The amount of vapor in the impact-generated protolunar disk carries implications for the dynamics, devolatilization, and moderately volatile element (MVE) isotope fractionation during lunar ...formation. The equation of state (EoS) used in simulations of the giant impact is required to calculate the vapor mass fraction (VMF) of the modeled protolunar disk. Recently, a new version of M-ANEOS ("Stewart M-ANEOS") was released with an improved treatment of heat capacity and expanded experimental Hugoniot. Here, we compare this new M-ANEOS version with a previous version ("N-SPH M-ANEOS") and assess the resulting differences in smoothed particle hydrodynamics (SPH) simulations. We find that Stewart M-ANEOS results in cooler disks with smaller values of VMF and results in differences in disk mass that are dependent on the initial impact angle. We also assess the implications of the minimum "cutoff" density (\(\rho_{c}\)), similar to a maximum smoothing length, that is set as a fast-computing alternative to an iteratively calculated smoothing length. We find that the low particle resolution of the disk typically results in \(>40\%\) of disk particles falling to \(\rho_c\), influencing the dynamical evolution and VMF of the disk. Our results show that choice of EoS, \(\rho_{c}\), and particle resolution can cause the VMF and disk mass to vary by tens of percent. Moreover, small values of \(\rho_{c}\) produce disks that are prone to numerical instability and artificial shocks. We recommend that future giant impact SPH studies review smoothing methods and ensure the thermodynamic stability of the disk over simulated time.
Optical stellar polarimetry in the Perseus molecular cloud direction is known to show a fully mixed bi-modal distribution of position angles across the cloud (Goodman et al. 1990). We study the Gaia ...trigonometric distances to each of these stars and reveal that the two components in position angles trace two different dust clouds along the line of sight. One component, which shows a polarization angle of -37.6 deg +/- 35.2 deg and a higher polarization fraction of 2.0 +/- 1.7%, primarily traces the Perseus molecular cloud at a distance of 300 pc. The other component, which shows a polarization angle of +66.8 deg +/- 19.1 deg and a lower polarization fraction of 0.8 +/- 0.6%, traces a foreground cloud at a distance of 150 pc. The foreground cloud is faint, with a maximum visual extinction of < 1 mag. We identify that foreground cloud as the outer edge of the Taurus molecular cloud. Between the Perseus and Taurus molecular clouds, we identify a lower-density ellipsoidal dust cavity with a size of 100 -- 160 pc. This dust cavity locates at l = 170 deg, b = -20 deg, and d = 240 pc, which corresponds to an HI shell generally associated with the Per OB2 association. The two-component polarization signature observed toward the Perseus molecular cloud can therefore be explained by a combination of the plane-of-sky orientations of the magnetic field both at the front and at the back of this dust cavity.
Switzerland Reacts to EU State Aid Decision Robinson, Philip; Huber, Markus F; Hull, Howard R ...
Journal of International Taxation,
05/2007, Letnik:
18, Številka:
5
Trade Publication Article
On February 13, 2007, the European Commission and Switzerland issued statements regarding the sustainability of certain Swiss cantonal tax regimes. The EC is maintaining that cantonal tax relief ...afforded to "holding companies," "auxiliary companies," and "mixed companies" is tantamount to state aid. The Swiss federal government has issued a clear rejection of the EC's claims.
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