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Banerjee R.,Satyendra Nath Bose National Center for Basic science | Gangopadhyay S.,West Bengal State University
General Relativity and Gravitation | Year: 2011

We calculate the Komar energy E for a noncommutative inspired Schwarzschild black hole. A deformation from the conventional identity E = 2STH is found in the next to leading order computation in the noncommutative parameter θ (i.e. √θe-M2/θ)) which is also consistent with the fact that the area law now breaks down. This deformation yields a nonvanishing Komar energy at the extremal point TH = 0 of these black holes. We then work out the Smarr formula, clearly elaborating the differences from the standard result M = 2STH, where the mass (M) of the black hole is identified with the asymptotic limit of the Komar energy. Similar conclusions are also shown to hold for a deSitter-Schwarzschild geometry. © 2011 Springer Science+Business Media, LLC. Source


Pal S.,Satyendra Nath Bose National Center for Basic science
Computational Materials Science | Year: 2013

Using ab initio calculation, we investigate systematically the structural and electronic properties of Ni2Nb1+xSn1-x (x = 0, 0.25, 0.50). Here, projector augmented wave approach (PAW) implemented in the Vienna ab initio simulation package (VASP) within generalized gradient approximation (GGA) for the exchange-correlation functional has been used. In this article, it is reported that though Ni2NbSn and Ni 2Nb1.25Sn0.75 have no structural transformation, Ni2Nb1.5Sn0.5 can transform to tetragonal structure from cubic L21 phase. The cubic lattice parameter decreases with Nb doping at Sn sites in off-stoichiometric alloys. The alloys are in paramagnetic phase in all the structures. The hybridization between Ni and Nb 3d states triggers the tetragonal distortion. Due to Nb doping in cubic L21 phase, there is a significant change in total density of states (DOSs) at Fermi energy (EF) (N(EF)). N(E F) increases with increasing Nb doping. But, N(EF) decreases during structural transformation of Ni2Nb 1.5Sn0.5. The superconducting critical temperature (T C) also changes with Nb doping in cubic phase and tetragonal distortion because TC very much depends on N(EF).© 2013 Elsevier B.V. All rights reserved. Source


Chakraborty A.,Satyendra Nath Bose National Center for Basic science | Manna S.S.,Satyendra Nath Bose National Center for Basic science | Manna S.S.,Max Planck Institute For Physik Komplexer Systeme
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

Using a model of wealth distribution where traders are characterized by quenched random saving propensities and trade among themselves by bipartite transactions, we mimic the enhanced rates of trading of the rich by introducing the preferential selection rule using a pair of continuously tunable parameters. The bipartite trading defines a growing trade network of traders linked by their mutual trade relationships. With the preferential selection rule this network appears to be highly heterogeneous characterized by the scale-free nodal degree and the link weight distributions and presents signatures of nontrivial strength-degree correlations. With detailed numerical simulations and using finite-size scaling analysis we present evidence that the associated critical exponents are continuous functions of the tuning parameters. However the wealth distribution has been observed to follow the well-known Pareto law robustly for all positive values of the tuning parameters. © 2010 The American Physical Society. Source


Mohanty J.S.,Indian Institute of Technology Madras | Xavier P.L.,Indian Institute of Technology Madras | Chaudhari K.,Indian Institute of Technology Madras | Bootharaju M.S.,Indian Institute of Technology Madras | And 3 more authors.
Nanoscale | Year: 2012

We report the synthesis of luminescent AuAg alloy quantum clusters (QCs) in bovine serum albumin (BSA), for the first time, with experimentally determined atomic composition. Mixing of the as-synthesized protein-protected Au and Ag clusters resulted in the formation of alloy AuAg clusters within the BSA. Mass spectrometric analysis of the product of a 1:1 molar ratio reaction mixture of Au QC@BSA and Ag QC@BSA suggested that the alloy clusters could be Au 38-xAg x@BSA. Further analyses by standard techniques revealed that the alloy cluster core of ∼1.2 nm diameter is composed of nearly zero valent Au and Ag atoms that exhibit distinctly different steady state and time resolved excited state luminescence profiles compared to the parent clusters. Tuning of the alloy composition was achieved by varying the molar ratio of the parent species in the reaction mixture and compositional changes were observed by mass spectrometry. In another approach, mixing of Au 3+ ions with the as-synthesized Ag QC@BSA also resulted in the formation of alloy clusters through galvanic exchange reactions. We believe that alloy clusters with the combined properties of the constituents in versatile protein templates would have potential applications in the future. The work presents interesting aspects of the reactivity of the protein-protected clusters. This journal is © 2012 The Royal Society of Chemistry. Source


Baksi A.,Indian Institute of Technology Madras | Xavier P.L.,Indian Institute of Technology Madras | Chaudhari K.,Indian Institute of Technology Madras | Goswami N.,Satyendra Nath Bose National Center for Basic science | And 2 more authors.
Nanoscale | Year: 2013

We report the evolution and confinement of atomically precise and luminescent gold clusters in a small protein, lysozyme (Lyz) using detailed mass spectrometric (MS) and other spectroscopic investigations. A maximum of 12 Au0 species could be bound to a single Lyz molecule irrespective of the molar ratio of Lyz : Au3+ used for cluster growth. The cluster-encapsulated protein also forms aggregates similar to the parent protein. Time dependent studies reveal the emergence of free protein and the redistribution of detached Au atoms, at specific Lyz to Au3+ molar ratios, as a function of incubation time, proposing inter-protein metal ion transfer. The results are in agreement with the studies of inter-protein metal transfer during cluster growth in similar systems. We believe that this study provides new insights into the growth of clusters in smaller proteins. © 2013 The Royal Society of Chemistry. Source

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