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Guwāhāti, India

Purkayastha A.D.,Handique Girls College
Pramana - Journal of Physics | Year: 2013

The purpose of this paper is to examine the energy content of the inflationary Universe described by Kantowski-Sachs space-time in quasilocal approach of teleparallel gravity and in the Hamiltonian structure of the teleparallel equivalent of general relativity. The teleparallel versions of field equations are also derived in such a space-time. © Indian Academy of Sciences. Source


Senapati U.S.,Handique Girls College | Sarkar D.,Gauhati University
Journal of Materials Science: Materials in Electronics | Year: 2015

The present study reports an environment friendly method for the synthesis of zinc sulphide (ZnS) nanoparticles using an aqueous extract of Elaeocarpus floribundus (Indian olive) leaf that acts as a capping as well as a stabilizing agent. X-ray diffraction and selected area electron diffraction studies confirm cubic structure of the nanoparticles. Transmission electron microscopy shows spherical in shape of the particles with diameter ranging from 8 to 3 nm. Static and high frequency optical dielectric constants are determined for all the samples. The optical band gap calculated from Tauc’s plot is found to increase from 3.8 to 4.1 eV. The refractive index of the samples is calculated using Moss and Herve–Vandamme models. The room temperature photoluminescence spectra of the samples show a broad peak centred at 440 nm. The biomolecules involve in the formation of ZnS nanoparticles are studied by Fourier transform infrared spectroscopy analysis. The possible growth mechanism of the synthesized ZnS nanoparticles is also discussed. Current–voltage characteristics under illumination exhibit anomalous behaviour, it shows peak through sudden rise and fall of current with increase of voltage. © 2015, Springer Science+Business Media New York. Source


Chakrabarty D.,Handique Girls College
International Journal of Agricultural and Statistical Sciences | Year: 2014

A method has been framed for determining the natural limits (lower limit and upper limit) of annual total rainfall at a location by the application of the area property of Gaussian distribution. The method has been applied in determining the natural limits of annual total rainfall in the context of India. Source


Senapati U.S.,Handique Girls College | Sarkar D.,Gauhati University
Superlattices and Microstructures | Year: 2015

Zinc sulphide (ZnS) nanoparticles are prepared by a simple, economic and green synthesis route. X-ray diffraction patterns confirm zinc blend structure. ZnS formation is confirmed through chemical analysis by energy dispersive analysis of X-rays. Transmission electron microscopy reveals formation of nanosize with dimension in the range of 8-2 nm. Band gap of the nanocrystals is found to lie in the range of 4.51-4.65 eV. Photoluminescence study indicate defect like vacancies. The growth mechanism of ZnS nanoparticles is discussed with the help of Fourier transform infrared spectroscopy and thermogravimetric analysis. The materials show high dielectric constant compared to its bulk counterpart. The dielectric loss of the samples shows anomalous behaviour. The frequency dependent A.C. conductivity of the samples is discussed both in high and low frequency regimes. Current-voltage (I-V) characteristic performed under dark and under illumination, shows excellent light response of the material. © 2015 Elsevier Ltd. All rights reserved. Source


Phukan K.,Handique Girls College | Devi N.,Cotton College
International Journal of ChemTech Research | Year: 2012

A general, efficient and simple methodolgy for biocatalytic reduction of a diverse set of carbonyl compounds at room temperature using freshly cut ripen fruit of Lycopersicumesculentum (tomato) in aqueous medium has been reported. It was found that in addition to reduction of simple carbonyls to the corresponding primary and secondary alcohols, the prochiral ketones,both cyclic and acyclic, could be reduced to chiral secondary alcohols in a generalized way. Very high enantioselectivity (92-99%) with moderate to excellent chemical yields (70-95%) were observed. Most of the reductions were completed within 25-35 h. The regioselectivity of the biocatalyst is well established by the reduced product of cinnamaldehyde where the C = C bond was not reduced in the present investigation. The synthesized products were characterized by melting points, TLC, FT-IR and 1H NMR data. Mild reaction condition, simple operation, and easy availability of tomato fruit reveal this protocol as an attractive and alternative eco-friendly option for general reduction of all types of carbonyl compounds. Source

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