Synthesis of TiO2–SiO2/polymer core–shell microspheres with a microphase‐inversion method

A novel microphase‐inversion method was proposed for the preparation of TiO₂–SiO₂/poly(methyl methacrylate) core–shell nanocomposite particles. The inorganic–polymer nanocomposites were first synthesized via a free‐radical copolymerization in a tetrahydrofuran solution, and the poor solvent was added slowly to induce the microphase separation of the nanocomposite and result in the formation of nanoparticles. The average particle sizes of the microspheres ranged from 70 to 1000 nm, depending on the reaction conditions. Transmission electron microscopy and scanning electron microscopy indicated a core–shell morphology for the obtained microspheres. Thermogravimetric analysis and X‐ray photoelectron spectroscopy measurements confirmed that the surface of the nanocomposite microspheres was polymer‐rich, and this was consistent with the core–shell morphology. The influence of the synthetic conditions, such as the inorganic composition and the content of the crosslinking monomer, on the particle properties was studied in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3911–3920, 2006     

Determination of 17 kinds of banned organochlorine pesticides in water by activated carbon fiber-solid phase microextraction coupled with GC-MS.

Activated carbon fiber (ACF) as extraction fiber for solid-phase microextraction (SPME) and its application for the analysis of banned organochlorine pesticides (OCPs) were investigated. Firstly, ACF was activated by different concentration of zinc chloride, which indicated that ACF activated by 60% zinc chloride had a reasonable specific surface area, pore volume and pore distribution. Secondly, the parameters for the ACF-SPME procedure, the adsorption and desorption conditions, were also optimized when coupled with gas chromatography-mass spectrometry (GC-MS). Thirdly, the ACF-SPME was used to analyze 17 kinds of OCPs in water. The linearity of most pesticides was found to be between 0.2 and 50 microg/l with GC-MS under the selected ion monitoring (SIM) acquisition mode. The limits of detection (LOD) at the sub microg/l were obtained. The work demonstrated here shows that ACF is a promising alternative for the SPME procedure.     

Dependence of excess bismuth content in precursor sols on ferroelectric and dielectric properties of Bi3.25La0.75Ti3O12 thin films fabricated by chemical solution deposition

Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were fabricated on Pt/Ti/SiO₂/Si(1 0 0) substrates by chemical solution deposition (CSD), and the dependence of ferroelectric and dielectric properties of the as-deposited BLT thin films on excess Bi content in precursor sols was studied. It is found that the prepared BLT thin film shows the best polarization-electric field, capacitance-voltage and dielectric constant (?_r)-frequency characteristics, when the value of excess Bi content in precursor sols is 10%. In detail, its remnant polarization (2P_r) value is 40 μC/cm², the capacitance tunability is 21% measured at room temperature under conditions of an applied voltage of 8 V and measurement frequency of 10 kHz, and the ?_r is 696 at 100 kHz frequency.     

Rational Homotopy Theory and Nonnegative Curvature

in this note, we answer positively a question by Belegradek and Kapovitch about the relation between rational homotopy theory and a problem in Riemannian geometry which asks that total spaces of which vector bundles over compact non-negative curved manifolds admit （complete） metrics with non-negative curvature.     

利用低能质子束产生高强度放射性束流

加拿大TRIUMF实验室利用¹¹C成功验证了一种产生高强度(～10⁸ions/s)放射性束流的方法. 该方法不同于普通在线同位素分离方法, 它利用了13MeV的低能强流质子束, 可以产生一系列核天体物理实验感兴趣的高强度放射性束流.     

新型稀土电子输运材料Tb(AcA)3·phen

Kido等人在文献[1]中报导,在研究有机电致发光(OEL)器件时发现,斓系化合物不能很好地传输载流子.但是,我们在实验中却现Tb(AcA)3phen·不仅是一种很好的OEL发射材料.而且具有很强的电子输运能力.     

Multiple impulse solutions to McKean's caricature of the nerve equation. I—existence

McKean's caricature of the nerve equation: is considered. The H in (1) is the Heaviside function. We prove the existence of multiple impulse solutions consisting of any finite number of pulses. These solutions are referred to as n-ple impulse solutions, where n is an arbitrary positive integer.     

钌催化二氧化碳加氢合成甲酸的研究

钌催化二氧化碳加氢合成甲酸的研究张俊忠，李忠，王辉，王常有（太原工业大学煤化所Ｃ１室，太原０３００２４）关键词ＣＯ_２催化加氢，甲酸合成，钌络合催化剂１．前言由于ＣＯ２对环境、气候和生态等方面带来愈加恶劣的影响以及碳资源的日益短缺，近年来对ＣＯ２开发?..     

后处理温度对ZrO2气凝胶超细粉织构和结构的影响

运用神效儿宝治疗小儿厌食症２１０例，总有效率为９５．２％，显效率为６２．４％。该药使用、携带方便、见效快，疗效短，无毒副作用。实验证明，该药能显著提高胃蛋白酶含量，减慢肠管推进性运动，提高动物耐疲劳、耐缺氧能力，提高巨噬细胞吞噬率及血清补Ｃ３含量，且无毒副。作用