Theses and Dissertations
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ArticleModernization of historical Avian Leukosis Virus extraneous agent testing( 2023-12)The Virus Serum Toxin Act was enacted to ensure that veterinary biologics produced in the United States are safe and effective for the prevention of animal disease. The advancements in technology and transportation over the last century led to formation of the Center for Veterinary Biologics that is now the responsible body for regulating veterinary biologics in the United States. A part of that regulation includes requirements for manufacturers of veterinary biologics to test materials derived from avian origin or for end product use in poultry, for extraneous replicating Avian Leukosis Virus (ALV). ALV is a ubiquitous pathogen of chickens responsible for significant economic losses in the poultry industry. Current veterinary biologic testing for extraneous ALV includes a 21-day continuous growth period in chick embryo fibroblasts (CEFs) produced from Specific Pathogen Free Eggs followed by examination for the ALV p27 antigen using biological assays. The purpose of this research was to shorten the time needed to detect low levels of ALV, determine if new technologies such as real-time polymerase chain reaction (PCR) could benefit this extraneous testing, and find an alternative cell line that was free of endogenous ALV. A literature review describes the history of ALV research and testing for extraneous ALV through the past century, the challenges of the current testing process, and potential modifications to the testing process. Two reverse transcription PCRs including a real-time PCR assay were found to be as or more sensitive than the current p27 ELISA testing. In addition, through cell culture examination it was determined that low levels of ALV can be detected effectively after 10 days in continuous culture. Although endogenous ALV- free cell lines were tested, none met the criteria needed to replace the current CEFs used for testing.
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ArticleExploiting the Pi-Complexation Capability of Silver(I) and Copper(I) Ions in Ionic Liquids for Olefin and Paraffin Separations( 2023-12)Separating olefins from structurally-similar paraffins is difficult as they generally possess indistinguishable chemical properties. To achieve their separation, the selective and reversible π-complexation capability of silver(I) and copper(I) ions has been employed in separation systems. However, the utilization of traditional solvents (e.g., water and organic solvents) for dissolving such metal ions is limited as they are often plagued with solvent evaporation and poor facilitation of π-complexation, resulting in a diminished olefin/paraffin selectivity. Ionic liquids (ILs) are nonmolecular solvents possessing low vapor pressure, high thermal stability, a melting point lower than 100 °C, and structural tunability that can alternate traditional solvents in olefin/paraffin separation systems involving silver(I) and copper(I) ions. However, limited information on the π-complexation capability of such metal ions in IL media prevents their broader applications. In this study, experimental factors that may affect the interaction between olefins and silver(I) ion/IL media, such as silver salt type, IL structure, temperature, and exposure gas type, are systematically examined by gas chromatographic (GC) methods. When silver bis[(trifluoromethyl)sulfonyl]imide ([Ag+][NTf2-]) was dissolved in imidazolium-based ILs with [NTf2-] anions, stable silver(I) ion-olefin complexation could be achieved even under harsh conditions, including elevated temperatures and hydrogen atmosphere. Moreover, longer alkyl substituents on the imidazolium cation of the IL provided a stronger interaction between the silver(I) ion/IL stationary phase and olefins. Based on the optimized conditions, a theoretical equilibria model was developed to describe olefin partitioning between inert carrier gas (mobile phase), 1-decyl-3-imidazolium ([C10MIM+]) [NTf2-] IL solvent, and [Ag+][NTf2-] that was treated as a pseudophase. Analyte partition coefficients and thermodynamic parameters of solvation were determined using the model. Moreover, changes in olefin partition coefficients upon silver(I) ion reduction promoted by applying hydrogen-involving gas mixtures and elevated temperatures to the [Ag+][NTf2-]/[C10MIM+][NTf2-] IL stationary phases were monitored. As reduction proceeded within the silver(I) ion/IL stationary phase, chromatographic selectivity for olefins over paraffins tended to decrease gradually. Olefin/paraffin separation performance of other systems utilizing π-complexation capability of metal ions was also examined. By applying the poly(1-decyl-3-vinylimidazolium [NTf2-]) polymeric ionic liquid (PIL) impregnated with silver(I) ion as a GC stationary phase, silver(I) ion-olefin complexation was facilitated more effectively than the IL with structural similarities ([C10MIM+][NTf2-]). Partitioning of olefins and paraffins in a GC system involving copper(I) ion/IL stationary phases could also be studied using the chromatographic equilibria model. When [Cu+][NTf2-] was incorporated into the [C10MIM+][NTf2-] IL, copper(I) ion acted as a pseudophase similar to the case of silver(I) ion-containing IL. Interestingly, its π-complexation strength can be enhanced by heating to elevated temperatures while water introduction results in an opposite effect.
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ArticlePremature Rayleigh jets in a millimeter-scale water drop levitated in a strong electric field( 2023-12)Soft matter electrostatic levitation (SEL) is a containerless processing technique that plays an important role in investigating different challenging areas of physics. An area of interest is the study of crystallization and nucleation theory. The measurement of the thermophysical properties of solutions at high supersaturation levels is extremely challenging because of the heterogeneous nucleation sites, such as the container walls that initiate crystallization at low supersaturation levels. The SEL was developed at Iowa State University (ISU) in collaboration with the Korea Research Institute of Standards and Science (KRISS). This technology levitates colloidal suspensions, sodium sulfate, and other solutions. The levitation is achieved when charged liquid drops are freely suspended in the air by the electrostatic field generated between a pair of vertical electrodes. This non-contact environment allows the samples to levitate without contamination by container walls. The samples are allowed to evaporate and crystallize at high supersaturation levels. The measurements of thermophysical properties at high supersaturation levels can be achieved. However, a different challenge was observed during the experiments, where the charged samples were found to jet during the levitation. This phenomenon causes the loss of the samples. Furthermore, the information on the thermophysical properties during the jetting process still needs to be discovered. Jetting is a phenomenon where the surface of the charged drops breaks up into an elongated cone shape, or sometimes a filament or drops fly out of the surface. The experiments conducted on colloidal suspensions with the SEL found that a filament with a cylindrical shape was being thrown off the top surface of the samples. However, a Taylor cone was observed for experiments on deionized water. This instability is an obstacle to achieving the thermophysical properties’ measurements at high supersaturation levels. As a result, this study focuses on investigating the jetting phenomenon. Rayleigh described this phenomenon in 1882, where the model describes the isolated charged drops. In addition, in 1924, Taylor derived a jetting model for uncharged drops in an electric field. This current work uses deionized water (DI water) to study the jetting phenomenon. All the samples were jetting below the Rayleigh and Taylor limits, and this phenomenon was called a premature jet. Also, all the samples were found to have a continuous charge loss during the levitation. The continuous charge loss and jetting below the limits contradict the Rayleigh theory. As a result, this work will likely identify the mechanism of the premature jet and the continuous charge loss. Finally, an oscillation method will be applied to the levitated drops to measure the surface tension of the samples to show how the surface charge and the external electric field affect the effective surface tension.
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ArticleDevelopment and integration of a perceptive robotic grinding system( 2023-12)This thesis presents the development and integration of a perceptive robotic system to eliminate the risks of manual grinding for foundry operators by providing a flexible automation solution. At foundries across the world, human operators perform manual grinding to remove excess material and transform castings into their final shape. Extensive research has highlighted the significant health risks associated with manual grinding in foundries, such as excessive exposure to airborne dust, noise-induced hearing loss, and severe musculoskeletal damage. To address these concerns, foundries have begun exploring technologies to aid operators ergonomically or automate the grinding process. However, current automation approaches struggle to adapt to casting variation and a wide product mix without real-time input from a human operator. To support the grinding of high variety castings in foundry environments, a robotic system that leverages operator markings to determine where to grind was designed and implemented. Inspired by the previous work of Schimpf et al., the Sketch & Grind Robotic System improves grinding capability by integrating industry-leading hardware with perception and control improvements. Hardware and software developments were necessary for each system component to ensure seamless integration and achieve overall system performance. Current industry practices were investigated to establish an initial abrasive grinding tool for the Sketch & Grind Robotic System. An algorithm within the Sketch & Grind process was developed to enable concave boundaries to mark complex quality issues and avoid obstructions. A complementary process, Scan-N-Plan, was implemented on the Sketch & Grind Robotic System hardware, and the Sketch & Grind process was partially integrated to extend functionality for a foundry implementation. Through these developments, system functionality was realized, and the capabilities of Sketch & Grind were extended. This work supported a broader collaboration between research and industry partners to advance perceptive robotic grinding solutions for foundries. It will culminate in an upcoming industry implementation of the system at a steel foundry.
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ArticleEliciting interactive oral communication samples through a spoken dialogue system to measure interactional competence( 2023-12)Measuring language ability is an inseparable part of any language education system or any institution that involves the use of a foreign/second language. This measurement serves many different purposes, including but not limited to evaluating learning and predicting ability in future contexts where a language is the primary channel of communication. Traditionally, tests of language ability treated language as comprising four separate skills, i.e., reading, listening, speaking, and writing. However, this view was replaced by a more integrated view of skills and resulted in tests that included tasks that involved two or more of these skills. For instance, to test speaking ability, some tasks ask test takers to read a passage, listen to a lecture, and synthesize information from these two sources in summary speech. This approach makes designing tasks more involved, especially because they must reflect the underlying construct they aim to measure at the same time. A further complication in designing these tests stems from the fact that there is not a single universal language ability construct that test developers can use. Each construct in the literature is born out of contextual factors, and test developers need to be aware of many constructs or be able to create or synthesize one from the existing models or constructs based on their needs. Then, they will have to operationalize this construct into test tasks that can elicit language samples and produce scores that are reflective of the construct. Apart from the test design, there is also the involved step of administering the test. While this step might be as simple as giving a multiple-choice test, sometimes it requires the coordination of a host of complex components and different people such as raters, proctors, etc. Many institutions cannot afford the time and resources required to design and administer such tests, and they might resort to using externally designed ones that might not reflect their needs. With tests like oral communication, examiners and raters must be trained to deliver and score the tests even when an external test is used. This might push some institutions to forego tests of oral communication completely or relegate this test to a low-stake one by minimizing its score impact on the overall language ability test they are implementing. The present work explored the possibility of addressing some of these challenges in the context of oral communication. More specifically, it focused on measuring interactional competence, an important aspect of oral communication (OC) construct, through a spoken dialogue system to address the challenges of choosing or synthesizing a construct, operationalizing that construct, and administering the test. This spoken dialogue system, called Shahryar, elicited 10 two-and-a-half-minute interactive oral communication samples related to topics common to university students. Shahryar also included an interactive avatar to study the effects of simulating human presence. Ninety-six speakers of English as a foreign/second language completed the discussions with Shahryar. Then, 10 human raters evaluated these samples using a four-level interactional competence rating scale developed and evaluated by the researcher, distributing the samples in a way that each sample received ratings from four to five raters. The rating scale was originally developed and evaluated in the context of a human-to-human paired oral communication task by Neiriz (2023). This rating scale has four subsections, i.e., topic management, turn management, breakdown repair, and interactive listening, and is developed based on the metaphorical conceptualization proposed by Galaczi and Taylor (2018). The scores from human raters were analyzed through a many-facet Rasch measurement, and the results indicated that the test takers could be separated into four levels of IC ability with three raters and three tasks. The qualitative analysis of the interviews with test takers and raters suggested not all aspects of IC manifested through conversations with Shahryar stemming from the nature of communication with a computer, and further modifications to the program and test taker preparation might be needed to reliability elicit all aspects of IC included in the rating scale. However, both test takers and raters found many useful aspects of Shahryar, making it a promising alternative to human-to-human OC test tasks in some contexts. The results from this study shed light on the possibility of implementing automated oral communication test delivery with a focus on IC. The findings have implications for both test developers with limited resources and language learners who lack access to affordable oral communication tests designed based on our recent understanding of oral communication ability.