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101.
A combination of iterative Jacobsen’s hydrolytic kinetic resolution and reduction of a ketone for the construction of a 1,3-polyol moiety are key steps en route to a total synthesis of (+)-cryptocarya diacetate. 相似文献
102.
本文为戴安邦教授及其学生们关于多碱化学的研究的回顾和总结 ,叙述了他的早期工作 ,Cr3 的水解聚合 ,富马酸和马来酸存在下Cr3 的水解聚合 ,及稀土离子的水解聚合。这项研究对实用领域是有益的 ,诸如核化学 ,鞣革及塑料与金属的粘接 相似文献
103.
Long-term hydrothermal aging of polyamide 6 (PA6)/glass fibre (GF) composites was conducted and the effects of the GF on variations of structure and properties of the composites with aging time were investigated. It was found that the first stage of aging was a Fickian process and corresponded to the physical absorption of water until equilibrium, resulting in a slight change of reduced viscosity and chemical structure of the PA6. The water diffusing process was slowed down slightly by addition of the GF. The second stage of aging was the initiation process of hydrolytic degradation of PA6, resulting in a rapid decrease of reduced viscosity and an increase of end group content. In the final stage of aging, the relative weight gain (Wr) dropped, the reduced viscosity decreased and the end groups increased slowly. The degradation rate and carbonyl index of PA6 increased with increasing GF content, and the increasing rate of end groups concentration of the composites was higher than that of pure PA6 during the aging process, indicating addition of GF accelerated the hydrolysis degradation and oxidative aging of PA6. In mechanical property tests, compared with unaged samples of the composites which underwent matrix rupture around the matrix-fiber interfacial layer, for aged samples several smooth fibres without coatings were pulled out and the interfacial debonding was the main failure mode, causing severe deterioration in mechanical properties. The hydrolytic degradation activation energy (Ea) was calculated through a method based on the Arrhenius model by considering both temperature and humidity as environment factors; with increasing GF content, Ea decreased, indicating that the addition of GF made PA6 easier to degrade. 相似文献
104.
来源于厌氧微生物的乙酰辅酶A合成酶/一氧化碳脱氢酶(ACS/CODH)含有金属Ni和Fe所组成的多达7个金属簇中心,能够催化CO和CO2的可逆氧化还原,并利用CO/CO2和H2作为碳源和能源合成乙酰辅酶A. 近年来,随着全球能源危机和温室效应等环境问题的加重,这类金属蛋白酶的研究日益成为人们关注的热点. 电子顺磁共振光谱(EPR)作为一种研究金属价态和配位结构的有效技术,从20世纪80年代开始便被广泛地应用到该酶的研究中. 该文将从ACS/CODH的各个金属簇中心入手,介绍每个金属中心的结构、功能和EPR研究. 相似文献
105.
A convergent first stereoselective total synthesis of decarestrictine O via RCM protocol starting from 1,3-propanediol and propylene oxide is reported. 相似文献
106.
Zhiqiang Feng Guoqiang Fan Hongxia Wang Changyou Gao Jiacong Shen 《Macromolecular rapid communications》2009,30(6):448-452
Hollow polyphosphazene microcapsules have been fabricated by the covalent layer‐by‐layer assembly of polydichlorophosphazene (PDCP) and hexamethylenediamine (HDA) on aminosilanized silica particles, followed by core removal in a HF/NH4F solution. The hollow and intact microcapsules in both wet and dry states have been characterized by transmission electron microscopy and confocal laser scanning microscopy. The chemical structure of the microcapsules has been verified by FT‐IR spectroscopy. The microcapsules could be hydrolytically degraded in a phosphate buffer at biological pH.
107.
由于人肝细胞色素P450 2C亚家族与临床药物代谢的密切关系,其研究已引起人们的广泛关注。本文综述了四种人肝细胞色素P450 2C,着重综述了其中的三种:CYP2C9,CYP2C8,CYP2C19的研究进展。评述了CYP2C9,CYP2C8和CYP2C19的某些氨基酸残基在催化过程中的作用,这三种酶的基因多态在不同人种中的分布及药物代谢的差异,以及它们与用药的特异性及某些疾病的易感性的联系,介绍了目前提出的CYP2C8的底物药效团模型,最后总结了CYP2C9,CYP2C8,CYP2C19,CYP2C18的主要特性。 相似文献
108.
P. N. Lavrenko O. V. Okatova K. A. Andreeva B. Schulz 《Journal of Thermal Analysis and Calorimetry》2000,59(3):741-746
Translational diffusion of poly-2,5-(1,3-phenylene)-1,3,4-oxadiazole (PMOD) in solution in 96% sulphuric acid was studied,
and intrinsic viscosity was measured at different stages of thermal degradation. Polymer solution has previously been subjected
to heating at temperature ranging from 75 to 104°C and then investigated at 26°C. A monotonic decrease in intrinsic viscosity
and the molecular mass, M, of degraded products with increasing degradation temperature was detected. The rate constant of the degradation process
has been obtained from the change in M of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated
by using the temperature dependence of the rate constant. The activation energy (E =102±8 kJ–1 ) is close to that obtained previously for the hydrolysis of poly-2,5-(1,4-phenylene)-1,3,4-oxadiazole (PPOD) in sulphuric
acid (106 kJ–1 ), the rate constant being approximately twice in the value.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
109.
110.