Numerical solution of linear models in economics: The SP-DG model revisited

In general, complex and large dimensional models are needed to solve real economic problems. Due to these characteristics, there is either no analytical solution for them or they are not attainable. As a result, solutions can be only obtained through numerical methods. Thus, the growing importance of computers in Economics is not surprising. This paper focuses on an implementation of the SP-DG model, using Matlab,developed by the students as part of the Computational Economics course. We also discuss some of our teaching/learning experience within the course, given for the first time in the FEP Doctoral Programme in Economics.SP-DG Model, Output, Inflation, Numerical Simulation, Teaching of Economics

Invasion Percolation Between two Sites

We investigate the process of invasion percolation between two sites (injection and extraction sites) separated by a distance r in two-dimensional lattices of size L. Our results for the non-trapping invasion percolation model indicate that the statistics of the mass of invaded clusters is significantly dependent on the local occupation probability (pressure) Pe at the extraction site. For Pe=0, we show that the mass distribution of invaded clusters P(M) follows a power-law P(M) ~ M^{-\alpha} for intermediate values of the mass M, with an exponent \alpha=1.39. When the local pressure is set to Pe=Pc, where Pc corresponds to the site percolation threshold of the lattice topology, the distribution P(M) still displays a scaling region, but with an exponent \alpha=1.02. This last behavior is consistent with previous results for the cluster statistics in standard percolation. In spite of these discrepancies, the results of our simulations indicate that the fractal dimension of the invaded cluster does not depends significantly on the local pressure Pe and it is consistent with the fractal dimension values reported for standard invasion percolation. Finally, we perform extensive numerical simulations to determine the effect of the lattice borders on the statistics of the invaded clusters and also to characterize the self-organized critical behavior of the invasion percolation process.Comment: 7 pages, 11 figures, submited for PR

Emprego da levedura Pichia membranifaciens CE015 imobilizada em suporte de alginato de cálcio para redução da acetofenona.

Neste trabalho apresentamos o emprego da levedura Pichia membranifaciens CE015 imobilizada em suporte de alginato de cálcio como agente para biorredução. Esta se revelou, a partir de uma triagem, como um potencial agente biocatalítico, uma vez que foram obtidos 76% de conversão da acetofenona ao 1-feniletanol com 98% de ee (S). Em seguida, investigou-se o efeito do emprego das células íntegras imobilizadas em suporte de alginato de cálcio como agentes de biorredução. Em um primeiro ensaio estudou-se a cinética de redução da acetofenona nos tempos de 3 até 96 horas, obtendo-se uma conversão máxima de 87% ao respectivo álcool com 95% de ee. Em seguida, foi estudada a reutilização das esferas em mais 2 ciclos, porém, houve um decréscimo para 67% de conversão mantendo-se constante ee de 95%

Plantas medicinais utilizadas na medicina etnoveterinária praticada na ilha do Marajó.

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Inhibitory Effect of Ethanolic Extract of Propolis on Corrosion of Ferritic Stainless Steel in Chloride Media

This work evaluates the inhibitory effect of ethanolic extract of propolis (EEP) on the corrosion of AISI 409 stainless steel (SS) in chloride media. Additions of 100, 200, and 500 μL of EEP in an aqueous sodium chloride solution were performed. The inhibitory effect on the SS was evaluated using electrochemical impedance spectroscopy (EIS) measurements up to 720 hours in immersion. EEP additions of 200 μL and 500 μL increased the polarization resistance of the SS. After 720 hours of immersion, the highest impedance was identified for the SS in solution with 500 μL of EEP. The maximum inhibition efficiency observed for addition of 500 μL of EEP in solution was 98.1 %, after 360 h of immersion. This work is licensed under a Creative Commons Attribution 4.0 International License