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31.
Several research groups have reported the presence of nanometer-sized particles (nanoslabs) in clear solutions, which precipitate the crystalline MFI (ZSM-5) structure. Debate about the growth mechanism for Al-free ZSM-5 (silicalite-1) has revolved around growth by small silicate units (monomers, dimers, etc.) from solution vs growth by nanoslab addition. A model developed for precipitation of uniform sized colloids by addition of sub-colloidal precursor units has been adapted for this zeolite synthesis system. Parameter values were adjusted for the simulation results to match experimental observations from work reported previously, at least to the extent possible. The model involved the simultaneous solution of up to 6000 ordinary differential equations, and required computation times of up to 24 h. The results shed light on the crystal growth mechanism, but pose questions for further investigations of the nucleation mechanism. 相似文献
32.
Braulio Insuasty Fernando Fernandez Jairo Quiroga Rodolfo Moreno Roberto Martinez Enrique Angeles Ruban Gavito Regina H. S. De Almeida 《Journal of heterocyclic chemistry》1998,35(4):977-981
The reaction of 1,2-diaminobenzenes with substituted 1,2-dibenzoyl-1,2-dibromoethanes constitutes a convenient synthetic route to the hitherto 2-(p-R-benzoylmethylene)-3-(p-R-phenyl)-1H-quinoxalines. Structures of all products were elucidated by ir, 1H and 13C-nmr, mass spectra data. X-Ray crystallography data confirm assigned structures. 相似文献
33.
间规聚苯乙烯的化学改性 总被引:4,自引:0,他引:4
介绍了间规聚苯乙烯(sPS)的结构,特性和各种化学改性方法,包括在sPS侧链苯环上引入磺酸基,卤素等功能基因,在sPS分子链末端引入马来酸酐,丙烯酸酯等极性基因,与氢化丁二烯-苯乙烯热塑性弹性体(SEBS)形成接枝共聚物,及其与各类烯烃单体的共聚,对进一步拓宽sPs的应用领域具有重要意义。 相似文献
34.
Chemical effects on Kβ/Kα X-ray intensity ratios for some Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn compounds are studied experimentally. The X-ray spectra were measured by using a Si (Li) solid state detector with high resolution. The vacancies were produced by heavily filtered 241Am gamma rays. It is found that the Kβ/Kα X-ray intensity ratios measured with compounds deviated up to 43% from the corresponding values of the pure elements. The values for pure elements are compared with the other experimental and with theoretical values. 相似文献
35.
为了解佛山市产母、新生儿血铅水平及其相关影响因素 ,采用电感耦合高频等离子体发射光谱法 ,于 2 0 0 2年 5~ 9月 ,取本院产科产母静脉血及其新生儿脐血 1 5 2例 ,进行血铅、钙、锌、铁、铜和锰水平测定 ,按妇幼保健管理卡内容 ,进行相关记录。结果表明 ,产母血铅水平90 1± 3 4 8μg/L ,BPb≥ 1 0 0 μg/L者占 2 0 3 9% ;新生儿脐血铅水平 89 2± 3 1 6μg/L ,铅中毒率为2 2 3 7% ;母子血铅值呈显著正相关 (r=0 85 7,P <0 0 1 ) ,产母血铅值与其血钙、铁值显著负相关 (r=0 2 66,-0 3 0 1 ,P <0 0 5 ) ;城郊产母及新生儿血铅水平显著高于城区。揭示市郊孕妇、新生儿血铅较高 ,血钙、锌、铁含量影响血铅水平 相似文献
36.
Perišić-Janjić Nada U. Ž. Jovanović Bratislav Janjić Natasa J. Rajković Olga S. Antonović Dušan G. 《平面色谱法杂志一现代薄层色谱法》2003,16(6):425-432
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of nine newly synthesized s-tri-azines has been studied by thin-layer chromatography on C18/UV254... 相似文献
37.
38.
H. A. Ergül S. Topcuo?lu E. Ölmez Ç. K?rbaşo?lu 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(1):133-136
Summary Radionuclide (137Cs, 238U, 232Th and 40K) concentrations were determined in a sediment trap and bottom sediment samples collected from a station at the eastern Turkish
coast of the Black Sea. The specific activity of the 137Cs radionuclide in the settling particles ranged from 0.04±0.01 to 0.10±0.02 Bq. g-1dry weight. The calculated flux rate of the 137Cs was between 0.37 and 2.59 Bq. m-2. d-1in the sampling periods of 2002 and 2003. The 137Cs concentration in the bottom sediment profile were between 0.039±0.013-9.083±0.017 Bq. g-1dry weight in the same station. The vertical profile of the radionuclides suggests that they have little mobility during the
17 years after the Chernobyl accident. 相似文献
39.
Oxidation of alcohols to corresponding carbonyl compounds by coenzyme PQQ-trimethyl ester was performed in the presence of aluminum t-butoxide or aluminum chloride under anaerobic conditions. Reduced PQQTME (PQQTMEH2) was obtained by acidification of an aluminum complex of reduced PQQTME which was isolated in the reaction. 相似文献
40.
Removal of methyl violet from aqueous solution by perlite 总被引:2,自引:0,他引:2
The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective. 相似文献