共查询到19条相似文献，搜索用时 125 毫秒
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通过一些偏序关系刻画了左密码群并半群、局部正则密码群并半群、局部左正则密码群并半群.证明了完全正则半群S是左密码群并半群当且仅当M=≤;S是局部正则密码群并半群当且仅当B=≤;S是局部左正则密码群并半群当且仅当P=≤. 相似文献
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定义和研究了1类新的正规纯正群并半群,即WLR-正规纯正群并半群,并且给出了这类半群的一些性质和结构的刻画. 相似文献
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在完全正则半群簇的子簇格中,首先用等式((x0y0)0z0)0 = (x0(y0z0)0)0 定义了一个子簇,并举例说明它是
完全正则半群簇的真子簇,追加等式x(yz)0x(yz)0 = (yz0)0x(yz)0 和(xy)0z(xy)0z = (xy)0z(x0y)0z,定义前一
子簇的又一子簇,并举例说明这3个等式相互独立,证明了这3个等式恰好给出了纯正群并半群簇和密码群并半群
簇的上确界. 相似文献
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利用L~*-幂单半群和R~*-幂单半群,给出具有良恰当断面的富足半群的一个对称的织积结构定理.此结论去掉了拟理想这个重要的前提,且比已有结论的形式更简单.其结果是对逆断面和恰当断面中相应结果的丰富和推广,为进一步研究该类半群的结构、性质及刻画其上的同余奠定了坚实的理论基础. 相似文献
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通过具体刻画中心密码群并半群上的最小纯正同余ρ0={(a,b)∈S×S|a0=b0,ab-1∈C(S)}和中心完全正则半群上的最小Clliford同余ρyg={(a,b)∈S×S| a0=b0,ab-1∈C(S)},得出((y)∩ρyg)是中心完全正则半群上的最小纯正同余.Abstract： This paper aims to prove that((y)∩ρyg)is the least orthogroup congruence on central completely regular semigroups,by studying the least orthogroup congruence on central cryptogroups ρ0={(a,b)∈S×S| a0=b0,ab-1∈C(S)}and the least Clifford congruence on central completely regular semigroups ρrG={(a,b)∈S×S|aD6,ab1∈C(S)} 相似文献
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Apolipoprotein B-48 is the product of a messenger RNA with an organ-specific in-frame stop codon 总被引：63，自引：0，他引：63
S H Chen G Habib C Y Yang Z W Gu B R Lee S A Weng S R Silberman S J Cai J P Deslypere M Rosseneu 《Science (New York, N.Y.)》1987,238(4825):363-366
The primary structure of human apolipoprotein (apo) B-48 has been deduced and shown by a combination of DNA excess hybridization, sequencing of tryptic peptides, cloned complementary DNAs, and intestinal messenger RNAs (mRNAs) to be the product of an intestinal mRNA with an in-frame UAA stop codon resulting from a C to U change in the codon CAA encoding Gln2153 in apoB-100 mRNA. The carboxyl-terminal Ile2152 of apoB-48 purified from chylous ascites fluid has apparently been cleaved from the initial translation product, leaving Met2151 as the new carboxyl-terminus. These data indicate that approximately 85% of the intestinal mRNAs terminate within approximately 0.1 to 1.0 kilobase downstream from the stop codon. The other approximately 15% have lengths similar to hepatic apoB-100 mRNA even though they have the same in-frame stop codon. The organ-specific introduction of a stop codon to a mRNA appears unprecedented and might have implications for cryptic polyadenylation signal recognition and RNA processing. 相似文献
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Bemisia tabaci is a cryptic species complex, causing significant loss on many agriculturally important crops worldwide. Knowledge on species composition and diversity within B. tabaci complex is critical for evolving sustainable pest management strategies. Here we investigate the whitefly species complex in soybean in major soybean growing states of India. The mitochondrial cytochrome oxidase gene subunit-1(mt COI) based phylogenetic relationships established using Bayesian methods indicated the existence of three cryptic species namely AsiaⅠ, AsiaⅡ1, and AsiaⅡ7. All the haplotypes detected in the study could be assigned to these three cryptic species following the species demarcation criteria of 3.5% divergence threshold. Of these, AsiaⅡ1 was found to be predominant with wide spread distribution across the surveyed regions from cool temperate zones to hot and humid tropical plains. On the contrary, cryptic species AsiaⅡ7 showed localized distribution. The AsiaⅡ1 exhibited the highest haplotype diversity and AsiaⅠ showed high level of nucleotide diversity. There was a significantly high genetic differentiation among these three cryptic species. The MEAM 1, a dreadful invasive species was not detected in the specimens tested in the current study. The diversity and distribution of three cryptic species is discussed in the light of current knowledge on distribution of whitefly species in India and yellow mosaic disease observed during sampling survey. 相似文献
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隐性雌性选择(CFC)作为配后性选择,是近年来引起生物学家重视的新领域.隐性雌性选择自提出以来就一直引起广泛争议.介绍了隐性雌性选择的定义、检验以及隐性雌性选择的可能机制;并就隐性雌性选择研究需要深入的问题进行了讨论. 相似文献
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农业产品结构调整是农业结构调整的首要内容，我国当前农产品总量矛盾基本化解，结构性矛盾凸现，表现在国内和国际两个市场。调整农产品结构可从生产力和生产关系两个层面着手：从生产力层面，需大力推行农产品标准化生产；面向国际市场，大力发展我国具有比较优势的农产品的生产；调整农产品的品种、品质结构，发展名牌农产品等。从生关系层面，要转变农民观念，下决心调整农产品结构；充分发挥政府在农业产品结构调整中的职能，包括发挥政府的经济管理职能，政府为经济服务的职能，政府政策支持经济发展的职能等。 相似文献
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Brachiopods and coralline sponges are the dominant taxa of a series of parallel pantropical communities found in cryptic habitats of Recent coral reefs, where these organisms may cover almost the entire available surface area. It is suggested that the continued survival and success of these and other groups of considerable paleontological importance resulted from their occupation of cryptic reef habitats after competition with more rapidly growing hermatypic corals in the Middle Jurassic when scleractinian reefs first appeared. 相似文献
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Celikel R McClintock RA Roberts JR Mendolicchio GL Ware J Varughese KI Ruggeri ZM 《Science (New York, N.Y.)》2003,301(5630):218-221
Thrombin bound to platelets contributes to stop bleeding and, in pathological conditions, may cause vascular thrombosis. We have determined the structure of platelet glycoprotein Ibalpha (GpIbalpha) bound to thrombin at 2.3 angstrom resolution and defined two sites in GpIbalpha that bind to exosite II and exosite I of two distinct alpha-thrombin molecules, respectively. GpIbalpha occupancy may be sequential, as the site binding to alpha-thrombin exosite I appears to be cryptic in the unoccupied receptor but exposed when a first thrombin molecule is bound through exosite II. These interactions may modulate alpha-thrombin function by mediating GpIbalpha clustering and cleavage of protease-activated receptors, which promote platelet activation, while limiting fibrinogen clotting through blockade of exosite I. 相似文献
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为了明确阿拉尔垦区棉田烟粉虱种群隐种以及烟粉虱捕食性天敌种类,采集阿拉尔十二团棉田中的烟粉虱及烟粉虱捕食性天敌,利用B-F/B-R和Q-F/Q-R特异性引物通过PCR检测烟粉虱隐种类型,利用烟粉虱TB-F/TB-R 94585特异性引物检测捕食性天敌肠道内是否存在烟粉虱DNA。结果表明:新疆阿拉尔垦区烟粉虱为MED隐种,初步发现烟粉虱的捕食天敌涵盖4个目5个科7种,包括多异瓢虫Adonia variegata、多异瓢虫幼虫、东亚小花蝽Orius sauteri Poppius、中华通草蛉Chrysoperla sinica 幼虫、黄褐新园蛛Neoscone doenitzi、灌木新园蛛Neoscona adianta、直伸肖蛸Tetragnatha extensa。结论:利用SCAR分子标记技术可以快速检测阿拉尔垦区烟粉虱害虫捕食性天敌种类。 相似文献