Theses and Dissertations

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  • Publication
    The genesis of metamorphosed Proterozoic massive sulfide occurrences in central Colorado: Geological, mineralogical and sulfur isotope constraints
    ( 2022-12) Berke, Edward Higgins ; Spry, Paul G ; Johnson, Benjamin W ; Kerton, Charles ; Geological and Atmospheric Sciences
    Paleoproterozoic massive Cu-Zn±Pb±Au±Ag sulfide deposits metamorphosed to the middle-upper amphibolite facies in central-south Colorado formed in a volcanic-arc setting on the edge of the Yavapai crustal province. Previously published U-Pb ages on spatially-related granitoids range from ~1.9 to ~1.1 Ga, while Pb isotope studies on galena from massive sulfides suggests mineralization formed at around 1.8-1.7 Ga. Some deposits in the Dawson-Green Mountain trend (DGMT) and in the Gunnison belt are composed of Cu-Zn-Au-(Pb-Ag) mineralization that were overprinted by later Au-(Ag-Cu-Bi-Se-Te) mineralization. Sulfide mineralization is spatially related to bimodal, mafic-felsic volcanic rocks (gabbro, amphibolite, rhyolite, and dacite) and granitoids but it occurs mostly in biotite-garnet-quartz±sillimanite±cordierite schists and gneisses, spatially related to nodular sillimanite rocks, and in some locations, exhalative rocks (iron formations, gahnite-rich rocks, quartz-garnetite). The major metallic minerals of the massive sulfides include chalcopyrite, sphalerite, pyrite, pyrrhotite, and magnetite, with minor galena and gahnite. Altered rocks intimately associated with mineralization primarily consist of various amphiboles (gedrite, tremolite, and hornblende), gahnite, biotite, garnet, cordierite, and rare högbomite. The Zn/Cd ratios of sphalerite (44 to 307) in deposits in the DGMT fall within the range of global volcanogenic massive sulfide (VMS) deposits but overlap with sphalerite from sedimentary exhalative (Sedex) deposits. Sulfur isotope values of sulfides (δ34S = -4.4 to +6) suggest sulfur was largely derived from magmatic sources and that variation in isotopic values resulting from thermochemical sulfate reduction is due to small differences in physicochemical conditions. The preferred genetic model is for the deposits to be bimodal-mafic (Gunnison) to mafic-siliciclastic VMS deposits.
  • Publication
    “For this additional burden we had no additional help”: First-year composition and writing program administration at Iowa State from 1869 to 1939
    ( 2023-08) Payton, Colin ; Mackiewicz, Jo ; Anders, Abram ; Aune, Jeanine ; Huffman, Sarah ; Rood, Craig ; English
    This dissertation is a history of Iowa State University’s composition program from 1869 to 1939, including its origins in the idea of the land-grant college. Unlike many histories of composition and rhetoric, instead of exclusively tracing the rhetorical theories that influenced the composition curricula, this history also investigates the political pressures imposed upon the English department due to Iowa’s land-grant politics, as well as the writing program administrators’ (WPA) adaptations to these external influences. I found repeated examples of the land-grant college mission, which was itself a hotly contested ideal, wielded by various interest groups to either protect or to attack the composition curriculum. External influences, however, did not pour unmitigated into the first-year composition (FYC) program. Emerging from this investigation was the importance the WPA as a mitigator of external influences, including their cultivation of new pedagogies, curricular designs, and faculty labor rights. To accomplish this uncommon historical perspective taking, I developed three methodological heuristics that guided my investigation: (1) centering the institution’s influence on a composition program’s history, (2) observing the program’s changes over time and across administrations, and (3) focusing on WPAs and the transitions between their administrations. These methodologies allow this history to rejoin composition’s larger narratives, especially conversations about how ideologies enter the composition program and the origins of writing program administration.
  • Publication
    Why does convection growth upscale faster into lines in 1-km simulations compared to 3-km: An examination using CM1
    ( 2023-08) Luthi, Samuel T ; Gallus Jr., William A. ; Franz, Kristie J. ; Williams, Ian N. ; Geological and Atmospheric Sciences
    It is known from previous research that differences exist in model simulations of convective mode as horizontal grid spacing is refined from 3-km to 1-km. It is of particular interest as to why 3-km model simulations depicting clusters of cells tend to adopt a more linear structure in 1-km simulations. One theory is that this increase in linear structures at finer horizontal grid spacings is due simply to the resolving of stronger vertical motion in a 1-km run compared to a 3-km run along the leading edge of the MCS, while other theories hold that stronger cold pools create stronger lift to more rapidly create a linear morphology. CM1 was used to simulate an array of MCSs with varying wind profiles (RKW u-wind, Weisman-Klemp Multicell u-wind) and a constant thermodynamic profile (Weisman-Klemp analytic sounding). A line of seven randomly-spaced warm bubbles was used to initiate convection. Similar trends were found in rainwater and graupel mixing ratios, as well as in cold pool intensities when compared with Squitieri and Gallus (2022a). The change in Δ? from 3-km to 1-km is more impactful on the number, cumulative area, and intensity of updrafts than the change in the number of vertical levels. In 1-km Δ? simulations, gravity waves appear to play the most dominant role in the increase of vertical motion that initiates new convection for growth into lines. 3-km Δ? simulations appear to have their upscale growth into lines being driven by ascent caused by the collision of convective cold pools.
  • Publication
    Program verification using dynamic invariants and theorem prover: Exploratory study on Daikon and SAW
    ( 2023-08) Pal, Sanchayani ; Basu, Samik ; Cohen, Myra ; Tian, Jin ; Computer Science
    Program verification, in general, is undecidable. In the recent years, SMT/SAT solver based proof assistants and theorem provers have been deployed to prove desirable (e.g., necessary pre-/post-conditions of functions) properties of programs in a semi-automatic fashion relying on some expert knowledge and guidance. In this context, we investigate the viability of Software Analysis Workbench (SAW) infrastructure and Daikon invariant detector tool in verifying properties of programs. Our main objective is to deploy Daikon to generate relevant invariants of programs automatically, and then utilize those invariants to develop functional specifications of programs. We conjecture that such specifications can be automatically translated into executable languages (such as Cryptol) and can be effectively utilized to prove desired properties of programs. This is likely to minimize expert knowledge necessary to develop program specifications, thus improving the applicability of proof assistants and theorem provers in effectively checking the properties of programs.
  • Publication
    Mycobacterium bovis in U.S. feral swine – history, diagnostics, and comparative experimental infection
    ( 2023-08) Hill, Dana ; Jones, Doug ; Thacker, Tyler ; Yaeger, Michael ; Fasina, Olufemi ; Lehmkuhl, Aaron ; Veterinary Pathology
    Bovine tuberculosis (bTB), caused by Mycobacterium bovis, has a long history on the Hawaiian island of Moloka’i where disease spillover from infected cattle into feral swine was identified in the 1980s, cattle were temporarily removed from the island, and disease spillback from feral swine into cattle was subsequently confirmed in the early 1990s. This ignited a 10-year-long bTB surveillance study of Moloka’i wildlife, including feral swine, axis deer, and mongoose from 1999-2008. The last bTB positive cow on Moloka’i was identified in 1997 followed by 26 consecutive years of negative annual testing. That is, up until 2021 when a recent epizootic bTB outbreak on Moloka’i confirmed that several cattle are infected with a strain of M. bovis with single-nucleotide polymorphism (SNP) pattern homologous to 2008 isolates taken from feral swine. The debate remains whether Moloka’i feral swine fit the criteria of a spillover host, an amplifier host, or a wildlife maintenance host for bTB. Determination of bTB host status is complex, requiring extensive epidemiological data from naturally infected populations and is crucial in bTB-disease mitigation and eradication efforts. We aimed to identify surveillance and diagnostic challenges of bTB and infer bTB-host status of genetically distinct populations of U.S. feral swine. Diagnostic test performance for bTB was retroactively compared between a wildlife surveillance study from Moloka’i feral swine (1999-2008) and routine U.S. cattle surveillance (1999-2010). Additionally, experimental infection of U.S. feral swine from distinct genetic backgrounds provides insights into bTB host status potential by highlighting differing pathophysiology and immunology. Tissues from Moloka’i feral swine and cattle originating from the United States of America were submitted to the National Veterinary Services Laboratories (NVSL) in Ames, IA for bTB testing. Mycobacterial culture (current gold standard) from abattoir cattle samples identified more bTB-positive cases than formalin-fixed paraffin-embedded (FFPE) polymerase chain reaction (PCR), while for field sample collections from Moloka’i feral swine the opposite was observed. A total of 63,764 cattle samples were received by NVSL compared with 452 feral swine submissions. bTB was confirmed by culture and/or PCR in 741 cases for cattle (1.16% positive) and 15 cases for feral swine (3.32% positive). Results and disparities between histopathology, PCR, and culture were investigated. Culture identified 39 additional bTB cases from cattle that were missed by PCR while, for feral swine, PCR identified more bTB cases (n = 13) than culture (n = 8). Histopathology identified more lesions as mycobacteriosis compatible than were verified by culture or FFPE PCR for both cattle and feral swine samples but proved to be a valuable and rapid initial screening test in the bTB diagnostic decision-making tree. A multimodal approach to bTB diagnostics, utilizing histopathology, culture, and PCR in parallel, was beneficial in identifying and correcting discrepant results for both cattle and feral swine submissions. Eurasian wild boar descendants from Texas and Polynesian swine from Hawaii were experimentally infected with M. bovis to compare disease susceptibility, pathology, and immunology. A low dose of M. bovis produced tuberculous lesions within 5/6 (83%) Moloka’i and 3/4 (75%) Texas pigs, with distinct lesion profiles and host immunity. Longitudinal sampling of peripheral blood throughout infection indicates highly variable humoral and cell-mediated immune responses as evidenced by antibody production on dual path platform (DPP) and interferon-gamma (IFN-γ) production from peripheral blood mononuclear cells (PBMCs) restimulated with various mycobacterial antigens. Moloka’i-origin swine mounted cell mediated and humoral immune responses to bTB infection on while infected Texas-origin pigs had undetectable antibody responses against MPB83 and ECH. These results suggest unique immune responses and lesion profiles in genetically distinct U.S. feral swine experimentally infected with M. bovis. Feral swine are susceptible to disease caused by M. bovis and diagnostic test performance varies with species and method of collection. The historical information and inherent differences observed between the two groups of pigs used for this study support the hypothesis that Moloka’i feral swine are acting as a maintenance host for bTB and contribute to disease spillback events into domestic livestock.