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探论了矿物在生命起源前化学中的可能作用.强调了涉及生物要素从无机形态转化为简单的有机分子的反应.详细讨论了3个中心问题①矿物可能促进的反应类型;②地球早期具有催化潜力的矿物的存在;③用于评估矿物在地球早期生命起源前化学中所扮演的角色的可行的研究策略和方法.  相似文献   

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One of the most useful diagnostic therian features is the division of the lateral surface of the scapula into two fossae separated by a scapular spine. A new model to describe this evolutionary innovation based on ontogenetic data is provided, consistent with information provided by recent fossil discoveries. The development of the scapula in three didelphid and one dasyurid marsupials using histological sections was studied. Only the ventral, acromial portion of the scapular spine, which originates from the anterior margin of the scapular blade, is preformed in cartilage. The major dorsal portion is formed at a later stage by appositional bone, which expands from the perichondral ossification of the scapula into an intermuscular aponeurosis between the supra-and infraspinatus muscles. This intermuscular aponeurosis inserts more or less in the middle of the lateral surface of the developing scapula. Thus, the floor of the supraspinous fossa is already present at the beginning of scapular development, simultaneous with the infraspinous fossa. The portion of the scapular spine that is situated dorsal to the acromial process is hypothesized to be a neomorphic structure of therians. The dorsal portion of the scapular spine evolved as additional attachment for powerful supraspinatus and infraspinatus muscles meeting near the middle of the lateral scapula.  相似文献   

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In an attempt to understand the origin of living systems we encounter the following problems: How can we conceive the origin of the first self-reproducing forms, and by means of what stimuli could a constant increase in the complexity of such forms commence? How can a translation apparatus for genetic information develop? One cannot that such an apparatus for the synthesis of enzymes can function alone without the interference of enzymes themselves, which, however, could only become available after the construction of the apparatus itself. What stimulus mechanism is conceivable that leads to the division of the genetic apparatus into a replication system, and an enzyme-synthesis system?The main problem therefore, is not the search for basic theoretical concepts. It is not a question which can be answered by means of specific experiments. One should rather explore the principal possibilities of how molecules combine to produce more and more complicated functional units. We look for the fundamental structural changes in the organizational systems and the driving forces initiating these developments. Questions concerning the detailed chemical realization are of secondary importance. In trying to solve the puzzle of how the genetic apparatus is gradually built up as complex aggregates of molecules, we consider a consistent causal chain of simple and transparent physicochemical model steps.  相似文献   

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中国政府一贯重视环境保护倡导在公平、公正、合理的基础上解决全球环境问题,并身体力行,认真履行所应承担的国际义务。我国积极参加了历次缔约方会议和有关国际会议,积极参与国际履约谈判。在我国积极倡议下,在《议定书》下建立了旨在帮助发展中国家履约的多边基金机制。我国政府于1989年9月正式加入了《保护臭氧层维也纳公约》,1991年6月签署了《关于消耗臭氧层物质的蒙特利尔议定书》伦敦修正案。  相似文献   

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本文结合排污权试点地区排污权交易实际业务,研究阐述排污权交易信息化工作的总体框架,对排污权交易试点阶段的信息化工作探索具有重要的意义。  相似文献   

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