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Maiti S.K.,Saha Institute of Nuclear Physics | Maiti S.K.,Narasinha Dutt College | Dey M.,Saha Institute of Nuclear Physics | Sil S.,Visva Bharati Santiniketan | And 2 more authors.
EPL | Year: 2011

Electronic transport in a one-dimensional mesoscopic ring threaded by a magnetic flux is studied in the presence of Rashba and Dresselhaus spin-orbit interactions. A completely analytical technique within a tight-binding formalism unveils the spin-split bands in the presence of the spin-orbit interactions and leads to a method of determining the strength of the Dresselhaus interaction. In addition to this, the persistent currents for ordered and disordered rings have been investigated numerically. It is observed that the presence of the spin-orbit interaction, in general, leads to an enhanced amplitude of the persistent current. Numerical results corroborate the respective analytical findings. © 2011 EPLA.

Alam M.S.,Jamia Millia Islamia University | Mukherjee D.,Australian National University | Mondal A.S.,Visva Bharati Santiniketan | Dewangan G.C.,Inter-University Center for Astronomy and Astrophysics | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

We present spectral and energy-dependent timing characteristics of the hard X-ray transient IGR J17497-2821 based on XMM-Newton observations performed five and nine days after its outburst on 2006 September 17. We find that the source spectra can be well described by a hard (γ ~ 1.50) power law and a weak multicolour disc blackbody with inner disc temperature kTin ~ 0.2 ke V. A broad iron Ka line with FWHM ~ 27 000 km s-1, consistent with that arising from an accretion disc truncated at large radius, was also detected. The power density spectra of IGR J17497-2821, derived from the high-resolution (30 μs) timing-mode XMM-Newton observations, are characterized by broad-band noise components that are well modelled by three Lorentzians. The shallow power-law slope, low disc luminosity and the shape of the broad-band power density spectrum indicate that the source was in the hard state. The rms variability in the softer energy bands (0.3-2 keV) found to be ~1.3 times that in 2-5 and 5-10 keV energy bands. We also present the energy-dependent timing analysis of the RXTE/PCA data, where we find that at higher energies, the rms variability increases with energy. © 2015 The Authors.

Mahali K.,Visva Bharati Santiniketan | Roy S.,Shibpur Dinobundhoo Institution | Dolui B.K.,Visva Bharati Santiniketan
Journal of Solution Chemistry | Year: 2013

Standard transfer Gibbs energies (Δ Gt 0 (i)) (Δ G t 0 (i)) and entropies (Δ St 0 (i)) (Δ S t 0 (i)) of transfer of the homologous α-amino acids: glycine, dl-alanine, dl-α-amino butyric acid and dl-nor-valine (nor-val) from protic ethylene glycol (EG) to proton/cation-phobic dipolar aprotic acetonitrile (ACN) mixed solvents with 0, 20, 40, 60, 80 and 100 wt% ACN compositions have been determined at 25 C. For this purpose solubilities of the α-amino acids were measured by "formol titrimetry" at 15, 20, 25, 30 and 35 C. The chemical components of these Gibbs energies (Δ Gtch 0 (i)) (Δ G t, ch 0 (i)) and entropies (TΔ S tch 0 (i)) (T Δ S t, ch 0 (i)) of the homologous α-amino acids have been computed by subtracting the cavity effects and dipole-dipole interaction effects. The chemical contributions of transfer energetics of these homologous α-amino acids are determined by different types of interactions. The decreased acidity, basicity, H-bonding capacity, solvophilic solvation and solvophobic solvation and increased dispersion and soft-soft interaction of ethylene glycol and acetonitrile mixtures, as compared to EG, are the guiding factors. The characteristics of the solvation thermodynamics of α-amino acids in protic EG and proton/cation-philic dipolar aprotic DMF mixed solvent systems studied earlier are also discussed here for comparison. © 2013 Springer Science+Business Media New York.

Das A.,Jadavpur University | Choudhury S.R.,Jadavpur University | Choudhury S.R.,Geological Survey of India | Estarellas C.,University of the Balearic Islands | And 6 more authors.
CrystEngComm | Year: 2011

Two nickel(ii) malonate coordination compounds, namely (C5H 7N2)4[Ni(C3H2O 4)2(H2O)2](ClO4) 2 (1) and (C5H7N2) 4[Ni(C3H2O4)2(H 2O)2](PF6)2 (2) [where C 5H7N2 = protonated 2-aminopyridine, C 3H4O4 = malonic acid, ClO4 - = perchlorate, PF6 - = hexafluoridophosphate], have been synthesized from purely aqueous media, and their single-crystal structures have been determined by X-ray diffraction. As anticipated, various weak forces, i.e. lone pair-π, π-π and anion-π interactions, play a key role in stabilizing the self-assembly process observed for both compounds. Intricate combinations of lone pair-π, π-π and anion-π interactions of the type lone pair-π/π-π/π-anion-π/π-lone pair and lone pair-π/π-π/π-anion are observed that are fully described, including by computational methods. The theoretical calculations allow estimating the strength of these π contacts. © The Royal Society of Chemistry 2011.

Chakrabarty K.,Visva Bharati Santiniketan | Basak A.,Visva Bharati Santiniketan | Ghosh A.,Visva Bharati Santiniketan | Das G.K.,Visva Bharati Santiniketan
Journal of Theoretical and Computational Chemistry | Year: 2016

ONIOM studies were performed on the transition structure (TS) of organocatalytic direct aldol reaction by using ionic liquid supported benzoic acid (ILS-PhCO2H) as an additive. Results obtained from this computation suggest direct involvement of ILS-PhCO2H in the TS as a proton donor. It has also come out from the present study that, the counter ion of the ILS-acid additive may also play significant role to maintain the proper TS geometry by holding the organocatalyst and the acid additive close together during the course of reaction. © 2016 World Scientific Publishing Company.

Adhikari H.,Visva Bharati Santiniketan
International Journal of Gerontology | Year: 2011

Background: In this globalized world, societal change has impacted on family structure and the roles and relationships of its family members. In recent times extreme competitiveness amongst family members has given rise to a new structure known as the 'super trader' family rather than the traditional nuclear, joint or extended family. Method: One hundred people over 60 years old from rural and urban areas at a ratio 1: 1 through simple purposive random sampling have been studied to examine the current social situation of the elderly. The study was concentrated on the social, educational, occupational and marital background of the elderly people to assess their living situation. Result: The elderly living in urban or rural areas are facing an unhealthy, lonely and unhappy existence. Often they are accommodated in their families, but are mostly separated from the younger family members. They may be psychologically ill and unhappy because their position in the family is not respected and is undervalued. They are often seen as the structural head, but are non-functional in terms of participation in power and decision-making process in the family. Conclusion: In order to protect the elderly and their lifelong experiences it is important that they are respected and their value is recognized by the younger members of the family. Copyright © 2011, Taiwan Society of Geriatric Emergency & Critical Care Medicine. Published by Elsevier. Taiwan LLC. All rights reserved.

PubMed | Visva Bharati Santiniketan and University of Hyderabad
Type: | Journal: Scientific reports | Year: 2016

Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied.

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