Structure and Properties of Multilayered PET/PC Composites

Summary : With the aid of layer multiplying coextrusion techniques, polymer composites comprising up to thousand of uniform and alternating layers polyethylene terephthalate (PET) and polycarbonate (PC) were produced. Morphology and micromechanical deformation processes in these composites were investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). In particular, the effect of thickness of individual layers on the large strain deformation micromechanisms was analyzed. On decreasing the thickness of individual polymer layers, a transition in deformation mechanism from two-component behaviour (i.e. the localization of shear bands in individual layer) to one-component-like behaviour (with the shear bands passing unhindered through different layers) was observed at the layer thickness of ca. 1 µm. On further decreasing the layer thickness below 100 nm, the composites exhibited homogeneous plastic deformation (i.e. no localization of deformation). In contrast to pure PET, even after long annealing, the composites showed tough behaviour during tensile loading.     

The study of the reduced α-width and ANC of O states through its sequential breakup

In this work we theoretically study using continuum-discretized-coupled channel (CDCC) theory, the resonant breakup of ¹⁶O by comparison with a recent measurement. The ground state Asymptotic Normalization Coefficient (ANC) and the alpha spectroscopic factor of ¹⁶O are evaluated in this work. The peripheral aspect of resonance breakup through a ²⁺$2^{+}$ unbound state has been also studied.     

Gap solitons in a model of a superfluid fermion gas in optical lattices

We consider a dynamical model for a Fermi gas in the Bardeen-Cooper-Schrieffer (BCS) superfluid state, trapped in a combination of a 1D or 2D optical lattice (OL) and a tight parabolic potential, acting in the transverse direction(s). The model is based on an equation for the order parameter (wave function), which is derived from the energy density for the weakly coupled BCS superfluid. The equation includes a nonlinear self-repulsive term of power 7/3, which accounts for the Fermi pressure. Reducing the equation to the 1D or 2D form, we construct families of stable 1D and 2D gap solitons (GSs) by means of numerical simulations, which are guided by the variational approximation (VA). The GSs are, chiefly, compact objects trapped in a single cell of the OL potential. In the linear limit, the VA predicts almost exact positions of narrow Bloch bands that separate the semi-infinite and first finite gaps, as well as the first and second finite ones. Families of stable even and odd bound states of 1D GSs are constructed, too. We also demonstrate that the GS can be dragged without much distortion by an OL moving at a moderate velocity (, in physical units). The predicted GSs contain ∼10³-10⁴ and ∼10³ atoms per 1D and 2D settings, respectively.     

Periodic solutions of a singularly perturbed delay differential equation

A singularly perturbed differential delay equation of the form

(1)     

Method for Lippmann-Schwinger equations

A recently proposed degenerate-kernel scheme for solving Fredholm integral equations of the second kind is extended to singular equations of the Lippmann-Schwinger type. Numerical calculations of on- and off-shell t-matrix elements are carried out at positive and negative energies, for the ¹S₀ Reid soft-core nucleon-nucleon potential. Satisfactory convergence is achieved, even with the simplest version of the s     

Interactions and correlations of particulate inclusions in a columnar phase

We calculate the elastic-field-mediated interaction between macroscopic particles in a columnar hexagonal phase. The interaction is found to be long-ranged and non-central, with both attractive and repulsive parts. We show how the interaction modifies the particle correlations and the column fluctuations. We also calculate the interaction of particles with the topological defects of the columnar phase. The particle-defect interaction reduces the mobility of the defects. Received 14 March 2002 and Received in final form 13 August 2002 RID="a" ID="a"e-mail: rjoy@physics.iisc.ernet.in     

Understanding of nuclear quadrupole interactions of 35 Cl, 79 Br and 129 I and binding energies of solid halogens at first-principles level

This paper deals with the understanding at a first-principles level of the nuclear quadrupole interaction (NQI) parameters of solid chlorine, bromine and iodine as well as the intermolecular binding of these molecules in the solid. The electronic structure investigations that we have carried out to study these properties of the solid halogens are based on the Hartree–Fock Cluster approach using the Roothaan variational procedure with electron correlation effects included using many-body perturbation theory with the empty orbitals used in the perturbation theory investigations for the excited states. The results of our investigations provide good agreement with the measured NQI parameters primarily from the Hartree–Fock one electron wave-functions with many-body effects making minor contributions. The binding (dissociation) energies for the molecules with the solid state environment on the other hand arises from intermolecular many body effects identified as the Van der Waals attraction with one-electron Hartree–Fock contribution being repulsive in nature.     

Frequency-resolving spatiotemporal wave-front sensor

We report on a high-resolution wave-front sensor that measures the complete spatial profile of any frequency component of a laser field containing multiple frequencies. This probe technique was developed to address the necessity of measuring the spatial overlap of the carrier field with each sideband component of the field exiting the output port of a gravitational-wave interferometer. We present the results of an experimental test of the probe, where we were able to construct the spatial profile of a single radio-frequency sideband at the level of -50 dBc.