Master of Science, The Ohio State University, 1989, Engineering Mechanics

Committee: Carl Popelar (Advisor); Vernal Kenner (Other) Subjects:

Doctor of Philosophy, Miami University, 2022, Chemistry and Biochemistry

The pursuit of both spin-crossover systems (SCO) and the single-ion magnets (SIM) escalate with the due to their potential application in memory storage devices, quantum computing, switchers, and sensors. Intense research over the years has been conducted to develop SCO complexes and SIM with larger total spin and zero-field splitting for the spin-based application. A strong understanding of the effect of the local chemistry and structural features on the spin and magnetic properties is a necessity for these applications. Therefore, work in this dissertation use solution-state NMR spectroscopy to explore the orientation of the principal magnetic axis and the influence of the local chemistry and structural features on spin properties and electronic relaxation of the three different sets of Co(II) complexes. As the first step in chapter 2, we studied the orientation of the magnetic axis of the five-coordinate Co(II) single-ion magnets (SIMs) in mixed ligand (N3O2 and N3OS) environments using paramagnetic relaxation enhancements. Here we used the NMR relaxation measurements and crystallographic metrics to extract the electron spin relaxation time using the Solomon-Bloembergen-Morgan equation. The analysis of the temperature dependent correlation time was used to propose the correct orientation of the magnetic axis in the solution. In the next three chapters, we focused on studying Co(II) complexes containing two sets of variably-substituted trispyrazolylmethane (Tpm), and bispyrazolylpyridine (bpp) ligand. Chapter 3 represents the association of the counterion of the series of cobalt(II) bis-trispyrazolylmethanes. Here focuses to examine the distances between counterion nuclei (BF4− and PF6−) and metal center using 19F NMR relaxation measurements. Both chapters 3 and 4 focused on the determining impact of the methyl and halogen substitution on the electronic relaxation and the association of counterion in the solution of bpp complexes. In both chapters, 19F and 1 (open full item for complete abstract)

Committee: David Tierney PhD (Advisor); Michael Crowder PhD (Committee Chair); John Rakovan PhD (Committee Member); Kevin Yehl PhD (Committee Member); Robert McCarrick PhD (Committee Member) Subjects: Chemistry; Inorganic Chemistry; Physical Chemistry

PhD, University of Cincinnati, 2020, Engineering and Applied Science: Materials Science

Dynamic mechanical analysis of nanocomposites is important in the assessment of performance and reliability of the material. However not much is known about the relaxation behavior of nanographene sheets (NGS)/polyimide composites. In this work, the relaxation behavior of polyimide and NGS/ polyimide composite was investigated as function of frequency, time, and temperature. Also, the effect of loading was examined to optimize the strength and durability. A modified form of Williams-Landel-Ferry equation (WLF) was utilized with the calculated frequencies to obtain constants C1 and C2. Cole-Cole plots were used to examine the behavior of polyimide and graphene reinforced polyimide and it showed that the composite displayed a good fit to a single-relaxation-time. The activation energy for alpha and beta transitions were determined and Master curves for the nanocomposites were constructed and used to predict the lifetime of the composites. Dielectric relaxation of the composite under various temperatures and frequencies was investigated. It was shown that the electrical properties of the composites increased with increasing weight fraction of graphene. As graphene/polyimide composites has dense morphology, their use as electrode material requires creating pores. Poly (lactic acid) additive was used to create porous graphene/polyimide composite structures. The cured porous composite showed a one phase structure. Lifetime and relaxation modulus for porous NGS/polyimide nanocomposites were determined. The lifetime of the porous composites was shown to be lowered while its damping ability improved.

Committee: Jude Iroh Ph.D. (Committee Chair); Gregory Beaucage Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member); Donglu Shi Ph.D. (Committee Member) Subjects: Materials Science

Master of Music (MM), Ohio University, 2018, Music Therapy (Fine Arts)

Female college students have reported experiencing higher stress levels than their male counterparts. Relaxation techniques that alleviate psychological stress by helping them reach a better mental/emotional state may be more helpful for coping with stress. Music relaxation intervention in audio recorded forms were found to be effective for multi-faceted consequences of stress. However, effects of its live forms presented by a music therapist for alleviating psychological stress among female college students remain under-researched. This pilot study explored the impact of a live music relaxation intervention on female college students who self-reported as stressed (N = 31). The objectives of this study were to assess changes in five pre- and post-intervention states: negative affect, positive affect, contentment, relaxation responses, and observable relaxation responses. The focus of this study was to learn about qualitative differences in participants' subjective experience with the intervention. Thus, self-reports were chosen to assess the aforementioned mental states. To provide insightful information for future investigations, the researcher also collected information about participants' satisfaction levels and subjective experiences with the applied intervention. Results of the primary research questions indicate that benefits of the applied intervention for stressed female college students may be associated with decreasing states of negative affect, promoting relaxation, and relaxing muscle tension. Although positive affect scores dropped post-intervention, the ten positive affect items contained higher arousal words, which might not be appropriate descriptors for the participants' subjective experience with the applied intervention. Results of the secondary research questions indicate that all participants were either somewhat satisfied (19.4%) or very satisfied (80.6%) with the experience, and most participants (93.5%) expressed willingness to receive a comp (open full item for complete abstract)

Committee: Kamile Geist (Committee Chair); Richard Wetzel (Committee Member); Peggy Zoccola (Committee Member); Brent Beeson (Committee Member) Subjects: Behavioral Psychology; Music; Psychology

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

The glass transition is a central phenomenon controlling key properties of a wide variety of materials, ranging from polymers, organic and inorganic molecules to metals. Derived applications can be found in solar storage panels, global communications, tires, consumer electronics and so forth. Despite two centuries of dedicated research attempting to elucidate the fundamental mechanisms, no consensus on how a glass is formed is reached. Molecular dynamics (MD) simulation has been used as a powerful conduit for probing the nanoscale dynamics and has contributed significantly to the modern understanding of the glass transition, which by nature is a nanoscale problem where the decisive local structural relaxation spans from 1-10 nm. However, supercooled simulations in the past 30 years have shown an inability to probe the local relaxation time, ta, longer than 100 ns on most commercially available hardware. This limitation has posed serious threats to a full-fledged understanding of the glass transition and to the ability of simulation to quantitatively predict the glass transition measured at the laboratorial timescale, which by convention is defined at 100 s. In this work, we develop a bootstrapping quench-anneal approach for efficient supercooled simulation which collects well equilibrated data. This algorithm is named Predictive Stepwise Quenching (PreSQ) and has been integrated into a fully automated workflow. PreSQ demonstrates superior data reproducibility and offers at least 100-fold enhancement in efficiency over any existing protocols for supercooled simulation. PreSQ enables key insights into the underlying mechanisms of glass formation. The precipitous dynamic arrest that causes the glass transition has long been linked to the underlying particle localization. Through PreSQ, an unprecedented supercooled data covering more than 50 chemistries and 3000 data points, spanning 7+ decades of relaxation timescale, has been generated. From this remarkable data (open full item for complete abstract)

Committee: David Simmons (Advisor); Kevin Cavicchi (Committee Chair); Bryan Vogt (Committee Member); Mesfin Tsige (Committee Member); Malena Espanol (Committee Member) Subjects: Physics; Polymers

Doctor of Philosophy, The Ohio State University, 2015, Welding Engineering

Abstract Increasing the steam temperature and pressure in coal-fired power plants is a perpetual goal driven by the pursuit of increasing thermal cycle efficiency and reducing fuel consumption and emissions. The next target steam operating conditions, which are 760°C (1400°F) and 35 MPa (5000 psi) are known as Advanced Ultra Supercritical (AUSC), and can reduce CO2 emissions up to 13% but this cannot be achieved with traditional power plant construction materials. The use of precipitation-strengthened Nickel-based alloys (superalloys) is required for components which will experience the highest operating temperatures. The leading candidate superalloys for power plant construction are alloys 740H, 282, and 617. Superalloys have excellent elevated temperature properties due to careful microstructural design which is achieved through very specific heat treatments, often requiring solution annealing or homogenization at temperatures of 1100 °C or higher. A series of postweld heat treatments was investigated and it was found that homogenization steps before aging had no noticeable effect on weld metal microhardness, however; there were clear improvements in weld metal homogeneity. The full abstract can be viewed in the document itself.

Committee: John Lippold (Advisor); Boian Alexandrov (Committee Member); Antonio Ramirez (Committee Member) Subjects: Materials Science; Metallurgy

Doctor of Philosophy, University of Akron, 2015, Chemistry

Multiple systems were studied to advance the understanding of the chemical composition of the materials. These materials contained various structures or structures within different physical phases. Solid-state NMR techniques were used to probe effects of different chemical processes and environmental conditions on the chemical structures and phase composition of these materials. Much of the high thermal and chemical resistance of poly(vinylidene-co-hexafluoropropylene) is gained from cross-linking. The insolubility of the cross-linked fluoroelastomer has prevented the characterization of the structure at the cross-link site by NMR. Samples from each of the four stages of the cross-linking of poly(vinylidene-co-hexafluoropropylene) were analyzed with solid-state NMR to determine the chemical structure at the cross-linking site and the effects of cross-linking on the mobility of the elastomer chains. Spectral overlap from chemical shift dispersion hindered the use of simple 1D techniques to assign structural components to peaks in the NMR spectra. Relaxation studies that measured T1, T2, and T1ρ relaxation times were used to assign new peaks in the NMR spectra to the fluoride salts that are produced during cross-linking. The NMR relaxation data also indicated no reduction in the mobility of the fluoroelastomer from cross-linking. The chemical structure of the cross-link site was partially characterized by 2D-NMR. However, the amorphous nature of the polymer inhibited a full characterization of this location with 2D-NMR techniques. The structures that were identified at the cross-link site supported proposed structures. Solutions of NaCl and dextrose used in the preservation of premixed drugs were analyzed to distinguish the solid and liquid phases over a temperature range of -60 to 20 °C. The large chemical shift dispersion in the NMR spectra made analysis of the frequency domain data difficult. The time domain data of the single pulse NMR experiments were analyzed (open full item for complete abstract)

Committee: Peter Rinaldi Dr. (Advisor); Chrys Wesdemiotis Dr. (Committee Member); David Modarelli Dr. (Committee Member); Leah Shriver Dr. (Committee Member); Elizabeth McCord Dr. (Committee Member); Toshikazu Miyoshi Dr. (Committee Member) Subjects: Analytical Chemistry; Chemistry

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

Spin crossover is a physical phenomenon that occurs when the metal center in a complex has more than one stable electron configuration. Complexes of this type are typically characterized in the solid state for their potential applications in display devices, digital memory, and sensors. This dissertation consists of four chapters that investigate solution NMR relaxation enhancements in spin crossover-related complexes of Fe(II), Co(II) and Zn(II). Chapter 2 presents paramagnetic relaxation enhancements of Co(II) bis-trispyrazolylmethane in comparison to previously reported studies on Co(II) bis-trispyrazolylborate. Electron spin relaxation rates extracted from the individual measurement of the proton relaxation enhancements show structural dynamics occur at a higher temperature range in the trispyrazolylmethane complex. Often the counterion identity of spin crossover complexes affects the behavior of the metal center. In the case of [Fe(bpp)2]+2, the counterion has been shown to promote or inhibit spin transition. Chapters 3 and 4 are focused on determining how an anion not coordinated to the metal center can have such an effect. Chapter 3 presents a full solution characterization of the Co(II) analogs of bispyrazolylpyridine complexes to obtain a reference of thermal effects in the absence of spin crossover behavior. In this chapter, solution UV-vis, EPR, and NMR relaxation measurements of [Co(bpp)2]X2 (bpp=2,6-bis(pyrazol-1-yl)pyridine; X= BF4-, PF6-) are presented. Chapter 4 probes the relaxation of the counterion nuclei within bpp chelates using the relaxation measurements for solution distance calculations. Comparison of relaxation measurements of chelates containing paramagnetic, diamagnetic, and spin crossover active metal centers shows the BF4- counterion is more tightly associated than the PF6- counterion in solution. Variable-temperature proton NMR of the Fe(II) chelates reveals that, although it is not spin crossover active in solid state, [Fe(bpp)2][PF6] (open full item for complete abstract)

Committee: David Tierney PhD (Advisor); Michael Crowder PhD (Committee Chair); Robert McCarrick PhD (Committee Member); Gary Lorigan PhD (Committee Member); Elisabeth Widom PhD (Committee Member) Subjects: Chemistry; Inorganic Chemistry; Physical Chemistry

Master of Science in Sport Studies, Miami University, 2013, Exercise and Health Studies

Researchers have been divided on whether to include relaxation prior to imagery or not and research findings have been mixed. Although relaxation prior to imagery has been suggested to increase concentration on the imagery and imagery vividness it has not been scientifically studied before. The purpose of the present study was to compare the effectiveness of relaxation prior to PETTLEP imagery on soccer free-kick performance, concentration on imagery, and imagery vividness compared to PETTLEP imagery without relaxation and a control group. Participants were 16 elite soccer players, assigned to three groups (relaxation prior to PETTLEP, PETTLEP only, and control), participated in a five week intervention, took part in a soccer free-kick task, and answered questionnaires to evaluate concentration and imagery vividness. The results revealed that the relaxation prior to PETTLEP group significantly improved their concentration on imagery and scored significantly higher on subjective free-kick scores than the PETTLEP only group, but the PETTLEP only group had in general more imagery vividness.

Committee: Robert Weinberg (Advisor); Thelma Horn (Committee Member); Robin Vealey (Committee Member) Subjects: Kinesiology; Psychology

Doctor of Philosophy, The Ohio State University, 2006, Industrial and Systems Engineering

Compression molding has emerged as a promising technology for manufacturing aspherical glass lenses. In this method a glass gob or blank is pressed in a single operation into the shape of a finished lens. Annealing of the formed lens is then performed to achieve optical quality. The process is net shape, environment friendly and suitable for high volume production but has some inherent limitations which have prevented it from being used for industrial lens production. This dissertation research seeks a fundamental understanding of the molding process by adopting a combined experimental, analytical and numerical Finite Element Method (FEM) approach. Preliminary experiments were performed involving molding of a test aspherical glass lens on a commercial machine to study process capability to manufacture an optic component within the desired specifications. Experiments were also performed to determine the effect of different molding parameters on the final molded lens quality. A compression molding machine was designed and built in the laboratory. High temperature elastic modulus measurements were performed using Brillouin light scattering technique. The measured glass properties were used as input to the numerical simulation of cylinder compression experiments and lens molding. A numerical FEM simulation model of lens molding was developed and predictions were compared with the experiments. A 1D analytical heat transfer model during lens annealing has been presented that takes into account transient heat transfer at the glass-mold boundary. The possibility of implementing molding to make microlens array, freeform lens and diffractive lens has also been demonstrated. Experimental results have showed that molding process is capable of producing precision glass lenses with shape and form accuracy comparable to lenses manufactured using conventional abrasive techniques. Within the range investigated, the experiments did not show a significant influence of the molding para (open full item for complete abstract)

Committee: Allen Yi (Advisor) Subjects:

Master of Science, University of Akron, 2008, Physics

In an attempt to understand the effect of intense ultrasound on the devulcanization of unfilled and filled isoprene rubber (IR), melts and networks, non spectroscopic solid state NMR proton transverse relaxation (T2) and pulsed gradient diffusion measurements were performed. At 70.50C, the T2 relaxation decay of the unfilled and 35phr carbon black filled was successfully described by two-component four-parameter model. The long component mainly arose from the unentangled sol, dangling ends and oligomers, and the short component was due to the entangled sol and crosslinked network. Sonication increased intermolecular mobilities, while curing reversed this effect. The long and short T2 components in CB filled IR without processing oil increased with increasing sol generated, while no such increase was observed in the IR extended with oil. Thus, processing oil significantly altered the dependence of both T2 components on the sol fraction. The high melt molecular weight (M) without a low M tail precluded diffusion measurements. The IR melts were then degraded ultrasonically with and without subsequent vulcanization. It lowered and broadened the molecular weight distribution. This made it possible to conduct pulsed gradient diffusion experiments; the diffusion spectrum is bimodal. Here the T2 decays are consistent with a three- component model with six parameters. The additional component here is the intermediate T2 component. The results obtained were quantitatively related to earlier work in natural rubber.

Committee: Ernst Von Meerwall (Advisor) Subjects: Physics, General

Doctor of Philosophy, University of Akron, 2007, Polymer Science

Surfaces of most liquids in contact with air have higher entropy and lower melting temperature than the corresponding bulk liquids. Exceptions include materials consisting of linear chains such as n-alkanes, alkane analogues, and poly(n-alkyl acry-late)s, for which the surfaces remain frozen above the bulk melting temperature. We have studied the profound effect of this surface freezing on the static and the dynamic properties of these materials. Along with being a unique 2D effect, the surface frozen monolayer is a perfect example of the quasi 2D-crystal. Hence, it provides an opportunity to study the mechanical properties of 2D solids. Surface sensitive tools such as infrared-visible sum frequency generation spectroscopy, Wilhelmy balance, oscillating bubble surface rheometer, and X-ray synchrotron scattering were used in our investigation. The difference between the surface melting and the bulk melting temperatures is much higher for the poly(n-alkyl acrylate)s compared to their small molecule counterpart, n-alkanes. We have attributed this difference to the partial crystallinity of the alkyl side chains at the surface and the additional length of the surface frozen layer due to the ester linkage in the case of polymers. Surface freezing leads to a large surface rearrangement in binary blends of poly(n-alkyl acrylate)s differing only in a couple of methylene side chain units. Only 2 wt.% of the longer side chain component is enough to cover the surfaces below the surface freezing temperature. In addition, the surface transition temperature for the longer side chain component depends weakly on the bulk composition. A comparison of our experimental data with a newly developed thermodynamic model suggests that almost all the side chains of a surface molecule are present in the surface layer upon ordering. The surface transition has significant effects on the dynamic properties of these materials. The wetting dynamics of the poly(n-alkyl acrylate)s are dramatically m (open full item for complete abstract)

Committee: Ali Dhinojwala (Advisor) Subjects:

Master of Arts, The Ohio State University, 1980, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1969, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2024, Chemistry

Human immunodeficiency virus (HIV) and other RNA viruses pose a major threat to human health. Current therapeutic options are limited due to the multifaceted protein-RNA interactions that drive the lifecycle of HIV. The human heterogeneous nuclear ribonucleoprotein (hnRNP) H is a dynamic RNA-binding protein (RBP) that participates in many stages of RNA metabolism in humans and viruses alike, including in HIV type 1 (HIV-1). G-tracts—stretches of RNA consisting of three or more consecutive guanines—are the binding partners of hnRNP H. G-tracts are important splicing elements, and, due to their abundance, HIV-1 can recruit hnRNP H to bind to viral G-tracts within its genome. The interactions between hnRNP H and G-tracts can be studied using common 2D NMR techniques such as heteronuclear single quantum correlation (HSQC) or nuclear Overhauser effect spectroscopy (NOESY), but they are often cumbersome and require isotopic enrichment in nutrient-poor media. Fluorine (19F) NMR spectroscopy is a viable 1D alternative to 2D methods used for characterizing proteins, owing to both the excellent sensitivity of 19F and the much lower time cost it takes in running 1D versus 2D NMR experiments. The usefulness of 19F NMR is highlighted through two separate projects that reveal mechanistic insights into hnRNP H:G-tract molecular recognition. 19F is NMR active and is not found in essentially any biological system, making it suitable for studying protein-nucleic-acid interactions. 19F NMR spectroscopy can be coupled with paramagnetic relaxation enhancement (PRE), the effect of which can be measured in order to study non-specific interactions in a dynamic environment. Here, 19F NMR PREs are used in order to gain both qualitative and quantitative distance-dependent information about hnRNP H:G-tract binding (Chapter 2). 19F NMR spectroscopy can also be used to monitor changes in protein-RNA complexes resulting from drug binding as part of a larger screening pipeline dubbed “Targeting of (open full item for complete abstract)

Committee: Blanton Tolbert (Advisor); Divita Mathur (Advisor); Fu-Sen Liang (Committee Chair); Robert Salomon (Committee Member); Thomas Gerken (Committee Member); Metin Karayılan (Committee Member) Subjects: Biochemistry; Biophysics; Chemistry; Molecular Biology

Master of Science, University of Akron, 2024, Polymer Engineering

Highly branched low-density polyethylene (HB-LDPE) synthesized from solely ethylene monomer through Brookhart-type α-diimine nickel or palladium catalysts have unique microstructure, low melting temperature and thermal plastic elastomer (TPE) properties. With the increasing demand for recyclable material, synthesis of HB-LDPE has been extensively studied. However, details of its microstructure and the impact of the microstructure on solid structure as well as mechanical/thermal properties have not been fully understood. In this study, various characterizations and mechanical testing are conducted on HB-LDPE entries synthesized by original Brookhart catalyst, 8-p-tolylnaphthylimino substituted sandwich catalyst, and a multinuclear heterogeneous crosslinked catalyst. First, 13C solution-state NMR spectroscopy was employed to obtain detailed insights into their branch structure, including branch density, identity and localization. Using chemical superposition methods, detailed localization structure of the branches were revealed. Formation mechanisms of several localization structures are proposed in supplementary for existing chain walking mechanisms. Second, the solid structure of HB-LDPEs was investigated by using differential Scanning calorimetry (DSC), X-ray diffraction (XRD) and solid-state NMR spectroscopy. The formers are no longer capable of quantitative characterization due to the low crystallinity. Through solid-state 13C NMR analysis, it was found that some entries are entirely amorphous, while the others are semi-crystalline entries which range between 1 and 5 %. The molecular dynamics in the crystalline phase is characterized through 13C spin-lattice relaxation time (T1C), which ranges from 4s to 80s, implying a variable crystalline size. By examining the combination of microstructure and crystalline structure, it is revealed that only those entries with both low levels of long chain branching (LCB) below 10 b/1kC and short chain branching (SCB) below (open full item for complete abstract)

Committee: Toshikazu Miyoshi (Advisor); Junpeng Wang (Committee Member); James Eagan (Committee Chair) Subjects: Materials Science; Molecular Chemistry; Molecular Physics

Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

As technology continues to evolve and diversify, so too does the complexity of soft polymeric devices. It has become increasingly important to develop a set of design criteria for polymer synthesis and fabrication that corresponds to success in electrical engineering and robotics spaces. Polymer material interfaces are widely employed in such devices due to their versatility and excellent characteristics. One goal is to expand the repertoire of polymeric substrates suitable for fabrication of inkjet-printed electronics. This work will focus on strategies for maintaining high conductivity in hydrophilic flexible electronics, while other strategies have been employed previously for hydrophobic substrates. It was found that by pre-treating poly(vinyl alcohol) solutions with trace quantities of an inorganic salt such as magnesium chloride, electronic sensors could be fabricated with high resolution and a low fabrication temperature of 80°C. This demonstrates the importance of the organic-inorganic interfaces in electronic properties. Mg-treated films maintained sheet resistance values of 0.2 Ohms/square, comparable to bulk silver, under both wet and dry conditions, 0-90° curvature, and 0-6% strain. To better understand the design criteria for polymers in soft robotics, a model system of a bilayer composed of an elastic and viscoelastic film was investigated. Bilayer films of SEPS elastomer and butyl rubber demonstrate reversible curvature upon strain-hold-release mechanical cycling. These curvatures and relaxation times can be described with linear and nonlinear spring-dashpot viscoelastic models. Simulations from FEA based on these models showed excellent correlation to the measured values, especially in the generalized Maxwell model. Generalized Maxwell predicts curvature over time with the lowest overall mean absolute scaled error of 0.519, which corresponds to a 4.9% difference from the second lowest error model and 76.8% difference from the highest error mod (open full item for complete abstract)

Committee: Gary Wnek (Committee Chair); Lei Zhu (Committee Member); Hatsuo Ishida (Committee Member); Kathryn Daltorio (Committee Member) Subjects: Electrical Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2023, Polymer Science

We have elucidated details of how the microscopic structure and dynamics of filler in reinforced rubbers influence mechanical properties. Studies were performed on highly loaded, silica-filled, crosslinked styrene-butadiene rubber (SBR). Properties of the compounds studied were varied by addition of silane coupling agents, silicas of different surface area, and by addition of well-characterized, anionically-polymerized, low molecular weight, dimethylamino end-functionalized SBR additives of linear or star molecular architecture. Samples were probed with a combination of Ultra-small Angle X-ray Scattering/Small Angle Scattering (USAXS/SAXS), X-ray Photon Correlation Spectroscopy (XPCS), and mechanical measurements. Investigation of samples with or without silane coupling agents confirms that coupling agents enhance filler dispersion. This enhanced dispersion leads to slower filler dynamics when the rubber is strained and a slower change in dynamics over time. These slower dynamics and slower evolution of dynamics correlate with slower macroscopic stress relaxation. Our work also examines the temporally heterogenous dynamics that underlie the stress relaxation process. During stress relaxation, filler dynamics intermittently speed up and slow down. These results indicate that while macroscopic stress relaxation appears to be a relatively simple process, the microscopic behavior is complex. Studies on rubbers containing high surface area, milled silica under dynamic strain reveal that while rubber containing milled silica and monosulfidic coupling agent shows a large Payne effect, the breakdown of filler is suppressed. We infer that debonding and/or yielding of bridging bound layers is responsible for the Payne effect in this sample. These bridging layers provide this rubber with a high modulus and low hysteresis. Addition of end-functionalized SBRs to rubber drastically affects mechanical properties. Rubber containing conventional silica and 20 kg/mol difunctio (open full item for complete abstract)

Committee: Mark Foster (Advisor); Roderic Quirk (Other); Jutta Luettmer-Strathmann (Committee Member); Mesfin Tsige (Committee Member); Junpeng Wang (Committee Member); Li Jia (Committee Chair) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Determination of high-resolution three-dimensional structures of biological macromolecules is essential to studying their physiological functions. In recent years direct proton detection based magic angle spinning solid-state NMR has emerged as a widely applicable atomic-resolution structural tool that permits structure and dynamics studies of biological systems that are challenging for the usual structural techniques such as cryo-electron microscopy, X-ray crystallography, and solution-state NMR. In spite of remarkable recent progress in the accurate structural elucidation of biosystems, the widespread application of solid-state NMR for structural studies of large biosystems is hampered due to the dearth of unambiguous long-distance structural restraints. The conventional solid-state NMR approaches rely on upon through space 13C-13C and 13C-15N magnetic dipole-dipole coupling measurement to obtain structural restraints, which become vanishingly small for distances in the 5-6 A regime and beyond. The paucity of long-range restraints from traditional through space dipolar coupling measurement-based approaches can be circumvented by site-specific incorporation of paramagnetic center to modified locations of a natively diamagnetic protein using a covalently bound paramagnetic tag. The introduction paramagnetic center in the diamagnetic system leads to the generation of large electron-nuclear hyperfine coupling interactions – which manifest themselves in NMR spectra as pseudocontact shifts (PCSs) and paramagnetic relaxation enhancement (PREs). The measurement of the magnitude of the electron-nuclear interactions can be used to obtain long-distance structural restraints for high-resolution structure calculation. In the solution state, PCSs and PREs measurements have been extensively utilized as long-range structural restraints for the analysis of the structure and interactions of biological macromolecules. However, the widespread applications of PCSs and PREs in solid-s (open full item for complete abstract)

Committee: Prof. Christopher Jaroniec (Advisor) Subjects: Chemistry

Doctor of Philosophy, University of Toledo, 2022, Educational Psychology

This study utilized a convergent-parallel mixed methods design to explore the usefulness of a remote relaxation-based intervention's ability to foster mindfulness and self-determination for stress management by collegiate athletes. Although stress is a common experience related to college retention, collegiate athletes experience additional stressors related to athletic training and performance. Through thematic analysis, this research found that collegiate athletes identified managing academics, time management, use of technology, and finances as primary stressors. A remote relaxation-based intervention was offered the participants an opportunity to learn and experience deep breathing, guided imagery, mandala coloring, and self-hand massage interventions designed to increase mindfulness and coping for stress management while strengthen the basic psychological needs. Participant self-reports, identified that they were able to learn active coping skills that allowed them to manage stressors. They demonstrated mindfulness related to identification of their stress through their self-reports of symptoms, need for interventions, and benefits of techniques learned. Although statistical significance was not found, triangulation of the data allowed for a rich understanding of participants experiences and demonstrated that the participants were able to utilize the techniques learned to manage their stress levels with positive outcomes. Participants also reported that they were utilizing the techniques learned outside of the intervention sessions to manage stress. At the conclusion of the interventions, participants reported that if such interventions were made available to them on campus, nearly half reported they would utilize these resources again, demonstrating buy-in for the usefulness of the techniques by the participants.

Committee: Revathy Kumar (Advisor) Subjects: Educational Psychology; Higher Education; Mental Health; Peace Studies; Recreation