Physical Sciences and Mathematics Commons^™

The Effects Of Free Volume And Processing On The Development Of Gas Separation Membranes, Jacob Schekman

Dissertations

Structure, thermal, mechanical, gas transport, and free volume properties of thiol-ene based systems are investigated and discussed. In the pursuit of generating low energy-cost polymer membranes for gas separation, it became apparent that UV-curing of thiol-ene materials presented several routes toward achieving this goal. Network structure plays a vital role in determining the gas transport properties of membrane materials. UV photopolymerization techniques provide a means to rapidly vitrify network morphologies which can be tuned depending on choice of monomer. Thiol-ene monomers offer a broad range of precursor materials from which to choose for the design of functional membrane materials.

Chapter …

Variability In Semidiurnal Surface And Internal Tides In Global Ocean Model Simulations, Harpreet Kaur

Dissertations

This dissertation focuses on semidiurnal (D2) surface and internal tides. Chapter 2 investigates the transition of M₂ barotropic Kelvin waves into Hybrid Kelvin-Edge (HKE) waves and the associated generation of internal tides at widening shelves using theory and a realistic global baroclinic Hybrid Coordinate Ocean Model (HYCOM) simulation. To understand the effect of complex, realistic bathymetry on the HKE wave transition, we perform quasi-realistic barotropic HYCOM simulations of the Celtic Sea/Bay of Biscay shelf areas. We conclude that the HKE wave transition is most likely masked by the effects of complex bathymetry and offshelf baroclinic fluxes cannot be exclusively …

Biophysical Factors Affecting Habitat Suitability For Crassostrea Virginica, Jason D. Tilley

Dissertations

Oyster reefs provide a variety of important ecosystem services. However, the mortality rate of eastern oyster, Crassostrea virginica, the dominant species that produces oyster reefs in the northern Gulf of Mexico, is increasing at an alarming rate due to a variety of abiotic and biological factors. I examined how biophysical factors, including the less-studied fatty acid profiles of the suspended particulate matter on which oysters feed, influenced morphometric condition of C. virginica.

I sampled suspended particulate matter (SPM) and oysters in-situ in the western Mississippi Sound, which historically supported the majority of oyster production in Mississippi waters. Sampling …

A Computational Kinetics Model To Quantify Radiation Induced Chemical Products Of Atmospheric Gas Mixtures, Patrick Ables

Dissertations

This research is focused on the development of a computational model which will calculate the effects of radiation on the chemical composition of the atmosphere. The approach utilizes the open-source chemical kinetics toolkit Cantera to model the creation of radiation-induced reactant species within irradiated air mixtures. Chemical solutions are iteratively stepped toward chemical equilibrium within a ‘constantly stirred’ (homogeneous) reactor of fixed volume. Three different radiation chemistry models are implemented in several different pulsed and continuous radiation schemes. The first model includes the mechanisms and rates of a pulse radiation model from the literature to test the validity of the …

The Mobility Of Long-Lived Radioisotopes And Their Burial In The Marine Environment, Neil Redmond

Dissertations

Marine sediments record chemical signals that reflect past environmental conditions. It is important to establish how these signals are created and whether they may be altered over time so that they can be useful for reconstructing ocean history. Measurements of uranium isotopes are used as a novel proxy for sedimentary diagenetic processes (Chapter 2). Because ²³⁴U can be ejected from mineral lattice during the decay of ²³⁸U, it creates a pool of U in porewater that is potentially mobilized and then deposited elsewhere in the core. We found that alpha-recoiled ²³⁴U is sensitive to differences in sediment …

Connecting Social And Ecological Systems In Small-Scale Fisheries In The Philippines, Sara Eisler Marriott

Dissertations

Nearly 50% of all marine fish capture in the Philippines is from artisanal fisheries, most of which is un- or under-reported. As in many emerging nations around the world, the Philippines cannot fully address overfishing by managing only half of the catch that comes from commercial fisheries. Marine reserves are a popular governance strategy for conservation and of growing interest for fisheries management. Many marine reserves in the Philippines, however, are not considered effective. In 2014, Rare, an international NGO, implemented a community-based management program to increase the effectiveness of the marine reserves, and while it found biomass increased, there …

Origin And Structure Of The First Sharp Diffraction Peak Of Amorphous Solids, Devilal Dahal

Dissertations

Several explanations have been reported in the literature about the origin of extended-range oscillations (EROs) in the atomic pair-correlation function of amorphous materials. Although the radial ordering beyond the short-range order of about 5 Å has been extensively studied in amorphous materials, the exact nature of the radial ordering beyond a nanometer is still not resolved. This dissertation address this problem and explains the nature of the EROs by using high-quality models of amorphous silicon (a-Si) obtained from Monte Carlo and Molecular Dynamics simulations. The extended-range ordering in a-Si is examined through radial oscillations on the length …

Software Protection And Secure Authentication For Autonomous Vehicular Cloud Computing, Muhammad Hataba

Dissertations

Artificial Intelligence (AI) is changing every technology we deal with. Autonomy has been a sought-after goal in vehicles, and now more than ever we are very close to that goal. Vehicles before were dumb mechanical devices, now they are becoming smart, computerized, and connected coined as Autonomous Vehicles (AVs). Moreover, researchers found a way to make more use of these enormous capabilities and introduced Autonomous Vehicles Cloud Computing (AVCC). In these platforms, vehicles can lend their unused resources and sensory data to join AVCC.

In this dissertation, we investigate security and privacy issues in AVCC. As background, we built our …

Evaluating The Impact Of Submarine Groundwater Discharge On Nutrients And Trace Elements In Coastal Systems: The Examples Of The Tuckean Swamp (Australia) And The Mississippi Sound (Usa), Amy Moody

Dissertations

Submarine groundwater discharge (SGD) is the advective flow of both fresh terrestrial groundwater and recirculating seawater through aquifer sediments, which is released into the coastal ocean. In this dissertation, I evaluated the impact of SGD on the distributions and input of trace metals and nutrients. In the Tuckean Swamp, an estuary in Australia dominated by coastal acid sulfate soils, I determined the impact of groundwater on Ba and U during the flood season, when the local aquifer is flushed out after a rapid increase in water table elevation. For Ba and U, groundwater contributed up to 18 and 66 % …

A Study Of Red Snapper (Lutjanus Campechanus) Ecology In The Northern Gulf Of Mexico And The Effect Of Variable River Outflow Using Stable Isotope Analysis Of The Food Web And Eye Lenses, Caitlin C. Slife

Dissertations

In the Mississippi Bight and surrounding waters, river outflow impacts the basal resources of the Red Snapper food web, altering carbon sources and impacting prey and predator isotopes. In this study, the impact of riverine outflow on nutrients, particulate organic matter (POM), and physical water parameters on Red Snapper and their food web was analyzed using stable isotope and stomach content analysis over 5 years. The Mississippi, Pearl, Pascagoula, and Mobile rivers were included in the analysis of river impact. The Mississippi and Mobile rivers were found to significantly impact nutrients and POM in the region. River outflow was also …

Coastal Geomorphic Response To Sea-Level Rise, Storms, And Antecedent Geology: Examples From The Northern Gulf Of Mexico, Clayton Dike

Dissertations

Sea-level rise and tropical cyclone activity are threatening coastlines around the world. Past geologic coastal responses can be used to inform future scenarios. This three-part study examines the response of coastal systems to sea-level rise, storms, sediment supply, and antecedent geology over the past ~ 140 ka.

The first study is of the Bay St. Louis, Mississippi, coastal system along the northern Gulf of Mexico incorporating sediment supply, subsidence, and antecedent topography paired with an examination of geologic response to sea-level fall and rise. I used core and geophysical data that resolve incised valleys and other subsurface deposits from ~ …

Data Collection And Machine Learning Methods For Automated Pedestrian Facility Detection And Mensuration, Joseph Bailey Luttrell Iv

Dissertations

Large-scale collection of pedestrian facility (crosswalks, sidewalks, etc.) presence data is vital to the success of efforts to improve pedestrian facility management, safety analysis, and road network planning. However, this kind of data is typically not available on a large scale due to the high labor and time costs that are the result of relying on manual data collection methods. Therefore, methods for automating this process using techniques such as machine learning are currently being explored by researchers. In our work, we mainly focus on machine learning methods for the detection of crosswalks and sidewalks from both aerial and street-view …

Designing Dynamic And Degradable Polymeric Materials With Thiol-X Chemistries, Reese Sloan

Dissertations

With plastic production poised to increase in coming years, there arises a need to develop new polymeric materials designed to combat the global pollution crisis. A commonly utilized approach in addressing this challenge is to employ a responsive functional moiety into the polymer architecture. Thiol-X reactions, a commonly utilized class of “click” reactions, have garnered broad implementation in new stimuli-responsive materials. This work specifically focuses on utilizing radical-mediated thiol-ene coupling and base-catalyzed thiol-isocyanate reactions to develop a library of ternary thiol-ene/thiourethane covalent adaptable networks (CANs) and hydrolytically labile poly(thioether ketal) thermoplastics. CANs are a class of network materials capable of …

A New Model For Predicting The Drag And Lift Forces Of Turbulent Newtonian Flow On Arbitrarily Shaped Shells On The Seafloor, Carley R. Walker, James V. Lambers, Julian Simeonov

Dissertations

Currently, all forecasts of currents, waves, and seafloor evolution are limited by a lack of fundamental knowledge and the parameterization of small-scale processes at the seafloor-ocean interface. Commonly used Euler-Lagrange models for sediment transport require parameterizations of the drag and lift forces acting on the particles. However, current parameterizations for these forces only work for spherical particles. In this dissertation we propose a new method for predicting the drag and lift forces on arbitrarily shaped objects at arbitrary orientations with respect to the direction of flow that will ultimately provide models for predicting the sediment sorting processes that lead to …

Hydrolytically Degradable Thermosets With Tunable Degradation Profiles Via Ketal-Based Crosslinks, Benjamin Alameda

Dissertations

Thermoset polymer networks are ubiquitous in the construction of high-performance materials due to their excellent mechanical properties, solvent resistance, and thermomechanical performance. However, the crosslinked structure that instills these materials with favorable performance also makes them incredibly resistant to degradation and are nearly impossible to recycle – adding to the ever-growing problem of plastic pollution. Hydrolytically degradable thermosets have emerged as a potentially sustainable alternative to traditional thermosets by affording networks that are inherently degradable in aqueous environments. This dissertation focuses on the development of hydrolytically degradable thermoset networks with tunable degradation behavior through the implementation of ketal-based crosslinks. Given …

Analyzing And Detecting Android Malware And Deepfake, Md Shohel Rana

Dissertations

Rapid advances in artificial intelligence (AI), machine learning (ML), and deep learning (DL) over the past several decades have produced a variety of technologies and tools that, among numerous cybersecurity issues, have enticed cybercriminals and hackers to design malware for the Android operating systems and/or manipulate multimedia. For example, high-quality and realistic fake videos, images, or audios have been created to spread misinformation and propaganda, foment political discord and hate, or even harass and blackmail people; these manipulated, high-quality and realistic videos became known recently as Deepfake. There has been much work done in recent years on malware analysis and …

Synthesis Of Molecular Probes For The Detection Of Toxic Analytes, Rashid Mia

Dissertations

Two different types of molecular probes have been synthesized. The first family of probes is the coumarin class of compounds. These chemodosimters are referred to as Low Molecular Weight Fluorescent probes (LMFP). The other type of molecular probe is a macrocycle known as a pillar[5]arene receptor.

The chemodosimters (2.12a-c and 3.12a) were synthesized in four to five steps. The photophysical properties were extensively studied in various solvent systems (DMSO, CH₃CN, DMF, MeOH, EtOH, Me₂CO, MeCO₂Et, CHCl₃, C₆H₅Me, and C₆H₆). Dimethyl sulfoxide (DMSO) …

Controlling Degradation With Force And Light, Brad Davis

Dissertations

Stimuli-responsive polymers respond to changes in their environment by altering their physical and chemical properties. Their responsiveness allows them to be used as sensors, mechanical actuators, delivery systems, and can yield either elongated lifetimes through healing mechanisms or shortened lifetimes through triggered degradation. Still a growing field in polymer science, researchers seek to expand the capabilities of these materials by improving their specificity, range, and mechanisms of both the stimuli and the response. The work presented explores stimuli-responsive materials, focusing on mechanical and light stimuli, and how to gain control of the response by specific changes in the polymeric material. …

Ensemble Data Fitting For Bathymetric Models Informed By Nominal Data, Samantha Zambo

Dissertations

Due to the difficulty and expense of collecting bathymetric data, modeling is the primary tool to produce detailed maps of the ocean floor. Current modeling practices typically utilize only one interpolator; the industry standard is splines-in-tension.

In this dissertation we introduce a new nominal-informed ensemble interpolator designed to improve modeling accuracy in regions of sparse data. The method is guided by a priori domain knowledge provided by artificially intelligent classifiers. We recast such geomorphological classifications, such as ‘seamount’ or ‘ridge’, as nominal data which we utilize as foundational shapes in an expanded ordinary least squares regression-based algorithm. To our knowledge …

Doping Of Conjugated Polymers: Preparation, Characterization And Device Fabrication, Kan Tang

Dissertations

Semiconducting conjugated polymers (CPs) as emerging materials for advanced electronic applications such as sensors, OPVs, and OEFTs has become an intriguing research topic in the past decades. It opens a new avenue of “flexible” electronics, which has shown great potential in next-generation electronic devices.

However, due to the nature of CP materials and related solution processing techniques, unlike almost perfectly crystalline silicon materials, CPs in the solid-state often exhibit much lower crystallinity if it is not complete amorphous, which severely hinder the electronic property and optical property of the materials. The crystallinity of CPs in a film is often uniquely …

Photopolymer Networks With Tunable Command Destruct Properties, William Walker

Dissertations

Photoinduced thiol-catalyzed hydrogen abstraction and beta-scission of acyclic benzylidene acetals is demonstrated as a new route to “command-destruct” polymer thermosets. Using this approach, we show that poly(thioether acetal) networks synthesized via thiol-ene photopolymerization rapidly degrade to alkyl benzoate byproducts when triggered with light, transitioning from solid to liquid within seconds. The light-driven construction and destruction processes, accessible via distinct differences in kinetics, are readily amendable for photopatterning, additive/subtractive manufacturing, and wavelength-selective applications.

The first chapter of this dissertation details the development of command-destruct poly(thioether acetal) networks via a previously unexplored mechanism for polymer degradation. The degradation mechanism is confirmed via …

Synthesis And Self-Assembly Of Amphiphilic Block Copolymers For The Fabrication Of Non-Spherical Polymersomes, Tamuka Chidanguro

Dissertations

Polymersomes, also known as polymer vesicles, have gained a lot of interest over the past two decades. These hollow spherical systems are made via the self-assembly of amphiphilic block copolymers and have found use in a range of areas from drug delivery, to cellular models, to nanoreactors. Their hollow nature allows them to carry hydrophilic cargo in their inner compartment and hydrophobic cargo in their membrane. Over the last decade, increasing efforts have focused on controlling the morphology of polymersomes. Research has shown that polymersome morphology plays an important role for instance in drug delivery, where tubular or rod-like vesicles …

The Power Of Sulfur: A Study Of An Isothiocyanate Chiral Derivatizing Agent, Thioamide Based Chiral Solvating Agents, And The Geometry Of Sulfonamides, Emily B. Crull

Dissertations

This three-part dissertation is connected by the thread of utilizing sulfur-based functional groups, hence the power of sulfur. The first project was the development of a pentafluorobenzene based isothiocyanate chiral derivatizing agent (CDA), a class of compounds that differentiate enantiomers through covalent bond formation. This project, which was addressed using a combination of synthetic and computational methods and NMR analysis, gave rise to an CDA that was highly selective for amines and computationally predictable. Branching off of that, the second project demonstrated the use of two thioamide chiral solvating agents (CSAs), which had never been reported as a core functional …

A Component-Wise Approach To Smooth Extension Embedding Methods, Vivian Montiforte

Dissertations

Krylov Subspace Spectral (KSS) Methods have demonstrated to be highly scalable methods for PDEs. However, a current limitation of these methods is the requirement of a rectangular or box-shaped domain. Smooth Extension Embedding Methods (SEEM) use fictitious domain methods to extend a general domain to a simple, rectangular or box-shaped domain. This dissertation describes how these methods can be combined to extend the applicability of KSS methods, while also providing a component-wise approach for solving the systems of equations produced with SEEM.

Data-Driven Approaches To Complex Materials: Applications To Amorphous Solids, Dil Kumar Limbu

Dissertations

While conventional approaches to materials modeling made significant contributions and advanced our understanding of materials properties in the past decades, these approaches often cannot be applied to disordered materials (e.g., glasses) for which accurate total-energy functionals or forces are either not available or it is infeasible to employ due to computational complexities associated with modeling disordered solids in the absence of translational symmetry. In this dissertation, a number of information-driven probabilistic methods were developed for the structural determination of a range of materials including disordered solids to transition metal clusters. The ground-state structures of transition-metal clusters of iron, nickel, and …

Semantic Classification Of Multidialectal Arabic Social Media, Tom Rishel

Dissertations

Arabic is one of the most widely used languages in the world, but due in part to its morphological and syntactic richness, resources for automated processing of Arabic are relatively rare. Arabic takes three primary forms: Classical Arabic as seen in the Qur’an and other classical texts; Modern Standard Arabic (MSA) as seen in newspapers, formal documents, and other written text intended for widespread distribution; and dialectal Arabic as used in common speech and informal communication. Social media posts are often written in informal language and may include non-standard spellings, abbreviations, emoticons, hashtags, and emojis. Dialectal Arabic is commonly used …

Structural Origin Of Thermal, Mechanical Properties And Morphological Behaviors Of Semiconducting Polymers, Song Zhang

Dissertations

The past decades have witnessed a surging exploration of semiconducting polymers for the application of wearable and flexible organic electronic devices. Despite the increased amounts of molecular engineered polymers and their much-improved electrical performances, a systematic study of the structure-thermal/mechanical property-morphology relationship of semiconducting polymers is still less investigated.

To understand the thin-film mechanical properties, a pseudo-free standing tensile tester was self-built and utilized to obtain their real-time stress-strain behaviors through uniaxial stretching on top of the water surface. It also enables the first quantitative measurement of fracture energy on ultrathin polymeric films. Through multiple mechanical testing methods (i.e., strain-rate …

Efficient Denoising Of High Resolution Color Digital Images Utilizing Krylov Subspace Spectral Methods, Eva Lynn Greenman

Dissertations

The solution to a parabolic nonlinear diffusion equation using a Krylov Subspace Spectral method is applied to high resolution color digital images with parallel processing for efficient denoising. The evolution of digital image technology, processing power, and numerical methods must evolve to increase efficiency in order to meet current usage requirements. Much work has been done to perfect the edge detector in Perona-Malik equation variants, while minimizing the effects of artifacts. It is demonstrated that this implementation of a regularized partial differential equation model controls backward diffusion, achieves strong denoising, and minimizes blurring and other ancillary effects. By adaptively tuning …

Microplankton Dynamics In The River-Dominated Mississippi Bight, Adam D. Boyette

Dissertations

The Mississippi Bight (MSB) is a river-dominated continental margin influenced by multiple large river systems, including the Mississippi River, Alabama and Tombigbee rivers via Mobile Bay, and numerous smaller rivers, creeks, and bayous. This is part of a biologically-rich ecosystem that supports the second largest fishery industry by volume in the United States. Despite our understanding of the linkages between primary production with higher trophic levels, there remains limited studies quantifying these trophic interactions in this system. Microplankton (µm) community dynamics and trophic connectivity between primary producers and heterotrophic protists represent a critical nexus influencing overall biological productivity in this …

Assessing The Real-Time Lagrangian Predictability Of The Operational Navy Coastal Ocean Model In The Gulf Of Mexico, Lea Kristen Locke

Dissertations

This study quantitatively assesses the drift predictive skill of Fleet Numerical Meteorology and Oceanography Center’s (FNMOC’s) operational ocean models which are used to support a wide range of military and civilian applications. Overall, the findings of this work support the recommendation of spatial filtering for regional-scale ocean model velocity fields used in deep-water drift applications. In conjunction with filtering, the use of a pure particle drift algorithm is suggested for short-term forecasts and a drift algorithm including a sub-grid scale, random flight, parameterization for predictions requiring extended forecast predictions.

Drift prediction skill is quantified through metrics of in-cloud percentage, distance …