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71.
五味子对心血管、免疫系统及CNS具有调节作用,阐述了五味子中有效成分木脂素和多糖保护心室重构的作用. 相似文献
72.
Preparation of rare-earth-modified medical stone powders and their application as conductive fillers
Traditional metal conductive fillers are expensive and prone to oxidation. Thus, the development of new conductive powders as fillers is urgently needed. A novel gaseous penetration technology was adopted to prepare La-doped medical stone powders(La-MSPs), which are inexpensive mesoporous materials, as a new kind of conductive filler material. The prepared La-MSPs attained a resistivity of 450 ?·m and were used as a filler to prepare conductive coatings with epoxy resin as the resin matrix. The influence of the La-MSPs dosage on the resistance and hardness of the coatings was also determined. The resistance and the hardness both decreased with increasing filler dosage. Finally, the optimum recipe of the conductive coatings with the most suitable fillers dosage(55 wt%) was obtained. The hardness and resistance of the coatings with 55 wt% La-MSPs were HV 4 and 5.5 × 10~7 ?, respectively. 相似文献
73.
语音识别中HMM与自组织神经网络结合的混合模型 总被引:9,自引:0,他引:9
基于隐马尔可夫模型和自组织神经网络模型提出了一种用于语音识别的混合模型,给出了训练调整权向量的算法,实验结果表明其在语音识别中具有很好的性能· 相似文献
74.
75.
Jinsong Li Dayuan Chen Zhiming Han Ziyu Zhu Duancheng Wen Qingyuan Sun Zhonghua Liu Minkang Wang Li Lian Jun Du Pengyan Wang Hemin Zhang 《科学通报(英文版)》2002,47(6):467-469
Interspecies somatic nuclear transfer (NT) may provide a new approach for preservation of the endangered rare species. Previous
interspecies cloning studies have shown that a nucleus from a quiescent somatic cell supports early development of reconstructed
embryos in the ooplasm from another species. In this study, we transferred nonquiescent somatic cells from a giant panda into
the perivitelline space of the enucleated rabbit oocytes. After electrofusion (at the rate of 71.6%) and electrical activation,
4.2% of the panda-rabbit reconstructed embryos developed to blastocyst in vitro. For improving the development rate of reconstructed embryos, we used serial NT in this study, i.e. blastomeres from reconstructed
morulae were transferred into the perivitelline space of the enucleated rabbit oocytes. The fusion rates in the groups of
serial I, serial II and serial III were 79.5%, 84.1% and 78.0%, respectively, having no difference with that of somatic group.
And the blastocyst rates in serial NT groups were 19.4%, 13.5% and 10.3%, respectively, which are significantly higher than
that in somatic NT group. These results indicate that the nuclei from nonquiescent somatic cells can support early development
of reconstructed embryos and serial NT can improve the development rate of interspecies reconstructed embryos.
These authors contributed equally to this work. 相似文献
76.
目前世界能源发展由化石能源向新能源转化,天然气作为清洁的化石能源是两者过渡最好的选择。鄂尔多斯盆地延安地区山西组地层是中国陆相页岩气勘探潜力较大的层系,近年来已经获得了巨大的勘探开发成果。为进一步加深对该地区的地质认识,以鄂尔多斯盆地延安地区山西组泥页岩为研究对象,综合应用野外露头、岩心、测井等资料,开展山西组岩石类型、岩相类型、沉积相展布研究。结果表明:延安地区山西组泥页岩主要发育泥质硅质页岩(S-3)、黏土岩(CM)、含钙/硅质黏土页岩(CM-1)、含钙/黏土质硅质混合页岩(M-2)四种岩相类型。页岩、粉砂质泥岩、碳质泥岩、细粒砂岩4种岩石类型。发育滨浅湖亚相、三角洲前缘亚相和前三角洲亚相,研究区水下分流河道砂体呈南北条带状发育。通过有机质成熟度(Ro)、有机碳含量(TOC)、暗色泥岩厚度将岩相进一步划分为3种类型,其中Ⅰ型岩相为油气勘探有利岩相,在山1段主要分布在延长东部地区、北部地区,山2段主要分布在甘泉下寺湾地区。 相似文献
77.
研究了广枣-肉豆蔻片的制备过程并对其质量进行控制。基于《中国药典》(2020年版)片剂项要求,考察片剂的外观性状、硬度、崩解时限、重量差异及脆碎度;采用高效液相色谱法测定广枣-肉豆蔻片中4种抗氧化成分的含量。结果表明,片剂外表光滑,色泽均匀,硬度值处于30~40 N,崩解时限控制在10 min内,脆碎度小于1%;槲皮素、原儿茶酸、甲基丁香酚、肉豆蔻醚分别在0.16~0.8μg/mL(r=0.999)、4~20μg/mL(r=0.999)、8~40μg/mL(r=0.999)、100~500μg/mL(r=0.999)内呈良好的线性关系,平均回收率分别为99.3%、101.6%、100.3%、99.3%。且方法学验证项下精密度、稳定性和重复性试验的相对标准偏差(relative standard deviation, RSD)数值均未超过2%。该含量测定方法操作简便、专属性强、结果准确可靠,可为复方蒙药广枣-肉豆蔻片的质量标准提供参考。 相似文献
78.
CHENSanfeng GUANYu TURan SUNWengai LIJilun 《科学通报(英文版)》2005,50(7):641-646
NifA in AzospiriUum brasilense plays a key role in regulating the synthesis and activity of nitrogenase in response to ammonia and oxygen available. In this work we used the yeast two-hybrid system to identify the proteins that interact with NifA. The nifA gene was fused to the yeast two-hybrid vector pGBD-C2, and three A. brasilense Sp7 genomic libraries for use in yeast two-hybrid studies were constructed. Screening of the libraries identified four clones encoding proteins that interact with NifA. The confirmation of the interactions of each gene product of the four clones and NifA were carried out by exchanging the vectors for nifA and the four clones and by mutageneses of the four clones with shift reading frame experiments in yeast two-hybrid studies. DNA sequence analyses showed that two clones encode proteins containing PAS domains that play an important role in signal transduction. One clone has high similarity with the fhuE gene of Escherichia coli, whose gene product is involved in iron uptake and transportation, and the other clone encodes an unknown protein. 相似文献
79.
80.
为了提高煤矿井下机车调度效率、防止机车碰撞、堵塞,根据井下调度特点建立了机车运行赋时Petri网模型。针对原有启发式A*搜索算法存在的易陷入局部最优的缺点,提出了基于petri网的并发变迁遴选算法,引入变迁并发度概念,与启发式A*搜索算法相结合,得到改进的A*搜索算法。经过改进后算法的回溯计算,得到Petri可达图上的最佳路径,从而得出最优调度策略。根据以上算法进行MATLAB建模,最终仿真结果表明,经过改进的启发式A*搜索算法有效的避免了陷入局部最优解,其计算得出的调度路径及调度策略资源消耗量最少,调度效率较高且未出现机车堵塞碰撞等问题。 相似文献