Rammohan College

Kolkata, India

Rammohan College

Kolkata, India
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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.


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.


PubMed | University of Calcutta, Indian Association for The Cultivation of Science, Indian Institute of Technology Bombay, Rammohan College and St Xaviers College
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2015

We propose a strategy of using a stochastic optimization technique, namely, simulated annealing to design optimum laser pulses (both IR and UV) to achieve greater fluxes along the two dissociating channels (O(18) + O(16)O(16) and O(16) + O(16)O(18)) in O(16)O(16)O(18) molecule. We show that the integrated fluxes obtained along the targeted dissociating channel is larger with the optimized pulse than with the unoptimized one. The flux ratios are also more impressive with the optimized pulse than with the unoptimized one. We also look at the evolution contours of the wavefunctions along the two channels with time after the actions of both the IR and UV pulses and compare the profiles for unoptimized (initial) and optimized fields for better understanding the results that we achieve. We also report the pulse parameters obtained as well as the final shapes they take.


Brahma P.,Gurudas College | Dutta S.,Rammohan College
Frontiers in Mechanochemistry and Mechanical Alloying | Year: 2011

Nanophase materials with an average grain sizes ranging from 2 to 20 nm exhibit novel properties relative to conventional materials. Recently, we reported that the mechanical milling of Fe3O4 powders produced nanometer sized particles (∼7 nm) which exhibited a phase transition from cubic (Fe3O4) to hexagonal (α- Fe2O3) phase. In this paper, we present results on the synthesis of nanosized α-Fe2O3 produced by mechanical milling for 1 to 10 h. Some unusual electrical conductivity characteristics were observed. The X-ray diffraction analyses show only the presence characteristic lines of hematite in the ball milled samples. Particle sizes measured from X-ray line broadening varied from 7 to 11 nm. TEM micrograph for the ball milled samples show distribution of particle size. A drastic change of electrical resistivity has been observed from the electrical measurements of different ball milled samples. The resistivity variation of the unmilled sample can be ascribed to typical band conduction. A decrease of about two orders of magnitude of resistivity was observed for the specimen ball milled for 10 h. The resistivity variation of the two activated processes was observed with activation energies of ∼ 0.06 and ∼ 0.7eV, respectively. Large and small particle sizes are responsible for the two activation energies. © CSIR-National Metallurgical Laboratory, Jamshedpur-831007, India, 2011.


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.


Basu S.,Rammohan College | Choudhury U.R.,National Test House ER | Das M.,Rammohan College | Datta G.,Rammohan College
International Journal of Phytomedicine | Year: 2013

The uses of herbal medicines worldwide provide an excellent opportunity for India to look into the therapeutic compounds from ancient system of therapy, Ayurveda. Since ancient time, Amorphophallus campanulatus has been considered as medicinal plant with multiple protective activities. So, the present study was aimed to identify the various phytochemical constituents in the ethanolic and aqueous extracts of Amorphophallus campanulatus tuber by GC-MS analysis. The ethanolic and aqueous extracts of Amorphophallus campanulatus were dissolved in absolute ethanol (1 mg/ml). 10μl of this sample was then injected for gas chromatography- mass spectrometric (GC-MS) analysis. The results for the first time revealed the presence of several bioactive components both in the ethanolic as well as in the aqueous extracts. However, the ethanolic extract showed quantitatively higher amount of these components than the aqueous extract as is clearly indicated by higher % peak area of the compounds in the ethanolic extract. Some components of biological importance include Hexadecanoic acid and its methyl and ethyl esters, Heptadecanoic acid, Linoleic acid and its ester, Oleic acid, Stigmasterol, 1, 3, 5, benzenetriol, 4H-Pyran-4-one, 2, 3-dihydro-3, 5 -dihydroxy-6-methyl-, Squalene and Vitamin E. Thus the results of the present study is an evidence to support the traditional usage of A. campanulatus which possess several known and unknown bioactive components. By identifying and isolating these components, new drugs can be formulated to treat various diseases.


Basu S.,Rammohan College | Das M.,Rammohan College | Datta G.,Rammohan College
International Journal of Research in Pharmaceutical Sciences | Year: 2012

The use of herbal medicines worldwide had provided an excellent opportunity to India to look for therapeutic compounds from our ancient system of therapy, Ayurveda, which can be utilized for development of new drug. Amorphophallus campanulatus is grown wild and cultivated all over India. It is very popular for its edible corms and leaves, especially in Assam and Bengal and is cultivated there as a common food crop. Since ancient time, it has been considered as medicinal plant in Sushruta Samhita and Ayurveda. It is recommended for different ailments like digestive disorders, piles, buccal ulcers and as liver stimulant in Dravyaguna Vigyan. So, the ethanolic and aqueous extracts of this tuber were screened for the presence of in vitro antioxidant potential against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, ferric reducing power, hydroxyl radical, superoxide radical and lipid peroxidation. Total phenolic and flavonoid contents of both the extracts were also evaluated. IC 50 values of ethanolic and aqueous extract of Amorphophallus campanulatus represented 676.37 and 820.46 μg/ml respectively for DPPH; 665 and 968.64 μg/ml respectively for hydroxyl radical scavenging activity; 703.33 and 1097.61 μg/ml respectively for superoxide radical scavenging activity and 842.83 and 1337.35 μg/ml respectively in case of lipid peroxidation inhibition. The total phenol for ethanolic and aqueous extract was estimated to be 194.4 ± 2.2 mg % w/w and 104.6 ± 1.24 mg % w/w respectively (mg Gallic acid equivalent per gm dry weight of sample) and that of flavonoid was 6.75 ± 1.2 mg w/w and 1.50 ± 0.23 mg % w/w respectively (mg of Rutin equivalent per gm dry weight of sample). Ethanolic extract shows maximum antioxidant capacity in comparison to aqueous extract and hence can be utilized in future as therapeutic agent against free radical induced oxidative stress. © JK Welfare & Pharmascope Foundation.


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.


Basu S.,Rammohan College | Sen A.,Rammohan College | Das M.,Rammohan College | Nath P.,Rammohan College | Datta G.,Rammohan College
International Journal of Pharma and Bio Sciences | Year: 2012

Amorphophallus campanulatus, Alocasia indica and Colocasia esculenta are very popular for their edible corms and leaves, especially in Assam and Bengal and are cultivated there as common food crops. Besides, they are also considered as medicinal plants in Sushruta Samhita and Ayurveda. So, the ethanolic extracts of these tubers were screened for the presence of in vitro antioxidant potential against 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical, ferric reducing power, hydroxyl radical and superoxide radical. Total phenolic and flavonoid contents of all the extracts were also evaluated. The results revealed that the ethanolic extracts of all the tubers possessed antioxidant property. Among the three, Amorphophallus campanulatus showed significantly higher (P<0.01) antioxidant potential in scavenging free radical than that of Alocasia indica and Colocasia esculenta. This higher ability to scavenge free radicals by Amorphophallus campanulatus may be attributed to the presence of higher amount of polyphenols and flavonoids in it, than the other two tubers as evidenced from our result. Thus the ethanolic extracts of these tubers can be utilized in future as therapeutic agent against free radical induced oxidative stress.

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