2020 MU dissertations - Access restricted to UM
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Item Investigating increased shear stress and physical activity as strategies to improve vascular insulin sensitivity(University of Missouri--Columbia, 2020) Walsh, Lauren K.; Padilla, Jaume[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Impaired vasodilator actions of insulin in type 2 diabetes (T2D) result in blunted insulin-stimulated skeletal muscle capillary perfusion which limits nutrient delivery and contributes to glycemic dysregulation. Thus, identification of strategies to improve vascular insulin sensitivity in T2D is paramount. Evidence suggests that acute bouts of exercise may improve insulin-stimulated vasodilation in vascular beds exposed to increases in blood flow. Thus, I hypothesize that increases in blood flow-associated shear stress, in the absence of muscle contraction, on the vascular endothelium renders the vasculature more insulin-responsive. This idea was tested in (i) cultured endothelial cells, (ii) isolated and pressurized skeletal muscle arterioles from swine, and (iii) humans. I found that, in confirmation of my hypothesis, previous exposure to shear stress primed the vasculature to become more insulin-responsive across all three tested models. Next, I sought to determine whether impaired skeletal muscle capillary perfusion in response to insulin in T2D was determined by an impairment in the vasodilation of upstream resistance arteries. Interestingly, the data indicated that increased leg vascular conductance, an indication of resistance artery vasodilation, during a hyperinsulinemic-euglycemic clamp was positively correlated with insulin-stimulated skeletal muscle capillary perfusion in T2D, but not in healthy subjects, suggesting that insulin-stimulated muscle perfusion in T2D is in part determined by vasodilation of resistance arteries. And finally, the hypothesis that indices of microvascular insulin resistance and overall vascular dysfunction in T2D would be improved by participation in an eight-week exercise program, in the form of increased walking, was interrogated. Despite an improvement in popliteal artery flow-mediated dilation, microvascular insulin resistance was not improved in T2D following an eight-week walking program. In conclusion, I provide evidence to suggest that increased shear stress subsequently renders the vascular endothelium more insulin-responsive, that individuals with T2D increase skeletal muscle perfusion via a divergent mechanism compared to healthy subjects, and that an exercise program in the form of 8-weeks of walking was not sufficient to improve skeletal muscle microvascular insulin resistance in individuals with T2D.Item Merging technology development of trapped ion mobility spectrometry quadrupole time-of-flight mass spectrometry with biological investigation of Medicago truncatularoot exudates(University of Missouri--Columbia, 2020) Schroeder, Mark; Sumner, Lloyd W.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] "New commercial ion mobility instrumentation has the potential to improve current analytical techniques, but developments need to be applicable to real-world problems. Analytically challenging biological samples (i.e. root exudates) can be improved by this application of new ion mobility instrumentation. To this end, I have established an analytical reference library and developed new instrumentation methods (Bruker timsTOF Pro) to be applied specifically for specialized plant metabolites. I have also developed a method for collecting biological samples specifically for the new instrumentation. Utilizing this co-development strategy, new technology coupled with biological objectives, the capabilities of both have been improved" --From Chapter 1.Item The visual language of identity : women's seals in Scotland and Ireland, c. 1100-1400(University of Missouri--Columbia, 2020) Rancour, Brittany; Stanton, Anne Rudloff[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] My dissertation explores the visual expression of the power and authority of secular women in Scotland and Ireland from the twelfth through the fourteenth centuries. I approach this large topic with a study of the small: the seals found on documents. Seals function like our signatures today; they add our authority to documents and are expressive of our power. Unlike our contemporary signatures, however, seals also bore signs of the identity of the person that used them. The iconography, size, and shape of a seal signified a person's social standing and gender. Women from the highest social classes possessed oval seals with full standing figures and heraldic emblems and women lower down the social ladder owned oval-shaped, non-figural seals. Women in medieval Scotland and Ireland followed a visual language of identity, drawing from well-established images found in church sculpture, tombs, and manuscript illuminations. The ubiquity of the images ensured that they would be widely understood. The spread of sealing culture as well as the spread of international artistic fashions into the western peripheries of the European world was a result of Norman (and Anglo-Norman) influence. This study brings the seals of women in Scotland and Ireland within the lively scholarly discourse about identity and visual culture in the expansive orbit of late medieval England and France by considering the varying degrees of how foreign influence was adopted within the two Gaelic worlds.Item Teachers' views of the mathematical capabilities of students with disabilities : a mixed methods study(University of Missouri--Columbia, 2020) Mason, Erica N.; Lembke, Erica[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Students with disabilities often have difficulty demonstrating mathematical understanding on conventional measures. One reason for this difficulty could be an instructional opportunity gap. Federal law, recent case law, and recommendations from professional organizations converge on the need for students with disabilities to have access to mathematical learning opportunities aimed at rigorous learning outcomes. However, beyond the existence of these policies and recommendations, enactment relies on individual teachers. Recent research suggests teachers views of their students' mathematical capabilities may relate to the enactment of learning opportunities aimed at rigorous learning outcomes. A mixed methods study was conducted in order to understand teachers' views of the mathematical capabilities of students with disabilities. General education mathematics teachers gave unproductive explanations for students' struggle and articulated rationales for instructional adjustments aimed at unproductive learning outcomes. When examined more closely, teachers' views qualitatively and quantitatively differed between students with and without disabilities.Item Using feedback linearization to alter the performance of multiple linear hydraulic-actuators powered by the same pump(University of Missouri--Columbia, 2020) Muhi, Laheeb Noori; Manring, Noah D.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In this study, a feedback linearization technique is presented to improve the tracking and energy performances of a hydraulic system using multiple linear hydraulic-actuators with both actuators being powered by the same pump. This research uses two open-centered 4-way valves to control the displacement of the two hydraulic actuators for a wheel loader implement system, based upon an input command from the operator who is modeled as a first-order system with a bandwidth frequency of 2 Hz. The feedback linearization control method is used to adjust the operator input based on the measurement of fluid pressure on one side of each actuator, and the pump pressure that supplies both valves with no additional sensing needed. The feedback linearization improves the tracking performance as measured by the R-squared value and increases the bandwidth frequency for lift and dump actuator thereby the operator's fatigue is decreased by 7.50, 7.25, and 6.75 times for the lift actuator and 6, 4, 4.5 times for the dump actuator under constant, step, and sinusoidal loading, respectively. Also, the feedback linearization reduces the overall energy consumption for the system during an applied step load by 9.79%, however, it increases the consumption by 0.37% and 5.12% during applied constant and sinusoidal loading, respectively. Moreover, a slight increment in feedback linearization gains reduces the energy consumption by 8.82%, 18.52%, and 4.75% during an applied constant, step, and sinusoidal loading, respectively. Finally, the feedback linearization technique improves the robustness of the system by rejecting external disturbances and nearly eliminating the load dependence of the tracking response over a wide range of operating frequencies. This finding suggests that the operators should have less difficulty learning how to operate the machine with this controller, and the overall productivity of the machine should increase.