High resolution high signal-to-noise spectral profiles of the 8498 and 8542 Å lines of the Ca II infrared triplet (IRT) have been obtained for a sample of quiescent and active dwarfs from spectral types F8 to K5. Line core intensity indices are related to the stellar spectral type, effective temperature, gravity and rotation. The Ca II IRT spectra

The following are the main findings: (1) Fragments with typically 1021Mx preserve their identity and even survive to the decay of the sunspots. (2) Each fragment has a very precise location in the whole ensemble. (3) The incomplete coalescense of the fragments leaves interstices which are penetrated by hot gas. This gives a natural explanation of

High-resolution white light and H-alpha observations are used to study the development of 15 large active solar regions. The behavior of the magnetic fragments which coalesce to form mature spots and the nature of the subphotospheric flux rope are examined. It is found that fragments with fluxes of about 10 to the 21st Mx preserve their identity

The authors have analyzed far-IR (IRAS) data for a sample of optically selected Seyfert galaxies. The far-infrared emission is uncorrelated, or at best weakly correlated, with the UV-optical emission from these sources. The authors find the far-IR emission to be extended in a number of objects. They discuss the possibility that Seyfert galaxies are

Details of the present work will be published in Rev. Mexicana Astron. Astrofis.

Four main aspects of umbral and penumbral fine structures are considered: brightness and morphology, magnetic field, velocity and oscillations. The author discusses a model in which penetrative convection produces peripheric umbral dots and upward flowing matter which is channeled outwards, pushing the magnetic field aside. The possibility of a non