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151.
Summary Meiosis in 14 interspecific F1 hybrids with three chromosomal levels (triploid, tetraploid, hexaploid; 2n=28, 37 and 55) between Brassica napus L. and 2x and 4x cabbage (B. oleracea var. capitata L.) was studied. The oleracea genome from B. napus maintained close homology with the c genome of cabbage while the campestris genome of B. napus showed partial homology with the c genome contained in the hybrids. Genotypic influence on chromosome pairing was indicated. Structural chromosome differences and spontaneous chromosome breakage and reunion were suggested as causes for the abnormalities which related to the unbalance of the genotypes. The divergence of the genomes of B. napus and B. oleracea and the need for the qualification of the term secondary association were discussed.Contribution No. J. 673, Research Station, Agriculture Canada, St. Jean, Québec. 相似文献
152.
153.
Xu J Bjursell MK Himrod J Deng S Carmichael LK Chiang HC Hooper LV Gordon JI 《Science (New York, N.Y.)》2003,299(5615):2074-2076
The human gut is colonized with a vast community of indigenous microorganisms that help shape our biology. Here, we present the complete genome sequence of the Gram-negative anaerobe Bacteroides thetaiotaomicron, a dominant member of our normal distal intestinal microbiota. Its 4779-member proteome includes an elaborate apparatus for acquiring and hydrolyzing otherwise indigestible dietary polysaccharides and an associated environment-sensing system consisting of a large repertoire of extracytoplasmic function sigma factors and one- and two-component signal transduction systems. These and other expanded paralogous groups shed light on the molecular mechanisms underlying symbiotic host-bacterial relationships in our intestine. 相似文献
154.
Chiang TC 《Science (New York, N.Y.)》2004,306(5703):1900-1901
155.
Abdo AA Ackermann M Ajello M Allafort A Baldini L Ballet J Barbiellini G Bastieri D Bechtol K Bellazzini R Berenji B Blandford RD Bloom ED Bonamente E Borgland AW Bouvier A Brandt TJ Bregeon J Brez A Brigida M Bruel P Buehler R Buson S Caliandro GA Cameron RA Cannon A Caraveo PA Casandjian JM Çelik Ö Charles E Chekhtman A Cheung CC Chiang J Ciprini S Claus R Cohen-Tanugi J Costamante L Cutini S D'Ammando F Dermer CD de Angelis A de Luca A de Palma F Digel SW do Couto e Silva E Drell PS 《Science (New York, N.Y.)》2011,331(6018):739-742
A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory. 相似文献
156.
Four food grade additives-sodium ascorbate, sodium bicarbonate, sodium carbonate-10-hydrate, and ferrous sulfate-7-hydrate-were selected as the basic ingredients to formulate the controlled atmosphere agents which could effectively remove oxygen and release carbon dioxide. The mathematical models giving the relationships between the formulations and the responses (oxygen and carbon dioxide contents) were developed using response surface methodology (RSM). Within 8-24 h, the oxygen and carbon dioxide contents of all tested formulations could reach constant levels, in the ranges of 2-9% and 0-41%, respectively. These formulations were considered to be effective, safe, and easy to prepare and could be applied to wide varieties of food products. 相似文献