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  • Author or Editor: B. Shukla x
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Abstract  

Recoil reactions of128I in liquid methyl iodide, ethyl iodide and n-butyl iodide target systems in the presence of benzene diluent have been studied by the charged plate technique. The investigations have been carried out over a wide range of diluent concentration. It has been observed that there are more collected recoil charged128I species on the anode than on the cathode. The presence of benzene diluent in the target systems prior to neutron irradiation reduces the recoil collection on both electrodes.

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Abstract  

Basic formulations used in the sedimentary210Pb dating technique are derived from fundamental considerations. The formulations are applicable to models that assume either a constant rate of supply (CRS) of unsupported210Pb to the sediments or a constant initial concentration (CIC) of this210Pb in the sediments. A previously proposed expression linking age discrepancy to mass sedimentation rates afforded by the two models is found to be inadequate in explaining the observed discrepancy between the CIC and CRS ages of segments of an undisturbed sediment core. It is noted that this age discrepancy is attributable to the mathematical treatment of data in the two models. A new expression, relating age discrepancy to the fluxes of unsupported210Pb obtainable by the two models, is derived and found to give more accurate and consistent results.

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Abstract  

Ammonium molybdophosphate (AMP) was irradiated with electrons up to a dose of 1 MGy. X-ray diffraction patterns and FT-IR of irradiated and control AMP samples were recorded. Uptake of137Cs from nitric acid in the range of 0.2 to 10 mol·dm–3 was estimated by a batch equilibration technique. AMP undergoes perceptible changes in its physico-chemical characteristics on irradiation with electrons. Uptake of137Cs from nitric acid by irradiated AMP was nearly the same as the control AMP in the nitric acid concentration range of 6 to 10 mol·dm–3 and relatively higher in the range of 0.2 to 6 mol·dm–3. The results are discussed in terms of available information on the physicochemical properties of 12-heteropoly acids and their salts.

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Abstract  

Lead-210 dates are assigned to a sediment core retrieved from McKay Lake, Ottawa, Canada. Sediment mixing is found to have little, but discernible, influence on the age/depth profile. Consideration of mixing yields lower estimates of the derived ages, in agreement with the prediction based on a mathematical model. The inferred dates support the previous assignments based on Ambrosia horizon and the known occurrence of a catastrophic event. The procedures used in the calculation of the age profiles are fully described.

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Abstract  

The study summarizes radiological characteristics of Banduhurang open cast mine which includes qualitative and quantitative behavior of 222Rn concentration, external gamma radiation level over the mine pit as well as in its adjoining environment, long-lived alpha (LLα) activity concentration associated with the respirable size of ore dust and assessment of dose to the mine workers in 2006–2008. The investigations reveal that geometric means (χg) of measured radon concentration were 36.39, 38.69, 26.64 and 24 Bq m−3 with respective geometric standard deviations (σg) were 1.52, 1.55, 1.36 and 1.68 Bq m−3 and χg of gamma absorbed dose rates were 0.54, 0.64, 0. 45 and 0.15 μGy h−1 with respective σg were 1.63, 1.53, 1.52 and 1.72 μGy h−1 over the mine pit, ore yard, waste yard and in the surrounding environment within a 10 km radius to the mine, respectively. The χg of LLα activity was observed to be 16 mBq m−3 with σg of 1.9 mBq m−3. The annual mean effective dose equivalent received by the member radiation workers of Banduhurang mine was estimated to 1.41 mSv y−1, which is about 7% of the prescribed dose limits of 20 mSv y−1.

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Abstract  

Tracer diffusion of131I ions is studied at different temperatures /20°C–50°C/ in 2.5% agar gel containing sodium and potassium sulphate solutions over a wide range of concentrations. The results are in qualitative agreement with the theoretical values in the concentration range 10–6–10–1M. Agar gel shows an obstruction effect to diffusional flow. The activation energy for tracer diffusion was found to be of the order of 16.3 kJ mol–1.

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The aim of this study was to isolate and identify three biologically active flavonoids, quercetin, kaempferol, and apigenin, from the hydrolyzed methanolic extract of three indigenous medicinal Cordia species, i.e., Cordia macleodii, Cordia dichotoma, and Cordia rothi barks using preparative thin-layer chromatography (TLC) and high-performance (HP)TLC methods. The isolation of flavonoid fraction was accomplished by preparative TLC method using reference standard. For achieving good separation, a mobile phase of toluene–ethyl acetate–GAA–formic acid (5:5:0.5:1) was used. The ultraviolet (UV)-based densitometry determination was carried out at 254 nm in reflection—absorption mode. The antioxidant compounds in the samples were screened through 2,2-diphenyl-1-picrylhydrazyl (DPPH) derivatization method. The method was partially validated in terms of linearity, specificity, and sensitivity. All three standards showed good linearity in the range of 2500–7500 ng with respect to area. Limit of detection (LOD) and limit of quantitation (LOQ) for quercetin were 9.4 and 28 ng; for apigenin, 30 and 92 ng; and for kaempferol, 57 and 173 ng. From the analysis, quercetin (0.21%) and kaempferol (0.19%) in C. rothi and apigenin (0.28%) in C. dichotoma were found to be the highest. The isolation and identification of these flavonoids have not yet been found in the literature and they are reported in this study for first time. From this, it is concluded that planar chromatography has a potential as a rapid and simple tool for the identification and quantification of phytochemicals in complex mixtures and marker-based samples.

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Abstract  

A brief study on dissolved radionuclides in aquatic environment, especially in ground water, constitutes the key aspect for assessment and control of natural exposure. In the present study the distribution of natural uranium and 226Ra concentration were measured in ground water samples collected within a 10 km radius around the Narwapahar uranium mine in the Singhbhum thrust belt of Jharkhand, India in 2007–2008. The natural uranium content in the ground water samples in this region was found to vary from 0.1 to 3.75 μg L−1 with an average of 0.87 ± 0.73 μg L−1 and 226Ra concentration was found to vary from 5.2 to 38.1 mBq L−1 with an average of 13.73 ± 7.34 mBq L−1. The mean annual ingestion dose due to intake of natural uranium and 226Ra through drinking water pathway to male and female adults population was estimated to be 6.55 and 4.78 μSv y−1, respectively, which constitutes merely a small fraction of the reference dose level of 100 μSv y−1 as recommended by WHO.

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Abstract  

In the environs of uranium mining, milling and processing facilities and in the uranium mineralized terrain, a little higher ambient radon concentration and gamma radiation level may be expected in comparison with natural background. The present study gives a brief account of atmospheric radon concentration, gamma absorbed dose rate and radiation dose received by the members of public in the vicinity of Narwapahar uranium mine. The ambient radon concentration in the air in the study area was found to vary from 5 to 107 Bq m−3 with geometric mean of 24 Bq m−3 and geometric standard deviation of 1.74 Bq m−3. The measured gamma absorbed dose rate in air at 1 m above the ground ranged from 87 to 220 nGy h−1 with an overall arithmetic mean of 128 ± 18.5 nGy h−1. The mean annual effective dose received by the members of public from inhalation of radon and its progeny and external gamma exposure was estimated to be 0.32 mSv year−1, which is comparable to other reported values elsewhere.

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