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Material and Photonic Engineering on Lead Selenide Nanocrystal Films for Mid-infrared Emitter Development
No full textLead selenide (PbSe) is a IV-VI semiconductor material and is known to have a high absorption coefficient. This property comes from its narrow band gap (0.27eV) and strong interaction with light within the material. This means that it efficiently absorbs a significant amount of light relative to its thickness. The high absorption coefficient makes it a promising material also for solar cell absorbers, as it efficiently converts light into electrical current over a broad wavelength range. Research on PbSe has been ongoing for nearly a century, with continuous advancements in understanding its properties and potential applications. The full extent of its physical properties remains underutilized in practical devices. Despite significant advancements in recent technologies, there is still considerable potential for improving the performance and cost-efficiency of miniaturized MIR gas sensing systems. This thesis aims to develop a narrowband mid-infrared emitter by leveraging photonic engineering techniques applied to lead selenide (PbSe) nanocrystals. A key challenge lies in the inherently low radiative efficiency of PbSe, particularly at room temperature, where non-radiative processes, most notably Auger recombination tend to dominatecarrier dynamics. The first chapter of the thesis presents an overview of the properties of Lead Selenide (PbSe) and High Contrast Gratings (HCG) in the context of mid-infrared photodetection. It examines various PbSe growth techniques, emphasizing the relevance of the Chemical Bath Deposition method. Furthermore, it introduces a novel approach known as Oriented Attachment, underscoring its role in improving the material characteristics of PbSe. Chapter two of the thesis focused on deposition PbSe using Chemical Bath Deposition method, which allow the cost-effective and scalable fabrication of MIR photonic devices. In this study, I employed the water bath method to grow uniform PbSe nanocrystals using the Oriented Attachment technique on amorphous substrates. Different parameters were varied during the growth process and their effects were critically analysed. In chapter three, I studied about the annealing effects on PbSe sample. After annealing with nitrogen at different temperatures, photo luminesce significantly improved.Surface morphologies before and after the annealing of PbSe thin films were studied by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The chapter four of this thesis explores the nanostructure design simulated using RSoft software, followed by the fabrication methods applied to lead selenide samples which includes the photolithography process. This work contributes to the goal of developing compact, cost-effective, low-power, and highly efficient on-chip MIR narrowband emitter for chemical sensing applications. This work explores methods to enhance PbSe film quality, along with the design and fabrication of photonic structures on PbSe samples, potentially improving the performance of PbSe-based MWIR sensingplatforms. Additionally, the potential future work aimed at enhancing the performance of PbSe emitters and photodetectors will be discussed in the concluding section of the thesis
RECONSTRUCTING THE DRIVERS OF EXHUMATION WITHIN THE CANADIAN ROCKY MOUNTAIN FOLD-THRUST BELT USING LOW-TEMPERATURE THERMOCHRONOLOGY
No full textThe Rocky Mountain fold-thrust belt (RMFTB) in Canada has been a key locality for understanding geometries and kinematics of thin-skinned deformation. Despite its role as a global analogue for fold-thrust belts, questions persist regarding the timing and duration of deformation. In part, this is because the exhumation associated with RMFTB deformation has been subsequently overprinted by Eocene –Miocene unroofing and more recent glaciation. To resolve the timing of shortening in the RMFTB, we applied low-temperature thermochronology to major faults across the Rocky Mountain fold-thrust belt within Jasper National Park and the surrounding areas. We report zircon U-Pb, zircon fission-track (ZFT), and zircon (U-Th)/He (ZHe) data from the hanging wall of nine faults which cut Proterozoic to Cretaceous strata across a ~145 km east-west transect. One sample from the Omineca belt yielded a ZFT age ~100 Ma and a ZHe age ~20 Ma, which we interpret to record mid-Cretaceous ductile deformation and early Miocene extensional exhumation of the Omineca belt. Samples from the hanging walls of thrust faults in the Main and Front Ranges yielded ZFT ages ~230 – 100 Ma which we suggest record Triassic subduction initiation and mid-Cretaceous RMFTB related shortening. The Main and Front Ranges yielded associated ZHe ages of ~ 60 – 30 Ma which we interpret to record the final early Eocene stages of thrusting and/or onset of extensional exhumation. Within the Foothills, thrust faults yielded ZFT ages ~360 – 100 Ma with associated ZHe ages ~110 – 60 Ma. We suggest these represent Cretaceous RMFTB related shortening, as well as the presence of unreset zircons derived from the arc. Our data suggest that Triassic subduction initiation along the margin of the Canadian Cordillera may have played a larger role in the evolution of the RMFTB than previously recognized. In addition, we find that the single-grain ZFT ages from the shallowly buried samples yield distinct age-rare earth element trends, suggesting a potential geochemical influence on ZFT annealing kinetics. Low temperature thermochronology and associated thermal history modelling from hanging-walls of major faults supports continuous rock cooling from the early Triassic to the Paleocene in the southern RMFTB, which we interpret to reflect long-lived shortening. We find evidence for Cenozoic exhumation in the RMFTB, consistent with regional studies that document large-scale erosion that post-dates shortening related deformation. We suggest that RMFTB propagation was directly linked to orogen-scale development and records protracted shortening as well as extensive post-orogenic erosional unroofing
WAITIN’ ON THE WORKPLACE TO CHANGE: MANAGERIAL CONTROL, RESTAURANT INDUSTRY DYNAMICS, AND TIPPED WORKER RESISTANCE
No full textThis study investigates how industry dynamics and managerial control shape tipped workers’ resistance behaviors in the restaurant service industry. Specifically, interview participants were employees working in Oklahoma, a state with the lowest minimum wage laws for tipped workers in the restaurant industry. Analysis of interviews with servers and bartenders revealed that managerial control, in the Edwards (1979) sense of simple arbitrary control, often shaped when, how, and whether tipped workers engaged in resistance; specifically, workers tended to engage in routine resistance behaviors based on constantly evolving evaluations of fairness. Arbitrary control forms and income volatility led to chronic evaluations of (un)fairness by tipped workers, thus increasing uncertainty and precarity in the workplace
STRATIGRAPHIC VARIABILITY AND PETROPHYSICAL CHARACTERISTICS OF THE PENNSYLVANIAN PRUE SANDSTONE AND OSWEGO LIMESTONE, CENTRAL LINCOLN COUNTY, OKLAHOMA
No full textABSTRACTThe Prue Sandstone in Lincoln County, Oklahoma is interpreted to have been deposited in a tidally influenced deltaic environment. The Prue Sandstone consists of three main subenvironments: incised valley fills, distributary channels, and fluvial flood plains. Distributary channels are characterized by light gray, medium to fine grain micaceous sandstones with localized flaser and wavy laminations. Fluvial flood plains exhibit planar laminations to wavy laminations of fine-grained gray sandstone and dark mudstone. Coal in the upper Prue Sandstone is associated with fluvial flood plains. Coal is discontinuous in the study area and separated by sandstones and shales. The Oswego Limestone represents a shallow-marine to marine environment that was situated along a southwest-northeast trending shoreline. The Excello Shale separates the Oswego Limestone and the Prue Sandstone and is thin and continuous across the study area. While both the Oswego Limestone and the Prue Sandstone are known hydrocarbon reservoirs in Lincoln County, Oklahoma, their stratigraphy, sedimentology, and reservoir characteristics have not been extensively studied. Therefore, this study explores the Prue Sandstone and Oswego Limestone structure, lithology, total porosity, effective porosity, water saturation, and bulk volume hydrocarbon through well-log analysis and 3-D geostatistical modeling. In the 224-mi2 (580 km2) study area, >400 wells were used for stratigraphic correlations. Of the 400 wells used for correlations, 198 wells were digitized to provide a combination of gamma-ray, neutron-porosity, bulk-density, and resistivity logs. Two wells close to the study area provide core from selected intervals. Subsurface correlation and mapping and petrophysical analyses of the Prue Sandstone and Oswego Limestone were based on well-log data. The Oswego Limestone and Prue Sandstone thickness vary from ~2–45 ft (~0.61–13.71 km) and v ~50–150 ft (~15.24–45.72m), respectively. Petrophysical analysis of the sandstones within the Prue Sandstone indicate effective porosity values from 1–33% and Sw values from 21–100%. The Oswego Limestone total porosity varies from 0–26% and Sw values range from 20–100%. Three-dimensional reservoir models of the Oswego Limestone and Prue Sandstone illustrate the high reservoir heterogeneity across the study area that is controlled by the stratigraphic variability of lithologies and their depositional trends
Kataikaḷ: Navigating Home And Sense Of Belonging As Queer Desi/South Asian Transnational Graduate Students In Higher Education
No full textThis dissertation illuminates the lived experiences of Queer Desi/South Asian Transnational Scholars (QDTS), specifically graduate students in Higher Education Institutions (HEIs) situated in the United States. The purpose of this research study was to understand how QDTS scholars, specifically graduate students, negotiate and navigate identity formation, belonging, and home within hostile academic and sociopolitical spaces in the Global North that are shaped by colonial logics and values of neoliberalism, white supremacy, and cisheteropatriarchy. This work is informed by de/colonial, Par/Des(i) ontoepistemic and Queer Transnational Feminist framings. Using Kataikaḷ (கதைகள்)—a hybridized, de/colonial, contemplative, and creative qualitative methodology grounded in South Asian storytelling, astrology, and cultural traditions of Kiḷi jōtiṭam (கிளி ஜோதிடம்) and Harikatha Kalakshepam and analysis through paintings, this dissertation moves away from damage-centric and deficit ideologies that dominate discourse surrounding Queer People of Color (QPoC) and emphasizes resistance, resilience, and self-authorship while disrupting homogenized and essentialized notions of belonging, home, and South Asian and Queer identities by situating the fluid, non-linear, and situated experiences of QDTS. This dissertation also offers readers an interactive, reflective, and creative session where they can engage with the QDTS Kataikaḷ through a deck of cards inspired by Kiḷi jōtiṭam and Tarot, informed by their stories and the paintings from analysis to foster deeper connection and meaningful engagement
Linking Phylogeny and Ecology to Enigmatic Freshwater Mussel Shell Morphologies
No full textVirtually all organisms rely on external morphology to interact with the environment, which makes observable differences between species, the fundamental unit of biodiversity, an exceptionally useful means of classification. Consequently, high morphological variation within-species regularly leads to ecological and phylogenetic hypotheses that do not reflect evolutionary history. Studies describing phylogenetic splits between species that are nearly indistinguishable are becoming more common and not only do species with a high degree of morphological similarity create headaches for biologists, but it illustrates a need to combine multiple lines of evidence to discover species, understand their evolution, and inform their conservation. I investigated patterns of interspecific and intraspecific morphological trait diversity in a group of North American freshwater mussels to better understand how biogeographic history and environment influence speciation and ecological interactions. In my first chapter, I worked to reconstruct phylogenetic relationships in the Pleurobemini, a tribe of mussels that contains multiple species with shell morphologies that heavily overlap. Adding to the confusion, several species also exhibit a pattern of shell morphology that is linked to hydrologic gradients. Historically, these shell morphology differences caused back-and-forth taxonomic changes that have become even more complex as molecular sequencing has revealed unrecognized species diversity. Recent genetic studies have attempted to provide some clarity to this situation, but taxonomic changes have thus far remained incomplete. In an effort to help rectify the taxonomy of some pleurobemines, I conducted extensive geographic sampling of the genus Fusconaia and some closely related species as the first step to building a backbone phylogenetic framework. I used a combination of DNA barcoding, traditional shell morphometrics, and low coverage whole genome sequencing, also known as genome skimming, to overcome previous sampling limitations. With my barcoding data, I constructed a taxonomically comprehensive phylogeny and identified samples that were good candidates for genome skimming. I extracted mitochondrial genomes and developed a set of target-capture probes from genome skimming data then conducted an in-silico target-capture sequencing experiment with hundreds of ultraconserved elements (UCEs). I obtained key pieces of information from maximum likelihood and species tree phylogenetic analyses of mitochondrial genomes and UCEs; specifically I found mitonuclear discordance. While molecular evidence can be strongly supportive of taxonomic hypotheses, a purely molecular approach is insufficient to make robust determinations. Before making taxonomic determinations, I conducted morphometric analyses of five poorly sampled lineages and confirmed strong correlations between shell inflation and stream size in the species Fusconaia flava. After accounting for variation in hydrologic habitat, morphometric analyses showed mean shape was different at the species level but also identified strong morphological overlap at the individual level. Overall, the phylogenetic discordance I found between two specific lineages most closely fit a pattern of mitochondrial introgression but conducting additional testing for hybridization went beyond the capabilities of my datasets. Although my analyses had almost an adverse effect by deepening the taxonomic mystery, I demonstrated genome skimming may be a useful approach for future studies. For my second chapter, I used both tree-based and non-tree-based methods to more completely explore species boundaries between species in the Fusconaia flava complex. I generated additional genomic data using the “3RAD” restriction-site associated DNA sequencing approach and explicitly sampled individuals I previously identified as possible hybrids as well as species I did not expect there to be gene flow between. I obtained thousands of single nucleotide polymorphisms (SNPs) that allowed me to reconstruct phylogenetic relationships, perform population-level genomic analyses, and generate a time-calibrated phylogeny. Using several approaches including a sparse non-negative matrix factorization method, principal component analysis, and the program TreeMix, I was able to infer population splits and estimate admixture. Based on the admixture coefficients I estimated, I used a phylogenetic network approach called SNaQ to test for hybridization and reticulate evolution. To estimate divergence times, I used the SNAPP module implemented in BEAST to generate a time-calibrated species tree. Lastly, I conducted population genomic analyses focusing on populations in the Red River in Oklahoma and tested for an isolation-by-distance effect. What I discovered was that the F. flava species complex appears to be highly structured and gene flow does not appear to be widespread. Most importantly, I was able to rule out hybridization and incomplete lineage sorting as the mechanisms causing mitonuclear discordance and instead my analyses strongly suggested a pattern of mitochondrial introgression was causing mitonuclear discordance in two Fusconaia lineages. My population genomic analyses also suggested isolation-by-distance was unlikely in Red River Fusconaia and instead aligned more closely with patterns of reproductive isolation. Although I did identify isolated instances of probable hybridization, gene flow appears to be spatially limited. These low levels of gene flow seemingly align with my estimated divergence times which show speciation likely occurred during the Pliocene and early Pleistocene epochs. In my third chapter, I wanted to understand if there was an underlying significance to a pattern of shell shape variation known as Ortmann’s Law of Stream Position. Ortmann’s Law of Stream Position is a hypothesis that posits laterally compressed shells found in small creeks become more inflated (wider) as the stream transforms into a large river. I previously confirmed shell inflation increases as a function of flow rate but did not investigate changes in other traits like shell thickness. From a functional standpoint, I wanted to identify if shell thickness and shell width were correlated and if stouter shells found in large rivers are more advantageous by acting as a sort of anchor, whereas compressed shells allow the mussel to move more freely. To investigate shell thickness, I digitized museum specimens with micro-computed tomography (micro-CT scanning) and extracted hydrologic data for each collection locality. In conjunction with my micro-CT scanning study, I conducted a fluvial experiment with wild Fusconaia individuals from the Gasconade River, USA to identify how small river and large river analogs respond to different flows. Using historical hydrology measurements from the Gasconade River, I scaled flume conditions to mimic natural high and low flow events and quantified locomotion by measuring valve movement with Hall sensors. Across six trials, I found statistically significant evidence that mussels from small river habitats make more locomotory movements than mussels from large river habitats. Interestingly, I also found large river mussels appeared to move primarily during high flow which suggests the objective of their movements may not be to burrow but to stabilize themselves during high flows. My hypotheses are also supported by my comparison of shell thickness which showed median thickness is highly correlated with shell width which indicates wider shells are also denser. Consequently, denser-shelled mussels appear to be able to withstand higher dislodgement forces whereas thinner-shelled mussels are able to displace sediments more efficiently to take refuge in the streambed. Finally, in my fourth chapter I synthesized the results of my first and second chapters to formally revise the taxonomy of two Fusconaia lineages. I resurrected the species Fusconaia hebetata and formally described a new species which I named Fusconaia vaughnae. This research is a significant contribution to systematic malacology and is part of a growing body of work designed to more completely understand freshwater mussel evolution. I have demonstrated how phylogenetic frameworks underpin ecological hypotheses, which is important for understanding the origin and function of anatomical features. Holistically, I have demonstrated that underlying patterns of morphological variation are more complex than we typically perceive them to be. Freshwater mussels in particular are a fascinating study system that can offer a glimpse into past speciation events and life in riverine environments. However, in the face of extinction from the worst effects of climate change and habitat destruction, mussels also serve as a sort of “canary in the coal mine” and remediating taxonomic issues surrounding Fusconaia will undoubtably facilitate more accurate taxon-based conservation of a group of mussels containing cryptic diversity and endangered species
THE VISUAL LANGUAGE OF TORNADO WARNINGS: PERCEPTION AND EMOTIONAL RESPONSE ACROSS FORMAT AND EXPOSURE
No full textTornadoes are one of the most dangerous weather hazards in the United States, prompting theNational Weather Service to continuously evaluate how warnings are communicated to the public. Amid concerns that over-warning may erode public trust and a belief that current warnings can be further refined, this study employed a mixed design to test the effectiveness of traditional versus probabilistic tornado warning formats. A total of 347 participants were randomly assigned to receive one of the two formats across three simulated exposures. The study measured perceived likelihood, severity, message clarity, information sufficiency and seeking, and protective action intention, all components of the Protective Action Decision Model. It also measured cognitive load, Perceived Message Sensation Value, message fatigue, and desensitization, all novel applications from the field of health communication. While the probabilistic format was consistently rated as more novel, emotionally arousing, and dramatic— without invoking significant mental effort—traditional formats were rated significantly higher in perceptions of likelihood, severity, and protective action intention when averaged across all three exposures. Contrary to prevailing assumptions, participants did not perceive high message fatigue; in fact, individuals reporting higher fatigue indicated greater trust in forecasters. These findings suggest that probabilistic warnings amplify perceived threat in the most at-risk areas and reduce perceived threat in regions farther from the core impact zone. Fears of over-warning are not supported by the available data
MODEL OF DIVERSE UNDERGRADUATE PERCUSSION CURRICULUM FOR THE REPRESENTATION OF WOMEN COMPOSERS
No full textThe purpose of this research is to develop an undergraduate percussion curriculum basedon repertoire and resources composed by women. The study aims to promote a more equitable distribution of diverse programming within the percussion community, with the potential to increase the number of women who pursue advanced education and professional careers in the field. This document proposes and analyzes a model undergraduate curriculum that includes detailed repertoire lists for marimba, vibraphone, snare drum, and timpani, all featuring works by women composers. I thereby address the longstanding gender imbalance in percussion repertoire, offering practical tools that place the work of women composers at the center of undergraduate study. A curriculum grounded in these works provides educators with accessible resources to diversify their pedagogical approaches. This curriculum seeks to broaden students’ musical horizons by introducing them to a variety of perspectives and encouraging the growth of both technical skill and expressive artistry. A comprehensive overview of foundational techniques for each primary percussion instrument highlights essential elements for achieving technical command and musical fluency. The curated repertoire is thoughtfully matched to these core competencies, offering a sequential approach that supports the development of both technical precision and expressive interpretation. It amplifies underrepresented voices and fosters a more inclusive learning environment—one that has the potential to inspire and empower more women to continue in the discipline. The inclusion of women’s voices in percussion pedagogy also supports the development of male allies and strengthens a studio culture rooted in equity. This work contributes to long-term cultural change within the percussion field, challenges traditional gender norms, and expands the range of repertoire studied and performed
2025-26 budget.
No full textThe University of Central Oklahoma submits its budget for the upcoming fiscal year to the Oklahoma State Regents for Higher Education for final approval. This document is a copy of the approved budget for FY26
