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Kolkata, India

Chandra Barui N.,Surendranath College
Quaternary International | Year: 2011

Fresh sub-surface peat samples were collected and palynologically investigated from two different locations at Rajarhat area, N-24Paraganas, 20 km northeast of Kolkata where work was done in connection with building construction. The pollen analytical investigation of the collected peat samples reflected the existence of a large number of core mangroves and some fresh water elements and ferns from a peat layer located at the depth of about 2.2 m-3.5 m below the surface. The present investigation reveals the age of the peat layers ranging from 2665 to 6530 BP, confirming the Holocene age of the samples. The dominant pollen grains recorded from the samples were Heritiera, Excoecaria, Avicennia, Bruguiera, Barringtonia, Rhizophora, Sonneratia, Suaeda, Phoenix paludosa, Nipa and a large number of fern spores including Acrostichum and grass pollen, reflecting a diversity of mangrove vegetation. The variability of the vegetation in the peat from bottom to top shows the change of monsoon months during the Holocene in the BengalBasin. The swampy halophytic vegetation of the Holocene is to some extent comparable to the present day vegetation of the Sunderbans. © 2010 Elsevier Ltd and INQUA.

Bose A.,Vidyasagar University | Gangopadhyay S.,Surendranath College | Saha S.C.,Vidyasagar University
Journal of Optical Communications | Year: 2012

Employing the simple series expression based on Chebyshev technique, we predict the fundamental modal field inside the core as well as cladding in case of dispersion-shifted trapezoidal and dispersion-flattened graded and step W fibers. This formalism also estimates cladding decay parameters (W) of the said fibers. The analysis involves use of a linear relationship of the ratio of first and zero order modified Bessel functions in the form K1(W)/K 0(W) with 1/W over a wide and practical range of W values appropriate for guidance of only fundamental mode in such fibers. The present method prescribes analytical expressions for the concerned propagation characteristics and these are executable with little computations. Our results are found to match excellently with the available exact results.

Bagchi B.,University of Calcutta | Choudhury A.G.,Surendranath College | Guha P.,Sn Bose National Center For Basic Science
Modern Physics Letters A | Year: 2013

We explore the Jacobi last multiplier (JLM) as a means for deriving the Lagrangian of a fourth-order differential equation. In particular, we consider the classical Pais-Uhlenbeck problem and write down the accompanying Hamiltonian. We then compare such an expression with our alternative derivation of the Hamiltonian that makes use of the Ostrogradski's method and show how a mapping from the one to the other is achievable by variable transformations. © 2013 World Scientific Publishing Company.

Choudhury A.G.,Surendranath College | Guha P.,Max Planck Institute for Mathematics in the Sciences | Guha P.,Sn Bose National Center For Basic Science
Journal of Physics A: Mathematical and Theoretical | Year: 2010

We consider a large class of polynomial planar differential equations proposed by Cherkas (1976 Differensial'nye Uravneniya 12 201-6), and show that these systems admit a Lagrangian description via the Jacobi last multiplier (JLM). It is shown how the potential term can be mapped either to a linear harmonic oscillator potential or into an isotonic potential for specific values of the coefficients of the polynomials. This enables the identification of the specific cases of isochronous motion without making use of the computational procedure suggested by Hill et al (2007 Nonlinear Anal.: Theor. Methods Appl. 67 52-69), based on the Pleshkan algorithm. Finally, we obtain a Lagrangian description and perform a similar analysis for a cubic system to illustrate the applicability of this procedure based on Jacobi's last multiplier. © 2010 IOP Publishing Ltd.

Guha P.,Sn Bose National Center For Basic Science | Choudhury A.G.,Surendranath College
Pramana - Journal of Physics | Year: 2011

We employ Jacobi's last multiplier (JLM) to study planar differential systems. In particular, we examine its role in the transformation of the temporal variable for a system of ODEs originally analysed by Calogero-Leyvraz in course of their identification of isochronous systems. We also show that JLM simplifies to a great extent the proofs of isochronicity for the Liénard-type equations. © Indian Academy of Sciences.

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