我国土壤侵蚀状况与主要影响因素分析

我国土壤侵蚀面积达 492万km2 ,占国土总面积的 5 1 .2 % ,已严重影响和制约着国民经济的发展和社会的安定。 1 998年洪灾便是土壤侵蚀对大自然的最大惩罚 ,现已引起社会各界的重视。为了从中吸取经验教训 ,对土壤侵蚀与降雨 ,土壤侵蚀与坡长、坡度 ,土壤侵蚀与植被建设三个大的方面作了系统分析 ,研究土壤侵蚀产生的原因和发展规律 ,从中可以知道这三个方面是影响土壤侵蚀的最为关键因子 ,并找出其对生态环境的危害性 ,提出最佳的综合防治对策 ,将土壤侵蚀的危害降低到最低程度

黄土高原(陕西部分)雨水资源化潜力初步分析

根据黄土高原（ 陕西部分） 的１４５ 个雨量观测站的３０ａ 逐月降水资料，分析了陕西雨水资源的时空分布特征，并在次基础上，分别对西北地区的作物地土壤拦蓄潜力，陕北、渭北、关中３ 地区居民工矿与交通用地的雨水汇流潜力进行了测算。初步结果为：两北地区作物地年总无效蒸发耗水达３３ ×１０８ ｍ３ ，若采取集流保墒措施，年可减少蒸发损失６－４ ×１０８ ｍ３ ；３ 地区居民工矿与交通用地年可汇流６－２７ ×１０８ ｍ ３ ，若一半用于粮食生产，并采取节水灌溉，初步推算黄土高原地区可增产粮食约２８－８ ×１０８ ｋｇ。

纳豆的研究与应用

纳豆的研究与应用李宁（中国科学院沈阳应用生态研究所，１１００１５）纳豆是一种简单易得的有营养的优质发酵食品。它是将接种过纳豆菌（Ｂａｃｉｌｌｕｓｎａｔｔｏ）的蒸煮大豆在适当温度、湿度下发酵得到的。纳豆以其特殊的风味广受日本人的喜爱，它作为传统食物在日...

中国国民的健康指数及其区域差异

用“健康指数”来表征我国国民的健康状况,以预期寿命为核心,选择27项与寿命有密切关系的、能反映人的身体素质和文化素质的健康指标,综合求得健康指数,基本上反映了各地区人群的健康状况及其区域差异,表明我国大城市和东南沿海地区人群的健康状况较好,西部地区稍差。

席佛碱催化剂(Salen Co(Ⅲ))催化二氧化碳和环氧氯丙烷的共聚

利用席佛碱催化体系催化二氧化碳(CO2)和环氧氯丙烷(ECH)共聚反应,合成出新型环状碳酸酯(ECHCO2)。利用红外光谱、核磁等方法对产物进行了表征。结果表明,最优化的试验温度是60℃,这一催化剂体系催化的活性高达920 polymer/(mol Co h),并且有较高的选择性,高达99%。

Synthesis and high efficiency green light-emitting diode of a soluble polymer

A soluble polymer emitting green color with high efficiency was synthesized. Bright green electroluminescence devices, both single layer and multilayer, were fabricated. The luminous efficiency was improved dramatically. Carrier injection from the electrodes to the emissive layer and concomitant green electroluminescence from the emissive layer were observed. A luminance of 920 cd/m(2) and luminous efficiency of 5.35 1m/W were achieved at a drive voltage of 15 V for the multilayer device. (C) 1997 Elsevier Science S.A.

Synthesis of lanthanide-alkylaluminium bimetallic complexes and studies on their catalytic activities for polymerization of some polar monomers

Three new lanthanide (Ln)-alkylaluminium (Al) bimetallic complexes with the formula [(mu-CF3CO2)(2)Ln(mu-CF3CHO2)AIR(2) . 2THF](2) (Ln = Nd, Y, R=i-C4H9 (i-Bu); Ln=Eu, R=C2H5(Et); THF=tetrahydrofuran) were synthesized by the reaction of Ln(CF,CO,), (Ln=Nd, Y) with HAI (i-Bu)(2) and of Eu(CF3CO2)(3) with AlEt(3), respectively. Their crystal structures were determined by X-ray diffraction at 233 K. [(mu-CF3CO2)(2)Nd (mu-CF3CHO2)Al(i-Bu)(2) . 2THF](2) (Nd-Al) and [(mu-CF3CO2)(2)Y(mu-CF3CHO2)Al(i-Bu)(2) . 2THF](2) (Y-Al) are isomorphous and crystallize in space group with a=12.441(3) Angstrom [12.347(5) Angstrom for Y-Al], b=12.832(3) Angstrom [12.832(4) Angstrom], c=11.334(3) Angstrom [11.292(8) Angstrom], alpha=104.93 (2)degrees [104.45(4)degrees], beta=98.47(2)degrees [98.81(4)degrees], gamma=64.60(2)degrees [64.30(3)degrees], R=0.519 [0.113], R(w)=0.0532 [0.110], Z=1 and [(mu-CF3CO2)(2)Eu(CF3CHO2)AlEt(2) . 2THF](2)(Eu-Al) in space group P2(1)/n with a=11.913(6) Angstrom, b=14.051(9) Angstrom, c=17.920(9) Angstrom, alpha=101.88(11)degrees, beta=gamma=90 degrees, R=0.0509, R(w)=0.0471 and Z=2. The six CF3CO2- (including CF3CHO2-) of each complex, among which pairs are equivalent, coordinated to Ln and Al in three patterns: (A) the two oxygen atoms in one of the three CF3CO2- type coordinated to two different Ln; (B) the two oxygen atoms in the second of CF3CO2- type coordinated to Ln and Al, respectively; (C) one of the two oxygen atoms in the third CF3CO2- type bidentately coordinated to two Ln and another oxygen coordinated to Al and one of the two Ln, respectively. Unlike types A and B, in type C the carboxyl carbon with a hydrogen atom bonded to it was found to appear as an sp(3)-hybridized configuration rather than an sp(2)-one. 1D and 2D NMR results further confirmed the existence of such a disproportionated CF3CHO2- ligand. Methyl methacrylate (MMA) and epichlorohydrin (ECH) could be polymerized by Y-Al or Eu-Al as a single-component catalyst and highly syndiotactic poly(MMA) was obtained. THF could also be polymerized by Y-Al in the presence of a small amount of ECH.

Study on the Films Forming Process of Nanosized SnO2 Colloid Particles at the Gas-Liquid Interface

The hydrosol of SnO2 nanoparticles are prepared by the method of colloid chemistry. The free piling up process of nanosized SnO2 colloid particles are investigated at the gas-liquid interface by LB and Brewster Angle Microscopy techniques. The result indicates that solid state monolayer and multilayer of SnO2 nanoparticles can be formed at the gas-liquid interface only by aging the sol in air or compressing it without amphiphiles surfactant.

SnO_2水溶胶气-液界面纳米胶粒成膜过程

采用胶体化学法制得稳定的SnO_2纳米粒子水溶胶．在LB膜槽内，用膜天平考察了溶胶在陈化和匀速压缩过程中，气—液界面表面压力的变化情况，并用布儒斯特角显微镜（BAM），直接观察了陈化过程中界面胶体粒子的自由密堆积成膜过程，和匀速压缩过程中界面胶体粒子的压缩成膜过程，结果发现，新制（或刮净后）的溶胶表面处于亚稳态，而久置的溶胶表面处于稳定状态，并且溶胶气—液界面的纳米波粒，可通过陈化和压缩，密堆积成固态和类固态膜.

高纯氧化钬的电感耦合等离子体原子发射光谱分析及光谱干扰的校正

本文提出了以PGS-2型平面光栅摄谱仪与Plasma Therm ICP-5000D射频发生器联用,乙醇溶液预去溶进样方法,直接同时测定高纯氧化钬中5个稀土杂质元素的方法,并讨论了基体浓度对分析方法检出限的影响和光谱干扰及其校正。当样品溶液中稀土总浓度为5mg/ml时,测定下限分别为铽0.003％,镝、铒和铥0.002％,钇0.0003％。其相对标准偏差为2.8％～7.4％。

STRUCTURE OF HEXAMETHYLENETETRATELLURAFULVALENE DIIODIDE

C12H12I2Te4, M(r) = 920.44, monoclinic, P2(1)/n, a = 10.942 (2), b = 14.924 (2), c = 11.415 (2) angstrom, beta = 104.32 (1)-degrees, V = 1806.0 (5) angstrom 3, Z = 4, D(x) = 3.38 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 100.7 cm-1, F(000) = 1592, T = 294 K, R = 0.033 for 1828 observed reflections. One of the Te atoms is bonded to the two I atoms, which are on either side of the molecular plane. The Te-I distances are 2.963 (1) and 2.961 (1) angstrom, which means oxidation at the Te atom instead of at the C = C bonds.

同位素稀释-火花源质谱法分析人参样品中微量元素

本文采用同位素稀释-火花源质谱法定量分析了吉林野山参,园参及高丽参中30多种微量元素的含量。测定下限2μg/g,相对标准偏差在5～28％以内。

Isolation of the main light-harvesting chlorophyll a/b-protein complex from thylakoid membranes of marine alga, Bryopsis corticulans by a direct method

The main chlorophyll a/b light-harvesting complex (LHC 11) has been isolated directly from thylakoid membranes of marine green alga (Bryopsis corticulans Setch.) by two consecutive runs of anion exchange and gel-filtration chromatography. LHC 11 proteins in the membrane extracts treated with 3% n-Octyl-b-D-glucopyranoside (OG) obtained specific binding ability on Q Sepharose column, and thus were isolated from the thylakoid membranes in a highly selective fraction. The monomeric, trimeric and oligomeric subcomplexes of LHC 11 have been obtained by fractionation of the LHC 11 mixes with sucrose density gradient ultracentrifugation. The SDS-PAGE analysis of peptide composition and absorption spectrum showed that LHC 11 monomers, trimers and oligomers prepared through this work were intact and in high purity. Our report is the first to show that it is possible to purify LHC If directly from thylakoid membranes without extensively biochemical purification.

Sequence analysis and functional study of thymidylate synthase from zebrafish, Danio rerio

The thymidylate synthase (TS), an important target for many anticancer drugs, has been cloned from different species. But the cDNA property and function of TS in zebrafish are not well documented. In order to use zebrafish as an animal model for screening novel anticancer agents, we isolated TS cDNA from zebrafish and compared its sequence with those from other species. The open reading frame (ORF) of zebrafish TS cDNA sequence was 954 nucleotides, encoding a 318-amino acid protein with a calculated molecular mass of 36.15 kDa. The deduced amino acid sequence of zebrafish TS was similar to those from other organisms, including rat, mouse and humans. The zebrafish TS protein was expressed in Escherichia coli and purified to homogeneity. The purified zebrafish TS showed maximal activity at 28 degrees C with similar K-m value to human TS. Western immunoblot assay confirmed that TS was expressed in all the developmental stages of zebrafish with a high level of expression at the 1-4 cell stages. To study the function of TS in zebrafish embryo development, a short hairpin RNA (shRNA) expression vector, pSilencer 4.1-CMV/TS, was constructed which targeted the protein-coding region of zebrafish TS mRNA. Significant change in the development of tail and epiboly was found in zebrafish embryos microinjected pSilencer4.1-CMV/TS siRNA expression vector.