长江渔业资源变动和管理对策

长江是我国的第一大河 ,水系支流众多 ,流域面积广阔 ,鱼类资源极为丰富[1]。长江盛产青鱼、草鱼、鲢、鳙、铜鱼、圆口铜鱼、长吻、鲶、黄颡鱼、鲤、鲫、鲥、刀鲚、风鲚、鳗鲡等许多名贵经济鱼类 ,是著名的四大家鱼、鳗鲡等许多经济鱼类的原种基地 ,其品质是我国所有水系中最优的 ,作为基因遗传是其他任何水系或人工方式所不能替代的[2 ,3]。长江又是我国淡水苗种的重要生产基地 ,如四大家鱼、鳗鲡鱼苗 ,历史年产量曾高达 3 0 0亿尾和 2亿尾[4 ]。因此 ,长江渔业资源的盛衰变化对我国的淡水渔业有着举足轻重的影响。长江捕捞渔业自 2 0世…     

次生针阔混交林动态经营后空间结构动态分析

本文运用"时空替代"方法和分形理论,探讨了对现有的次生针阔混交林实施"团块状保留母树团"经营后,不同经营时间林分组成树种的空间结构的动态变化。得出随经营时间的推移,乔木层占据空间的总体能力逐渐增强,也趋于稳定,形成多层次的林冠郁闭,同时红松、椴树、水曲柳逐渐占据优势地位;而灌木层与乔木层相反,随经营时间的推移占据空间的能力逐渐减小并趋于稳定,在它们中,经营之初占优势地位的喜光种类逐渐退出,以典型针阔混交林下种类如丁香、山梅花、刺五加逐渐占据优势。反映出该经营方式促进了林分快速地向典型的红松针阔混交林演替的趋势。     

ANALYSIS OF REVEGETATION DYNAMICS ON THE VOLCANO USU,NORTHERN JAPAN,DEFORESTED BY 1977–1978 ERUPTIONS

Vegetation dynamics were monitored from 1983 to 1987 near the summit of the volcano Usu which had almost completely been deforested by 1–3 m thick volcanic deposits in 1977–1978. A permanent quadrat survey for five years confirmed the high mortality of seedlings. Since seedling mortality appeared mostly due to the frequent erosion of the volcanic deposits, ephemeral annuals and well-rooted perennials or woody plants were successful here. The high mortality of seedlings resulted in intensive fluctuation of plant density in all habitats. However, owing to the expansion of perennials, once they became established, the plant cover increased from year to year. In particular, Polygonum sachalinense and Petasites japonicus var. giganteus, seeds of which were frequently provided from their community vegetatively recovered on the wall of the caldera rim soon after the eruptions, were remarkably contributive to the revegetation. The excavation of those perennial plants demonstrated that they were derived not only from the seeds but also vegetatively from the old stumps buried in the former topsoil by extending their rhizomes up to the present ground surface.     

枯草杆菌蛋白酶E的分子动力学模拟和随机动力学模拟

在同源蛋白质序列比较的基础上;利用毕汝昌小组计算机图象系统得到的粗结构,作了能量极小化,分子动力学模拟,随机动力学模拟,得到了枯草杆菌蛋白酶的空间结构.并将该结构与已知同源蛋白质的空间结构进行了比较.     

红松胚胎发育及其淀粉的动态

本文观察了红松胚胎发育及其淀粉的分布全过程。红松合子位于颈卵器中上部,分裂时形成的纺锤体与颈卵器长轴呈一定角度,第一次有丝分裂产生2个游离核,它们边下沉边进行第二次有丝分裂,形成4个游离核排列成一层.接着进行第三次有丝分裂产生8个游离核,排成两层并形成细胞壁。第四次分裂产生16个细胞排成四层,组成了原胚,经一个半月的生长发育及胚胎选择阶段,7月中旬进入幼胚的发育时期。8月上旬幼胚已经进行组织和器官分化,此时淀粉逐渐由珠孔端向合点端方向推移,9月末种子成熟。     

EVOLUTIONARY EPIDEMIOLOGY AND THE DYNAMICS OF ADAPTATION

The mean fitness of a population, often equal to its growth rate, measures its level of adaptation to particular environmental conditions. A better understanding of the evolution of mean fitness could thus provide a natural link between evolution and demography. Yet, after the seminal work of Fisher and its renowned "fundamental theorem of natural selection," the dynamics of mean fitness has attracted little attention, and mostly from theoretical population geneticists. Here we analyze the dynamics of mean fitness in the context of host-parasite interactions. We illustrate the potential relevance of this analysis under different scenarios ranging from a simple situation in which a parasite evolves in a homogeneous host population to a more complex one with host-parasite coevolution. In each case, we contrast the effects of natural selection, recurrent mutations, and the change of the biotic environment, on the dynamics of adaptation. Decoupling these three components helps elucidate the interplay between evolutionary and ecological dynamics. In particular, it offers new perspectives on situations leading to evolutionary suicide. As mean fitness is an easily measurable quantity in microbial systems, this analysis provides new ways to track the dynamics of adaptation in experimental evolution and coevolution studies.     

微管骨架的动态特性及其调控

微管骨架是细胞骨架系统的主要组成成员,大多数微管的一个显著特征便是具有能够不断解聚、聚合的动态特性,这是微管骨架完成诸多生理功能的重要保证。本文着重介绍了有关微管的动态模型及其体内、体外组装的不同特点,并进一步探讨了生物体在各层次、各水平上对细胞内微管行为的调控。     

现代化分支杆菌菌库和基因库的建立与管理

医院分支杆菌菌库和基因库的建立 ,应用了计算机管理 ,不仅使各类菌及其相关资料得到系统管理 ,也为进一步研究和临床制定治疗计划提供了可靠信息 ,是医院现代化建设不可缺少的一环。     

蜘蛛的饲养与管理

简明介绍室内饲养蜘蛛的方法和应注意的问题,包括饲养器具,食物及生活史观察等。     

PHYSIOLOGY AND MANAGEMENT OF THE CLIMACTERIC

Women in the climacteric should have a thorough medical investigation, reassurance, and endocrine therapy when indicated.Estrogens give prompt relief to the large number of women with sympathetic nervous system symptoms during the climacteric.Estrogens are most effective when given parenterally followed by short periods of oral administration.Estrogens should be given only for actual need and withdrawn after symptoms disappear.Androgens are useful in the immediate control of functional bleeding and also for alleviating symptoms in patients who respond poorly to estrogens or for whom estrogens are contraindicated.The addition of vitamin B to parenteral endocrine therapy apparently enhances the effect of the hormone.     

亚洲飞蝗在中国新疆维吾尔自治区的发生与防治

从亚洲飞蝗在新疆发生基地的生境特点;形成和消退过程,分析亚洲飞蝗灾害发生消退的原因。自然条件变化和人们经济活动常改变亚洲飞蝗发生基地的生态条件及环境,并诱发或抑制飞蝗灾害的发生。文章指出根治亚洲飞蝗灾害的有效途径是贯彻“改治并举、根除蝗”的方针;加强蝗情监测;适时防治以及通过水利建设和农田开垦,改变飞蝗发生基地和生态条件等。