Santiniketan, India
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Maity S.,Center for Environmental Studies | Roy S.,Siksha Bhavana | Bhattacharya S.,Siksha Bhavana | Chaudhury S.,Center for Environmental Studies
European Journal of Soil Biology | Year: 2011

Biomarkers allow the evaluation of possible biochemical effects under various metal contaminations in the terrestrial environment. In order to attain this objective adult, sexually mature Lampito mauritii were exposed to different concentrations of lead (Pb) and zinc (Zn) separately for 28 days and concentrations of metallothionein were assessed by radioassay method using 203Hg. A significant increase in tissue metallothionein level was recorded in L. mauritii exposed to Pb and Zn contaminated soil. Thus it may be surmised that metallothioneins are directly involved in metal ion detoxification and helps L. mauritii to survive in metal contaminated soil. Moreover the sensitivity of this biochemical parameter observed in L. mauritii exposed to Pb and Zn can be used as reliable biomarker in monitoring metal pollution. © 2010 Elsevier Masson SAS.


Ghosh M.,Integrated Science Education and Research Center | Mora A.K.,Bhabha Atomic Research Center | Nath S.,Bhabha Atomic Research Center | Chandra A.K.,North - Eastern Hill University | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

(Graph Presented) Photophysical properties of free base tetraphenylporphyrin and its zinc analog are investigated in detail in solvents of varying polarity by using steady state and time-resolved techniques. Both the porphyrins are excited at the Soret band to have better signal-to-noise ratio. Also, the fluorescence emission measurements are carried out by using dilute solutions (∼10-7 mol/L) of the fluorophores in order to minimize the self-quenching effect. It is observed that the steady state absorption and emission characteristics of the porphyrin molecules are mainly affected by polarizability (via refractive index) rather than polarity (via dielectric constant) of the moderate to highly polar solvents. As the molecules are highly symmetric in the ground state, the associated dipole moments are found to be very low from quantum chemical calculations performed by density functional theory method by using Gaussian 03 package. The dipole moments associated with the first excited singlet state of the porphyrins are computed by applying solvatochromic Stokes' shift method. To the best of our knowledge, this is the first attempt to calculate the excited state dipole moments of the porphyrins used in the present investigations. Also, fluorescence quantum yield, fluorescence lifetime of the first excited singlet state, radiative and non-radiative rate constants of the porphyrins are reported in solvents of varying polarity. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.


Ghosh M.,Integrated Science Education and Research Center | Nath S.,Bhabha Atomic Research Center | Hajra A.,Siksha Bhavana | Sinha S.,Integrated Science Education and Research Center
Journal of Luminescence | Year: 2013

Self-quenching of the fluorescence emission of tetraphenylporphyrin at high concentrations in toluene at the ambient temperature (300 K) is discussed in detail based on steady state and time-resolved fluorescence measurements. The fluorescence self-quenching is mainly attributed to re-absorption effect and the Förster type resonance energy transfer process (homotransfer). The re-absorption effect is found to deform the fluorescence emission spectra significantly in energy positions as well as relative intensities of different peaks at high concentrations. Nearly ideal fluorescence emission spectra are observed at a concentration ∼10-7 mol/L. Moreover, there is an apparent enhancement of the fluorescence lifetime value of tetraphenylporphyrin in toluene at high concentrations, especially on the blue side of the fluorescence emission spectra. To the best knowledge of the authors, this is the first detail report on the fluorescence self-quenching of porphyrins in liquid medium. This finding carries great importance in view of the widespread research on porphyrins in the fields of solar light harvesting, artificial photosynthesis, photodynamic therapy, etc. © 2013 Elsevier B.V. All rights reserved.


Sinha S.S.,Indian Association for The Cultivation of Science | Mondal D.,Indian Association for The Cultivation of Science | Bag B.C.,Siksha Bhavana | Ray D.S.,Indian Association for The Cultivation of Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

We propose a scheme for quantum Brownian motion of a particle in a fermionic bath. Based on the spin coherent-state representation of the noise operators and a canonical thermal distribution of the associated c numbers, we derive a quantum analog of generalized Langevin equation for quantum-mechanical mean position of the particle subjected to an external force field. The approach allows us to map the quantum problem on a classical setting. The quantum dispersion around the mean can be estimated order by order by a set of quantum correction equations up to a desired degree of accuracy for a given nonlinear potential. We derive a quantum diffusion equation for free particle and show that quantization, in general, enhances the mean-square displacement. Increase in temperature leads to suppression of mean-square displacement. The method is based on canonical quantization procedure and may be used for understanding diffusive transport and thermally activated processes in a fermionic bath. © 2010 The American Physical Society.


Saha S.,University of Calcutta | Roy U.,Siksha Bhavana | Sinha D.D.,University of Calcutta
MATEC Web of Conferences | Year: 2016

Vehicular ad hoc network (VANET) is considered as a sub-set of mobile ad hoc network (MANET). VANET can provide road safety by generating collision warning messages before a collision takes place, lane change assistance; can provide efficient traffic system by introducing cooperation among vehicles; and can also improves in infotainment applications like cooperative file accessing, accessing internet, viewing movies etc. It provides smart Transportation System i.e., wireless ad-hoc communication among vehicles and vehicle to roadside equipments. VANET communication broadly distinguished in two types; 1) vehicle to vehicle interaction, 2) vehicle to infrastructure interaction. The main objective of VANET is to provide safe, secure and automated traffic system. For this automated traffic techniques, there are several types of routing protocols has been developed. MANET routing protocols are not equally applicable in VANET. In the recent past Roy and his group has proposed several study in VANET transmission in [1-3]. In this study, we propose a modified AODV routing protocol in the context of VANET with the help of dqueue introduction into the RREQ header. Recently Saha et al [4] has reported the results showing the nature of modified AODV obtained from the rudimentary version of their simulation code. It is mainly based on packet delivery throughput. It shows greater in-throughput information of packet transmission compare to original AODV. Hence our proposal has less overhead and greater performance routing algorithm compared to conventional AODV. In this study, we propose and implement in the NCTUns-6.0 simulator, the neural network based modified dqueue AODV (dqAODV) routing protocol considering Power, TTL, Node distance and Payload parameter to find the optimal route from the source station (vehicle) to the destination station in VANET communications. The detail simulation techniques with result and output will be presented in the conference. © Owned by the authors, published by EDP Sciences, 2016.


Singha D.K.,se National Center for Basic science | Majee P.,Siksha Bhavana | Mondal S.K.,Siksha Bhavana | Mahata P.,se National Center for Basic science
European Journal of Inorganic Chemistry | Year: 2015

By an isomorphous substitution strategy, a three-dimensional metal-organic framework (MOF), [Y1.8Eu0.2(PDA)3(H2O)1]·2H2O (1; PDA = 1,4-phenylenediacetate), has been synthesized by solvent-assisted liquid grinding and direct heating. Dehydrated 1 (1') shows strong red photoluminescence through the antenna effect upon excitation at 240 nm. The red emissive property was used for the visual detection of nitroaromatic explosives in acetonitrile through luminescence quenching. Importantly, 1' exhibited high sensitivity towards the sensing of 2,4,6-trinitrophenol (TNP), 1,3-dinitrobenzene (DNB), 2,4-dinitrotoluene (DNT), 4-nitrotoluene (NT), and nitrobenzene (NB) at very low concentrations (0 to 20 μM). The estimated KSV (quenching constant based on linear Stern-Volmer plots) values are in the range 15.9 × 104-1.1 × 104 M-1, which are amongst the highest values known for nitroaromatic-sensing materials. For 1', sensing of TNP down to 23 ppb has been achieved. The luminescence of a three-dimensional metal-organic framework (MOF) with aromatic-ligand-sensitized Eu3+ activators is useful for sensing trace amounts of nitroaromatic explosives in solution through the quenching phenomenon. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Nandi M.,Siksha Bhavana | Uyama H.,Osaka University
Chemical Record | Year: 2014

In this article we discuss those materials that have recorded the highest adsorption capacities for the greenhouse gas CO2 under ambient conditions as well as at different temperatures and pressures. For convenience, the materials have been categorized under four categories, viz., porous carbon, metal-organic, zeolite and mesoporous silica, and porous organic frameworks. It has been found that the gas adsorption property significantly relies on several factors such as high surface area and pore volume and the presence of N-, O- and S-containing moieties. The presence of a microporous structure and strong interaction between the CO2 molecules with the framework through H-bonding or dipole-quadrupole interactions facilitates adsorption of the gas. © 2014 The Chemical Society of Japan and Wiley-VCH, Weinheim.


Ghosh D.K.,Siksha Bhavana | Mandal G.,East West University of Bangladesh | Chatterjee P.,Siksha Bhavana | Ghosh U.N.,Siksha Bhavana
IEEE Transactions on Plasma Science | Year: 2013

Cylindrical and spherical modified Korteweg-de Vries equations are derived for ion-acoustic solitary waves (IASWs) in an unmagnetized, collisionless electron-positron-ion plasma consisting of warm ion fluid and q-nonextensive distributed electrons and positrons by using standard reductive perturbation method. The effects of nonplanar geometry, nonextensivity of electrons and positrons, and other plasma parameters on nonlinear dynamics of cylindrical and spherical IASWs are studied numerically. Numerical results indicate that the amplitude of the soliton is large in spherical geometry in comparison with cylindrical geometry, and both the electron and positron nonextensive parameter has a significant effect on the structure of the nonplanar IASWs. © 1973-2012 IEEE.


Ghosh D.K.,Siksha Bhavana | Chatterjee P.,Siksha Bhavana | Das B.,Dhaltikuri K N High School
Indian Journal of Physics | Year: 2012

Dust acoustic solitary waves (DASWs) in an unmagnetized dusty plasma consisting of mobile dust particle, superthermal/non-Maxwellian electrons (represented by kappa distribution) and Boltzmann distributed ions are studied in the frame work of nonplanar geometry. Using reductive perturbation technique, the modified Korteweg-de Vries equation is derived. Numerically, the effects of spectral index kappa on the properties of DASWs in nonplanar geometry is discussed. It is found that the spectral index kappa changes the amplitude and width of the DASWs in nonplanar geometry significantly. The present investigation may be helpful in the understanding of the nonlinear propagation of waves in the pulsar's magnetosphere. © 2012 IACS.


Ghosh U.N.,Siksha Bhavana | Chatterjee P.,Siksha Bhavana
Indian Journal of Physics | Year: 2012

The head-on collision of dust acoustic solitary waves in a three-component unmagnetized dusty plasma with Boltzmann distributed electrons, nonthermal ions and negatively charged dust grains has been investigated using the extended Poincaré-Lighthill-Kuo method. The effects of the ratio of electron temperature to ion temperature on the phase shift have also been studied. It is found that the presence of nonthermal ions play a significant role on the collision of dust acoustic solitary waves. There are real implementation of present results in different regions of space, viz cometary tails, upper and lower mesosphere, Jupiter's magnetosphere, etc. © 2012 IACS.

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