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- Title
- PROBE EFFECTS DURING CONCENTRATION DETERMINATION IN SCANNING ELECTROCHEMICAL MICROSCOPY
- Creator
- Mirabal, Alex
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
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Efficient, sustainable chemical reactions will play a large role in addressing many growing issues, including alternative energy production, greenhouse gas conversion, and pharmaceuticals. Electrochemical reactions are attractive due to their relatively mild reaction conditions and direct use of electricity. The understanding and design of the local liquid-solid interface will guide future progress in electrocatalytic reactions.Over time, nature has evolved many highly efficient reactions...
Show moreEfficient, sustainable chemical reactions will play a large role in addressing many growing issues, including alternative energy production, greenhouse gas conversion, and pharmaceuticals. Electrochemical reactions are attractive due to their relatively mild reaction conditions and direct use of electricity. The understanding and design of the local liquid-solid interface will guide future progress in electrocatalytic reactions.Over time, nature has evolved many highly efficient reactions through enzymatic reactions. These long-studied catalysts provide complex reaction environments that: 1) enhance interaction with reactants, 2) protect intermediates from side reactions, 3) increase the rates of reactions, and 4) selectively react to a specific product. The overarching lesson to be learned is that the local reaction environment plays a large role in the catalyst’s reactivity, selectivity, and efficiency. One way to characterize the local environment is through scanning electrochemical microscopy (SECM), in which a small electrochemical probe is rastered over an interface. A quantitative correlation of the probe response to concentration provides a direct measurement of the local environment. The presence of the SECM probe itself can induce changes in the local environment. Comparing the changed local environment (in situ) to what it would be without the probe present (operando), shows large differences of up to 120% under specific operating conditions. A few physical parameters such as the surface site geometry are shown to have an impact on how significant the probe effects are. Additional parameters such as the tip geometry and tip-surface separation are also to have an impact. A finite element method (FEM) simulation informed by experiments is used to examine the above-mentioned tip effects. It is found that fitting responses to other frequently used electrochemical measurements, such as approach curves and CVs, to parameterize the model appropriately describes experimental SECM results. We first apply this method to study platinum nanoparticles, where a ~50 nm resolution is the highest resolution to our knowledge for AFM-SECM. Through statistical analysis of the surface, an isolated nanoparticle SECM response is correlated with a concentration profile. It is found that the concentration profile has minimal probe effects due to the use of a conical electrode. Applying a similar approach, we also study the probe effects in pH detection during hydrogen evolution and CO2 reduction. Where we match experimental results to parameterize the system. It shown that there is a pH difference of up to ~7 pH units underneath the probe due to hindered diffusion. However, even with these large differences, the probes are still able to reflect the trends seen without the probe present. Moreover, it is shown that the physical parameters have correlated responses, indicating that hindered diffusion is controlled by the insulation radius and tip-surface separation. Finally, the importance of the analyte is discussed with regard to its interaction with the tip. In addition to the concentration impact on the response signal, the compatibility with the tip need be considered. Degradation of the tip and/or the redox couple of choice will detrimentally affect the ability to examine the local interface. We show that, of the redox couples examined, ferrocene-based compounds appear to best satisfy the most crucial factors of stability and mild redox potentials. Overall, this work studies and removes the impact of the probe for local concentration detection using SECM. This work acts as a guide to quantitatively study the local environment of electrocatalyzed reactions. This is realized through a combined experimental-FEM approach in which the simulation is informed by experiments such that it’s representative of the experimental environment.
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- Title
- THE ORIGINATION AND IMPLEMENTATION OF THE NATIONAL WETLANDS POLICY OF UGANDA : ENVIRONMENT, KNOWLEDGE, AND POWER FROM THE LATE NINETEENTH CENTURY TO PRESENT
- Creator
- Doyle-Raso, John
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
In the 1980s, following widespread environmental and intellectual changes associated with “swamp reclamation” that in Uganda had started in the early twentieth century, proponents of the emerging science of “wetland conservation” sought to influence the practices and thinking of people across the country. To do so, they created a national wetlands policy based on decentralized “community-based” projects. Yet, farmers’ and investors’ engagements with reclamation have continued. Meanwhile, the...
Show moreIn the 1980s, following widespread environmental and intellectual changes associated with “swamp reclamation” that in Uganda had started in the early twentieth century, proponents of the emerging science of “wetland conservation” sought to influence the practices and thinking of people across the country. To do so, they created a national wetlands policy based on decentralized “community-based” projects. Yet, farmers’ and investors’ engagements with reclamation have continued. Meanwhile, the Ugandan wetlands policy became internationally influential for its groundbreaking approach to interdisciplinary questions about governance, emphasizing economic analyses based on concepts such as “ecosystem services” and “Environmental Economic Valuation.” Ugandan wetland conservationists have had more influence abroad than domestically, as in Uganda neoliberalization and recentralization have limited the power of the community-based groups who have worked through the national policy. Using a range of sources including but not limited to archives and interviews with conservationists, this dissertation historicizes the Ugandan wetlands conservation policy. It comprises two parts addressing overlapping time periods. The first three chapters consider the origination of this policy by analyzing environmental and intellectual changes in southeastern and southwestern Uganda, leading to the creation in the late-twentieth century of environmental regulations. The latter three chapters examine how conservationists have tried implementing the policy in rural and urban places, and in relation to the national emblem of Uganda – the Grey Crowned Crane. They have focused their efforts on community-based projects outside Protected Areas promoting indigenous knowledges and practices to obtain economic benefits from wetlands that conservationists. This approach was an early manifestation of connected trends in international developmentalist networks. Furthermore, the limitations on its implementation have become pivotal in the global histories of neoliberalization, decentralization, and recentralization. Historicizing Ugandan wetland conservationism contributes to four scholarly literatures. 1) Analyzing community-based projects outside “Protected Areas” advances the historiographies of conservation and watershed management in Africa by considering the significances of neoliberalization, decentralization, and recentralization beyond extraordinary legal cases. 2) Examining intellectual changes in this history – including an emphasis on community-based projects, use of the concept of ecosystem services, and the promotion of indigenous knowledges and sciences – reveals connections between changes in environmental science and global trends in developmentalism. 3) Focusing on these changes in Uganda builds on analyses of environmental management in political power there by identifying the importance of an underexamined resource in entrenched land conflicts, and by uncovering early institutional bases of recentralization. 4) Because Ugandan wetland conservationists were global leaders in policy creation, citizen science, and more changes in scientific thinking, researching their work reveals how African scientists have navigated tensions between their local, national, and international interlocutors to become internationally influential. Studying the history of Ugandan wetland conservationism reveals how different people’s engagements with changes in environmental thinking have reshaped environments and livelihoods, as well as influenced international scientific networks.
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- Title
- ANALYSIS OF ERWINIA AMYLOVORA POPULATION DYNAMICS AT FLOWER BLOOM AND FURTHER SYSTEMIC MOVEMENT OF THE PATHOGEN THROUGH HOST TISSUE
- Creator
- Slack, Suzanne M.
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Population dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These...
Show morePopulation dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These large 100-fold increases seem to occur at night, indicating that Erwinia amylovora is able to infect flowers in colder field temperatures than previously reported. In tandem, timing of antibiotic application relative to E. amylovora presence on flower stigmas had little impact on population dynamics, with streptomycin and kasugamycin consistently reducing populations while oxytetracycline was more variable. This study also led to the identification that Kasumin is prone to photodegradation. Culturable bacteria, yeast, and fungal populations were assessed over the course of bloom in relation to application of a biological control agent yeast (Aureobasidium pullulans) and a contact sterilant. Though populations fell rapidly directly after application, by 24 hours all populations returned to pre-spray levels. In regards to further systemic spread, a type three secretion system effector was indicted in blocking the abscission of infected flowers. The use of prohexadione calcium (Pro-ca) and acibenzolar-S-methyl (ASM) reduced internal E. amylovora spread in a seemingly synergistic manner on young trees, with rates of 28.3 g Pro-Ca + 28.3 g ASM or 56.6 g Pro-Ca + 28.3 g ASM. The sum of this work gives us a better understanding of E. amylovora population dynamics in field conditions as well as the population response to current treatment options.
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- Title
- Face Anti-Spoofing : Detection, Generalization, and Visualization
- Creator
- Liu, Yaojie
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Face anti-spoofing is the process of distinguishing genuine faces and face presentation attacks: attackers presenting spoofing faces (e.g. photograph, digital screen, and mask) to the face recognition system and attempting to be authenticated as the genuine user. In recent years, face anti-spoofing has brought increasing attention to the vision community as it is a crucial step to prevent face recognition systems from a security breach. Previous approaches formulate face anti-spoofing as a...
Show moreFace anti-spoofing is the process of distinguishing genuine faces and face presentation attacks: attackers presenting spoofing faces (e.g. photograph, digital screen, and mask) to the face recognition system and attempting to be authenticated as the genuine user. In recent years, face anti-spoofing has brought increasing attention to the vision community as it is a crucial step to prevent face recognition systems from a security breach. Previous approaches formulate face anti-spoofing as a binary classification problem, and many of them struggle to generalize to different conditions(such as pose, lighting, expressions, camera sensors, and unknown spoof types). Moreover, those methods work as a black box and cannot provide interpretation or visualization to their decision. To address those challenges, we investigate face anti-spoofing in 3 stages: detection, generalization and visualization. In the detection stage, we learn a CNN-RNN model to estimate auxiliary tasks of face depth and rPPG signals estimation, which can bring additional knowledge for the spoof detection. In the generalization stage, we investigate the detection of unknown spoof attacks and propose a novel Deep Tree Network (DTN) to well represent the unknown spoof attacks. In the visualization stage, we find “spoof trace, the subtle image pattern in spoof faces (e.g., color distortion, 3D mask edge, and Moire pattern), is effective to explain why a spoof is a spoof. We provide a proper physical modeling of the spoof traces and design a generative model to disentangle the spoof traces from input faces. In addition, we also show that a proper physical modeling can benefit other face problems, such as face shadow detection and removal. A proper shadow modeling can not only detect the shadow region effectively, but also remove the shadow in a visually plausible manner.
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- Title
- YOUNG COLLEGE MEN’S BELIEFS ABOUT NONPROFESSIONAL HELP-SEEKING FOR DEPRESSION
- Creator
- Na, Hana
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Low rates of psychological help seeking among young males with depression havereceived significant research attention. However, most prior studies have focused on why the population seeks or does not seek psychological help from formal/professional sources. The present study examined the beliefs of 193 young male college students to predict their intentions to seek psychological help from friends, the most preferred source of help for this group. The study assessed the constructs of the...
Show moreLow rates of psychological help seeking among young males with depression havereceived significant research attention. However, most prior studies have focused on why the population seeks or does not seek psychological help from formal/professional sources. The present study examined the beliefs of 193 young male college students to predict their intentions to seek psychological help from friends, the most preferred source of help for this group. The study assessed the constructs of the reasoned action approach and their underlying beliefs, taking two possible contributing factors to men’s lower help-seeking into account: masculine ideology and perception of depression as masculine or feminine. Results revealed that intention to seek help from friends for depression was associated only with injunctive and descriptive norms and their underlying beliefs surrounding three referents: friends (injunctive and descriptive), fathers (injunctive only), and other family members (descriptive only). Relevant normative beliefs surrounding those referents were not sensitive to young male college students’ masculine ideology and its interaction with depression perception. These findings, in conjunction with the results of the audience segment analyses indicating the importance of the opinions and behaviors of specific referent groups, suggest that injunctive normative beliefs with father and friend referents and descriptive normative beliefs with friend referents are key beliefs that persuasive health messages should focus more on to promote help-seeking from friends among young male college students with depressive disorders, regardless of their adherence to traditional masculine norms and perception of depression as masculine or feminine.
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- Title
- SQUATTING TO MAKE ENDS MEET : SOUTHERN ITALIAN MIGRANTS AND THE RIGHT TO A HOME IN 1970S ITALY AND WEST GERMANY
- Creator
- Jacobson, Sarah Bryanne
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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This comparative study examines how southern Italian migrants faced social and political exclusion within and outside of their nation-state in the decades following the Second World War. Using Turin, Italy and Frankfurt am Main, West Germany as case studies, I investigate how urban renewal plans and discriminatory rental practices exacerbated housing shortages and induced migrants to live in precarious housing conditions. Taking inspiration from recent conceptualizations of citizenship put...
Show moreThis comparative study examines how southern Italian migrants faced social and political exclusion within and outside of their nation-state in the decades following the Second World War. Using Turin, Italy and Frankfurt am Main, West Germany as case studies, I investigate how urban renewal plans and discriminatory rental practices exacerbated housing shortages and induced migrants to live in precarious housing conditions. Taking inspiration from recent conceptualizations of citizenship put forth by historians Geoff Eley, Jan Palmowski, and Kathleen Canning, I show citizenship to be a contingent and contested category. By articulating housing claims and engaging in contest, southern Italian migrants and other disadvantaged residents pushed for an expansion and more equitable administration of institutionalized social service practices. By marching in the streets, going on rent strike, and occupying apartment buildings, migrants’ collective actions highlighted governing bodies’ failed promises to deliver a baseline standard of living. Southern Italians, allies, and news media channels frequently used women’s and children’s voices to amplify migrants’ claims to safe and affordable housing, portraying their motivations as apolitical and need-based in a time when internal security grew in importance. As extraparliamentary groups and domestic and international terrorist organizations threatened the existing sociopolitical order in both Italy and West Germany, city council debates became embroiled in questions of legality and whether to evict or accommodate housing occupiers. I complicate dominant narratives that center on tensions between self-identifying activists and police, as emblemized by conflict over housing in the streets, to show how city administrations began to differentiate between housing occupations conducted out of social need and those they perceived as part of more radical political movements. In turn, migrants and other socioeconomically disadvantaged occupiers were more amenable to negotiations with city officials, pushing for reforms within existing systems rather than more revolutionary changes. Overall, I argue that migrants challenged the socioeconomic and political practices that treated them as temporary residents or second-class citizens. By occupying the very spaces that had previously symbolized their marginalization, they exerted a right to state aid and assistance while subsequently reconfiguring the social fabric of their neighborhoods and communities. As local administrations reluctantly responded to their claims, they shifted definitions of urban citizenship and enacted reforms that had ramifications for housing and migration policies.
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- Title
- Exploring drivers of the research-implementation gap in large carnivore conservation
- Creator
- Hoffmann, Claire F.
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The number of scientific publications centered on threats to large carnivore populations has increased exponentially over the last two decades. However, this notable growth in research effort has not resulted in a commensurate positive impact on the population status of those carnivore species. My dissertation explores a range of drivers that may be contributing to this evident disconnect between research effort and conservation impact in large carnivore conservation. Each chapter delves into...
Show moreThe number of scientific publications centered on threats to large carnivore populations has increased exponentially over the last two decades. However, this notable growth in research effort has not resulted in a commensurate positive impact on the population status of those carnivore species. My dissertation explores a range of drivers that may be contributing to this evident disconnect between research effort and conservation impact in large carnivore conservation. Each chapter delves into a different step in the processes of research and conservation practice in which this research-implementation gap may be perpetuated. In Chapter 1, I conducted a review to assess whether taxonomic bias was evident among the published literature on carnivore depredation of livestock in sub-Saharan Africa. I used lexical analysis to compare the central large carnivore species in each study to the species identified as the primary livestock depredator. I found that, while the spotted hyena (Crocuta crocuta) tended to be the primary livestock depredator, the African lion (Panthera leo) was the most common focal species. I argued that this pattern is likely due to the African lion’s charisma and its role as a global rallying point for conservation funding. In Chapter 2, I developed a framework to represent linkages among the different components of the complex systems in which human-wildlife coexistence must occur. With the assistance of a collaborative team, I used this framework to explore emergent themes from semi-structured interviews on human-wildlife coexistence in Northern Tanzania. We found that the nature of human-elephant interactions amplified the negative impacts of human-carnivore interactions, and decreased human willingness and capacity to participate in interventions designed to promote human-wildlife coexistence. In Chapter 3, I quantified carnivore-livestock encounter rates, attack rates, and depredation risk at bomas in Laikipia, Kenya. I found that carnivores encountered potential livestock prey far more often than they attacked, and that these encounter rates exhibited notable temporal patterning at multiple resolutions. Furthermore, spotted hyenas (Crocuta crocuta) had substantially higher encounter and attack rates than any other carnivore species, and thus posed the greatest depredation risk for livestock. I concluded that better understanding of species-specific encounter rates such as those I explored will aid in the prediction of depredation risk, and therefore the mitigation of carnivore depredation of livestock. In Chapter 4, I applied three geostatistical measures to assess spatial clustering in data describing carnivore depredation of livestock in the Maasai steppe region of Tanzania. My analysis revealed that the spatial patterns of carnivore depredation of livestock tended not to significantly differ from random. I concluded that other drivers of spatial randomness may be obscuring patterns of depredation. Thus, analysis of research to inform depredation interventions must carefully apply diagnostic approaches to ensure accurate interpretation of spatial patterning. I conclude my dissertation with a summary of key findings and recommendations to improve research efforts to better bridge the research-implementation gap moving forward. This dissertation incorporates a diversity of research techniques, which provide a range of valuable contributions to current understanding of the research-implementation gap and large carnivore conservation.
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- Title
- A NEW BRAZILIAN ENERGY PORTFOLIO : THE CASE FOR SUN AND WATER
- Creator
- Brown, Erik Jacob
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The Amazon is a delicate ecosystem that has global-scale environmental and climatologicalimpact, and is at risk of overdevelopment, over-modification and destruction. Issues associated with the installation and operation of traditional reservoir-dam systems in the Amazon are examined, and it is suggested to supplement the current Brazilian energy portfolio and replace future dam plans with hybrid in-stream generator and photovoltaic systems to provide for distributed renewable microgrids as...
Show moreThe Amazon is a delicate ecosystem that has global-scale environmental and climatologicalimpact, and is at risk of overdevelopment, over-modification and destruction. Issues associated with the installation and operation of traditional reservoir-dam systems in the Amazon are examined, and it is suggested to supplement the current Brazilian energy portfolio and replace future dam plans with hybrid in-stream generator and photovoltaic systems to provide for distributed renewable microgrids as well as on-grid power needs. These systems can be installed at various scales, from a single-household off-grid implementation, up through and including offsetting or replacing current and future planned large-scale dams for on-grid use. This solution offers a socially and environmentally safer alternative to dams, by reducing or eliminating several issues with reservoir-based dams: deforestation for reservoirs, flooding from reservoirs, displacement of local families, inhibition of sediment and marine life transport, and greenhouse gas emissions. The financial and energetic feasibility of the proposed system is compared, including transmission costs, to several common electrification methods. Other supporting topics are also investigated, such as the fish-friendly design of in-stream devices, and the maximum reach of the proposed hybrid microgrid system relative to the in-stream deployment sites.
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- Title
- SYNTHESIS AND CHARACTERIZATION OF BIOACTIVE GLASS-CERAMIC PARTICLES WITH ADVANCED ANTIBACTERIAL PROPERTIES FOR APPLICATIONS IN BONE REGENERATION
- Creator
- Pajares Chamorro, Natalia
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Bacterial infections are major surgical complications, which have worsened due to the continued evolution of drug-resistance. In coping with the decay of the antibiotic era, scientists eagerly search for alternative treatments. Multi-functional biomaterials capable of combating infections while triggering tissue regeneration are of great interest. For example, bioactive glasses have been regularly used to deliver drugs and regenerate tissue owed to their unique bone-bonding ability. Doping...
Show moreBacterial infections are major surgical complications, which have worsened due to the continued evolution of drug-resistance. In coping with the decay of the antibiotic era, scientists eagerly search for alternative treatments. Multi-functional biomaterials capable of combating infections while triggering tissue regeneration are of great interest. For example, bioactive glasses have been regularly used to deliver drugs and regenerate tissue owed to their unique bone-bonding ability. Doping the bioactive glass structure with broad-spectrum biocide ions such as Ag+ confers advanced antibacterial properties. The release of Ag+ is controlled by the degradation process of the glass network, maintaining the dose within a therapeutic window that is not cytotoxic to eukaryotic cells. Despite the extensive research performed on Ag-doped bioactive glasses, their regenerative properties in bone tissues have been rarely investigated. This thesis presents promising interactions between Ag-doped bioactive glass (Ag-BG) microparticles and osteoprogenitor cells, providing evidence of the ability to support bone regeneration. Ag-BG’s degradation provoked cell proliferation and cell differentiation in vitro and demonstrated healing of critical calvaria defects in mice after one month of implantation, thanks to the release of Si and Ca ions. Additionally, Ag-BG was antibacterial against Staphylococcus aureus (S. aureus), the most common cause of bone-degenerative diseases like osteomyelitis, and demonstrated low proclivity to induce resistance. The antibacterial potential originated from the degradation by-products of the structure. The mechanism of inhibition was built upon four main sources from higher to lower contribution: Ag+ release, oxidative stress, mechanical damage by nano-sized debris, and osmotic effect. In addition, Ag-BG was capable of restoring ineffective antibiotics with cell-wall-related inhibitory mechanisms by simple combinatorial therapies, rendering them effective in clearing infections. This unprecedented functionality of Ag-BG was expanded with antibiotic depots, where Ag-BG served as a carrier for an ineffective drug. Bioactive glass nanoparticles (BGNs) have been proposed to advance biological and antibacterial properties compared to their micro-sized counterparts. However, the challenges of producing BGNs with multifold metallic ions in a reproducible manner have limited their use. Here, the Stöber method was comprehensively studied to understand the effect of process variables on BGNs’ composition, structure, and morphology. The use of methanol as solvent and the early addition of metallic ion reagents before catalysis helped improved their cation incorporation within the glass network. Extended stirring was key to achieving the targeted composition and controlling the particle size. Monodispersed 10 nm Ag-doped BGNs (Ag-BGNs) were achieved. These Ag-BGNs were stronger antimicrobial weapons, providing bacterial inhibition within hours of treatment. The biological properties were not significantly advanced in the Ag-BGNs compared to Ag-BG; however, cell proliferation, differentiation, and bone re-growth were still provoked. These Ag-BGNs were used as fillers in hydrogel nanocomposites with natural matrices consisting of collagen type I or extracellular matrix. Ag-BGNs distributed homogeneously along the polymer fibrils and allowed polymerization within hours at physiological conditions. These materials hold potential for injectable devices, designing minimally invasive single-step treatment for debilitating bone infections while promoting tissue recovery.
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- Title
- COMPOSITION – PROCESSING – MICROSTRUCTURE – PROPERTY RELATIONSHIPS OF THE ZINC-MAGNESIUM SYSTEM FOR ABSORBABLE BIOMEDICAL IMPLANT APPLICATIONS
- Creator
- Hernández Escobar, David
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Absorbable metals have the potential to serve as the next generation of temporary medical implants by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their incorporation in the market could greatly reduce the need and risks associated with additional surgeries and other complications often related to permanent devices. Despite the extensive research on magnesium (Mg) and iron (Fe) based alloys over the last two decades, they have not exhibited an...
Show moreAbsorbable metals have the potential to serve as the next generation of temporary medical implants by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their incorporation in the market could greatly reduce the need and risks associated with additional surgeries and other complications often related to permanent devices. Despite the extensive research on magnesium (Mg) and iron (Fe) based alloys over the last two decades, they have not exhibited an optimal combination of mechanical properties, biocompatibility, and controlled degradation rate for absorbable implant applications. Zinc (Zn) and Zn-based alloys have recently emerged as an alternative, as they have demonstrated an attractive combination of in vivo biocompatibility and degradation behavior. However, their mechanical properties are generally insufficient for load-bearing implant applications.In this dissertation, Zn-xMg (x = 3, 10, 30 wt.%) hybrid samples were synthesized for the first time using high-pressure torsion (HPT) to mechanically bond pure Zn and Mg disks. These samples were characterized to investigate their processing-microstructure-property relationships. The effects of HPT on the microstructural and hardness evolution were systematically studied in all the materials, with special emphasis on the regions of highest plastic deformation. The effects of post-deformation annealing (PDA) on the Zn-3Mg hybrid were also investigated. Also, an as-homogenized Zn-3Mg (wt.%) alloy was HPT-processed and subjected to PDA, and the microstructure and hardness evolution was compared with that of the Zn-3Mg hybrid. In addition, four different biodegradable coatings (based on zinc phosphate (ZnP), collagen (Col), and Ag-doped bioactive glass nanoparticles (AgBGN)) were synthesized by chemical conversion, spin-coating, or a combination of both, on the as-homogenized Zn-3Mg alloy substrates. The effects of the coatings on the in vitro degradation behavior, cytocompatibility, and antibacterial activity were evaluated.A significant microstructural refinement was obtained after HPT processing for 30 turns, reaching equiaxed grains of ~ 200 nm in both the Zn-3Mg hybrid and alloy. Unlike in the alloy, HPT induced the nucleation of Mg2Zn11 and MgZn2 intermetallic compounds, as well as the formation of supersaturated solid solutions in the hybrid, both of which led to maximum hardness values in the range of ~ 220-230 HV. PDA resulted in both an increased hardness (up to ~ 250 HV) and strain rate sensitivity. A plastic deformation model is proposed to explain the strain-hardening behavior of the hybrid after PDA, which suggested an enhanced strength-ductility relationship. This was consistent with the strain rate sensitivity results from nanoindentation.In vitro degradation of ZnP coated samples for 21 days immersion showed a controlled weight loss over time associated with a decreased corrosion rate, while maintaining a physiological pH range of 7.5-7.6. The uncoated, ZnP coated, and Col-AgBGN coated sample extracts led to higher cell viability over 6 days culture, which generally increased with extract concentration. In addition, the Col-AgBGN coated samples led to ~ 31 % bacterial viability, compared to the ~ 65-75 % of the other samples, hence, indicating a strong antibacterial effect.Overall, the insights gained from this dissertation enabled a better understanding of the composition-processing-microstructure-property relationships of the Zn-Mg system and served as a roadmap for the design of hybrid materials with enhanced mechanical properties. Moreover, the synthesis of biodegradable coatings has potential to tailor the Zn-Mg materials for specific biomedical implant applications.
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- Title
- Studies in Ligand Unbinding Transition State Plasticity for Kinetics-Oriented Drug Design
- Creator
- Lotz, Samuel D.
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The dominant objective in drug design historically has been to improve drug efficacy through increasing affinity of drug binding under equilibrium conditions. However, a complete understanding of drug efficacy in non-equilibrium living organisms requires knowledge of the kinetics of drug (un)binding. While kinetics-oriented drug design has gained popularity it is still hampered by a number of limitations, not limited to the availability of structural models for ligand (un)binding transition...
Show moreThe dominant objective in drug design historically has been to improve drug efficacy through increasing affinity of drug binding under equilibrium conditions. However, a complete understanding of drug efficacy in non-equilibrium living organisms requires knowledge of the kinetics of drug (un)binding. While kinetics-oriented drug design has gained popularity it is still hampered by a number of limitations, not limited to the availability of structural models for ligand (un)binding transition states. In general these kinds of simulations are very difficult to achieve due to the long natural timescales of these processes (seconds to minutes) compared to the short timescales at which MD is computed (femtoseconds). In this thesis we address these limitations through computational methods for simulating full, unbiased, unbinding trajectories of inhibitors of drug targets with clinical interest. This is accomplished primarily by applying an enhanced sampling technique, called weighted ensemble (WE), over classical molecular dynamics (MD) simulations. Our approach is drastically more efficient than brute-force simulation methods, requires no biasing forces or other force field modifications, and is shown to work for a variety of systems of interest. Using these methods we are able to model, at all-atom resolution, the structure of unstable transition states for inhibitors of clinical interest of the soluble epoxide hydrolase (sEH) enzyme. This enzyme is implicated in a number of therapeutics including treatment of diabetic neuropathic pain. Critically, we also investigate the role of transition state plasticity in lead optimization. Towards this we developed a model for predicting plasticity from experimental data and a strategy for verifying these predictions which was applied in the context of sEH lead optimization.
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- Title
- Analysis of Positional Bias Within Multiple Stimulus Without Replacement Preference Assessments
- Creator
- Miranda, David Ray Gutierrez
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Positional bias is a pattern of responding to a specific location that can be influenced by response effort and/or prior learning history. Within the contexts of preference assessments, positional bias create additional variables that make ascertaining true preferences within a preference assessment more difficult. Prior research on positional bias within preference assessments have focused primarily on its use in paired stimulus assessments due to the complex nature of the multiple-stimulus...
Show morePositional bias is a pattern of responding to a specific location that can be influenced by response effort and/or prior learning history. Within the contexts of preference assessments, positional bias create additional variables that make ascertaining true preferences within a preference assessment more difficult. Prior research on positional bias within preference assessments have focused primarily on its use in paired stimulus assessments due to the complex nature of the multiple-stimulus without replacement preference assessment. The present study is a secondary analysis that utilized four different methods to measure side bias and center bias for 19 young children with autism spectrum disorders. Results indicate that participants had varying degrees of biased responding but collectively engaged in little biased responding. Present study includes discussion of general patterns of responding, an analysis of the four methodologies, and general recommendations for the application of these methodologies.
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- Title
- "Wellness Starts with Me" : Choir Teacher Wellness Experiences and Perceptions
- Creator
- McNickle, Colleen Bartimoccia
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The purpose of this study was to examine the experiences of choir teachers in a Collaborative Teacher Study Group (CTSG) as they met to discuss wellness in music education and collaborated to include principles and strategies of wellness in their teaching amidst the COVID-19 pandemic. Research questions included (1) How did CTSG members describe their perceptions and experiences of wellness in music education? (2) How did CTSG experiences impact participants’ professional practice? (3) How...
Show moreThe purpose of this study was to examine the experiences of choir teachers in a Collaborative Teacher Study Group (CTSG) as they met to discuss wellness in music education and collaborated to include principles and strategies of wellness in their teaching amidst the COVID-19 pandemic. Research questions included (1) How did CTSG members describe their perceptions and experiences of wellness in music education? (2) How did CTSG experiences impact participants’ professional practice? (3) How did CTSG experiences impact participants’ perceptions and expectations of wellness in music education? This instrumental case study examined the case of one CTSG comprised of five choral music educators. As the COVID-19 pandemic affected nearly every aspect of teacher and student wellness, the context of COVID-19 was of special interest. I began data collection with two preliminary interviews in July, wherein participants shared their teaching histories, philosophies, and styles, discussed the impacts of COVID-19 on their teaching and personal lives, and suggested wellness discussion topics for CTSG meetings. The CTSG then met virtually for seven meetings during the months of August and September of 2020. Participants completed weekly check-ins through November and took part in one final interview in November of 2020. Participants shared a desire for wellness resources, displayed eagerness to implement wellness plans for self and students, and perceived a toll on their mental health due to the ever-present uncertainty of teaching conditions during COVID-19. The CTSG served as a place of community, commiseration, and collaboration, as participants studied wellness topics such as self-care, boundaries, emotional endurance, social and emotional learning, mindfulness, physical wellness, and music as wellness. Teachers workshopped and collaborated on policies, classroom expectations, lesson plans, and personal wellness plans which they then implemented in their classrooms and personal lives.
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- Title
- Digital Evolution in Experimental Phylogenetics and Evolution Education
- Creator
- Kohn, Cory
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The creation and evaluation of known evolutionary histories and the implementation of student investigatory experiences on evolution are difficult endeavors that have only recently been feasible. The research presented in this dissertation is related in their shared use of digital evolution with Avidians as a model study system, both to conduct science research in experimental phylogenetics and to conduct education research in curricular intervention to aid student understanding.I first...
Show moreThe creation and evaluation of known evolutionary histories and the implementation of student investigatory experiences on evolution are difficult endeavors that have only recently been feasible. The research presented in this dissertation is related in their shared use of digital evolution with Avidians as a model study system, both to conduct science research in experimental phylogenetics and to conduct education research in curricular intervention to aid student understanding.I first present background discussions on the Avidian digital evolution study system—as implemented in Avida and Avida-ED—and its favorable use in experimental phylogenetics and biology education owing to its greater biological realism than computational simulations, and greater utility and generality than biological systems. Prior work on conducting experimental evolution for use in phylogenetics and work on developing undergraduate lab curricula using experimental evolution are also reviewed. I establish digital evolution as an effective method for phylogenetic inference validation by demonstrating that results from a known Avidian evolutionary history are concordant, under similar conditions, to established biological experimental phylogenetics work. I then further demonstrate the greater utility and generality of digital evolution over biological systems by experimentally testing how phylogenetic accuracy may be reduced by complex evolutionary processes operating singly or in combination, including absolute and relative degrees of evolutionary change between lineages (i.e., inferred branch lengths), recombination, and natural selection. These results include that directional selection aids phylogenetic inference, while stabilizing selection impedes it. By evaluating clade accuracy and clade resolvability across treatments, I evaluate measures of tree support and its presentation in the form of consensus topologies and I offer several general recommendations for systematists. Using a larger and more biologically realistic experimental design, I systematically examine a few of the complex processes that are hypothesized to affect phylogenetic accuracy—natural selection, recombination, and deviations from the model of evolution. By analyzing the substitutions that occurred and calculating selection coefficients for derived alleles throughout their evolutionary trajectories to fixation, I show that molecular evolution in these experiments is complex and proceeding largely as would be expected for biological populations. Using these data to construct empirical substitution models, I demonstrate that phylogenetic inference is incredibly robust to significant molecular evolution model deviations. I show that neutral evolution in the presence of always-occurring population processes, such as clonal or Hill-Robertson interference and lineage sorting, result in reduced clade support, and that selection and especially recombination, including their joint occurrence, restore this otherwise-reduced phylogenetic accuracy. Finally, this work demonstrates that inferred branch lengths are often quite inaccurate despite clade support being accurate. While phylogenetic inference methods performed relatively well in both theoretically facile and challenging molecular evolution scenarios, their accuracy in clade support might be a remarkable case of being right for misguided reasons, since branch length inference were largely inaccurate, and drastically different models of evolution made little difference. This work highlights the need for further research that evaluates phylogenetic methods under experimental conditions and suggests that digital evolution has a role here. Finally, I examine student understanding of the importance of biological variation in the context of a course featuring a digital evolution lab. I first describe the Avida-ED lab curriculum and its fulfillment of calls for reform in education. Then I describe the specific education context and other course features that aim to address student conceptualization of variation. I present a modified published assessment on transformational and variational understanding and findings regarding student understanding of variation within an evolution education progression. Finally, I offer suggestions on incorporating course material to engage student understanding of variation.
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- Title
- EXPLORING THE IMPACT OF BIOGAS QUANTITY AND QUALITY IN DIFFERENT DIGESTER TYPES WITH VARIATIONS IN TEMPERATURE
- Creator
- Barrios Arosemena, Maria Ines
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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The energy sector in the U.S. has been pushing for policies such as the Renewable Portfolio Standard (RPS) to mitigate the impacts of GHG emissions. Biogas from anaerobic digesters is a viable form of renewable energy, due to its CH4 composition, it can be used as a replacement for power and heat generation or upgraded and sold as biomethane. This study analyzed the effects of temperature in biogas quality and quantity of dairy cow manure in order to compare two main systems, a CSTR and a...
Show moreThe energy sector in the U.S. has been pushing for policies such as the Renewable Portfolio Standard (RPS) to mitigate the impacts of GHG emissions. Biogas from anaerobic digesters is a viable form of renewable energy, due to its CH4 composition, it can be used as a replacement for power and heat generation or upgraded and sold as biomethane. This study analyzed the effects of temperature in biogas quality and quantity of dairy cow manure in order to compare two main systems, a CSTR and a covered lagoon. A biochemical methane potential (BMP) test was performed to determine material biodegradability of dairy cow manure with respect to temperature. The results show that all samples are anaerobically biodegradable with samples yielding 86, 168, 440, 475 and 448 L biogas per kg initial VS for 15°C, non-mixed; 20°C, non-mixed; 30°C, non-mixed; 39°C, non-mixed; and 39°C, mixed, respectively. The BMP results demonstrated so significant difference between 30°C, non-mixed; 39°C, non-mixed; and 39°C, mixed, respectively. In addition, the effects of psychrophilic, unregulated, and mesophilic conditions were tested in small scale lab pilot digesters. Results show that mesophilic condition yielded the highest cumulative biogas production, while the psychrophilic and unregulated conditions presented higher methane yield. A life cycle analysis was performed to compare two popular anaerobic digestion systems, a CTSR and a covered lagoon, versus current manure management systems for dairy cow manure. The LCA revealed that both systems have less environmental burdens when compared to current waste management systems and a CSTR has less environmental burdens than a covered lagoon.
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- Title
- SOLIDARITY & RESISTANCE : WOMEN’S PERSPECTIVES ON EMPOWERMENT THROUGH SELF HELP GROUPS
- Creator
- Mishra, Manasi
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Development interventions mostly aim to ‘empower’ rural women by increasing their income and livelihood but rarely consider the voices of their beneficiaries. I study the meanings and experiences of empowerment or nari shakti as understood and described by rural women who lead self-help groups (SHGs) engaged in savings, micro-credit and income generation. I conducted the research in the central Himalayan region of rural India in Uttarakhand State using in-depth interviews with 11 SHG leaders....
Show moreDevelopment interventions mostly aim to ‘empower’ rural women by increasing their income and livelihood but rarely consider the voices of their beneficiaries. I study the meanings and experiences of empowerment or nari shakti as understood and described by rural women who lead self-help groups (SHGs) engaged in savings, micro-credit and income generation. I conducted the research in the central Himalayan region of rural India in Uttarakhand State using in-depth interviews with 11 SHG leaders. The findings indicate that the participants experience empowerment as solidarity and collective power that manifest in the form of self-reliance, courage, and independence. The participants associate their self-reliance with courage and inner strength which they have built as a means to survive the pain and struggle. Their stories of nari shakti are also stories of pain and struggle.This research implies the need to examine perspectives of feminists on empowerment related interventions. Further research is needed on how micro-credit SHGs help build collective action that can challenge patriarchal power structures and bring about social change. Such research can help provide solutions on how non-profits can utilize feminist strategies of consciousness raising while still meeting donor expectations for the SHG programs.
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- Title
- Cooking and Coalescence : Exploring the Construction of Community and Cuisine at Morton Village
- Creator
- Painter, Jeffrey Matthew
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Over the last few decades, archaeologists have found increasing evidence for migration and other forms of population movement among precontact Indigenous groups in North America, creating dynamic social interactions that directly impacted local communities and regional networks. In some cases, these interactions appear to have stimulated new cultural developments, such as the growth of larger communities and the development of new institutions or practices, which helped to shape the history...
Show moreOver the last few decades, archaeologists have found increasing evidence for migration and other forms of population movement among precontact Indigenous groups in North America, creating dynamic social interactions that directly impacted local communities and regional networks. In some cases, these interactions appear to have stimulated new cultural developments, such as the growth of larger communities and the development of new institutions or practices, which helped to shape the history of these regions. In response, archaeologists have begun to shift their focus toward understanding how these multi-cultural, or coalescent, communities were formed and the processes that made them successful. A number of mechanisms have been identified that promoted integration in these communities, but, so far, research has focused on large-scale organizational changes, such as the development of new social institutions, over small-scale, everyday interactions. In this dissertation, I examine foodways practices and their role in coalescence to demonstrate that small-scale interactions were also critical for community integration and coalescence. To investigate these practices, I conducted ceramic use-alteration and spatial analyses at Morton Village, a site of on-going coalescence in the central Illinois River valley, as well as at two comparative sites, Larson and the Tremaine Complex, in order to examine cooking and consumption practices in pre- and post-migration contexts. Comparisons of data from these sites revealed that some traditional foodways practices were maintained by the migrant and local residents at Morton Village, while other practices were slowly shifting, creating a unique cuisine at the site. Through both larger communal events and everyday cooking, shifts in foodways at Morton Village may have helped to link migrant and local residents together, promoting community integration from the bottom-up. This research indicates that everyday interactions can also be critical for successful coalescence, not just large-scale organizational changes, demonstrating that multi-scalar approaches are needed to better understand this process.
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- Title
- "I Filled a Lot of Gaps" : How and Why Early Career Teachers Expand Induction Support Systems with Social Media
- Creator
- Staudt Willet, Kenneth Bret
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Early career teachers face numerous challenges during their transition from teacher preparation programs into professional employment contexts. With many more opportunities for professional learning available today, early career teachers must navigate an increased number of potentially conflicting messages about what and how to teach. This study explores the support systems that early career teachers construct during induction and how they use social media for this purpose. These systems can...
Show moreEarly career teachers face numerous challenges during their transition from teacher preparation programs into professional employment contexts. With many more opportunities for professional learning available today, early career teachers must navigate an increased number of potentially conflicting messages about what and how to teach. This study explores the support systems that early career teachers construct during induction and how they use social media for this purpose. These systems can be understood as professional learning networks (PLNs) consisting of tools, people, and spaces and useful for improving teaching and learning. Interviews with early career teachers provide evidence of reasons why they develop PLNs as well as what tools, people, and spaces they include in these support systems. Findings demonstrate that early career teachers construct induction support systems to navigate change, scarcity of resources, and conflicting teaching beliefs. Early career teachers look for tools for planning, enacting practice in the classroom, and connecting socially. People in early career teachers’ support systems included both in-school and out-of-school connections. Interviewees described how they use various social media platforms in their induction support systems as well as boundaries they maintain around social media use. Finally, early career teachers described their engagement on social media in terms of browsing, asking, and exchanging. Implications of these findings are discussed for early career teachers, teacher educators, and education leaders—especially regarding how stakeholders can help alleviate induction pressures on early career teachers. This study contributes insight into the convergence of tensions experienced by early career teachers as they consider whether and how to construct support systems during induction, including if and how to look for help on social media.
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- Title
- PRECISION DIAGNOSTICS AND INNOVATIONS FOR PLANT BREEDING RESEARCH
- Creator
- Hugghis, Eli
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Major technological advances are necessary to reach the goal of feeding our world’s growing population. To do this, there is an increasing demand within the agricultural field for rapid diagnostic tools to improve the efficiency of current methods in plant disease and DNA identification. The use of gold nanoparticles has emerged as a promising technology for a range of applications from smart agrochemical delivery systems to pathogen detection. In addition to this, advances in image...
Show moreMajor technological advances are necessary to reach the goal of feeding our world’s growing population. To do this, there is an increasing demand within the agricultural field for rapid diagnostic tools to improve the efficiency of current methods in plant disease and DNA identification. The use of gold nanoparticles has emerged as a promising technology for a range of applications from smart agrochemical delivery systems to pathogen detection. In addition to this, advances in image classification analyses have allowed machine learning approaches to become more accessible to the agricultural field. Here we present the use of gold nanoparticles (AuNPs) for the detection of transgenic gene sequences in maize and the use of machine learning algorithms for the identification and classification of Fusarium spp. infected wheat seed. AuNPs show promise in their ability to diagnose the presence of transgenic insertions in DNA samples within 10 minutes through colorimetric response. Image-based analysis with the utilization of logistic regression, support vector machines, and k-nearest neighbors were able to accurately identify and differentiate healthy and diseased wheat kernels within the testing set at an accuracy of 95-98.8%. These technologies act as rapid tools to be used by plant breeders and pathologists to improve their ability to make selection decisions efficiently and objectively.
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- Title
- Method development for capillary electrophoresis mass spectrometry (CE-MS)-based proteomics and application to uncovering proteome dynamics of zebrafish embryos during early embryogenesis
- Creator
- Chen, Daoyang
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
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Reversed-phase liquid chromatography (RPLC) coupling with tandem MS (MS/MS) is often the method of choice in both peptide-centric bottom-up proteomics (BUP) and proteoform-centric top-down proteomics (TDP) studies. In recent years, capillary zone electrophoresis (CZE)-MS has attracted attention as another platform in proteomics due to high separation efficiency, high sensitivity, and complementarity to LC-MS. This work is dedicated to developing novel CE-MS-based methods for large-scale...
Show moreReversed-phase liquid chromatography (RPLC) coupling with tandem MS (MS/MS) is often the method of choice in both peptide-centric bottom-up proteomics (BUP) and proteoform-centric top-down proteomics (TDP) studies. In recent years, capillary zone electrophoresis (CZE)-MS has attracted attention as another platform in proteomics due to high separation efficiency, high sensitivity, and complementarity to LC-MS. This work is dedicated to developing novel CE-MS-based methods for large-scale proteomics and applies them to study the proteome dynamics of zebrafish embryos during early embryogenesis.In Chapter 2, a sample stacking method, dynamic pH junction, was systematically investigated and employed to improve CZE’s sample loading capacity for large-scale BUP. The results of the optimized system represent the highest loading capacity, the highest peak capacity, and the widest separation window of CZE for peptide separation to date. The automated CZE-MS system opened the door to using CZE-MS for large-scale BUP. In Chapter 3, for the first time, a strong cation exchange (SCX)-RPLC-CZE-MS/MS platform was established for deep BUP and phosphoproteomics. The platform approached comparable performance to the modern 2D-LC-MS/MS for deep proteomic sequencing evident by identifying 8200 protein groups and 65,000 unique peptides from a mouse brain proteome digest, 11,555 phosphopeptides from the HCT116 cell line. SCX-RPLC-CZE-MS/MS and 2D-LC-MS/MS showed good complementarity in protein, peptide, and phosphopeptide IDs. In Chapter 4, a quantitative BUP study was performed on zebrafish embryos across four developmental stages during the maternal-to-zygotic transition (MZT) via coupling isobaric tag for relative and absolute quantitation (iTRAQ) chemistry with both RPLC-MS/MS and CZE-MS/MS. Expression kinetics of nearly 5000 proteins including over 100 transcription factors (TFs) across four early embryonic stages were determined. The protein expression profiles fall into several different clusters and accurately reflect the important events during early embryogenesis. Further studies of the expression profiles of TFs revealed that the differentially expressed TFs during the MZT show wave-like expression patterns. Top-down proteomics (TDP) aims to directly characterize proteoforms in cells. CZE-MS/MS has been demonstrated as a useful tool for TDP. In Chapter 5, for the first time, we evaluated various semiempirical models for predicting proteoforms’ electrophoretic mobility using large-scale TDP data sets from earlier CZE–MS/MS studies. Linear correlations were achieved between the experimental and predicted μef of E. coli proteoforms and histone proteoforms (R2 = 0.98), demonstrating that the μef of proteoforms in CZE-MS can be predicted accurately, which could be useful for validating the confidence of proteoform IDs from a database search. In Chapter 6, we concluded the results of this dissertation and provided our expectations for future studies.
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