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Interpolation-Based Immersed Finite Element Analysis Using Higher-Order Curved Foreground Meshes
Get PDFImmersed finite element analysis is most broadly characterized by using a domain and mesh that is unfitted to the boundaries of the body intended for study. A complex body can be immersed within a larger, geometrically simple domain, allowing a well-structured, unfitted mesh to be easily generated. However, the unfitted mesh complicates evaluating integrals over the body. This inspired the development of the interpolation-based immersed finite element method, where the discrete function space on the immersed mesh is interpolated into the discrete function space on the body-fitted mesh. The interpolation causes the bilinear and linear form to be expressed with regard to the body-fitted function space. Thus, element assembly occurs using the body-fitted mesh, just as it would in a non-immersed context. I first describe the process for developing an interpolation-based immersed finite element code from a traditional finite element code. I implement isoparametric elements on curved geometric boundaries and construct a basis of higher-order Lagrange polynomials in both the foreground and background meshes. I perform a series of three numerical experiments and show the interpolation-based immersed finite element method maintains optimal higher-order error convergence rates in the H1-norm.</p
Linking Cyanobacterial Carboxysome Maturation, Permeability, and Equilibria via Redox Dynamics
Get PDFWith history spanning from the first known fossils and oxygenating the Earth’s atmosphere, to performing 25% of modern annual carbon fixation, the photosynthetic prokaryotes, cyanobacteria, are fundamental to life on Earth. They accomplish this feat of carbon fixation by implementing an efficient CO2-concentrating mechanism (CCM) featuring proteinaceous bacterial microcompartments called carboxysomes. The CCM drives the formation of a CO2-rich environment inside carboxysomes where the carbon-fixing machinery, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and carbonic anhydrase, are housed. The internal environment of carboxysomes is more oxidizing than the surrounding cytosol but the chemical permeability across the protein shell of carboxysomes is largely unknown. In this thesis I utilize a redox-sensitive GFP construct with timelapse fluorescence microscopy to track the redox state of immature and mature carboxysomes under perturbed conditions (high/low [CO2] and addition of redox agents). These experiments have revealed that the redox state and permeability of carboxysomes are dynamic, responding to environmental changes, and capable of returning to the initial steady-state conditions. This work provides critical understanding of the redox-based mechanisms driving carbon-fixing regulation and robustness under changing environmental state essential for implementation of carboxysomes in biotechnological applications and climate change.</p
Quantum Control in a Two-Dimensional Ion Microtrap Array
Get PDFTwo-dimensional arrays of ions can be used as probes of fundamental physics and tools to investigate collective quantum phenomena due to their quantized internal and motional energies that can be coupled between particles. However, most two-dimensional ion arrays form around a single minimum of a smooth potential. This configuration makes individual control of motional interactions between ions challenging, because changes to the curvature of a shared potential well are experienced by all ions in the trap.
In this work, I present a different architecture for creating such arrays of trapped ions: the two-dimensional ion microtrap array. These microfabricated, chip-based devices instead create several potential energy minima that can be individually controlled through the application of local potentials, which may be altered dynamically over the course of a single experiment. The ion microtrap array used in this work confines three beryllium-9 ions on the corners of an equilateral triangle that has side lengths of 30 µm. I will discuss the performance of this device, including ion heating rates, and then present the results of experiments that demonstrate predictable quantum control of the ions we trap.
The first experiment demonstrates our ability to precisely manipulate the positions of the ions to achieve individual addressing with light beams. In the second experiment, we couple a single quantum of motional energy (a phonon) to multiple ions in the trap to create and manipulate entangled states of quantum motion. The third experiment dynamically tunes the system to directly observe a topological Berry phase using a single phonon. These results show this two-dimensional ion microtrap array is a fully tunable system that can be used to study static and time-dependent interactions and also create, manipulate, and entangle harmonic oscillators while maintaining coherence and conserving energy for a single excitation. </p
Real-time Cognitive State Estimates Modeling Using Embedded Measures for Adaptive Human-Autonomy Teaming
Get PDFIt has been proposed that intelligent autonomous systems that dynamically estimate operator cognitive states can adapt their behavior to better aid human operators and enhance team performance. This capability is crucial for astronaut support during deep space missions, where communication delays with ground control limit timely assistance. Previous research on cognitive state estimation has generally focused on single states, observable factors (e.g., task load), and the use of multiple sensors simultaneously.
While our laboratory demonstrated an adaptive autonomous system that changed modes based on real-time estimates of trust, workload, and situation awareness, it exhibited limited accuracy, potentially due to being trained on data from a non-adaptive system. Subsequent research performed a study that compared the predictive performance of multiple models with various feature availability variations, but did not account for the effects of mode changes. To address this, we developed multiple models trained on data from subjects interacting with both a non-adaptive and an adaptive autonomous system. First, we trained models on the group that interacted with the adaptive autonomous system, incorporating users' background information, real-time sensor data, human-system interactions, and novel features related to adaptation frequency and consistency of the autonomous system mode. Next, we trained and tested models built with exhaustive search followed by stepwise regression under optimizing for the Bayesian Information Criterion (BIC) using datasets from the adaptive group (N=10), the non-adaptive group (N=14), and a combined dataset (N=24). Finally, we explored three modeling methods with different feature down-selection approaches. Our results indicate that the combined dataset model focusing solely on human-system interaction features trained with exhaustive search followed by stepwise regression under BIC provided the most robust and best-performing prediction of operator trust, workload, and situation awareness. For example, the mean MAE (Mean Absolute Error) across 100 Monte Carlo Cross Validations for trust was 8.75, which was much smaller than the mean MAE by always predicting the median of the scale (as a baseline), which was 18.19. Similar results were found for models predicting workload and situation awareness.
This work enhances the state of the art in terms of the potential of adding new features that capture the interaction with an adaptive autonomous system, necessary datasets for training to have a more robust model when applied to unseen subjects, and approaches for building models to predict operator cognitive states for use in adaptive autonomous systems.</p
The “Autistic Accent”: Can People Really Guess if Someone is Autistic Based on How They Speak?
Get PDFThis study aims to investigate whether the average listener can identify autistic speakers based solely on phonetic patterns found in autistic speech. Participants completed a listening-based survey where they were asked to assess the person’s autistic status. The percentage of correct answers, d-prime, and certainty scores were analyzed both for the participants and the speakers. Results showed that middle-aged participants outperformed the younger and older age groups. They also suggest that women are more likely to be labeled ‘not autistic’ compared to their male counterparts. Finally, the ultimate conclusion is that the ‘autistic accent’, as investigated in purely phonetic terms in the current study, is slightly perceivable. These results have implications for linguistic profiling and perceptions of neurodivergence.</p
Three Essays in Applied Microeconomics
Get PDFThis dissertation consists of three chapters in applied microeconomics. The first two coverpolicy changes, one in the labor market and one in policing, while the third examines historical labor markets.
Right-to-Work (RTW) laws are a common state policy that outlaw union security agreements and thus decrease union funding. Previous estimates of RTW laws' influence on union density, wages, and employment have varied extremely widely. Using the early-to-mid 2010s implementation of RTW laws in five U.S. states, I estimate the short-run impacts of the policy on labor markets using a synthetic difference-in-differences estimation strategy. RTW laws lead to a 1 percentage point decrease in union membership overall and a 2 percentage point decrease in industries that are more highly unionized. They also contribute to a small but weakly significant increase in the employment to prime-age labor force ratio despite a decrease in people employed. This is due to a 0.9 percentage point decrease in the labor force participation rate that is concentrated among older individuals. RTW laws do not lead to a statistically significant change in workers wages on aggregate, but do lead to a 30.0% increase in the union non-union wage gap and a 5.7% decrease in wages for Black workers. RTW also appears to increase firm concentration and lower business dynamism as the number of firms, establishments, new business applications, and new firm formations all decrease at statistically significant levels. Together this provides evidence that RTW laws decrease union density but do not increase labor demand by attracting firms in the short-run. In response to RTW, unions may change their negotiating focus to prioritize wages while Black workers tend to be disproportionately negatively impacted by the weakening of unions.
In the wake of George Floyd's death and the ensuing protests throughout the country, Colorado passed SB-217, a police reform bill. This bill remains the widest police reform bill passed since and included a number of provisions restricting police use of violence while increasing the legal accountability of officers to the public. This paper evaluates the impact of the legislation on policing outcomes in Colorado. SB-217 did not impact police-involved deaths, crime incidents, arrests, clearance rates, or a host of other measures related to policing. It may have led to about a 3.28 percentage point decrease in the proportion of crime incidents that were violent crimes. There also appears to have been no change in the composition of police. This provides evidence against SB-217 having a large impact on both police behavior and perceptions of policing as a profession.
Military service has long been an economic vehicle for Americans to achieve higher socioeconomic outcomes. The Civil War marked the first time that Black Americans entered the U.S. Army, and for many it was their first formal employment as free men. At the time, many of the modern benefits of military service did not yet exist. This paper estimates the benefit of military service in the Civil War for Black Americans by estimating the impact of human capital accumulation on the probability of high-skill work in the future. Black Americans developed human capital through experience in ranked leadership roles that developed skills that would have been difficult to build otherwise. Experience in a high-ranking role increases the probability of high-skill work after the war by about 36 percentage points. This evidence suggests that military service may have been valuable to Black Americans outside of the implications of the war's outcome despite few formal benefits.</p
Suburban Planning Politics: How Urban Design and Local Governance Can Build a Healthy Future in the Denver Metro Suburbs
Get PDFThis dissertation investigates the politics of health in relation to the built environment and the suburban development processes in the Denver Metropolitan Area (DMA). Focusing on suburban communities such as Arvada, Broomfield, and Centennial, this study explores how urban planning processes reflect individual, group, and community values around public health, sustainability, and growth. By examining these understudied suburban areas, the research offers a new perspective on how smaller urban environments shape public health outcomes through planning and development practices. This study bridges the gap between bureaucratic planning procedures and the long-term public health effects that emerge from these processes. It identifies how urban planning decisions influence the social experience of place and residents’ well-being, often in ways not directly addressed by policymakers. Through a mixed-methods urban ethnographic approach, the research incorporates interviews with local leaders, visual sociological methods, content analysis of primary documents such as comprehensive plans, and thematic review of public hearings on local development projects. This approach captures the complexities of suburban development politics and its relationship to public health. The research highlights several key findings. First, city comprehensive plans in the DMA demonstrate limited integration of public health considerations, with plans often over-emphasizing car-centric designs while promoting integrated land-use strategies that encourage walkability, bikeability, and public transit use. Second, the results reveal a tension between the region’s goal of environmental stewardship and local development, which suburban cities attempt to balance while managing fiscal sustainability concerns. Additionally, the current planning practices have significant procedural issues with entrenched social inequalities that ultimately continue a status quo of restricting flexibility in land-use, reinforcing historical patterns of unequal access to urban resources such as parks, healthy food stores, and affordable housing and transportation. Planning commissions, composed of residents with varying levels of expertise, play a pivotal role in mediating between developers, professional planners, policymakers, and community members. However, they often face limitations stemming from outdated zoning or building codes and procedural constraints, which hinder their ability to significantly influence healthier development patterns. The dissertation identifies the need for improved public engagement strategies, including more deliberative planning commission hearings and simplified evaluation criteria for proposed developments. To promote healthier suburban environments in the DMA, this research points towards several different research and policy directions. Prioritizing environmental stewardship to slow unsustainable growth, refining comprehensive plans and zoning laws to enable mixed-use development, and expanding the sociological lens beyond major urban areas are a few key steps. Additionally, fostering citizen-driven, localized planning with clear evaluation metrics can strengthen public participation and ensure that diverse community needs are being addressed. This dissertation contributes to the urban sociology scholarship by showcasing the political and social dynamics that shape suburban development. By focusing on smaller cities, it challenges traditional urban sociological theories that have primarily studied major metropolitan areas and urban cores, offering practical insights for fostering healthier, more equitable suburban communities.</p
The Power of People, Places, and Pedagogical Practices
Get PDFThis dissertation investigated multiple aspects of power of place course-based undergraduate research experiences (PoP-CUREs) at a diverse range of institutes of higher education. This research explored aspects of self-efficacy, science identity, and predictors of science civic engagement in students and personas of instructors.
Chapter 1 investigates the student experience in an online bee DNA barcoding CURE taught at Pima Community College (PCC). This chapter qualitatively explores student research self-efficacy and science identity through participation in Bee the CURE. This work demonstrated that undergraduate community college students were able to make gains in research self-efficacy and science identity during a remote instruction research experience.
Chapter 2 extended the work from the first chapter with the course shift to a hybrid model where lecture was conducted online, and the laboratory was in-person. Students at PCC continued with Bee the CURE. Using a mixed-method approach, student research self-efficacy and science identity increased in both semesters of this study. Predictors of science civic engagement found increases in civic knowledge and action in both semesters.
Chapter 3 builds upon prior research by Zagallo and colleagues (2019) in developing instructor personas for participants in professional learning. This study found three of the four personas in this professional learning community of practice that were present in the original study. An additional two personas were identified and described in this work.
This dissertation adds evidence to the benefits for students from participation in place-based and community-engaged CUREs, and how students develop research self-efficacy, science identity, and science civic engagement. Further, understanding the identities, expectations, teaching philosophies, and institutional contexts of instructors who are interested in implementing CUREs will help professional learning designers create training that will lead to greater adoption of evidence-based practices.</p
LGBTQ+SEA: Identity, Family, and Community Among First and Second Generation Queer And Trans Southeast Asians
Get PDFDespite the long and varied histories of gender and sexual diversity among Southeast Asian populations both pre- and post-colonization, sociological research on the experiences of immigrant populations from this region in Western societies is scarce. Immigration scholars have examined gendered norms and expectations for immigrant populations in the United States, but rarely do they consider gender and sexuality-based differences beyond a cis-heteronormative lens. In an effort to address this gap, the following study utilizes Telles and Sue’s concepts of the ethnic core and ethnicity continuum to explore the processes of self-identification, familial experiences, and engagement with community resources among first and second-generation queer and trans Southeast Asians. The findings of this study contribute to a more nuanced understanding of how the intersections of race, ethnicity, gender, and sexuality create unique challenges and opportunities for this population.</p
German Newspaper Coverage of Climate Change or Global Warming, 2004-2025 - November 2025
No full textThe Media and Climate Change Observatory Data monitors 131 sources (across newspapers, radio and TV) in 59 countries in seven different regions around the world. Data is assembled by accessing archives through the Lexis Nexis, Proquest and Factiva databases via the University of Colorado libraries. More information may be found at: http://mecco.colorado.edu.</p
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