Master of Science, The Ohio State University, 2017, Mechanical Engineering

Perovskite crystals have been widely researched and applied in the field of solar cell engineering, and recently in the field of high energy photon detection. Within the nuclear detection industry, there is a desire for new, cost-effective materials for the use of gamma spectroscopy. This thesis sets out to produce a new hybrid inorganic – organic metal halide perovskite based, low-cost gamma spectroscopy detector. With the aid of Professor Haung's group from the University of Nebraska-Lincoln, various perovskite device structures are fabricated and tested. To assist in the verification of the experimental results, the energy spectrum for the nuclear decay of the 137Cs isotope is generated through modeling of real-time pulse height analysis with simulation software Geant4. A well-defined 137Cs energy spectrum is acquired by using a CH3NH3PbBr2.94Cl0.06 single crystal at room temperature. The energy spectrum obtained, along with supporting data, provides evidence of how perovskite single crystal can successfully detect high energy photons. The low cost, simple synthesis, and excellent radiation hardness of the hybrid perovskites make them ideal candidates for radiation detector materials.

Committee: Lei Cao Ph.D (Advisor); Vaibhav Sinha Ph.D (Committee Member) Subjects: Electrical Engineering; Mechanical Engineering; Nuclear Engineering

Doctor of Philosophy, University of Akron, 2020, Chemistry

The receptors embedded in cell membranes are essential for signaling in response to various stimuli or communicating with neighboring cells. In order to target these membrane proteins for drug discovery, it is essential to understand their interactions with each other in the live cell. Techniques such as structural studies, interactions in solution, and live cell fluorescence have all aided in determining the details of protein-protein complex formation. Here fluorescence cross-correlation spectroscopy (FCCS) is used to elucidate these events in live cells. This method allows analysis of fluorescent protein intensity fluctuations to gain insight on protein diffusion and oligomerization in the 2D cell membrane. The research presented here aimed to determine homotypic and heterotypic interactions for the plexin/neuropilin/semaphorin family of proteins. These membrane proteins are involved with tissue patterning in the developing embryo and play various roles in disease. While truncated, soluble domains have been studied in some capacity, the full-length receptor complexes have not been completely explored and FCCS allows insight to their network of interactions. Chapter I and II give an introduction to these receptors and an overview of the FCCS methods used. Chapters III and IV focus on the degree of interaction between Neuropilin-1 (Nrp1), Plexin A2, Plexin A4, and Plexin D1 when stimulated by Semaphorin 3A or Semaphorin 3C. These combinations have been implicated in various cancers and this work resolves interactions which may aid in the design of new therapeutic strategies. Chapter V looks at the oligomerization of the transmembrane domains of Nrp1, Plexin B1, Plexin B2, and Plexin D1 using FCCS and computational predictions. Most experiments agreed with the simulations, showing individual motifs which enhanced or disrupted helix interactions, while also revealing that competition in the live cell may prevent some of the interactions predicted in isolation. Chapte (open full item for complete abstract)

Committee: Adam Smith (Advisor); Leah Shriver (Committee Member); Michael Konopka (Committee Member); Sailaja Paruchuri (Committee Member); Nic Leipzig (Committee Member) Subjects: Biochemistry; Biophysics; Chemistry

Doctor of Philosophy (PhD), Ohio University, 2018, Physics and Astronomy (Arts and Sciences)

The question of the immutability of the traditional "magic numbers" and structure of exotic nuclei near to shell closures has long been an area of interest both experimentally and theoretically. The neutron-rich Mg isotopes around N=20 are examples of a region where the expected spherical shell gap has narrowed or disappeared entirely. The "Island of Inversion," centered around 32Mg, is a region where a narrowed N=20 shell gap and collective np-nh excitations result in nuclei with deformed ground states. However, despite years of theoretical and experimental efforts, a complete picture of the detailed nature of deformation in this region has not been achieved and the level schemes remain largely incomplete for many of these neutron-rich nuclei. Furthermore, the presence of rotational band structures, which are key signatures of deformation, have only recently been observed in this region. Two experiments were performed at the National Superconducting Cyclotron Laboratory (NSCL) in order to probe the structure of the A=33 isobars in the "island of inversion." A beta-decay experiment (NSCL e14063) was performed to investigate the level schemes and decay schemes for the decay of 32Na to 32Mg, 33Na to 33Mg, 33Na to 33Mg to 33Al, and 33Mg to 33Al. The details of the experiment are discussed and level schemes and decay schemes, along with the implications for the observed structure. Additionally, the half-lives for 32,33Na and 33Mg were determined. A measurement (NSCL e11029) of the low-lying level structure of 33Mg populated by a two-stage projectile fragmentation reaction and studied with GRETINA was also performed. The experimental setup is discussed along with the gamma-ray singles and gamma-gamma coincidence analysis used to construct the level scheme for 33Mg. The experimental level energies, ground state magnetic moment, intrinsic quadrupole moment, and gamma-ray intensities are compared to a leading order rotational model in the strong-coupling limit. Lastl (open full item for complete abstract)

Committee: Heather Crawford (Advisor); Carl Brune (Committee Member); Daniel Phillips (Committee Member); Alexander Neiman (Committee Member); Katherine Cimatu (Committee Member) Subjects: Nuclear Physics; Physics

PhD, University of Cincinnati, 2016, Engineering and Applied Science: Nuclear and Radiological Engineering

Some of the major safety concerns in the nuclear power industry focus on the readiness of nuclear power plant safety systems to respond to an abnormal event, the security of special nuclear materials in used nuclear fuels, and the need for physical security to protect personnel and reactor safety systems from an act of terror. Routine maintenance and tests of all nuclear reactor safety systems are performed on a regular basis to confirm the ability of these systems to operate as expected. However, these tests do not determine the reliability of these safety systems and whether the systems will perform for the duration of an accident and whether they will perform their tasks without failure after being engaged. This research has investigated the progression of spindle asynchronous error motion determined from spindle accelerations to predict bearings failure onset. This method could be applied to coolant pumps that are essential components of emergency core cooling systems at all nuclear power plants. Recent security upgrades mandated by the Nuclear Regulatory Commission and the Department of Homeland Security have resulted in implementation of multiple physical security barriers around all of the commercial and research nuclear reactors in the United States. A second part of this research attempts to address an increased concern about illegal trafficking of Special Nuclear Materials (SNM). This research describes a multi element scintillation detector system designed for non – invasive (passive) gamma ray surveillance for concealed SNM that may be within an area or sealed in a package, vehicle or shipping container. Detection capabilities of the system were greatly enhanced through digital signal processing, which allows the combination of two very powerful techniques: 1) Compton Suppression (CS) and 2) Pulse Shape Discrimination (PSD) with less reliance on complicated analog instrumentation.

Committee: Randall Allemang Ph.D. (Committee Chair); Sam Glover Ph.D. (Committee Member); David L. Brown Ph.D. (Committee Member); Henry Spitz Ph.D. (Committee Member) Subjects: Nuclear Engineering

Doctor of Philosophy (PhD), Ohio University, 2016, Physics and Astronomy (Arts and Sciences)

The ³H(d,γ)⁵He reaction and the ³H(d,γ)/ ³H(d,n) branching ratio have been measured using a 500–keV pulsed deuteron beam incident on a titanium tritide target of stopping thickness at the Edwards Accelerator Laboratory. The time–of–flight technique has been used to distinguish the γ–rays from neutrons in the bismuth germinate (BGO) γ–ray detector. A stilbene scintillator and an NE–213 scintillator have been used to detect the neutrons from the ³H(d,n)α reaction using both the pulse–shape discrimination and time–of–flight techniques. A target holder with an ion–implanted silicon detector at a fixed angle of 135° to the beam axis to simultaneously measure α–particles as a normalization for the number of neutrons was incorporated to reduce the uncertainty in the neutron yield over the preliminary measurement. The γ–rays have been measured at laboratory angles of 0°, 45°, 90°, and 135°. Information about the γ–ray energy distribution for the unbound ground state and first excited state of ⁵He have been obtained experimentally by comparing the BGO data to Monte Carlo simulations. The reported branching ratios for each angle contain only contributions from the ground-state γ–ray branch.

Committee: Carl Brune PhD (Advisor); Daniel Phillips PhD (Committee Member); Joseph Shields PhD (Committee Member); Morgan Vis PhD (Committee Member) Subjects: Nuclear Physics

Master of Science, The Ohio State University, 2016, Nuclear Engineering

Primordial terrestrial radiation is mainly a consequence of the radioactive decay of nuclei in three naturally occurring decay series known as uranium series, actinium series, and thorium series. The parent nuclei along with the progeny (decay products) of these decay series can be found in various concentrations in Earth's crust. Among the progeny, 226Ra is of greatest concern. 226Ra is water soluble and it decays to 222Rn which is a gas, which allows these two radionuclides to migrate considerable distances. 226Ra is found in shale at relatively high concentrations compared to other rock formations making shale a naturally occurring radioactive material (NORM). One concern with hydraulic fracturing is that the extraction of the gas embedded in the shale formation buried deep within Earth's crust is bringing radioactive nuclides to Earth's surface. This thesis is focused on the development of gamma-ray spectroscopic methods to determine the radium concentration in drill cuttings and water that is produced by hydraulic fracturing. The methods rely upon the development of secular equilibrium between 226Ra and its progeny. Only the countrate of the 214Bi 609 keV gamma-rays is counted and compared to the countrate of 137Cs activity doped in standards. Measurement methods are unique in that two factors are used to correct for the varying sample attenuation of the 214Bi 609 keV gamma-ray resulting from varying compositions and densities in each sample. Measurements are made with a 137Cs point source that is placed on top of the sample and is used for one correction factor, and Monte Carlo simulations of the response of an HPGe gamma-ray detector are used for the other correction factor. For a representative drill cutting sample, the product of the correction factors equals approximately 0.89. For a representative water sample, the product of the correction factors equals approximately 1.17.

Committee: Thomas Blue PhD (Advisor); Raymond Cao PhD (Committee Member) Subjects: Nuclear Engineering

MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering

This research paper explores the possibility that treating nanomaterials with radiation from neutrons or photons will simulate the processes of diffusion and mass transfer, recovery and recrystallization, formation and interaction of defects. The defects in irradiated CNTs are mostly restricted to the outer layers. Although they appear to be well separated at the beginning, the increase in dosage may cause them to melt and eventually thicken. The most common structural defects one can notice in CNTs are atomic vacancies, topological defects, dangling bonds, microvoids and Stone-Wales defects. When graphene is irradiated there is a possibility that the high-energy particles induce morphological changes. Increase in dosage of radiation is inversely proportional to the probability of production of complex defects. Graphene has a unique property of hosting lattice defects in reconstructed atom arrangements. These defects locally increase the reactivity of the structure and allow adsorption of other atoms on graphene. The most common structural defects in graphene are Stone-Wales defects, single vacancies, reconstructed double vacancies, adatoms or interstitial atoms, substitutional impurities and line defects or one dimensional defects. Raman Spectroscopy and Thermo-Gravimetric Analysis were used in characterizing the materials and Transmission Electron microscope to image the materials before and after exposure to irradiation. To further study how the irradiation modified the nanomaterials some of them were dispersed in water. The pristine samples do not disperse due to the lack of defects while the ones exposed to radiation show that they form a homogenous mixture in some cases.

Committee: Henry Spitz Ph.D. (Committee Chair); Sam Glover Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2013, Engineering and Applied Science: Nuclear and Radiological Engineering

This research improves the measurement of activity deposited in the axillary lymph nodes through the following specific aims:A. Determine the confounding influence of 241Am deposited in organs adjacent to the axillary lymph nodes by simultaneous solution of response functions for measurement of 241Am deposited in the liver, lungs, and skeleton.Hypothesis: A series of direct, organ-specific measurements can be used to account for measurement interference for the axillary lymph nodes from activity deposited in other organs.Radioactive material deposited in multiple organs of the body is likely to confound a result of an in vivo measurement performed over the lungs for routine occupational exposure monitoring. The significance of this interference was evaluated by measuring anthropometric torso phantoms containing lungs, liver, skeleton and axillary lymph nodes, each with a precisely known quantity of 241Am uniformly distributed in the organs. Arrays of multiple high resolution germanium detectors were positioned over organs within the torso phantom containing 241Am or over proximal organs without activity to determine the degree of measurement confounding due to photons emitted from other source organs. A set of four mathematical response functions describe the measured count rate with detectors positioned over each of the relevant organs and 241Am contained in the measured organ or one of the other organs selected as a confounder. Simultaneous solution of these equations yields the activity deposited in each of the relevant organs. The matrix solutions described represent a technically valid method for adjusting a result of 241Am measured in one organ for interferences that may arise from 241Am deposited elsewhere, so internal dose from radioactive materials known to deposit in multiple organs may be evaluated based upon in vivo measurements.B. Select the size and type of detector that offers the greatest sensitivity for 241Am in axillary lymph nodes measurements wit (open full item for complete abstract)

Committee: Henry Spitz Ph.D. (Committee Chair); Sam Glover Ph.D. (Committee Member); J. Kim Ph.D. (Committee Member); Paul Succop Ph.D. (Committee Member) Subjects: Nuclear Engineering

Doctor of Philosophy, The Ohio State University, 2009, Nuclear Engineering

The IAEA will require advanced technologies to effectively safeguard nuclear material at envisioned large scale nuclear reprocessing plants. This dissertation describes results from simulations and experiments designed to test the Multi-Isotope Process (MIP) Monitor, a novel safeguards approach for process monitoring in reprocessing plants. The MIP Monitor combines the detection of intrinsic gamma ray signatures emitted from process solutions with multivariate analysis to detect off-normal conditions in process streams, nondestructively and in near-real time (NRT). Three different models were used to predict spent nuclear fuel composition, estimate chemical distribution during separation, and simulate spectra from a variety of gamma detectors in product and raffinate streams for processed fuel. This was done for fuel with various irradiation histories and under a variety of plant operating conditions. Experiments were performed to validate the results from the model. Three segments of commercial spent nuclear fuel with variations in burnup and cooling time were dissolved and subjected to a batch PUREX method to separate the uranium and plutonium from fission and activation products. Gamma spectra were recorded by high purity germanium (HPGe) and cadmium zinc telluride (CZT) detectors. Hierarchal Cluster Analysis (HCA) and Principal Component Analysis (PCA) were applied to spectra from both model and experiment to investigate spectral variations as a function of acid concentration, burnup level and cooling time. Partial Least Squares was utilized to extract quantitative information about process variables, such as acid concentration or burnup. The MIP Monitor was found to be sensitive to the induced variations of the process and was capable of extracting quantitative process information from the analyzed spectra.

Committee: Richard Christensen PhD (Advisor); Richard Denning PhD (Committee Member); Xiaodong Sun PhD (Committee Member) Subjects: Engineering; Nuclear Chemistry; Radiation

Master of Science, University of Toledo, 2013, Geology

Coastal dunes of Lake Michigan and corresponding down-wind lakes are studied for links between dune activity and climatic forcing; to date, little is certain about climate control on dune activity. By unveiling relationships between climate variables and dune activity, it becomes possible to associate the activity of dunes with certain climatic conditions. In this study wind, temperature, precipitation, drought, evaporation, and lake level are correlated individually with 210Pb/137Cs/7Be dated sand deposits from core samples taken in a small lake in the lee side of a dune ridge near Saugatuck, Michigan. Linear regressions were run to evaluate the strength of their relationship year-by-year, and offsets of one to two years. Visual correlations were also attempted by evaluating the trends in the annular data sets. While year-by-year R2 values were not strong, or mixed results made them inconclusive, visually examined trends showed more promising correlations. The strongest correlations existed between sand percent by weight, drought, and lake level. Discrepancies between trends were acceptable within the limits of associated error with isotopic dating methods, and showed a relationship between rising or high lake levels, wet conditions, and strong eolian activity (based on increased presence of sand in lake sediment). The implications of this research are that dune activity is linked to periods of wet conditions and storminess, and results can be used as a modern analogue for coastal dune activity during times of high lake level.

Committee: Timothy Fisher PhD (Committee Chair); David Krantz PhD (Committee Member); Johan Gottgens PhD (Committee Member); Richard Becker PhD (Committee Member) Subjects: Climate Change; Earth; Environmental Geology; Environmental Science; Geography; Geological; Geology; Geomorphology; Paleoclimate Science