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261.
262.
The complex [closo-3,3-(PPh_3)_2-3-H-3,1,2-RhC_2B_9H_(11)]has a rich derivative chemistrythat is currently under active investigation.The resultant compound shows an increasing stabilitythat is often associated with metallocarboranes.This paper deals with the novel and the produc-tion area of carborane complexes of transition metals.The paper indicates that some reactions can easily proceed and the resulting compound hassome new properties and uses.K[18-crown-6][closo-3-Ph_3P-3-CH_2Ph-3-Br-3,1,2-RhC_2B_9H_(11)]can be synthesized by the reaction of K[18-crown-6][(Ph_3P)_2RhC_2B_9H_(11)]withbromo-toluene under the condition of dry benzene.IR and ~1H,~(11)B,~(31)p nuclear magnetic reso-nance and elemental analysis comfirm the structure for this species with one carborane groupbonded to the central metal. 相似文献
263.
By analyzing U and Th isotopic compositions of 41 samples in two stalagmites from Hulu Cave, Nanjing, we first discovered that variations of 238U and d 234U0 along the stalagmite growth-sequence (covering a period from 75 to 18 kaBP) are in high similarity to summer insolation curve at 33°N and d 18O-based climate record of the studied stalagmites. The concentration of 238U is mainly controlled by content of organic matter in the soil above the cave. This mechanism can be used to explain our result that 238U curve of stalagmites is in phase with fluctuation of the d 18O record of the same stalagmites and summer insolation at cave locality. However, 238U concentration curve vs. age is, in amplitude, inconsistent with the climatic curves, possibly due to complex processes of soil-water-rock interaction. d 234U0 indicates pedogenic intensity of soil profile above the cave and sensitively reflects alternations of pedogenesis and aeolian accumulation processes of Xiashu loess in Nanjing. Consequently, uranium concentration and its isotope ratio in stalagmites may provide a new proxy for climate change. 相似文献
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本文通过论述部分运动竞赛项目,在比赛中教练员与场内运动员及运动员之间的相互沟通的形式和方法,运用实例分析,说明手语指挥在运动竞赛中的可行性及其作用。 相似文献
266.
Tectonic affinity of Paleozoic stratigraphic slices along the northern margin in Dabie Orogen, central China: evidence from Pb isotope of rocks 总被引:5,自引:0,他引:5
Metavolcanic and metasedimentary rocks from the Paleozoic tectono-stratigraphic units along the northern margin in the Dabie orogen show that there are two types of Pb isotopic compositions, which have some affined regularity with tectonic subdivision. Compared with the main tectonic units of the Qinling orogen, the Dingyuan Formation should be the part of the South Qinling orogenic belt or the northern margin of the Yangtze craton, characterized by less radiogenic Pb isotopic composition, and the Guishan Formation, Nanwan Formation-Foziling Group and the Carboniferous should be the part of the North Qinling orogenic belt which is extended to the east, characterized by more radiogenic Pb isotopic composition. These facts combined with the distribution of the geological units suggest that the Paleozoic subduction zone between the Yangtze and North China cratons should be located in the north boundary of the Nanwan Formation-Foziling Group or somewhere that is covered by the Nanwan Formation-Foziling Group now. From the Pb isotopic evidence and suggestion presented here, one aspect of the constraint is provided for determining the position of the Triassic collision suture between the two cratons. 相似文献
267.
The violaxanthin de-epoxidase gene was cloned from rice (Oryza sauva subsp japonica). The full length of the cDNA is 1887 bp, encoding a 446-amino acids protein with the transit peptide of 98 amino acids. The
bacterial expression vector pET-Rvde was constructed and the expression quantity of the exogenous protein increased with the
induction time by 0.4 mmol/L IPTG. Its molecular weight was similar with that of the native VDE. Western blotting indicated
that the expressed protein has immunological reaction with the VDE polyclonal antibody. The absorbance spectrum together with
xanthophyll pigments quantification by HPLC demonstrated that the expressed VDE has its enzyme activity, which can de-epoxidate
violaxanthin into antheraxanthin and zeaxanthin in vitro. 相似文献
268.
阐述了固定床加压热天平(PBBR)系统的工作原理和指标,讨论了影响天平稳定的因素,并就该系统的可靠性进行了验证和分析,说明了该系统优于吊蓝式加压热天平系统。在PBBR系统上,测定了沈北褐煤在1173.15K时制成的煤焦在101.3~3039kPa和1073.15~1273.15K下与H_2,CO_2反应的动力学。结果表明:CO_2和H_2与煤焦的反应都是一级的;CO_2与煤焦的反应活性大于H_2与煤焦的反应活性;研究了温度,压力对CO_2、H_2与煤焦气化反应的碳转化率的影响,计算了CO_2和H_2气化反应的表观活化能和反应活化能,并对CO_2和H_2气化反应机理模型进行探讨。 相似文献
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Shamir门限体制可以用来解决多个人共享一个密钥的问题。但是,如果有多个密钥需要让一组成员的部分或者全部成员共享,如果还用Shamir门限体制来解决,就会导致每一个共享方案都需要一个门限体制,也就是说每个成员必须保存一个或多个身份密钥,这显然是不方便也是不安全的。我们利用基于角色的访问控制(RBAC)的思想,提出了一种新的多密门限体制方案,其显著的优点就是在保证安全性的前提下,每一个参与者须且仅需拥有一个身份密钥。因此,该方案不仅具有RBAC的所有优点,而且对于共享者来说也非常方便。 相似文献