We have performed photometric optical observations of a sample of 17 core-dominated radio-loud quasars (CRLQs) and 17 radio-quiet quasars (RQQs). The aims were to confirm the existence of microvariations in strictly radio-quiet objects and to compare the properties of the variations in both types of quasars. Great care was taken to avoid selection

IAUC 6933 available at Central Bureau for Astronomical Telegrams.

IAUC 6931 available at Central Bureau for Astronomical Telegrams.

The three-dimensional P-wave velocity structure of Mt. Etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs. Results show a near-vertical low-velocity zone that extends from beneath the central craters to a depth of 10 km. This

In recent years, the capability to detect and analyse solar oscillation acoustic modes has greatly improved. The development of ground based networks like GONG or BiSON and the use of space platforms like SOHO has allowed us to study the structure and dynamics of the Sun with unprecedented precision.

We present quantitative analyses of 7 galactic O stars of spectral types from O3 to O6. By means of classical hydrostatic and planeparallel models we find the so-called He and Mass Discrepancies for a number of stars of our sample. We also prove the need of line-blocking for the correct reproduction of these spectra. For stars with effective