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991.
彭富连 《湖南师范大学自然科学学报》1986,(2)
文[1]讨论了Laplace双曲型方程的四种定解问题的适定性,本文关于Laplace双曲型方程提出了一个新的定解问题,并证明了它的适定性。 相似文献
992.
本文分析研究了地方煤矿设备管理中存在的问题,以此为基础提出了加强地方煤矿设备管理的有关措施。本文认为,当前地方煤矿管理工作的主要问题是在设备管理工作中,包括设备购进、使用和维护等各方面缺乏效益观点。必须从效益观点出发提出明确的目标,制定相应的措施,才能搞好地方煤矿设备管理工作。 相似文献
993.
Youngren KK Coveney D Peng X Bhattacharya C Schmidt LS Nickerson ML Lamb BT Deng JM Behringer RR Capel B Rubin EM Nadeau JH Matin A 《Nature》2005,435(7040):360-364
In mice, the Ter mutation causes primordial germ cell (PGC) loss in all genetic backgrounds. Ter is also a potent modifier of spontaneous testicular germ cell tumour (TGCT) susceptibility in the 129 family of inbred strains, and markedly increases TGCT incidence in 129-Ter/Ter males. In 129-Ter/Ter mice, some of the remaining PGCs transform into undifferentiated pluripotent embryonal carcinoma cells, and after birth differentiate into various cells and tissues that compose TGCTs. Here, we report the positional cloning of Ter, revealing a point mutation that introduces a termination codon in the mouse orthologue (Dnd1) of the zebrafish dead end (dnd) gene. PGC deficiency is corrected both with bacterial artificial chromosomes that contain Dnd1 and with a Dnd1-encoding transgene. Dnd1 is expressed in fetal gonads during the critical period when TGCTs originate. DND1 has an RNA recognition motif and is most similar to the apobec complementation factor, a component of the cytidine to uridine RNA-editing complex. These results suggest that Ter may adversely affect essential aspects of RNA biology during PGC development. DND1 is the first protein known to have an RNA recognition motif directly implicated as a heritable cause of spontaneous tumorigenesis. TGCT development in the 129-Ter mouse strain models paediatric TGCT in humans. This work will have important implications for our understanding of the genetic control of TGCT pathogenesis and PGC biology. 相似文献
994.
不同溶剂对七台河煤萃取效果的影响 总被引:2,自引:0,他引:2
采用常压沸点下回流萃取方法,选用6种不同的有机溶剂对七台河煤进行了萃取研究,并利用CC/MS联用法对各萃取物的组成进行了分析。但不同的有机溶剂对七台河煤的萃取率相差很大。溶剂的电子受—授能力、溶解度参数、沸点、酸碱性都会对萃取效果产生不同程度的影响。实验证明,在萃取过程中,含有良好的氢键受体、很强的电负性羰基氧的有机溶剂,含n个孤对电子的胺类有机溶剂对七台河煤的萃取率都较大;溶剂萃取过程遵循“相似相溶”规律;呈碱性的有机溶剂对七台河煤的萃取率较大。结果表明,利用有机溶剂萃取法从煤中得到高附加值产品在技术上是可行的。 相似文献
995.
胡连《新闻公报》中使用了“体认”“尽速”“愿景”等新词,还启用了个别历史词和其他词,使其呈现出了与传统公文迥异的语体风格,笔者认为这是公文语言风格的一次重大变革,是公文语言发展新态势的明显信号。 相似文献
996.
LIUXiaolin JIANGNing HEPeng LUDajun SHENAn 《科学通报(英文版)》2005,50(7):652-657
Fermentation of the pentose sugar xylose to produce ethanol using lignocellulosic biomass would make bioethanol production economically more competitive. Saccharomyce cerevisise, an efficient ethanol producer, cannot utilize xylose because it lacks the ability to convert xylose to its isomer xylulose. In this study, XYLA gene encoding xylose isomerase (XI) from Thermoanaerobacter tengcongensis MB4T and XKS1 gene encoding xylulokinase (XK) from Pichia stipitis were cloned and functionally coexpressed in Saccharomyces cerevisiae EF-326 to construct a recombinant xylose-utilizing strain. The resulting strain S. cerevisiae EF 1014 not only grew on xylose as sole carbon source, but also produced ethanol under anaerobic conditions. Fermentations performed with different xylose concentrations at different temperatures demonstrated that the highest ethanol productivity was 0.11 g/g xylose when xylose concentration was provided at 50 g/L. Under this condition, 28.4% of xylose was consumed and 1.54 g/L xylitol was formed. An increasing fermentation temperature from 30℃ to 37℃ did not improve ethanol yield. 相似文献
997.
JIANGHaiyan WANGJianhua WUPeng LIYongchun WANGGuoying 《科学通报(英文版)》2005,50(10):975-979
A total of 210 soybean samples collected from different areas of Heilongjiang Province were analyzed by PCR to detect the presence of RR (Roundup Ready) soybean ingredient. Results showed that CaMV35S promoter was not detected in all samples. CP4-EPSPS gene was amplified in 13 samples, but all of them were proved to be false positives in restriction endonuclease digestion analysis of PCR products. Further analysis by nested PCR indicated that there were no RR soybean ingredients in the samples. Besides, the amplified fragments of 0xl by CP4-EPSPS primers were sequenced, and the results confirmed again the fact that this fragment was not from CP4-EPSPS gene. 相似文献
998.
ZHANG Hongping ZHU Wenyao PENG Junhuan & HUANG Cheng . Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai China . Graduate School of the Chinese Academy of Sciences Beijing China . Key Laboratory of Advanced Engineering Survey of SBSM Tongji University Shanghai China 《科学通报(英文版)》2005,50(13):1373-1381
The periodic solar activities strongly affect the ioniza-tion of the ionosphere. Sudden enhancements in soft and hard solar X-ray and EUV radiation during solar flare can produce an immediate increase in ionospheric ionization in various degrees at different heights; altogether, they are called sudden ionospheric disturbances (SIDs), which are generally recorded as sudden increase of total electron content (SITEC), the short wave fadeout (SWF), sudden frequency deviation (SFD), sudden ph… 相似文献
999.
1000.