Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited

Luminous Galactic OH/IR stars have been identified as massive (>4-5 M_s) AGB stars experiencing HBB and Li production. Their Rb abundances and [Rb/Zr] ratios derived from hydrostatic model atmospheres, are significantly higher than predictions from AGB nucleosynthesis models, posing a problem to our understanding of AGB evolution and nucleosynthesis. We report new Rb and Zr abundances in the full sample of massive Galactic AGB stars, previously studied with hydrostatic models, by using more realistic extended model atmospheres. We use a modified version of the spectral synthesis code Turbospectrum and consider the presence of a circumstellar envelope and radial wind. The Rb and Zr abundances are determined from the 7800 A Rb I resonant line and the 6474 A ZrO bandhead, respectively, and we explore the sensitivity of the derived abundances to variations of the stellar (Teff) and wind (M_loss, beta and vexp) parameters in the extended models. The Rb and Zr abundances derived from the best spectral fits are compared with the most recent AGB nucleosynthesis theoretical models. The new Rb abundances are much lower (even 1-2 dex) than those derived with the hydrostatic models, while the Zr abundances are similar. The Rb I line profile and Rb abundance are very sensitive to the M_loss rate but much less sensitive to variations of the wind velocity-law and the vexp(OH). We confirm the earlier preliminary results based on a smaller sample of massive O-rich AGB stars, that the use of extended atmosphere models can solve the discrepancy between the AGB nucleosynthesis theoretical models and the observations of Galactic massive AGB stars. The Rb abundances, however, are still strongly dependent of the M_loss, which is unknown in these AGB stars. Accurate M_loss rates in these massive Galactic AGB stars are needed in order to break the models degeneracy and get reliable Rb abundances in these stars.Comment: Accepted for publication in A&A, 14 pages, 12 figures, 4 table

Hot bottom burning and s-process nucleosynthesis in massive AGB stars at the beginning of the thermally-pulsing phase

We report the first spectroscopic identification of massive Galactic asymptotic giant branch (AGB) stars at the beginning of the thermal pulse (TP) phase. These stars are the most Li-rich massive AGBs found to date, super Li-rich AGBs with logE(Li)~3-4. The high Li overabundances are accompanied by weak or no s-process element (i.e. Rb and Zr) enhancements. A comparison of our observations with the most recent hot bottom burning (HBB) and s-process nucleosynthesis models confirms that HBB is strongly activated during the first TPs but the 22Ne neutron source needs many more TP and third dredge-up episodes to produce enough Rb at the stellar surface. We also show that the short-lived element Tc, usually used as an indicator of AGB genuineness, is not detected in massive AGBs which is in agreement with the theoretical predictions when the 22Ne neutron source dominates the s-process nucleosynthesis.Comment: Accepted for publication in Astronomy & Astrophysics Letters (7 pages, 5 figures and 1 table); final version (language corrected

Dimension two vacuum condensates in gauge-invariant theories

Gauge dependence of the dimension two condensate in Abelian and non-Abelian Yang-Mills theory is investigated.Comment: 10 page

Contribution à la connaissance des Trichoptères (Trichoptera) du Rif (Nord du Maroc)

L´étude de 6376 spécimens des Trichoptères récoltés dans 103 localités de la chaîne rifaine marocaine entre 2006 et 2010 et la compilation des citations bibliographiques concernant ce groupe d´insectes, ont permis l´identification de 41 espèces dans la zone. Cet inventaire faunistique a enrichi la faune du Rif de 7 espèces non citées antérieurement dans cette zone. Une check-list des Trichoptères identifiées est fournie et la distribution géographique à l´intérieur et à l´extérieur des bassins versants Rifains est discutée pour chacune des espèces, ainsi que quelques notes taxonomiques concernant quelques espèces

Un estudio sobre el álgebra de conjuntos basado en registros semióticos

Basados en la teoría de Registros Semióticos de Duval (Duval R.,2006) investigamos desde una postura cognitiva una problemática de enseñanza aprendizaje referida a la Teoría de Conjuntos, es un área que al igual que la lógica bivalente es fundamental para la construcción del conocimiento matemático. Realizamos un estudio de casos múltiples en dos universidades de la zona, donde la información que hemos recabado hasta ahora, dio cuenta fundamentalmente de las dificultades en las conversiones de registros naturales a gráficos, en conjunto con los tratamientos dentro de un mismo registro algebraico

Hamiltonian Noether theorem for gauge systems and two time physics

The Noether theorem for Hamiltonian constrained systems is revisited. In particular, our review presents a novel method to show that the gauge transformations are generated by the conserved quantities associated with the first class constraints. We apply our results to the relativistic point particle, to the Friedberg et al. model and, with special emphasis, to two time physics.Comment: 20 pages, Latex, references added, the "massless" sense of (87) is clarifie

Kibble-Zurek mechanism in driven-dissipative systems crossing a non-equilibrium phase transition

The Kibble-Zurek mechanism constitutes one of the most fascinating and universal phenomena in the physics of critical systems. It describes the formation of domains and the spontaneous nucleation of topological defects when a system is driven across a phase transition exhibiting spontaneous symmetry breaking. While a characteristic dependence of the defect density on the speed at which the transition is crossed was observed in a vast range of equilibrium condensed matter systems, its extension to intrinsically driven-dissipative systems is a matter of ongoing research. In this work we numerically confirm the Kibble-Zurek mechanism in a paradigmatic family of driven-dissipative quantum systems, namely exciton-polaritons in microcavities. Our findings show how the concepts of universality and critical dynamics extend to driven-dissipative systems that do not conserve energy or particle number nor satisfy a detailed balance condition

MANILA BAY WATERSHED SCORECARD: A GIS-BASED QUANTITATIVE WATERSHED HEALTH ASSESSMENT

Watershed health refers to the maintenance of the normal status of a watershed. With the use of Geographic Information Systems (GIS), a watershed health assessment framework was developed and applied to the Manila Bay Watershed (MBW) based on the sub-indices used by the US EPA and the Minnesota DNR. These three sub-indices were used and modified: geomorphology, connectivity, and hydrology. Geomorphology sub-index accounted for the effects of soil erosion using the Unit Stream Power-based Erosion/Deposition model (USPED). Connectivity sub-index considered the connection between habitats within three environments: terrestrial, aquatic, and riparian zone. Hydrology sub-index accounted for the effects of impervious cover and urbanization on the movement of water using three factors, namely, natural cover, tree cover, and loss of hydrologic storage. Land cover map was the most used dataset in this scorecard, where the maintained natural land covers generally received high scores and built-up areas received the lowest. The overall watershed health score of MBW is 75.713 from the mean of the three sub-indices. Pampanga River Basin, which is the largest river basin within the MBW, got the highest score of 79.462 since it consists of huge portions of maintained natural land cover. Manila River Basin, known to have dense built-up areas, got the lowest average of 60.773. On the provincial level, the province of Nueva Ecija got the highest score, and the National Capital Region (NCR) got the lowest. The developed framework successfully quantified a relative health score which can be used to rank and prioritize subwatersheds, and to measure in totality the improvement or degradation of subwatershed/s over time