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Chakraborty J.,St Pauls Cathedral Mission College | Ianelli S.,Vialedelle Science
Polyhedron | Year: 2013

Three copper(II) tridentate (NNO) Schiff base azido complexes, [Cu(L 1)(N3)] (1), [Cu2(L2) 2(μ2-1,1-N3)2] [Cu(L 2)(N3)] (2) and [Cu(L3)(N3)] (3) have been synthesized and characterized [where HL1 = 1-(N-5-methoxy-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane], HL 2 = 1-(N-ortho-hydroxyacetophenimine)-2,2-diethyl-aminoethane and HL3 = 1-(N-salicylideneimino)-2-(N,N-diethyl)-aminoethane]. The structure of complex (1) has been determined by single crystal X-ray diffraction analysis. In 1, out of four coordination sites of copper(II) ion, three are occupied by the NNO donor atoms of a tridentate Schiff base ligand, HL 1 and the remaining site is occupied by terminal nitrogen of azido moiety. All the complexes exhibit high catalytic activity in epoxidation reactions of a variety of olefins with tert-butyl-hydroperoxide in acetonitrile. The catalytic efficacy of the copper(II) complexes has been studied in different solvent media. The antimicrobial activity of the complexes and their Schiff base ligand has also been studied. © 2013 Elsevier Ltd. All rights reserved.

We present a theoretical investigation of coupling optics involving a laser diode and circular core graded index single mode fiber via a parabolic microlens on the fiber tip to predict the nature of suitable refractive index profile for the first time in connection with optimum coupling. The study is carried out in absence and presence of possible transverse and angular misalignments. By employing Gaussian field distributions for both the source and the fiber and also ABCD matrix for parabolic microlens under paraxial approximation, we formulate analytical expressions for the concerned coupling efficiencies. The investigations are performed for two different light-emitting wavelengths of 1.3 μm and 1.5 μm for such fibers with different refractive index profile exponents. Further, it is observed that out of the studied refractive index profiles, triangular index profile having the dispersion-shifted merit comes out to be the most suitable profile to couple laser diode to such abovementioned fiber for two wavelengths of practical interest. The analysis should find use in ongoing investigations for optimum launch optics for the design of parabolic microlens either directly on the circular core graded index single mode fiber tip or such fiber attached to single mode fiber to achieve long working distance. © 2016 The Optical Society of India

Mahapatra S.,St Pauls Cathedral Mission College | Das T.K.,University of Calcutta
Modern Physics Letters A | Year: 2011

Phase shifts produced by two supersymmetric partner potentials satisfy a simple relation. One expects that the phase shift can be obtained algebraically, if the potential is shape invariant. We show that this is true only for a special class of shape invariant potentials. Among known shape invariant potentials, only the Coulomb potential satisfy this requirement. The Coulomb phase shift can be obtained analytically, which agrees with the well-known standard result. © 2011 World Scientific Publishing Company.

Mahapatra S.,St Pauls Cathedral Mission College
Few-Body Systems | Year: 2012

Calculation of the low-lying resonance state of 15C is performed using a two-body model ( 14C+n) with the application of Supersymmetric Quantum Mechanics (SSQM). The effective two-body potential presents a shallow well followed by a low and wide barrier. Large spatial extension of the halo state causes loss of accuracy due to numerical difficulties in calculating low-lying resonances. Use of SSQM permits one to construct an isospectral potential with a deep well followed by a high barrier which can effectively trap the system and hence facilitates the numerical calculation of resonance states more accurately than the original shallow potential. This method gives quite accurate result for the resonance energy of the 3/4 + state of 15C. Calculated width of this state also agrees fairly well within the experimental error bar. © 2011 Springer-Verlag.

Ramaprabhu P.,University of North Carolina at Charlotte | Karkhanis V.,University of North Carolina at Charlotte | Banerjee R.,St Pauls Cathedral Mission College | Varshochi H.,University of North Carolina at Charlotte | And 2 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

From nonlinear models and direct numerical simulations we report on several findings of relevance to the single-mode Rayleigh-Taylor (RT) instability driven by time-varying acceleration histories. The incompressible, direct numerical simulations (DNSs) were performed in two (2D) and three dimensions (3D), and at a range of density ratios of the fluid combinations (characterized by the Atwood number). We investigated several acceleration histories, including acceleration profiles of the general form g(t)∼tn, with n≥0 and acceleration histories reminiscent of the linear electric motor experiments. For the 2D flow, results from numerical simulations compare well with a 2D potential flow model and solutions to a drag-buoyancy model reported as part of this work. When the simulations are extended to three dimensions, bubble and spike growth rates are in agreement with the so-called level 2 and level 3 models of Mikaelian [K. O. Mikaelian, Phys. Rev. E 79, 065303(R) (2009)10.1103/PhysRevE.79.065303], and with corresponding 3D drag-buoyancy model solutions derived in this article. Our generalization of the RT problem to study variable g(t) affords us the opportunity to investigate the appropriate scaling for bubble and spike amplitudes under these conditions. We consider two candidates, the displacement Z and width s2, but find the appropriate scaling is dependent on the density ratios between the fluids - at low density ratios, bubble and spike amplitudes are explained by both s2 and Z, while at large density differences the displacement collapses the spike data. Finally, for all the acceleration profiles studied here, spikes enter a free-fall regime at lower Atwood numbers than predicted by all the models. © 2016 American Physical Society.

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