A spectral ratio, similar to that of von der Lühe (1984), is proposed to derive information on the degradation of the mean granular power spectrum at a position outside the disk centre. It has the advantage that the modulation transfer function is obtained directly from the data, without making any assumption on turbulence theory to describe the

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The present examination of the relation between the global parameters of spiral galaxies and their morphological type represents rotational velocity V at 25 mag/sq arcsec radius against this radius R for a 56-galaxy sample. Isolines of total mass, angular momentum, and mean surface density, plotted above the V-R diagram for isolated galaxies with

The gaseous component of the reflection nebula surrounding HD 26676 is investigated by comparing the UV spectrum of the star with that of the foreground star HD 26793. The physical properties of the cloud are constrained under the assumption of Mg photoionization and H ionization by cosmic rays and taking into account the effect of the stellar

Measurements of lithium in stars of different galactic populations such as young open clusters (Alpa Per, Pleiades, Praesepe, Coma, Hyades), very young stellar associations (Taurus-Auriga, Chamaeleon, Ophiuchus clouds), intermediate and old open clusters (NGC 752, M 67, NGC 188), old disk stars, and halo stars give the observational framework from