Doctoral Dissertations (Winter 2014 to Present)

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New submissions to the University of Delaware Doctoral Dissertations collection are added as they are released by the Graduate College. In most cases the Graduate College deposits all dissertations from a given semester after the official graduation date.

Doctoral dissertations from 1948 to present are also available online through Dissertations & Theses @ University of Delaware. Check DELCAT to locate print or microform copies of dissertations that are not available online.

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Caregiver Strain and Quality of Life: Exploring the Moderating Role of Caregier Age in an I/DD Context
Sticinski, Ethel Virginia
The number of diagnosed cases of intellectual and developmental disabilities (I/DD) has risen in the last few decades, and advances in healthcare and support services have increased the life expectancy for this population. Policy changes promoting residential choice have resulted in more people with I/DD living at home with aging family caregivers. Caregiving for offspring with I/DD can lead to caregiver strain, which affects the quality of life (QoL) of both the caregiver and the family unit. While research on caregiver strain and its impact on QoL is growing, the moderating role of caregiver age and perceptions of mutuality remain underexplored. Aging caregivers face unique barriers compared to younger caregivers, and mutuality has been shown in other research contexts to mitigate caregiver strain, though this may vary across the life course. This explanatory-sequential mixed-methods study utilized Family Systems Theory and the Strengths and Vulnerabilities Integration (SAVi) model to examine caregiver age and mutuality as moderators in the relationship between caregiver strain and QoL. The study also investigated potential interactions between caregiver age and mutuality to explore whether mutuality’s moderating role evolves over time. Quantitative data was collected through a cross-sectional online survey with n=186 participants. Sixteen participants who completed the online survey were then invited to engage in semi-structured interviews for qualitative data collection, selected based on their age and responses to the quantitative survey. Qualitative data were analyzed in conjunction with quantitative findings. Moderation analyses indicated that caregiver age and mutuality alone did not moderate the caregiver strain-QoL association. However, there was a three-way interaction between caregiver strain, age and mutuality suggesting that higher mutuality levels weakened the association between caregiver strain and QoL–but only among younger caregivers. Qualitative data both supported and expanded quantitative findings. Specifically, caregivers of all ages reported significant strain; however, their experiences varied. Older caregivers described more physical strain than younger caregivers, indicating a greater need for tangible support. Recommendations are proposed for measurement approaches, policy development, and programmatic interventions. Keywords: intellectual and developmental disabilities (I/DD), caregiver strain, mutuality, caregiver age, family systems theory, strengths and vulnerabilities integration model (SAVi), moderation analysis, semi-structured interviews, mixed methods, explanatory sequential.
CONTRIBUTION OF MEDIAL SEPTAL MODULATION TO SPATIAL WORKING MEMORY THROUGH OPTOGENETIC MANIPULATIONS
Gemzik, Zachary Meyer
Working memory (WM) is a critical function needed to interact with our environment and those around us. WM refers to the ability to hold information “online” and actively manipulate that information for successful use in task-relevant behavior. One way to further examine WM, is by modeling WM in rodents by assessing aspects of spatial working memory (SWM). SWM in rodents refers to the ability to maintain goal-relevant information over a temporal delay and successfully recall that information when it is needed. The underlying neural mechanisms involved in SWM are believed to be orchestrated by the septo-hippocampal theta oscillations. Septo-hippocampal theta oscillations are known to synchronize the hippocampal network through a vast expansion of GABAergic inhibitory influence. The intricate local connections and physiology of the medial septum (MSA) and reciprocal inhibitory influences returning from the hippocampus, pace theta oscillations in the hippocampal formation and temporally organize hippocampal and prefrontal cell assemblies. Septo-hippocampal theta oscillations are reported to offer a method of communication between the prefrontal cortex and hippocampus, of which both are critical for SWM. My hypothesis is that the MSA provides a critical modulatory influence on hippocampal-prefrontal theta communication, which is necessary for optimal SWM performance. To investigate the role of MSA during SWM, I first demonstrate that MSA is crucial for SWM maintenance (Aim 1). Next, I paced hippocampal theta oscillations via MSA optogenetic theta stimulation during short and extended delays to determine whether MSA theta stimulation is beneficial to task performance (Aim 2). Lastly, I examined the impact of MSA theta stimulation on hippocampal-prefrontal communication by assessing theta coherence between the two regions (Aim 3). My results demonstrate that MSA activity is crucial for SWM maintenance during a hippocampal-dependent conditional discrimination working memory task. In addition, I found that MSA theta stimulation during SWM maintenance enhances choice accuracy, specifically on trials where the working memory demand was prolonged. This finding may be explained by observations in Aim 3, of MSA theta stimulation altering dorsal hippocampal (dHPC) and medial prefrontal cortex (mPFC) theta power dynamics and enhancing dHPC-mPFC theta synchrony over the extended delay trials. These results highlight a vital role for septo-hippocampal theta in SWM. Moreover, they extend the implications of theta stimulation for therapeutic interventions by providing foundational evidence for its effects in non-pathological models.
AXIN2 dysregulates WNT-target gene expression via crosstalk between WNT/ꞵ-catenin and retinoic acid signaling pathways in APC-mutant CRCs
Zhang, Chi
APC mutation is the most common colorectal cancer (CRC) driver mutation, yet CRC patients carrying APC mutation have more favorable survival compared to those with only wild-type APC. The Overall Goal of my research is to determine how AXIN2 dysregulation contributes to development and growth of CRC, and how to therapeutically target AXIN2 in APC-mutant CRCs. Through NanoString transcriptome profiling and western blot, I discovered that instead of functioning as a negative regulator of WNT/β-catenin signaling, AXIN2 up-regulates WNT-target gene expression in CRC cells carrying mutant APC. To further explore the mechanism of this novel function of AXIN2, I propose the Overall Hypothesis: AXIN2 up-regulates WNT-target gene expression through down-regulation of WNT-signaling activity and up-regulation of retinoic acid (RA) signaling activity in CRC cells with mutant APC. To test this hypothesis, I conducted ChIP-seq data analysis and identified a set of WNT- and RA-signaling pathway component genes that are transcriptionally co-regulated by both WNT- and RA-signaling activity. This finding led to a novel WNT- and RA- signaling transcriptional co-regulation model in which both TCF/LEF and RAR/RXR transcription factors’ binding determine target gene transcription, but with different responsiveness in regulating the transcription rate. Such difference in responsiveness was confirmed by CRC patient RNA-seq results from GDC/TCGA. I then implemented the transcriptional co-regulation model mathematically into an ordinary differential equation (ODE) model and fitted the model to APC-mutant CRC cell proteomic data measured by mass spectrometry. Simulation results of the model are consistent with my western blot, ALDEFLUOR, and TCF/LEF reporter assay results on WNT-target gene expression in AXIN2-modulated CRC cell lines. Upon establishing that AXIN2 up-regulates most WNT-target gene expression via promoting RA-signaling activity only in APC-mutant CRC cells but not in APC-wild-type ones, I further designed a chemotherapy plan utilizing AXIN2's dual capability to (1) inhibits WNT-target gene expression and stem cell population in normal colon tissue (most carrying wild-type APC); and (2) promotes WNT-target gene expression and CRC tumor stem cell population (most carrying mutant APC), by combining it with 5-FU. I have tested such treatment plan on CRC patient-derived tumor organoids and results indicated that lower level of AXIN2 significantly enhances 5-FU's effectiveness to target cancer stem cell self-renewal capability. Overall, my findings support the hypothesis that AXIN2 positively regulates expression of WNT-target genes in CRC cells carrying mutant APC via cross-talk between WNT- and RA- signaling pathways, based on transcriptional co-regulation of pathway components. And I showed that AXIN2 knockdown can be used in combination with chemotherapy agents (e.g. 5-FU) to improve treatment effectiveness, potentially lowering chemo-resistance and promote healthy tissue recovery in clinical CRC treatment.
Essays on Well-being
Akcan Barto, Yasemin
Abstract This dissertation comprises two essays on the relationship between public policy and individual well-being. The first chapter investigates the causal impact of the Earned Income Tax Credit (EITC), one of the largest U.S. antipoverty programs, on subjective well-being (SWB), measured by self-reported happiness and life satisfaction, using two quasi-experimental strategies. I exploit variation in state-level EITC supplements over time and construct a simulated instrumental variable to estimate the effect of net income on SWB, accounting for potential labor supply endogeneity. Leveraging federal and state policy changes that vary by family structure, I find that while the EITC significantly increases household income, its effects on SWB are mixed. A $1,000 increase in generosity modestly raises SWB, especially during peak tax refund months, whereas increases in net income alone do not consistently improve SWB. The second chapter examines the impact of state-mandated financial education on adult financial well-being (FWB), using variation in the timing and intensity of high school curriculum requirements across U.S. states. Drawing on repeated cross-sectional data from the National Financial Capability Survey (NFCS) and a composite FWB measure, I employ a staggered difference-in-differences framework and event study design. The results show no overall evidence that mandates affect FWB. While mandate intensity (course, test, or both) yields no significant effects, requiring a course alone has a statistically significant positive impact.
HOTEL BOOKING CURVES: TAXONOMY, ALGORITHMIC EFFECTIVENESS AND COMPUTATIONAL EFFICIENCY
Liu, Xuan
Accurate demand forecasting is fundamental for hotel revenue management. This dissertation explores how booking curves—representing cumulative reservations over time—can be better categorized and used to generate more accurate forecasts using k-Nearest Neighbors (k-NN) algorithms. Drawing on over 3.8 million daily booking observations, which were aggregated into more than 70,000 booking curves from 50 U.S. hotels, the research is organized into three studies. The first study examines whether booking curves can be meaningfully categorized using unsupervised clustering. Both Euclidean-based and adaptive polynomial clustering were conducted for the categorization, it revealed three consistent behavioral segments: early, mid, and last-minute bookers. The second study investigates how variations in k-NN configuration—such as the number of neighbors (k), distance metrics, and weighting arrangements—affect forecasting accuracy across different booking horizons. Results show that the optimal combination of k-NN features vary by hotel booking horizon length. The third study evaluates whether pre-clustering booking curves before applying k-NN algorithm improves computational efficiency. Both clustering methods significantly reduced processing time with only modest trade-offs in forecast accuracy. Overall, these findings offer a practical framework for developing hotel demand forecasting systems that balance accuracy and scalability. By aligning behavioral segmentation with horizon-specific algorithm tuning, this research provides actionable strategies for revenue managers to enhance forecast precision while reducing computational complexity. Additionally, the results demonstrate that algorithm efficiency can be significantly improved through thoughtful clustering, making the approach well-suited for real-time, data-intensive operational environments.
UTTERANCE PHENOMENA IN SYNTAX
Altınok, Dursun
This dissertation explores utterance-oriented phenomena in syntax, focusing on the integration of discourse-related elements into sentence structure. Utterance-oriented phenomena are sentence-peripheral, conversational linguistic expressions that convey expressive meaning in terms of speaker attitude. By analyzing data from Turkish and Japanese, the dissertation presents a formal syntactic framework that accommodates these phenomena within an expanded syntactic hierarchy, particularly through the functional projection of the Utterance Phrase (UttP). The empirical data representing utterance-oriented phenomena come from three different constructions in this work: utterance oriented markers, gapped right dislocation and gapless right dislocation. Utterance-oriented markers, a class of discourse particles that satisfy the criteria for being utterance-oriented phenomena, are argued to base-adjoined to UttP either at the head level or the phrasal level. Gapped right dislocation in Turkish and Japanese is taken to involve a rightward syntactic movement to UttP, where they adjoin to the phrasal level. Gapless right dislocation, which come in different forms, are associated with different syntactic structures depending on their syntactic, semantic and pragmatic properties. The dissertation overall contributes to the broader understanding of how syntactic structure interfaces with discourse, offering a nuanced view of how conversational phenomena are syntactically represented across these two languages, with a potential cross-linguistic implications.
Identification of the Wnt Maturation Complex
Henesey, Kate M
Wnt signal transduction is fundamental to human development and is responsible for maintaining cellular homeostasis later in life. During development, reduced or absent Wnt signaling results in a wide range of developmental defects and aberrant signaling in adults is recognized as a primary driver of cancers. Strikingly, Wnt signaling is so indispensable to bodily function that any perturbation or disruption throughout the pathway can lead to developmental defect or cancer; prominent examples include focal dermal hyperplasia, osteogenesis imperfecta, and colorectal cancer. While the numerous Wnt ligands and target receptors in receiving cells have been extensively studied, the maturation of virtually all Wnt ligands within sending cells is relegated to highly conserved yet understudied components, Porcupine (Por) and Wntless (Wls). Our initial characterization of Por and Wls function within the model organism Drosophila melanogaster to produce functional Wnt has informed much of our understanding of Wnt ligand maturation. Further characterization of the mechanisms by which these players interact to produce mature, active Wnt ligand is essential to better delineate how Wnt signaling is regulated. Herein we provide identification and initial characterization of the Wnt Maturation Complex. We discovered that Wls forms homo-dimers dependent upon intermolecular disulfide bridge formation, and these Wls dimers interact with both Wnt and Porcupine (2:1, Wls-Wnt, Wls-Por). Remarkably, this provides a universal mechanism for Wls dimerization and a possible explanation for the uncharacterized Wnt hand-off between Por and Wls in early ER Wnt processing. The overarching goals of this work are two-fold: to characterize disulfide bonded Wls dimer interactions in forming Wnt maturation complexes and to characterize disulfide bonded Wls dimer importance in Wnt post-translational modification, secretion, and signaling. We have generated various tagged forms of Drosophila Por and Wls wild-type (WT) and conserved cysteine mutants that are used in co-immunoprecipitation experiments to examine the importance of Wls disulfide bonds in forming early Wnt maturation complexes. To determine if Wls cysteine mutants affect post-translational modification, secretion, and signaling, we used readouts of Wnt N-glycosylation by western blot, secretion into media by western blot, and canonical Wnt signaling activity indicated by ß-catenin levels in western blot and by transcriptional reporter assays. This work will lead to an understanding of how Wls dimers function within a cell to produce functional Wnt ligand, impacting our comprehension of Wnt cellular dynamics, processing, and secretion mechanisms. Results from this work have the potential to identify targeted therapeutics for diseases fueled by aberrant Wnt signaling.
PERFORMANCE, STABILITY, AND TRANSPORT STUDIES OF HYDROXIDE EXCHANGE MEMBRANE ELECTROLYZERS
Oliveira, Alexandra -- ProQuest MARC21RDA - Sept 2025
With the global transition to renewable energy, some sectors like the chemical industry, heavy-duty transportation sector, and long-term energy storage are difficult to decarbonize by electricity alone. Green hydrogen production by water electrolysis can play a critical role to meet these needs, but it must reach economic viability before widespread commercial implementation is possible. The current electrolysis technologies include alkaline water electrolyzers (AELs) and proton exchange membrane electrolyzers (PEMELs). AELs use a concentrated liquid alkaline electrolyte and are very durable but have limited efficiencies for hydrogen production. PEMELs use a zero-gap solid polymer electrolyte to achieve high efficiencies and hydrogen production rates, but they generate an acidic environment that is corrosive to all but expensive titanium and platinum-group metal (PGM) materials. Hydroxide exchange membrane electrolyzers (HEMELs) are a promising new technology that uses a solid hydroxide-conducting polymer electrolyte. This balances the efficiency of PEMELs with the alkaline environment of AELs, giving HEMELs the opportunity to produce green hydrogen at high efficiencies with low capital cost. Currently, HEMELs are a very immature technology which requires improvements in performance and stability before it is commercially viable. In this work, we strive to understand the operating mechanisms of HEMELs and how they contribute to performance and stability. We then propose new designs of the membrane electrode assembly (MEA) and operating conditions to improve performance and stability. The HEMEL anode is one of the greatest sources of overpotential due to its limited kinetic activity and poor stability. Through a novel corrosion-based synthesis of a self-supported NiFeOOH-20F oxygen evolution electrocatalyst, we eliminate the wash out of catalyst. We investigate synthesis techniques to increase the catalyst loading and alter the microstructure of the electrode to further improve performance. In a careful investigation of three different microstructural parameters of the self-supported anode, we determine that anodes with small pores and high porosity can yield improved HEMEL performance. With these improved electrodes, we study the water transport in HEMELs operating at high current densities, where the cathode can rapidly lose water and demonstrate increases in overpotential. We isolate the sources of this overpotential and determine that the dry out of polymer lowers the conductivity of the electrolyte, particularly within the cathode catalyst layer and at the interface between catalyst layer and membrane. By increasing the ionomer content in the catalyst layer and introducing an interfacial layer of ionomer at the membrane, we reduce the overpotential at high currents by more than 500 mV and determine that maintaining a conductive interface is most important to reduce the efficiency losses associated with cathode dry out. Lastly, we explore the tolerance of HEMELs to potential contaminants that might be present under commercial operation. We find that CO2 carbonation can poison the MEA with carbonate and bicarbonate ions, similar to carbonation in HEM fuel cells. These unfavorable ions can reduce the conductivity of the membrane and ionomer and cause additional overpotentials through the formation of a pH gradient across the cell. We determine that (bi)carbonates are not a serious detriment to cell performance and durability because they can be purged to the anode at high current densities, where they are decomposed back into CO2 and removed, at the cost of up to 200 mV. Operation with dilute KOH can remedy this problem by reducing the pH gradient. Other anion contaminants, however, such as those found in tap water, can cause detrimental performance and stability losses and corrode the NiFe anode catalyst. Chloride and bromide at tap water concentrations are likely responsible for the corrosion, suggesting that removing halide contaminants or using grades of water in between DI and tap water are worth pursuing in future research. These findings can help increase HEMEL efficiencies to make them competitive with existing water electrolysis technologies and act as guidelines for commercial operation.
Nanostructured and Microstructured Biomaterials via Phase Separation of Stimuli-responsive Resilin-like Polypeptides
Patkar, Sai -- ProQuest MARC21RDA - Sept 2025
Modulation of inter- and intramolecular interactions between bioinspired designer molecules can be utilized for developing functional structures that mimic the complex hierarchical organization of multicomponent assemblies observed in nature. Furthermore, such multistimuli-responsive molecules offer orthogonal tunability for generating versatile multifunctional platforms via independent biochemical and biophysical cues. This dissertation harnessed the remarkable mechanical and physicochemical properties of intrinsically disordered resilin-like polypeptides (RLPs) for generating nanostructured and microstructured biomaterials via their stimuli-responsive phase separation. The native extracellular matrix (ECM) is characterized by structural and compositional heterogeneity across various length scales. Current state-of-the-art in soft-matter patterning techniques to produce sophisticated ECM mimics are limited due to their reliance on expensive equipment and multiple time- and energy-intensive steps. In the first aim of this work, opportunities to produce bi-component elastomeric matrices by exploiting the liquid-liquid phase separation (LLPS) of RLPs are reported. Temperature-triggered LLPS of RLPs can be precisely controlled by altering their amino acid composition. Hence, the photocrosslinking of distinct morphologies of multicomponent RLP solutions during LLPS presents exciting opportunities for developing a simple biofabrication method. This research enabled fine-tuning of pore diameters and shear storage moduli of microstructured hydrogels by manipulating sequence-encoded differences in phase separation of multicomponent RLP formulations. The developed microstructured hydrogels can be utilized as cell- instructive materials to support regenerative medicine applications. While RLPs can be stimuli-responsive, the disorder encoded in their secondary structure has limited their usage for creating structurally defined nanoassemblies. Hence, there exist no studies with the use of short RLP-based sequences for generating stimuli-responsive materials which are ordered on the nanoscale. In contrast, computationally designed coiled-coil peptides or ‘bundlemers’ have demonstrated versatility for producing programmable 1D, 2D, and 3D nanostructures via covalent assembly of peptide bundles with complementary functional groups. To afford them physical responsiveness, for the second aim of this work, two different bundlemer- forming peptides were functionalized with thermoresponsive RLPs of various lengths to induce hierarchical nanostructure assembly via the temperature-triggered phase separation of the RLP motifs. Genetic fusion to the coiled-coil bundles not only displayed the short RLPs in an ordered fashion, but also substantially increased their transition temperature, below which the ordered display of collapsed RLPs promoted 1D-like assembly into nanofibers. Extending the research findings from the first two aims, bundlemer-forming peptides were fused to the N- and C- termini of compositionally distinct yet similar RLPs. The resulting genetically fused conjugates exhibited improved thermal stability and retained sequence-encoded control over thermoresponsiveness. The influence exerted by the ordered helical domains on the RLPs and on each other, could be further altered by manipulating the phase separation of RLPs in response to additional environmental stimuli such as pH, salt identity, and ionic strength. Transmission electron microscopy indicated that assembly at high temperature (80°C) mediated the formation of ribbon-like structures. These investigations helped to establish the design parameters for sequence- encoded control over inter- and intramolecular interactions of ordered and disordered building blocks to create hybrid and responsive materials with defined nano- and microstructures.
OPENING THE BLACK BOX: AN ACTIVE APPROACH TO EXPLANATION METHODS IN MACHINE LEARNING
Russell, Emily -- ProQuest MARC21RDA - Sept 2025
With the popularity of machine learning methods ever on the rise, it is more important than ever to create models that can be trusted. This dissertation presents an integrated active framework for explainable AI (XAI) that enhances the transparency of machine learning models, which are especially critical in high-stakes decision-making scenarios. The importance of model transparency is emphasized, as opaque decision-making processes in AI can lead to mistrust and ethical concerns. In this research, we include an in-depth exploration of the current landscape of explanation methods within the XAI field, paying particular attention to feature-importance-based methods, which provide insights into model decision-making by highlighting the relevance and impact of different features on model predictions. Through this exploration, we discuss key challenges and opportunities for improving explainability in machine learning. In addition to the introduction of two novel feature-importance-based explanation methods, the core contributions of this dissertation are: (1) our investigation into the nature and solvability of the weakly supervised object localization (WSOL) problem and (2) an introduction of an integrated active framework for active XAI, wherein models are trained with an active awareness of their own explainability in relation to a chosen explainer. This approach ensures that models trained within this framework are not only accurate but also maximizes interpretability and transparency in its decision-making process (i.e., attain minimum risk with maximum explainability). This framework contributes to the ongoing efforts to enhance the trustworthiness and accountability of AI systems, paving the way for more responsible and ethical AI deployment in high-stakes domains.
Synthesis of bioorthogonal muramyl glycans that illuminate and track bacterial peptidoglycan
(University of Delaware, 2019) DeMeester, Kristen E.
Bacterial peptidoglycan (PG) is one of the essential polymers for life. This intricate network of glycans and peptides has an inherent ability to protect both humans and bacterial cells by serving as a target for antibacterial reagents and a regulator for innate immune processing of a healthy microbiome. Details surrounding the immunostimulatory properties of PG fragments that contain a key component of this polymer, the monomeric unit N-acetyl muramic acid (NAM), are not understood, leaving questions surrounding how the innate immune system recognizes and responds selectively to pathogen particles unanswered. In this thesis, fundamental methodology was developed to incorporate NAM based chemical probes into the bacterial peptidoglycan via biochemical pathways of commensal and pathogenic bacterial cells. This methodology permitted the bacterial peptidoglycan to be selectively illuminated and subsequent processing by innate immune cells could be tracked. These tools are incredibly valuable to the fields of microbiology and immunology. In showcase experiments the methodology was used to demonstrate that different bacteria can produce their own unique peptidoglycan fragmentation patterns, allowing a molecular signature for each bacterium to be encoded into the innate immune system. This information is critical for selective antibacterial therapeutic design and will allow direct manipulation of host - microbiome interactions at the bacterial peptidoglycan level.
Dubai goes global: toward a new model of development?
(University of Delaware, 2011) Chehab, Sara Jane
The dissertation develops the Dubai development model and studies the impact of good governance practices on Dubai's growth. The model includes the goals, strategies, policies, management structure, and governing principles followed by Dubai. Various challenges and external forces influence and hinder the model. The dissertation borrows the World Bank's governance framework and studies how transparency, control of corruption, regulation, accountability, and the rule of law have had an effect on Dubai's development. It traces Dubai's history from 1833 until 2010, pinpoints its economic successes and challenges, looks at the effects of migrants' presence on the economy and society, studies the structure of the Dubai government, and places the city in a regional setting by comparing it to Abu Dhabi and Qatar.The dissertation develops the Dubai development model and studies the impact of good governance practices on Dubai's growth. The model includes the goals, strategies, policies, management structure, and governing principles followed by Dubai. Various challenges and external forces influence and hinder the model. The dissertation borrows the World Bank's governance framework and studies how transparency, control of corruption, regulation, accountability, and the rule of law have had an effect on Dubai's development. It traces Dubai's history from 1833 until 2010, pinpoints its economic successes and challenges, looks at the effects of migrants' presence on the economy and society, studies the structure of the Dubai government, and places the city in a regional setting by comparing it to Abu Dhabi and Qatar.The dissertation is original because it extracts a development model tailored to Dubai and the Arab Gulf region. It offers recommendations to places that are currently emulating Dubai's successes. The dissertation adds new empirical data to the existing literature and assesses the Arab Gulf region's developmental patterns in a critical way. It finds that Dubai's development model is solid because it builds on a history of economic liberalism. It can become sustainable if Dubai adopts various good governance practices.
Development of biocompatible 3-D networks by bioorthogonal crosslinking
(University of Delaware, 2021) Zhang, He
Due to the bioorthogonality, high selectivity and exceptional reaction rates, the inverse-electron-demand Diels-Alder cycloaddition between tetrazines and strained alkene or alkyne dienophiles has been increasingly applied to the development of novel biomaterials. Adapting established procedures, I successfully synthesized various tetrazine (Tz) and trans-cyclooctene (TCO) derivatives and conjugated them to hyaluronic acid (HA), peptides and poly(ethylene glycol) (PEG). These conjugates have been used in various tissue engineering projects in our group. ☐ Using the biorthogonal building blocks, I developed microfibrous scaffolds with a stiff poly(e-caprolactone) (PCL) core and a soft HA shell. The scaffold was prepared by electrospinning of PCL, followed by tetrazine-ligation mediated covalent layer-by-layer (cLBL) assembly. The resultant scaffolds support the attachment and growth of stiff-primed primary vocal fold fibroblasts (VFFs), and effectively suppress myofibroblast differentiation. ☐ Our collaborative team discovered that, in the presence of Si-Rhodamine (SiR) dyes, dihydrotetrazine (DHTz), a Tz precursor that is unreactive towards TCO, can be photo-catalytically activated to Tz under near infrared (NIR) light to induce rapid bioorthogonal chemistry. In the absence of light or SiR, a mixture of HA-DHTz and HA-TCO is a transparent liquid. Upon exposure to NIR light, instantaneous gelation occurred both in vitro under cell culture conditions and in vivo subcutaneously in mice. ☐ Using a slower dienophile (norbornene, Nb), I prepared a soft bulk gel by mixing HA-Tz and peptide-based bisNb with a Tz/Nb ratio of 5:2. Overlaying an aqueous solution of low molecular weight HA-TCO on the gel disk initiated a diffusion controlled interfacial biorthogonal crosslinking to stiffen the network. The time and duration of the interfacial crosslinking can be readily tuned. This platform has been successfully utilized to control stem cell function spatially and temporally. ☐ Collectively, this work demonstrates multiple novel methods to construct 3D network utilizing bioorthogonal chemistry, enabling the establishment of dynamic and cell-instructive matrices for tissue engineering applications.
Peptidoglycan fragment microarray platform for human immune system investigation
(University of Delaware, 2021) Zhou, Junhui
The human immune system's interaction with the bacterial cell wall plays a pivotal role in a variety of human diseases, such as Lyme Arthritis and Crohn's disease. The component of the bacterial cell wall, peptidoglycan (PG), is a mesh-like polymer made up of repeat carbohydrate units crosslinked by peptide chains. However, there are modifications on the carbohydrate and atypical peptides among pathogenic and commensal strains of bacteria. The study of this critical structure has been hampered by a lack of chemical probes derived from PG and tools for high throughput monitoring of PG interactions in both innate and adaptive immunity. Consequently, new chemical probes were synthesized based on PG to study their response against serum antibodies and immune proteins. The array takes advantage of the ability to produce synthetic PG fragments with amine linkage points (Chapter 3). The microarray assay was validated using a monoclonal antibody (mAb), 2E7, that targets muramyl dipeptide (MDP), a canonical minimal immunostimulatory structure of PG. The data showed that the immune system generates different pools of IgG versus IgA among individuals, suggesting that these pools could serve as a potential diagnostic tool for personal therapy (Chapter 2). ☐ To better assess the immunostimulatory properties of these fragments, we sought to develop the synthesis of the fragments, which would be released from the pathogenic bacteria. One crucial fragment is a product release from the lytic transglycosylases, 1,6-anhydro-disaccharide fragments; this feature is present in Tacheal Cytotoxin (TCT). The synthesis route of this important immunological fragment is 20-30 steps in good to excellent yields at a multi-gram scale. Moreover, the synthesis offers several derivation points presenting the opportunity for future probe development and medicinal chemistry campaigns (Chapter 5). ☐ To better understand the natural PG fragments released from the bacterial cell wall, our research laboratory developed a methodology to install bioorthogonal handles into the carbohydrate backbone of the PG. The probe with an azido group labeled on the 3-OH group of the MurNAc expanded the biological toolbox from the initial report of 2-amino probes. This MurNAc derivative was installed into the backbone of the bacterial cell wall and verified using mass spectrometry. Whole cells were fluorescently labeled via click chemistry and visualized using super-resolution microscopy. This bioorthogonal labeling strategy will help to address fundamental questions surrounding PG's role in immunology and microbiology, such as the physiology-relevant immunostimulatory fragments and tracking of bacteria PG in macrophage model systems (Chapter 4). ☐ The synthetic PG fragment library and the microarray incorporated with those fragments provide a platform to investigate human innate and adaptive immunity against bacterial muropeptides. Ultimately, this dissertation reveals "antibody fingerprints" and gene induction diversities for different PG muropeptides, suggesting that PG muropeptides for autoantibody investigation and immune signaling are too complex to be represented by minimal bioactive PG fragments such as MDP, iE-DAP, and N-glycolyl MDP (ng-MDP).
Increasing primary care adherence in behavioral health settings among adults with serious mental illnesses and substance use disorders
(University of Delaware, 2021) Foraker, Charis L.
Adults with Serious Mental Illnesses (SMIs) and Substance Use Disorders (SUDs) continue to demonstrate poor utilization of primary care services attributed to a lack of client engagement. In Delaware, adults with SMIs and SUDs have increased and the majority of premature mortality in this population is a result of undermanaged medical conditions. Improving the health of this population is dependent upon utilizing the primary care system. The aim of this this Quality Improvement project was to use Motivational Interviewing (MI) to promote behavioral change, specifically, to increase primary care visits in adult clinic members who utilized services for SMIs and SUDs. An integrated health clinic in Newark, Delaware, was the project location that provided services to adults with SMIs and SUDs. During a routine mental health telehealth visit, counselors approached clients who were 18 years of age and older, had a SMI and/or SUD, and received associated services. Counselors administered a questionnaire that inquired about using primary care services at the site and incorporated techniques of MI tailored for primary visit adherence. There were 421 clients took the questionnaire between October 23, 2020 through November 27, 2020. The percentage of 421 primary care appointments kept by clients was measured pre and post intervention. These measures were found to have increased from 2.3% to 5.9%. MI was an effective strategy to increase the percentage of primary care visits in adults with SMIs and SUDs in this clinical setting. However, more application of MI tailored for primary care adherence in adults with SMIs and SUDs is needed to support the sustainability of this outcome.
Characterizing the cellular requirements involved in the stability of a human innate immune receptor
(University of Delaware, 2022) Ukaegbu, Ophelia Ifunanya
The innate immune system is the body’s first line of defense against invading pathogen-associated molecular patterns (PAMPs). It relies on innate immune receptors such as Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) to initiate an immune response. NOD2 plays a pivotal role in bacterial peptidoglycan (PG) recognition, leading to the release of anti-inflammatory molecules via the NF-κB pathway. Three single nucleotide polymorphisms of NOD2 are implicated in the pathogenesis of Crohn’s disease (CD), a type of Inflammatory Bowel Disease (IBD) that affects the gastrointestinal tract. NOD2 CD variants are unstable and consequently it leads to their inability to respond to PG ligands. Previous studies have shown that some level of activation and stability is restored upon overexpressing the transcriptionally regulated Heat Shock Protein, HSP70. Additionally, an inducible increase of O-GlcNAcylation, a type of protein glycosylation that is tightly controlled by the enzymes O-linked β-N-acetylglucosamine transferase (OGT) and O-GlcNAcase (OGA), regulates NOD2 activity. However, the molecular mechanism and requirements of these actions have not been elucidated. NOD2 is glycosylated by OGT, but the specific O-GlcNAc residues that orchestrate NOD2 function are unknown. My thesis focused on probing critical protein interactions and modification sites that are crucial for NOD2 function as well as understanding the role of OGT and HSP70 on downstream NOD2-signaling. In working towards this goal, I showed that site-directed mutagenesis of a predicted O-GlcNAc modified serine residue into cysteine affects glycosylation, signaling, binding, and stability of NOD2. Furthermore, a novel interaction between NOD2 and OGT in the presence of HSP70 was identified, forming a NOD2:OGT: HSP70 complex. The complex formation was validated further by a web-based server, ZDOCK, that predicts protein-protein interactions based on a scoring system. Additionally, our findings suggest that O-GlcNAcylation modification of NOD2 is important for HSP70 binding in the cell, and both OGT and HSP70 work in concert to stabilize NOD2. ☐ In this work, I also developed chemical biology tools and mass spectrometric strategies for studying NOD2 glycosylation. UDP-sugar donors, which are ultimately used by OGT in the glycosylation reaction, were chemoenzymatically synthesized by OGT. Proteomic workflows were developed in an effort to identify the O-GlcNAcylated residues of NOD2. Two potential O-GlcNAcylation modification sites were identified by LC-MS/MS analysis using two search algorithms, SEQUEST and Byonic. Ultimately, these findings illuminate molecular mechanisms for modifying and potentially stabilizing NOD2 and CD-associated variants.
Understanding evidence and its use in out-of-school time programs
(University of Delaware, 2025) Lentz, Arielle Kathleen
Across a number of fields, “evidence” provides valuable information as to what works in practice. In out-of-school time (OST) settings, including before school, after school, and in the summer, we have observed as funders increasingly require programs to use “evidence” or “evidence-based practice” to obtain funds, with inconsistency among funders in how this term is used and defined. While evidence serves as valuable information that can guide programs in creating the best possible environment for young people, families, and communities, K-12 scholars have shown that evidence means different things to different people, and that several organizational and individual factors influence whether and how it is used in practice. If the use of evidence is tied to high stakes matters such as the operational funding for programs, we must deepen our understanding of what this term means in the field and how professionals use it in practice. Without this information, certain types of programs might face disadvantages in complying with requests for evidence use in funding applications. ☐ In this dissertation, I use two papers to critically examine what evidence means in the OST field, how professionals use evidence, and what factors influence the use of research as evidence. Overall, these studies demonstrate that OST programs are largely evidence-informed. However, many OST funders use the term “evidence” without defining what they mean by this word. When funders do define “evidence,” their definition is “research,” whereas OST professionals conceptualize the term more often as “data” or their own professional experiences. Several factors influence the use of evidence as research among professionals, including leadership, policy, staff, and partnership support, as well as professionals’ beliefs about whether research is relevant, valuable, and actionable. Taken together, findings can be used to encourage more critical consideration of what types of evidence we elevate in the field, and how calls for evidence, especially research, might systematically disadvantage some programs from obtaining funding. Additionally, this research can build greater external recognition of the value of OST programs as intentional, evidence-informed programs that can support young people, families, and communities beyond the school day.
Utilizing non-thermal atmospheric plasma (NTAP) for electrified chemical manufacturing and enhanced catalysis
(University of Delaware, 2025) Nguyen, Darien K.
As climate change accelerates, decarbonizing the chemical industry, one of the largest contributors to greenhouse gas emissions, has become increasingly urgent. This substantial contribution stems largely from the industry’s heavy reliance on fossil-fuel energy and carbon-intensive thermal processes. Process electrification offers a promising pathway to replace these fossil fuel-based processes with cleaner, more efficient alternatives powered by sustainable electricity. Among these, non-thermal atmospheric plasma (NTAP) emerges as a versatile electrified platform due to its non-equilibrium nature, which enables molecular activation at ambient temperatures and pressures, overcoming activation barriers without the need for combustion-based heating. ☐ This dissertation investigates the application of NTAP to decarbonize chemical production through direct chemical transformations, particularly of plastic waste and its derivatives, as well as through catalyst enhancement. Chapters 2 and 3 explore the chemical transformation of abundant and inert liquid n-alkanes into long-chain oxygenates via the plasma-liquid interface, with Chapter 3 advancing this work through process intensification using a continuous-flow biphasic microreactor. This reactor design enhances the plasma-liquid interfacial area, enabling higher production rates and improved efficiencies, while offering modularity and scalability. ☐ Building on this foundation, Chapter 4 demonstrates the extension of this platform to plastic waste-derived paraffins, enabling the transformation of plastics and biomass waste into renewable surfactants. These hybrid waste-derived surfactants exhibit superior performance compared to commercial surfactants produced from fossil fuels. In Chapter 5, the scope of plasma-assisted plastics upcycling is further expanded through the development of a novel NTAP method for bulk oxidation of polymers such as low-density polyethylene (LDPE). These bulk-oxidized LDPE materials serve effectively as compatibilizers in mixed plastic blends, offering a promising route for recycling mixed plastic waste streams. ☐ Chapter 6 continues the theme of plastics upcycling, shifting focus to the recycling of per- and polyfluoroalkyl substances (PFAS)-coated textiles. We demonstrate that NTAP is a highly effective method for removing polymeric PFAS coatings from UV- and water-resistant textiles, outperforming conventional Soxhlet and microwave extraction. In addition to removing the majority of PFAS coatings, plasma treatment transforms hydrophobic fabrics into hydrophilic ones, thereby enhancing glycolysis depolymerization through improved solvent uptake. ☐ Finally, Chapters 7 and 8 pivot to utilizing NTAP as a surface activation technique for catalyst engineering. Chapter 7 demonstrates rapid surface oxidation activated carbon supports via NTAP, enhancing metal dispersion. Chapter 8 employs a plasma-based method for complete ligand removal from nanocatalysts without altering particle morphology. Both approaches contribute to improved catalytic performance for key biomass transformations. ☐ Collectively, this dissertation establishes NTAP as a powerful electrified technology for decarbonizing chemical production by enabling new pathways for hydrocarbon valorization, engineering advanced catalysts, and advancing sustainable chemical manufacturing.
Hidden labor and legacies: Colored Conventions, Black women and educational activists
(University of Delaware, 2025) Burgher, Denise Georgette
In spite of their absence from archives and records, Black women educators enacted and taught the principles of what I term, Sacred Black citizenship through institutions ranging from the Invisible Church, the formal Black church, early Black benevolent societies and the Colored Conventions Movement. Sacred Black citizenship was explicitly taught, modeled, and practiced in homes, Sunday school benches and classrooms for well over a century. Black teachers taught and molded Black citizens long before American laws and jurisprudence conceived of the possibility of Black American citizenship and are responsible for creating and articulating a Black rhetoric I call, Sacred Black Testimony. In fact, it was these thousands of Black students who would go on—within a hundred years of enslavement and in spite of the crushing force of laws, dominant white religion, culture, and habit—to demand and realize civil rights in the twentieth century. These righteous demands forced a national reckoning with the contradictions between the ideas and ethics of American life and law with the deeply racist, unfair brutish realities. Educational activists developed the premises of American public education which came to inform and shape national educational activism leading eventually to the formation of the Department of Education in 1979. This dissertation traces the lives and labors of Black women through nineteenth century records and archives of their activism ending with an analysis of Delaware as a case study of Black women’s educational activism nationally. I contend that it is through the careful examination of nineteenth century Black women educational activists who created a praxis of their faith that we can trace and understand the promises and challenges of American public education as they taught Sacred Black citizenship to their students and encouraged them to claim their rights and privileges as full citizens.
Do you know them?: maintaining Black family bonds during Reconstruction
(University of Delaware, 2025) Anderson, Olivia Denise
Freedom, for freed people in the United States, could take several forms, but the reunification of family was a priority for most, if not all. The federal government, their resources, and the state government, though tasked with aiding the reunification process during Reconstruction provided little support and often prevented the reunification process with laws and societal expectations thrust on freed people. I analyze the federal and state government’s role in the reunification process, and freed people’s response to their intervention, through three methods: marriage, child apprenticeship, and information wanted advertisements published in the newspapers. The tenacious attitude to maintain and rekindle relationships lost by slavery are a significant Africanism found in the freed population and crucial to their survival after slavery.

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