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FABRICATION AND INTEGRATION OF RF PASSIVES CIRCUITS VIA AEROSOL JET PRINTING
No full textThesis (M.S.)--Michigan State University. Electrical and Computer Engineering - Master of Science, 2025Aerosol Jet Printing is a fabrication technique that is gaining attention from researchers in academia and commercial fields. It offers the ability to print high resolution conductive and resistive material and custom dielectric substrates that can be used in passive component fabrication. This thesis will explore three main projects. The first is the increasing of the thickness of dielectric substrates and investigating the effects of scaling up the size of dielectric substrates. The goal is to develop processes that can be repeated to reach larger dielectric thicknesses that are beneficial for certain applications such as antenna design and chip packaging. The second project is experimenting with commercially available resistive inks of different polymer loading to test their viability in fabricating common passive RF components. This is desirable because currently if you want to integrate a passive component into a printed circuits it requires an entirely different process than printing that could cause additional losses, yield issues, and cost. The third project is combining the first two projects to fabricate a fully aerosol jet printed rectangular patch antenna array with integrated power divider and attenuator. This is to investigate the viability of integrating passives into larger printed systemsDescription based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
RADIATION FROM EXTREME SOURCES : STUDYING ULTRA-HIGH DOSE RATE RADIOBIOLOGY WITH LASER-DRIVEN ION ACCELERATORS
No full textThesis (Ph.D.)--Michigan State University. Physics - Doctor of Philosophy, 2025Advances in laser-plasma acceleration have enabled the generation of intense ion beams from compact, table-top laser systems. These laser-driven ion accelerators (LDIAs) can produce high intensity proton pulses with ultra-short duration and extremely high dose rates, presenting new opportunities for radiobiological research in previously inaccessible regimes. This dissertation investigates the use of LDIAs as novel radiation sources for studying ultra-high dose rate radiobiology, with a focus on enabling controlled, repeatable investigations into the FLASH effect---a phenomenon where radiation delivered at dose rates exceeding 40~Gy/s appears to spare normal tissue while maintaining tumor control.A major component of this work is the design, simulation, and experimental implementation of compact, permanent magnet-based beam transport systems for LDIA-generated protons at the BELLA iP2 beamline at the Lawrence Berkeley National Laboratory. These transport systems address the challenges posed by the large divergence and broad energy spectra of LDIA beams, enabling efficient delivery of high-intensity proton beams to biological targets. Multiple exposure platforms, including both LDIA and conventional sources, were established and characterized across the laboratory to support interdisciplinary radiobiological experiments. Significant work on dosimetry was done to verify the doses delivered to biological samples exposed at these sources through Monte Carlo modeling and the use of radiochromic film. Through this integration of high power lasers, accelerator physics, and radiobiology, the work presented here establishes new capabilities for investigating dose delivery, beam quality, and biological responses in the ultra-high dose rate regime. The results support the viability of LDIAs as a research tool for advancing the understanding of the FLASH effect and exploring the future of compact, high-impact radiotherapy platforms.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
"I AM NOT AN EXCEPTIONALLY GIFTED TEACHER, BUT I AM AN EXCEPTIONALLY SUPPORTED TEACHER" : CONTINUED SUPPORTS FOR MAKING MEANING OF SCIENCE TEACHING FOR SOCIAL JUSTICE WITH NOVICE TEACHERS
No full textThesis (Ph.D.)--Michigan State University. Curriculum, Instruction, and Teacher Education - Doctor of Philosophy, 2025What it means to learn to teach has been a fundamental question that has driven educational research for decades. As scholars have studied the process of learning to teach, the sociopolitical climate has continued to shape the teacher preparation process, which includes the pedagogies and practice promoted in TPPs, the format and methods that teacher educators use to support novices, as well as the populations that we aspire to teach. Complicating the matter, TPPs tend to conclude prior to a novice\u2019s first year of teaching, meaning that the teachers are largely left to their own devices when tasked with translating teaching practices into a K-12 setting. Coined as the two-worlds pitfall (Feiman-Nemser & Buchmann, 1986), this field of study seeks to examine how novices can better be supported to incorporate the pedagogies and practices from a TPP into K-12 setting. Making matters more complicated, the field has started to advocate for a form of science teaching that embraces social justice initiatives in order to promote equity in science education spaces (NASEM, 2024). This form of teaching, Science Teaching for Social Justice (STSJ henceforth) requires that teachers critically examine their own sociocultural life experiences and consider how systems of power and oppression have intersected with themselves, their students, and the content that they teach. The work is complex and requires teachers to separate out their love for a field while also reconciling with how that same field may reify oppression through education. Thus, this dissertation seeks to better understand, and act on, the levers that influence how and why a novice science teacher (NST) decides to enact STSJ practices during their first year of teaching in a K-12 setting. By conceptualizing teacher learning as meaning making, this study examines how NST make meaning of STSJ practices in their specific context. This study follows Mac, Willow and Aubrey, three White, NSTs from the same TPP, through their first year of teaching through a sociotransformative approach (Rodriguez & Morrison, 2019). Data were generated through individual consultations with each teacher, wherein teachers identified goals and obstacles, and then worked alongside the researcher to co-generate support systems that would help to ameliorate their situation. Data include field notes of consultations, teacher-generated artifacts, unit and lesson planning documents, and a post-consultation interview with each participant. This study found that as NSTs maneuver through their first year of teaching, they do make meaning of how to incorporate notions of STSJ into their first-year teaching practice. Mac, Willow and Aubrey all sought to make meaning of how STSJ could be re-configured within their specific context. Furthermore, as teachers attempted to make meaning of STSJ in their context, they did so by attending to the discursive environment that they taught in: Mac shaped her 1st year teaching practice around notions of Race Evasion present in her community; Aubrey shaped her 1st year teaching practice around notions of Native Resilience and Colonialism; and Willow shaped her 1st year teaching practice around notions of environmental racism and student activism. In each case, the NST\u2019s meaning making was inseparable from the sociopolitical environment that they taught in. These findings imply that first year teachers can engage in STSJ, but doing so requires teacher educators to support their novice teachers beyond the normalized timeline of teacher preparation programs. Further, taking an asset-based approach to supporting first-year teachers is important, as it helps teachers to build confidence in their early teaching career, which, in turn, may help to promote STSJ.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
UNDERSTANDING SLIMY SCULPIN POPULATION DECLINES IN THE GREAT LAKES
No full textThesis (Ph.D.)--Michigan State University. Fisheries and Wildlife - Doctor of Philosophy, 2025The Laurentian Great Lakes benthos has undergone a variety of changes related to invasive species, changing predator abundance, and shifting food webs that reduced the availability of native prey resources. Slimy sculpin (Cottus cognatus) were one of the most abundant benthic prey fish that were preyed upon by lake trout and burbot and slimy sculpin selectively fed upon on the historically abundant Diporeia (Diporeia spp.). Today, round goby (Neogobius melanostomus) and dreissenid mussels (zebra: Dreissena polymorpha; quagga: D. bugensis) are the dominant benthic prey fish and benthic macroinvertebrates and are hypothesized to be responsible for the decline of many native prey fish and macroinvertebrates. Within this dissertation we investigate hypotheses related to round goby competition, lake trout predation, or dreissenid mussel increases that could explain the recent declines in slimy sculpin abundance in many of the Great Lakes. In chapter 1, we observe competition over space and artificial spawning shelters between round goby and slimy sculpin in a laboratory setting at temperatures reflective of their offshore overlap. In chapter 2, we model slimy sculpin population dynamics at various regional ports trawl surveyed by the USGS dating from the 1970\u2019s to 2019 and test covariates related to changing lake trout predation pressure, round goby competition, and dreissenid mussel abundance. In chapter 3, we attempt to observe slimy sculpin and round goby presence/absence on rocky reef habitat in northern Lake Michigan with eDNA and camera drone surveys and report on fish community composition and laboratory experiments observing round goby and slimy sculpin eDNA shedding and decay rates. Overall, our goal was to better understand the potential drivers and mechanisms of slimy sculpin declines in the Great Lakes and provide information that could inform fisheries management about the potential to preserve native benthic prey fish diversity and the associated adaptive capacity of the Great Lakes.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
PHYSICS-INFORMED CRYSTAL PLASTICITY MODELING FOR BODY-CENTERED-CUBIC METALS
No full textThesis (Ph.D.)--Michigan State University. Physics - Doctor of Philosophy, 2025Understanding and modeling the plastic deformation of body-centered cubic (BCC) metals remains a central challenge in materials science due to the complex nature of BCC dislocation mechanisms.This dissertation applied a physics-informed approach in crystal plasticity modeling for BCC metals by addressing three core challenges: experimental-model calibration consistency, dislocation mobility formulation, and constitutive model completeness.The first study investigates the reliability of using surface-based measurements for calibrating crystal plasticity models for bulk materials.Plastic deformation behavior is most conveniently assessed by characterization on a surface, but whether such observations are representative of bulk properties is uncertain. Motivated by reported inconsistencies in slip resistance probed at different depths, we investigated (i) whether the average slip family activity is affected by the presence of a surface and (ii) how the kinematic nature of available slip families influences a potential surface effect. The slip family activity as a function of distance from the surface was extracted from full-field crystal plasticity simulations of random polycrystalline BCC and hexagonal close-packed (HCP) metals as examples of high multiplicity of slip systems per family \vs a mixture of low and high multiplicity across slip families. Under certain conditions, a deviation from bulk slip activity is observed up to about two grains from the surface. For the easiest (least slip-resistant) family, a surface effect of decreasing activity with depth emerges if the number of slip systems falls below about six. For harder families, slip activity always increases with depth. These phenomena are explained on the basis of varying constraints with depth in connection with the kinematic properties of slip families in the material.The second study develops a generalized mobility law for dislocations in BCC metals based on the kink-pair mechanism.Dislocation mobility laws are key to dislocation-density-based crystal plasticity modeling. For dislocations following the kink-pair mechanism, however, existing formulations are often restricted to specific regimes due to the complex interplay between stochastic kink-pair nucleation and lateral kink migration. In this study, the average dislocation velocity under the kink-pair mechanism is formulated as a function of five variables: kink-pair nucleation rate, kink migration velocity, dislocation segment length, critical kink-pair width, and kink height. Through probabilistic cellular automaton simulations, the propagation of conceptual dislocation segments is tracked across a wide range of conditions, and the resulting average velocities are systematically fit using a hyperbolic tangent function. The resulting full-range formulation remains valid for arbitrary combinations of the five variables, and is therefore compatible with a wide variety of underlying kinetic laws. Comparisons with established models demonstrate the consistency and robustness of the new formulation, making it suitable for diverse material systems in which the kink-pair mechanism governs dislocation motion.The third study presents a comprehensive constitutive model that explicitly differentiates between edge and screw dislocation populations.The model incorporates distinct mobility laws for each dislocation character, reflecting the fundamental differences in their motion mechanisms: screw dislocations move via a thermally activated kink-pair process, while edge dislocations glide more readily with lower thermal sensitivity. In addition, separate density evolution laws are developed for edge and screw dislocations, accounting for processes such as dipole formation, annihilation, and interaction-driven hardening. The model includes physically motivated mechanisms such as cross-slip for screws and climb for edges, which further enrich the fidelity of dislocation evolution under complex loading conditions. Implemented within the DAMASK simulation platform, the model is built with a modular structure that allows each mechanism to be activated or deactivated independently. This design enables systematic investigations into the role and interplay of individual features, supporting both predictive simulations and fundamental studies of BCC deformation behavior.Collectively, this work lays the foundation for a robust and extensible framework for modeling the plastic behavior of BCC metals.It provides a deeper understanding of the microstructural mechanisms governing deformation and offers practical tools for predictive simulation of advanced metal systems under varied thermomechanical conditions.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
EVALUATING THE EFFECT OF LARVAL PRESERVATION METHODS ON BLOW FLY CUTICULAR HYDROCARBONS
No full textThesis (M.S.)--Michigan State University. Forensic Science - Master of Science, 2025As one of the first insect groups to colonize decomposing remains, Calliphoridae (blow flies) are essential in forensic entomology. Forensic entomologists can estimate the minimum postmortem interval (minPMI) of decomposing remains by determining the species and age of immature blow fly specimens present on the remains. Previous research has demonstrated that blow fly cuticular hydrocarbon (CHC) profiles can be used to distinguish specimens by species and age, potentially assisting in minPMI estimation. However, these prior studies either analyzed specimens immediately upon collection, or after the specimens were frozen prior to analysis. In practice, blow fly larvae are often preserved with other methods, and the effects of these methods on CHC profiles have not been investigated. This thesis aims to evaluate differences in the CHC profiles of field-collected blow fly larvae caused by preservation method and storage time. Larvae collected from decomposing stillborn swine (Sus scrofa) carcasses were preserved with three common methods: freezing, hot water killing (HWK), and smothering with ethanol (EtOH). Frozen larvae were stored dry at -20 \ub0C. Hot water killed larvae were submerged in near-boiling (> 80 \ub0C) water for approximately one minute, then removed and stored in solutions of 95% EtOH at room temperature. Ethanol-smothered larvae were directly stored in solutions of 95% EtOH at room temperature. Specimens were stored for up to six months and removed from storage periodically for extraction of their CHC profiles and analysis using gas chromatography-mass spectrometry. Cuticular hydrocarbon profiles were statistically compared using principal component analysis, non-metric multidimensional scaling, and permutational multivariate analysis of variance. In comparison to HWK larvae and EtOH smothered larvae, frozen larvae have the most consistent CHC profiles and experience the fewest changes in CHCs with respect to storage time. Therefore, preservation of larvae by freezing is recommended for CHC analysis as the other methods can cause alterations to CHC profiles due to interactions with EtOH and increased rates of sample degradation.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
MODELING NITROUS OXIDE (N2O) EMISSIONS AT DIFFERENT SPATIAL AND TEMPORAL SCALES
No full textThesis (Ph.D.)--Michigan State University. Earth and Environmental Sciences \u2013 Doctor of Philosophy, 2025Agricultural soils are the largest anthropogenic source of nitrous oxide (N2O), a potent, long-lived greenhouse gas and ozone-depleting substance. Yet despite decades of research, practical mitigation in row-crop systems is constrained by three gaps: (1) national and global inventories report totals rather than crop-resolved emissions and rarely attribute changes to drivers such as harvested area, fertilizer inputs, or nitrogen-use efficiency, leaving emission-intensity patterns and their causes poorly understood; (2) existing prediction tools are difficult to scale or perform inconsistently, especially for short, high-magnitude flux events; and (3) management guidance evaluates practices in isolation instead of prescribing region-specific bundles tuned to climate and soils. This dissertation addresses these gaps by (i) producing a global accounting of crop-specific N2O emissions intensity and their major drivers , (ii) developing a multi-model hybrid framework that improves daily flux prediction, including peaks, and (iii) conducting a large-area scenario analysis that quantifies how tillage, winter-rye cover crops, and residue handling interact with climate and soils across the U.S. Midwest.In Chapter 1, I provide an overview of the research motivation and a comprehensive literature review. In this chapter, I synthesize the biogeochemical controls on N2O (nitrification, denitrification, and their sensitivity to mineral N, labile C, temperature, moisture, pH, and texture). I review the strengths and limitations of measurement techniques and IPCC inventory tiers, and compare process-based models approached with machine learning. In Chapter 2, I present the first global, spatially explicit assessment of N2O emissions intensity (emissions per unit of production) for 136 crops across 180 countries in 2005 and 2020, at a high spatial resolution. By coupling crop-specific activity data with different emission factors, I map where intensity is high, where it is falling, and why. Decomposition analysis attributes change to crop type, yield, area, and nitrogen use efficiency, revealing hotspots for targeted mitigation and cases, such as a ~40% decline in intensity concurrent with yield gains, where productivity and climate goals already coexist. This chapter provides a decision-ready baseline for prioritizing mitigation by crop and country, rather than relying solely on national totals. In Chapter 3, I develop a Ensemble Modeling Systems (EMS) that blends the strengths of process-based models with a stacked ensemble of machine-learning algorithms to predict daily N2O fluxes. The framework is trained and evaluated on a large, diverse dataset of manual chamber measurements from long-term U.S. field sites encompassing multiple crops and management regimes. It reproduces both the timing and the size of emission peaks with high agreement to observations, including at locations not used for training. To quantify uncertainty, Monte Carlo analyses incorporate model structure and weather-input variability into the predictions. Interpretable learning (via SHAP) reveals that soil organic carbon, ammonium, nitrate, water-filled pore space, above-ground biomass, and soil temperature are the primary controls, aligning the model\u2019s behavior with established biogeochemical mechanisms. The result is a transferable and explainable predictor suited to regional inventories and scenario testing where measurements are sparse. In Chapter 4, I apply the hybrid framework across a large Midwestern cropland domain over a roughly decade-long period to evaluate a group of realistic management pathways, including conventional tillage versus no-till, the presence (with corn-soybean rotation) or absence of winter rye (continuous corn), and partial removal of maize stover and/or rye biomass. Three messages emerge. First, transitioning from conventional tillage to no-till reduces annual N2O emissions on average, with most of the benefit occurring off-season. This suggests that winter moisture, freeze\u2013thaw cycles, and short-lived substrate pulses are the primary drivers. Second, introducing rye generally increases emissions under conventional tillage, and this increase is more modest in long-established no-till systems. Removing a portion of the rye biomass at termination consistently softens these increases. Third, harvesting a large share of maize stover is typically counterproductive for N2O emissions in humid landscapes, regardless of tillage practices. These averages mask strong spatial structure: no-till is a robust mitigator in the semi-arid Great Plains, offers smaller, texture-dependent benefits in the Upper Midwest, and is roughly neutral in the fine-textured, wetter Eastern Corn Belt unless paired with rye management that limits spring surges of labile carbon and nitrogen. Seasonally, conservation tillage flattens the annual curve and shifts the peak earlier, whereas rye or stover removal tends to elevate late-spring emissions under conventional tillage and, to a lesser extent, under no-till. In Chapter 5, I synthesize the dissertation\u2019s findings into actionable guidance. I argue that emissions intensity, not totals, should guide where to act; that off-season fluxes must be measured, modeled, and incentivized; and that bundled, region-specific practices outperform one-size-fits-all prescriptions. Based on the findings, I recommend prioritizing no-till as a first-order strategy; pair rye with no-till and consider partial rye removal; and approach widespread stover harvest in humid regions with caution, while outlining next steps such as off-season focused field experiments with diverse soil and climate, integration of remote sensing with the hybrid framework, and multi-objective optimization that includes yield, soil carbon, and N losses. Collectively, the thesis delivers datasets, models, and maps that enable researchers, advisors, and policymakers to target durable N2O mitigation without sacrificing productivity.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
THREE ESSAYS ON RENEWABLE ENERGY
No full textThesis (Ph.D.)--Michigan State University. Agricultural, Food and Resource Economics - Doctor of Philosophy, 2025This dissertation consists of three essays studying issues related to renewable energy, including ethanol, biodiesel, and solar energy. The COVID-19 pandemic induced numerous supply chain shocks in U.S. agricultural markets, creating a desire to disentangle commodity price impacts caused by unique changes in food and non-food agricultural product demand. Using a data-modified version of the relative price of a substitute method, essay one distinguishes the consequences of the sharp decline in U.S. automotive fuel demand from the consequences of non-ethanol demand changes in the U.S. corn market. Results suggest that\u2013due to the renewable fuel standard and ethanol-gas price linkages\u2013COVID-19 affected corn markets more so than other agricultural commodities. The onset of the COVID-19 pandemic reduced Illinois cash prices for corn by approximately 18%. The majority of this impact (approximately 16%) was driven by pandemic-induced reductions in ethanol demand. Ethanol-driven and total impacts were greater in locations farther from terminal markets. Essay two develops an integrated, theoretically consistent framework based on the relative price of a substitute method from Carter and Smith (2007) to evaluate the cumulative and incremental effects of a series of interceding events on market prices. We apply this framework to measure the price impacts of the EU ban on palm oil use in biodiesel production. The EU has proposed various policies to eliminate its use of palm oil, including the Palm Oil Resolution that proposed phasing out palm oil in biofuel use by 2020, the Renewable Energy Directive II (REDII) that restricts the use of high-risk indirect land-use change biofuels, and the Directive designating palm oil as a high-risk indirect land-use change feedstock. Using our modified RPS method, we find that\u2013among these policies\u2013the adoption of the REDII is associated with the largest impact. In total, EU limits on palm oil use in biodiesel production have resulted in a 28.56% reduction in international palm oil prices and revenue losses of about $1.7 billion for the Malaysian palm oil industry. Contrary to the concerns of some, we do not find evidence that the ban was beneficial to EU canola oil producers. Essay three examines the rebound effect in residential nighttime electricity consumption following rooftop solar adoption. Using a two-stage difference-in-differences design that accounts for staggered adoption timing, we analyze a panel of more than 23,000 households in Northern and Central California from 2015 to 2019. We find that solar adoption increases nighttime consumption by roughly 8 percent, providing robust evidence of a rebound effect. The magnitude of this effect varies substantially across policy regimes. Under NEM 1.0 with a standard tiered rate, it is modest and reflects a pure rebound effect. Under NEM 1.0 with time-of-use rates, the effect is substantially larger, as strategic load-shifting compounds the rebound from income and substitution effects. Under NEM 2.0, the effect is intermediate, reflecting how non-bypassable charges and interconnection fees temper the load-shifting incentives of mandatory TOU rates. Heterogeneity analyses reveal that the rebound effect is greater for households with high pre-treatment consumption and for those with larger effective solar system sizes. Together, the results highlight how tariff design and household characteristics shape behavioral responses to solar adoption, with important implications for policy evaluation, environmental accounting, and grid management.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
CHARACTERIZATION OF INCREASED SERUM AND GLUCOCORTICOID-INDUCIBLE KINASE 1 GENE EXPRESSION IN THE VENTRAL TEGMENTAL AREA BY DRUGS OF ABUSE AND STRESS
No full textThesis (Ph.D.)--Michigan State University. Neuroscience - Doctor of Philosophy, 2025Substance use disorder (SUD) is a highly prevalent psychiatric disorder but despite this prevalence, treatment options for SUD remain inadequate. Furthermore, SUD is highly comorbid with other psychiatric illnesses, such as depression, contributing to the difficulty of developing effective therapeutics. A major reason for unsuccessful treatment is our limited understanding of the neurobiology underlying these disorders. Both drugs of abuse and stress can modulate the function of the dopamine (DA) neurons in the ventral tegmental area (VTA) that are instrumental for proper motivated behavior. Therefore, our lab seeks to identify cellular and molecular changes in the VTA that underlie drug and stress responses. We previously found that repeated injections of morphine or cocaine increase the expression of the gene serum\u2013 and glucocorticoid- inducible kinase 1 (Sgk1) in the VTA using RNA sequencing. Furthermore, chronic social defeat stress (CSDS) induces Sgk1 in the VTA as well, highlighting it as a common target for both drugs and stress in the VTA. Although we previously found that chronic drug exposure increases Sgk1 expression in the VTA 24 hours later, it was unclear whether similar regulation occurs with acute drug exposure and how persistent Sgk1 expression changes are. For this dissertation, I investigated other key timepoints in which drugs of abuse can induce molecular changes within the VTA such as acute exposure and abstinence. I discovered that acute exposure to morphine via a single injection is sufficient to increase VTA Sgk1 expression 1 hour later, but not 24 hours late. Furthermore, Sgk1 induction did not persist through abstinence. Drugs of abuse cause a sensitization of behavioral and molecular responses following repeated drug exposure such that subsequent exposures display enhanced effects; thus, I also investigated whether Sgk1 expression is sensitized by morphine exposure. However, I found that Sgk1 expression is not affected by prior morphine exposure. Together, these data indicate that acute and chronic morphine exposure regulate Sgk1 expression differently. Both acute and chronic exposure elicit an induction of Sgk1 1 hour later, likely due to Sgk1 being an immediate early gene, while only chronic exposure causes a more persistent Sgk1 induction (24 hours later) likely from activation of downstream signaling pathways involving Sgk1. Given that multiple classes of drugs of abuse increase VTA Sgk1, and our previous observation of an CSDS-induced increase in VTA Sgk1, we wanted to know if this regulation translated to other forms of stress. I found that subchronic variable stress, acute restraint stress, and repeated restraint stress all increase VTA Sgk1 expression. I then determined whether this stress-induced increase in VTA Sgk1 expression was driven by VTA DA neurons. Using transgenic mice and viral-mediated deletion strategies I discovered that neither Sgk1 knockout from VTA DA neurons, or all VTA neurons, was sufficient to blunt the stress effect, suggesting Sgk1 induction is occurring in non-neuronal cells. Given recent reports in the literature that VTA astrocytes respond to both stress and drugs of abuse and can modulate VTA DA function, I used RNAscope to assess Sgk1 expression in VTA astrocytes and found that both chronic morphine and acute restraint stress increase Sgk1 expression in VTA astrocytes. Together, my studies provide a more expansive understanding of how drugs of abuse and stress affect Sgk1 induction in the VTA, and the specific cells responsible. Future studies should determine the functional role, molecularly and behaviorally, of Sgk1 induction in VTA astrocytes by drugs of abuse and stress, as these will help determine if targeting Sgk1 is a feasible therapeutic option for treatment of comorbid SUD and depression.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
Investigating New Applications of a Statistical Method to Compare Mass Spectra of Seized Drug Samples
No full textThesis (M.S.)--Michigan State University. Forensic Science - Master of Science, 2025The definitive identification of newly emerging controlled substances, including variousfentanyl analogs and synthetic opioids, can be challenging when comparing highly similar electron-ionization (EI) mass spectra. Previous research has demonstrated the ability of the unequal variance t-test to statistically distinguish or associate mass spectra of various seized drug samples. The unequal variance t-test method identifies discriminating ions between two mass spectra, with previous research demonstrating the reliability of these ions for discrimination. In this work, the unequal variance t-test method used to statistically compare EI mass spectra is further evaluated in two ways. First, the effect of mass spectral selection on the association and discrimination of fentanyl isomers is evaluated. And second, a new application of the method as a tool to select variables for the development of multivariate classification models is investigated. In this first part of this work, positional isomers of fentanyl analogs were analyzed by gas chromatography-mass spectrometry (GC-MS). Mass spectra collected at the chromatographic peak apex and averaged across the peak width at half height were statistically compared using the unequal variance t-test method. The number and identity of reliable discriminating ions as well as the ability to associate and discriminate the isomers was consistent regardless of mass spectral selection. In the second part of this work, the unequal variance t-test method was evaluated as a variable selection tool prior to development of linear discriminant analysis (LDA) models for classification. Classification success of structural and positional isomers of fentanyl analogs was equivalent or improved upon using the unequal variance t-test method for variable selection compared to the more traditional method using principal component analysis (PCA).Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references