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71.
H. S. Sharma R. B. Manolkar J. V. Kamat S. G. Marathe 《Fresenius' Journal of Analytical Chemistry》1993,347(12):486-490
Summary Graphite has been employed as a working electrode in the controlled potential coulometric determination of uranium and plutonium. The couples U(VI)/U(IV) and Pu(IV)/Pu(III) employed for analysis have diverse redox potentials and commonly the working electrodes employed are mercury and platinum. A graphite electrode in the shape of a beaker showed satisfactory performance for the quantitative reduction of U(VI) to U(IV) and Pu(IV) to Pu(III) and also for quantitative oxidation of Pu(III) to Pu(IV). Studies on the levels of the background current, blank values and their reproducible behaviour in acid media have been carried out with a view to achieve good precision and accuracy. A software-based predictive evaluation technique of end-point charge has been investigated. The results have shown that the graphite electrode can be used for the determination of both uranium and plutonium in the presence of each other with a precision and accuracy of better than ±0.5%. 相似文献
72.
73.
Assuming the validity of the universal multiplicity hypothesis of quantum chromodynamics, we estimate bounds on quark gluon coupling (αS) and quark mass (m) from the experimental data on charged hadron multiplicities. We obtain 0.3 < αS < 0.5 and m ≈ 100 MeV. Our analysis also suggests the universal quark confinement region to be ≈ O (mπ?1). Comparison with experiment is made for both the hadronic and leptonic induced reactions. 相似文献
74.
Yoram S. Papir Sudhir Kapur Charles E. Rogers Eric Baer 《Journal of Polymer Science.Polymer Physics》1972,10(7):1305-1319
The relaxation behavior of nylon 6 from 4.2 to 300°K was investigated as a function of orientation, anisotropy and moisture content by using an inverted free-oscillating torsion pendulum. Three new relaxations, δ at 53°K, ? below 4.2°K, and ζ at 20°K, were discovered. The characteristics of these new relaxations strongly depend on the orientation anisotropy, and concentration of adsorbed water in the specimens. The results suggest that the mechanism of the γ process is associated with the motions of both the polar and methylene units. The mechanism of the β relaxation is postulated to originate with motions of both non-hydrogen-bonded polar groups and polymer—water complex units. The behavior of the α peak is consistent with the hypothesis that it originates with the rupture of interchain hydrogen bonding due to the motions of long-chain segments in the amorphous regions. Finally, the data strongly support the proposition that two types of water, tightly bound and loosely bound, exist in nylon 6. 相似文献
75.
76.
M. J. Kamat R. Kaimal T. R. Saranathan 《Fresenius' Journal of Analytical Chemistry》1981,307(1):19-20
Summary A d. c. arc Spectrographic method employing the carrier distillation technique has been developed for the determination of the non-rare earth impurities Bi, Cu, Fe, Mg, Mn, Ni, Pb and Sn in Dy2O3 in the range of 1–100 ppm. The sample is ground with 5% AgCl containing 1000 ppm of Ge as internal standard. The average precision of the method in terms of the coefficient of variation of the concentration is 12–15% for the different impurities.
Bestimmung von Verunreinigungen (außer Seltenen Erden) in gereinigtem Dysprosiumoxid — Ein spektrographisches Verfahren mit Hilfe der Trägerdestillation
Zusammenfassung Die Verunreinigungen Bi, Cu, Fe, Mg, Mn, Ni, Pb und Sn werden im Bereich von 1 bis 100 ppm mit Hilfe der Gleichstrombogenanregung bestimmt. Die Dy2O3-Probe wird mit 5 % eines Trägergemisches vermahlen, das aus AgCl mit 1000 ppm Ge (als innerem Standard) besteht. Die durchschnittliche Genauigkeit der Bestimmungen liegt bei 12–15%.相似文献
77.
Girishkumar G Hall TD Vinodgopal K Kamat PV 《The journal of physical chemistry. B》2006,110(1):107-114
Single-wall and multiwall carbon nanotubes are employed as carbon supports in direct methanol fuel cells (DMFC). The morphology and electrochemical activity of single-wall and multiwall carbon nanotubes obtained from different sources have been examined to probe the influence of carbon support on the overall performance of DMFC. The improved activity of the Pt-Ru catalyst dispersed on carbon nanotubes toward methanol oxidation is reflected as a shift in the onset potential and a lower charge transfer resistance at the electrode/electrolyte interface. The evaluation of carbon supports in a passive air breathing DMFC indicates that the observed power density depends on the nature and source of carbon nanostructures. The intrinsic property of the nanotubes, dispersion of the electrocatalyst and the electrochemically active surface area collectively influence the performance of the membrane electrode assembly (MEA). As compared to the commercial carbon black support, single wall carbon nanotubes when employed as the support for anchoring the electrocatalyst particles in the anode and cathode sides of MEA exhibited a approximately 30% enhancement in the power density of a single stack DMFC operating at 70 degrees C. 相似文献
78.
Pradnya Nalawade Sergej Naumov Sudhir Kapoor 《Journal of Physical Organic Chemistry》2013,26(11):870-878
The bimolecular electron transfer from p‐amino benzhydrazide (PABH) and its meta‐derivative (m‐amino benzhydrazide (MABH)) to specific one‐electron oxidant results in the formation of anilino radical. In case of PABH, reaction with ?OH radicals results in the synchronous formation of adduct as well as anilino radical. The interesting observation is that the yield of the anilino radical increases with increase in pH. The effect of substitution also has a significant effect on the formation of adduct. In case of MABH, significant yield of anilino radical gets form on reaction with ?OH radical. The free radical electron transfer from PABH and MABH to parent radical cation of non‐polar solvent also results in the formation of anilino radical only suggesting that the radical cation of PABH and MABH has short life time. The above results were supported by quantum chemical calculations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
79.
Sudhir R. Jain 《Physics letters. A》2008,372(12):1978-1981
We present the exact solution for the Schrödinger equation for a particle inside an N-dimensional regular simplex shaped enclosure. This result extends and unifies the earlier results for equilateral triangle and K-tetrahedron billiards. 相似文献
80.
Parlato MC Kamat MN Wang H Stine KJ Demchenko AV 《The Journal of organic chemistry》2008,73(5):1716-1725
Two stable classes of thioimidoyl derivatives, S-benzoxazolyl (SBox) and S-thiazolinyl (STaz) glycosides, were investigated as glycosyl donors for solid-phase oligosaccharide synthesis. It was demonstrated that these derivatives are suitable for both glycosyl acceptor-bound and glycosyl donor-bound strategies, commonly employed in resin-supported oligosaccharide synthesis. 相似文献