关于正规p-补的一个定理

本文削弱了《内-外-∑群与极小非∑群》(陈重穆)一文中定理10.10A:条件而得到相同的结果,即定理 设G是有限群,p是|G|的素因子,且对|G|的任一素因子q有p(?)q-1 ),P是G的p-Sylow子群.若对于P的任一非平凡循环子群P,N_G(P)与C_G(P)都有正规p-补,则G为p-幂零群.     

In vitro reactivation of anaphase spindle elongation using isolated diatom spindles

A key step for analysing the mechanochemistry of mitosis would be the isolation of a functional spindle capable of anaphase chromosome movement in vitro. Although Mazia and Dan first isolated spindles in 1952, with one or two possible exceptions, isolated spindles are non-functional. An alternative approach has used permeabilized cells to study anaphase chromosome movement, but these preparations are biochemically and morphologically complex, and hence difficult to analyse. We describe here a simple procedure for isolating diatom spindles which are capable of anaphase spindle elongation in vitro. With addition of ATP, the two half-spindles slide completely apart, with concomitant decrease in the zone of overlap. Electron microscopy reveals decreased numbers of microtubules throughout the spindle after ATP addition and confirms the complete absence of structures beyond the spindle poles. These results are inconsistent with theoretical models of mitosis which suggest that spindle poles are pushed apart by microtubule growth, are pulled apart by external forces applied to the poles, or are released from tension generated during spindle formation. The results are consitent with models that postulate mechanical interactions in the zone of microtubule overlap as a factor in spindle elongation.     

A family of mammalian Na+-dependent L-ascorbic acid transporters.

Vitamin C (L-ascorbic acid) is essential for many enzymatic reactions, in which it serves to maintain prosthetic metal ions in their reduced forms (for example, Fe2+, Cu+), and for scavenging free radicals in order to protect tissues from oxidative damage. The facilitative sugar transporters of the GLUT type can transport the oxidized form of the vitamin, dehydroascorbic acid, but these transporters are unlikely to allow significant physiological amounts of vitamin C to be taken up in the presence of normal glucose concentrations, because the vitamin is present in plasma essentially only in its reduced form. Here we describe the isolation of two L-ascorbic acid transporters, SVCT1 and SVCT2, from rat complementary DNA libraries, as the first step in investigating the importance of L-ascorbic acid transport in regulating the supply and metabolism of vitamin C. We find that SVCT1 and SVCT2 each mediate concentrative, high-affinity L-ascorbic acid transport that is stereospecific and is driven by the Na+ electrochemical gradient. Despite their close sequence homology and similar functions, the two isoforms of the transporter are discretely distributed: SVCT1 is mainly confined to epithelial systems (intestine, kidney, liver), whereas SVCT2 serves a host of metabolically active cells and specialized tissues in the brain, eye and other organs.     

SO_2两转两吸流程中“ⅢⅠ-ⅣⅡ”和“ⅢⅡ-ⅣⅠ”换热情况浅析

通过工艺计算,定量分析比较 Ｓ Ｏ２ 转化中“ⅢⅠ－ ⅣⅡ”和“ⅢⅡ－ ⅣⅠ”两种换热流程的差异,论证了就换热情况而言,“ⅢⅠ－ ⅣⅡ”流程优于“ⅢⅡ－ ⅣⅠ”流程     

多元函数的中值定理

将多元函数在有向光滑曲线上的增量与在某点处的方向导数联系起来得到一个多元函数的中值定理,并由此得到可用方向导数研究多元函数性质的一些结果     

用柱层析和TLC分离小麦PGIP和植保素

植物抗病能力大小的测定需要比较准确可靠且相对简便的办法。采用接种病菌于植物上观察染菌情况虽然直观,但受病菌本身的生理状态及外界环境影响很大,且不便于定量的表述。因此,选择合适的生理生化指标作为植物抗性大小的衡量标准,对于植物病理的研究具有重要的意义。选择了小麦体系的两种抗性物质－ 小麦植保素和 Ｐ Ｇ Ｉ Ｐ作为小麦的抗性指标来分离分析