A thorough analysis of the sensitivities of the four Stokes profiles to the physical quantities involved in the local thermodynamic equilibrium (LTE) line formation is presented. We point out the ambiguities on the definition of a mean depth of formation of a given spectral line and on the use of Contribution Functions for the ascription of a

IAUC 5945 available at Central Bureau for Astronomical Telegrams.

We present spectropolarimetric observations of a sample of three quasars selected because of their very different broad-band polarization properties. All of the objects in the sample show frequency-dependent polarization degree (FDP), and two of them also show frequency-dependent polarization position angle (FDPA). We have not detected polarization

We construct cocycles on the Lie algebra of pseudo- and q-pseudodifferential symbols of one variable and on their close relatives: the sine-algebra and the Poisson algebra on two-torus. A ``quantum'' Godbillon-Vey cocycle on (pseudo)-differential operators appears in this construction as a natural generalization of the Gelfand-Fuchs 3-cocycle on

Recent isotopic and mineralogical studies have demonstrated a temporal and chemical link between the Chicxulub multiring impact basin and ejecta at the Cretaceous-Tertiary boundary. A fundamental problem yet to be resolved, however, is identification of the projectile responsible for this cataclysmic event. Drill core samples of impact melt rock

We discuss narrow band CCD imaging of NGC 4861 in continua at 4500 A, 5300 A and 6300 A as well as in Hα, Hβ and (O III] λ5007 A lines. We find that the system exhibits a double nucleus structure and a counter-tail to the well-known northeast chain of HII regions. The mean value of lines and continua frames for the main body brightness distribution