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991.
Lipophilic tea polyphenols (LTP) were prepared by catalytic esterifieation of green tea polyphenols (GRIP) with hexadeeanoyl chloride. A novel long-chain aeyl-derivative of epigalloeateehin-3-o-gallate(EGCG) was first isolated from purification of LTP by high-speed eountereurrent ehromatography (HSCCC)using a solvent system composed of n-hexane-ethyl acetate-methanol-water ( 1 : 1 : 1 : 1, v/v) . The moleeularstructure of the acyl-derivative, Epigallocatechin-3-O-gallate-4‘-O-hexadeeanate , was elucidated by meansof elemental analysis, IR, 1H-NMR and MS spectra. 相似文献
992.
The technique of neutron activation analysis (NAA) has been employed to measure the content of 29 kinds of elements in the sample of Yaozhou porcelain bodies,Then a fuzzy cluster analsis has been conducted to the NAA data and a diagram of the dynamic fuzzy cluster analysis has been achived,The results indicate that the batch of ancient Yaozhou porcelain bodies,which were of different overglaze color and were produced by different kilns during a period of over 800 years from the Tang Dynasty (618-907 A.D.) to the Yuan Dyansty(1271-1368 A.D.) ,has shared a stable and concentrated raw material source,Provenances of porcelain bodies from different times ,though having their specific independence ,enjoy a close relationship and are not far from one another,Provenances of porcelain bodies made during the Tang Dynasty and the Five Dynasties (907-960 A.D.)are found to be closer to one another,while those of the Song (960-1279A.D.) and the Jin Dynasty (1115-1234 A.D.)are comparatively concentrated in certain areas and are different from those of the Tang Dynasty .Both the tri-colored glazed pottery made in Yaozhou kilns during the Tang Dynasty and the Yaozhou porcelain bodies of the Tang period are from the same provenance. 相似文献
993.
GAOTao MENGGuowen ZHANGLide 《科学通报(英文版)》2003,48(11):1090-1092
Photoluminescence (PL) properties of porous anodic alumina (PAA) films prepared by using electrochemical anodization technique in a mixed solution of oxalic and sulfuric acid have been investigated. The PAA films have an intensive ultraviolet PL emission around 350 nm, of which a possible PL mechanism has been proposed. It was found that the incorporated oxalic ions, which could transform into PL centers and exist in the PAA films, are responsible for this ultraviolet PL emission. 相似文献
994.
Pitfalls in the analysis of ancient human mtDNA 总被引:3,自引:0,他引:3
YAOYonggang ZHANGYaping 《科学通报(英文版)》2003,48(8):826-830
The retrieval of DNA from ancient human specimens is not always successful owing to DNA deterioration and contamination although it is vital to provide new insights into the genetic structure of ancient people and to reconstruct the past history. Normally, only short DNA fragments can be retrieved from the ancient specimens. How to identify the authenticity of DNA obtained and to uncover the information it contained are difficult. We employed the ancient mtDNAs reported from Central Asia (including Xinjiang, China) as an example to discern potentially extraneous DNA contamination based on the updated mtDNA phylogeny derived from mtDNA control region, coding region, as well as complete sequence information. Our results demonstrated that many mtDNAs reported are more or less problematic.Startim, from a reliable mtDNA phylogeney and combining the available modern data into analysis, one can ascertain the authenticity of the ancient DNA, distinguish the potential errors in a data set, and efficiently decipher the meager information it harbored. The reappraisal of the mtDNAs with the age of more than 2000 years from Central Asia gave support to the suggestion of extensively (pre)historical gene admixture in this region. 相似文献
995.
GAO Lin WANG Dongyan LI Yang BU Dingfang CHANG Lin PANG Yongzheng QI Yongfen & TANG Chaoshu . Institute of Cardiovascular Disease Research Peking University First Hospital Beijing China . Department of Physiology Peking University Health Science Center Beijing China 《科学通报(英文版)》2003,48(10):983-987
Homocysteine (Hcy), a highly reactive sulfur- containing amino acid, is an intermediate product of methionine metabolism. Elevation of plasma Hcy has been widely studied as an independent risk factor for many cardiovascular diseases such as atherosclerosis, thrombosis, etc.[1]. Inherited hyperhomocysteinemia cases usually suffer from occlusion or thrombosis in arteries and large veins before the age of 20. Hyperhomocysteinemia significantly reduces the survival rate[2] and dilatation functi… 相似文献
996.
Thermodynamic evolution of lithosphere of the North China craton: Records from lower crust and upper mantle xenoliths from Hannuoba 总被引:1,自引:0,他引:1
LIU Yongsheng * GAO Shan LIU Xiaoming CHEN Xiaoming ZHANG Wenlan & WANG Xuance . Faculty of Earth Sciences China University of Geosciences Wuhan China . The State Key Lab for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing China . Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi抋n China Correspondence should be addressed to Liu Yongsheng 《科学通报(英文版)》2003,48(21):2371-2377
Lithospheric thinning in East China attracts much attention of geologists. In many cases where a lithospheric thinning is inferred, the trigger for instability is a preced-ing episode of crustal thickening by the continental colli-sion[1]. Lithospheric processes (e.g. lithospheric thinning) could be recorded by the thermal history of the lower crustal and upper mantle xenoliths. Xu et al.[2] suggested that the cooling (from >1200 to 850℃) recorded by spinel harzburgite from Northeast China … 相似文献
997.
998.
通过论述消防应急平台的定义、组成及建设模式,介绍应急指挥系统的特点及功能等,来论述CDMA无线图像传输技术在消防工作中的应用。 相似文献
999.
1000.
通过论述消防应急平台的定义、组成及建设模式,介绍应急指挥系统的特点及功能等,来论述CDMA无线图像传输技术在消防工作中的应用。 相似文献