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Alstonerine属于单萜吲哚生物碱,除其结构很有特征外,还报道对两株人肺癌细胞具有细胞毒性,因此,它自然就成为合成化学的重要目标.已经有多种合成策略用于构建这个结构体系:包括Pictet-Spengler反应和Dieckmann缩合反应、烯烃复分解关环反应、膦配体催化的[4+2]关环/Friedel-Craft环化、氮杂-Diels-Alder反应/分子内Heck反应、Pauson-Khand反应等.本工作根据构建环系的不同反应系统总结了Alstonerine的合成方法.大部分合成反应步骤较多,适合工业生产的有效合成方法还有待于进一步探索. 相似文献
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根据前列腺素的结构特点,着重讨论用Corey的逆合成法进行推导合成,并讨论前列腺素的合成方法和研究进展,参考文献11篇。 相似文献
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取代喹啉新化合物的光化学合成谭成权(大连大学化学化工系116622)谭成权51岁,教授,从事金属有机化合物的合成及反应、杂环化合物的合成及氮杂二烯的光化学反应研究。1997-06-30收稿关键词1-N-苯甲酰基-4-氨基-1-氮杂丁二烯紫外光照射光环... 相似文献
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NH3是一种重要的化工原料,是氮肥工业的基础.但常规的合成NH3技术,能量消耗是十分巨大的,占总成本的70%[1].而且其生产条件恶劣、设备庞大、运行费用高.因此,从60年代起,许多试图在温和条件下合成NH3的新方法应运而生[2].其中,常压非平衡等离子体合成NH3是较为理想的一种.它是将H2、N2气体按一定比例混合,在超强窄脉冲电场中产生流光放电,使气体分子激发、电离、自由基化,成为高浓度的非平衡等离子体,高活化状态的H、N原子化合成为NH3分子. 相似文献
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合成子和合成等效剂是有机合成的发展过程中提出的新概念。深刻了解这一概念及其有关知识对于提高有机合成设计水平和发展有机合成设计技巧,尤其在运用计算机进行有机合成路线的择优中,都具有一定的意义。本文将分别就合成子、合成等效剂以及合成子的类型转换作一介绍。 相似文献
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CO加氢合成异丁烯研究进展与展望 总被引:1,自引:0,他引:1
综述了由合成气选择性合成异丁烯的各种催化剂体系,比较和评价了这几种催化剂体系的活性,选择性以及反应条件,重点概述了文献对这一反应机理的研究,并展望了这一领域存在的研究机遇。 相似文献
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综述了壳聚糖、甲壳素在污水处理、电化学、原子吸收光谱、高效液相色谱、吸光光度法中的应用。引用文献28篇。 相似文献
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P.N. Joshi N.K. Ramaswamy M.K. Raval T.S. Desai P.M. Nair U.C. Biswal 《Journal of photochemistry and photobiology. B, Biology》1993,20(2-3):197-202
Wheat seedlings, grown for 7 days in the light, were allowed to senesce in the light or dark, and the change in the photosystem II (PS II) photochemistry of chloroplasts isolated from the primary leaves of these seedlings was investigated. The decrease in oxygen evolution and the fast fluorescence results indicated that the impairment of PS II in the leaves of seedlings senescing in the light was different from that in the leaves of seedlings senescing in the dark. Thermoluminescence studies showed a structural modification in the QB protein of chloroplasts isolated from leaves senescing in the light and an alteration in the S state transition of chloroplasts isolated from leaves senescing in the dark. 相似文献
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Here we report on the role of oxygen in the evolution of radial heterogeneity in the fibre structure and properties of PAN fibres stabilized in air and vacuum at different temperatures. Modulus mapping by Nano-indentation showed heterogeneous modulus distribution in the fibres treated in air, while no variation in modulus was observed in fibres processed in vacuum. Raman spectroscopy and elemental analysis revealed that the temperature dependent oxygen diffusion from skin to core of the fibres assisted in the evolution of higher extent of sp2-hybridized carbons in the skin compared to core of the air treated samples. Conversely, no radial structure variations were observed in the vacuum treated fibres. Higher modulus in the skin of air-treated fibres was due to the formation of compact structures which was associated with the enhanced intermolecular interactions facilitated by the formation of C=C bonds within the polymer backbone, promoted by oxidative-dehydrogenation reaction. Supporting these observations, the fracture morphology examined by SEM showed a brittle fracture in the skin and ductile fracture in the core. 相似文献
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Calibration methods for microdialysis sampling were studied in the muscle and adipose tissue of rats. Both the delivery method and the no-net-flux method were used to determine the extraction efficiency (EE) of acetaminophen and caffeine in both tissues. There was no concentration dependence of the EE either in vitro or in vivo for either acetaminophen or caffeine. The EEs determined by the delivery and no-net-flux methods were not different. However, the EEs of both caffeine and acetaminophen determined in vitro were significantly higher than those determined in the muscle and adipose. This indicates that mass transfer in the tissue is the rate-determining factor for the EE in vivo. The relative difference between the EE in vitro and the EE in the muscle was smaller than the difference between the EE in vitro and the EE in the adipose. In addition, the EE in the muscle decreased more than the EE in the adipose after the animal was euthanized. This indicated that exchange between the extracellular fluid and plasma is the rate-determining step in mass transport relative to microdialysis sampling. This has a more significant effect on the EE in the muscle than the EE in the adipose. Both the delivery and no-net-flux methods can be used to calibrate microdialysis probes in the muscle and adipose. 相似文献
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Skupińska Jadwiga Karpińska Monika Ołówek Maria Kasprzycka-Guttman Teresa 《Central European Journal of Chemistry》2005,3(1):28-39
The PdCl2/Fe/I2/Py catalytic system (Py-pyridine), reported to be highly active in the reaction of nitrobenzene carbonylation to ethyl phenylcarbamate
was studied. The present paper describes the role of catalyst components and its effect on the activity and selectivity of
the catalyst. The increase in the amount of PdCl2 in the system while retaining a constant level of the other catalyst components, results in the increase of both carbamate
and aniline yields. The increase in the amount of iron while retaining the other components constant, initially causes an
increase in the carbamate yield; however, at Fe: Pd ratios higher than 36, the carbamate yield remains constant. The change
in the amount of iron has no effect on the amount of aniline formed in the system. An increase in the amount of iodine in
the system while retaining the other components constant, results in a decrease in carbamate yield and a considerable increase
in the aniline yield of the reaction products. 相似文献
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The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised. 相似文献
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煤烘玉米和饮水为介质地氟病区骨畸形病人全血尿多元素含量的分析 总被引:1,自引:1,他引:0
李福成 《广东微量元素科学》2000,7(3):37-41
采集了贵族个煤烘玉米为主要介质和河北2个饮水为介质氟病区内骨畸形病人的全血、尿、检测了其中8种元素含量,结果表明,贵州各氟病区少儿骨软化与成年骨硬化畸形病人的全血铝、钙、磷、铁和尿氟、铝均显著高于同龄对照组,尿磷均低于同龄对照组。少儿骨软化病人全血锌均下降,尿锌多下降。某水型氟病区骨软化经产妇尿氟、全血铜升高;骨软化少年全血铝显著升高,锌、铁下降,尿氟升高,尿锌,磷下降。海边的典型氟骨症病人全血、 相似文献
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Hiroshi Hasegawa 《应用有机金属化学》1997,11(4):305-311
Seasonal changes in the distribution of arsenic species were observed in a dredged area in the southern basin of Lake Biwa, Japan. The concentrations of dimethylarsenic acid [DMAA(V)] became comparable with those of inorganic forms during a stratification period. DMAA(V) increased not only in the photic zone but also in the hypolimnion. In the photic zone, an increase in DMAA(V) was observed with the yearly maximum of water temperature. In the hypolimnion, the seasonal changes in methylarsenicals differed from those in surface waters. DMAA(V) maxima appeared seasonally under sub-anoxic conditions and developed regionally at the redox boundary and above the sediment surface. The DMAA(V) concentrations increased in the initial period of oxygen depletion and just after the disappearance of anoxia, while they diminished in the anoxic hypolimnion by midsummer. The seasonal behavior of trivalent methylarsenicals, which are readily oxidized in oxic environments, was similar to that of DMAA(V). The total arsenic concentration in the surface layer rose to a maximum in late summer. Methylarsenicals did not increase in such a way that the total arsenic concentration increased during summer. © 1997 by John Wiley & Sons, Ltd. 相似文献
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Effect of plasticizer concentration on the hysteresis,tear strength and stress-relaxation characteristics of black-loaded rubber vulcanizate 总被引:1,自引:0,他引:1
N. K. Dutta 《Colloid and polymer science》1991,269(4):331-342
The effect of plasticizer concentration on the stress softening, tear strength and stress relaxation of black loaded bromobutyl rubber vulcanizate has been investigated. The stress softening in the rubber vulcanizate, an energy dissipative process at higher strain, may be explained primarily by changes that take place in the rubber phase of the filled vulcanizate. Increased plasticizer concentration leads to decrease in the equilibrium hysteresis. A quantitative relationship between energy density and hysteresis has been derived, which is applicable at and below the elongation at break. Increase in plasticizer concentration results in decrease in the effective diameter of the tip of the tear, which in turn decreases the tear strength. Rate of relaxation decreases with increase in the plasticizer concentration in the carbon-black-filled vulcanizate. 相似文献