Evolution of microstructure and optical properties of TiO2/Au nanocomposite

TiO2/Au nanocomposite has been synthesized by mixing Au with milled TiO2 nanopowder through wet chemical route. The effect of Au on the microstructural and optical properties of TiO2 nanopowder has been studied by XRD, FESEM, UV Visible, PL and FTIR techniques. Our study indicates that Au causes the decrease of crystallite size of TiO2 by accumulating on the circumference of these nanoparticles. TiO2/Au nanocomposite exhibits strong spectral response in the visible range due to the surface plasmon effect. Band gap of TiO2 nanopowder reduces from 3.4 eV to 3.1 eV while making composite with Au. The PL spectra showed that emission peak intensity of TiO2 nanopowder decreases in the presence of Au. The reductions in band gap and electron-hole recombination in TiO2/Au nanocomposite suggest that TiO2/Au could be a good candidate for photocatalysis

Roughness of Sandpile Surfaces

We study the surface roughness of prototype models displaying self-organized criticality (SOC) and their noncritical variants in one dimension. For SOC systems, we find that two seemingly equivalent definitions of surface roughness yields different asymptotic scaling exponents. Using approximate analytical arguments and extensive numerical studies we conclude that this ambiguity is due to the special scaling properties of the nonlinear steady state surface. We also find that there is no such ambiguity for non-SOC models, although there may be intermediate crossovers to different roughness values. Such crossovers need to be distinguished from the true asymptotic behaviour, as in the case of a noncritical disordered sandpile model studied in [10].Comment: 5 pages, 4 figures. Accepted for publication in Phys. Rev.

Self-dual Maxwell Chern-Simons Solitons In 1+1 Dimensions

We study the domain wall soliton solutions in the relativistic self-dual Maxwell Chern-Simons model in 1+1 dimensions obtained by the dimensional reduction of the 2+1 model. Both topological and nontopological self-dual solutions are found in this case. A la BPS dyons here the Bogomol'ny bound on the energy is expressed in terms of two conserved quantities. We discuss the underlying supersymmetry. Nonrelativistic limit of this model is also considered and static, nonrelativistic self-dual soliton solutions are obtained.Comment: 18 pages RevTex, 2 figures included, to appear in Phys. Rev.

Role of electric charge in shaping equilibrium configurations of fluid tori encircling black holes

Astrophysical fluids may acquire non-zero electrical charge because of strong irradiation or charge separation in a magnetic field. In this case, electromagnetic and gravitational forces may act together and produce new equilibrium configurations, which are different from the uncharged ones. Following our previous studies of charged test particles and uncharged perfect fluid tori encircling compact objects, we introduce here a simple test model of a charged perfect fluid torus in strong gravitational and electromagnetic fields. In contrast to ideal magnetohydrodynamic models, we consider here the opposite limit of negligible conductivity, where the charges are tied completely to the moving matter. This is an extreme limiting case which can provide a useful reference against which to compare subsequent more complicated astrophysically-motivated calculations. To clearly demonstrate the features of our model, we construct three-dimensional axisymmetric charged toroidal configurations around Reissner-Nordstr\"om black holes and compare them with equivalent configurations of electrically neutral tori.Comment: 14 pages, 7 figure

New record of a marine bivalve (Family: Pinnidae) from Chilika Lagoon, Bay of Bengal

1039-1044Present study describes the newly reported marine bivalve species Atrina serrata from the marine influenced region of Chilika lagoon. This is the first time ever to record an Atlantic bivalve species from the shallow coastal waters of Indian subcontinent. With the paucity of information, the study isn’t reached to any conclusion regarding the possible reason of occurrence, since multiple parameters are governing on the distribution of a species. However, this finding will help to understand the changed or changing benthic ecology of shallow water coastal ecosystem such as Chilika after opening of the lagoon inlets