Strings in some Bianchi type cosmologies

Some Bianchi type cosmological models-two in four and one in higher dimensions-are here studied in the context of cosmic strings. The physical implications of the models are briefly discussed. It is interesting to note that cosmic strings do not occur in Bianchi type V cosmology.     

Universal nature of particle displacements close to glass and jamming transitions

We examine the structure of the distribution of single particle displacements (van Hove function) in a broad class of materials close to glass and jamming transitions. In a wide time window comprising structural relaxation, van Hove functions reflect the coexistence of slow and fast particles (dynamic heterogeneity). The tails of the distributions exhibit exponential, rather than Gaussian, decay. We argue that this behavior is universal in glassy materials and should be considered the analog, in space, of the stretched exponential decay of time correlation functions. We introduce a dynamical model that describes quantitatively numerical and experimental data in supercooled liquids, colloidal hard spheres, and granular materials. The tails of the distributions directly explain the decoupling between translational diffusion and structural relaxation observed in glassy materials.     

Finite Inhomogeneous Shearing Deformations of a Transversely Isotropic Incompressible Material

The present paper deals with finite inhomogeneous shearing deformations of a slab of a special anisotropic solid. Two cases according to the directions of the anisotropic director of the medium are examined. In one case the solution reduces to a quadrature and gives an exact deformation field for particular values of the material constants. In the other case an exact solution is obtained. All such solutions reduce to the same existing solution for the corresponding isotropic elastic material. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of silver nanoparticles in an aqueous suspension of graphene oxide sheets and its antimicrobial activity

A solution-based approach to the synthesis of silver (Ag) nanoparticles by chemical reduction of AgNO(3) in a graphene oxide (GrO) suspension is demonstrated. X-ray diffraction and transmission electron microscopy indicate that the Ag nanoparticles, of size range 5-25nm, were decorated on the GrO sheets. The size and shape of the Ag nanoparticles are dependent on the concentration of the AgNO(3) solution. Antimicrobial activity of such hybrids materials is investigated against the Gram negative bacteria Escherichia coli and Pseudomonous aeruginosa. The bacterial growth kinetics was monitored in nutrient broth supplemented with the Ag nanoparticle-GrO suspension at different conditions. It was observed that P. aeruginosa is comparatively more sensitive to the Ag nanoparticle-GrO suspension.     

Leading-Order Dynamics of Gravity-Driven Flows in?Free-Standing Soap Films

We derive the leading-order equations that govern the dynamics of the flow in a falling, free-standing soap film. Starting with the incompressible Navier?CStokes equations, we carry out an asymptotic analysis using parameters that correspond to a common experimental setup. We account for the effects of inertia, surface elasticity, pressure, viscous stresses, gravity, and air drag. We find that the dynamics of the flow is dominated by the effects of inertia, surface elasticity, gravity, and air drag. We solve the leading-order equations to compute the steady-state profiles of velocity, thickness, and pressure in an experiment in which the film is in the Marangoni elasticity regime. The computational results, which include a Marangoni shock, are in good accord with the experimental measurements.     

A note on supersymmetry and magnetic fields

Conclusion In the present article we have considered two supersymmetric non-abelian gauge theories in the presence of an external magnetic field. In has been shown that the effect of the magnetic field breaks suppersymmetry at the one-loop level; however, if supersymmetry is already broken spontaneously at the tree level, then the magnetic field effect does not restore it at the one-loop level. These facts could be used in SUSY GUT models (which are used to describe the early universe), to study phase transition in those models.     

Finite Inhomogeneous Radial Expansion (Contraction) and Longitudinal Shearing of an Isotropic Compressible Elastic Circular Cylindrical Shell

We have first obtained that the equations of equilibrium governing the finite radial expansion (contraction) and longitudinal shearing of a circular cylindrical shell become uncoupled for a class of harmonic materials (a class of isotropic homogeneous compressible elastic materials). Next it has been assumed that the dilatation is uniform. Following this the exact solutions of the uncoupled equations of equilibrium have been obtained for a simple harmonic material which is reduced to the Neo-Hookean material for the incompressible case. The deformation is nonhomogeneous in nature. The stresses have been obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Domain formation and orbital ordering transition in a doped Jahn-Teller insulator

The ground state of a double-exchange model for orbitally degenerate e(g) electrons with Jahn-Teller lattice coupling and weak disorder is found to be spatially inhomogeneous near half filling. Using a real-space Monte Carlo method we show that doping the half-filled orbitally ordered insulator leads to the appearance of hole-rich disordered regions in an orbitally ordered environment. The doping driven orbital order to disorder transition is accompanied by the emergence of metallic behavior. We present results on transport and optical properties along with spatial patterns for lattice distortions and charge densities, providing a basis for an overall understanding of the low-doping phase diagram of La1 - xCaxMnO3.     

Synthetic studies directed toward the proposed structure for heteroscyphic acid A

A route to the carbon skeleton of the proposed structure for heteroscyphic acid A was developed utilizing a Mn(III)/Cu(II) mediated oxidative free-radical cyclization and nucleophilic addition to (3-methylpentadienyl)iron(1+) cation.