The power spectrum of solar convection flows from high-resolution observations and 3D simulations

We compare Fourier spectra of photospheric velocity fields from very high resolution IMaX observations to those from recent 3D numerical magnetoconvection models. We carry out a proper comparison by synthesizing spectral lines from the numerical models and then applying to them the adequate residual instrumental degradation that affects the observational data. Also, the validity of the usual observational proxies is tested by obtaining synthetic observations from the numerical boxes and comparing the velocity proxies to the actual velocity values from the numerical grid. For the observations, data from the SUNRISE/IMaX instrument with about 120 km spatial resolution are used, thus allowing the calculation of observational Fourier spectra well into the subgranular range. For the simulations, we use four series of runs obtained with the STAGGER code and synthesize the IMaX spectral line (FeI 5250.2 A) from them. Proxies for the velocity field are obtained via Dopplergrams (vertical component) and local correlation tracking (horizontal component). A very good match between observational and simulated Fourier power spectra is obtained for the vertical velocity data for scales between 200 km and 6 Mm. Instead, a clear vertical shift is obtained when the synthetic observations are not degraded. The match for the horizontal velocity data is much less impressive because of the inaccuracies of the LCT procedure. Concerning the internal comparison of the direct velocity values of the numerical boxes with those from the synthetic observations, a high correlation (0.96) is obtained for the vertical component when using the velocity values on the log($tau_{500}$) = -1 surface in the box. The corresponding Fourier spectra are near each other. A lower maximum correlation (0.5) is reached (at $tau_{500}$ = 1) for the horizontal velocities as a result of the coarseness of the LCT procedure.Comment: 12 pages, 9 figures, accepted in A&

The Efficient Computation of Bounds for Functionals of Finite Element Solutions in Large Strain Elasticity

We present an implicit a-posteriori finite element procedure to compute bounds for functional outputs of finite element solutions in large strain elasticity. The method proposed relies on the existence of a potential energy functional whose local minima, over a space of suitably chosen continuous functions, corresponds to the problem solution. The output of interest is cast as a constrained minimization problem over an enlarged discontinuous finite element space. A Lagrangian is formed were the multipliers are an adjoint solution, which enforces equilibrium, and hybrid fluxes, which constrain the solution to be continuous. By computing approximate values for the multipliers on a coarse mesh, strict upper and lower bounds for the output of interest on a suitably refined mesh, are obtained. This requires a minimization over a discontinuous space, which can be carried out locally at low cost. The computed bounds are uniformly valid regardless of the size of the underlying coarse discretization. The method is demonstrated with two applications involving large strain plane stress incompressible neo-hookean hyperelasticity.Singapore-MIT Alliance (SMA

Spectra of weighted algebras of holomorphic functions

We consider weighted algebras of holomorphic functions on a Banach space. We determine conditions on a family of weights that assure that the corresponding weighted space is an algebra or has polynomial Schauder decompositions. We study the spectra of weighted algebras and endow them with an analytic structure. We also deal with composition operators and algebra homomorphisms, in particular to investigate how their induced mappings act on the analytic structure of the spectrum. Moreover, a Banach-Stone type question is addressed.Comment: 25 pages Corrected typo

Structural Interdependence among Colombian Departments

This paper advances on the analysis of the structural interdependence among Colombian departments. The results show that Bogotá has a large influence in the other regional economies through its purchasing power. Additionally, it can be observed a centerperiphery pattern in the spatial concentration of the effects of the hypothetical extraction of any territory. From a policy point of view, the main findings reaffirm the role played by Bogotá in the polarization process observed in the regional economies in Colombia in the last years. Any policy action oriented to reduce these regional disparities should take into account that, given the structural interdependence among Colombian departments, new investment in the lagged regions would flow through Bogotá and the major regional economies.Input-output; extraction method; Colombia Classification JEL: R12; R15.

A Discrete Choice Experiment to Elicit the Willingness to Pay for Health Insurance by the Informal Sector Workers in Sierra Leone

The current health care financing system in Sierra Leone is unsustainable and poses challenges ranging from increased in out of pocket health care expenditure to accessibility problems, particularly in rural areas where living standards are low and health care facilities are scarce. This paper investigates whether privately financed health Insurance can improve the accessibility to formal health care in Sierra Leone and mitigate the effects of OOPs on poor households. To do so, we estimate the Willingness To Pay (WTP) for health insurance among informal sector workers in Sierra Leone using a Discrete Choice Experiment approach. Eight informal sector activities were selected namely – petty trading, subsistence farming, commercial bike riding, cattle rearing, fishing, tailoring, mining and quarrying. A random effect logit model is used to estimate households’ WTP for an improvement in coverage, choice of health care provider and a reduction in waiting time. Our study reveals that households were WTP more to have better attributes (better coverage, less waiting time) and to go to a faith - based provider. Our findings also suggest that location – rural versus urban – matters in determining the WTP since urban households were WTP more for health insurance than their rural counterparts, (SLL 54,348 or $7.34) and (SLL 37,250.5 or$5.03), respectively