Digital Commons Network^™

An Integrated Drought Index (Idi) Incorporating Physical And Social Aspects, Rebecca L. Lanier

Master's Theses

The purpose of this research was to determine significant bio-physical (physical and environmental) and social variables that can be integrated into a drought index to predict areas susceptible to drought. Severe drought events are capable of causing millions of dollars in damage. The 1988 drought caused the United States approximately $40 billion in damage. Drought forecasting, modeling, and detection have, therefore, become imperative to understand the social, economic and environmental impacts of droughts, and also to explore how these impacts play a role in the occurrence of a drought. A number of drought indices widely used in the U.S. rely …

The Vascular Flora Of Wayne County, Mississippi, Daniel M. Mcnair

Master's Theses

The vascular flora of Wayne County, Mississippi, was surveyed from 2013–2015, and the species of native and naturalized plants are listed. In total, 1,135 species were identified from field collections, previously collected herbarium specimens, and field observations. These belong to 556 genera and 165 families. Four of these species represent first recorded occurrences in the state of Mississippi: Blyxa aubertii Rich., Gomphrena serrata Pav. ex Moq., Isoetes valida (Engelm.) Clute, and Polypogon interruptus Kunth. GPS coordinates are given for important collection sites representing the diversity of plant communities in the county. All voucher specimens from the survey are deposited in …

A Statistical Model For The Prediction Of Dissolved Oxygen Dynamics And The Potential For Hypoxia In The Mississippi Sound And Bight, Andreas Moshogianis

Master's Theses

Hypoxia events occur when dissolved oxygen concentrations fall below the minimum threshold (dissolved oxygen concentrations < 2 mg O₂ L^-1) necessary to avoid respiratory distress among aquatic organisms. In the Mississippi Sound and Bight, hypoxia is most prevalent from late-spring through late summer. Since hypoxia events can have dramatic effects on coastal fisheries, the spatial and temporal magnitude of hypoxia presents a clear threat to the productive fisheries in the northern Gulf of Mexico. Long-term hydrographic data were collected from eight sampling stations on a monthly basis from January 2009 to December 2011 along a cross-shelf transect from the mouth of …

Identities And Motives Of Naturalist Development Program Attendees And Their Relation To Professional Careers, Jennifer A. Mraz

Dissertations

In recent years, there has been much concern over the decline of biologists who actually identify themselves to be naturalists, which negatively impacts the field of conservation and the study of biology as a whole. This could result in a decrease in individuals who participate in naturalist-like activities, such as informal environmental education and environmental volunteerism. The purpose of my study was to determine what discourse identities were held by naturalist development program participants, how these discourse identities related to their volunteer motives in environmental settings, and how discourse identity related to professional careers. I defined identity through the lens …

Hybrid Aryl-Ether-Ketone And Hyperbranched Epoxy Networks, John Misasi

Dissertations

In this dissertation, relationships between chemical structures, cure kinetics and network architectures are correlated to bulk mechanical properties for novel, hybrid epoxy-amine networks. The work is split into two primary sections: the first is the synthesis and characterization of multifunctional glassy networks based on aryl-ether-ketone diamine curatives, while the second is based on the synthesis and characterization of hyperbranched epoxy polymers and their resulting networks.

Three aryl-ether-ketone (AEK) diamines of increasing molecular weights were synthesized and used to cure 4,4’-tetraglycidylether of diaminodiphenylmethane (TGDDM); the resulting networks were compared to 4,4’-diaminodiphenyl sulfone cured TGDDM. Architectural differences were created by varying cure …

Olfactory Enrichment In California Sea Lions (Zalophus Californianus), Mystera M. Samuelson

Dissertations

In the wild, California sea lions (Zalophus californianus) are exposed to a wide array of sensory information at all times. However, it is impossible for captive environments to provide this level of complexity. Therefore unique procedures and practices are necessary for the maintenance of physiological and psychological health in captive animals (Wells, 2009). This project aims to explore the behavioral effect of scent added to the environment, with the goal of improving the welfare of captive sea lions by introducing two scent types: 1.) Natural scents, found in their native environment, and 2.) Non-natural scents, not found in …

Macrobenthic Communities In The Northern Gulf Of Mexico Hypoxic Zone: Testing The Pearson-Rosenberg Model, Shivakumar Shivarudrappa

Dissertations

The Pearson and Rosenberg (P-R) conceptual model of macrobenthic succession was used to assess the impact of hypoxia (dissolved oxygen [DO] ≤ 2 mg/L) on the macrobenthic community on the continental shelf of northern Gulf of Mexico for the first time. The model uses a stress-response relationship between environmental parameters and the macrobenthic community to determine the ecological condition of the benthic habitat. The ecological significance of dissolved oxygen in a benthic habitat is well understood. In addition, the annual recurrence of bottom-water hypoxia on the Louisiana/Texas shelf during summer months is well documented.

The P-R model illustrates the decreasing …

Hydrogen Bond-Mediated Structural Order In Hydroxylated Bis-Mpa Dendritic Polymers: Experimental And Molecular Dynamics Simulation Study, Maliha N. Syed

Dissertations

Dendritic architectures are echoed throughout nature. While the significance of these pervasive patterns is not entirely clear, connections between their structures and physical properties are fascinating to contemplate. Particular interest has been paid to a family of synthetically manufactured and commercially available dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer. Composed of two hydroxyls and a carboxyl group, bis-MPA based structures hydrogen bond (H-bond) profusely. Given the high concentration and unique spatial orientation of end-groups, as well as the multitude of carbonyl, ester, and ether interior H-bond acceptors, a set of distinct H-bond organizations may be observed …

Asymmetric Synthesis Of Cα-Methyl-Γ- And Δ-Amino Acids From A Common Synthon And Evaluation Of Thionyl Chloride Assisted Peptide Esterifications, Emily Rose Vogel

Dissertations

C^α-methyl-γ- and δ-unnatural amino acids (UAAs) are important class of biomolecules used extensively as structural scaffolds, peptidomimetics, and in the development of pharmaceuticals. Due to steric congestion surrounding the quaternary center, asymmetric preparation of α,α-disubstituted UAAs are synthetically challenging. Herein, two methods for the synthesis of chiral synthons to prepare C^α-methyl-γ- and -δ-UAAs are reported. A crucial step in both strategies includes an enzymatic hydrolysis of prochiral malonic esters with pig liver esterase (PLE). The first method utilizes the Meyer Schuster rearrangement to prepare α,β-unsaturated diesters synthons, but the preparation of the precursor propargyl alcohol decomposes …

Recreation Ecology Of Colorado Fourteeners: An Assessment Of Trail Usage And Impacts, James C. Ewing

Master's Theses

The popularity of climbing Colorado’s 14,000 ft. peaks, or “Fourteeners”, has risen dramatically in recent years, raising important sustainability and management questions. Moreover, groups managing the peaks operate with major capital constraints so their efforts need to be informed, prioritized, and efficient. This paper gauges the dynamics of trail usage, explanatory variables, and recreational impacts across all 58 Fourteeners, and details evaluation adjustments that minimize error and produce results in-step with the resource management framework. Relative to a baseline study completed in 2005, substantial changes occurred in trail usage and impact dynamics. The greatest changes were concentrated on peaks previously …

Development Of Dual-Cure Hybrid Polybenzoxazine Thermosets, Jananee Narayanan Sivakami

Dissertations

Polybenzoxazines are potential high performance thermoset replacements for traditional phenolic resins that can undergo an autocatalytic, thermally initiated ring - opening polymerization, and possess superior processing advantages including excellent shelf-life stability, zero volatile loss and limited volumetric shrinkage. The simplistic monomer synthesis and availability of a wide variety of inexpensive starting materials allows enormous molecular design flexibility for accessing a wide range of tailorable material properties for targeted applications. Despite the fact, once fully cured, benzoxazines are difficult to handle due to their inherent brittleness, leaving a very little scope for any modifications. The motivation of this dissertation is directed …

Human Impacts On Fire In De Soto National Forest, Mississippi, U.S.A., Charles Raymond White

Master's Theses

Fire is a common occurrence in the longleaf pine (Pinus palustris) forests of the Southeast United States. Prescribed fire is used to manage these threatened ecosystems, but information regarding historical fire activity is unknown. My goals were to determine the historical fire regimes in De Soto National Forest (DSNF), southern Mississippi, and determine the influence of climate and land use history on fire activity at two study sites: Fern Gulley Ridge (FGR) and Death Scar Valley (DSV). The composite mean fire interval during the prescribed burning period (1980–2013) was 3.4 years. During settlements periods, fire intervals at FGR …

Lorentz Invariant Spacelike Surfaces Of Constant Mean Curvature In Anti-De Sitter 3-Space, Jamie Patrick Lambert

Master's Theses

In this thesis, I studied Lorentz invariant spacelike surfaces with constant mean curvature H = c in the anti-de Sitter 3-space H³₁(−c²) of constant curvature −c². In particular, I construct Lorentz invariant spacelike surfaces of constant mean curvature c and maximal Lorentz invariant spacelike surfaces in H³₁(−c²). I also studied the limit behavior of those constant mean curvature c surfaces in H³₁(−c²). It turns out that they approach a maximal catenoid in Minkowski 3-space E³₁ as c → …

The Distribution Of Dissolved Barium Along The U.S. Geotraces North Atlantic Transect: Impact Of Biogeochemical Processes, Circulation And Phase Association, Karen Renee Grissom

Master's Theses

During the last four decades, since the completion of the GEOSECS program, there has been a growing interest in the biogeochemical cycle of barium (Ba) due to its potential as a proxy for interpreting the geologic record. The typical barium distribution exhibits removal in the upper water column and regeneration at depth, consistent with its classification as a bio-intermediate element and similar to the nutrient-like profiles of silicic acid and alkalinity. To better constrain the uses of Ba, trace element clean samples were collected during the North Atlantic US GEOTRACES cruises.

The cycling of barium in the North Atlantic region …

Habitat Selection Of Gulf-Strain Striped Bass, Morone Saxatilis: Relationships To Dynamic Abiotic Environmental Characteristics Within The Biloxi River, Mississippi, Jennifer Lynne Green

Master's Theses

The purpose of this project was to provide insights about the short- and long-term patterns of habitat selection of Gulf-strain Striped Bass, Morone saxatilis, based on spatially and seasonally variable abiotic environmental characteristics (water temperature, dissolved oxygen (DO), salinity, specific conductivity, and pH) in the Biloxi River, MS system. Juvenile hatchery-reared and feral adult Gulf-strain Striped Bass were acoustically-tagged and continuously monitored via active and passive telemetry from November 2012 – June 2014. Each month the available abiotic environmental characteristics of 40 random locations within the Biloxi River, along with sub-habitat conditions occupied by acoustically-tagged Gulf-strain Striped Bass, were …

Biogeochemical Alteration Of Particulate Pyrogenic Organic Carbon (Pyc), Jason Matthew Stuart

Master's Theses

The resistance of plant derived pyrogenic organic carbon (pyC) to abiotic and biotic means of degradation has led to increased interest in the role of pyC as a potential carbon sink, as well as a strategy for sequestering atmospheric CO2 to mitigate excess carbon emissions. Though much research pertaining to the fundamental properties of pyC degradation have been performed in a controlled lab setting, there has been very little work regarding pyC degradation in a field setting where factors such as precipitation and temperature fluctuate seasonally. This work focuses on various degradation characteristics of two …

Morphology-Property Relationship For Binary Organic Thin Films, Alyssa Lynn Griffin

Master's Theses

Organic thin films can be readily mass-produced through solution-based fabrication methods including ink-printing and solution-casting because their light weight, flexibility, and inexpensive sources. Their applications range from organic field-effect transistors (OFET), organic solar cells (OSC), to organic light emitting diodes (OLEDs). Compared with pure component films, binary organic thin films (BOTF) allows for novel characteristics and specialized features to handle more demanding tasks. Due to the complex intermolecular interactions in BOTF, various microscopic phases with different morphological and electronic properties may be formed and this information is difficult to extract through conventional bulk measurements.

Organic thin films can be readily …

Naturalists’ Perspectives On The Use Of Mobile Technology During A Nature Hike, Aubin Marishka Radzewicz St. Clair

Master's Theses

Naturalists act as our link between scientific knowledge and the public’s understanding of natural history and conservation efforts. In order for them to succeed, they need access to reference materials as well as up-to-date information (Mankin, Warner, & Anderson, 1999). Incorporating mobile technology (i.e. tablets) into naturalists’ endeavors in natural history and environmental education can be used as supportive and educational tools. My project investigated how newly trained naturalists used tablet technology while leading groups of children on nature hikes. I investigated naturalists’ views on the use of mobile technology as a tool during the hikes. My research was guided …

On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo

Dissertations

Meshless methods utilizing Radial Basis Functions~(RBFs) are a numerical method that require no mesh connections within the computational domain. They are useful for solving numerous real-world engineering problems. Over the past decades, after the 1970s, several RBFs have been developed and successfully applied to recover unknown functions and to solve Partial Differential Equations (PDEs).
However, some RBFs, such as Multiquadratic (MQ), Gaussian (GA), and Matern functions, contain a free variable, the shape parameter, c. Because c exerts a strong influence on the accuracy of numerical solutions, much effort has been devoted to developing methods for determining shape parameters which provide …

Solution Of Nonlinear Time-Dependent Pde Through Componentwise Approximation Of Matrix Functions, Alexandru Cibotarica

Dissertations

Exponential propagation iterative (EPI) methods provide an efficient approach to the solution of large stiff systems of ODE, compared to standard integrators. However, the bulk of the computational effort in these methods is due to products of matrix functions and vectors, which can become very costly at high resolution due to an increase in the number of Krylov projection steps needed to maintain accuracy. In this dissertation, it is proposed to modify EPI methods by using Krylov subspace spectral (KSS) methods, instead of standard Krylov projection methods, to compute products of matrix functions and vectors. This improvement allowed the benefits …

Application Of A New Tree-Ring Based Drought Reconstruction Method At Multiple Forest Sites Across Indiana, U.S.A., Kayla Mechelle Pendergrass

Master's Theses

This thesis research used techniques of dendrochronology to investigate the efficacy of using multiple co-occurring species (MCOS) in a climate reconstruction model compared to a single species (SS) in four old-growth forests in Indiana: Pioneer Mothers Memorial Forest (PM), Donaldson Woods (DW), Hoot Woods (HW), and Lilly Dickey Woods (LD). The objectives of this study were to [1] evaluate the climate response of all chronologies (n = 19; 7 species) to determine the most appropriate climate variable for reconstruction and [2] determine if the MCOS model outperforms the SS model at each individual study site. Model comparison was conducted …

Assessing Biogeochemical Impacts And Environmental Conditions Associated With Cross-Shelf High Chlorophyll Plumes In The Northern Gulf Of Mexico, Erin Brooke Jones

Dissertations

The northern Gulf of Mexico is a complex marine system subject to episodic physical phenomena such as loop current eddies. Flow fields generated by these eddies can result in cross-shelf exchanges between riverine influenced shelf waters and the offshore water column. This study considers the impacts of high chlorophyll plumes (HCPs) resulting from cross-shelf exchanges to the bio-optical properties of affected waters and how these plumes are influenced by their environment. The seasonal, interannual and decadal chlorophyll cycles of the Gulf of Mexico and the northern Gulf of Mexico are described to provide context for evaluating the ecological effects of …

Polymerization Of Blocked Isocyanate Functional Polymer Surfaces And Post-Polymerization Modification By Thiol-Isocyanate Reactions, Chase A. Tretbar

Honors Theses

Direct polymerization of isocyanate-functional monomers has been achieved with controlled radical polymerizations (CRP) for precisely engineered modification platforms with highly reactive side chains. However, despite the success of these strategies, the inherent reactivity of isocyanates still leads to adverse side reactions, such as hydrolysis, that are difficult to suppress. Phenol, lactam, and oxime-based blocking agents have been used to limit the reactivity of isocyanates in applications such as multicomponent urethane coating systems. The reactivity of these blocked isocyanates can be restored by thermal deprotection of the blocking agent to achieve the desired reactions. In this work, we use blocked isocyanate-functional …

A Comparison Of Habitat And Geomorphic Changes On East Ship Versus Sand Islands Mississippi, 2007-2014, Carlton Peter Anderson

Master's Theses

ABSTRACT

A COMPARISON OF HABITAT AND GEOMORPHIC CHANGES ON EAST SHIP VERSUS SAND ISLANDS MISSISSIPPI, 2007-2014

by Carlton Peter Anderson

May 2015

The islands of the Mississippi-Alabama (MS-AL) barrier island chain along the micro-tidal northern Gulf of Mexico are highly dynamic coastal features subject to rapid changes in habitat, geomorphology, and elevation by natural and anthropogenic disturbances, such as hurricanes, subsidence, sea-level rise, and dredging activities. The purpose of this study was to compare elevation, total volume, habitat-type coverage, and short-term change between “naturally” formed East Ship Island and “man-made” Sand Island (Disposal-Area 10). This study used a combination of …

A Study On Photodegradation And The Fate Of Pyrogenic Carbon, John Thomas Howell

Master's Theses

Accounting for all possible sources of atmospheric CO₂ is a pressing issue today due to the increasing effects of climate change. Estimates suggested that on the order of 1.3 million tons of dissolved pyrogenic carbon (pyDOC) could be entering the northern Gulf of Mexico annually. Assessing the fate of pyDOC in aquatic systems is crucial to understanding ecosystem impacts and potential feedback to climate change. Current research indicates that despite a generally lower susceptibility to biodegradation than their unpyrolyzed equivalents, pyrogenic carbon is not environmentally inert. While the role of microorganisms on the fate and transformation …

Marine Snow Settling Velocities At An Oil Spill Site And A Control Site In The Northern Gulf Of Mexico, Clayton Hugh Dike

Master's Theses

After budgeting for response efforts and natural processes, over one million barrels of oil from the BP oil spill were unaccounted for. A hypothesis coined "The Dirty Blizzard" formed subsequent to observations of large and numerous oiled marine snow aggregates amidst the surface slick proposed that a large quantity of oil sank to depth via the aggregates. Having reached the seafloor, aggregates were subject to microbial degradation and to redistribution due to bottom currents. To assist in characterizing redistribution of particles near the seafloor, sediment traps, marine snow cameras, and acoustic Doppler current profilers (ADCPs) were deployed at two sites …

Geographical Analysis Of Hub City Transit, Joshua Adam Watts

Master's Theses

This study assess Hub City Transit, the public bus system of Hattiesburg, MS. Statistical analysis is used to determine how well the transit system serves low income areas of the city. A 0.5 mile buffer was applied to the bus routes to determine the coverage of the transit system. Areas of disorder along the routes were also assessed to analyze the landscape routes pass through. Lastly, an analysis of ridership on each route was performed to determine the most heavily used areas, as well as to assess where riders are going on each route.

The findings show that Hub City …

Procedural Content Generation: Using A.I. To Generate Playable Content, Osler Kendall Moore Jr.

Honors Theses

This thesis is about using Artificial Intelligence in regards to Procedural Content Generation to help try and avoid a deadlock scenario in a hypothetical dungeon exploring game. The deadlock scenario is essentially having a key being placed in a room that’s inaccessible to the player. An example of such a scenario would be if the key to room A being in Room B, the key to room B was in room A, and the player was in room C. The program generates the dungeon world with a random number of rooms inside it, each room also having a random number …

Modeling The Diffusion Of Heat Energy Within Composites Of Homogeneous Materials Using The Uncertainty Principle, Elyse M. Garon

Honors Theses

The purpose of this project is to model the diffusion of heat energy in one space dimension, such as within a rod, in the case where the heat flow is through a medium consisting of two or more homogeneous materials. The challenge of creating such a mathematical model is that the diffusivity will be represented using a piecewise constant function, because the diffusivity changes based on the material. The resulting model cannot be solved using analytical methods, and is impractical to solve using existing numerical methods, thus necessitating a novel approach.

The approach presented in this thesis is to represent …

Analysis Of The Mechanical Properties Of Dgebf/4,4’-Dds Thermoset Systems As A Function Of Cure Rate, Chase B. Thompson

Honors Theses

The relationship between macroscopic mechanical and thermal properties and ramp rate during cure of epoxy-amine systems consisting of the epoxide resin digylcidyl ether of bisphenol F (DGEBF, provided Hexion specialty chemicals) and 4,4-diaminodiphenyl sulfone (4,4-DDS, provided by Atul Sulpho) were probed using Dynamic Mechanical Analysis (DMA), Positron Annihilation Lifetime Spectroscopy (PALS), and compression testing. These systems were cured in a programmable oven; the samples were heated from 35°C to 180°C at ramp rates of 0.5, 1.0, 1.5, 2.0, 2.5, 5.0, 10, and 15°C/min. Even as the ramp rates during the cure of these materials was changed, there was very little …