Master's Theses (Fall 2009 to Present)

Permanent URI for this collection

New submissions to the University of Delaware Master's Theses collection are added as they are released by the Graduate College. The Graduate College 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, 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 (now known as the Longwood Fellows Program) submitted between 1970 - 2004 are available online.


More information is available at Dissertations & Theses.

Browse

Recent Submissions

Now showing 1 - 20 of 2334
  • Item
    The impact of booking lead time on hotel customers' willingness to pay for more lenient cancellation terms
    (University of Delaware, 2024) Gong, Yuqing
    In the post-pandemic world, travelers have become acutely aware of the risks and uncertainties related to future travel. Lenient cancellation terms are regarded as an effective means to alleviate travelers’ worries and encourage them to make reservations. However, more lenient cancellation terms can negatively impact hotel revenue. Previous research found that travelers are willing to pay for lenient cancellation terms and that the value decreases as the check-in date approaches, but it did not distinguish between different types of travelers. This study addresses that gap by separating leisure and business travelers and varying the levels of cancellation terms. The study employs conjoint analysis and finds that leisure travelers are more willing to pay for more lenient cancellation terms further from the check-in date, with a decreasing value within 30 days of check-in. Beyond 30 days, the willingness to pay decreases. For business travelers, WTP generally remains stable from 60 days ahead to 7 days ahead, except for a drop 3 days before the check-in date. These findings partly differ from the hypothesis that the willingness to pay will decrease as the check-in date approaches for leisure travelers and remain stable for business travelers. The reason may be relative to customers’ purchase behavior that leisure travelers prefer to search for the best deal until the last minute, while business travelers prioritize meeting their travel requirements. These findings will provide valuable insights for the hotel revenue practice.
  • Item
    The recovery of denitrification potential after thin layer sediment placement: Does sediment composition influence functional recovery?
    (University of Delaware, 2024) Leaseburg, Emma Elizabeth
    Sediment thin layer placement (TLP) applications are used to mitigate losses in coastal wetland cover caused by anthropogenic and climate-related pressures. Although biophysical characteristics such as vegetation and hydrology can recover quickly after sediment placements, biogeochemical processes like denitrification may take much longer to reach equivalence with natural marsh systems. As a result, the use of biochar, a C-rich material formed from the pyrolysis of organic matter, as a sediment amendment to improve functional recovery within placed sediments has gained recent interest. To understand how sediment N-removal processes recover after sediment placement restorations, I conducted a 1.5-year manipulative field study which implemented small scale TLPs within a Delaware tidal marsh. Two sediment treatments were applied within 1m2 wooden frames overtop of the marsh surface: (1) unamended sediments collected from a nearby tidal creek and (2) biochar amended sediments which consisted of 10% (v/v) P. australis biochar and creek sediments. These sediment treatments were applied to a native S. alterniflora zone and adjacent invasive P. australis zone and subsequently sampled seasonally beginning 1 year after sediment placement. Sediment cores and porewater samples were taken across the growing season to measure denitrification potentials, sediment and porewater nutrients, and functional gene abundances (nirS and nirK). ☐ The recovery of sediment denitrification potential was influenced primarily by vegetation recovery after sediment placement rather than by the presence or absence of biochar in the sediment applied. Overall, denitrification potentials were greatest in the S. alterniflora zone compared to the adjacent P. australis zone. Within each zone, denitrification potentials were equivalent between biochar amended and unamended sediment treatments. When compared against denitrification potentials from nearby undisturbed reference sediments, sediment treatments within the S. alterniflora zone possessed comparable denitrification potentials by the end of the experiment. In contrast, denitrification potentials within the P. australis sediment treatments lagged significantly behind those in reference sediments. Differences in vegetation recovery between the two vegetation zones after sediment placement likely explain the lagging denitrification potentials in the P. australis plots as S. alterniflora reestablished much quicker (after 16 months) than P. australis, highlighting the importance of plant-soil interactions which strongly influence sediment N removal processes. ☐ Biochar amendments did not improve denitrification potentials in either vegetation zone possibly because the influence of biochar was masked by the greater influence of vegetation establishment. The P. australis biochar used in this study may not have possessed suitable physicochemical properties capable of enhancing denitrification as seen in other studies. It is possible that P. australis biochar (or a biochar of a different feedstock) produced under optimal conditions may have provided the enhanced N removal ecosystem service, however, in this study, both biochar amended and unamended sediments possessed equivalent denitrification potentials to the reference S. alterniflora marsh. ☐ This thesis demonstrates that vegetation establishment after TLP is a significant factor controlling the return of marsh ecosystem functional capacity. While biochar has been utilized in a variety of environments to improve N-removal processes, its application in our TLP experiments was unproductive. Additional studies are needed to confirm biochar’s influence on sediment biogeochemical processes in tidal marshes. For example, biochar production conditions and parent feedstock material have a significant influence on the resulting structure and thus function of biochar in the environment. The influence of these parameters should be evaluated in future laboratory and field studies to identify what biochar properties are most beneficial for promoting denitrification. Spatial variability must also be constrained as the results of this study are most applicable for the Mid-Atlantic region and for biochar amendments within thin (~5cm) sediment placements. Optimal dosages for biochar amendments must also be developed as only one dose (10% v/v) was assessed in the present study. While this thesis provides tidal marsh managers with information that they may leverage to restore N-removal services within their marsh systems, much work is still needed to understand if and how biochar can be utilized effectively within tidal marsh restorations.
  • Item
    Simulation of tsunami-induced sediment transport and coastal morphology change
    (University of Delaware, 2024) Malone, Christopher J.
    Throughout history, tsunamis have consistently impacted the United States, affecting both the East and West Coasts. The National Tsunami Hazard Mitigation Program (NTHMP) currently develops maximum potential tsunami inundation maps for the U.S. East Coast (USEC) utilizing a range of tsunami sources. However, these maps do not yet account for the impact of sediment transport and changes in coastal morphology, due to the incomplete understanding and validation of these factors. The USEC features sandy shorelines and is largely shielded by barrier islands protecting inland areas. Previous simulations, which excluded sediment transport and morphological change, indicate that tsunami waves could overtop these barrier islands and sandy coasts, posing a threat to the inundated areas and mainland. Historical tsunamis have demonstrated that such inundation can cause significant erosion and deposition further inland and offshore, driven by sediment dynamics, resulting in altered landforms and damage to harbors and coastal infrastructure. ☐ This research aims to advance understanding of the extent of hazards and sediment transport processes from past tsunamis and enhance predictions for future events by improving an existing sediment transport and morphology model. This model integrates sediment transport processes into the Boussinesq hydrodynamic model, FUNWAVE-TVD. Improvements include optimizing the hindered settling coefficient, refining the settling velocity equation, incorporating bed load transport, and enhancing the interaction between hydrodynamics and sediment transport in flows with high sediment concentrations. This upgraded model has been validated against wave flume experiments that examined hydrodynamics, sediment transport, and morphological changes under varying conditions of wave forms and land slopes. It has also been validated against observations of tsunami-induced morphological changes during the 2011 Tohoku event. The findings demonstrate that the new model effectively replicates observed hydrodynamics and patterns of erosion and deposition across all tested scenarios, thereby improving hazard assessment capabilities of the model under diverse hydrological and bathymetric conditions. Following successful experimental validation, the model was applied to Suffolk County, NY, a low-lying coastal community along the USEC protected by a barrier island. Analysis using four potential tsunami sources revealed that tsunamis can cause significant morphological changes to the barrier island and modify hazard extents. These results underscore the importance of including sediment transport models coupled with hydrodynamic analyses in future tsunami risk assessments.
  • Item
    Comparative analysis reveals host-dependent diversity in 16 novel Bradyrhizobium bacteriophages
    (University of Delaware, 2024) Morgese, Emily A.
    Bacteriophages, or phages for short, are a group of viruses that infect bacteria. They are the most abundant biological entity on the planet, outnumbering their bacterial hosts 10-fold in some ecosystems. Phages shape ecosystems by controlling host abundance, driving host evolution via horizontal gene transfer and aiding in the cycling of nutrients. Bradyrhizobium is an important genus of bacteria, due to the ability of some species to nodulate the roots of soybean (Glycine max), where it supplies its host with a direct source of biologically fixed nitrogen. Optimizing this symbiosis can reduce or eliminate the use of polluting synthetic nitrogen fertilizers, making agriculture more sustainable and environmentally friendly. The presence of phages in soil ecosystems likely impacts the symbiotic relationship between soybean and its Bradyrhizobium partners by altering competition between strains of Bradyrhizobium for root nodulation sites. Studying these phages could eventually help farmers harness their abilities to control nodulation competition to promote nodulation and nitrogen fixation by more symbiotically effective strains and thereby sustainably enhance soybean yields. ☐ My research characterized sixteen virulent phages isolated from ten Delaware soils that infect Bradyrhizobium strains symbiotic with soybean. These phages were examined for their host range and morphology, and by full genome DNA sequencing and analysis. These analyses revealed host-specific diversity in phage morphotypes and genomic composition and identified four distinct and novel phage species. All phages isolated against B. elkanii, regardless of the bacterial strain against which they were isolated, had very similar morphologies and host ranges and were grouped together into one species based on their nucleotide identity. The phages isolated against B. diazoefficiens were more diverse and, based on nucleotide identity, represented three unique species of phage. The B. elkanii phages studied could be of future interest due to their broad host ranges and ability to lyse less symbiotically efficient Bradyrhizobium strains, therefore making these phages potential candidates for enhancing soybean yield by controlling nodulation in favor of highly effective N-fixers.
  • Item
    The scaling of motor output in rapid isometric contractions and dynamic agility sub-movements
    (University of Delaware, 2024) Calabrese, Christopher
    This study investigated the rates of force production and muscle activity in young adults during both isometric and dynamic conditions, aiming to extend the quantification of rate-scaling to whole-body agility-related movements. Twenty healthy participants, free of neurological disorder and musculoskeletal injury, and equally divided by gender were recruited. Participants performed various tasks involving isometric force pulses and dynamic agility sub-movements while muscle activity was recorded via electromyography (EMG) from the lateral gastrocnemius, tibialis anterior, soleus, and peroneus longus. ☐ In the isometric force pulse protocol, the dominant foot of the subjects was secured in a custom force measuring device, and maximal voluntary contractions (MVCs) were recorded for normalization. Participants then performed rapid force pulses at varying percentages of their own MVC, with five sets of twenty pulses each. Dynamic tasks included lateral stepping, forward and backward stops, and a cutting task, all performed at three self-selected intensities. Ground reaction forces and EMG signals were synchronized and collected. ☐ Results showed a significant positive relationship between peak rate of force development (RFD) and peak force across all tasks, with R² values ranging from 0.517 to 0.870. Linear regression models quantified these relationships, and all tasks demonstrated significant rate-scaling (p < 0.001). EMG measures of excitation were significantly associated with peak RFD, indicating modulation of neuromuscular activity. While correlations between task-specific RFD scaling factors and overall agility assessed by the Agility T-Test were not statistically significant, trends suggested moderate associations. ☐ This research provides evidence of rate-scaling from ground reaction forces during simple change-of-direction tasks and highlights the modulation of neuromuscular excitation in response to varying force demands. These findings have implications for sports science, rehabilitation, and training, suggesting potential for dynamic task studies in at-risk populations to evaluate neuromuscular control and intervention efficacy.
  • Item
    The efficacy of apical-out chicken enteroids as a model for screening eubiotics
    (University of Delaware, 2024) Mann, Peter
    Antibiotic restrictions in food animal production have led to the need for alternatives to achieve comparable effects. Study of feed additives to replace antibiotics, termed eubiotics, are often studied in vivo. In vitro models however have seen interest due to their lower cost and higher throughput while still mimicking the intestine in certain aspects. A recently developed apical-out chicken enteroids model was evaluated for its ability to serve as a functional representative of the in vivo chicken intestine for purposes of studying tight junction barrier permeability, inflammatory response, and oxidative stress. In addition, five eubiotics of monobutyrin, calcium butyrate, monolaurin, carvacrol, and curcumin were studied through these aspects of the intestine to identify their potential as beneficiaries to the broiler intestine. Enteroids were isolated from Cobb500 broiler chicks at embryonic age 18 with enteroids then transferred to T75 flasks for 24 hours at 37.5°C at 5% CO2. On day 1 of culture enteroids were transferred to well plates and then media was changed along with eubiotic addition on day 2. After 24-hour incubation, enteroids were challenged with either ethylenediaminetetraacetic acid (EDTA), lipopolysaccharides (LPS), or menadione. EDTA and LPS additions were followed by use of fluorescein isothiocyanate-dextran (FD4) to determine epithelial integrity and menadione followed by CellRox to identify reactive oxygen species (ROS) presence. PrestoBlue reagent was also utilized as a measurement of viability. Gene expression was determined through isolation of RNA from treated enteroids with and without eubiotic and/or challenge followed by cDNA preparation and evaluation through RT-PCR. Enteroids were found to exhibit peak viability starting at day 3 of culture, with prior days necessary to achieve optimal development. Expression of selected markers for stem cells, tight junction, and inflammation had significant changes, with stem cell expression decreasing and tight junction and inflammation expression increasing over time. Both LPS and menadione challenges resulted in significant increases in FD4 permeability and ROS generation, respectively. LPS additionally significantly reduced the mRNA expression of tight junction genes in addition to significantly increasing inflammatory cytokine expression, while menadione significantly decreased antioxidant gene expression. All tested eubiotics showed a decrease in enteroid integrity as dosages increased in concentration, with viability determined by PrestoBlue either showing increases or no change. Monobutyrin, calcium butyrate, and monolaurin each significantly decreased epithelial permeability to FD4, with all having beneficial impacts towards tight junction expression in addition to monobutyrin and calcium butyrate towards preventing LPS induced inflammation. Carvacrol and curcumin each reduced ROS generation induced by menadione, as well as increased expression of select antioxidant enzymes. These results together suggest that this apical-out chicken enteroids model sufficiently models tight junction capacity, inflammation, and oxidative stress in an in vitro setting. Additionally, monolaurin effectively protects the epithelial integrity of the enteroids along with monobutyrin and calcium butyrate achieving the same in addition to reducing inflammatory status under challenge. Furthermore, carvacrol and curcumin each alleviate oxidate stress in the face of challenge conditions.
  • Item
    Developing stable plasmid transformation techniques for anaerobic gut fungi
    (University of Delaware, 2024) Khim, Kunwoo
    Lignocellulosic feedstock degradation is a critical process in acquiring sustainable fuel and high-value chemicals. Anaerobic gut fungi (AGF), microorganisms residing in herbivore guts, have promising potential in the lignocellulose biodegradation process, because of their distinctive plant carbohydrate binding and biomass degradation ability through multiple carbohydrate-activating enzymes and their assembly into fungal cellulosomes that synergistically enhance biodegradation rates. Although there has been a successful attempt to develop a genetic engineering toolkit for transforming gene cassettes into an AGF system, CAZyme expression through this system was never investigated, and it is also transient, relying on periodic DNA dosing. ☐ Hence, we attempted to improve this pre-developed genetic engineering technique for AGF. First, we tried expressing CAZymes through this system. At the same time, we investigated candidate sequences that would support autonomous replication of gene cassette on AGF, ranging from yeast 2-micron plasmid, Neocallimastix giraffe GF-Ma genomic DNA library, and random AT sequence library. Although we were not fully able to confirm the expression of CAZymes through the current AGF transformation platform, we confirmed that out of 3 candidate sequences, yeast 2-micron plasmid exhibits longer and higher expression of proteins compared to the current transformation platform for AGF, opening the possibility for further research.
  • Item
    Rhythm & roots: Black and insurgent ecologies of orisha music
    (University of Delaware, 2024) Graham, Chad Kehinde
    Lukumi people reconstructed their ritual music tradition from Yorùbáland in Cuba through the improvisation of their ecology or ecophilosophy. Although Cuba presented a set of environment conditions different from those of the Bight of Benin and Spanish colonists tried to impose a discordant relationship between them with the land, Yorùbá people developed a harmonic and improvisational relationship with the environment on their own terms. Through historical analysis, content analysis of orisha songs and material analysis of the accompanying instruments, this work considers what and who the environment was to orisha devotees. They reaffirmed their commitment to the natural world through the performance of their ritual music, in opposition to the terms of order that produced them to property, thus revealing a cyclical relationship between the material world and sound. That relationship was essential for the reconstitution of the instruments, rhythms and sounds which their ways of knowing required.
  • Item
    Verifiable encrypted computations
    (University of Delaware, 2024) Ahmed, Omar Atef Abdelaleem
    The ubiquitous usage of cloud computing has revolutionized the way individuals and organizations access and process their data. By delivering numerous services on the internet, cloud computing allows users to store vast amounts of data and perform heavy computations on them without the need to manage complex local computing resources. This innovative technology offers scalable, cost-efficient, and flexible access to storage, computing resources, and applications. Moreover, cloud computing allows businesses to deliver their products and services easily and effortlessly across the globe. ☐ Given that widespread usage of cloud computing and the instrumental development to the world, cloud servers are an alluring target for cyber-attackers who seek to eavesdrop on or steal users’ sensitive data. The providers of cloud computing are also another threat, where malicious cloud providers can access users’ confidential information for their own benefit, such as targeting users with advertisements. ☐ One solution to these concerns is using cryptography. Cryptography is a way to protect our data by transforming them into unreadable form that prevents unauthorized entities from accessing our data. It works well when users want to protect their data when stored on remote servers or during communication. However, this traditional cryptography falls short when we need to perform computations on the data. In this case, a user will have to reveal his encrypted data to the cloud provider to allow performing the computations on them. ☐ To address the shortcomings of traditional cryptography. People tend to use another form of cryptography called Fully Homomorphic Encryption (FHE). FHE allows performing computations on encrypted data, without the need to reveal them. In this thesis, we propose frameworks that enable non-experienced users to seamlessly use homomorphic encryption techniques to securely outsource computations to untrusted cloud providers. Furthermore, we complement this by adding the integrity component, Zero-Knowledge Protocols, so that users can verify the correctness of the computations performed, thus protecting against cheating providers. Moreover, this thesis investigates the design of new optimized functional units to allow users to perform non-linear operations on encrypted data.
  • Item
    The impact of high dietary glucose on amyloid-beta proteotoxicity in Caenorhabditis elegans
    (University of Delaware, 2024) Kerslake, Emylee Ann
    Alzheimer’s disease (AD) is the leading neurodegenerative disorder worldwide, with an estimated 60 million individuals currently afflicted. Pathological features of this debilitating condition include amyloid-beta (Aβ) accumulation, bioenergetic defects, increased oxidative stress, and impaired glucose metabolism. Since there is currently no disease-modifying treatment for AD, it is essential to understand how modifiable risk factors such as diet impact disease onset and progression. It is difficult to determine the impact of specific nutrients in humans due to complex diet, organismal complexity, genetic diversity, and indirect effects of the gut microbiome. Individuals with abnormal blood sugar levels and glucose utilization are at greater risk for AD, likely because glucose is required to fuel neuronal function. Yet we lack an understanding of how the interplay between glucose and other macro/micronutrient availability impacts brain health. To investigate the effect of excess sugar on amyloid-beta proteotoxicity, I used a transgenic strain of C. elegans expressing the toxic human Aβ1-42 peptide in the body wall muscles, which produces AD-like pathogenic features such as a time-dependent paralysis that mimics progression of the disease, reduced ATP levels, and increased reactive oxygen species. We discovered that glucose supplementation accelerated paralysis in Aβ animals that consumed OP50 E. coli yet had no effect on worms fed HB101 E. coli. While vitamin B12 can protect against Aβ-induced proteotoxicity, B12 is not the factor in the HB101 diet that nullifies the toxic effects of excess glucose levels. To determine how this diet was protective we performed RNA-Seq and observed downregulation of the predicted facilitated glucose transporter F14E5.1 (fgt-2) in animals fed HB101. Loss of fgt-2 slowed Aβ-induced paralysis, alleviated bioenergetic defects, and reduced ROS accumulation in Aβ animals fed OP50. In the presence of excess glucose, the fgt-2(tm3206) mutation abrogated accelerated Aβ-induced paralysis, resulting in a similar time to paralysis regardless of the diet consumed. These findings suggest that fgt-2 impacts Aβ-induced proteotoxicity, potentially by modulating glucose metabolism via glucose transporter availability. However, fgt-2 is not the primary glucose transporter in C. elegans, and its function is not entirely known. In order to further investigate the significance of glycolytic transport in Aβ-induced proteotoxicity, I crossed the Aβ transgene with fgt-1, the primary glucose transporter. Loss of fgt-1 resulted in an accelerated time to paralysis, suggesting the importance of the role glucose import plays. Loss of both fgt-1 and fgt-2 produces a similar result to the fgt-1 single mutant, indicating that either the protective effects of fgt-2 rely on fgt-1 or the function of the primary glucose transporter is crucial regardless of protection elsewhere. Overall, my research highlights the importance of glycolytic transport for overall well-being while demonstrating the impact excess sugar intake has on disease pathologies.
  • Item
    Reducing social pressure in spatially coordinated voluntary home buyout programs using a connected bidding mechanism
    (University of Delaware, 2024) Taylor, Laura
    Coastal and non-coastal homeowners face an increasing number of challenges related to nuisance flooding events due to sea level rise and high precipitation events. Homeowners exposed to flood risk have options aiming to protect (by building preventative structures such as levees or beach nourishment), accommodate (by elevating structures or providing home flood prevention), or to participate in managed retreat (where homes are bought by the government and converted to green space in perpetuity). Managed retreat in the form of voluntary buyouts can be a long-term adaptation strategy that allows individuals to purposely relocate without the stress and expenses of being stuck in areas of repeated and severe flooding while trying to sell their homes on their own. A challenge of current voluntary buyout programs, the majority of which are partly funded by the Federal Emergency Management Agency (FEMA), ignores spatial dependencies in both homeowner welfare (as many homeowners suffer loss of community when their neighbors move away) and the potential local benefits from creating large, connected open spaces (that serve as flood buffers and reduce infrastructure and cost of utilities to the area). One option that has been used in the land conservation context as well as in a small number of cases related to coastal buyouts uses a financial incentive on top of a home’s fair market value (FMV) to increase acceptance rates (Dineva et al. 2023). However, this can create pressure when encouraging coordinated actions between neighbors where home values are heterogeneous and some homeowners either categorically do not want to move or place a higher value on their home than the incentive can cover. Group action commonly uses an “all-or-nothing” approach where the incentive being implemented is conditional on everyone within the group participating. This project seeks to experimentally test a novel group-based “connected” bidding mechanism to encourage spatial coordination while minimizing group pressure. The experiment uses an unframed design with heterogeneous costs of tokens as a proxy for home values. Student participants are randomly assigned to a group of four and given information on the assessed fair market value (“FMV”) and cost of a token, which is heterogeneous across participants. We test three within-subject treatments: control (individual FMV offers); Agglomeration Bonus (AB); and Connected Bidding (CB). In the AB treatment, participants are given the opportunity to accept an offer 10% above their FMV conditional on everyone else in their group accepting. The CB treatment instead allows participants to provide an anonymous bid that they would need to give up their token, which is then summed with the other three group members’ bids to form a connected bid, where the lowest connected bids will be accepted to be implemented until the predetermined budget is exhausted. Sessions are randomly assigned which treatment to start with, and each AB and CB treatment includes a two-minute chat box with group members, as well as a fallback option where participants can give up their token for FMV to reduce group pressure. Our results do not support our central hypothesis that the CB treatment would be more efficient at generating buyouts with heterogeneity and decrease pressure and increase fairness perceptions with group action. We attribute this absence of findings to a combination of participant confusion or inattention, and a diffusion of social pressure due to too low stakes in our setting and hedging of earnings across rounds.
  • Item
    Effects of climate change and food waste policy information on students' attitudes and behavior
    (University of Delaware, 2024) Rahman, Md Abedur
    Every year in the US, 30 to 40 percent of edible food is wasted, generating 4% of overall greenhouse gas (GHG) emissions. It is estimated that university and college students, particularly those living on campus and using dining facilities, generate approximately 624,371 tons of food waste (FW) annually, contributing to GHG emissions. In response to the economic and climate change impacts of FW, the US government in 2015 announced a FW-reduction goal to cut FW by 50% by 2030. Using before and after surveys, this study investigated changes in the University of Delaware (UD) students’ perceptions of FW generation in dining halls, homes, and restaurants following exposure to information on either the climate change impacts of FW or government FW policy. Using non-parametric Wilcoxon signed-rank tests and Ordinary Least Squares (OLS) regression models, the study assessed changes in perception of students’ self and others’ FW generation and factors affecting those perceptions. Following the government FW policy intervention, students' perception of their own and others’ FW generation decreased in the university setting, and the climate change informational intervention reduced students’ perception of others’ FW generation at home. A decrease in the perception of others’ food waste generation indicates how people expect others to react to the same information. Along with changes in perception of FW generation, the study also revealed changes in students’ FW-related attitudes and knowledge of the climate change impacts of FW, due to the survey and informational interventions. However, the information interventions did not increase students’ willingness to accept (WTA) FW reduction initiatives in the dining halls. OLS models revealed varying impacts of demographic variables such as gender, age, income, membership of environmental organizations, and dietary habits on students’ perception of self and others’ FW generation in different settings. It also revealed the impacts of environmental concerns and the perception of the responsibility of dining halls on students' self and others’ FW generation perception. The OLS model revealed that only female students and students from urban communities significantly reduced their perceived FW generation at home after the informational interventions. Results indicate the effectiveness of climate change impacts and government FW policy intervention in FW reduction among university students. As those interventions affected students’ knowledge, behavior, and perception of FW generation- they could be used to target FW reduction among the students, particularly in the university setting.
  • Item
    Suitability models for floating offshore wind farms along the U.S. Mid-Atlantic margin
    (University of Delaware, 2024) Rodenbach, Elizabeth
    The Bureau of Ocean Energy Management, in support of the United States’ (U.S.) national energy goals, designated eight draft wind energy areas (WEAs) along the Mid-Atlantic continental margin of the U.S. Draft WEAs E-1, E-2, and F are all deepwater sites (>1,500 meters), requiring the use of floating offshore wind technologies. This thesis investigates the suitability of deploying floating wind technologies in draft WEAs E-1, E-2, and F, focusing on the potential impacts of geohazards in the region. Geological data of the slope gradient, seafloor complexity, and sediment type were analyzed via ArcGIS Pro to produce five weighted overlay suitability analysis models. The results suggest that all three draft WEAs are suitable locations for the deployment of floating offshore wind turbines. WEA E-1 is the most complex and contains the highest slope gradients (up to 35°), but shows minimal risk in the southern half of the area. WEA E-2 is the opposite and has a much more suitable northern half, due to the massive Washington Canyon that extends out to the WEA’s southwestern border. WEA F, though a very small area, is an optimal location with no submarine canyons in close proximity and the lowest slope gradients among the WEAs. These findings, though indicative of feasible locations for floating turbines, are meant to shed light on the potential risks of developing on the Mid- Atlantic continental slope and rise. Further geological surveying is needed in the region prior to any development, as seabed features change over time and the likelihood of slope failure varies.
  • Item
    Gait synthesis and controller design for dynamic 3D bipedal robot walking
    (University of Delaware, 2024) Thanki, Dhruv Ashwinkumar
    The advancement of humanoid robots continues to open new avenues for automation and efficiency across various sectors. This thesis documents the development of dynamic gait synthesis and controller design for a 3D bipedal robot, focused on achieving stable and efficient locomotion. A detailed examination of a floating-base hybrid dynamic model demonstrates how it encapsulates the complex interactions between the robot’s multi-body system and the environment. Utilizing advanced control strategies, including Hybrid Zero Dynamics (HZD) and trajectory optimization frameworks, the study generates an offline library of optimized gaits. This library is proposed to assist in motion planning within clustered spaces by enabling the switching between gaits as needed. Results confirm the robot’s capability to maintain stability and adapt to different terrains, underscoring its applicability in assistive technologies and industrial automation. The research underlines the potential of humanoid robots to enhance operational efficacy in complex real-world settings, promoting their integration into human-centric environments.
  • Item
    Evaluating the feasibility of a lateral-flow assay for HIV Nef
    (University of Delaware, 2024) Singh, Ashika Shyam
    Human Immunodeficiency Virus (HIV) pathology deals with lymph nodes, and a delay in anti-retroviral therapy initiation leads to progressive immune system failure. Accurate and prompt diagnosis is critical for initiating effective treatment and improved clinical outcomes. Current HIV detection assays utilize transient biomarkers, resulting in a narrow detection window period. The thesis discusses the development of a competitive lateral flow immunoassay (LFA) for detecting HIV protein Nef, a potentially stable biomarker. Leveraging 40 nm gold nanoparticles as the optical sensors, the critical component of the assay, i.e. the effective concentration of Nef immobilized on the test zone and the strength of the detecting conjugates were optimized. The performance and repeatability of the assay were evaluated with an adequate sample size, determined by power analysis. The mean detection limit for different assay batches was determined to be 12.52 ± 0.29 ng/mL. The rigorous assessment demonstrated a 95% confidence level, i.e., a large effect size was observed when negative and positive test results were compared from the same batch. The repeatability analysis confirms the consistency of the LFA concerning the detection limit within the batch. However, the inter-assay repeatability of the current system is poor. The study is the first report evaluating the feasibility of developing a competitive LFA for detecting Nef. It aims to highlight the potential of LFA for detecting a stable HIV protein as an initial mode of assessment for high-risk individuals and for monitoring the infection. While further refinements are necessary to enhance clinical suitability, this research lays the groundwork for innovative advancements in HIV screening and monitoring.
  • Item
    Native parasitoid wasps in the genus Anastatus (Hymenoptera: Eupelmidae) as a potential biological control agent for the invasive spotted lanternfly (Lycorma delicatula)
    (University of Delaware, 2024) Williams, Cat
    This project sought to understand the role native Anastatus (Hymenoptera: Eupelmidae) can play in the management of the invasive spotted lanternfly (Lycorma delicatula, Hemiptera: Fulgoridae) through two objectives. First, spotted lanternfly egg masses were collected opportunistically and reared to obtain parasitoids for rearing and use in behavioral assays. A total of 591 egg masses were collected in 2023 with 52 Anastatus reduvii emerging from these egg masses. The emergence rates of parasitoids from parasitized singly collected egg masses ranged from 1.45% to 7.69%, with an average of 3.45%. Seven generations were reared on Halyomorpha halys (Hemiptera: Pentatomidae) eggs after the initial parasitoid emergences, totaling 2,241 parasitoids in colony. The second objective sought to assess the behavioral responses of reared Anastatus reduvii to spotted lanternfly and Poblicia fuliginosa (Hemiptera: Fulgoridae) egg masses and egg mass coatings through behavior tracking and observational behavior coding. No significant differences were found for distance traveled, duration in the arena, angular velocity, or velocity between treatments. The only behavior to demonstrate a significant difference between egg mass exposures was circling, while all other coded behaviors did not demonstrate any significant differences.
  • Item
    Characterizing the devastating rice blast fungus, Sagnaporthe oryzae and a potential biocontrol agent, Bacillus velezensis strain S4
    (University of Delaware, 2024) Wockenfuss, Anna
    Plant diseases caused by fungal pathogens cause severe problems for agriculture as they greatly reduce crop yield, with some species causing up to 100% crop loss. Managing these fungal plant pathogens are of the utmost importance as the global economy and crop production relies heavily on cereal crops such as wheat, rice, maize and barley. Traditional methods in mitigating fungal pathogens, typically including fungicides, are ineffective against certain pathogens that have developed resistance, an example of this being the rice blast fungus, or Magnaporthe oryzae. M. oryzae kills enough rice to feed 60 million people per year, and thus has become a focal point in the field of plant pathology, where it is regarded as a model organism. Since the usage of fungicides in this instance is not effective, scientists must look for alternatives and now favor the use of biological control agents (BCAs), an environmentally friendly way of disease management. Common BCAs are found within the bacterial genus, Bacillus, which act as a plant growth promoting bacteria (PGPB). Bacillus velezensis strain S4 was isolated and sequenced from biochar-amended agricultural soil in Delaware. Upon genomic analysis and plate assays, B. velezensis strain S4 putatively encodes antifungal compounds, and enzymes including cellulases and proteases. M. oryzae in the presence of B. velezensis strain S4 displays hyphal lesions, reduced radial growth, and decreased appressorium formation, all of which could affect its pathogenicity. RNASeq analysis of this bacterial-fungal interaction revealed 69 differentially expressed genes (DEG) in M. oryzae, including toxin biosynthesis. All together B. velezensis strain S4 shows potential as a BCA for M. oryzae; observing specific aspects of this interaction could yield more insight into how fungi defend themselves against bacteria.
  • Item
    Encoding hydrogel actuation with flow-templated architecture
    (University of Delaware, 2024) Tran, Minh T.
    Recent advances in additive manufacturing have accelerated the fabrication of designer soft actuators. In particular, multi-material direct ink writing allows users to selectively embed stimuli-responsive material in 3D printed parts and program macroscopic deformations with exquisite control. In comparison to other soft actuator manufacturing techniques, direct ink writing (DIW) offers high templating precision and flexibility in architectural design. However, DIW of soft actuators suffers from some of the same drawbacks as encountered in layer-by-layer additive manufacturing. Sequential deposition of layers requires long build times, limits the resolution to the diameter of the print nozzle, and excludes ink materials that exhibit poor interfacial adhesion. While these manufacturing constraints may be perfectly manageable during actuator prototyping, they limit generalization and capacity on larger production scales. To circumvent some of these manufacturing bottlenecks, here we developed a continuous processing scheme that exploits viscoplastic, laminar flow to build and program the deformation of soft actuators. Inspired by techniques used to structure polymeric melts, we design custom millifluidic devices that force disparate streams through serpentine splitting, rotation, and recombination elements. These elements multiply the incoming 2D composition field across the cross-sectional area while preserving its relative spacing and orientation. Serial repetition of elements compounds multiplication, allowing the heterogeneous distribution to be efficiently shrunk before it is dissipated by diffusive mixing. The ‘advective assemblers’ extrude precisely structured multi-material filaments, which can then be arranged into objects along a conventional 3D printing path. Preassembling the lower levels of hierarchy in flow overcomes intrinsic challenges in layer-by-layer deposition, including improving interlayer adhesion and maintaining high volumetric throughput while maintaining fine layer resolution. ☐ Unlike self-assembly or directed-assembly, advective assembly is dictated by rheology rather than chemistry. Granular inks with sufficiently high yield stress flow as a plug and stabilize streamlines even through abrupt flow elements. Provided that the flowing streams are rheologically matched, materials with different chemistries can be predicatively structured and extruded in a single processing step. We exploit this universality to manufacture hydrogel actuators sensitive to different environmental triggers, specifically temperature and light. We formulate multiple hydrogel precursor inks by combining two polymers, N-isopropylacrylamide (NIPAM) and poly(ethylene glycol) diacrylate (PEGDA), with viscoplastic poly(acrylic acid) (PAA) microgel particles and photo-sensitive iron(II,III) oxide nanoparticles. The microgels serve as a viscoplastic carrier fluid that preserves the fidelity of patterned concentration maps. After polymerization, the distribution of stimuli-responsive components causes gel filaments to swell differentially when triggered, giving rise to shape changes that persist over tens of centimeters. Deformation is predicatively programmed by changing the concentration density map by simply adjusting the relative flow rates of incoming streams. Modulating the flow rate over the course of the print creates smoothly varying, intermediate structures that bend in multiple directions. The unique structures achieved, and the geometrically dictated, chemistry-agnostic operating principles used to achieve them, provide a new means to fabricate actuators for a variety of applications.
  • Item
    Improving stormwater infiltration with pneumatic air fracturing
    (University of Delaware, 2024) Osei Tutu, Nana Abena Konadu
    Infiltration basins are one example of stormwater infrastructure where infiltration must be maintained for the system to perform as designed. Unfortunately, sediment buildup and sometimes low-permeability native subsurface geological media within a few feet of the ground surface impede operation. When infiltration capacity is limited, pneumatic air fracturing may improve and maintain sufficient stormwater infiltration and, in some cases, encourage plant root growth. Here, we evaluate the utility of pneumatic air fracturing to remediate stormwater infiltration basins that drain poorly. Pneumatic air fracturing was conducted in 2020 and 2022 at two basins managed by the Delaware Department of Transportation. Using side-by-side control and treated sections, short and long-term improvements (0 – 33 months) in media properties and stormwater infiltration were assessed at shallow and deeper depths (0 – 100cm) using dynamic cone penetrometer, saturated hydraulic conductivity, and dyed water infiltration tests. Results indicate that pneumatic air fracturing significantly reduces the effects of compaction, resulting in an immediate reduction in soil penetration resistance of 67 ± 9%. Saturated hydraulic conductivity also increases, and while these increases diminish with time, they are 100 ± 30% after 12 months. However, these benefits are primarily at > 20 cm depth, at least at these test sites. For both basins, pneumatic air fracturing fixed the perpetual water-logged surface conditions that diminished basin performance. This is the first application of decompaction with pneumatic air fracturing to infiltration basins to increase stormwater infiltration in the US. We discuss the possibility of using similar pneumatic air fracturing on other infiltration basins where the loss of infiltration capacity is a concern.
  • Item
    Material characterization and fatigue lifetime prediction of a reinforced PEM fuel cell membrane
    (University of Delaware, 2024) Roosevelt, Rosch
    Proton Exchange Membrane (PEM) fuel cells are pivotal in advancing clean energy technologies due to their high efficiency and minimal environmental footprint. However, a significant barrier to their widespread adoption is the durability of the fuel cell membrane, which degrades both mechanically and chemically during regular operation. The mechanical degradation is largely correlated to the repeated swelling and deswelling of the membrane due to varying hygrothermal loads. The introduction of a composite membrane by inserting an inert reinforcement layer has improved its chemical and mechanical stability. This study investigates the factors influencing reinforced membrane failure due to mechanical degradation in PEM fuel cells under different environmental conditions. ☐ This thesis encompasses a detailed material characterization of the membrane to understand its viscoelastic-elastoplastic and hygrothermal expansion properties. Additionally, a water transport model was developed to incorporate the spatio-temporal distribution of water in a membrane. Building on this, a representative volume finite element model of a Fuel Cell stack was created to predict the fatigue crack initiation of the membrane due to a pre-existing catalyst layer flaw. This was done by calculating the plastic dissipation energy (PDE) accumulation in a membrane in the vicinity of a flaw, under fatigue loading. The theoretical predictions were compared with experimental data to validate the model. The effects of temperature, humidity and clamping pressure on the PDE accumulation were examined. The findings highlight the importance of optimizing operational parameters to enhance the longevity of PEM fuel cells. ☐ This work contributes to the development of more durable PEM fuel cells by providing insights into the mechanical behavior of the membrane under various operating conditions. The implications of this research can have a positive impact on improving fuel cell reliability, thus advancing the feasibility of PEM fuel cells for commercial and industrial applications.