On the long-term correlation between the flux in the Ca II H & K and Halpha lines for FGK stars

The re-emission in the cores of the Ca II H & K and H$\alpha$ lines, are well known proxies of stellar activity. However, these activity indices probe different activity phenomena, the first being more sensitive to plage variation, while the other one being more sensitive to filaments. In this paper we study the long-term correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$, two indices based on the Ca II H & K and H$\alpha$ lines respectively, for a sample of 271 FGK stars using measurements obtained over a $\sim$9 year time span. Because stellar activity is one of the main obstacles to the detection of low-mass and long-period planets, understanding further this activity index correlation can give us some hints about the optimal target to focus on, and ways to correct for these activity effects. We found a great variety of long-term correlations between $\log R'_{HK}$ and $\log I_{H\alpha}$. Around 20% of our sample has strong positive correlation between the indices while about 3% show strong negative correlation. These fractions are compatible with those found for the case of early-M dwarfs. Stars exhibiting a positive correlation have a tendency to be more active when compared to the median of the sample, while stars showing a negative correlation are more present among higher metallicity stars. There is also a tendency for the positively correlated stars to be more present among the coolest stars, a result which is probably due to the activity level effect on the correlation. Activity level and metallicity seem therefore to be playing a role on the correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$. Possible explanations based on the influence of filaments for the diversity in the correlations between these indices are discussed in this paper.Comment: 18 pages, 13 figures, 4 tables, accepted for publication in Astronomy and Astrophysic

Notes on the Two-brane Model with Variable Tension

Motivated by possible extensions of the braneworld models with two branes, we investigate some consequences of a variable brane tension using the well established results on consistency conditions. By a slight modification of the usual stress-tensor used in order to derive the braneworld sum rules, we find out some important constraints obeyed by time dependent brane tensions. In particular it is shown that the tensions of two Randall-Sundrum like branes obeying, at the same time, an Eotvos law, aggravate the fine tuning problem. Also, it is shown that if the hidden brane tension obeys an Eotvos law, then the visible brane has a mixed behavior allowing a bouncing-like period at early times while it is dominated by an Eotvos law nowadays. To finalize, we discuss some qualitative characteristics which may arise in the scope of dynamical brane tensions, as anisotropic background and branons production.Comment: 7 pages, 1 figure, accepted for publication in Physical Review

Black string corrections in variable tension braneworld scenarios

Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, what is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenarioComment: 12 pages, 5 figures, accepted in PR

Two-branes with variable tension model and the effective Newtonian constant

It is shown that, in the two brane time variation model framework, if the hidden brane tension varies according to the phenomenological Eotvos law, the visible brane tension behavior is such that its time derivative is negative in the past and positive after a specific time of cosmological evolution. This behavior is interpreted in terms of an useful mechanical system analog and its relation with the variation of the Newtonian (effective) gravitational `constant' is explored.Comment: 15 pages, no figure, accepted for publication in Physical Review

Associação entre patologia espermática e perda da motilidade do espermatozoide caprino congelado na presença de Catalase.

O objetivo deste estudo foi determinar as relações entre a morfologia espermática no sêmen fresco e motilidade pós-descongelação no sêmen caprino criopreservado em diluente contendo Catalase. Dezesseis ejaculados foram coletados de três bodes da raça Alpina Americana. Após a avaliação do sêmen, as amostras foram classificadas de acordo com a morfologia espermática em dois grupos: A (total de espermatozoides anormais - TEA &#8805;30%, n=6) e B (TEA &#8804; 15%, n=10). O sêmen foi diluído em diluidor Tris-gema contendo Catalase (1, 5, ou 10 U/ml/400 x 106 espermatozoides) ou sem antioxidante (controle). Nas amostras do grupo A, a motilidade espermática (MT) média no sêmen fresco, foi 71% e o TEA 38%. Já no grupo B, a MT foi 86% e o TEA 14%. Após a descongelação, a MT, TEA, CD/F e CDG foram significativamente maiores (P < 0,05) no grupo A do que no B; enquanto que a TDM foi menor no grupo A. A adição de catalase em 1 e 5U/mL teve um efeito significativo (P <0,05) na MT e TDM no grupo A enquanto que acima de 5U/mL induziu uma diminuição na motilidade em ambos os grupos. O grupo com alto percentual de patologia espermática, possivelmente estava passando por estresse oxidativo e nesse caso, a adição de catalase foi suficiente para proteger as células contra a perda de motilidade

Coleta e preparação de material botânico.

bitstream/item/50177/1/fd430001.pdf1 folder

Conhecendo espécies de plantas da Amazônia: ingá-costela (Inga capitata desv. - Leguminosae).

bitstream/item/102979/1/COM-TEC-243.pd