A computational study on the gas phase reaction of Os^＋ with N2O

The reaction of Os~+(~6D,~4F) with N_2O has been investigated at B3LYP/TZVP and CCSD(T)/6-311+G~* levels of theory.The mechanisms corresponding to O-atom and N-atom transfer reactions have been revealed.It was found that on the sextet reaction surface both the O-atom and N-atom transfer reactions undergo through direct-abstraction mechanism,leading to the formation of OsO~+ and OsN~+,whereas on quartet surface the two reactions undergo through O-N bond or N-N bond insertion mechanism.The calculated energ...     

How to estimate the effect of an intense meteor shower on human space activities

In the present age, the potential threat to space projects coming from some intense meteor storms has been noticed. Especially, the increasing activities of mankind in space for scientific, commercial and military purposes have led to an increase in safety-related problems about the satellites, space stations and astronauts. Several new techniques for observing meteors and meteor showers have been developed. However, how to estimate even predict the effect of an intense meteor shower should be further studied. The initial definition about a meteor storm based on visual observations with a Zenithal Hourly Rate of over one thousand seems insufficient, since it only means a storm or burst of meteors in numbers. In 2006 the author suggested a synthetical index of the potential threats about intense activities of meteors; however, it is too complex to determine several parameters. In this paper, the author suggests a Special True Number Flux Density (STNFD). Set a certain energy-limit, or a certain electric-charge-limit, and then calculate the number flux density. Through the comparison between two of the 10 strong meteor showers in recent years it is found that the important factor affecting the space flight security is not only the number of meteoroids, but also their velocities, their average energy and the population index r. Calculations show that Giacobinids, even June Bootids, should be one of the most hazardous meteor showers.     

Synthesis and biological evaluation of andrographolide derivatives as potent anti-HIV agents

A series of Andro derivatives were described and evaluated for their anti-HIV activity in vitro.Compound 10 and 16b,of which TI were>10,had some anti-HTV-l activity in vitro.Therein,compound 10 which was the best potent compound,could serve as a new lead for further development of anti-AIDS agents.     

Empirical likelihood hypothesis test on mean with inequality constraints

Hypothesis test on the population mean with various inequality constraints is studied in this paper.The empirical likelihood method is applied to construct test statistics.Limiting distributions of the empirical likelihood ratio test statistics are proven to be a weighted mixture of chi-square distributions.Numerical results are presented to show the validity of the proposed method.     

A Novel Sesquiterpene Isolated from Stereum sp. 8954

The basidiomycete Stereum sp. 8954 was collected in Xishuangbanna, Yunnan Province, and the mycelium of Stereum sp. 8954 was separated from fruit body and deposited in Laboratory for Conservation and Utilization of Bio-resources, Yunnan University. After fermentation, a novel sesquiterpene was isolated from the culture of the strain. The present paper deals with the structural elucidation of the new compound. Experimental Stereum sp. 8954 was fermented with PDA medium (10 L) at 26 oC fo…     

A New Sesquiterpenoid from Magnolia delavayi

A new sesquiterpenoid was obstained from the leaves of Magnolia delavayi. Its structure was determined as 8β-acetoxy-10α-ethyloxy-guaia-4α, 11-diol on the basis of spectral evidence.     

Lignan glucoside from Sinopodophyllum emodi and its cytotoxic activity

A new lignan glycoside was isolated from the n-butanol extract of the roots and rhizomes of Sinopodophyllum emodi.On the basis of spectral evidences,its structure was established and named as 4,5-didemethylpodophyllotoxin 7’-O-β-D-glucopyranoside. This compound showed cytotoxicity against four human cancer cell lines(Hela,K562,SH-SY5Y and CNE) in vitro.     

活体植物中β-胡萝卜素分子的二级拉曼散射谱

利用显微拉曼光谱技术对从法国梧桐树新鲜采集得到的树叶做了测试分析，在可见光514.5nm激发下，不对样品做任何提纯，直接得到了树叶中β－胡萝卜素分子的一级和二级拉曼光谱。根据对β－胡萝卜素分子拉曼散射位于2000－3100cm^-1之间和2000cm^-1以下谱线的仔细分析对比，得到了二级拉曼谱和一级谱的倍频、和频关系。实验研究表明，控制样品表面的激光强度和信号积分时间，不破坏活体树叶中的分子结构和构象，这为研究植物在不同的环境生长状况提供一种实时实地测量技术。此外讨论了用共焦显微拉曼研究活体植物的优点及限制。     

光纤双向应变-位移点式传感器

选择不同间距的基片自由端和不同长度的自由悬垂光纤研制了利用光纤弯曲损耗的光纤双向应变-位移传感器.该传感器可分别用于测量应变和位移.实验表明:悬臂梁上的应变标准误差约为～26 με.微位移架上的位移标准误差约～0.06 mm.基本满足建筑结构对测量精度的要求.     

NixZry(x:y=1∶2或2∶1)团簇的量子化学研究

根据化学键理论和拓扑学原理,设计了非晶态团簇NixZry(x:y=1:2或2：1,x+y≤9）的几十种可能的构型,并应用量子化学从头算方法对它们的几何构型进行了优化,分析比较了这些构型的能量和稳定性。结果表明对于NixZry(x:y=1:2）低对称性的平面构型最稳定,而NixZry(x:y=2：1）三棱柱构型最稳定。这可能是由于两者外层价电子的数量差异所致：Zr仅有4价电子,较适宜配位数低的平面构型,而Ni(4s^23d^8),更适宜立体构型。