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Quantifying Erosion Rates of the Mission Hills Along the Calaveras, Mission, and Hayward Faults in Northern California to Better Understand the Role of Fault Geometry on Surface Topography
Get PDFThe San Francisco Bay Area lacks publications on erosion rates and their relationship to restraining bend fault geometry. This thesis presents a detailed geochronologic study of erosion rates from the Mission Hills along the Calaveras, Mission, and Hayward faults located northeast of San Jose, California. The goals are to provide erosion rate values where none currently exist and to gain a better understanding of how fault geometry influences topography along restraining bends. To quantify the erosion rate of these faults, river sediments containing 10Be were collected from 14 catchments using well-established protocols. Of the successfully processed samples, the erosion rates fell within the predicted trends with minimal exceptions. The values of calculated erosion rates range from 0.047 ± 0.005 mm/yr to 0.161 ± 0.019 mm/yr. Watersheds near the Mission fault stepover zone have higher erosion rates. Generally speaking, these watersheds exhibit high local relief and steep channel slopes. Lower erosion rates are primarily found away from the restraining step-over zone and are in watersheds that contain lower values of local relief and channel steepness. Channel steepness appears to be the most significant topographic metric associated with erosion rates and local faulting, as this project determined that the landscape formed by tectonics exerts greater control over its formation than lithology
Modeling Lensed Quasars with Neural Posterior Estimation: Complex Mass Models
Get PDFThe Vera C. Rubin Observatory is expected to discover ∼ 103 galaxy-scale strongly lensed AGN systems during its 10 year operation conducting the Legacy Survey of Space and Time (LSST). I use a machine learning neural posterior estimation method to automatically model these systems with the intention of using them for time-delay cosmography, to constrain the Hubble constant and, ultimately, the properties of Dark Energy. In the work shown here, the neural network that I utilize is trained on simulated lens systems with simple mass distributions that consist of a single main deflecting galaxy. I am testing the robustness of the posterior inferences of the lens system parameters made by the neural network when adding sub-galactic structure to the main deflector in the form of dark subhalos and a single luminous pertrubing mass. To test these predictions I simulate test sets of 100 mock Hubble Space Telescope (HST) quality lenses and add complex mass to the plane of the main deflector in the form of either a single luminous perturbing mass or a realistic population of dark subhalos. The presence of the luminous perturber introduces a bias in the Fermat potential of ∼ 6%, indicating a similar bias in H0, while reducing the precision of the model by a factor of 1.25. This indicates the need to train our network with a more complex, realistic mass model that includes small-scale mass structures
California Utility-scale Solar Energy Land Use Impacts on Species and Ecosystems
Get PDFUtility-scale solar energy (USSE), defined as projects of at least 1 megawatt, is rapidly expanding in California, which generated 37.5% of its electricity from renewables in 2023, with 24% coming from solar. While USSE supports decarbonization, it can also cause environmental harm, including biodiversity loss, habitat fragmentation, and land conversion. This study uses ArcGIS Pro 3.4.0 and public environmental data to analyze the spatial distribution of USSE projects, land use changes from 2013 to 2023, and occurrences of at-risk species across California’s bioregions. USSE development is heavily concentrated in the Mojave Desert, San Joaquin Valley, and Colorado Desert, which are regions with both high solar potential and ecological sensitivity. Between 2013 and 2023, shrublands declined by approximately 15,451 acres, agricultural land by approximately 11,692 acres, and grassland/pasture by approximately 8,238 acres. Across USSE sites, 107 occurrences of at-risk species were documented, including federally and state-listed species. Only observed occurrences were counted, although modeling suggests additional species may be present. The findings highlight the ecological impacts of solar expansion and emphasize the need for improved siting strategies that balance renewable energy goals with biodiversity conservation
Finding floral and faunal species richness optima among active fire regimes
Get PDFChanging fire regimes have important implications for biodiversity and challenge traditional conservation approaches that rely on historical conditions as proxies for ecological integrity. This historical-centric approach becomes increasingly tenuous under climate change, necessitating direct tests of environmental impacts on biodiversity. At the same time, widespread departures from historical fire regimes have limited the ability to sample diverse fire histories. We examined 2 areas in California\u27s Sierra Nevada (USA) with active fire regimes to study the responses of bird, plant, and bat communities to a broad spectrum of temporal, spatial, and severity patterns of fire. Bird and plant species richness peaked in the first decade following fire. Species richness was highest with moderate burn severity for birds and with low burn severity for plants. Bat richness increased with longer mean fire-return intervals and was greatest in landscapes that included predominantly unburned areas or moderate to high burn severity patches. All taxa responded positively to pyrodiversity, with effect sizes varying with the metric used to assess variation in fire patterns. Our results suggest that restoring historical fire regimes would benefit biodiversity relative to most contemporary dry forests in California, but that total species richness would be highest under somewhat more frequent and varied severity fires than historical targets would indicate. Given the variable optima among taxa, managing for a range of complementary conditions that create local and landscape heterogeneity would best accommodate diverse flora and fauna and other forest conservation objectives
Sill Stacking in Subseafloor Unconsolidated Sediments and Control on Sustained Hydrothermal Systems: Evidence From IODP Drilling in the Guaymas Basin, Gulf of California
Get PDFMagma emplacement in the top unconsolidated sediments of rift basins is poorly understood. We compare two shallow sills from the Guaymas Basin (Gulf of California) using core data and analyses from IODP Expedition 385, and high-resolution 2D seismic data. We show that magma stalling in the top uncemented sediment layer is controlled by the transition from siliceous claystone to uncemented silica-rich sediment, favoring flat sill formation. Space is created through a combination of viscous indentation, magma-sediment mingling and fluidization processes. We show that sills emplace above the opal-A/CT diagenetic barrier. Our model suggests that in low magma input regions sills emplace at constant depth from the seafloor, while high magma input leads to upward stacking of sills, culminating in a funnel-shaped intrusions. Our petrophysical, petrographic, and textural analyses show that magma-sediment mingling creates significant porosity (up to 20%) through thermal cracking of the assimilated sediment. Stable isotope data suggest carbonate formation at 70–90°C, consistent with background geothermal gradient at 250–325 m depth. The unconsolidated, water-rich host sediments produce little thermogenic gas through contact metamorphism, but deep diagenetically formed gas bypasses the low-permeability top sediments via hydrothermal fluids flowing through the magma plumbing system. This hydrothermal system provides a steady supply of hydrocarbons at temperatures amendable for microbial life, serving as an incubator that may be abundant in magma-rich young rift basins and play a key role in sustaining subseafloor ecosystems
The association between cardiac vagal activity and urinary catecholamine: Investigating the effect of race and sex
Get PDFBlack individuals are at greater risk for the development of cardiovascular diseases compared to White individuals. Autonomic nervous system (ANS) dysregulation has been identified as a significant risk factor contributing to racial disparities in cardiovascular disease, yet systematic racial differences that affect the measurement of ANS activity among White and Black participants are likely obscuring understanding about ANS-health disparity links. Moreover, sex differences in ANS activity have been observed. Thus, efforts to elucidate the comparability of ANS indices across race and sex are needed. This study aimed to investigate the effects of race and sex on the associations between two indices of ANS activity—cardiac vagal activity and urinary catecholamines—in a sample of White and Black participants from the MIDUS 2: Biomarker Project (N = 967 adults aged 34 – 84; 81 % White, 57 % female). Participants self-reported their sociodemographic and health information and completed biomarker assessments. Cardiac vagal activity was assessed via heart rate (HR) and heart rate variability (HRV); urinary catecholamines were assessed via epinephrine and norepinephrine. Black participants displayed higher HRV activity and lower levels of urinary catecholamines relative to White participants. Moreover, our results revealed small but significant correlations between urinary catecholamines and cardiac vagal activity across both races, though the nature of these relations varied across race, sex, and ANS index. The correlations between HR and epinephrine and norepinephrine were stronger among Black male participants compared to White male participants. Our results highlight the importance of clarifying the functional equivalence of different ANS indices across race and sex
Cross-species real-time detection of trends in pupil size fluctuation
Get PDFPupillometry is a popular method because pupil size is easily measured and sensitive to central neural activity linked to behavior, cognition, emotion, and perception. Currently, there is no method for online monitoring phases of pupil size fluctuation. We introduce rtPupilPhase—an open-source software that automatically detects trends in pupil size in real time. This tool enables novel applications of real-time pupillometry for achieving numerous research and translational goals. We validated the performance of rtPupilPhase on human, rodent, and monkey pupil data, and we propose future implementations of real-time pupillometry
Reinforcement Learning Methods for Assistive and Rehabilitation Robotic Systems: A Survey
Get PDFAdvancements in robotic systems aimed at improving mobility for individuals with disabilities have required more sophisticated control and navigation methods. Traditional control approaches often lack the complexity and adaptability needed for the high-dimensional nature of human activities. Consequently, reinforcement learning (RL) has emerged as a dynamic and effective framework for managing robotic actions in complex and unpredictable human environments. This article reviews the integration of RL in robotic systems for enhancing the mobility of individuals with disabilities, addressing the limitations of traditional control methods in complex and unpredictable environments. We critically analyze various RL algorithms, discussing their advantages and challenges in assistive and rehabilitation applications. The study highlights the ongoing development of these algorithms, presenting current research directions, future prospects, and key challenges to achieving higher autonomy in assistive robots. Our findings underscore the potential of RL to improve adaptability and effectiveness in robotic control and navigation, offering insights into advancing these technologies for practical implementations
Seasonal Variation and Response of Surf Zone Fish Assemblages to Environmental Variables in the Northeast Pacific
Get PDFLocated at the land-sea interface, the highly dynamic sandy beach and surf zone ecosystem is one of the coastal zones used most intensely by humans (e.g., recreation, fishing, tourism). Surf zones are also important as fish habitat; however, the factors structuring fish assemblages in the surf zone are relatively understudied due to challenges associated with sampling this dynamic environment. To investigate temporal influences on surf zone fish communities, we evaluated seasonal trends in the fish assemblage and associations with environmental conditions using baited remote underwater video stations (BRUVS) at four beaches on the Northeast Pacific coast (California, USA) from July 2020 to June 2021. Our study region is characterized by strong seasonality in productivity (due to spring upwelling) and the wave climate (in response to winter storms), making it an ideal location for evaluating seasonal change in surf zone fish. We found that surf zone fish assemblages exhibited marked seasonality and site-to-site variability. Two species of surfperch (Amphistichus argenteus and A. koelzi) and leopard sharks (Triakis semifasciata) were more common in the winter and spring, corresponding with surfperch spawning, while flatfishes were more abundant in the summer. Fish species composition was most affected by distance from shore (as a proxy for surf zone width), visibility, water temperature, percent cover of combined macroalgae and surfgrass, and breaker wave height, with significant effects detected for distance from shore and breaker height. Fish species that exhibited higher abundance in the winter, including A. argenteus, A. koelzi, and T. semifasciata, were associated with larger waves and wider surf zones. Our results highlight the influence of seasonal variation in environmental conditions on fish communities in the dynamic, coastal surf zone ecosystem, with potential management implications for several highly abundant species targeted by recreational fisheries
Protecting traditional cultural expressions: Law, Indigenous protocols, library practices
Get PDFThis study responds to contemporary international policy developments focused on protecting Indigenous creative work classified as Traditional Cultural Expressions. The study claims that states’ interests continue to guide policies in this area, compromising the relationship between regulations and the aspirations and needs of Indigenous communities. The study uses comparative methodology and content analysis to develop this argument. The study also highlights the significance of partnerships between Indigenous communities and cultural institutions that may function as alternative means to protect Indigenous creative works. The study explores cases from Indigenous communities and cultural institutions in New Zealand, the USA, and Mexico to develop this argument. The findings, while limited to the exploratory character of the study, may inform relevant library practices and support further research