A precessing jet model for the PN K 3-35: simulated radio-continuum emission

The bipolar morphology of the planetary nebula (PN) K 3-35 observed in radio-continuum images was modelled with 3D hydrodynamic simulations with the adaptive grid code yguazu-a. We find that the observed morphology of this PN can be reproduced considering a precessing jet evolving in a dense AGB circumstellar medium, given by a mass loss rate \dot{M}_{csm}=5x10^{-5}M_{\odot}/yr and a terminal velocity v_{w}=10 km/s. Synthetic thermal radio-continuum maps were generated from numerical results for several frequencies. Comparing the maps and the total fluxes obtained from the simulations with the observational results, we find that a model of precessing dense jets, where each jet injects material into the surrounding CSM at a rate \dot{M}_j=2.8x10^{-4} {M_{\odot}/yr (equivalent to a density of 8x10^{4} {cm}^{-3}, a velocity of 1500 km/s, a precession period of 100 yr, and a semi-aperture precession angle of 20 degrees agrees well with the observations.Comment: 6 pages, 4 figures, accepted to MNRA

NAFTA, Trade and Development (Robert A. Blecker and Gerardo Esquivel)

Freihandelszone; Wirtschaftslage; Außenhandel; NAFTA-Staaten

NAFTA, Trade, and Development

The post-Keynesian tradition contains two different models of long-run growth in open economies -- the model of export-led cumulative causation (ELCC) originally conceived by Nicholas Kaldor and the model of balance-of-payments-constrained growth (BPCG) developed by A.P. Thirlwall. These models diverge significantly in their core underlying assumptions. For example, they disagree about whether long-term gains in relative price competitiveness are possible and whether import demand constrains long-run growth. The two modeling approaches also yield conflicting policy implications. For example, some ELCC models imply that a domestic demand stimulus can boost long-run growth by sparking a virtuous circle of cumulative causation (including an endogenous increase in productivity growth), while most BPCG models imply that only policies that raise the income elasticity of export demand or lower the income elasticity of import demand can permit faster growth in the long run. The fact that both models have found econometric support suggests that each contains empirically supported elements, but the tests that have been conducted to date have not had sufficient power to distinguish between them. This paper will present both models in a common analytical framework to compare their theoretical differences and policy implications. The paper will argue that a generalized BPCG model that allows for financial flows and relative price effects can incorporate the cumulative causation feedbacks from the ELCC approach while also imposing the balance of payments equilibrium condition that is missing from the latter. The paper will also explore under what conditions different versions of the models apply.

Velocity statistics from spectral line data: effects of density-velocity correlations, magnetic field, and shear

In a previous work Lazarian and Pogosyan suggested a technique to extract velocity and density statistics, of interstellar turbulence, by means of analysing statistics of spectral line data cubes. In this paper we test that technique, by studying the effect of correlation between velocity and density fields, providing a systematic analysis of the uncertainties arising from the numerics, and exploring the effect of a linear shear. We make use of both compressible MHD simulations and synthetic data to emulate spectroscopic observations and test the technique. With the same synthetic spectroscopic data, we also studied anisotropies of the two point statistics and related those anisotropies with the magnetic field direction. This presents a new technique for magnetic field studies. The results show that the velocity and density spectral indices measured are consistent with the analytical predictions. We identified the dominant source of error with the limited number of data points along a given line of sight. We decrease this type of noise by increasing the number of points and by introducing Gaussian smoothing. We argue that in real observations the number of emitting elements is essentially infinite and that source of noise vanishes.Comment: 12 pages, 10 figures. Accepted for publication in MNRA

New Variable Jet Models for HH 34

We consider newly derived proper motions of the HH 34 jet to reconstruct the evolution of this outflow. We first extrapolate ballistic trajectories for the knots (starting from their present-day positions and velocities) and find that at ~1000 yr in the future most of them will merge to form a larger-mass structure. This mass structure will be formed close to the present-day position of the HH 34S bow shock. We then carry out a fit to the ejection velocity versus time reconstructed from the observed proper motions (assuming that the past motion of the knots was ballistic) and use this fit to compute axisymmetric jet simulations. We find that the intensity maps predicted from these simulations do indeed match reasonably well the [S II] structure of HH 34 observed in Hubble Space Telescope images