Digital Commons Network^™

Multi-Scale Computational Modeling Of Metal/Ceramic Interfaces, Abu Shama Mohammad Miraz

Doctoral Dissertations

Multi-scale atomistic calculations were carried out to understand the interfacial features that dictate the mechanical integrity of the metal/ceramic nanolaminates. As such, first principles density functional theory (DFT) calculations were performed to understand the electronic and atomistic factors governing adhesion and resistance to shear for simple metal/ceramic interfaces, whereas molecular dynamics (MD) simulations were performed to observe the impact of interfacial structures, such as misfit dislocation network geometries and orientation relationships, on interfacial mechanical properties.

For the DFT investigation, we choose metals with different crystal structures, namely - Cu (fcc), Cr (bcc) and Ti (hcp) along with a variety of …

Progress On The Use Of Surface-Immobilized Elastin-Like Polymers As A Stimuli-Responsive Biosensor For Interleukin-6 Detection, Marissa Morales

Doctoral Dissertations

Elastin-Like-Polymers (ELPs) are intrinsically disordered biopolymers with an amino acid structure comprised of the pentapeptide repeat sequence [VPGXG]n (V = valine, P = proline, G = glycine, X = guest residue, and n = total number of repeat sequences). ELPs are stimuli-responsive meaning below their transition temperature, ELPs are structurally disordered, highly solvated, and soluble in aqueous solutions. Above their transition temperature, ELPs experience coalescence and phase separation as intermolecular and intramolecular contacts form within the hydrophobic regions of the ELPs. The transition temperature of ELPs is influenced by the hydrophobic surface area, as well as changing solvent conditions including …

Cosmic Diffuse Gamma-Ray Background Measurement With The Advanced Scintillator Compton Telescope (Ascot), Tejaswita Sharma

Doctoral Dissertations

The primary goal of my research was to measure the cosmic diffuse gamma-ray (CDG) background in the energy range of 0.4 - 2.5 MeV using the balloon flight data from the Advanced Scintillator Compton Telescope (ASCOT). ASCOT is a medium-energy gamma-ray Compton telescope that uses commercially available high performance scintillators—Cerium Bromide (CeBr3) and p-terphenyl—along with silicon photomultipliers (SiPMs) for light readout. It was built to address the lack of data in the gamma-ray energy range of 0.4 - 20 MeV. ASCOT was successfully launched on 2018 July 5 from the NASA Columbia Scientific Balloon Facility in Palestine, TX. We performed …

Existence Of Mutual Stabilization In Chaotic Neural Models, John Parker

Doctoral Dissertations

Recent work has demonstrated that interacting chaotic systems can establish persistent, periodic behavior, called mutual stabilization, when certain information is passed through interaction functions. In particular, this was first shown with two interacting cupolets (Chaotic Unstable Periodic Orbit-lets) of the double scroll oscillator. Cupolets are highly accurate approximations of unstable periodic orbits of a chaotic attractor that can be generated through a control scheme that repeatedly applies perturbations along Poincaré sections. The decision to perturb or not to perturb the trajectory is determined by a bit in a binary control sequence. One interaction function used in the original cupolet research …

Mathematical Analysis Of A Model Of Blood Flow Through A Channel With Flexible Walls, Madeline Mayes Edwards

Doctoral Dissertations

The present research is devoted to the problem of stability of the fluid flow moving in a channel with flexible walls and interacting with the walls. The walls of the vessel conveying fluid are subject to traveling waves. Experimental data shows that the energy of the flowing fluid can be transferred and consumed by the structure (the walls), which induces “traveling wave flutter.” The problem of stability of fluid-structure interaction splits into two parts: (i) stability of fluid flow in the channel with harmonically moving walls and (ii) stability of solid structure participating in the energy exchange with the flow. …

Qunatum Transport Phenomena And Non-Trivial Spin Structures, Domenico Andreoli

Doctoral Dissertations

Quantum Transport is an important part of condensed matter physics. With the discoveryof non-trivial spin textures new transport phenomena have given rise to possible alternatives to conventional electronic devices. Studying how these phenomena occur is of utmost importance to the success of these new devices. A theoretical understanding is developed through out this thesis with focus on 2-D spin textures known as Skyrmions. The main topic discussed through-out these works will be how the condensed matter community at large thinks the Skyrmion is directly responsible for what is known as the Topological Hall Effect. It will be argued that the …

Life, Liberty, And The Pursuit Of Police Officer Acquittals: Jurors' Explicit And Implicit Racism, Donovan Corson Kelley

Doctoral Dissertations

Less than .001% of cases involving police officers killing suspects result in trial convictions; acquittals are significantly higher for Black victims than for White victims. The purpose of this dissertation was to examine if explicit and implicit racism amongst jurors helped explain why police officers are rarely convicted of murder, especially in cases with Black victims. In a pilot study in which mock jurors read a trial summary involving an officer killing an unarmed victim who was either Black or White, jurors were more likely acquit officers on trial for killing a Black victim than a White victim. In Study …

An Improv-Able Legacy: Shining The Composition Spotlight On Viola Spolin’S Improvisational Pedagogy, Cory Richard Chamberlain

Doctoral Dissertations

This dissertation is an archival study of the works of Viola Spolin who is considered by many to be the founding mother of improvisational theater. During her life she published Improvisation for the Theater which is essential reading for anyone interested in doing improvisational theater as well as Theater Games for The Classroom where she adapted some of her techniques and games to an educational setting outside of theater. Along with these works, I was able to examine two of her unpublished works, a handbook on education and What’s Your Score? as well as various notes, correspondences and interviews housed …

Speeding-Up A Random Search For The Global Minimum Of A Non-Convex, Non-Smooth Objective Function, Arnold C. Englander

Doctoral Dissertations

The need to find the global minimum of a highly non-convex, non-smooth objective function over a high-dimensional and possibly disconnected, feasible domain, within a practical amount of computing time, arises in many fields. Such objective functions and/or feasible domains are so poorly-behaved that gradient-based optimization methods are useful only locally – if at all. Random search methods offer a viable alternative, but their convergence properties are not well-studied. The present work adapts a proof by Baba et al. (1977) to establish asymptotic convergence for Monotonic Basin Hopping, a random search method used in molecular modeling and interplanetary spacecraft trajectory optimization. …

Molecular Simulation Studies Of Dynamics And Interactions In Nucleic Acids, Lev Levintov

Doctoral Dissertations

In my thesis work, I conducted molecular simulation studies to explore dynamics and interactions in nucleic acids. I began my work by applying conventional molecular dynamics (MD) simulations to study the local and global dynamics of the transactivation response (TAR) element from the type-1 human immunodeficiency virus (HIV-1) and the effect of binding of ligands on the dynamics of TAR RNA. I determined that the TAR RNA structure was stabilized on binding of ligands due to the decreased flexibility in helices that comprise TAR RNA. This rigidity of the TAR RNA structure was coupled with the decreased flipping of bulge …

Essays On The Unintended Effects Of Tobacco Control Policies On Adolescent Health Behaviors, Rebecca Sen Choudhury

Doctoral Dissertations

My dissertation examines the unintended consequences of tobacco control policies on adolescent health behaviors and outcomes. The first essay examines the effects of cigarette taxes on teenagers’ physical activity. Smoking and physical activity are both strategies for weight management, and exercise may be a way to reduce some of the ill effects of smoking. These different links suggest that cigarette taxes could either increase or decrease physical activity. We explore this relationship using repeated cross-sectional 1991-2017 data from the national and state Youth Risk BehaviorSurveillance System (YRBS), combined with state-level policies and controls. Our smoking participation results confirm past work; …

Structural And Binding Studies Of The Polar Organizing Protein Z (Popz) Using Nmr Spectroscopy, Christopher Taylor Nordyke

Doctoral Dissertations

The polar organizing protein Z (PopZ) is an intrinsically disordered protein from Caulobacter crescentus that is necessary for the formation of three-dimensional microdomains at the cell poles, where it functions as a hub protein that recruits multiple regulatory proteins. Although a large portion of the protein is predicted to be disordered, PopZ can self-assemble into polymeric superstructure scaffolds that directly bind to at least ten different proteins. Here, we report the solution NMR structure of PopZΔ134–177, a truncated variant of PopZ that does not self-assemble but retains the ability to interact with heterologous proteins. We show that the unbound form …

Performance Evaluation And Review Framework Of Robotic Missions (Perform): Autonomous Path Planning And Autonomy Performance Evaluation, Allisa Dalpe

Doctoral Dissertations

The scope of this work spans two main areas of autonomy research 1) autonomous path planning and 2) test and evaluation of autonomous systems. Path planning is an integral part of autonomous decision-making, and a deep understanding in this area provides valuable perspective on approaching the problem of how to effectively evaluate vehicle behavior.

Autonomous decision-making capabilities must include reliability, robustness, and trustworthiness in a real-world environment. A major component of robot decision-making lies in intelligent path-planning. Serving as the brains of an autonomous system, an efficient and reliable path planner is crucial to mission success and overall safety. A …

Why Are We Doing This: How Students Find Meaning In Research Writing Across Contexts, Scott Lasley

Doctoral Dissertations

Building on the work of Eodice, Geller, and Lerner and other Composition and Higher Education scholars, my dissertation examines what factors create a meaningful research writing experience. Specifically, this study explores two research questions: 1) How do advanced-level student writers define themselves as writers who use research? 2) How do those identities influence how they understand and utilize research writing concepts? I pursued these questions through a year-long, IRB-approved, qualitative study of junior and senior university students across the disciplines, including English, Neuroscience, and Computer Engineering. Using surveys and interviews, I asked them about meaningful research writing they have done …

"I Know You're Family": An Exploration Of The Enduring Relevance Of A Pre-College Summer Bridge Program For Underrepresented Minoritized Students, Kathryn Slater

Doctoral Dissertations

The proposed dissertation investigates the enduring relevance of a pre-college summer bridge program for underrepresented minoritized (URM) students who participate in the program as an entry point into a predominantly White institution (PWI). Using narrative inquiry and a critical frame, this dissertation uses individual interviewing and focus group data to understand the experiences of 10 URM summer bridge program participants at different points in their undergraduate academic career. For the purposes of this study, relevance of a summer bridge program for URM students refers to the ways in which deliberate and proactive programming helps students to develop academic and socio-emotional …

Nanoelectronic Devices For Sensitive Detection Of Biomarkers In Healthcare Monitoring, Md Niazul Islam Khan

Doctoral Dissertations

In recent years, biosensors have seen an exponential rise of their applications in a number of fields including the field of health care monitoring, particularly in point-of-care diagnostics. With the contemporary rise of nanotechnology, these biosensors have experienced an ever-growing inclusion of nano scale electronic devices or nanoelectronic devices to exploit the plethora of advantages of nanoelectronics. The performances of these nanoelectronic devices, however, largely depend on the nanomaterials used. Especially, carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene have proven to be superior candidates compared to others because of their multitude of electronic and mechanical properties suitable for …

“We Feminine Foresters”: Women, Conservation, And The Usda Forest Service, 1850-1970, Rachel D. Kline

Doctoral Dissertations

The traditional narrative of the Forest Service places the mythic “two-fisted” male ranger as the focus of its history. The reality is that without women he would not have gotten the job done. Women’s work as advocates, foresters, rangers’ wives, clerks, information and education specialists, scientific researchers, and lookouts reveals that although women were excluded from the male domain of forestry, they created a distinct female tradition within the Forest Service—what one called a “feminine forestry” that proved without women, the Forest Service would not have achieved its accomplishments or growth throughout the twentieth century. Throughout their work, women spread …

Exploring Mathematical Connections Preservice Teachers Make Between Abstract Algebra And Secondary Mathematics: Implications For Learning And Teaching, Cammie Gray

Doctoral Dissertations

Abstract algebra has been identified as an important course for preservice secondary mathematics teachers because much of the abstract algebra content is connected to, and thus relevant for, secondary mathematics teaching (Wasserman et al., 2017). However, many preservice teachers do not recognize the usefulness of an undergraduate abstract algebra course and see no relation between abstract algebra and secondary school mathematics (Christy & Sparks, 2015; Ticknor, 2012). While much of the research regarding preservice teachers making connections to secondary school mathematics in abstract algebra has been conducted in courses designed for preservice teachers, the research suggests that most universities with …

Discourses Of Diversity: A Qualitative Case Study Of World Language Pedagogies Through An Intersectional Lens, Sheri Dion

Doctoral Dissertations

Schools are becoming more linguistically and racially diverse in K-12 settings, yet there is relatively little research that explores how language teachers incorporate student and community diversities in their pedagogies. Situated at one, northeastern public secondary school in the United States, this research offers a qualitative case study of language pedagogies through an intersectional lens to investigate the mechanisms and contexts through which inequities arise. Data is collected from the following sources: teacher interviews, classroom observations, teachers’ syllabi, and student de-identified work. This study employs intersectionality (Collins & Bilge, 2016; Crenshaw, 1989, 2010) as a primary theoretical lens and critical …

Justice System Outcomes Of Children Referred For Sexual Offenses, Kei Saito

Doctoral Dissertations

The proliferation of increasingly punitive sex crime legislation in the United States have extended to include children adjudicated of sexual offenses. Using data from the Florida Department of Juvenile Justice, this dissertation examined the impact of three factors on sentencing outcomes for children referred for illegal sexual behaviors: race, same-sex victim, and county of referral. (1) Black children were disproportionately arrested for sexual offenses compared to any other racial/ethnic group. However, Black children in the sample were less likely to face harsher outcomes compared to Caucasian children, such as adjudication and ordered to register as a sex offender. (2) Children …

Wind, Wave, And Engineering Effects On Tidal Inlet Morphodynamics, Joshua Lincoln Humberston

Doctoral Dissertations

This body of work examines the hydro- and morpho-dynamics of tidal inlets using a diverse array of research tools. A custom X-band radar system (RIOS) is designed and used to track the evolution of shoal features over the ebb-tidal delta at Oregon Inlet, NC. Analysis of the data reveals that alongshore shoal migration rates are closely correlated to wave driven alongshore sediment transport, and also that the cross-shore bedform migration rates are tightly correlated with a sub-tidal water level gradient though the inlet. A follow up experiment with in-situ sensors suggests that the sub-tidal gradient is set up by regional …

An Empirical Evaluation Of Visual Cues For 3d Flow Field Perception, Andrew Harlan Stevens

Doctoral Dissertations

Three-dimensional vector fields are common datasets throughout the sciences. They often represent physical phenomena that are largely invisible to us in the real world, like wind patterns and ocean currents. Computer-aided visualization is a powerful tool that can represent data in any way we choose through digital graphics. Visualizing 3D vector fields is inherently difficult due to issues such as visual clutter, self-occlusion, and the difficulty of providing depth cues that adequately support the perception of flow direction in 3D space. Cutting planes are often used to overcome these issues by presenting slices of data that are more cognitively manageable. …

An Evaluation Of The Process Used To Develop And Administer An Employee Culture Survey In A Public Research University, Danielle B. Allen

Doctoral Dissertations

In October of 2015, AROS, a faculty-supervised, student-led consulting group affiliated with the Louisiana Tech Industrial-Organizational Psychology doctoral program (arosconsulting.org), was contracted by the President and Vice President of a public research university to develop and administer a survey to gauge the climate, operations, and alignment of proceedings with the University’s strategic objectives (Valadez, Allen, Lovell, & Toaddy, 2015). AROS conducted interviews with key stakeholders and focus groups with University members (faculty, staff, and students), wrote and refined the list of survey items, programmed the survey into the online platform, and administered the survey to all faculty, staff, and students. …

The Impact Of Block Scheduling On Student Achievement, Graduation Rate, And Attendance At The High School Level, Sedric G. Clark

Doctoral Dissertations

The purpose of this study was to determine the impact of block scheduling on student achievement, graduation rate, and attendance at the high school level. The study was a mixed methods study that compared existing data from three high schools from the same school district in a southern state which all moved from a traditional schedule to a block schedule and back to a traditional schedule over the same period of time. The study results included the comparison of composite ACT scores and attendance rates from the years pre-block implementation, the years of block implementation, and the years post-block implementation. …

Halloysite Modified 3d Printer Filament For Medical And Industrial Uses, Antwine William Mcfarland Jr.

Doctoral Dissertations

Thermoplastics can be used as a replacement or alternative for a variety of medical and commercial products. The addition of halloysite nanotubes further enhance the strength and functionality of the composite. The aim of this project was to evaluate the capability polylactic acid (PLA) to be enhance with halloysite nanotubes and other additives. We created a nanocomposite that offered similar stabilization to titanium surgical plates but with the added benefit of bone generation through recruitment and differentiation of mesenchymal stem cells. Varying amounts of PLA and polycaprolactone were combined with growth factor doped halloysite nanotubes or silicon nitrate then extruded …

Performance And Retention Of Female Engineering Students When Placed In A Gender Parity Course, Allie Corinne Deleo-Allen

Doctoral Dissertations

Though women earn the majority of bachelor’s degrees in the United States of America, they are in the vast minority of those earning degrees in engineering, only 24%. In an effort to ultimately increase the number of women graduating with degrees in engineering, our study focused on improving the retention of first-year female students.

We set out to discover if female engineering students, who traditionally are in the minority of their student body, would have an increase in their performance and retention when placed in a manipulated course environment of gender parity (50% women, 50% men). Our study followed 129 …

Properties And Structures Of Alkali Molybdenum Iron Phosphate Glasses For Nuclear Waste Immobilization, Jincheng Bai

Doctoral Dissertations

"The development of glasses to immobilize nuclear wastes requires a detailed understanding of how composition affects the critical properties required to design wasteforms, including thermal stability and chemical durability. Those properties depend on the molecular-level structures of the glasses. The principal objective of this research was to develop a comprehensive understanding of the composition-structure-property relationships, including the effects of processing conditions, for glasses in the alkali- molybdenum-iron-phosphate systems that could then be used to inform the development of wasteforms of interest to the US Department of Energy.

The molecular-level structures of the alkali molybdenum iron phosphate glasses were analyzed by …

Neogene Dinoflagellate Cysts From The Tropical Americas, Damian Cardenas

Doctoral Dissertations

"Marine palynomorphs, mainly dinoflagellate cysts and acritarchs, constitute excellent proxies for biostratigraphic and paleoceanographic studies in neritic sequences. Neogene marine palynological studies have mostly focused on the Northern Hemisphere, resulting in the scarcity of dinoflagellate cysts and acritarchs from tropical latitudes. Forty samples encompassing the late Chattian-late Burgidalian time interval (~24.1- 17.3 Ma) in the Southern Caribbean were analyzed for their marine palynological contents. A biostratigraphic scheme for the region is proposed and includes the upper Chattian-lower Aquitanian Minisphaeridium latirictum Interval Zone (~23.9-22.0 Ma), the upper Aquitanian Achomosphaera alcicornu Interval Zone (~22.0-20.3 Ma), and the Burdigalian Cribroperidinium tenuitabulatum Interval Zone …

Spatiotemporal Variations Of Upper Crustal Anisotropy Along The San Jacinto Fault Zone In Southern California And The Fairview Region In Central Oklahoma, Enyuan Jiang

Doctoral Dissertations

"To discern spatial and explore the possible existence of temporal variations of upper crustal anisotropy along an ~15 km section of the San Jacinto Fault Zone (SJFZ) in California, and in the Fairview, Oklahoma, region, we conduct systematic shear wave splitting (SWS) investigations using local S-wave data recorded by seismic stations. Strong spatial variations in crustal anisotropy are revealed by 1694 and 405 pairs of splitting parameters (including the fast polarization orientation and the splitting time), respectively. For both areas, for raypaths traveling through the fault zones, the fast orientations are parallel to the faults and may be attributed to …

Catalytic Carbon Dioxide Hydrogenation To Methanol/Dimethyl Ether Over Copper-Based Catalysts, Xiao Fan

Doctoral Dissertations

Direct synthesis of dimethyl ether (DME) via CO₂ hydrogenation has received great attention, owing to the global warming caused by CO₂ emission and increasing energy demand worldwide. In this works, three major aspects of bifunctional catalysts development were studied: (1) investigation of the roles of interaction in the CuO-ZnO-ZrO₂-Al₂O₃/HZSM-5 bifunctional catalysts, (2) deactivation and regeneration of CuO-ZnO-ZrO₂-Al₂O₃ with different zeolitic catalysts for one-step CO₂ hydrogenation to dimethyl ether, and (3) study on the enhancement of activity and stability of CZZA/HZSM-5 bifunctional catalysts via the introduction of …