We study the process of formation of spiral structure extending the classical Turing's model to the case of a disk of stars and gas with diferencial rotation.

The studies of the emergence of magnetic flux across the convection zone show how the individual magnetic tubes rise toward the surface at the same time remaining anchored at the interface between the convection zone and the radiative interior. A number of recent numerical simulations, in particular, reproduce several observed features of the

The thin flux tube approximation cannot describe some important phenomena occurring during the journey of the tubes across the convection zone. This review summarizes five of those processes. One of them is related to the dramatic off-axis expansion suffered by the top of some magnetic tubes of moderate field strength in the middle of the

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Se informa sobre el estado actual del Círculo Meridiano Automático de San Fernando-San Juan. El instrumento (Grubb-Parson, de 178mm de abertura y 2665 mm de distancia focal) es gemelo del que se encuentra en las Islas Canarias, y fue instalado durante los meses de julio y agosto de 1996 en la estación astronómica ``Dr. C.U.Cesco" (El Leoncito

The ISOPHOT Interactive Analysis PIA, is a calibration, scientific analysis and visualization tool for accessing and processing ISOPHOT data. ISOPHOT is one of the instruments on board the Infrared Space Observatory ISO, launched in November 1995 by the European Space Agency. PIA is an IDL based package, comprising around 1500 routines including a