理解IPv6

IPv6是IETF设计的下一代互联网协议，用来取代现有的、已经存在20多年的IPv4协议。但现行的IPv6协议还比较复杂化和多元化，且IPv6本身的标准也还有待完善。要想理解IPv6必须掌握所有相关的协议，这是一件比较困难的事情。为了方便研究人员能够更为系统的了解IPv6协议，本书总结归纳出IPv6所有必要的性质，使读者可以快速简单地进入到IPv6的世界。     

无线传感器质心定位算法的研究与改进

提出了一种将经验公式与质心法相结合的定位算法,以提高质心算法的定位精度。     

Chemical structure and biological activity of the Caenorhabditis elegans dauer-inducing pheromone

Pheromones are cell type-specific signals used for communication between individuals of the same species. When faced with overcrowding or starvation, Caenorhabditis elegans secrete the pheromone daumone, which facilitates communication between individuals for adaptation to adverse environmental stimuli. Daumone signals C. elegans to enter the dauer stage, an enduring and non-ageing stage of the nematode life cycle with distinctive adaptive features and extended life. Because daumone is a key regulator of chemosensory processes in development and ageing, the chemical identification of daumone is important for elucidating features of the daumone-mediated signalling pathway. Here we report the isolation of natural daumone from C. elegans by large-scale purification, as well as the total chemical synthesis of daumone. We present the stereospecific chemical structure of purified daumone, a fatty acid derivative. We demonstrate that both natural and chemically synthesized daumones equally induce dauer larva formation in C. elegans (N2 strain) and certain dauer mutants, and also result in competition between food and daumone. These results should help to elucidate the daumone-mediated signalling pathway, which might in turn influence ageing and obesity research and the development of antinematodal drugs.     

Effects of various media on tissular and cellular structures of the superior cervical ganglion of the rat

Summary The superior cervical ganglia of the rat have been incubated in vitro for 1 h in basal medium Eagle (BME) with Hanks' salts, BME with Earle's salts, Krebs' solution and NCTC 109 medium. Comparison of the cell areas, established by a semi-automatic quantitative method, shows that the three former induce a 30–35% neuronal retraction, whereas NCTC 109 has no effect. Thus this latter medium seems the best one for studies using incubation of these cells.We are indebted to Miss M. Vio, Mrs J. Bottini, Mr C. Cataldo and Mr P. Cau for their helpful assistance.