Radio-telemetric evidence of migration in the gregarious but not the solitary morph of the Mormon cricket (Anabrus simplex: Orthoptera: Tettigoniidae)

 The Mormon cricket, Anabrus simplex, is one of just a few species of katydids (or bushcrickets, Orthoptera: Tettigoniidae) that, like migratory locusts, appear to have solitary and migratory morphs. Using radio telemetry we studied movements of individuals of two morphs of this flightless species. Individuals within each migratory band had similar rates of movements along similar directional headings whereas solitary individuals moved little and showed little evidence of directionality in movement. Our results also add to other recent radio-telemetry studies showing that flightless insects of 1–2 g in mass can be tracked successfully using these methods. Received: 28 February 2000 / Accepted in revised form: 19 June 2000     

Hopanoid Biosynthesis and Function in Bacteria

   Hopanoids are pentacyclic triterpenoid lipids occurring in bacteria. They are synthesized from isopentenyl units which are formed in a new biosynthetic route leading to isopentenyl diphosphate. Six C₅ units are joined to form squalene, the immediate precursor in hopanoid synthesis. In a highly complex cyclization reaction that shares considerable similarities with that of oxidosqualene to sterols, the hopane skeleton is formed from squalene by the squalene-hopene cyclase. Recent elucidation of the X-ray structure of this membrane-bound cyclase has shed some light on the properties of this unusual enzyme. The active site is located in a cavity within the enzyme. The squalene substrate diffuses through a channel structure from the membrane into this cavity and is there transformed into hopene. Polar side chains are attached to hopene resulting in the amphiphilic molecular structure of many hopanoids. These hopanoids are membrane components involved in regulating membrane fluidity and stability. However, the many structural variants of hopanoids indicate that they may have other interesting but as yet unknown functions.     

微机上冲裁CAD系统的开发

此文介绍了一套在微机上开发的冲裁CAD系统。它以Foxbase作为数据库管理系统,Trubo C为编程语言,能进行冲裁件图形输入与显示、工艺性分析、优化单排排样和选择板材规格、冲裁件尺寸识别和模具刃口尺寸计算、冲裁力和压力中心计算、以及凹模周界尺寸计算等。本系统主界面为下拉式菜单界面,全中文提示,人机界面友好,具有较好的可扩充性和容错性。     

The application of life cycle assessment to design

This paper explores the practical application of life cycle assessment (LCA) to product system development. While life cycle assessment methods have been studied and demonstrated extensively over the last two decades, their application to product design and development has not been critically addressed. Many organizational and operational factors limit the integration of the three LCA components (inventory analysis, impact assessment and improvement assessment) with product development. Design of the product system can be considered a synthesis of individual decisions and choices made by the design team, which ultimately shape the system's environmental profile. The environmental goal of life cycle design is to minimize the aggregate environmental impacts associated with the product system. Appropriate environmental information must be supplied to decision makers throughout each stage of the development process to achieve this goal. LCA can serve as a source of this information, but informational requirements can vary as the design moves from its conceptual phase, where many design choices are possible, to its detailed design and implementation. Streamlined approaches and other tools, such as design checklists, are essential. The practical use of this tool in product development also depends on the nature and complexity of the product system (e.g. new vs. established), the product development cycle (time-to-market constraints), availability of technical and financial resources, and the design approach (integrated vs. serial). These factors will influence the role and scope of LCA in product development. Effective communication and evaluation of environmental information and the integration of this information with cost, performance, cultural and legal criteria will also be critical to the success of design initiatives based on the life cycle framework. An overview of several of these design initiatives will be presented.