Bubbling and bistability in two parameter discrete systems

We present a graphical analysis of the mechanisms underlying the occurrences of bubbling sequences and bistability regions in the bifurcation scenario of a special class of one dimensional two parameter maps. The main result of the analysis is that whether it is bubbling or bistability is decided by the sign of the third derivative at the inflection point of the map function.Comment: LaTeX v2.09, 14 pages with 4 PNG figure

GALEX Observations of Diffuse UV Radiation at High Spatial Resolution from the Sandage Nebulosity

Using the GALEX ultraviolet imagers we have observed a region of nebulosity first identified as starlight scattered by interstellar dust by Sandage (1976). Apart from airglow and zodiacal emission, we have found a diffuse UV background of between 500 and 800 \phunit in both the \galex FUV (1350 -- 1750 \AA) and NUV (1750 -- 2850 \AA). Of this emission, up to 250 \phunit is due to \htwo fluorescent emission in the FUV band; the remainder is consistent with scattering from interstellar dust. We have estimated the optical constants to be $a = 0.3; g = 0.7$ in the FUV and $a = 0.5; g = 0.7$ in the NUV, implying highly forward scattering grains, plus an extragalactic contribution of as much as 150 \phunit. These are the highest spatial resolution observations of the diffuse UV background to date and show an intrinsic scatter beyond that expected from instrumental noise alone. Further modeling is required to understand the nature of this scatter and its implications for the ISM.Comment: Total 20 pages, Figures 9, Accepted for publication in Astrophysical Journa

Measurement of Dust Optical Properties in Coalsack

We have used FUSE and Voyager observations of dust scattered starlight in the neighborhood of the Coalsack Nebula to derive the optical constants of the dust grains. The albedo is consistent with a value of $0.28 \pm 0.04$ and the phase function asymmetry factor with a value of $0.61 \pm 0.07$ throughout the spectral range from 900 -- 1200 \AA, in agreement with previous determinations as well as theoretical predictions. We have now observed two regions (Ophiuchus and Coalsack) with intense diffuse background radiation and in both cases have found that the emission is due to light from nearby hot stars scattered by a relatively thin foreground cloud, with negligible contribution from the background molecular cloud.Comment: Total 19 pages, Figures 9, Accepted for publication in Astrophysical Journa

Observations of Diffuse Ultraviolet Emission from Draco

We have studied small scale (2 arcmin) spatial variation of the diffuse UV radiation using a set of 11 GALEX deep observations in the constellation of Draco. We find a good correlation between the observed UV background and the IR 100 micron flux, indicating that the dominant contributor of the diffuse background in the field is the scattered starlight from the interstellar dust grains. We also find strong evidence of additional emission in the FUV band which is absent in the NUV band. This is most likely due to Lyman band emission from molecular hydrogen in a ridge of dust running through the field and to line emissions from species such as C IV (1550 A) and Si II (1533 A) in the rest of the field. A strong correlation exists between the FUV/NUV ratio and the FUV intensity in the excess emission regions in the FUV band irrespective of the optical depth of the region. The optical depth increases more rapidly in the UV than the IR and we find that the UV/IR ratio drops off exponentially with increasing IR due to saturation effects in the UV. Using the positional details of Spitzer extragalactic objects, we find that the contribution of extragalactic light in the diffuse NUV background is 49 +/- 13 photon units and is 30 +/- 10 photon units in the FUV band.Comment: 30 pages, 13 figures, Accepted for publication in The Astrophysical Journal (ApJ), November 2010, v723 issu

Electrorheological Generalized Dispersion of Soluble Matter through a Poorly Conducting Fluid Saturated Porous Media

In this paper, we investigate the effects of electric field, viscosity variation parameter and porous parameter on the generalized dispersion of an unsteady convective diffusion through a poorly conducting fluid in a channel bounded by rigid parallel plates using Generalised dispersion model of Gill and Sankarasubramanian. A two dimensional flow has been considered and the resulting partial differential equations have been solved analytically. The relative unsteady dispersion coefficient is numerically computed and found that the increase in conductivity variation parameter and decrease in viscosity variation parameter, decreases the dispersion coefficient initially and increases gradually. We have also estimated the contribution of diffusion and pure convection on the generalized dispersion coefficient. The effect of pure convection decreases mean concentration compared to combined effect of convection and diffusion

Effects of Magnetic field and Viscous Dissipation on Oberback Convection in a Chiral Fluid and Mass Transfer Flow through porous media

A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superposable mirror image of a molecule. Chiral fluid is a fluid which has molecules and exhibits the chirality. The influence of viscous dissipation on convective flow, heat transfer, and mass transfer through viscous incompressible chiral fluid through a vertical porous layer immersed in porous medium in the presence of a uniform magnetic field is investigated. The coupled non-linear equations governing the motion are solved analytically using the regular perturbation method with Eckert number Ecas perturbation parameter. The effect of magnetochiral number M, porous parameter σ, Grashof number Gr, Eckert number E, and Schmidt number Sc on velocity, temperature distribution, mass flow rate, skin friction and rate of heat transfer are depicted graphically and some important conclusions are drawn

Effect of oral exposure of mycobacterium avium intracellulare on the protective imunity induced by BCG

The relative protective efficacy of oral administration of mycobacteria as compared to the conventional intradermal route of vaccination has been assessed in guinea pigs. Skin test reactivity to partially purified protein derivative and protective immunity to challenge with virulent Mycobacterium tuberculosis were used as parameters of protective immunity. Oral immunisation of guinea pigs either with BCG or with Mycobacterium avium intracellulare induces skin test reactivity and protective immunity comparable to that induced by intradermal route of vaccination. Oral exposure of Mycobacterium avium intracellulare prior to oral or intradermal dose of BCG did not interfere with the protective immunity induced by BCG in guinea pigs challenged with Mycobacterium tuberculosis H37Rv