PhD, University of Cincinnati, 2017, Arts and Sciences: Chemistry

A considerable number of dietary supplements suspected of containing phosphodiesterase-5 (PDE-5) inhibitors and substituted phenethylamines have been analyzed by the U.S. Food and Drug Administration. Often these samples are found to contain the active pharmaceutical ingredients (API) such as sildenafil or phentermine, and in many cases, products contain multiple PDE-5 inhibitors or substituted phenethylamines. In an analytical setting, it is important to confirm the presence of any API with two or more independent methods, and this requirement can often put undo strain on a laboratory. The development and use of methods that inherently contain two unique identification techniques is preferred, and the creation and validation of three of those methods is outlined here. First, direct deposit Fourier transform infrared detection and mass spectrometric detection (GC/FT-IR/MS) is used to identify PDE-5 inhibitors. Generally, GC/MS is not generally used for this category of drugs due to low volatility; PDE-5 inhibitors often co-elute and can produce non-specific electron ionization fragmentation patterns. In contrast, FT-IR has been proven to be more selective for identifying PDE-5 inhibitors, but is generally not as sensitive as spectrometric techniques. However, it has been shown that each technique can compensate for the other, which allows a wider range of usability. Using this combined technique can save time and resources while still delivering a high level of certainty in identification by providing results from two scientifically uncorrelated techniques. Multiple reference standards were utilized for method validation, including determination of linearity, dynamic range, and limit of detection. Second, a single HPLC-UV method has been developed for the determination of PDE-5 inhibitors and related analogs in pharmaceutical dosage forms and dietary supplement products. Using this protocol, 14 PDE-5 inhibitor compounds can be separated and determined in a single an (open full item for complete abstract)

Committee: Peng Zhang Ph.D. (Committee Chair); Anna Gudmundsdottir Ph.D. (Committee Member); Laura Sagle Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, Case Western Reserve University, 2015, EECS - Electrical Engineering

This project has developed an energy-efficient, high data-rate, impulse radio ultra wideband (IR-UWB) transceiver, operating in three channels within 3–5 GHz for centimeter-to-meter range biotelemetry. Fabricated in 90 nm 1P/9M CMOS, the transceiver integrates an all-digital transmitter with a waveform-synthesis pulse generator and a timing generator for pulse modulation and phase scrambling that, as well as a noncoherent receiver with front-end RF amplification/filtering, self-correlation for energy detection and digital synchronization of the baseband clock and data. The transmitter provides great flexibility in reconfiguring the UWB pulse waveform in the time domain (e.g., overall shape, amplitude, duration) as well as its power spectral density (PSD) in the frequency domain (e.g., center frequency, bandwidth, peak level). A fully integrated receiver would also significantly reduce its power consumption as compared to that of a discrete implementation, addressing another limitation for true portability of the centimeter-range transceiver and greatly enhancing energy efficiency per received bit in the wireless link. The receiver RF front-end can provide up to 37 dB of gain with adjustable bandwidth, sharp roll-off and tunable center frequency at 3.5, 4 and 4.5 GHz for channel selection and robustness against out-of-band noise/interference. Employing a miniaturized, UWB, chip antenna for the transmitter and receiver, wireless transmission of pseudo-random binary sequence (PRBS) data at rates up to 75 Mb/s over 10 cm–1 m is shown for portable application. Further, employing a high gain horn antenna for the receiver, wireless transmission of PRBS data at rates up to 125 Mb/s over 50 cm–4 m is shown for stationary application with transmitter and receiver energy consumption of 14 pJ/pulse and 0.15 nJ/b, respectively, from 1.2 V. To address the problem of data rate in high-channel-count neurochemical monitoring, we demonstrated proof-of-concept feasibility of utilizin (open full item for complete abstract)

Committee: Pedram Mohseni (Advisor); Dominique Durand (Committee Member); Francis Merat (Committee Member); Soumyajit Mandal (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering

Doctor of Philosophy, Miami University, 2013, Chemistry and Biochemistry

This dissertation describes the development and application of methods and instrumentation for qualitative and quantitative sample analyses by infrared and Raman spectroscopies. An introduction to the concepts and methods utilized is provided in Chapter 1. A comparative evaluation of solid-core silver halide fiber optics and hollow silica waveguides was performed on the basis of the transmission of mid-infrared radiation using a fiber optic coupling accessory and an infrared microscope is presented in Chapter 2. Increased transmission was reproducibly observed between two identical hollow waveguides due to minimization of insertion and scattering losses resulting from the hollow core. Chapter 3 presents an evaluation of a mid-infrared, attenuated total (internal) reflection (ATR) probe accessory utilizing hollow waveguides based on transmission and signal-to-noise. Quantitative analyses of aqueous succinylcholine chloride and ethanol solutions were also performed. An in situ Raman study of nitrogen incorporation in thin films of zinc oxide using a temperature-controlled reaction cell is discussed in Chapter 4. Monitoring nitrogen incorporation in thin films of zinc oxide at elevated temperatures in the presence of nitrogen-containing precursor reagents proved inconclusive using the proposed method. Chapter 5 presents an evaluation of dispersive and Fourier transform (FT-) Raman spectroscopies for on-line process control in the bottling industry. FT-Raman was determined to be more applicable for on-line determinations of poly(ethylene terephthalate) bottle thickness due to the availabilities of such benefits as increased laser power and fluorescence rejection. Preliminary data from the development of an inverted ATR imaging microscope are discussed in Chapter 6. The inverted optical design of the microscope permits simultaneous viewing of the sample with white light and the collection of infrared spectral images. Summaries of the presented research are pro (open full item for complete abstract)

Committee: André Sommer PhD (Advisor); Neil Danielson PhD (Committee Chair); Jonathan Scaffidi PhD (Committee Member); David Oertel PhD (Committee Member); Lei Kerr PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry

Doctor of Philosophy, University of Akron, 2013, Polymer Engineering

Physical and chemical changes during the complex multi-step thermal imidization reaction were investigated including all processing steps (solution casting, drying and imidization), using newly developed highly instrumented measurement systems. These instruments allowed us to observe the dynamic relationship between the bound solvent evaporation that causes relaxation and chain orientation during the imidization. Drying and imidization of PMDA-ODA solutions in NMP were investigated by a novel custom designed measurement system that tracks real time weight, thickness, surface temperature, in-plane and out-of-plane birefringence. At low temperature drying stage (T<120°C), the weight and thickness reductions occurred rapidly as a result of solvent evaporation. All the parameters started leveling off while the out of plane birefringence steadily increased and reached a plateau at longer drying times. When the temperature was increased for imidization reaction (T=200°C), additional weight loss accompanied by temporary reduction of birefringence was observed due to evaporation of bound solvent as solvent molecules decomplexed from the polymer chains and plasticized the film. During the latter stage, out-of-plane birefringence rose rapidly as the polymer chains increasingly became oriented with their chain axes were preferentially oriented in the film plane. Throughout the whole process the in-plane birefringence remained zero. For the first time, these real time measurements allowed us to quantitatively show the dynamics between chain relaxation due to evaporation of the decomplexed solvent molecules, and orientation development due to decreased chain mobility caused by imidization reaction and increasing Tg for the PMDA-ODA/NMP solutions. In addition, the dynamics of this interplay was investigated by varying the processing conditions: initial casting thickness and drying temperature. Chemical conversion, bound solvent and chain orientation that take place du (open full item for complete abstract)

Committee: Mukerrem Cakmak Dr. (Advisor); Mark Soucek Dr. (Committee Member); David Simmons Dr. (Committee Member); Coleen Pugh Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Polymer Chemistry; Polymers

Master of Science, The Ohio State University, 2009, Food Science and Nutrition

Fourier-Transform infrared (FT-IR) spectroscopy is a simple, fast and highly specific technology that can provide valuable insights into the complex chemical make-up of foods. Infrared provides tools, especially in the fingerprint region of the spectrum, to detect specific compounds in biological systems without the use of time-consuming methods or the use of hazardous organic solvents. Advances in FT-IR instrumentation and pattern recognition techniques have made it possible to extract information related to composition and conformation of food components from the spectra. We have evaluated the capability of infrared spectroscopy in classification and quantification of chemical compounds of interest for the dairy (butter) and tomato industries. Authentication is a critical quality issue for organic products since consumers are willing to pay 10-40% price premiums. There is a need for rapid and reliable analytical tools for determination of authenticity since traditional methods often involve time-consuming and laborious processes. Our objective was to evaluate the application of infrared spectroscopy combined with pattern recognition techniques to discriminate among organically and conventionally-produced butter in relation to quality and authenticity. Spectra from butter purchased from a local market (Columbus, OH) were collected by using Attenuated total reflectance (ATR) spectroscopy and analyzed using soft independent modeling of class analogy (SIMCA), a multivariate classification technique. This simple protocol generated unique mid-infrared signature profiles that permitted the chemically-based classification of butter samples based on manufacturer and production practice (organic vs. conventional). By using the spectral region from 1400-800 cm-1, multivariate (SIMCA) modeling showed well-separated clusters that discriminated among butter samples according to manufacturer, due to -HC=CH- trans bending out of plane vibration modes, (966 cm-1) presumably attrib (open full item for complete abstract)

Committee: Luis Rodriguez-Saona PhD (Advisor); Jeff Culbertson PhD (Committee Member); David Min PhD (Committee Member) Subjects: Food Science

Doctor of Philosophy, The Ohio State University, 2008, Computer and Information Science

This thesis addresses the fundamental tasks of detecting objects in images, recovering their location, and determining their silhouette shape. We focus on object detection techniques that 1) enable simultaneous recovery of object location and object shape, 2) require minimal manual supervision during training, and 3) are capable of consistent performance under varying imaging conditions found in real-world scenarios. The work described here results in the development of a unified method for simultaneously acquiring both the location and the silhouette shape of specific object categories in outdoor scenes. The proposed algorithm integrates top-down and bottom-up processing, and combines cues from these processes in a balanced manner. The framework provides the capability to incorporate both appearance and motion information, making use of low-level contour-based features, mid-level perceptual cues, and higher-level statistical analysis. A novel Markov random field formulation is presented that effectively integrate the various cues from the top-down and bottom-up processes. The algorithm attempts to leverage the natural structure of the world, thereby requiring minimal user supervision during training. Extensive experimental evaluation shows that the approach is applicable to different object categories, and is robust to challenging conditions such as large occlusions and drastic changes in viewpoint. For static camera scenarios, we present a contour-based background-subtraction technique. Utilizing both intensity and gradient information, the algorithm constructs a fuzzy representation of foreground boundaries called a Contour Saliency Map. Combined with a low-level data-driven approach for contour completion and closure, the approach is able to accurately recover object shape. We also present object detection and segmentation approaches that combine information from visible and thermal imagery. For object detection, we present a contour-based fusion algorithm for b (open full item for complete abstract)

Committee: James Davis (Advisor) Subjects: Computer Science

Doctor of Philosophy, Miami University, 2010, Chemistry and Biochemistry

This dissertation describes the use of infrared and Raman microspectroscopic methods for the analysis of small mineral inclusions in kidney biopsies and efforts to quantitatively analyze components at the localized mineral/tissue interface. Chapter 1 provides a background on the current state of kidney stone disease research and also describes the instrumental methods utilized. Chapter 2 presents the use of attenuated total internal reflection (ATR) infrared spectroscopy to generate calibration curves for mixtures of powdered kidney stone components. This study demonstrates that reproducible quantitation can be achieved if the particle sizes of the components are small and comparable. ATR imaging was employed to analyze kidney biopsies with small mineral inclusions in Chapter 3. ATR imaging has several benefits over other infrared sampling methods (primarily transflection and transmission) for the analysis of kidney biopsies due to the smaller focused beam size achievable and the reduced optical pathlength that eliminates spectral artifacts. Chapter 4 describes an investigation into small particle analysis with transmission infrared microspectroscopy and ATR imaging. The results of the study show that spectral artifacts are dependent on the particle's size and shape and it is anticipated that this research will provide a framework for the analysis of particles below the diffraction limit. Chapter 5 presents a comparative study of Raman microspectroscopy and ATR imaging for kidney biopsy analysis. Using both methods in unison allows the investigator to obtain a full spectroscopic picture of the sample. Because Raman interrogates a larger, more uncontrolled sample volume, ATR may be more beneficial for quantitative studies. Chapter 6 summarizes the presented research and discusses future work.

Committee: Andre J. Sommer PhD (Advisor); Neil D. Danielson PhD (Committee Chair); Andrew P. Evan PhD (Committee Member); Thomas L. Riechel PhD (Committee Member); Lei L. Kerr PhD (Committee Member) Subjects: Analytical Chemistry

Master of Arts (MA), Wright State University, 2024, International and Comparative Politics

In 1948, the international community came together and promised to “prevent and punish” genocides under the Convention on the Prevention and Punishment of the Crime of Genocide (Genocide Convention). Despite the Genocide Convention's commitment to humanitarian intervention, states are selective and inconsistent in intervention. While there are many case studies done on state motivation for intervention, statistical studies are rarely done and a system for predicting what variables will likely produce humanitarian intervention on a wide scale has not been explored. This study uses a Cross-Sectional Time Series Estimator Model to track whether states were more likely to intervene in genocides over time since signing the Genocide Convention. It also tested whether valuable goods and shared borders made states more prone to intervention. The results concluded that the Genocide Convention has no correlation to states willingness to intervene in genocides. It also did not provide evidence that valuable goods are a factor in humanitarian intervention. The test did support the hypothesis that shared borders make states more likely to intervene in genocides. Future studies should focus on increasing the data pool to include more genocides and testing more variables in hopes of creating a system to predict humanitarian intervention in genocides.

Committee: Liam Anderson Ph.D. (Advisor); Vaughn Shannon Ph.D. (Committee Member); Carlos Costa Ph.D. (Committee Member) Subjects: International Relations; Political Science

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Damaging UV radiation from the sun can lead to the formation of mutagenic photoproducts. The fate of initial electronic excited states in both DNA nucleobases and double-stranded DNA has been of considerable interest over the last few decades. Despite the progress that has been made in understanding the mechanisms for electronic deactivation, there has been considerably less effort placed on understanding the mechanisms for vibrational cooling following ultrafast electronic deactivation, in large part due to complex and competing pathways for vibrational relaxation. In this thesis, I present the ultrafast vibrational relaxation dynamics of a series of methylated nucleobase derivatives. By systematically varying the number of hydrogen bond donor and acceptor groups, the role of both the chemical modification and the solvent dependent relaxation dynamics were uncovered. In all of the molecules studied, the nearly isoenergetic carbonyl and ring modes decay were found to decay with very different initial dynamics. This discrepancy was attributed to differences in intramolecular relaxation pathways due to differences in mode-specific couplings, rather than differences in the density of accessible states. Despite very different initial dynamics, both the ring and carbonyl modes thermalized with a shared, global time constant. One of the most intriguing observations is that this rate limiting relaxation step mirrors that found following electronic deactivation, despite more than an order of magnitude difference in excitation energies. In combination with experimental studies, theoretical modeling was used to resolve spectroscopic signatures of vibrational relaxation. Together, these results should play an important role in the development of future studies of vibrational relaxation dynamics.

Committee: Bern Kohler (Advisor); Alexander Sokolov (Committee Member); Christopher Jaroniec (Committee Member) Subjects: Physical Chemistry

Doctor of Philosophy (PhD), Wright State University, 2023, Electrical Engineering

Since their invention in 1958, Integrated Circuits (ICs) have become increasingly more complex, sophisticated, and useful. As a result, they have worked their way into every aspect of our lives, for example: personal electronic devices, wearable electronics, biomedical sensors, autonomous driving cars, military and defense applications, and artificial intelligence, to name some areas of applications. These examples represent both collectively, and sometimes individually, multi-trillion-dollar markets. However, further development of ICs has been predicted to encounter a performance bottleneck as the mainstream silicon industry, approaches its physical limits. The state-of-the-art of today's ICs technology will be soon below 3nm. At such a scale, the short channel effect and power consumption become the dominant factors impeding further development. To tackle the challenge, projected by the ITRS (International Technology Roadmap for Semiconductors) a thinner channel layer seems to be the most viable solution. This dissertation will discuss the feasibility of using 2D (two-dimensional) materials as the channel layer. The success of this work will lead to revolutionary breakthroughs by pushing silicon technology to the extreme physical limit. Starting from graphene in 2004, 2D materials have received a lot of attention associated with their distinct optical, electrical, magnetic, thermal, and mechanical properties. In the year 2010, IBM demonstrated a graphene-based field effect transistor with a cut-off frequency above 100 GHz. The major challenge of applying graphene in large-scale digital circuits is its lack of energy bandgap. Other than carbon, a variety of graphene-like 2D materials have been found in various material systems, like silicene, germanene, phosphorene, MoS2, WS2, MoSe2, HfS2, HfSe2, GaS, and InS, etc. Among all the 2D materials, silicene appears to be the most favored option due to its excellent compatibility with standard silicon technology. Simil (open full item for complete abstract)

Committee: Yan Zhuang Ph.D. (Advisor); Ray Siferd Ph.D. (Committee Member); Junghsen Lieh Ph.D. (Other); Marian K. Kazimierczuk Ph.D. (Committee Member); Saiyu Ren Ph.D. (Committee Member); Henry Chen Ph.D. (Committee Member) Subjects: Chemical Engineering; Chemistry; Electrical Engineering; Engineering; Materials Science; Nanoscience; Nanotechnology; Packaging; Physics; Quantum Physics; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2023, Agricultural, Environmental and Developmental Economics

From a farmer to a policymaker, various stakeholders influence and are affected by the agricultural environment. This dissertation includes three essays that delve into the decision-making within the agricultural environment, exploring the incentives and outcomes for the stakeholders involved. With a focus on countries significant for global agriculture and food supply, these essays have important implications domestically and for the United States. My first essay evaluates herding as a potential source of bias in the USDA's international baseline projections. As USDA's annual Agricultural Baseline Projections contribute significantly to agricultural policy in the United States, their accuracy is vital. Although the bias in the baselines has been documented in the literature, its sources have not been evaluated yet. I propose herding, a behavioral phenomenon, as a potential bias-inducing choice in the preparation of the projections. My results provide strong evidence for the herding of projection trends toward the United States and suggest that herding is rational and error-reducing only for corn yield and wheat import projections but not for other crops and variables, thereby impacting not only the agricultural policy in the US but also global agricultural markets. The second essay evaluates the impact of an environmental policy that restricts land use for farmers in the context of the Brazilian Amazon, an area of crucial importance for global food supply. By analyzing the effects on both landowning farmers and landless peasants, this study examines the incentives generated and their subsequent influence on illegal occupations and land conflicts. The findings suggest that the policy leads to an increase in illegal occupations while decreasing land conflicts. Furthermore, by exploring heterogeneity in the impact relative to land values, I find that landowning farmers and squatters both make strategic choices about whether to engage in conflict depending on the (open full item for complete abstract)

Committee: Ani Katchova (Advisor); Brian Roe (Committee Member); Leah Bevis (Advisor) Subjects: Agriculture; Economics; Environmental Economics

Master of Science (MS), Ohio University, 2023, Civil Engineering (Engineering and Technology)

Tire particles (TP) are the largest source of microplastics in nature. However, the adsorption behavior of TP needs to be better understood. TP used in this study were generated from cryo-milling and aged with 30% nitric acid. Single and competitive adsorption isotherm experiments were conducted to investigate the potential of TP as carriers of heavy metals. Langmuir and Freundlich models were used to analyze adsorption data. Competitive adsorption demonstrated a reduction in the adsorption capacity of TP. The preference for lead to copper by TP was explained by the physical and chemical properties of the metals. The adsorption capacity was maximum at the pH range of 6-12 for lead, and for copper, it was pH 10. pH, zeta potential, FT-IR, and XPS results indicated that electrostatic attraction and surface complexation were involved in the heavy metal adsorption on TP.

Committee: Lei Wu Dr. (Advisor); Natalie Kruse-Daniels Dr. (Committee Member); Daniel Che Dr. (Committee Member); Guy Riefler Dr. (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy, University of Akron, 2022, Polymer Science

Novel modifications of styrene-butadiene rubber were studied using conventional curatives, sulfur curing packages or peroxides, to efficiently utilize supramolecular reinforcement strategies that improve the mechanical properties of rubber. Thiol-ene coupling proved to be an effective method for modifying styrene-butadiene rubber during peroxide curing, but it was inadequate when attempted during sulfur vulcanization. Supramolecular reinforcement was achieved by grafting mercapto-functionalized sodium phosphate esters to styrene-butadiene rubber during peroxide curing which electrostatically associate. The association strength between these ionic grafts played a critical role in determining the degree of reinforcement. Possible mechanisms by which reinforcement occurs were discussed and, at low grafting densities, at least one mechanism was determined not to play a major role. It was shown that substantial modification of cis-1,4-polyisoprene does not occur by thiol-ene coupling and that another chemical means must be used to modify this substrate. Reagents consisting of thioaldehydes derived from thiosulfinates were used in Alder-ene reactions to modify cis-1,4-polyisoprene. Based on this chemistry, new grafting and crosslinking agents were developed that react quickly and at relatively low temperatures. Important elements in the molecular design of these curatives were discussed and it was demonstrated that good mechanical properties are attainable.

Committee: Li Jia (Advisor); Mark Foster (Committee Chair); Shing-Chung Wong (Committee Member); Tianbo Liu (Committee Member); James Eagan (Committee Member) Subjects: Chemistry; Materials Science; Molecular Chemistry; Morphology; Nanoscience; Nanotechnology; Organic Chemistry; Polymer Chemistry; Polymers

Master of Science in Computer Engineering, University of Dayton, 2022, Electrical and Computer Engineering

Image compression algorithms are the basis of media transmission and compression in the field of image processing. Decades after their inception, algorithms such as the JPEG image codec continue to be the industry standard. A notable research topic gathering momentum in the field of compression is deep learning (DL). This paper explores the opti- mization of DL models for ideal image compression and object detection (OD) applications. The DL model to be optimized is based upon an existing compression framework known as the CONNECT model. This framework wraps the traditional JPEG image codec within two convolutional neural networks (CNNs). The first network, ComCNN, focuses on com- pressing an input image into a compact representation to be fed into the image codec. The second network, RecCNN, focuses on reconstructing the output image from the codec as similarly as possible to the original image. To enhance the performance of the CONNECT model, an optimization software called Optuna wraps the framework. Hyperparameters are selected from each CNN to be evaluated and optimized by Optuna. Once the CONNECT model produces ideal results, the output images are applied to the YOLOv5 OD network. This paper explores the impact of DL hyperparameters on image quality and compres- sion metrics. In addition, a detection network will provide context to the effect of image compression on computer vision applications.

Committee: Bradley Ratliff (Committee Chair); Eric Balster (Committee Member); Barath Narayanan (Committee Member) Subjects: Computer Engineering

Doctor of Philosophy, Case Western Reserve University, 2021, Physics

The ever-increasing number of applications requiring semiconductor materials at their core is driving the need to understand certain oxide and nitride materials. In this thesis, we investigate two of such classes. The first of those is the class of wide band-gap oxides and includes materials like β-〖Ga〗_2 O_3 and the 〖(〖Al〗_x 〖Ga〗_(1-x))〗_2 O_3 alloy system. β-〖Ga〗_2 O_3 is the most stable of the five phases in which 〖Ga〗_2 O_3 is found to exist. With a significantly high experimentally measured band gap of 4.5-4.9 eV, it is touted to be an excellent material for high-power electronics and UV transparent optoelectronic applications. Using first-principles calculations, we study this material and present the electronic band structure calculations using the quasiparticle self-consistent GW method. Next, we extend this study to the alloy system 〖(〖Al〗_x 〖Ga〗_(1-x))〗_2 O_3 in which 〖Ga〗_2 O_3 is alloyed with an even higher band-gap material, 〖Al〗_2 O_3. We study the system in both the phases, α and β, present the electronic band structures for varying compositions of Al ranging from 0% to 100%, and predict the most favorable composition and phase for such an alloy to exist. The second class of materials in this thesis is the alloy system formed by the combination of group III- and II-IV nitrides, GaN and 〖ZnGeN〗_2, respectively. In particular, we study the vibrational properties of 〖ZnGeGa〗_2 N_4. 〖ZnGeGa〗_2 N_4, at 50% composition, is an octet-preserving and lowest energy superlattice of half a cell of 〖ZnGeN〗_2 and half GaN along the b-axis of 〖ZnGeN〗_2 in the 〖Pbn2〗_1 structure. Using Density Functional perturbation theory implemented in ABINIT, the phonon modes at the zone center, Γ allow us to calculate longitudinal optical-transverse optical splittings using Born effective charges. In addition, the IR and Raman spectra along with the phonon density of states, and the phonon band structure are presented. Lastly, we study the transition metal (open full item for complete abstract)

Committee: Walter Lambrecht (Advisor) Subjects: Condensed Matter Physics; Materials Science; Physics

MS, University of Cincinnati, 2020, Engineering and Applied Science: Aerospace Engineering

The combustor and exhaust dynamics of four different RDC configurations are studied via visualization using a mid-infrared camera that acquires frames at multiple exposure times. In one-wave operation significant swirl is imparted on fresh reactants by the rotation of the detonation wave, while counter-rotation de-swirls reactants. Significant pre-burning of fresh reactants was also found regardless of operational mode. At higher-flow rates, waves exhibit a distinct double-lobed shape, similar to the cell structure seen in detonation theory, but much larger in width, indicating that this may be one wave about to split into two. There are extensive regions of unburnt reactants that exist near the outer wall indicating poor mixing of reactants. The extent of the unburnt reactants is seen to have an effect on the shape of the exhaust by dictating whether it is angled outward, straight, or angled inward. Spatial partial orthogonal decomposition performed on the combustor showed that the inclination of fresh reactants was in fact a distinct flow feature. SPOD also showed multiple swirling structures in the exhaust during one-wave modes. These structures were noticeably absent in counter-rotating propagation. A newly designed flow-through RDC is manufactured and tested in order to characterize its operating map. A mixture of hydrogen and air at varying air mass flow rates and equivalence ratios are tested. The combustor was unable to light off or operated as a deflagration at all tests at 0.2 kg/s, and a majority of tests at 0.3 kg/s, indicating that the bulk velocity of the air may have been too low. Detonations were seen only at a small handful of conditions, only at 0.4 and 0.5 kg/s of air. The rest of the test cases operated as transition points, where they saw switches between deflagration and detonation throughout the test. These existed just below stoichiometric, all the way to rich conditions. Interesting was the transition from detonation to deflagration which (open full item for complete abstract)

Committee: Ephraim Gutmark Ph.D. (Committee Chair); Shaaban Abdallah Ph.D. (Committee Member); Daniel Cuppoletti Ph.D. (Committee Member) Subjects: Aerospace Materials

Master of Science (M.S.), University of Dayton, 2020, Chemical Engineering

The use of cost-effective bio-based materials, such as lignin, offers the potential to replace commercially available, expensive synthetic petroleum materials which are currently used in the production of fibers and plastics. Many lignin-based nano-scale fibers have the potential to be used in a vast range of applications, ranging from automobiles to the electronics industry. These nanofibers can also be used in chemical separations and adsorption technologies. Unfortunately, lignin possesses a low molecular weight, and therefore polymer blends are used for the production of lignin-based nanofibers. Hence there is a need to optimize and understand polymer-polymer interactions of lignin and a carrier polymer to ultimately generate nanofibers with desired characteristics. In this study, two types of lignin, low sulfonate (LSL) and alkali, kraft lignin (AL) were investigated and combined with polyacrylonitrile-co-methyl acrylate (PAN-MA) for the fabrication of nanofibers using electrospinning techniques. The polymers were solubilized in N,N dimethylformamide (DMF) and prepared at different PAN-MA:lignin ratios ranging from 100:0 to 50:50 at varying total polymer concentrations ranging from 10 wt % to 20 wt %. Using solvent evaporation, PAN-MA/lignin films were obtained and the polymer arrangements, phase separation, and morphology were studied via polarized optical microscope (POM) and scanning electron microscopy (SEM). AL blends showed good miscibility with PAN-MA at higher concentrations wherein LSL blends found to have phase separation. Rheological characterization of LSL and AL in PAN-MA polymer solutions included flow sweep, frequency sweep, and amplitude sweep tests, which were used to gain insights into the effects of lignin type and ratios in the polymer solutions. Electrospinning of various PAN-MA/lignin solutions proceeded at an operating voltage of 15 kV with currents varying between 0-2 µA and at a 0.003 ml/min constant flow rate. Thermal and chem (open full item for complete abstract)

Committee: Erick Vasquez Dr. (Committee Chair); Donald Klosterman Dr. (Committee Member); Kenya Crosson Dr. (Committee Member) Subjects: Automotive Engineering; Chemical Engineering; Chemistry; Environmental Engineering; Materials Science; Nanotechnology; Polymers; Sustainability

Doctor of Philosophy, University of Akron, 2020, Polymer Science

Scientific discovery has constantly revolutionized society. In the last decade (2010-2020), there has been numerous discoveries including detecting the first gravitational waves or revolutionizing the study of ancient DNA. In the last decade, there are countless material science innovations including the emphasis on the materials genome initiative. The U.S federal government placed prominent attention on advance materials development for a secure economy and human wellbeing. However, research and development yielding scientific breakthrough is very slow and challenging process. In order to overcome these challenges and accelerate discovery, combinatorial material science tools can be deployed. The combinatorial toolbox consist of combinatorial libraries and high throughput evaluation. Combinatorial library creation aims to generate systematic and deliberate chaos while high throughput screening aims to test, capture, and organize chaos. In the material science space, combinatorial libraries aim to generate various material samples with high variation. High throughput aims to rapidly test, monitor, and compile data to develop fundamental structure property correlations. This dissertation aims to integrate the areas of combinatorial material science with additive manufacturing material fabrication and utilizes high throughput imaging techniques. In this dissertation, Chapter I provides the historical background on combinatorial material science techniques with an emphasis on material development. Chapter II shows the materials, methods, and instrumentation used in the study. Chapter III introduces direct write additive manufacturing as a combinatorial fabrication technique. Chapter III integrates static mixers for precise placement in 3D printed objects. The fundamental groundwork is established to develop additive manufacturing technique that creates discrete gradients, precise variation, and placement. Chapter IV demonstrates both combinatorial fabrication (open full item for complete abstract)

Committee: Andrey Dobrynin (Advisor); Kevin Cavicchi (Advisor); Yu Zhu (Committee Member); Matthew Becker (Committee Member); Steven S.C Chuang (Committee Member) Subjects: Polymer Chemistry; Polymers

MS, University of Cincinnati, 2020, Engineering and Applied Science: Electrical Engineering

In the present work, we examine binary (Na2O)x(P2O5)100-x glasses in the 0 < x < 61% composition range, and confirm the existence of the three generic elastic phases, namely, Flexible Phase, Intermediate Phase (IP) and Stressed-Rigid Phase by extending the previous work done on these glasses. Our experiments include investigating these glasses and understanding the molecular subtleties using Infrared reflectance, Raman Scattering and Modulated Differential Scanning Calorimetry (MDSC). Furthermore, we show the existence of the two elastic phase transitions in ((Na2O)x(P2O5)100-x) glasses using InfraRed Reflectance measurements by analyzing the Threshold Behavior of the Longitudinal Optic and the Transverse Optic (LO-TO) mode frequency splitting in the IP composition range (37.5% = x = 46.0%). From the IR reflectance measurements, we established glass sample dryness along with providing testimony for the existence of the triad of modes associated with the symmetric vibration of the P=Ot stretch of the Q2 local structures (?s P=Ot (Q2)), a majority mode associated with the Long Chains (LCs) and two satellite modes corresponding to the Large Rings (LRs) and the Small Rings (SR). The compositional variation in the mode scattering strength of these satellite modes is in total agreement with the high configurational entropy of the IP glasses that leads ageing to be suppressed qualitatively. IR reflectance measurements reveal rich TO and LO responses of these dry and homogeneous glasses that permitted us to decode the glass molecular structure by interpreting the phenomenon of the LO-TO mode frequency splitting, an uncharted territory in Phosphate Glasses. Deducing compositional trends in the LO-TO mode frequency splitting, remarkably, also display a square-well like minimum in the IP composition range (37.5% < x < 46%), defining the elastic phase transitions optically for the first time; a result that banks upon the notion of glass network compaction (Volumetric Wi (open full item for complete abstract)

Committee: Punit Boolchand Ph.D. (Committee Chair); Marc Cahay Ph.D. (Committee Member); Rashmi Jha Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, University of Akron, 2020, Polymer Science

Melanin is a ubiquitous pigment found in animals, plants, and microorganisms, which is widely known for its UV light absorption capacity, high antioxidant activity, and other unique properties. The most common commercial sources are synthetic melanin: polydopamine (PDA) and poly(L-3,4-dihydroxyphenylalanine) (PDOPA), and natural melanin: sepia melanin. Here, we extract melanin from black knot fungus (Apiosporina morbosa), a pathogenic fungus that grows on several fruit trees, using acid/base extraction method and elucidate the chemical structure of the extracted melanin by Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. The extraction yield is around 10% and the characterization results prove that its chemical structure is similar to synthetic melanin, PDA and PDOPA, which illustrates that the extracted melanin is eumelanin. Scanning electron microscopy (SEM) images show irregular morphology of melanin. Also, the extracted melanin shows a broadband UV light absorption similar to melanin extracted from other sources. Because of the low cost of black knot fungus and it being an invasive species, it can serve as a cheaper alternative source of melanin, which could be applied as UV light absorbers and antioxidant reagents in the future.

Committee: Ali Dhinojwala (Advisor); Toshikazu Miyoshi (Committee Member) Subjects: Chemical Engineering; Polymers