Swimming with ShARCS: Comparison of On-sky Sensitivity With Model Predictions for ShaneAO on the Lick Observatory 3-meter Telescope

The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS - Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20\% higher throughput across the $JHK$ bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.Comment: 13 pages, 5 figures, SPIE Astronomical Telescopes + Instrumentation, Montreal 201

Mass Degeneracies In Self-Dual Models

An algebraic restriction of the nonabelian self-dual Chern-Simons-Higgs systems leads to coupled abelian models with interesting mass spectra. The vacua are characterized by embeddings of $SU(2)$ into the gauge algebra, and in the broken phases the gauge and real scalar masses coincide, reflecting the relation of these self-dual models to $N=2$ SUSY. The masses themselves are related to the exponents of the gauge algebra, and the self-duality equation is a deformation of the classical Toda equations.Comment: 10 pages LaTeX (previous copy truncated

In vivo functional neurochemistry of human cortical cholinergic function during visuospatial attention

Cortical acetylcholine is involved in key cognitive processes such as visuospatial attention. Dysfunction in the cholinergic system has been described in a number of neuropsychiatric disorders. Levels of brain acetylcholine can be pharmacologically manipulated, but it is not possible to directly measure it in vivo in humans. However, key parts of its biochemical cascade in neural tissue, such as choline, can be measured using magnetic resonance spectroscopy (MRS). There is evidence that levels of choline may be an indirect but proportional measure of acetylcholine availability in brain tissue. In this study, we measured relative choline levels in the parietal cortex using functional (event-related) MRS (fMRS) during performance of a visuospatial attention task, with a modelling approach verified using simulated data. We describe a task-driven interaction effect on choline concentration, specifically driven by contralateral attention shifts. Our results suggest that choline MRS has the potential to serve as a proxy of brain acetylcholine function in humans

The Acanthus Leaf in Classical Phases of American Architecture, 1800-1900

The purpose of this investigation is to show the extensive use and persistence of the acanthus motif in American exterior and interior architecture during the period of 1800 to 1900. This study is based upon the predominance of the leaf motif as it occurred in domestic, civic, commercial, and ecclesiastical building of New England, the Middle Atlantic states, and the South, and the Midwest. Data for this study has been compile from available literature concerning the occurrence of the acanthus leaf in American architecture, including Nineteenth-Century architectural handbooks and iconographic collections. Information regarding regional adaptations of the leaf motif has been obtained from a form letter survey sent to the thirty historical societies. Photographs have been used to aid in illustrating the prominence of the acanthus leaf in decoration. Through the ages the acanthus leaf has been a prominent decoration in the field of architecture. In its decorative forms, the acanthus motif imitated its thistle-like leaf but with subsequent use and development its design became more symbolic and abstract. The acanthus motif attained its height as ornamentation in American architecture during the Greek Revival. Throughout the entire period, 1800-1900, the acanthus motif expressed its classical origins; however, during the middle of the Nineteenth Century this leaf ornament assumed abstraction in both domestic and ecclesiastical decorations. During the last two decades of the century, the acanthus motif has occurred less frequently in architectural ornamentation than any other time from 1800 to 1900.</p