The effect of grain drift on the structure of (Post-) AGB winds

We have developed an implementation for the momentum transfer force in numerical two fluid hydrodynamics. This form of the frictional coupling between gas and grains is consistent with the microscopic interactions between the two components. The coupling force gives rise to a drift velocity of the grains with respect to the gas. We apply this mechanism to the outflow of (Post-) AGB objects. Our numerical hydrodynamics code calculates self consistently the dynamics of these outflows, as well as the nucleation and growth of grains and equilibrium chemistry of the gas. Grain nucleation and growth are processes that depend strongly on the rate of gas-grain collisions. Hence, the drift velocity becomes an important variable. The tight connection between grain chemistry and drift causes the system to become extremely sensitive to small changes in almost any parameter. This may be a cause for deviation from (spherical) symmetry and structure.Comment: To appear in "Asymmetrical Planetary Nebulae II: from Origins to Microstructures" ASP Conference Series, J.H. Kastner, N. Soker, & S.A. Rappaport, ed

Bank-Based Versus Market Based Financial System: Does it Really Matter?

There is no simple answer to the question of why financial systems and firm financing vary from country to country. The most commonly used classification for the types of financial systems is the distinction of the bank-based and market-based financial system. In the studies conducted in economics and finance literature, it can be seen that these two systems cannot reveal an absolute superiority in terms of growth and prosperity in the countries. Our analysis state that in view of the future direction of the Turkish financial system, it may be thought that efforts to establish a "hybrid financial system" that can combine the bank-based financial system and the relatively superior aspects of the market-based financial system will be better. Keywords: Bank-based, Market-based, Mixed-system, Financial System, Turkey DOI: 10.7176/EJBM/11-9-17 Publication date:March 31st 201

Three-Dimensional Adaptive Mesh Refinement Simulations of Point-Symmetric Nebulae

Previous analytical and numerical work shows that the generalized interacting stellar winds model can explain the observed bipolar shapes of planetary nebulae very well. However, many circumstellar nebulae have a multipolar or point-symmetric shape. With two-dimensional calculations, Icke showed that these seemingly enigmatic forms can be easily reproduced by a two-wind model in which the confining disk is warped, as is expected to occur in irradiated disks. In this contribution we present the extension to fully three-dimensional adaptive mesh refinement simulations of such an interaction.Comment: 4 pages, 2 figures, to appear in "Asymmetrical Planetary Nebulae III" editors M. Meixner, J. Kastner, N. Soker, & B. Balick (ASP Conf. Series). Movies are available at http://www.strw.leidenuniv.nl/AstroHydro3D/movies/index.htm

On Random Walks with a General Moving Barrier

Random walks with a general, nonlinear barrier have found recent applications ranging from reionization topology to refinements in the excursion set theory of halos. Here, we derive the first-crossing distribution of random walks with a moving barrier of an arbitrary shape. Such a distribution is shown to satisfy an integral equation that can be solved by a simple matrix inversion, without the need for Monte Carlo simulations, making this useful for exploring a large parameter space. We discuss examples in which common analytic approximations fail, a failure which can be remedied using the method described here.Comment: 6 pages, 7 figures, submitted to Ap