993 resultados para 179-1107


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利用 Ofloxacin处理获得了纤细裸藻和中型裸藻无叶绿体突变株。吸收光谱测定和自荧光显微观察证明突变株无叶绿素合成 ,DAPI染色方法显示突变株细胞不存在质体 DNA,而无色的长变胞藻细胞中仍有可检测质体 DNA,说明二突变株质体已消失。 SDS- PAGE显示野生种和突变株各有特异蛋白表达。

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国家自然科学基金39500016

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The classes of continuous-time flows on Rn×p that induce the same flow on the set of p- dimensional subspaces of Rn×p are described. The power flow is briefly reviewed in this framework, and a subspace generalization of the Rayleigh quotient flow [Linear Algebra Appl. 368C, 2003, pp. 343-357] is proposed and analyzed. This new flow displays a property akin to deflation in finite time. © 2008 Yokohama Publishers.

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于1997年11月,在广东省汕头地区饶平县海面采集棕囊藻,采用显微观察和光谱分析方法,进行形态特征与毒素结构的研究。结果表明,该种藻具有两种不同的藻体形态:一种是不运动的球形群体(直径0.1一3cm),外具胶质被,群体内的细胞有近千至数万个,每个细胞(直径3-7.5μm)有2-3个黄褐色的叶绿体;另一种是游动的单细胞,具有两根几乎等长的鞭毛和一根短的定鞭丝(也称为附着鞭毛或触丝),常呈球形。将反复冻融或冷冻干燥的藻细胞经有机溶剂提取,用新鲜牛血球测定显示出具有强的溶血毒素特性。溶血毒素经硅胶柱层析纯化,被

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Current models of motor learning posit that skill acquisition involves both the formation and decay of multiple motor memories that can be engaged in different contexts. Memory formation is assumed to be context dependent, so that errors most strongly update motor memories associated with the current context. In contrast, memory decay is assumed to be context independent, so that movement in any context leads to uniform decay across all contexts. We demonstrate that for both object manipulation and force-field adaptation, contrary to previous models, memory decay is highly context dependent. We show that the decay of memory associated with a given context is greatest for movements made in that context, with more distant contexts showing markedly reduced decay. Thus, both memory formation and decay are strongest for the current context. We propose that this apparently paradoxical organization provides a mechanism for optimizing performance. While memory decay tends to reduce force output, memory formation can correct for any errors that arise, allowing the motor system to regulate force output so as to both minimize errors and avoid unnecessary energy expenditure. The motor commands for any given context thus result from a balance between memory formation and decay, while memories for other contexts are preserved.

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比较了红球藻HB748株在MCM,BBM及BG-11.3种培养基中的生长.结果表明:HB748在这3种培养基中前4d的平均生长速率分别为0.97d-1,0.77d-1和0.63d-1,存在显著差异;然而,在BBM和BG-11中添加MCM中所含等量VB12后,748株在3种培养基中的生长速率趋于一致,表明VB12,是HB748维持较好的前期生长的必需成分;在VB12的需求满足后.3种培养基无机组分的差异对HB748前期生长影响甚微.

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报道了一种用于气相色谱质谱联用仪和微机之间实现数据传输和处理的方法。方法可更有效地利用质谱仪采集的数据,解决了工作站处理数据的局限性。经数据格式转换,原始数据可以在微机上实现色谱峰再现,从而为色谱条件的优化和定量数据处理创造了条件。

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人工感染GCHV-861后,对处于潜伏期、发病期和恢复期等不同时期的草鱼内脏组织匀浆上清液进行逆转录聚合酶链式反应(RT-PCR)扩增,除恢复期的1条草鱼外,其余样品均得到特异扩增带,而对照组都没有,预示着RT-RCR技术对于草鱼出血病的早期诊断、防治及抗病有种具有重要意义。另外,对于显症出血病草鱼的肝、肾、脾、鳃、肌肉和肠道等组织器官进行检测,结果都为阳性,首次证实了GCHV存在于肝脏中,并对此作了进一步的讨论。

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白暨豚某些内科疾病的防治刘仁俊,赵庆中(中国科学院水生生物研究所,武汉430072)STUDYONTHEPREVENTIONANDTREATMENTOFSOMEINTERNALDISEASESINLIPOTES¥LiuRenjunandZhaoQin...

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在鄂西的五峰、宜都、宜昌、当阳及神农架林区一带,采集到裸藻门植物16属140种(包括变种和变型)。属于绿色裸藻类的有116种,无色裸藻类的有24种,其中有5个新种,7个新变种,3个新变型,有20种是我国新记录。在采集区域内的地形大体上可以分成三种不同的类型,即:山岳地区(采得裸藻5种),河谷盆地地区(采得裸藻40种)和沿长江丘陵地区(采得裸藻128种)。静止水体由于地形的差异,体积的大小和水质的肥沃程度不同,都对裸藻门植物的生长有重要的影响。

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本文分析研究了鲮鱼属间杂交和亲本自交的胚胎发育时序和热量要求、胚后发育的形态特征、以及胚胎染色体组等方面的差异;并讨论了这些差异与各种杂交不亲和表现之间的相关性。明确地指出,决定鱼类杂交不亲和性的主要因素是亲本间核型的差异和核质间的矛盾程度。双亲的核型差异较大时,杂交胚胎往往在发育中途夭亡而成活率极低,甚至完全得不到仔鱼。核型相同或相似的亲本,其杂交子代的成活率一般甚高;但也可能与核型著异较大的组合一样,因核、质基因组表达的模式或调控机制等存在着差异,以及它们对外界环境条件的要求有矛盾,乃使胚后发育的速率

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A series of laboratory-scale T-bar penetrometer tests have been conducted on a clay bed virgin consolidated from reconstituted high plasticity marine clay. This investigation was mainly concerned with the effects on the penetration resistance of rate of penetration and the presence of free water on the surface of the clay bed. The rate of penetration varied between 0.005mm/s and 50mm/s. The results showed that the nature of soil resistance was 'undrained' over the range of speeds studied, and the resistance showed a marked viscous rate effect. The virgin consolidated clay bed exhibited an increase in penetration resistance by up to 35% for a factor 10 increase in rate of penetration much larger than values previously reported for kaolin. The presence of water on the surface of clay bed had a profound impact on penetration resistance, particularly on the remoulded strength obtained by taking the T-bar through successive penetration and extraction cycles. This was true even when the remoulding cycles were conducted without the T-bar breaking through the clay surface.

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团头鲂血居吸虫病是1965年和1973年先后在湖北省浠水县鱼池发现。1.0—1.5寸大的鱼种往往因患此病而死亡。其病原体是文献中未报导过的两种血居吸虫,并一种命名为鲂血居吸虫新种Sanguinicola megalogramae sp.nov.另一种暂列为血居吸虫未定种Sanguincolasp。 较详细地观察和记述了鲂血居吸虫成虫的形态、生态,以及卵、毛蚴、尾蚴等的形态和发育情况。查清了鲂血居吸虫的中间宿主是一种扁卷螺——白旋螺 Gyraulus albus Muller,还进行了尾蚴对鱼苗的感染试验。

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Largemouth bronze gudgeon (Coreius guichenoti) is a medium-sized fish endemic from the upper Yangtze River of China and its survival is threatened by the construction of the Three Gorges Dam. This study reports 20 new polymorphic microsatellites from a repeat-enriched genomic library with a mean number allele of 5.2, and observed and expected heterozygosities ranging from 0.035 to 1, and from 0.13 to 0.917, respectively. In a cross-species amplification test, nine of the 37 tested loci were found to be also polymorphic in a congeneric species, brass gudgeon (C. heterodon). In addition, other four loci from common carp (Cyprinus carpio) were also polymorphic in C. guichenoti. Out of these 24 polymorphic microsatellites, only three loci significantly deviated from Hardy-Weinberg equilibrium in the sampled population (P < 0.0025), and all pairwise tests for linkage disequilibrium among loci were nonsignificant after applying sequential Bonferroni correction (P > 0.0026). These novel microsatellites provide sufficient levels of polymorphism for studies on population genetics and conservation in C. guichenoti and its related species.

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The phylogeny of Oedogoniales was investigated by using nuclear 18S rDNA sequences. Results showed that the genus Oedocladium, as a separated clade, was clustered within the clade of Oedogonium; whereas the genus Bulbochaete was in a comparatively divergent position to the other two genera. The relationship among the species of Oedogonium was discussed, focusing on ITS-2 phylogeny analyzed combining with some morphological characteristics. Our results showed that all the dioecious nannandrous taxa involved in this study were resolved into one clade, while all the monocious taxa were clustered into another clade as a sister group to the former. The report also suggests that the dioecious macrandrous taxa form a paraphyly and could be more basally situated than the dioecious nannandrous and the monoecious taxa by means of molecular phylogeny and morphotype investigations.