Time filter

Source Type

Kolkata, India

Das S.K.,Indian Association for The Cultivation of Science | Bhunia M.K.,Indian Association for The Cultivation of Science | Motin Seikh M.,Visva Bharati University | Dutta S.,Rammohan College | Bhaumik A.,Indian Association for The Cultivation of Science
Dalton Transactions | Year: 2011

A new porous Co(ii)-salicylate metal-organic framework material has been synthesized hydrothermally through the reaction of Co(ii) chloride with sodium salicylate under mild alkaline pH conditions. To get an idea about the structural aspect of the material from the powder X-ray diffraction (PXRD) pattern, MAUD program has been successfully utilized and the assigned peaks match very well with a new tetragonal phase (space group, P4mm) having the unit cell parameters: a = b = 12.957 (0.042) Å; c = 12.738 (0.019) Å; α = β = γ = 90°, V = 2138.73 Å3. N 2 adsorption/desorption analyses suggested the material is highly porous in nature having high BET surface area and pore dimensions of 2.0-3.0 nm, which is within the range of small mesopores. Thermogravimetric analysis (TGA) revealed that the H2O molecules may be removed from the framework without collapsing the structure and the material is stable up to ca. 573 K. The material is characterized thoroughly by using different characterization tools such as TEM, SEM, UV-visible reflectance spectroscopy, FT IR spectroscopy and photoluminescence spectroscopy. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the cobalt atom and presence of other elements within the framework. The material shows interesting magnetic properties, where the magnetic moments monotonically increase with the decrease in temperature down to 9 K. Below 9 K there is a steep increase in magnetization on further lowering the temperature, thereby suggesting the onset of a long range ferromagnetic transition with ferromagnetic Curie temperature, T C = 8.5 K. Furthermore, the M-H curve at 2 K shows a clear hysteresis loop with a coercive field 150 Oe and remnant magnetization 0.8 μB/f.u. © The Royal Society of Chemistry 2011.

Hajra P.,Indian Association for The Cultivation of Science | Dutta S.,Rammohan College | Brahma P.,Gurudas College | Chakravorty D.,Indian Association for The Cultivation of Science
Journal of Magnetism and Magnetic Materials | Year: 2011

Co3O4 nanocrystals of sizes in the range 17.533.1 nm were grown within a solgel-derived silica glass matrix. Rietveld analysis of the X-ray diffraction data showed that the crystals had tetragonal symmetry. This was explained as arising due to a tensile strain induced at the glasscrystal interface as a result of thermal expansion mismatch between the phases. The crystals showed ferromagnetic behaviour with superparamagnetism setting-in at temperatures above 15 K. They also exhibited ferroelectric characteristics with large remanent polarization. Change in dielectric constant as a function of magnetic field was observed in these nanocomposites. This was discussed on the basis of magnetostriction effect. © 2010 Elsevier B.V. All rights reserved.

Das S.,Rammohan College
Turkish Journal of Zoology | Year: 2016

The presence of vertebrate hormones in invertebrates is a well-established fact. Their physiological roles are still far from clear in various invertebrate systems including insects. This review provides some positive evidence toward the establishment of the biological role of vertebrate hormones in silkworm, Bombyx mori Linnaeus, 1758, with special emphasis on sex steroids. © TÜBİTAK.

Ghosh S.,Rammohan College | Bhattacharya S.,IITUP
ACM International Conference Proceeding Series | Year: 2015

From the early age of technology mankind is always fascinated about capturing the scenes around them. These photographs work as an important media to know and understand the past. Unfortunately, due to aging, repetitive usage and in presence of external reagents, the perceptual quality of these old images degrade severely. Thus, restoration of vintage photographs is an important application of digital image processing. In this paper we propose an algorithm which is able restore an image suffered with contrast fading and color cast. The approach can not only restore grayscale images but also is able to binarize archival documents. © 2015 ACM.

Hajra P.,Indian Association for The Cultivation of Science | Brahma P.,Gurudas College | Dutta S.,Rammohan College | Banerjee S.,University of Calcutta | Chakravorty D.,Indian Association for The Cultivation of Science
Journal of Magnetism and Magnetic Materials | Year: 2012

Cr 2O 3 nanoparticles of sizes from 24 to 12 nm were synthesized by mechanical grinding. Magnetic hysteresis loops were observed in the temperature range 5300 K. Zero-field magnetization measurements showed two peaks, at low temperature in the range 3652 K and at high temperature in the range 255290 K. They were found to shift to higher temperatures as the particle size was reduced. This was ascribed due to the enhancement of the effective anisotropy constant with a decrease in particle size. The exchange bias was found to increase as the particle size became smaller. This is believed to arise due to an increase in uncompensated spins as a result of large surface area created. © 2011 Elsevier B.V. All rights reserved.

Discover hidden collaborations