28 research outputs found
The dusty AGB star RS CrB: first mid-infrared interferometric observations with the Keck Telescopes
We report interferometric observations of the semi-regular variable star RS
CrB, a red giant with strong silicate emission features. The data were among
the first long baseline mid-infrared stellar fringes obtained between the Keck
telescopes, using parts of the new nulling beam combiner. The light was
dispersed by a low-resolution spectrometer, allowing simultaneous measurement
of the source visibility and intensity spectra from 8 to 12 microns. The
interferometric observations allow a non-ambiguous determination of the dust
shell spatial scale and relative flux contribution. Using a simple
spherically-symmetric model, in which a geometrically thin shell surrounds the
stellar photosphere, we find that ~30% to ~70% of the overall mid-infrared flux
- depending on the wavelength - originates from 7-8 stellar radii. The derived
shell opacity profile shows a broad peak around 11 microns (tau ~ 0.06),
characteristic of Mg-rich silicate dust particles.Comment: Accepted for publication in ApJ Letter
Observations of DG Tauri with the Keck Interferometer
We present the first science results from the Keck Interferometer, a
direct-detection infrared interferometer utilizing the two 10-meter Keck
telescopes. The instrument and system components are briefly described. We then
present observations of the T Tauri object DG Tau, which is resolved by the
interferometer. The resolved component has a radius of 0.12 to 0.24 AU,
depending on the assumed stellar and extended component fluxes and the model
geometry used. Possible origins and implications of the resolved emission are
discussed.Comment: 10 pages, 2 figures, to appear in ApJ Letter
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Incorporating long-term climate change in performance assessment for the Waste Isolation Pilot Plant
The United States Department of Energy (DOE) is developing the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico for the disposal of transuranic wastes generated by defense programs. Applicable regulations (40 CFR 191) require the DOE to evaluate disposal-system performance for 10,000 yr. Climatic changes may affect performance by altering groundwater flow. Paleoclimatic data from southeastern New Mexico and the surrounding area indicate that the wettest and coolest Quaternary climate at the site can be represented by that at the last glacial maximum, when mean annual precipitation was approximately twice that of the present. The hottest and driest climates have been similar to that of the present. The regularity of global glacial cycles during the late Pleistocene confirms that the climate of the last glacial maximum is suitable for use as a cooler and wetter bound for variability during the next 10,000 yr. Climate variability is incorporated into groundwater-flow modeling for WIPP PA by causing hydraulic head in a portion of the model-domain boundary to rise to the ground surface with hypothetical increases in precipitation during the next 10,000 yr. Variability in modeled disposal-system performance introduced by allowing had values to vary over this range is insignificant compared to variability resulting from other causes, including incomplete understanding of transport processes. Preliminary performance assessments suggest that climate variability will not affect regulatory compliance
Effect of Anticonvulsant Drugs In Vivo On Rat Pineal N-Acetyltransferase (EC 2.3.1.5) and Hydroxyindole-O-Methyltransferase (EC 2.1.1.4)
Depression of nocturnal pineal serotonin N-acetyltransferase activity in castrate male rats
Parameter sensitivity studies of selected components of the Waste Isolation Pilot Plant repository/shaft system /
"SAND89-2030.""Printed March 1990.""Prepared by Sandia National Laboratories ... for the United States Department of Energy under contract DE-AC04-76DP00789"--Cover."Sandia report."Cover title.Includes bibliographical references (pages 187-191).Mode of access: Internet