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131.
A Minor New Flavone from Scutellaria baicalensis Georgi 总被引:1,自引:0,他引:1
A new flavone,6,2′-dihydroxy-5,7,8,6′-tetramethoxyflavone,was isolated from the roots of Scutellaria baicalensis. Its structure was established on the basis of spectral evidences. 相似文献
132.
考察了茂环上不同取代基及钛上阴离子配体对茂基钛配合物/正丁基锂催化体系加氢活性和稳定性的影响。在充分发挥该体系催化活性的条件下,由配合物Cp2TiCl2、Cp2TiF2和Cp2Ti[OC6H3(CH3-2)Cl-4]2组成的催化体系对辛烯-1加氢的最高活性(或初活性)达到46 ̄58s^-1。 相似文献
133.
在低钯含量活性非均布Pd/Al2O3催化剂上,实现了富氧条件下,氢部分选择性催化还原NO过程,低温、富氧条件下NO的转化率高达80%-100%。NO直接分解实验表明,600℃,NO分解转化率在无氧时为17.3%,有0.5%氧存在时接近于0。氢非选择性还原NO条件下,100℃以下,NO转化率为100%。根据实验结果及文献,推测了氢部分选择性还原NO过程中可能存在的反应,不同的反应温度下,NO脱除反应有所不同。在115℃以下,NO还原产物为NH3;115℃-155℃,NO还原产物为NH3、N2O和N2;155℃以上,NO还原产物中无NH3存在。NO还原反应与氢氧反应是平行的竞争反应。 相似文献
134.
135.
硝酸根离子介质中偏钛酸钡的水热合成 总被引:1,自引:0,他引:1
以硝酸和钛酸四丁酯为原料,在240℃的碱液中成功地制备了四方相BaTiO3运用XRD、DSC和IR等技术碱度、硝酸根离子、钛源活性、填充度等因素对BaTiO3形成、粒度和物相的作用,KOH最适宜浓度为1.0mol/L,碱液中BaTiO3是BaO-TiO2体系中最稳定的物相,硝酸根离子参与了BaTiO3晶体的成核和生长,钛源的高活性和高填充度有利于四方BaTiO3的形成。 相似文献
136.
series of chitosan samlpes with 91% deacetylation but different molecular weight were obtained by varying the time of chitosan solution in acetic acid aqueous solution at 70℃.The viscosities and flow behavior of the concentrated solutions of chitosan were investigated in 10% (vol%) formic acid aqueous solution after the solutions were prepared for two days by using RPX-705 Rheopexy Analyzer.For each chitosan sample,at the concentration of 3.5 g/100ml,the log (ηr/η0)versus lgγη0,M curves superimpose each other within the same rheogramme. Then the relationship between log nr and lgM was studied under different shear rates.For the highest M sample, the experimental data deviate from the straight lines greatly. This was because the chitosan chain degradated in acid solution during dissolving. The molecular weights were measured in acid solution after two days of dissolving, they were right on their own straight lines. However,no obvious degradation was observed after two days in the same solution for the other lower M chitosan sam-ples. In addition, the plot of nr against M was not a straight line,probaly due to particular interaction of chitosan. 相似文献
137.
A procedure for the Raman spectra calculation of vitreous and molten silicates was presented in this paper. It includes molecular dynamics MD simulation for the generation of equilibrium configurations, Wilson's GF matrix method for the calculations of eigenfrequencies and corresponding vectors, electro-optical parameters method (EOPM) for the Raman intensity calculations, and the bond polarizability model (BPM) for the determination of polarizability and polarizability derivative. One of the most important characteristics of this procedure is the achievement of the partial Raman spectra of five tetrahedral units, as well as the total spectral envelope. In this paper, the calculation was carried out for the vitreous and molten calcium silicates with different compositions and at various temperatures. It is worthwhile to note that the calculation is based on statistical configurations distribution in the space and so it is not needed to artificially adjust the full width at half maximum (FWHM) of spectra. It was also tested through the good agreement of the calculated spectra with the experimental, including some regularity of spectral properties. According to the calculation, the symmetrical stretching of whole tetrahedral units, to which the stretching of Si-O(nb) bond gives the main contribution to intensity, is proven to be the dominance in the high-frequency range (800-1200 cm(-1)) and the symmetrical bending of Si-O(b)-Si, to which the stretching of Si-O(b) bond exhibits the main contribution, is the dominance in the medium-frequency range (400-700 cm(-1)). As the first theoretical results, the Raman scattering coefficient of each Q(i) was found little change along with the variation of composition and temperature. 相似文献
138.
trans-7α-carbomethoxy-decal-1-one (2) yields a mixture of the two oxy-esters 6 and 7 on reacting with MeMgX. Ratios were measured for reactions performed in benzene (with X = I) and in THF (with X = Cl). The small variations of the ratios as compared to those obtained in analogous experiments performed with methyl (2-oxo-cyclohexyl)-propionate 4 and methyl 4-methyl-5-oxo-hexanoate 5 suggest that conformational mobility plays a fundamental role in determining the variations of stereospecificity with varying the reaction conditions. Competitive Grignard reactions among 2,4 and 5 show that their reactivities are in the order 4>2>5 ( = 1.7; =0.8) when reactions are performed in benzene with X I and 2>4>5 (= 0.56; =0.25) when reactions are performed in THF with X C1. The experimental data are interpreted in terms of anchimeric assistance given by the ester group to the reactions of the keto group in conformationally mobile δ-keto esters. The occurrence of this effect depends on the reaction conditions which can favour, or not, folded transition states. 相似文献
139.
Solid complex of terbium nitrate with a novel tetrapodal ligand, 1,1,1′,1′-tetra(2-pyridinecarboxylester)-di(trimethylpropane) was prepared. This new complex with the formula of [TbL(NO3)](NO3)2·2H2O was charact-erized by elemental analysis, molar conductivity, IR spectroscopy and thermal analysis. At the same time, the luminescent property of the complex was also studied. 相似文献
140.
疏水缔合型增稠剂聚(丙烯酰胺-丙烯酸高级酯)的合成及增稠性能研究 总被引:5,自引:0,他引:5
采用沉淀聚合法合成了聚(丙烯酰胺-丙烯酸十四酯),聚(丙烯酰胺-丙烯酸十六酯)和聚(丙烯酰胺-丙烯酸十八酯),重点讨论了共聚物中疏水基团数量及疏水基团链长对增稠性能的影响。采用凯达尔定氮法和动态热分析(DMTA)测定了共聚物的组成及玻璃化温度。 相似文献