Paper: astro-ph/0510305
Date: Tue, 11 Oct 2005 08:34:18 GMT (957kb)

Title: Hydraulic/Shock-Jumps in Protoplanetary Disks

Authors: A. C. Boley and R. H. Durisen

Comments: 39 pages, 18 figures, 1 table, submitted to ApJ. Some images have
been degraded in quality for submission to Archive
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In this paper, we describe the nonlinear outcome of spiral shocks in
protoplanetary disks. Spiral shocks, for most protoplanetary disk conditions,
create a loss of vertical force balance in the post-shock region and result in
rapid expansion of the gas perpendicular to the disk midplane. This expansion
has characteristics similar to hydraulic-jumps, which occur in incompressible
fluids. We present a theory to describe the behavior of these
hydraulic/shock-jump hybrids (hs-jumps) and then compare the theory to
three-dimensional hydrodynamics simulations. We discuss the fully
three-dimensional shock structures that hs-jumps produce and discuss possible
consequences of hs-jumps for disk mixing, turbulence, and evolution of solids.

\\ ( http://arXiv.org/abs/astro-ph/0510305 , 957kb)

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Paper: astro-ph/0510306
Date: Tue, 11 Oct 2005 10:11:38 GMT (41kb)

Title: Evolution of PAH Features from Proto- to Planetary Nebulae

Authors: R. Szczerba, N. Si\'odmiak and C. Szyszka

Comments: 4 pages, 3 figures, 1 table, to appear in the Proceedings of the
conference "Planetary Nebulae as Astronomical Tools", edited by R. Szczerba,
G. Stasi\'nska, and S. K. G\'orny, AIP Conference Proceedings, Melville, New
York
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With the aim to investigate the overall evolution of UIR band features with
hardening of UV radiation (increase of the star's effective temperature) we
have analysed ISO spectra for 32 C-rich stars: 20 proto-planetary nebulae and
12 planetary nebulae with Wolf-Rayet central stars. In this contribution we
discuss variations in the peak position of UIR bands among analysed objects,
and demonstrate that variations in the ``7.7'' to 11.3 microns flux ratio are
correlated with the effective temperature (probably due to an increase of the
ionization state of their carriers).

\\ ( http://arXiv.org/abs/astro-ph/0510306 , 41kb)