The density matrix approach to polarized radiative transfer is reviewed, with particular emphasis on the physical assumptions that are at the basis of the recent developments achieved by means of this formalism. In particular it is shown that two of the basic hypotheses (the hypothesis of neglecting correlation effects between thermal velocity and

The Universidad Complutense de Madrid (UCM) Survey is a long-term project aiming at finding and analysing star-forming galaxies detected by their H$alpha$ emission in Schmidt objective-prism plates. The instrumental set-up limits the volume of the Universe surveyed to a redshift $zlesssim0.045$. So far we have discovered several hundred emission

Simultaneous UV and X-ray observations of the blazar PKS 0521-365 are combined with radio, IR, optical, and y-ray data taken at different epochs to study the overall emission from 10 to 1023 Hz. The flux distribution declines from the IR to the UV range (alpha0pt uv = 1.4 + 0.1), but hardens at higher frequencies. The remarkably flat X-ray spectrum

IAUC 6347 available at Central Bureau for Astronomical Telegrams.

Inversion techniques of the radiative transfer equation for polarized light are presented as one of the best current procedures to infer the vector magnetic field, as well as other quantities governing the physical state of the atmospheric layers that photons are coming from. Several characteristics of the various available inversion procedures are

We present new high quality continuum-subtracted Hα images of the grand-design galaxies NGC 157, NGC 3631, NGC 6764 and NGC 6951. We have determined the positions, angular sizes, and fluxes of their individual HII regions, and describe statistical properties of the HII region samples. We construct luminosity functions for all the HII regions in the