Physical Sciences and Mathematics Commons^™

Optical Properties, Electronic Structures And High Pressure Study Of Nanostructured One Dimensional Titanium Dioxide By Synchrotron Radiation And Spectroscopy, Ankang Zhao

Electronic Thesis and Dissertation Repository

One dimensional (1D) titanium dioxide (TiO₂) nanomaterials have been extensively studied in recent years due to their superior electrical, optical mechanical and chemical properties compared with their bulk counterparts. Two different kinds of 1D TiO₂ nanomaterials, TiO₂ nanowires (TiO₂ NW) and TiO₂ nanotubes (TiO₂ NT), are studied in this thesis by using various techniques.

In one study, TiO₂ NW synthesized by hydrothermal method and a series of calcinated TiO₂ NW were investigated by using absorption near edge structures (XANES), X-ray diffraction (XRD) and X-ray excited optical luminescence (XEOL). It is found …

In Situ High-Pressure Studies Of Energetic Materials By Vibrational Spectroscopy And X-Ray Diffraction, Liang Zhou

Electronic Thesis and Dissertation Repository

Nitrogen-rich materials have been considered as the most promising replacement of traditional energetic materials due to the large energy gap between the different nitrogen allotropes as well as the generation of environmental friendly nitrogen gas as the end-product. As a result, methods of synthesizing the nitrogen-rich materials have received increasing attention. Apart from the traditional chemical synthesis, high-pressure technique had been proved an effective tool to create such kinds of materials. However, several issues still existed concerning the high-pressure synthesis of energetic materials. Therefore, searching for precursors is of great interest. Here we report studies of four promising precursors, 5-aminotetrazole, …

Sensitivity Analysis Of Minimum Variance Portfolios, Xiaohu Ji

Electronic Thesis and Dissertation Repository

The purpose of this thesis is to conduct a sensitivity analysis of the investment allocation decisions made, not within a modern portfolio theory, but within a capital asset pricing model framework. For analytic tractability, we made the simplification (of some current practical interest) that investors have the objective of minimizing the variance of their portfolios without reference to the expected returns to be obtained from these portfolios. Our analytic results reveal how the minimum variance portfolio composition, expected return and risk would change with respect to the changes of the underlying asset correlations and volatilities. We give the investors instructions …

Pricing And Hedging Index Options With A Dominant Constituent Stock, Helen Cheyne

Electronic Thesis and Dissertation Repository

In this paper, we examine the pricing and hedging of an index option where one constituents stock plays an overly dominant role in the index. Under a Geometric Brownian Motion assumption we compare the distribution of the relative value of the index if the dominant stock is modeled separately from the rest of the index, or not. The former is equivalent to the relative index value being distributed as the sum of two lognormal random variables and the latter is distributed as a single lognormal random variable. Since these are not equal in distribution, we compare the two models. The …

Modelling Credit Value Adjustment Using Defaultable Options Approach, Sidita Zhabjaku

Electronic Thesis and Dissertation Repository

This thesis calculates Credit Value Adjustment on defaultable options. The prices of default- able European options are computed through analytical, quadrature approximation and Monte Carlo simulations under the assumption of a constant rate of default. Subsequently, we propose to inversely relate the company’s instantaneous rate of default to its underlying stock price, re- sulting in a non-constant rate of default. This allows for a new approach to estimate the default of company different from previous work where default is calculated through historical data. The rationale behind this idea relies on the fact that price of the stock plunges before the …

Allostratigraphy, Sedimentology And Paleogeography Of The Cretaceous Upper Fort St. John Group (Upper Albian-Lower Cenomanian) In Northeastern British Columbia, Piotr Jan Angiel

Electronic Thesis and Dissertation Repository

The upper Albian to lower Cenomanian succession in northeastern British Columbia was deposited in the proximal foredeep and is greatly vertically expanded relative to the more eastern part of the basin. The study interval has a wedge-shaped geometry, and is ~780 m thick in the west and thins dramatically to ~280 metres over a distance of ~170 km. Rapid facies changes result in lithostratigraphic units being strongly diachronous. In order to determine depositional history, the present study subdivided the Upper Fort St. John Group into 16 genetically-related allomembers. The new allostratigraphic correlations established in this thesis combined with previous studies, …

Molecular Gas In The Circumstellar Environment Of Unusual Evolved Stars, Sarah E. Malek

Electronic Thesis and Dissertation Repository

As low- and intermediate mass stars (with masses up to 8-9 solar masses) age, they experience a series of evolutionary changes which culminate in the removal of nearly their entire envelope through extensive mass loss. The ejected material cools down, which allows for the formation of molecules and the nucleation of dust grains in the circumstellar environment (CSE) of the star. Much about the properties and composition of the gas and dust in these CSEs is not well understood.

Here, we study the rich CSEs of two unusual evolved stars by analyzing spectral observations in the infrared and using molecular …

Hierarchical Classification And Its Application In University Search, Xiao Li

Electronic Thesis and Dissertation Repository

Web search engines have been adopted by most universities for searching webpages in their own domains. Basically, a user sends keywords to the search engine and the search engine returns a flat ranked list of webpages. However, in university search, user queries are usually related to topics. Simple keyword queries are often insufficient to express topics as keywords. On the other hand, most E-commerce sites allow users to browse and search products in various hierarchies. It would be ideal if hierarchical browsing and keyword search can be seamlessly combined for university search engines. The main difficulty is to automatically classify …

Reliability Models Applied To Smartphone Applications, Sonia Meskini

Electronic Thesis and Dissertation Repository

Smartphones have become the most used electronic devices. They carry out most of the functionalities of desktops, offering various useful applications that suit the user’s needs. Therefore, instead of the operator, the user has been the main controller of the device and its applications, therefore its reliability has become an emergent requirement. As a first step, based on collected smartphone applications failure data, we investigated and evaluated the efficacy of Software Reliability Growth Models (SRGMs) when applied to these smartphone data in order to check whether they achieve the same accuracy as in the desktop/laptop area. None of the selected …

The Impact Of Lateral Electron Disequilibrium On Stereotactic Body Radiation Therapy Of Lung Cancer, Brandon Disher

Electronic Thesis and Dissertation Repository

Stereotactic Body Radiation Therapy (SBRT) is an effective treatment option for patients with inoperable early-stage lung cancer. SBRT uses online image-guidance technology [e.g. cone-beam CT (CBCT)] to focus small-fields of high energy x-rays onto a tumour to deliver ablative levels of radiation dose (e.g. 54 Gy) in a few treatment fractions (e.g. 3). For the combination of these treatment parameters and a low density lung, lateral electron disequilibrium (LED) can potentially occur, reducing lung and tumour doses. The goal of this thesis was to determine the impact of LED on stereotactic body radiation therapy for lung cancer.

The effect of …

Piv-Based Investigation Of Hemodynamic Factors In Diseased Carotid Artery Bifurcations With Varying Plaque Geometries, Sarah Kefayati

Electronic Thesis and Dissertation Repository

Ischemic stroke is often a consequence of complications due to clot formation (i.e. thrombosis) at the site of an atherosclerotic plaque developed in the internal carotid artery. Hemodynamic factors, such as shear-stress forces and flow disturbances, can facilitate the key mechanisms of thrombosis. Atherosclerotic plaques can differ in the severity of stenosis (narrowing), in eccentricity (symmetry), as well as inclusion of ulceration (wall roughness). Therefore, in terms of clinical significance, it is important to investigate how the local hemodynamics of the carotid artery is mediated by the geometry of plaque. Knowledge of thrombosis-associated hemodynamics may provide a basis to introduce …

Diffusionless Transition In Tricosane And Reversible Inhibition Of Calcium Oxalate Monohydrate: Two Studies Of Crystal Growth, Shailesh S. Nene

Electronic Thesis and Dissertation Repository

The process of crystal growth has been intensively studied, for both its academic interest and industrial importance. I report here two studies of crystal growth.

The normal alkanes are an interesting, both in terms of their intrinsic properties and because many biological materials contain hydrocarbon domains. The normal alkanes often exhibit complicated phase behaviour, with phase diagrams containing multiple solid phases. We report here a curious pattern of twinned domains seen in one phase of tricosane (C23H48), which we have studied by X-ray diffraction, as well as by optical and atomic force microscopy. This pattern is seen in the rotator …

Stochastic Simulation Of Multiple-Station Ground Motions And Its Applications, Taojun Liu

Electronic Thesis and Dissertation Repository

Approaches to simulate single- and multiple-component multiple-station ground motion records with target spatial coherency and spatial correlation structures are developed for scenario events in this study. To develop the approaches, spatial correlation of the Fourier amplitude spectrum for a random orientation and for two orthogonal directions is assessed, and empirical equations are suggested. Moreover, spatial coherency of ground motions for two orthogonal horizontal directions is estimated using actual records from seven seismic events. Empirical coherency function is suggested for the components of records in two orthogonal horizontal directions at single and multiple recording stations. It was also found that the …

On Evolution Dynamics And Strategies In Some Host-Parasite Models, Liman Dai

Electronic Thesis and Dissertation Repository

In this thesis, we use mathematical models to study the problems about the evolution of hosts and parasites. Firstly, we study a within-host age-structured model with mutation and back mutation which is in the form of partial differential equations with double-infections by two strains of viruses. For the case when the production rates of viruses are gamma distributions, the PDE model can be transferred into an ODE one. Then, we analyze our model in two cases: one is without mutation, and the other is with mutation. In the first case, we prove that the two strains of viruses without mutation …

Studies Of The Charge Storage Properties Of Poly(Bithiophene) And Amorphous Carbon Nitride, Timothy Adam Forristal

Electronic Thesis and Dissertation Repository

The charge storage properties of several potential materials for battery applications have been investigated. Poly(bithiophene) films were prepared by potentiostatic and potentiodynamic electropolymerization methods. These films were then subject to galvanic cycles at varying rates and to various potential limits in order to explore their use as electrodes in a battery. Potentiodynamically deposited films retain their charge better over multiple cycles. By comparing to data collected by atomic force microscopy, we conclude that these films are less crystalline than films deposited potentiostatically and are better suited for the volume changes that occur when being charged and discharged.

Amorphous carbon nitride …

Approximation Of Exchange-Correlation Potentials For Orbital-Dependent Functionals, Alexei Kananenka

Electronic Thesis and Dissertation Repository

Density-functional theory (DFT) is the most widely used method of modern computational chemistry. All practical implementations of DFT rely on approximations to the unknown exchange-correlation functional. These approximations may be devised in terms of energy functionals or effective potentials. In this thesis, several approximations of the latter type are presented.

Given a set of canonical Kohn–Sham orbitals, orbital energies, and an external potential for a many-electron system, one can invert the Kohn–Sham equations in a single step to obtain the corresponding exchange-correlation potential, vXC(r). We show that for orbitals and orbital energies that are solutions of the Kohn–Sham equations with …

Development Of Novel Contrast Agents For Magnetic Resonance Imaging, Mark Milne

Electronic Thesis and Dissertation Repository

Magnetic resonance (MR) has outstanding potential as a noninvasive imaging modality. Possessing spatial resolution at the millimeter scale, MR imaging of anatomical features is unrivalled by other imaging techniques. Although MR imaging has outstanding spatial resolution it suffers from inherently low signal intensity. With a low sensitivity, the signal to noise ratio is low; thus MRI scans may take upwards of an hour to generate an acceptable image without a contrast agent. This drawback clearly justifies the need for contrast agents and the long held interest in their development.

Our development of novel MRI contrast agents focuses on the synthesis …

Topological Properties Of Modular Networks, With A Focus On Networks Of Functional Connections In The Human Brain, Estefania Ruiz Vargas

Electronic Thesis and Dissertation Repository

Complex network theory offers useful approaches to analyze the structural and functional properties of real life networks. In this work, we explore some of the mathematical concepts of network theory and study real life systems from a complex network perspective. We pay particular attention to networks of connections within the human brain. We analyze weighted networks calculated from full functional magnetic resonance imaging (fMRI) data acquired during task performance. The first novelty of this study is the fact that we retain all of the connections between all of the voxels in the full brain fMRI data. We then evaluate the …

Investigations Of The Crystallization Processes Of Molecular Sieves, Lu Zhang

Electronic Thesis and Dissertation Repository

Molecular sieves have been used extensively in industrial fields. A better understanding of their crystallization processes is very useful for controlling the structural properties in order to meet the industrial needs. This thesis focuses on examining the crystallization of several catalytically important molecular sieves by dry gel conversion (DGC) method which includes steam-assisted conversion (SAC) and vapor-phase transport (VPT), or hydrothermal synthesis (HTS) method or a combination of both.

For SAPO-34 templated by DEA, it crystallizes similarly under SAC and VPT conditions. It forms from the transformation of a semi-crystalline layered phase. When morpholine was used as the template, the …

Electrochemical Evaluation Of Ionic Liquids For Biphasic Extraction Of Metal Ions Common To Spent Nuclear Fuel, Thomas J. Stockmann

Electronic Thesis and Dissertation Repository

Over the past 30 years electrochemistry at a liquid|liquid interface has been used to observe and quantify simple ion transfer (IT) as well as ligand assisted, or facilitated ion transfer (FIT) reactions. Liquid|liquid electrochemistry has developed to where valuable thermodynamic constants – for example, the metal ion to ligand stoichiometry and overall complexation constant, β, in FIT - can be evaluated using cyclic voltammetry (CV). Recently, ionic liquids (ILs) have shown greater metal ion extraction efficiencies in water-IL biphasic separations relative to conventional molecular organic solvents. In this way, they are of interest to the nuclear industry for applications …

Accelerated Imaging Techniques For Chemical Shift Magnetic Resonance Imaging, Curtis N. Wiens

Electronic Thesis and Dissertation Repository

Chemical shift imaging is a method for the separation two or more chemical species. The cost of chemical shift encoding is increased acquisition time as multiple acquisitions are acquired at different echo times. Image acceleration techniques, typically parallel imaging, are often used to improve the spatial coverage and resolution. This thesis describes a new technique for estimating the signal to noise ratio for parallel imaging reconstructions and proposes new image reconstructions for accelerated chemical shift imaging using compressed sensing and/or parallel imaging for two applications: water-fat separation and metabolic imaging of hyperpolarized [1-¹³C] pyruvate.

Spatially varying noise in …

Modeling Leafhopper Populations And Their Role In Transmitting Plant Diseases., Ji Ruan

Electronic Thesis and Dissertation Repository

This M.Sc. thesis focuses on the interactions between crops and leafhoppers.

Firstly, a general delay differential equations system is proposed, based on the infection age structure, to investigate disease dynamics when disease latencies are considered. To further the understanding on the subject, a specific model is then introduced. The basic reproduction numbers $\cR_0$ and $\cR_1$ are identified and their threshold properties are discussed. When $\cR_0 < 1$, the insect-free equilibrium is globally asymptotically stable. When $\cR_0 > 1$ and $\cR_1 < 1$, the disease-free equilibrium exists and is locally asymptotically stable. When $\cR_1>1$, the disease will persist.

Secondly, we derive another general delay differential equations system to examine how different life stages of leafhoppers affect crops. The basic reproduction numbers $\cR_0$ is determined: when …

The Study Of Nanophotonic Switching Mechanisms In Photonic And Metallic Heterostructures, Joel Cox

Electronic Thesis and Dissertation Repository

In this thesis, nanophotonic switching mechanisms and light-matter interactions are explored in photonic and metallic heterostructures and nanocomposites. These heterostructures are made using various combinations of photonic crystals (PCs), quantum dots (QDs), and graphene or metal nanoparticles (MNPs).

PC heterostructures are formed by combining different PCs so that photons in a specific energy range can propagate in certain regions along one direction and cannot propagate in others. This band structure engineering is used to form photonic quantum wells (PQWs) that have discrete energy states along one dimension. By simulating the photon transmission along the direction of confinement, resonant photon tunnelling …

Electrochemiluminescence Of Thienyltriazoles, Iridium Complexes, Au25 Clusters And Pbs Nanoparticles, Kalen N. Swanick

Electronic Thesis and Dissertation Repository

Electrogenerated chemiluminescence or electrochemiluminescence (ECL), produces light in the vicinity of a working electrode by the excited species of a luminophore formed via electron transfer between radical cations and anions, which are electrogenerated. In order for the ECL system to be efficient, the radicals must be stable in solution. This can be enhanced by adding co-reactants such as benzoyl peroxide (BPO) and tri-n-propylamine (TPrA) that produce strong oxidizing or reducing radicals upon redox reactions. ECL pairs electrochemical and spectroscopic methods and is a powerful analytical technique that is highly sensitive and selective.

A comprehensive, mechanistic study of ECL …

The Synthesis, Reactivity And Electrochemical Study Of Metallocene Substituted Α-Diimine Ligands, Eleanor Magdzinski

Electronic Thesis and Dissertation Repository

The synthesis of transition metal complexes containing redox-active ligands or ligands with redox-active substituents have been areas of ongoing interest in chemical research. To date, only a handful of examples involving redox-active ligands containing main group centres have been reported.

This thesis presents work on the development of novel redox-active ligands utilizing an assortment of nitrogen-based frameworks (diiminopyridine (DIMPY), 1,4-diaza-1,3-butadiene (DAB), N-heterocyclic carbene (NHC)) that contain metallocene substituents (ferrocene and an understudied redox-active Co(III) moiety). Initially the syntheses of an N, N’-differocenyl diiminopyridine and its low-valent chalcogen (S²⁺, Se²⁺, Te²⁺) and pnictogen …

Optimization Of A Boundary Element Approach To Electromagnet Design With Application To A Host Of Current Problems In Magnetic Resonance Imaging, Chad T. Harris

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a valuable methodological approach in both basic research and clinical practice. However, significant hardware advances are still needed in order to further improve and extend the applications of the technique. The present dissertation predominantly addresses gradient and shim coil design (sub-systems of the MR system).

A design study to investigate gradient performance over a set of surface geometries ranging in curvature from planar to a full cylinder using the boundary element (BE) method is presented. The results of this study serve as a guide for future planar and pseudo-planar gradient systems for …

Ecological Constraints And The Evolution Of Cooperative Breeding, David Mcleod

Electronic Thesis and Dissertation Repository

Cooperative breeding is a social behaviour in which certain individuals will opt to delay or forgo their own reproduction in order to help other individuals. Cooperative breeding is one of the most conspicuous examples of cooperation in nature. However, theoretical understanding of why this behaviour occurs is lacking and contradictory. In this thesis, I examine the role played by ecological constraints on the emergence of cooperative breeding. Contrary to previous results, I find that ecological constraints do matter, provided the population dynamics are properly accounted for. I also examine the long-term evolutionary dynamics of cooperative breeding, and obtain the optimal …

Fluorescent Cytidine Analogues, Kirby J. Chicas

Electronic Thesis and Dissertation Repository

Three luminescent cytidine analogues have been synthesized in order to perform SNP analysis by fluorescence spectroscopy. Herein is described the synthesis of 6-pyrenylpyrrolocytidine (PypdC), its photophysical characterization, and its subsequent incorporation into oligodeoxynucleotides (ODNs). The behavior of PypdC in ODNs is described as well as fluorescence intensity changes with respect to the match and mismatch cases. In order to obtain a greater understanding of pyrene’s interaction with pyrrolocytidine, a congener, pyrenyl ethynyl cytidine (PyEtdC) was synthesized. The congener was photophysically studied and prepared for oligo synthesis. Finally, exploration into indole substituted pyrrolocytidines (pdCs) was undertaken to explore new pdC structures.

New Mineralogical And Geochemical Characterization Of Martian Meteorites: Implications For Habitability And Astrobiological Exploration Of Mars, Jared N. Shivak

Electronic Thesis and Dissertation Repository

Mars is thought to have shared many similarities with the Earth during its history, leading to extensive research into the potential for life to arise on Mars. Here, a thorough mineralogical and geochemical characterization of primary and secondary phases in Martian meteorites Los Angeles, Zagami, and Nakhla was performed. This novel approach assesses their potential to host life and build on previous studies that focused on either astrobiological or geological factors. These meteorites were found to contain abundant iron-rich phases that can act as microbial substrates. Investigation of alteration phases in Nakhla allowed for the identification of a new secondary …

The Continuum Linear Polarization Signature Of Classical Be Stars, Robbie J. Halonen

Electronic Thesis and Dissertation Repository

Classical Be stars are rapidly-rotating, massive stars that exhibit distinct observational characteristics due to the presence of enveloping, equatorial disks of gas. While diligent observation of these objects has established a reliable description of their geometric and kinematic properties, our understanding of classical Be stars remains distressingly limited on the dynamical front. Principally, we lack a satisfactory characterization of the physical process(es) through which the gaseous disks form and dissipate. In order to understand the mechanisms that govern the development of these enigmatic stars, we use computational codes to produce theoretical models of these objects and their environments. We compare …