Gregory A. Shields

Learn More
Despite more than 2 decades of neuroimaging investigations, there is currently insufficient evidence to fully understand the neurobiological substrate of auditory hallucinations (AH). However, some progress has been made with imaging studies in patients with AH consistently reporting altered structure and function in speech and language, sensory, and(More)
The rotator interval and the long head of the biceps brachii tendon are anatomically closely associated structures believed to confer stability to the shoulder joint. Abnormalities of the rotator interval may be acquired or congenital and are associated with instability of the long head of the biceps brachii tendon. Clinical and arthroscopic diagnoses of(More)
We investigate the relationship between black hole mass, MBH, and host galaxy velocity dispersion, σ∗, for QSOs in Data Release 3 of the Sloan Digital Sky Survey. We derive MBH from the broad Hβ line width and continuum luminosity, and the bulge stellar velocity dispersion from the [O iii] narrow line width (σ[O III]). At higher redshifts, we use Mg ii and(More)
Chemical abundances provide important clues to the evolution of galaxies. Ionized nebulae are one of the main sources of chemical abundance measurements, especially in external galaxies. Studies of H II regions have shown that the overall metallicity of galaxies increases with galactic luminosity, and that spiral galaxies characteristically have radial(More)
We present measurements of the gas-phase C/O abundance ratio in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the Hubble Space Telescope. The C/O ratios increase systematically with O/H in both galaxies, from log C/O ≈ −0.8 at log O/H = −4.0 to log C/O ≈ −0.1 at log O/H =(More)
Imaging and spectroscopy with HST show that LBQS 0103−2753 (V = 17.8, z = 0.848) is a binary quasar with a separation of 0 .3 or 2.3 kpc. This is by far the smallest separation binary quasar reported to date. The two components have very different spectra, including the presence of strong broad absorption lines (BALs) in component A only. The emission-line(More)
We use QSO emission-line widths to examine the MBH −σ∗ relationship as a function of redshift and to extend the relationship to larger masses. Supermassive black holes in galactic nuclei are closely related to the bulge of the host galaxy. The mass of the black hole, MBH , increases with the bulge luminosity and with the velocity dispersion of the bulge(More)