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  • Author or Editor: S. Santra x
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Monthly changes in species diversity of aquatic macrophytes (richness and Simpson’s diversity index) were studied in relation to various limnological predictors (including their time lag effects) of two tropical ponds, over a period of three years, using regression analysis with correction for temporal autocorrelation.The monthly mean ± SD number of total plant species was 6±2 and 2±1 in Pond 203 and Pond 206, respectively, with significant pond effect. Immediate and 2-months lag of water temperature in the ‘species rich’ pond (Pond 203) appeared to be the significant predictors for Simpson’s diversity index and total plant species richness, respectively. Secchi depth (1-month lag) was found to be the significant predictor for Simpson’s diversity index in ‘less species rich’ pond (Pond 206), while total plant species richness was not found to be influenced by any limnological predictor. Comparative literature review on maximum number of plant species per pond revealed low richness in tropical and subtropical ponds than their temperate counterparts. Among different growth forms, maximum number of emergent and submerged plant species per pond was also less in tropical climates.

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Barium borosilicate glass (BaBSG) is proposed as a potential candidate for vitrification of nuclear waste generated from thoria based nuclear reactors. Along with fission products, activation products and many inactive chemicals, like fluorine in the form of HF are expected to be present in the dissolver solution with nuclear waste. As vitrification occurs at high temperature, it is important to quantify fluorine in BaBSG. Due to its complex matrix, most of the wet chemical and nuclear analytical methods encounter problems in the estimation of fluorine. Particle induced γ-ray emission (PIGE) method has been standardized for non-destructive determination of fluorine contents in BaBSG samples utilizing measurement of prompt gamma-rays from 19F (p, p’γ) 19F reaction. Experiments have been carried out with thick pellet targets prepared in cellulose matrix using 4 MeV proton beam from the folded tandem ion accelerator at BARC, Mumbai. For obtaining current normalized count rate of interest, beam current variation was monitored by the Rutherford backscattering spectrometry (RBS) method as well as by the in situ approach using an externally added element sensitive to PIGE. In this paper standardization of PIGE methods for F determination, validation of methods using synthetic samples, and application to BaBSG samples are reported.

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