2-D Radiative Transfer in Protostellar Envelopes: II. An Evolutionary Sequence

We present model spectral energy distributions, colors, polarization, and images for an evolutionary sequence of a low-mass protostar from the early collapse stage (Class 0) to the remnant disk stage (Class III). We find a substantial overlap in colors and SEDs between protostars embedded in envelopes (Class 0-I) and T Tauri disks (Class II), especially at mid-IR wavelengths. Edge-on Class I-II sources show double-peaked spectral energy distributions, with a short-wavelength hump due to scattered light and the long-wavelength hump due to thermal emission. These are the bluest sources in mid-IR color-color diagrams. Since Class 0 and I sources are diffuse, the size of the aperture over which fluxes are integrated has a substantial effect on the computed colors, with larger aperture results showing significantly bluer colors. This causes overlap in color-color diagrams between all evolutionary states, especially in the mid-IR. However the near-IR polarization of the Class 0 sources is much higher than the Class I-II sources, providing a means to separate these evolutionary states. We varied the grain properties in the circumstellar envelope, allowing for larger grains in the disk midplane and smaller in the envelope. We find that grain growth in disks of Class I sources can be detected at wavelengths greater than 100 $\mu$m. Our image calculations predict that the diffuse emission from edge-on Class I and II sources should be detectable in the mid-IR with the Space Infrared Telescope Facility (SIRTF) in nearby star forming regions (out to several hundred parsecs).Comment: A version with high-resolution images is available at http://www.astro.wisc.edu/glimpse/glimpsepubs.htm

Nowhere minimal CR submanifolds and Levi-flat hypersurfaces

A local uniqueness property of holomorphic functions on real-analytic nowhere minimal CR submanifolds of higher codimension is investigated. A sufficient condition called almost minimality is given and studied. A weaker necessary condition, being contained a possibly singular real-analytic Levi-flat hypersurface is studied and characterized. This question is completely resolved for algebraic submanifolds of codimension 2 and a sufficient condition for noncontainment is given for non algebraic submanifolds. As a consequence, an example of a submanifold of codimension 2, not biholomorphically equivalent to an algebraic one, is given. We also investigate the structure of singularities of Levi-flat hypersurfaces.Comment: 21 pages; conjecture 2.8 was removed in proof; to appear in J. Geom. Ana

Computer-Based Assessment of Non-Cognitive Attributes of Occupational Therapy Students: A Pilot Evaluation

Purpose: Holistic admissions tools have been considered for use to diversify student admissions. The ability to screen non-cognitive attributes of applicants is an important element of holistic admissions. The objective of this study was to establish instrument reliability, inter-rater reliability, validity, item discrimination, item difficulty, and bias of the Computerized Assessment of Non-Cognitive Attributes of Health Care Professionals (CANA-HP). Methods: A novel methodology was developed to screen non-cognitive attributes of health profession applicants. Using a cross-sectional design, a convenience sample of students invited for interviews into a Mid-western occupational therapy program were recruited for participation. The 37 participants who consented, completed a demographic survey followed by the 12 question CANA-HP. Results: Open-ended questions had adequate internal reliability, discrimination, and difficulty. Multiple choice questions had low reliability and discrimination. No correlation was found between the CANA-HP and standardized cognitive assessments, except non-science GPA which was significantly correlated to the total open-ended (essay) scores and total overall score. Conclusions and Recommendations: The CANA-HP was not biased toward individuals from varied demographic backgrounds. Predictive validity of this tool and non-cognitive measurements of success are still needed. Occupational therapists in educational settings could consider adding open-ended ethical questions to the application process when interviews are not feasible. Classes in the non-sciences and other non-cognitive markers of success may also help identify students with ‘grit’ and critical reasoning which are important to practicing clinician

2-D Radiative Transfer in Protostellar Envelopes: I. Effects of Geometry on Class I Sources

We present 2-D radiation transfer models of Class I Protostars and show the effect of including more realistic geometries on the resulting spectral energy distributions and images. We begin with a rotationally flattened infalling envelope as our comparison model, and add a flared disk and bipolar cavity. The disk affects the spectral energy distribution most strongly at edge-on inclinations, causing a broad dip at about 10 um (independent of the silicate feature) due to high extinction and low scattering albedo in this wavelength region. The bipolar cavities allow more direct stellar+disk radiation to emerge into polar directions, and more scattering radiation to emerge into all directions. The wavelength-integrated flux, often interpreted as luminosity, varies with viewing angle, with pole-on viewing angles seeing 2-4 times as much flux as edge-on, depending on geometry. Thus, observational estimates of luminosity should take into account the inclination of a source. The envelopes with cavities are significantly bluer in near-IR and mid-IR color-color plots than those without cavities. Using 1-D models to interpret Class I sources with bipolar cavities would lead to an underestimate of envelope mass and an overestimate of the implied evolutionary state. We compute images at near-, mid-, and far-IR wavelengths. We find that the mid-IR colors and images are sensitive to scattering albedo, and that the flared disk shadows the midplane on large size scales at all wavelengths plotted. Finally, our models produce polarization spectra which can be used to diagnose dust properties, such as albedo variations due to grain growth. Our results of polarization across the 3.1 um ice feature agree well with observations for ice mantles covering 5% of the radius of the grains.Comment: Accepted for publication in ApJ, 37 pages, 13 figures (several figures reduced in quality; find original version at http://gemelli.colorado.edu/~bwhitney/preprints.html

One-dimensional Chern-Simons theory

We study a one-dimensional toy version of the Chern-Simons theory. We construct its simplicial version which comprises features of a low-energy effective gauge theory and of a topological quantum field theory in the sense of Atiyah.Comment: 37 page

Neutrally reinforced holes in symmetrically laminated plates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76616/1/AIAA-46360-396.pd

Principal Investigator Views of the IRB System

We undertook a qualitative e-mail survey of federally-funded principal investigators of their views of the US human subjects protection system, intended to identify the range of investigator attitudes. This was an exploratory study with a 14% response rate. Twenty-eight principal investigators responded; their comments were analyzed to show underlying themes, which are here presented along with supporting quotations

Large variation in the Rubisco kinetics of diatoms reveals diversity among their carbon-concentrating mechanisms

While marine phytoplankton rival plants in their contribution to global primary productivity, our understanding of their photosynthesis remains rudimentary. In particular, the kinetic diversity of the CO₂-fixing enzyme, Rubisco, in phytoplankton remains unknown. Here we quantify the maximum rates of carboxylation (Kcatᶜ), oxygenation (Kcatᵒ), Michaelis constants (K m) for CO₂ (K C) and O₂ (K O), and specificity for CO₂ over O₂ (SC/O) for Form I Rubisco from 11 diatom species. Diatom Rubisco shows greater variation in KC (23-68 μM), SC/O (57-116mol mol⁻¹), and KO (413-2032 μM) relative to plant and algal Rubisco. The broad range of KC values mostly exceed those of C₄ plant Rubisco, suggesting that the strength of the carbon-concentrating mechanism (CCM) in diatoms is more diverse, and more effective than previously predicted. The measured k cat c for each diatom Rubisco showed less variation (2.1-3.7s⁻¹), thus averting the canonical trade-off typically observed between KC and kcatᶜ for plant Form I Rubisco. Uniquely, a negative relationship between KC and cellular Rubisco content was found, suggesting variation among diatom species in how they allocate their limited cellular resources between Rubisco synthesis and their CCM. The activation status of Rubisco in each diatom was low, indicating a requirement for Rubisco activase. This work highlights the need to better understand the correlative natural diversity between the Rubisco kinetics and CCM of diatoms and the underpinning mechanistic differences in catalytic chemistry among the Form I Rubisco superfamily

High-resolution Near-Infrared Images and Models of the Circumstellar Disk in HH 30

We present Hubble Space Telescope (HST) Near-Infrared Camera and Multi-object Spectrometer (NICMOS) observations of the reflection nebulosity associated with the T Tauri star HH 30. The images show the scattered light pattern characteristic of a highly inclined, optically thick disk with a prominent dustlane whose width decreases with increasing wavelength. The reflected nebulosity exhibits a lateral asymmetry in the upper lobe on the opposite side to that reported in previously published Wide Field Planetary Camera 2 (WFPC2) images. The radiation transfer model which most closely reproduces the data has a flared accretion disk with dust grains larger than standard interstellar medium grains by a factor of approximately 2.1. A single hotspot on the stellar surface provides the necessary asymmetry to fit the images and is consistent with previous modeling of the light curve and images. Photometric analysis results in an estimated extinction of Av>~80; however, since the photometry measures only scattered light rather than direct stellar flux, this a lower limit. The radiative transfer models require an extinction of Av = 7,900.Comment: Accepted for publication in Ap.