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51.
Two series of nano-sized N-containing MOx–ZnO (M: Fe, W) composite powders were synthesized by spray pyrolysis. The nitrogen content was controlled from 500 to 2100 ppm by changing the powder ingredients and spray pyrolysis temperature. Ultraviolet-visible (UV-Vis) spectra indicated that the N-containing MOx–ZnO powders absorbed not only ultraviolet light (λ<387 nm) like pure ZnO powder, but also part of visible light (λ<650 nm). Acetaldehyde decomposition was used as a probe reaction to evaluate the photocatalysis of these composite powders. The photocatalytic activity of the N-containing ZnO powder was pronouncedly enhanced by the WO3 addition under both UV and visible-light irradiation. However, that of the N-containing ZnO powder was suppressed by the Fe2O3 addition. A model of the semiconductor energy-band structure is proposed to explain the enhancement and suppression of photocatalytic activity. 相似文献
52.
Manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) concentrations were determined in the brain regions of normal 1-, 3-, 5-, 7-, 14-, 21-, 42-, 77-, and 147-day-old Wistar rats using inductively coupled plasma mass spectrometry (ICP-MS), and their maps were illustrated in color to visually compare the distribution of the elements at various stages of the growth process. Sagittal slices (1-mm thickness) sectioned at the level of the substantia nigra were divided into 18 regions, and the small slice samples were digested in microwave-assisted closed vessels for ICP-MS measurement. Mn, Fe, Cu, and Zn concentrations increased region-specifically with age, and their distributional maps showed some characteristics. These findings are discussed in terms of needs for these trace elements in the normal brain. Among new findings about their brain distribution, it is especially noteworthy that higher concentrations of Mn, Fe, and Zn were observed in the substantia nigra compared with those in neighboring regions. The mapping method in this work is expected to open up possibilities for screening of the in vivo element–element interrelationships among these essential elements. 相似文献
53.
N. Ibriş J. Mirza-Rosca A. Santana T. Vişan 《Journal of Solid State Electrochemistry》2002,6(2):119-125
The corrosion and passivation of Zn powder particles dispersed in a paste electrode immersed in 0.5 M Na2SO4 and 5×10–3 M Na2HPO4 solutions were studied mainly by electrochemical impedance spectroscopy. The role played by diffusion in the mechanism of
anodic oxidation of zinc powder particles has been shown. It was demonstrated that the anodic reactionof Zn powder in neutral
or near neutral media involves at least two adsorbed intermediates. By simulating the porous structure of the electrode, some
information about porous nature of zinc electrode could be extracted.
Electronic Publication 相似文献
54.
A direct catalytic asymmetric Mannich-type reaction of isomerizable aliphatic imines is described. A Et2Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity (up to 99% ee), albeit in modest to low diastereoselectivity. 相似文献
55.
二水草酸锌脱水的热分解动力学研究 总被引:10,自引:0,他引:10
提出一种多升温速率-等温法确定机理函数g(α)的新方法;并用迭代的等转化率法求出较为可靠的活化能Ea;在Ea和g(α)的基础上计算出指前因子A.用该法对二水草酸锌(ZnC2O4•2H2O)脱水反应的热分解动力学三因子进行了求算,得出Ea为87.22 kJ•mol-1, A为4.2120×108~7.2328×108 s-1;以及随机成核和随后生长型机理函数Am(Avrami-Erofeer),其积分形式g(α)=[-ln(1-α)] 1/m和微分形式f(α)=m(1-α)•[-ln(1-α)](1-1/m),调节因子m=1.85~2.00. 相似文献
56.
Galina A. Selivanova Leonid M. Pokrovskii Vitaliy D. Shteingarts 《Journal of fluorine chemistry》2004,125(12):1829-1834
Chlorine-containing polyfluorinated anilines and meta-phenylenediamines undergo selective hydrodechlorination easily upon reduction by zinc in aqueous ammonia. A new approach is thus provided to synthetically valuable, partially fluorinated arylamines based on utilizing polyfluorochloroarenes, which are available as intermediates of perfluoroarene production from perchloroarenes. When chlorine atoms are present in positions both ortho and para to the amino group, para chlorine is initially eliminated. Based on this reaction, a one-pot synthesis of partially fluorinated 4-aminopyridines from 3,5-dichlorotrifluoro- and 3-chlorotetrafluoropyridine has been realized. 相似文献
57.
The influence of structural modifications of the diamine ligand and the ZnR2 precursor in the [ZnR2-diamine]-catalyzed asymmetric hydrosilylation of prochiral ketones with PMHS in aprotic medium is reported. A new diamine ligand giving up to 91% ee in the reduction of acetophenone is described. The scope of this reduction system has been investigated using variously functionalized ketones and some deactivation pathways have been identified. 相似文献
58.
丁先露 《广东微量元素科学》1996,3(3):49-51
用维宝康治疗小儿缺锌综合征98例,结果表明,服用维宝康一个疗程后,患者临床症状明显改善发锌值升高,总有效率为96%,未见毒副作用,是较好的补锌制剂。 相似文献
59.
Peggy S. Eis Józef Kuśba Michael L. Johnson Joseph R. Lakowicz 《Journal of fluorescence》1993,3(1):23-31
Time-resolved fluorescence resonance energy transfer (FRET) measurements were used to measure distance distributions and intramolecular dynamics (site-to-site diffusion) of a 28-residue single-domain zinc finger peptide in the absence and presence of zinc ion. Energy transfer was measured between TRP14 and a N-terminal DNS group. As expected, the TRP-to-DNS distance distribution for zinc-bound peptide is shorter and narrower (R
av=11.2 Å,hw=2.8 Å) than the metal-free peptide (R
av=20.1 Å,hw=14.5 Å). The degree of mutual donor-to-acceptor diffusion (D) was also determined for these distributions. For zinc-bound peptide there is no detectible diffusion (D0.2 Å2/ns), whereas for metal-free peptide a considerable amount of motion is occurring between the donor and the acceptor (D=12 Å2/ns). These results indicate that the zinc-bound peptide folds into a unique, well-defined conformation, whereas the metal-free conformation is flexible and rapidly changing. The absence of detectible mutual site-to-site diffusion between the donor and the acceptor in the metal-bound zinc finger peptide indicates that intramolecular motion is essentially frozen out, on the FRET time scale, as a consequence of zinc coordination.Dedicated to the memory of Barbara D. Wells. 相似文献
60.
A spot test was implemented in a flow-injection system for the spectrophotometric determination of zinc in digests of plant materials. It is based on the influence of Zn2+ on the oxidation rate of 1-naphthylethylenediamine (NED) by hexacyanoferrate(III) under acidic conditions. In order to control the precipitate formation and to maintain the resulting suspension, a micellar medium was established by adding Triton X-100. The proposed system handles about 65 samples per hour, meaning 72 μg NED and 9.0 mg K3[Fe(CN)6] per determination. Baseline drift is usually <0.01 absorbance per hour and the analytical signals for 0.5-2.5 mg l−1 Zn range within ca. 0.07-0.45 absorbance. Linearity of the analytical curve is fair (r>0.999, n=6) and detection limit was estimated as 0.2 mg l−1 Zn. Results are precise (R.S.D.<1%, n=10) and in agreement with flame atomic absorption spectrometry and with certified values of standard reference materials. 相似文献