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81.
G. R. Relan A. N. Dubey A. U. Bhanu S. Vaidyanathan 《Journal of Radioanalytical and Nuclear Chemistry》1994,182(2):437-443
A derivative spectrophotometric method has been developed for the determination of uranium at mg level in presence of iron in 1M HNO3 medium. Its application was extended to the determination of uranium is magnesium diuranate (Yellow Cake), an input material to the Uranium Conversion Plant. The second derivative absorbance at 408.2 nm was used for its quantification since at this wavelength the absorbance due to iron is negligibly small and that due to uranium is significant. The uranium content was found to be directly porportional to the amplitude at 408.2 nm. It was demonstrated that the impurities present in yellow cake do not interfere. The method is simple, fast, needs no prior separation and enables direct measurement of yellow cake samples which is an important requirement from the point of view of nuclear materials accounting. 相似文献
82.
P. K. Kalsi L. R. Sawant R. C. Sharma S. Vaidyanathan 《Journal of Radioanalytical and Nuclear Chemistry》1994,187(4):265-275
A narrow span (E
o
±0.1 V) controlled potential coulometric method has been developed for the determination of neptunium in 1M H2SO4 with a RSD of 0.2%. The main advantage of this method over the existing coulometric methods is that it can tolerate up to a 5-fold excess of plutonium. The method involves carrying out the electrolysis to about 97% and calculating by an iterative computation the formal electrode potential in situ, which is used to calculate the total amount present in the sample. The method consists in oxidation of all the neptunium to Np (VI) by Ce(IV), destruction of excess Ce(IV) and reduction of Np(VI) to Np(V) by NaNO2, destruction of excess nitrite by sulfamic acid followed by coulometric titration of Np(V) to Np(VI). 相似文献
83.
Manley JM Kalman MJ Conway BG Ball CC Havens JL Vaidyanathan R 《The Journal of organic chemistry》2003,68(16):6447-6450
A new synthesis of 3-[(4-amido)pyrrol-2-yl]-2-indolinones has been developed, where the amide side chain was installed prior to pyrrole formation. This strategy precludes the need to use any coupling reagents to install the amide side chain. This process includes a zinc-free alternative to the Knorr pyrrole synthesis. 相似文献
84.
G. R. Relan A. N. Dubey S. Vaidyanathan 《Journal of Radioanalytical and Nuclear Chemistry》1996,204(1):15-22
A ratio derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at mg levels in 1M HNO3 medium. In this method the overlapping spectra of uranium and plutonium are well resolved by making use of the first derivative of the ratios of their direct absorption spectra. The derivative ratio absorbances of uranium and plutonium are measured at 411.2 and 473.8 nm, respectively for their quantification. The method is simple, fast and does not require separation of uranium and plutonium. Another salient feature of the method is that it does not lead to generation of analytical waste thereby minimising the efforts required for the recovery of plutonium. Uranium in the conc. range of 10–25 mg/g and plutonium in the conc. range of 0.5 to 2 mg/g (U/Pu ratio varying from about 10 to 25) were determined in the same aliquot with a precision and accuracy of about 0.5% and 1%, respectively. 相似文献
85.
One-photon absorption coefficients of InSb and GaAs are calculated using the first order perturbation theory assuming a two band model in which the interband energy difference is given by The results obtained are in much better agreement with the experimental data than the results of first order perturbation calculations using parabolic bands. 相似文献
86.
87.
Brady F. Cress Ujjwal Bhaskar Deepika Vaidyanathan Asher Williams Chao Cai Xinyue Liu Li Fu Vandhana M‐Chari Fuming Zhang Shaker A. Mousa Jonathan S. Dordick Mattheos A. G. Koffas Robert J. Linhardt 《Angewandte Chemie (International ed. in English)》2019,58(18):5962-5966
Heparin is a highly sulfated, complex polysaccharide and widely used anticoagulant pharmaceutical. In this work, we chemoenzymatically synthesized perdeuteroheparin from biosynthetically enriched heparosan precursor obtained from microbial culture in deuterated medium. Chemical de‐N‐acetylation, chemical N‐sulfation, enzymatic epimerization, and enzymatic sulfation with recombinant heparin biosynthetic enzymes afforded perdeuteroheparin comparable to pharmaceutical heparin. A series of applications for heavy heparin and its heavy biosynthetic intermediates are demonstrated, including generation of stable isotope labeled disaccharide standards, development of a non‐radioactive NMR assay for glucuronosyl‐C5‐epimerase, and background‐free quantification of in vivo half‐life following administration to rabbits. We anticipate that this approach can be extended to produce other isotope‐enriched glycosaminoglycans. 相似文献
88.
W.V. McLevige K.V. Vaidyanathan B.G. Streetman J. Comas L. Plew 《Solid State Communications》1978,25(12):1003-1008
Secondary ion mass spectrometry (SIMS) has been used with differential resistivity and Hall effect measurements to study the 900°C diffusion of implanted Be in GaAs. Some outdiffusion of Be into the Si3N4 encapsulant occurs for surface Be concentrations above 1 × 1018cm?3. However, excellent agreement between the electrical and atomic profiles indicates that 85–100% of the Be remaining after annealing is electrically active. The concentration-dependent diffusion observed for implanted Be in GaAs was not significantly altered in experiments using hot substrate implants, two-step anneals, or annealing with Ga and As overpressure. 相似文献
89.
90.
Co1−xZnxFe2O4 (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization (Ms) and the size of the particles were measured at room temperature. The magnetization (Ms) was found to decrease with the increase in zinc substitution. The magnetic particle size (Dm) of the fluid was found to vary from 11.19 to 4.25 nm decreasing with the increase in zinc substitution. 相似文献