Use of the Electrostatic Classification Method to Size 0.1 μm SRM Particles—A Feasibility Study

The use of the electrostatic classification method for sizing monodisperse 0.1 μm polystyrene latex (PSL) spheres has been investigated experimentally. The objective was to determine the feasibility of using electrostatic classification as a standard method of particle sizing in the development of a 0.1 μm particle diameter Standard Reference Material (SRM). The mean particle diameter was calculated from a measurement of the mean electrical mobility of the PSL spheres as an aerosol using an electrostatic classifier. The performance of the classifier was investigated by measuring its transfer function, conducting a sensitivity analysis to verify the governing theoretical relationships, measuring the repeatability of particle sizing, and sizing NIST SRM 1691, 0.269 μm and NIST SRM 1690, 0.895 μm particles. Investigations of the aerosol generator’s performance focused on the effect of impurities in the particle-suspending liquid on the resulting particle diameter.The uncertainty in particle diameter determined by electrical mobility measurements is found to be −3.3% to +3.0%. The major sources of uncertainty include the flow measurement, the slip correction, and a dependence of particle size on the aerosol flow rate. It was found that the classifier could be calibrated to indicate the correct size to within 0.1% for both SRM particle sizes if the defined classification length is decreased by 1.9%.     

Perl语言及其应用

Ｐｅｒｌ语言最适于扫描任意的文本文件，并可以从中提出并报告有关信息。本文首先说明了Ｐｅｒｌ语言的使用范围、特性和基本数据类型、语法、然后将Ｐｅｒｌ语言与常用的Ｃ语言进行比较，总结了Ｐｅｒｌ语言的优点及弱点，最后介绍了作者以Ｐｅｒｌ语言为工具所做的一个应用软件－ｈｔｍ１２ｌａｔｅｘ，并说明了作者使用Ｐｅｒｌ语言的体会。     

负载型稀土催化体系催化合成聚异戊二烯的研究

以MgCl_2为载体,制备了一种新型负载型催化体系-NdCl_3·TBP/MgCl_2-Al(i-Bu)_3体系,探讨了该催化体系催化异戊二烯聚合的某些规律.结果表明,该体系对异戊二烯聚合具有较高的活性,以载钕量3%的催化活性为佳,所得聚合物的分子量较高,分子量分布窄,GPC曲线呈单峰分布,经IR和~(13)C-NMR联合测定表明,聚合物顺-1,4含量在95%左右.     

Slip Correction Measurements of Certified PSL Nanoparticles Using a Nanometer Differential Mobility Analyzer (Nano-DMA) for Knudsen Number From 0.5 to 83

The slip correction factor has been investigated at reduced pressures and high Knudsen number using polystyrene latex (PSL) particles. Nano-differential mobility analyzers (NDMA) were used in determining the slip correction factor by measuring the electrical mobility of 100.7 nm, 269 nm, and 19.90 nm particles as a function of pressure. The aerosol was generated via electrospray to avoid multiplets for the 19.90 nm particles and to reduce the contaminant residue on the particle surface. System pressure was varied down to 8.27 kPa, enabling slip correction measurements for Knudsen numbers as large as 83. A condensation particle counter was modified for low pressure application. The slip correction factor obtained for the three particle sizes is fitted well by the equation: C = 1 + Kn (α + β exp(−γ/Kn)), with α = 1.165, β = 0.483, and γ = 0.997. The first quantitative uncertainty analysis for slip correction measurements was carried out. The expanded relative uncertainty (95 % confidence interval) in measuring slip correction factor was about 2 % for the 100.7 nm SRM particles, about 3 % for the 19.90 nm PSL particles, and about 2.5 % for the 269 nm SRM particles. The major sources of uncertainty are the diameter of particles, the geometric constant associated with NDMA, and the voltage.     

组分对VAE乳液水泥复合防水涂料的性能影响

采用VAE乳液和硅酸盐类水泥为主要原材料,研究了该体系中各组分对涂料性能的影响,结果表明:与不掺水泥的VAE乳液防水涂料相比,这种复合防水涂料的拉伸强度、粘结强度和耐水性均有大幅度提高,是一种综合性能更优的新型防水材料.     

聚合物水泥防水涂料用丙烯酸酯乳液的制备

目的制备出高弹性、高稳定性、高防水性聚合物水泥防水涂料用丙烯酸酯乳液，克服常规聚合物水泥防水涂料用乳液弹性低和防水性差的弊端．方法采用分子设计、粒子形态的概念，用甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）为原料，以十二烷基苯磺酸钠（DSB）和烷基酚聚氧乙烯醚（OP-10）的混合乳化剂为乳化体系，过硫酸铵（APS）为引发剂，引入甲基丙烯酸（MAA）功能性单体和N-羟基丙烯酰胺或丙烯酰胺活性交联单体，采用预乳化半连续种子乳液聚合工艺．结果设计低玻璃化温度（Tg）、引入功能性单体及活性交联单体可以提高丙烯酸酯乳液的弹性、稳定性和防水性．结论得出较佳的工艺条件为：（1）预乳化阶段：单体滴加时间t=45min、预乳化温度01=45℃、搅拌器转速为500～550r／min；（2）种子乳液聚合阶段：反应温度02=80℃、反应时间t=4h、搅拌器转速为280～300r／min．     

丙烯酸酯共聚物乳液混凝土中聚合物与混凝土的化学作用

本工作是研究聚合物混凝土中聚合物与水泥水化产生的氢氧化钙的化学作用。以丙烯酸酯共聚物乳液为代表,用红外分析的方法研究了乳液与氢氧化钙及氢氧化锌发生的化学反应,以及产物的结构,得到了聚合物与混凝土的化学作用是使强度提高的一个因素,以及微量物质氢氧化锌的加入可能会改善聚合物的耐久性的结论。     

The Growth of Latex Particles during the VAc/BA Copolymerization

The semi-continuous seeded emulsion eopolymerization of vinyl acetate and butyl acrylate was carried out with hydroxyethyl cellulose as a colloid stabilizer. The morphology of the latex particle and the relationship between the reaction time and the average particle diameter and/or the conversion ratio during the polymerization were invstiguted. The experimental results shaw that the morphology of the latex particle possesses the stable sterie construction. In the seeded polymerizution, the average particle diameter of latex decreased while the conversion ratio increased. At the second term of the emulsion copolymerization （the growth stage of particle size）, the latex particle average diameter increased with copolymerization continuously, but the instantaneous conversation ratio was not large, so it was very necessaO to properly prolong the time during the holding temperature stage.     

Diffusive motions in living cytoplasm probed by laser Doppler microscopy

We have examined cytoplasmic motions in growing pollen tube tips using laser Doppler microscopy, a non-invasive and non-destructive technique. The observed correlation functions were consistent with the existence of diffusive motions in the tip cytoplasm. Further analysis of the data revealed the existence of at least two major and a third, minor, diffusing species in the cytoplasm. Information from quantitative electron microscopy and from published literature values of cytoplasmic viscosity was used to tentatively identify the organelles contributing to the observed diffusive motions. It is concluded that motions of mitochondria and secretory vesicles dominate the observed correlation functions with a minor component detected from either ribosomes or the microfilament network. Sources of variation in the observed data are discussed, as are the physical limitations that prevent a more positive analysis of the present data.