Astrophysics and Astronomy Commons^™

The Evolution Of Dwarf-Irregular Galaxy Ngc 1569: A Kinematic Study Of The Stars And Gas, Megan C. Johnson

Physics and Astronomy Dissertations

The evolution and formation of dwarf galaxies has great importance to our knowledge of cosmological history from the Big Bang through the present day structure we observe in our local universe. Dwarf galaxies are believed to be the "building blocks" of larger galaxies, which implies that interactions and mergers of these small systems must have occurred frequently in the early universe. There is a population of starburst dwarf irregular (dIm) galaxies that seem to have characteristics indicative of interactions or mergers. One of these dIm galaxies is the nearby post-starburst NGC 1569. This dissertation project explores the stellar and gas …

Optical Spectroscopy Of Massive Binary Stars, Stephen J. Williams

Physics and Astronomy Dissertations

This is a spectroscopic and photometric study of suspected close binary systems among the massive stars. The stars studied here include stars with temperatures ranging from 45,000 Kelvin (K) to 15,000 K, corresponding to spectral types ranging from O3 V to B5 III, masses between 47 Solar Masses and 5 Solar Masses, and absolute V magnitudes from -6.28 to -2.0. I categorize 30 targets according to my spectroscopic observations into groups with no radial velocity variability, single-lined, and double-lined variability. My analysis of the 18 constant velocity stars results in estimates of stellar effective temperature, T_eff, gravity, log …

Diagnosing Changes In Cells Using Ftir Microspectroscopy, Jing Guo

Physics and Astronomy Dissertations

Fourier transform infrared (FTIR) microscopy has shown promise as an analytical tool for detecting changes in cells and tissues, such as those due to viral infection, apoptosis induction or malignancy. In many cases, diagnosis via FTIR microscopy can be undertaken on a timescale shorter than that required for other physical or histological techniques.

In this work we have used FTIR microscopy to study Vero cells that have been infected with herpes simplex virus (type I) and adenovirus. We have studied cellular samples at various time intervals following exposure to the virus. Several spectral regions were identified that allow discrimination between …

Mechanisms Of Multistability In Neuronal Models, Tatiana Malashchenko

Physics and Astronomy Dissertations

Multistability is a fundamental attribute of the dynamics of neuronal systems under normal and pathological conditions. The mechanism of bistability of bursting and silence is not well understood and to our knowledge has not been experimentally recorded in single neurons. We considered four models. Two of them described the dynamics of a leech heart interneuron: the canonical model and a low-dimensional model. The other two models described mammalian pacemakers from the respiratory center.

We investigated the low-dimensional model and identified six different types of multistability of dynamical regimes. We described six generic mechanisms underlying the co-existence of oscillatory and silent …

The Self-Calibration Method For Multiple Systems At The Chara Array, David P. O'Brien

Physics and Astronomy Dissertations

The self-calibration method, a new interferometric technique using measurements in the K′-band (2.1 μm) at the CHARA Array, has been used to derive orbits for several spectroscopic binaries. This method uses the wide component of a hierarchical triple system to calibrate visibility measurements of the triple’s close binary system through quasi-simultaneous observations of the separated fringe packets of both. Prior to the onset of this project, the reduction of separated fringe packet data had never included the goal of deriving visibilities for both fringe packets, so new data reduction software has been written. Visibilities obtained with separated fringe packet data …