Theoretical studies suggest that C/O and Mg/Si are the most important elemental ratios in determining the mineralogy of terrestrial planets. The C/O ratio controls the distribution of Si among carbide and oxide species, while Mg/Si gives information about the silicate mineralogy. We present a detailed and uniform study of C, O, Mg, and Si

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We performed numerical simulations of mergers between gas-rich disc galaxies, which result in the formation of late-type galaxies. Stars formed during the merger end up in a thick disc that is partially supported by velocity dispersion and has high [α/Fe] ratios at all metallicities. Stars formed later end up in a thin, rotationally supported disc

Attention is given to problems which arise when an attempt is made to use observational material to clarify the mechanisms responsible for the heating of the chromosphere in a late-type star, in order to derive a clearer physical view of the nature of a chromosphere, its relation to the underlying photosphere, and the overlying corona. Problems

We spatially resolved the symbiotic star CI Cam, about 6 months after its April 1998 outburst, using the IOTA stellar interferometer. We measured the diameter of the dust shell in the H and K infrared bands over a range of position angles. We will discuss the relationship between these results and other ongoing observations of CI Cam.

We present optical broad- and narrow-band imaging of a sample of a dozen barred galaxies. These images are analysed in conjunction with our previously published near-infrared imaging of their central regions and with literature values for, e.g. bar strengths and the total star formation activity of the galaxies. We present B, I and Hα images, and