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Physical Sciences and Mathematics Commons™

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Astrophysics and Astronomy

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Georgia State University

2008

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Do R_{Aa} And R_{Cp} Quantify Nuclear Medium Effects?, Robert Adrian Zaballa Nov 2008

Do R_{Aa} And R_{Cp} Quantify Nuclear Medium Effects?, Robert Adrian Zaballa

Physics and Astronomy Dissertations

With the use of an incoherent binary nucleon-nucleon collision model of heavy ion collisions for simulating particle production, it is demonstrated that the nuclear modification factors, R_{AA} and R_{CP}, are less than unity for hard scattering in the absence of any nuclear modification effects. The nuclear modification factor R_{dAu} is also shown to approach or exceed unity only if p_T broadening is taken into account. With a simple phenomenological parameter, the mean nucleon energy loss fraction, this model yields particle distributions that are comparable to those of experiment. The nuclear geometry is described by the Glauber model, and particle production …

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The Separated Fringe Packet Survey: Updating Multiplicity Of Solar-Type Stars Within 22 Parsecs, Christopher Donald Farrington Nov 2008

The Separated Fringe Packet Survey: Updating Multiplicity Of Solar-Type Stars Within 22 Parsecs, Christopher Donald Farrington

Physics and Astronomy Dissertations

Over the past half century, multiplicity studies have provided a foundation for the theories of stellar formation and evolution through understanding how likely it is that stars form alone or with companions. If spectroscopic orbits are combined with techniques that can determine visual orbits, we can access the most fundamental parameter of stellar evolution, stellar mass. This dissertation is composed of two main sections. The first involves the investigation of the seminal multiplicity study of Duquennoy & Mayor (1991b) which has been the ``gold standard" for solar-type stars for nearly 20 years. Improvements in technology in the intervening years have …

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Theory Of Electronic And Optical Properties Of Nanostructures, Prabath Hewageegana Nov 2008

Theory Of Electronic And Optical Properties Of Nanostructures, Prabath Hewageegana

Physics and Astronomy Dissertations

"There is plenty of room at the bottom." This bold and prophetic statement from Nobel laureate Richard Feynman back in 1950s at Cal Tech launched the Nano Age and predicted, quite accurately, the explosion in nanoscience and nanotechnology. Now this is a fast developing area in both science and technology. Many think this would bring the greatest technological revolution in the history of mankind. To understand electronic and optical properties of nanostructures, the following problems have been studied. In particular, intensity of mid-infrared light transmitted through a metallic diffraction grating has been theoretically studied. It has been shown that for …

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Short-Wave Infrared Diffuse Reflectance Of Textile Materials, Terence Haran Nov 2008

Short-Wave Infrared Diffuse Reflectance Of Textile Materials, Terence Haran

Physics and Astronomy Theses

This thesis analyzes the reflectance behavior of textiles in the short-wave infrared (SWIR) band (1 – 2 microns) in order to identify/design potential diagnostic tools that allow the remote detection of human presence in a scene. Analyzing the spectral response of fabrics in the SWIR band has gained significant interest in the remote sensing community since it provides a potential path to discriminate camouflaged clothing from backgrounds that appear similar to the object of interest in the visible band. Existing research, originating primarily from the textiles community, has thoroughly documented the behavior of clothing fabrics in the visible band. Other …

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Investigation Of Fundamental Black Hole Properties Of Agn Through Optical Variability, Wesley Thomas Ryle Jul 2008

Investigation Of Fundamental Black Hole Properties Of Agn Through Optical Variability, Wesley Thomas Ryle

Physics and Astronomy Dissertations

Active galactic nuclei (AGN) are known to vary in brightness in all regions of the electromagnetic spectrum and over a wide range of timescales. Many methods have been utilized to transform this observed variability into meaningful information about the central engines of AGN. One such technique, adapted from time series analysis of galactic x-ray binary systems, has been used to detect a characteristic break timescale in the power density spectra of x-ray variability in Seyfert galaxies. This timescale, thought to be related to instabilities in the accretion disk, appears to scale with black hole mass over many orders of magnitude. …

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Electron Spectroscopic Study Of Indium Nitride Layers, Rudra Prasad Bhatta Mar 2008

Electron Spectroscopic Study Of Indium Nitride Layers, Rudra Prasad Bhatta

Physics and Astronomy Dissertations

Surface structure, chemical composition, bonding configuration, film polarity, and electronic properties of InN layers grown by high pressure chemical vapor deposition (HPCVD) have been investigated. Sputtering at an angle of 50-70 degrees followed by atomic hydrogen cleaning (AHC) was successful in removing the carbon contaminants. AHC is found to be the most effective cleaning process to remove oxygen contaminants from InN layers in an ultrahigh vacuum (UHV) system and produced a well ordered surface. Auger electron spectroscopy (AES) confirmed the cleanliness of the surface, and low energy electron diffraction (LEED) yielded a 1×1 hexagonal pattern demonstrating a well-ordered surface. High …

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