Expanded Very Large Array observations of the H66{\alpha} and He66{\alpha} recombination lines toward MWC 349A

We have used the greatly enhanced spectral capabilities of the Expanded Very Large Array to observe both the 22.3 GHz continuum emission and the H66{\alpha} recombination line toward the well-studied Galactic emission-line star MWC 349A. The continuum flux density is found to be 411 $\pm$ 41 mJy in good agreement with previous determinations. The H66{\alpha} line peak intensity is about 25 mJy, and the average line-to-continuum flux ratio is about 5%, as expected for local thermodynamic equilibrium conditions. This shows that the H66{\alpha} recombination line is not strongly masing as had previously been suggested, although a moderate maser contribution could be present. The He66{\alpha} recombination line is also detected in our observations; the relative strengths of the two recombination lines yield an ionized helium to ionized hydrogen abundance ratio y+ = 0.12 $\pm$ 0.02. The ionized helium appears to share the kinematics of the thermally excited ionized hydrogen gas, so the two species are likely to be well mixed. The electron temperature of the ionized gas in MWC 349A deduced from our observations is 6,300 $\pm$ 600 K.Comment: Accepted for publication in ApJ

Algebraic Multigrid for the Multi-Ion Transport and Reaction Model - A Physics-Aware Approach

Electrochemical processes are essential in the manufacturing of a very broad range of products. The multi-ion transport and reaction model (MITReM) is used to simulate such electrochemical processes. The governing partial differential equations (PDEs) are discretized in space by a combined finite element and residual-distribution scheme. The discrete system is linearized with Newtons method which results in a series of linear systems. The focus of this work is on the development of a stable and efficient point-based algebraic multigrid (PAMG) method for the solution of the linear systems which arise in the MITReM simulation. The new PAMG approach makes use of physics-aware smoothing and coarse-grid correction techniques. This means that it, explicitly, takes important physical propertie s of the PDE system into account. We introduce a reordering framework which makes it possible to use physics-oriented matrix-based measures for strength of connectivity to derive application-specific point orderings for smoothing. The frameworks generality not only allows the determination of suited permutations of the variables for the electrochemical simulations considered, but also for other convection- and/or migration-dominated simulation tasks. We introduce a heuristic Peclet number to locate areas causing numerical difficulties within the hierarchy of the algebraic multigrid (AMG) method for scalar PDEs as well as systems of PDEs. We investigate several coarse-grid correction techniques which take this information into account and show results for the convection-diffusion equation, the migration-diffusion system and the MITReM. We motivate the use of the physics-aware PAMG components and apply the approach for a range of geometries and chemical setups with scientific and industrial relevance. Our numerical experiments illustrate, in particular, that physical properties of the underlying problem have to explicitly be considered for constructing efficient and robust AMG-based methods

SMA Imaging of the Maser Emission from the H30α\alpha Radio Recombination Line in MWC349A

We used the Submillimeter Array to map the angular distribution of the H30$\alpha$ recombination line (231.9 GHz) in the circumstellar region of the peculiar star MWC349A. The resolution was 1\farcs2, but because of high signal-to-noise ratio we measured the positions of all maser components to accuracies better than 0\farcs01, at a velocity resolution of $1 kms$. The two strongest maser components (called high velocity components) at velocities near -14 and $32 kms$ are separated by 0\farcs048 \pm 0\farcs001 (60 AU) along a position angle of 102 \pm 1\arcdeg. The distribution of maser emission at velocities between and beyond these two strongest components were also provided. The continuum emission lies at the center of the maser distribution to within 10 mas. The masers appear to trace a nearly edge-on rotating disk structure, reminiscent of the water masers in Keplerian rotation in the nuclear accretion disk of the galaxy NGC4258. However, the maser components in MWC349A do not follow a simple Keplerian kinematic prescription with $v \sim r^{-1/2}$, but have a larger power law index. We explore the possibility that the high velocity masers trace spiral density or shock waves. We also emphasize caution in the interpretation of relative centroid maser positions where the maser is not clearly resolved in position or velocity, and we present simulations that illustrate the range of applicability of the centroiding method.Comment: 23 pages with 9 figures (two of these figures are vertically aligned as Figure 4) submitted to the Astrophysical Journa

Job protection renders minimum wages less harmful

Individual labour productivities are often unobservable for firms when hiring new workers. Job protection may prevent firms ex post from using information about labour productivities. We show that a binding minimum wage introduced in the presence of job protection will lead to lower unemployment levels than predicted by the standard labour market model with heterogeneous labour and full information. --Minimum wages,unemployment,hidden information,labour market regulation

Asymmetric Information Renders Minimum Wages Less Harmful

We show that a minimum wage introduced in the presence of asymmetric information about worker productivities will lead to lower unemployment levels than predicted by the standard labour market model with heterogeneous labour and symmetric information.minimum wages, unemployment, asymmetric information, labour market regulation

Welfare Effects of Immigration in a Dual Labor Market

The paper analyses the welfare effects of immigration when some sectors of the economy are characterized by wage bargaining between unions and employers. We show that immigration is unambiguously beneficial if the wage elasticity of labor demand in the competitive sectors is smaller than in the unionised sectors. In the opposite case, the welfare effect of immigrat ion is ambiguous; little immigration then reduces the native population's welfare, whereas large scale immigration tends to enhance welfare.Immigration policy, trade unions, welfare

Mobility and the Role of Education as a Commitment Device

European integration forces system competition within European countries. This competition has important implications for both the public pay-as-you-go pension scheme and the public education system. Without labor mobility, each generation has an incentive to invest in the human capital of the subsequent generation in order to maximize pension payments. It is a popular belief that increasing labor mobility decreases the incentives to finance the education of the subsequent generation. This paper shows that this is not true if human capital investment increases the mobility of the subsequent generation and can thus be used as a commitment device for low taxes.Education, intergenerational transfers, commitment

Ageing Municipalities, Gerontocracy and Fiscal Competition

We develop a simple model of fiscal competition among ageing municipalities. When ageing advances, gerontocracies and social planners gradually substitute publicly provided goods aimed at the mobile young population for publicly provided goods for the elderly. Thissubstitution process does not only depend on the ageing itself but also on crowding effects and on the regional distribution of the elderly population. We show that fiscal competition prevents the exploitation of the young. When the share of the elderly is sufficiently large, theutility of the young is even higher in gerontocracies than in welfare maximizing societies. Due to fiscal competition, the gerontocracies will provide even more of the publicly provided good for the young than the social planner.demographic change, fiscal competition, publicly provided goods

The empirical relevance of minimum wages for the low-wage sector

Niedriglohn, Mindestlohn, Wirtschaftlichkeit, Arbeitsplatz, Deutschland, Low wages, Minimum wage, Economic effectiveness, Job, Germany

Subprime Crisis and Board (In-)Competence: Private vs. Public Banks in Germany

We examine evidence for a systematic underperformance of Germany’s state-owned banks in the current financial crisis and study if the bank losses can be traced to the quality of bank governance. For this purpose, we examine the biographical background of 593 supervisory board members in the 29 largest banks and find a pronounced difference in the finance and management experience of board representatives across private and state-owned banks. Measures of “boardroom competence” are then related directly to the magnitude of bank losses in the recent financial crisis. Our data confirms that supervisory board (in-)competence in finance is related to losses in the financial crisis. Improved bank governance is therefore a suitable policy objective to reduce bank fragility.governance, supervisory boards, banking, financial crisis