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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.

Ghosh R.,Bhairab Ganguly College | Debnath U.,Bengal Engineering and Science University
International Journal of Theoretical Physics | Year: 2012

This work is motivated by the work of Kim et al. (Mod. Phys. Lett. A 23:3049, 2008), which considered the equation of state parameter for the new agegraphic dark energy based on generalized uncertainty principle coexisting with dark matter without interaction. In this work, we have considered the same dark energy interacting with dark matter in emergent, intermediate and logamediate scenarios of the universe. Also, we have investigated the statefinder, kerk and lerk parameters in all three scenarios under this interaction. The energy density and pressure for the new agegraphic dark energy based on generalized uncertainty principle have been calculated and their behaviors have been investigated. The evolution of the equation of state parameter has been analyzed in the interacting and non-interacting situations in all the three scenarios. The graphical analysis shows that the dark energy behaves like quintessence era for logamediate expansion and phantom era for emergent and intermediate expansions of the universe. © 2011 Springer Science+Business Media, LLC.

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.

Bhadra D.,Bhairab Ganguly College | Bhadra D.,Indian Association for The Cultivation of Science | Masud M.G.,Indian Association for The Cultivation of Science | De S.K.,Indian Association for The Cultivation of Science | And 2 more authors.
Applied Physics Letters | Year: 2013

A two-phase multifunctional La2CoMnO6 (LCMO)/Poly-vinylidene fluoride 0-3 flexible nanocomposite (NCOMP) thick films have been prepared. Interestingly, this NCOMP shows linear increase of magnetoelectric voltage coefficient (MVC) with applied dc magnetic-bias fields up to 5 kOe, exhibiting no sign of hysteresis. For the typical LCMO concentration, fLCMO = 0.15, the maximum MVC measured is 1.45 mV cm-1 Oe-1 (using 50 kHz resonant signal). This low dielectric loss (∼0.12) NCOMP also showed intriguing high magnetodielectric effect (∼10%) around the ferromagnetic transition temperature (Tc ∼ 230 K) with minimal leakage current. Such results make the present nanocomposite significantly important for the development of magnetic field tuned electronic devices. © 2013 American Institute of Physics.

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.

Bhadra D.,Bhairab Ganguly College | Bhadra D.,Indian Association for The Cultivation of Science | Masud M.G.,Indian Association for The Cultivation of Science | De S.K.,Indian Association for The Cultivation of Science | Chaudhuri B.K.,Indian Association for The Cultivation of Science
Journal of Physics D: Applied Physics | Year: 2012

Flexible magnetoelectric 0-3 composite films formed with high dielectric (ε r10 4) CuO microparticles in a polyvinylidene fluoride (PVDF) polymer matrix showed multifunctional properties. The films prepared by the hot-moulding technique exhibit low-loss high relative permittivity (ε eff10 3) with good ferroelectric behaviour (with P-E loop) at the percolation threshold (f CuO=f c0.25). Dielectric, ferroelectric, magnetic and direct magnetoelectric properties of the composites depend strongly on the CuO filler concentration (f CuO). Interesting low field magnetoelectric response appears with about 5% decrease in ferroelectric polarization in the insulating composite (f CuO=0.20) along with 7.5% increase in the magnetodielectric coefficient under a magnetic field of 6kG in the semiconducting percolative composite at room temperature. At this field, a maximum magnetoelectric voltage coefficient of 1.45mVcm 1Oe 1 was obtained. Even though the CuO sample is paramagnetic at ambient temperature, this typical composite film exhibits weakly ferromagnetic (with M-H loop) behaviour indicating multiferroic character. Our result represents an important step towards practical device applications using the high dielectric and magnetoelectric effects. © 2012 IOP Publishing Ltd.

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.

Ghosh R.,Bhairab Ganguly College | Debnath U.,Bengal Engineering and Science University
European Physical Journal Plus | Year: 2014

We have discussed the correspondence of the well-accepted f(G) gravity theory with two dark energy models: (m, n)-type holographic dark energy ((m, n)-type HDE) and entropy-corrected (m, n)-type holographic dark energy. For this purpose, we have considered the power law form of the scale factor a(t) = a0tp, p > 1. The reconstructed f(G) in these models has been found and the models in both cases are found to be realistic. We have also discussed the classical stability issues in both models. The (m, n)-type HDE and its entropy-corrected version are more stable than the ordinary HDE model. © 2014, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

Mukherjee T.,Bhairab Ganguly College | Mukherjee M.,Saha Institute of Nuclear Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

We study the positron-nitrogen-molecule scattering process under the rovibrational coupling method to include the effect of rotational and vibrational motion of the nuclei dynamically during the scattering process. Here we compute the angle integrated elastic and (state-to-state) rotational excitation, elastic and (state-to-state) vibrational (summed over rotational) excitation, and total (summed over rotational and vibrational) cross sections for the incident positron energy between 0.0 and 10 eV. However, in present paper we concentrate our discussion on the results in the lower-energy region, especially below 3.0 eV. To calculate the cross sections we use the model correlation polarization potential to include the distortion effect of the target electronic state in the presence of the positron. The calculated total cross sections are compared with the theoretical calculations and experimental results. The present theoretical results agree quite well with the recent theoretical and measured values. The vibrational and rotational elastic and excitation cross sections are also compared with the existing theoretical results. The state-to-state potential coupling and dynamical coupling effects on different cross sections are studied. © 2015 American Physical Society.

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