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- Author or Editor: S. Srivastava x
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We report on the room temperature ferromagnetism observed in heat treated nanocrystalline diamonds. By systematic annealing of nanocrystalline diamond, graphitic nanoclusters having finite magnetization with well-defined hysteresis and coercivity, and a Curie temperature (TC) well above 400 K (estimated TC ~ 590 K), were synthesized. Using detailed analysis of the structural modification at various annealing stages, with Raman Spectroscopy and High Resolution Transmission Electron Microscopy, we show that the carbon bonding configuration has important consequence to the observed magnetism in these samples. These findings could lead to controlled fabrication of metal free magnetic carbon system.
Abstract
The elemental concentration of uranium in the samples collected from the ground water and the canal water in the Bathinda district of Punjab state, India, have been investigated using X-ray fluorescence technique. The residues obtained after drying the water samples were analysed using the energy dispersive X-ray fluorescence spectrometer consisting of Mo-anode X-ray tube equipped with selective absorbers as an excitation source and an Si(Li) detector. The uranium concentration values in significant fraction of the shallow ground water samples from the hand pumps is found to be above the permissible level of 15 ppb recommended by World Health Organisation for the drinking water, and its values in the canal water samples are below 5 ppb. To investigate the flyash from the coal-fired thermal power plants as a possible source of ground water contamination, the water samples collected from the surroundings of the power plants and the flyash samples were also analyzed. The results rule out flyash as a source of uranium contamination. Agrochemical processes occurring in the calcareous soils in the region are the favoured potential source of uranium contamination of the ground water.
Abstract
The paper describes the simultaneous determination of 14N and 15N isotopes in opium by proton induced γ-ray emission (PIGE) technique. The isotopic ratio of 14N and 15N is a useful parameter for assigning provenance of (seized) illicit drugs. The measurement, non-destructive in nature, is performed on pellets made up of opium powders and is based on the prompt detection of 2.313 and 4.4 MeV γ-rays emanating from 14N(p,p′γ)14N and 15N(p,αγ)12C nuclear reactions respectively, induced simultaneously by 3.6–3.8 MeV proton beam. Positive as well as negative deviations from the natural isotopic abundance (99.63:0.37) were observed in the samples. The precision of the measurements is about 4%. The methodology provides an easy and rapid approach to determine the isotopic ratio of 14N and 15N and has been used for the first time in the analysis of opium.
