Polarization-dependent discharge in fibers of semiconducting ladder-type polymer

We report results on polarization-dependent photoinduced discharge in oriented fibers and films of ladder-type, electron-transporting polymer poly (benzimidazobenzophenanthroline), BBL. The photocarrier generation efficiency in the fiber which is indicated by the rate of discharge, is found to be distinctly higher for light polarized parallel to the fiber axis as compared to the radially perpendicular direction . Similar results, with photocarrier generation efficiency anisotropy ~ 10 are obtained for oriented films. These observations are different from previously obtained results on polyparaphenylenevinylene (PPV). The results are compared with the polarization-dependent steady- state photoconductivity measurements. We interpret these results on the basis of molecular and macroscopic features of the material.Comment: This article has been accepted for publication in applied physics letters and tentatively to be published in March 12, 2001 issu

Distribution of the delay time and the dwell time for wave reflection from a long random potential

We re-examine and correct an earlier derivation of the distribution of the Wigner phase delay time for wave reflection from a long one-dimensional disordered conductor treated in the continuum limit. We then numerically compare the distributions of the Wigner phase delay time and the dwell time, the latter being obtained by the use of an infinitesimal imaginary potential as a clock, and investigate the effects of strong disorder and a periodic (discrete) lattice background. We find that the two distributions coincide even for strong disorder, but only for energies well away from the band-edges.Comment: Final version with minor corrections in text, 4 pages, 2 PS figure

Element test experiments and simulations: from dry towards cohesive powders

Findings from experiments and particle simulations for dry and cohesive granular materials are presented with the goal to reach quantitative agreement between simulations and experiments. Results for the compressibility, tested with the FT4 Powder Rheometer are presented. The first simulation results involve the strain controlled uniaxial compression of frictionless polydisperse spheres in a biaxial box using a linear visco-elastic contact model.\ud \ud As main result, the evolution of pressure as a function of volume fraction is reported. Our anisotropic, uniaxial findings compare astonishingly well with results for purely isotropic compression. Concerning the second stress response, namely anisotropy, we present the evolution of the deviatoric stress as a function of the volume fraction, which cannot be measured with the FT4 experiment, but requires a bi-axial experiment

Bed blockers: A study on the elderly patients in a teaching hospital in India

A cross-sectional study of in-patients over the age of 60 years was conducted at district McGann Hospital, Shimoga on patients who were classified as bed blockers. Level of dependency and cognitive function of these patients were assessed using Barthel scale and Abbreviated mental test (AMT) respectively. Median age of the study population was 67 years; majority of them were men. Most of them were admitted in the medical ward and the median time to be labeled as bed blocker was 32 days. These bed blockers were a weak group of patients with an average 3.1 pathology per case. Majority of them suffered from neurological disorders and cardiovascular disease. High level of dependence was noted with a mean Barthel score of 29.68 (Range 0 -100). Low levels of cognitive function was also noted among these patients with a mean AMT of 4.76 (Range 0 -10).These findings demonstrate that the bed blockers in McGann hospital suffer not only from genuine health problems but also have a high dependency level in activities of daily living which hamper their discharge to the community. Community based rehabilitation using an intersectoral approach may help at least the less dependent to return home

Laminar and turbulent flows over spherically blunted cone and hyperboloid with massive surface blowing

Numerical solutions are presented for the flow over a spherically blunted cone and hyperboloid with massive surface blowing. Time-dependent viscous shock-layer equations are used to describe the flow field. The boundary conditions on the body surface include a prescribed blowing-rate distribution. The governing equations are solved by a time-asymptotic finite-difference method. Results presented here are only for a perfect gas-type flow at zero angle of attack. Both laminar and turbulent flow solutions are obtained. It is found that the effect of the surface blowing on the laminar flow field is to smooth out the curvature discontinuity at the sphere-cone juncture point, which results in a positive pressure gradient over the body. The shock slope increases on the downstream portion of the body as the surface blowing rate is increased. The turbulent flow with surface blowing is found to redevelop a boundary-layer-like region near the surface. The effects of this boundary-layer region on the flow field and heating rates are discussed