Stellar adiabatic mass loss model and applications

Roche-lobe overflow and common envelope evolution are very important in binary evolution, which is believed to be the main evolutionary channel to hot subdwarf stars. The details of these processes are difficult to model, but adiabatic expansion provides an excellent approximation to the structure of a donor star undergoing dynamical time scale mass transfer. We can use this model to study the responses of stars of various masses and evolutionary stages as potential donor stars, with the urgent goal of obtaining more accurate stability criteria for dynamical mass transfer in binary population synthesis studies. As examples, we describe here several models with the initial masses equal to 1 Msun and 10 Msun, and identify potential limitations to the use of our results for giant-branch stars.Comment: 7 pages, 5 figures,Accepted for publication in AP&SS, Special issue Hot Sub-dwarf Stars, in Han Z., Jeffery S., Podsiadlowski Ph. ed

Tidal friction in close-in satellites and exoplanets. The Darwin theory re-visited

This report is a review of Darwin's classical theory of bodily tides in which we present the analytical expressions for the orbital and rotational evolution of the bodies and for the energy dissipation rates due to their tidal interaction. General formulas are given which do not depend on any assumption linking the tidal lags to the frequencies of the corresponding tidal waves (except that equal frequency harmonics are assumed to span equal lags). Emphasis is given to the cases of companions having reached one of the two possible final states: (1) the super-synchronous stationary rotation resulting from the vanishing of the average tidal torque; (2) the capture into a 1:1 spin-orbit resonance (true synchronization). In these cases, the energy dissipation is controlled by the tidal harmonic with period equal to the orbital period (instead of the semi-diurnal tide) and the singularity due to the vanishing of the geometric phase lag does not exist. It is also shown that the true synchronization with non-zero eccentricity is only possible if an extra torque exists opposite to the tidal torque. The theory is developed assuming that this additional torque is produced by an equatorial permanent asymmetry in the companion. The results are model-dependent and the theory is developed only to the second degree in eccentricity and inclination (obliquity). It can easily be extended to higher orders, but formal accuracy will not be a real improvement as long as the physics of the processes leading to tidal lags is not better known.Comment: 30 pages, 7 figures, corrected typo

Silicate alteration mechanisms

Transmission electron microscopy shows that mineral alteration mechanisms are at least partly controlled by the structure of the altering mineral. Silicates of Fe and Mg with extended sequences of metal-oxygen octahedra change to trioctahedral layer-silicates showing a preferred orientation to the original mineral. Olivine, pyroxene, and biotite conform to this scheme, their alteration products inherit much of their structure. By contrast, framework silicates (which have tetrahedral Al) contribute little of their structure directly to clay-minerals, and alter via an amorphous phase to dioctahedral layer silicates.La microscopie électronique à transmission montre que les mécanismes d'altération des minéraux sont contrôlés, du moins jusqu'à un certain degré, par la structure du minéral qui subit l'altération. Les silicates de Fe et Mg avec des séquences étendues d'octaèdres à métaux et oxygène se changent en silicate phylliteux triocta-édriques,qui montrent une orientation préférentielle par rapport au minéral originel L'olivine, le pyroxene et la biotite se conforment à ce système ; les produits issus de leur altération héritent d'une grande partie de leur structure. Par contraste, les fedspaths et minéraux associés (qui contiennent de l'Ai tétraédrique) ne contri¬ buent que très peu par leur structure aux minéraux argileux, et s'altèrent à travers une phase amorphe pour devenir des silicates phylliteux dioctaédriques .Eggleton R.A, Smith K. L. Silicate alteration mechanisms. In: Pétrologie des altérations et des sols. Vol. I : Pétrologie expérimentale. Colloque international du CNRS, Paris 4-7 juillet 1983. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1983. pp. 45-53. (Sciences Géologiques. Mémoire, 71

Silicate alteration mechanisms

Transmission electron microscopy shows that mineral alteration mechanisms are at least partly controlled by the structure of the altering mineral. Silicates of Fe and Mg with extended sequences of metal-oxygen octahedra change to trioctahedral layer-silicates showing a preferred orientation to the original mineral. Olivine, pyroxene, and biotite conform to this scheme, their alteration products inherit much of their structure. By contrast, framework silicates (which have tetrahedral Al) contribute little of their structure directly to clay-minerals, and alter via an amorphous phase to dioctahedral layer silicates.La microscopie électronique à transmission montre que les mécanismes d'altération des minéraux sont contrôlés, du moins jusqu'à un certain degré, par la structure du minéral qui subit l'altération. Les silicates de Fe et Mg avec des séquences étendues d'octaèdres à métaux et oxygène se changent en silicate phylliteux triocta-édriques,qui montrent une orientation préférentielle par rapport au minéral originel L'olivine, le pyroxene et la biotite se conforment à ce système ; les produits issus de leur altération héritent d'une grande partie de leur structure. Par contraste, les fedspaths et minéraux associés (qui contiennent de l'Ai tétraédrique) ne contri¬ buent que très peu par leur structure aux minéraux argileux, et s'altèrent à travers une phase amorphe pour devenir des silicates phylliteux dioctaédriques .Eggleton R.A, Smith K. L. Silicate alteration mechanisms. In: Pétrologie des altérations et des sols. Vol. I : Pétrologie expérimentale. Colloque international du CNRS, Paris 4-7 juillet 1983. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1983. pp. 45-53. (Sciences Géologiques. Mémoire, 71

Frequência e riqueza de cupins em áreas de plantio de eucalipto no litoral norte da Bahia

O objetivo deste trabalho foi avaliar a frequência e a riqueza de espécies de cupins que ocorrem em áreas de reflorestamento com eucalipto. As amostras foram coletadas em três áreas de Eucalyptus recém-colhido, em dezembro de 2005, por meio de seis transectos de 100 m de comprimento por 2-m de largura, subdivididos em 20 parcelas (2x5 m) contíguas. Cada parcela foi amostrada por uma hora por pessoa, e de cada subdivisão foram retiradas 12 amostras de 20x20x20 cm de profundidade, das quais foram coletadas 21-espécies de cupins, pertencentes a duas famílias e 16 gêneros. Dez espécies foram consideradas dominantes, todas da família Termitidae, das quais as de maior frequência foram Amitermes amifer e Nasutitermes corniger. O grupo funcional xilófago teve o maior número de espécies (11) e a maior frequência. Espécies conhecidas como pragas em eucalipto tiveram frequência abaixo do limite de dominânci