Adenine Abundance in a Collapsing Molecular Cloud

A vital ingredient of DNA molecule named adenine may be produced by successive addition of HCN during molecular cloud collapse and star formation. We compute its abundance in a collapsing cloud as a function of the reaction rate and show that in much of the circumstances the resulting amount may be sufficient to contaminate planets, comets and meteorites. We introduce a $f$-parameter which may be used to study the abundance where radiative association takes place.Comment: Six pages and one figure. Accepted for Publication in Indian Journal of Physics (April 1, 2000 issue

Global Solutions of Viscous Transonic Flows in Kerr Geometry I: Weak Viscosity Limit

We present fully general relativistic equations governing viscous transonic flows in vertical equilibrium in Kerr geometry. We find the complete set of global solutions (both for Optically thick and optically thin flows) in the weak viscosity limit. We show that for a large region of parameter space, centrifugal pressure supported standing shocks can form in accretion and winds very close to the black hole horizon, both for co-rotating and contra-rotating flows. We compute the nature of the shear tensor for complete transonic solutions and discuss the consequences of its reversal properties.Comment: Latex 10 pages, special macro psfig.tex are include

Spectral Softening due to Winds in Accretion Disks

Accretion flows may produce profuse winds when they have positive specific energy. Winds deplete matter from the inner region of the disk and makes the inner region thinner, optically. Since there are fewer electrons in this region, it becomes easier to Comptonize this part by the soft photons which are intercepted from the Keplerian disk farther out. We present a self-consistent picture of winds from an accretion disk and show how the spectra of the disk is softened due to the outflowing wind.Comment: 6 Latex pages and three figures. Correction in figure description. Published in Indian Journal of Physics, V. 72B, p. 565-569, 199