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Chicago Ridge, IL, United States

Colman H.,Wilbur Wright College
Applied Categorical Structures | Year: 2011

We propose a notion of 1-homotopy for generalized maps. This notion generalizes those of natural transformation and ordinary homotopy for functors. The 1-homotopy type of a Lie groupoid is shown to be invariant under Morita equivalence. As an application we consider orbifolds as groupoids and study the notion of orbifold 1-homotopy type induced by a 1-homotopy between presentations of the orbifold maps. © 2010 Springer Science+Business Media B.V.

Kruger A.J.,Wilbur Wright College | Richter M.J.,University of California at Davis | Seifahrt A.,University of Chicago | Carr J.S.,U.S. Navy | And 3 more authors.
Astrophysical Journal | Year: 2012

We present findings for DoAr 24E, a binary system that includes a classical infrared companion. We observed the DoAr 24E system with the Spitzer Infrared Spectrograph (IRS), with high-resolution, near-infrared spectroscopy of CO vibrational transitions, and with mid-infrared imaging. The source of high extinction toward infrared companions has been an item of continuing interest. Here we investigate the disk structure of DoAr 24E using the column densities, temperature, and velocity profiles of two CO absorption features seen toward DoAr 24Eb. We model the spectral energy distributions found using T-ReCS imaging and investigate the likely sources of extinction toward DoAr 24Eb. We find the lack of silicate absorption and small CO column density toward DoAr 24Eb suggest that the mid-infrared continuum is not as extinguished as the near-infrared, possibly due to the mid-infrared originating from an extended region. This, along with the velocity profile of the CO absorption, suggests that the source of high extinction is likely due to a disk or disk wind associated with DoAr 24Eb. © 2012. The American Astronomical Society. All rights reserved..

Kruger A.J.,Wilbur Wright College | Richter M.J.,University of California at Davis | Carr J.S.,U.S. Navy | Najita J.R.,National Optical Astronomy Observatory | And 3 more authors.
Astrophysical Journal | Year: 2013

Our Spitzer IRS observation of the infrared companion Glass Ib revealed fine-structure emission with high ionization ([Ne III]/[Ne II] = 2.1 and [S IV]/[S III] = 0.6) that indicates that the gas is likely illuminated by hard radiation. While models suggest that extreme-ultraviolet radiation could be present in T Tauri stars, this is the first detection of [S IV] and such a high [Ne III]/[Ne II] ratio in a young star. We also find that Glass Ib displays the molecules HCN, CO2, and H2O in emission. Here we investigate the Glass I binary system and consider possible mechanisms that may have caused the high ionization, whether from an outflow or disk irradiation. We also model the spectral energy distributions of Glass Ia and Ib to test if the system is a young member of the Chameleon I star-forming region, and we consider other possible classifications for the system. We find that Glass Ib is highly variable, showing changes in continuum strength and emission features at optical, near-infrared, and mid-infrared wavelengths. The optical light curve indicates that a central stellar component in Glass Ib became entirely visible for 2.5 years beginning in mid-2002 and possibly displayed periodic variability with repeated, short-period dimming during that time. As the fine-structure emission was not detected in observations before or after our Spitzer IRS observation, we explore whether the variable nature of Glass Ib is related to the gas being highly ionized, possibly due to variable accretion or an X-ray flare. © 2013. The American Astronomical Society. All rights reserved.

Kim H.,Wilbur Wright College | Sulaimon S.,Wilbur Wright College | Menezes S.,Illinois Institute of Technology | Son A.,Wilbur Wright College | Menezes W.J.C.,Wilbur Wright College
Journal of Chemical Education | Year: 2011

Molecular modeling is a powerful tool used for three-dimensional visualization and for exploring electrostatic forces involved in drug transport. This tool enhances student understanding of structure-property relationships, as well as actively engaging them in class. Molecular modeling of several central nervous system (CNS) drugs is used to examine the factors that affect their ability to penetrate the blood-brain barrier. Seventy-eight molecules with known experimental log(BB) values [log(BB) = log(Cbrain/Cblood), where Q, rain and Cblood are the equilibrium molar concentrations of the drug molecule in the brain and the blood, respectively] were selected from the literature and their three-dimensional models constructed using the Spartan software program. For each molecule, the percent polarity was calculated using a space-filling model (PSA%, polar surface area percentage) and an electrostatic potential map that was constructed from the wave function obtained from a single-point energy calculation, using the EDF2 density functional model (PA%, polar area percentage). Plots of these ratios against the experimental log(BB) values clearly display the general trend that the blood-brain barrier penetration decreases as the extent of polarity of a molecule increases. These plots were used to examine the mechanisms for blood-brain barrier penetration by drug molecules belonging to a study set consisting of 10 CNS-active and 3 CNS-inactive drugs. Values of PSA% or PA% greater than ~15% favor uptake transporter or efflux transporter mediated molecular crossing of the blood-brain barrier. In addition, highly lipophilic drug molecules (PSA% or PA% less than ~10%) most likely cross the blood-brain barrier by passive diffusion. These results are in agreement with previous experimental studies. Given the relative ease of polar surface area ratio calculations, its influence on drug transport mechanisms is a suitable topic to include in undergraduate curriculum. Several instructional exercises have been included.

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