神农架地区珍稀植物沿河岸带的分布格局及其保护意义

在神农架香溪河流域从源头到河口的不同海拔高度沿河岸带共设置 4 0个与河流方向平行的10 0m× 10m的样带 ,进行了植物群落学调查研究 .结果表明 ,沿河岸带分布有珍稀植物 14种 ,占神农架地区珍稀植物总数的 4 2 .4 % .这些珍稀物种主要分布在海拔 12 0 0～ 180 0m山地常绿阔叶落叶阔叶混交林带 ,珍稀植物种类的物种丰富度在中等海拔高度上最大 .珍稀植物的种类可划分为低海拔、中等海拔和高海拔 3组 .针对珍稀植物的分布特点 ,明确指出应重视河岸带在生物多样性、尤其是珍稀物种保护方面

Effects of silicon incorporation on composition, structure and electric conductivity of cubic boron nitride thin films

We have achieved in-situ Si incorporation into cubic boron nitride (c-BN) thin films during ion beam assisted deposition. The effects of silicon incorporation on the composition, structure and electric conductivity of c-BN thin films were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electrical measurements. The results suggest that the content of the cubic phase remains stable on the whole with the incorporation of Si up to a concentration of 3.3 at.%, and the higher Si concentrations lead to a gradual change from c-BN to hexagonal boron nitride. It is found that the introduced Si atoms only replace B atoms and combine with N atoms to form Si-N bonds, and no evidence of the existence of Si-B bonds is observed. The resistance of the Si-doped c-BN films gradually decreases with increasing Si concentration, and the resistivity of the c-BN film with 3.3 at.% Si is lowered by two orders of magnitude as compared to undoped samples.

Java程序中数组越界和空指针错误的静态分析

介绍了静态分析的相关背景知识,对Java程序中数组越界和空指针错误的常见表现形式进行了归类,并通过实验评估了现有的Java静态分析工具功能,指出了其在跨过程分析中的不足,并对如何改进进行了讨论.

榆林市工业“三废”污染及其治理对策

IEECAS SKLLQG

科尔沁沙地4种植物抗旱性的比较研究

对科尔沁沙地小叶锦鸡儿、紫穗槐、差巴嘎蒿和胡枝子 4种植物的若干水分生理生态指标进行了测定 .结果表明 ,小叶锦鸡儿具有低水势、高持水力和束缚水 /自由水比及水分利用效率 ,抗旱性强 ;紫穗槐的各项指标与小叶锦鸡儿相反 ,抗旱性最差 ;差巴嘎蒿虽然水势较高 ,但它的持水力高 ,束缚水 /自由水比和水分利用效率都较高 ,抗旱性也较强 ,但次于小叶锦鸡儿 ;胡枝子的水势和持水力较低 ,束缚水 /自由水比及水分利用效率一般 ,它的抗旱性强于紫穗槐 ,但比差巴嘎蒿差 .

On characterization of organic structures - A highly discriminating molecular topological index

A new molecular topological index, EATI is proposed based on the extended adjacency matrix, It has a hitherto unheard of power of discrimination and can be applied to discriminate various kinds of organic compounds, such as structures containing heteroatoms, etc.. Thus EATI might be possibly used as supplementary reference for CAS Registry Numbers for structure documentation.

有机化合物结构的唯一性表征方法研究──一个高选择性的拓扑指数

以扩展连接矩阵ＥＡ的幂级数函数为基础，建立了一个新的拓扑指数ＥＡＴＩ，该指数对１～２２个碳原子的所有３８０７４３４个烷烃异构体的指认并不出现简并，且能区分含杂原子的化合物，其唯一性良好。该指数可用于数据库中替代ＣＡＳ登录号进行结构的编码、管理及检索。

RELATIONSHIP BETWEEN CONFORMATION OF TASTE COMPOUNDS AND THEIR ACTIVITIES

The conformation analysis and study on structure-taste relation-ships of 4 taste compounds have been performed, the results reveal that the sweetnees will decrease with the increase of the specific dihedral angle O-1-C-2-C-3-C-4, and the mechanism was intepreted.

15个乙烯-乙烯基化合物共聚物的取代基参数

本文应用取代基参数(SCS)方法处了15个EV共聚物的~(12)C NMR谱.它们是:(1)乙烯-α-烯烃共聚物,即乙烯-丙烯共聚物.乙烯-丁烯-1共聚物,乙烯-4-甲基-1-戊烯共聚物,乙烯-己烯-1共聚物和乙烯-辛烯-1共聚物;(2)乙烯-含氧乙烯基共聚物,即乙烯-甲基丙烯酸N,N-二甲基胺乙酯共聚物,乙烯-丙烯酸甲酯共聚物.乙烯-丙烯酸共聚物,乙烯-乙酸乙烯酯,乙烯-乙烯醇,乙烯-氧化碳共聚物(ECO)(?)乙烯-卤代乙烯共聚物及其它EV共聚物,即乙烯-氯化乙烯共聚物(包含氯化聚乙烯),乙烯-溴化乙烯共聚物,乙烯-苯乙烯共聚物(包含氢化丁二烯-苯乙烯共聚物)和乙烯-丙烯腈共聚物、得到了15种取代基的SCS参数.

味觉化合物的构象与活性的关系

味觉化合物的构象与活性的关系许禄，姚喻元（中国科学院长春应用化学研究所应用谱学开放实验室，长春，１３００２２）关键词味觉化合物，分子力学，构象分析分子结构和味觉的相关性是一个非常活跃的研究领域，许多人从不同的侧面进行这方面的研究，并总结出一定的规律［...