The All Sky Young Association (ASYA): a new young association

To analyze the SACY (Search for Associations Containing Young stars) survey we developed a method to find young associations and to define their high probability members. These bona fide members enable to obtain the kinematical and the physical properties of each association in a proper way. Recently we noted a concentration in the UV plane and we found a new association we are calling ASYA (All Sky Young Association) for its overall distribution in the sky with a total of 38 bonafide members and an estimated age of 110 Myr, the oldest young association found in the SACY survey. We present here its kinematical, space and Li distributions and its HR diagram.Comment: To appear in "Young Stars and Planets Near the Sun", Proceedings of IAU Symposium No. 314 (Cambridge University Press), J.H. Kastner, B. Stelzer, S.A. Metchev, ed

How many nucleosynthesis processes exist at low metallicity?

Abundances of low-metallicity stars offer a unique opportunity to understand the contribution and conditions of the different processes that synthesize heavy elements. Many old, metal-poor stars show a robust abundance pattern for elements heavier than Ba, and a less robust pattern between Sr and Ag. Here we probe if two nucleosynthesis processes are sufficient to explain the stellar abundances at low metallicity, and we carry out a site independent approach to separate the contribution from these two processes or components to the total observationally derived abundances. Our approach provides a method to determine the contribution of each process to the production of elements such as Sr, Zr, Ba, and Eu. We explore the observed star-to-star abundance scatter as a function of metallicity that each process leads to. Moreover, we use the deduced abundance pattern of one of the nucleosynthesis components to constrain the astrophysical conditions of neutrino-driven winds from core-collapse supernovae.Comment: 13 pages, published in Ap

Dynamics of two interacting particles in classical billiards

The problem of two interacting particles moving in a d-dimensional billiard is considered here. A suitable coordinate transformation leads to the problem of a particle in an unconventional hyperbilliard. A dynamical map can be readily constructed for this general system, which greatly simplifies calculations. As a particular example, we consider two identical particles interacting through a screened Coulomb potential in a one-dimensional billiard. We find that the screening plays an important role in the dynamical behavior of the system and only in the limit of vanishing screening length can the particles be considered as bouncing balls. For more general screening and energy values, the system presents strong non-integrability with resonant islands of stability.Comment: REVTEX manuscript, 4 figures (1 ps + 3 gif, Postscript versions available upon request). Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.htm

'Et in Arcadia ego': Panosfski en perspectiva

En el presente ensayo se analiza la biografía científica del célebre historiador del arte Erwin Panofsky, intentando evaluar su legado a la historia del arte y de la cultura a partir de los comentarios críticos, explícitos o implícitos, que nos ha dejado Ernst H. Gombrich en el conjunto de sus escritos. Por lo análogo de su trayectoria profesional, las relaciones con el Warburg Institute, los intereses comunes en el ámbito de estudio, la amistad y el reconocimiento mutuo que se tuvieron en vida, las opiniones y críticas de E. H. Gombrich son especialmente autorizadas y valiosas para juzgar, ya cercanos a los cuarenta años de su muerte, las ideas y presupuestos teóricos de Panofsky

En el centenario del viaje a Oriente. Fotografías, cartas y dibujos

En 2011 se cumple el centenario del viaje a Oriente de Le Corbusier, con el que de alguna manera da fin a su periodo de formación autodidacta. Con este ensayo se desea evocar el contexto artístico e intelectual del joven Jeanneret en el momento de iniciar el viaje, a partir de algunas cartas que envía a Charles L’Eplattenier y a William Ritter, prestando especial atención al carácter finalista que van adquiriendo sus dibujos, bocetos y pinturas en aquellos decisivos meses

Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation

This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution in optical spectroscopic indicators, from Ca II H & K to Ca II IRT lines, using the spectral subtraction technique. We have found that this system presents an orbital period variation, higher than previously detected in other RS CVn systems. We determined an improved orbital solution, finding a circular orbit with a period of 3.274 days. We derived the stellar parameters, confirming the subgiant nature of the primary component and obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the primary and secondary components respectively. From our kinematic study, we can deduce its membership to the Castor moving group. Finally, the activity study has given us a better understanding of the possible mechanisms that produce the orbital period variation.Comment: Latex file with 16 pages, 18 figures. Available at http://www.ucm.es/info/Astrof/invest/actividad/actividad_pub.html Accepted for publication in: Astronomy & Astrophysics (A&A

Enseñanza de Inteligencia Artificial e Ingeniería del Conocimiento

nivel mundial en la unificación de los contenidos que se imparten en el primer curso que un estudiante de Informática recibe en Inteligencia Artificial e Ingeniería del Conocimiento (INCO). El alcance y la diversidad de problemas a los que estas materias están dirigidas incrementa aun más la necesidad de crear un programa coherente e integrado en sí mismo, y con el Plan de Estudios de la Institución en la que se imparte. Evidentemente, la unión de todos los temas tratados en los libros de Inteligencia Artificial e Ingeniería del Conocimiento, "comúnmente aceptado", sería demasiado extenso, mientras que la intersección de todos ellos no suele incluir todo aquello que es considerado importante