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41.
以一种新型的醌类光敏剂—菌生素 (HMB)为模型化合物 ,利用量子化学从头算HF/ 6 31G和含时密度泛函TD B3LYP/ 6 31G方法计算研究了卤代作用对醌类光敏剂分子性质和光敏活性的影响 .结果发现 ,卤代作用降低了HMB母体的HOMO和LUMO能级 (EHOMO和ELUMO)及其差值△E ,随卤族元素从上到下 ,EHOMO和ELUMO呈增大趋势 ,而△E呈减小趋势 ,使得分子激发光谱有不同程度的红移 ,在增加PQP三重态量子产率的同时降低了分子最低三重激发态的能量 ,两种作用相互抵消 ,使得卤代物的 1O2 量子产率与母体相似 ;增加了分子的绝热电子亲合势 ,使分子产生O2 -的能力下降 ;卤原子的引入 ,降低了HMB母体分子内氢键的强度 ,同时使顺式构型的分子内质子传递势垒增大 ,而使反式构型势垒减小 . 相似文献
42.
Michaël Ternon 《Tetrahedron》2004,60(39):8721-8728
FRET based systems are some of the best methods available to detect and monitor proteolytic activity. To enhance fluorescent signals and hence assay sensitivity, two different systems were developed using two different dendrimeric constructs. In the first case, a triple branched dendrimer bearing three dansyl groups was used to enhance assay sensitivity and showed a significant enhancement of fluorescence following enzymatic cleavage. In another example, a tris-fluorescein probe, that undergoes self-quenching, was utilized in a combinatorial library synthesis to map the substrate specificity of proteases. 相似文献
43.
医疗和危险废物高温洁净热处理及环境力学 总被引:3,自引:0,他引:3
结合2003年中国的突发危害公众健康的事件,分析了医疗、化学战剂及危险废物的分类、特性,比较了各种高温热处理技术的基本要求,方法分类和设备特点,包括:各类焚烧炉、热解炉和等离子体裂解装置.还对前处理工艺要求,尾气处理工艺等进行了分析讨论,讨论了防止二次污染的技术手段,特别介绍了二噁英等高危险性产物的特性.还介绍了发达国家的医疗废物和危险废物的管理、处置和二次污染防治等情况. 相似文献
44.
《Magnetic resonance in chemistry : MRC》2003,41(8):626-628
15N isotopic enrichment was necessary for the unequivocal assignment of the 1H NMR lines to the protons in the NH–OH fragment of benzohydroxamic acid, BHXA, C6H5CONHOH, in dry dimethyl sulfoxide solutions. The assignment [δ(NH) = 11.21, δ(OH) = 9.01, 1J(15N,1H) = 102.2 Hz, 2J(15N,1H) <1.5 Hz], which is opposite to that used by other authors, confirms the assignment extended to BHXA by Brown and co‐workers from the spectra of acetohydroxamic acid. The enrichment allowed also assignment of the 29Si lines in the spectra of disilylated benzohydroxamic acid, (Z)‐tert‐butyldimethylsilyl N‐tert‐butyldimethylsilyloxybenzoimidate (2) and (Z)‐tert‐butyldiphenylsilyl N‐tert‐butyldiphenylsilyloxybenzoimidate (3), and confirmed structure of the monosilylated products, N‐tert‐butyldiphenylsilyloxybenzamide (4) and N‐tert‐butyldiphenylsilyloxy benzoimidic acid (5). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
45.
Archana Devi 《European Polymer Journal》2007,43(6):2422-2432
Cardanol-based novolac-type phenolic resins were synthesized with different mole ratios of cardanol-to-formaldehyde, viz., 1:0.6, 1:0.7, and 1:0.8. These novolac resins were epoxidized with molar excess of epichlorohydrin at 120 °C in basic medium. The epoxidized novolac resins were, separately, blended with different weight ratios of carboxyl-terminated polybutadiene liquid rubber ranging between 0-25 wt% with an interval of 5 wt%. All the blends were cured at 150 °C with 40 wt% polyamide. The formation of various products during the curing of blend samples has been studied by Fourier-transform infra-red spectroscopic analysis. The tensile strength and elongation-at-break of the cured samples increased up to 15 wt% in the blend and decreased thereafter. This blend sample was also found to be most thermally stable system. The blend morphology, studied by scanning electron microscopy analysis, was finally correlated with the structural and property changes in the blends. 相似文献
46.
47.
N. A. Anikin A. S. Mendkovich M. B. Kuzminskiy A. M. Andreev 《Russian Chemical Bulletin》2008,57(2):428-430
A new fast computational method for mass calculations of docking complexes by the AM1/PM3 semiempirical methods is proposed.
The computation time is shortened by at least an order of magnitude compared to alternative schemes of quantum chemical calculations.
The root-mean-square deviation of the AM1 calculated energies of formation of complexes from the results obtained by conventional
diagonalization procedure is at most 0.4 kcal mol−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 418–420, February, 2008. 相似文献
48.
R. W. Home 《Physics in Perspective (PIP)》2005,7(4):473-490
I survey highlights of the practice of physics and allied sciences in Melbourne,Australia, from the 1850s, soon after Europeans
first settled in the area, to the present. I note recognizable sites of past and current physical-science activity that may
be visited, as well as exhibits of historic items of physics apparatus. I trace the role of physics, in the course of a century
and a half, in the evolution of a pioneering settlement into a large city embedded in a modern industrial economy. 相似文献
49.
U.Deva Priyakumar 《Tetrahedron letters》2004,45(12):2495-2498
A novel preference for planar tetracoordination was observed over the conventional tetrahedral arrangement in a new series of C5H2, C5H4, C5H41+/2+ and related compounds. The stability of these molecules is assessed with the ring-opening barriers, HOMO-LUMO gap, singlet-triplet energy differences and nucleus independent chemical shift values. 相似文献
50.
Summary The potential of liquid chromatography-mass spectrometry (LC-MS) has been studied for the simultaneous determination of sixteen carbamate and organophosphorus pesticides in honeybees using a traditional sample preparation protocol based on acetone extraction and dichloromethane partitioning. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ES) interfaces were compared. APCI offered better sensitivity and specificity for a higher range of pesticides. Limits of quantification were from 0.01 to 0.17 mg kg–1, at which recoveries obtained were between 64 and 93%, except for pirimicarb that was at 13%, with relative standard deviations ranging from 7 to 20%. Fenitrothion, fenoxycarb, methiocarb and phoxim were found in bees from Valencian Community beehives at concentrations between 0.03 and 3.75 mg kg–1. 相似文献