Matsumoto and Yoshimura [hep-ph/9910393] have argued that there are loop corrections to the number density of heavy particles (in thermal equilibrium with a gas of light particles) that are not Boltzmann suppressed by a factor of e at temperatures T well below the mass M of the heavy particle. We argue that this conclusion follows from an inappropriate definition of the number density of the he...

Damped Lyα galaxies provide a sample of young galaxies where chemical abundances can be derived throughout the whole universe with an accuracy comparable to that for the local universe. Despite a large spread in redshift, HI column density and metallicity, DLA galaxies show a remarkable uniformity in the elemental ratios rather suggestive of similar chemical evolution if not of an unique popula...

The revision of the photospheric abundances proferred by Asplund et al has rendered opacity theory inconsistent with the seismologically determined opacity through the Sun. This highlights the need for a direct seismological measurement of solar abundances. Here we describe the technique used to measure abundances with seismology, examine our ability to detect differences between solar models u...

We present preliminary chemical abundance analyses of a group of high-velocity metal-poor stars. This report describes our work in progress. We examine the derived abundances in the context of previous studies of metal-poor stars with unusual abundances and/or extreme galactocentric orbits. Included in this sample are BD+80 245, a star previously known to have unusually low α-element abundances...

The pioneering observations of Spite & Spite showed lithium abundances in halo dwarfs to be almost uniform, irrespective of metallicity and mass over a range of effective temperatures from ∼5600 K up to the main-sequence turnoff. They inferred that the observed abundance was “hardly altered” from that produced in the hot Big Bang. Subsequent efforts have endeavoured to determine how small or la...

Stellar spectra derived from multiple-object bre-fed spectroscopic radial-velocity surveys, of the type feasible with, among other examples, AUTOFIB, 2dF, HY-DRA, NESSIE, and the Sloan survey, diier signiicantly from those traditionally used for determination of stellar abundances. The spectra tend to be of moderate resolution (around 1 A) and signal-to-noise ratio (around 10-20 per resolution ...

Extensive spectroscopic studies of stars with and without planets have concluded that stars hosting planets are significantly more metal-rich than those without planets. More subtle trends of different chemical elements begin to appear as the number of detected extrasolar planetary systems continues to grow. I review our current knowledge concerning the observed abundance trends of various chem...

The results of optical spectroscopy of H II regions in a sample of southern dwarf irregulars consisting of five dwarf galaxies in the Centaurus A group, four dwarfs in the Sculptor group, and eight additional dwarf galaxies are presented. Oxygen abundances are derived using the direct method where [O III]λ4363 is detected; otherwise, abundances are derived with the bright-line method using the ...