Physical Sciences and Mathematics Commons^™

Evaluating Predictability In The Community Earth System Model In Response To The Eruption Of Mount Pinatubo, Abigail Laurel Gaddis

Doctoral Dissertations

A central goal of climate research is to determine the perceptible effects of climate change on humans; in other words, the regional and decadal scale effects of carbon dioxide forcing. Identifying the most pronounced and long-lasting responses of climate variables to forcing is important for decadal prediction since forcing terms are a source of predictability on those time scales. Powerful volcanic eruptions provide a transient forcing on the climate system, creating a test bed for climate models. In this study, the Mount Pinatubo eruption is simulated in the Community Earth System Model, CESM1.0, for three model configurations: fully coupled T85 …

Complex Magnetism In Noncentrosymmetric Magnets, Nirmal Jeevi Ghimire

Doctoral Dissertations

Broken inversion symmetry in a crystal lattice allows an extra term called the Dzyaloshinskii-Moriya (DM) interaction in the magnetic Hamiltonian. The DM interaction tends to align spins in perpendicular orientation and therefore competes with the exchange interaction that favors collinear spins. This competition results in different modulated chiral magnetic structures depending on the relative strength of the two interactions. Skyrmion, soliton and magnetic blue phases are some of the anticipated structures. This dissertation extends the search for these exotic magnetic structures using various techniques to study the magnetism in the noncentrosymmetric magnets Cr₁₁Ge₁₉ [chromium eleven germanium nineteen], …

Copper Mediated, Transmetallation Coupling Reactions Using High Intensity Ultrasound, Bryan J. Musolino

Doctoral Dissertations

This dissertation summarizes research efforts focused on the use of boron and copper acetate to form new carbon-carbon and carbon-heteroatom bonds. Two new methods were developed using high intensity ultrasound as the reaction energy source. The first focused on the homocoupling of various aryl compounds using a commercially available polymer support. The use of this polymer support allows the reaction to proceed in an aqueous solvent system with only minimal preparation. The product yields were better than values reported in the literature using traditional reaction conditions and reaction times were decreased from 24-72 hours to 6 hours. The second method …

Investigation Of Time And Position Resolved Alpha Transducers For Multi-Modal Imaging With A D-T Neutron Generator, Joshua William Cates

Doctoral Dissertations

Deuterium-Tritium (D-T) neutron generators have been used as an active interrogation source for associated particle imaging (API) techniques. The D-T reaction yields a 14.1 MeV neutron and a 3.5 MeV alpha (or assoicated) particle, projected nearly back-to-back. The kinetics of the reaction allow the direction and initial time of the neutron to be determined utilizing position sensitive detectors for both the alpha and neutron. This information facilitates multi-modal fast neutron imaging of inspection objects and closed containers to infer the geometry within them and the presence of special nuclear material (SNM). Since position and time of interaction of the alpha …

Borel Complexity Of The Isomorphism Relation For O-Minimal Theories, Davender Singh Sahota '99

Doctoral Dissertations

In 1988, Mayer published a strong form of Vaught's Conjecture for o-minimal theories (1). She showed Vaught's Conjecture holds, and characterized the number of countable models of an o-minimal theory T if T has fewer than 2K ° countable models. Friedman and Stanley have shown in (2) that several elementary classes are Borel complete. This work addresses the class of countable models of an o-minimal theory T when T has 2N ° countable models, including conditions for when this class is Borel complete. The main result is as follows.

Theorem 1. Let T be an o-minimal theory in a countable …

Neutron Scintillation Detectors Based On Polymers Containing Lithium-6 For Radiation Portal Monitor Applications, Andrew Neil Mabe

Doctoral Dissertations

The work presented herein describes an investigation of four main types of thin film polymer scintillators containing ⁶Li [lithium-6] for neutron detection: polystyrene containing ⁶LiF [lithium-6 fluoride] and a preblended fluor mixture comprising 2,5-diphenyloxazole and 1,4-bis(5-phenyloxazol-2-yl)benzene; poly(styrene-co-lithium maleate) containing salicylic acid; poly[styrene-co-lithium maleate-co-2-phenyl-5-(4-vinylphenyl)oxazole]; and poly(styrene-co-lithium 4-vinylbenzoate). A variety of chemical and physical characterizations as well as optical and scintillation characterizations were performed to guide the development of optimized compositions of each type of polymer film. The scintillation performances of optimized compositions of each type of polymer film were calibrated using …

Finite Difference And Discontinuous Galerkin Finite Element Methods For Fully Nonlinear Second Order Partial Differential Equations, Thomas Lee Lewis

Doctoral Dissertations

The dissertation focuses on numerically approximating viscosity solutions to second order fully nonlinear partial differential equations (PDEs). The primary goals of the dissertation are to develop, analyze, and implement a finite difference (FD) framework, a local discontinuous Galerkin (LDG) framework, and an interior penalty discontinuous Galerkin (IPDG) framework for directly approximating viscosity solutions of fully nonlinear second order elliptic PDE problems with Dirichlet boundary conditions. The developed frameworks are also extended to fully nonlinear second order parabolic PDEs. All of the proposed direct methods are tested using Monge-Ampere problems and Hamilton-Jacobi-Bellman (HJB) problems. Due to the significance of HJB problems …

Optimal Control For Management In Gypsy Moth Models, Marco Vinisio Martinez

Doctoral Dissertations

The gypsy moth, Lymantria dispar (L.), is an invasive species and the most destructive forest defoliator in North America. Gypsy moth outbreaks are spatially synchronized over areas across hundreds of kilometers. Outbreaks can result in loss of timber and other forestry products. Greater losses tend to occur to the ecosystem services that forests provide, such as wildlife habitat, carbon sequestration, and nutrient cycling. The United States can be divided in three different areas: a generally infested area (populations established), an uninfested area (populations not established), and a transition zone between the two. There are different management programs matching these different …

Sociobiophysicality, Cold War, And Critical Theory: Human-Ecological Transformation And Contemporary Ecological Subjectivity, Alexander Stoner

Doctoral Dissertations

The United States is an important global player in resource depletion, energy use, waste production, and other indicators that contribute to economic threats to humanity’s ecological future. Critical theory provides conceptual tools that are uniquely well-suited to more fully comprehend the links between economic progress and ecological deterioration. In key regards, the present situation is the continuation as well as amplification of political-economic, social and cultural features that took hold during the Cold War, and which demand rigorous sociological focus, scrutiny and analysis. To date, however, sociology has barely begun to assess the consequences that resulted from the Cold War …

Long Time Asymptotics Of Ornstein-Uhlenbeck Processes In Poisson Random Media, Fei Xing

Doctoral Dissertations

The Models of Random Motions in Random Media (RMRM) have been shown to have fruitful applications in various scientific areas such as polymer physics, statistical mechanics, oceanography, etc. In this dissertation, we consider a special model of RMRM: the Ornstein-Uhlenbeck process in a Poisson random medium and investigate the long time evolution of its random energy. We give complete answers to the long time asymptotics of the exponential moments of the random energy with both positive and negative coefficients, under both quenched and annealed regimes. Through these results, we find out a dramatic difference between the long time behavior of …

Predicting Threat Potential Using Cyber Sensors, Mark Anthony Thompson

Doctoral Dissertations

The proliferation of the Internet has created a culture of a connected society dependent upon technology for communication and information sharing needs. In this dissertation, we hypothesize that attackers are increasingly using electronic resources that are capable of leaving a digital footprint, such as social media services, e-mail, text messages, blogs, and websites for the communication, planning, and coordination of attacks. In its current form, however, traffic analysis is primarily concerned with using communications volume to extract intelligence information, but largely ignores the content of communications transmissions that is needed to meet the security challenges and demands of continually emerging …

A Mathematical Model And Numerical Method For Thermoelectric Dna Sequencing, Liwei Shi

Doctoral Dissertations

DNA sequencing is the process of determining the precise order of nucleotide bases, adenine, guanine, cytosine, and thymine within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases in a strand of DNA. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Thermoelectric DNA sequencing is a novel method to sequence DNA by measuring the heat that is released when DNA polymerase inserts a deoxyribonucleoside triphosphate into a growing DNA strand. The thermoelectric device for this project is composed of four parts: …

The Measurement Of The Dielectric Constant Of Concrete Pipes And Clay Pipes, David Mcgraw

Doctoral Dissertations

To optimize the effectiveness of the rehabilitation of underground utilities, taking in consideration limitation of available resources, there is a need for a cost effective and efficient sensing systems capable of providing effective, in real time and in situ, measurement of infrastructural characteristics. To carry out accurate non-destructive condition assessment of buried and above ground infrastructure such as sewers, bridges, pavements and dams, an advanced ultra-wideband (UWB) based radar was developed at Trenchless Technology Centre (TTC) and Centre for Applied Physics Studies (CAPS) at Louisiana Tech University (LTU). One of the major issues in designing the FCC compliant UWB radar …

Generalized Finite-Difference Time-Domain Schemes For Solving Nonlinear Schrödinger Equations, Frederick Ira Moxley Iii

Doctoral Dissertations

The nonlinear Schrödinger equation (NLSE) is one of the most widely applicable equations in physical science, and characterizes nonlinear dispersive waves, optics, water waves, and the dynamics of molecules. The NLSE satisfies many mathematical conservation laws. Moreover, due to the nonlinearity, the NLSE often requires a numerical solution, which also satisfies the conservation laws. Some of the more popular numerical methods for solving the NLSE include the finite difference, finite element, and spectral methods such as the pseudospectral, split-step with Fourier transform, and integrating factor coupled with a Fourier transform. With regard to the finite difference and finite element methods, …

Exploration Of Aqueous Interfaces And Their Effect On Ion Behavior, Oneka T. Cummings

Doctoral Dissertations

An in-depth understanding of a wide range of physical, chemical, atmospheric and biological processes can only be achieved after the structure and dynamics of interfaces and the interfacial behavior of aqueous species, such as ions, are thoroughly studied and understood. This dissertation describes computational studies conducted to gain a more comprehensive understanding of such interfaces and the behavior of ions in the bulk and interfacial regions of the (1) air/water interface, and (2) alkane/water interfaces.

At the air/water interface the effect of counterion (sodium cations) charge and the influence of ion pairing on anion (chloride) propensity for the air/water interface …

Mechanisms Of Nutrient Limitation And Nutrient Acquisition In Managed And Unmanaged Forest Ecosystems, Matthew A. Vadeboncoeur

Doctoral Dissertations

Understanding the interactions between global change, human and natural disturbances, and other factors on biogeochemical processes in forests is necessary to ensure the sustainability of forest management. Here I report the results of several investigations into nutrient acquisition processes in the forests of New Hampshire. I begin with a meta-analysis of fertilization studies showing that phosphorus (P) and calcium (Ca) as well as nitrogen (N) may limit primary production in deciduous forests of the region. Because these limiting nutrients are all removed from the ecosystem when trees are harvested, I compared nutrient budgets under a range of harvesting scenarios with …

New Applications Of Boron Dihalides And Organotrifluoroborates In Organic Synthesis, Kelly Elizabeth Hall

Doctoral Dissertations

This dissertation summarizes research focused on the use of boron dihalides and organotrifluoroborates in organic synthesis. The boron dihalide mediated aryl propargyl ether cleavage reactions to generate the corresponding aryl alcohols were investigated to explain the mechanistic pathway of using boron trihalides and boron dihalides in propargyl ether cleavage reactions. The results of this study strongly support that the mechanistic pathway for these reactions follows the pathway shown in this dissertation. In addition, the use of polymer-supported organotrifluoroborates for radiolabeling reactions was also investigated. The results of these studies support the use of polymer supported organotrifluoroborates in radiolabeling reactions as …

Geographic And Temporal Epidemiology Of Campylobacteriosis, Jennifer Weisent

Doctoral Dissertations

Campylobacteriosis is a leading cause of gastroenteritis in the United States. The focus of this research was to (i) analyze and predict spatial and temporal patterns and associations for campylobacteriosis risk and (ii) compare the utility of advanced modeling methods. Laboratory-confirmed Campylobacter case data, obtained from the Foodborne Diseases Active Surveillance Network were used in all investigations.

We compared the accuracy of forecasting techniques for campylobacteriosis risk in Minnesota, Oregon and Georgia and found that time series regression, decomposition, and Box-Jenkins Autoregressive Integrated Moving Averages reliably predict monthly risk of infection for campylobacteriosis. Decomposition provided the fastest, most accurate, user-friendly …

1,2,4-Triazine-Accelerated Azide-Alkyne Cycloaddition And Synthesis Of Metalloenzyme Inhibitors, Belinda Shea Lady

Doctoral Dissertations

The work of this dissertation describes the design and synthesis of 1,2,4-triazine ligands and other N-containing heterocycles and their use in the copper-catalyzed azide-alkyne cycloaddition (CuAAC). A variety of ligands were synthesized to probe the steric and electronic demands required for use in the CuAAC reaction. Substituents on the 1,2,4-triazine were systematically altered and the core 1,2,4-triazine modified to determine the most active ligand. Additional experiments explored the variability in the reaction conditions, such as solvent choice, use of reducing agents, and optimal stoichiometry. Under optimum conditions 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine and copper (II) tetrafluoroborate in the presence of triethylamine was found to …

Application Of Computational Molecular Biophysics To Problems In Bacterial Chemotaxis, Davi Ortega

Doctoral Dissertations

The combination of physics, biology, chemistry, and computer science constitutes the promising field of computational molecular biophysics. This field studies the molecular properties of DNA, protein lipids and biomolecules using computational methods. For this dissertation, I approached four problems involving the chemotaxis pathway, the set of proteins that function as the navigation system of bacteria and lower eukaryotes.

In the first chapter, I used a special-purpose machine for molecular dynamics simulations, Anton, to simulate the signaling domain of the chemoreceptor in different signaling states for a total of 6 microseconds. Among other findings, this study provides enough evidence to propose …

Novel Bimetallic Plasmonic Nanomaterials, Ritesh Sachan

Doctoral Dissertations

Plasmonic nanomaterials have attracted a lot of attention recently due to their application in various fields such as chemical and biological sensing, catalysis, energy harvesting and optical devices. However, there is a need to address several outstanding issues with these materials, including cost-effective synthesis, tunability in plasmonic characteristics, and long term stability. In this thesis, we have focused on bimetallic nanoparticles (NPs) of Ag and Co due to their immiscibility as well as their individual properties. First, a pulsed laser induced dewetting route was used to synthesize Ag-Co bimetallic plasmonic NPs. An synthesis parameter space was derived to show the …

Effects Of Traffic Noise On The Social Behavior Of Tufted Titmice (Baeolophus Bicolor)., Jessica Lynn Owens

Doctoral Dissertations

The presence of traffic noise and its potential effects on wildlife is a burgeoning topic of research within the fields of conservation behavior, animal behavior, ecology and wildlife management. Accumulated data from these efforts, mostly correlative and rarely-experimental, suggest that traffic noise induces a myriad of species-specific changes to population dynamics, breeding behavior and acoustic structure of avian song. However, the degree of generalizability of these findings is confounded by the limited variety of behaviors studied within a relatively small sample of species. This original research provides experimental evidence of the effects of simulated and real traffic noise on previously …

Femtosecond Laser Patterned Templates And Imprinted Polymer Structures, Deepak Rajput

Doctoral Dissertations

Femtosecond laser machining is a direct-write lithography technique by which user-defined patterns are efficiently and rapidly generated at the surface or within the bulk of transparent materials. When femtosecond laser machining is performed with tightly focused amplified pulses in single-pulse mode, transparent substrates like fused silica can be surface patterned with high aspect ratio (>10:1) and deep (>10 μm) nanoholes. The main objective behind this dissertation is to develop single-pulse amplified femtosecond laser machining into a novel technique for the production of fused silica templates with user-defined patterns made of high aspect ratio nanoholes. The size of the …

Fluorescence Spectroscopy With Correlated Atomic Force Microscopy Of Gold Nanoparticles And Meso-Scale Ribbons, Meredith Marie Therrien

Doctoral Dissertations

Studies on the optical properties of gold nanoparticles are of great interest due to the size and shape control and easy adaptability through functionalization to most any application, everything from nanomedicine to nanosensing. Gold nanoparticle optical properties change with size, morphology, and environment. Gold nanospheres were explored to determine the effect of environmental change, from many particles in solution to a single particle immobilized and in air, on fluorescence peak position. A statistical distribution of single gold nanorod fluorescence spectra demonstrate the spectral changes associated with slight variations in size. In solution, gold nanorods self-absorb and only exhibit bulk gold …

Toward Message Passing Failure Management, Wesley B. Bland

Doctoral Dissertations

As machine sizes have increased and application runtimes have lengthened, research into fault tolerance has evolved alongside. Moving from result checking, to rollback recovery, and to algorithm based fault tolerance, the type of recovery being performed has changed, but the programming model in which it executes has remained virtually static since the publication of the original Message Passing Interface (MPI) Standard in 1992. Since that time, applications have used a message passing paradigm to communicate between processes, but they could not perform process recovery within an MPI implementation due to limitations of the MPI Standard. This dissertation describes a new …

Nature And Degree Of Aqueous Alteration Of Outer Main Belt Asteroids And Cm And Ci Carbonaceous Chondrites, Driss Takir

Doctoral Dissertations

CM (Mighei-like) and CI (Ivuna-like) carbonaceous chondrites are primitive meteorites that consist of some of the most pristine matter known in the Solar System. They are thought to be genetically related to outer Main Belt asteroids (C-, D-, G-, F-, T-, and B-types) that span the 2.5 < a < 4.0 AU region. They are also thought to be the source that might have delivered water and organics to terrestrial planets during their accretion. The goal of this dissertation is to develop reliable 3-µm [micron] spectral indicators that can place constraints on the degree and location of aqueous alteration in the outer Main Belt region, and on the nature of phyllosilicate mineralogy on the surface of these asteroids. To that end, we have undertaken combined petrologic, geochemical, and spectroscopic analyses of CM and CI chondrites and outer Main Belt asteroids. Using the SpeX spectrograph/imager at NASA Infrared Telescope Facility (IRTF), we measured near-infrared (NIR: 0.7-4.0 µm) spectra of 40 outer Main Belt asteroids that allowed the identification of four 3-µm spectral groups, each of which presumably reflects a distinct surface mineralogy. We also measured spectra of 9 CM chondrites (in addition to the CI chondrite Ivuna) in the laboratory under asteroid-like conditions. These measurements revealed three spectral groups of CM chondrites, all of which are distinct from the spectrum of Ivuna on the basis of the 3-μm band center and shape of spectra, showing that distinct parent body aqueous alteration environments experienced by different carbonaceous chondrites can be distinguished using reflectance spectroscopy. All CM and CI chondrites in the present study are found to be similar to the group of asteroids that are located in the 2.5 < a < 3.3 AU region and exhibit a sharp 3-µm feature, attributed to OH-stretching in hydrated minerals. However, no meteorite match was found for asteroids with a rounded 3-µm feature that are located farther from the Sun (3.0 < a < 4.0 AU), or for groups with distinctive spectra like 1 Ceres or 52 Europa.

Tuning Sol-Gel Phase Diagrams Of Doubly Thermosensitive Hydrophilic Diblock Copolymers In Water, Naixiong Jin

Doctoral Dissertations

This dissertation presents the synthesis of stimuli-responsive hydrophilic diblock copolymers and the study of their behavior in water under various conditions. The polymers were made by “living”/controlled radical polymerization. Chapter 1 presents a background of this dissertation. Chapters 2-4 describe a family of doubly thermosensitive diblock copolymers with a small amount of carboxylic acid groups incorporated into either one or both blocks. The lower critical solution temperature (LCST) of the weak acid-containing block increases with increasing pH due to the ionization of carboxylic acid. Chapter 5 presents the preparation of pH-sensitive diblock copolymer micelle-embedded agarose hydrogels.

Chapter 2 describes the …

Quantitative Techniques For Pet/Ct: A Clinical Assessment Of The Impact Of Psf And Tof, Joshua Donald Schaefferkoetter

Doctoral Dissertations

Tomographic reconstruction has been a challenge for many imaging applications, and it is particularly problematic for count-limited modalities such as Positron Emission Tomography (PET). Recent advances in PET, including the incorporation of time-of-flight (TOF) information and modeling the variation of the point response across the imaging field (PSF), have resulted in significant improvements in image quality. While the effects of these techniques have been characterized with simulations and mathematical modeling, there has been relatively little work investigating the potential impact of such methods in the clinical setting. The objective of this work is to quantify these techniques in the context …

Resonance Hyper-Raman Characterization Of Nonlinear Chromophores, Christopher Bennett Milojevich

Doctoral Dissertations

Hyper-Raman spectroscopy is a nonlinear optical probe which can be used to explore the multi-photon properties of molecules. Three studies are presented in this dissertation. The first study is a combined experimental investigation of the surfaceenhanced hyper-Raman scattering with a theoretical study of the electronic states of the Rhodamine 6G molecule. This study demonstrates that hyper-Raman spectroscopy can be used to probe electronic states which are one-photon inaccessible. The second study involves a comparison of experimentally measured resonance hyper-Raman spectra to first-principles calculations of the resonance hyper-Raman scattering. This study shows the utility of coupling hyper-Raman spectroscopy and hyper-Raman calculations …

Hydraulic Properties Of Variably-Saturated Porous Media Determined Using Quantitative Neutron Radiography, Misun Kang

Doctoral Dissertations

The theoretical understanding of fluids in unsaturated porous media has improved substantially over the last several decades. Water retention curves remain a central pillar in the theoretical framework for modeling of water flow in unsaturated porous media. Use of the average water retention function in models to simulate water flow in porous media can result in inaccurate predictions due to the variations in water content and matric potential with elevation within the medium. As a result, point water retention curve data are needed for testing existing numerical and analytical models and for improving our ability to predict unsaturated water flow. …