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Kolkata, India

Mukherjee T.,Bhairab Ganguly College | Dutta D.,Bhabha Atomic Research Center
Radiation Physics and Chemistry | Year: 2010

In the bubble model of positronium annihilation in liquids, the inward contractile force on the bubble surface is described through classical surface tension of the liquids. In the present calculation, we adopted a simple quantum mechanical approach to describe the bubble surface energy in terms of the motion of a representative quasi-free electron outside the bubble. The bubble parameters (radius, potential, etc.) for different liquids obtained using the prescribed model are consistent with the results obtained using classical surface tension. © 2010 Elsevier Ltd.

Jana A.,University of Calcutta | Koner R.,Bhairab Ganguly College | Weyhermueller T.,Max Planck Institute for Chemistry | Lemoine P.,University of Paris Descartes | And 2 more authors.
Inorganica Chimica Acta | Year: 2011

The present work reports syntheses, crystal structures and variable-temperature magnetic properties of three copper(II)-iron(II/III) compounds [{CuIIL1}{FeIIIL1(H 2O)2}](ClO4) (1), [{CuIIL 1FeII(H2O)3}{CuIIL 1}2](ClO4)2 (2) and [{Cu IIL2FeII(H2O)3}{Cu IIL2}2](ClO4)2· H2O·CH3COCH3 (3), where H 2L1 = N,N′-ethylenebis(3-ethoxysalicylaldimine) and H2L2 = N,N′-o-phenylenebis(3-ethoxysalicylaldimine). Compounds 2 and 3 are tetrametallic [2 × 1 + 1 × 2] cocrystals of one diphenoxo-bridged dinuclear CuIIFeII and two mononuclear CuII moieties, while compound 1 is a dimetallic [1 × 1 + 1 × 1] cocrystal of one mononuclear FeIII and one mononuclear CuII moieties. The overall topology of 1 is one-dimensional. Tetrametallic (in 2 and 3) and one-dimensional (in 1) self-assemblies are generated due to weak noncovalent interactions. Variable-temperature magnetic susceptibility measurements reveal that iron(II) or iron(III) centers in 1-3 remain in high-spin state. Compounds 2 and 3 exhibit weak antiferromagnetic interaction; the J values in the dinuclear core are -22.5 and -13.7 cm-1, respectively, compound 1 exhibits very weak antiferromagnetic interaction (J = -0.25 cm-1) propagated through the weak noncovalent bonds. © 2011 Elsevier B.V.

Ghosh R.,Bhairab Ganguly College
Astrophysics and Space Science | Year: 2012

This work investigates the validity of the generalized second law of thermodynamics in modified f(R) Horava-Lifshitz gravity proposed by Chaichian et al. (Class. Quantum Grav. 27: 185021, 2010), which is invariant under foliation-preserving diffeomorphisms. It has been observed that the equation of state parameter behaves like quintessence (w>-1). We study the thermodynamics of the apparent, event and particle horizons in this modified gravity. We observe that under this gravity, the time derivative of total entropy stays at positive level and hence the generalized second law is validated. © 2012 Springer Science+Business Media B.V.

Ghosh R.,Bhairab Ganguly College | Pasqua A.,University of Trieste
European Physical Journal Plus | Year: 2013

The present work is motivated by the study of the paper K. Karami, A. Abdolmaleki, J. Cosmol. Astropart. Phys. 04, 007 (2012), where the generalized second law (GSL) of thermodynamics has been investigated for a flat FRW universe for three viable models of f(T) gravity. We have here considered a non-flat universe and, accordingly, studied the behaviors of the equation-of-state (EoS) parameter ω and of the deceleration parameter q. Subsequently, using the first law of thermodynamics, we derived the expressions for the time derivative of the total entropy of a universe enveloped by apparent horizon. In the next phase, with the choice of scale factor a(t) pertaining to an emergent universe, we have investigated the sign of the time derivatives of total entropy for the models of f(T) gravity considered. © 2013 Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

Basu A.K.,University of the West Indies | Basu M.,Bhairab Ganguly College | Adesiyun A.A.,University of the West Indies
Acarologia | Year: 2012

In this review article, the authors present an overview on ticks which are found on humans and animals in Trinidad and Tobago. Hitherto, 896 valid species of ticks are reported from throughout the world, but so far only 23 tick species belonging to seven genera have been recorded in Trinidad and Tobago. The growing significance of ticks in medical and veterinary fields emphasizes the need for further studies on the ecology of ticks and the epidemiology of tick-borne diseases. © Basu A.K. et al.

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