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 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.

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Production of neo acids from biomass-derived monomers
(University of Delaware, 2024) Andini, Erha Andini
Neo acids are highly branched carboxylic acids currently produced from fossil fuels. In this work, we produce renewable neo acids from lignocellulosic biomass-derived furan and keto acids via C-C coupling through hydroxyalkylation/alkylation (HAA), followed by ring-opening of furans through hydrodeoxygenation (HDO). We show effective C-C coupling over acid catalysts. Catalyst screening and multi-parameter optimization using machine learning optimize the yield and elucidate the correlation between variables and outcomes. We demonstrate selective furan ring-opening without affecting the carboxylic acid to make neo acids using a co-catalyst involving Pd supported on carbon and metal triflate.
Inferring bearing capacity from sonar backscatter: application from a muddy field site
(University of Delaware, 2024) Park, Sun Woo
This study expands on the application of sediment classification using acoustic backscatter and combine it with drop penetrometer data to test if the bearing capacity of the sediment layer can be related to the backscatter intensity. Total area of 5.14 km2 was surveyed using a vessel mounted multibeam sonar and AUV mounted side scan sonar on the Potomac river near Indian Head, Maryland. 9 sediment grabs were taken during October 2022 field work, and 18 contemporaneous grab samples and drop penetrometer measurements were taken during February 2023. Backscatter mosaic with the geotechnical data was used to train a supervised classification algorithm in ArcGIS Pro. Applying the data interpretation techniques developed so far to cohesive fluvial environment has shown good agreement between backscatter intensity and bearing capacity (precision: 0.75, accuracy: 0.78). This could have practical applications in coastal and riverine construction in muddy environments, allowing for fast and cost effective analysis of bearing capacity of a large site. Unexploded ordnance (UXO) in munition test sites could also be managed using sonar surveys since ordnance mobility and burial could have improved prediction with bed bearing capacity data (Trembanis and DuVal, 2021). This coordinated geoacoustic and geotechnical survey approach would reduce the risk of UXO site management since minimal contact with the bottom is necessary.
Understanding the impact of lignin-derivable non-isocyanate polyurethane (NIPU) chemistry on electrospinnability and fiber quality
(University of Delaware, 2024) Mahmood, Maida
Polyurethanes (PUs) are a critical component of the global polymer industry but mainly are derived from fossil fuels and contain hazardous precursors. Non-isocyanate polyurethanes (NIPUs) derived from lignocellulosic biomass, not only provide a safer and sustainable alternative to conventional PUs but also contain functional groups that can alleviate processing challenges and improve electrospinnability. In this work, lignin-derivable bisguaiacol A (BGA)-NIPU (one methoxy group on each aromatic ring with dimethyl bridging substitution) and bisguaiacol F (BGF)-NIPUs (one methoxy group on each aromatic ring without dimethyl bridging substitution) are used to fabricate electrospun fiber mats; and the impact of lignin-derivable NIPU chemistries on electrospinnability and fiber quality is studied. It was found that the presence of methoxy groups in lignin-derivable NIPUs led to a 10-50% increase in viscosity as compared to the bisphenol A (BPA)-NIPU control (no methoxy groups with a dimethyl substitution). Additionally, the absence of dimethyl substitution led to the highest viscosity and completely bead-free fibers in BGF-NIPU in comparison to BPA-NIPU and BGA-NIPU. This work provides an understanding of structure-processing relationships for the electrospinning of lignin-derivable NIPUs. These insights can help inform future studies regarding manufacturing of bio-based NIPU fibers and fiber-composites for different applications.
Bridge elements' weight determination and components' condition prediction using machine learning approach
(University of Delaware, 2024) Abiona, Qozeem Olatunbosun
Managing the deterioration of the bridge components and elements has continued to be one of the major concerns for the Departments of Transportation (DOTs) in the United States due to the huge cost needed for constructing new bridges. To avert disasters that could lead to severe losses, deterioration models have been created to predict the future condition of the deck while attributing the deterioration to different factors elicited by engineering and statistical techniques. Previous deterioration models have been more like linear regression models and did not predict the discretized value of the deck condition rating. A prediction of 6.51 was approximated to be a condition rating of 7, which is inappropriate for a discrete data type. This research project uniquely combines all the bridge features identified in the literature by applying principal component analysis (PCA) to capture the variance in the dataset needed to predict the condition of the bridge components. Feedforward Artificial Neural Network (ANN) models were created using different numbers of principal components and the performances were compared with that of the base model that uses all the features collected from the literature. It was observed that 9, 9, and 10 principal components are needed to create a deterioration prediction model that gives a better prediction accuracy than the base model that uses all the bridge features in the Deck, Superstructure, and Substructure respectively. The deterioration of the bridge elements is also known to influence the condition rating of the bridge components and the overall condition of the bridge. The weight or importance of the bridge elements influences the maintenance, repair, and replacement (MRR) schedule of the Departments of Transportation (DOTs) and the resource allocation to the structures. The DOTs currently use a cost-based approach to assign weight to bridge elements which can be in terms of the loss accrued during downtime or the amount needed for the replacement of the element. However, this approach does not consider the bridge element's structural relevance to the bridge's overall performance. This research also uniquely uses the Random Forest (RF) algorithm, an ensemble of decision trees, to evaluate the importance of different elements to the condition of the bridge components and the overall condition of the bridge. The analysis focused on 15 bridge design types in Delaware, Maryland, Pennsylvania, Virginia, and West Virginia and discovered that the weight of bridge elements is not constant as insinuated by the cost-based approach but varies based on its relevance to the bridge's structural performance. The resultant bridge elements’ weight can be used to construct the Bridge Health Index (BHI) equations for the different bridge types. The novel approach herein provides the DOT personnel with data-driven evidence to determine which set of bridge elements to prioritize in their maintenance actions to improve the components' condition, and the overall condition of their bridge inventory and to ascertain if the elements receiving the highest priority in the MRR schedule and budget allocation are also the same set of elements that bridge inspectors regard as needing attention. Furthermore, the technique presented also serves as an approach for synthesizing the bridge component and element-level data and aids the conversion process between the two important datasets.
Investigating the role of coastal wetland on per- and polyfluoroalkyl substances (PFAS) transport
(University of Delaware, 2023) Pavia, Ashley
Per- and polyfluoroalkyl substances (PFAS) are a large group of chemicals that have been widely used in manufactured and commercial products. They are persistent emerging contaminants that have been linked to adverse health effects in wildlife and humans. Few studies have assessed how PFAS compounds are transported and distributed throughout coastal watersheds and their effects on coastal ecosystems. This study assesses the spatial distribution and composition of PFAS in a tidal salt marsh and investigates how geochemical and hydrological conditions affect their fate and transport. We used St. Jones Reserve, a tidal marsh positioned between a military base and Delaware Bay, as the study site. We collected groundwater, porewater, and sediment from seven sites that span across three marsh zones with contrasting geochemical and hydrological conditions, and surface water from the tidal creek at high and low tide. Our study reveals a consistent pattern in the vertical distribution of PFAS within the salt marsh and elevated PFAS concentrations in the subsurface environment across seasons. Our findings highlight dissolved organic carbon (DOC) as a potential factor influencing the distribution of PFAS in the marsh ecosystem. The results of this study improve our understanding of PFAS mobility in the environment and the factors that affect their fate and transport as they migrate to the ocean. The information generated in this study can be used to develop models to predict PFAS fate and transport and strategies for protecting coastal water supplies and ecosystems.
Modulation of innate stomatal defense response in plants by Salmonella enterica under gravistimulation
(University of Delaware, 2023) Totsline, Noah
Spaceflight presents plants and microorganisms with the evolutionarily novel environment of microgravity. Plant responses to gravistimulation occur at the molecular and physiological level. Studies suggest plant susceptibility to phytopathogens is increased under spaceflight microgravity. Human pathogens, particularly enteric pathogens of the Gram-negative family Enterobacteriaceae, act as cross-kingdom pathogens by suppressing and evading plant innate immunity to colonize and persist in intracellular spaces. As humans venture deeper into space for greater amounts of time, the production of nutritious and safe food during spaceflight is essential to protecting human health. Spacecraft are closed systems in which a microbiome can be introduced via cargo deliveries or from the human crew. There exists an alarming knowledge gap regarding plant interactions with human foodborne pathogens in microgravity. Despite stringent pre-launch biosafety precautions, several genera of foodborne pathogens persist aboard the International Space Station (ISS). Space-grown plants on the ISS have also been colonized by a diverse community of bacteria and fungi, including pathogen-containing genera. Elucidation of interactions between plants and human pathogens under altered gravistimulation could highlight potential food safety risks. The purpose of this study was to determine if gravistimulation by vertical clinorotation alters susceptibility of lettuce (Lactuca sativa L.) to suppression of defensive stomatal closure and colonization by Salmonella enterica serovar Typhimurium. A slow-rotating 2-D clinostat (0-4 RPM) was used to gravistimulate inoculated in-vitro plants. Confocal microscopy was used to measure width of stomatal apertures at 0, 3, 6, and 9 hours post inoculation. Confocal Z-stacking was used to measure the depth of bacterial ingression within stomata. We found 1) different rates of clinorotation dramatically influenced stomatal width in uninoculated plants. 2) clinorotation significantly enhanced Salmonella ability to suppress stomatal closure, particularly at 2 RPM. 3) Bacteria could be observed deeper within stomatal cavities in rotated plants compared to unrotated.
Factors influencing spatial patterns and trends in migratory landbird stopover across Texas and Louisiana
(University of Delaware, 2023) Crandall, Amanda
To optimize energy and speed each migration season, Nearctic-Neotropical landbirds must navigate the climate of the airspace during flight, and the heterogeneity of the landscape as they stopover to rest and refuel. With a diverse environment ranging from arid to temperate, proximity to the Gulf of Mexico, the presence of some of the brightest cities in the United States, and the existence of multiple major migration routes, Texas (TX) and Louisiana (LA) represent a unique landscape to study how climate and land cover factors influence where migrants choose to stopover, how these relationships vary seasonally, and how they change over time. I used 26 years of data (1995-2020) from 15 NEXRAD weather surveillance radars distributed across TX and LA to calculate bird densities and distributions in relation to environmental variables. I first fit boosted regression tree (BRT) models among an ensemble of 196 overlapping modeling frames (400 km x 400 km in extent) stratified across the study area to determine the relative importance and beta relationships between 26 environmental predictor variables and 13 years of seasonal mean bird density. I found a high degree of spatial and seasonal nonstationarity in variable importance and the directions of beta relationships, reflecting potential differences in species compositions and migration strategies, as well as complex interactions between abiotic and biotic factors influencing stopover distributions. Consistently important variables included temperature, precipitation, distance to artificial light at night (ALAN), and east-west winds. Interestingly, I found evidence of attraction to bright light at the broad scale and avoidance of bright light at the fine scale that varied depending on the mean distance to ALAN across the landscape. My results suggest that attraction to bright light was greater in areas that were on average further from ALAN, while avoidance of bright light was greater in areas that were on average closer to ALAN. To expand upon my findings and investigate how changes to the landscape and climate influence changes in stopover densities and distributions over time, I used generalized additive models (GAMs) to examine the relationships between 35 predictor variables, their top-ranking interactions, and trends in seasonal mean bird density from1995-2020. Similar to the results of the spatial BRT models, I found a high degree of seasonal and geographic variability across TX and LA. Generally, however, temperature, east-west winds, and their interactions were highly important variables in influencing bird density trends over time. In the fall, stopover density increased in warmer areas and areas that became warmer over time, while in the spring, cooler areas and areas that became cooler were correlated with increases in bird density. In addition, spring stopover density increased further from bright ALAN where winds were blowing fastest from the east, suggesting that easterly winds may be outweighing the effects of light attraction. Spring stopover density decreased further from bright ALAN where winds were blowing fastest from the west, suggesting that westerly winds may be contributing to the effects of light attraction. In the fall, easterly winds may be outweighing the effects of light attraction. Overall, quantification of the direction and magnitude of these relationships is novel for the south-central region of the U.S. and provides a strong foundation for future studies that investigate the regional relationships I found in more detail. Moreover, understanding the effects of climate trajectories and their combinations with factors like ALAN intensity and urban development, can aid in enacting preventative measures for landbird conservation.
Design of structured illumination via multi-objective optimization in dynamic X-ray tomosynthesis
(University of Delaware, 2023) Restrepo, Carlos
Dynamic coded X-ray tomosynthesis (CXT) uses a set of encoded X-ray sources to interrogate objects lying on a moving conveyor mechanism. The sample is reconstructed from encoded measurements received by uniform linear array detectors. This work introduces a multi-objective optimization (MO) method for structured illuminations, balancing reconstruction quality and radiation dose in dynamic CXT systems. The MO framework is established based on a dynamic sensing geometry with binary coding masks. The Strength Pareto Evolutionary Algorithm 2 (SPEA-2) is used to solve the MO problem by jointly optimizing the coding masks, locations of X-ray sources, and exposure moments. Computational experiments are implemented to assess the proposed MO strategy. Additionally, an analysis based on singular value decomposition was carried out to examine the condition number of the resulting sampling matrices. To ensure that the reconstruction framework does not have dependencies on a particular sample movement, two different movement sequences were employed. The results show that the proposed strategy can obtain a set of Pareto optimal solutions with different levels of radiation dose and better reconstruction quality than benchmark settings under diverse sampling conditions.
A ballast box to study the effect of sand fouling on ballast, track stiffness, track deformation, and predicting maintenance time
(University of Delaware, 2023) Alzhrani, Mohammed Abdullah J
Railroad track crossings through sandy areas, like deserts, face the unique challenge of sand infiltrating into the ballast, leading to ballast fouling. Geographical conditions make these areas particularly prone to windblown sand infiltration, causing fine sand to gradually fill the ballast voids, ultimately resulting in fouling issues. Over time, fouled ballasts become a significant concern because of their negative impacts on track performance. ☐ This study explores the impact of ballast fouling primarily caused by sand infiltration on track deflection, stiffness (modulus), and overall track degradation. The main goal is to establish a clear relationship between these factors and fouling levels due to sand infiltration. ☐ The research was conducted at the University of Delaware's Civil Engineering laboratory, utilizing an 18-cubic-foot (0.67 cubic yards) ballast box. A rail/tie/fastener assembly was placed on the ballast and subjected to cyclic loading at a rate of 12 cycles per minute. The testing began with clean ballast, and dynamic load tests were carried out under simulated vehicle wheel loading conditions for up to five hours, with load-deflection behavior recorded during each cycle. Sand was introduced to the ballast in two series: Series 1, representing unconsolidated tests, and Series 2, simulating progressive fouling. These tests were repeated with varying levels of sand fouling, ranging from moderate to severe. Load deflection curves were analyzed using the Beam on Elastic Foundation (BOEF) theory to determine track modulus (stiffness) values and cumulative deformation, corresponding to cumulative plastic strain under repeated wheel loading. ☐ The study's results reveal a consistent pattern in load deflection curves, track modulus values, and cumulative plastic strain for different levels of sand fouling. It was observed that as sand fouling increased, both track stiffness (modulus) and track settlement also increased, aligning with field measurements conducted under similar conditions. ☐ As a result of these findings, a predictive application was developed to estimate maintenance time based on the degree of fouling. This application can offer valuable insights into maintenance planning and decision-making for tracks traversing sandy regions.
Identifying patterns and drivers of movement of the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae)
(University of Delaware, 2023) Sammarco, Ben
Alphitobius diaperinus is a ubiquitous pest of poultry houses found worldwide. They live in the litter of commercial poultry houses, especially broiler chicken houses. In high numbers they reduce poultry feed efficiency, cause stress and injury to birds, act as a reservoir for poultry diseases, and cause damage to structures and insulation in the house. Distribution and patterns of movement of A. diaperinus within broiler houses has been documented, but the specific environmental cues and behavioral drivers that govern those patterns are not well understood. I conducted a series of behavioral assays to evaluate the response of A. diaperinus to several wavelengths of light and the presence of water. I found that A. diaperinus adults and larvae are repelled by several wavelengths of light, but burrowing behavior is not connected to this response to light. I also found that A. diaperinus is repelled by water when in a normal, hydrated state, but is attracted to water when dehydrated, and this attraction is stronger than the repulsion from light. On a broader scale, A. diaperinus is believed to originate in Africa as a nest associate of several bird species, however the historical pattern of dispersal across the world is not known. As a preliminary survey to assess the viability of genetic tools to illuminate these historical patterns I sampled broiler house populations of A. diaperinus from several farms in the Eastern United States and Europe and sequenced the mitochondrial cytochrome oxidase subunit I gene. I analyzed the diversity of this gene between houses, farms, states, and nations, and found that broiler house A. diaperinus populations are very homogenous at the cytochrome oxidase subunit I gene.
A sociological examination of disordered eating and body satisfaction among transgender and nonbinary individuals
(University of Delaware, 2023) Gavnik, Adam
Transgender, nonbinary, and other gender nonconforming communities have grown in visibility over recent years, and this visibility is associated with an increase in academic research on the health and wellbeing of these communities. Social science research has established that, compared to cisgender individuals, transgender and nonbinary people face an increased risk of mental health concerns such as disordered eating and body dissatisfaction. However, there is a dearth of research that explains this disparity. The current study uses 20 in-depth interviews with transgender and nonbinary adults to explore the factors that produce their eating habits and attitudes towards their bodies. Findings reveals the impact of micro-level factors such as individual health, gender dysphoria, and gender affirming care. Meso-level analysis emphasized the role of gender attribution and accountability in shaping participants’ relationship with food and their bodies, as well as social learning processes of food and body-related norms. Macro-level themes highlighted unique ways that trans and nonbinary identity shape experiences of embodiment and beauty ideals. Overall, this research elucidates the individual, interactional, and institutional factors that may contribute to elevated rates of disordered eating among trans and nonbinary people. Such findings indicate the complexity of these phenomena and the need for explanations that go beyond physical gender dysphoria.
Barely there: an analysis of stealthing as a social problem
(University of Delaware, 2023) Mey, Clara
The rise of stealthing, the colloquial term for nonconsensual condom removal, as a social problem does not fit into existing constructionist frameworks. It was brought into the popular lexicon following the publication of a law journal article in 2017 titled “’Rape-Adjacent’: Imagining Legal Responses to Nonconsensual Condom Removal” by Alexandra Brodsky. Brodsky’s paper subsequently went “viral,” and was cited many times as the impetus for public interest in stealthing. Following this article, Brodsky does not behave as an anti-stealthing activist, nor is there the development of an anti-stealthing social movement, yet it continues to be discussed in the media and by policymakers, leading to legislation in California, identical to the proposal in Brodsky’s paper. My paper analyzes the rise of stealthing as a social problem, utilizing media articles published in the U.S. between 2017 and 2022. I employ both quantitative and qualitative methods of content analysis to examine this data and see how stealthing was framed in the media. I found that Brodsky’s construction set the direction that the framing would take, but that the media itself fleshed out those framings. In the case of stealthing, media and journalists took on a more active claimsmaking role and I argue that Brodsky’s original framing made stealthing an appealing topic for media companies, encouraging them to continue to cover it even without continued outside claims and that Brodsky’s background as a law student was a major influence in that construction.
Using remote sensing to examine wintering waterfowl distributions and ecology in the United States to create a novel avian influenza virus biosecurity tool for the poultry industry
(University of Delaware, 2023) Hardy, Matthew James
The ongoing global HPAI outbreak in commercial poultry, first reported in the USA in February 2022 has emphasized the need for improved food biosecurity and novel approaches pertaining to nationwide wild bird surveillance. The Mid-Atlantic (MA) and Central Valley of California (CVC) are critical sites for waterfowl species in the winter, which promotes the interface between wild and domestic birds and increases the risk of an HPAI outbreak. Improving the understanding between predictors of wintering waterfowl distributions on both the fine and broad scale will allow facility managers to make more informed biosecurity decisions. Using the network of US NEXRAD’s and fine scale GPS-tracking of known HPAI reservoirs; Greater Snow Geese (Anser caerulescens atlanticus) (N = 59) and Canada Geese (Branta canadensis) (N = 9), my objectives were to 1) model winter waterfowl distributions at the broad scale in the MA and CVC as a function of weather, temporal, and environmental characteristics using boosted regression tree modelling and 9 years of NEXRAD data (2014–2023); 2) use high frequency GPS-tracking of geese for four winters (2019–2023) to demonstrate how a percentile risk ranking system can be used to gauge exposure to wintering waterfowl prior to an HPAI outbreak and discuss a risk management analysis framework for facility managers; and 3) use high frequency GPS-tracking of geese for four winters (2019–2023) to model waterfowl exposure in goose points per hour at individual poultry facilities as a function of temporal, geographic, and landcover predictors. ☐ I was able to capture the variability in effect size of 28 different covariates across space and time within two geographic regions which are critical to nationwide poultry and egg production. In general, environmental and geographic predictors had the strongest relative effect on predicting wintering waterfowl distributions in both regions, while land cover composition had regional and temporal specific effects. Daily mean temperature was a major predictor of increasing waterfowl distributions in both regions throughout the winter, while precipitation had differing effects, increasing waterfowl densities in the MA, while decreasing in general within the CVC. Increasing waterfowl densities in California are strongly tied to the flooding of the landscape and rice availability, whereas waterfowl in the MA, where water is less limiting, are generally governed by waste grain availability and emergent wetland on the landscape. Waterfowl distributions in the MA generally increased when distances to the Atlantic coast and lakes decreased, while increasing waterfowl distributions in the CVC were more strongly tied to decreasing distances to lakes. ☐ I demonstrated how a percentile ranking system based on goose points per hour at individual poultry facilities may be successfully used as a metric to predict AI outbreaks at poultry facilities within the Delmarva Peninsula in the Mid-Atlantic region of the US. Seven facilities that had an H5N1 outbreak during a 34-day window were within the 78th – 99th percentile of risk based on this system, with one facility even being ranked within the ‘top-25’ of 6,021 facilities. I was also able to document the first ever fine scale movement of wintering waterfowl in proximity to poultry facilities, with the minimum distance for Canada Geese (CANG) and Greater Snow Geese (GSGO) being documented at 3.9 m and 1.7 m respectively to poultry facilities. Exactly one-third of all Delmarva Peninsula poultry facilities had waterfowl present across winters, which is an alarming rate given our small sample size relative to the entire populations of both species. ☐ I was able to capture the spatial and temporal variability in mean exposure rate of geese in proximity to poultry facilities within a region of high poultry farm production across four winters. Time of the winter was the best predictor of goose exposure for both species, with GSGO generally greater during mid-late winter and CANG fairly consistent across the entire winter. Colder winter temperatures (particularly below 0°C) exponentially increases the rate of GSGO exposure at farms as they feed on waste grain to offset energy deficits. Goose exposure was similarly high for both species across the winter during both the day and night and emphasizes the need for 24 hr surveillance. Facilities that were closer to sewage treatment facilities, national wildlife refuges, waterbodies, or the coast had higher relative goose exposure, highlighting the importance of these sites at various times through the winter for geese. Many inland sites also have relatively high rates of goose exposure and geographic features such reservoirs, lakes, quarries, and gravel/sand pits may play a disproportionate role in supporting large numbers of geese.
Comparison of efficacy of appliances to be used at home and other places for fresh produce decontamination and cleaning
(University of Delaware, 2023) Raymond, Kassidy
Consumers need assistance in avoiding food-borne outbreaks associated with bacteria such as Salmonella. For fresh produce, heat treatments are not typically an option. In this study, three appliances with non-thermal technology were tested to determine efficiency and efficacy of washing and sanitizing fresh produce. Two of the appliances are currently available to the public, while one is still in development and testing in our laboratory. Grape tomatoes and spring salad mixes were used as samples to provide different surface textures: smooth and rough. They were inoculated using two methods, dip or spot inoculation, with a four-strain Salmonella cocktail to achieve an initial population of approximately 8-log CFU/g. The apparatuses involved used either ozone, ultrasonic, or ultrasound to treat the samples, and the samples are treated within 4 gallons of water at 3, 6 and 9 minutes, respectively. The results for inactivation of the Salmonella included about a 3-log reduction for tomatoes, and about less than a 1-log reduction for salad when sanitized with ozone, and ozone with ultrasound, and about a 3-log reduction for tomatoes and about a 2-log reduction for salad when sanitized with shortwave ultraviolet light radiation. The effect of duration of treatment time on Salmonella inactivation can be noted here, as the longer the samples underwent each treatment, the number of bacterial colonies reduced. At 3 minutes, the UV apparatus had the best inactivation amount compared to the other two apparatuses. In terms of texture and color change, the UV with water agitation did not significantly affect texture and color, the use of ozone significantly affected texture, and the combination of ozone with ultrasound significantly affected texture and color. In the future, UV with water agitation could be a viable alternative – instead of washing under running water- for consumers who want to keep the quality of their fresh produce.
Calibration of SKALA v2 Antennas for IceCube-Gen2
(University of Delaware, 2023) Brewer, Isabella
The SKALA-v2 is a radio antenna optimized for the 50-350 MHz band that will be used in the IceCube-Gen2 Surface Array, an upgrade to the existing IceCube Observatory. The planned IceCube-Gen2 Surface Array will expand IceCube’s ability to detect and reconstruct cosmic rays. Cosmic rays are immensely energetic nuclei accelerated in space. At the highest energies, they have to be detected indirectly, meaning that cosmic ray detectors on Earth have to be sensitive to secondary particles produced in cosmic ray air showers. Radio emission is one process through which these secondary particles can be detected. ☐ The IceCube-Gen2 Surface Array will introduce stations with radio antennas and scintillation panels, increasing the energy range of existing surface detectors and measuring the cosmic ray energy spectrum at higher energies. The radio antennas will also increase the detector’s sensitivity to mass-sensitive observables such as the depth of the shower maximum. ☐ Characterizing SKALA v2 was carried out through initial laboratory tests con- ducted at the University of Delaware and measurements of the antenna pattern when using an anechoic chamber. The measurements taken in the anechoic chamber were then compared to simulations from the manufacturer. Additionally, the Low Noise Amplifiers (LNAs) in the antennas were characterized. The results of the LNA cali- bration revealed it is necessary to calibrate the LNAs while attached to the antenna (because the LNAs are impedance matched to the antennas). ☐ Plans for a prototype station at the University of Delaware are also discussed, as well as background radio spectra from the roof of Sharp Laboratory.
Unraveling T-cell and endothelial cell interactions through computational analyses
(University of Delaware, 2023) Umesh, Krithika
A continuous challenge in drug delivery is to achieve tissue and organ-specific targeting, in particular to places like the lymph node and brain, where many difficult-to-treat diseases reside. This challenge is due to organ-specific endothelial barriers that possess unique cell membrane proteins and serve as restrictive barriers to molecules, particles, and cells moving from the systemic circulation into the tissue parenchyma. However, immune cells navigate these barriers regularly, particularly when patrolling lymph nodes and responding to brain cancer. As such, we sought to uncover unique interactions between local endothelial cells and immune counterparts to enable an analysis pipeline of tissue-specific receptor binding pairs that may ultimately advance the development of therapeutics finely tuned for precise tissue-specific targeting. This pipeline has generated preliminary data that uncovers distinct cell-cell interactions between local endothelium and T-lymphocytes across two key endothelial barriers i.e., lymph node and the blood-brain barrier, from publicly available single-cell RNA sequencing datasets through computational analyses. The differential expression analysis of HEV vs brain endothelial cells and naïve vs activated T lymphocytes led to the identification of various cell-type specific markers. The co-expression analysis revealed expression patterns of cell surface markers and identification of modules of co-expressing genes. The cell-cell communication analysis helped in identifying binding partners of markers expressed on HEV with that of naïve T lymphocytes and markers expressed on brain endothelial cells with that of activated T lymphocytes. This approach offers the opportunity to shed light on the signaling mechanisms involved in these interactions.
Surrogate adsorption energy exchange-correlation functional difference model using electron density-derived features
(University of Delaware, 2023) Chen, Eric
In this work, we develop a surrogate adsorption energy difference model to predict the difference in adsorption energy in the LDA xc and the PBE xc in small hydrocarbons on the Pt(111) surface. By fitting adsorbate atoms’ DDEC6 bond orders to the metallic surface and the overall charge transfer, we build an interpretable model based on atom-atom electron overlap that estimates adsorption energy difference to approximately 0.06 eV mean absolute error. We then apply the model to Ni, Ir, and Pd surfaces by accounting for the lattice constant to estimate the adsorption energy difference within 0.06 eV. Importantly, corrections can easily be understood and related to LDA and PBE’s different treatments of the systems’ atoms’ electron density overlaps and overall charge transfer from the adsorbate to the surface.
Investigation of conforming mixed finite elements with quadratic pressure approximations
(University of Delaware, 2023) Botchway, Douglas
To simulate the response of saturated geomaterials requires a numerical approach such as the finite element method that employs a generalized Biot formulation. Under isothermal conditions, the primary dependent variables are displacements (u) and pore pressure (ϑ), which are suitably coupled. The resulting finite elements are mixed and are historically referred to as “u-p” elements. Traditionally, such elements employ quadratic and linear approximation for u and ϑ, respectively. Since, according to Darcys law, the velocity of flow of the pore fluid is proportional to the gradient of the pore pressure, the approximate velocity is thus constant over an element. In slow “consolidation-type” problems the accurate computation of such velocities is not crucial, as they are generally very small. The need to accurately simulate the effects associated with rising sea levels, rapidly rising flood waters, etc., however, now requires that accurate approximate velocities be computed. This is particularly true in higher permeability soils. Consequently, robust, and computationally efficient higher-order u-p elements need to be used in simulating such problems. ☐ The aim of the present study was to investigate a mixed finite element method with quadratic pressure approximation. The elements of interests are the T15P6c triangle and the Q17P8c quadrilateral. These elements are collectively known as higher-order elements (HO). For reference and performance assessment, the so-called Taylor hood (TH) elements, bubble function (BF) elements and equal order interpolation (EOI) elements are also used in the analysis. ☐ The HO element performance related to the specific temporal integration algorithm used to integrate the finite element equations in time is first assessed. When considering a soil with a relatively high permeability, for a temporal integration parameter of 0.500, all TH, BF and EOI investigated produced oscillations in the excess pore pressure at nodes near the permeable boundary. By contrast, the T15P6c elements exhibited only very minor oscillations and no oscillation were noticed for the Q17P8c elements. Oscillations disappear when the temporal integration parameter is changed to 1.00. For simulations involving relatively low permeabilities, oscillations appear only in the first few time steps. ☐ Secondly the stability of HO elements during initial response is assessed and compared to TH, EOI and BF elements. TH, BF and EOI elements exhibit varying degrees of pore pressure oscillations very shortly after the application of an instantaneously applied pressure that is maintained constant. Oscillations associated with the Q4P4c (EOI element) were significantly greater than those associated with the TH and BF elements. The initial response of the HO elements was superior to that of the TH, BF and EOI elements investigated. After the first-time step, the response of all the TH, BF, EOI and HO elements was oscillation-free. ☐ Finally, the HO elements were assessed using one-dimensional singly drained consolidation problem with a single consolidating layer and then with two consolidating layers. For the former all the TH, BF, EOI and HO elements considered in this study accurately simulate the problem of one-dimensional consolidation of a single soil layer with single drainage. Relatively coarse meshes of T15P6c and Q17P8c elements produced results that were very similar to those obtained using finer meshes of TH, BF and EOI elements with linear pressure approximation. The Q8P4c, Q9P4c, T6P3c, and T7P3c exhibited some slight oscillations in the normalized excess pore pressure response for the dimensionless time factor Tv = 0.001. The HO elements did not overestimate the analytical solution. For the two-layer soil problem T15P6C and Q17P8C did not overshoot the analytical solution for a value of Tv = 0.001 and both exhibited no oscillations or other inconsistencies at the interface between the two soil layers.
Investigating the impact of hydrogen bonding in blends containing lignin-derivable polymers
(University of Delaware, 2023) Li, Sonia C.
In this work, poly(acrylic acid) (PAA) was blended with lignin-derivable polymers to investigate the effects of hydrogen bonding on phase behavior. Polymers are ubiquitous to society, but many are made from petroleum-based products that cause environmental concerns. The use of lignocellulosic biomass (LCB) reduces the burden of petroleum products. Lignin is an underused component of LCB that can be deconstructed and used as a platform for high-value products. Lignin-derivable polymethacrylates, such as poly(guaiacyl methacrylate) and poly(syringyl methacrylate), have desirable glass transition temperatures (Tgs) and provide various mesophases for applications like pressure-sensitive adhesives if used in biobased block polymers. Polymer blends are synthetically less intensive and could provide alternative methods to leverage the desirable properties for these polymethacrylates. Fourier transform infrared spectroscopy was used to show that hydrogen bonding occurs between the methoxy group of the polymethacrylates and the hydroxyl group of the PAA. The phase behavior of the blends was estimated for a range of compositions and temperatures, compared to differential scanning calorimetry results, and used to determine the limitations of the model. Overall, the results of this work provided insight into the hydrogen-bonding interactions in the system and an estimation of its phase behavior across a range of compositions and temperatures.
Receptors of second messengers involved in anti-phage defense
(University of Delaware, 2023) Perkowski, Julia
Cyclic nucleotide-based second messengers (cNSMs) play a crucial role in regulating diverse cellular functions. In bacterial systems, scientific understanding was previously dominated by purine derivatives like cyclic di-AMP, cyclic di-GMP, and cyclic GMP-AMP. However, recent discoveries have introduced novel purine-based cyclic trinucleotides and a range of pyrimidine-containing cNSMs. These newfound players orchestrate bacterial anti-phage defense systems such as CBASS and Pycsar. These systems, encoded in conserved operons distributed widely in the bacterial kingdom, underscore their importance in mediating immune responses against phages. Despite their prevalence, the underlying mechanisms of these defense these systems remain mysterious, primarily due to lack of confirmed protein receptors for pyrimidine-containing cNSMs. Cyclic UMP, cyclic CMP, cyclic UMP-AMP, and cyclic AMP-AMP-GMP each have single identified protein receptor, leaving other pyrimidine-containing cNSMs without confirmed binding partners. ☐ To unravel the functional mysteries of these novel cNSMs, a series of pulldown assays used cNSMs as "bait" molecules to extract potential receptors from cell lysates. A comparative analysis with control pulldowns revealed that candidate receptors from cNSM-immobilized pulldowns are predominantly involved in metabolic processes. Furthermore, a comprehensive domain analysis uncovered a recurring pattern of domains associated with proteins integral to cellular metabolism among the identified receptor candidates. ☐ While further binding assays using purified proteins is imperative to confirm the legitimacy of these candidates as true receptors, the preliminary findings suggest a broader functional landscape for these novel cNSMs in bacterial physiology. Beyond their anticipated roles in anti-phage defense, these cNSMs may wield multifaceted functions within bacterial systems, elevating their significance in microbial biology.

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