Detection of an anatoxin-a(s)-like anticholinesterase in natural blooms and cultures of cyanobacteria/blue-green algae from Danish lakes and in the stomach contents of poisoned birds

Ten natural bloom samples of cyanobacteria from the Danish lakes Knud s? (5), Ravn s? (4), and Salten Langs? (1) collected during 1993-1995 were assayed for toxicity by mouse bioassay, for acetylcholinesterase inhibiting activity by a colorimetric method, and for microcystins by enzyme-linked immunosorbent assay. In the mouse bioassay, seven samples were neurotoxic, two were non-toxic and one gave a protracted toxic response. One of the non-toxic and the single protracted toxic sample both contained anticholinesterase activity equivalent to 4 micrograms anatoxin-a(s) g-1. The neurotoxic samples contained equivalents to 20-3300 micrograms anatoxin-a(s) g-1. The highest anticholinesterase activities (equivalent to 2300 and 3300 micrograms anatoxin-a(s) g-1, respectively) were found in samples collected from Lake Knud s? in connection with bird-kills in 1993 and 1994. Small amounts of microcystins (0.1-0.9 microgram g-1) were detected in all samples but one. All Lake Knud s? and Lake Ravn s? samples were dominated by Anabaena lemmermannii, and the Lake Salten Langs? sample by several species of Anabaena. Gel filtration profiles indicated similarity between the toxic component from the Lake Knud s? 1994 bloom with registered bird-kills and anatoxin-a(s) isolated from Anabaena flos-aquae NRC-525-17. Anticholinesterase-producing cultures of A. lemmermannii were isolated from the Lake Knud s? 1993 bloom. These laboratory cultures produced anatoxin-a(s) equivalents of 29-743 micrograms g-1. Other cultures of A. lemmermannii isolated from Lake Knud s? and Lake Ravn s? were hepatotoxic or non-toxic. Dead birds collected from Lake Knud s? during the neurotoxic 1993 Anabaena bloom possibly died from cyanobacterial toxicosis. The stomach contents contained colonies and single trichomes of Anabaena, and anticholinesterase activities equivalent to 2.1-89.7 micrograms anatoxin-a(s) kg-1 body weight and microcystins (53-95 ng kg-1) were also detected.     

长江螺山站高水位流量关系和城陵矶（莲花塘）控制水位的研究

螺山站高水位流量关系是确定长江城陵矶（莲花糖）控制水位的基本依据，从基本的河道水力学规律出发，考虑涨落率修正、瞬时比降修正，计算各时段点的代表性比降，和相应糙率，求出均值，根据断面资料，得出高水位的稳定流曲线，并以各日流量转化的稳定流点，进行验证，精度很好，分析了河段区间流量对螺山站稳定流量的影响。阐明了螺山站稳定流量的变化情况和趋势，推求了各次大洪水的超额洪量，计算出莲花糖以上的总入流，根据现今的湖区及槽蓄容积进行洪水演进，计算1954年特大洪水的超额洪量，并分析节三峡水库拦洪后对长江中下游超额水量的影响；对莲花塘不同防洪控制水位进行了技术经济分析和评价，提出了抬高控制水位的具体建议。     

由乙腈一步法制备乙酸丁酯的研究

以丁醇和制备丙烯腈的副产物乙腈为原料 ,采用一步法合成了乙酸丁酯。通过正交实验得到了影响反应的 4种因素。确定了最佳的工艺条件为 :催化剂的量为样品质量的 40 % ;n(CH3CN)∶ n(C4 H9OH) =1∶ 1 .0 5 ;反应温度为 1 0 5℃ ;反应时间为 8h。在此反应条件下 ,乙酸丁酯的收率为 88.8% ,纯度可达 99.5 %。并用气相色谱及红外光谱对产品的纯度进行了表征     

轧机主传动万向联轴器辊端接头结构探讨

分析了衬板槽平面与叉头十字轴孔轴线的相对位置对辊端接头应力的影响 ,研究了轧辊扁头与衬板之间间隙所产生的冲击和应力集中 ,讨论了辊端接头中部过渡段结构对应力分布和制造质量的影响。提出辊端接头结构设计的优化方案     

功率电子器件用AlN陶瓷基板的研制

阐述了AlN陶瓷的烧结原理 ,分析了烧结工艺参数对大面积AlN基板性能的影响 ,成功研制出了高热导率(190W /m·K)、大面积 (14 0mm× 90mm)、翘曲度为 2 0 μm/5 0mm的AlN陶瓷基板。     

钨合金废料的资源再生利用技术

钨是一种稀有金属，钨合金具有高的强度、硬度，较好的耐高温性、耐密性和良好的电性能。广泛应用于航空航天工业、兵器工业、核工业、信息产业、汽车工业和钢铁工业等行业。目前，钨资源短缺，钨合金价格高、用量大，因此各国都把废弃的钨合金作为宝贵的第二钨资源加以再生利用。本文综述了钨合金的再生利用现状，分别总结了硬质合金、高比重合金、钨铜合金和钨材的再生利用技术，并利用生态环境材料的观点。对每种再生利用技术作了简单的评价。     

Effect of Synergistic Anticorrosion Treatments on Cycling Stability of Mg-Based Hydrogen Storage Electrode

In this paper, any two of the three anticorrosion agents, that is emulsifier (OP-10), soluble glass (Na2O·nSiO2) and glycerin (C3H8O3), were treated simultaneously on the surface of amorphous (a-) MgNi+5% Ml2Mg17 (Ml denotes the lanthanum-rich mish metal) electrode and the electrolyte. Effect of the synergistic anticorrosion treatment on charging/discharging cycle stability of the electrode was investigated. Contrasted with single treatment method, the cycling stability of the electrodes was further improved. The desirable synergistic anticorrosion method was that the electrode was treated by the soluble glass, and that OP-10 was added into the electrolyte. The cyclic voltammogram (CV) results of the electrode show clearly that the anticorrosion agent can change the electrochemical activity and mechanism of the electrode. The concentration of the anticorrosion agent in the electrolyte treated by the synergistic anticorrosion method was also investigated. The appropriate concentration of the anticorrosion agents in the electrolyte is 0.143%.     

机械结构动态改进技术在电动机振动噪声防治中的应用

本文介绍了结构实验模态分析、灵敏度分析和局部结构改进分析等先进的结构动态改进技术的基本原理,并由此对Y112M-4型电动机的机座进行了计算和分析,确定出一个结构改进方案.经实际改进试验验证,这一改进可有效地抑制电动机电磁振动和电磁噪声的传递,具有明显的减振降噪作用.     

基于μCLinux的NAT设备的设计与开发

NAT(网络地址翻译)技术有效地解决了IP地址紧缺的问题,为实现IPv4到IPv6的平滑过渡发挥了巨大的作用.在一个体积小、重量轻、价格低廉的嵌入式平台上实现NAT设备具有很好的实际意义.文中介绍了NAT技术的原理和实现过程,在自行设计的ARM7嵌入式硬件平台上基于μCLinux操作系统实现了NAT的功能,并通过实现其他相关功能,构建了完整的NAT设备,完成了小型网络接入Internet的方案.