920 resultados para B-12


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The annealing behaviour of B implants in the millisecond time regime using a combination of swept line beam and background heating is compared with isothermal annealing with heating cycles of a few seconds. Carrier concentration profiles show that under annealing conditions which restrict diffusion, millisecond processing gives higher activation of B implants than isothermal heating. Transmission electron microscopy shows that millisecond annealing also results in a lower defect density.

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To test the hypotheses of modern human origin in East Asia, we sampled 12,127 male individuals from 163 populations and typed for three Y chromosome biallelic markers (YAP, M89, and M130). All the individuals carried a mutation at one of the three sites.

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As an endangered animal group, musk deer (genus Moschus) are not only a great concern of wildlife conservation, but also of special interest to evolutionary studies due to long-standing arguments on the taxonomic and phylogenetic associations in this group. Using museum samples, we sequenced complete mitochondrial cytochrome b genes (1140 bp) of all suggested species of musk deer in order to reconstruct their phylogenetic history through molecular information. Our results showed that the cytochrome b gene tree is rather robust and concurred for all the algorithms employed (parsimony, maximum likelihood, and distance methods). Further, the relative rate test indicated a constant sequence substitution rate among all the species, permitting the dating of divergence events by molecular clock. According to the molecular topology, M. moschiferus branched off the earliest from a common ancestor of musk deer (about 700,000 years ago); then followed the bifurcation forming the M. berezouskii lineage and the lineage clustering M. fuscus, M. chrysogaster, and M. leucogaster (around 370,000 years before present), interestingly the most recent speciation event in musk deer happened rather recently (140,000 years ago), which might have resulted from the diversified habitats and geographic barriers in southwest China caused by gigantic movements of the Qinghai-Tibetan Plateau in history. Combining the data of current distributions, fossil records, and molecular data of this study, we suggest that the historical dispersion of musk deer might be from north to south in China. Additionally, in our further analyses involving other pecora species, musk deer was strongly supported as a monophyletic group and a valid family in Artiodactyla, closely related to Cervidae. (C) 1999 Academic Press.

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参考鳗鲡等鱼类线粒体 DNA序列进行了中国花鲈线粒体 DNA细胞色素 b基因片断的引物设计、PCR扩增及其序列测定。得到中国花鲈的碱基序列为 4 10 bp,其 A、T、G、C含量分别为 10 1bp(2 4 .6 3% )、112 bp(2 7.32 % )、72 bp(17.56 % )、12 5bp(30 .4 9% ) ,与鳗鲡等其他鱼类相同基因片断序列碱基含量相似。

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本发明涉及一种肉、奶牛B超活体取卵方法,属生物技术领域。本方法的吸卵真空泵的压力为50-90mmHg,吸卵液为含0.5-1%,青-链霉素和5-10IU肝素的磷酸缓冲液,洗卵液为含5-12%,BCS的磷酸缓冲液和改良的基础培养液-Hepes液;采卵频率为1次/4天/头;穿刺对象为所有直径≥2mm的卵泡;取1-3级的卵母细胞分装、备用;对7-8岁的供体经产牛按程序注射等量的外源性FSH,总量为30-55μg;对≥14岁的老年牛按程序肌肉注射总量为150-200μg的外源性FSH,以提高卵母细胞发育潜能。本发明的优点在于,从活体可重复、无损伤获取卵母细胞;≥2mm直径卵泡作为穿刺对象和每4天1次的取卵频率保证了卵母细胞的质量和发育同步性;用外源性FSH诱导可提高卵母细胞的发育潜能;本方法的取卵效果佳。

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对肉牛(莫累灰×婆罗门) 利用B 超活体取卵,研究不同年龄和促卵泡素(FSH) 对平均卵泡数、平均卵母细 胞数、平均可利用卵母细胞(COC) 数、卵母细胞回收率、COC 回收率、囊胚率和平均囊胚数的影响。结果表明:肉牛 B 超活体所取卵的数量和质量受年龄的影响,青年牛好于经产牛,经产牛好于老年牛;适量注射FSH 可以提高经产 牛和老年牛的囊胚率和(或) 平均囊胚数。

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Phylogenetic relationships among 15 species of wood mice (genus Apodemus) were reconstructed to explore some long-standing taxonomic problems. The results provided support for the monophyly of the genus Apodemus, but could not reject the hypothesis of paraphyly for this genus. Our data divided the 15 species into four major groups: (1) the Sylvaemus group (A. sylvaticus, A. flavicollis, A. alpicola, and A. uralensis), (2) the Apodemus group (A. peninsulae, A. chevreri, A. agrarius, A. speciosus, A. draco, A. ilex, A. semotus, A. latronum, and A. mystacinus), (3) A. argenteus, and (4) A. gurkha. Our results also suggested that orestes should be a valid subspecies of A. draco rather than an independent species; in contrast, A. ilex from Yunnan may be regarded as a separate species rather than a synonym of orestes or draco. The species level status of A. latronum, tscherga as synonyms of A. uralensis, and A. chevrieri as a valid species and the closest sibling species of A. agrarius were further corroborated by our data. Applying a molecular clock with the divergences of Mus and Rattus set at 12 million years ago (Mya) as a calibration point, it was estimated that five old lineages (A. mystacinus and four major groups above) diverged in the late Miocene (7.82-12.74 Mya). Then the Apodemus group (excluding A. mystacinus) split into two subgroups: agrarius and draco, at about 7.17-9.95 Mya. Four species of the Sylvaemus group were estimated to diverge at about 2.92-5.21 Mya. The Hengduan Mountains Region was hypothesized to have played important roles in Apodemus evolutionary histories since the Pleistocene. (C) 2004 Elsevier Inc. All rights reserved.

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The government of the People's Republic of China through a 2007 agreement with the Government of the Republic of Uganda, has establishment of an Agricultural Technology Demonstration Center (ATDC). The first phase covering the building of aquaculture infrastructure at Kajjansi ARDC is complete and the second operation phase has started in which facilities for cage culture have been set up in the Napoleon gulf, northern Lake Victoria near Jinja. The cage facility is aimed at boosting fish farming within the lake as a diversification to the traditional pond fish culture technology. NaFIRRI scientists as well as Chinese experts undertook a baseline survey in the chosen cage site on 12 March 2012. The survey covered determination of water depth, water transparency, measurement of selected physical-chemical parameters (temperature,dissolved oxygen, conductivity and pH; determination of the nutrient status and study of algae, invertebrate and fish communities at the site. Materials and methodologies used in the survey were based on the Standard Operating Procedures (SOPs) of NaFIRRI. The study area was divided into three study sites. Site 1 (upstream) was at 8.9 metre depth while site 2 (proposed cage site) and site 3 (downstream) were 6 and 4.3 metres deep respectively. Water transparency was lowest at site 1 (1.58 m) and highest at site 3 (1.64 m). Dissolved oxygen at the three sites ranged from 6.0 to 8 mg/I. Water temperature profiles fluctuated within narrow limits between 26.5 and 27.5 DC. Measurements of pH were between 7 (neutral) and 8 (alkaline) while electrical conductivity was between 98 and 101 uS/em. These observed physical-chemical parameters at the study site were considered suitable for cage fish rearing purposes. Nitrite-nitrogen levels varied within narrow limits from 0.043 to 0.0453 mgtl. Similarly, Ammonia-nitrogen varied between 0.015 and 0.0185 mg/1. Soluble reactive phosphorus (SRP) level was highest at site 3 (O.012mgll) compared to that at sites 1 and 2 (0.009mgll). Total suspended solids (TSS) were higher at site 1 (83.3mgll), thereafter decreasing to lower levels at sites 2 (24.8mgtl) and 3 (19.8mgl) respectively. The nutrient level results observed here all fall below the maximum permissible limits by NEMA and therefore the site is recommended for cage culture The algal community was constituted by four major groups: Blue greens,Greens, Cryptophytes, and Diatoms with blue greens as the common and dominant group. High algal biomass (19944961 ugtL) of the dominant blue green algae was observed at site 1 compared site 2 and 3 (58655.2 & 27487. 7 ugtL) respectively. Occurrence of toxicin producing algae: microsytis and cylindrospermopsis in the proposed cage area was considered to be of not much significance as their concentrations were below harmful levels. However, monitoring their presence, biomass and seasonality will be critical in order to follow when and where they occur and at what time of the year for ease of management of the cages

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银额果蝇昆明群体有丝分裂中期核型中存在B染色体, 出现频率为69.1%在已 研究过的来自各个地区的银额果蝇中, 昆明群体的B染色体频率最高。B染色体 数目为1—6条。该群体内单雌系间的B染色体数目不同, 个体间和细胞间的B染色 体数目也不同。在核型中, B染色体最小, 形态稳定, 点状, C-带和G-带呈阳性 。 图版1图2表1参12

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To investigate the genetic diversity between the populations of woolly flying squirrels (Eupetaurus) from the eastern and western extremes of the Himalayas, partial mitochondrial cytochrome b gene sequences (390-810bp) that were determined from the museum specimens were analyzed using maximum parsimony (MP) and maximum likelihood (ML) methods. The molecular data reveal that the two specimens that were collected in northwestern Yunnan (China) are members of the genus Eupetaurus. Reconstructed phylogenetic relationships show that the populations of Eupetaurus in the eastern and western extremes of the Himalayas are two distinct species with significant genetic differences (12%) and diverged about 10.8 million years ago. Eupetaurus is significantly different from Petaurista and Pteromys. The level of estimated pairwise-sequence divergence observed between Eupetaurus and Petaurista or Pteromys is greater than that observed between Eupetaurus and Trogopterus, Belomys, Glaucomys, or Hylopetes. Considering the divergence time of the two Eupetaurus groups, the glaciations and the uplift of the Himalayas and Qinghai-Tibet plateau during the Pliocene-Pleistocene period might be the major factors affecting the present distribution of Eupetaurus along the Himalayas. (C) 2004 Elsevier Inc. All rights reserved.

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用细胞色素b(Cyt b)基因特异性引物,对萍乡肉红鲫(Carassius auratus var.pingxiangnensis)的线粒体Cytb基因进行PCR扩增和双向测序。在12个个体中均得到序列一致的Cytb基因全序列,长度为1 140 bp。其A、T、G、C含量分别为28.2%(321)、28.8%(328)、14.8%(170)和28.2%(321),A+T含量(57%)明显高于G+C含量(43%),与其他水生动物相同基因片段碱基含量相似。该基因中密码子第1位核苷酸中4种碱基组成较为均衡;第2

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采用PCR技术获得了中国鲿科鱼类线粒体DNA细胞色素b基因1138bp全序列.所得序列与GenBank中分布于日本、韩国和俄罗斯的鲿科2属9种鱼类同一基因序列排序,并选用鲇形目鲇科的大口鲇、钝头鮠科的鳗尾缺和伦氏(鱼央)以及脂鲤目的断线脂鲤作外类群.分析了细胞色素b基因序列,计算了Kimura双因子遗传距离和鲿科鱼类线粒体DNA的进化速率,用最大简约法和邻接法构建了鲿科鱼类分子系统树,得出如下结论:(1)线粒体DNA序列分析显示所测定的鲇形目鱼类细胞色素b基因序列中,存在3bp的缺失;(2)系统发育分析显

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采用PCR技术获得了14种主要分布于东亚的低等鲤科鱼类细胞色素b基因的全序列. 所得1 140 bp细胞色素b基因序列与10种取自GenBank, 分布在北美和欧洲的相关鲤科鱼类的同一基因序列一起排序后, 得到了24种鲤科鱼类的DNA序列矩阵. 此矩阵经过最大似然(maximum likelihood)法计算后获得了低等鲤科及相关种类的系统发育分支图解. 分支系统图显示鲤科的雅罗鱼亚科和亚科鱼类并不形成单系类群. 亚科鱼类中的马口鱼、等是原始的鲤科鱼类, 处于分支图的基部. 而其余的亚科鱼类则分散