983 resultados para 150-902
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在分子系统发生学研究中,因为线粒体基因组相对于其他分子标记具有明显的优越性,所以线粒体基因组已经逐渐成为一个研究后生动物系统发生的基本工具。螠虫动物大约有150多种,因为它体节不分节,具有真体腔的和两边对称的特性,所以在传统分类学上,人们把螠虫动物归类为一个独立的门。然而,螠虫动物和环节动物门的关系一直以来存在着很多的争议。越来越多的形态学和分子数据证明,我们应该重新考虑螠虫动物门的独立地位的合理性,因为大量包括形态和分子方面的证据都表明螠虫动物门很有可能起源于类似环节动物的祖先。本研究利用线粒体基因组作为系统发生研究的工具,对这个问题进行了进一步的探索研究。我们对一种螠虫动物代表种---单环刺螠(Urechis unicinctus)的线粒体全基因组序列进行测定,单环刺螠线粒体基因组DNA的总长度为15,761 bp,A+T含量为61.9%,包含13个蛋白质编码基因,22个tRNA基因,2个核糖体RNA基因,1个长度为923 bp的非编码区,37个基因都编码在同一条链上。基因顺序排列和基于氨基酸序列构建的系统发生树两方面的证据都支持:螠虫动物可能起源于环节动物。
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We have resolved the solid-liquid phase transition of carbon at pressures around 150GPa. High-pressure samples of different temperatures were created by laser-driven shock compression of graphite and varying the initial density from 1.30g/cm3 to 2.25g/cm3. In this way, temperatures from 5700K to 14,500K could be achieved for relatively constant pressure according to hydrodynamic simulations. From measuring the elastic X-ray scattering intensity of vanadium K-alpha radiation at 4.95keVat a scattering angle of 126°, which is very sensitive to the solid-liquid transition, we can determine whether the sample had transitioned to the fluid phase. We find that samples of initial density 1.3g/cm3 and 1.85g/cm3 are liquid in the compressed states, whereas samples close to the ideal graphite crystal density of 2.25g/cm3 remain solid, probably in a diamond-like state.
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Se presentaron los resultados de la modificación y adaptaciones de la red pelágica 124/1800 para la captura del recurso Vinciguerria.
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Collection : Théâtre contemporain illustré ; 156e et 157e livraisons
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Collection : Théâtre contemporain illustré ; 156e et 157e livraisons
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Servicios registrales
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Servicios registrales
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Servicios registrales
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Credit to S.D. Woodruff from Pratt and Company for $150.00, Sept. 7, 1876.