Physical Sciences and Mathematics Commons^™

Structural And Magnetic Properties Of Manganites Pr1-XCa1+XMno4, Oxypnictides Cefeaso1-XFX, And Filled Skutterudite Pros4As12, Songxue Chi

Doctoral Dissertations

We present neutron scattering, with triple-axis and time-of-flight spectrometers, to study the structural and magnetic properties of the layered manganites Pr_1-xCa_1+xMnO₄ (PCMO), and to determine the crystalline electric field (CEF) levels in iron pnictides CeFeAsO_1-xF_x and filled skutterudite compound PrOs₄As₁₂.

For the single-layered manganites PCMO, four dopings (x=0.5, 0.45, 0.40 and 0.35) have been studied. At half-doping, the system first becomes charge- and orbital- ordered (CO/OO) near T_CO = 300 K and then develops CE-type antiferromagnetic (AF) order below T_N = 130 K. …

Explicit Methods In The Nuclear Burning Problem For Supernova Ia Models, Viktor Chupryna

Doctoral Dissertations

Most modern astrophysical problems such as supernova simulation require application of state-ofthe- art computational tools. Despite the fact that number of nuclei included in coupled simulations tends to be small, problems such as nuclear burning networks are often part of a large set of interconnected programs that require significant computing resources. Expansion of the nuclear reaction network to realistic sizes can easily make element and energy production the leading consumer of both time and memory in simulations. Therefore, in solving nuclear reaction networks coupled to (radiation) hydrodynamics in astrophysics simulations, the development of methods capable of improving on the traditional …

Adsorption Of Propane On The Magnesium Oxide (100) Surface And Synthesis Of Anodized Aluminum Oxide, Michael John Felty

Doctoral Dissertations

This work is divided into two parts: the adsorption of propane on the magnesium oxide (100) surface and the synthesis of anodized aluminum oxide. The adsorption properties of propane on the MgO (100) surface were investigated using high-resolution volumetric isotherm techniques and a computational study was accomplished using Materials Studio. From the adsorption work, the two-dimensional isothermal compressibility, the isosteric heat of adsorption, the differential enthalpy, and the differential entropy of adsorption can be calculated. Three distinct layers of propane were observed to form on the MgO (100) surface and it was determined that a phase transition occurs at 162 …

Molecular Hydrogen Adsorbed On Mgo (100) Surfaces: A Thermodynamic Study, Lillian Ruth Frazier

Doctoral Dissertations

The thermodynamics of molecular hydrogen adsorbed on MgO (100) surfaces has been examined using high resolution volumetric adsorption isotherm techniques. These studies were undertaken using highly perfect, narrow size distributed MgO nanocubes with essentially single (100) facet exposure and extremely high chemical purity. A narrowly spaced (in temperature) series of isotherms were performed between the temperatures of ~7K and the triple point (13.8 K) using H₂ and D₂ gas.

A minimum of five, and in some cases seven, discrete adsorption steps are clearly observed in each isotherm trace. Analysis of these data indicate that the monolayer film forms …

Sb-Corla: Schema-Based Constructivist Robot Learning Architecture, Yifan Tang

Doctoral Dissertations

This dissertation explores schema-based robot learning. I developed SB-CoRLA (Schema- Based, Constructivist Robot Learning Architecture) to address the issue of constructivist robot learning in a schema-based robot system. The SB-CoRLA architecture extends the previously developed ASyMTRe (Automated Synthesis of Multi-team member Task solutions through software Reconfiguration) architecture to enable constructivist learning for multi-robot team tasks. The schema-based ASyMTRe architecture has successfully solved the problem of automatically synthesizing task solutions based on robot capabilities. However, it does not include a learning ability. Nothing is learned from past experience; therefore, each time a new task needs to be assigned to a new …

Collective Behavior Of Interacting Magnetic Nanoparticles, Noppi Widjaja

Doctoral Dissertations

In the past, Low Dimensional Materials by Design group at ORNL in collaboration with students from the University of Tennessee, have successfully tailored and studied magnetic nanostructures in 2D, 1D and 0D spatial confinement on Cu(111) substrates. They observed a striking collective ferromagnetic long-range order in Fe-nanodots on Cu(111) surface which can be stabilized through the indirect exchange interaction mediated by the substrate. This type of magnetic interaction was expected to have little effect on promoting a global ferromagnetic order in a randomly distributed dot assembly. It is for certain that we need a better understanding of the relative roles …

Emergent Phenomena In Spatially Confined Manganites, Thomas Z. Ward

Doctoral Dissertations

Rare earth manganites exhibit colossal magnetoresistance (CMR). There is evidence that alloyed single crystal materials in this class can display electronic inhomogeneity in which areas with vastly different electronic and magnetic properties can form and coexist in phase separated domains ranging in size from a few nanometers to micrometers. This phase separation (PS) is of particular interest, as it has been suggested that it is the central feature that leads to CMR in manganites, the Mott transition in VO₂ and may play a role in high-TC superconductivity in cuprates. However there is debate as to its precise role.

The …

Scalable Graph Algorithms With Applications In Genetics, Yun Zhang

Doctoral Dissertations

Graph theoretical approaches have been widely used to solve problems arising in bioinformatics and genomic analysis. In particular, enumeration problems such as maximal clique and maximal biclique finding are cores for addressing many biological problems, such as the integration of genome mapping data. However, the enumeration problems may become computation and memory bot- tlenecks for genome-scale elucidation of biological networks due to their NP-hard nature and the huge memory requirements.

Therefore, this research is interested in developing exact, scalable, and efficient algorithms for these biological problems. The Clique Enumerator including a maximal clique enumeration algo- rithm and its parallel …

A Socioeconomic Study Of The Non-Industrial Private Forest Landowner Wood Supply Chain Link In The Cumberland Plateau Region Of Tennessee, Kevin Patrick Hoyt

Doctoral Dissertations

The Cumberland Plateau in Tennessee currently is experiencing widespread forest parcelization and changes in species composition as a result of changes in land use and ownership. These changes can be attributed partially to industrial forest land divestiture, the lingering effects of the 1998 – 2002 Southern Pine Beetle (SPB) epidemic, and expanding development due to increasing population growth. The region has recently become a focus of debate concerning land use change, land management practices, and the effects on biodiversity.

A stratified random sample of 1600 Nonindustrial Private Forest (NIPF) landowners owning 40 or more acres of forestland were surveyed obtaining …

Forestry Extension In Tennessee: Comparing Traditional And Web-Based Program Delivery Methods, Samuel Wayne Jackson

Doctoral Dissertations

As the traditional forestry Extension clientele in Tennessee changes, Extension professionals need to adapt and deliver programs in such a way as to reach the maximum audience while ensuring the educational benefit of the program and remaining within budget. The development of the Internet and associated web-based programs presents a new tool by which Extension professionals can develop and deliver educational programs to clientele.

This study compared two Extension program delivery methods, web-based and traditional field-based. A series of field workshops were held and participants were surveyed. From these field workshops, a web-based program was developed and was marketed to …

Assessing The Tree-Ring Oxygen Isotope Hurricane Proxy Along The Atlantic And Gulf Coastal Seaboards, Usa, Whitney L. Nelson

Doctoral Dissertations

A recent increase in hurricane activity has put coastal populations at risk. To better understand hurricane activity, it is necessary to look beyond the modern instrumental record, using proxy records to establish modes of past variability. The utility of a newly developed tree-ring oxygen isotope proxy is further assessed. I present oxygen isotope time series from three sites: Francis Marion and Sandy Island, South Carolina and Eglin Air Force Base, Florida. Proxy results are verified against the instrumental record of hurricane occurrence. The sites record similar percentages (45% for Francis Marion and Sandy Island, 63% for Eglin Air Force Base) …

New Carbon-Carbon Bond Forming Reactions Mediated By Boron And Transition Metal Halides, Travis R. Quick

Doctoral Dissertations

This dissertation summarizes the recent use of boron and transition metal halides to form new carbon-carbon bonds. Several novel reactions have been discovered. These include the haloallylation of aryl aldehydes with boron trihalide; alkyne-aldehyde couplings mediated by boron trihalide to give either (Z,Z)-1,5-dihaloalkenes or (Z,E)-1,5- dihaloalkenes; dehydroxylation of benzylic alcohols and in situ generated benzylic alcohol salts with iron(III) chloride and triethylsilane to afford diarylmethanes; and, the alkenylation of allylic, benzylic, and propargylic alcohols with phenylacetylenes and titanium(IV) halide. The results of these studies strongly imply a cationic mechanism. The reaction methodology of the research described herein can be characterized …

The Adsorption Of 2-Ketogluconate By Goethite, Jessica Suzanne Journey

Masters Theses

The low-molecular-mass-organic acid, 2-ketogluconate (kG), has been found to exist in significant concentrations in the rhizosphere of agricultural soils. Adsorption of kG by constant potential mineral surfaces may influence soil chemical processes. This study examines influence of temperature, pH, and ionic environment on the adsorption of kG by goethite. When kG was present on the surface of goethite, the pH_pzc decreased by approximately 0.4 pH units, from pH 7.6 to pH 7.2, suggesting that kG is chemisorbed to the goethite surface via ligand exchange mechanisms. The adsorption of kG by goethite is a function of pH and ionic strength. …

Tree-Like Spaces With The Fixed-Point Property, Realized As Inverse Limits Of Special Finite Trees, Jennifer Katherine Aust

Masters Theses

In this paper, we explore some properties of inverse limit sequences on sub-spaces of Euclidean n-space. We address some well-known examples, in particular the example by David Bellamy of the "tree-like" continuum that does not have the fixed-point property. We highlight some spaces with the fixed-point property that are between snake-like continua and Bellamy's example in their level of complexity. Specifically, we prove the fixed-point property for inverse limits of limit sequences on the unit interval and on the n-ad (in two configurations), and for inverse limits that can be mapped via a continuous function with small point pre-images to …

Heats Of Solvation Of Organic Liquids In Room Temperature Ionic Liquids, Paula Jeanette Beach

Masters Theses

Ionic liquids are of potential use in industry as reusable, non-polluting solvents. Their thermochemical properties need to be known to facilitate planning of processes and experiments using these solvents. Two ionic liquids: 1-Butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6 or [bmim]PF6) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim]NTf2) were studied using a calorimeter. Various organic liquids were introduced into the solvents and their heats of solution were measured and tabulated. Potential effects of certain functional groups such as alcohol, amine, carboxylic acid, ketone, and aldehyde were examined as well as aromatics versus chains and saturated rings.

The Use Of Lanthanide Triflates As A Method For Reducing Ytterbium(Iii) To Ytterbium(Ii), Latasha Michelle Garrett

Masters Theses

High purity lutetium (99.999%) is employed in the manufacture of cerium-doped lutetium oxyorthosilicate. Such lutetium is in high demand because the cerium-doped lutetium oxyorthosilicate is the best gamma-detecting scintillator known. Solvent extraction is the most widely used method for separating the rare earths on an industrial scale at 99.999% purity. However, this process is time consuming and requires 80-100 separation stages. The major difficulty in pure lutetium production is the separation from the adjacent element, ytterbium. If ytterbium(III) could be reduced to ytterbium(II), this would permit a different chemistry between ytterbium(II) and the trivalent state elements, allowing a more facile …

A Note On Hamel Bases, Jeremy S. Higdon

Masters Theses

The purpose of this paper is to discuss certain properties of Hamel bases. In particular, we reprove and generalize a theorem of R. Mabry (Aequations Mathematicae 71 (2006) p. 294-299) on the non-existence of nontrivial Hamel bases closed under multiplication.

The Evaluation Of A Chemical Fingerprinting Technique For Identifying The Sources Of In-Stream Sediments, Robert Alexander Hull

Masters Theses

Sediment is often listed as one of the main contributors to the impairment of surface waters throughout the United States. Sediment source identification is difficult in watersheds with complex combinations of land-uses and non-point sources because of the complexities involved in correlating water quality data, which are relatively easy to collect, to the source of a degrading component. The elemental properties of a particular soil on the landscape may be viewed as a “fingerprint”. A comparison of the elemental fingerprints of potential sources and in-stream sediment may be used to establish sediment source. The objectives of this investigation were to …

Biochemical Reactions Instigating Vision – Parameter Sensitivity Analysis, Sophonie Ketcha Tchoua

Masters Theses

The purpose of this work is to investigate the sensitivity of parameters involved in a cascade of biochemical reactions occurring in photoreceptor cells in the retina of the eye. This cascade constitutes the first stage of the elaborate process of vision, by which light captured in a photoreceptor generates an electrical signal. It is this signal that travels to the brain enabling vision.

Sensitivity on parameters was performed on an ODE model of the biochemical cascade using two methods. One method used SimLab, a statistical sensitivity analysis program. We found that there are at most five important parameters out of …

Experimental Determination Of Emissivity And Resistivity Of Yttria Stabilized Zirconia At High Temperatures, Howard Mosley Frederick

Masters Theses

The emissivity and resistivity of yttria stabilized zirconia (YsZ), Y₂O₃-ZrO₂, a ceramic material that has been specially fabricated for use as an electrically powered high temperature air heater are determined for temperatures above 2000 K. Published results of measurements of emissivity and resistivity of yttria, zirconia, and their alloys at temperatures above 2000 K are rare in the technical literature. A survey of literature describing the properties of YsZ, particularly literature concerning the ionic conduction process at high temperatures, is assembled to provide a theoretical basis for the formulation of a temperature and resistivity …

Environmental Analysis And White Cell Applications Ftir Spectroscopy, Maria Gabriela Oliveros

Masters Theses

The research is concerned with atmospheric chemistry & physics, and analyzing the environment with respect to the quantity of molecules is in the air we breathe. Fourier Transform Infrared Spectroscopy is used to identify the IR active molecules in our atmosphere. FTIR Spectrometer determines the intensity loss for molecules that have absorbed IR light. The FTIR spectroscopy is performed using the light from the sun or a carbon rod light source in the lab. A Sun-tracking device was employed to direct the sunlight into the spectrometer. Open-path measurements were made using multiple mirror reflections of the carbon rod light source …

Optimal Control Of Epidemic Models Involving Rabies And West Nile Viruses, Timothy Joseph Clayton

Doctoral Dissertations

This research considers the application of Optimal Control theory to minimize the spread of viral infections in disease models. The population models under consideration are systems of ordinary differential equations and represent epidemics arising due to either rabies or West Nile virus. Optimal control strategies are analyzed using Pontryagin’s Maximum Principle and illustrated based upon computer simulations.

The first model describes a population of raccoons and its interaction with the rabies virus, thus dividing the animals into four classes: susceptible, exposed, immune, and recovered (SEIR). The model includes a birth pulse during the spring of the year and …

Landscape Level Dynamics In An Endangered Mountain Ecosystem, Northern Rocky Mountains, U.S.A., Saskia L. Van De Gevel

Doctoral Dissertations

The purpose of this dissertation research was to investigate the extent of natural and anthropogenic impacts on declining whitebark pine communities. My research used dendroecology to study multicentury changes in these threatened communities to assess current and past forest dynamics and the overlapping effects of white pine blister rust, mountain pine beetle, and climate change in the northern Rocky Mountains.

I created whitebark pine (host) and subalpine fir (nonhost) chronologies and collected species composition, stand structure, and forest health data in sites along a latitudinal transect through the Rocky Mountains in western Montana. The standstructure data indicate over 70% of …

A Measurement Of Open Charm Using Single Muons At Forward Angles For P+P Collisions At Center Of Mass Energy 200 Gev, Donald Eric Hornback

Doctoral Dissertations

This dissertation presents the measurement of single muons from the semi-leptonic decay of heavy quark mesons (charm and bottom) in √s=200 GeV p+p collisions at the Relativistic Heavy Ion Collider at Brookhaven National Lab. The data were recorded in 2005 by the PHENIX experiment. The PHENIX muon spectrometer measures particles at forward angles from approximately 15º to 33º relative to the beam line in both forward and backward directions.

A new analysis technique was developed to estimate and subtract backgrounds from light hadrons in a statistical fashion to reveal the yield of heavy flavor single muons. The yield of single …

Collision-Induced Dissociation Of Multiply-Charged Anions, Nasrin Mirsaleh Kohan

Doctoral Dissertations

Electrospray ionization has proven to be a powerful method for the study of multiply-charged-anions (MCA) in the gas-phase. Stability of the MCA toward ionic fragmentation and electron detachment has attracted wide interest. The stability of dianions is due to the “repulsive Coulomb barrier” to the addition or removed of an excess electron to a negative ion. The repulsive Coulomb barrier (RCB) is primarily the result of a long-range Coulomb repulsion and the short-range polarizibility attraction between an electron and a negative ion. The RCB can render unbound MCAs metastable or add stability to bound MCAs. In this dissertation, a collision-induced …

Scalable, Data- Intensive Network Computation, Huadong Liu

Doctoral Dissertations

To enable groups of collaborating researchers at different locations to effectively share large datasets and investigate their spontaneous hypotheses on the fly, we are interested in de- veloping a distributed system that can be easily leveraged by a variety of data intensive applications. The system is composed of (i) a number of best effort logistical depots to en- able large-scale data sharing and in-network data processing, (ii) a set of end-to-end tools to effectively aggregate, manage and schedule a large number of network computations with attendant data movements, and (iii) a Distributed Hash Table (DHT) on top of the generic …

Synthesis Of Two Thiol-Terminated Disaccharides And A Mannose-Branched Glycodendrimer, Chao Wang

Doctoral Dissertations

The glycocalix, a complex structure of lipids and glycoproteins, forms the cellular surface of all cells and serves to mediate a variety of events such as cell–virus recognition, cell–cell recognition, immunological response, metastasis, and fertilization. Moreover, the glycocalix is specific for a particular species, cell type, and developmental status. Alterations in the glycocalix have been found in association with many pathological conditions such as cancer and tuberculosis. Investigation of the interactions between the glycocalix and its associated proteins will lead to a fundamental understanding of these important processes.

Multivalent interactions are characterized by the simultaneous binding of multiple ligands on …

Advancing Data Analysis For Spectroscopic Imaging By Combining Wavelet Compression With Chemometrics, Robert Daryl Luttrell

Doctoral Dissertations

Spectroscopic imaging is a vital tool for studying heterogeneous samples such as bacteria and tissue. Its ability to acquire spatially resolved information allows for identification and classification of the various constituents within a sample. Spectroscopic imagers quickly acquire thousands to tens of thousands of spectra per measurement. These data are often arranged in the form of a 3-dimensional (3D) data cube which contains two spatial dimensions and one spectral dimension. This large amount of data is beneficial for gaining a thorough understanding about the distributions of chemical information. If too little information is measured, important chemical behavior may be overlooked. …

The Applications Of The Tracer Particle Method To Multi-Dimensional Supernova Simulations, Ching-Tsai Lee

Doctoral Dissertations

A new tracer particle implementation has been developed for the 2D supernova code ”CHIMERA”. 2D supernova simulations have been performed for a wide range of progenitors, between 10 and 25 solar mass. In the case of the Heger12 model, we have obtained a successful explosion. Analysis of the tracer particle data generated by supernova simulations reveals the aspherical geometry of the ejecta. Using the hydrodynamic trajectories provided by the tracer particles, we have performed the nucleosynthesis calculations in the post processing approximation, including the effects of neutrino captures, to understand the nucleosynthesis consequences of these models.

The Qse-Reduced Nuclear Reaction Network For Silicon Burning, Suzanne T. Parete-Koon

Doctoral Dissertations

Iron and neighboring nuclei are formed by silicon burning in massive stars before core collapse and during supernova outbursts. Complete and incomplete silicon burning is responsible for the production of a wide range of nuclei with atomic mass numbers from 28 to 70. Because of the large number of nuclei involved, accurate modeling of these nucleosynthetic stages is computationally expensive. For this reason, hydrodynamic models of supernovae often employ a limited set of nuclei to track the nuclear energy generation until nuclear statistical equilibrium is reached. These limited approximations do not include many of the reaction channels important for the …