Physical Sciences and Mathematics Commons^™

Associations Of Total Activity Counts And Physical Activity Intensity Levels With The Metabolic Syndrome: A Structural Equation Modeling Approach, Dana Lizbeth Wolff

Doctoral Dissertations

To clarify the protective benefits of physical activity (PA), epidemiologists and public health researchers continue to seek improved methods of assessing PA. In particular, accelerometers have gained acceptance with researchers as they provide reliable estimates of PA and can record both the amount and intensity of ambulatory movement. However, there is concern that accelerometer data reduction techniques may not provide quantitatively accurate measurements of time spent in various PA intensity categories. One way to circumvent these inaccuracies is to use the accelerometer-derived total activity counts (TAC), which is a more direct expression of what the monitor records.

In order to …

Gastrointestinal Microbial Diversity And Diagenetic Alteration Of Bone From The American Alligator (Alligator Mississippiensis), Sarah Wheeler Keenan

Doctoral Dissertations

One of the most challenging questions in paleobiology is how bone transforms from a living tissue into a fossil. In life, the gastrointestinal tract microbiome of an animal promotes host health. But, in death, these microbial communities, as well as soil communities, begin to degrade tissue, including bones. Using the American alligator from coastal wetland habitats as a model system, the gastrointestinal tract microbiome was found to contain microbial communities consisting of Fusobacteria, Proteobacteria, Bacteroidetes, and Firmicutes, with variations based on tissue type along the length of the digestive tract. The overall dominance of Fusobacteria is distinct from any other …

Development Of Optical Sensors For Chemical Detection, Jonathan Kelly Fong

Doctoral Dissertations

Detection of biodiesel at low and high concentrations in diesel is highly desired in the aviation and fuel industries. Cross contamination of jet fuel with biodiesel may impact the thermal stability and freezing point which can cause deposits in the fuel system or cause the fuel to gel, leading to jet engine operability problems and possible engine flameout. A dye doped optical sensor utilizing the dye Nile Blue Chloride has been developed for quick and direct detection of biodiesel which mainly contains fatty acid methyl esters (FAME). The sensing mechanism relies on the solvatochromatic properties of the dye which undergoes …

Indefinite Knapsack Separable Quadratic Programming: Methods And Applications, Jaehwan Jeong

Doctoral Dissertations

Quadratic programming (QP) has received significant consideration due to an extensive list of applications. Although polynomial time algorithms for the convex case have been developed, the solution of large scale QPs is challenging due to the computer memory and speed limitations. Moreover, if the QP is nonconvex or includes integer variables, the problem is NP-hard. Therefore, no known algorithm can solve such QPs efficiently. Alternatively, row-aggregation and diagonalization techniques have been developed to solve QP by a sub-problem, knapsack separable QP (KSQP), which has a separable objective function and is constrained by a single knapsack linear constraint and box constraints. …

The Development Of Apci Mass Spectrometry Based Systems For Quantitative Real-Time Monitoring Of Process-Scale Homogenous And Heterogeneous Reactions, Zhenqian Zhu

Doctoral Dissertations

The dissertation presents solutions to monitor industrial chemical processes quantitatively in real time by mass spectrometry. Chapter 1 presents the background of atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Chapters 2-6 present methods developed based on flow injection analysis coupled to atmospheric pressure chemical ionization mass spectrometry (FIA/APCI-MS) for quantitative real-time monitoring of homogeneous and heterogeneous reactions conducted at molar concentrations.

Chapter 2 introduces auto-sampling FIA/APCI-MS with the ability to overcome potential sample overloading when molar concentration samples were analyzed without sample pretreatment procedures. A homogenous Michael-addition reaction between phenethylamine and acrylonitrile was conducted at room temperature and monitored quantitatively …

A Study In Conjugated Polymers: From Solution Properties Of P3ht To Synthesis Of Highly Functionalized Conjugated Polymers; Moving Toward Block Copolymers And Beyond, Justin Taylor Roop

Doctoral Dissertations

Conjugated polymers have been the focus of intense research for more than a decade now, and advances in this field are beginning to materialize in the production of high-efficiency opto-electronic materials that may led to the generation of energy without the need for fossil fuels. However, these current materials have not been shown to be capable of reaching efficiency levels high enough to be competitive with the siliconbased solar cells that are the standard today. We embarked on a journey in this work to help the next step in conjugated polymer research be attained. We have done just that through …

Stability, Erosion, And Morphology Considerations For Sustainable Slope Design, Isaac Andres Jeldes Halty

Doctoral Dissertations

The construction of more natural and sustainable earth slopes requires the consideration of erosion and runoff characteristics as an integral part of the design. These effects not only result in high costs for removal of sediment, but also a profound damage to the ecosystem. In this dissertation, innovative techniques are developed such that more natural appearing slopes can be designed to minimize sediment delivery, while meeting mechanical equilibrium requirements. This was accomplished by: a) examining the fundamental failure modes of slopes built with minimum compaction (FRA) to enhance quick establishment of forest, b) investigating the geomechanical and erosion stability of …

A Method To Control Morphology Of Bhj Opvs Using End-Functionalized Poly(3-Hexylthiophene)(P3ht) Grafted To Sqds, William Michael Kochemba

Doctoral Dissertations

Improving the power conversion efficiency of organic photovoltaic devices based on polymer-nanoparticle bulk heterojunctions remains a significant challenge that limits the commercial production of these technologies. There are a number of factors that contribute to the efficiency of photovoltaic devices including absorption, charge generation and charge separation, which ultimately rely on the morphology of the bulk heterojunction active layer. My work aims to improve these processes by developing a method to prepare end-group functionalized π[pi]- conjugated polymers that will be used to decorate the surface of nanoparticles thereby tailoring the interface between the polymer and the nanoparticle. This work involves …

Neutron Polarimetry With Polarized 3he For The Npdgamma Experiment, Matthew Martin Musgrave

Doctoral Dissertations

Cold neutrons enable the study of the fundamental interactions of matter in low-energy, low-background experiments that complement the efforts of high-energy particle accelerators. Neutrons possess an intrinsic spin, and the polarization of a beam of neutrons defines the degree to which their spins are oriented in a given direction. The NPDGamma experiment uses a polarized beam of cold neutrons to make a high precision measurement, on the order of one part in 100 million, of the parity-violating asymmetry in the angular distribution of emitted gamma-rays from the capture of polarized neutrons on protons. This asymmetry is a result of the …

Increasing The Throughput Of Liquid Chromatography, Joseph John Stankovich

Doctoral Dissertations

In this manuscript the ramifications of operating very high pressure chromatographic (VHPLC) instruments at high linear velocities is discussed. Operating at higher inlet pressures causes thermal conditions inside the column to change to an extent that can alter the reproducibility and accuracy of the chromatograms produced. The experiments discussed in this dissertation were focused on the manner in which the mobile phase is eluted through the column; by either constant flow, constant pressure, operator controlled or programmed constant pressure, and conditions which keep the heat loss at the columns wall constant. Additional experiments included other practical considerations in system performance …

Neutron Scattering Studies Of Cuprates And Iron Pnictides, Mengshu Liu

Doctoral Dissertations

Presented within are neutron scattering studies of several different high temperature superconducting materials: BaFe_1.9Ni_0.1As₂ [Barium Iron Nickel Arsenic], BaFe_1.85Ni_0.15As₂ [Barium Iron Nickel Arsenic], Ba_0.67K_0.33Fe₂As₂ [Barium Potassium Iron Arsenic], and Pr_0.88LaCe_0.12CuO_4-y [Praseodymium Lanthanum Cerium Copper Oxide]. The main focus is on the magnetic excitations within the systems.

For BaFe_1.9Ni_0.1As₂ [Barium Iron Nickel Arsenic], we measured the intensity of its magnetic excitations and compared the results with excitations in antiferromagnetic non-superconducting BaFe₂As_{2 …}

Geospatial Characterization Of Fluvial Wood In A Midwestern, Semi-Confined Alluvial River System, Derek Joseph Martin

Doctoral Dissertations

Large woody debris (LWD) has become universally recognized as a key component of the ecological and geomorphological function of river systems. The use of LWD as a restoration tool in Midwestern river systems is widespread, yet LWD-related restoration strategies are primarily supported by research from the Pacific Northwest or other physiographically similar regions. The purpose of this dissertation research was to investigate the longitudinal arrangement patterns of LWD and to characterize LWD and its effects on sediment storage within the Big River, a Midwestern river system located in the Missouri Ozarks. I adopted a multi-scale approach to analyze (1) large-scale …

Double-Hinged Di-1,2,4-Triazoles For Synthesis Of Breathing Mofs, Christopher Ray Murdock

Doctoral Dissertations

Employing semi-rigid di-1,2,4-triazoles as ligands has led to the formation of a plethora of Metal-Organic Framework (MOF) architectures. The ability for the ligands to exhibit multiple conformations through a “hinge” effect allows for the formation of a multitude of MOF topologies and dimensionalities. Employment of a di-triazole containing a central trans-butene moiety was initially studied and led to the formation of two three-dimensional copper MOFs. The frameworks can be synthesized independently, but a reaction occurs in water wherein the kinetic product is used as a reagent to synthesize the topologically distinct thermodynamic product.

Additional testing of reaction conditions with …

Methods For Quantitative Local Structure Analysis Of Crystalline Materials Employing High Performance Computing, Tara Marie Michels-Clark

Doctoral Dissertations

A fundamental computational methodology was investigated to extract quantitative local structure information from single crystal diffuse scattering data. The principles of a highly efficient, parallelizable local structure analysis using massively parallel computing resources at Oak Ridge National Laboratory (ORNL) are demonstrated on an organic hydrocarbon compound containing stacking faults, Tris(bicyclo[2.1.1]hexeno)benzene. A probabilistic model of the stacking variations with a five layer interaction depth was developed. The final model structure motif statistics are verified using the steady state distribution of Markov matrix representing the four to five layer transitions. The computations revealed that highly parallelizable “structure-clones” could replace less computationally efficient …

Asymptotic Behavior Of A Class Of Spdes, Parisa Fatheddin

Doctoral Dissertations

We establish the large and moderate deviation principles for a class of stochastic partial differential equations with a non-Lipschitz continuous coefficient. As an application we derive these principles for an important population model, Fleming-Viot Process. In addition, we establish the moderate deviation principle for another classical population model, super-Brownian motion.

Properties Of Ideal-Based Zero-Divisor Graphs Of Commutative Rings, Jesse Gerald Smith Jr.

Doctoral Dissertations

Let R be a commutative ring with nonzero identity and I an ideal of R. The focus of this research is on a generalization of the zero-divisor graph called the ideal-based zero-divisor graph for commutative rings with nonzero identity. We consider such a graph to be nontrivial when it is nonempty and distinct from the zero-divisor graph of R. We begin by classifying all rings which have nontrivial ideal-based zero-divisor graph complete on fewer than 5 vertices. We also classify when such graphs are complete on a prime number of vertices. In addition we classify all rings which …

Numerical Solutions For Problems With Complex Physics In Complex Geometry, Yifan Wang

Doctoral Dissertations

In this dissertation, two high order accurate numerical methods, Spectral Element Method (SEM) and Discontinuous Galerkin method (DG), are discussed and investigated. The advantages of both methods and their applicable areas are studied. Particular problems in complex geometry with complex physics are investigated and their high order accurate numerical solutions obtained by using either SEM or DG are presented. Furthermore, the Smoothed Particle Hydrodynamics (SPH) (a mesh-free weighted interpolation method) is implemented on graphics processing unit (GPU). Some numerical simulations of the complex flow with a free surface are presented and discussed to show the advantages of SPH method in …

Numerical Simulation Of Hydrogen Absorption/Desorption Processes In Cylindrical Metal-Hydrogen Reactors For Hydrogen Storage, Fei Han

Doctoral Dissertations

Hydrogen is one of the best fuels because of its high calorific value and environmental friendliness. However, because of its low density, it has storage problems such as high pressure, large volume requirements, heavy weight and safely risks; this quality prevents its wide usage and commercialization.

Researchers have found that some metal/inter-metallic compounds/alloys, such as Mg, La, LaNi5, ZrV2, Mg2Ni and Ti 2Ni, can react with hydrogen and attain relatively large amounts of hydrogen at a relatively low pressure and near normal temperature. Under certain conditions, hydride can desorb hydrogen quickly. Thus, the metal- hydrogen reaction could be a practical …

Vulnerability Analysis Of Cyber-Behavioral Biometric Authentication, Abdul Serwadda

Doctoral Dissertations

Research on cyber-behavioral biometric authentication has traditionally assumed naïve (or zero-effort) impostors who make no attempt to generate sophisticated forgeries of biometric samples. Given the plethora of adversarial technologies on the Internet, it is questionable as to whether the zero-effort threat model provides a realistic estimate of how these authentication systems would perform in the wake of adversity. To better evaluate the efficiency of these authentication systems, there is need for research on algorithmic attacks which simulate the state-of-the-art threats.

To tackle this problem, we took the case of keystroke and touch-based authentication and developed a new family of algorithmic …

Privacy And Trustworthiness Management In Moving Object Environments, Sashi Gurung

Doctoral Dissertations

"The use of location-based services (LBS) (e.g., Intel's Thing Finder) is expanding. Besides the traditional centralized location-based services, distributed ones are also emerging due to the development of Vehicular Ad-hoc Networks (VANETs), a dynamic network which allows vehicles to communicate with one another. Due to the nature of the need of tracking users' locations, LBS have raised increasing concerns on users' location privacy. Although many research has been carried out for users to submit their locations anonymously, the collected anonymous location data may still be mapped to individuals when the adversary has related background knowledge.

To improve location privacy, in …

Investigation Of Fluids Flow Behavior In Nano-Scale Channels By Using Optic Imaging System, Qihua Wu

Doctoral Dissertations

"Tight gas and shale gas reservoirs are characterized to have small pores with diameters in nanometer (nm) range. The physics of fluid flow in nanopores is poorly understood. Knowing the fluid flow behavior in the nano-range channels is of major importance for stimulation design, gas production optimization and calculations of the relative permeability of gas in tight shale gas systems. In this work, a lab-on-chip approach for direct visualization of the fluid flow behavior in nano-scale channels was developed using an advanced epi-fluorescence microscopy method combined with a nano-fluidic chip. The nanofluidic chips with different dimensions were designed and fabricated. …

Aerogels As Diverse Nanomaterials, Abhishek N. Bang

Doctoral Dissertations

"Aerogels are 3-D light-weight nanoporous materials pursued for their low thermal conductivity, low dielectric constant and high acoustic attenuation. Those exceptional macroscopic properties of aerogels are dependent on the chemical nature of nanoparticles, complex hierarchical solid skeletal framework and porosity. Also, the free space can become host for functional guests such as pharmaceuticals. In chapter I, we investigated randomly mesoporous bio-compatible polymer-crosslinked dysprosia aerogels as drug delivery vehicles and demonstrated storage and release of drugs under physiological conditions. Comparative study with ordered and randomly mesoporous silica showed high drug uptake and slower release rate for random nanostructures (silica or dysprosia) …

Cross-Layer Schemes For Performance Optimization In Wireless Networks, Quanmin Ye

Doctoral Dissertations

"Wireless networks are undergoing rapid progress and inspiring numerous applications. As the application of wireless networks becomes broader, they are expected to not only provide ubiquitous connectivity, but also support end users with certain service guarantees.

End-to-end delay is an important Quality of Service (QoS) metric in multihop wireless networks. This dissertation addresses how to minimize end-to-end delay through joint optimization of network layer routing and link layer scheduling. Two cross-layer schemes, a loosely coupled cross-layer scheme and a tightly coupled cross-layer scheme, are proposed. The two cross-layer schemes involve interference modeling in multihop wireless networks with omnidirectional antenna. In …

Synthesis And Properties Of Transition-Metal Arsenide Nanostructures: From Superparamagnetism To Superconductivity, Prachi Desai

Doctoral Dissertations

"This dissertation study focuses on developing new protocols for synthesis of nanostructured transition-metal pnictides including superconducting LiFeAs and studying their structure- property relationship. Nanostructured materials are known to differ in properties compared to their bulk counterparts owing to enhanced surface area and increased packing efficiency in devices. Synthetic chemistry skills and nanofabrication techniques like wet chemistry, electrodeposition, solvothermal, hydrothermal and lithography, are extremely useful for creating nanostructures of these functional materials. This is a challenging task simply because maintaining the phase composition same as that of the bulk material along with achieving nanostructures (nanoparticles, nanowires, nanopillars etc.) simultaneously is not …

Crustal Thickness And Vp/Vs Beneath The Western United States: Constraints From Stacking Of Receiver Functions, Uranbaigal Purevsuren

Doctoral Dissertations

"This study investigates crustal characteristics beneath the western United States. Crustal parameters, including crustal thickness (H), mean Vp/Vs, and the sharpness of the Moho as quantified by the amplitude of the P-to-S converted phases from the Moho, are measured at a total of 1000 permanent and portable broadband seismic stations using over 150,000 receiver functions recorded between 1988 and 2012. The study area is composed of a diverse set of tectonic provinces formed by a series of tectonic events, and is thus ideal for investigating crustal formation and modification by different tectonic processes. The resulting crustal thickness varies from …

Investigation Of Projectile Coherence Effects In Fully Differential Studies Of 75 Kev Proton - H₂ Collisions, Sachin Sharma

Doctoral Dissertations

"Fully differential cross sections (FDCS) have been measured for single ionization of H₂ by 75 keV proton impact with varying transverse coherence length of the projectiles. As reported in recent years, the scattering angle dependence of the doubly differential cross sections (DDCS) are significantly affected by the projectile coherence properties. The interference structures were observed for the coherent beam, however were absent for an incoherent beam. Interestingly, the FDCS measurements for fixed momentum transfer do not suggest significant differences between the coherent and incoherent cross sections. However, for the FDCS with fixed recoil-ion momentum, clear differences between the two …

Semiconductor Nanocrystals For Novel Optical Applications, Jong-Sik Moon

Doctoral Dissertations

“Inspired by the promise of enhanced spectral response, photorefractive polymeric composites photosensitized with semiconductor nanocrystals have emerged as an important class of materials. Here, we report on the photosensitization of photorefractive polymeric composites at visible wavelengths through the inclusion of narrow band-gap semiconductor nanocrystals composed of PbS. Through this approach, internal diffraction efficiencies in excess of 82%, two-beam-coupling gain coefficients in excess of 211 cm^-1, and response times 34 ms have been observed, representing some of the best figures-of-merit reported on this class of materials. In addition to providing efficient photosensitization, however, extensive studies of these hybrid composites …

Foundations Of Coverage Algorithms In Autonomic Mobile Sensor Networks, Mark Edward Snyder

Doctoral Dissertations

"Drones are poised to become a prominent focus of advances in the near future as hardware platforms manufactured via mass production become accessible to consumers in higher quantities at lower costs than ever before. As more ways to utilize such devices become more popular, algorithms for directing the activities of mobile sensors must expand in order to automate their work.

This work explores algorithms used to direct the behavior of networks of autonomous mobile sensors, and in particular how such networks can operate to achieve coverage of a field using mobility. We focus special attention to the way limited mobility …

Multiple Security Domain Nondeducibility In Cyber-Physical Systems, Gerry W. Howser

Doctoral Dissertations

"Cyber-physical Systems (CPS) present special problems for security. This dissertation examines the cyber security problem, the physical security problem, the security problems presented when cyber systems and physical systems are intertwined, and problems presented by the fact that CPS leak information simply by being observed. The issues presented by applying traditional cyber security to CPS are explored and some of the shortcomings of these models are noted. Specific models of a "drive-by-wire'' automobile connected to a road side assistance network, a "Stuxnet type'' attack, the smart grid, and others are presented in detail.

The lack of good tools for CPS …

Speciation Dynamics Of An Agent-Based Evolution Model In Phenotype Space, Adam David Scott

Doctoral Dissertations

"This dissertation is an exploration of phase transition behavior and clustering of populations of organisms in an agent-based model of evolutionary dynamics. The agents in the model are organisms, described as branching-coalescing random walkers, which are characterized by their coordinates in a two-dimensional phenotype space. Neutral evolutionary conditions are assumed, such that no organism has a fitness advantage regardless of its phenotype location. Lineages of organisms evolve by limiting the maximum possible offspring distance from their parent(s) (mutability, which is the only heritable trait) along each coordinate in phenotype space. As mutability is varied, a non-equilibrium phase transition is shown …