相尺寸和铁添加剂对W—Cu（20wt％）复合粉末烧结行为的影响

研究了钨-20％铜(W-20wt％Cu)复合粉末中相尺寸和少量铁对烧结行为的影响。两种混合粉末分别由湿法冶金(H)或机械合金化(M)合成。机械合金化粉末由纳米级W—Cu混合物和微米级W和Cu晶粒组成。不合Fe和掺杂0．2wt％Fe的湿法冶金粉的相尺寸为150nm-450nm。加热和在10900C—1250℃(3min～80min)下处理后的相对密度对烧结进行了研究。粒度较粗的纯的湿法冶金粉压坯烧结获得了最低密度(88％)：较小的相尺寸或Fe添加剂增加烧结的密度。纯细和掺杂的粗湿法冶金粉达到了最高密度(96％一98％)。Fe添加剂显著降低了导电性。     

工业纯钛在不同温度下的屈服应力应变

前言晶粒度、杂质含量、应变速率和试验温度都影响工业纯钛的屈服点。如果晶粒度小于50微米,在室温下就可观测到上屈服点和下屈服点。屈服落差随钛中氧和氮的含量而增加。     

梁赞有色冶金工厂采用钛装置

在梁赞有色冶金工厂的主要工序中采用了含硫酸盐和金属氟化物杂质的硫酸腐蚀溶液,气体含硫化物,氟化物和二氧化碳,氟,氯以及硫酸蒸气。由于材料快速腐蚀破坏,所用装置的工作寿命不长。在某些工序中应用钛制装置可以延长其使用寿命,降低生产消耗,强化工艺过程。在湿法冶金,微尘回收和配料干燥车间所进行的、BT1—0、BT5—1钛合金与X18H10T、X17H13M2T钢的对比腐蚀试验(见表)表明:在大多数研究介质中     

Rationally designed inhibitors as tools for comparing the mechanism of squalene-hopene cyclase with oxidosqualene cyclase

The inhibition of squalene-hopene cyclase (SHC) (E.C. 5.4.99.-), an enzyme of bacterial membranes catalyzing the formation of pentacyclic sterol-like triterpenes, was studied by using different classes of compounds originally developed as inhibitors of oxidosqualene cyclase (OCS) (E.C. 5.4.99.7), the enzyme of eukaryotes responsible for the formation of tetracyclic precursors of sterols. The mechanism of cyclization of squalene by SHC, beginning with a protonation of the 2,3 double bond by an acidic residue of the enzyme, followed by a series of electrophilic additions of the carbocationic intermediates to the double bonds, is similar to the mechanism of cyclization of 2,3-oxidosqualene by OSC. The inhibitors studied included: (i) analogs of the carbocationic intermediates formed during cyclization, such as aza-analogs of squalene and 2,3-oxidosqualene; (ii) affinity-labeling inhibitors bearing a methylidene reactive group; and (iii) vinyldioxidosqualenes and vinylsulfide derivatives of the substrates. Comparison of the results obtained with the two enzymes, SHC and OSC, showed that many of the most effective inhibitors of OSC were also able to inhibit SHC, while some derivatives acted as specific inhibitors. Differences could be easily explained on the basis of the different substrate specificity of the two enzymes.     

Silphinene Sesquiterpenes as Model Insect Antifeedants

Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11-acetoxy-5-angeloyloxysilphinen-3-one (1), 11-acetoxy-5-tigloyloxysilphinen-3-one (2), 11-acetoxy-5-iso- butyryloxysilphinen-3-one (3), 11-hydroxy-5-angeloyloxysilphinen-3-one (4), 11,5-dihydroxysilphinen-3-one (5), 11,5-diacetoxysilphinen-3-one (6), 5,11-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect.     

二氯苯醚菊酯与甲基对硫磷、毒死蜱和马拉松混用对欧洲玉米螟的增效研究

All 等人(1977)曾分析二氯苯醚菊酯与选择的有机磷和氨基甲酸酯杀虫剂对玉米穗虫(Heliothis zea)及烟芽夜蛾(H.Virescens)幼虫的协同作用。在对这两种虫的实验室和田间试验结果中,发现二氯苯醚菊酯加上甲基对硫磷或灭多虫具有增效作用。在某些情况下,包括二氯苯醚菊酯的二元混合物防治这两种害虫的药量可以降至单用量的10％。他们没有阐明增效作用的机制。     

黄色物质在含铜介质中的解毒作用

可溶性黄色有机物(黄色物质)普遍存在于含有水的环境里,它通过影响含水有机体中矿物质的输送和转化,以及对机体本身物质发生的作用,而影响到生态环境。对这种黄色物质虽然已经作了很多研究,但在化学上和物理上还是不清楚的。一般认为在自然水中游离的黄色微小颗粒,是来自腐败了的有机质,是一种水溶性的抽提物。木质素是植物体的基本组成物,是一类稳定的、黄褐色的腐败中间产物腐植质或腐植酸物质的前体(?)。腐植酸物质分为腐植酸(碱可溶的)和黄腐酸(酸可溶的)两部份。这些化合物在水中不溶解,而且当从土壤或沉积物中抽提出来时又特别容易被分解。黄色腐败产物中的黄色物质,常称它为可溶性腐植质(可溶性腐植酸)从有些数据如元素组成、可见     

低能耗合成氨生产的联合能量回收系统

采用氨生产能量回收系统的现有装置,可以使每吨氨的能耗从8.4×10~6千卡降为7.0×10~6千卡。     

碳纤维与复合材料的回顾(第一部分)

在论文将分为两部分,目的是要回顾碳纤维及其原丝的生产技术、纤维结构及其主要性能(第一部分).并总结目前树脂基或水泥基碳纤维复合材料的现状(第二部分)。     

侧流塔的最小回流比

蒸馏塔的设计需要估算最小回流比。本文指出如何计算有一股或多股侧流的蒸馏塔最小回流比。