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  • Author or Editor: G. Singh x
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Abstract  

The nitrate complexes of copper, nickel and zinc with diethylenetriamine (dien) i.e. [Cu(dien)2](NO3)2, [Ni(dien)2](NO3)22H2O and [Zn(dien)2](NO3)2 have been prepared and characterised. Thermal studies were undertaken using TG-DTG, DSC, ignition delay (t id) and ignition temperature (IT) measurements. Impact sensitivity was measured using drop mass technique. The kinetic parameters for both non-isothermal and isothermal decomposition of the complexes were evaluated by employing Coats-Redfern (C-R) method and Avrami-Erofeev (A-E) equations (n=2 and 3), respectively. The kinetic analysis, using isothermal TG data, was also made on the basis of model free isoconversional method and plausible mechanistic pathways for their decomposition are proposed. Rapid process was assessed by ignition delay measurements. All these complexes were found to be insensitive towards impact of 2 kg mass hammer up to the height limit (110 cm) of the instrument used. The heat of reaction (?H) for each stage of decomposition was determined using DSC.

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Poor emergence is a major problem in soybean [ Glycine max (L.) Merrill]. A high emergence count leading to an optimum plant stand is a pre-requisite to obtain high grain yields. The results of three experiments on emergence in soybean are reported in this paper. Two field experiments were conducted to study the influence of wheat straw mulch, farmyard manure (FYM) mulch and seed soaking in water on the emergence of soybean under normal conditions. Immediately after sowing, covering rows of soybean with 3 t wheat straw ha −1 (row mulch) or the whole plot with 6 t wheat straw ha −1 (plot mulch) showed a profound effect on improving both the speed of emergence and the final emergence count. Row mulch with 5 t FYM ha −1 only improved emergence in one year and its effect was not as great as with straw mulch. Soaking the seeds in water (on-farm seed priming) for 4, 8 or 16 h reduced emergence drastically. Another field experiment was conducted to study the effect of different mulching treatments or crust breaking in alleviating the crust effect of simulated rain on the emergence of soybean. Covering the soybean rows with 3 t wheat straw ha −1 (row mulch) either before or after simulated rain improved the emergence count. Covering the soybean rows with 5 t FYM ha −1 or breaking the crust also improved emergence, though the effects were not as good as with wheat straw mulch. The results suggest that the use of wheat straw mulch or FYM mulch can improve emergence in soybean in both normal and crusted soils, possibly by lowering the maximum soil temperature and conserving soil moisture.

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Effects of one pre-emergence herbicide (terbutryn/terbuthylazine) and one post-emergence herbicide (bentazone) along with unweeded and hand-weeded controls on weeds and on the nodulation, nitrogenase activity, nitrogen content, growth and yield of pea (Pisum sativum) were studied. Terbutryn/terbuthylazine was applied pre-emergence @ 1.40, 2.80 and 5.60 kg/hawhereas bentazone was sprayed 6 weeks after sowing @ 1.44, 2.88 and 5.76 kg/h. Terbutryn/terbuthylazine controlled all the weeds very effectively, whereas bentazone did not control some weeds such as Polygonum aviculare, Poa annua and Elymus repens. The herbicides decreased the number of nodules, the dry weight of nodules, the nitrogenase activity, the shoot dry weight, the nitrogen content in the straw and seeds, and the seed yield of peas, the effects generally being higher at higher rates of application. The adverse effects of herbicides on these parameters might be due to their effects on plant growth, as both the herbicides are known to adversely affect photosynthesis. Nitrogenase activity did not correlate well with plant-N content or shoot dry weight. However, there was a strong relationship between plant biomass and plant-N content, which suggests that researchers can rely on these parameters for studying the effects of treatments on nitrogen fixation, rather than measuring nitrogenase activity.

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Thirteen Sugarcane yellow leaf virus isolates causing yellow midrib and irregular yellow spot patterns from six states of India were characterized by RT-PCR assays. SCYLV-615F and SCYLV-615R primers were used as forward and reverse primer pairs and the amplified products were cloned and sequenced. Comparative coat protein sequence analysis confirmed that all the SCYLV-Indian isolates were clustered into two major groups confirming the existence of two strains of SCYLV affecting sugarcane crops of India. However, all the 13 isolates under study were found related with Cuban isolate and belong to the CUB genotype. We concluded that YLD in India is caused by two genotypes CUB and IND, rather than by three genotypes as reported earlier. In a separate experiment, the member of both of the phylogenetic groups were found to be transmitted by the sugarcane aphid Melanaphis sacchari from infected to healthy sugarcane suggesting its secondary spread in nature.

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In a pot experiment the effects of the length of incubation period and the pre-emergence application of terbutryn/terbuthylazine at 2.80 kg a.i. ha-1 or post-emergence application of bentazone at 2.88 kg a.i. ha-1 on the nitrogenase activity in intact pea plants were measured in situ by the acetylene reduction assay. An incubation period of 10 min resulted in the highest nitrogenase activity. As the length of the incubation period increased to 30 or 60 min the total as well as the specific nitrogenase activity decreased. Terbutryn/terbuthylazine decreased the total nitrogenase activity at all three (i.e. vegetative, flowering and seed-filling) stages, whereas bentazone resulted in a significant decrease at the flowering stage only. However, terbutryn/terbuthylazine-treated plants had the highest specific nitrogenase activity both at the flowering and seed-filling stages.

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The effects of the pre-emergence application of terbutryn/terbuthylazine at 1.40 and 2.80 kg a.i./ha and prometryn at 1.70 and 3.40 kg a.i./ha and the post-emergence application of bentazone at 1.44 and 2.88 kg a.i./ha were studied on nodulation, root and shoot growth in two pea varieties, namely Rex and Guido. Of these the lower rates are the recommended rates for field application. Bentazone even at the recommended rate decreased nodule dry weight, whereas all three herbicides at double the recommended rate (except terbutryn/terbuthylazine in Rex) decreased the number and dry weight of nodules. Terbutryn/terbuthylazine and bentazone decreased root dry weight to a greater extent, whereas prometryn had only a slight effect. Shoot growth was adversely affected by all three herbicides in both the varieties, but prometryn and bentazone had less adverse effects in Rex than in Guido. Compared to the recommended rate, the herbicides had a greater adverse effect on nodulation at double the recommended rate.

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Abstract  

The etching and annealing behaviour of heavy ion nuclear tracks have been studied in glass detectors namely sodalime, phosphate and quartz using optical absorption spectroscopy. All these glass detectors were exposed at 90° and 45° for different ions, with collimated beams of varying energies. The absorption difference spectrum was employed to describe the annealing kinetics. A mathematical relation proposed in our laboratory was used to explain the annealing behaviour of radiation damage due to heavy ion beams in glass detectors. The activation energy was obtained from a new formulation and is found to be 0.16 eV in sodalime, 0.56 eV for phosphate and 0.69 eV for quartz glass detectors.

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Abstract  

Six isomeric dimethyl anilinium bromides (DMABr) have been prepared and characterized by elemental and spectroscopic studies. Thermal decomposition of these salts has been studied by TG and simultaneous TG-DTA techniques. Kinetic parameters have been evaluated from isothermal TG data using contracting area and contracting cube equations. The decomposition pathways have also been suggested which involves simultaneous sublimation (at lower temperature) and dissociative vaporization/decomposition (at higher temperature).

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Abstract  

Two bis(bipyridine) polymeric metal nitrate complexes with 4,4’-bipyridine of simple formula like [M(bipy)2](NO3)2⋅xH2O (where M=Co, Ni and Cu; x=4, 2 and 0, respectively) have been prepared and characterized. Their thermal decomposition has been undertaken using simultaneous TG-DTG-DTA and DSC in nitrogen atmosphere and non-isothermal TG in air atmosphere. Isothermal TG has been performed at decomposition temperature range of the complexes to evaluate the kinetics of decomposition by applying model-fitting as well as isoconversional method. Possible mechanistic pathways have also been proposed for the thermolysis. Ignition delay measurements have been carried out to investigate the response of these complexes under the condition of rapid heating.

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