Physical Sciences and Mathematics Commons^™

Distributed Load Testing By Modeling And Simulating User Behavior, Chester Ira Parrott

LSU Doctoral Dissertations

Modern human-machine systems such as microservices rely upon agile engineering practices which require changes to be tested and released more frequently than classically engineered systems. A critical step in the testing of such systems is the generation of realistic workloads or load testing. Generated workload emulates the expected behaviors of users and machines within a system under test in order to find potentially unknown failure states. Typical testing tools rely on static testing artifacts to generate realistic workload conditions. Such artifacts can be cumbersome and costly to maintain; however, even model-based alternatives can prevent adaptation to changes in a system …

Synthesis Of Structurally Diverse Molecular Scaffolds Enabled By Protected Oxyallyl Cations, Joshua Andrew Malone

LSU Doctoral Dissertations

This dissertation focuses on the synthesis of diverse molecular scaffolds through the use of protected oxyallyl cation intermediates. Chapter One provides background on the generation and applications of oxyallyl and silyloxyallyl cations, while focusing on the direct nucleophilic capture of theses intermediates to generate functionalized ketones and silylenolates. Chapter Two depicts our approach to generate six-membered silyloxyallyl cations through the use of mild Brønsted acid activation. Regioselective nucleophilic capture of these intermediates successfully produced diverse a,a’-substituted silylenol ethers enabled by polar solvent and residual water.

Chapter three details strategies to generate 1,4-dicarbonyl compounds, focusing on the capture of cationic intermediates …

Measurements And Mitigation Of Scattered Light Noise In Ligo, Corey Daniel Austin

LSU Doctoral Dissertations

The Advanced LIGO (aLIGO) detectors use 1064 nm lasers to measure the tiny fluctuations in spacetime that occur when gravitational waves pass through the earth. LIGO makes use of advanced coating methods and materials to limit the amount of light that scatters from the main beam, but some amount of light does scatter. This stray light can interact with surfaces inside the interferometer that are not seismically isolated and then recombine with the main beam, introducing excess noise into the gravitational wave channel. This thesis reviews the methods for modeling scattered light with ray tracing software and analytical models, for …

Deep-Ultraviolet Laser Ablation For Biomolecular Analysis, Oluwaremilekun Omowunmi Lawal

LSU Doctoral Dissertations

New sampling and ionization techniques were developed using a deep-ultraviolet (DUV) laser at 193 nm wavelength for analysis of large biomolecules. A micrometer spatial resolution DUV laser ablation and capture system was constructed to sample tissue biomolecules. The spot size measurements of the focused beam showed that subcellular spots with ca. 2 μm diameter can be readily achieved with this wavelength. To demonstrate the extraction of tissue biomolecules with the DUV laser, regions of tissue sections were ablated and captured for offline proteomic and genomic analysis. The proteomic studies revealed that the tissue proteins were ejected without fragmentation and that …

Structure And Dynamics Of Phospholipid Vesicles And The Dependence On Nanoscale Interactions With Molecules Of Varying Complexity, Lakshapathy Widanelage Judith Upeka De Mel

LSU Doctoral Dissertations

In this dissertation, molecular interactions and changes imposed by nano-scale structures on phospholipid vesicles were investigated. 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) large unilamellar vesicles (LUVs) were used as the model system. Understanding changes of the bilayer structure, interfacial properties, lipid dynamics, and self-assembly, allows bridging relationships between biological cell membrane structure and dynamics to cellular functionalities. For example, membrane curvature changes are linked to membrane protein functions, although the exact mechanisms of control are not yet understood. Moreover, the knowledge gained from vesicle models allows exploring novel strategies for drug delivery applications. To achieve this, DOPC LUVs were synthesized and characterized by a …

Computational Investigations Of Battery Electrolytes, Ke Li

LSU Doctoral Dissertations

In this dissertation, the structure and dynamics of battery electrolytes were investigated using atomistic molecular dynamics (MD) simulations. Battery electrolytes play a key role in transporting ions between the cathode and anode. The chemical stability and ionic conductivity of electrolytes influence battery performance. In order to design better electrolytes, one needs an understanding of the relationship between electrolyte structure, dynamics, and bulk properties. To bridge the gap between the macroscopic phenomenon and the hidden molecular physics, in the first project we focused on probing an ether-based electrolyte, chosen for its relevance in sodium-based batteries. Through studying the impact of concentration …

Adsorption And Reconfiguration Of Amphiphiles At Silica-Water Interfaces: Role Of Electrostatic Interactions, Van Der Waals Forces And Hydrogen Bonds, Yao Wu

LSU Doctoral Dissertations

The ability to explore and predict metastable structures of hybrid self-assemblies is of central importance for the next generation of advanced materials with novel properties. As compared to their thermodynamically stable forms, the kinetically stabilized materials show improved functionality potentially over their stable counterparts. The self-assembly processes usually originate from weak intermolecular interactions, involving a dynamic competition between attractive and repulsive interactions. These weak forces, including van der Waals (vdW), electrostatic interaction and the hydrogen bonding (H-bonding), can be tuned by external stimuli, e.g., confinement, temperature and ionization, and consequently driving hybrid materials into different configurations. It is challenging to …

Methods For 1,2-Cis-Selective O-Glycosylation And Synthesis Of An A. Baumannii Lipooligosaccharide Core Disaccharide, Ashley Fulton

LSU Doctoral Dissertations

This dissertation focuses on the formation of organic thin films on gold surfaces and synthesis of oligosaccharides. Chapter one, is a brief introduction on the utility of thin films, as well as ways to characterize thin films, as well as, a report on the attempt to form organic thin films on Au(111) surfaces using photoredox catalysis.

Glycoconjugates on cell surfaces serve as important mediators of intercellular recognition, adhesion, and viral infection. Due to the significant role that glycoconjugates play on the surface of cells, oligosaccharide synthesis is of great interest. Chapter two, is an extensive review of oligosaccharide synthesis, its …

Synthesis And Investigation Of Amphiphilic Polypeptoids For Environmental And Biological Applications, Tianyi Yu

LSU Doctoral Dissertations

Polypeptoids are an emerging class of peptidomimetic polymers featuring N-substituted polyglycine backbones. Polypeptoids are cyto-compatible and backbone degradable, making them appealing to many biological applications. When the highly polar polyamide backbone is coupled with non-polar aliphatic side chains, polypeptoids can be considered as facial amphiphiles. Without extensive hydrogen bonding along the backbone, the conformation of polypeptoid is largely controlled by the N-substituent structures. The hydrophobicity-lipophilicity balance of polypeptoids can be readily tuned with the N-substituent structures as well as the molar ratio between the hydrophilic and hydrophobic segments in their copolymers. In view of these combined attributes, …

A Study Of 26al(P, Γ)27si With The Silicon Array For Branching Ratio Experiments (Sabre), Erin Courtney Good

LSU Doctoral Dissertations

The observation of the radioisotope ²⁶Al is an indicator of ongoing nucleosynthesis in the Galaxy due to its short lifetime (t_1/2 = 7.2 × 10⁵ yr) on Galactic timescales. It is thought to be synthesized in several different environments in our Galaxy, one of which is in classical novae. Classical novae are stellar explosions that occur on the surface of a white dwarf in a binary system with a main sequence star. The isotopic production resulting from the nucleosynthesis that drives these explosions can be modeled with the input of nuclear reaction rates. In recent years, many …

A Phase-Field Approach To Diffusion-Driven Fracture, Friedrich Wilhelm Alexander Dunkel

LSU Doctoral Dissertations

In recent years applied mathematicians have used modern analysis to develop variational phase-field models of fracture based on Griffith's theory. These variational phase-field models of fracture have gained popularity due to their ability to predict the crack path and handle crack nucleation and branching.

In this work, we are interested in coupled problems where a diffusion process drives the crack propagation. We extend the variational phase-field model of fracture to account for diffusion-driving fracture and study the convergence of minimizers using gamma-convergence. We will introduce Newton's method for the constrained optimization problem and present an algorithm to solve the diffusion-driven …

Adaptive Data Migration In Load-Imbalanced Hpc Applications, Parsa Amini

LSU Doctoral Dissertations

Distributed parallel applications need to maximize and maintain computer resource utilization and be portable across different machines. Balanced execution of some applications requires more effort than others because their data distribution changes over time. Data re-distribution at runtime requires elaborate schemes that are expensive and may benefit particular applications.

This dissertation discusses a solution for HPX applications to monitor application execution with APEX and use AGAS migration to adaptively redistribute data and load balance applications at runtime to improve application performance and scaling behavior. This dissertation provides evidence for the practicality of using the Active Global Address Space as is …

Using Spatial Analysis And Machine Learning Techniques To Develop A Comprehensive Highway-Rail Grade Crossing Consolidation Model, Samira Soleimani

LSU Doctoral Dissertations

The safety of highway-railroad grade crossings (HRGC) is still an issue in the United States of America (USA). The grade crossing is where a railroad crosses a road at the same level without any over or underpass. To improve the safety of crossings, the crossings’ condition should be explored from several aspects such as engineering design (speed limit, warning signs, etc.), road condition (number of lanes, surface markings, etc.), rail design (the type of track, ballast, etc.), temporal variables (weather, visibility, time of day, lightning, etc.), social variables (population, race, etc.), and last but not least, spatial variables (the type …

Modeling Anatomic Changes For Adaptive Radiotherapy In Locally Advanced Lung Cancer Patient Population, James Alexander Kavanaugh

LSU Doctoral Dissertations

Anatomic changes occurring mid-treatment for patients undergoing radiation therapy for locally advanced lung cancer can degrade the quality of the intended treatment plan. These changes include tumor regression, geometric misalignment, and lung density changes (atelectasis and pleural effusion), and are visible on the daily 3D cone beam CT (CBCT). To maintain the intended treatment quality, adaptive radiotherapy (ART) can be employed to modify the treatment plan to account for these anatomic changes. However, the evaluation on when to adapt is currently completed manually by the treating clinicians, resulting in a subjective and inconsistent application. To address these limitations, a series …

Transition Metal Complexes Of Pyridyltriazole And Bipyridine Ligands, Sen Gao

LSU Doctoral Dissertations

Four Ni(II) complexes have been obtained with the pyridyltriazole ligand, bpt, or the bis(pyridyltriazole) ligand, m-xpt, in chapter 2. This work was carried out as a comparison with the previously established coordination chemistry of copper(II) with bpt and m-xpt. Initially, the reaction between Ni(II) and bpt only produced one mononuclear compound, [Ni(bpt)₂(H₂O)₂](NO₃)₂ (1). In order to study the formation of Ni-bpt and Ni-m-xpt complexes in solution, mixtures of Ni(NO₃)₂ and ligand (m-xpt or bpt) were prepared in different ratios and …

Second Harmonic Generation Spectroscopy And Microscopy Of Liposomes, Nanoparticles, And Cells, Prakash Hamal

LSU Doctoral Dissertations

Second harmonic generation (SHG) is used to investigate the factors that impact nanoparticle-based drug-delivery applications. In the first study, molecular adsorption and transport kinetics of a positively-charged dye, malachite green isothiocyanate (MGITC), is characterized at the surface of different colloidal liposomes in water using SHG spectroscopy. The molecular interactions of MGITC is compared to our previous investigations with malachite green (MG). In comparison to MG, MGITC demonstrates stronger adsorption and faster transport through lipid membranes. Correspondingly, the SHG experimental results are in excellent agreement with the molecular dynamics (MD) simulations results. A key finding illustrates the importance of functional groups, …

Solvation Structures And Dynamics Of Small Molecules: Experimental And Computational Studies Using Carbonyl Vibrational Modes As Probe, Xiaoliu Zhang

LSU Doctoral Dissertations

Solutions are ubiquitous in both the global environment and the human body, and play a significant role in scientific research and industrial production. The structures and dynamics of solutions have been studied for centuries. However, conventional experimental methods, whose intrinsic measuring time is on the order of nanoseconds to microseconds, could not detect the fast dynamics taking place in the solution on the timescale of femto- and pico-second. In this dissertation, the ultrafast two-dimensional infrared (2DIR) spectroscopy was applied to characterize the structure and dynamics in three different types of solutions on the sub-picosecond timescale. Linear Fourier transform infrared spectroscopy …

Some Results On Seymour’S Second-Neighborhood Conjecture And On Decompositions Of Graphs, Farid Bouya

LSU Doctoral Dissertations

This dissertation consists of two parts. In the first part, I examine Seymour’s Second-Neighborhood Conjecture, which states that every orientation of every simple graph has at least one vertex v such that the number of vertices of out-distance 2 from v is at least as large as the number of vertices of out-distance 1 from it. I present alternative statements of this conjecture using the language of linear algebra, the last one being completely in terms of the inverse of some matrix. In the second part of this dissertation, comprising of Chapters 2 and 3, I examine two conjectures on …

The Medium-Term And Event-Scale Tropical Cyclone-Driven Morphodynamics Of A Vulnerable Barrier System With Emphasis On The Role Of Backbarrier Wetlands, Cody Lee Johnson I

LSU Doctoral Dissertations

Coastal mainland barriers and barrier islands provide the first line of defense against oceanic and meteorological forces. Coastal morphological change, which may degrade these barrier's defensive capabilities, occurs over a range of time scales, from geological epochs (>1000 years) to hours and seconds. Coastal morphological change at a vulnerable, but economically strategic, barrier system---the Caminada-Moreau Headlands, Louisiana---is investigated in terms of tropical cyclone impacts and their effects over a 15 year LIDAR survey time series. Analysis of the barrier's three-dimensional morphodynamics at medium-term (decadal) time scales reveals that, while subaerial volume was approximately conserved through time, the impact of …

Characterization Of Shallow Subsurface Hydrology In Large Fine-Grained Floodplains, Mary Grace Lemon

LSU Doctoral Dissertations

Floodplains are hydrologically dynamic, receiving water from overbank events, hyporheic flows, local precipitation, and regional groundwater sources. These sources are variously important contributors to the heterogeneous floodplain water pool that includes matrix water in soil micropores, mobile water in soil macropores, groundwater below the rooting zone, ephemeral to seasonal surface storage, and permanent surface water features such as oxbow lakes, sloughs, and other secondary channels. All sources may be ecologically relevant for floodplain vegetation, but the exact roles of each source in both controlling soil water and shallow groundwater recharge and in controlling floodplain water drainage are not well understood, …

Southwest Pacific Tropical Cyclone Frequency And Intensity Related To Observed And Modeled Geophysical And Aerosol Variables, Rupsa Bhowmick

LSU Doctoral Dissertations

The dissertation focuses on western region of Southwest Pacific Ocean (SWPO)

basin (135E - 180, and 5S - 35S) tropical cyclone (TC) climatology using observed

and modeled data. The classification-based machine learning approach

identifies the synoptic geophysical and aerosol environment favorable or unfavorable

for TC intensification and intensity change prior to landfall incorporating

observational and satellite data. A multiple poisson regression model with varying

temporal monthly lags was used to build a relationship between the number of

monthly TC days with basin wide average dust aerosol optical depth (AOD), sea

surface temperature (SST), and upper ocean temperature (UOT). This idea …

Quantum Criticality In Strongly Correlated Electron Systems, Samuel Obadiah Kellar

LSU Doctoral Dissertations

The study of the Hubbard model in three dimensions contains a variety of phases dependent upon the chosen parameters. This thesis shows that there is the indication of a zero temperature phase transition at a finite doping. The Hubbard model has been used to identify a similar quantum critical point in two dimensions. The presented results continue these investigations. The system demonstrates a strange metal phase at finite temperature which cannot be described in term of the conventional Fermi liquid. While there have been extensive studies over the past three decades for such materials in two dimensions, there are few …

Identifying Structure Transitions Using Machine Learning Methods, Nicholas Walker

LSU Doctoral Dissertations

Methodologies from data science and machine learning, both new and old, provide an exciting opportunity to investigate physical systems using extremely expressive statistical modeling techniques. Physical transitions are of particular interest, as they are accompanied by pattern changes in the configurations of the systems. Detecting and characterizing pattern changes in data happens to be a particular strength of statistical modeling in data science, especially with the highly expressive and flexible neural network models that have become increasingly computationally accessible in recent years through performance improvements in both hardware and algorithmic implementations. Conceptually, the machine learning approach can be regarded as …

Antimicrobial Strategies For Topical Applications, Kelsey Marie Lopez

LSU Doctoral Dissertations

Bacteria can thrive in diverse environments and are often harmless or beneficial. Bacteria in digestive tracts is one example of beneficial bacteria; however, bacteria can be harmful and when this type proliferates, it can cause infections within hosts. Bacterial infections are easily treated with antibiotics in most cases. However, bacteria are also capable of developing mutations which could cause them to become multi-drug resistant and eventually, “superbugs.” Therefore, the development of novel antimicrobial agents and materials capable of combating drug-resistant bacteria is necessary. Research presented in this dissertation focuses on different strategies for minimizing and preventing topical bacterial infections using …

Design, Synthesis And Characterization Of New Superconductors, Xin Gui

LSU Doctoral Dissertations

Design and synthesis of new materials are a long-standing goal for chemistry, physics and material science, especially those with intriguing properties such as magnetism and superconductivity. With consideration and incorporation of the highlights in some existing design rules, we successfully designed and discovered the superconductivity in BaPt₂Bi₂, SrSnP and Yb_xPt₅P.

With the help of valence electron counting method, we synthesized a new intermetallic compound, BaIr₂Ge₂, which was then found to be non-superconducting above 1.8 K. Thus, we considered both valence electron counting and chemical pressure adjustment to reach …

Sediment Transport And Geomorphological Evolution In The Transgressive Ship Shoal, Louisiana: Insights From Geophysical Observation, Modeling, And Machine Learning Studies, Haoran Liu

LSU Doctoral Dissertations

Ship Shoal has been a high-priority target sand resource for dredging activities to restore the eroding barrier islands in Louisiana, USA. Many studies have been performed in Ship Shoal in recent decades, but our knowledge of temporal and spatial variations of sediment transport and post-dredge morphology is still limited. The objectives of this dissertation are to explore the sediment infilling process, the spatial and temporal evolution of the morphology of dredge pits near and on Ship Shoal by using multiple methods. Scientific methods used in this study include (a) geophysical observation using bathymetry, side-scan and subbottom technique, (b) sediment transport …

Multigrid Methods For Elliptic Optimal Control Problems, Sijing Liu

LSU Doctoral Dissertations

In this dissertation we study multigrid methods for linear-quadratic elliptic distributed optimal control problems.

For optimal control problems constrained by general second order elliptic partial differential equations, we design and analyze a $P_1$ finite element method based on a saddle point formulation. We construct a $W$-cycle algorithm for the discrete problem and show that it is uniformly convergent in the energy norm for convex domains. Moreover, the contraction number decays at the optimal rate of $m^{-1}$, where $m$ is the number of smoothing steps. We also prove that the convergence is robust with respect to a regularization parameter. The robust …

Copper And Ruthenium Pyridyltriazole Complexes And Their Reactivity Toward Carbon Dioxide And Water, Fatemeh Khamespanah

LSU Doctoral Dissertations

A variety of pyridyltriazole ligands are readily available via click type cycloaddition of alkynylpyridines and azides. We made functionalized tetradentate m-xylylenebis(pyridyltriazole) (m-xpt) ligands with NH₂ and NMe₂ electron-donating and NO₂ electron-withdrawing substituents on the pyridine moieties. Complexation of these ligands with Cu(II) gives dimeric macrocycles with square pyramidal geometry at Cu centers. Previous work in our lab with the unsubstituted [Cu₂(m-xpt)₂(NO₃)₂]²⁺ complex showed reduction to Cu(I) by using ascorbate as reducing agent. Oxidation of the Cu(I) solution in air results in formation of …

Investigating Geochemical Processes Of Fluid-Rock Interactions On Materials Related To Energy And Environment, Zelong Zhang

LSU Doctoral Dissertations

Understanding the potential processes of radionuclides released from nuclear waste forms is essential to the safe disposal and containment of nuclear waste. Iodoapatite, a potential waste form for radioiodine, was chosen as a model system to examine the impact by common aqueous anions on iodine release processes. Four semi-dynamic leaching tests were performed using 0.1 mol/L NaCl, Na₂CO₃, Na₃PO₄, and Na₂SO₄ solutions respectively under 90 °C, 1 bar, fixed S/V ratio 5/m (sample surface area to solution volume), and with 24-hour replacement of the leaching solutions. Solution analysis and …

Benthic Nitrogen Dynamics In Response To Deltaic Succession, Anthropogenic Fertilization And Hurricane Events In An Emerging Coastal Deltaic Floodplain Within The Mississippi River Delta Plain, Song Li

LSU Doctoral Dissertations

Increasing concentrations of nitrogenous fertilizer (NO₃^-) in rivers have potentially altered benthic nitrogen (N) cycling in coastal deltaic floodplains at the continental margins of major rivers. Here I evaluated the N removal capacity of a newly emergent coastal deltaic floodplain [Wax Lake Delta (WLD)] within the Mississippi River Delta Plain using continuous flow-through incubations. I investigated the response of benthic N dynamics in WLD to deltaic succession, anthropogenic fertilization and hurricane events. The estimated annual NO₃^- removal of 896 Mg N yr^-1 in WLD accounts for 10 to 27% of total NO₃^{- …}