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31.
Lijun Zhang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》1996,17(10):1735-1747
The finite element method is combined with the mode-matching method and the multi-mode network method to analyze the scattering and radiation characteristics of a class of planar dielectric waveguide discontinuities. Unlike the conventional method to treat the radiation as a source-field problem, in the present approach, the dispersion characteristics of dielectric guided-wave structures are calculated first, and then the radiation problem is transferred to the propagation problem of a series of surface-waves and space waves from the viewpoint of scattering, thus the analysis is tremendously simplified. 相似文献
32.
Visible light induced photocatalytic reaction of rhodamine B dye via 12-tungstosilicic acid in water
Using 12-tungstosilicic acid (SiW124-) as the catalyst, rhodamine B (RhB) dye in an aerated aqueous solution can undergo an effective photocatalytic stepwise N-deethylation process under visible light irradiation, and dioxygen is reduced to hydrogen peroxide by the reducedSiW12 4-. This provides the potential for moving polyoxometalate-based photocatalytic processes from the near-UV into the visible region of the spectrum. 相似文献
33.
Amal A. El Daibani Yuecheng Xi Lijun Luo Xue Mei Chunyang Zhou Shin Yasuda 《Natural product research》2020,34(6):797-803
AbstractPrevious studies have revealed sulfation as a major pathway for the metabolism of hesperetin, naringenin and apigenin. The current study was designed to identify the human cytosolic sulfotransferase (SULT) enzyme(s) capable of sulfating these flavonoid compounds. Of the thirteen human SULTs, six (1A1, 1A2, 1A3, 1B2, 1C4, 1E1) displayed significant sulfating activity toward hesperetin, five (1A1, 1A2, 1A3, 1B2, 1C4) displayed sulfating activity towards naringenin, and four (1A1, 1A2, 1A3, 1C4) showed sulfating activity towards apigenin. Of the four human organ specimens tested, liver and intestine cytosols displayed much higher hesperetin-, naringenin- and apigenin-sulfating activity than lung and kidney cytosols. Moreover, sulfation of hesperetin, naringenin and apigenin was shown to take place in HepG2 human hepatoma cells and Caco-2 human colon adenocarcinoma cells under cultured conditions. Taken together, these results provided a biochemical basis underlying the metabolism of hesperetin, naringenin and apigenin through sulfation in humans. 相似文献
34.
Experimental and modeling study on decomposition kinetics of methane hydrates in different media 总被引:6,自引:0,他引:6
Liang M Chen G Sun C Yan L Liu J Ma Q 《The journal of physical chemistry. B》2005,109(40):19034-19041
The decomposition kinetic behaviors of methane hydrates formed in 5 cm3 porous wet activated carbon were studied experimentally in a closed system in the temperature range of 275.8-264.4 K. The decomposition rates of methane hydrates formed from 5 cm3 of pure free water and an aqueous solution of 650 g x m(-3) sodium dodecyl sulfate (SDS) were also measured for comparison. The decomposition rates of methane hydrates in seven different cases were compared. The results showed that the methane hydrates dissociate more rapidly in porous activated carbon than in free systems. A mathematical model was developed for describing the decomposition kinetic behavior of methane hydrates below ice point based on an ice-shielding mechanism in which a porous ice layer was assumed to be formed during the decomposition of hydrate, and the diffusion of methane molecules through it was assumed to be one of the control steps. The parameters of the model were determined by correlating the decomposition rate data, and the activation energies were further determined with respect to three different media. The model was found to well describe the decomposition kinetic behavior of methane hydrate in different media. 相似文献
35.
36.
Jingfei Luan Zhigang Zou Minghui Lu Guoyou Luan Yanfeng Chen 《Research on Chemical Intermediates》2006,32(1):31-42
In2BiTaO7 was synthesized using the solid-state reaction method and its photocatalytic properties were investigated. The results of
powder X-ray diffraction (XRD) indicated that the compound crystallizes in the pyrochlore-type structure, cubic system with
space group Fd-3m. The lattice parameter is 10.6972(1) ?. In addition, the compound shows strong optical absorption in the
visible region (λ > 420 nm) and the band gap of In2BiTaO7 was estimated to be about 2.47 eV. For the photocatalytic reaction, H2 or O2 evolution was observed from CH3OH/H2O or AgNO3 solution respectively with In2BiTaO7 as the photocatalyst under visible light irradiation, indicating that In2BiTaO7 is responsive to visible light for splitting water. Furthermore, the catalyst remained photoactive in the wavelength range
up to 510 nm. Photocatalytic degradation of methylene blue (MB) dye over the compound was further investigated under visible
light irradiation. The results showed that complete removal of aqueous MB could be achieved after irradiation for 135 min
over In2BiTaO7. Furthermore, under visible light irradiation In2BiTaO7 showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation. 相似文献
37.
不同类型聚合物溶液对采油残余油的作用机理研究 总被引:6,自引:0,他引:6
通过实验测定了HPAM溶液和黄原胶溶液的流变性、在多孔介质中的流变性和残余阻力系数 ,计算了衰竭层效应 .用不同的浓度和注入速度进行了驱油实验 .提出聚合物分子缠结作用的增强不仅引起表观粘度增加或衰竭层厚度降低 ,而且使平行于油水界面的拉动残余油的力增加 ,从而使残余油饱和度降低 ,采收率提高 .随浓度增加 ,HPAM溶液的表观粘度和残余阻力系数增加 ,衰竭层厚度减小 ;黄原胶溶液的浓度高于缠结浓度时 ,衰竭层厚度和表观粘度变化不大 .注入速度增加时 ,两种聚合物溶液的衰竭层厚度均降低 ,HPAM溶液的残余阻力系数不变 ,粘弹性增加 ;而黄原胶溶液的残余阻力系数下降 .不同浓度和注入速度情况下两种聚合物溶液的驱油结果证实了文中提出的聚合物分子缠结作用和衰竭层效应对残余油的作用机理 .分子结构的不同是造成两种聚合物溶液在多孔介质中渗流规律和对残余油作用机理的差别的根本原因 . 相似文献
38.
With P(CH3)3 as the probe molecule adsorbed on titanium silicalite (TS-1) zeolite, the special and important role of T12 site in MFI-type zeolite was clearly elucidated. There are altogether three active sites present in TS-1 zeolite with Ti at the T12 site. Owing to the preferential adsorption of probe molecules on the first Brönsted acidic site, the Ti12 center will probably fail to show Lewis acidity. The ionic [HP(CH3)3]+ species can be stabilized by the first or second Brönsted acidic site, with the former energetically favored. The latter was formed through the transfer of the ionic [HP(CH3)3]+ species from the first to the second Brönsted acidic site. 相似文献
39.
Summary The sorption of Th(IV) onto TiO2 was studied by the batch technique as a function of pH and ionic strength at moderate concentration (10-4-10-5 mol/l) and in the presence and absence of phosphate. It was found that the sorption rate of Th(IV) was relatively slow, the
sorption percent was abruptly increased from pH 2 to 4, and the sorption was decreased with increasing ionic strength as a
whole. In the concentration range of Th(IV) from trace concentration to 1.4 . 10-4 mol/l and in the absence of phosphate, the sorption isotherms were roughly fitted the Freundlich equation at different ionic
strengths and approximately constant pH. These sorption characteristics of Th(IV) onto TiO2 were compared with those of uranyl on the same sorbent. In addition, the positive effect of phosphate on the sorption of
Th(IV) onto TiO2 was demonstrated obviously and can be attributed to strong surface binding of phosphate, and the subsequent formation of
ternary surface complexes of Th(IV). The difference between the sorption characteristics of Th(IV) ions and uranyl ions onto
TiO2 is discussed. 相似文献
40.
催化动力学光度法测定痕量锰(Ⅱ) 总被引:11,自引:0,他引:11
研究了在Na2HPO4-NaOH介质中,Mn(Ⅱ)催化高碘酸钾氧化镁试剂1[4-(对硝基苯偶氮)间苯二酚]的反应及其动力学条件,建立了一种高灵敏、高选择性测定痕量Mn(Ⅱ)的新方法。可测0.01-2.5μg/25mL范围的锰(Ⅱ),方法的检测限为6.43×10^-11gm/mL。 相似文献