Doctoral Dissertations (Winter 2014 to Present)
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Browsing Doctoral Dissertations (Winter 2014 to Present) by Title
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Item A 3D photonic sensor integrated tissue model for strain sensing(University of Delaware, 2019) Geiger, Sarah J.The study of wound healing and wound healing therapies is motivated by the need to prevent the formation of thick scar tissue in pathologically healing wounds and tissues that rely on their elasticity and modulus to perform their function, such as cardiac and vocal fold tissues. The development of in vitro platforms that can detect cell-induced strain in mimics of healing wounds has expanded our understanding of the mechanical, chemical, and physical cues that drive wound healing. However, these platforms are limited in their resolution, dimensionality, and ability to gather information about changes in strain throughout thick, opaque tissue models. In this work we describe the development of flexible, deterministically buckled 3D photonic device arrays that are designed and fabricated to meet the specific spatial, temporal, and strain resolution requirements needed for the detection of cell-induced strains in a millimeters-thick tissue model. ☐ A polymer or silicone-clad Ge23Sb7S70 chalcogenide glass resonant cavity array is selected for this application, as high-quality chalcogenide glasses devices can be deposited at low temperatures onto flexible and cytocompatible substrates. However, the reliability of these and other highly sensitive chalcogenide glass devices is affected by their aging-induced structural relaxation. The refractive index shifts resulting from this relaxation are on the same order of magnitude as the index shifts used to small-scale strain with our device arrays. In order to overcome this limitation, we develop and demonstrate a high-precision refractometry technique that tracks small changes in the refractive index of Ge23Sb7S70 chalcogenide glass, down to 10-5 RIU. This technique allows us to both identify the aging mechanism in this glass with high accuracy and compare different index stabilization methods to optimize our device processing. ☐ The expected performance of these arrays was tested both through finite element modeling and a proof-of-concept in vitro experiment. In the modeling experiments, PDMS buckled geometries were deformed in cardiac graft tissue-like environments. From these experiments we showed that devices embedded in these materials could easily detect small, localized changes in stiffness theoretically caused by limited perfusion of growth factor throughout this model. In vitro, an SU-8 clad, symmetrically buckled device was exposed to a contracting collagen gel, and the device response as a result of this deformation was analyzed. ☐ These deterministically buckled arrays of polymer or silicone-clad chalcogenide glass resonant cavities demonstrate sensitivity to relevant strains in 3D cell culture platforms, excellent ease of use, and the potential for a wide range of applications. This technique can be used as a standalone, low cost, plug-and-play local strain gauge for use in soft material systems. Thus, this technique’s flexibility both in terms of its deformability and range of applications easily surpasses other methods of in vitro force or strain detection.Item 3D reconstruction from coded plenoptic sampling(University of Delaware, 2019) Zhou, MingyuanThe plenoptic function describes a scene in terms of light rays, it is a 7-dimensional function with spectral, directional, spatial, and temporal variation. Traditional plenoptic sampling is acquired either by employing a standard plenoptic camera or a camera array, and the spatial-angular sampling can be potentially used to model 3D surface. ☐ In this dissertation, I present three coded plenoptic sampling schemes, i.e., the rotational cross-slit (R-XSlit) plenoptic sampling, the wavelength coded plenoptic sampling, and the polarimetric plenoptic sampling. The additional coded sampling information, such as non-centric sampling, spectral sampling, and polarization sampling, are conducive to 3D reconstruction. Therefore, I also develop the corresponding 3D reconstruction framework for each of them. ☐ First, I introduce the R-XSlit plenoptic sampling scheme by exploiting a special noncentric camera called the crossed-slit or XSlit camera. An XSlit camera acquires rays that simultaneously pass through two oblique slits. I show that instead of translating the camera as in the pinhole case, we can effectively sample the 4D plenoptic sampling by rotating individual or both slits while keeping the camera fixed, which makes the plenoptic sampling coded in the spatial-angular domain. The theoretical analysis shows that it provides denser spatial-angular sampling, which is beneficial for scene reconstruction and rendering. I develop a volumetric reconstruction scheme for scene reconstruction. ☐ Second, I present two wavelength coded plenoptic sampling schemes in the visible and infrared spectrum respectively. I firstly design a compact system with lights and cameras arranged on concentric circles to acquire a concentric wavelength coded plenoptic sampling in the visible spectrum, the cameras on each ring capture images in a unique spectrum. I employ the Phong dichromatic model onto its plenoptic function for 3D reconstruction and spectral reflectance map estimation. Experiments show that our technique can achieve high accuracy and robustness in geometry recovery. Moreover, I present an infrared wavelength coded plenoptic sampling and develop a hybrid sensing framework to efficiently achieve pose estimation and face reconstruction by exploiting the captured reflected infrared rays from human eyes. ☐ Finally, I present a polarimetric plenoptic sampling framework for recovering 3D surfaces, the polarization of light is included in its plenoptic function. I employ a new analysis analogous to the optical flow to correlate the polarization radiance function with both surface normal and depth. The proposed framework effectively resolves the azimuth-zenith ambiguity by forming an over-determined system. Extensive experiments on both synthetic and real data demonstrate that the technique is capable of recovering extremely challenging glossy and textureless objects.Item A balancing act: examining the relationship between school leadership and political tension in education decision making(University of Delaware, 2023) Cahill, AmandaThe United States has a long history of political tension around education at the federal, state, and local level. District and school leaders must balance students’ learning and social needs while working to address political tension barriers on education decisions. Political tension involves the feeling of strain or anxiety around topics aligned with political ideology. The strain and anxiety generally result in difficulty with efficiently moving forward with clear decision making, specifically in education. Education decisions are choices made by district and school leaders that affect students’ growth academically within the school setting. Examples of education decisions could include restructuring the administration team, endorsing a specific curriculum, or implementing an enrichment program. Researchers have written extensively about effective leadership approaches but there is a lack of literature on strategies for how school leaders, particularly at the district level, can address political tensions that create barriers to decision making. School leaders' abilities to address political tension would support efficacious decision making with a focus on positive outcomes for students. ☐ Overtime, as politics has become more contentious, districts’ decision making has come under attack. These attacks significantly disrupt the ways in which school districts make and implement reforms, school improvements, policy changes, and the like. District and school leaders lack strategies and resources to proactively address political tension barriers which results in sporadic and often poorly implemented or communicated decision making. These implementation and communication failures are then poorly received by the community. The constant politicization of school decisions has caused leaders to focus on responding to political tensions, rather than focusing on decision making that can positively impact students’ learning needs. Therefore, it is imperative that educational leaders are equipped and prepared to address political tensions that cause barriers so that they can remain focused on decision-making processes that result in positively supporting students’ learning and social needs. Education leaders need both the resources and the opportunity to apply decision-making strategies that simultaneously address political tensions and remove barriers in order to communicate more effectively and work harmoniously with their school community. ☐ In my educational leadership portfolio (ELP), I focus specifically on how political tensions on the national level are influencing the decision making of local district and school leaders. I evaluated the relationship between district and school leaders’ decision-making process and political tension barriers within a rural school district in the Mid-Atlantic region. I used a rural school district as a case study to explore strategies district and school leaders need to manage political tension barriers without compromising decision making aimed at supporting student growth academically, socially, and emotionally. In this ELP, I gathered data through a case study. The ELP proposes a decision-making framework that district and school leaders can proactively utilize when they predict, or encounter, political tensions that result in barriers that may impede their ability to make decisions.Item A bioorthogonal hydrogel platform for the development of an engineered vocal fold tissue model(University of Delaware, 2022) Song, JiyeonVocal fold lamina propria, with a complex multilayered structure, exhibits optimal biomechanical properties for voice production. Vocal fold scarring disrupts the laminated structure, alters the tissue viscoelasticity, and severely compromises the phonatory function. Therapeutic interventions are limited because of the lack of understanding of molecular mechanisms contributing to vocal fold scarring. The situation is exacerbated due to the scarcity of healthy human tissues, inability of animal models to recapitulate the human physiology, and unavailability of in vitro physiologically relevant tissue models. ☐ The goal of this dissertation is to develop a bioorthogonal hydrogel platform for the engineering of a human vocal fold tissue model. To this end, hydrogel precursors tagged with bioorthogonal tetrazine (Tz), trans-cyclooctene (TCO), norbornene (Nb), thiol (SH) or acrylate (AC) groups were synthesized using hyaluronic acid, synthetic polymers, and bioactive peptides. Various dienophiles with different reactivities toward tetrazine were conjugate to matrix metalloprotease (MMP)-degradable peptides, integrin-binding RGD peptide, and basic fibroblast growth factor-mimetic peptide. The composition and purity of these conjugates were characterized by proton nuclear magnetic resonance (1HNMR), high performance liquid chromatography (HPLC), mass spectrometry (MS), and ultraviolet-visible spectroscopy (UV-vis). ☐ Using the modular building blocks, a lamina propria-mimetic construct with a layered structure was developed. Taking advantage of the exceptional rate of the Tz/TCO reaction, a diffusion-controlled interfacial crosslinking method was devised for the fabrication of a hydrogel sphere with a 3D core-shell pattern. By changing the ratio of the monofunctional capper and the bifunctional TCO crosslinker, hydrogels with a Young’s modulus ranging from 4 kPa to 20 kPa, comparable to that for human vocal fold LP, were obtained. Additionally, the diffusion-controlled method permitted precise spatial control of the enzymatic degradability and cell adhesivity in core and shell layers where homogeneously encapsulated human mesenchymal stem cells (hMSCs) exhibited different cell morphologies at each layer. ☐ Finally, a bioorthogonal hydrogel platform that recapitulates dynamic alterations in matrix properties during wound healing was engineered. The slow Tz/Nb was utilized to establish the covalent hydrogel networks for 3D cell encapsulation. The rapid Tz/TCO ligation enabled real time in situ modulation of the density of RGD ligands. The diffusion-controlled reaction also allowed the time-delayed introduction of RGD peptides to cell-laden hydrogel constructs, mimicking the progressive deposition of fibronectin during the early stage of wound healing. Transforming growth factor beta 1 (TGFβ1)-induced myofibroblast differentiation from primary vocal fold fibroblasts was observed only at a high RGD concentration, as evidenced by the development of alpha-smooth muscle actin (αSMA) positive F-actin stress fibers. The RGD-driven phenotype change was accompanied by enhanced cytokine secretions and matrix remodeling. ☐ Overall, I presented a powerful bioorthogonal platform for spatiotemporal presentation of biochemical and biomechanical signals to direct cellular responses and differentiation. This work represents the first step towards the development of a hydrogel-based cellular model of the human vocal fold lamina propria in both healthy and diseased states.Item A bounding surface plasticity-based hyperelastic constitutive model for unsaturated granular soils(University of Delaware, 2019) Kadivar, MehdiOne-third or more of the earth’s surface is situated in arid or semi-arid regions where the potential evaporation exceeds the precipitation and soils exist in their unsaturated state. Unsaturated soils are also abundant in most parts of the world where there is seasonal groundwater table fluctuation. The variation in the degree of saturation gives rise to a gamut of variability in soil’s hydromechanical behavior. The co-existence of pore-air and water in the void spaces and their interaction with each other and the solid particles are the main reasons why such variability exists and why unsaturated soils are more complex than saturated or dry ones. A robust understanding of the hydromechanical properties of unsaturated soils is crucial for geotechnical engineers worldwide, as well as for those concerned with the interaction of structures with the ground. Some engineering problems associated with unsaturated soils include precipitation-induced shallow-depth landslides, settlement of soil in the vadose zone, drainage of roadway materials, and borehole stability. ☐ Proper understanding of unsaturated behavior requires considerations that go beyond those available for saturated soils. In pursuit of addressing this requirement, a plethora of research has been devoted to measuring, modeling, predicting, and interpreting unsaturated soil behavior. Many theories for characterizing the mechanical response, methodologies for laboratory testing, as well as equipment to determine the constitutive parameters have been developed. Instruments to study in-situ behavior of unsaturated soils have also been promoted and used in a few cases. The outcomes of past research include: the development and critical evaluation of various forms of the effective stress principle and its fundamental role in determining strength and deformation properties of unsaturated soils; identification of independent state variables; development of failure envelopes and yield surfaces; formulation of macromechanical and micromechanical constitutive relationships; and formulation of suction-induced stress as a component of the intergranular stress tensor. Despite the volume of work dedicated to the field of unsaturated soil mechanics, compared to two-phase (i.e., saturated) soils, relatively few advancements have been made in the development of characterization frameworks for unsaturated soils. ☐ In this doctoral research, a novel, 14-parameter, state-dependent bounding surface plasticity model that simulates the behavior of unsaturated granular soils is developed. In the development of this model, a critical state compatible hyperelastic formulation for saturated granular soils is selected as a base model and is enhanced and extended to predict unsaturated granular soil behavior. Accounting for deformation phenomena in unsaturated soils, the elastoplastic response has no purely elastic component. The hyperelasticity and assumption of no purely elastic deformation sets this model apart from existing ones. To handle the inherent hydro-mechanical coupling in unsaturated soils, a newer generation stress framework, consisting of the Bishop-type effective stress with a second stress variable, is used in conjunction with a soil-water characteristic curve function. ☐ Available unsaturated soil data for sands and silty sands were used to calibrate, validate, and assess the performance of the new model. Additional laboratory data, consisting of a suite of consolidated drained triaxial shear tests, were generated. The shear strength and volumetric behavior of a native mid-Atlantic transitional silty sand were investigated under varying values of matric suction, confining pressure, strain rate, and fines content. The experimental results are used to validate the predictive capabilities of the new bounding surface plasticity constitutive model for unsaturated granular soils. It is shown that with a set of parameter values, the model realistically simulates the main features that characterize the shear and volumetric behavior of unsaturated granular soils over a wide range of matric suction, density, and net confining pressure. In the literature, it was observed that multiple analytical expressions exist for effective stress, critical void ratio, and soil water characteristic curve. To see the effects that variations in these different analytical forms have on the model simulations of unsaturated soil behavior, a parametric investigation is performed using the constitutive model developed and the aforementioned in-house generated laboratory data. It is observed that, depending on the desired prediction accuracy, a variety of functions (with varying numbers of model parameters) could be implemented as part of the constitutive model.Item A comparative evaluation of the microbiome effects on easy and hard keeper horses(University of Delaware, 2023) Johnson, Alexa C.B.Horses with different metabolic tendencies are anecdotally referred to as “easy” or “hard” keepers. Easy keepers (EK) tend to gain weight easily while hard keepers (HK) require extra feed to maintain body condition. Horses that do not struggle with maintaining a healthy weight are referred to as “medium keepers” (MK). The horse, as an obligate herbivore, relies on the gut microbiome to provide more than half of its energy requirements. Therefore, equine energetics and metabolism is greatly influenced by the gut microbiome. It is not yet known what causes a horse to be an EK, MK, or HK but, I hypothesize that the gut microbial structure and function play a vital role in equine metabolic tendencies. The dynamic interactions between the horse and its gut microbiome likely reflect individual capacities and genetics to harbor specific populations as well as host-specific abilities to utilize available nutrients. To test this central hypothesis regarding the microbial side of the conversation, these research projects focus on the bacterial and protozoal fractions. ☐ The first objective of this work was to develop a reliable and standardized tool for determining equine keeper status. The lack of a standardized method to identify equine keeper status requires reliance on the owner reported keeper statuses which is unreliable and irreproducible. The Equine Keeper Status Scale (EKSS) was developed and validated on data gathered from 240 horses. With EKSS assignments, incorrect keeper status assignments provided by owners was reduced by 60%. The EKSS was used in all further studies to identify EK, MK, and HK study cohorts. ☐ The second objective of the project was to compare bacterial composition (16S rRNA surveys) of EKSS statuses. 16S rRNA surveys of equine feces in an observational study (n=73) found differences in alpha and beta diversities and taxa abundances based on EKSS assignments. However, when a controlled cohort (n=12) was used, significances in alpha and beta diversities were lost, but unique bacterial cores and representative bacteria of each EKSS status were found. Determining the bacterial core of each EKSS status will aid during probiotic choice and probiotic development to target these key groups and improve EK and HK weight management strategies. ☐ The third objective was to compare protozoal composition (18S rRNA surveys) of EKSS statuses. As an extension to this objective, we sought to obtain reference sequences for uncharacterized protozoans to improve molecular methods to identify protozoans. Two previously unsequenced equine protozoan species (Blepharocorys valvata and Blepharoconus benbrooki) and two other equine protozoans (Tripalmaria dogieli, Cochliatoxum periachtum), were successfully single sorted and sequenced. After the addition of these sequences to the classifier, the protozoan (18S rRNA) profile of horses (n=39) in the Mid-Atlantic Region and EKSS statuses were evaluated. Thirty-five species level protozoans were identified in the Mid-Atlantic Region, and protozoal richness was lowest in HK horses compared to EK and MK animals (P = 0.05). Describing the commensal protozoal fraction is the first step towards ultimately understanding this population’s purpose during microbial metabolism and host health. ☐ The fourth objective was to determine if bacterial activities differed between EKSS statuses. Bacterial functionality between EKSS statuses was tested using PICRUSt to hypothesize fermentative differences between the gut microbiomes, and 48h in vitro challenge protocols. PICRUSt predictions were performed on the 16S rRNA surveys from the observational study (n=73) and found overall, 18 metabolism pathways were differentially abundant in EKSS statuses (P < 0.10); seven of which were significantly enriched in the EK representing both foregut metabolism (i.e. starch and lipid digestion), and hindgut metabolism (i.e. fiber and amino acid digestion). PICRUSt is inherently limited but these results indicate that the EK has an enhanced metabolic potential to breakdown feed and harvest energy compared to the MK and HK. ☐ In vitro experiments (n=12) demonstrated that the HK microbiome had the quickest and most drastic reaction to both carbohydrate and protein challenges. The slower metabolic response demonstrated by EK cultures may be a resiliency mechanism that these communities utilize to slow overall metabolism while increasing ATP production. These different bacterial responses suggest unique microbial strategies between keeper communities to maintain stability that may ultimately change metabolism patterns. ☐ In conclusion, the data collected from these studies supports our central hypothesis that the microbiome plays a pivotal role in equine keeper status. Our results suggest that bacterial activity and functionality are more influential towards equine keeper status than the bacterial composition. Results further suggest that the protozoan population is a significant contributor in equine keeper status and this population deserves further investigation.Item A comparison of three effect size indices for count-based outcomes in Single-Case Design studies(University of Delaware, 2023) Shrestha, PragyaIn Single-Case Designs (SCD), the outcome variable most commonly involves some form of count data. However, statistical analyses and associated effect size (ES) calculations for count outcomes have only recently been proposed. Three recently proposed ES methods for count data are: Nonlinear Bayesian effect size (Rindskopf, 2014), Log Response Ratio effect size (Pustejovsky, 2018), and Bayesian Rate Ratio effect size (Natesan Batley, Shukla Mehta, & Hitchcock, 2021). Although all three methods calculate ES for count outcome data and can be used with an ABAB design, they use either different statistical modeling or a different estimation framework (Bayesian or frequentist), they may assume the presence or absence of autocorrelation, which is frequently present in SCD data and it is yet to examine how the ES and standard error estimates from these three ES indices are affected by overdispersion, a common occurrence in count data. These fundamental differences call for a closer examination and comparison of the methods and estimates obtained. The proposed dissertation aims to investigate the interpretability and understandability of the estimates produced as proposed by May (2004), examine if the three ES indices can be converted to a common metric to facilitate comparison of the ES estimates, document the benefits and challenges while implementing each method, and examine the performance of these ES methods under positive autocorrelation and overdispersion using Monte Carlo Simulation. Schmidt (2007), a published SCD study that examined the effect of Class-wide Function-related Interventions Teams (CW-FIT) on reducing the disruptive behavior of three first grade students using an ABAB design, was used to examine the interpretability and understandability of the estimates produced and whether the indices can be converted to a common metric. It consisted of 3 cases with 4 phases (ABAB) for each case. For the simulation study, 1000 datasets for each case were simulated using pre-specified data parameters (number of cases, number of data points within each phase of a case, and phase means) taken from Schmidt (2007) study and for various conditions of autocorrelation and overdispersion. A fully crossed factorial design with three autocorrelation (0.0, 0.2, 0.4) and four overdispersion (0.0001, 0.05, 0.1, 0.3) resulting in 12 simulation conditions for each case was used for the data generation purpose. All analyses were carried out in R software. Results indicate all three ES estimates are interpretable. LRR meets the understandability criteria, however both BRR and NLB require advance statistical knowledge to run the models. The three ES can be converted to a common metric because they are ratios of the mean count of the phases. Based on simulation, all the three methods produce almost unbiased estimates of the effect size under different data conditions, however the standard error is affected by autocorrelation and overdispersion. This dissertation can serve as a resource for other SCD researchers and applied practitioners to understand and interpret the different ES values from the LRR, NLB, and BRR methods and help them make better informed decision about which of the three ES indices to use in their own research study if there is presence of autocorrelation and overdispersion in their data.Item A dynamic network model with an application to interbank market(University of Delaware, 2023) Zhang, HaiciAmong central bankers and the wider academic community, interbank network analysis has received an increasing amount of attention over the past few years. In view of the high degree of interconnectedness of the financial interbank network, network theory provides a natural framework for the study of the robustness of the interbank system as a whole and its resilience to risk contagion. A good understanding of the nature of the interconnections among the interbank network and of how these interconnections respond to changes in market conditions is also vital for policymakers when they are designing regulations and monitoring systemic risk. Aiming at understanding the dynamic interconnectedness in the banking system, this dissertation proposes three dynamic network models for the e-MID electronic interbank network. ☐ In the first part of this dissertation, we propose a Bayesian dynamic interbank network model where three mechanisms control the likelihood of a link between two banks: (i) a time-series interbank activity index that expresses overall confidence of interbank across time, (ii) bank-specific latent variables describing banks’ tendency to be borrowers or lenders, and (iii) covariates characterizes pairwise past relationships. A large fraction of previous research on interconnectedness studies static and aggregated interbank networks which only reveal information about long-term connectedness (such as core-periphery structure) inside a network, and lack of studies exploring the dynamics of interbank networks. To address this research gap, we formulate a flexible dynamic interbank network model and design its novel sampling method for computational efficiency. We then demonstrate the superiority of our proposed method in a variety of areas. First, we use the proposed cross-sectional latent variables instead of general network topology statistics to explore whether these variables are representative of changes in network topology and can be used to predict macroeconomic variables that reflect the health of the banking system. Secondly, we evaluate the goodness-of-fit of the model with interbank link predictions and evaluate the results using AUC and different prediction errors. In addition, we propose two proxies for relationship lending based on information sharing, using the latent variables in our proposed model. Based on the regression results, the two proxies are significant during both the pre-crisis and crisis periods. To make the model to be more interpretive from the view of probability theory, rather than linking the binary data of the adjacency matrix to a latent variable with a probit link, we assume that the binary data has a Bernoulli distribution with a probability of success rate which is a logiit transformation of the three underlying trading mechanisms discussed in the first study. Though it makes the results more interpretive, more constraints and auxiliary variables are applied to make the estimation process converge. ☐ In the second part, we apply a GC-LSTM ( GCN units that are embedded into the LSTM framework) deep learning approach to model dynamic interbank networks. The deep learning model has to use in transportation ((Lei et al. (2019)) and social networks ((Martinez-Jaramillo et al. (2014)) but it has not been applied to any financial interbank transaction data. To see whether the deep learning model is good at capturing the spatial-temporal information of interbank network topology and making a good prediction, we apply this method to analyze the e-MID dataset. Compared with the statistical dynamic network methods, the deep learning method requires fewer assumptions and easier parameter estimation strategies. The results validate that our model outperforms the benchmarks in terms of AUC and PRAUC. Meanwhile, we also compare the results for crisis and pre-crisis periods, we find that the deep learning model is better than the traditional models in both crisis time and pre-crisis periods. In addition, the GC-LSTM model is better at predicting future links in the crisis period than the traditional statistical models which indicates that the model without statistical underlying assumptions is better at capturing structure change.Item A dynamic tunable platform to manipulate fibroblast activation(University of Delaware, 2023) Cao, ZhengAdverse remodeling of the heart after myocardial infarction (MI), also known as cardiac fibrosis, will lead to the stiffening and anisotropic conversion of myocardium tissue and stoppage of blood throughout the body, which will eventually cause death. The annual cost for treatment of MI causes a heavy burden to patients. However, most current treatments are limited to the implantation of cardiac patches, cardiac stents, and bypass surgery, which are non-targeted therapies. Moderate myocardial fibrosis contributes to the positive regeneration of the heart after MI, whereas excessive fibrosis can lead to irreversible remodeling and impair the function of the heart. Thus, a systematic investigation of cardiac fibrosis development and myocardium remodeling after MI is in urgent need in order to unveil the mechanism of cardiac fibrosis development and translate it into targeted therapeutic strategies. ☐ In vitro substrates have been broadly applied in the biomedical field as disease model platforms for physiological and pathological processes. Creating an in vitro model for post-MI tissue study that can mimic the physical properties of an infarcted heart with spatial-temporal variation is critical as the building block, yet there has not been an effective device used to recapitulate the dynamic nature of the infarcted heart tissue. The recent emergence of novel material with stiffness-tunability in response to an external magnetic field, magnetorheological elastomers (MREs), reveals an excellent in-situ modulation of stiffness with a wide range which provides a promising tool for biomedical applications. However, the widening of the hysteresis loop observed in MREs is not identical to the characteristic hysteresis loop of the soft ferromagnetic material, which was previously attributed to particle motion. Thus, unraveling particle motion within the matrix is an urgent need and a critical step to explain the magnetic hysteresis loop widening of MREs, which will facilitate and expand its biomedical applications. ☐ Ultrasoft MREs made by incorporating carbonyl iron particles into soft Sylgard 527 polydimethylsiloxane (PDMS) showed large magnetic-field-dependent changes in their stiffness changes. Our recent studies exhibited the widening of the magnetic hysteresis loop in these soft MREs compared to the relatively pinched loop observed for the stiffer MREs. This interesting behavior made us hypothesize that iron particle displacement in response to the external magnetic field within the soft PDMS matrix contributes to the magnetic hysteresis loop widening. We experimentally validated our hypothesis by tracking fluorescently labeled carbonyl iron particle motion in the MREs responding to various magnetic field strengths. Particle coating and bioconjugation of fluorophores were also characterized to validate the success of modification and retention of the magnetic properties of modified carbonyl iron particles. Our findings for the first time demonstrate the successful modification of carbonyl iron particles and observe that particles primarily move along the external magnetic field direction within the MREs material and such particle displacement results in the magnetic hysteresis loop widening. ☐ One of the physical cues after MI is cardiac tissue stiffness with spatial-temporal variation. The infarct border zone, a tissue region that is situated between infarcted tissue and adjacent healthy tissue, exhibits gradient stiffness change. The border region is of great importance and interest in the inflammatory and remodeling after MI involving infarction expansion, fibrosis formation, and reparative process. The efforts researchers have been building have advanced the development of a variety of in vitro platforms to mimic the microenvironment of infarct border region allowing us to have a more controllable and cost-effective approach to characterize the microenvironment features. Whereas the dynamic nature of gradient stiffness of infarct border zone has not yet been achieved. In this work, we use MREs as our base material to fabricate an innovative 2D in vitro platform with the capability of in-situ modulation on the stiffness gradient mimicking the continuously changing microenvironment of infarcted myocardium. This allows us to examine the inflammatory response of primary cardiac fibroblasts (NHCF-V) in a spatiotemporal manner regarding the different biomarkers’ expression, including αSMA, TGF-β, ACTA2, COLI/III, and MMP1. We found that cardiac fibroblasts exhibit spatially different activation and cytokine secretion in the infarcted and remote regions within the same model and presented a phenotypic conversion as time proceeded. COL1A1/3A1 and MMP1 exhibit a more robust regulation at 24 h. Additionally, the tunability of such a gradient stiffness model allows us to modulate the stiffness gradient on demand, either increasing or decreasing the stiffness gradient, to mimic different stages during remodeling process. Recognizing that remodeling is guided by many different types of cues that co-exist in vivo, it is also important to recognize that these cues may cooperate or compete to ultimately direct remodeling. Specifically, we examine the competition and cooperation of a chemical cue (anti-fibrotic drug, A 83-01) and mechanical cue (substrate softening) in tandem to attenuate fibrotic biomarker responses of cardiac fibroblasts. Individual intervention by drug and softening exhibited a competitive and/or cooperative effect on the combined intervention in order to regulate fibrosis. This work reveals the spatiotemporal variation of fibrotic response in cardiac fibroblasts as well as the complexity of anti-fibrotic drug dosing and stiffness-varying interactions on cardiac fibroblasts. This platform with a more realistic microenvironment will not only provide us with a unique in vitro tool to study disease progression mechanisms, such as cardiac fibrosis, but also serve as a cost-effective, pathophysiological relevant model for potential therapeutics screening. ☐ Topography, particularly the anisotropic structure of heart tissue, is another important physical cue in the in vivo cellular microenvironment after MI. Integrating anisotropic features with stiffness-tunable materials not only allow us to construct both physiological and pathological relevant building block but also enable us to probe interactions between topography and stiffness cues. In this study, we introduced an alternative MRE as our in vitro substrate, EcoGel MREs, which retains higher anisotropic pattern fidelity than conventional MREs. Our results indicate that the combination of dynamic changes in stiffness with and without topographic cues induces different effects on the alignment and activation or deactivation of myofibroblasts. Specifically, cells cultured on patterned substrates exhibited a more aligned morphology than cells cultured on flat material; moreover, cell alignment was not dependent on substrate stiffness. On a patterned substrate, there was no significant change in the number of activated myofibroblasts when the material was temporally stiffened, but temporal softening caused a significant decrease in myofibroblast activation, indicating a competing interaction of these characteristics on cell behavior.Item A graph limit approach to seriation(University of Delaware, 2023) Mishura, TeddyThe study of graph limit theory began in earnest in 2006 with the publication of the paper Limits of dense graph sequences by Lovász and Szegedy. Through the lens of homomorphism densities—the probability that a random map from a fixed graph F to a graph G is a homomorphism—this paper introduced new tools to the mathematical world that allowed sufficiently large networks to be viewed as random samples from a suitably chosen symmetric function w : [0, 1]2 → [0, 1] called a graphon. Furthermore, Lovász and Szegedy showed that this method of convergence is equivalent to convergence in a specific norm known as the cut norm, where graphs are embedded into [0, 1]2 as step function in the form of their adjacency matrices and the distance is calculated between these step functions. This allows for graph theoretical questions to be translated into questions about step functions, where more standard tools of analysis can be employed. Furthermore, in the reverse direction, one can study how analytical properties of the function can affect the combinatorial properties of its sampled graphs. ☐ We address this question in the context of geometric graphs, whose edge structure is derived from a linear embedding in R. This forces their adjacency matrices to increase toward the main diagonal, also known as the Robinson property, and one that easily translates to graphons. Given a convergent sequence of graphs that become increasingly close to geometric graphs—in the sense of the cut norm—can one claim the limiting object must also be Robinson? This question was solved completely in the affirmative for dense graph sequences, which are sequences of graphs Gn with positive edge density |E(Gn)|/n2 . We therefore focus on graph sequences that are not dense, e.g. whose edge density tends to 0, which corresponds to studying graphons that are unbounded but have finite p-norm. Such graphs are often referred to as being sparse. ☐ Specifically, we introduce and investigate a graph parameter Λ that measures by how much a graphon “fails” to be Robinson, and which is continuous with respect to the cut norm. We also develop a method that constructs Robinson approximations of Lp graphons such that the difference in cut norm between the original graphon and the approximation is dependent on Λ of the original; thus, the closer to being Robinson the original graphon is, the better the approximation.Item A history of African-American public school education in Louisville, Kentucky, 1840-1956(University of Delaware, 2017) Jones, S. SeabrookThis dissertation examines African-American public school education in Louisville, Kentucky, beginning with the free black community’s creation of private schools for their children in the 1840s and concluding with the desegregation of the city’s public schools in 1956. Throughout this period, the local black community’s primary obstacle in securing improvements to black education in Louisville was the local white community’s belief in the superiority of their city’s black schools relative to public schools for African-Americans elsewhere in Kentucky and the rest of the South. ☐ The comparative strength of Louisville’s public schools for black students was demonstrable. As discussed in chapters two and three, my research found that the Board of Education of Louisville spent more money on their black schools than almost anywhere in the South. These schools had an entirely African-American faculty led by black administrators. This faculty also enjoyed wages seven times higher than those paid to black teachers elsewhere in Kentucky. Over the years, the Board built a number of fine facilities for African-American schools. However, while Louisville whites prided themselves of these facts, the local black community fought a continuous battle to achieve equality for their children with what the city’s white children received. ☐ My historical analysis shows how throughout the existence of separate schools for African-American children in Louisville, black citizens’ ability to exert influence over local politics directly correlated with their ability to affect change for black public schools. This accounts for the school board providing the same curriculum for white and black elementary schools and allocating white citizens’ taxes to help pay for black public schools from the ratification of the Fifteenth Amendment through a restructuring of school board elections in 1910 that rendered the black vote nearly obsolete. As examined in chapters four and five, once the black community’s political influence over the Board of Education waned, dramatic fissures in spending and curriculum emerged between white and black schools at all levels. Fortunately, national party shifts led to a revival of black political relevance in Louisville as Republicans fought to keep the loyalty of black voters who had begun absconding for the Democratic Party in the 1930s. Chapter six observes how Louisville’s African-American citizens used this opportunity to force the Board of Education to include black school facilities in their bond issues and, most impressively, to equalize black and white teachers’ salaries in the final years of the Great Depression. ☐ The seventh and concluding chapter of this study examines the 1956 desegregation of public schools in Louisville. Although nationally heralded by the press and politicians as a success, my research highlights the limits of this desegregation. The few white students in formerly black institutions and the Board of Education’s resistance to faculty desegregation served as indicators that the Board’s primary concern was not achieving racially-equitable schools, but was instead creating a desegregation plan palatable to the city’s white citizens. ☐ This dissertation is the first comprehensive exploration of the history of African-American public school education in Louisville, Kentucky, prior to desegregation.Item A kinomic analysis of the immunometabolic effects of antibiotic alternatives in necrotic enteritis disease models(University of Delaware, 2021) Johnson, Casey NicoleSince the restriction and removal of antibiotic growth promotors, resulting from both new regulations as well as public pressure, the poultry industry has seen a re-emergence of financially devastating disease, most notably necrotic enteritis. Necrotic enteritis has been estimated to cost the global poultry industry $6 billion annually. The economic consequences attributable to necrotic enteritis mostly result from the sub-clinical form of the disease, which can go unnoticed until slaughter due to a lack of overt clinical signs. Finding alternatives to antibiotic growth promotors has become a major area of research and many facets of this problem need to be considered in order to begin to find solutions. Looking at disease pathogenesis is one necessary component to finding more effective and efficient alternatives and to be able to better target problems such as necrotic enteritis more specifically. Looking at the mode of action of antibiotic alternative feed additives shown to have beneficial disease mitigating and growth promoting effects in addition to beginning to understand the host effects of antibiotic growth promotors will also be necessary to begin to replace the beneficial effects lost with the removal of antibiotic growth promotors. This work has been done to advance all of these frontiers. Necrotic enteritis and its predisposing factors were used both as disease challenge models and as a means to evaluate the disease mitigating effects and mechanism of action of antibiotic alternatives. ☐ Necrotic enteritis highlights how dysregulation of gut immune responses can have devastating consequences. The gut is the site of nutrient absorption and an important immune organ. As such, the gut has been considered the prototypical immunometabolic organ. Immunometabolism, being the study of the cross-talk between immune responses and metabolic pathways represents a rational research approach for studying an enteric disease and the effects of potentially disease mitigating feed additives. ☐ Most immune signaling and metabolic pathways contain key intermediates regulated by protein kinases. Kinomics involves the analysis of phosphorylation events, catalyzed by protein kinases. Phosphorylation is a predominant post-translational modification of proteins that plays a key role in regulating and mediating most cellular signaling. Species-specific kinome peptide arrays allow for a high-throughput method of measuring these phosphorylation events. Differences in phosphorylation target sites between species requires the use of species-specific kinome peptide arrays. The kinome peptide array protocol generates data regarding immunometabolic changes occurring between treatments and controls. This research approach enables us to explore the immunometabolic effects of our disease challenge models compared to healthy controls as well as the effects of antibiotic alternatives in the same context. ☐ The yeast cell wall components of Saccharomyces cerevisiae have been the focus of studies searching for antibiotic alternatives. Feed additives containing these components are currently in use by the broiler industry and have shown beneficial effects on growth and performance. In chapter 2, the effects of a crude yeast cell wall extract (YCW) and purified yeast cell wall components beta-glucan (BG) and mannoproteins (MPT) in the context of an experimental model of necrotic enteritis (NE) are reported on. The NE model used for this study involved the use of an infectious bursal disease virus vaccine and a Clostridium perfringens (C. perfringens) challenge. All groups other than unchallenged control were given the same NE challenge. Groups included unchallenged control, NE challenged, YCW, BG, MPT, and BG+MPT. Weight gain was recovered to control in the BG+MPT group. The weight gain in all other groups was not statistically significantly different from either the control or the NE challenged groups. Kinome peptide array and subsequent STRING analyses on jejunal tissue revealed changes in innate immune response and cell death or apoptosis between the BG+MPT and NE challenge groups. Closer analysis of peptide function revealed in the NE challenge group most phosphorylation changes indicated a decrease in functions promoting cell growth and survival and induced cell death. The BG+MPT group showed a reversal of these changes. While we observed clear differences in the phosphorylation status of key peptides between challenge and BG+MPT treated groups, often these peptides phosphorylation status was not significantly altered in the BG alone, MPT alone, and YCW treatment groups. It is possible that the differences in these peptides phosphorylation state are a key aspect of the difference in growth response we observed here, either allowing the disease to take hold and negatively affect growth in the case of the challenge group or reducing disease severity and limiting growth effects in the case of the BG+MPT group. Thus, the lack of significant change in phosphorylation of these specific peptides may be the reason we do not see a significant improvement in growth due to treatment with YWC, BG alone, or MPT alone. In other words, these peptides described previously may be critical determinants of disease severity and the growth effects due to this NE challenge model. The mRNA expression of pro- and anti-inflammatory cytokines were measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The results indicated an effect on cytokine gene expression in response to the NE challenge and further changes in response to the various treatment groups. These results were consistent with the kinome peptide array analysis, showing that rather than a return to control, the treatments had distinct impacts further separating the treatment groups from either the control or NE challenged groups. In summary, this paper indicates that a combination compound used as a feed additive, BG+MPT, is able to recover weight gain in NE challenged birds as well as confer unique cellular signal transduction in the guts of challenged broilers. The responses appear centered on inducing cell growth responses and reducing cell death or apoptosis and innate inflammatory responses, but rather than returning the tissue to a control-like state, the treatment appears to generate compensatory signaling to reduce disease severity. ☐ In chapter 3, the mechanism of action of a postbiotic product in the context of a C. perfringens challenge in broiler chickens is reported on. A postbiotic product contains the byproducts of bacteria fermentation including metabolites, short-chain fatty acids, and functional peptides, among others. These products are thought to have the potential for a direct effect on the host rather than relying on the microbiome to produce the same byproducts. C. perfringens is one of, if not the major, contributing factor to the development of necrotic enteritis in broilers. Administration of the postbiotic product improved weight gain, decreased C. perfringens colony count, and reduced lesion scores and mortality between the two replicate trials. Kinome peptide array analysis showed a distinct response to the postbiotic product in the jejunum of both disease challenged and unchallenged broilers. Looking at peptide phosphorylation events unique to the postbiotic, postbiotic plus C. perfringens challenge, and the C. perfringens challenge groups, STRING analysis results showed immune related signaling in the top 20 GO biological processes in the postbiotic and C. perfringens challenge groups, this signaling was absent in the postbiotic plus C. perfringens challenge group. The protein identifiers input into STRING were unique to each group, so despite immune signaling showing up in both the postbiotic and C. perfringens challenge tables, the members of the signaling pathways were unique suggesting key differences in these signaling pathways. This is further supported by a visualization comparing the phosphorylation events of these two groups that shows that many of the events on the same peptide were differentially phosphorylated in different directions when each group was compared to control, which indicates a differential effect between the two groups. The lack of immune signaling pathways in the postbiotic plus C. perfringens challenge group suggest that the combination treatment may mitigate the disease inducing effects of the C. perfringens challenge. When the complete lists of significantly differentially phosphorylated peptides for the postbiotic and C. perfringens challenge groups were input into STING, the results showed signaling changes indicating an impact on innate immune signaling in the C. perfringens challenge group not observed in the postbiotic treatment group. The postbiotic treatment group results reflect an immune-modulatory/anti-inflammatory impact by the metabolite on jejunal tissue. The phosphorylation events indicate inhibition of such signaling pathways as mTOR, NF-κB, and PI3K-Akt. These are pathways commonly seen being activated during an active/proinflammatory immune response. In summary, the metabolite product being evaluated seems to impart an immune-modulatory effect on jejunal tissue in broilers. This could be important in maintaining a healthy gut, especially considering the withdraw of in-feed antibiotics which are widely believed to impart an anti-inflammatory effect in the gut. The gut needs to maintain both a state of tolerance (to commensal microbes) as well as a readiness to respond (to pathogenic organisms). This balance must be maintained in order to allow for optimum growth efficiency and health.Item A Long Road Ahead: Road Asset Management in conditions of Uncertainty in the Eastern CaribbeanNibbs, FarahRoad infrastructure is one of the most important and valuable publicly owned physical infrastructure assets in Small Island Developing States (SIDS).But there are a variety of challenges associated with road infrastructure for these SIDS in the 21st century. These concerns stem from a variety of factors, ranging from operating conditions, frequent natural hazard events, and the under-developed technological, human, and financial resource environments which presents limitations to data collection, processing and analysis needed for sound decision making for road asset management. By far, the biggest determinants affecting asset management in Eastern Caribbean SIDS are government policies, and the will and commitment to engage in asset management. Governments decide national priorities and influence the major course of economic and social activities. It is political institutions or the state that determines the rules, and conditions for the functioning of various departments and agencies that participate in road infrastructure management. This affects the financial standing of these agencies and departments and in consequence their asset management decisions. The financial system relates to government policies and determines the availability of the funding necessary for asset management activity. This is turn affects the financial decisions that are made by directors or public works departments and other road agencies. With road infrastructure that is insufficiently financed-and in most cases poorly developed, there is a high degree of disaster vulnerability of road assets, and this consequently extends to the communities which depend on such vital infrastructure. This offers a complex challenge for decision- makers having to plan proactive road infrastructure strategies and policies in an environment which presents a high level of uncertainty associated with frequent natural hazard impacts. Within this complexity, however, is an opportunity to move from traditional road asset management approaches which have largely ignored the unique contextual nuances of island nations and the impacts of frequent natural hazard events on roads, to new approaches which incorporates adaptation-based strategies that reflect – at least to some extent - the uncertainty of the problems facing these island nations. This dissertation was motivated by these issues and investigates the asset management maturity of road agencies in the Eastern Caribbean for road management. Factors influencing asset management maturity were identified using interviews and surveys. Building on these observations, the research also investigated how uncertainty can be addressed to improve adaptation against frequent natural hazard risks to roads in these islands. Mixed research methods (qualitative and quantitative) were used for analysis and to understand and examine the maturity levels of asset management and practices of disaster risk management among governments in the region. This also served as the basis to inform and develop a strategy for implementing an adaption-based asset management framework specific to SIDS. A sequential exploratory research design was used, and the research was conducted in two phases. Phase One examined the factors influencing asset management maturity in the Eastern Caribbean .The results of Phase One showed that the Eastern Caribbean is severely hampered in its capabilities for road asset management. While Phase Two explored natural hazard impacts and disaster risk management for road infrastructure in the region. Phase Two demonstrates that while natural hazards pose a significant threat to road infrastructure in the region, government agencies charged with the responsibility for disaster and road management remain woefully under-prepared to deal with the uncertainties and threats posed by such events. A novel framework for adaption-based asset management was developed from the insights gleaned from the survey and interviews. This framework combines elements from the Plan-Do-Check-Act Deming Cycle and the Federation of Canadian Municipalities framework (PDCA-FCM). The PDCA-FCM framework was designed to address asset management limitations in the Eastern Caribbean struggling with frequent and intense natural hazard impacts which creates conditions of uncertainty in decision making and planning for road asset management. The framework should be implemented on a regular cycle to build a base for asset management and assemble the resources to proactively address the need for adaptation to regular and extreme natural hazard events. Therefore, the framework recognizes the limitations and challenges faced by SIDS and offers opportunities for incremental improvements over time.Item A longitudinal study of undergraduate women's sense of belonging in active learning calculus(University of Delaware, 2024) Griffin, Casey R.Women continue to be underrepresented in undergraduate STEM majors. Prior studies identify women’s sense of belonging, or the extent to which one feels like an accepted member of an academic community, as a key contributor to their decisions to stick with or leave their STEM majors. Women’s social connectedness and perceived competence have been found to be two key contributors to their sense of belonging. Prior studies suggest that providing active learning opportunities may also support women’s sense of belonging. However, there lacks consensus on the particular types of active learning opportunities that best support students. This mixed methods dissertation investigates women’s sense of belonging in a two-semester undergraduate Calculus course designed to provide frequent opportunities for students to engage in active learning. Calculus is a good context in which to investigate women’s sense of belonging because it can serve as a gatekeeper course for STEM majors and can be an especially critical leak in the STEM pipeline. In Chapter 2, I explore changes in women’s sense of belonging and factors that contribute to their sense of belonging, such as social connectedness, perceived competence, and the features of the learning environment. Findings indicate that women’s sense of belonging, social connectedness, and perceived competence increased significantly in the first semester of the course. Higher levels of sense of belonging and social connectedness were maintained for the remainder of the year, but this was not the case for perceived competence. Quantitative and qualitative results suggest that the relative influence of social connectedness and perceived competence changed over time, with social connectedness having a greater influence on sense of belonging by Week 7 of the course. Women consistently reported that their social connectedness with classmates was a top contributor to their sense of belonging. Features of the learning environment (i.e., classroom climate and learning opportunities) were not as likely to be reported as top contributors to women’s sense of belonging. However, women who did describe the impact of features of the learning environment on their sense of belonging noted ways that these features impacted their sense of belonging both directly and indirectly via their social connectedness and/or perceived competence. Further, without prompting, they identified specific learning opportunities such as group work and interactive lecture as particularly impactful. In Chapter 3, I dig deeper into women’s perspectives on what instructors can do to support their sense of belonging, specifically through the learning opportunities instructors provide (i.e., group work, interactive lecture, individual work, and traditional lecture) and the ways instructors convey care. Findings indicate that while women described benefits of all four learning opportunities on their perceived competence, they were much more likely to attribute their sense of belonging and social connectedness to interactive learning opportunities like group work and interactive lecture. Further, in their descriptions of ways the instructor supported their sense of belonging, women identified ways the instructors showed care through the ways they facilitated the learning opportunities. Findings from these two papers highlight the importance of providing opportunities for women to develop social connectedness with their classmates and instructor, particularly in times when their perceived competence may be vulnerable. I conclude with areas for future work and implications for Calculus instructors interested in retaining women in STEM majors.Item A machine learning approach to improve scalability and robustness of variational quantum circuits(University of Delaware, 2024) Kulshrestha, AnkitQuantum computing is an emerging new field that aims to leverage the power of a “quantum computer” to solve problems which are currently considered to NP-Hard or NP-Complete. The key idea is to encode inputs as quantum states and device a system where the measured outcomes correspond to a solution of the given problem. While a fault-tolerant quantum computer is still a theoretical possibility, we are able to evaluate the potential of quantum algorithms by running them on a class of devices called Noisy Intermediate Scale Quantum (NISQ) computers. ☐ The advantage of having access to NISQ computers is that they allow for immediate verification of the speedup provided by a proposed quantum algorithm. However, there are significant downsides to the current generation of these devices. Most notable of them are limited gate depth, high sensitivity to noise, ability to scale to only a few number of qubits and a tendency to get stuck in “barren plateaus”. In this research proposal, we introduce and define some key problems encountered in the simulation of quantum algorithms on NISQ devices. We then propose mitigating solutions inspired from machine learning methods and show the ecacy of our methods by simulating different types of variational algorithms on NISQ devices.Item A microvessel-on-a-chip for studying how tumor-derived factors prime the endothelium for extravasation(University of Delaware, 2022) Sperduto, John LewisMetastasis is a leading cause of disability and death from cancer. Each year, 50% of new cancer patients are diagnosed with metastasis and must undergo immediate and aggressive treatment. Within 5 years, 60% of these patients will die. ☐ These statistics translate to staggering mortality. In 2020 alone, 5.8 million patients died from metastasis. By 2040, this mortality will increase to an estimated 8.4 million deaths. ☐ Yet few effective treatments for metastasis exist. One reason is poor understanding about how circulating tumor cells escape through the endothelium into the surrounding tissue of distant organs. This process, called extravasation, is critical. If extravasation does not occur, distant metastases cannot form and 5-year survival increases from 25% to 56%. Better understanding extravasation is therefore key to stopping distant metastasis and reducing the mortality of metastasis overall. ☐ However, studying extravasation is challenging. One major roadblock is modeling extravasation and its underlying pathophysiology in vitro. Current culture models lack mechanical cues fundamental to producing an endothelial monolayer that replicates the endothelium in vivo. Improved modeling of extravasation in vitro could provide better understanding of its pathophysiology in vivo. This dissertation thus aimed to create a microvessel-on-a-chip model for studying extravasation and its underlying processes in vitro with physiological relevance and high spatiotemporal resolution not possible with traditional culture models. ☐ The first objective was developing the model. This consisted of reviewing existing microvessel-on-a-chip models for their advantages and disadvantages, then using this information to design the model, and finally developing processes to fabricate the model and form endothelial microvessels inside it. ☐ The second objective was developing tools to quantify key metrics of endothelial phenotype and function from the model. This consisted of developing a toolbox of image processing pipelines and corresponding ImageJ macros for quantifying permeability, patency, protein expression, and morphology. This toolbox provides a semi-automated method to obtain high-resolution data that is laborious, cumbersome, and often inaccurate to obtain via manual means while also offering new ways to quantify the aforementioned properties. ☐ The third objective was validating if the model can produce endothelial microvessels that replicate key properties of the endothelium in vivo. This consisted of quantifying the permeability, patency, protein expression, and morphology of microvessels cultured under static, flow, and inflammatory stimuli. Results show that flow is necessary to replicate the desired properties from in vivo. Furthermore, the microvessels exhibit very low permeabilities to 70kDa (~1E-08 cm/s) and 10kDa (~1E-07 cm/s) dextrans, few-to-no focal leaks (<1 leak/mm), dense and continuous adherens junctions, cell elongation and orientation with flow, cytoskeletal alignment with flow, and an appropriate response to inflammatory stimuli. ☐ The fourth and final objective was to apply the model to study how tumor proteins and tumor extracellular vesicles can prime the endothelium to facilitate extravasation. Results show that tumor proteins have a strong capacity to disrupt and inflame the endothelium: they increased permeability, decreased patency, and shifted endothelial cells to a more mesenchymal phenotype. In contrast, tumor extracellular vesicles showed limited capacity, if any, to disrupt or inflame the endothelium. While preliminary, these results raise important questions the current paradigm that tumor extracellular vesicles prime the endothelium for extravasation and highlight the utility of the microvessel-on-a-chip for studying this process. ☐ In total, this dissertation presents a microvessel-on-a-chip model for studying extravasation and its underlying processes in vitro. This model provides a promising addition to existing culture models and affords newfound physiological relevance and spatiotemporal resolution. By doing so, it can advance understanding of extravasation and thereby help improve treatments for metastasis.Item A mixed methods exploration of writing motivation among diverse adolescents(University of Delaware, 2024) Cruz Cordero, Tania MaríaWriting motivation has been deemed a critical aspect of the writing process because motivation affects how students engage with the writing process, how much effort and time they exert in the tasks, and the quality of their written products (Graham, 2018). Writing motivation has been the focus of recent studies on how to improve the discouraging levels of writing proficiency in young students, and the gaps between students from different racial, ethnic, and socioeconomic groups (National Center for Education Statistics, 2012). However, prior studies are limited in the methodologies used to characterize heterogeneity in writing motivation, the writing motivation constructs used to this end, the diversity of students represented in the samples, and the exploration of how writing motivation profiles relate to key motivational beliefs like achievement goals, and to writing performance. The present dissertation aims to address these gaps through a mixed methods exploration of what motivates a diverse sample of middle school students from a school district in the Mid-Atlantic region of the U.S. ☐ The study consisted of four phases. In Phase 1, I used latent profile analysis (LPA) to identify distinct profiles of writing motivation based on seven motives of writing: curiosity, involvement, emotional regulation, relief from boredom, grades, competition, and social recognition. The profiles were thoroughly described by comparing their demographic composition, scores in three achievement goal orientations (i.e., mastery, performance-approach, and performance-avoidance), and a concurrent measure of writing performance. Moreover, in Phase 2, I conducted semi-structured interviews with a randomly selected group of students from each profile and conducted a thematic analysis to complement students’ quantitative evaluations of the seven motives with rich qualitative data. In Phase 3, I used a path SEM model to test the mediating role of achievement goal orientations in the relationship between the writing motivation profiles and a distal measure of writing performance. Finally, in Phase 4, I integrated the quantitative and qualitative results to generate meta-inferences about the profiles of writing motivation of diverse middle school students. ☐ Findings identified four distinct profiles of writers based on the seven writing motives. Students from all profiles valued all the motives to a certain extent, and grades and curiosity were consistently rated as top motives for writing. Nonetheless, integrated results suggested that three of the profiles were clearly driven by something specific. Personal Interest Driven Writers (PIDW) were motivated to write when the writing task was perceived as interesting or was perceived to bring personal benefits in the short- or long-term. Self-Expression Driven Writers (SEDW) were driven to write by a desire to express their emotions, ideas, and opinions and connect with the reader, and express overall positive attitudes toward writing. Performance Driven Writers (PDW) valued grades and competition as their strongest motives to write and wrote out of a desire to succeed over their peers and be recognized as top performers. On the contrary, Non-Specific Drive Writers (NSDW) were characterized by having high profile means in all seven motives, but no specific themes emerged to identify a specific drive for this seemingly high motivation to write. ☐ The profiles significantly differed in their demographic composition with the SEDW profile having more girls and Grade 6 students, the PDW profile having more boys and Grade 8 students, and the NSDW profile having higher percentages of students in special education and ELL status. Moreover, the profiles significantly differed in writing performance and achievement goal orientations. Furthermore, the SEM model supported the mediating role of performance-avoidance goals in the relationship between writing motivation profiles and writing performance. Notably, NSDW students had the highest performance-avoidance goals and strongest subsequent relationship to low distal writing performance. ☐ This study is the first one to employ a mixed methods design to systematically investigate what motivates diverse young adolescents to write in their ELA class, and the effects of heterogeneity in writing motivation on their performance in an argumentative writing task. The findings about the distinct profiles based on motives, and the significant differences in demographic composition, achievement goals, and writing performance, have significant implications for researchers of writing motivation and for practitioners who aim to motivate students as a means to enhance their writing performance.Item A multi-case study of teacher classroom practice following participation in computer science professional development(University of Delaware, 2023) Sheridan, Scott T,This dissertation uses a multi-case study approach to investigate teachers’ use of computer science (CS) tools and pedagogical approaches in the classroom following their participation in a computer science integration professional development (PD) program. Seven teacher participants took part in a weeklong PD program and received follow up support from CS undergraduate students taking part in a service-learning course at the local university. Observations, interviews with teachers and undergraduates, and undergraduate reflections were analyzed using a constant comparative methodology to determine themes around tool use, pedagogical practice, and undergraduate roles and perceptions. Findings support that teachers’ use of CS tools and resources were likely affected by multiple factors, including professional development, outside peer influences, and teachers’ CS content and technical knowledge. Furthermore, teachers’ use of pedagogical practices was influenced by their use of tools, resources, and background knowledge. Finally, findings indicated that the unique undergraduate support model offered benefits to both teachers and students although guidance may be necessary to provide all constituents with the most productive experiences. This dissertation provides insight into the factors that influence teachers who are new to CS education the ability to implement CS learning opportunities into their classrooms.Item A preliminary evaluation of the feasibility, acceptability, and health behavior outcomes of a community-based group health coaching for cancer survivors program: a mixed-methods RE-AIM study(University of Delaware, 2023) Berzins, Nicole J.In the United States, there are currently more than 18 million people living with and beyond cancer with that number expected to increase to 22 million by 2030. This growing population often experiences additional long-standing health challenges, including long-lasting side effects from treatment, an increased risk of cancer recurrence, and having or developing a comorbidity such as diabetes or cardiovascular disease. This can have impacts throughout the lifetime in both physical and mental health, as well as quality of life. It has been found that a substantial cancer burden may be prevented through behavioral lifestyle modifications, such as increasing physical activity, improving diet habits, improving duration and quality of sleep, and managing stress. However, adherence to these behaviors remains low. ☐ Health coaching, a process by which trained coaches help clients establish sustainable behavior changes that align with their strengths and values through client-centered interactions and goal setting, has been shown to be effective at eliciting improvements in the aforementioned behaviors in a variety of populations, including cancer patients and survivors. While typically delivered in a one-on-one format, it can be costly, requires more trained coaches, and is not time efficient to reach a large number of people. As such, health coaching in a group format has started to emerge, however, less is known about this mode as it is still in its early stages of development. Therefore, the purpose of this dissertation was to (1) explore existing group health coaching interventions targeting cancer survivors, specifically examining program composition and measured outcomes, (2) to develop and assess the feasibility and acceptability of a group health coaching program for cancer patients and survivors in a community-based setting using a videoconferencing platform, as well as to assess the preliminary effects of the program on a variety of behavioral lifestyle factors, and (3) to evaluate the program using the RE-AIM (Reach, Effectiveness, Adoption, Implementation, and Maintenance) framework. ☐ A scoping review of the literature was first conducted. A systematic search strategy was used between October 2021 and February 2023 to identify intervention studies focused on group health coaching with cancer patients and survivors. Seven studies met the criteria. These studies focused on physical activity, diet, weight loss, or some combination thereof utilizing group health coaching by itself or as one component of an exercise and/or diet intervention. There was a wide range of measured outcomes, which loosely grouped into: feasibility/acceptability; physical activity/exercise; body composition and biomarkers; diet; distress, quality of life, fatigue; and other. Overall, studies were found to be feasible and showed positive results for weight loss, diet, and quality of life. Findings for physical activity, distress, and fatigue were mixed. Additionally, variability was found in many of the group health coaching components. This review suggests group health coaching in the cancer patient and survivor population is still in the nascent stages. However, these studies were deemed highly feasible and satisfactory to the participants, and positive outcomes were associated with these interventions. Future research should consider expanding upon these findings with more robust studies. ☐ Guided by the findings of the scoping review, a community-based group health coaching program was developed. Six group health coaching sessions over a three-month period addressing the topics of stress management, physical activity, sleep, and diet were offered to cancer patients and survivors across the state of Delaware using a videoconferencing platform. Sessions were facilitated by health coaches trained through a National Board for Health and Wellness Coaching accredited training program. Data was collected using a convergent mixed methods approach. Surveys were sent pre- and post-intervention on topics including physical activity, eating habits, perceived stress, anxiety, depression, sleep, and quality of life, followed by post-program focus groups and in-depth interviews. Data on recruitment, attrition, attendance, fidelity, retention, safety, and barriers and facilitators to implementation were also assessed. Survey results were analyzed using repeated measures multilevel modeling. Inductive thematic analysis was used to analyze qualitative data. Overall, this intervention was considered feasible to implement and found acceptable by both participants and health coaches. A total of 26 participants attended an average of 74% of coaching sessions. Coaching participants also noted a moderate increase in total weekly physical activity minutes (p= 0.032, d=0.50). A small increase was seen in weekly moderate-vigorous physical activity frequency (p=0.045, d=0.39). Additionally, a moderate increase was found in functional wellbeing (p<0.001, d=0.50). This suggests group health coaching may be a feasible and acceptable way to promote behavior change in cancer patients and survivors, particularly for physical activity and functional wellbeing. ☐ The group health coaching program was then evaluated using the RE-Aim framework. The main outcomes of this study were mapped onto the five dimensions of RE-AIM. As mentioned, 26 participants attended an average of 74% of coaching sessions with an overall fidelity rate of 89.7%. Participants were more likely to be female, White, older, have a higher educational attainment, and have had breast cancer than the state population. The biggest adaptation included extending the time of sessions. The primary support to implementation included the use of NBHWC trained coaches while the primary barrier was the videoconferencing platform. While some challenges for recruitment and implementation were noted, the program will transition to a completely community-based project going forward. ☐ In summary, group health coaching with the cancer population was feasible to implement and found to be acceptable to cancer patients and survivors in the state of Delaware. It was successfully implemented within a community setting and may be particularly effective for changing physical activity levels and physical functioning scores. Provided in this format, the cancer patients and survivors are provided with peer support beyond what the coach alone can provide and allows for ongoing learning and connection with others, despite participants having different cancers and being in different places in their journey. Going forward, the program will be refined based on feedback from participants and coaches before being implemented within Cancer Support Community Delaware locations across the state.Item A recipe for success: designing flexible professional learning for foundational skills(University of Delaware, 2022) Wheedleton, Kimberly S.This Executive Leadership Portfolio (ELP) seeks to address the problem of how to design a flexible baseline professional learning architecture which both fits in the Professional Development Center for Educator’s (PDCE) 1:1 preparation model and allows for specialist customization that maintains quality and meets the unique professional learning needs of PDCE’s partners. To determine a potential solution to this problem, a professional learning design project was developed and built, along with accompanying implementation tools, to support teacher implementation of the differentiated instruction model as presented in How to Plan Differentiated Reading Instruction: Resources for Grades K-3 (Walpole & McKenna, 2017). The professional learning design was informed through an iterative try/fail/redesign process within five successive professional learning partnerships. The final professional learning design and implementation tools were then tested to determine their feasibility for addressing the problem by implementing them in a sixth partnership. ☐ Results from the sixth professional learning partnership suggest that, if implemented as designed, the flexible baseline professional learning architecture can feasibly allow PDCE’s Literacy Instructional Specialists to provide synchronous, customized, differentiated professional learning sessions which fit the Center’s 1:1 preparation model, maintain quality, and meet the unique professional learning needs of each partnership. An unforeseen outcome of the partnership was that with additional revisions, the professional learning architecture was also able to provide asynchronous professional learning support. While those initial revisions to the professional learning architecture and accompanying implementation tools extended the preparation time beyond the 1:1 ratio, once completed, feasibility for 1:1 preparation can likely be realized for asynchronous applications as well.