Porto Oscillation Code (POSC)

The Porto Oscillation Code (POSC) has been developed in 1995 and improved over the years, with the main goal of calculating linear adiabatic oscillations for models of solar-type stars. It has also been used to estimate the frequencies and eigenfunctions of stars from the pre-main sequence up to the sub-giant phase, having a mass between 0.8 and 4 solar masses. The code solves the linearised perturbation equations of adiabatic pulsations for an equilibrium model using a second order numerical integration method. The possibility of using Richardson extrapolation is implemented. Several options for the surface boundary condition can be used. In this work we briefly review the key ingredients of the calculations, namely the equations, the numerical scheme and the output.Comment: Accepted for publication in Astrophysics and Space Science

Construction of a non-standard quantum field theory through a generalized Heisenberg algebra

We construct a Heisenberg-like algebra for the one dimensional quantum free Klein-Gordon equation defined on the interval of the real line of length $L$. Using the realization of the ladder operators of this type Heisenberg algebra in terms of physical operators we build a 3+1 dimensional free quantum field theory based on this algebra. We introduce fields written in terms of the ladder operators of this type Heisenberg algebra and a free quantum Hamiltonian in terms of these fields. The mass spectrum of the physical excitations of this quantum field theory are given by $\sqrt{n^2 \pi^2/L^2+m_q^2}$, where $n= 1,2,...$ denotes the level of the particle with mass $m_q$ in an infinite square-well potential of width $L$.Comment: Latex, 16 page

Comportamento do fósforo em solos argiluviados da Região do Alentejo: sorção de fosfato

O Encontro decorreu na Universidade do Algarve.O poster apresenta os resultaos de um estudo sobre o comportamento do fósforo em solos argiluviados da Região do Alentejo

Phosphate desorption in luvisols and solonetz from a Mediterranean region

Poster apresentado no 6th International Phosphorus Workshop, que decorreu em Sevilha de 27 de Setembro a 1 de Outubro de 2010.Transfer of P from soil to water is controlled by the P retention capacity in the solid phase, namely by the equilibrium between adsorbed and precipitated forms. Desorption of P and/or phosphate dissolution govern the amount of P released into drainage water, runoff or freshwater. Soil P evaluated by Olsen method showed a strong correlation with the capacity of soil to desorb P and, within certain limits, to the transfer of P to water. This transfer of P relates to losses that occur either in surface horizons, or in subsurface horizons (to drainage water, to runoff or by soil erosion to freshwater)

Narrowband Photon Pair Source for Quantum Networks

We demonstrate a compact photon pair source based on a periodically poled lithium niobate nonlinear crystal in a cavity. The cavity parameters are chosen such that the emitted photon pair modes can be matched in the region of telecom ultra dense wavelength division multiplexing (U-DWDM) channel spacings. This approach provides efficient, low-loss, mode selection that is compatible with standard telecommunication networks. Photons with a coherence time of 8.6 ns (116 MHz) are produced and their purity is demonstrated. A source brightness of 134 pairs(s.mW.MHz)$^{-1}$ is reported. The high level of purity and compatibility with standard telecom networks is of great importance for complex quantum communication networks