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101.
Wei Lei Wei Shen Ming Li College of Chemistry Chemical Engineering Southwest University Chongqing People's Republic of China liming@swu.edu.cn 《Molecular simulation》2013,39(6):637-643
The electronic structures of monomers, oligomers and polymers of poly(p-phenylenevinylene) (PPV) derivatives are calculated and analysed based on density functional theory (DFT) methods. The influences of different substituent groups on the band gaps are discussed. Strong relationships are found between band-gap and bond length alternation (BLA) of polymers, and between band-gap and Wiberg bond index (WBI). Analysis of nuclear independent chemical shift (NICS) reveals that oligomers with similar energy gaps have close values of NICS. 相似文献
102.
小麦高分子量麦谷蛋白亚基的遗传变异与小麦加工品质改良 总被引:1,自引:0,他引:1
高分子量麦谷蛋白亚基(HMW-GS)是小麦胚乳中一种具有多态性的蛋白质组分,在面团中它们可以通过相互之间或与低分子量麦谷蛋白亚基(LMw-Gs)之间形成二硫键来组成麦谷蛋白多聚体。由于其在小麦面粉加工所需的粘性和弹力方面具有极其重要的作用,过去几十年间在小麦加工品质相关蛋白研究方面的工作大多数集中在高分子量麦谷蛋白亚基上。近几年在高分子量麦谷蛋白亚基及其编码基因的鉴定、基因的遗传变异以及不同变异在小麦加工品质中的作用方面进行了大量研究。本文对近几年在HMW-GS领域的研究进展进行综述并且重点讨论HMW-GS的变异及其对小麦品质育种的重要意义。 相似文献
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以纤维素为原料,以自制的不同硅铝比ZSM-5(38)/Al-MCM-41微-介孔复合分子筛为催化剂,在固定床反应器上进行了催化热解实验。采用XRD表征分子筛,采用GC-MS分析生物油成分,考查了催化剂的改变对生物质热解产物及生物油成分的影响。实验结果表明:添加催化剂后,生物油产率降低,且其含水率也有所增加。与未添加催化剂相比,生物油中D L-2,3-丁二醇有明显提高。其中,ZSM-5(38)/Al-MCM-41(20)最有利于苯酚、愈创木酚(2-甲氧基-苯酚)的生成。此外,这几种催化剂均有利于小分子化合物的生成,其中,ZSM-5(38)有利于C4~C5化合物的生成,微-介孔复合分子筛则有利于C6~C8化合物的生成。 相似文献
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由于冠状动脉支架介入治疗具有手术创伤小、操作简单、见效快、病人恢复时间短等诸多优点,在治疗心血管动脉粥样硬化或血栓堵塞方面,有逐渐替代外科搭桥手术的趋势。虽然血管支架技术在临床已经有广泛应用,治疗效果也有明显的改善,但是依然存在许多不足需要改进。本文首先回顾了血管支架的发展历程,然后针对血管支架研究中与血流动力学相关的几个待解决的问题进行了论述,以期从血流动力学的角度为血管支架的改进和发展提出建议。 相似文献
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Zhifeng Xiao~ Yaxian Kong~ Shufa Yang~ Meiyu Li~ Jinhua Wen~ Lingsong Li~ ~Peking University Stem Cell Research Center Cell Biology.Department Peking University Health Science Center Beijing China 《Cell research》2007,(1)
Neural stem cells (NSCs) constitute the cellular basis for embryonic brain development and neurogenesis.The processis regulated by NSC niche including neighbor cells such as vascular and glial cells.Since both vascular and glial cellssecrete vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF),we assessed the effect ofVEGF and bFGF on NSC proliferation using nearly homogeneous NSCs that were differentiated from mouse embryonicstem cells.VEGF alone did not have any significant effect.When bFGF was added,however,VEGF stimulated NSCproliferation in a dose-dependent manner,and this stimulation was inhibited by ZM323881,a VEGF receptor (Flk-1)-specific inhibitor.Interestingly,ZM323881 also inhibited cell proliferation in the absence of exogenous VEGF,suggestingthat VEGF autocrine plays a role in the proliferation of NSCs.The stimulatory effect of VEGF on NSC proliferationdepends on bFGF,which is likely due to the fact that expression of Flk-1 was upregulated by bFGF via phosphoryla-tion of ERK1/2.Collectively,this study may provide insight into the mechanisms by which mieroenvironmental nichesignals regulate NSCs. 相似文献
109.
Characterization of human embryonic stem cell lines by the International Stem Cell Initiative 总被引:1,自引:0,他引:1
International Stem Cell Initiative Adewumi O Aflatoonian B Ahrlund-Richter L Amit M Andrews PW Beighton G Bello PA Benvenisty N Berry LS Bevan S Blum B Brooking J Chen KG Choo AB Churchill GA Corbel M Damjanov I Draper JS Dvorak P Emanuelsson K Fleck RA Ford A Gertow K Gertsenstein M Gokhale PJ Hamilton RS Hampl A Healy LE Hovatta O Hyllner J Imreh MP Itskovitz-Eldor J Jackson J Johnson JL Jones M Kee K King BL Knowles BB Lako M Lebrin F Mallon BS Manning D Mayshar Y McKay RD Michalska AE 《Nature biotechnology》2007,25(7):803-816
The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected. 相似文献
110.