Master's Theses (Fall 2009 to Present)

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New submissions to the University of Delaware Master's Theses collection are added as they are released by the Office of Graduate & Professional Education. The Office of Graduate & Professional Education deposits all master's theses from a given semester after the official graduation date.

University of Delaware master’s theses submitted between 1980 - Summer 2009 are available online through Dissertations & Theses @ University of Delaware. Use the library catalog, DELCAT Discovery, to search for all print or microform copies of master's theses 1980 - 2009 that are NOT available in Dissertations & Theses @ University of Delaware because Dissertations & Theses @ University of Delaware does NOT contain the complete collection of University of Delaware master's theses.

Master’s theses in the Longwood Graduate Program in Public Horticulture submitted between 1970 - 2004 are available online.

More information is available at Dissertations & Theses.


Recent Submissions

Now showing 1 - 20 of 2211
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    Structure function analysis of the conserved WWD domain in the System I bacterial holocytochrome C synthase, CcmF
    (University of Delaware, 2022) Grunow, Amber L.
    Cytochromes c are highly conserved proteins found in nearly all organisms including bacteria, plants and humans that function in electron transport chains for critical cellular functions 1. Each cytochrome c contains at least one molecule of covalently attached heme which is required for protein folding, stability and function 1–3. The covalent attachment of heme to apocytochrome c is referred to as cytochrome c biogenesis. There are three known pathways that accomplish heme attachment within the inner membrane space of the mitochondria in eukaryotes (System III) or the periplasm of prokaryotes (System II and I) 1. All Systems function to covalently attach heme to apocytochrome c yet use different mechanisms. This thesis will focus on the integral membrane protein, and holocytochrome c synthase, CcmFH, of System I which attaches heme to apocytochrome c in the final step of the pathway 4. CcmF has key features that are required for function including four conserved histidines, a stable b-heme located in the transmembrane domain and a highly conserved WWD domain that has been shown to directly interact with heme in other proteins 5,6. Therefore, I hypothesize that the WWD domain in CcmF is required for holocytochrome c synthase activity. ☐ To test this hypothesis, alanine scanning was performed on the WWD domain in CcmF to determine which amino acids are necessary for cytochrome c biogenesis. Further biochemical analyses of each alanine mutant determined the heme environment in each variant and their protein interaction partners. These studies have shown that two alanine mutants in the WWD domain of CcmF displayed non-functional phenotypes. The inability of these two variants to perform the holocytochrome c synthase function was not due to a defect in heme binding nor to the disruption of known protein-protein interactions. Overall, this study demonstrates that the WWD domain is necessary for synthase function in CcmF.
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    Toward mental health prediction using browsing history for predictive and soft labeling
    (University of Delaware, 2022) Nilipour, Sahar
    Web browsing data is increasingly being explored as a passive window into the daily lives of users to assess levels of internet addiction and other mental health markers. In this work, I determine whether such approaches can be applied to data generated by the HabitLab platform to assess the community of users for signs of anxiety, depression, and loneliness. HabitLab is a Chrome-based browser plugin that offers users tools to monitor and optimize the time they spend on various websites that negatively impact their productivity while passively logging their browsing sessions. As part of an initial explorative study, 66 HabitLab users completed a paid Qualtrics survey during the height of the COVID-19 pandemic in the US. I analyzed their response to several psychometric scales included on the survey and paired their results with their web browsing data. I then developed several features from this data to characterize their behaviors and used Machine Learning techniques (e.g., SVM, Random Forest) to attempt to learn relationships between their responses. I trained both Classification and Regression models, as I had access to both the real valued scores and their interpretations for most of the mental health scales. The results suggest that the models (specifically regression models), are capable of learning some of the scales; achieving over 80% accuracy for predicting Anxiety and Sleep Disturbance. As the long-term goal of the HabitLab team is to transform the plugin into a Digital Wellbeing and Occupational Health platform, these results can be used to inform: (i) future onboarding and demographic intake questionnaires, (ii) efforts to develop features based on web usage data and predictive models of mental health status, and (iii) facilitate anonymous community assessment through soft labeling approaches.
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    The effects of repetitive head impacts on neurocognitive function
    (University of Delaware, 2022) Fasoranti, Zarek O.
    Introduction: There has been an increase in concern regarding the effects of sports related Repetitive Head Impacts (RHI) during contact and/or collision sport participation. Furthermore, the duration of an athlete’s participation in collision sports may present a “dose-response” effect whereby longer duration of play results in poorer cognitive function. Therefore, the purpose of this study was to utilize an established cognitive assessment, the Trail Making Test (TMT), to assess how neurocognitive functioning is affected by sport type played (i.e., collision, contact, and non-contact) and collision sport career duration. ☐ Methods: The TMT (TMT-A, TMT-B, TMT-Diff) completion times of collegiate student-athletes from two universities participating in non-contact, contact, and collision sports were utilized. A One-Way ANOVA compared TMT-A, TMT-B, and TMT-Diff times between non-contact, contact, and collision sport athletes and significant main effects were followed with Tukey post-hoc tests. A regression analysis was used to assess whether sports career duration predicted TMT performance. ☐ Results: There was a significant main effect for TMT-B and TMT-Diff. For the TMT-B, the collision sports group (43.8 + 13.0 sec) were significantly slower (p<0.001) than non-Contact (39.1 + 10.6 sec, d= 0.4). In the TMT-Diff score, the Collision sports group had a significantly larger difference (p = 0.001, d= 0.55) (23.4 + 11.6 sec) than the non-contact sport (17.6 + 9.2 sec). Years of sport participation was not a significant predictor for TMTA (p = 0.60, R2=0.0008), TMTB (p = 0.29, R2=0.003) or TMT-Diff performance (p = 0.17, R2=0.006). ☐ Conclusion: In conclusion the results suggest that career duration at the collegiate level may not be a predictor of neurocognitive performance. However, collision sports participation in college results in small (d= 0.4) but significant differences in cognitive function which raises concern about cognition across the lifespan. Future studies need to continue to monitor former contact and collision sports athletes as they age to identify potential neurophysiological effects of RHI and aging.
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    AMBERff at scale: multimillion-atom simulations with AMBER force fields in NAMD
    (University of Delaware, 2022) Jones, Peter Eugene
    All-atom molecular dynamics (MD) simulations are an essential structural biology technique with a demonstrated record of groundbreaking biological discoveries. The application of MD simulations to study large-scale biomolecular systems containing millions of atoms can reveal incredible details about viral and cellular processes that are inaccessible to experimental methods. Classical MD simulations rely on "force fields" carefully parameterized for each class of biomolecule to accurately describe molecular motion. Importantly, the AMBER family of force fields (AMBERff) includes a more accurate and extensively validated description of nucleic acids. Yet, it is not currently tractable to use AMBERff for multimillion-atom simulations, the minimum scale required to study the activity and emergent properties of biologically-relevant systems. To address this, the authors take advantage of the direct cancellation between the potential energy functions to refactor several popular force fields within AMBERff into the CHARMM file format. These refactored files are compatible with the freely-available NAMD software, which supports MD simulations of biomolecular systems up to two billion atoms on leadership-class supercomputers. Direct comparison of the single point energies for a comprehensive set of test systems show that this process preserves the integrity of the AMBERff force fields. Further, case studies using wellcharacterized biological systems show that these refactored files faithfully reproduce a number of biophysical properties across several classes of biomolecules. Implementation of AMBERff for NAMD will enable application of the leading nucleic acid force field for investigation of viral and cellular processes that involve genome.
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    An examination of multiple components of emotional processing theory as predictors of symptom change in prolonged exposure for posttraumatic stress disorder
    (University of Delaware, 2022) Kelly, Alyssa
    Cyclospora cayetanensis is a lesser studied member of the Apicomplexan family of protozoa, which includes more well studied protozoan genera like Cryptosporidium, Eimeria, and Toxoplasma. However, C. cayetanensis is an important protozoan parasite that continues to cause outbreaks of gastroenteritis associated with contaminated fresh produce. Cyclospora oocysts may be transmitted through contaminated surface water, thereby making reliable detection imperative for public health and produce safety. Cyclospora is still considered an emerging pathogen by many, due to the limited understanding and large data gaps surrounding the transmission and survival of oocysts in the environment limitations in detection of oocysts. Polymerase chain reaction (PCR) analysis is used for detection of a presumptive positive water sample. Filtration using the ZVI-sand filtration achieved a 4.30-log reduction of Cryptosporidium parvum compared to 1.82 log reduction using sand filtration. When comparing the two filtration systems, there was a significant difference in efficacy (p < 0.05) with ZVI-sand filtration yielding larger reductions of C. parvum oocysts. For reduction of Eimeria tenella oocysts, ZVI-sand filters achieved a 6-log reduction, whereas sand-only filtration achieved a 2.3-log reduction. There was a significant difference (p < 0.05) in ability to inactivate and remove E. tenella oocysts, the ZVI-sand filtration performed better compared to the sand alone filtration. This study investigated the effects of gaseous chlorine dioxide at varying treatment times on Cryptosporidium parvum on produce, baby cut carrots and grape tomatoes. Grape tomatoes (approx.40g) and baby-cut carrots (approx. 35g) were spot inoculated (106 oocysts) with 100-µl of C. parvum suspension in 10-µl droplets randomly distributed on the produce samples. Inoculated produce samples were treated with 50 g of each gaseous chlorine dioxide precursor for 0, 1 and 3 hours in a 35-L enclosed chamber. Significant reductions were shown at both 1 hour and 3-hour treatment times for both produce types. The results of this work will facilitate the development of novel on-farm filtration technology and guidelines for commercial applications to control parasitic pathogens in agricultural water, thus improving the safety of produce and control of protozoa in agricultural water. A total of seventy-two water samples were collected regularly from various sites in Delaware and Maryland over the course of 17 months (June 2017-October 2018). DNA Primer Sequences for Cryptosporidium Genus-specific PCR Amplification (18S rRNA) used, followed by further testing using VspI and DraII restriction fragment length polymorphism enzyme for speciation confirmation. The nested PCR amplicons were digested with one unit of VspI for distinction between C. parvum and C. hominis. For distinction of C. parvum, C. baileyi and C. serpenti, the nested PCR amplicon were digested with one unit DraII. Twenty-four out of seventy-two water samples were confirmed to contain Cryptosporidium parvum. Through further testing using restriction fragment length polymorphism analysis, one water sample was confirmed to harbor C. cayetanensis or E. neischulzi, which have genetic similarities to Cryptosporidium species. A single sample was identified to be either C. baileyi or C. serpenti, which do not infect humans. Knowledge of parasitic organisms in potential irrigation water sources are essential for correct implementation of water testing and water treatment.
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    Investigating the role of MARF1-like (MFL) endoribonuclease genes in Arabidopsis
    (University of Delaware, 2021) Bogdan, Catherine J.
    RNA decay in eukaryotes is mainly carried out by exoribonucleases and endoribonucleases, but the latter have been underappreciated. In metazoan nonsense-mediated mRNA decay (NMD), the endoribonuclease SMG6 cleaves certain mRNAs, leaving the 5' and 3' fragments to be degraded by the exosome and XRN1, respectively. Though SMG6 orthologs are absent in plants, recent studies in Arabidopsis thaliana indicate that some NMD transcripts are cleaved by an unknown endoribonuclease, and their 3' fragments over-accumulate in the absence of XRN4 (the plant cytosolic homolog of XRN1). Metazoan MARF1 is an endoribonuclease in humans and mice that cleaves targeted mRNAs via its catalytic NYN domain. Arabidopsis has several different NYN domain-containing proteins that we predicted to be homologs of metazoan MARF1. Importantly, one of these proteins (AtMFL1) localizes to P-bodies and has an RNA-dependent association with critical NMD factor AtUPF1. I therefore hypothesized that MARF1-like (MFL) endoribonucleases play a role in post-transcriptional control of gene expression in plants. ☐ The major goal of this project was to study the role of selected MFL endoribonucleases in Arabidopsis, particularly AtMFL1. Here I report the organ-specific expression of the AtMFL genes- AtMFL1 and AtMFL2 are ubiquitously expressed in all major organs, while AtMFL3 is minimally expressed in certain organs. I also report the subcellular localization of the AtMFL proteins- AtMFL1 localizes to cytosolic foci, AtMFL2 localizes to the cytosol and cytoskeleton, and AtMFL3 localizes to the nuclear membrane and cytosolic aggregates. Additionally, I report that AtMFL1-like proteins with catalytically active NYN domains are evolutionarily℗ conserved across many plant species. Finally, I provide evidence for the role of AtMFL1 as a cytosolic endoribonuclease that is involved in mRNA degradation.
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    Apiaceous vegetables mitigate acrolein-induced lung injuries in C57BL/6J male mice
    (University of Delaware, 2021) Redding, Mersady C.
    Acrolein (Acr) is a ubiquitous, highly reactive aldehyde, abundant in polluted air and cigarette smoke. Acr causes oxidative stress and a cascade of catalytic events and has, thereby, been associated with increased risk of pulmonary disease and other inflammatory diseases. Apiaceous vegetables (carrot family vegetables) are noteworthy for dietary prevention of inflammation and various cancers. However, whether API could prevent Acr-induced pulmonary toxicity has not yet been explored. In this study, we investigated the effects of API on Acr-induced pulmonary damages in male C57BL/6J mice. A total of 20 mice were assigned to either negative control (NEG group; AIN-93G diet only), positive control (POS group; AIN-93G+Acr) or apiaceous vegetable intervention group (API group; AIN-93G+21% API+Acr). After one week of dietary intervention, the POS and API mice were exposed to Acr (10 µmol/kg body weight daily) for five days. During the treatment period, assigned diets remained the same. Prominent indicators of toxicity within the lungs of POS mice were found, including mucus accumulation, macrophage infiltration, and hemorrhage, which appeared to be ameliorated in API mice. Serum and lung inflammation markers, such as tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), were also increased by Acr while reduced by API. Furthermore, poly (ADP-ribose) polymerase (PARP; a necrosis marker) was increased in the POS group while decreased in the lungs of API mice. Similarly, DNA repair genes [e.g., breast cancer type 1 susceptibility protein (Brca1) and proliferating cell nuclear antigen (Pcna)] within the lungs were decreased in POS compared to NEG, but the genes were normalized in API mice. In the liver, API upregulated expression of glutathione S-transferases (GST), which enhanced the metabolism of Acr into water-soluble 3-hydroxypropyl mercapturic acid for excretion, which is consistent with observed reductions in serum Acr-protein adducts. In conclusion, apiaceous vegetables may provide protection against Acr-induced pulmonary damages via downregulation of inflammatory pathways and/or enhancement of the detoxification of Acr.
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    The course of breastfeeding and duration of feeding human milk in infants with congenital heart disease
    (University of Delaware, 2021) Russel, Sarah M.
    Background: Although mothers of children with congenital heart disease are able to breastfeed successfully, the research on this population is limited and the effect of breastfeeding challenges and social support on human milk duration is unknown. Research aims/questions: This study aimed to describe the course of breastfeeding in infants with CHD from birth to 12 months of age, with a focus on breastfeeding characteristics (e.g., early lactation experiences, breastfeeding challenges, sources of breastfeeding support) and their relationship to the exclusivity and duration of feeding human milk. Methods: This study was a prospective, observational study conducted at The Children's Hospital of Philadelphia between 2015-2018. Participants were followed throughout the infant's first year of life, with 9 total contacts. Questionnaires were administered to mothers at each visit to obtain information on feeding type, sources of support, and challenges faced during breastfeeding. Results: 75 mother-infant dyads were enrolled. 93% of mothers reported having challenges, the most common (38%) being the infant having trouble latching. The majority of support was received within the first 0.5 months of the infant's life from lactation consultants (72%) and nurses (62%). The mean duration of 'any human milk' and 'human milk only' was 6.4 months and 3.19 months, respectively. Duration of 'human milk only' was related to mothers reporting infants having trouble sucking (p=0.03) and not having enough milk (p=0.04). Human milk durations were not related to receiving support. Conclusion: Mothers of infants with congenital heart disease were able to successfully provide their infants with human milk, despite commonly facing breastfeeding challenges and rehospitalizations.
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    A low-energy dense dietary pattern: a narrative review
    (University of Delaware, 2021) Burns, Kaelyn F.
    A low-energy dense dietary pattern is promoted throughout dietary recommendations for the purpose of promoting diet quality and overall health. However, little work has identified effective approaches for achieving a low-energy dense diet, making the implementation of dietary recommendations challenging. The purpose of this thesis project was to conduct a narrative review to examine energy density used within extant literature. The narrative review aims to examine the approaches used to implement a low-energy dense dietary pattern within dietary interventions while describing the success of the intervention and how a low-energy dense dietary pattern compares to other dietary strategies in improving dietary and health outcomes. The narrative review underscores the work of basic feeding studies and observational research which have demonstrated that a diet low in energy density is associated with a reduced energy intake and positive health outcomes. Ten dietary intervention studies with the explicit goal of altering participant dietary energy density were reviewed and the impact the intervention had on dietary energy density, diet quality, energy intake, and weight were described. Implementation of a low-energy dense diet was accomplished through two different approaches; modifying the consumption of food/nutrient groups that impact energy density or applying one of various proposed energy density classification methods. Across interventions, consuming a low-energy dense dietary pattern had similar results compared to other dietary intervention strategies in regard to impact on the reviewed health outcomes. Interventions that used an energy density classification method to implement a low- energy dense dietary pattern appeared to have more consistency across studies in regard to reducing participant dietary energy density, diet quality, energy intake, and weight management when compared to the approach of modifying the consumption of food/nutrient groups that impact energy density.
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    Quantifying dynamic, complex vocal sequences emitted by freely interacting mice
    (University of Delaware, 2020) Armus, Lauren
    Animals rely on social communication to find mates, establish dominance, and coordinate group behavior. The house mouse, Mus musculus, emits a series of sequential vocal signals to communicate. Because the majority of mouse vocal signals are ultrasonic and undetectable to humans, a microphone array is necessary for localizing and accurately attributing vocal signals to specific mice in a social setting. Using a microphone array system, we recorded the vocalizations and social behavior from 11 groups of adult mice, each consisting of two females and two males. Mice in each group were allowed to freely interact for five hours. We observed that distinct types of individual calls emerge as male mice perform specific social actions, and that the signals consequently affect the behavior of a social partner. There is, however, a lack of detailed knowledge about the sequential structure of vocal signals and their relation to distinct behaviors. Here, we thoroughly characterize the structure and context in which sequentially emitted vocal signals, attributed to specific individual animals, are produced during innate behaviors. Strikingly, we showed that the sequences contain signals with opposite acoustic structures when emitted by mice in aggressive and non-aggressive roles of a social behavior. This provides direct evidence that social partners vocally interact in sequential arrangements and that distinct combinations of vocal signals depend on the behavior of the vocalizer. These findings yield novel characteristics of mouse communication patterns, which will ultimately lead to better understanding of the neural basis of social communication and innovative treatments for communication disorders.
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    Rayleigh criterion applied to radial velocity planet searches
    (University of Delaware, 2023) Ramirez Delgado, Victor
    The Rayleigh criterion determines the resolution limit of a periodogram, which is the minimum frequency separation required to barely resolve two sinusoids. Neglecting to consider the Rayleigh criterion may result in a false interpretation of a long-period signal or a spurious claim that two closely spaced periodogram peaks represent two distinct physical processes. This thesis demonstrates how the Rayleigh criterion can help astronomers avoid false positives caused by artifacts of uneven time intervals between observations. We use the Rayleigh criterion to show that the frequency separation between planet 55 Cncd and the stellar activity cycle is too small to distinguish the two phenomena based on published radial velocity data alone. We also demonstrate that the radial velocity signal of contested planet HD99492~c cannot be separated from zero frequency according to the Rayleigh criterion. Finally, we demonstrate that a cubic polynomial is a better fit to the long-term RV variability of Barnard's star than a sinusoid with a frequency that is statistically indistinguishable from zero. This work concludes that astronomers searching for periodic signals should consider the Rayleigh resolution criterion as part of their discovery validation.
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    Intimate partner violence and the criminal legal system
    (University of Delaware, 2023) Derr, Kate
    The paper examines the role of the criminal-legal system in relationships in which the participant experience intimate partner violence. The criminal-legal system has greatly expanded since the 1980s and disproportionately affects the Black community and other marginalized groups. This study analyzes the life histories of intimate partner violence (IPV) victims and offenders and their interaction with the criminal-legal system by using semi-structured interviews with 18 participants. ☐ Analysis of the interviews was conducted utilizing a Black feminist criminology framework to understand the interlocking nature of race, gender, and class and its effects on public policy effectiveness. My analysis uncovered three emerging themes among the research participants: IPV is one problem among many, victims were arrested when they sought help, and some women use the criminal-legal system to escape. This study found a relationship between criminal-legal system impact and multiple IPV relationships. Combined with the themes uncovered in this analysis, this research supports policy interventions that advocate for alternative methods to policing in intimate partner violence relationships, promote robust social safety nets, and provide expanded support to domestic violence programs that offer drug and alcohol addiction services, housing and job assistance, and mental health support.
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    Similar microbiome compositions of nymphal blacklegged ticks (Ixodes scapularis) infected and uninfected with Borrelia burgdorferi in Delaware
    (University of Delaware, 2023) Casey, Tyler
    Pathogens can be influenced by their host's microbiome, and this can have consequences for pathogen dynamics. Therefore, characterizing the microbiome of hosts, particularly vectors, may help explain pathogen transmission patterns and facilitate the development of novel transmission-blocking approaches. Borrelia burgdorferi is a bacterium that is transmitted by blacklegged ticks (Ixodes scapularis) in the eastern and upper midwestern United States and causes Lyme disease in humans. Borrelia burgdorferi has been hypothesized to be susceptible to exclusion from the midgut of blacklegged ticks by other bacteria, however, blacklegged tick microbiomes have not been characterized across the entire geographical range of the tick. Here we compare the microbiomes of nymphal blacklegged ticks infected and uninfected with B. burgdorferi collected at three sites across Delaware, a highincidence state for Lyme disease. Infected and uninfected ticks did not differ in alpha diversity of their microbiomes and had similar microbiome compositions after removing B. burgdorferi from the analysis. Tick microbiomes varied among sampling locations in terms of both alpha and beta diversity, demonstrating that the tick microbiome can differ over small spatial scales. We also found at least one tick infected with the emerging pathogen B. miyamotoi. We compare our results to the growing literature of blacklegged tick microbiome studies and suggest that there is currently only limited evidence that tick microbiomes consistently influence the probability of ticks being infected with B. burgdorferi in nature.
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    Berm migration and munitions motion under scaled storm events
    (University of Delaware, 2023) Chapman, Emily
    From the time of the First World War until 1970, unused munitions used to be disposed into the sea. A century later, these unused munitions are still becoming exposed onshore endangering the public and marine life. The migration and exposure of these unused munitions in the nearshore under extreme events is poorly understood. In the United States, coastal regions are home to about 128 million people or nearly 40% of the whole population. Coastal erosion will continue to worsen as storms intensify due to sea level rise driven by climate change. As a result of the erosion of natural beach defenses, infrastructure and populations close to coastal areas will endure flooding. It’s crucial to predict the migration of geomorphological features such as berms in order to understand the erosion processes. ☐ The goal of this study is to take an initial look at how to bring these two topics, berms and munitions, together by studying the processes that drive munitions of variable density to migrate and bury in the berm. A large-scale experiment at Institut national de la recherche scientifique (INRS) in Quebec City, Canada was conducted to study these processes. Mantoloking Beach, NJ and Hurricane Sandy were scaled to replicate the beach profile and wave conditions, respectively. One hundred fifty-five munitions of variable density were deployed for this experiment. Three cases from the experiment were analyzed for this study: a low-forcing case, a high-forcing case, and a longer-period wave case. ☐ In addition to the forcing conditions established during each case, the root mean square wave height was calculated to understand the hydrodynamics for each of the 3 cases. The force going into the swash zone was compared to the accretion and erosion found in the berm. The greater the force going in, the greater the accretion or erosion found in the berm. Less dense munitions had greater net migrations than their denser counterparts. Munitions deployed on the berm crest migrated onshore while the munitions starting on the berm face migrated offshore.
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    The effects of social norm and threat of enforcement on willingness to pay for septic system maintenance
    (University of Delaware, 2023) Crittenden, Abigail
    Failing septic systems are a major contributor to nonpoint source pollution that causes significant environmental and public health damage. While 60 million people in the US are serviced by septic systems there is relatively little research on how septic system owners make decisions regarding the maintenance of their systems. Septic system failure rates in the US have been measured at over 25%(Mohamed 2009; James et al. 2016). Because of these relatively high failure rates, it is particularly important to determine what can be done to encourage homeowners to comply with the needs of their septic systems. This research involves a field experiment to be conducted in 2023 with adult homeowners in Delaware making decisions related to their septic systems. Message treatments will be tested to determine which are most effective at improving homeowners’ willingness to improve the maintenance of the septic systems. Specifically, homeowners submit cost-share bids into an auction for a voucher for a local septic system company to come to their house to pump out their system and conduct an inspection to make sure that it is functioning correctly. This service is valued at approximately $300. Using a between-subject design, the bid behavior in the control group (no message) will be compared to participants who either receive a social norm treatment (75% of homeowners successfully maintain their septic systems) or a threat message (reminding homeowners that a failing septic system can lead to significant fines imposed by the state government). In addition to the experimental design, we will also gather information about homeowners’ baseline knowledge about their septic systems. Based on the results, we will discuss policy options for influencing homeowner behavior and reducing environmental externalities from failing septic systems.
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    Deep ocean circulation changes across the Mid-Pleistocene Transition
    (University of Delaware, 2023) Symes, Emily
    The Mid-Pleistocene Transition (MPT), occurring between ~1250 to 700 Ka (1.25 to 0.7 Ma) marks a fundamental change in Earth’s climate system when the glacial cyclicity of Earth changed from 41 to 100 Kyr. This observed change occurred independently of changes in solar insolation suggesting changing internal climate dynamics might have driven the transition. The South Pacific represents the largest fraction of the Southern Ocean and hence an important target region for studying internal climate dynamics during the MPT. Here, we use sediment core U1541 (54˚13’S, 125˚25’W, 3604 m) collected during the International Ocean Discovery Program (IODP) Expedition 383 to investigate changes in deep ocean circulation and the role of these changes played in solidifying the conditions of the MPT. ☐ In this thesis, we present an authigenic Nd isotope (expressed as εNd) time series from Site U1541 from 1500 – 500 ka. εNd shifts can be interpreted as tracking changes in the mixing proportions of two water mass end members, unradiogenic Atlantic (εNd ~-13.5) and radiogenic Pacific sourced waters (PSW, εNd ~-4). In our record, the proportions of water mass end members fluctuate across climate cycles with glacial cycles reflecting more pacific source water, indicative of weakened Meridional Overturning Circulation (MOC). Across the MPT, we have observed three periods of increased PSW influence at ~1250 ka (MIS 38), ~900 ka (MIS 22), and ~650 ka (MIS 16) interpreted as periods of a more complete breakdown in MOC than other glacials. The ~1250 ka event predates previous research suggesting ~900 ka was the first event of such magnitude. Comparison of our results with the ice volume (using δ18Osw, a direct proxy of ice volume or sea level change) record for ODP 1123 (Elderfield et al., 2012) shows there is a strong correlation between the deep ocean circulation changes observed and global ice volume suggesting there is a mechanistic link between the two variables. We propose this link is a shift in the nature of Antarctic glaciers from terrestrial sourced to glaciomarine. The influx of freshwater into the surrounding oceans from melting glaciomarine glaciers near the Sub-Antarctic front (SAF) has the potential to destabilize the water column producing perturbations in deep ocean circulation of the magnitude observed in our record. The MPT ocean circulation perturbations could have promoted increased drawdown in CO₂ and ice growth to produce the 100 kyr cycles of the MPT.
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    Can leaf area index and plant height measurement improve sensor-based nitrogen recommendations and yield prediction for corn?
    (University of Delaware, 2023) Newswanger, Jeremy
    Nitrogen (N) management remains a significant challenge for corn growers due to the unpredictability and influence of weather conditions, soil properties, and soil biological activity on N transformations in the soil. Innovative technology is needed to assist farmers in making accurate in-season N recommendations to improve N use efficiency (NUE) and reduce the environmental impacts of N losses. Sensor-based aerial imagery can be collected using unmanned aerial vehicles (UAVs) to assist with N management decisions and help improve NUE. However, there are limitations associated with vegetative indices from aerial imagery in guiding N decisions because the indices can reach a “saturation point” once the corn canopy closes. We hypothesized that adding leaf area index (LAI) data and plant height measurements could improve our understanding of how plant biomass is related to the vegetative indices for predicting corn N response by adding in a third dimension to the analysis. Corn N rate trials were established in Delaware, Maryland, and Pennsylvania (0, 30, 60, 90, 120, and 150% of university-based N rates; DE and MD did not have a 0 N rate) and four replicates in a randomized complete block design. In-season UAV-multispectral imagery, LAI, and plant height measurements were obtained at the V6 and R2 corn growth stages. Plant height was also derived from UAV imagery using structure from motion (UAV-SFM) using Pix4D photogrammetry software. Drone-derived vegetative indices, UAV-SFM, and LAI were used to predict the sidedress N rates and grain yields, which were compared to yield data at harvest. ☐ The PA and DE sites exhibited a yield response to the N rate; however, the MD site was non-responsive. At the PA location, the N rate at the yield plateau occurred at 166 kg ha-1, with an in-season sensor-based N recommendation of 159 kg ha-1 and an economic optimum N rate (EONR) of 180 kg ha-1. At the DE site, the N rate at the yield plateau was 315 kg ha-1, with rates of 81 and 219 kg ha-1 for the in-season recommendation and EONR, respectively. We saw a significant LAI response to N rate only at the PA site (P-value = .0027), whereas there was a significant plant height response to N rate at the DE site (P-value = .0029). The in-field plant height measurements and the UAV-SFM did not correlate 1:1 across all three sites and relationships were inconsistent across sites. As such, UAV-SFM derived plant height was deemed as an unsuitable proxy for the in-field plant height measurements across sites. The normalized difference red edge index (NDRE) was the best predictor of corn grain yield at the R2 stage (r2 = .951, P-value < .0001); the addition of LAI and plant height to the predictive model marginally improved upon the yield prediction of NDRE (r2 = .9621 and .9708, respectively). Therefore, NDRE alone is still the recommended vegetative index for predicting corn yield. Further studies are needed to explore the contribution of biomass estimates on in-season N recommendations and yield prediction.
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    Implementation of circFISH to quantify the expression and cellular localization of circNFIX in cerebral palsy
    (University of Delaware, 2023) Hoque, Parsa Sanjana Binte
    Cerebral Palsy (CP) is the most common disability of motor function in children, characterized by impairments in movement, normal activity, and posture. Children with spastic CP are affected by muscle tissue defects, including reduced cross-sectional area, decreased muscle mass and volume, increased sarcomere length, disrupted neuromuscular junctions (NMJ) and reduced satellite-cell (SC) number. However, the underlying mechanisms contributing to such muscle alterations remain elusive. Regulatory non`-coding RNAs called circular RNAs (circRNAs) have been studied to play important roles in different physiological processes and dysregulation of circRNAs have been associated with different cancers and many other pathologies. Recently circNFIX has been observed to be a regulatory factor in myogenic differentiation, showing differential expression in various stages of myogenesis, and can be potentially characterized as a key player in myogenic alterations in CP. This led to the hypothesis that circNFIX might be a key regulator in CP associated musculoskeletal development. In this study, circFISH was implemented to simultaneously image circNFIX and its linear isoform, linNFIX in SC-MBs and differentiated myotubes of spastic CP patients and healthy controls. Significant differences in circNFIX counts and cellular localization pattern in SC-MBs and myotubes between CP and healthy controls were observed. Additionally, RNAse R treatment resulted in significant reduction in linNFIX levels with minimal change in circNFIX levels. CircNFIX knockdown SCs showed significant reduction in circNFIX counts. Significant differences in nuclear and cytoplasmic distribution of circNFIX in both proliferating and differentiated cells point towards regulatory functions of circNFIX that might be at play. The results further reinforce the potential involvement of circNFIX in the regulation of CP muscles. Further investigation of circNFIX with respect to its involvement in muscle development and cellular functions can aid in shedding light on the underlying mechanisms of CP associated muscle defects.
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    The Lumbee tribe & narratives of intergenerational coping with hazards
    (University of Delaware, 2023) Dyck, Sydney
    The Lumbee Tribe is in the state of North Carolina on the eastern coast of the United States of America. It is home to a distinct population of Indigenous people who have faced multiple disasters, mainly flooding due to hurricanes. The effects of disasters compound with adverse factors within the community, such as a lack of housing support, healthcare access, and governmental resources. Since the United States federal government does not recognize the Lumbee Tribe, the tribe is federally unsupported in times of disaster, such as during repeat flooding and throughout the COVID-19 pandemic. In this research project, I examined these aspects through the lens of intergenerational trauma. First, I gathered data on the impacts of disasters and colonialism on the prevalence of intergenerational trauma among the population through qualitative interviews with Lumbee Tribal members and community stakeholders. Amidst data collection, I conducted fieldwork mainly in the towns of Lumberton and Pembroke. I used an inductive, open-coding approach to identify themes within the data. While examining the adverse effects of these systemic challenges, I focused on the insight into the Lumbee community's capacity for self-sufficiency and resilience, specifically to their cultural connections and ability to adapt and support one another. This data represents aspects of the lived experiences of the Lumbee people regarding disasters, colonialism, and intergenerational trauma and has the potential to call attention to tangible resources and discussions of sovereignty within the community. ☐ Keywords: disasters, intergenerational trauma, Indigenous people, and COVID-19
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    Using an unoccupied aerial vehicle to study Clapper Rail demography in the salt marshes of coastal Delaware, USA
    (University of Delaware, 2023) Glasko, Hailey E
    Unoccupied Aerial Vehicles (UAVs) provide novel methods to study wildlife in a potentially more efficient manner than traditional methods. UAV methods can be particularly useful for studying secretive marsh birds, as marsh accessibility varies greatly, and UAVs can provide access to otherwise inaccessible areas. I used a UAV equipped with a thermal imaging camera to search for Clapper Rail (Rallus crepitans) and other tidal marsh birds nesting in salt marshes on the Delaware coast, USA in 2021 - 2022. I conducted traditional ground-based systematic nest searches with a field crew at two intensive sites with different levels of accessibility. I piloted the UAV equipped with a thermal imaging camera over the same two sites and compared the number of nests detected between ground surveys and the thermal camera deployed on the UAV. I completed thermal imaging flights before sunrise for the greatest thermal contrast between the nests and the marsh vegetation. I ground-truthed suspected nest points after each flight to confirm that the point was a nest and determine which marsh bird species each nest belonged to, as distinguishing species from the thermal imaging alone is difficult. I found that the UAV detected fewer Clapper Rail nests than ground surveys in the accessible sites (17 and 28 nests respectively) and the UAV detected more Clapper Rail nests than the ground surveys where access was low (16 and 5 nests respectively). I also detected nests of tidal marsh passerines like Seaside Sparrow (Ammospiza maritima), Marsh Wren (Cistothorus palustris), and Red-winged Blackbird (Agelaius phoeniceus), indicating that thermal imaging flights with UAVs could be used to document smaller species breeding in tidal marshes. Using data collected in 2021 and 2022, I compared the efficiency of each method of finding marsh bird nests (ground surveys vs UAV) to determine method efficiency. I found that the UAV covered more area than the systematic nest searches, but on average took more time than the systematic nest searches. I also conducted photogrammetric surveys of the vegetation at all study sites to gain insight into the marsh vegetation characteristics at and around Clapper Rail nests. I compared these characteristics at nest points and random points to determine if a difference could be detected. I found that Clapper Rail nest sites contained 60% more low marsh, 40% less high marsh, and 20% less upland than the random points. Given the current conservation challenge associated with maintaining tidal marsh breeding birds during rapid increases in sea-levels, a non-invasive and rapid survey method that can efficiently document and quantify breeding and vegetation characteristics can aid in prioritizing marshes for conservation, management, or restoration.