Physical Sciences and Mathematics Commons^™

Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl

Faculty Publications

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends …

Time-Dependent Neutral Stochastic Functional Differential Equations Driven By A Fractional Brownian Motion, B Boufoussi, S Hajji, E Lakhel

Communications on Stochastic Analysis

No abstract provided.

A Stochastic Transport Theorem, Pedro Catuogno, Simão N Stelmastchuk

Communications on Stochastic Analysis

No abstract provided.

Mean-Field Limit Versus Small-Noise Limit For Some Interacting Particle Systems, Samuel Herrmann, Julian Tugaut

Communications on Stochastic Analysis

No abstract provided.

Stochastic Integral Representations Of F-Selfdecomposable And F-Semi-Selfdecomposable Distributions, Nadjib Bouzar

Communications on Stochastic Analysis

No abstract provided.

Solution Of The Dirichlet Problem For A Linear Second-Order Equation By The Monte Carlo Method, José Villa-Morales

Communications on Stochastic Analysis

No abstract provided.

Moments Estimates For Local Times Of A Class Of Gaussian Processes, Olga Izyumtseva

Communications on Stochastic Analysis

No abstract provided.

Probability Distributions And Orthogonal Polynomials Associated With The One-Parameter Fibonacci Group, Andreas Boukas, Philip Feinsilver, Anargyros Fellouris

Communications on Stochastic Analysis

No abstract provided.

On The Second Fundamental Theorem Of Asset Pricing, Rajeeva L Karandikar, B V Rao

Communications on Stochastic Analysis

No abstract provided.

Influence Of The Mississippi River On Pseudo-Nitzschia Spp. Abundance And Toxicity In Louisiana Coastal Waters, Sibel Bargu, Melissa M. Baustian, Nancy N. Rabalais, Ross Del Rio, Benjamin Von Korff, R. Eugene Turner

Faculty Publications

The presence of domoic acid (DA) toxin from multiple species of Pseudo-nitzschia is a concern in the highly productive food webs of the northern 1,* 2,3 2 1 1,4 1 1 2 3 4 Gulf of Mexico. We documented the Pseudo-­nitzschia presence, abundance, blooms, and toxicity over 3 years along a transect ∼100 km west of the Mississippi River Delta on the continental shelf. Pseudo-nitzschia were present throughout the year and occurred in high abundances (>10 cells l ) in the early spring months during high Mississippi River (MSR) flow (∼20,000 m s ) but were most abundant ( …

Density Functional Theory Calculations On The Doping Sequence Of Mnxfen(1-X)Ge, Jordan C. Ball

Honors Theses

No abstract provided.

Size-Dependent Top-Down Control On Phytoplankton Growth By Microzooplankton In Eutrophic Lakes, Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner

Faculty Publications

We hypothesized that the grazing on phytoplankton by the microzooplankton community is size-dependent and, therefore, the top-down control on phytoplankton by microzooplankton community could be one possible mechanism explaining why small phytoplankton become less abundant than large phytoplankton in eutrophic waters. We tested this hypothesis using the dilution method to measure microzooplankton grazing rates and phytoplankton growth rates in the eutrophic waters of the Barataria estuary, southeastern Louisiana. Microzooplankton grazing rates on the slower growing, small phytoplankton (\5 lm) were higher than on the large phytoplankton ([20 lm) which had relatively faster growth rates. The proportional loss of the small, …

Twisted Reflection Positivity, Mostafa Ahmad Hayajneh

LSU Doctoral Dissertations

Reflection positivity has several applications in both mathematics and physics. For example, reflection positivity induces a duality between group representations. In this thesis, we coin a new definition for a new kind of reflection positivity, namely, twisted reflection positive representation on a vector space. We show that all of the non-compactly causal symmetric spaces give rise to twisted reflection positive representations. We discover examples of twisted reflection positive representations on the sphere and on the Grassmannian manifold which are not unitary, namely, the generalized principle series with the Cosine transform as an intertwining operator. We give a direct proof for …

Properties Of Polynomial Identity Quantized Weyl Algebras, Jesse S. F. Levitt

LSU Doctoral Dissertations

In this work on Polynomial Identity (PI) quantized Weyl algebras we begin with a brief survey of Poisson geometry and quantum cluster algebras, before using these as tools to classify the possible centers of such algebras in two different ways. In doing so we explicitly calculate the formulas of the discriminants of these algebras in terms of a general class of central polynomial subalgebras. From this we can classify all members of this family of algebras free over their centers while proving that their discriminants have the properties of effectiveness and local domination. Applying these results to the family of …

A Direct Study Of 20ne(Alpha,P)23na With The Helical Orbit Spectrometer (Helios), Jianping Lai

LSU Doctoral Dissertations

Type Ia Supernovae are thermonuclear explosions that occur on CO white dwarfs in binary systems, completely disrupting the system. While the exact progenitor of these events is unclear, there have been several studies exploring the nucleosynthesis that drives these stellar explosions. These studies have shown that a handful of reactions have a significant effect on Type Ia Supernova nucleosynthesis, specifically 12C(alpha, gamma), 12C+12C, 20Ne(alpha, p), 20Ne(alpha, gamma), and 30Si(p, gamma). While the 20Ne(alpha,p)23Na reaction has been shown to be one of the five most influential reactions, it has not been directly been measured at astrophysically relevant energies. We performed direct …

Application Of Biomass Derived Materials In Nanocomposites And Drilling Fluids, Kunlin Song

LSU Doctoral Dissertations

Tar is inevitably produced from biomass thermochemical processes, and is often disposed as an industrial waste, leading to environmental pollution. As a result of its high carbon content, tar was expected to be a promising precursor for manufacturing carbon materials. Consequently, low-cost porous carbon nanofibers (CNFs) using tar, polyacrylonitrile (PAN), and silver nanoparticles was fabricated through electrospinning and subsequent stabilization and carbonization processes. The continuous electrospun nanofibers were obtained with diameters ranging from 392 to 903 nm. The addition of biomass tar resulted in increased fiber diameters, reduced thermal stabilities, and slowed cyclization reactions of PAN in the as-spun nanofibers. …

Direct Measurements Of Nuclear Reactions In Hot Stellar Environments, Kevin Thomas Macon

LSU Doctoral Dissertations

Understanding the origins of intermediate mass nuclei requires accurate knowledge of nuclear reaction rates. This thesis addresses two projects targeting measurements of nuclear cross sections relevant in hot astrophysical environments. Direct measurements of neutron capture on ⁶⁷Zn and ⁶⁸Zn were performed using the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center (LANSCE). A new ⁶⁸Zn(n,&gamma) cross section in the neutron energy range from 150 eV to 850 keV and Maxwellian-Averaged Cross Sections from 20 keV-100 keV are presented along with the details of the analysis. These reaction rates are important for …

Vegetation Influences Microbial Community Structure And Methane Emissions In Southeastern Louisiana Wetlands, Anthony Jason Rietl

LSU Doctoral Dissertations

Methane has a warming potential 28 times that of carbon dioxide and has been increasing in the Earth’s atmosphere since 1750. An understanding of the dynamics of methane emissions from natural sources is becoming increasingly important as we may need to mitigate emissions from these sources in the future to help reduce the effects of climate change. Wetlands are the single largest natural source of methane; however, little attention has been given to how plant species, biota, and interactions between above and belowground communities and microbial communities may affect methane emissions. First, microbial community structure and function was assessed for …

Geologic Extremes Of The Nw Himalaya: Investigations Of The Himalayan Ultra-High Pressure And Low Temperature Deformation Histories, Dennis Girard Donaldson

LSU Doctoral Dissertations

This dissertation focuses on two extremes of orogenic development in the Himalaya: the timing of early ultra-high pressure related tectonics and the subsequent emplacement of the high grade Greater Himalayan Crystallines. The Himalayan orogeny is one of if not the best example of ongoing collisional systems, marked by the ongoing convergence of the Indian and Asian continents. The presence of coesite in the Tso Morari complex respresents subduction of the Indian continental crust to ultrahigh-pressure (UHP) conditions. However, the timing of UHP metamorphism is debated, creating an uncertainty in the calculation of subduction and exhumation rates. Petrologic and geochronologic analyses …

Method Of The Riemann-Hilbert Problem For The Solution Of The Helmholtz Equation In A Semi-Infinite Strip, Ashar Ghulam

LSU Doctoral Dissertations

In this dissertation, a new method is developed to study BVPs of the modified Helmholtz and Helmholtz equations in a semi-infinite strip subject to the Poincare type, impedance and higher order boundary conditions. The main machinery used here is the theory of Riemann Hilbert problems, the residue theory of complex variables and the theory of integral transforms. A special kind of interconnected Laplace transforms are introduced whose parameters are related through branch of a multi-valued function. In the chapter 1 a brief review of the unified transform method used to solve BVPs of linear and non-linear integrable PDEs in convex …

A Conditioned Gaussian-Poisson Model For Default Phenomena, Tyler Brannan

LSU Doctoral Dissertations

We introduce a new model to study the behavior of a portfolio of defaultable assets. We refer to this model as the Gaussian-Poisson model. It builds upon one-factor Gaussian copula models and Poisson models (specifically Cox processes). Our model utilizes a random variable Y along with probability measures ℙ^• and ℙ^†. The measures ℙ^• and ℙ^† will act as market pricing measures and are obtained via conditioning. The random variable Y will act as a default descriptor.

We provide the distribution of Y under both ℙ^• and ℙ^†. We use a conditional …

Theory And Utility Of The Three Isotope Fractionation Relationship, Justin Alan Hayles

LSU Doctoral Dissertations

The field of isotope geochemistry began with the study of oxygen isotope geothermometry, most famously for carbonates. Traditionally oxygen isotope studies are only concerned with the relationship between one rare isotope, oxygen-18, and the common isotope, oxygen-16. In these cases, the abundance of the third stable isotope, oxygen-17 is ignored because for almost all terrestrial processes the 17O-16O relationship roughly scales with the 18O-16O relationship through a fractionation processes and is thought to not provide any new information. However, the discovery of large “mass independent” isotope effects for ozone chemistry has driven a multitude of uses for triple isotope relationships. …

Evolution Semigroups For Well-Posed, Non-Autonomous Evolution Families, Austin Keith Scirratt

LSU Doctoral Dissertations

The goal of this dissertation is to expand Berhard Koopman's operator theoretic global linearization approach to the study of nonautonomous flows. Given a system with states x in a set \Omega (the state space), a map t\to \gamma(t,s,x) (t\geq s \geq 0) is called a global flow if it describes the time evolution of a system with the initial state x \in \Omega at time t \geq s \geq 0. Koopman's approach to the study of flows is to look at the dynamics of the observables of the states instead of studying the dynamics of the states directly. To do …

Biomedical Applications Of Thiol-Acrylate Polymers, Leah Alyce Garber

LSU Doctoral Dissertations

The development of biocompatible polymers using thiol-acrylate Michael addition reactions between not only acrylates and thiols but also between amines and acrylates were demonstrated. The synthesis of an in situ tertiary amine catalyst initiates the propagation steps of the polymerization process by subsequently reacting with trimethylolpropane tris (3-mercaptopropionate) (TMPTMP). A few notable characteristics of this reaction are tunable gel times, the capability of reaching high polymer conversion and suitable mechanical strength. With addition of hydroxyapatite to the polymeric phase and foaming, a porous bone composite was produced. Further osteogenisis and in vivo work using the PETA-co-TMPTMP (HA) composite material was …

Garbage Collection For General Graphs, Hari Krishnan

LSU Doctoral Dissertations

Garbage collection is moving from being a utility to a requirement of every modern programming language. With multi-core and distributed systems, most programs written recently are heavily multi-threaded and distributed. Distributed and multi-threaded programs are called concurrent programs. Manual memory management is cumbersome and difficult in concurrent programs. Concurrent programming is characterized by multiple independent processes/threads, communication between processes/threads, and uncertainty in the order of concurrent operations. The uncertainty in the order of operations makes manual memory management of concurrent programs difficult. A popular alternative to garbage collection in concurrent programs is to use smart pointers. Smart pointers can collect …

An Investigation Of Environmentally Persistent Free Radical (Epfr) Formation In Contaminated Soils Using Surrogate-Based Model Systems, Ugwumsinachi Godwin Nwosu

LSU Doctoral Dissertations

Environmentally persistent free radicals (EPFRs) have recently attracted attention due to their properties that detrimental to the health of living organisms. Earlier studies devoted to the formation of combustion generated particulate matter (PM) showed that EPFRs formed as a result of the association of aromatic chlorinated hydrocarbons with transition metal centers. Based on our previous studies, the amounts of EPFRs formed at Superfund soil sites contaminated with pentachlorophenol (PCP) are ~30 times higher compared to those formed at the neighboring uncontaminated soil sites, showing that EPFR formation is not confined to combustion generated particle. In order to design viable remediation …

Studies Of The Properties Of Designed Nanoparticles Using Atomic Force Microscopy, Steve Matthew Deese

LSU Doctoral Dissertations

The purpose of the research in this dissertation was to elucidate the intrinsic properties of how nanoparticles are different from bulk materials. This was done by mechanical and electronic studies of the properties of designed nanoparticles using advanced modes of atomic force microscopy. Information relating to the work functions, contact potential difference, Young’s Moduli, elasticity, and viscoelasticity can be investigated using state-of-the-art atomic force microscope (AFM) experiments. Subsurface imaging of polystyrene encapsulated cobalt nanoparticles was achieved for the first time using Force Modulation Microscopy (FMM) in conjunction with contact mode AFM. Previously prepared sample of polystyrene coated cobalt nanoparticles were …

Fundamental Studies Of Humic Acid's Influence On Pollutant Toxicity To Aquatic Organisms, Rachel Dawn Deese

LSU Doctoral Dissertations

The main purpose of the research presented in this dissertation was to further understand the intricate and convoluted interactions between natural organic material, biological entities, and pollutants. This was achieved by utilizing humic acids (HAs) from differing sources, chemically modified humic acid, two biological entities (model biomembranes and Artemia Franciscana), and three types of pollutants (cations, surfactants, and carbon nanotubes). Fluorescence spectroscopy and model biomembranes were used to measure the change in HA’s ability to interact with the biomembranes in the presence of cations. Three differently sourced HAs, chemical modified HAs, and a range of cations were studied to elucidate …

Global A Priori Estimates And Sharp Existence Results For Quasilinear Equations On Nonsmooth Domains., Karthik Adimurthi

LSU Doctoral Dissertations

This thesis deals obtaining global a priori estimates for quasilinear elliptic equations and sharp existence results for Quasilinear equations with gradient nonlinearity on the right. The main results are contained in Chapters 3, 4, 5 and 6. In Chapters 3 and 4, we obtain global unweighted a priori estimates for very weak solutions below the natural exponent and weighted estimates at the natural exponent. The weights we consider are the well studied Muckenhoupt weights. Using the results obtained in Chapter 4, we obtain sharp existence result for quasilinear operators with gradient type nonlinearity on the right. We characterize the function …

Synthetic Efforts Towards The Synthesis Of Prostaglandin Pgf2a, Amy Marie Pollard

LSU Doctoral Dissertations

This dissertation describes strategies for synthesizing prostaglandin PGF2α. Our synthetic design creates the stereochemistry needed for the core and side chains of the target prostaglandin PGF2 alpha and PGF2 alpha synthase selective analogues while incorporating iodocyclization desymmetrization of acyclic dienes. A model system for 4-(iodomethyl)-6-methyl-1,3-dioxan-2-one was developed and synthesized for our target compound 4-(2-(benzyloxy)ethyl)-6-(iodomethyl)-5-vinyl-1,3-dioxan-2-one. Both compounds were successfully synthesized providing useful stereocenters for completing the synthesis of prostaglandin PGF2 alpha. Efforts toward total stereochemical control of PGF2α include the partial syntheses of bis-diethylanimedimethylsilane and of (4S,5S)-2-((1E,3E)-penta-1,3-dien-1-yl)-4,5-diphenyl-1,3-ditosyl-1,3,2-diazaborolidine.