Physical Sciences and Mathematics Commons^™

Decay Spectroscopy Of 134sb Using X-Array And Saturn, Graeme E. Morgan

LSU Doctoral Dissertations

The ground-state decay of ¹³⁴Sb is reported by the current evaluated nuclear data to be dominated by a 0^-→0⁺ first-forbidden Gamow-Teller transition to the ground state of ¹³⁴Te. In 2013, a recoil-ion time-of-flight (RI-TOF) spectroscopy measurement of ¹³⁴Sb with the Beta-decay Paul Trap (BPT) indicated that the ground-state feeding of ¹³⁴Te is weaker than reported. Simulation work of ¹³⁴Sb ground-state decays replicated the RI-TOF results with the addition of a theorised 5-MeV state that was fed with ~17% of the total β-decay strength. To search for higher energy states and transitions that …

Struggling To Be Positive Problem Solvers – A Study On The Relationship Of Elementary Mathematical Self-Concept, Gender, Learner Identification, And Productive Struggle Trajectories On Constructed Response Questions When Being Taught With A Standardized Curriculum, Kali D. Rogers

LSU Doctoral Dissertations

Mathematical word problems are some of the most difficult problems for students to solve due to their complexity and relationship to real-world situations (Şahin et al., 2014; Verschaffel et al., 2020). With math being known for right-or-wrong answers, these open-ended questions cause much confusion and frustration, specifically for students of various subgroups. In the last several decades, educational teaching expectations have shifted from engaging, self-created learning to robotic and redundant curriculum expectations that induce a ‘teaching to the test’ environment (Shafiyeva, 2021). Mathematics is the powerhouse of where students can experience and succeed with productive struggle learning that teaches the …

Examining The Authenticity Of The 'Ether Model' In Certain O-Glycosylation Reactions, Varad Vinayak Agarkar

LSU Doctoral Dissertations

Acinetobacter baumannii is a gram-negative bacterium species that is responsible for nosocomial infections. It has shown antibiotic resistance and has been designated an urgent threat by the CDC. In Chapter 1, I highlight my efforts in the synthesis of a Kdo building block in the journey towards the construction of an A. baumannii lipooligosaccharide (LOS) core pentasaccharide- a potential candidate for glycoconjugate vaccine against A. baumannii infection. I talk about various optimizations and improvements in the Kdo monosaccharide synthesis and the mechanistic insights I provided about a critical transformation in the synthetic sequence.

Chemical O-glycosylation is a significant research …

Multiphoton Quantum Sensing, Fatemeh Mostafavikhatam

LSU Doctoral Dissertations

While the fundamental principles of light-matter interaction are well-understood and drive countless technologies, the world of multiphoton processes remains a fascinating puzzle, holding the potential to drastically alter our understanding of how light interacts with matter at its most basic level [1–4]. This rich interplay of light and matter unveils novel phenomena that can be harnessed for sensing with exceptional precision, as exemplified by multiphoton quantum sensing. This thesis delves into the applications of multiphoton quantum protocols, particularly in imaging, communication, and plasmonic sensing, to surpass classical limitations and achieve enhanced sensitivity. We explore the potential of multiphoton quantum processes, …

Molybdenum Alkylidyne Complexes With Phenoxide Ligands For Alkyne Metathesis, Marvin L. Stewart Jr

LSU Doctoral Dissertations

Abstract

Alkyne metathesis is a powerful synthetic tool, which provides easy access to complex organic molecules in a single-step. It is a dynamic covalent reaction that scrambles alkynes, carbon-carbon triple bonds (C≡C). Molybdenum- or tungsten-alkylidyne (Mo≡C, W≡C) complexes are typically used as catalyst to cleave and reform alkyne bonds. Our goal has been to gain a deeper understanding of the intrinsic differences between functional ligands by the development of novel phenoxide ligands.

In chapter 2 we explore the detailed synthesis of novel phenoxide podand ligands in an effort to identify their mo-alkylidyne complexes. We were able to synthesize a variety …

Benthic Community Response To The Impacts Of Proposed Sediment Diversions In Louisiana Estuaries, Jillian C. Tupitza

LSU Doctoral Dissertations

Sediment diversions designed to mitigate land loss in coastal Louisiana will likely cause ecosystem-wide shifts. The first diversion, planned for Barataria Bay, will divert fresh water and sediment from the Mississippi River into the surrounding wetlands to help them keep pace with high rates of relative sea-level rise (RSLR). Estuarine benthic communities were used in this study as tools to characterize ecological patterns in the context of anticipated salinity changes. I reviewed relevant literature, conducted a two-year survey of Barataria Bay benthos, executed a reciprocal transplant experiment to describe changes that might occur in both community composition and trophic dynamics, …

The Lowest Discriminant Ideal Of Cayley-Hamilton Hopf Algebras, Zhongkai Mi

LSU Doctoral Dissertations

Discriminant ideals are defined for an algebra R with central subalgebra C and trace tr : R → C. They are indexed by positive integers and more general than discriminants. Usually R is required to be a finite module over C. Unlike the abundace of work on discriminants, there is hardly any literature on discriminant ideals. The levels of discriminant ideals relate to the sums of squares of dimensions of irreducible modules over maximal ideals of C containing these discriminant ideals. We study the lowest level when R is a Cayley-Hamilton Hopf algebra, i.e. C is also a Hopf subalgebra, …

All-Optical Probes Of Particle-Like Charge Migration Dynamics, Kyle A. Hamer

LSU Doctoral Dissertations

Particle-like charge migration (CM) is the coherent, back-and-forth motion of a positively-charged electron hole along the backbone of a molecule following a sudden ionization. CM in small molecules generally occurs on an Angstrom (10^-10 m) spatial scale and an attosecond (10^-18 s) timescale. I use time-dependent density-functional theory (TDDFT) to simulate CM modes in organic molecules, and to explore all-optical probes of this attosecond electron dynamics using high-harmonic spectroscopy (HHS). By leveraging my results from previous studies of two-center interferences in carbon dichalcogens, in which I separated the harmonic signal into contributions from individual Kohn-Sham orbitals, I first …

Reducibility Of Schrödinger Operators On Multilayer Graphs, Jorge Villalobos Alvarado

LSU Doctoral Dissertations

A local defect in an atomic structure can engender embedded eigenvalues when the associated Schrödinger operator is either block reducible or Fermi reducible, and having multilayer structures appears to be typically necessary for obtaining such types of reducibility. Discrete and quantum graph models are commonly used in this context as they often capture the relevant features of the physical system in consideration.

This dissertation lays out the framework for studying different types of multilayer discrete and quantum graphs that enjoy block or Fermi reducibility. Schrödinger operators with both electric and magnetic potentials are considered. We go on to construct a …

Finite Monodromy And Artin Representations, Emma Lien

LSU Doctoral Dissertations

Artin representations, which are complex representations of finite Galois groups, appear in many contexts in number theory. The Langlands program predicts that Galois representations like these should arise from automorphic representations and many examples of this correspondence have been found such as in the proof of Fermat's Last Theorem. This dissertation aims to make an analysis of explicitly computable examples of Artin representations from both sides of this correspondence. On the automorphic side, certain weight 1 modular forms have been shown to be related to Artin representations and an explicit analysis of their Fourier coefficients allows us to identify the …

The Modular Generalized Springer Correspondence For The Symplectic Group, Joseph Dorta

LSU Doctoral Dissertations

The Modular Generalized Springer Correspondence (MGSC), as developed by Achar, Juteau, Henderson, and Riche, stands as a significant extension of the early groundwork laid by Lusztig's Springer Correspondence in characteristic zero which provided crucial insights into the representation theory of finite groups of Lie type. Building upon Lusztig's work, a generalized version of the Springer Correspondence was later formulated to encompass broader contexts.

In the realm of modular representation theory, Juteau's efforts gave rise to the Modular Springer Correspondence, offering a framework to explore the interplay between algebraic geometry and representation theory in positive characteristic. Achar, Juteau, Henderson, and Riche …

Subgroups Of Coxeter Groups And Stallings Foldings, Jake A. Murphy

LSU Doctoral Dissertations

For each finitely generated subgroup of a Coxeter group, we define a cell complex called a completion. We show that these completions characterizes the index and normality of the subgroup. We construct a completion corresponding to the intersection of two subgroups and use this construction to characterize malnormality of subgroups of right-angled Coxeter groups. Finally, we show that if a completion of a subgroup is finite, then the subgroup is quasiconvex. Using this, we show that certain reflection subgroups of a Coxeter are quasiconvex.

Analytic Wavefront Sets Of Spherical Distributions On The De Sitter Space, Iswarya Sitiraju

LSU Doctoral Dissertations

In this work, we determine the wavefront set of certain eigendistributions of the Laplace-Beltrami operator on the de Sitter space. Let G′ = O_1,n(R) be the Lorentz group, and let H′ = O_1,n−1(R) ⊂ G′ be its subset. The de Sitter space dSⁿ is a one-sheeted hyperboloid in R^1,n isomorphic to G′/H′. A spherical distribution is an H′-invariant eigendistribution of the Laplace-Beltrami operator on dSⁿ. The space of spherical distributions with eigenvalue λ, denoted by D_λ^H'(dSⁿ), has dimension 2. We construct a basis for the space of …

Applied Depositional Geosystems Of The Coos Bay Basin, Oregon: Organic Geochemistry, Maturation, Paleoenvironmental Reconstruction And Biostratigraphy Of The Coaledo Delta During The Middle Eocene Climatic Optimum (Meco), Allison K. Barbato

LSU Doctoral Dissertations

The Coos Bay Basin on the southwestern coast of Oregon is a forearc basin that contains exceptionally preserved Eocene to Miocene, tidal to wave-dominated, shallow deltaic to deep marine sediments of the Coaledo Delta. Coastal depositional environments are known to host source, reservoir, and seal rocks. Climate, topographic relief, and geographical position all play an important role in regional vegetation development and oceanic setting. This study assesses 84 outcrop and 12 core samples from Coos Bay for their organic geochemical characteristics and microfossil assemblage to provide source rock characterization information, organofacies descriptions, environmental reconstructions, and age control.

Results indicate the …

Thermal Frontal Polymerization – Applications In Coatings And Composites, Maria Martinez

LSU Doctoral Dissertations

Thermal frontal polymerization has long been used as a method to cure composites and coatings. However, this is the first time these applications have been used without the use of a catalyst, for the case of composites and coatings.

Chapter 2 discusses how to optimize cure-on-demand, thin layer coatings, using frontal polymerization. Previously, for the use of curing thin layer coating using thermal FP, it was known to just make the formulation viscous enough, as this would prevent premature quenching caused by heat loss. It was discovered that for a given layer thickness, a minimum viscosity and initiator concentration were …

Modeling And Numerical Analysis Of The Cholesteric Landau-De Gennes Model, Andrew L. Hicks

LSU Doctoral Dissertations

This thesis gives an analysis of modeling and numerical issues in the Landau-de Gennes (LdG) model of nematic liquid crystals (LCs) with cholesteric effects. We derive various time-step restrictions for a (weighted) $L^2$ gradient flow scheme to be energy decreasing. Furthermore, we prove a mesh size restriction, for finite element discretizations, that is critical to avoid spurious numerical artifacts in discrete minimizers that is not well-known in the LC literature, particularly when simulating cholesteric LCs that exhibit ``twist''. Furthermore, we perform a computational exploration of the model and present several numerical simulations in 3-D, on both slab geometries and spherical …

Characterizing And Mitigating Transient Noise In Ligo Observatories For Gravitational Wave Detection, Jane Glanzer

LSU Doctoral Dissertations

The existence of gravitational waves is predicted by Albert Einstein's Theory of General Relativity. Commonly referred to as "ripples in spacetime", these waves are generated by some of the most violent and energetic processes in the universe. Despite their theoretical prediction over a century ago, it wasn't until 2015 that the Advanced LIGO (aLIGO) interferometers in Hanford, WA and Livingston, LA directly detected gravitational waves for the first time, confirming Einstein's theory and ushering in a new era of astrophysics.

Detecting gravitational waves requires incredible precision. Because of the extreme sensitivity required, it is possible for the gravitational wave data …

The Homotopy Cardinality Of The Representation Category, Justin Murray

LSU Doctoral Dissertations

Given a Legendrian knot in (R^3, ker(dz − ydx)) one can assign a combinatorial invariants called ruling polynomials. These invariants have been shown to recover not only a (normalized) count of augmentations but are also closely related to a categorical count of augmentations in the form of the homotopy cardinality of the augmentation category. In this article, we prove that that the homotopy cardinality of the n-dimensional represen- tation category is a multiple of the n-colored ruling polynomial. Along the way, we establish that two n-dimensional representations are equivalent in the representation category if they are “conjugate homotopic”. We also …

Surface And Bulk Properties Of Multi-Component Metal Alloys, Frank A. Mckay Iii

LSU Doctoral Dissertations

While HEAs have been studied extensively for their material properties, their potential as catalysts remains widely unexplored. To explore the feasibility of CoCrFeNi as a catalyst for the hydrogen evolution reaction, the results of X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS) experiments are compared to electrochemical experiments and theoretical calculations. XPS shows that this surface forms passive oxides with a propensity of Cr > Fe > Co, with no evidence of Ni oxidation. From comparison to calculations, it is shown that the electrochemical activity is enhanced in a partially oxidized state. The lack of Ni oxidation suggests that …

Investigating Gulf Coast Aquifer System: Stratigraphy Reconstruction, Inverse Modeling, And Groundwater Stress Assessment, Shuo Yang

LSU Doctoral Dissertations

The Mississippi Embayment aquifer system (MEAS) and the Coastal Lowlands aquifer system (CLAS) provide substantial groundwater resources for human activities in the U.S. Gulf Coastal Plain. However, the overexploitation has led to groundwater depletion in the MEAS and the CLAS, threatening sustainable groundwater use. Such concern highlights the crucial need for an advanced understanding of stratigraphy and groundwater in these aquifer systems, which is essential for effective regional groundwater management. This dissertation presents a comprehensive investigation of MEAS and CLAS in the Louisiana and southwestern Mississippi region, encompassing three fundamental dimensions: stratigraphy reconstruction, groundwater modeling, and groundwater stress assessments. A …

Auslander-Reiten Triangles On A Bounded Derived Category Of Constructible Complexes, Vishnu Prasad Sivaprasad

LSU Doctoral Dissertations

In this dissertation, concepts from homological algebra are used to study the existence of Auslander-Reiten triangles.

Auslander-Reiten triangles are closely related to representable functors, and the main theorem characterizes the existence of representable functors in a specific bounded derived category of constructible complexes.

Under certain boundedness conditions, a specific bounded derived category is shown to have Auslander-Reiten triangles.

Attochemistry Regulation Of Charge Migration, Aderonke Folorunso

LSU Doctoral Dissertations

Charge migration (CM) is a coherent attosecond process that involves the movement of localized holes across a molecule. This phenomenon is potentially useful to understand the fundamental principles of photochemistry, such as light harvesting. The first part of this dissertation discusses the molecular modes of attosecond charge migration. In this work, we used first-principles calculations to investigate the modes of charge migration (CM) in halogenated hydrocarbon chains at attosecond timescales. We have simulated the creation of a localized hole on the halogen atom using constrained density functional theory (DFT) and then tracked its subsequent dynamics with time-dependent DFT (TDDFT). Our …

Performative Mixing For Immersive Audio, Brian A. Elizondo

LSU Doctoral Dissertations

Immersive multichannel audio can be produced with specialized setups of loudspeakers, often surrounding the audience. These setups can feature as few as four loudspeakers or more than 300. Performative mixing in these environments requires a bespoke solution offering intuitive gestural control. Beyond the usual faders for gain control, advancements in multichannel sound demand interfaces capable of quickly positioning sounds between channels. The Quad Cartesian Positioner is such a solution in the form of a Eurorack module for surround mixing for use in live or studio performances.

Diffusion/mixing methods for live multichannel immersive music often rely on the repurposing of hardware …

Extended Defects And Linear Junctions At The Surfaces Of Topological Insulators, Eklavya Thareja

LSU Doctoral Dissertations

Topological Insulators (TIs) have emerged as promising candidates for spintronics and quantum computing applications. Two properties that underlie these applications are the locking of spin and momentum of the surface electrons and topological protection of surface states. While the existence of gapless surface states is guaranteed by topology, as long as time-reversal symmetry is intact, other properties of the surface states are still tunable. Spin-momentum locking makes these states immune to scattering from non-magnetic point impurities. However, extended defects can scatter the states even with electrostatic potential. We show that a line defect with magnetic and electrostatic potential scattering hosts …

Vibriosis: An Integrated Study Of Ecology, State Policy, And Health Communication, Ruth Akintoye

LSU Doctoral Dissertations

The CDC reports fatalities within one to two days for 20% of victims of a Vibrio vulnificus infection. This flesh-eating bacterium is part of the Vibrio genus, which comprises various pathogenic species responsible for the human illness, Vibriosis, which is estimated at 80,000 annual cases in the US, according to the CDC.

A vibriosis public health concern exists, but there's no mandatory national surveillance system. This study reveals that only 19 states mandate vibriosis reporting, leaving a gap in understanding the incidence of disease from this flesh-eating bacterium.

This research comprises four studies that advance our knowledge of vibriosis through …

Controlling Guest Binding To Transition Metal Hosts Via Redox Stimuli, Jasmine S. Sanford

LSU Doctoral Dissertations

Several metal complexes were investigated as potential hosts to execute controllable host- guest interactions using a redox stimulus. Previously, our group has synthesized new Cu^II m-xylylenebis(pyridyltriazole) (m-xpt) hosts and their redox properties were analyzed. In Chapter 2, we take advantage of the Cu^II host’s ability to perform redox to investigate its interaction with chloride guest ions. This study was executed with two main Cu-xpt hosts: [Cu₂(m- xpt)₂(NO₃)₂](PF₆)₂ and [Cu₂(m-xpt)₂Cl₂]Cl₂. The host-guest interaction was analyzed with additions …

Design, Synthesis And Post Functionalization Of Bodipy Dyes For Use As Chemo Sensors., Caroline Njeri Ndung'u

LSU Doctoral Dissertations

An overview of BODIPYs history, basic structure, electronic properties is described. Additionally, their attribute of tenability in their photophysical and electronic properties has been discussed. Lastly, their application in the biomedical field as bio imaging, labeling, chemo sensors and photosensitizers are also discussed. In Chapter 2, a library of meso- Pyridyl and meso pyridinium BODIPY dyes was designed, synthesis and comparison on their photophysical, electrochemical and cytotoxic studies done. From this study chlorine atoms at the 2, 6 positions was shown to enhance their relative fluorescence quantum yields in different organic solvents and water. In chapter 3, 8(meso)-pyridyl-BODIPYs with a …

Probing The Consequences Of Irreversibly Trapping Iron In Bacterioferritin Using Chemical And Genetic Approaches--An Omics Study, Leo S. Fontenot Jr.

LSU Doctoral Dissertations

Antibiotic resistant bacteria pose one of the most urgent threats to public health. Pseudomonas aeruginosa is a multi-drug resistant bacterium for which new antibiotics are urgently needed. My research is focused on understanding and validating iron metabolism as a target for antibiotic development by analyzing the metabolic profiles of iron-starved P. aeruginosa cells caused by irreversibly trapping iron in bacterioferritin. Iron is an essential nutrient for bacteria; however, the reactivity of the Fe²⁺ ion and insolubility of the Fe³⁺ ion present significant challenges to bacterial cells. Iron storage proteins oxidize Fe²⁺ using O₂ and H_{2 …}

Computational Investigations Of Polymer Electrolytes In Aqueous Solutions, Hishara Keshani Gallage Dona

LSU Doctoral Dissertations

Polymer electrolyte membranes, an intriguing category of soft materials, are characterized by polymer backbones tethered with negatively or positively charged functional groups, finding applications from biological macromolecules to electrochemical separations in fuel cells. This dissertation focuses on computational investigations of polymer electrolytes in aqueous solutions using polypeptoids and ion exchange membranes. Polypeptoids, highly tailorable peptidomimetic polymers lacking backbone hydrogen bonding or chirality, were used as model systems. Micelles formed from these polypeptoid polymers exhibited electrostatic repulsion, which competes with charge-sodium interactions, adding complexity to predicting micelle shapes. This research refined the design strategy, enhancing micelle shape and structure through precise …

Sequence-Defined Ionic Peptoid Polymers: Synthesis, Characterization, And The Role Of Charge Patterning, Bailee N. Barrett

LSU Doctoral Dissertations

This work explores the role of positionally defined charges on the self-assembly behavior of a series of sequence-defined peptoid block copolymers. The unique ability to precisely control the number and position of each monomer unit along the polymer chain makes this system particularly well suited for uncovering how changes in monomer sequence alter the resulting structures. We employ a number of scattering techniques to uncover how systematically repositioning a single ionizable monomer, along an otherwise neutral polymer chain, alters the self-assembled micellar structures and subsequently their responsiveness to changes in their local environment.

Chapter 1 reviews previous efforts to transition …