The study of thermoelectric phenomena in solids provides a wealth of opportunity for exploration of the complex interrelationships between structure, processing, and properties of materials. As thermoelectricity implies some type of coupled thermal and electrical behavior, it is expected that a basic understanding of transport behavior in materials is the goal of such a study. However, transport properties such as electrical resistivity and thermal diffusivity cannot be fully understood and interpreted without first developing an understanding of the material's preparation and its underlying structure. It is the objective of this dissertation to critically examine a number of diverse systems in order to develop a broad perspective on how structure-processing-property relationships differ from system to system, and to discover the common parameters upon which any good thermoelectric material is based. The alloy systems examined in this work include silicon-germanium, zinc oxide, complex intermetallic compounds such as the half-Heusler MNiSn, where M = Ti, Zr, or Hf, and rare earth chalcogenides.

Crenulative turbulence is a nonlinear extension of the Bell-Plesset instability, usually observed in a converging system in which there is a nonhomogeneous response of stress to strain and/or strain rate. In general, crenelation occurs in any circumstance in which the mean flow streamlines converge the material more strongly than the compressibility can accommodate. Elements of the material slip past each other, resulting in local fluctuations in velocity from that of the mean flow, producing a type of turbulence that is more kinematic than inertial. For a homogeneous material, crenelation occurs at the atomic or molecular scale. With nonhomogeneous stress response at larger scales, the crenulative process can also occur at those larger scales. The results are manifested by a decrease in the rate of dissipation to heat, and by the configurationally-irreversible mixing of nonhomogeneities across any mean-flow-transported interface. We obtain a mathematical description of the crenulative process by means of Reynolds decomposition of the appropriate variables, and the derivation of transport equations for the second-order moments that arise in the mean-flow momentum and energy equations. The theory is illustrated by application to the spherical convergence of an incompressible fluid with nonhomogeneous distribution of kinematic viscosity.

Transmission Electron Microscopy (TEM), combined with X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) was employed to investigate a proprietary and multicomponent AB{sub 2} type Nickel-Metal Hydride (Ni-MH) battery alloy. This material was prepared by High Pressure Gas Atomization (HPGA) and examined in both the as-atomized and heat treated condition. TEM examination showed a heavily faulted dendritic growth structure in as-atomized powder. Selected Area Diffraction (SAD) showed that this region consisted of both a cubic C15 structure with lattice constant a=7.03 and a hexagonal C14 structure with lattice parameter a=4.97 {angstrom}, c=8.11 {angstrom}. The Orientation Relationship (OR) between the C14 and C15 structures was determined to be (111)[1{bar 1}0]{sub C15}//(0001)[11{bar 2}0]{sub C14}. An interdendritic phase possessing the C14 structure was also seen. There was also a very fine grain region consisting of the C14 structure. Upon heat treatment, the faulted structure became more defined and appeared as intercalation layers within the grains. Spherical particles rich in Zr and Ni appeared scattered at the grain boundaries instead of the C14 interdendritic phase. The polycrystalline region also changed to a mixture of C14 and C15 structures. These results as well as phase stability of the C15 and C14 structures based on a …

A search for decays of the B{sub c} meson was performed using data collected from 1990--1995 with the OPAL detector on or near the Z{sup 0} peak at LEP. The decay channels B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, B{sub c}{sup +} {r_arrow} J/{psi}a{sub 1}{sup +} and B{sub c}{sup +} {r_arrow} J/{psi}{ell}{sup +}{nu} were investigated, where {ell} denotes an electron or a muon. Two candidates are observed in the mode B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, with an estimated background of (0.63 {+-} 0.20) events. The weighted mean of the masses of the two candidates is (6.32 {+-} 0.06) GeV/c{sup 2}, which is consistent with the predicted mass of the B{sub c} meson. One candidate event is observed in the mode B{sub c}{sup +} {r_arrow} J/{psi}{ell}{sup +}{nu}, with an estimated background of (0.82 {+-} 0.19) events. No candidate events are observed in the B{sub c}{sup +} {r_arrow} J/{psi}a{sub 1}{sup +} decay mode, with an estimated background of (1.10 {+-} 0.22) events. Upper bounds at the 90% confidence level are set on the production rates for these processes.

A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast ({approx} 100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical approaches, allowing for the refinement of potential energy surfaces as well as dynamical models. After a brief overview, a detailed account of the construction of the experimental apparatus is presented. Documentation of the data acquisition program is contained in the Appendix. The first experimental demonstration of the technique is then presented for I{sub 2}{sup -} photodissociation, modeled using a simulation program which is also detailed in the Appendix. The investigation of I{sub 2}{sup -} photodissociation in several size-selected I{sub 2}{sup -}(Ar){sub n} (n = 6-20) and I{sub 2}{sup -}(CO{sub 2}){sub n} (n = 4-16) clusters forms the heart of the dissertation. In a series of chapters, the numerous effects of solvation on this fundamental bond-breaking reaction are explored, the most notable of which is the recombination of I{sub 2}{sup -} on the ground {tilde …

In a mortality study of white males who had worked at the Rocky Flats Nuclear Weapons Plant between 1952 and 1979, an increased number of deaths from benign and unspecified intracranial neoplasms was found. A case-control study nested within this cohort investigated the hypothesis that an association existed between brain tumor death and exposure to either internally deposited plutonium or external ionizing radiation. There was no statistically significant association found between estimated radiation exposure from internally deposited plutonium and the development of brain tumors. Exposure by job or work area showed no significant difference between the cohort and the control groups. An update of the study found elevated risk estimates for (1) all lymphopoietic neoplasms, and (2) all causes of death in employees with body burdens greater than or equal to two nanocuries of plutonium. There was an excess of brain tumors for the entire cohort. Similar cohort studies conducted on worker populations from other plutonium handling facilities have not yet shown any elevated risks for brain tumors. Historically, the Rocky Flats Nuclear Weapons Plant used large quantities of chemicals in their production operations. The use of solvents, particularly carbon tetrachloride, was unique to Rocky Flats. No investigation of the …

A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

This thesis is written to advance the reader's knowledge of precision-engineering principles and their application to designing machines that achieve both sufficient precision and minimum cost. It provides the concepts and tools necessary for the engineer to create new precision machine designs. Four case studies demonstrate the principles and showcase approaches and solutions to specific problems that generally have wider applications. These come from projects at the Lawrence Livermore National Laboratory in which the author participated: the Large Optics Diamond Turning Machine, Accuracy Enhancement of High- Productivity Machine Tools, the National Ignition Facility, and Extreme Ultraviolet Lithography. Although broad in scope, the topics go into sufficient depth to be useful to practicing precision engineers and often fulfill more academic ambitions. The thesis begins with a chapter that presents significant principles and fundamental knowledge from the Precision Engineering literature. Following this is a chapter that presents engineering design techniques that are general and not specific to precision machines. All subsequent chapters cover specific aspects of precision machine design. The first of these is Structural Design, guidelines and analysis techniques for achieving independently stiff machine structures. The next chapter addresses dynamic stiffness by presenting several techniques for Deterministic Damping, damping designs that …

The {sup 16}O(e,e'p)#8; reaction was studied in the #6;first physics experiment performed at Jefferson lab Hall A. In the quasielastic region cross sections were measured for both quasi#11;parallel and perpendicular kinematics at q = 1000 MeV and #2;{omega} = 445#14;#14;#15; MeV. From the data acquired in quasi#11;parallel kinematics#4; longitudinal and transverse response functions#4; R{sub L} and R{sub T} were separated for E{sub miss} < 60 MeV. The perpendicular kinematics data were used to extract R{sub LT}, #4; R{sub T},#4; and R{sub L#16;} + V{sub TT}/V{sub L}R{sub TT} response functions for the same E{sub miss} range and for P{sub miss} < 310 MeV#18;c. The {sub 16}O(#7;e,#4;e'p)#8; cross section was measured in the dip region at q = 1026 MeV and #2; {omega} = 586#12;#15;#19;#2; MeV for 10 MeV <#3; E{sub miss} < 320 MeV. This thesis presents the results for the missing energy continuum (#7;E{sub miss}>25#4; #3;#15; MeV)#8; from this experiment.

The focus of this dissertation is the use of chromatographic methods coupled with electrospray mass spectrometry (ES-MS) for the determination of both organic and inorganic compounds in aqueous solutions. The combination of liquid chromatography (LC) methods and ES-MS offers one of the foremost methods for determining compounds in complex aqueous solutions. In this work, LC-ES-MS methods are devised using ion exclusion chromatography, reversed phase chromatography, and ion exchange chromatography, as well as capillary electrophoresis (CE). For an aqueous sample, these LC-ES-MS and CE-ES-MS techniques require no sample preparation or analyte derivatization, which makes it possible to observe a wide variety of analytes as they exist in solution. The majority of this work focuses on the use of LC-ES-MS for the determination of unknown products and intermediates formed during electrochemical incineration (ECI), an experimental waste remediation process. This report contains a general introduction to the project and the general conclusions. Four chapters have been removed for separate processing. Titles are: Chapter 2: Determination of small carboxylic acids by ion exclusion chromatography with electrospray mass spectrometry; Chapter 3: Electrochemical incineration of benzoquinone in aqueous media using a quaternary metal oxide electrode in the absence of a soluble supporting electrolyte; Chapter 4: The …

Inductively coupled plasma mass spectrometry (ICP-MS) has become the method of choice for elemental and isotopic analysis. Several factors contribute to its success. Modern instruments are capable of routine analysis at part per trillion levels with relative detection limits in part per quadrillion levels. Sensitivities in these instruments can be as high as 200 million counts per second per part per million with linear dynamic ranges up to eight orders of magnitude. With standards for only a few elements, rapid semiquantitative analysis of over 70 elements in an individual sample can be performed. Less than 20 years after its inception ICP-MS has shown to be applicable to several areas of science. These include geochemistry, the nuclear industry, environmental chemistry, clinical chemistry, the semiconductor industry, and forensic chemistry. In this introduction, the general attributes of ICP-MS will be discussed in terms of instrumentation and sample introduction. The advantages and disadvantages of current systems are presented. A detailed description of one method of sample introduction, laser ablation, is given. The paper also gives conclusions and suggestions for future work. Chapter 2, Quantitative analysis of solids by laser ablation inductively coupled plasma mass spectrometry using dried solution aerosols for calibration, has been removed …

Addition of a novel anionic surfactant, namely lauryl polyoxyethylene sulfate, to an aqueous-acetonitrile electrolyte makes it possible to separate nonionic organic compounds by capillary electrophoresis. Separation is based on differences in the association between analytes and the surfactant. Highly hydrophobic compounds such as polyaromatic hydrocarbons are well separated by this new surfactant. Migration times of analytes can be readily changed over an unusually large range by varying the additive concentration and the proportion of acetonitrile in the electrolyte. Several examples are given, including the separation of four methylbenz[a]anthracene isomers and the separation of normal and deuterated acetophenone. The effect of adding this new surfactant to the acidic electrolyte was also investigated. Incorporation of cetyltrimethylammonium bromide in the electrolyte is shown to dynamically coat the capillary and reverse electroosmotic flow. Chiral recognition mechanism is studied using novel synthetic surfactants as chiral selectors, which are made from amino acids reacting with alkyl chloroformates. A satisfactory separation of both inorganic and organic anions is obtained using electrolyte solutions as high as 5 M sodium chloride using direct photometric detection. The effect of various salts on electrophoretic and electroosmotic mobility is further discussed. Several examples are given under high-salt conditions.

The peak profile of individual degranulation events from the on-column release of serotonin from single rat peritoneal mast cells (RPMCs) was monitored using capillary electrophoresis with laser-induced native fluorescence detection (CE-LINF). Serotonin, an important biogenic amine, is contained in granules (0.25 fL) within RPMCs and is extruded by a process termed exocytosis. The secretagogue, Polymyxin B sulfate, was used as the CE running buffer after injection of a single RPMC into the separation capillary to stimulate the release of the granules. Because the release process occurs on a ms time scale, monitoring individual exocytotic events is possible with the coupling of high-speed CE and LINF detection.

This research explores the application of a new technique, termed electrochemically modulated liquid chromatography (EMLC), to the chiral separations of pharmaceutical compounds. The introduction section provides a literature review of the technique and its applications, as well as brief overview of the research described in each of the next two chapters. Chapter 2 investigates the EMLC-based enantiomeric separation of a group of chiral benzodiazepines with {beta}-cyclodextrin as a chiral mobile phase additive. Chapter 3 demonstrates the effects of several experimental parameters on the separation efficiency of drug enantiomers. The author concludes with a general summary and possible directions for future studies. Chapters 2 and 3 are processed separately.

This report summarized the four parts of the research study and describes the general conclusions. Individual chapters have been removed for separate processing. The chapter titles are: A study of the dissociation of CH{sub 3}SH{sup +} by collisional activation: Observation of non-statistical behavior; High resolution vacuum ultraviolet pulsed field ionization photoelectron band for OCS{sup +}(X{sup 2}{Pi}): An experimental and theoretical study; Rotationally resolved pulsed field ionization photoelectron bands of H{sub 2}{sup +} ({Chi}{sup 2}{Sigma}{sup +}{sub g}, v{sup +} = 0--18); and Rotationally resolved pulsed field ionization photoelectron bands of HD{sup +} ({Chi}{sup 2}{Sigma}{sup +}, v{sup +} = 0--21).

Numerous researchers have studied the relevant material properties of so-called AB{sub 5} alloys for battery applications. These studies involved LaNi{sub 5} substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relationship between gas atomization processes, powder particle solidification phases, and hydrogen absorption properties of ultra fine (< 25 {micro}m) atomized powders with high surface area for enhanced battery performance. Concurrently, development of a gas atomization nozzle that is more efficient than all current designs is needed to increase the yield of ultrafine AB{sub 5} alloy powder for further processing advantage. Gas atomization processing of the AB{sub 5} alloys was demonstrated to be effective in producing ultrafine spherical powders that were resilient to hydrogen cycling for the benefit of improving corrosion resistance in battery application. These ultrafine powders benefited from the rapid solidification process by having refined solute segregation in the microstructure of the gas atomized powders which enabled a rapid anneal treatment of the powders. The author has demonstrated the ability …

The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV{sub 2}O{sub 4}. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV{sub 2}O{sub 4} is introduced [removed for separate processing]. The preparation methods employed by the author for nine LiV{sub 2}O{sub 4} and two Li{sub 1+x}Ti{sub 2{minus}x}O{sub 4} (x = 0 and 1/3) polycrystalline samples are introduced in Chapter 3. The subsequent structural characterization of the LiV{sub 2}O{sub 4} and Li{sub 1+x}Ti{sub 2{minus}x}O{sub 4} samples was done by the author using thermogravimetric analysis (TGA), x-ray diffraction measurements and their structural refinements by the Rietveld analysis. The results of the characterization are detailed in Chapter 3. In Chapter 4 magnetization measurements carried out by the author are detailed. In Chapter 5, after briefly discussing the resistivity measurement results including the single-crystal work by Rogers et al., for the purpose of clear characterization of LiV{sub 2}O{sub 4} it is of great importance …

This report describes the following: introduction to photoluminescence detected magnetic resonance (PLDMR); introduction to {pi}-conjugated systems; PLDMR measurements on poly(p-phenylene)-type ladder polymers; PLMDR measurements on poly(p-phenylene ethylene); and PLDMR measurements on C{sub 70}, polythiophene, poly(p-phenylene vinylene) and Dan-40. Appendices to this report describe: Operation of ODMR (optically detected magnetic resonance) spectrometer; ODMR system parameters; and Special purpose circuitry.

Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm{sup {minus}1}). In the past decade, the most exciting development in the field of photoionization and photoelectron spectroscopy has been the availability of high resolution, tunable ultraviolet (UV) and vacuum ultraviolet (VUV) laser sources. The laser pulsed field ionization photoelectron (PFI-PE) scheme is currently the state-of-the-art photoelectron spectroscopic technique and is capable of providing photoelectron energy resolution close to the optical resolution. The author has focused attention on the photoionization processes of some sulfur-containing species. The studies of the photoionization and photodissociation on sulfur-containing compounds [such as CS{sub 2}, CH{sub 3}SH, CH{sub 3}SSCH{sub 3}, CH{sub 3}CH{sub 2}SCH{sub 2}CH{sub 3}, HSCH{sub 2}CH{sub 2}SH and C{sub 4}H{sub 4}S (thiophene) and sulfur-containing radicals, such as HS, CS, CH{sub 3}S, CH{sub 3}CH{sub 2}S and CH{sub 3}SS], have been the major subjects in the group because sulfur is an important species contributing to air pollution in the atmosphere. The …

Supported metal catalysts typically consist of particles with sizes less than 10 nm, and because of the small crystallite size, low coordination number sites (edges and corners) represent a significant fraction of all surface sites. Furthermore, it has been demonstrated that adsorption rates can be much greater at these low coordination sites than on basal plane sites. What has not been generally appreciated, however, is that preferential adsorption at edge and corner sites may explain the mechanism by which a promoter, or the addition of a second metal to form a bimetallic, can alter the selectivity and rate of reaction. For example, the measurements of hydrogen adsorption onto supported Ru-Ag catalysts show marked decreases in the amount of hydrogen adsorbed relative to the amount adsorbed on Ru catalysts. Although it is known that Ag does not dissociatively adsorb hydrogen, this decrease cannot be explained by a simple one-to-one site blocking mechanism unless Ag preferentially populates edges and corners, thereby reducing the number of Ru edge sites. Indeed, Monte Carlo simulations of Ru-Group IB metal catalysts predict that Group IB metal atoms preferentially populate corner and edge sites of ruthenium crystals. This evidence, taken together, suggests that adsorption occurs preferentially at …

In this dissertation, the author reports on the surface structure of i-Al-Pd-Mn twofold, threefold, fivefold and i-Al-Cu-Fe fivefold surfaces. The LEED studies indicate the existence of two distinct stages in the regrowth of all four surfaces after Ar{sup +} sputtering. In the first stage, upon annealing at relatively low temperature: 500K--800K (depending on different surfaces), a cubic phase appears. The cubic LEED patterns transform irreversibly to unreconstructed quasicrystalline patterns upon annealing to higher temperatures, indicating that the cubic overlayers are metastable. Based upon the data for three chemically-identical, but symmetrically-inequivalent surfaces, a model is developed for the relation between the cubic overlayers and the quasicrystalline substrate. The model is based upon the related symmetries of cubic close-packed and icosahedral-packed materials. These results may be general among Al-rich, icosahedral materials. STM study of Al-Pd-Mn fivefold surface shows that terrace-step-kink structures start to form on the surface after annealing above 700K. Large, atomic ally-flat terraces were formed after annealing at 900K. Fine structures with fivefold icosahedral symmetry were found on those terraces. Data analysis and comparison of the STM images and structure model of icosahedral Al-Pd-Mn suggest that the fine structures in the STM images may be the pseudo Mackay (PMI) clusters …

The syntheses of polycarbosilanes and polysilanes as silicon carbide ceramic precursors have been active research areas in the Barton Research Group. In this thesis, the work is focused on the preparation of polycarbosilanes and polysilanes as stoichiometric silicon carbide precursor polymers. The syntheses of the precursor polymers are discussed and the conversions of these precursors to silicon carbide via pyrolysis are reported. The XRD pattern and elemental analyses of the resulting silicon carbide ceramics are presented. Silicon monoxide is an important intermediate in the production of silicon metal. The existence of silicon monoxide in gap phase has been widely accepted. In the second part of this thesis, the generation of gaseous silicon monoxide in four different reactors and the reactions of gaseous silicon monoxide towards organic compounds are discussed.

The Artificial Intelligence field of Integrating Multiple Learned Models (IMLM) explores ways to combine results from sets of trained programs. Aroclor Interpretation is an ill-conditioned problem in which trained programs must operate in scenarios outside their training ranges because it is intractable to train them completely. Consequently, they fail in ways related to the scenarios. We developed a general-purpose IMLM solution, the Combiner, and applied it to Aroclor Interpretation. The Combiner's first step, Scenario Identification (M), learns rules from very sparse, synthetic training data consisting of results from a suite of trained programs called Methods. S1 produces fuzzy belief weights for each scenario by approximately matching the rules. The Combiner's second step, Aroclor Presence Detection (AP), classifies each of three Aroclors as present or absent in a sample. The third step, Aroclor Quantification (AQ), produces quantitative values for the concentration of each Aroclor in a sample. AP and AQ use automatically learned empirical biases for each of the Methods in each scenario. Through fuzzy logic, AP and AQ combine scenario weights, automatically learned biases for each of the Methods in each scenario, and Methods' results to determine results for a sample.

Thesis written by a student in the UNT Honors College discussing John F. Kennedy's rise through American politics, his death, and the conspiracy theories that surround his assassination.