Center of Light Curves for Whitney Fold and Cusp

The generic, qualitative, local behavior of center-of-light curves near folds and cusps are studied. The results apply to any finite number of lens planes.Comment: 2 pages, 1 figure, to appear in the ``Proceedings of the Ninth Marcel Grossmann Meeting on General Relativity,'' eds. V. Gurzadyan, R. Jantzen, & R. Ruffini, World Scientific (Singapore

Gravitational Microlensing Near Caustics I: Folds

We study the local behavior of gravitational lensing near fold catastrophes. Using a generic form for the lensing map near a fold, we determine the observable properties of the lensed images, focusing on the case when the individual images are unresolved, i.e., microlensing. Allowing for images not associated with the fold, we derive analytic expressions for the photometric and astrometric behavior near a generic fold caustic. We show how this form reduces to the more familiar linear caustic, which lenses a nearby source into two images which have equal magnification, opposite parity, and are equidistant from the critical curve. In this case, the simplicity and high degree of symmetry allows for the derivation of semi-analytic expressions for the photometric and astrometric deviations in the presence of finite sources with arbitrary surface brightness profiles. We use our results to derive some basic properties of astrometric microlensing near folds, in particular we predict for finite sources with uniform and limb darkening profiles, the detailed shape of the astrometric curve as the source crosses a fold. We find that the astrometric effects of limb darkening will be difficult to detect with the currently planned accuracy of the Space Interferometry Mission. We verify our results by numerically calculating the expected astrometric shift for the photometrically well-covered Galactic binary lensing event OGLE-1999-BUL-23, finding excellent agreement with our analytic expressions. Our results can be applied to any lensing system with fold caustics, including Galactic binary lenses and quasar microlensing.Comment: 37 pages, 7 figures. Revised version includes an expanded discussion of applications. Accepted to ApJ, to appear in the August 1, 2002 issue (v574

Assay of the Reverse Osmosis Purified Water in the Life Science Building at Bowling Green State University, Ohio

Contaminated water sources can cause problems for scientific research and result in costly delays and failures of experiments. At Bowling Green State University, the reverse osmosis supply circulating in the Life Sciences Building has been measurably contaminated for nearly three years, corresponding to a change in servicing of the system. While servicing has been accelerated, the contamination in the system remains. The focus of this research was to identify the species of bacteria and fungi growing inside of the water system so that it might alert those servicing the system, and to begin to eliminate the contamination. Reverse osmosis water samples were collected from various floors of the building and spread onto LB (Luria-Bertani) and MEA (Malt Extract) culture plates. Microbial growth was evident on 93% of the plates. Each separate colony was isolated, followed by DNA extraction and sequencing. Genus and species were determined and the information was presented to the firm that services the reverse osmosis system in order to determine a plan to decontaminate or replace the current plumbing system, and to determine the best way to assure the delivery of water that can be used in scientific research projects

Spectral mapping of brain functional connectivity from diffusion imaging.

Understanding the relationship between the dynamics of neural processes and the anatomical substrate of the brain is a central question in neuroscience. On the one hand, modern neuroimaging technologies, such as diffusion tensor imaging, can be used to construct structural graphs representing the architecture of white matter streamlines linking cortical and subcortical structures. On the other hand, temporal patterns of neural activity can be used to construct functional graphs representing temporal correlations between brain regions. Although some studies provide evidence that whole-brain functional connectivity is shaped by the underlying anatomy, the observed relationship between function and structure is weak, and the rules by which anatomy constrains brain dynamics remain elusive. In this article, we introduce a methodology to map the functional connectivity of a subject at rest from his or her structural graph. Using our methodology, we are able to systematically account for the role of structural walks in the formation of functional correlations. Furthermore, in our empirical evaluations, we observe that the eigenmodes of the mapped functional connectivity are associated with activity patterns associated with different cognitive systems