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  • Author or Editor: S. Jain x
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Abstract  

The sorption of some monovalent, divalent and trivalent metal ions has been studied on a mixed and doped hydrous oxide of iron and zirconium (with iron as a major constituent). The sorption of Sr2+, Cr3+ and Cd2+ was found to be exceptionally high, besides this, the mixed oxide also exhibits significant uptake of Rb+ and Cs+ ions. The effect of doping is quite interesting as the uptake of Fe3+ increases 2-increases 2-fold when the mixed oxide is doped with Sn(II) ion. An enhancement of the same magnitude is also observed in the case of La3+ ions. The amount of maximum uptake was determined and found to be linearly related to the ionic potentials, i.e. charge to radius ratios of the entering cations.

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Abstract  

A mixed hydrous Fe(III)–Zr(IV) exhibits enhanced adsorption of anions in comparison to its constituent oxides. The uptake has been observed at pH 2.0, as a function of initial salt concentration and the product shows specific affinity for Cl, SO 4 2– and PO 4 3– ions. Doping the mixed oxide with Sn(II) improves its sorption capability for halide ions, while no significant enhancement is observed in the case of polyvalent anions.

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Abstract  

Modification of the room temperature phase (IV-III) of ammonium nitrate (AN) has been attempted using a variety of potassium salts namely, KF, KCl, KI, KNO3, K2CO3, K2SO4, KSCN and K2Cr2O7. No phase transition was observed when AN containing 1–2% by mass of these potassium salts is heated from room temperature (25C) onwards in DTA and DSC scans, but the linear expansion due to phase transition was still observable in TMA measurements. Complete arrest of the linear expansion occurs only when a higher concentration of the additive is used. Similarly, in thermal cycling experiments, complete phase modification in the temperature range -80 to 100C occurs only with a higher percentage of the potassium salt. The extent of modification, however, is found to be dependent both on the concentration, and the type of the anion. Potassium dichromate when used as an additive modifies the phase as well as the decomposition pattern of AN.

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Abstract  

Half-life of241Pu is of great importance in nuclear technology. In view of large variation in the values (13–15 y) reported till 1974 in literature, efforts have been made in different laboratories to determine this half-life with high precision and accuracy. In our laboratory, it has been determined by different methods which may be classified in two categories, viz. (1) parent decay method, and (2) daughter growth method. In the parent decay method, change in isotope ratios241Pu/239Pu,241Pu/240Pu and241Pu/242Pu was studied periodically by a thermal ionization mass spectrometer. Single as well as double ratio method was used to calculate the half-life. In the daughter growth method, the half-life was obtained in four independent ways. These were (1) alpha spectrometry taking239Pu and242Pu separately as reference isotopes and studying periodically the increase in alpha activity ratio, (2) alpha proportional counting for observing periodically the change in total alpha activity, (3) isotope dilution alpha spectrometry using243Am as a spike, (4) isotope dilution mass spectrometry using243Am as a spike. In all these methods, synthetic mixtures were prepared for achieving high precision and accuracy in different measurements. Based on the results obtained in this laboratory and the values reported by other laboratories, a half-life value of 14.4±0.1 y is recommended. The paper reviews the past history, puts forth the present status, highlights the current trends for studying the effect of chemical composition of plutonium on the half-life of241Pu and presents the future requirements for achieving higher accuracy in the half-life of241Pu.

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Abstract  

Relative activity method offers the potentiality of providing half-life values over a wide range in a short time for different -emitting transactinium isotopes. The method involves the preparation of a synthetic mixture using another isotope of the same element followed by the determination of atom ratio and -activity ratio by thermal ionization mass spectrometry and -spectrometry, respectively. A double dilution technique is described which helps in maintaining the atom ratios as well as -activity ratios close to unity so that these could be determined with high precision and accuracy. Results obtained on the half-lives of232U,238Pu,242Pu and243Am using double dilution technique in relative activity method are summarized. Requirements, advantages and applications of this technique for determining the half-lives of other transactinium isotopes are presented.

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Molecular markers provide novel tools for linkage mapping of QTLs of target traits and can greatly enhance the efficacy of breeding programs to improve mineral (iron and zinc) density in rice. A F2 population derived from the cross between high-yielding (PAU201) and iron-rich (Palman 579) indica rice varieties displayed large variation for various physio-morphological traits including grain yield per plant and iron and zinc contents. Transgressive segregation for grain iron and/or zinc contents was noticed in some F2 individuals with one of the F2 plants having exceptionally higher iron (475.4 μg/g) as well as zinc (157.4 μg/g) contents. Grain iron content showed significant positive correlation (r = 0.523) with grain zinc content indicating the feasibility of improving iron and zinc levels simultaneously in rice grain. Two parental rice varieties displayed polymorphism at 76 of the 100 SSR loci, which were used to map the QTLs associated with mineral content in grains. Composite interval mapping (CIM) analysis by Win QTL cartographer 2.5 revealed a total of eleven QTLs for mineral content (eight for Fe and three for Zn) in rice grains on chromosomes 2, 3, 7, 10 and 12.

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Antioxidants are added to the polymers to suppress oxidation during the service life. The paper deals with determination of stabilizer (VANOX-SKT) antioxidant in polyamides using a differential scanning calorimeter. Normally the amount of antioxidants is determined using HPLC method which takes more than 48 hours for sample preparation. A series of polyamide samples with known content of antioxidants (0.0–0.8%) are analysed using DSC form −50 to 350 °C in oxygen atmosphere keeping Al-crucibles open. For all the compositions a linear relationship was found forΔH (heat of degradation) and induction time under isothermal conditions at 220 °C which enables the antioxidant VANOX-SKT to be determined in unknown samples.

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The thermal ignition behaviour of various mixtures of organic fuels, magnesium and ammonium nitrate (AN) has been examined by differential thermal analysis technique. It has been observed that the thermal decomposition/ignition of organic fuel-AN mixtures is modified significantly in the presence of magnesium metal. The decomposition characteristics of the binary mixtures of AN with various metals indicate the specific action of magnesium and zinc in lowering the decomposition temperature. A possible explanation for the low temperature decomposition is given in terms of the solid state reaction causing the fusion of AN which further reacts with the metal resulting in a highly exothermic reaction.

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