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We describe the results of a search for time variability of the fine structure constant alpha using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm and mm absorption systems provide four independent samples, spanning approximately 23% to 87% of the age of the universe. Each sample yields a smaller alpha in(More)
Accepted —. Received —; in original form — ABSTRACT An experimental search for variation in the fundamental coupling constants is strongly motivated by modern high-energy physics theories. Comparison of quasar absorption line spectra with laboratory spectra provides a sensitive probe for variability of the fine structure constant, α, over cosmological(More)
We present first results from a program to measure the chemical abundances of a large (N > 30) sample of thick disk stars with the principal goal of investigating the formation history of the Galactic thick disk. We have obtained high resolution, high signal-to-noise spectra of 10 thick disk stars with the HIRES spectrograph on the 10m Keck I telescope. Our(More)
Disseminated osseous tuberculosis is a rare disease. This is a report of two cases of disseminated osseous tuberculosis imaged with MRI at 1.5-T, CT, plain radiography and bone scintigraphy. CT and plain radiography demonstrated either highly destructive or cystic lesions with sclerotic margins. Bone scintigraphy and plain radiography were quite insensitive(More)
The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of(More)
We present extensive early photometric (U BV Rr ′ Ii ′ JHK s) and spectroscopic (optical and near-infrared) data on supernova (SN) 2008D as well as X-ray data on the associated X-ray transient (XRT) 080109 which was serendipitously discovered in Swift data during follow-up observations of SN Ib 2007uy in the same galaxy, NGC 2770. Our data span a time range(More)
We present new chemical abundance measurements of 16 damped Lyα systems at z > 1.5 and update our previous abundance analyses. The entire database presented here was derived from HIRES observations on the Keck I telescope, reduced with the same software package, and analysed with identical techniques. Altogether, we present a large, homogeneous database of(More)
Recent analysis of five gamma-ray burst (GRB) afterglow spectra reveal the absence of molecular hydrogen absorption lines, a surprising result in light of their large neutral hydrogen column densities and the detection of H 2 in similar, more local star-forming regions like 30 Doradus in the LMC. Observational evidence further indicates that the bulk of the(More)