Physical Sciences and Mathematics Commons^™

Molecular Products From The Thermal Degradation Of Selected Tobacco Components: Lignin, Tyrosine, Glutamic Acid, And Modeling Of Lignin Pyrolysis Using Chemkin Combustion Suite, Joshua Kiprotich Kibet

LSU Doctoral Dissertations

This study explores the thermal decomposition behavior of selected tobacco components: lignin, tyrosine, and glutamic acid using the system for thermal diagnostic studies (STDS) in an in-line gas chromatography-mass spectrometer analytical technique. The pyrolysis conditions employed in this study were a flowing atmosphere of nitrogen and 4% O2 in nitrogen at a residence time of 0.2 seconds for a total pyrolysis time of 3 minutes. The results identified common relationships between the two modes of reaction atmospheres, as well as some differences. While some products were favored by an inert regime, some were favored under an oxidative regime. Oxidative pyrolysis …

Spatial Structure And Dynamics Of The Plant Communities In A Pro-Grading River Delta : Wax Lake Delta, Atchafalaya Bay, Louisiana, Melissa Carle

LSU Doctoral Dissertations

River deltas are dynamic depositional environments that are controlled to varying degrees by coastal and fluvial forces. Plant communities in deltas respond to many of the same allogenic forces that shape delta geomorphology. This study examines the factors that influence plant community development, productivity, and species distributions in the Wax Lake delta, a young, actively pro-grading river delta in coastal Louisiana, USA. A species distribution map created using high-resolution 8-band WorldView-2 imagery was found to have an overall accuracy of 75 percent. Classification tree analysis suggested that most of the observed variation in plant species distributions within the delta can …

Quantum Simulations On Square And Triangular Hubbard Models, Kuang-Shing Chen

LSU Doctoral Dissertations

In this thesis we try to understand the unconventional superconducting mechanism on cuprates and organic superconductors (or sodium cobaltates) which can be modeled by a two-dimensional square- and triangular-lattice Hubbard model respectively. The formation of the superconducting dome requires explanations of feasible scenarios. Generally speaking, pairing strength is provided by magnetic fl_x001D_uctuations in the strongly correlated region and the structure of the Fermi surface in this region will favor superconducting pairings with a certain type of symmetry. For the cuprate physics, a superconducting dome composed of d-wave pairings has been identified experimentally. We study the Hubbard model on square lattices …

Ecosystem Metabolism In Coastal Plain Streams Of Southeast Louisiana : Environmental And Watershed Effects, Jonathan L. West

LSU Doctoral Dissertations

Since its introduction in 1956, the use of open-system, diel dissolved oxygen curves for estimating the components of ecosystem metabolism in the lotic setting have been important in determining the current ecosystem theory of streams, both spatially among multiple systems and longitudinally within the same system, as well as identifying potentially impaired systems, especially when contrasted with streams considered unimpaired. Several factors have been identified as controls on both components of ecosystem metabolism and include light, nutrients, and stable substrates for gross primary production (GPP) and a source of organic matter (OM) for ecosystem respiration (ER). Stream size is important …

Fluorescent Materials For Chemical Sensing, Brian Gerard Imsick

LSU Doctoral Dissertations

Materials incorporating fluorescent π-electron conjugated molecular species for sensing and imaging are advantageous over other detection or identification methods such as colorimetric reporters. Fluorescent materials offer easy recognition of binding events due to the highly sensitive nature of fluorescence techniques down to the single molecule level. The properties of fluorescent molecules allow for rapid attenuation of observable readout due to the facile transport of excited state energy via both inter- and intramolecular pathways. This dissertation primarily focused on the development and study of a general platform for ratiometric fluorescent chemosensing using surface-immobilized oligomers, as well as in depth explorations of …

Silica Polypeptide-Based Colloids: Physical Properties And Novel Materials, Cornelia Rosu

LSU Doctoral Dissertations

The investigation of polypeptide composite particles, PCPs, is described. The production of mesoporous and polycolloid architectures is also addressed. PCPs were prepared by both growing form and grafting to method. They consist of a core made of silica, silica-coated magnetite or silica-coated cobalt. Some of the particles were covalently labeled with fluorescein isothiocyanate. Several polypeptides were chosen for attachment on the core: poly(γ-stearyl-L-glutamate), PSLG, poly(Nε-carbobenzyloxy-L-lysine), PCBL and poly(o-benzyl-L-tyrosine), PBTY. Attachment of a well-characterized alkyne-end terminated PSLG and PCBL to an azide- functionalized particle yielded PCPs with a desired sparse coverage. A blend of techniques such as FTIR, XPS, TEM, HTEM, …

Surface Studies Of Organic Thin Films Using Scanning Probe Microscopy And Nanofabrication, Venetia Denae Lyles

LSU Doctoral Dissertations

Porphyrins and metalloporphyrins have unique chemical and electronic properties and thus provide useful model structures for nanoscale studies of the role of chemical structure for electronic properties. Porphyrins have been proposed as viable materials for molecular-based information-storage devices, gas sensors, photovoltaic cells, organic light-emitting diodes and molecular wires. The function and efficiency of porphyrins in devices is largely attributable to molecular architecture and how the molecules are self-organized. Modifications of the porphyrin macrocycle, peripheral groups or bound metal ions can generate a range of electrical, photoelectrical or magnetic properties. The conductive properties are greatly influenced at the molecular level by …

Super-Aptamer Bio-Imprinted Hydrogels : An Investigation Into The Optimization And Characterization Of Cross-Linked Polymeric Materials Displaying Macromolecular Amplified Responses, Nicholas Alexander Gariano

LSU Doctoral Dissertations

It is becoming more important to detect ultra-low concentrations of analytes for biomedical, environmental, and national security applications. Equally important is that new methods should be easy to use, inexpensive, portable, and if possible allow detection using the naked eye. Detection of low concentrations of analytes generally cannot be achieved directly, but requires signal amplification by catalysts, macromolecules, metal surfaces or supramolecular aggregates. The rapidly progressing field of macromolecular signal amplification has been advanced using conjugated polymers, chirality in polymers, solvating polymers and polymerization/depolymerization strategies. The use of molecularly imprinted polymers is ideal for creation of novel sensors to meet …

Investigations Into Alkene Hydration And Alkene Oxidation Catalysis, William Schreiter

LSU Doctoral Dissertations

Bimetallic Ni complexes Ni21M and Ni21R and monometallic transition metal complexes were investigated as possible alkene hydration catalysts under a multitude of different reaction conditions. All attempts at performing this catalytic reaction failed to give any alcohol products. Catalytic screening experiments were conducted using a mixture of racemic-et,ph-P4 and meso-et,ph-P4, 1M and 1R, and various transition metals. These experiments gave several different products including 1-phenylethanol from styrene. During the course of the hydration experiments, an aldehyde product was identified from experiments conducted with the bimetallic complexes in air. Experiments have shown that the aldehyde is produced from the oxidative cleavage …

Patterns And Pathways Of Wetland Sedimentation And Landscape Change In Coastal Louisiana, Andrew William Tweel

LSU Doctoral Dissertations

Coastal Louisiana wetlands exist in a dynamic physical environment and retracted dramatically in the last century. Here I examine the spatial and temporal variability of this landscape with an emphasis on the interactions between anthropogenic landscape modifications and geological processes.

The Mississippi River watershed underwent drastic changes during the past 200 years, beginning with widespread land clearing and, later, large-scale reservoir construction. These modifications caused increases in suspended sediment concentrations, then sharp decreases, and have remained relatively stable since 1960. I show how changes in land area of the Mississippi River birdfoot delta reflect these fluctuations, and that they are …

Advancing The Field Of Polypeptoids Through The Synthesis Of Novel Architectures And Thermoresponsive Polymers, Samuel Henry Lahasky

LSU Doctoral Dissertations

Peptidomimetic polymers are an emerging class of polymers that are structurally related to polypeptides. Due to their structural similarities, these polymers can be used to study some of the physical aspects of polypeptides (for example, protein folding). They are also increasingly being used in the fields of biology and drug-delivery. Some members of peptidomimetic polymers include polyacrylamides, polyoxazolines and polypeptoids. Polymer synthesis and characterization has been performed for both polyacrylamides and polyoxazolines, with research dating back to the 1950s and 1980s respectively. Research in the field of polypeptoids has not been as extensive; however, emerging synthetic strategies are allowing for …

Toward Digitizing The Human Experience : A New Resource For Natural Language Processing, Jerry Scott Weltman

LSU Doctoral Dissertations

A long-standing goal of Artificial Intelligence is to program computers that understand natural language. A basic obstacle is that computers lack the common sense that even small children acquire simply by experiencing life, and no one has devised a way to program this experience into a computer. This dissertation presents a methodology and proof-of-concept software system that enables non-experts, with some training, to create simple experiences. For the purposes of this dissertation, an experience is a series of time-ordered comic frames, annotated with the changing intentional and physical states of the characters and objects in each frame. Each frame represents …

Laser Ablation Sample Transfer For Mass Spectrometry, Sung-Gun Park

LSU Doctoral Dissertations

In this research, a new ambient sampling technique for mass spectrometry was developed that uses an infrared laser to ablate materials under ambient conditions that are captured in a solvent or on a surface. An infrared optical parametric oscillator (OPO) laser system at 3 μm wavelength was focused onto samples for ablation at atmospheric pressure. The ablated materials were transferred to a solvent or surface. For off-line electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) analysis, the ablated material was captured in a static solvent droplet that was deposited on a MALDI target or flow-injected into a nanoelectrospray source. The …

Strongly Correlated Ultra-Cold Bosonic Atoms In Optical Lattices, Kalani Hettiarachchilage

LSU Doctoral Dissertations

A major focus in condensed matter physics is to study the origin of exotic quantum phases such as coexistent and inhomogeneous phases, quantum criticality, and secondary ordered phases close to quantum critical points. Exotic phenomena in strongly correlated systems occur due to competing complex interactions of spin, charge, lattice, and orbital degrees of freedom. Complex quantum phases in strongly correlated systems are challenging, but they might be very useful due to their possible functionality to make advance devices. In order to understand, utilize, and optimize such behaviors, we need to improve our understanding of these systems. Studies in cold atom …

A Semigroup/Laplace Transform Approach To Approximating Flows, Ladorian Nichele Latin

LSU Doctoral Dissertations

It is well known that all flows in a state space O induce a semigroup of linear operators on an appropriately chosen vector space of functions (observables) from O into a vector space Z (observations). After choosing appropriate continuity assumptions on the flow, the associated semigroup will be strongly continuous and will have a linear, infinitesimal generator A. The purpose of this dissertation is to explore approximation methods for linear semigroups and/or Laplace transform inversion methods in order to reconstruct the flow starting with the linear generator A . In preparing for these investigations, we collect some of the essential …

Photometric Variability Of X-Ray Sources In The Galactic Bulge, Christopher Tillman Britt

LSU Doctoral Dissertations

The Chandra Galactic Bulge Survey (GBS) undertakes to find and classify X-ray sources in the Galactic Bulge. Of these X-ray sources, there is likely a significant minority which are Low Mass X-ray Binaries: systems containing either a neutron star or black hole that is accreting matter from a roughly stellar mass companion via Roche-Lobe overflow. I use optical time-series photometry from the Mosaic-II instrument on the Blanco 4m telescope at the Cerro Tololo Inter-American Observatory to identify counterparts to new X-ray sources in the GBS. Of those that are variable in brightness, I use the morphology of the changes and …

Decade-Scale Nutrient Enrichment Effects On Wetland Plant Community Structure, Function, And Stability, Sean A. Graham

LSU Doctoral Dissertations

Human activities have increased the supply of nitrogen (N) and phosphorus (P) to coastal waters worldwide, threatening coastal wetlands with excess nutrient loading and subsequent eutrophication. In this dissertation, I present results from two decade-scale fertilization experiments in a Sagittaria lancifolia dominated oligohaline marsh that examined the species-, community-, and ecosystem-level effects of nutrient enrichment. My objectives were to determine (1) which nutrient limits primary production, (2) how increased supply of the limiting nutrient affects plant community structure and function, both above- and belowground, and (3) whether nutrient over-enrichment compromises ecosystem stability. Overall, significant changes in plant growth occurred with …

Chemical Composition And Structure Study Of Surfaces And Ultrathin Films Of Complex Compounds, Yi Li

LSU Doctoral Dissertations

Complex Materials, such as transition-metal oxides (TMOs) with exotic properties provide immense opportunities in condensed matter and materials science. The signature and challenge of these materials is the multitude of competing ground states that can be tuned or manipulated by doping, structural modification, strain induction, or the application of external stimulus. In the past few years, it is becoming increasingly clear that surfaces/interfaces, thin films, and heterostructures of TMOs, display a rich diversity of fascinating properties that are related to, but not identical to, the bulk phenomena. The fundamental issues for the understanding of these emergent phenomena include the structure …

Recovery Of Understory Bird Movement In Post-Pasture Amazonia, Luke L. Powell

LSU Doctoral Dissertations

I sought to understand how forest fragmentation and secondary growth affect avian movement at the Biological Dynamics of Forest Fragments Project (BDFFP) near Manaus, Brazil. When deforested areas are abandoned, secondary forests regenerate, allowing rainforest animals to gradually recovery their ability to use formerly inhospitable habitat. My colleagues and I captured 2773 understory birds of ten foraging guilds along the edges of primary forest fragments and variable secondary forest. Age of secondary forest along edges was the most important variable driving capture rates on primary/secondary edges. Mean recovery to pre-isolation capture rates was 26 years after abandonment, but terrestrial insectivores …

Incorporating Science-Based Approaches Into The Rapid Assessment Of Wetlands And Streams : Validation, Restoration Trajectory, And Method Development, Jacob Franklin Berkowitz

LSU Doctoral Dissertations

Human alterations within wetlands and streams have resulted in a decrease in ecological functions and associated benefits to society. The scientific literature highlights the functional benefits provided by ecosystems including flood protection, nutrient cycling, and habitat maintenance. Additionally, legislation and regulatory policy require mitigation and restoration as compensation for declines in ecological functions. As a result, the need for practical, repeatable, and technically sound ecosystem assessment methods remains essential to natural resource management. However, few studies determine the validity of rapid assessment approaches by applying quantitative parameters, especially with respect to biogeochemical functions. We assessed biogeochemical functions applied to restored …

New Strategies For The Synthesis Of Porphyrinoids, Moses Inyanje Ihachi

LSU Doctoral Dissertations

ABSTRACT Chapter 1 describes the most stable isomer of porphyrin called porphycene. In this chapter photodynamic therapy (PDT) is explained, and the application of porphycenes in PDT is also described. Other biological applications and its uses in catalysis are also summarized here. The general chemical reactions of porphycenes are also explained. Chapter 2 involves the synthesis of pyrroles and bipyrroles. Functionalization of pyrrollic substituents is demonstrated using organometallic coupling reactions like Stille coupling and Grubbs olefin metathesis. The synthesis of divinyl bipyrroles is intended to provide an important precursor to porphycene synthesis via ring closing metathesis using Grubbs catalyst. Chapter …

Extra Structures On Three-Dimensional Cobordisms, Xuanye Wang

LSU Doctoral Dissertations

A Topological Quantum Field Theory (TQFT) is a functor from a cobordism category to the category of vector spaces, satisfying certain properties. An important property is that the vector spaces should be finite dimensional. For the WRT TQFT, the relevant 2 + 1-cobordism category is built from manifolds which are equipped with an extra structure such as a p1-structure, or an extended manifold structure. In chapter 1, we perform the universal construction of [3] on a cobordism category without this extra structure and show that the resulting quantization functor assigns an infinite dimensional vector space to the torus. In chapter …

Environmentally Persistent Free Radicals (Epfrs) In Pm₂.₅ : Their Contribution To Hydroxyl Radical Formation And Atmospheric Transformation, William Micheal Gehling, Jr.

LSU Doctoral Dissertations

Previous research demonstrated environmentally persistent free radicals (EPFRs) will form on particulate surfaces under combustion conditions (temperature range of 150-400 °C) from reactions of organic precursors with redox-active transition metals. With an understanding of how these EPFRs form, it is necessary to determine how they behave in a natural environment after emission. To better understand this, the nature of EPFRs in ambient PM2.5 under simulated atmospheric conditions was investigated. Ambient PM2.5 samples were collected at a roadside ambient monitoring site near heavy interstate traffic and major industrial activity. The EPFR concentration and general radical structure were determined with EPR spectroscopy. …

Experimental And Computational Studies Of Environmentally Persistent Free Radicals (Epfrs) Formation, Lucy W. Kiruri

LSU Doctoral Dissertations

The first part of the thesis investigates the use of theoretical quantum calculations for the study of EPFRs as the initial and fundamental step in the formation of polychlorinated dibenzo-p-dioxin and dibenzofuran. The computational model comprised of density functionals (B3LYP, PBE1PBE, and M06) and two types of basis set namely: LANL2DZ for all atoms and GEN (LANL2DZ for metals and aug-cc-pVDZ for non-metals). Full mechanisms of EPFRs formation over (CuO)1-8, and aluminum oxide clusters were studied. The most stable intermediates and products have been determined and compared to available experimental data. In case of (CuO)1-8 clusters, the small clusters are …

Phase Behavior Of Silica-Polypeptide Hybrid Particles Immersed In Cholesteric Liquid Crystals, Melissa Elizabeth Collins

LSU Doctoral Dissertations

Silica-polypeptide hybrid particles are core-shell colloids. Established synthetic methods ensure uniformly sized cores and provide the ability to have magnetic or fluorescent inclusions. The polypeptide shell is highly functional in its ability to respond to stimuli through changes in shape and formation of ordered phases above certain concentrations or temperatures. This research explores the interactions of hybrid particles mixed with polypeptides dispersed in solution. Depletion theory, which considers mainly entropic interactions between particles, can be used to explain the phase behavior of colloids. Due to the chemical similarities between the polypeptides attached to the surface and those free in solution, …

Searching For New Gamma-Ray Sources Using Earth Occultation Imaging With The Cgro/Burst And Transient Source Experiment, Yuan Zhang

LSU Doctoral Dissertations

Earth occultation provides a means of monitoring gamma-ray sources over the entire sky. This technique has been demonstrated with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) active from 1991 to 2000, and is now being used with the Gamma-ray Burst Monitor (GBM) instrument on the Fermi mission. Although this approach provides a powerful wide field monitoring capability, the BATSE and GBM implementations of this technique have so far limited the analysis to a catalog of previously identified sources. In this dissertation, an indirect imaging method is described that permits searching for unknown sources …

Effects Of Stress And Water Saturation On Seismic Velocity And Attenuation In Near Surface Sediments, James Michael Crane

LSU Doctoral Dissertations

Seismic investigation in the near-surface is complicated by highly attenuating media, large interparticle stresses, and variable water saturation, so new tools and methodology are necessary to understand the relationships between velocity, attenuation, and physical properties of the propagating media. A new shear wave source is developed for investigation of gas-charged, organic-rich sediments because compressional waves are highly attenuated and currently available sources are inadequate. The new source compares favorably to a traditional hammer impact source, producing a signal with a broader-band of frequencies (30-100Hz cf. 30-60Hz) and signal-to-noise ratios (SNR) equivalent to ~3 stacked hammer blows to the hammer impact …

Multiplicity Formulas For Perverse Coherent Sheaves On The Nilpotent Cone, Myron Minn-Thu-Aye

LSU Doctoral Dissertations

Arinkin and Bezrukavnikov have given the construction of the category of equivariant perverse coherent sheaves on the nilpotent cone of a complex reductive algebraic group. Bezrukavnikov has shown that this category is in fact weakly quasi-hereditary with Andersen--Jantzen sheaves playing a role analogous to that of Verma modules in category O for a semi-simple Lie algebra. Our goal is to show that the category of perverse coherent sheaves possesses the added structure of a properly stratified category, and to use this structure to give an effective algorithm to compute multiplicities of simple objects in perverse coherent sheaves. The algorithm is …

The Development Of Capillary Electrophoresis Assays To Study Enzyme Inhibition, Sherrisse Kelly Bryant

LSU Doctoral Dissertations

New methods for studying enzymes and enzyme inhibition using capillary electrophoresis (CE) were developed and applied. Because CE is a separation technique, spectral interference is minimized by separation of substrates, products, inhibitors, and sample matrix components. Two types of CE enzyme assays were explored in this dissertation research. The first assay was based on optically gated vacancy capillary electrophoresis (OGVCE) with laser-induced fluorescence detection (LIF). This approach involves periodic photobleaching of fluorescent substrates and products. The initial goal of the study was to develop an assay for adenosine deaminase (ADA). A fluorescent ADA substrate was synthesized; however, the substrate was …

Program Analysis : Termination Proofs For Linear Simple Loops, Hongyi Chen

LSU Doctoral Dissertations

Termination proof synthesis for simple loops, i.e., loops with only conjoined constraints in the loop guard and variable updates in the loop body, is the building block of termination analysis, as well as liveness analysis, for large complex imperative systems. In particular, we consider a subclass of simple loops which contain only linear constraints in the loop guard and linear updates in the loop body. We call them Linear Simple Loops (LSLs). LSLs are particularly interesting because most loops in practice are indeed linear; more importantly, since we allow the update statements to handle nondeterminism, LSLs are expressive enough to …