Regular black holes in f(G)f(G) gravity

In this work, we study the possibility of generalizing solutions of regular black holes with an electric charge, constructed in general relativity, for the $f(G)$ theory, where $G$ is the Gauss-Bonnet invariant. This type of solution arises due to the coupling between gravitational theory and nonlinear electrodynamics. We construct the formalism in terms of a mass function and it results in different gravitational and electromagnetic theories for which mass function. The electric field of these solutions are always regular and the strong energy condition is violated in some region inside the event horizon. For some solutions, we get an analytical form for the $f(G)$ function. Imposing the limit of some constant going to zero in the $f(G)$ function we recovered the linear case, making the general relativity a particular case.Comment: 22 pages, 25 figures.Version published in EPJ

On the κ\kappa-Dirac Oscillator revisited

This Letter is based on the $\kappa$-Dirac equation, derived from the $\kappa$-Poincar\'{e}-Hopf algebra. It is shown that the $\kappa$-Dirac equation preserves parity while breaks charge conjugation and time reversal symmetries. Introducing the Dirac oscillator prescription, $\mathbf{p}\to\mathbf{p}-im\omega\beta\mathbf{r}$, in the $\kappa$-Dirac equation, one obtains the $\kappa$-Dirac oscillator. Using a decomposition in terms of spin angular functions, one achieves the deformed radial equations, with the associated deformed energy eigenvalues and eigenfunctions. The deformation parameter breaks the infinite degeneracy of the Dirac oscillator. In the case where $\varepsilon=0$, one recovers the energy eigenvalues and eigenfunctions of the Dirac oscillator.Comment: 5 pages, no figures, accepted for publication in Physics Letters

Liquid mixtures involving fluorinated alcohols: The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol) Experimental and Simulation

Liquid mixtures involving fluorinated alcohols: The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol) Experimental and Simulation Pedro Duartea, Djêide Rodriguesa, Marcelo Silvaa, Pedro Morgadoa, Luís Martinsa,b and Eduardo J. M. Filipea* aCentro de Química Estrutural, Instituto Superior Técnico, 1049-001 Lisboa, Portugal bCentro de Química de Évora, Universidade de Évora, 7000-671 Évora, Portugal Fluorinated alcohols are substances with unique properties and high technological value in the pharmaceutical and chemical industries. Trifluoroethanol (TFE), in particular, displays a number of unusual properties as a solvent. For example, it dissolves nylon at room temperature and is effectively used as solvent in bioengineering. The presence of the three fluorines atoms gives the alcohol a high ionization constant, strong hydrogen bonding capability and stability at high temperatures. In the pharmaceutical industry, TFE finds use as the major raw material for the production of inhalation anesthetics. Mixtures of TFE and water (known as Fluorinols®) are used as working fluids for Rankine cycle heat engines for terrestrial and space applications, as a result of a unique combination of physical and thermodynamic properties such as high thermal efficiency and excellent turbine expansion characteristics. Environmentally, TFE is a CFC substitute with an acceptable short lifetime and with small ozone depletion potential. Additionally, TFE is known to induce conformational changes in proteins and it is used as a co-solvent to analyze structural features of partially folded states. The (ethanol + TFE) system displays an interesting and peculiar behaviour, combining a negative azeotrope with high positive excess volumes. In this work, liquid mixtures of (ethanol + TFE) were investigated. The densities of the mixtures were measured as a function of composition between 278K and 338K and at pressures up to 700 bar. The corresponding excess volumes as a function of temperature and pressure, the isothermal compressibilities and thermal expansivities were calculated from the experimental results. The mixtures are highly non-ideal with excess volumes ranging from 0.8 - 1.0 cm3mol-1. Finally, molecular dynamic simulations were performed to model and interpret the experimental results. The Trappe force field was used to simulate the (TFE + ethanol) mixtures and calculate the corresponding excess volumes. The simulation results are able to reproduce the correct sign and order of magnitude of the experimental VE without fitting to the experimental data. Furthermore, the simulations suggest the presence of a particular type of hydrogen bridge between ethanol and TFE, that can help to rationalize the experimental results

Family Farming and Biodiesel: rural development in Central-Western Brazil

A produção de biodiesel no Brasil iniciou-se em 2005. O Programa Nacional de Produção e Uso do Biodiesel (PNPB) objetivou integrar agricultores familiares como fornecedores de matéria-prima para as indústrias de biodiesel, reduzindo assim a pobreza e promovendo o desenvolvimento rural. A integração de agricultores familiares foi revista devido a predominância da soja na cadeia de produção do biodiesel. Este estudo teve como objetivo comparar os mecanismos institucionais desenvolvidos por agricultores familiares e agentes econômicos em Mato Grosso a partir de dois diferentes estudos que ocorreram entre 2011 e 2013. O contexto teórico da Nova Economia Institucional foi necessário para identificar os mecanismos contratuais e de mercado desenvolvidos – arrendamento de maquinário, adicional de preço, fontes de financiamento e os pacotes tecnológicos – para aumentar a renda familiar e contribuir para o sucesso do PNPB em Mato Grosso. A presença destes mecanismos em diferentes regiões indica a difusão do conhecimento na rede produtiva da soja

Avaliação da aptidão agrícola das terras do Campo Experimental da Embrapa Acre.

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Thermal performance of a passive solar office building in Portugal

This paper presents the thermal performance of a Passive Solar Office Building in Portugal in winter and summer 2006 and 2007. This Building, called Solar XXI, pretends to be an example of passive design both for heating and cooling. It contains a direct gain system assisted by a solar thermal system for winter conditions. In summer a ground cooling system (buried pipes) is used to cool the building, together with night cooling strategies. It also integrate in the vertical south envelope a Photovoltaic System (12 kWp) which provide around 12 MWh per year plus a 6kWp in the car parking, which correspond to around 76% of the electric energy consumption of the building. The integration of the PV system, in the building was done in such a way, that it is possible to recovery the heat production from the PV in order to be used for heating purpose