Physical Sciences and Mathematics Commons^™

Prediction Of Dislocation Densities In Pure Metals And Alloys, J. Garey Weaver, Enrique Martinez

Chemistry Summer Research Program

No abstract provided.

Combining Alginate Beads With Methylene To Create A Biosensor To Assess The Quality Of Milk, Vivien Zheng, Barbara Guinati, Carlos D. Garcia

Chemistry Summer Research Program

No abstract provided.

Characterizing Metabolic Activity Of Fish Liver Microsomes Towards Fluoxetine In Four Fish Species Using Michaelis-Menten Enzyme Kinetics, Morgan Steiner

Honors College Theses

Discharge of pharmaceuticals into the environment is of emergent concern due to the unknown long-term effects on aquatic organisms. Wastewater treatment plants are not effective in completely removing pharmaceuticals, allowing them to be discharged into aquatic systems. To investigate the potential effects of fluoxetine, a common antidepressant, on aquatic species, the potential of four freshwater fish species to metabolize this drug was investigated. Livers from redbreast sunfish, bluegill, striped jumprock and bluehead chub were collected, homogenized, and centrifuged to collect the microsomes. These microsomes were used in an assay to determine the in vitro hepatic metabolism of fluoxetine by cytochrome …

Hydrothermal Synthesis Of Frustrated Lanthanide Pyrochlores And Transition Metal Double Perovskites And Germanates, Matthew S. Powell

All Dissertations

Magnetically frustrated materials hold promise of unique behavior allowing for the novel study of quantum phenomena. Such materials are poised to become an integral foundation for technological advancement in the post-Silicon Age. Crystalline materials are given special focus where the rigid lattice allows more detailed study of these quantized effects and frustration behavior. As opposed to polycrystalline powders, large single crystals can be preferentially aligned enabling the study of anisotropic behavior. Two cubic structure types have garnered significant interest due to their 3-D tetrahedral arrangement of symmetry-related metal centers with the potential for magnetic frustration: pyrochlores and perovskites.

The supercritical …

Impacts Of Preferential Flow On Tc-99and Np-237 Vadose Transport In Soils At The Savannah River Site, Josh Parris

All Theses

Since the 1950s, the United States has produced approximately 90,000 metric tons of spent nuclear fuel (SNF) (Office of Nuclear Energy, 2022); however, no long-term storage solutions are available. Technecium-99 and neptunium-237, two fission products found in SNF, readily form highly mobile species in oxidizing conditions (Hu, 2008; Bondietti, 1979) and have respective half-lives of 2.13 x 10⁵ and 2.14 x10⁶ years (Hu, 2010). Considering these characteristics, ⁹⁹Tc and ²³⁷Np are two risk-driving isotopes found in SNF storage. The process of macropore-facilitated preferential flow, transport through cracks within a soil matrix, has been recognized to increase …

Elucidation Of Active Site And Mechanism Of Metal Catalysts Supported In Nu-1000, Hafeera Shabbir

All Dissertations

Advances in extraction of shale oil and gas has increased the production of geographically stranded natural gas (primarily consisting of methane (C1) and ethane (C2)) that is burned on site. A potential utilization strategy for shale gas is to convert it into fuel range hydrocarbons by catalytic dehydrogenation followed by oligomerization by direct efficient catalysts. This work focuses on understanding metal cation catalysts supported on metal-organic framework (MOF) NU-1000 that will actively and selectively do this transformation under mild reaction conditions, while remaining stable to deactivation (via metal agglomeration or sintering). I built computational models validated by experimental methods to …

Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston

All Dissertations

Overall, the objective of this dissertation was to investigate the degree of sorption for the alkali cations on rutile to ascertain the impact of different cation properties, such as ion size and charge density, on sorption mechanics as well as probe how the ion may alter the surface – aqueous interface. Initial molecular dynamic simulations and batch experiments showed minimal surface sorption for any alkali cation at relatively low concentrations while simultaneously suggesting the enthalpy of deprotonation shifts slightly in the presence of the alkali cations at different ionic strengths. The cations are likely causing small reorientations of the near-surface …

Isolation And Characterization Of Extracellular Vesicles From Various Biological Matrices Using Capillary-Channeled Polymer (C-Cp) Fiber Solid-Phase Extraction Spin-Down Tips, Kaylan Jackson

All Dissertations

A number of recent works have emphasized the need to isolate nanometer-scale analytes, like extracellular vesicles (EVs), from various biologically-relevant fluids. Exosomes are a subset of small EVs that range from 30-200 nm in diameter that serve as biomolecular snapshots of their cell of origin containing mother cell-specific DNA, miRNA, mRNA, and proteins. As critical components of intercellular communication, exosomes and other EVs play significant roles in many physiological and pathological processes. Diverse populations of these vesicles can be collected from biofluids, including blood, saliva, and urine, from cell culture conditioned media and primary cells, and even from plant …

Development Of Plasmonic And X-Ray Luminescence Nanoparticles For Bioimaging And Sensing Applications, Meenakshi Ranasinghe

All Dissertations

This dissertation discusses the development of plasmonic and X-ray luminescence nanoparticles (~100 nm) to use in bioimaging and sensing applications. The nanoparticles have interesting optical properties compared to their atomic levels and bulk materials. The optical properties of nanomaterials can be controlled by changing size, shape, crystal structure, etc. Also, they have a large surface area that can be functionalized with biomolecules. Therefore, the optical properties and biofunctionalized nanomaterials are useful in biomedical applications such as targeted drug delivery, bioimaging, and sensing. The overall theme is to use nanoparticles with interesting optical properties compared to their atomic levels and bulk …

Understanding Dynamics Of Polymers Under Confinement: A Molecular Dynamics And Neutron Scattering Study, Supun Samindra Kamkanam Mohottalalage

All Dissertations

The current study probes the structure, dynamics, and rheological behavior of associating polymers including ionomers in melts and solutions as well as conjugated polymers confined into nanoparticles, using molecular dynamics (MD) simulations and neutron scattering techniques. The study focuses on two families of associative polymers, ion containing macromolecules and conjugated polymers.

Polymers that consist of ionizable groups along their backbone found uses in a broad range of applications. Examples include light weight energy storage and generation systems, and biomedical applications, where the polymers act as ion exchange membranes, and actuators. The ionic groups tend to form clusters that are in …

Isolation Of Proteins And Extracellular Vesicles Via Capillary-Channeled Polymer Fiber Stationary Phases, Lacey Billotto

All Theses

Capillary-channeled polymer (C-CP) fiber stationary phases have been developed by the Marcus lab as an alternative approach to traditional, commercially-available silica-based supports for biomacromolecule separations. C-CP columns are created with natural and synthetic base polymers in a variety of chemistries and shapes, allowing for customization of separations, while providing low material costs and ease of construction. The stationary phase is virtually nonporous with respect to the size of proteins and can operate under high linear velocities (~100 mm s^-1) while maintaining relatively low backpressures. As a result of these hydrodynamic benefits, low flow resistance at high volume flow …

Application Of A 14c-Assay To Assess Methanotrophic Biodegradation Of Tce In Low Ph Groundwater, Evan Groome

All Theses

Current biological strategies for remediating trichloroethylene (TCE) in low pH aquifers (i.e., pH14C-TCE assay was developed to determine pseudo first-order rate constants for the degradation of TCE in microcosms containing soil and groundwater from the Boeing Michigan Aeronautical Research Center (BOMARC) superfund site, where the pH ranges from 4.1 to 4.9. The ¹⁴C-TCE assay was also adapted to calculate soil-normalized rate constants for data from this site, as well as data that Szwast²¹ collected from the Beltsville Agricultural Research Center (BARC). In addition to natural attenuation, biostimulation through amendments of methane and nutrients were also assessed. This treatment …

Competition Between Halogen And Chalcogen Bonding And Their Role In Probing Organic Transformations, Andrew Peloquin

All Dissertations

Halogen bonding, the attractive interaction of an electrophilic region on a halogen atom with a nucleophilic region on another atom or molecule, provides a highly directional tool in forming solid-state motifs. This interaction, along with the related chalcogen bonding interactions, forms powerful synthons, which, when combined with other typical intermolecular attractions such as hydrogen bonding, allow for the design of supramolecular structures and inputs to crystal engineering. This dissertation research serves two primary purposes: (1) to catalog halogen and chalcogen bonding interactions with various donor molecules and (2) to utilize these interactions to probe interesting organic transformations.

In order to …

Radioluminescence Based Biochemical Sensing And Imaging Strategies To Measure Local Drug Release And Ph, Gretchen B. Schober

All Dissertations

In this dissertation we describe methods for measuring infection relevant biochemical analytes using radioluminescent and ultrasound luminescent materials. Films and nanoparticles fabricated with europium doped gadolinium oxysulfide (Gd₂O₂S:Eu³⁺) are used to quantitatively measure radiolabeled pharmaceutical concentration, specifically tritium labeled vancomycin (³H-vancomycin). Europium and dysprosium doped strontium aluminate is used to fabricate an ultrasound modulated, pH sensing film. These methods are indicated for theranostic evaluation of implant associated infection. Bacterial biofilms are inherently resistant to traditional antibiotic treatment and can coat biomedical implants. These biofilm related infections are difficult or impossible to eradicate …

State-Based Biological Communication, Nathan Clement

All Theses

Allostery (1) is the process through which proteins self-regulate in response to various stimuli. Allosteric interactions occur between nonadjacent spatially distant residues (1), and they are exhibited through the correlated motions (2) and momenta of participating residues. The location of allosteric sites in proteins can be determined experimentally but computational methods to predict the location of allosteric sites are being developed as well (2-4, 10). Experimental and computational methodologies for locating allosteric sites can be used to design specific targeted drug delivery (5-6, 19), but these methods have not yet …

Synthesis Of Fluorinated Monomers And Polymers For Various Applications, Cassandra J. Hager

All Dissertations

The world of industry utilizes a variety of polymers for various applications in many prominent fields. From electronics to food storage, the versatility of this class of chemistry has been widely proven. The Thrasher research group undertook a program dedicated towards the development of a library of fluorinated materials that focused on the synthesis and characterization of perfluoroalkoxy (PFA) copolymers of tetrafluoroethylene (TFE) and perfluoroalkyl trifluorovinyl ethers. One aim of the project was to improve upon the mechanical strength and wearability of commercial PFA resins by incorporating bulkier perfluoroalkoxy trifluorovinyl ether monomers into these copolymers. In addition to focusing on …

Extractive Membranes For The Detection And Screening Of Waterborne Plutonium, James Foster

All Dissertations

The development of rapid screening tools for special nuclear materials remains a crucial focus for nonproliferation efforts. Traditional approaches for the analysis of trace-level Pu isotopes in water requires tedious and time-consuming sample preparation steps that do not lend well to expeditious screening. Therefore, a novel analytical method that combines both Pu concentration and source preparation into a single detection system would make for an invaluable tool for nuclear security applications. Extractive membranes absorbers can help to fulfill this role as they are capable of concentrating Pu to detectable limits while subsequently serving as alpha spectrometry sample sources. In Chapter …

Automated Parallel Optimization Of Simulation Parameters Using Modified Nelder-Mead Simplex Algorithm, Erina Mills

All Dissertations

Computational simulations used in many fields have parameters that define models that are used to evaluate simulated properties. When developing these models, the goal is to choose the parameters that best replicate a set of desired properties. Mathematical optimization methods can be used to optimize the simulation parameters by defining a function that uses simulation parameters as input and outputs a value describing how well a set of experimental properties are reproduced.

Because simulated properties are often calculated using stochastic sampling methods, this optimization involves an objective function that is noisy and expensive to evaluate. Also, optimization of the simulation …

Synthesis And Molecular Processes Governing Self-Healing Polymeric Materials, Siyang Wang

All Dissertations

Self-healing polymers capable of recovering from physical damages are promising materials for advanced technologies. In these studies, we developed routes to achieve self-healable properties in acrylic-based copolymers that rely on non-covalent dipolar interactions present in essentially all polymeric materials. Using a combination of spectroscopic tools, thermo-mechanical analysis, and molecular dynamic (MD) simulations, these studies have shown that dipolar interactions lead to conformational changes of macromolecular segments which, in turn, result in self-healing without external intervention. This dissertation also describes the development of novel self-healable acrylic-based covalent adaptable networks (CANs) that combine reprocessing and self-healing properties. The utilization of dipolar interactions …

A Performance Evaluation Of Architectural Coatings To Preserve Aerosol Paint On Concrete, Riley Morris

All Theses

The growing movement of assigning cultural and heritage value to graffiti and street art is one without a preservation solution to ensure the longevity of these works in-situ in an outdoor environment. The goal of this thesis was to provide a comprehensive evaluation of six architectural topcoats’ performance when applied as a conservation treatment to outdoor aerosol graffiti and street art on concrete substrate. An artist’s quality, durable, color-fast spray-paint was applied to twenty-eight concrete test panels to mimic the application of graffiti or street art. Six topcoats, Prosoco SC-1, Prosoco Gloss n’ Guard WB, Keim Faceal Oleo HD®, Keim …

Light Harvesting And Electrically Conducting Metal-Organic Frameworks, Monica Gordillo Varela

All Dissertations

Composed of metal clusters nodes and organic linkers, metal-organic frameworks (MOFs) have emerged as versatile platforms with unparalleled chemical and structural tunability, synthetic facility, permanent porosity, and size-selective guest encapsulation capability. These features make them potential candidates for a variety of applications such as gas storage,drug delivery, catalysis,and sensing. In recent years, the introduction of redox- and photoactive components have yielded stimuli-responsive electronic and photonic MOFs and expanded their utility in molecular electronics and energy storage devices/technologies.

Chapter one describes the light-harvesting ability of a porphyrin-based MOF. Herein, we have demonstrated spontaneous solvothermal growth of [100]-oriented uniform pillared-porphyrin framework-11 (PPF-11) …

Valorization Of Biopolymers And Biomass To Produce Materials For A More Circular Economy, Moira Lauer

All Dissertations

With a globally increasing population and largely unchecked consumption of raw materials, human society is on track for devastating consequences. Two industries responsible for utilizing massive amounts of raw materials and generating equally gargantuan quantities of waste are the packaging and infrastructure sectors. In 2017 in Europe, for example, packaging reached a record 173 kg of packaging waste per capita. One of the largest packaging consumers is the food industry, in which 40% of packaging is made of petroleum-derived single-use plastic, leading to a massive carbon imbalance. “The Built Environment,” on the other hand, is responsible for about 50% of …

Synthesis Of Nanoparticles In A Silicate Matrix, Tatiana Alexandra Estrada-Mendoza

All Dissertations

Nanoparticle synthesis is the driving force behind research and development in nanotechnology. The development of more tailored nanoparticles for different uses is increasing the need for more efficient and cleaner synthetic methods. The use of sodium silicate matrix for the synthesis of various nanoparticles is a novel strategy requiring minimum laboratory set up. Exploratory studies that are presented and discussed here highlight the robust nature, versatility, and multifaceted role this matrix plays in the synthesis of nanoparticles. This dissertation focuses on the synthesis and properties of plasmonic hybrid nanoparticles and metal sulfide nanoparticles. The introductory chapter highlights the importance of …

Development Of Capillary-Channeled Polymer (C-Cp) Fiber As Stationary Phase For Biological Sample Application, Lei Wang

All Dissertations

Capillary-channeled polymer (C-CP) fibers as an alternative support/stationary phase for biomacromolecule separations on analytical and preparative scales have been developed by Marcus research group. The combination of the fiber micro- and macro-structures and in-column orientation allows operation at comparably high linear velocities (~100 mm s-1) without excessive system backpressure. The ability to move fluid efficiently through the structure is complemented by the fact that the fiber physical structure is effectively nonporous with respect to the size of proteins, therefor there is no significant intrafiber diffusion. Ultimately, these factors combine for protein separations that are devoid of appreciable van Deemter C-term …

X-Panding Halogen Bonding Interactions: Hybrid Cocrystals Composed Of Ionic Halides, Iodine And Organoiodines, Khadijatul Kobra

All Dissertations

Halogen bonding referred to as an attractive, noncovalent interaction between an electrophilic region of a halogen atom X (acts as Lewis acid) and a nucleophilic region of a molecule Y (acts as Lewis base). Such interactions and the resulting polymeric networks play an important role in many fields related to crystal engineering, including for example, the fabrication of liquid crystals and novel drug design. The application of halogen bonding has particular promise in biological systems by increasing the lipophilicity of drugs to improve penetration through lipid membranes and tissues, enabling better intracellular delivery.

Based on this concept, my research at …

Nano-Scintillators As Next Generation Tools For Optogenetics, Ashley Dickey

All Dissertations

Optogenetics is a technique that is used to study neural pathways and has the ability to activate or silence synaptic behavior using visible light. Currently, the visible light sources used for optogenetics are surgically implanted into the brain tissue, but this harmful and invasive technique may be avoided if suitable scintillating nanoparticles can be inserted via injection. The proposed nano-scintillator particles must adhere to rigorous parameters including being under 100 nm, uniform, nontoxic, and dispersible to be successful in this biological system. The phase, crystallinity, and dopant concentration must be optimized to absorb X-ray radiation and emit photons of the …

Nanomaterials-Based Electrodes For Lithium-Ion Batteries And Alcohol Fuel Cells, Lakshman K. Ventrapragada

All Dissertations

This dissertation describes my research on surfactant-free synthesis of nanomaterials with applications for alcohol fuel-cell electrodes, and design and fabrication of nanomaterials-based current collectors that improve the performance of lithium-ion batteries (LIBs) by replacing existing current collectors.

Chapter 1 provides a background on the electroanalytical tools used in this research, and an introduction to fuel cells and LIBs.

Chapter 2 describes a novel synthesis method for fabricating gold-graphene composites by laser ablation of a gold strip in water. A well-known limitation in the fabrication of a metal-graphene composite is the use of surfactants that strongly adsorb on the metal surface …

Superresolution Mapping Of Energy Landscape For Single Charge Carriers In Plastic Semiconductors, Yifei Jiang, Jason Mcneill

Publications

The performance of conjugated polymer devices is largely dictated by charge transport processes. However, it is difficult to obtain a clear relationship between conjugated polymer structures and charge transport properties, due to the complexity of the structure and the dispersive nature of charge transport in conjugated polymers. Here, we develop a method to map the energy landscape for charge transport in conjugated polymers based on simultaneous, correlated charge carrier tracking and single-particle fluorescence spectroscopy. In nanoparticles of the conjugated polymer poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1′-3}-thiadiazole)], two dominant chain conformations were observed, a blue-emitting phase (λmax = 550 nm) and a …

A Convenient Miniature Test Platform For Polyelectrolyte Membrane Fuel-Cell Research, Jamie A. Shetzline, Saheed Bukola, Stephen E. Creager

Publications

A simple and convenient small-scale fuel-cell test platform was created from a commercial compression fitting and graphite rod current collectors and used to conduct diagnostic tests on disk-shaped membrane-electrode assemblies (MEAs) fabricated from Nafion membranes and Nafion-impregnated platinum-on-carbon-cloth anodes and cathodes. A key advantage of this test platform is that it requires very little material, perhaps just a few milligrams, to conduct a fuel-cell test on a supported catalyst. Electrochemically-active surface area (ECSA) values for supported platinum on carbon-cloth electrodes were obtained by in-situ(in the fuel cell) and ex-situ (in liquid electrolyte) cyclic voltammetry on similarly-prepared electrodes, and values …

A Targeted Drug Delivery Strategy For Trypanosomiasis Towards A Diastereoselective Boronate Ester Mediated Intramolecular Diels-Alder Cycloaddition, Heeren Manoj Gordhan

All Dissertations

Human African trypanosomiasis (HAT), commonly called African sleeping sickness, is caused by bloodstream form Trypanosoma brucei and has the potential to affect millions of people in sub-Saharan Africa. Treatments have existed for the past fifty years, but are characterized by severe adverse side-effects and poor efficacy. Trypanosomes generate ATP through glycolysis, or the metabolism of glucose, which is catalyzed by enzymes called hexokinases (TbHK1 and TbHK2) in trypanosomes. Through high-throughput screenings (HTS) and structure-activity relationships (SAR), both hexokinases could be targeted with small molecules to inhibit the first step in the glycolytic pathway of trypanosomes. Of the two hexokinases, TbHK1 …