Physical Sciences and Mathematics Commons^™

Stm And Arpes Studies Of Epitaxial Multilayer Ag On Cu(110) And Ni(110), Weichang Zhao

LSU Doctoral Dissertations

Ag nanostructures of multilayer coverages (< 30 monolayers) epitaxially self-assembled on Cu(110) and Ni(110) have been explored by scanning tunneling microscopy (STM), angle-resolved photoelectron emission spectroscopy (ARPES), and low energy electron diffraction (LEED). We have studied varied nanostructure morphologies self-assembled depending on different deposition/annealing processes and coverages, their atomic structures, growth behaviors and mechanisms, and the electronic structures of nanowires. At nominal coverages of 1.2 ML < ¦È < ~10 ML, there are two epitaxial structures on Cu(110) and Ni(110). One is a Ag(110) multilayer film, which has a superstructure with lateral periodic units of eight and three/four substrate lattice constants along [¯110] and along [001] respectively. Another is that of Ag(110) nanowires surrounded by pseudohexagonal Ag(111) monolayer. The Ag(110) nanowires are triangular in cross section. The two side surfaces are faceted and the long axis is atomically straight along [¯110]. Typical lengths are within the range of 100 ~ 5000 Å, widths 70 ~ 300 Å, side slopes 10 ~ 30º, and heights 5 ~ 60 Å. The Ag nanowires present extraordinary anisotropy with observed aspect ratios (length:width) of up to 20:1. The Ag(110) nanowires are in-registry with the substrate along [001], but not along [¯110]. At coverages of ~ 10 ML < ¦È < ~25 ML, there also exist two different nanostructures, the nanowires and a Ag(110) atomically-flat film with some pits as deep as down to the substrate and a one-dimensional quasiperiodic superstructure along [001]. There are two basic separations of the superstructural stripes: one is three lattices wide (~11 Å) and the other is two lattices wide (~7 Å). Both of nanostructures are stable at temperature up to at least 200 ¡ãC and not inter-transformable. The growth of the nanowires is driven by the elastic strain mechanism, but the growth of the atomically-flat film is driven by electronic growth mechanism originated from the electron quantum confinement in the vertical direction of the film. The ARPES of the nanowires shows dispersion in the vertical and the [¯110] directions, but no dispersion in the [001] direction because of the limited width (~ 200 Å).

Microelectrophoresis System Utilizing Conductivity Detection Analyzing Biological Molecues, Michelle Galloway

LSU Doctoral Dissertations

Microfabrication technology has proven to be a valuable tool for creating polymer-based devices utilized in chemical and biochemical assays. Although, reducing the size of the device allows for short analysis times and reduces the reagent demand to ultrasmall volumes (< 1 nanoliter), a resulting consequence is the constraint placed on the limits of detection associated with the detector hardware required for readout. To overcome such constraints, laser-induced fluorescence (LIF) is often employed as a detection method as it provides low detection limits, which approach the single molecule level. Unfortunately, most LIF systems do not offer the benefits of miniaturization, with the detector components (i.e. laser, optics, filters) often times requiring a much larger footprint compared to the device. Another readout strategy that has shown promise for these devices is conductivity detection. Detection can be accomplished using either conventional-size or microfabricated electrodes, which can be integrated on the device. Although conductivity has been commonly used to detect inorganic or small organic species, the potential for detection of biological species has received little attention. In this work, an integrated conductivity detector was developed for the analysis of amino acids, peptides, proteins, and oligonucleotides (double-stranded DNA). Using the detector, mass detection sensitivities in the range of 10^-18 - 10^-21 moles were achieved. To increase the throughput of the system a state-of-the-art, multichannel device with a conductivity array detector was devised. This device, which consists of a 16-channel fluidic network and a printed circuit board, is geared toward automating three-processing steps onto a single fluidic platform including purification, preconcentration and detection for downstream parallel processing.

The Radon-Gauss Transform, Vochita Mihai

LSU Doctoral Dissertations

Gaussian measure is constructed for any given hyperplane in an infinite dimensional Hilbert space, and this is used to define a generalization of the Radon transform to the infinite dimensional setting, using Gauss measure instead of Lebesgue measure. An inversion formula is obtained and a support theorem proved.

Electronic Structural Investigations Of Bi- And Polymetallic Complexes Using Quantum Mechanical Methods, Zakiya Sheni Wilson

LSU Doctoral Dissertations

Understanding the dynamics influencing chemical reactivity is essential for properly exploiting matter into more useful purposes. In that manner, computational chemistry is a tool frequently used to study chemical properties at the most intimate level, i.e. the single molecule.

With this work, we probe the chemistry governing a variety of multi-faceted bi- and polymetallic compounds. To date our research consists of four major projects: bimetallic rhodium-catalyzed hydroformylation and aldehyde-water shift hydrocarboxylation catalysis; a novel linear M-H-M interaction in a bridged bis(dialkylphosphino)methane complex of nickel; and CeBe₁₃, a heavy fermion conductor. Computational investigations on these systems allow us to …

Quantification Of Marine Sediment Properties From Planar And Volumetric Pore Geometries, Allen Hagerman Reed

LSU Doctoral Dissertations

Pore geometry and topology are important determinants of sediment physical properties, such as porosity and permeability. They also influence processes that occur in the sediment, such as acoustic propagation, attenuation, and dispersion, single- and multi-phase fluid flow, and hydrodynamic dispersion. This study uses images to evaluate pore geometry and topology of ooid (subspherical particles) and siliclastic (angular quartz) sand that was collected from the marine environment south of Bimni Bahamas and Ft. Walton Beach, FL, respectively. Image analysis techniques and predictive tools enable insight into the relationships among sediment pore geometry, topology, and physical properties for these differently shaped sands. …

The Syntheses Of Novel Indicators And Materials For Chiral Separation, Rolanda Johnson

LSU Doctoral Dissertations

The colorimetric properties of resorcinarene solutions had not been fully investigated since von Baeyer's initial synthesis. We find that the solutions containing resorcinarene macrocycles develop color upon heating or standing. In the presence of saccharides, these solutions exhibit significant color changes which are readily observable by visual inspection. We determined that the solution color is due to macrocycle ring opening and oxidation. The optical responses to saccharides are due to complexation of the sugar with the acyclic chromophores. We have applied these mechanistic insights towards the challenging problems of the visual detection of saccharides and other important biologically analytes. In …

Address Optimizations For Embedded Processors, Sai Pinnepalli

LSU Doctoral Dissertations

Embedded processors that are common in electronic devices perform a limited set of tasks compared to general-purpose processor systems. They have limited resources which have to be efficiently used. Optimal utilization of program memory needs a reduction in code size which can be achieved by eliminating unnecessary address computations i.e., generate optimal offset assignment that utilizes built-in addressing modes. Single offset assignment (SOA) solutions, used for processors with one address register; start with the access sequence of variables to determine the optimal assignment. This research uses the basic block to commutatively transform statements to alter the access sequence. Edges in …

Pattern-Based Model Transformation: A Metamodel-Based Approach To Model Evolution, Sheena Judson Miller

LSU Doctoral Dissertations

Software systems continue to grow in complexity at a rapid pace, creating systems that are complex to build and evolve. The problems that accompany changes in requirements, system upgrades, and error correction produce a desire for software evolution methods that increase the efficiency and effectiveness of adapting complex software to changes. As software systems evolve, design models must be modified to accommodate the required changes. Techniques that control the changes to models in a systematic manner are a key to model evolution. A process that improves the ability to effectively modify a design, thereby enhancing design qualities, supports the need …

Leaf Litter Processing By Macrodetritivores In Natural And Restored Neotropical Mangrove Forests, Gary Eugene Raulerson

LSU Doctoral Dissertations

Knowledge of mangrove litter dynamics is crucial to an understanding of the energetic links between mangrove ecosystems and nearby estuaries and coastal waters. Previous research into the role played by macrodetritivores in Neotropical mangrove litter processing has been contradictory. This study used leaf tethering to examine the effects of macrodetritivores on initial rates of mangrove litter degradation in South Florida, USA. Leaf litter dynamics experiments were run in both natural and restored mangrove forests to assess functionality of the restoration projects. Although less important than in some other parts of the world (e.g., the Indo-Pacific), macrodetritivores played a significant role …

Applications Of The Titanium Catalyzed Cyclocarbonylation Towards Natural Product Syntheses, Jongtae Yang

LSU Doctoral Dissertations

Recently an efficient methodology, a hetero Pauson-Khand reaction, based on titanium-catalyzed cyclocarbonylation of tethered enals for the general preparation of ¥ã-butyrolactone rings, which are typically embedded in polycyclic systems of many natural products was reported. To demonstrate this new strategy, the total syntheses of the natural products asteriscanolide and ginkgolide were investigated. The first part of this work is dedicated to synthetic efforts toward the total synthesis of asteriscanolide. Approaches highlighted by the [2,3]-Wittig rearrangement, the thermal silyloxy-Cope rearrangement, and a titanium-catalyzed cyclocarbonylation, which is the pivotal step to afford the ¥ã-butyrolactone ring. This study firmly established the utility of …

Investigation Of Structure-Property Relationships Of Heavy-Fermion Materials, Robin Macaluso

LSU Doctoral Dissertations

This work focuses on how local structural features influence large effective masses, magnetism, and superconductivity that are yet to be understood in heavy-fermion materials. Three sets of structurally-related materials are discussed in light of dimensionality, layering effects, choice of transition metal, coordination, and structural distortions: LnnMIn3n+2 (Ln = La, Ce; n = 1, 2, ‡; M = Co, Rh, Ir), CePdGa6, and Ce2PdGa12, and CeNiSb3. The LnnMIn3n+2 (n = 1, 2, ‡; Ln = La, Ce; M = Rh, Ir) intergrowth homologous series presents a unique opportunity to study structure-property relationships. LnnMIn3n+2 (Ln = La, Ce; n = 1, 2; …

Spatial Analyses And Growth Of Trees In Selected Bottomland Hardwood Stands, Luben D. Dimov

LSU Doctoral Dissertations

Sustainable management and conservation of the extensive bottomland hardwood forest resource in the southeastern U.S. requires a good understanding of basic structural and competitive relationships within these forests. To gain an insight into these relationships, plot information from stands in Arkansas, Louisiana, and Mississippi were analyzed. The effects of individual tree attributes, distance-dependant, and distance-independent competition measures on 5-yr radial growth of red oak crop trees were examined. Selected species included cherrybark oak (Quercus pagoda Raf.), water oak (Q. nigra L.), and Nuttall oak (Q. nuttallii Palmer). Spatial continuity of tree variables was explored through geostatistical analysis. Finally, spatial distribution …

Protein Aggregation Studies: Inhibiting And Encouraging Β-Amyloid Aggregation, Jed Paul Aucoin

LSU Doctoral Dissertations

This work demonstrates peptide-based aggregation mediation of fibril forming peptides, notably β-amyloid (1-40), Aβ_1-40. To achieve the goals of this work, Aβ_1-40 aggregation was governed by ionic strength, temperature, and pH. After controlling and reproducing Aβ_1-40 aggregate formation (fibrils), each peptide-based aggregation mediator was evaluated for its ability to self-aggregate and to possess surface-active properties. The incorporation of these mediators in Aβ_1-40 solutions changed the surface tension and produced aggregate complexes of mediator and Aβ_1-40. Evidence that Aβ_1-40 fibril formation may be mediated by disorder-to-order transitions has been observed by layer formation …

Tuning Polymeric Chiral Surfactants For Enhanced Enantiomeric Recognition In Micellar Electrokinetic Chromatography, Jepkoech Tarus

LSU Doctoral Dissertations

The research presented in this dissertation involves the synthesis, modification, characterization, and the application of polymeric surfactants in micellar electrokinetic chromatography (MEKC). Sodium undecenoyl-L-Leucinate (L-SUL) was synthesized and modified by use of alkali metal counterions, alcohols, and Triton X-102. Characterization of the modified poly-L-SUL was performed in order to elucidate the structural changes on the surfactants by use of four techniques. While surface tensiometry was used for the determination of the critical micelle concentration (cmc), fluorescence measurements were used for the determination of the polarity of the modified polymeric surfactants. The information about the size of the polymeric surfactants was …

Spectroscopic And Synthetic Studies Relating To A Dirhodium Hydroformylation Catalyst, Petia Gueorguieva Gueorguieva

LSU Doctoral Dissertations

The main goal of this dissertation research was to further study and characterize our bimetallic hydroformylation catalyst, rac-[Rh₂(nbd)₂(et,ph-P4)](BF₄)₂, and to fully identify the catalytically inactive mono- and dirhodium complexes formed upon fragmentation of the catalyst under hydroformylation conditions. Various in situ NMR methods such as 1D ¹H and ³¹P, and 2D COSY, HMBC, and HMQC were employed and indicated the formation of the key catalyst, [rac-Rh₂H₂(μ-CO)₂(CO)₄(et,ph-P4)]²⁺, 4, and a number of other Rh-phosphine species on and off the catalytic cycle. …

Orbit Structure On The Silov Boundary Of A Tube Domain And The Plancherel Decomposition Of A Causally Compact Symmetric Space, With Emphasis On The Rank One Case, Troels Roussau Johansen

LSU Doctoral Dissertations

We construct a G-equivariant causal embedding of a compactly causal symmetric space G/H as an open dense subset of the Silov boundary S of the unbounded realization of a certain Hermitian symmetric space G₁/K₁ of tube type. Then S is an Euclidean space that is open and dense in the flag manifold G₁/P', where P' denotes a certain parabolic subgroup of G₁. The regular representation of G on L²(G/H) is thus realized on L²(S), and we use abelian harmonic analysis in the study thereof. In particular, …

Synthesis, Characterization And Study Of Novel Reagents For The Detection Of Saccharides And Amino Acids, Nadia Nadette St. Luce

LSU Doctoral Dissertations

The design of synthetic receptors for the recognition and sensing of saccharides and amino acids is currently a major challenge. This is due to inherent structural similarity and a lack of chromophoric or fluorophoric properties of these compounds. The synthesis and study of novel detection agents for bioactive molecules as well as mechanistic studies are presented herein. The elucidation of the mechanism by which tetraarylboronic acid resorcinarene interact with sugar molecules and promote a solution color change is explored. This vast collaborative study, reveals that DMSO solutions of boronic acid functionalized resorcinarene macrocycles afford visual color changes upon heating or …

Attachment Of Oligonucleotide Probes To Polymer Biochips And Its Application For The Detection Of Point Mutations, Yun Wang

LSU Doctoral Dissertations

This dissertation is on the fabrication of polymer-based microfluidic arrays for the detection of genetic mutations. Poly(methyl methacrylate) was chosen as one of the polymer substrate materials due to its low background noise, low adsorption of biomolecules, and low assembly temperature. The surface modification of polymer substrates for covalent attachment of oligonucleotide probes, the construction of fluidic channels/arrays, and hybridization kinetics will be covered. As an example of the application, point mutation detection using immobilized arrays constructed in microfluidic devices will be demonstrated. The PMMA surface was derivatized with N-lithioethylenediamine solution to introduce amine groups, which were utilized for the …

Class Groups And Norms Of Units, Costel Ionita

LSU Doctoral Dissertations

Our object of study is relative quadratic extensions of algebraic number fields. In 'Class Number Parity', the authors P.E. Conner and J. Hurrelbrink study in detail the cases of real and CM-extensions. In this paper we generalize some of the results without any assumption on the type of the relative quadratic extension.

A Distributed Quadtree Dictionary Approach To Multi-Resolution Visualization Of Scattered Neutron Data, Rion Dooley

LSU Doctoral Dissertations

Grid computing is described as dependable, seamless, pervasive access to resources and services, whereas mobile computing allows the movement of people from place to place while staying connected to resources at each location. Mobile grid computing is a new computing paradigm, which joins these two technologies by enabling access to the collection of resources within a user's virtual organization while still maintaining the freedom of mobile computing through a service paradigm. A major problem in virtual organization is needs mismatch, in which one resources requests a service from another resources it is unable to fulfill, since virtual organizations are necessarily …

Comparison Studies Of The Mechanistic Formation Of Polyhalogentaed Dibenzo-P-Dioxins And Furans From The Thermal Degradation Of 2-Bromophenol And 2-Chlorophenol, Catherine Spearing Evans

LSU Doctoral Dissertations

Emissions of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) from hazardous waste incinerators, and many other sources for combustion have been considered environmentally hazardous and a major health threat. Recently, a growing number of materials containing brominated hydrocarbons, commonly used flame retardants, have been disposed in municipal and hazardous waste incinerators. This results in the increased potential for formation of PBDD/Fs and other hazardous combustion by-products. In contrast to chlorinated hydrocarbons, the reactions of brominated hydrocarbons have been studied only minimally. In fact, studies have shown that brominated phenols form higher yields of PBDD/Fs than the …

Dynamics Of Complex Polymer Solutions: Putting Diffusion To Work And Exploring Rigid Rod Diffusion, Garrett John Doucet

LSU Doctoral Dissertations

This dissertation is concerned with random coil and rodlike polymer diffusion in complex solutions. The development of fluorescence photobleaching recovery, FPR, as a technique to determine polymer molecular weight distributions by measuring the diffusion distribution and converting it to a molecular weight distribution using a calibration curve is first covered. Fluorescently tagged probes were individually dissolved in polymer solutions at negligible amounts and measured with FPR to construct the calibration curve of self-diffusion vs. molecular weight. Once calibration curves were constructed, bimodal distributions were separated using the matrices corresponding to the calibration curves. The diffusion of the probes and separation …

Application Of Disturbance Theory To Assess Impacts Associated With A Three-Dimensional Seismic Survey In A Freshwater Marsh In Southwest Louisiana, Aaron Stuard Bass

LSU Doctoral Dissertations

This study examined various practical and theoretical aspects of disturbance in a coastal wetland marsh in southern Louisiana. A literature review approached disturbance ecology from both practical and theoretical perspectives and assessed its applicability to developing broad predictive models. However, specific knowledge of environmental variables, competitive relationships, and the interactive effects of multiple disturbances are required for meaningful usage of these models. The Lacassine National Wildlife Refuge (LNWR) proved to be an ideal laboratory to test various aspects of ecological disturbance theory. I found that the primary disturbances affecting the LNWR have been hurricanes, droughts, water-level manipulations, prescribed burning, oil …

New Insights Into The Binding Site Formation And The Performance Of Molecularly Imprinted Polymers, Hyunjung Kim

LSU Doctoral Dissertations

Molecularly imprinted polymers (MIPs) are finding important applications in the field of separation science, catalysis, sensor, and immunoassays. To optimize the performance of the MIPs, it is essential to understand the underlying mechanism of the process. This research focuses on understanding binding site formation and performance, and improvement of the MIPs. Chapter 1 introduces the concept of the MIPs, and binding isotherm and affinity distribution of heterogeneous binding sites in the MIPs. Chapter 2 describes fundamental studies conducted to understand the binding site formation of the MIPs. The number of binding sites (N) and the number average association constant (Kn) …

Modeling Longleaf Pine (Pinus Palustris Mill) Wood Properties Using Near Infrared Spectroscopy, Brian Kipling Via

LSU Doctoral Dissertations

This research demonstrated model development for important wood properties using near infrared spectroscopy (NIR); it considered the effect of outside sources of error, and the ability of NIR to measure fiber morphology. Strength, stiffness, and density were successfully modeled from wood samples taken throughout 10 longleaf (Pinus palustris Mill) trees. Principal components and multiple linear regression were compared for performance in prediction of density, strength, and stiffness. I found both modeling techniques to yield similar prediction accuracies. However, I found that density could be estimated through Beer-Lambert’s law since the absorbance at all wavelengths increased with density. Also, 5 of …

On Qualitative Properties And Convergence Of Time-Discretization Methods For Semigroups, Mihaly Kovacs

LSU Doctoral Dissertations

In this dissertation we use functional calculus methods to investigate convergence and qualitative properties of time-discretization methods for strongly continuous semigroups. Stability, convergence, and preservation of contractivity (or norm-bound) of the semigroup under time-discretization is investigated in a Banach space setting. Preservation of positivity, concavity and other qualitative shape properties which can be described via positivity are treated in a Banach lattice framework. The use of the Hille-Phillips (H-P) functional calculus instead of the Dunford-Taylor functional calculus allows us to extend fundamental qualitative results concerning time-discretization methods and simplify their proofs, including results on multi-step schemes and variable step-sizes. We …

Asymptotic Laplace Transforms, Claudiu Mihai

LSU Doctoral Dissertations

In this work we discuss certain aspects of the classical Laplace theory that are relevant for an entirely analytic approach to justify Heaviside's operational calculus methods. The approach explored here suggests an interpretation of the Heaviside operator ${cdot}$ based on the "Asymptotic Laplace Transform." The asymptotic approach presented here is based on recent work by G. Lumer and F. Neubrander on the subject. In particular, we investigate the two competing definitions of the asymptotic Laplace transform used in their works, and add a third one which we suggest is more natural and convenient than the earlier ones given. We compute …

Non-Linear Development Of The Secular Bar-Mode Instability In Rapidly Rotating Neutron Stars, Shangli Ou

LSU Doctoral Dissertations

We present results from investigations of the nonlinear development of the secular bar-mode instability that is driven by gravitational radiation-reaction (GRR) forces in rotating neutron stars. Our fully three-dimensional hydrodynamical simulations have shown that, in the absence of any competing viscous effects, initially uniformly rotating axisymmetric n=1/2 polytropic stars with a ratio of rotational to gravitational potential energy greater than the critical limit are driven by GRR forces to a bar-like structure, as predicted by linear theory. The pattern frequency of the bar slows to nearly zero, that is, the bar becomes almost stationary as viewed from an inertial frame …

Foreland Basins: Lithospheric Flexure, Plate Strength And Regional Stratigraphy, John Londono

LSU Doctoral Dissertations

Foreland basin subsidence through time is reproduced in this study, as the flexure of an elastic beam in an inviscid fluid under the vertical stress, caused by discrete-distributed loads. Thus, seismostratigraphic data from the Timor Sea peripheral foreland basin, in northwestern Australia, and the Putumayo retroarc foreland basin in the Colombian Andes, are forward modeled, at chronostratigraphic intervals, to assess the evolving geodynamic conditions of the basins. Results show that the accommodation in foreland basins varies as the depositional basement is vertically adjusted according to the regionally isostatic compensation of the lithosphere. Distributed tectonic (thrust belts) and sedimentary loads that …

Synthesis And Characterization Of Superparamagnetic Silica--Homopolypeptide Composite Particles, Sibel Turksen

LSU Doctoral Dissertations

Hierarchical construction and characterization of core-shell composite particles of interest are presented. The research described shows interest in new types of polymers that provide chirality and responsiveness which have been ignored for so long. The general synthetic design described in this document can be readily used as a model for other systems. Core-shell composite systems of interest consist of silica or silica-coated cobalt cores grafted with a homopolypeptide shell, mostly poly(epsilon-carbobenzyloxy-L-lysine) or poly(gamma-benzyl-L-glutamate). Core particles were decorated with amino groups through a silylation reaction. The amino groups initiated the polymerization (with attachment) of N-carboxyanhydride (NCA) monomers, resulting in a homopolypeptide …