排序方式: 共有54条查询结果,搜索用时 546 毫秒
41.
ZHAO Liang XU Zhi-Qiang WU Chang-Chun XIE Fu-Xin NI Shi-ShengDepartment of Chemistry Anhui University Hefei Anhui S ChinaLUO YiInternational Programs Anhui University Hefei Anhui China 《中国化学》1997,(2)
In this paper we report a chemical oscillation catalyzed by [Ni(Me2[14]1,3-diene N4)]2+ (Me2[14]l,3-diene N4 denotes 2,3-dimethyl-l,4,8,ll-tetraazacyclotetradeca-1,3-diene) in BrO3--pyruvic acid-H2SO4 system.The domain of the existence of the oscillation was obtained.The effects of initial concentration of the components on the oscillation were studied.The features of the oscillations were described in detail.We also examined the effects of Ag+,Hg2+,CCl4,free radical inhibitors,etc.on the osillations. 相似文献
42.
In this paper we report a chemical oscillation catalyzed by [Ni(Me2[14]l,3-diene N4)]2+ (Me2[14]1,3-diene N4 denotes 2,3-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,3-diene) in BrO3-pyruvic acid-H2SO4 system. The domain of the existence of the oscillation waa obtained. The effect of initial concentration of the components on the oscillation were studied. The features of the oscillations were described in detail. We also examined the effects of Ag+, Hg2+, CCl4, free radical inhibitors, etc. on the oscillations. 相似文献
43.
Two new iridoid glycosides designated as senburiside III (2) and senburiside IV (3), together with one known iridoid glycoside senburiside I (1) and three known secoiridoid glucosides swertiamarin (4), gentiopicroside (5) and sweroside (6), were isolated from the whole plant of Swertia franchetiana. The structures of the two new compounds were elucidated by spectroscopic methods. 相似文献
44.
以天然五环三萜类化合物齐墩果酸为原料, 通过氧化、酯化、环合和曼尼希等反应, 对A环2, 3位和28位进行结构修饰, 设计合成了16个衍生物; 通过理化性质、质谱和核磁数据确定了化合物结构. 对合成的衍生物进行了体外α-葡萄糖苷酶抑制活性筛选, 结果表明, 受试化合物在200 μg/mL浓度下显示出不同程度的酶抑制活性. 初步构效关系分析表明, 28位游离羧基是活性必需基团, 3位羟基或相应的氢键供体取代基有利于提高活性. 相似文献
45.
Bacterial infections and the associated morbidity and mortality due to bacterial pathogens in wounds and medical implants have been increasing as most of current coatings cannot fulfill all the requirements including excellent intrinsically antibacterial activity, low cytotoxicity, and favorable physical properties. Herein, we present a kind of antibacterial hydrogel based on ε-poly(L-lysine) (EPL) grafted carboxymethyl chitosan (CMC-g-EPL) as the inherently antibacterial matrix and the surplus EPL as highly efficient antimicrobial agent. Such hydrogels possess tunable swelling abilities with water absorption percentages of 800%-2000% and modulus varying from 10 kPa to 100 kPa, and exhibit two-stage excellent antibacterial behavior. First, the free EPL can be released from the hydrogel network for quick and highly efficient bacteria killing with 99.99% of efficacy; second, the grafted EPL endows hydrogel matrix with prolonged intrinsically antibacterial activity, especially when most of free EPL is released from the hydrogel. Overall, we provide a new insight for preparing highly effective antibacterial hydrogels. 相似文献
46.
基于大气激光后向散射光谱,研究和设计了探测大气CO2浓度的Raman激光雷达,其发射机采用Nd:YAG激光的三倍频354.7nm作为工作波长,发射的单脉冲能量350mJ,重复频率20Hz;接收机采用了光电倍增管(量子效率25%)和光子计数器(计数速率200MHz),探测CO2的Raman散射371.66nm(频移1285cm-1信号,(1小时累加)近地面2.5km以内信噪比不小于8.采用组合滤光片来抑制强的354.7nm Mie-Rayleigh后向散射和氧气375.4nm Raman后向散射对信号的严重干扰.比较分别来自大气CO2和参考气体N2的Raman后向散射回波,可反演出大气中CO2的相对浓度. 相似文献
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近年来,带电离官能团取代的大环成为大环化学研究的热点之一 [1~ 3]。这类大环除了环的腔径及环上配位原子种类对不同离子具有配位选择性外,其电离官能团的酸碱效应,也产生对 pH敏感的配位选择性。另外,由于大环骨架的相对刚性,刚柔相济的作用还起到提高配位能力,改进选择性的效果。迄今为止,人们对全氮取代的氮杂大环及其配合物作了相当深入的研究 [4~ 6],部分氮取代的氮氧杂大环及其配合物的研究还很少 [7,8]。从研究配体配位性能的观点来看,改变大环上氮取代的电离官能团数目可以进一步开发出具有良好选择性的配体。本文报道… 相似文献
49.
从理论上分析了激光被聚焦到高压气体内可能发生各种非线性现象的规律及其相互作用和相互干扰.在实验中把Nd:YAG四倍频激光聚焦到充有甲烷的拉曼管内,测各阶斯特克斯光输出能量与气压pa、透镜焦距f和输入能量Ep之间的关系.实验结果与理论分析定性地相符合,这就为我们优化和利用受激拉曼过程提供了理论和实验依据.
关键词:
非线性过程
受激拉曼散射
四波混频
激光诱导离解 相似文献
50.
A new N,N′-diacetic acid substituted azacrown ether containing thiophere ring ligand(H2L) has been synthesized by using salicylaldehyde, diamine, thiophene and bromoacetic acid as starting materials. With this ligand, its lanthanide complexes [ML(NO3)]·nH2O(M=La,Ce,Pr,Nd,Sm,Eu,Dy,Er,Yb;n=2 or 3) are prepared. These compounds are characterized by elemental analysis, IR, 1H NMR, MS and conductivity measurements. The results show that ether oxygen, carboxy oxygen, nitrogen atoms and nitrate ion are coordinated to the metal ion. 相似文献