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  • Author or Editor: S. Roy x
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Abstract  

A scenario is presented for the transport of the Chernobyl radioactive debris across Canada and the Arctic. It is based on the analysis of the103Ru/137Cs ratios in terms of the Chernobyl release pattern. The ratios which ranged from 0.2 to more than 4.0 were associated with four different phases of the Chernobyl emissions which lasted 10 days, from April 26 to May 6, 1986. Debris from the initial phase /ratios of 0.2 to 0.5/ and the last phase /ratios above 2.5/ would have entered Canada on a very broad front extending from northern Quebec to the North West Territories by way of Greenland and the Arctic; debris from the second phase /ratios of 0.5 to 2.0/ and the third phase /ratios of 2.0 to 2.5/ would have entered Canada from the west after travelling by way of northern Siberia and the Bering Sea.

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In acid soil, Al is solubilised into a phytotoxic form, Al(H2O)6 3+ which is known as Al3+. Al toxicity is the primary growth-limiting factor for plants in acid soils. Breeding of rice for Al tolerance are important approach for increasing grain yield in acid soils. In the present endeavour, rice genotypes were screened at seedling stage based on vigour index, root tolerance index and hematoxylin staining in stressed nutrient solutions to select the tolerant genotype(s) against Al toxicity. It was observed that use of different screening indices for Al toxicity tolerant genotypes of rice have given different results. Thus, screening of tolerant genotypes using one index may lead to inappropriate conclusion. Comparing all the selection indices it was found that Radhunipagal and UBKVR-16 were the common genotypes which fallen into tolerant class for every index. Finally genotypes were grouped into different clusters using D2 statistic to find out whether the tolerant genotypes fall into one cluster. Those two Al toxicity tolerance genotypes were grouped into one cluster, which strengthens our findings.

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Abstract  

Some new coordination polymers have been synthesized by combining adipyl bis-biuret and azelyl bis-biuret with metals of first transition series viz Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). They were characterized by elemental analysis, infrared and reflectance spectral and magnetic studies. A detailed thermal study was carried out and thermal stability compared. The results obtained have been discussed.

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Abstract  

Attempt has been made to develop methodologies for preconcentration of chromium in the biodegradable polymer beads. The uptake behaviors for chromium have been studied with Ca-alginate (CA) and Fe-doped calcium alginate (Fe-CA) beads. The work also aims to study the differential attitude of CA and Fe-CA towards Cr(III) and Cr(VI) so that, depending on the oxidation state of chromium effluent, environmentally sustainable methodologies can be prescribed for removal of chromium. Radiotracer 51Cr has been chosen as precursor of stable chromium throughout the experiment. It was found that Fe-CA beads are suitable for removal of Cr(III) and Cr(VI) while CA beads can be used for the speciation and separation of Cr(III) and Cr(VI) at pH 5.

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Abstract

Polycrystalline ceramic samples of Bi2Sn2−xTixO7 (x = 0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by conventional solid-state reaction method. The effect of homovalent cation (titanium) substitution on the Sn-site on the structural, morphological, electrical and thermal properties of the pure Bi2Sn2O7 ceramics have been studied by X-ray diffraction (XRD) followed by scanning electron microscopic techniques, dc conductivity and modulated differential scanning calorimetry. The XRD analysis carried out by performing the Rietveld refinement using the space group Fd3m indicates that the increase of titanium contents do not lead to any secondary phase. The grain size distributions of all the samples were investigated by SEM. It was found that the grain sizes are strongly influenced by the addition of titanium to the system. The frequency and temperature dependent dielectric studies have been carried out. The dc conductivity measurement was carried out for all the compounds and the activation energies were calculated using the relation σ = σ0 exp(−E a/kT). The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the specific heat, heat flow and other thermal parameters of the compounds. The results are discussed in detail.

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Abstract  

The yields for the loss of chromophore of Ni(II) and Cu(II) complexes of metronidazole,G(-Ni(II)M) andG(-Cu(II)M), reached almost zero when their aqueous solutions were -irradiated in the presence, of 0.4 mol·dm–3 of MeOH, EtOH,i-PrOH andt-BuOH in aerated medium. However, under N2O saturated conditions, these yields attained limiting values which suggests that the hydroxyalkyl radicals, derived from the alcohols by reaction with OH, react with the complexes in deaerated medium. But in aerated medium they react preferentially with O2. The rate constants for the reactions of the different hydroxyalkyl radicals with the complexes have been determined by the flash photolysis technique and the plausible mechanisms for the reactions have been suggested.

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Abstract  

Cosmic ray neutron interactions with indium, used as electrical contact within a Ge diode, the diode itself and the surrounding materials can give rise to a large number of photopeaks in the 50 to 1300 keV region of background spectra of Ge spectrometers with a passive shield. The nuclear processes and decays involved in the production of these photopeaks are discussed. These cosmic ray produced photopeaks are compared with those due to primordial radionuclides. Some useful information can be drawn from these measurements on the contribution of the cosmic rays on the background of Ge detectors with a passive shield.

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