Call number: LD2668 .T4 1948 M65 / Master of Science

This dissertation investigates the properties of the metal-containing absorption lines seen in quasar spectra which have Z(abs) < < Z(em). These systems, which probably originate in the halos of galaxies at high redshift, are then compared to observations of the halo and interstellar medium of the Milky Way. We obtained echelle spectra at the Multiple Mirror Telescope (MMT) of the Z = 1.79 absorption system of the quasar B2 1225+317. The velocity profiles showed complex structure which varied from ion to ion, with ionization and column densities varying from component to component. The relative colums were consistent with the expectations for approximately interstellar abundance, low density material, in equilibrium with the ultraviolet radiation field of a spiral galaxy for λ > 912 A, and the integrated light from QSOs at Z = 1.79 for λ < 912 A. The aggregate C IV profile has a width of about 450 km/sec, larger than that expected for a single galaxy halo, however. With the MMT spectrograph and echellette grating, and MMT echelle, we studied the properties of three other redshift systems of B2 1225+317, which are optically thin at the Lyman limit, but have saturated Lyman alpha, and unlike material in the Milky Way, have strong C IV and no detectable C II. In some cases Si III and Si IV are weakly detected. Constructing photoionization models, we derive low total densities, cloud diameters on the order of a few kiloparsecs, and abundances which are consistent with the interstellar values. We calculated the contribution of quasars to the UV radiation field as a function of redshift. The calculated field depends on a number of uncertain assumptions, which were varied in order to estimate their effect on the result. Finally, we discuss an important input into these calculations, the continuum spectral energy distribution for quasars, with particular attention to the extreme ultraviolet.

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Recent development of sources and detectors in the THz regime (300 GHz to 3 THz) has enabled the precise measurement of material properties, including complex refractive indexes and loss tangents. Using our developed THz spectrometer, new data, in particular, of biological tissues has been used to develop potential THz medical imaging applications. In this paper, an overview of a 0.1-3 THz, with sub-GHz resolution spectroscopy system is presented that has been designed in particular to measure biological samples and provide data that will used to determine initial viability of THz medical imaging applications.

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The ceramic composite system containing Al₂O₃ and SiCw has seen multiple uses depending on its processing method. Both the thermomechanical properties and the electrical properties have piqued the interest for potential commercial applications. These include cutting tool inserts and microwave heating elements. Composite samples made by extrusion were pressureless sintered and characterized as a function of frequency, bias, sample length, and whisker orientation. Dry pressed percolated specimens containing different amounts of sintering aids were hot pressed and spark plasma sintered. The microstructure and electrical properties were compared.

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X-Ray emission techniques have been developed for the analysis of unusual and difficult samples that cannot be analyzed by conventional analytical techniques. Three X-ray techniques have been investigated, including radioisotope-induced X-ray fluorescence (RXRF), proton-induced X-ray emission (PIXE) and high resolution PIXE. Low flux radioisotope X-ray sources have been used to non-destructively characterize the elements present in photographic papers and emulsions. The information obtained has proven valuable for cataloging and preserving photographic prints of historical significance. Radioisotope X-ray sources have also been used in the development of low-cost, portable instrumentation useful for quantitating a variety of toxicological samples, including urine and feces samples to determine the elimination rates of X-ray contrast media containing dysprosium. The PIXE technique has been applied to the analysis of forensic samples, including bullet lead, tissue fragments and thin metal coatings, and has been compared with other non-destructive methods of analysis. Sample preparation techniques and analytical procedures have been developed for general, thin target, quantitative PIXE analysis. These procedures were applied to the analysis of five NBS standard reference materials, and to the analysis of deep-sea ferromanganese nodules. A high resolution (2 eV) PIXE system has been developed to aid in the deconvolution of overlapping X-ray peaks encountered in conventional PIXE spectra. This system has been applied to the measurement of chemical shifts in the X-ray emisson spectra of transition metal compounds.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy