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排序方式: 共有1154条查询结果,搜索用时 31 毫秒
991.
Milan Maji Mossaraf Hossain Madhumita Chatterjee Shyamal Kumar Chattopadhyay Vedavati G. Puranik Pinak Chakrabarti Saktiprosad Ghosh 《Polyhedron》1999,18(27):1436-3739
Reaction of Ru(PPh3)2Br2 with the NNS chelating tridentate ligand 2-pyridyl-N-(2′-methylthiophenyl)methyleneimine (L) led to the isolation of the ruthenium(II) complex [Ru(L)(PPh3)Br2]. Reactivity of this complex with different bidentate chelating ligands revealed that the products are quite different from those obtained by reacting Ru(L)(PPh3)Cl2 (the corresponding cis dichloro complex) with the same ligands under comparable conditions. The mixed chelates were isolated and characterised by elemental analysis, magnetic moment measurement and by different spectroscopic methods along with their precursor. Electrochemistry of the complexes was examined by cyclic voltammetry using a platinum working electrode and a Ag/AgCl electrode as reference. The crystal structure of [Ru(L)(PPh3)Br2] disclosed that, unlike Ru(L)(PPh3)Cl2, the two bromo ligands are in trans position and this explained the difference in its reactivity pattern from the corresponding chloro complex. 相似文献
992.
A new reagent system using rhodamine‐B dye for the determination of selenium is described. The method is based on the reaction of selenium with acidified potassium iodide to liberate iodine. The liberated iodine bleaches the pink colour rhodamine‐B, which is measured at 555 nm. Beer's law is obeyed over the concentration range of 1–10 μg of selenium final solution volume of 25 mL (0.04–0.4 ppm) and the apparent molar absorptivity and Sandell's sensitivity was found to be 1.96× 105 l mol?1 cm?1 and 0.0004 μg cm?2, respectively. The method is simple, sensitive, and selective and is satisfactorily applied to micro‐level determination of selenium in various environmental and cosmetic samples. 相似文献
993.
Chatterjee K. Dollimore D. Alexander K. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):629-639
Hydroxy benzoic acids were subjected to rising temperature thermogravimetric analysis. After optimizing the procedural variables,
the kinetics of decomposition was determined and methyl paraben was taken as the calibration compound to characterize the
evaporation patterns for the ortho and meta derivatives. The E
act values for ortho, meta and para derivatives were 64.8, 78.2, and 119.1 kJ mol–1, respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 124525±0.8, units being in the SI system. The vapor pressure plots were generated for the ortho and meta derivatives; ΔH
vap for these two compounds were obtained as 66.7 and 80.4 kJ mol–1, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
994.
A procedure is described for the determination of total manganese in pyrolusite. The sample is decomposed with hydroxylamine hydrochloride solution. The residue left after filtration is fused with sodium carbonate and extracted again with hydroxylamine hydrochloride solution. A suitable aliquot is titrated with EDTA at pH 10, with Eriochrome Black T as indicator, after masking of interfering elements. 相似文献
995.
A. M. Chatterjee F. P. Price S. Newman 《Journal of Polymer Science.Polymer Physics》1975,13(12):2391-2400
In the melt crystallization of isotactic polypropylene, poly(ethylene oxide) and poly(butene-1) in contact with substrates, the existence of a fixed number of nucleating sites on the substrate surfaces has been established. When these sites become active successively (the transient in the number of nuclei is long) during crystallization, pseudohomogeneous nucleation on the substrate occurs. Nucleation rates for poly(butene-1) and poly(ethylene oxide) on substrates and in bulk have been measured. These data can be used for comparing the nucleating ability of substrates. Estimates of the variation of bulk nucleation rates from one volume element to another as well as for repeated crystallization within a given volume element have been included. Finally, the temperature coefficients of heterogeneous nucleation rates have been combined with the temperature coefficient of spherulitic growth rate of poly(butene-1), to yield values of the interfacial energy parameters appearing in the theory of heterogeneous nucleation. The quantitative characterization of the nucleating ability of substrates by this method is an improvement over the mere use of nucleation densities or nucleation rates. 相似文献
996.
We demonstrate the method of averaging for conservative oscillators which may be strongly nonlinear, under small perturbations including delayed and/or fractional derivative terms. The unperturbed systems studied here include a harmonic oscillator, a strongly nonlinear oscillator with a cubic nonlinearity, as well as one with a nonanalytic nonlinearity. For the latter two cases, we use an approximate realization of the asymptotic method of averaging, based on harmonic balance. The averaged dynamics closely match the full numerical solutions in all cases, verifying the validity of the averaging procedure as well as the harmonic balance approximations therein. Moreover, interesting dynamics is uncovered in the strongly nonlinear case with small delayed terms, where arbitrarily many stable and unstable limit cycles can coexist, and infinitely many simultaneous saddle-node bifurcations can occur. 相似文献
997.
998.
P.K. Chatterjee K.V. Vaidyanathan M.S. Durschlag B.G. Streetman 《Solid State Communications》1975,17(11):1421-1424
Low temperature (6°K) photoluminescence measurements have been performed on GaAs annealed under various conditions, to study defects generated by outdiffusion of the constituent atoms. Several defect-related luminescence peaks have been observed and associated with Ga and As outdiffusion. The outdiffusion of these elements during annealing to 850°C in vacuum and with Ga or As overpressure and SiO2 coatings is studied by monitoring the intensities of these peaks. 相似文献
999.
Ohne Zusammenfassung 相似文献
1000.