Circumnuclear stellar population, morphology and environment of Seyfert 2 galaxies: an evolutionary scenario

We investigate the relation between the characteristics of the circumnuclear stellar population and both the galaxy morphology and the presence of close companions for a sample of 35 Seyfert 2 nuclei. Fifteen galaxies present unambiguous signatures of recent episodes of star formation within $\approx$300 pc from the nucleus. When we relate this property with the Hubble type of the host galaxy, we find that the incidence of recent circumnuclear star formation increases along the Hubble sequence, and seems to be larger than in non-Seyfert galaxies for the early Hubble types S0 and Sa, but similar to that in non-Seyfert galaxies for later Hubble types. Both in early-type and late-type Seyferts, the presence of recent star-formation is related to the galaxy morphology in the inner few kiloparsecs, as observed in HST images through the filter F606W by Malkan et al., who has assigned a late ``inner Hubble type'' to most Seyfert 2s with recent nuclear star-formation. This new classification is due to the presence of dust lanes and spiral structures in the inner region. The presence of recent star formation in Seyfert 2 nuclei is also related to interactions: among the 13 galaxies of the sample with close companions or in mergers, 9 have recent star formation in the nucleus. These correlations between the presence of companions, inner morphology and the incidence of recent star formation suggest an evolutionary scenario in which the interaction is responsible for sending gas inwards which both feeds the AGN and triggers star-formation. The starburst then fades with time and the composite Seyfert 2 + Starburst nucleus evolves to a ``pure'' Seyfert 2 nucleus with an old stellar population.Comment: 12 pages, 6 figures, 2 table

Estádio de adaptação de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) em hospedeiros alternativos.

A principal praga-alvo na cultura do milho é a lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), que, pela sua ampla distribuição temporal e geográfica constitui-se em uma das espécies mais nocivas nas regiões tropicais das Américas. O objetivo foi avaliar o estádio de adaptação de S. frugiperda em 17 espécies hospedeiras, cultivadas ou selvagens, mais comuns no agroecossistema brasileiro. As plantas foram cultivadas em cinco épocas, entre 2006 e 2008, utilizando o milho como ladrão. Larvas de S. frugiperda recém-eclodidas foram individualizadas e confinadas em copo plástico (50 mL), onde foram alimentadas com seções de folha nova de cada hospedeiro. O alimento foi substituído a cada dois dias por folhas frescas. Quatro variáveis biológicas foram avaliadas e utilizadas para se calcular um Índice de Adaptação (IA). Os resultados indicaram que a sobrevivência inicial de S. frugiperda variou de 100%, no milho, a 46%, no arroz. O período larval variou de 12,6 dias, no milho, a 27,1 dias, na grama batatais. A biomassa de pupa variou de 173,1 mg, no carrapicho, a 294,2 mg, no milho. O índice de adaptação, calculado com base nas variáveis biológicas de S. frugiperda, nos hospedeiros avaliados, variou de 17,43, no milho cultivado na época I, a 1,46, na cana-de-açúcar na época III. Para corrigir o efeito de época sobre o índice de adaptação de S. frugiperda nos hospedeiros, foi calculado o Índice Relativo de Adaptação (IRA), com base no índice de adaptação no milho (100%). Assim, com base no índice relativo de adaptação, estimado em condições de laboratório, os hospedeiros alternativos ao milho, para S. frugiperda, podem ser assim ordenados, do maior para o menor índice: sorgo granífero, sorgo selvagem, milheto, capim-tanzânia, amendoim, capim-marandu, capim-braquiária, caruru-de-porco, trigo, soja, algodão, feijão, arroz, capim-carrapicho, grama batatais e cana-de-açúcar

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

A symplectic realization of the Volterra lattice

We examine the multiple Hamiltonian structure and construct a symplectic realization of the Volterra model. We rediscover the hierarchy of invariants, Poisson brackets and master symmetries via the use of a recursion operator. The rational Volterra bracket is obtained using a negative recursion operator.Comment: 8 page

Practical implementation of an interior point nonmonotone line search filter method

Versão não definitiva do artigoHere we present a primal-dual interior point nonmonotone line search filter method for nonlinear programming. The filter relies on three measures, the feasibility, the centrality and the optimality presented in the optimality conditions, considers relaxed acceptability criteria for the step size and includes a feasibility restoration phase. The evaluation of the method is until now made on small problems and a comparison is provided with a merit function approach