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排序方式: 共有596条查询结果,搜索用时 240 毫秒
21.
F. Cerdá C. Kremer D. Gambino E. Kremer 《Journal of Radioanalytical and Nuclear Chemistry》1994,186(4):291-301
Electrolytic reduction of pertechnetate was performed in aqueous solution containing -acceptor ligands. Cyanide and 1,10-phenanthroline were the selected ligands. In both cases, electrolyses produced a cathodic TcO2 deposit and soluble Tc complexes. When cyanide was the ligand, the complexes formed were [Tc (CN)6]5– and [TcO2 (CN)4]3–. When working with the amine, [Tc (phen)3]2+ and another positively charged species were found after reaction. Results are compared with previous studies with amines, and the usefulness of the electrolytic route to obtain Tc complexes is evaluated. 相似文献
22.
Photoelectron Spectra and Molecular Properties. 133. Trifluoromethyldisulfane and Derivates F3CSSX (X?CF3, F, Cl, Br) The He(I) photoelectron spectra of trifluoromethyldisulfane F3CSSH and its derivatives F3CSSX (X?CF3, F, Cl, Br) are assigned by Koopmans correlations, IE = ?ε, with MNDO eigenvalues and by radical cation state comparison. Of special interest are the n/n splittings, which amount to 1.15 eV F3C? SS? F or 0.87 eV in F3? SS? Cl, and the dependance of which on the dihedral angle ω(XS? SX), on the SS bond length and on the acceptor effect of the F3C substituents is discussed. 相似文献
23.
Christine Bauhofer Hansjürgen Mattausch Reinhard K. Kremer Arndt Simon 《无机化学与普通化学杂志》1995,621(9):1501-1507
The Gadolinium Carbide Halides, Gd4C2X3 (X = Cl, Br) The compounds Gd4C2X3 (X = Cl, Br) and Tb4C2Br3 have been prepared by reaction of the metals (RE), REX3, and C in sealed Ta capsules at 1 100° and 1 300°C, respectively. Monophasic samples of Gd4C2Br3 and Tb4C2Br3 were obtained by reacting stoichiometric mixtures of the starting materials for five days. The needle shaped crystals are bronze-coloured and sensitive to air and moisture. Gd4C2X3 crystallizes in the space group Pnma (No. 62) with lattice constants a = 1 059.6(4), b = 368.4(1), c = 1 962.7(8) pm (Gd4C2Cl3), a = 1 084.4(1), b = 373.0(1), c = 2 036.1(1) pm (Gd4C2Br3). According to Guinier photographs, Tb4C2Br3 is isotypic (a = 1 074.3(2), b = 370.6(1), c = 2 019.4(1) pm). In the crystal structure C is octahedrally coordinated by Gd. The Gd6 octahedra are linked via common edges to form corrugated layers. The X-anions coordinate all free edges and corners of these layers and connect them via Xi? Xi contacts parallel [001]. Gd4C2Br3 shows metallic conductivity. The magnetic susceptibility follows at high temperatures a Curie Weiss law with an effective moment of 7.95 μB. At temperatures below 50 K antiferromagnetic order is observed. 相似文献
24.
A new ternary ruthenium oxide Na(2)RuO(4) was prepared and shown to crystallize with a new structure type. Single crystal X-ray diffraction measurements reveal that Na(2)RuO(4) consists of RuO(4) chains made up of RuO(5) trigonal bipyramids by sharing axial corners. Na(2)RuO(4) is a magnetic semiconductor with a variable range hopping behavior, and its molar magnetic susceptibility chi(mol) has a broad maximum at approximately 74 K. The derivative d(chi(mol).T)/dT exhibits a peak at 37.7 K which has been confirmed by heat capacity measurement to be due to long-range antiferromagnetic ordering. 相似文献
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This paper reviews derivatisation processes applied in chromatographic determination of acidic herbicides (with carboxyl and phenol groups), mainly in aqueous environmental samples. The discussion focuses on the basic derivatisation reactions used to convert herbicides to derivatives to make them analysable by gas chromatography, and possibly to reduce detection limits and/or increase extraction recovery from aqueous samples. The reactions are transesterification, esterification, silylation, alkylation, and extractive and pyrolytic alkylation. The reagents used to conduct the reactions are numerous. Diazomethane is a very efficient methylation reagent but explosive and toxic. Methyl iodide also ensures rapid and efficient methylation. Benzyl bromide can be used directly in water but derivatisation yield is low and reproducibility is poor. Butyl chloroformate and dimethyl sulfite can also be used for derivatisation in water, and acetic anhydride can be used for in-situ derivatisation of phenolic herbicides. For increasing selectivity of GC detection pentafluorobenzyl bromide (for ECD) and (2-cyanethyl)dimethyl(diethylamino)silane (for NPD) have been applied. Very characteristic ions are produced in mass spectra if silyl groups are introduced, e.g. by using bis(trimethylsilyl)trifluoroacetamide. Tetramethylammonium, trimethylphenylammonium, tetraalkylammonium, and trimethylsulfonium hydroxides and salts can by used for derivatisation at elevated temperature in the GC injection port. Extractive alkylation is relatively efficient if tetraalkylammonium salts with long chain alkyl groups are used. 相似文献
27.
Gao X Butler IS Kremer R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):27-35
We report here the use of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy to analyze normal human epidermal keratinocytes prior to and following malignant transformation. Our analysis indicates specific Raman spectral differences between immortalized (HPK1A) and malignant ras transformed (HPK1A-ras) cells. In addition, striking spectral differences are seen in the DNA isolated from these cells and particularly in the 843/810 cm(-1) ratio with values of 1.6 +/- 0.13 in HPK1A cells and 0.68 +/- 0.09 in HPK1A-ras cells (mean +/- S.D., n = 12, P < 0.001) indicating specific alterations in the backbone conformation markers following malignant transformation. Subsequently, we analysed the effect of a strong inhibitor of keratinocyte growth, the Vitamin D analog EB1089, on the Raman spectra of intact cells and on the 843/810 cm(-1) ratio in the DNA isolated from both cell lines. Specific changes were observed in intact cells in the 1300-750 cm(-1) region. Furthermore, the 843/810 cm(-1) ratio of isolated DNA from HPK1A cells was not affected by EB1089 but significantly increased in DNA isolated from HPK1A-ras cells so much that it became closer to the value observed for HPK1A cells (1.07 +/- 0.10). Our data suggest that Raman analysis of DNA and in particular the 843/810 cm(-1) ratio can provide useful indices of malignant transformation and efficacy of anticancer agents. 相似文献
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