Master's Theses (Fall 2009 to Present)

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

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

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

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Now showing 1 - 20 of 2034

100 Hz 512x512 SLEDS system design
(University of Delaware, 2014) Nabha, Kassem
Infrared (IR) detectors applications are widely used across fields from scientific and military to medical and industrial. IR can detect information that human eyes cannot perceive allowing the advancement in science and technology. ☐ Due to the importance of the infrared detectors in today's world, it is necessary to accurately test and characterize these detectors with a frame of reference related to the application. IR projection systems are a great way to characterize the detectors because they can be used as high accuracy reference. ☐ Described in this work is a 512x512 super-latticed light emitting diode system (SLEDS) operating at a frame rate of 100Hz. This system has been fully developed, tested, and corrected for non-uniformity (NUC). Further work will be done to achieve higher frame rates and two frequencies of emission (colors) instead of one.
210Polonium and 210lead radionucidles in the Delaware and Chesapeake estuarine and coastal regions
(University of Delaware, 2013) Marsan, David
One of the primary objectives of this thesis is to present an integrated study of the 210Pb and 210Po radioactive tracers, and assess their use as tracers for particle and trace element export from different estuarine and coastal environments. In order to achieve this main objective, the thesis was split into three sections, each enhancing the understanding of the natural radionuclides 210Pb and 210Po in the estuarine and costal system. Chapter 1 is dedicated to testing the sampling and analytical methods of 210Po and 210Pb extraction from estuarine and coastal waters, specifically comparing the two most widely used scavenging methods, Fe(OH)3 and CoRAPDC. The chapter describes experiments conducted on about 100 samples collected from the Delaware estuary, Chesapeake estuary, Delaware intertidal marsh and an offshore continental slope site. Data in the chapter clarifies the accuracy and reliability of each method and includes suggestions to enhance them. Other details include results of calculations, error propagation, spike calibration, plating efficiency and the MnO2 scavenging method. Chapter 2 presents a synthesis of the estuarine and coastal biogeochemistry of 210Po and 210Pb in the Delaware and Chesapeake estuaries. A single box model is presented using steady state equations to determine residence times of the radionuclides. This chapter presents five highlights: 1) How 210Pb and 210Po dissolved and particulate data can revel key biogeochemical processes and rates in estuaries; 2) Are regional differences in estuaries dominated by a single or compilation of biogeochemical process; 3) Do subRoxic bottom waters affect the distribution of 210Po and 210Pb; 4) Can disequilibria between parent (210Pb) and grandRdaughter (210Po) be used to identify and quantify principle processes; 5) Will a simple mass balance model result in reliable net scavenging residence times for the Delaware and Chesapeake estuaries. Chapter 3 will advance the simple single boxRmodel from chapter 2 to a more complex twoRlayer model. The model will include evaluations of the fate of not only 210Po and 210Pb in the Delaware and Chesapeake estuaries but also the trace elements Fe, Cu, Cd, Ni, Zn, Pb, Cr, Co and Mn. Residences times, presented as halfRlives along with rates and partition coefficients will be identified for the water column including at the sediment water interface. The thesis will revisit the major conclusions obtained from the work presented along with suggestions for future work. Appendix sections include supporting hydrographic data and a compilation of salt marsh trace metal results conducted in Graz, Austria. Trace metal work included a suite of 26 elements measured in a core, two species of mussels, Spartina)alterniflora marsh plant and the sea surface microlayer (SML) from an intertidal Delaware salt marsh.
3D permeability characterization of fibrous media
(University of Delaware, 2010) Okonkwo, Kenneth
In Liquid Composite Molding (LCM) processes, a liquid resin is forced to flow through dry fibrous preform, usually fabrics, to impregnate it and create the composite part in net or near-net shape. The principal advantage of LCM processes is their capacity to produce high fiber volume fraction and high quality parts under low pressure at low cost. The main conditions for successful manufacturing are complete filling of the mold and perfect impregnation of the reinforcement material. If these conditions are not met the structural properties of the finished part are significantly impaired by defects like voids. The mold filling depends on the permeability of the fibrous media. Permeability is an intrinsic property of fiber reinforcement, which includes all interactions between fibers and fluid and characterizes the ease of flow through the medium. The complete prediction of second-order permeability tensor is critical to understanding and prediction of flow in the resin transfer molding process of thick composites or where the flow process is three dimensional In this thesis a new approach for characterizing the three dimensional permeability tensor of fabrics used as reinforcement in liquid injection molding processes from a single experiment is presented and validated. In this approach, a liquid is injected into a preform placed in a mold containing 192 electrical resistance flow sensors radially embedded in the top and the bottom platens of the mold. The proposed method uses an optimization routine in which the permeabilities in a 3D flow simulation of the identical mold is updated continuously until the error between the simulation arrival times at all the 192 sensor locations and the experimental arrival time is minimum. The optimization routine systematically changes the values of the components of the permeability tensor using golden search method until the best match is obtained. The validation and sensitivity of this method is explored and it has been shown that this technique is promising for permeability characterization. The approach is shown to be valid for reinforcements with anisotropic and isotropic nature The advantage of this approach is that it can be used to obtain permeability values from a single experiment; there is no need to scale the circular injection inlet, and it is not limited to principal permeability values. The sensors utilized are unobtrusive to the flow unlike say optic fibers embedded in the fabric that interfere with the flow of the test fluid. The electrical resistance sensors used in this approach are embedded in mold platens instead and which flush with the surface. The method can be used to help predict and understand resin flow behavior during liquid molding of advanced composite materials.
95 GHz silicon germanium low noise amplifier as front-end receiver for sparse aperture millimeter wave imaging
(University of Delaware, 2015) Wright, Andrew Alexander
Demand for the ability to navigate in degraded visual environments (DVE) such as dust, smoke, and fog, has lead the development of millimeter wave (mm-wave) real-time imaging systems. Millimeter wavelength radiation has shown that the wavelengths are long enough to penetrate the obscurants while also allowing sufficient resolution. A low attenuation atmospheric window in the 95 GHz region has pushed for these systems to operate at these millimeter wavelength frequencies. Due to low signal levels at these frequencies, the system requires high gain in the front-end to boost the signals of mm-wave frequencies. This involves collecting the electromagnetic waves with a horn antenna and then amplifying the signal with a low noise amplifier (LNA) to maximize the signal to noise ratio (SNR). In photonics-based imaging systems, the mm-wave signal is then up-converted to optical domain, where it then propagates through optical fibers to an infrared camera for further processing. The horn, LNA and up-converter comprise a single module. A large distributed array of modules, around 200, are required for a real-time mm-wave imaging system capable of peering through DVE. As a result, pushing this technology to higher frequencies can be very costly, due to the high prices of individual high frequency components. Therefore, an alternative technology is required to keep the costs to a minimum. One approach to controlling costs of components operating at higher frequencies is to adopt an alternative amplifier technology. Conventionally, commercially available GaAs and InP LNAs are used to obtain high gain at the high frequencies, but at 95 GHz, each amplifier used to be thousands of dollars. Since then, costs for each amplifier decreased to $100. With each module requiring three or more amplifiers, costs become prohibitively high for many applications. Therefore, this thesis focuses on the development of a 95 GHz amplifier using silicon germanium (SiGe) technology to obtain the required high gain while maintaining low costs. To date, extensive efforts have been made in the development of SiGe amplifier technology and high gain was demonstrated at the W-band. However, existing amplifier technology does not meet the requirements of the mm-wave imager. In particular, major limitation is the 3-dB bandwidth of the gain curve. A distributed aperture system with a wide field of view and broadband response will experience a phenomenon known as fringe-washing if an off-axis signal arrives with significant delay between the receivers on the opposite ends of the longest baseline. Severe fringe-washing occurs when this delay of the projected baseline is comparable to the correlation time of the signal, i.e. the inverse bandwidth of the system. To mitigate fringe-washing, each module must limit the bandwidth of operation, which can be accomplished either with a filter or an amplifier. Since filters can be lossy, ideally a narrow-band amplifier is preferred. In this thesis, using the basic principle of amplifier design, an LNA is developed based on advanced SiGe-foundry processes to operate in the 95 GHz regime. The advantage of a custom SiGe amplifier is the ability to design it to meet the imager's specific demands, including gain, noise figure, bandwidth, and power consumption in a single low cost device. This thesis details such design, and includes the discussion of tradeoffs and limitations imposed by the commercial SiGe-foundry processes employed.
A suite of agronomic factors can offset the effects of climate variability on rainfed maize production in Kenya
(University of Delaware, 2022) Oluoch, Kevin Ong'are
Achieving food security in sub-Saharan Africa (SSA) is a multidimensional challenge. SSA reliance on food imports is expected to grow in the coming decades to meet the population's demand, projected to double to over 2 billion people by 2050. In addition, climate change is already affecting food production and supply chains across the region. Addressing these multiple food security challenges will necessitate rapid enhancements in agricultural productivity, which is influenced by a host of demographic, agronomic, and climatic factors. We use statistical approaches to examine rainfed maize in Kenya, where maize cultivation and consumption are widespread and central to livelihoods and national food security. We find that improving a suite of agronomic factors will have a greater effect on rainfed maize productivity than demographics and can offset the effects of climate change. These findings could also offer insights into similar challenges for other crops in Kenya and other SSA countries.
The abdominal fat contribution to adiposity in chickens divergently selected for fatness or growth: Cross-model elucidation and validation of gene expression
(University of Delaware, 2013) Resnyk, Christopher
The domestic chicken (Gallus domesticus) is an important global source of high-quality dietary protein and a widely used biological model. Decades of intensive genetic selection have established the remarkable growth rate of the commercial broiler today; however, increased growth rate has been accompanied by the magnification of several unfavorable traits. This thesis addresses abdominal fatness, one of the traits that are incidentally amplified by selection for increased growth. Excessive fatness, coupled with several unique avian features of metabolism (i.e., fasting hyperglycemia and insulin insensitivity), parallels conditions observed in humans with metabolic diseases. Thus, understanding the genetic influence on excessive fatness in chickens will not only serve to improve the quality of production from an agricultural standpoint, but will also advance the knowledge of metabolic disorders in humans. Four experimental lines of meat-type chickens that were divergently selected for either a large difference in abdominal (visceral) fatness or in growth rate were used to characterize the role of adipose tissue (classically thought to have a minimal lipogenic contribution) in regulating adiposity. At the age of selection (9 weeks), the fat line (FL) and lean line (LL) chickens exhibit a 2.5-fold difference in abdominal adipose weight, while their body weight and feed intake are similar. The high growth (HG) and low growth (LG) chickens were divergently selected for either high (HG) or low (LG) body weight at 8 and 32 weeks of age resulting in a 2.7-fold increase in bodyweight and an 8-fold increase in abdominal fatness (as a percentage of BW) in HG chickens on average from 1 through 11 weeks. The adipose transcriptomes of these four genotypes (FL compared to LL and HG compared to LG) were analyzed at 1 through 11 weeks of age using the Del-Mar 14K Chicken Integrated Systems microarray, and at a single age (7 weeks) by RNA sequencing. Microarray analysis of abdominal fat in FL and LL chickens revealed 131 differentially expressed (DE) genes (FDR≤0.05) as the main effect of genotype, 254 DE genes as an interaction of age and genotype and 3,194 DE genes (FDR≤0.01) as the main effect of age. The most notable discoveries in the abdominal fat transcriptome during juvenile development were higher expression of many genes involved in hemostasis in the LL and up-regulation of numerous adipogenic and lipogenic genes in FL chickens. Many of these DE genes belong to pathways controlling the synthesis, metabolism and transport of lipids or endocrine signaling pathways activated by adipokines, retinoids and thyroid hormones. The importance of these processes in regulating adiposity in abdominal fat of FL and LL chickens was reinforced by the deep RNA sequencing analysis at 7 weeks. Remarkably, the highest expressed genes at this age included those involved in the metabolism of lipid and carbohydrates which are functionally associated with endocrine system and metabolic disorders. There were 1,687 DE genes between fat and lean chickens at 7 weeks including transcription factors and metabolic enzymes which have direct influences on lipogenesis and adipogenesis. The findings of the microarray analysis were further verified by the abundance of DE hemostatic factors uncovered by RNA sequencing analysis. This deep sequencing analysis also revealed a number of ectopically expressed genes suggesting that visceral fat functions autonomously as well as an endocrine organ in the regulation of lipid metabolism and perhaps feed intake. Microarray analysis of HG and LG chickens at 1 through 11 weeks of age revealed DE genes (FDR≤0.05) as the main effect of genotype (321 genes), the interaction of age and genotype (718 genes), and the main effect of age (2,918 genes). RNA sequencing at 7 weeks uncovered 280 DE genes (FDR≤0.1). Similar to the FL, HG chickens over-express many genes involved in adipogenesis and lipogenesis (including biosynthesis of fatty acids, cholesterol and triglycerides) which could at least partially account for their increase in abdominal fatness. Conversely, LG chickens up-regulate several energy producing processes (i.e., peroxisomal -oxidation, mitochondrial -oxidation, ketogenesis and oxidative phosphorylation) early on in juvenile development which are likely responsible for their extreme leanness. Hemostasis also appears to have a critical role in the maintenance of the lean phenotype at the age of maximal difference in adiposity in these chickens (7 weeks). These findings validate abdominal fat as a major contributor to adiposity in response to either divergent selection on abdominal fatness in the FL and LL or body weight in the HG and LG chickens.
Abundance and size of the sea scallop population in the Mid-Atlantic Bight
(University of Delaware, 2013) Walker, Justin
The stock of the Mid-Atlantic Bight sea scallop fishery is assessed every year through the use of various dredging and imaging techniques. The sustainability of the fishery depends on the proper setting of the yearly catch limits based on the assessment of the preceding year. Within the past 10 years, digital image surveys have been explored as a potential method to supplement the yearly dredged based surveys. AUVs have been shown to be a successful platform for rapidly and accurately performing seafloor image surveys of benthic habitats. In 2011, a Teledyne-Gavia autonomous underwater vehicle (AUV) with a hull-mounted camera was used to non-invasively optically and acoustically image 313 km of the seafloor within the Mid-Atlantic Bight at a constant altitude of 2 m. Survey transects were completed at 24 open access ground locations and 3 additional locations within the Elephant Trunk Access Area. Trained image analysts, using a scallop counting and sizing algorithm developed for this stock assessment, were able to enumerate and size sea scallops within the collected 250,000 seafloor images, finding that the region had an overall scallop density of 0.027 scallops/m2. Georeferenced data was tagged by the AUV inertial navigation system (INS) to every seafloor image, allowing for unprecedented meter scale spatial analysis of the sea scallop distribution. The relationship between image subsampling and the accuracy of the resulting scallop density was explored via simulations run on the image analysis results. Eight AUV transects were resurveyed by a New Bedford commercial scallop dredge for shell height calibration data and to calculate the harvest efficiency of the dredge (0.60). Image analysis and backscatter data collected by the AUV’s 900 kHz side-scan sonar were used to classify seafloor substrate types. The surveyed scallop strata were classified as 98.6% sandy seafloor with the remaining 1.4% representing intermittent shell hash, mounds, and ripples. The side-scan backscatter data revealed other varied seafloor texture, including escarpments from scallop dredge trawling and wave created sorted bedforms. Seafloor dredge scar area measured from the side-scan backscatter data and National Oceanic and Atmospheric Administration (NOAA) vessel monitoring system (VMS) tracking data were used as a proxy for fishing effort. Increased dredging was found to positively skew shell height distributions.
Abundance of the Asian shore crab Hemigrapsus sanguineus in and adjacent to the Delaware Bay: evidence of invasive crash and return of native species
(University of Delaware, 2013) Schab, Corey
The Asian shore crab Hemigrapsus sanguineus has been introduced to multiple rocky habitats outside its native range and is considered an invasive species on the East Coast. The Delaware Bay region represents one of these locations and contains established populations of this intertidal, brachyuran species. Previous studies conducted in the University of Delaware Harbor, a location within this invaded region, indicated that H. sanguineus had displaced native mud crabs as the dominant species in this habitat. This trend had been observed at many locations in the North American range of the species. However, surveys conducted a decade later, during 2011 and 2012, have indicated a reverse in the previous trend and have shown significantly higher abundance and biomass of Panopeus herbstii, a native mud crab, compared to H. sanguineus. These results document the first evidence of a decline in the population of H. sanguineus along the East Coast of the USA.
Abundance, diversity, and activity of ammonia-oxidizing prokaryotes in the coastal arctic ocean in summer and winter
(University of Delaware, 2009) Christman, Glenn
Ammonia oxidation, the first step in nitrification, is performed by certain Betaand Gammaproteobacteria and mesophilic Crenarchaea to generate metabolic energy. Ammonia monooxygenase (amoA) genes from both Bacteria and Crenarchaea have been found in a variety of marine ecosystems, but the relative importance of Bacteria versus Crenarchaea in ammonia oxidation is unresolved, and seasonal comparisons are rare. In this study, we compare the abundance of betaproteobacterial and crenarchaeal amoA genes in the coastal Artic Ocean during summer and winter seasons over two years. Betaproteobacterial and crenarchaeal amoA genes were present in both seasons, but were more abundant during the winter. Archaeal amoA genes were more abundant than betaproteobacterial amoA genes in the first year, but betaproteobacterial amoA was more abundant than archaeal amoA the following year. Summer and winter betaproteobacterial amoA clone libraries were significantly different. Gene sequences of amoA were similar to those found in temperate and polar environments. The ratio of archaeal amoA gene copies to Marine Group I crenarchaeal 16S rRNA genes averaged 2.9 over both seasons, implying that ammonia oxidation was common in Crenarchaea at this location. Nitrification rates were highest in the winter when ammonia oxidizer abundance was greatest, suggesting that ammonia oxidation plays an important role in coastal arctic waters during the winter when the ocean is ice covered and photosynthesis is at a minimum.
Acculturation, diet and psychological health of Asian international students at the University of Delaware
(University of Delaware, 2015) Jiang, Heng
Background: Accumulating evidence showed that immigrants change their diet and experience various psychological problems in acculturation process. International students in United States are increasing rapidly and more than 50% of them are from Asian countries. However, little is known about the diet and psychological health of Asian international students along with acculturation level. Aims: This study aims to describe the dietary nutrient intakes and psychological health status of Asian international students at the University of Delaware after their immigration to the U.S. Methods: Online survey was sent out including demographic questionnaire, dietary screener questionnaire (DSQ), Asian American Multidimensional Acculturation Scale (AAMAS) and Kessler 6 (psychological screener). Linear regression models were fit to examine the association between normally distributed diet and acculturation data and demographic characteristics. Beta and 95% CI were reported. For non-normally distributed diet and acculturation data, Kruskal-Wallis was performed and median and interquartile range were presented. Results: We observed a trend for bicultural food consumption. Individuals more acculturated to American culture had lower Kessler 6 score (Beta -0.04; 95% CI -0.3, 0.2),those showed higher attachment to original culture had higher Kessler 6 score (Beta 1.1; 95% CI -0.3, 2.4). Specifically, the higher host culture language acquirement and original language maintenance, the better performance on Kessler 6.
Accumulation of sediment and radionuclides in tidal marshes of the Murderkill River Estuary, Delaware
(University of Delaware, 2010) Stuart, Dack
This thesis examines patterns and rates of sediment accumulation and tidal marsh accretion in the Murderkill River estuary, Delaware, with special emphasis placed on changes in accumulation rates and sediment physical properties associated with historical land-use practices, such as mosquito ditching. Over 90% of United States Atlantic East coast salt marshes have been ditched to some degree, but little quantitative work has been done to examine the specific effects on marsh sedimentary processes. An understanding how these ditches have affected sediment delivery to and retention on the marsh platform will provide insight into how ditched marshes are likely to respond to changes in sea level, sediment availability and vegetative growth. To investigate historical changes in sediment composition of the marsh sediment column, the specific contributions of mineral and organic solids and water/entrapped gas were determined from measurements of sediment dry-bulk density and loss-on-ignition. Additionally, grain-size analysis was conducted to determine the textural composition of sedimentary particles delivered to the marsh. Downcore profiles of the radionuclides 210Pb and 137Cs were used to determine sediment accumulation and marsh accretion rates, to develop chronologies for the sediment column, and also as indicators of sediment transport pathways within the marsh. In addition, an historical investigation was conducted to learn more about past land-use practices and sources of human disturbance in the estuarine system. Spatial and temporal variations in the relative contributions of organic and mineral matter to total sediment volume show that marsh accumulation in the Murderkill is dominated by mineral matter and that the organic contribution has varied little over the past century. At two upriver sites, changes in dry-bulk density, loss-on-ignition and grain size were observed and interpreted to correspond to the transition from freshwater marsh to brackish marsh. Although the cause of this change is unknown, it cannot be directly associated with mosquito ditching in the lower estuary due to the distance separating these sites from ditched areas. Vertical accretion rates (0.3−0.7 cm/yr) determined for undisturbed marsh sites are comparable to rates computed for other salt marshes of the greater Delaware Estuary. Radionuclide focusing factors for the marsh sites indicate that the Murderkill is a well-mixed estuary, consistent with results from a previous study of hydrodynamics of the Murderkill River. Temporal changes in accumulation (organic vs. mineral) were observed at one inter-ditch site, but the change cannot be directly associated with ditching activities because similar trends are not evident in other inter-ditch cores. Ditches filled rapidly with mineral mud after being excavated but have not matched the adjacent marsh elevation, possibly because they are acting as the preferred tidal pathways into and out of the marsh. Ditches have not significantly affected the median grain size and sorting of inter-ditch or ditch sites compared to a similarly located non-ditched location. There is no evidence to suggest ditches have deprived the marsh platform of suspended sediment in order to infill. The sedimentary record suggests that the effects of ditching on the adjacent marsh platform are subtle and not always similar among depositional sites. Thus, the results of this study suggest that there is no specific sedimentary response to ditching in ditched or non-ditched areas of the same marsh.
Accuracy and convergence of the Asymptotic Single Risk Factor formula in a large credit portfolio
(University of Delaware, 2016) Houser, Madelyn R.
According to international banking standards, all financial institutions must classify the risks associated with the credit portfolios they hold. Mathematical approximations of default distributions are among the most common ways of assessing such risk. Understanding the errors of these approximations is crucial for generating reliable credit portfolio default risk calculations. We consider the error associated with Vasicek’s Asymptotic Single Risk Factor model for the cumulative distribution of losses in a portfolio of N companies. We analytically and numerically verify the scaling of the error to be O(N–1), scaling as the reciprocal of the number of companies. Our results provide insight into the error associated with one of the most commonly used credit risk models and serve as a model for future work in examining the errors of more complex, hierarchical structural models.
Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment
(University of Delaware, 2016) Luo, Jing
Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. ☐ Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. ☐ Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.
The acquisition of relative clause structures in L2 French
(University of Delaware, 2018) Dickens, Kayla Raye
Anecdotal evidence as well as research with second-language French learners (for example, Hollerbach 1994 and Walz 1981a) show that learners struggle to properly acquire the complex system of relativization in French. This study analyzes the acquisition of relative clauses in the context of Universal Grammar. Universal Grammar proposes that language acquisition relies on an innate, abstract linguistic system that helps language learners—in both first-language (L1) and second-language (L2) contexts—develop intuitions about grammaticality and create novel utterances. In the L2 context, the question of the influence of the pre-existing L1 grammar on the development of the mental grammar in the L2, a phenomenon known as L1 transfer, remains open. ☐ The present study describes the order of acquisition of several relative clause types for instructed learners across several levels of L2 French at a medium-sized Mid-Atlantic research university based on the results of a grammaticality judgment task and a short production task. The possible role of L1 transfer is considered at each stage, along with other variables such as experience abroad. In the final chapter, the pedagogical implications of these results and instructional strategies to improve learners’ acquisition of relative structures at each level of instruction are discussed.
"An act apart": tea-drinking, play and ritual
(University of Delaware, 2013) Ranalli, Kristina
Studies of tea-drinking emphasize gentility as a fundamental value in early American culture and primarily examine the eighteenth century. But tea continued to be consumed widely in the nineteenth century, and the manufacture and use of miniature tea sets as toys for children suggests a playful element to culture. How did children use these objects, and what does that mean? This study examines several miniature tea sets, children's book illustrations, one novel, and domestic advice manuals in order to provide a clearer picture of tea-drinking practices in the understudied nineteenth century, and the use of tea in children's play. It ultimately examines both tea-drinking and play as ritual practices that challenge the limits of the ordered world. Its conclusions complicate the notion of tea-drinking as an exclusively genteel practice and contribute to the ongoing scholarly discussion surrounding the meaning and purpose of play in human behavior.
Activity and abundance of bacterial groups in the Sargasso Sea and Mid-Atlantic Bight
(University of Delaware, 2011) Grim, Sharon
Microbial communities are essential to the processing of dissolved organic matter and nutrients in the ocean. Molecular methods are used to assess phylogenetic structure and activity within marine bacterial populations. However, types of activity and varying abundances can affect bacterial contributions to biogeochemical and organic matter fluxes. The goals of this study were to evaluate activity levels of rare and abundant bacterial groups in the Mid-Atlantic Bight and Sargasso Sea, and to compare shifts in the active and total bacterial populations on a short temporal scale with changing activity levels. Bacteria that are replicating their DNA are active members of the community. Thus, a metric for bacterial activity is to monitor DNA synthesis. I assessed bacterial activity via DNA replication using incorporation of a thymidine analog, 5-bromo-2’-deoxyuridine, into bacterial DNA. Denaturing gradient gel electrophoresis and sequencing were used to generate profiles of the total and active populations in the Sargasso Sea and Mid-Atlantic Bight in spring and summer. Total and active communities were 65-95% similar within seasons, indicating that most bacteria are actively dividing. Bacterial groups varied in activity within each sample. SAR11 (Alphaproteobacteria) was active and abundant throughout communities. Another alphaproteobacterial member, a Rhodobacter sp., was enriched only in active communities. Additionally, representatives of Bacteroidetes and Gammaproteobacteria were more active than their abundances suggested. In marine systems, abundances of bacterial members may not be indicative of their activity levels. I used tag pyrosequencing of the 16S rDNA V1-V2 region to compare the active and total communities from spring and summer 2009 and 2010 in the Mid-Atlantic Bight and Sargasso Sea. Activity levels of a majority of bacterial taxa were proportional to their abundances in the total community. However, I observed differential activity in bacteria of varying abundances and activity. Flavobacteria (Bacteroidetes) were between 5 and 20% of the total community in both environments, but were consistently more active than suggested by their abundances. Rhodobacterial (Alphaproteobacteria) ribotypes were active, rare members of the Mid-Atlantic Bight bacterial community. In the Sargasso Sea, SAR86 (Gammaproteobacteria) was more active when rare. SAR11 was consistently abundant in both locations and seasons, but had discrepancy in activity levels relative to abundance. Changes in the active bacterial community also influenced the composition of the total community in spring 2009 of the Mid-Atlantic Bight and spring 2010 of the Sargasso Sea. Rare and active bacteria, such as unclassified bacteria in the Sargasso Sea and rhodobacters in the Mid-Atlantic Bight, become more abundant members of the microbial population within 12-96 hours of sampling. The research in this thesis investigated differential activity of bacterial groups in the Sargasso Sea and Mid-Atlantic Bight. I analyzed bacterial activity at fine phylogenetic and temporal scales. I identified rare and abundant bacterial taxa with higher or lower activity levels than expected. Furthermore, I observed shifts in community structure with changes in bacterial activity and environmental conditions. By profiling changing activity levels of bacterial taxa and rapid responses in community structure, this study examined the interplay of diversity and activity in microbial assemblages, and contributed to knowledge of the ecology of marine microbes.
Acute effect of cocoa on vascular function in chronic kidney disease patients: a pilot study
(University of Delaware, 2014) Ferreira, Courtney
Chronic kidney disease (CKD) is associated with an increased prevalence of cardiovascular disease (CVD) and these individuals often die of CVD before reaching end-stage kidney disease. Dysfunction of the endothelial lining of the blood vessels may cause a worsening of kidney function and increase the CVD risk in this population. Dietary polyphenol consumption, specifically flavonoids, has been associated with reduced CVD risk. Cocoa is a rich source of flavanols, a flavonoid subclass, and has been shown to improve vascular function and prevent CVD in several populations, but not yet in CKD. The aim of this study was to determine the effects of acute cocoa ingestion on endothelial-dependent dilation in subjects with CKD. We hypothesized that brachial artery flow-mediated dilation (FMD), a measure of endothelial function would increase and arterial stiffness and wave reflection would decrease from baseline to two hours following ingestion of 26 g of cocoa (CO) as compared to a placebo (PL). Seven patients with CKD (4M/3F; 53.7 ± 5.1 y) completed the randomized, double-blind, placebo-controlled trial. FMD at baseline (CO 3.96 ± 0.8%, PL 5.05 ± 1.6%) and 2 h post ingestion (CO 5.12 ± 0.9%, PL 7.6 ± 2.8%) was not significantly different between the conditions (p>0.05). Further, the delta change in FMD was not different (CO δ 1.16 ± 0.9 %, PL δ 2.55 ± 1.7%; p>0.05). Arterial stiffness as assessed by carotid-femoral pulse wave velocity did not significantly differ over time (CO δ -0.61 ± 0.7 m/s, PL δ 0.66 ± 0.4 m/s; p>0.05) nor did wave reflection as assessed by augmentation index (CO δ -1.43 ± 2.7, PL δ 1.71 ± 1.5%; p>0.05). In conclusion, our pilot study did not find any significant change in vascular function following ingestion of 26 g of cocoa suggesting that this dose may not be sufficient to rescue vascular dysfunction in this group of patients with CKD.
Adaptations of the shoulder to overhead throwing in youth athletes
(University of Delaware, 2013) Astolfi, Matthew
Introduction: Due to the high repetition and force associated with overhead throwing anatomical adaptations are observed in elite and professional level baseball athletes however, little is known about their origin and progression. This is especially concerning because the incidence of chronic shoulder injuries in youth baseball is on the rise and may precipitate lifelong biomechanical alterations and associated pathologies. Arm dominance and throwing have been correlated with structural changes in older throwers including humeral retroversion (HR), and posterior capsule thickness (PCT) yet the influence of age on these adaptations is unknown. Purpose: To investigate the relationship of age and arm dominance on measures of HR, PCT, subacromial space (SAS), glenohumeral internal rotation (GHIR), external rotation (GHER), posterior shoulder tightness (PST). Methods: Thirty-five subjects ages eight to twelve years old, participating in organized youth baseball underwent testing using Diagnostic Ultrasound and measurements of glenohumeral internal rotation, external rotation, and posterior shoulder tightness were obtained. Results: The dominant arms had significantly less HR (p < .001), and GHIR (p< .001), but greater PCT (p< .01), and GHER (p< .001) than the non-dominant arm. Dominant IR was significantly different between the under 10-year-old group and the over 10-year-old group. There were no differences with regard to PST between shoulders or age groups. A significant, strong, negative correlation between dominant GHIR and GHER (r= -.395, p< .05), a significant, strong, negative correlation between HR and GHIR (r= -.431, p=.01), and a significant, strong, positive correlation between HR and GHER (r= .448, p< .01) were observed. Dominant PCT was strongly, positively correlated with GHER (r= .322, p= .059) was observed. Conclusions: The alterations in a youth baseball sample are similar to those observed in older baseball athletes. This is the first study to demonstrate greater PCT in the dominant arm of youth baseball athletes. The magnitude of HR differences in youth was shown to be similar to older baseball athletes. Alterations in glenohumeral ROM displayed similar trends of increased GHER, and decreased GHIR. The youth baseball population is developing adaptations consistent with older baseball athletes, indicating further research is needed to determine the developmental mechanisms in youth, and the potential injury risks associated with such adaptations in youth.
Adaptive management strategies on the Chesapeake Bay regarding TMDLs
(University of Delaware, 2018) Cunningham, Alexis
In December 2010, the United States (U.S.) Environmental Protection Agency (EPA) released a cleanup plan for the Chesapeake Bay known as the Total Maximum Daily Load (Bay TMDL). The Bay TMDL document established nutrient and sediment allocations with the goal of having practices and controls in place for an expected. ☐ 60 percent reduction of the nutrient and sediment pollution loads by 2017, with all practices and controls installed by 2025 to meet water quality standards in the Bay. The seven Bay watershed jurisdictions within the watershed developed Watershed Implementation Plans (WIPs) to meet the nutrient and sediment allocations. Though considerable resources have been committed to the implementation of the Bay TMDL, there is growing concern that the Bay TMDL is not resulting in improved attainment of water quality standards in the Bay. ☐ This study will disseminate research results evaluating and assessing adaptive management strategies for the Bay TMDL based on the effectiveness of existing water quality initiatives. Adaptive management strategies and practices are essential to addressing those uncertainties posed by the inefficiencies of current Bay water quality strategies. ☐ Methods employed are (1) semi-structured interviews of federal and state government staff members involved in the implementation of the Bay TMDL and of stakeholders, including NGOs and farmers, who can shed light on the efficacy, successes, constraints and prioritization of adaptive management strategies in the context of the Bay TMDL and (2) water quality data analysis. TMDL plan performance and programs are then measured using program evaluation tools. This approach facilitates the assessment of different resource sustainability and restoration programs as well as defined priorities and objectives. ☐ This research will provide information and insight into the decision-making process as well as highlight the possible reasons behind any ineffectiveness of the TMDL. The Chesapeake Bay may benefit from the application of suggested adaptive management strategies, which include integrative, flexible and responsive management policies.
Additive manufacturing of graded dielectrics
(University of Delaware, 2014) Roper, David A., Jr.
The ability to fabricate electromagnetic (EM) materials with graded dielectric properties would benefit a variety of interesting applications, such as low profile antennas, antireflective surfaces, passive beam formers (e.g. Luneburg lenses), graded index lenses, and structural and armored radomes. Recently there has been a surge in commercial 3D free-forming printing technologies. These systems employs additive manufacturing methods to create complicated 3D structures using a host of different techniques, including stereo lithography (SLA), fused deposition modeling (FDM) and selective laser sintering (SLS). While popular for a wide range of applications, commercial 3D printers use a limited library of materials that make them unsuitable for many EM applications including the fabrication of graded dielectrics. In this thesis, I present a custom developed printer that is designed specifically for realizing materials with integrated three dimensionally varying dielectric properties is described. This system utilizes an ultrasonic dry powder deposition head to pattern high dielectric powders onto a low loss dielectric substrate. After stacking and processing, the result is a mechanically rigid composite plate with an embedded 3D variation in dielectric properties. Specifically, I will present detailed methods for fabricating (i.e. system design), calibrating and characterizing composite panels with graded dielectric properties. I will also present several practical applications of this new methodology.

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