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In situ vibrational spectroscopic investigation of C{sub 4} hydrocarbon selective oxidation over vanadium-phosphorus-oxide catalysts

Description: n-Butane selective oxidation over the VPO catalyst to maleic anhydride is the first and only commercialized process of light alkane selective oxidation. The mechanism of this reaction is still not well known despite over twenty years of extensive studies, which can partially be attributed to the extreme difficulties to characterize catalytic reactions real-time under typical reaction conditions. In situ spectroscopic characterization techniques such as Infrared spectroscopy and laser Raman spec… more
Date: May 10, 1999
Creator: Xue, Z.Y.
Partner: UNT Libraries Government Documents Department
open access

Inductively coupled plasma mass spectrometry for stable isotope metabolic tracer studies of living systems

Description: This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the an… more
Date: May 10, 1999
Creator: Luong, E.
Partner: UNT Libraries Government Documents Department
open access

Atom transfer and rearrangement reactions catalyzed by methyltrioxorhenium, MTO

Description: Methyltrioxorhenium (MTO) catalyzes the desulfurization of thiiranes by triphenylphosphine. Enormous enhancement in rate is observed when the catalyst is pretreated with hydrogen sulfide prior to the reaction. Using 2-mercaptomethylthiophenol as a ligand, the author synthesized several model complexes to study the mechanism of this reaction. With suitable model systems, they were able to show that the active catalyst is a Re(V) species. The reactions are highly stereospecific and very tolerant … more
Date: May 10, 1999
Creator: Jacob, J.
Partner: UNT Libraries Government Documents Department
open access

Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system

Description: Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are … more
Date: December 10, 1999
Creator: Beckman, Sarah E.
Partner: UNT Libraries Government Documents Department
open access

Development and evaluation of high resolution quadrupole mass analyzer and an inductively coupled plasma-Mach disk

Description: By definition a plasma is an electrically conducting gaseous mixture containing a significant concentration of cations and electrons. The Inductively Coupled Plasma (ICP) is an electrodeless discharge in a gas at atmospheric pressure. This discharge is an excellent one for vaporizing, atomizing, and ionizing elements. The early development of the ICP began in 1942 by Babat and then by Reed in the early 1960s. This was then followed by the pioneering work of Fassel and coworkers in the late 1960… more
Date: December 10, 1999
Creator: Amad, Ma'an Hazem
Partner: UNT Libraries Government Documents Department
open access

Fast methods for analysis of neurotransmitters from single cell and monitoring their releases in central nervous system by capillary electrophoresis, fluorescence microscopy and luminescence imaging

Description: Fast methods for separation and detection of important neurotransmitters and the releases in central nervous system (CNS) were developed. Enzyme based immunoassay combined with capillary electrophoresis was used to analyze the contents of amino acid neurotransmitters from single neuron cells. The release of amino acid neurotransmitters from neuron cultures was monitored by laser induced fluorescence imaging method. The release and signal transduction of adenosine triphosphate (ATP) in CNS was s… more
Date: December 10, 1999
Creator: Wang, Ziqiang
Partner: UNT Libraries Government Documents Department
open access

Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

Description: This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end… more
Date: December 10, 1999
Creator: Wong, Sze-Shun Season
Partner: UNT Libraries Government Documents Department
open access

Liquid metal extraction of Nd from NdFeB magnet scrap

Description: This research involves using molten magnesium (Mg) to remove neodymium (Nd) from NdFeB magnet scrap by diffusion. The results show that liquid metal extraction of Nd may be a viable and inexpensive method for recovering the expensive rare earth element Nd for use in Mg castings.
Date: December 10, 1999
Creator: Xu, Yanchen
Partner: UNT Libraries Government Documents Department
open access

Wave propagation in ordered, disordered, and nonlinear photonic band gap materials

Description: Photonic band gap materials are artificial dielectric structures that give the promise of molding and controlling the flow of optical light the same way semiconductors mold and control the electric current flow. In this dissertation the author studied two areas of photonic band gap materials. The first area is focused on the properties of one-dimensional PBG materials doped with Kerr-type nonlinear material, while, the second area is focused on the mechanisms responsible for the gap formation a… more
Date: December 10, 1999
Creator: Lidorikis, Elefterios
Partner: UNT Libraries Government Documents Department
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