids emphasizes those features of polyisoprenyl
glycolipid biosynthesis that are relevant to their functions as targets of CD1-mediated T cell responses.
Received 16 March 2001; received after revision 19 April 2001; accepted 23 April 2001 相似文献
88.
以太网应用于工业网络控制系统是控制网络的发展方向。由于它采用CSMA/CD媒体访问机理,对工业过程中的时间要求严格的控制过程会产生响应上的时间不确定性。在工业网络中采用交换式以太网和全双工以太网的方法来消除传统以太网中存在的网络操作的不确定性。就此对目前采用的交换式以太网技术和全双工以太网技术做了合理的分析,并给出了具体实施的方法。 相似文献
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