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  • Author or Editor: A. Khan x
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Abstract  

A sensitive spectrophotometric method has been developed for the determination of microamounts of thorium using 0.05% thorin in a 3M perchloric acid solution as a chromogenic reagent and measuring the absorbance at 544 nm. The complex of thorium thus formed, is stable for more than two months with a constant absorbance of ±0.55%. Beer's law is obeyed from 0 to 25 g g–1 of thorium in a solution with a molar absorptivity (544 nm) = 1.69×104 M–1 cm–1 at 26±1 °C. Among the anions tested, only phosphate, acetate and cyanide at >200-fold excess of thorium interfere in the determination, whereas cations like Zn(II), Al(III), Na(I), Mg(II), and Ca(II) do not effect the absorbance. Thorium can be determined in the presence of oxalate, nitrate, tartrate, sulfate, thiosulfate, citrate, and ascorbate. The accuracy of the method has been checked by measuring the known concentration of thorium in the range of 100 g-5 mg g–1 and found to be in the range of 7.7–0.9%. The method has been applied successfully to determine thorium at g g–1 level in local ore samples with a precision of ±0.3%. The sensitivity of the method on Sandell's scale is 0.082±0.002 g g–1 cm–1.

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A total of 32 bacterial isolates including Mesorhizobium (N=10), Azotobacter (N=12) and phosphate-solubilizing bacteria (N=10) were isolated and tested for siderophore, HCN, ammonia, indole acetic acid production and phosphate solubilization in vitro . The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates, M. ciceri RC3 and A. chrococcum A4 displayed 35 and 14 μg ml −1 of IAA, respectively, whereas Bacillus produced 19 ( Bacillus PSB1) and 17 μg ml −1 ( Bacillus PSB10) of IAA in Luria Bertani broth. The diameter of the P solubilization zone varied between 4 ( Bacillus PSB1) and 5 mm ( Bacillus PSB10) and a considerable amount of tricalcium phosphate (7 and 8 μg ml −1 by Bacillus PSB1 and Bacillus PSB10, respectively) was released in liquid medium, with a concomitant drop in pH. The effects of N 2 -fixing and PS bacteria on the growth, chlorophyll content, seed yield, grain protein and N uptake of chickpea plants in field trials varied considerably between the treatments. Nodule number and biomass were significantly greater at 90 days after sowing (DAS), decreasing by 145 DAS. Seed yield increased by 250% due to inoculation with M. ciceri RC3 + A. chroococcum A4 + Bacillus PSB10, relative to the control treatment. Grain protein content ranged from 180 ( Bacillus PSB1) to 309 ng g −1 ( M. ciceri RC3 + A. chroococcum A4 + Bacillus PSB10) in inoculated chickpea. The N contents in roots and shoots differed considerably among the treatments.

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Abstract  

Fission neutron spectrum averaged cross-sections were measured for the reactions64Zn(n, p)64Cu,67Zn(n, p)67Cu and68Zn(n, )65Ni by the activation technique, using radiochemical separations and -spectroscopy. The preparation of64Cu and67Cu in a nuclear reactor was studied. The64, 67Cu was separated from zinc matrix activity using anion exchange column technique.

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Abstract  

An X-ray fluorescence spectrometric multivariable regression procedure is described for the determination of titanium and molybdenum in special steels and alloys in the concentration range from 9.41% down to 120 μg/g using Ti Kα1,2 and Mo Kα1,2 analyte lines. In general, better results have been achieved in first order base curve polynomials using LiF (200) crystal in combination with scintillation counter (SC) or krypton proportional counter (KPC). However, LiF (220)+SC combination also yields favorable results for Mo. The measured concentrations of Ti and Mo for BAS alloy steel standards agree very well with their certified values. The automated XRFS method for the determination of Ti and Mo appears to be free from matrix effects and is suitable for their measurement in special steels and alloys down to 120 μg/g concentration of Ti with a precision of 3.2% and an accuracy of ±2.5% and for Mo down to 350 μg/g with a precision of <1% and an accuracy of ±1.1%. The sensitivities for these lowest concentrations are calculated to be 5960 counts/mass %/s and 8000 counts/mass %/s for Ti and Mo, respectively.

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Abstract  

Large columns containing aluminum oxide (Al2O3) or gel (e.g. zirconium molybdate) are needed to prepare 98Mo(n,γ)99Mo→99mTc column chromatographic generators that results in large elution volumes containing relatively high 99Mo impurity and low concentrations of 99mTc. The decrease in radioactive concentration or specific volume concentration of 99mTc places a limitation on some pharmaceutical kits (DTPA, MIBI, ECD, etc.) or clinical procedures. We report on the post elution concentration of 99mTc using in house prepared lead cation-exchange and alumina columns. Using these columns high bolus volumes (10–60 mL 0.02M sodium sulfate) of 99mTc can conveniently be concentrated in 1 mL of physiological saline. This approach also works very effectively to prepare high specific volume solutions of 99mTc-pertechnetate from a fission based 99Mo/99mTc generator in the second week of its normal working life.

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Abstract  

Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD) analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol−1 for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT.

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A diallel cross involving six wheat varieties, namely Sehar 06, Punjab 96, GA 2002, Barani 83, Kohistan 97 and Chakwal 86 was carried out to determine the mode of gene action for some physio-morphological traits under water stress conditions. Analysis of variance showed highly significant differences among genotypes for all the traits studied. Additive type of gene action with partial dominance was observed for flag leaf area, stomatal frequency, leaf venation, days to heading and spike density while 100-grain weight was controlled by over dominance. Additive type of gene actions shows the fruitfulness of early selection for the traits while over dominance type of gene action indicates selection in later generations. Epistasis was absent for all the traits studied.

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