Interpretation of Infrared Vibration-Rotation Spectra of Interstellar and Circumstellar Molecules

Infrared vibration-rotation lines can be valuable probes of interstellar and circumstellar molecules, especially symmetric molecules, which have no pure rotational transitions. But most such observations have been interpreted with an isothermal absorbing slab model, which leaves out important radiative transfer and molecular excitation effects. A more realistic non-LTE and non-isothermal radiative transfer model has been constructed. The results of this model are in much better agreement with the observations, including cases where lines in one branch of a vibration-rotation band are in absorption and another in emission. In general, conclusions based on the isothermal absorbing slab model can be very misleading, but the assumption of LTE may not lead to such large errors, particularly if the radiation field temperature is close to the gas temperature.Comment: 10 pages, 5 figures, ApJ in pres

Ionized Gas in the Galactic Center: New Observations and Interpretation

We present new observations of the [Ne II] emission from the ionized gas in Sgr A West with improved resolution and sensitivity. About half of the emission comes from gas with kinematics indicating it is orbiting in a plane tipped about 25\degree\ from the Galactic plane. This plane is consistent with that derived previously for the circumnuclear molecular disk and the northern arm and western arc ionized features. However, unlike most previous studies, we conclude that the ionized gas is not moving along the ionized features, but on more nearly circular paths. The observed speeds are close to, but probably somewhat less than expected for orbital motions in the potential of the central black hole and stars and have a small inward component. The spatial distribution of the emission is well fitted by a spiral pattern. We discuss possible physical explanations for the spatial distribution and kinematics of the ionized gas, and conclude that both may be best explained by a one-armed spiral density wave, which also accounts for both the observed low velocities and the inward velocity component. We suggest that a density wave may result from the precession of elliptical orbits in the potential of the black hole and stellar mass distribution.Comment: 28 pages, 13 figures, ApJ in pres

Direct Imaging At 12 Microns Of The Star-Forming Region W51 IRS-2

Astronom

Ionized Gas Kinematics at High Resolution IV: Star Formation and a Rotating Core in the Medusa (NGC 4194)

NGC 4194 is a post-merger starburst known as The Medusa for its striking tidal features. We present here a detailed study of the structure and kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data include radio continuum maps with resolution up to 0.18\arcsec (35 pc) and a $12.8\mu$m [NeII] data cube with spectral resolution $\sim4$\kms: the first {\it high resolution, extinction-free} observations of this remarkable object. The ionized gas has the kinematic signature of a core in solid-body rotation. The starburst has formed a complex of bright compact \HII~regions, probably excited by deeply embedded super star clusters, but none of these sources is a convincing candidate for a galactic nucleus. The nuclei of the merger partners that created the Medusa have not yet been identified.Comment: to appear in Ap

R=100,000 Spectroscopy of Photodissociation Regions: H2 Rotational Lines in the Orion Bar

Ground state rotational lines of H2 are good temperature probes of moderately hot (200-1000 K) gas. The low A-values of these lines result in low critical densities while ensuring that the lines are optically thin. ISO observations of H2 rotational lines in PDRs reveal large quantities of warm gas that are difficult to explain via current models, but the spatial resolution of ISO does not resolve the temperature structure of the warm gas. We present and discuss high spatial resolution observations of H2 rotational line emission from the Orion Bar.Comment: 4 pages, 1 figure, Proceedings of the ESO Workshop on High Resolution Infrared Spectroscop

STOCKER CATTLE OWNERSHIP VS. CONTRACT GRAZING: A COMPARISON OF RISK-ADJUSTED RETURNS

Stocker cattle ownership is compared to contract grazing using stochastic simulation. Returns are evaluated for both cattle owners and caretakers in contract grazing agreements. For caretakers, contract grazing is significantly less risky than cattle ownership. For cattle owners, contracting reduces risk only slightly while significantly reducing expected returns.Livestock Production/Industries,

Preservice teacher beliefs about education from their experiences as K-12 students and members of an adolescent subculture

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Cynthia MacGregor.Vita.Ed. D. University of Missouri--Columbia 2009.Results from the National Assessment of Educational Progress test over the past 35 years have not shown significant, long term improvement of 17 year olds in math or reading. The purpose of the study was to describe beliefs preservice teachers bring to teacher preparation programs that arise from their K-12 experience and as members of an adolescent or youth subculture. Methods of phenomenology were used to address the research questions. From a sample of 162 preservice teachers, 11 themes depicting preservice teacher beliefs about education were identified. The influence of an adolescent or youth subculture in the development of the 11 themes seems obvious in four, related in four, and having no apparent connection to three of the themes. A mechanism of recycling beliefs about education through preservice teachers back to K-12 students is presented that illustrates how emerging adolescent beliefs may enter and how older, outdated beliefs are maintained within education culture. Implications for practice include the development of preservice teacher screening procedures that are able to identify the range of beliefs preservice teachers have about education. Once identified, teacher preparation programs must develop curriculum that will address those preservice teacher beliefs that run counter to program goals through guided reflection and increased exposure to desired behavior.Includes bibliographical reference