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Deb S.,University of Calcutta | Patra H.K.,University of Calcutta | Lahiri P.,University of Calcutta | Dasgupta A.K.,University of Calcutta | And 2 more authors.
Nanomedicine: Nanotechnology, Biology, and Medicine

The nanoparticle (NP) response of platelets is shown to be critically dependent on extent of preactivation of platelets by an agonist like ADP. A transition from de-aggregatory to aggregatory state is triggered in the presence of gold NPs (AuNP) only in such critical conditions. Adhered and suspended platelets respond differentially to NPs. Preactivation in the adhered state induced by shear force explains such observation. The NP effect is associated with enhanced release reaction, tyrosine phosphorylation and CD62P expression level. Unlike cancer cells, whose response is maximal when NP size is optimal (within the range 50 - 70 nm), the platelet response monotonically increases with reduction of the AuNP size. The uptake study, using quenching of quinacrine hydrochloride fluorescence by AuNP, indicates that accumulation 18 nm AuNP is several-fold higher than the 68 nm AuNP. It is further shown that AuNP response can provide a simple measure for thrombotic risk associated with nano-drugs. © 2011 Elsevier Inc. Source

Toschi A.,Vienna University of Technology | Hansmann P.,Vienna University of Technology | Hansmann P.,Max Planck Institute for Solid State Research | Sangiovanni G.,Vienna University of Technology | And 3 more authors.
Journal of Physics: Conference Series

Significant progress in the theoretical description of Mott-Hubbard metal-to-insulator transitions has been made in the last years, especially thanks to the LDA+DMFT approach (local density approximation + dynamical mean field theory). Obviously the main attention has been focused on the transition itself, as, for example, in the textbook case of the Cr-doped V 2O3. As we discuss here, however, also the study of the insulating phase, characterized by the opening of a visible Mott-Hubbard gap in the spectral functions is far from being trivial: Strong-correlation effects make this phase strongly sensitive to small changes of external parameters, much more than one would expect for an insulator. In this situation, requiring a full consistency of the theoretical calculations with data from different spectroscopies may provide the most precise estimate for the local Coulomb interaction U in the LDA+DMFT approach. © 2010 IOP Publishing Ltd. Source

Chatterjee S.,Chennai Mathematical Institute | Lahiri A.,Snbose National Center For Basic Science | Sengupta A.N.,Louisiana State University
Journal of Geometry and Physics

We develop a new differential geometric structure using category theoretic tools that provides a powerful framework for studying bundles over path spaces. We study a type of connection forms, given by Chen integrals, over path spaces by placing such forms within a category-theoretic framework of principal bundles and connections. A new notion of 'decorated' principal bundles is introduced, along with parallel transport for such bundles, and specific examples in the context of path spaces are developed. © 2013. Source

Devi Y.C.,Snbose National Center For Basic Science | Ghosh K.J.B.,Snbose National Center For Basic Science | Chakraborty B.,Snbose National Center For Basic Science | Scholtz F.G.,Stellenbosch University | Scholtz F.G.,National Institute for Theoretical Physics NITheP
Journal of Physics A: Mathematical and Theoretical

Beginning with a review of the completely operatorial formulation of noncommutative quantum mechanics in 2D and 3D spaces using Hilbert- Schmidt operators, we analyze the issue of maximal localization, both in position and phase space, of a single particle by using symplectic invariant formulation of uncertainty relation through the computation of the variance matrix. We then extend the analysis to multi-particles and carry out second quantization by introducing basis independent field operators. This then facilitates the computation of thermal correlation functions and the associated effective statistical potential in two- and three-dimensional non-commutative space using an operator formulation that makes no reference to a star product. The corresponding results for the Moyal and Voros star products are then easily obtained by taking the corresponding overlap with Moyal and Voros bases. The forms of the correlation function and the effective potential are found to be the same, except that in the Voros case the thermal wave length undergoes a non-commutative deformation, ensuring that it has a lower bound of the order of √θ. It is shown that in a suitable basis (called here quasi-commutative) in the multi-particle sector the thermal correlation function coincides with the commutative result both in the Moyal and Voros cases, with an appropriate non-commutative correction to the thermal length in the Voros case, and that the Pauli principle is restored. © 2014 IOP Publishing Ltd. Source

Saha-Dasgupta T.,Snbose National Center For Basic Science
Journal of Superconductivity and Novel Magnetism

Double-perovskite compounds with general formula ABB′O6, have attracted a lot of attention in recent years due to a variety of properties exhibited by them. In this paper, we will review our recent study on a number of double-perovskite compounds, namely La-doped Sr2FeMoO6, Cr-based family of compounds, Sr2CrXO6 (X=W, Re, Os), characterized with spectacularly high ferromagnetic transition temperatures and the magneto-capacitive compound, La2NiMnO6, We will discuss the signature of hybridization-driven antiferromagnetism in La-doped Sr2FeMoO6, while the parent compound, Sr2FeMoO6, is a half-metallic ferromagnet. The magnetism in the 3d-5d double perovskite Sr2CrXO6 (X=W, Re, Os) is found to be driven by the interplay of the hybridization-driven mechanism and the superexchange, which resulted into progressive increase of Tc as one moves from W to Re to Os at the B′ site. Our work, in the context of La2NiMnO6, identifies its superexchange-driven microscopic origin being responsible for the near room-temperature insulating ferromagnetic behavior. © 2012 Springer Science+Business Media New York. Source

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