s-Processing in the Galactic Disk. I. Super-Solar Abundances of Y, Zr, La, Ce in Young Open Clusters

In a recent study, based on homogeneous barium abundance measurements in open clusters, a trend of increasing [Ba/Fe] ratios for decreasing cluster age was reported. We present here further abundance determinations, relative to four other elements hav- ing important s-process contributions, with the aim of investigating whether the growth found for [Ba/Fe] is or not indicative of a general property, shared also by the other heavy elements formed by slow neutron captures. In particular, we derived abundances for yttrium, zirconium, lanthanum and cerium, using equivalent widths measurements and the MOOG code. Our sample includes 19 open clusters of different ages, for which the spectra were obtained at the ESO VLT telescope, using the UVES spectrometer. The growth previously suggested for Ba is confirmed for all the elements analyzed in our study. This fact implies significant changes in our views of the Galactic chemical evolution for elements beyond iron. Our results necessarily require that very low-mass AGB stars (M < 1.5M\odot) produce larger amounts of s-process elements (hence acti- vate the 13 C-neutron source more effectively) than previously expected. Their role in producing neutron-rich elements in the Galactic disk has been so far underestimated and their evolution and neutron-capture nucleosynthesis should now be reconsidered.Comment: ApJ accepte

Dynamos and Chemical Mixing in Evolved Stars

In low-mass Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) stars, anomalous mixing must transport material near the hydrogen-burning shell to the convective envelope. Recently, it was suggested that buoyant magnetic flux tubes could supply the necessary transport rate (Busso et al. 2007). The fields are assumed to originate from a dynamo operating in the stellar interior. Here, we show what is required of an $\alpha-\Omega$ dynamo in the envelope of an AGB star to maintain these fields. Differential rotation and rotation drain via turbulent dissipation and Poynting flux, so if shear can be resupplied by convection, then large-scale toroidal field strengths of \left\simeq3\times10^4 G can be sustained at the base of the convection zone.Comment: 7 pages, 3 figures. To appear in AIP Proceedings of the IXth Torino Workshop on AGB Nucleosynthesi

The Solar Photospheric Nitrogen Abundance: Determination with 3D and 1D Model Atmospheres

We present a new determination of the solar nitrogen abundance making use of 3D hydrodynamical modelling of the solar photosphere, which is more physically motivated than traditional static 1D models. We selected suitable atomic spectral lines, relying on equivalent width measurements already existing in the literature. For atmospheric modelling we used the co 5 bold 3D radiation hydrodynamics code. We investigated the influence of both deviations from local thermodynamic equilibrium (non-LTE effects) and photospheric inhomogeneities (granulation effects) on the resulting abundance. We also compared several atlases of solar flux and centre-disc intensity presently available. As a result of our analysis, the photospheric solar nitrogen abundance is A(N) = 7.86 +/- 0.12.Comment: 6 pages, 4 figure

A physics-based life prediction methodology for thermal barrier coating systems

A novel mechanistic approach is proposed for the prediction of the life of thermal barrier coating (TBC) systems. The life prediction methodology is based on a criterion linked directly to the dominant failure mechanism. It relies on a statistical treatment of the TBC's morphological characteristics, non-destructive stress measurements and on a continuum mechanics framework to quantify the stresses that promote the nucleation and growth of microcracks within the TBC. The last of these accounts for the effects of TBC constituents' elasto-visco-plastic properties, the stiffening of the ceramic due to sintering and the oxidation at the interface between the thermally insulating yttria stabilized zirconia (YSZ) layer and the metallic bond coat. The mechanistic approach is used to investigate the effects on TBC life of the properties and morphology of the top YSZ coating, metallic low-pressure plasma sprayed bond coat and the thermally grown oxide. Its calibration is based on TBC damage inferred from non-destructive fluorescence measurements using piezo-spectroscopy and on the numerically predicted local TBC stresses responsible for the initiation of such damage. The potential applicability of the methodology to other types of TBC coatings and thermal loading conditions is also discussed

Efecto de la quinagolida en la prevención del síndrome de hiperestimulación ovárica temprano

El síndrome de hiperestimulación ovárico (SHO) es una de las más temidas complicaciones de las técnicas de reproducción asistida (TRA). Es una patología iatrogénica que puede presentarse en formas moderadas y graves y, en algunos casos, llevar la paciente a la muerte. Mujeres sometidas a las TRA necesitan pasar por un proceso denominado hiperestimulación ovárica controlada (HOC) este proceso puede tener una respuesta exacerbada en hasta un 20% de los casos y la evolución para SHO en su forma grave en aproximadamente un 4%. Actualmente no hay forma completamente eficaz para la prevención del SHO que no afecte los resultados de los tratamientos de TRA. Se ha demostrado en animales que los agonistas de la dopamina pueden disminuir la incidencia de SHO y un estudio piloto en donantes de ovocitos sometidas a HOC confirmó estos hallazgos. El objetivo de este estudio es identificar la dosis efectiva de quinagolida, un agonista de la dopamina, para la prevención del SHO en su forma moderada/severa precoz. La quinagolida fue administrada a mujeres en riesgo para desarrollar SHO. Las pacientes recibieron 3 dosis distintas del fármaco y un grupo recibió placebo. Un total de 182 pacientes bajo tratamiento de FIV/ICSI fueron aleatorizadas con la siguiente distribución: 53 (29%) para el grupo placebo, 51 (28%) para recibir quinagolida 50 mg/día, 52 (29%) para recibir quinagolida 100 mg/día y 26 (14%) para recibir quinagolida 200 mg/día. No hubo diferencias estadísticamente significativas entre los grupos de tratamiento con respecto a la edad, IMC o etiología de la infertilidad. El SHO moderado y/o severo ocurrió en las siguientes frecuencias: 23% (12/53) para el placebo, 12% (6 / 51) para quinagolida 50 mg/día, 13% (7 / 52) para quinagolida 100 µg/día y 4% (1 / 26) para quinagolida 200 µg/día (Tabla 6). Cuando se combinaron los tres niveles de dosis, la quinagolida se asoció con una disminución significativa [P = 0.019; OR = 0.28 (0.09-0.81)] en la frecuencia de SHOP moderada y/o severo. El SHO moderado y/o severo ocurrió en las siguientes frecuencias: 23% (12/53) para el placebo, 12% (6 / 51) para quinagolida 50 mg/día, 13% (7 / 52) para quinagolida 100 µg/día y 4% (1 / 26) para quinagolida 200 µg/día (Tabla 6). Cuando se combinaron los tres niveles de dosis, la quinagolida se asoció con una disminución significativa [P = 0.019; OR = 0.28 (0.09-0.81)] en la frecuencia de SHOP moderada y/o severo. En los grupos quinagolida 50, 100 y 200 µg/día, el 6% (3 / 51), el 13% (7 / 52) y el 27% (7 / 26), respectivamente, abandonaron el estudio debido principalmente a eventos adversos relacionados con el sistema nervioso central y sistema digestivo. Las conclusiones del estudio fueron: El SHO es desencadenado por la administración de hCG en pacientes con riesgo para desarrollar el síndrome. La quinagolida es capaz de disminuir la incidencia del SHO de manera dosis-dependiente. El efecto de la quinagolida es más marcado en pacientes que no logran embarazo durante el ciclo de TRA, sugiriendo que pueden existir otros mediadores para el SHO en estas pacientes. La quinagolida no compromete los resultados de las TRA. La tolerabilidad de la quinagolida en altas dosis es reducida, aunque los efectos adversos tienden a disminuir a partir del tercer día de administración y ninguno es grave ni compromete la salud de la paciente o de su embarazo

Bicarbonate is required for migration of sperm epididymal protein DE/CRISP-1 to the equatorial segment and expression of rat sperm fusion ability

Numerous studies have demonstrated that sperm capacitation is a bicarbonate-dependent process. In the rat, capacitation has not been studied as much as in other species, mainly because of the difficulties in carrying out functional assays with this animal model. In the present study, we have examined the influence of bicarbonate in the overall rat sperm capacitation process by analyzing involvement of the anion in 1) protein tyrosine phosphorylation, 2) migration of epididymal protein DE (also known as CRISP-1) from the dorsal region to the equatorial segment of the sperm head that occurs during capacitation, and 3) ability of sperm to fuse with the egg. Incubation of sperm under capacitating conditions produced a time-dependent increase in protein tyrosine phosphorylation. This phosphorylation did not occur in the absence of HCO3- and rapidly increased by either exposure of sperm to HCO3- or replacement of the anion by a cAMP analog (dibutyryl-cAMP) and a phosphodiesterase inhibitor (pentoxifylline). The absence of HCO3- also produced a significant decrease in the percentage of cells showing migration of DE to the equatorial segment. This parameter was completely restored by addition of the anion, but dibutyryl-cAMP and pentoxifylline were not sufficient to overcome the decrease in DE migration. Sperm capacitated in the absence of HCO3- were unable to penetrate zona-free eggs independent of the presence of the anion during gamete coincubation. Exposure of these sperm to bicarbonate, or replacement of the anion by dibutyryl-cAMP and pentoxifylline, only partially restored the sperm fusion ability. Altogether, these results indicate that, in addition to its influence on protein tyrosine phosphorylation, bicarbonate is required to support other rat sperm capacitation- associated events, such as migration of DE to the equatorial segment, and expression of the ability of sperm to fuse with the egg.Fil: Da Ros, Vanina Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Munuce, María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Cohen, Debora Juana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Marin Briggiler, Clara Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Busso, Dolores. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Visconti, Pablo E.. University of Massachussets; Estados UnidosFil: Cuasnicu, Patricia Sara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin

Nucleosynthesis of light element isotopes in evolved stars experiencing extended mixing

We present computations of nucleosynthesis in red giants and asymptotic giant branch stars of Population I experiencing extended mixing. The assumed physical cause for mass transport is the buoyancy of magnetized structures, according to recent suggestions. The peculiar property of such a mechanism is to allow for both fast and slow mixing phenomena, as required for reproducing the spread in Li abundances displayed by red giants and as discussed in an accompanying paper. We explore here the effects of this kind of mass transport on CNO and intermediatemass nuclei and compare the results with the available evidence from evolved red giants and from the isotopic composition of presolar grains of AGB origin. It is found that a good general accord exists between predictions and measurements; in this framework we also show which type of observational data best constrains the various parameters. We conclude that magnetic buoyancy, allowing for mixing at rather different speeds, can be an interesting scenario to explore for explaining together the abundances of CNO nuclei and of Li.Comment: 8 pages, 7 figures, proceeding of 'The Origin of the Elements Heavier than Fe' September 24-28, 2008, Torino, Italy. PASA (accepted for publication

De meritocracia y emprendedurismo: la reproducción de las desigualdades sociales de los y las jóvenes durante el gobierno de Cambiemos

En este capítulo nos proponemos discutir la meritocracia y el emprendedurismo en los discursos y políticas del gobierno de Cambiemos, destinados principal aunque no únicamente a los y las jóvenes. A su vez, analizaremos la correlación de este discurso con la información ocupacional cuantitativa que provee la Encuesta Permanente de Hogares (EPH, Indec) correspondiente al año 2017.Facultad de Humanidades y Ciencias de la Educació