宽带IP城域网规划设计

本文针对当前宽带城域网的主流技术进行对照分析,设计出一个既能适应竞争形式需要、又能最大限度利用现有电信资源的宽带IP城域网,给出其整体设计原则和网络构架.     

Y chromosome sequence variation and the history of human populations

Binary polymorphisms associated with the non-recombining region of the human Y chromosome (NRY) preserve the paternal genetic legacy of our species that has persisted to the present, permitting inference of human evolution, population affinity and demographic history. We used denaturing high-performance liquid chromatography (DHPLC; ref. 2) to identify 160 of the 166 bi-allelic and 1 tri-allelic site that formed a parsimonious genealogy of 116 haplotypes, several of which display distinct population affinities based on the analysis of 1062 globally representative individuals. A minority of contemporary East Africans and Khoisan represent the descendants of the most ancestral patrilineages of anatomically modern humans that left Africa between 35,000 and 89,000 years ago.     

Association of phosphorylation of the T3 antigen with immune activation of T lymphocytes

In human T lymphocytes the antigen receptor (Ti) is associated non-covalently on the cell surface with the invariant T3 antigen which comprises 3 chains: two glycosylated polypeptides of relative molecular mass 26,000 (Mr 26K) and 21K (gamma and delta) and one non-N-glycosylated polypeptide of Mr 19K (epsilon). The proposed function of T3 is to transduce the activation signals delivered via the antigen receptor. Recently we have shown that phorbol esters, which stimulate protein kinase C, can induce phosphorylation of the gamma subunit of the T3 antigen. But the critical question is whether T3 phosphorylation occurs as a normal consequence of immune activation of T lymphocytes. In this respect, it has been shown that immune stimulation of murine T cells results in phosphorylation of Ti-associated polypeptides that may be the functional analogues of the human T3 antigen. We have therefore monitored T3 phosphorylation after exposure of human T cells to antigen or phytohaemagglutinin (PHA). The data show that both stimuli initiate phosphorylation of the gamma subunit of the T3 antigen which indicates that T3 phosphorylation is a physiological response to immune activation.