Parent Stars of Extrasolar Planets. XII. Additional evidence for trends with vsini, condensation temperature, and chromospheric activity

Several recent studies have reported differences in vsini, abundance-condensation temperature trends, and chromospheric activity between samples of stars with and without Doppler-detected planets. These findings have been disputed, and the status of these results remains uncertain. We evaluate these claims using additional published data and find support for all three.Comment: 4 pages, 4 figures; accepted for publication in MNRAS as a Lette

Los instrumentos de aplicación del enfoque gobernanza

El desarrollo del presente proyecto busca contribuir al estudio que asocia los instrumentos de gobierno con el enfoque gobernanza (Gz). En este tenor, se pretende que la óptica del enfoque gobernanza deje de ser sólo una densa reflexión y se le asocie con lo que los gobiernos pueden hacer para su realización. La literatura especializada ha producido un abundante acervo de contribuciones teóricas sobre gobernanza; a él le hemos aprendido que las sociedades contemporáneas han encontrado formas nuevas de gobernarse (sin el híper gubernamentalismo), redistribuyendo poderes y responsabilidades, además, no deja de ser un reconocimiento de que las formas democráticas de convivencia requieren de impulso y promoción. Justamente, una de las preguntas que se derivan es ¿Qué hacen y pueden hacer los gobiernos en escenarios emergentes de gobernación? De un mundo tan complejo como el gubernamental sustrajimos el papel de sus instrumentos. ¿Cómo se asocian los requerimientos de gobernanza con los instrumentos de gobierno? Ese es el problema que guía el análisi

Parent Stars of Extrasolar Planets. XI. Trends with Condensation Temperature Revisited

We report the results of abundance analyses of new samples of stars with planets and stars without detected planets. We employ these data to compare abundance-condensation temperature trends in both samples. We find that stars with planets have more negative trends. In addition, the more metal-rich stars with planets display the most negative trends. These results confirm and extend the findings of Ramirez et al. (2009) and Melendez et al. (2009), who restricted their studies to solar analogs. We also show that the differences between the solar photospheric and CI meteoritic abundances correlate with condensation temperature.Comment: 7 pages, 11 figures; to be published in MNRA

Existence and stability of traveling waves in a biologically constrained model of seizure wave propagation

Epilepsy -- the condition of recurrent, unprovoked seizures -- manifests in brain voltage activity with characteristic spatio-temporal patterns. One of the patterns typically observed during a seizure is a traveling wave. To characterize these waves, we analyze high-density local field potential (LFP) data recorded in vivo from human cortex during a seizure from three patients. We show that traveling wave patterns emerge in the LFP with consistent quantitative features. Using a mean-field approach we model the neuronal population activity observed in the LFP and obtain explicit traveling wave solutions for this model. We then employ the LFP data to constrain the model and obtain parameter configurations that support traveling wave solutions with features consistent with the observed LFP waves. In particular, our model formulation is able to capture the "reverberation" of the activity following the traveling wave that was found in the clinical data. We obtain biologically reasonable parameter estimates for two important features: the timescales of the model and the extent of the connectivity. In this way, we link the observed LFP waves during seizure to proposed biological mechanisms. We also study the linear stability of the traveling wave solutions by constructing an Evans function. We find for some parameters the existence of two waves: one wave is slow and narrow whereas the other wave is fast and wide. Moreover, the fast and wide wave has speed and width consistent with the observed LFP waves. We numerically analyze the Evans function to determine stability (instability) of the fast (slow) wave