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Electrodeposition of aluminum from phenoxide-based electrolytes
Get PDFModern nonaqueous aluminum electrolytes are pyrophoric, corrosive, and operate at high temperatures, limiting the development of aluminum electrochemistry and energy storage near ambient conditions. Herein we report 5 phenoxide-based electrolytes with similar Al₂(OR)₆ structures in the solid state which function at room temperature while lacking corrosive chlorides and pyrophoric metal-carbon bonds. The conductivities of five aluminum phenoxides were determined using impedance spectroscopy in ethereal solvents, the greatest of these being Al₂(OPhF₅)₆ (7.28 mS cm⁻¹) in 1,2-dimethoxyethane (DME). Al₂(OPhF₅)₆ was further investigated using ¹⁹F and ²⁷Al NMR and found to form at least 3 Al species in solution, for which the compounds: Al(OPhF₅)₃DME, [Al(OPhF₅)₂DME₄]⁺, and [Al(OPhF₅)₄]⁻ are proposed. The diffusivities of these complexes were determined using ¹⁹F DOSY NMR. These were used in conjunction with the Nernst-Einstein equation to determine dissociation fraction, which were found to fit well in all cases except those of higher concentrations. Al₂(OPhF₅)₆ was found using cyclic voltammetry to quasi-reversibly electrodeposit aluminum onto stainless steel electrodes, with a redox couple centered at −0.5 V vs Al/Al⁺³. Deposits were characterized by electron microscopy.Chemistr
Improving the gain, noise, and dark current performance of AlInAsSb digital alloy photodiodes grown by molecular beam epitaxy
Get PDFThis work interweaves fundamental molecular beam epitaxy considerations with
complex device design and growth of AlInAsSb digital alloy avalanche photodiode devices. These photodiode devices aim to serve as convenient, integrable, and highly-sensitive light sensors in the near- to mid-infrared spectral range. While approaching state of the art HgCdTe performance, further improvements in the dark currents and signal-to-noise ratio in AlInAsSb avalanche photodiodes could provide a (much sought after) III-V pathway to high-sensitivity infrared photodetection. In this report, we outline an extensive, multi-year study into the impacts that molecular beam epitaxy source material can have on the the AlInAsSb digital alloy materials platform. This fundamental work may seem historically fleshed-out an innocuous, but we find substantial unintentional doping impurities originate from aluminum source purity and preparation. In fact, we report first findings of unintentional
doping polarity inversion from source outgassing in a molecular beam epitaxy grown film. Other outgassing results like the group-V impacts on dark current are also reported. These effects have been found to play, unsurprisingly, a substantial role in the behavior of AlInAsSb digital alloy avalanche photodiode devices. Low unintentional doping aids greatly in device operation owing to electric field uniformity in the intrinsic regions of the material. Additionally, device design that was previously handcuffed by relatively high and varying unintentional doping was afterwards enabled. Here we also report these device improvements; they come in the form of a new, clever device architecture which
accesses the benefits of two distinct multiplication regions, and also improve “conventional” devices that take advantage of the strong electrostatic control granted by low and stable unintentional doping. This work highlights that minor improvements to the material growth and preparation can yield outsized benefits for the devices we make from them, and lays out pathways to further improvements in the years to come.Electrical and Computer Engineerin
Effective finite element discretization schemes for simulating coupled multiphysics in porous media
Get PDFThis dissertation presents a cutting-edge finite-element framework for simulating coupled multiphysics processes in porous media energy applications, including geothermal energy, hydraulic fracturing, frac-hits, CO₂ sequestration, black-oil and compositional reservoir simulation, and nuclear waste disposal. The framework employs Enriched Galerkin (EG) and phase-field finite-element methods to model the interaction of fluid flow, thermal energy, chemical transport, and geomechanical processes within the subsurface porous media.
Key contributions include adapting a diffusive formulation for flow and energy transport and leveraging a phase-field variable to integrate petrophysical properties across the fracture-matrix continuum. This eliminates artificial source terms at interfaces, enabling smoother, more accurate mass and energy transfer. The EG scheme, a computationally efficient variant of Discontinuous Galerkin (DG), captures sharp pressure, temperature, and compositional discontinuities while conserving local mass and energy. At the field scale, phase-field modeling simulates fracture mechanics without complex remeshing of the modeling grid, capturing fracture initiation, propagation, and interaction under varying stress conditions. This continuum-based approach enhances both the robustness and efficiency of geomechanical simulations. The phase-field framework is also extended to multiphase, multicomponent systems, modeling phase transitions and interfacial dynamics using the Allen-Cahn and Cahn-Hilliard equations. This eliminates reliance on empirical correlations and flash calculations, improving predictions for compositional and black-oil systems. The fixed-stress split technique enhances efficiency by decoupling mechanics from flow and energy equations, allowing specialized solvers and faster simulations than traditional monolithic approaches. Physics-based mesh adaptivity further optimizes simulations by refining mesh and discretization scheme independently for each physics domain. The MOOSE framework, used to develop the EG-phase-field framework, supports this decoupling by applying EG for flow, energy, and transport simulations and continuous Galerkin (CG) for mechanics, ensuring precise resolution of critical areas without uniform mesh constraints.
The framework is validated through analytical benchmarks, experimental modeling—including fracture profiling on 3D-printed Berea sandstone replicas, triaxial geothermal experiments, and mechanical frac-hit tests—and real-world applications, such as the FORGE geothermal initiative, Bakken frac-hit simulations, the FluidFlower experiment (SPE11 CO₂ sequestration case), and COUPLEX nuclear waste leakage scenarios. This research advances simulation capabilities by integrating advanced discretization techniques with enhanced computational efficiency, enabling more accurate and reliable modeling of porous media energy applications.Petroleum and Geosystems Engineerin
“It gave us all the opportunity to learn from each other” : the importance of peer interactions in the development of humanizing, critical, and responsive literacy teachers
Get PDFThis critical ethnography examines a diverse cohort of 12 literacy preservice teachers during their practice-based teacher preparation program. In the study, I drew on frameworks of dialogic learning (Vygotsky, 1978; Mercer, 2002) and culturally sustaining pedagogies (Alim & Paris, 2017) to understand how interactions with peers shaped preservice teachers’ critical and equity-oriented stances and practices. I provided a contextual overview of each field-based literacy course and my positioning as a researcher and teacher educator within each setting, respectively. I detailed how peer partnerships led to consistent findings across all field-based literacy courses and described unique findings with each course. Next, I highlighted three preservice teachers to illuminate how interactions and experiences with their peers in the cohort supported and shaped their identities and practices as teachers. The study’s findings supported previous studies in literacy teacher preparation that have shown that interactions with peers can support one another in learning to teach, the importance of recognizing and leveraging the expertise of Preservice Teachers of Color, the impact of intentionally designed practice-based experiences, and the importance of reflection in deepening perspectives and practices. Partnering with peers supported preservice teachers in applying their learning as they appreciated each other’s support and presence, built communal learning spaces with students, and navigated problems of practice together. Additionally, multiple opportunities to partner with peers positioned teachers agentically to expand their growing expertise alongside one another and benefited their development. The experiences of Christina, Rebecca, and Teal brought forward how the diverse identities, experiences, and perspectives of their peers in the cohort contributed to their development as culturally sustaining teachers. The implications for this study include considering how to continue disrupting the expert-novice divide in literacy teacher preparation, the need for learning opportunities that position preservice teachers as co-inquirers and collaborative professionals, and a call for teacher preparation programs to revisit and realign their core values to encourage more collective learning experiences where peers can support one another in learning to teach.Curriculum and Instructio
Surface chemistry of iron (oxy)hydroxides in engineered systems : microscopic investigation of the surface and surface complexation modeling of heavy metals adsorption
Get PDFIron hydroxide phases play a crucial role in controlling the fate and transport of metal ions in natural systems and are employed as coagulants to remove turbidity, natural organic matter, and trace metals. This comprehensive study aims to evaluate the differences in reactivity, structure, and morphology of iron hydroxides formed over varying time frames, ranging from amorphous solid phases developing within twenty to thirty minutes to more well-defined amorphous phases with some degree of crystallinity, and eventually to crystalline phases within a porous network. As a baseline crystalline phase, goethite is studied due to its well-established reactivity across various conditions and well-understood morphology, particularly with regard to crystal face distribution, which influences its reactivity and surface area for non-porous goethite phases. The first investigation explores whether Bayoxide (or E33), a goethite-based porous adsorbent, follows a similar reactivity trend. Previous research demonstrated its potential for arsenic and metal ion removal, but few studies have modeled its reactivity within complex systems containing multiple ions. The thermodynamics-based diffuse layer model (DLM) developed as a part of this chapter successfully accounts for variations in the point of zero charge (pHPZC) of E33 due to carbonate contamination and effectively models arsenate (As(V)) adsorption when competitive anions are present. In the second chapter, cation adsorption was studied in multi-solute systems, including cadmium, copper, lead and zinc. Modifications to the DLM database developed in 1990 were introduced, incorporating spectroscopic evidence and more realistic surface characteristics. These improvements enhanced the predictive metal ion modeling for Cd, Cu, Pb, and Zn. In the third chapter, the study delves into the precipitation of amorphous ferric hydroxide (FHO) nanoparticles over short time scales and in the presence of a range of anionic species, including Cl⁻, SO₄²⁻, NO₃⁻, and natural organic matter (NOM). The results showed the impact of different anions and NOM on FHO particle size and structure, providing a mechanistic understanding of primary particle and aggregate formation. The study emphasizes the significance of anion presence and co-precipitation of NOM in influencing FHO particle characteristics and coordination environments. Overall, these investigations significantly contribute to enhancing our understanding of the reactivity and morphology of iron hydroxides used in water treatment practices, as well as the complex interactions between adsorption and precipitation in dynamic water systems.Civil, Architectural, and Environmental Engineerin
Sweet spot maps for geologic hydrogen and helium in Texas (v4)
No full textThe impact of hydrogen and helium gas resources on the global economy is expected to grow substantially in the coming few decades. While helium has been extracted from the subsurface for several decades in association with natural gas fields, the idea of extracting hydrogen in its pure form from the subsurface (geologic hydrogen) is a relatively new concept that has generated considerable interest from the geoscience community in recent years.
The Bureau’s research aims to estimate the state’s geologic hydrogen and helium resources and to map prospective regions within Texas for both gases. As part of this effort, the BEG provides three distinct prospectivity maps that highlight regions favorable for hydrogen and helium resource potential. In the case of hydrogen, the research considers both natural and stimulated scenarios. The natural scenario is analogous to conventional oil and gas whereas the stimulated one involves engineered enhancement of certain subsurface hydrogen-generating reactions. In addition to regional-scale statewide prospectivity maps, the research focuses on a handful of specific areas within Texas where more detailed localized investigation can lead to sharper estimates of the resources.Bureau of Economic Geolog
Identification of brain-specific serine/threonine-protein kinase 1 as a protein kinase c epsilon substrate and its role in alcohol-related behaviors
Get PDFAlcohol use disorder (AUD) is a chronic relapsing condition and major public health issue with only three FDA approved treatment options. Protein kinase C epsilon (PKCε) signaling has been associated with various ethanol-related phenotypes including consumption, preference, sensitivity, and reward. PKCε signaling is also involved in increased anxiety like behavior which is known to contribute to increased alcohol consumption in humans. Pharmacological inhibition of PKCε signaling has been shown to reduce ethanol consumption, preference, and tolerance. These results have made PKCε signaling a target of interest for the development of treatments for AUD. However, little is known about the downstream targets of PKCε that contribute to its ethanol-related phenotypes. Identifying the signaling molecules downstream of PKCε that contribute to ethanol-related behaviors and responses may reveal additional targets for the development of AUD medications. To this end, we conducted a chemical genetic screen of PKCε substrates in the mouse brain and determined their association with ethanol and anxiety-related phenotypes (Chapter 1). Brain-specific serine/threonine-protein kinase 1 (BRSK1) is one of the downstream targets identified from this screen and is the main subject of investigation in this dissertation. I used in vitro kinase assays to further validate BRSK1 as a PKCε substrate and Brsk1 [superscript ⁻/⁻] mice to show that BRSK1 is related to both ethanol and anxiety-like behaviors in a sex-specific manner (Chapter 2). Finally, I examined how PKCε phosphorylation may regulate BRSK1 activation and kinase activity using phospho-mimic and phospho-null constructs of BRSK1 in combination with in vitro kinase activity assays (Chapter 3). I found that PKCε likely regulates BRSK1 activity via an inhibitory mechanism. Overall, this dissertation shows that BRSK1 is a downstream substrate of PKCε that is also involved in PKCε-dependent responses to ethanol and supports further investigation into the downstream targets of PKCε for their therapeutic potential in AUD and anxiety-related disorders.Neuroscienc
Cultivating the margins: market gardening in Classical and Hellenistic Greece
Get PDFThis dissertation examines market gardens in the Greek world from the 5th to 1st centuries BCE, investigating the socioeconomic and environmental dimensions of small-scale intensive cultivation. It asks what role gardens and the people who worked them played in local agricultural economies, to explore how different types of land were perceived, used, and valued. By focusing on garden-scale food production in and around cities, I am drawing attention to areas that have largely escaped the notice of scholars interested in ancient Greek economic life, arguing that their current neglect obscures a key component of food production and distribution as well as important cultural foodways through the inclusion of fresh fruits and vegetables in diet and cuisine. Specifically, I propose that market gardening provided a flexible economic outlet and a measure of self-sufficiency to urban residents in periods of food shortage driven by climate and conflict, focusing on Attica from the growth of Athenian democracy to the turbulent final centuries BCE. After an introduction reviewing the disparate literature on gardens and the ancient Greek economy, the dissertation will proceed in order of decreasing scale of analysis, from a food-systems approach across Attica to the examination of garden sites, ending with the paleoethnobotanical analysis of waterlogged plant remains preserved in Classical and Hellenistic wells in the Athenian harbor of Piraeus to illuminate the way these systems play out on the level of individual households.Classic
Network visualization and the labor of reference work : three case studies touching medieval and early modern book history
Get PDFNetwork analysis is a relatively new method in digital humanities, one which offers a new way of representing visually large quantities of data. Digital visualization can be thought of as a kind of reference work, and shares with reference work a pattern of being dismissed as a “mechanical,” and therefore less valuable, mode of scholarly production. This dissertation argues for the value of network visualization and reference works by applying network visualization techniques to the study of book history through three case studies: the early lending of manuscripts in the library of Sir Robert Cotton, the provenance of books in the Pforzheimer Collection at the Harry Ransom Center, and the co-transmission of Middle English verse texts as captured by the Digital Index of Middle English Verse.Englis
Priority and explanation in Aristotle's Metaphysics
Get PDFAristotle's work is marked by his interest in “priority,” of which he distinguishes several kinds. Central among them is priority in being (ousia) because it is crucial to understanding the structure of Aristotle's metaphysical framework. However, a precise definition of priority in being has proven to be elusive, largely because Aristotle is consistently unclear on the matter. Scholars have almost universally taken priority in being to be a kind of ontological priority, where this is understood in different ways. In fact, most assume at the outset that priority in being is a kind of ontological priority, then frame their inquiry accordingly. The result is what I call the Ontological Constraint: any interpretation of priority in being must be a plausible view of ontological priority. I show that this is a mistake. Ultimately, I argue that priority in being is a kind of “explanatory” priority that in some cases can resemble ontological priority, but that in others is wholly distinct. In its most crucial application, establishing the primitive layer of the Science of Being, priority in being is concerned with unity. The primitive items in the science are primitive unities—forms—and they explain the unity of posterior items.Philosoph