Physical Sciences and Mathematics Commons^™

A Geographical Approach For Integrating Belief Networks And Geographic Information Sciences To Probabilistically Predict River Depth, Nathan Lee Hopper

Dissertations

Geography is, traditionally, a discipline dedicated to answering complex spatial questions. Although spatial statistical techniques, such as weighted regressions and weighted overlay analyses, are commonplace within geographical sciences, probabilistic reasoning, and uncertainty analyses are not typical. For example, belief networks are statistically robust and computationally powerful, but are not strongly integrated into geographic information systems. This is one of the reasons that belief networks have not been more widely utilized within the environmental sciences community. Geography’s traditional method of delivering information through maps provides a mechanism for conveying probabilities and uncertainties to decision makers in a clear, concise manner. This …

Design And Synthesis Of Flexible And Functional Polybenzoxazine Thin Films, Austin David Baranek

Dissertations

Polybenzoxazines offer the unique ability to incorporate a variety of properties and functionality into a single polymer network through simple synthetic techniques. However, within benzoxazine materials exist certain drawbacks of which brittleness is the primary issue when exploring thin film applications. This brittleness leads to poor mechanical stability and would reduce the lifetime of any device sought after. It is, however, through the simplistic nature of the benzoxazine monomer synthesis that the mechanical stability could be addressed chemically, avoiding the complications of using rubber toughening agents or plasticizers. The monomer synthesis offers tailorability of both the phenol and amine to …

An Insight Into Asymmetric Synthesis And Bioorganic Applications Of Novel Cα- Methyl-Lysine, - Proline, - Nipocotic Acid Analogues, Souvik Banerjee

Dissertations

Prochiral malonic diesters consisting of a quaternary carbon center have been successfully converted into a different set of tBoc-Fmoc-α2,2-methyllysine-OH analogues through chiral malonic half-ester intermediates achieved via enzymatic (Pig Liver Esterase, PLE) hydrolysis. The selection of chiral half-ester intermediates, which vary from 1 to 6 methylene units in the side chain, are achieved in high optical purity (92% - 97% ee) and in good yields (65% - 72%). The PLE hydrolysis of malonic diesters with a variety of side chain lengths observed to obey the Jones’s PLE model as evidenced from the stereochemical configurations of the resulting chiral half-esters. The …

Iterative Solvers For Large, Dense Matrices, Eowyn Wilhelmina Cenek

Dissertations

Stochastic Interpolation (SI) uses a continuous, centrally symmetric probability distribution function to interpolate a given set of data points, and splits the interpolation operator into a discrete deconvolution followed by a discrete convolution of the data. The method is particularly effective for large data sets, as it does not suffer from the problem of oversampling, where too many data points cause the interpolating function to oscillate wildly. Rather, the interpolation improves every time more data points are added. The method relies on the inversion of relatively large, dense matrices to solve Annx = b for x. Based on the probability …

Biophysical Understanding Of Novel Synthetic Amyloid-Β (Aβ) Prions In Alzheimer's Disease, Amit Kumar

Dissertations

Oligomers of amyloid-β (Aβ) peptide are the primary toxic agents that play a pivotal role in the pathogenesis of Alzheimer’s disease (AD). Oligomers are the intermediates formed during the Aβ aggregation process leading up to insoluble fibrils. It is important to know that oligomers can also be formed via pathways that do not lead to fibril formation. Such ‘off-pathway’ oligomers would have significantly longer half-lives than the ‘on-pathway’ ones, which may result in prolonged toxicity to neuronal cells. Furthermore, neither the mechanism of neurotoxicity nor the potential mechanisms of propagation and proliferation to neighboring cells are well understood. Moreover, recent …

In Situ Quenching And Post-Polymerization Modification Of Telechelic Polyisobutylene, Todd Raymond Hartlage

Dissertations

Polyisobutylene (PIB) is a saturated hydrocarbon elastomer that can only be produced by cationic polymerization. The water-initiated, chain transfer controlled synthesis conducted on an industrial scale produces monofunctional PIB with mixed olefin end groups. Living cationic techniques produce mono- and di-functional telechelic PIB. In situ quenching is the process of adding functional molecules to the polymerization reactor after all monomer is consumed. These quencher species bond to the chain ends, installing their latent functionality onto the polymer chain. To date, all quenchers utilized have been soft π-nucleophiles.

In the first project, free thiols, both aromatic and aliphatic, are shown to …

Synthesis And Characterization Of Polyisobutylene-Block-Polyamides As Novel Thermoplastic Elastomers, Lauren Renee Kucera

Dissertations

Academic research has focused on two main areas of the living carbocationic polymerization (LCP) of isobutylene (IB): (1) the in-depth study and understanding of mechanistic features of the polymerization, and (2) the utilization and manipulation of the unique aspects of PIB in order to produce practically useful polymeric materials. The research included in this dissertation focuses mainly on the latter objective. This work details three main areas of research: (1) the copolymerization of PIB and polyamides (PA) to form novel thermoplastic elastsomers (TPEs), (2) the mechanical, physical and thermal properties of the novel PIB-PA materials, and (3) the use of …

Relation Between The Adsorption Behavior And Bulk Complexation In Oppositely Charged Polyelectrolyte-Surfactant Systems: Effect Of Polyelectrolyte Concentration, Molecular Weight, Charge Localization And Backbone Rigidity/Hydrophobicity, Vipul Suhas Padman

Dissertations

Due to a wide range of applications, much emphasis has been placed on understanding the physicochemical behavior of polyelectrolyte/surfactant complexes, both at air-water interface and in the bulk. However, the correlation between the adsorption behavior and complexation in the bulk is less explored. In this research, this correlation is investigated and its dependence on polyelectrolyte concentration, molecular weight, charge localization and backbone rigidity and hydrophobicity is studied. The polyelectrolyte concentration is normalized with respect to it critical overlap concentration in order to compare the polymer in same concentration regime. Different polyelectrolyte systems were used to analyze the polyelectrolyte structural effect: …

Investigations Toward Tunability Of Mechanical, Thermal, And Impact Properties Of Thiol-Ene Networks For Novel High Energy Absorbing Materials, Olivia Devon Mcnair

Dissertations

The UV polymerization of thiols with electron rich alkenes is a highly resourceful reaction that has been utilized by scientists within various disciplines to produce an even more versatile display of applications. This dissertation focuses on a newer application, thiol-ene network (TEN) materials for energy absorption devices. TEN networks display a host of positive polymer properties such as low stress, high optical clarity and uniformity, but they also suffer from unfavorable mechanical properties such as low toughness and elongation at break. The poor mechanical properties demonstrated by TENs prohibit them as choice materials for applications requiring thicker material forms, including …

Photopolymerization And Characterization Of Modified Thiol-Ene Networks, Bradley James Sparks

Dissertations

Photopolymerization provides a unique ability to control variables typically uncontrollable using traditional thermally initiated polymerization, thus leading to its use in a broad range of commercial operations. Many of the traditional photopolymers suffer from several setbacks, including oxygen inhibition, unwanted stress buildup which leads to bulk shrinkage, etc., which ultimately lead to diminished polymer performance. The photopolymerization of multifunctional thiols and alkenes has been shown to provide a means to improve upon the weaknesses of traditional photoinitiated polymerizations. The free radical polymerization of thiol and –ene monomers occurs via a series of free radical chain transfer events, as a result, …

Biological And Biologically Inspired Polymers For Interface Modification, Lea Clayton Paslay

Dissertations

Naturally occurring macromolecules are produced for a specific function and have the selectivity to accomplish objectives with little waste in energy. The scientific community strives to develop smart, efficient molecules on an economical scale, thus lessons can be learned from nature and applied to cost effective synthetic systems. First, the mimicry of naturally occurring antimicrobial peptides (AMPs) will be described. AMPs show great potential as alternatives to conventional antibiotics as they can selectively bind and eliminate pathogenic bacteria without harming eukaryotic tissues. Aqueous reversible addition–fragmentation chain transfer (RAFT) polymerization was utilized to prepare primary and tertiary amine containing AMP polymer …

Relationships Between Cure Kinetics, Network Architecture, And Fluid Sensitivity In Glassy Epoxies, Katherine Lea Frank

Dissertations

Relationships between chemical structure, cure kinetics, network morphology and free volume have been correlated with fluid ingress for glassy epoxy network blends. Polymers synthesized from diglycidyl ether of bisphenol-A (DGEBA) and diglycidyl ether of bisphenol-F (DGEBF) were blended with varying amounts of triglycidyl-m-aminophenol (TGAP), tetraglycidyl-4,4-diaminodiphenylmethane (TGMP), napthylamine (NA), adamantylamine (AA), and aminopropylisobutyl polyhedral oliogmericsilsesquioxane (AI-POSS) and cured with 3,3’- and 4,4’- diaminodiphenylsulfone (DDS) to control fractional free volume, average hole size and morphology.

Varying curing profiles introduced morphological changes resulting in differences in network architectures. Epoxy with 10% NA had a smaller V_h (71 ų) …

Utilizing Polymer Topology In Peptide-Based Block Copolymers: Unique Aqueous Assembly And Responsive Behavior, Jacob Griffin Ray

Dissertations

This document details work in the area of amphiphilic polypeptide-based block copolymers that are able to self-assemble into well-defined nanostructures in aqueous solution. The main focus of this work is to understand the impacts of polymer topology on self-assembly behavior and response to external stimulus, particularly pH. Poly(L-lysine) and poly(L-glutamic acid) are two pH-responsive, hydrophilic polypeptides that possess the unique property of undergoing α-helix to random coil secondary structure transitions with pH, and this responsiveness can lead to global morphology changes such as changes in aggregate size or even morphology transitions. These polypeptides are synthesized via ring opening polymerization of …

Gene Regulatory Network Reconstruction Using Dynamic Bayesian Networks, Haoni Li

Dissertations

High-content technologies such as DNA microarrays can provide a system-scale overview of how genes interact with each other in a network context. Various mathematical methods and computational approaches have been proposed to reconstruct GRNs, including Boolean networks, information theory, differential equations and Bayesian networks. GRN reconstruction faces huge intrinsic challenges on both experimental and theoretical fronts, because the inputs and outputs of the molecular processes are unclear and the underlying principles are unknown or too complex.

In this work, we focused on improving the accuracy and speed of GRN reconstruction with Dynamic Bayesian based method. A commonly used structure-learning algorithm …

Nanoparticle Filled Polymeric Systems For Gas Barrier And Flame Retardant Properties, Yingji Wu

Dissertations

Polymer composite gas barrier and fire retardant properties were studied in this investigation. An increase in the gas barrier property was observed by adding silicate nanotubes or clay nanoparticles into polymeric systems. Oxygen permeability, diffusivity, solubility and water vapor permeability were determined for polyimide/silicate nanocomposites with 0 to 9.99% (vol/vol) filler loading. Both oxygen and water vapor permeability for the system gradually decreased when adding increasing amounts of nanofiller up to 4.50% (vol/vol) and increase again after that. The permeability decrease was caused by both the diffusivity and solubility coefficient changes, although diffusivity (the tortuous factor) is the main reason …

Synthesis Of Polyhedral Oligomeric Silsesquioxane (Poss) Functionalized Carbon Nanotubes For Improved Dispersion In Polyurethane Films, Xiaonan Kou

Dissertations

Carbon nanotube (CNT) polymer nanocomposites are promising advanced materials. These materials exhibit the advantages of traditional polymeric materials, such as being light weight and easy to process, combined with the potential to exhibit enhanced mechanical, thermal and electrical properties compared to pure polymers. To achieve substantial improvement of composite properties at low CNT loading, uniform dispersion of CNTs in the polymer matrix and strong CNT-polymer interfacial interaction are needed. However, it is difficult to achieve adequate dispersion and interfacial interactions due to the inert nature of CNTs. In this project, polyhedral oligomeric silsequioxane (POSS) will be used as a dispersing …

Dynamic Bioactive Stimuli-Responsive Polymeric Surfaces, Heather Marie Pearson

Dissertations

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of –COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface …

Understanding Corrosion Protection And Failure Through Model Polymers In Thin Films, Joshua Smith Hanna

Dissertations

When developing a model polymeric system to facilitate in the detection of molecular and microscopic events that preface macroscopic corrosive failure; a better understanding of how polymers can indicate corrosion was accomplished. Initially, the thought that molecular chain scission as a necessity for corrosion to occur had to be tested. Through the utilization of high molecular weight thermoplastic (HMWTP) model polymers, it was found that corrosion protection did not correlate to the quantity of weak bonds within an epoxy-amine polymer matrix. Therefore more sensitive methods of detecting corrosion had to be developed since changes within the polymer matrix did not …

Polymer Surface Engineering Via Thiol-Mediated Reactions, Ryan Matthew Hensarling

Dissertations

Synthesis of polymer brushes to decorate a surface with desired functionality typically involves surface-initiated polymerization (SIP) of functional, but non-reactive monomers. This approach suffers major drawbacks associated with synthesizing sufficiently thick polymer brushes containing surface-attached polymer chains of high molecular weight at high grafting density (i.e. cost, synthetic effort and functional group intolerance during polymerization). The research herein seeks to circumvent these limitations by the decoration of surfaces with polymer chains bearing specific pendent functional groups amenable to post-polymerization modification (PPM). In particular, this dissertation leverages PPM via a specific class of click reactions – thiol-click – that 1) enables …

A Time Series Analysis Method Using Hidden Variables For Gene Network Reconstruction, Xi Wu

Dissertations

The DNA microarray technology can be applied to obtain time series data which contains thousands of genes and tens of time points. When confront the great amount of data points a fast and effective method must be constructed to extract useful information. The assumption that the interactions between genes are static in the time series data is made. After made the assumption how to reconstruct those interactions becomes a difficulty problem. Since the underlying interactions between genes are complicated, which involve transcription, translation and protein-protein interaction, to construct a model from physicochemistry is almost impossible/effortless. The popular methods constructed from …

Reification: A Process To Configure Java Realtime Processors, John Huddleston Heath

Dissertations

Real-time systems require stringent requirements both on the processor and the software application. The primary concern is speed and the predictability of execution times. In all real-time applications the developer must identify and calculate the worst case execution times (WCET) of their software. In almost all cases the processor design complexity impacts the analysis when calculating the WCET. Design features which impact this analysis include cache and instruction pipelining. With both cache and pipelining the time taken for a particular instruction can vary depending on cache and pipeline contents. When calculating the WCET the developer must ignore the speed advantages …

Microstructure, Vacancies And Voids In Hydrogenated Amorphous Silicon, Rajendra Timilsina

Dissertations

This dissertation presents a theoretical and computational study of microstructure, vacancies and voids in hydrogenated amorphous silicon (a-Si:H). The microstructure consists of all possible silicon-hydrogen bonding configurations such as SiH, SiH₂, SiH₃ and SiH₄. However, it is highly dominated (approximately 75% or even more) by monohydride (SiH) configurations. Furthermore, the hydrogen atoms locate in both clustered and diluted phases; as a result, the distribution becomes highly inhomogeneous. Approximately 5% of hydrogen atoms reside in a form of isolated monohydrides at the lower (7 at.%) concentration whereas such configurations do not appear at the higher concentrations …

Coastal Hurricane Damage Assessment Via Wavelet Transform Of Remotely Sensed Imagery, Ricky Carl Crowsey

Dissertations

This dissertation uses post storm imagery processed using wavelet transforms to investigate the capability of wavelet transform-based methods to classify post storm damage of residential areas. Five level Haar, Meyer, Symlets, and Coiflets wavelet transform decompositions of the post storm imagery are inputs to damage classification models of post hurricane and tornado damage. Hurricanes Ike, Rita, Katrina, and Ivan are examined as are the 2011 Joplin and Tuscaloosa tornadoes.

Wavelet transform-based classification methods yielded varying classification accuracies for the four hurricanes examined, ranging from 67 percent to 89 percent classification accuracy for classification models informed by samples from the storms …

New Dual Initiators For Polyisobutylene-Based Block And Star Polymers, Yaling Zhu

Dissertations

Polyisobutylene (PIB), available solely by living carbocationic polymerization (LCP), is a commercially important polymer with excellent thermal stability, good flexibility and extraordinary impermeability to gases. Due to these attractive properties, coupling PIB to other polymer blocks is expected to result in new and useful products. Two types of new dual initiators possessing initiating sites for both LCP and atom transfer radical polymerization (ATRP), have been designed for the preparation of AB linear and A2B miktoarm star copolymers, where A is PIB-based block copolymer that grows cationically and B is polyacrylate or other radically-derived polymer block, without intermediate modification.

Mono-cationic mono-radical …

Modern Approaches For Multifunctional Hydrolyzying Thiol-Ene Networks, Nicole Marie Mackey

Dissertations

Marine fouling has been an expensive and time-consuming process for navies and fishermen by the accumulation of marine algae and animals on artificial surfaces. Many coatings have been proposed to combat marine fouling in efforts to extend the lifetime of objects immersed in sea water. However, all coatings tested have either failed to resist fouling for a significant length of time or have released toxins into the environment. We have investigated an environmentally friendly approach to address the problem of marine fouling through the synthesis and preparation of a biocidal and a self-polishing coating. Both novel monomers were prepared containing …

Surface, Bulk, And Rheological Properties Of Polyhedral Oligomeric Silsesquioxane/High Density Polyethylene Nanocomposites, Robert Douglas Cook Jr.

Dissertations

In the formulation of high performance nanocomposites, control of miscibility and dispersion of filler material through a polymer matrix is of utmost importance. Due to their inorganic nature most nanofillers are insoluble in polymers, leading to costly/complicated surface modification as a primary means of increasing miscibility and interaction with organic matrices. Polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals offer an attractive alternative to conventional nanofillers. Due to their hybrid organic-inorganic nature, POSS has the potential to be tailored for miscibility in a wide range of organic matrices not by chemical surface modification but through modification of the molecular structure of the …

A Bisphenol-A-Based Resin System That Cures Via Triazole Ring Formation For Marine Composite Applications, Irene Elizabeth Gorman

Dissertations

Large composite panels, such as those utilized in marine applications, cannot be economically cured in an autoclave. For these structures the elevated temperatures necessary to achieve high crosslink density must come from the curing reaction itself. We are developing a resin system that cures via triazole ring formation (cycloaddition reaction of azides with terminal alkynes) instead of the traditional oxirane/amine reaction. The high exothermicity of the azido/alkyne reaction is expected to yield higher extents of reaction under ambient-cure conditions, making the resin system potentially suitable for "out-of-autoclave" curing processes. This work was conducted through a multi-tiered approach involving synthesis, kinetic …

Error Estimation Techniques To Refine Overlapping Aerial Image Mosaic Processes Via Detected Parameters, William Glenn Bond

Dissertations

In this paper, I propose to demonstrate a means of error estimation preprocessing in the assembly of overlapping aerial image mosaics. The mosaic program automatically assembles several hundred aerial images from a data set by aligning them, via image registration using a pattern search method, onto a GIS grid.

The method presented first locates the images from a data set that it predicts will not align well via the mosaic process, then it uses a correlation function, optimized by a modified Hooke and Jeeves algorithm, to provide a more optimal transformation function input to the mosaic program. Using this improved …

Molecular Network Development Of A Thermosetting Epoxy-Amine Polymer, Christopher Michael Sahagun

Dissertations

i ABSTRACT MOLECULAR NETWORK DEVELOPMENT OF A THERMOSETTING EPOXY-AMINE POLYMER by Christopher Michael Sahagun May 2012 Epoxy-amine resins find wide application as the matrix material of high performance polymer composites due to their favorable mechanical properties, thermal properties and solvent stability. These properties are derived from the complicated, highly crosslinked molecular network that is characteristic of these thermoset polymers. The connectivity of the molecular network has a strong influence on the physical performance of the finished part. Non-homogeneity in the network structure can degrade these favorable properties through the introduction of low-energy pathways for solvent penetration or fracture propagation. This …

The Investigation Of Asphaltene-Naphithenic Acid And Asphaltene-Surface Interactions, David Tristan Heaps

Dissertations

Asphaltenes represent a ubiquitous problem in the oil industry due to their adverse effects on recovery, production, and processing equipment. These problems have affected oil companies throughout the world, resulting in significant financial losses. In order to expand the existing body of knowledge related to asphaltenes, we have examined how the presence of naphthenic acids contributes to the particle aggregation and sedimentation behavior of asphaltene suspensions as well as how the physics and chemistry of a substrate affect asphaltene adsorption/deposition.

The flocculation of asphaltenes in the presence of naphthenic acids was investigated using dynamic light scattering (DLS), near-infrared spectroscopy (NIR), …