EFFECTS OF CULTURAL CONDITIONS ON THE SYNTHESIS OF SALMONELLA TOXIN

The influence of culture age, pH, aeration, and temperature on Salmonella toxin production was investigated using fermentor cultures containing casamino acids-yeast extract as a growth medium. About 75% or more of total Salmonella toxin was synthesized and released when the cultures were harvested during stationary phase of growth. Increased production and release of the toxin was also observed when the cultures were regulated at pH 6.0, 7. 0, or under alkaline control. The optimal temperature for the synthesis of Salmonella toxin was at 37°C; increased aeration of the cultures (500 rpm) appeared to enhance Samonella toxin production.     

THE INFLUENCE OF NUTRITIONAL FACTORS ON SYNTHESIS OF SALMONELLA TOXIN

The nutritional requirements for the synthesis of a cholera toxin-like toxin from Salmonella enteritidis serotype braenderup were examined. Toxin levels of both culture filtrates and sonicates were determined by the modified Chinese hamster ovary (CHO) floating cell assay. With few exceptions, most amino acids which contained charged polar R groups were stimulatory for Salmonella toxin synthesis. Glycerol enhanced toxin production to the largest extent; however, glucose was a poor carbon source suggesting that Salmonella toxin elaboration may be subject to catabolite repression. Biotin and Mn⁺⁺ were shown to increase the synthesis as well as release of this toxin. An ideal defined medium, supplemented with all the nutritional factors shown to stimulate toxin synthesis, was formulated. The amount of Salmonella toxin produced in this supplemented medium was about 82% of the total toxin elaborated when cultured in Casamino acids plus yeast extract.     

凯歌香槟：爱情成就的顶级香槟

在顶级香槟的酿造者中，唐·佩里侬——香槟的发明者是一个清心寡欲的本笃教派修道士；库克香槟的创始人则是一位一丝不苟的德裔酿酒商。而凯歌香槟的兴旺，却是因为一个年轻的寡妇——凯歌夫人这个香槟史上最有名的女人。     

Remote sensing and model simulation studies of the Norwegian coastal current during the algal bloom in May 1988

Abstract

The Chrysochromulina polylepis bloom in Skagerrak in May 1988 had severe consequences for the sea farming industry. Following the unexpected occurrence of the bloom combined remote-sensing and model studies of the mesoscale circulation of the Norwegian coastal current were performed in support of the daily forecasts of the advance of the algal front. A passive tracer included in the model simulated the drift path of the algae demonstrating the impact of meanders and eddies. Qualitatively the results of the simulation were in good agreement with the direct observations until the bloom culminated, suggesting dominance of the physical processes. In contrast, biological processes lead to the algal mortality during the retreat.     

多晶硅薄膜晶体管的表面氮钝化技术

采用N2O和NH3等离子钝化技术对多晶硅薄膜表面和栅氧表面进行了钝化处理。实验结果表明,该技术能有效降低多晶硅薄膜的界面态密度,提高多晶硅薄膜晶体管性能,二次离子质谱分析表明在p-Si/SiO界面有氮原子富积,说明生成了强的Si-N键。     

The development of an enterprise resources planning system using a hierarchical design pyramid

Today, manufacturers are measured by their ability to respond quickly to sudden, often unpredictable changes in customer needs and wants. Competition beyond the twenty-first century places an increased emphasis upon receiving business information that is accurate and up to date. In order to achieve this, a business planning and closed-loop manufacturing execution system must reflect how work is done, in order to support the overall business objectives without being limited by any hardware, software and human resource constraints. Enterprise resources planning (ERP) is considered to be the most effective computer application in the modern manufacturing industry which meets these requirements. However, only a few manufacturers can design and implement the system successfully. They encounter various problems during the design and implementation cycle. One of the major reasons why they cannot implement the system successfully is the inappropriate use of design and implementation methodology. A systematic design and implementation methodology is therefore proposed for ERP. Called the hierarchical design pyramid (HDP), it encompasses recent research on the ICAM definition method (IDEF) and the object-oriented methodology (OOM) as well as an architecture for any manufacturers who seriously consider ERP implementation.     

A Multimedia Presentation Toolkit for the World Wide Web

This paper describes the design and implementation of MPRES, a Multimedia Presentation Toolkit for the WWW. The WWW has seen phenomenal growth over the last couple of years. It has become a vast repository of multimedia information that is accessible to virtually anyone having a browser. MPRES is a multimedia presentation system that allows a user to compose and render a presentation consisting of objects referenced by their URLs (Uniform Resource Locators). It uses the concept of dynamic documents to render on a WWW browser, a sequence of multimedia scenarios, having objects of types such as audio, image, plaintext, HTML (Hypertext Markup Language) document and animation. MPRES Author, the authoring subsystem, allows the user to interactively test and compose such a presentation, using the Netscape Navigator to collect multimedia resources from the WWW. A presentation database stores the presentations and provides a convenient frontend for accessing them. © 1997 John Wiley & Sons,Ltd.