, rate constants have been evaluated for the overall radiolytic decomposition of alkali metal nitrates. This kinetic scheme is applicable in the low dose range. At higher doses, however, the radiation induced reaction, NO
may also contribute. The overall rate constants are 0.13×10–6 (LiNO3), 1.05×10–6 (NaNO3), 10.10×10–6 (KNO3), 9.50×10–6 (RbNO3) and 25.50×10–6 (CsNO3) kGy–1.
Gamma-ray induced decomposition of some divalent nitrates, viz. Mg(NO3)2·6H2O, Ca(NO3)2·4H2O, Sr(NO3)2, Ba(NO3)2, Zn(NO3)2·6H2O, Cd(NO3)2·4H2O, Hg(NO3)2·2H2O, Mn(NO3)2·4H2O, Cu(NO3)2·3H2O and trivalent nitrates, viz. Al(NO3)3·9H2O, Fe(NO3)3·9H2O, Cr(NO3)3·9H2O, Y(NO3)3·6H2O, In(NO3)3·3H2O, La(NO3)3·6H2O, Ce(NO3)3·6H2O, Pr(NO3)3·6H2O, Bi(NO3)3·5H2O has been studied in solid state at room temperature. G(NO
) values (after applying appropriate dose correction) have been found to vary in the range 0.12–3.16 and 0.069–2.15 for divalent and trivalent nitrates respectively. G'-values were calculated by dividing G by the ratio of number of electrons in nitrate ion to the total number of electrons in the nitrate salt. Cation size, its polarizing power, available free space in the crystal lattice and the number and location of water molecules seem to play a dominant role in radiolytic decomposition. For Zn, Sr, In, La and Ce nitrates dose variation studies have been carried out.
A series of rare earth zeolites of types X and Y were prepared by cation exchange. Thermal analysis curves (TG/DTA) were employed to estimate the structural changes in the zeolite framework. Analogous investigations were carried out by independent methods such as XRD and IR spectroscopy. The results indicate increased thermal stability on the replacement of sodium by rare earth. Partial replacement of rare earth by ammonium/hydrogen enhances the thermal stability. The type Y zeolites are more stable than those of X type.
A derivatograph was used to follow the modification of the skeleton structure and thermal stability of zeolites in sodium and ammonium forms. Analogous investigations were carried out by independent methods such as IR and X-ray. Comparison showed good agreement between the results. The controlled dealumination of the Y-type zeolite enhanced the thermal stability
DHOA (Di-n-hexyl-octanamide) is one of the alternative extractants to TBP (tri-n-butyl phosphate) known for the extraction
of uranium from moderate nitric acid medium without significant extraction of the fission products. Analytical application
of DHOA was explored to develop a methodology for determination of trace metallic constituents in uranium based nuclear materials.
This involved the separation of uranium matrix by 1.1 M DHOA-dodecane followed by the analysis of the raffinate for trace
constituents by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). A systematic study showed that four contacts
of 1.1 M DHOA-dodecane were required for quantitative extraction of U from 4 M HNO3 feed for the sample size of 1 g in 10 mL. The feasibility of using DHOA for extraction of U from trace metallic constituents
in U based fuel materials without losing trace quantities of analytes of interest was studied by using synthetic samples after
appropriate spiking of common impurities and critical elements at their required specification limits (common elements—5 ppm,
critical elements—1 ppm). A systematic study was carried out to compare the analytical performance of DHOA with TBP, which
revealed that DHOA could successfully be employed for the determination of 19 trace constituents with lower estimation limits
of 5 ppm for common impurities and 1 ppm for critical elements.
A systematic TG/DTG/DTA analysis is reported of anhydrous and heptahydrate forms of tris-phenanthroline and tris-pyridyl complexes of nickel(II), whose kinetic parameters were calculated by five different methods. The dehydration and de-ligation steps are descrete in Ni(phen)3Cl2 · 7 H2O, while those in Ni(bipy)3Cl2 · 7 H2O are mixed. Partial loss of the ligand is common for both hydrated and anhydrous compounds. In most cases the activation energyEa calculated from the mechanism-non-invoking equation of Horowitz and Metzger is in good agreement with that found from the mechanism-based relation of Mampel. There is an appreciable variation in magnitude in the results obtained from the different relations for the evaluation ofEa. It is inferred that such kinetic data are of significance in comparisons of the decomposition processes in related systems but not as absolute quantities.
Authors:D. Yadav, S. Gupta, V. Kulkarni, K. Rai and R. Behl
Inheritance of male sterility and fertility restoration of the A
system of cytoplasmic-nuclear male sterility in pearl millet was investigated using 12 crosses among three diverse male sterile lines (A-lines) and four diverse restorers (R-lines). Individual plants from R- lines were used to make crosses on A-lines. The segregation pattern of male sterile (S) and male fertile (F) plants observed in F
in two seasons at ICRISAT, Patancheru was suggestive more likely of a single-gene control of male sterility and fertility restoration. However, a 3-gene model of male sterility/fertility restoration where dominant alleles at any two of the three duplicate complimentary loci will lead to male fertility could not be ruled out, nor could be ruled out a 2-gene control with duplicate interaction. There was indication of variability even within a highly inbred R-line for fertility restoration gene(s). Depending on the genetic constitution of the R-lines at these loci, even the 3-gene model can lead to single-gene segregation ratios as observed in most of the F
and backcrosses, and 2-gene ratios as observed in a few F
and backcrosses. The deviations from these expected ratios in some of the crosses influenced by modifiers and environmental conditions generally resulted from the excess of fertile plants in the rainy season or excess of sterile plants in the dry season, the more so in crosses involving an A-line which has been reported to be relatively more unstable for male sterility.
Authors:M. N. Kulkarni, D. Rai, P. Pillai and V. S. Tomar
A Global Positioning System (GPS) permanent station has been established as a reference point at the Department of Civil Engineering of Indian Institute of Technology Bombay (IITB), by the IITB GPS group, and is continuously operating since January 2002. The station is being operated under a research project funded by the Department of Science and Technology (DST), Government of India, under the “National GPS Programme for Earthquake Studies”. A brief description of the station set up, the strategy used in determining its precise position, and some sample results are presented in this paper.
Authors:S. Sampath, N. K. Kulkarni and N. C. Jayadevan
Thermal decomposition of metal uranyl acetates is one of the best ways of preparation of uranates in crystalline form at low temperatures. Acetates of the type M(UO2)2(OAc)6·7H2O (M=Zn(II), Mg(II) and Ni(II) were prepared and characterised. Their X-ray powder diffraction analysis showed that they all belong to the orthorhombic crystal class.
Authors:L. Sawant, P. Kalsi, A. Kulkarni and S. Vaidyanathan
A differential pulse voltammetric method has been successfully used for the determination of uranium in low concentration streams of a uranium plant. The method gives a precision of about 13% to 7% in the range of 300 ppb to 15 ppm. The accuracy of the results was ascertained by comparing the values with those obtained by a spectrophotometric method. The method is simple, fast, sensitive, fairly accurate and does not require a preconcentration step.