The influence of chronic nicotine treatment on stress-induced gastric ulceration and emptying rate in rats.

Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid.     

复数,实数及实对称数据下Bruun FFT算法的实现

本文在复数、实数以及实对称数据下研究和实现了Ｂｒｕｕｎ ＦＦＴ算法。文章分析和评价了各种数据下ＢｒｕｕｎＦＦＴ的运算量和特点，提出了算法的实现结构和方法。最后给了ＴＭＳ３２０Ｃ３０上的运算时间，我们实现的算法比基２ＦＦＴ速度提高３５％。     

《科学》杂志主编唐纳德·肯尼丹论述2001年度的重大科技进展

每一年 ,《Ｓｃｉｅｎｃｅ》杂志的编辑们都要聚在一起讨论该年度重大科技进展的提名问题。面对众多的新发现 ,往往是很具有挑战性的。今年我们遇到了一个尤为困难的任务 :找到一个能够和果蝇以及其他生命体的基因组测序相当的科技成就。果蝇以及其他生命体的基因组测序这项成果不仅仅席卷了去年的重大科技进展奖 ,而且它还导致了众多的后续项目 ,这决不亚于人类基因组草图的发表。这些后续的成功成了本年度科学中无人认领的珍宝中的一部分 ,而且就像去年一样完好的保存着。本年度重大科技进展的提名像去年的一样使人难忘 ,它涉及了从纳米技…     

New Membranes Based on Polybenzimidazole for Polymer Fuel Cells

1 Results Acid-doped polybenzimidazoles[1] are particularly appealing because of high proton conductivity with no or low humidification and promising fuel cells performances. PBI, in fact, contains basic functional groups which can easily interact with strong oxo-acids, such as H3PO4 and H2SO4. The acid partially protonates the polymer and partially is freely dispersed in the polymer backbone, so allowing proton migration via Grotthuss mechanism along the anionic chains[2]. Anyway, a technological limit...     

P pili in uropathogenic E. coli are composite fibres with distinct fibrillar adhesive tips.

Escherichia coli is a frequent cause of several common bacterial infections in humans and animals, including urinary tract infections, bacteraemia and bacteria-related diarrhoea and is also the main cause of neonatal meningitis. Microbial attachment to surfaces is a key event in colonization and infection and results mainly from a stereochemical fit between microbial adhesins and complementary receptors on host cells. Bacterial adhesins required for extracellular colonization by Gram-negative bacteria are often minor components of heteropolymeric fibres called pili which must be oriented in an accessible manner in these structures to be able to bind to specific receptor architectures. P pili mediate the binding of uropathogenic E. coli to a digalactoside receptor determinant present in the urinary tract epithelium. We report here that the adhesin is a component of distinct fibrillar structures present at the tips of the pili. These virulence-associated tip fibrillae are thin, flexible polymers composed mostly of repeating subunits of PapE that frequently terminate with the alpha-D-galactopyranosyl-(1-4)-beta-D-galactopyranose or Gal alpha (1-4)Gal binding PapG adhesin.