烷基硼——不饱和化合物聚合反应的催化剂

Ziegler用三乙基铝为催化剂使乙烯聚合的工作是衆所周知的,这样,乙烯就可以不用压力而进行聚合。还在Ziegler工作以前,人们认为乙烯是属于不容易聚合的不饱和化合物之类,因此新的催化剂既然可以使乙烯进行聚合,那么似乎也可以用来引发其他易於聚合的单体。但是像丙烯腈和甲基丙烯酸甲酯这类单体在有三乙基铝存在时并不聚合,在苯乙烯的情况下虽有聚     

Recyclable,non-leaching antimicrobial magnetic nanoparticles

Recyclable antimicrobial magnetic nanoparticles, Fe₃O₄@P(St-co-AcQAC), were prepared through surfactantfree seeded emulsion polymerization involving a polymerizable, hydrophobic quaternary ammonium compound (QAC). These antimicrobial magnetic nanoparticles demonstrated excellent antimicrobial activities against both Grampositive and Gram-negative bacteria, and can be reused for multiple times.     

微量待测元素的富集(综述)

一、前言当分析方法的相对检出限高于样品中微量待测杂质的浓度(或含量)时,可以采用预富集法。富集能够确保除去基体或者大部分基体,有时还可除去一系列微量干扰组分。得到的富集物中微量杂质的浓度,通常均比原来样品中相应微量杂质的浓度高。此外,采用富集步骤时,称样量可以增大,待测元素的绝对量增加,因此,可降低(改善)微量待测元素的检出限,而且可能改善几百倍、甚至几千倍,有时改善相当可观。这正是广泛采用预富集法的主要原因,但不     

~(13)C核磁共振(六)

分子式为C_6H_8O的哪一个化合物与图E-11符合? 取谱条件: 溶剂:CDCl_3(δ77.2三重峰) 浓度:50V/V％温度:28℃测定频率:22.63MHz 去偶:上——~1H偏共振去偶(500次) 下——~1H宽带去偶(100次) [解答]C_6H_8O含有三个双键当量。在~(13)C谱中找到一个羰基(δ198.65)以及一个C=C键(δ150.6及129.85)。还余下一个双键与三个次甲基(δ38.2,25.75及22.95)。总结起     

流动注入吸附溶出—催化极谱氢波分析痕量铂

本文叙述一种流动注入吸附溶出一催化极谱测定痕量铂的新技术,它集中了溶出法、催化波和流动注入的优点,达到非常高的灵敏度和分析速度。实验给出了最佳载液组成、流速、注入体积、吸附富集电位和吸附时间等因素。本方法成功地进行了多种铂络合物、矿样和生物样品分析。     

Kinetics of the Oxidative Dehydrogenation of Propane over a VMgO Catalyst

The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃ over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at 10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of propane was found to be 122±6 kJ/mol.     

分子力学计算中的分形现象

在分子力学计算中,归属各稳定或亚稳构象的点在构象空间混杂分布,可形成分形结构.计算表明,(1)此分形结构有两个层次:在无镜面对称性吸引子周围,归属该吸引子及其镜面对映体的点相混杂形成第1层次分形结构,在各吸引区边界上,归属各吸引子的点混杂,形成第2层次分形结构.(2)分子力学参数对吸引区结构及大小有很大影响.上述结果可能为解决分子势能面上多能量极小点问题提供帮助.     

BIOMARKERS INDICATING SEDIMENTARY PALEOENVIRONMENTS

Samples involved in this paper are 35 pieces of crude oils and 43 pieces of source rocks, from which a series of biomarkers, capable of indicating paleoecology and paleoenvironment. This will provide a scientific basis for tracing back to sedimenta-y paleoenvironment and paleoecology.     

X-RAY STUDIES ON THE STRUCTURE OF DES-PENTAPEPTIDE INSULIN AT 2.4  RESOLUTION——SOLUTION OF THE PHASE PROBLEM USING THE ANOMALOUS SCATTERING OF CADMIUM AND THE DERIVATION OF A MODEL STRUCTURE

The three dimensional structure of des-pentaptide insulin has been solved at a resolu-tion of 2.4A. The structure determination was achieved without the use of heavy atom de-rivatives, by using only the phase information obtained from the seattering (both real andimaginary) of X-rays by cadmium ions present in the native crystal. Using this phase in-formation, a map, with figure of merit 0.56, was produced which enabled an initial modelof the protein to be constructed. Because of the novelty of this approach to the solutionof the phase problem the procedures used are explained in some detail.     

表示水的硬度的新单位

水的硬度由其中钙盐、镁盐(有时有两价的铁盐)含量的多少来决定。水的硬度通常以相对硬度来表示。各国硬度的表示法有所不同,多以某种体积水中CaO或CaCO_3的含量为基础。其他两价金属换算成等当量的钙化合物来计算。以前苏联用100升水中含1克CaO,即是在1升水中含10毫克CaO来表示水的硬度。在很早以前,当时在化学界中统治着盐的是由金属氧化物和非金属氧化物形成(例如由CaO和CO_2所形成的CaCO_3)的二元论的学说,就应用过