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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.

Aich S.,Satyendra Nath Bose National Center for Basic science | Mehta A.,Satyendra Nath Bose National Center for Basic science
European Physical Journal: Special Topics | Year: 2014

We examine the effects of preferential attachment on a model of competing clusters. In the original model, cluster masses grow at the expense of their neighbours; on a lattice, this is known to result in the asymptotic survival and indefinite growth of clusters which are isolated from each other. The presence of preferential attachment results in an inhomogeneous topology, where hubs monopolise the connections, while most other nodes are sparsely connected. Interestingly, this results in the protection of the less massive clusters from annihilation, to which the hubs are doomed. © 2014, EDP Sciences and Springer.

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.

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.

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.

Manna S.S.,Satyendra Nath Bose National Center for Basic science
Physica A: Statistical Mechanics and its Applications | Year: 2012

The growth of the average size 〈 smax〉 of the largest component at the percolation threshold pc(N) on a graph of size N has been defined as 〈 smax( pc(N),N) 〉∼ Nχ. Here we argue that the precise value of the 'growth exponent' χ indicates the nature of percolation transition; χ<1 or χ=1 determines if the transition is continuous or discontinuous. We show that a related exponent η=1-χ which describes how the average maximal jump sizes in the Order Parameter decays on increasing the system size, is the single exponent that describes the finite-size scaling of a number of distributions related to the fastest growth of the Order Parameter in these problems. Excellent quality scaling analysis are presented for the two single peak distributions corresponding to the Order Parameters at the two ends of the maximal jump, the bimodal distribution constructed by the weighted average of these distributions and for the distribution of the maximal jump in the Order Parameter. © 2012 Elsevier B.V. All rights reserved.

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.

Xavier P.L.,Indian Institute of Technology Madras | Chaudhari K.,Indian Institute of Technology Madras | Verma P.K.,Satyendra Nath Bose National Center for Basic science | Pal S.K.,Satyendra Nath Bose National Center for Basic science | Pradeep T.,Indian Institute of Technology Madras
Nanoscale | Year: 2010

We report the synthesis of highly luminescent, water soluble quantum clusters (QCs) of gold, which are stabilized by an iron binding transferrin family protein, lactoferrin (Lf). The synthesized Au QC@Lf clusters were characterized using UV-Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), photoluminescence (PL), matrix assisted laser desorption ionization mass spectrometry (MALDI-MS), FTIR spectroscopy and circular dichroism (CD) spectroscopy along with picosecond-resolved lifetime measurements. Detailed investigations with FTIR and CD spectroscopy have revealed changes in the secondary structure of the protein in the cluster. We have also studied Förster resonance energy transfer (FRET) occurring between the protein and the cluster. The ability of the clusters to sense cupric ions selectively at ppm concentrations was tested. The stability of clusters in widely varying pH conditions and their continued luminescence make it feasible for them to be used for intracellular imaging and molecular delivery, particularly in view of Lf protection. © 2010 The Royal Society of Chemistry.

Roy C.,Satyendra Nath Bose National Center for Basic science | Kundu S.,Satyendra Nath Bose National Center for Basic science | Manna S.S.,Satyendra Nath Bose National Center for Basic science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We present a study of the fiber bundle model using equal load-sharing dynamics where the breaking thresholds of the fibers are drawn randomly from a power-law distribution of the form p(b)∼b-1 in the range 10-β to 10β. Tuning the value of β continuously over a wide range, the critical behavior of the fiber bundle has been studied both analytically as well as numerically. Our results are: (i) The critical load σc(β,N) for the bundle of size N approaches its asymptotic value σc(β) as σc(β,N)=σc(β)+AN-1/ν(β), where σc(β) has been obtained analytically as σc(β)=10β/(2βeln10) for β≥βu=1/(2ln10), and for β<βu the weakest fiber failure leads to the catastrophic breakdown of the entire fiber bundle, similar to brittle materials, leading to σc(β)=10-β; (ii) the fraction of broken fibers right before the complete breakdown of the bundle has the form 1-1/(2βln10); (iii) the distribution D(Δ) of the avalanches of size Δ follows a power-law D(Δ)∼Δ-ξ with ξ=5/2 for Δ?Δc(β) and ξ=3/2 for Δ?Δc(β), where the crossover avalanche size Δc(β)=2/(1-e10-2β)2. © 2015 American Physical Society.

Agency: European Commission | Branch: FP7 | Program: CSA-CA | Phase: NMP-2008-2.6-3 | Award Amount: 872.26K | Year: 2009

In a globalized world energy is a decisive factor for the further development and economic and social well being of the nations and stability in the different world regions. Materials science and research has in the past significantly contributed to solving issues in sustainable energy technologies. To bring about advancement and improvements in energy technologies and to address sustainability, research in nano-materials is expected to contribute significantly to solutions in a highly competitive and increasingly globalize world. Such research will inevitably have to be coordinated at European level but also internationally. In Europe, materials researchers cooperate increasingly in EU funded projects and bilaterally with non-European countries. The EU has concluded S&T agreements and implementation arrangements with India. It foresees the coordination and the execution of joint projects. This proposal intends to address the strategic assessment including synergy analysis of nano-materials research needs in the EU and India. It will establish and communicate to DG RTD and DST the mutual interests and the topics for future coordinated calls to enable the decision & policy makers and the funding bodies to make better informed decisions and to better select the implementation mechanisms and instruments. Beside the assessment, the proposal also addresses the dissemination of the nano-materials research acquis in the field by organization of events. Finally, it will bring together researchers for future research collaboration, to exchange ideas for joint projects and to inform each other on their core competencies & expertise. The project aims at the generation and enhancement of knowledge in materials science and research especially nano-materials applied to sustainable energy technologies. It also aims to increase the deployment of these materials in the technologies in both regions.

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