Astrometric radio source catalogs

A review of the accuracy of radio interferometric positions of extragalactic sources is given. A mean catalog of radio positions is presented. With the accuracy currently attainable, radio observations can contribute significantly to the determination of astronomical constants.     

UNDERSTANDING AND SOLVING AMERICAN URBAN PROBLEMS: GEOGRAPHICAL CONTRIBUTIONS?

The genesis of most urban problems can only be understood in the context of the capitalist global economy in which the geography of development is necessarily countered by a geography of underdevelopment, at all spatial scales. Realization of this fundamental point implies that urban problems can never be solved within a capitalist context, only spatially rearranged. Geographers concerned with inequalities are therefore faced with a dilemma: either they work to redistribute welfare and illfare in the world or they work for the unmasking and replacement of capitalism.     

The 'second parameter': a memory from the globular cluster formation epoch

We study the correlations between the distribution of stars on the horizontal branch (HB), the HB morphology, and some other properties of globular clusters (GCs) in a large sample of GCs. We strengthen previous results that a general correlation exists only between HB morphology and metallicity. Correlations with other properties, e.g. central density and core radius, exist only for GCs within a narrow metallicity range. We conjecture that the lack of correlations with present properties of GCs (besides metallicity) is because the variation of the HB morphologies between GCs having similar metallicities is caused by a process, or processes, the effect of which was determined at the formation time of GCs. This process (or processes) is historically termed the 'second parameter', metallicity being the 'first parameter'. We then argue that the 'planet second parameter' model, where the presence of planets and to a lesser degree brown dwarfs and low-mass main-sequence stars is the 'second parameter', fits this conjecture. This is because the processes that determine the presence of planets and their properties occur during the formation epoch of the star and its circumstellar disc.