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Transition metal probes for ¹⁹F MRI-based biosensing
Get PDFMagnetic Resonance Imaging (MRI) is currently the most widely used imaging modality to diagnose biological pathologies. Traditional MRI tracks proton (¹H) nuclei in the body; however, given the high concentration of water in living species, images obtained contain significant background signal, hindering early diagnosis. To combat this, fluorine (¹⁹F) MRI can be used as there is no detectable fluorine in the body and the fluorine nucleus is similar to hydrogen: 100% isotopic abundance, 83% signal receptivity, and a nuclear spin of ½. Therefore, any signal from a ¹⁹F MRI will come from exogenous agents. Moreover, MRI probes can exploit transition metals to alter their relaxation times via paramagnetic relaxation enhancement (PRE) or change their chemical shift signal via pseudocontact shifts (PCS). Chapters 2-4 and Chapter 5 discuss how copper and iron, respectively, can be used to detect hypoxic/reducing regions while Chapter 6 shows how cobalt is able to detect various biological pH environments. Cellular hypoxia is oxygen deficiency caused by insufficient vasculature preventing blood flow to tumoral growths. Previous work demonstrated that fluorinating a well-known positron emission tomography (PET) imaging agent, CuATSM, would allow for “turn-on” signaling in hypoxic cancerous environments without using ionizing radiation. Second generation probes improved upon this work by adding fluorescence as a secondary modality (CuATSMF₃-Fl, Chapter 2), by increasing the fluorine concentration and introducing the agent as a nanoemulsion (CuL₁, Chapter 3), and by increasing the number of water solubilizing groups to allow for increased biocompatibility to overcome complications faced with nanoemulsions (CuATSMF₁₈, Chapter 4). Further, an iron-based probe was synthesized to allow for reversible detection of reducing environments (FeDO3ASF₅, Chapter 5). Favorable results obtained demonstrate the potential for in vivo feasibility of these probes. Sustaining physiological pH is vital for development, health, and survival. Mammalian blood contains a buffer to maintain a pH of 7.4. Chapter 6 discusses a cobalt-based imaging agent, CoNO2ASF₅, that provides a signal at different chemical shifts based on the surrounding pH. Overall, transition metal-based fluorinated imaging agents can provide a favorable MR signal selective to the biological analyte or environment imaged.Chemistr
Effect of sub-seismic reservoir heterogeneity on CO₂ plume migration : onshore Gulf of Mexico (Texas, USA)
Get PDFThis study examines the impact of sub-seismic faults and channels on CO₂ plume behavior in the Lower Miocene formation in an onshore area of the Texas Gulf of Mexico. This geological formation is characterized by heterogeneous reservoirs with an important amount of unconsolidated fluvial sandstones, where sub-seismic faults and channels are challenging to identify using conventional seismic methods. The research focuses on potential unintended lateral migration of CO₂ and changes to the area of review (AoR) size beyond the leasing area in carbon capture and storage (CCS) projects.
A methodology was developed to characterize sub-seismic faults and channels by integrating seismic data, literature correlations, and well log analysis. Fault seal capacity was estimated using a combination of shale gouge ratio (SGR) and transmissibility multiplier approaches, yielding fault transmissibility values higher than 0.1 as a realistic value for sub-seismic faults. Additionally, a workflow for generating capillary pressure and relative permeability curves was established, integrating literature data and well-known correlations. This workflow enables reservoir engineers to include these curves in the simulation even in data-scarce regions.
Experimental static models were built using available geological information, including 2D/3D seismic amplitude extractions, well log correlations, and core data integration. These were followed by dynamic simulations incorporating these sub-seismic features in synthetic, single-unit, and full-field models. Sensitivity analyses on geological uncertainties and sub-seismic fault characteristics revealed that sub-seismic faults with transmissibility values higher than 0.1 have minimal impact on the AoR size and shape. CO₂ migration was confined to high-permeability injection zones, while pressure dissipation occurred throughout the model, with low-permeability zones acting as pressure buffers.
The full-field models validated these findings under realistic operational constraints, demonstrating that sub-seismic features do not significantly influence unintended CO₂ migration or pressure buildup in most scenarios. Additionally, low-permeability zones were found to act as barriers to CO₂ flow and as pressure dissipation reservoir units, reducing AoR size and shape.
These findings suggest that operators should prioritize seismic-scale feature characterization and consider heterogeneous geological settings without the need of regional seals for CO₂ injection. Proper boundary definitions are critical for optimizing AoR size, minimizing costs, and enabling CCS projects in areas previously considered as unsuitable. - This study highlights the potential of composite confinement systems concept in enabling effective CO₂ storage in complex geological environments.Energy and Earth Resource
Ketosynthase gatekeeping yields insights into polyketide synthase engineering
Get PDFModular polyketide synthases (PKSs) are assembly line-like enzymes that produce medicinally relevant products such as the antibiotic erythromycin. Their modular nature makes them enticing engineering targets, though historically, engineered synthases have little to no activity. A recently updated module boundary implemented in small engineered synthases has shown over an order of magnitude more production than its traditional counterpart. To better test this new module definition, a BioBricks style approach was used to systematically test module combinations from the pikromycin synthase, which has a variety of different module types that result in each module having its own unique chemistry. 5 triketide synthases, 25 tetraketide synthases, and 125 pentaketide synthases using every possible module combination were constructed and their activities tested. Testing these synthases revealed that, while the updated modular boundary is superior to the traditional, there are still some hindrances to engineering synthases. However, there were clear trends in certain module combinations that either always worked in succession, or never worked in a particular order, likely due to gatekeeping functions of the ketosynthase (KS) domain. The gatekeeping activity of the KS was tested by mutating a conserved VMYH motif of a double bond accepting KS. Altering this motif changed the ratios of the products formed. This demonstrates that the KS acts as a gatekeeper, particularly for the substituents at the α- and β-carbons, and the module incompatibilities are likely due to gatekeeping properties at the γ- and δ-carbons of the intermediate. Strategies such as using promiscuous KSs, native bi-modules, and mutagenesis can be used to evade incompatibilities in PKS engineering due to KS gatekeeping. Another important interaction was investigated in an engineered synthase: the acyl carrier (ACP) and ketoreductase (KR) interface, which is important for setting the majority of stereocenters in a polyketide. Alanine scanning demonstrates that the interface between the two domains does not have strong interactions, indicating that the phosphopantetheinyl arm and polyketide intermediate may contribute to the interaction. By rationally engineering synthases with KS these interactions in mind, the full availability of chemistries accessible in PKSs can be used in engineered synthases, leading to new medicines.Biochemistr
Halogens in the sub-continental lithospheric mantle beneath the southwestern United States
Get PDFHalogens (F, Cl, Br, and I) are enriched in Earth’s surface reservoirs relative to the mantle, but subduction of altered lithosphere conveys halogens into the mantle and can result in variable enrichment of the mantle. The sub-continental lithospheric mantle (SCLM) has been suggested to be variably enriched in halogens through interaction with subduction-derived materials, but the quantity, distribution, and source of halogens in the mantle are uncertain. To address this uncertainty, this study examines halogen concentrations and stable isotope ratios of variably metasomatized lithospheric mantle peridotite xenoliths from the Colorado Plateau and Rio Grande Rift in the southwestern United States. This study finds that the SCLM beneath the southwestern United States has been variably enriched in Cl, Br, and I from a hydrous fluid but only minorly enriched in F. The source of this fluid is Cl-rich and F-depleted, and it has a high Cl isotope ratio relative to the depleted mantle, suggesting dehydrating altered oceanic crust or sub-crustal serpentinite in the subducted Farallon plate as the source of the fluid. This indicates that hydrated lower altered oceanic crust can convey volatile elements far from the trench resulting in volatile enrichment in both the SCLM and lower mantle. This study also finds that hydrous minerals largely control the F and Cl budget when they are present. In the anhydrous SCLM, F partitions variably between nominally anhydrous minerals (NAMs). In fertile peridotites, pyroxenes contain the majority of F, whereas olivine contains the majority of F in refractory peridotites due to compositional dependent F partitioning. This change in partitioning results in an increase in the bulk incompatibility of F in refractory peridotites, becoming more similar to Nb or Ba than to Nd to which it is often compared in the depleted mantle. Additionally, Cl is dominantly hosted along grain boundaries in recently metasomatized SCLM. The grain boundary host of Cl makes it more easily mobilized during melting or melt percolation, potentially leading to high Cl contents in low-degree melts derived from the SCLM.Earth and Planetary Science
Sub-50nm roll-to-roll nanoimprint lithography for manufacturing high-index inorganic nanophotonics
Get PDFPhotonic devices such as diffractive optics and metasurfaces are increasingly being utilized in extended reality (XR) displays and flat optics. High refractive index materials are the ideal choice in which nanostructures need to be fabricated for these applications. In addition, the desired patterns comprise of complex geometries such as slanted or multitiered nanostructures and variable pitch nanostructures with minimum feature size that is on the order of 1/10th or less of the operational wavelengths with aspect ratios approaching 10:1. Many of the current XR products in the market utilize direct nanoimprint of polymers with refractive index (RI) of 1.5-1.7 in the visible spectrum. Extending to higher RI beyond this using imprintable polymers has faced scalability challenges due to limitations in polymer material properties as well as inconsistent optical performance due to material variability, particularly over the lifetime of the device. Inorganic high-index materials can lead to best-in-class performance and reliability in these devices. However, etching of these nanoscale features in high-index substrates is difficult due to the inability to create volatile reactants during reactive ion etching requiring the use of ion milling which is known to be defect-prone. In addition, uniformity of etched geometries in nanoscale features with high aspect ratios and 3-dimensional geometries is critical as variations can significantly diminish the optical properties of these devices. In this dissertation, a scalable fabrication method for high-index inorganic waveguides and metasurfaces is explored that circumvents the need for etching nanoscale features in high-index materials. The key elements of this dissertation that contribute to the above capability are as follows: • Precision machine design for achieving continuous R2R nanoimprint for sub-50 nm high-throughput nano-manufacturing with sub-25 nm residual layer thickness • Plate-to-Roll (P2R) nanoimprint that enables the creation of a roll-based working template that is used in the above R2R nanoimprint equipment to allow long template life in volume manufacturing • Enhanced precision in nanofluidic-based processes such as nanoimprint lithography by incorporating spatiotemporal thermal actuation that could potentially address systematic nanoimprint defects during high speed patterning • A process that uses a switchable adhesive layer that can create detachable nanostructures with a deposited high-index material followed by precision layer transfer to enable the desired optical componentsMechanical Engineerin
Environmental and noise signals in terrestrial gravimetry
Get PDFObservations of time-variable gravity from terrestrial gravimeters have many applications, ranging from studies of Earth tides and volcanoes to modern redefinitions of the kilogram. Via three studies, this dissertation contributes to two areas of terrestrial gravimetry: study of environmental processes using terrestrial gravimeter observations, and mitigation of non-gravitational (noise) sources that contaminate terrestrial gravimeter observations. In the first study, we characterize environmental gravity variations at McDonald Observatory, in West Texas, using 3.5 years of superconducting gravimeter observations. Our objectives are: 1) to develop and assess gravity models of tides, atmospheric loading, and terrestrial hydrology for the site using SG observations; and 2) to enable more precise environmental correction of gravity and other geodetic observations at the site. From superconducting gravimeter observations, we generate an empirical tide model in the diurnal and semi-diurnal band. The empirical tide model differs by up to 2 µGal (1 µGal = 10⁻⁸ m/s²) from conventional tide models, suggesting mismodeling of regional air loads or ocean tides in conventional models, and/or instrument calibration error. Atmospheric loading and attraction is optimally modeled by a local barometric admittance of -0.25 µGal/mbar, or 16% below the conventional estimate, likely due to high site elevation. Predicted hydrologic loading and attraction generated from land and atmosphere reanalyses MERRA-2 and ERA5-Land aligns temporally with observed gravity change and local rain gauge data. Differences in magnitude between hydrologic predictions and observed gravity change might be explained by unmodeled local water loads, at spatial scales below model resolution. We suggest future work on modeling and studying local-scale hydrology using gravity and in-situ hydrologic datasets. The second and third studies are targeted investigations of noise sources that affect the most common absolute gravimeter, called the FG5. Observations from this gravimeter are used widely in many defense and science contexts. We contribute to ongoing efforts to eliminate bias and reduce scatter of its gravity estimates. In the second study, we profile newly-discovered FG5 noise, dubbed a spatial wave, that is thought to originate from uneven rotation of a pulley within the instrument. This noise might systematically bias gravity estimates by up to 1 µGal. We introduce methods to fully characterize and correct this error source. We demonstrate these methods on FG5 data from a Texas coastal site, and find that the spatial wave imparts a very small bias (0.1 µGal) on the final gravity estimate. We also discover two new spatial waves at higher frequencies. We determine by simulation that these new waves negligibly bias gravity estimates. FG5 operators can use our methods to determine if spatial waves are present in their datasets, to correct observations for a wave, and to assess correction effectiveness. In the third study, we quantify the effect of vibrations on bias and scatter of FG5 gravity estimates. Microseismic vibrations are known noise source affecting FG5 gravity estimates, however sensitivity of gravity estimates to vibrations has not been rigorously quantified for the FG5, as it has been for other gravimeters. Via a case study at a Texas coastal site, we show that a seismometer is a useful tool for studying and mitigating vibration contamination of FG5 gravity estimates. From seismic data, we identify environmental vibrational sources (wind, ocean, and human) and instrument-generated vibrations. We quantify sensitivity of gravity estimate scatter to vibrations in different frequency bands. From this we infer that FG5 gravity estimates are most sensitive to seismic vibrations in the 0.1-10 Hz band. We also develop methods for correcting gravity estimates for vibrations using seismic data. One of these methods is highly successful; it reduces gravity estimate scatter at our site by 34% and changes the mean gravity estimate by -0.6 µGal. Using the methods described, FG5 operators might deploy a seismometer to guide site selection and to predict and minimize the effects of vibrational noise.Earth and Planetary Science
Measuring and enhancing resilience of an increasingly multi-agent power grid
Get PDFRecently, resilience has gained momentum as a desired power grid characteristic among researchers, utilities, regulators, and the public. However, historically, reliability has been the focus of the electric sector, with long-established metrics and accepted reliability standards and guidelines. While reliability focuses on system hardening and preventing a disruption in the first place, resilience focuses on recovery and adaptation from disruption, internalizing the fact that the power grid cannot possibly be hardened against all hazards and that the consequence of the disruption needs to be evaluated.
Despite the interest in and need for a resilient power grid, quantifying power grid resilience continues to present challenges, with no agreed upon metric(s) in place. In order to understand the consequence of disruptions and appropriately measure and enhance resilience, the dissertation begins by identifying the critical functions of the power grid before developing the resilience quantification dimensions that are grounded in decision and network science. These dimensions are used in a literature review of current practices and then in our simulations focused on various metrics, disruption types, resilience strategies, and tradeoffs. The simulations are then extended to discuss resource-aware implementation strategies.
Specifically, Chapter One begins by first addressing the importance of the power grid, or its “critical function," and the services that the power grid provides. It then expands on the motivation to study the power grid in the context of the evolving energy landscape and the necessity of resilience in meeting these critical functions during and after disruptions. A detailed comparison of resilience and reliability is also given. After this introduction and motivation for researching power grid resilience, the research questions, scope of the dissertation, and dissertation chapter outlines are presented.
Chapter 2 provides in-depth definitions of concepts necessary to understanding, evaluating, and imparting resilience into the power grid. It begins with a high-level definition of power grid resilience to provide context and then goes into detailed discussions on the increasingly multi-agent nature of the power grid and implications for decision-making and optimization. Given this additional context from multiple fields of research and practice, the three resilience quantification dimensions are developed and introduced: time, critical function, and decision-making hierarchy. The first tracks the temporal progress of the disruption, while the second the system's operational progression through the disruption (i.e., ability to meet or deviation from meeting its critical function). The third supports optimization by embracing the decentralizing nature of decision-making in power grid dispatch and operation. The chapter concludes with a literature review on the current state of how these resilience quantification dimensions are used and implications/recommendations
Chapter 3 seeks to gain insights on resilience by using established metrics along with sensitivity analyses and post-processing. Using established metrics and existing models can help planners and dispatchers to make resilience-informed decisions despite a lack of formal resilience models. Leveraging the metric, “total market surplus”, developed by the Department of Energy (DOE) for the Grid Optimization (GO) challenge, is one approach. Although this metric has been traditionally used to signal efficiency and reliability, stress testing certain resilience strategies against it can support an understanding of how to adapt existing modeling efforts for resilience assessments and optimization. Further post-processing the dispatch results enables additional resilience insights. The simulations address emerging operating issues stemming from an increasingly multi-agent power grid, and highlight considerations for the critical function and temporal dimensions while maintaining a centralized optimization scheme for the decision-making hierarchy. Results indicate that flexible resources, especially in congested transmission networks support both efficiency/reliability and resilience.
Chapter 4 builds on the results that flexible resources may support multiple system objectives including resilience and reliability/efficiency by evaluating different disruption types against a resilience metric and appropriate optimization scheme. In this chapter, a multi-time-step framework and DC Optimal Power Flow (DCOPF) is applied to the IEEE 30-node network that is infused with flexible resources, to measure unserved load (MW) under transmission line derating scenarios, capturing increasingly common climatological events such as impacts of extreme heat on power flow. The three resilience quantification dimensions are addressed via measuring unserved load over the duration of the disruption using different time-steps, and a centralized optimization scheme. Results demonstrate the effectiveness of multi-time-step flexible resource management in enhancing system resilience and the impact of decision time windows.
The last chapter discusses how the three power grid resilience quantification dimensions facilitate the flexibility required to track and optimize such a complex network while also providing necessary frameworks for how to measure and enhance resilience in the context of other system objectives and requirements. Chapter five explicitly shows how the simulations in chapters 3 and 4 leverage the three resilience quantification dimensions and evaluate the usefulness of each. The resilience strategies along with the studied tradeoffs are also detailed and evaluated. At a high level, the simulations show that network flexibility is key to resilience, but that specific strategies need to be evaluated with objective-specific resilience metrics against realistic disruption types and other system objectives. Gaps and future work are also discussed, in addition to potential implementation decision-making support such as continued evaluation of system tradeoffs and the use of resilience-by-design and resilience-by-intervention concepts.
The objective of this dissertation is to provide a flexible framework for improving the resilience of an increasingly multi-agent and multi-service power grid. Simulations using various metrics, strategies, disruption-types, and analysis methods provide some additional resilience insights into the modernizing power grid and acknowledge the fact that there may be additional operating priorities. This will help to fill the gap in broadly accepted resilience metrics and optimization strategies for the bulk power system.Civil, Architectural, and Environmental Engineerin
Psycho-somatic coping mechanisms for race related stress among Black individuals
Get PDFPsycho-somatic practices, such as yoga, meditation, massage, herbalism, tai chi, qi gong, acupuncture, and chiropractic care have the potential to be useful coping strategies for Black individuals facing race-related stress. Racial discrimination has been historically linked to negative mental and physical health outcomes among the Black community. Although limited, there is a growing body of research to support psycho somatic coping mechanisms as particularly effective for mitigating the negative outcomes of race related stress. The purpose of this study is to explore the role of psycho-somatic coping mechanisms in buffering negative health outcomes from race-related stress and better understand attitudes about holistic wellness for Black individuals. Using a mixed methods analysis, I will assess the relationship between psycho-somatic practices and mental and physical health outcomes for Black individuals.Educational Psycholog