, 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.
An analysis of 258 papers published from Singapore and covered inScience Citation Index (SCI) 1979 and 1980 indicates that (1) much of R&D in Singapore pertains to medical research, (2) almost all the papers are published in English language periodicals published from the western world, (3) nearly two-thirds of Singapore's publication output is accounted for by the University of Singapore, and (4) by and large papers from Singapore are rarely cited, even if many of them have appeared in journals having impact factor greater than one.
Transition metal dithiocarbamate complexes, [M(S2CN(C2H5)(CH2CH2OH)] (M=Co, Ni, Cu, Zn and Cd) have been prepared and characterized by elemental analysis and infrared spectra. Thermal decomposition
of all the complexes occurs in two or three stages. The first stage in all the complexes is always fast with 65-70% mass loss.
In all cases the end product is metal oxide except in the case of cobalt complex which gives Co metal as an end product. During
decomposition of copper complex, first CuS is formed at ~300C which is converted into CuSO4 and finally CuO is formed. However, decomposition in helium atmosphere yields CuS. SEM studies of transition metal dithiocarbamates
reveal needle shape crystalline phase at room temperature and formation of metal sulphide/oxide at higher temperatures. The
activation energy varies in a large range of 33.8-188.3 kJ mol-1, being minimum for the Cu complex and maximum for the Zn complex possibly due to d10 configuration. In the case of Ni, Zn and Cd complexes the order of reaction is two suggesting bimolecular process involving
intermolecular rearrangement. However, in other cases it is a unimolecular process. Large negative values of ΔS# for all the complexes suggest that the decomposition process involves rearrangement.
Authors:D. Garg, S. Sareen, S. Dalal, R. Tiwari and R. Singh
Terminal heat referred to as increase in temperature during grain filling, is one of the important stress factors for wheat production and is responsible for decline in wheat production in many environments worldwide. In order to meet the challenges of high temperature ahead of global warming, concerted efforts are needed to evaluate wheat genotypes for heat tolerance and develop genotypes suitable for such stressed environments. Twenty-seven advanced wheat genotypes developed for stress and normal environments by different research centres were evaluated during 2009–10 and 2010–11 under timely sown (normal) and late sown (heat stress) environments. Analysis of variance revealed that the genotypes differed significantly in grain filling duration (GFD), grain growth rate (GGR) and thousand-grain weight (TGW). Out of 27 genotypes, 16 were found to be tolerant for thousand-grain weight under late planting (heat stress) during 2009-10 but only 12 were tolerant during 2010–11. Many of the genotypes registered more reduction in thousand-grain weight during 2010–11 as compared to 2009–10; the temperatures during 2009–10 were higher. The differences in grain filling duration under two conditions during both seasons as well as difference in temperatures during first half of grain filling explain the reduction pattern in the genotypes. GFD had significant negative correlation with temperatures during post heading period and the difference in GFD under two environments had positive correlation with these temperatures. The reduction in GFD had regression of 33.3% on reduction in GGR and reduction in GGR had regression of 41.6% on reduction in TGW genotypes AKW 1071, DBW 17, HS 277, K 7903, K 9107, NW 1014 and RAJ 3765 had less sensitivity to stress environments during both years.
Authors:R. Garg, V. Garg, I. Czakó-Nagy, S. Nagy, E. Kuzmann and A. Vértes
Mössbauer spectroscopy and X-ray diffractometry have been used to study Sm–Fe mixed oxides (with different SmFe atomic ratios) annealed at 550, 850, 1000 and 1250 °C. The room temperature Mössbauer spectra can be interpreted in terms of one, two or three sextets and in some cases by an additional doublet depending on the composition and the heat treatment. The sextets have been associated with SmFeO3 perovskite, Sm3Fe5O12 garnet and -Fe2O3 hematite. These results are in agreement with those of X-ray diffractometric measurements, which give a clear, evidence of the presence of these phases.
Authors:S. Singh, R. Malik, R. Garg, R. Devraj and P. Sheoran
Apart from the issue of sustainability and resource drain, the yield plateau in the rice-wheat cropping system of south-east Asia is the major area of concern. Realizing that genetic gain is a remote possibility, efforts are directed to management options for yield improvement. Adequate crop nutrition in general and nitrogen (N) in particular figure at the top among various management issues. A survey was conducted covering the rice-wheat belt of Haryana state, India representing Trans-Gangetic plains to know about on-farm practices related to N management in wheat crop and how far it deviates from the blanket recommendations given by State Agricultural Universities. The survey revealed that about 42.7 per cent farmers used either recommended dose of N (150 kg/ha) or less and others used higher dose of N. Positive correlation between the size of the farm and extent of N used was established. Whenever the farmers tended to use higher dose of N, they also tended to partition it in more number of splits (up to 3 splits, excluding basal application) staggering upto 54 days after sowing (DAS) as against the recommended practice of two splits (including basal application) within 35 DAS. The study confirmed deviation from the recommended practices of N management but major revelation came about reverse gap holding that the practice of N management in wheat crop being followed by the farmers is better in terms of grain yield. The NPhysical optimum and NEconomic optimum exceeded the current use (165.7 kg/ha) and recommended levels. This study suggests a fit case for the upward revision of recommended dose of N in wheat crop involving no element of risk as arising from aggravated problem of insect pest and disease complex. Nearly half of the farmers use either recommended dose of N or less than that and it is here, where opportunity lies in augmenting the wheat productivity by enhancing the existing level of N use.