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 Collection: UNT Theses and Dissertations
Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field

Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field

Date: December 2001
Creator: Niu, Chengyu
Description: Metal and oxide interactions are of broad scientific and technological interest in areas such as heterogeneous catalysis, microelectronics, composite materials, and corrosion. In the real world, such interactions are often complicated by the presence of interfacial impurities and/or high electric fields that may change the thermodynamic and kinetic behaviors of the metal/oxide interfaces. This research includes: (1) the surface hydroxylation effects on the aluminum oxide interactions with copper adlayers, and (2) effects of high electric fields on the interface of thin aluminum oxide films and Ni3Al substrate. X-ray photoelectron spectroscopy (XPS) studies and first principles calculations have been carried out to compare copper adsorption on heavily hydroxylated a- Al2O3(0001) with dehydroxylated surfaces produced by Argon ion sputtering followed by annealing in oxygen. For a heavily hydroxylated surface with OH coverage of 0.47 monolayer (ML), sputter deposition of copper at 300 K results in a maximum Cu(I) coverage of ~0.35 ML, in agreement with theoretical predictions. Maximum Cu(I) coverage at 300 K decreases with decreasing surface hydroxylation. Exposure of a partially dehydroxylated a-Al2O3(0001) surface to either air or 2 Torr water vapor results in recovery of surface hydroxylation, which in turn increases the maximum Cu(I) coverage. The ability of surface hydroxyl ...
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Metal Complexes of 2,3-Quinoxalinedithiol

Metal Complexes of 2,3-Quinoxalinedithiol

Date: May 1969
Creator: Ganguli, Kalyan Kumar, 1912-
Description: A series of new planar complexes with the dianion of 2,3-quinoxalinedithiol ligand has been prepared. The complexes have been characterized from the study of their analyses, magnetic moment, conductance, polarograms, electron spin resonance spectra, and electronic spectra, and compared with the available data on the corresponding maleonitriledithiolene and toluene-3,4-dithiolene complexes.
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Metal (II) Complexes with N-Salicylideneamino Acids

Metal (II) Complexes with N-Salicylideneamino Acids

Date: August 1969
Creator: Carlisle, Gene Ozelle
Description: Transition metal complexes derived from Schiff bases have rendered an important contribution to the development of modern coordination chemistry. Various stable compounds have been prepared having synthetic, biological, and physicochemical interest. In particular, complexes of salicylaldimines, B-ketoamines, and closely related ligand systems have been investigated.
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Metal Oxide Reactions in Complex Environments: High Electric Fields and Pressures above Ultrahigh Vacuum

Metal Oxide Reactions in Complex Environments: High Electric Fields and Pressures above Ultrahigh Vacuum

Date: August 2005
Creator: Qin, Feili
Description: Metal oxide reactions at metal oxide surfaces or at metal-metal oxide interfaces are of exceptional significance in areas such as catalysis, micro- and nanoelectronics, chemical sensors, and catalysis. Such reactions are frequently complicated by the presence of high electric fields and/or H2O-containing environments. The focus of this research was to understand (1) the iron oxide growth mechanism on Fe(111) at 300 K and 500 K together with the effect of high electric fields on these iron oxide films, and (2) the growth of alumina films on two faces of Ni3Al single crystal and the interaction of the resulting films with water vapor under non-UHV conditions. These studies were conducted with AES, LEED, and STM. XPS was also employed in the second study. Oxidation of Fe(111) at 300 K resulted in the formation of Fe2O3 and Fe3O4. The substrate is uniformly covered with an oxide film with relatively small oxide islands, i.e. 5-15 nm in width. At 500 K, Fe3O4 is the predominant oxide phase formed, and the growth of oxide is not uniform, but occurs as large islands (100 - 300 nm in width) interspersed with patches of uncovered substrate. Under the stress of STM induced high electric fields, dielectric ...
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Metallization and Modification of Low-k Dielectric Materials

Metallization and Modification of Low-k Dielectric Materials

Date: December 2008
Creator: Martini, David M.
Description: Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity ...
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Metals in Chemistry and Biology: Computational Chemistry Studies

Metals in Chemistry and Biology: Computational Chemistry Studies

Date: May 2007
Creator: Dinescu, Adriana
Description: Numerous enzymatic reactions are controlled by the chemistry of metallic ions. This dissertation investigates the electronic properties of three transition metal (copper, chromium, and nickel) complexes and describes modeling studies performed on glutathione synthetase. (1) Copper nitrene complexes were computationally characterized, as these complexes have yet to be experimentally isolated. (2) Multireference calculations were carried out on a symmetric C2v chromium dimer derived from the crystal structure of the [(tBu3SiO)Cr(µ-OSitBu3)]2 complex. (3) The T-shaped geometry of a three-coordinate β-diketiminate nickel(I) complex with a CO ligand was compared and contrasted with isoelectronic and isosteric copper(II) complexes. (4) Glutathione synthetase (GS), an enzyme that belongs to the ATP-grasp superfamily, catalyzes the (Mg, ATP)-dependent biosynthesis of glutathione (GSH) from γ-glutamylcysteine and glycine. The free and reactant forms of human GS (wild-type and glycine mutants) were modeled computationally by employing molecular dynamics simulations, as these currently have not been structurally characterized.
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Metamodeling-based Fast Optimization of  Nanoscale Ams-socs

Metamodeling-based Fast Optimization of Nanoscale Ams-socs

Date: May 2012
Creator: Garitselov, Oleg
Description: Modern consumer electronic systems are mostly based on analog and digital circuits and are designed as analog/mixed-signal systems on chip (AMS-SoCs). the integration of analog and digital circuits on the same die makes the system cost effective. in AMS-SoCs, analog and mixed-signal portions have not traditionally received much attention due to their complexity. As the fabrication technology advances, the simulation times for AMS-SoC circuits become more complex and take significant amounts of time. the time allocated for the circuit design and optimization creates a need to reduce the simulation time. the time constraints placed on designers are imposed by the ever-shortening time to market and non-recurrent cost of the chip. This dissertation proposes the use of a novel method, called metamodeling, and intelligent optimization algorithms to reduce the design time. Metamodel-based ultra-fast design flows are proposed and investigated. Metamodel creation is a one time process and relies on fast sampling through accurate parasitic-aware simulations. One of the targets of this dissertation is to minimize the sample size while retaining the accuracy of the model. in order to achieve this goal, different statistical sampling techniques are explored and applied to various AMS-SoC circuits. Also, different metamodel functions are explored for their ...
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Metamorphosis: William Faulkner's Incorporation of Short Stories into Longer Narratives

Metamorphosis: William Faulkner's Incorporation of Short Stories into Longer Narratives

Date: January 1961
Creator: Faught, Patsy Kelley
Description: This study analyzes these stories in their original and later forms, both to discover the types of changes Faulkner made and to determine whether or not he followed any pattern in the revisions.
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“A Metaphor for the Impossibility of Togetherness”: Expansion Processes in Gubaidulina’s First String Quartet

“A Metaphor for the Impossibility of Togetherness”: Expansion Processes in Gubaidulina’s First String Quartet

Date: August 2012
Creator: Stroud, Cara
Description: This thesis illustrates how I hear processes of expansion organizing musical materials in the First String Quartet. By employing a flexible approach to expansion and developing models of wedge and additive expansions beyond the bounds of specific voice-leading or rhythmic augmentation procedures, expansion processes can be understood in each of the varied episodes of the quartet. Gubaidulina’s use of expansion processes, embodied organically in pitch, rhythm, form, and physical space, unifies the episodic materials of the First String Quartet and provides an inevitable conclusion to the work’s loose narrative.
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Metaphors, Myths, and Archetypes: Equal Paradigmatic Functions in Human Cognition?

Metaphors, Myths, and Archetypes: Equal Paradigmatic Functions in Human Cognition?

Access: Use of this item is restricted to the UNT Community.
Date: December 2002
Creator: Kalpakidis, Charalabos
Description: The overview of contributions to metaphor theory in Chapters 1 and 2, examined in reference to recent scholarship, suggests that the current theory of metaphor derives from long-standing traditions that regard metaphor as a crucial process of cognition. This overview calls to attention the necessity of a closer inspection of previous theories of metaphor. Chapter 3 takes initial steps in synthesizing views of domains of inquiry into cognitive processes of the human mind. It draws from cognitive models developed in linguistics and anthropology, taking into account hypotheses put forth by psychologists like Jung. It sets the stage for an analysis that intends to further understanding of how the East-West dichotomy guides, influences, and expresses cognitive processes. Although linguist George Lakoff denies the existence of a connection between metaphors, myths, and archetypes, Chapter 3 illustrates the possibility of a relationship among these phenomena. By synthesizing theoretical approaches, Chapter 3 initiates the development of a model suitable for the analysis of the East-West dichotomy as exercised in Chapter 4. As purely emergent from bodily experience, however, neither the concept of the East nor the concept of the West can be understood completely. There exist cultural experiences that may, depending on historical and ...
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