DETECTION OF BACILLUS CEREUS DIARRHEAGENIC TOXIN USING A RAT LIGATED INTESTINAL LOOP ASSAY

A study was performed to determine if the rat ligated intestinal loop assay could detect Bacillus cereus diarrheagenic toxin. The results obtained indicated that this assay system could be used for such a purpose but it was not as sensitive as the young rabbit ligated ileal loop assay. When rats were used, concentrating the cell free culture filtrate of B. cereus 30- to 40-fold was necessary to detect diarrheagenic toxin activity with the intestinal loop assay.     

SENSITIVITY OF LISTERIA MONOCYTOGENES TO SPICES AT TWO TEMPERATURES

Thirteen spices were screened for growth inhibition effect against Listeria monocytogenes at 24°C using a concentration gradient plate method. Cloves, and oregano were the two most inhibitory spices with MIC values ranging from 0.5 to 0.7% (W/V). Inhibition was also detected with sage and rosemary (MIC of 0.7 to 1.0%) as well as nutmeg (MIC of 1.1–1.4%). Black pepper, chili, cinnamon, garlic, mustard, paprika, parsley and red pepper at a concentration up to 3.0% did not inhibit the growth of the organisms. The effect of cloves, oregano and sage on the growth and survival of L. monocytogenes Scott A was further tested in tryptic soy broth at both 4 and 24°C. At a concentration of 0.5 or 1.0%, cloves were bactericidal and oregano was bacteriostatic to this organism at both incubation temperatures. Sage at these two concentrations was bactericidal at 4°C and bacteriostatic at 24°C. When tested in sterile meat slurry, a 1.0% level of either cloves or oregano had little effect on the growth of L. monocytogenes Scott A at 4 or 24°C.     

基于关联度流量预测的加权局域模型

传统的混沌局域预测模型仅考虑相空间中邻近相点到预测中心的空间距离对预测中心动力学行为演化的影响,所以在嵌入维数比较高的时候,用来预测混沌时间序列时效果往往不是很好.本文提出了一种基于关联度的网络流量预测的加权零阶局域模型,该模型同时综合考虑到了空间距离和邻近相点与预测中心的关联程度这两个因素对预测效果的影响,因而在很大程度上克服了传统混沌局域模型的不足.通过模拟实验将该模型用于网络流量预测,模拟结果表明该模型的预测精度比传统的模型要好.     

Lightning Observation in 3D Using a Multiple LF Sensor Network and Comparison with Radar Reflectivity

A three‐dimensional (3D) lightning mapper consisting of multiple low‐frequency (LF) sensors has been developed to monitor thunderstorms and to estimate their charge structure. We have been conducting an observation campaign using the 3D lightning mapper in Kansai, Japan, since October 2012. In this study, we determine 3D source locations of intracloud and cloud‐to‐ground flashes and compare them with the radar reflectivity estimated by phased‐array radar (PAR) with high temporal and spatial resolution. Most LF sources are located in high radar reflectivity regions, confirming that the 3D LF lightning mapper monitors thunderstorms. A lightning flash with heavy branches is clearly imaged. Based on the bidirectional leader theory that negative and positive ends of a lightning leader develop simultaneously, we estimate the positive and negative charge regions in a thundercloud from the LF source locations. The radar reflectivity estimated by PAR supports the charge structure estimated by LF source locations.     

镇海加氢裂化装置循环氢压缩机组改造

介绍镇海炼油化工股份有限公司加氢裂化装置扩能改造中循环氢压缩机组的改造情况。主要改造了压缩机和汽轮机的通流部分 ,使压缩机流量从 2 11.0 7dam3 /h扩大到 2 5 9.5 0dam3 /h ,改造投资仅为 5 0 0× 10 4RMB $,比更换整套机组节约 130 0× 10 4RMB $。改造后机组运行平稳 ,性能完全满足工艺要求。     

认证系统与纠错码的应用研究

针对数字签名，探讨了纠错码理论和技术在数字签名中的重要作用，介绍了一类纠错码数字签名方案：提出了一种将签名与加密、纠错相结合的公钥密码新体制，新体制比较充分发挥了纠错码的潜在优势。本文研究指明了纠错码在认证系统中的应用前景。     

基于多Agent自动协商的电子商务系统的研究

本文首先分析了多Agent系统的特点,并对基于博弈论的商品价格自动协商的双向博弈模型及其运行过程进行了探讨.在此基础上,结合电子商务系统的实际需求,提出了一种基于多Agent自动协商的电子商务系统,对该系统的组成单元及其运行过程进行了详细阐述,为该系统的具体实施打下了基础.     

世界铬矿开发现状及投资建议

铬作为我国一种重要的战略资源。近年来,其消费量居世界第一位,然而,我国铬资源严重匮乏,供需矛盾日益突出。基于这一国情,鼓励开发利用国外资源将是缓解我国资源紧张最为有效的方法之一。本文从近年全球铬矿产出水平和主要生产国家、世界级大型铬矿山开发情况和主要铬生产企业产能情况三方面进行了系统的分析,得出适应我国实施海外投资的以下三点形势:1津巴布韦资源量大,但开发程度低;2国外铂族金属矿山中铬金属浪费严重;3世界铬矿业公司兼并、收购活动频繁。基于这一形势,提出如下建议:1津巴布韦是我国实施海外投资的优选地区;2我国可通过与国外铂族金属企业合作,综合利用铂矿中的铬资源;3我国可在频繁的的兼并、收购活动中作好投资规划和准备;4需借鉴国内外企业投资铬业的成功经验等。     

SOME MOLECULAR EFFECTS IN DRAG REDUCTION: A SUMMARY†

Dilute solutions of high molecular weight polymers have drawn a great deal of interest in recent years because of their drag reducing characteristics. It is well-known now that a substantial reduction in turbulent frictional drag can be achieved with a very small amount of polymeric additives, usually only a few parts per million by weight (ppmw) in concentration. This unique phenomenon has offered a new dimension in the design development of new marine systems for higher speed, longer range, larger payload as well as possibly quieter machinery. Although the discovery of this turbulent drag reduction phenomenon may be traced back to Toms¹ and Mysels² in the 1940's, the U.S. Navy's exploration of the turbulent drag reduction effect did not begin until the pioneering effort of Hoyt and Fabula in the 1960's. ³ During a period of several years in the early 19707apos;s, an interdisciplinary group at the Naval Research Laboratory undertook an intensive basic research effort to study the effects of polymer molecular structure on turbulent drag reduction. Model compounds were synthesized in the laboratory, and their drag reducing properties characterized. Polymers including polyacrylamide and its derivatives, polyacrylic acid, poiyphosphate and association colloids have been investigated. In this report, an attempt is made to highlight some of the results from that program in a brief summary form.