2019 MU dissertations - Freely available online
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Item Development of selective high-affinity fluorescent sensors for imaging neurotransmitters and application in cells and tissue(University of Missouri--Columbia, 2019) Zhang, Le; Glass, TimothyHerein, we develop a series of selective fluorescent sensors based on a quinolone core designed to image neurotransmitters catecholamines, serotonin and glutamate. Included are the main design strategy, synthesis, spectroscopic data (UV/Vis and fluorescence) and their applications in cells and tissue. NeuroSensor 510 (NS510) was designed and synthesized as a selective sensor for imaging norepinephrine. Formation of both an iminium ion and a boronate ester gave high affinity upon binding NS510 to norepinephrine. The sensor was able to label norepinephrine vesicles in chromaffin cells to give punctate staining. Moreover, the sensor was able to monitor norepinephrine exocytosis via correlation of total internal reflective fluorescence (TIRF) microscopy and amperometry. A NIR fluorescent sensor NS659 was developed based on the structure of NS510. Several different synthetic routes were attempted before the sensor was successfully prepared. Upon binding to serotonin, the sensor gave a relatively high affinity but with quenched fluorescence. Initial tests showed that the sensor could be used to label vesicles. Finally, a molecular sensor NS560 was developed to image glutamate. Fluorescence titrations showed that the sensor bound to glutamate to give a very large turn-on response. More importantly, the sensor should be able to differentiate glutamate from GABA due to the difference both in the emission wavelength and the fluorescence response. We tested this sensor in photoreceptor cells and observed that vesicles were labeled by this sensor. Destaining of the vesicles was observed via TIRF microscopy. Also, the sensor can label glutamate in cultured glutamatergic neurons, astrocytes and cortex brain.Item Water harvesting and condensation heat transfer enhancement induced with electrowetting-on-dielectric(University of Missouri--Columbia, 2019) Yan, Run; Chen, Chung-LungAs demand for the world's natural resources continues to rise, energy saving has become an urgent topic. Water harvesting and condensation heat transfer enhancement represent two vital energy-saving objectives. Many researchers have focused on alternating surface wettability by employing advanced materials or complex surface structures to achieve such goals; however, most of these approaches operate in a passive manner. In terms of active methods, electrowetting-on-dielectric (EWOD) has become a popular option owing to its excellent contact angle reversibility, switching speed, and long-term reliability in altering surface wettability. This dissertation presents a study of the EWOD effect on water harvesting and condensation heat transfer. It describes experimental and analytical studies concerning various characteristics such as EWOD-induced droplet dynamics, water capture capability, and heat transfer performance. It also quantifies water harvesting and condensation heat transfer enhancement. This dissertation is divided into four main studies, each of which considers different aspects of the effects of EWOD on water harvesting and condensation heat transfer. The first part of this dissertation (Chapter 2) describes microfabrication technologies to obtain EWOD devices, including low-pressure chemical vapor deposition, photolithography, sputtering deposition, and lift-off and spin coating. Mask designs with different electrode configurations and a device microfabrication protocol are also described. The second part of this dissertation (Chapter 3) presents an experimental investigation of EWOD-induced water harvesting enhancement. EWOD devices were tested in a high-humidity environment under mist flow. Compared with an uncharged EWOD device, the water capture capability of charged devices improved significantly. These results are of great importance, as they indicate strong potential for improvement in water-harvesting applications. The third part of this dissertation (Chapter 4) describes a visualization study of EWOD-regulated condensation droplet distribution. Side-by-side experiments were performed to compare charged and uncharged devices. Charged devices exhibited a regulated droplet distribution, faster droplet growth, more dispersed droplet distribution, and more large droplets. These experimental results introduced a novel approach to actively influence droplet distribution on microfabricated condensing surfaces and showed promise for improving the condensation heat transfer rate via EWOD. The fourth part of this dissertation (Chapter 5) discusses the EWOD effect on the condensation heat transfer coefficient and heat flux. The heat transfer coefficient and heat flux were compared on uncharged and charged (40V DC) EWOD devices. Experimental results demonstrated a positive effect of EWOD on condensation heat transfer. This approach could be incorporated into many industrial applications (e.g., heat exchanger fin surfaces, condensing surfaces of waste heat recovery systems, and components of electronic cooling packages) requiring high-efficiency heat dissipation. In summary, this work makes valuable contributions to the field of water harvesting and condensation heat transfer, proposing a new approach to research in these areas. Findings also detail a new tool to achieve water harvesting and condensation heat transfer enhancement via an active EWOD method.Item How financial decision-making changes when a marriage ends : evidence from the 1992-2016 health and retirement study(University of Missouri--Columbia, 2019) Xu, Chen; Yao, RuiTransitioning from being married to divorced or widowed is difficult, financially as well as emotionally. Individuals who had left money matters to their partners during marriage enter a period of decreased financial control after marital dissolution and need to build their capacity to manage their own finances. This research used the 1992-2016 Health and Retirement Study (HRS) to investigate the following questions: Compared to a marriage's financial decision maker, how does the non-decision maker assume financial control post-marriage and change asset allocation and wealth accumulation over time? Who loses out by remaining uninvolved in a marriage's financial decision-making? Descriptive analyses and a linear mixed regression model were used to explore whether, after becoming divorced or widowed, net worth is higher for financial decision makers than non-decision makers. A similar analysis was performed on the proportions of risky assets held in investment portfolios, examining whether proportions are higher for the decision makers. The results showed that divorce and widowhood were detrimental to financial health no matter a person's attributes. However, impacts disproportionately affected some groups, including respondents who were non-financial decision makers during marriage. Gender, race, and level of education also influenced how much marital dissolution impacted post-marriage asset allocation and wealth accumulation. The findings suggest that individual investors, financial planners, and researchers would benefit from figuring out how to design collaborative, responsive financial plans that enhance typically uninvolved persons' decision-making skills and adapt to life changes.Item Mechanisms of polar growth in the alphaproteobacterial order rhizobiales(University of Missouri--Columbia, 2019) Williams, Michelle A.; Brown, Pamela J.All bacteria elongate and divide to faithfully reproduce their cell shape. Understanding the mechanisms that drive bacterial morphology requires an intimate knowledge of how the cell wall is synthesized. During cell division, most bacteria synthesize new cell wall at mid-cell and the mechanism underlying this process is highly conserved. In contrast, there is a high degree of diversity in bacterial growth patterning during elongation. Bacteria in the Rhizobiales exhibit an atypical form of unipolar elongation, and the molecular mechanisms of how new cell wall is synthesized during growth and division currently remains unexplored. Using microfluidics and fluorescent cell wall probes we first investigated whether polar growth is conserved in a morphologically complex bacterium, Prosthecomicrobium hirschii. We showed that P. hirschii has a dimorphic lifestyle and can switch between a long-stalked, non-motile form and a short-stalked, motile form. Furthermore, we found that all morphotypes of P. hirschii elongate using polar growth, suggesting the polar elongation is a widespread feature of bacteria in this order. Next, we used the rod-shaped bacterium Agrobacterium tumefaciens as a model to investigate the precise mechanisms that drive polar elongation. We characterized a comprehensive set of cell wall synthesis enzymes in A. tumefaciens and identified penicillin-binding protein 3a (PBP3a) and PBP3b as a synthetic lethal pair that function during cell division, and PBP1a as an essential enzyme required for polar growth and maintenance of rod shape. Compositional analysis of the PBP1a depletion, suggested that LD-transpeptidase (LDT) enzymes may play an important role in polar growth. We identified three LDTs that likely function in polar growth. We also observed subpolar localization of LDTs, suggesting bacteria in the Rhizobiales may insert or remodel cell wall material in a subpolar zone during growth. Finally, we used RNA-seq to explore changes in gene expression during PBP1a depletion, revealing that that loss of PBP1a induces a lifestyle switch which mimics the switch from a free-living bacterium into a plant-associated state. The change in lifestyle is characterized by increased exopolysaccharide production and Type VI Secretion System activity and a decrease in flagella-mediated motility. This finding indicates that bacteria have a mechanism to sense changes in cell wall composition or integrity due to the loss of PBP1a and respond through changes in gene expression that impact physiology and behavior. This finding opens the door to future studies on the link between changes in cell wall composition and complex bacterial behaviors and lifestyles. Overall, this research provides mechanistic insights about the roles of cell wall synthesis during cell growth and division in the A. tumefaciens, which are conserved in other Rhizobiales, including agriculturally and medically species such as Sinorhizobium and Brucella.Item A mixed-methods research predicting intentions and perceptions about intimate partner violence screening among nursing students and nurse educators in Thailand(University of Missouri--Columbia, 2019) Udmuangpia, Tipparat; Bloom, Tina (Tina L.)IPV screening in healthcare settings is an effective secondary prevention strategy for IPV that can reduce negative consequences IPV survivors may experience. However, healthcare providers have not tended to screen patients or women who may experience IPV. Additionally, the curriculums of health professionals' students, particularly in the nursing curriculum, do not adequately prepare future healthcare providers for IPV screening. However, little research has addressed IPV screening or barriers to such screening regarding healthcare providers in global, particularly Thailand. This study was to examine the attitudes, subjective norms, and perceived behavioral controls of senior Thai nursing students to manage IPV and intention to perform of IPV screening. In addition, it also was to explore the perceptions of IPV screening in nursing education among senior-nursing students and nurse educators in Thailand. The Theory of Planned Behavior (TPB), which is a strong theory to predict intentional behavior, was used in this study as a theoretical framework. This study was conducted a mixed-methods, with primary data collection involving online surveys and focus groups with senior nursing students in Thailand and individual interviews with Thai nurse educators. The quantitative study was recruited by nursing students who were in the last years of nursing program and passed at least one nursing clinical practice course. The qualitative study, there were nursing students and nurse educators. The inclusion criteria were: nursing students who were in the last year of their nursing program and passed at least one nursing clinical practicum course: nurse educators who have at least ten years of experience in education and live in a province in Northeast Thailand. Nursing students who were studying in their first, second, and third year, and did not pass any nursing clinical practicum were excluded. Nurse educators who have less than ten years' experience were not recruited. The instruments of screening were developed by using attitudes, subjective norms, and perceived behavioral controls. There were 36 relevant items on a 5 Likert scales. The instruments were developed by previous studies and five experts. Two bilinguals experienced IPV experts did the forward-translation of the original English versions of the instruments into Thai. Institutional Review Board (IRB) was approval from University of Missouri and one of Boromarajonnani Colleges of Nursing in Northeast Thailand with waiver of documentation of consent. Analysis data as percentages, frequency, and standard deviation were described demographic data and attitudes, subjective norms, perceived behavioral control, and intention of IPV screening. Bivariate relationship as Spearman's Rho, Chi-square correlation, and Logistic regression were used to identify relationships between the variables. Content analysis with the Dedoose program was used. Categories were described. Totally 639 participants with nearly 60[percent] have ever trained regarding IPV and 89.84 [percent] of participants has intended of screening. There was a medium positively significant correlation between the attitude, subjective norm, perceive behavioral control and intention (r = 0.43-0.46). Gender, GPA, experienced of IPV training, having screening tool at the clinical site, have seen screening, experienced of screening, experienced abused, and experienced family abused were significantly associated with intention of screening, but number hours of training was not associated. Mediation was tested and attitude and subjective norm were mediators of the relationship between having a tool at clinical site and intention to screen, but perceived behavioral control was not a mediator. Moreover, attitude and subjective norm were predicted intention by 33 [percent]. The findings from qualitative research explained that participants perceived that IPV is a critical issue in Thailand, but it is difficult to identify because of the cultural consideration. Participants feel not well-prepared by school in terms of knowledge and training experience. Nurse educators also feel not confident in supervising. Addressing IPV into the nursing curriculum was highly recommended. This study is the first study to specifically explore the perceptions of IPV in nursing education in Thailand. The findings contribute to improving the nursing curriculum regarding IPV. More research is related to prepare nursing students to deal with IPV issue would be required.