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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- ItemCaregiver’s history of depressive symptoms and child affect expression in the context of structured interaction tasks(University of Delaware, 2009) Vahlsing, JuliaReduced positive emotionality (PE) in children of depressed mothers has been identified as a risk factor for later depression. In the current study we explored the associations between maternal history of depression, avoidance of emotions (experiential avoidance, EA), and sensitivity to child expression of affect in response to interactive tasks designed to elicit positive and negative affect. Participants were 32 caregivers and their preschool-aged children enrolled in a daycare center. Children interacted with both caregivers and experimenters. Caregiver’s history of depression and EA were associated with lower positive affect and sensitivity to child’s emotions respectively. In contrast to findings of low PE in children of depressed mothers, higher caregiver past depression scores were associated with the expression of more positive affect (interest/engagement/excitement) in their children and a tendency to express less negative internalizing affect. These findings were specific to interactions with the caregiver. This pattern of avoidance of emotion, decreased sensitivity to child affective expressions, and more positive and less negative child affect suggest a possible link between maternal depression and child emotion regulation.
- ItemMechanical model of an early stage osteoarthritis(University of Delaware, 2009) Chiravuri, VenkatOsteoarthritis (OA) is a common degenerative disease which affects the articular surfaces and adjacent tissues of human synovial joints. More than 20 million Americans are estimated to have OA. OA changes the entire joint; morphologically, biochemically, structurally and biomechanically. The early stages of OA are characterized by a roughened articular surface, with possible partial thickness defects. This may worsen with fibrillation and eventually full thickness damage on both surfaces resulting in bone on bone contact. Animal models are commonly used to study the pathophysiology of OA, providing us the insight into cartilage degeneration. There have been numerous surgery-based models of OA, which induce OA by some sort of trauma to the knee such as meniscectomy or anterior cruciate ligament transection. To overcome some of the problems inherent in these models, a mechanically induced model of uni-compartmental OA was developed that altered the mechanical loading of the knee of New Zealand white rabbit. The overall purpose of the research project was to develop a model of early-stage OA, to look for early adaptation in the cartilage and subchondral bone and to assess possible treatments. The research objectives of the current thesis are to determine changes in the knee articular cartilage and subchondral bone from tissue that underwent the mechanically induced OA model. To further interpret the experimental results of the animal model, a mathematical model is formulated that is used to predict the joint load and stress state at the articular surfaces. One of the specific purposes of the research is to determine the changes in material properties of the articular cartilage, mineral and trabecular structure of the subchondral bone and histology of the femoral and tibial joint surfaces in tissue under two different loading time periods of 2 and 4 weeks. The contralateral knees are to be used as internal controls. Correlations with the cartilage material properties to the subchondral bone changes are made. The second specific aim of the research is to formulate an analytical model of the knee joint of the New Zealand white rabbit under the mechanically induced loading model of OA that incorporates accurate three-dimensional geometry, external joint loading, deformable articular contact and non-linear ligament properties. The model is implemented to determine the loads and stresses on the tibial and femoral articular surfaces given the changing articular cartilage material properties at the 2 and 4 week loading time periods and in the contralateral control. The results of the testing showed that the properties of cartilage as well as the trabecular bone morphology were altered. For articular cartilage, aggregate moduli and permeability values showed significant changes towards an OA-like degeneration that increased with the time of loading. The bone mineral density and concentration was altered also in the subchondral bone with exposure to the altered loading. Histological evaluation showed surface damage only and loss of proteoglycan, but little full thickness damage. The results of the analytical model showed increased stresses in the femur which have led to the changes in the properties of both the cartilage and the trabecular bone morphology. The results in general indicate signs of early stage OA, formulating in a new mechanical model for early stage OA.
- ItemModeling of arterial hemodynamics(University of Delaware, 2009) Edwards, JonathanAccurate noninvasive measurement of the blood pressure waveforms throughout the body is clinically desirable, but difficult to accomplish. We use a computational model, based on a description of the architecture and mechanical properties of the arterial network and blood, to predict dynamic pressure throughout the arterial vasculature. Applanation tonometry was used to measure dynamic pressure noninvasively at the carotid, radial, and femoral arteries under different hemodynamic conditions (baseline, cold pressor test, and nitroglycerin). A pressure waveform from one recording site served as input to the model. Model parameters were adjusted to obtain the best fit between the pressures predicted at other locations and the pressures directly measured at those locations. The site whose pressure was used as the input was altered, and the ability to accurately predict pressures at the other sites was compared. In twenty one healthy subjects, the femoral and radial artery pressures have allowed most accurate prediction of pressures elsewhere. Vascular stiffness, resistance, and the dependence of stiffness on arterial diameter were estimated from the fitted model parameters. The model provides insight into the effects of physiological and pharmacological stimulation on arterial vascular properties in vivo. The model also provides a noninvasive estimate of central aortic pressure, which is valuable for understanding ventricular-vascular coupling in health and disease.
- ItemDesign tutorial and comparative analysis of printed circuit board production softwares for microcontroller & FPGA-based systems(University of Delaware, 2009) Hoover, RyanPrinted Circuit Board design and implementation is a research topic most any company or group manufacturing electronic devices must address. There are issues in every aspect of design, ranging from schematics to pad stacks to routing. An error in any one of these steps propagates through the remaining steps. There are many approaches and software packages for moving a design from schematics to a physical PCB. However, software packages can range from being free to costing thousands. This thesis describes the design process from start to nish of a multi-purpose FPGA-based printed circuit board in two competing software packages. It will detail issues encountered along the way, and how these issues were resolved. Commercially available products will be used throughout the process, including the Xilinx Spartan 3E FPGA. The di ering design processes in the software packages Cadence Allegro Design Entry HDL and Advanced Circuits PCB Artist will be detailed and explored in order to determine which characteristics of each package suites various types of hardware design. The goal of this project is to create a "reference manual" for students to use as a guide in choosing a software package and working through the PCB design process at the University of Delaware's Electrical and Computer Engineering Department. These two software packages are available to all students in the department to learn and design printed circuit boards.
- ItemDevelopment and application of an empirical loss analysis for woodframe buildings subject to seismic events(University of Delaware, 2009) Black, GregoryThis thesis introduces a new seismic loss model for woodframe buildings and examines how it can be used to provide input for the development of seismic performance objectives for woodframe buildings in terms of economic loss, a measure that is more directly useful to building owners than qualitative performance levels such as "Life Safety." The model employs a non-linear dynamic structural analysis program in order to determine the structural response of the woodframe buildings it analyzes. Next, it uses experimental and analytical fragility and repair cost data in order to translate the structural response into damage and damage into economic loss. The thesis demonstrates the use of the model using two-story, single-family homes as an example building category, although the model can actually be applied to any category of woodframe building. In this case, the model is applied to estimate losses as a function of ground motion intensity and building design. By incorporating actual ground motion recurrence data, the analysis is used to assess the interaction between hazard and loss for an example location. The results are discussed to illustrate how such an analysis can be used to help characterize estimated losses, define performance objectives, and guide design to meet those performance objectives. The results for the example case presented in this thesis reaffirm the importance of explicitly recognizing the large variability in losses and the contribution of non-structural and contents loss in performance-based design.
- ItemObserving changes in gender and sexuality in slasher film franchises(University of Delaware, 2009) Newby, BrianThe connection between horror and gender is nothing new. The context of psychoanalytic feminist film theory lends itself to the discussion of gender within the films themselves, but treats the films as a universe in and of themselves without any connection to society. The question I am asking in this paper is whether or not there are changes in the treatment of gender and sexuality in slasher films over time. If changes are observed, how do these changes reflect changes in the treatment of gender and sexuality in society? By using a reflection theory approach and a “doing gender” approach, I will discuss how changes in these films reflect changing social attitudes towards gender. I will do so by making observations about the autonomy and agency of primary female characters in these films, particularly the character referred to as the “Final Girl.”
- ItemMultiscale Monte Carlo study of epidermal growth factor receptor diffusion and dimerization(University of Delaware, 2009) Collins, StuartThe ErbB family of receptors is dysregulated in a number of cancers, and the signaling pathway of this receptor family is a critical target for several anti-cancer drugs. Therefore, a detailed understanding of the mechanisms of receptors activation is critical. However, despite a plethora of biochemical studies and single particle tracking experiments, the early molecular mechanisms involving epidermal growth factor (EGF) binding and EGF receptor (EGFR) dimerization are not as well understood. Due to the large disparity of time and length scales involved in receptor dimerization reactions, we adapt the coarse-grained Monte Carlo (CGMC) simulation framework to enable the simulation of in vivo receptor diffusion and dimerization. Using the CGMC method, spatial modeling of ligand-mediated membrane receptor dimerization reaction dynamics was performed. Furthermore, the simulations demonstrate the importance of spatial heterogeneity in membrane receptor localization. Mathematical models, especially one that takes into account spatial heterogeneity, show mechanistic understanding of receptor activation that may in turn enable improved future cancer treatments.
- ItemGrowth and organ differences between chicken lines selected for divergent growth rates(University of Delaware, 2009) Feierstein, ErikaSelecting chicken for enhanced meat production has altered the relative growth of organs in modern broiler lines, when compared with heritage lines. In this five week study, we compared the growth and feed efficiency of a heritage line, UIUC, with a modern production line, Ross 708. During this period, the body mass and feed efficiency of the modern strain was higher than that of the heritage line, indicating that the Ross 708 birds are more efficient at converting feed to body mass. The relative growth of the breast, heart, liver and intestine were also compared during these five weeks. The breast muscle of the heritage line constituted 9% of the total body mass at five weeks, while the breast mass of the modern line comprised 18% of the total body mass. In contrast, the relative size of the heart decreased after day fourteen in the modern line, suggesting that selection for increased breast muscle has translated to decreased relative heart muscle mass. The mass of the liver reached its peak earlier in the modern line than the heritage line, possibly improving nutrient utilization. Finally, the jejunum and ileum segments of the intestine were 20% longer in the modern line, indicating a potential increase in nutrient absorption.
- ItemFate, transport, and bioavailability of arsenic in manured and contaminated soils of Delaware(University of Delaware, 2009) Gardner, SheilaOver the past several years, trace element contamination, specifically arsenic (As), in soils and water has become an alarming environmental issue. All metal/metalloids are potentially hazardous at some concentration (Langdon et al., 2003), and As is known to be carcinogenic, phytotoxic, and biotoxic at extremely low concentrations. The most toxic forms of As are arsine gas, followed by inorganic trivalent compounds, organic trivalent compounds, inorganic pentavalent compounds, and finally elemental As (Cullen and Reimer, 1989). Inorganic As has been listed by the United States Environmental Protection Agency (USEPA) as a Class A human carcinogen and has been linked to bladder, kidney, liver, lung, and skin cancers, as well as impaired nerve function (Research Triangle Institute, 1998). In 2001 the USEPA reduced the allowable levels of As for oral intake in drinking water from 50 µg L-1 to 10 µg L-1, and states have been required to comply with this regulations since 2006. Delaware has complied with this standard since 2001. In 2004, the Delaware Department of Natural Resources and Environmental Control (DNREC) established an Interim Arsenic Soil Cleanup Standard for Residential Properties at 23 mg kg-1 for surface soils from zero to two feet below ground surface, and 101 mg kg-1 for subsurface soils from two to six feet below ground surface, which was a change from the previous standard of 11 mg kg-1. DNREC established the 10-5cancer risk (the potential risk for one additional cancer death caused by exposure to a carcinogen in a human population of 100,000 in a lifetime) for As at 4 mg kg-1, the hazard index value (the numerical value obtained by dividing a person’s expected daily intake of a non-carcinogen by a level which is not expected to produce toxic effects) at 23 mg kg-1, and the background level at 11 mg kg-1. Delaware Senate Bill 68, introduced in April 2005, established an As cleanup level of 6 mg kg-1; however, the bill was not passed into law based on previous research showing that the average background As concentration in Delaware soils is 11 mg kg-1 (DNREC, 2008). The primary sources of As introduction into the environment in Delaware are pesticides, poultry litter, and historical tanneries. An organic As compound known as Roxarsone is incorporated into poultry feeds to control Coccidiosis, increase growth rate, improve feed utilization, enhance pigmentation, and may be effective in suppressing Salmonella (Alpharma, 1999). Most of the As is excreted by the chicken and is incorporated into poultry litter (PL – a mixture of bedding material and manure). The use of PL as an agricultural soil amendment has been an ongoing process for many years on the Delmarva Peninsula, and it is apparent that the fate of As in soils, especially those that are sandy and prone to leaching, needs to be studied.
- ItemAbundance, diversity, and activity of ammonia-oxidizing prokaryotes in the coastal arctic ocean in summer and winter(University of Delaware, 2009) Christman, GlennAmmonia 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.
- ItemImplications of an inductive versus deductive approach to SLA grammar instruction(University of Delaware, 2009) Kuder, EmilyWhile there is generally great interest in how languages are learned in the modern classroom, the question arises as to what type of grammar instruction is most effective. This study examines the outcome of a deductive versus an inductive lesson teaching direct object pronouns in Spanish to 44 college-aged participants in two separate intermediate classes. The two groups of students were exposed to the opposing methods of instruction, then evaluated on their level of acquisition of the grammar structure in question using identical assessment measures. Feedback was solicited from the students following the lesson. The results of the study indicate that there was a slightly higher level of achievement as well as a higher level of satisfaction in the group exposed to the inductive lesson in comparison to the group exposed to the deductive lesson. Although this difference was not found to be statistically significant, it suggests that the inductive approach may have a more positive effect on learners than the traditional deductive approach.
- ItemThe effect of sodium bicarbonate or live yeast culture (Saccharomyces cerevisiae) on the metabolism and production of Lactating dairy cows(University of Delaware, 2009) Der Bedrosian, MichelleRecent studies have shown that feeding live yeasts to dairy cows has the ability to moderate ruminal pH. The objective of this study was to compare the effects of feeding live yeasts or sodium bicarbonate, a traditional buffer, on metabolic indices, digestibility of the total mixed ration (TMR) and milk production and composition in lactating dairy cows. Twenty-eight lactating Holstein cows (77 ± 31 days in milk, 39.4 ± 7.2 kg milk/d) were assigned to blocks by milk production, lactation number, and days in milk and randomly allocated to one of three treatments in a replicated 3 × 3 Latin square design.
- ItemTransformational leadership and outcomes: role of supervisor’s organizational embodiment(University of Delaware, 2009) Wu, HaoOrganizational identification has been proposed to mediate the transformational leadership-empowerment association. Using a sample of 327 employees, we examined supervisor’s organizational embodiment (SOE) as an intervening variable in the process. The results showed that SOE moderated the relationship between transformational leadership behavior and organizational identification, which in turn influenced empowerment. In addition, empowerment was found to mediate the relationship between TLB and in-role and extra-role performance.
- ItemAttitude control of a bio-inspired robotic fish with flexible pectoral fins(University of Delaware, 2009) Pi, LijuanMicro underwater vehicles (MUVs) have wide potential military, scientific and commercial applications. They are especially suitable for exploring dangerous and limited space. This thesis presents the development of a bio-inspired MUV equipped with flexible fins and attitude measurement sensors. The pair of flexible pectoral fins was driven by mini servo individually to mimic boxfish’s pectoral fin motion. Two sensor fusion methods (Kalman filter based on quaternion and Complementary filter based on Lie groups) was used to estimate robotic fish’s rotational movement. A simplified dynamic model for the robot fish’s attitude control was developed based on the theoretical analysis and experiment results. A linear PD controller was designed to achieve the robot fish’s attitude stabilization in the roll axis by controlling the flapping kinematics of the pectoral fins. Both simulation and experiment results show convergence of roll angles in point-to-point control and trajectory tracking of the desired motion.
- ItemTrusted software engine and PCB design for data consistency checking of commercial off-the-shelf (COTS) hardware(University of Delaware, 2009) DelVecchio, RaymondRecent trends in technology have pushed the majority of ASIC fabrication overseas. This high volume market leaves devices vulnerable to attack by adversaries who could potentially alter the design at the hardware level while at the foundry. This type of emerging threat, known as a hardware Trojan, can leave mission critical government or financial systems vulnerable to attacks that can lead to system failure. For much of the previous decade, software was the main focus of computer security, but the past few years have ushered in a new wave of hardware security research to safeguard against such attacks. This thesis provides insight into how hardware Trojans are classified, in addition to providing examples of exploits that can lead to sensitive information leakage in an encryption system. A Trojan detection system is proposed for a COTS AES encryption component, which is accompanied by a modular stacked PCB design to implement such a system.
- ItemBalance and neuropsychological performance following an acute bout of soccer heading(University of Delaware, 2009) Gilliam, MaryContext: Evidence illustrates a cumulative effect of multiple concussions or mild traumatic brain injuries. Research on the effect of an acute bout of soccer heading on brain function is not conclusive. Objective: To identify the effect of an acute bout of soccer heading on neuropsychological function and balance in athletes with a history of multiple concussions. Participants: Twenty-four NCAA Division I and III, and intramural athletes with a minimum of 4 years of competitive soccer experience composing 4 groups: subjects with a self-reported history of 1-2 concussions (EXP1), subjects with a self-reported history of 3 or more concussions (EXP2), and subjects with a self-reported history of 0 concussions randomly assigned to a control group (CON) and experimental group (EXP0). Intervention(s): During baseline testing, participants completed the ImPACT test, the Balance Error Score System (BESS), and the concussion symptom checklist (CSC). During session two, subjects repeated the baseline testing, and then completed 20 purposeful headers in 20 minutes. Immediately, participants repeated the ImPACT test, BESS test, and the CSC. Main Outcome Measure(s): Neuropsychological function as measured by the (ImPACT), balance deficiencies (BESS test), and self-reported symptom score (CSC). Results: On BESS test 1 (dual stance, firm surface) EXP2 had significantly (p=.046) greater errors post-heading than the other groups. For BESS test 2 (single leg stance, firm surface) EXP1 and EXP2 had significantly (p=.008) elevated scores both pre- and post-heading. On BESS test 3 (tandem stance, firm surface), test 4 (dual stance, foam surface), test 5 (single-leg stance, foam surface), and test 6 (tandem stance, foam surface) EXP2 had significantly (p=.001) more errors both pre- and post-heading than the other groups. No significant results were found on ImPACT scores. All groups had significantly (p=.025) higher CSC post-heading scores. Conclusions: This study found no significance between pre- and post-heading in any groups on the BESS test, ImPACT test, and the CSC. The EXP2 group performed worse overall on the more challenging BESS tests, but their scores did not significantly worsen as was hypothesized. Further research with a larger sample size may yield better results.
- ItemThe role of race and caretaker substance abuse in child protective services responses to child abuse reports(University of Delaware, 2009) Ralston, Kevin M.It is believed that approximately 30% of the child maltreatment cases involve a caretaker with a substance abuse problem. Previous literature has established a link between caretaker substance abuse and child maltreatment. However, little research has examined how caretaker substance abuse and race together influence the Child Protective Services investigation of child abuse reports. A series of regression analyses examine African American/White disparities at three distinct points in the investigation process: length of the investigation, substantiation, and disposition. The results do not indicate a racial disparity exists at any point in the investigation. Instead, other factors stereotypically associated with residents of poor inner-city communities, have the largest influence on the decision, especially in cases where a decision includes out-of-home placement or criminal justice involvement. This could indicate a medicalization of caretaker substance abuse in the cases that do not involve serious sanctions, while those cases deemed more serious, underlying stereotypes take over and influence the disposition of an investigation.
- ItemWe do know English: Philadelphia’s Czechoslovak Presbyterian Church of Jan Hus, 1926-1967(University of Delaware, 2009) Budd, JosephAbout 10,000 Slovak-speaking immigrants from Upper Hungary settled in the Philadelphia area between 1880 and 1920. They relied on hard work, thrift, and social networking rather than formal education to achieve social success. Ethnic Christian churches were established to enable them to worship and socialize in their native tongue, make sense of their lives in unfamiliar surroundings and forge an identity. Liturgies and practices were influenced by European events dating back to the Roman Empire. The Czechoslovak Presbyterian Church of Jan Hus, the last Slovak language church organized in Philadelphia, was formed by a group of people who broke away from their Roman Catholic parish in 1926. Their church was small, yet survived for 42 years. The assimilation of the church’s congregants into Philadelphia society is examined in this study. Philadelphia’s Slovak ethnic churches, in the early twentieth century, encouraged members to learn English, purchase homes and become U.S. citizens. As Slovak- Americans were assimilated into Philadelphia’s social structure, a goal of the churches was to help members preserve the Slovak language and old world traditions. After World War II, second and third generation Slovak-Americans intermarried and moved to distant neighborhoods where they joined local non-ethnic churches. Many of the founding church members passed away; others moved with their children. The social relevance of Philadelphia’s Slovak churches was no longer significant enough to attract them to the city. Consequently, the ethnic churches were forced to consolidate or close due to declining membership. Ironically, the demise of the ethnic churches was a direct result of the success of the founding members.
- ItemA case study: The impact of the 1962 northeaster on Delaware’s Atlantic coastline(University of Delaware, 2009) McCarty, ElizabethThe 1962 Northeaster, called by many “The Storm of the Century,” was one of Delaware‟s most devastating coastal storms. It lasted over more than five consecutive, semi-diurnal, perigean spring tidal cycles (Zhang et al., 2002). Maximum winds reached 112.7 km/hr (70 miles/hr), waves were an average of 6-9 m (20-30 ft), and the storm surge reached 2.9 m (10 ft) (Carey & Dalrymple, 2003). Overwash from beaches brought greater than 1.2 m (4 ft) of sand onto the streets, homes, and buildings of communities along the Delaware coastline (Podufaly, 1962). This thesis presents a case study of the impact of the 1962 Northeaster on Delaware‟s Atlantic Coast shoreline. The destructive nature of the storm is quantified using historical aerial photographs, shoreline change data, and Light Detection and Ranging (LiDAR) digital elevation maps. The potential impact of a future storm of this magnitude occurring along Delaware‟s modern shoreline is briefly discussed. Within a Geographic Information System (GIS) framework, georeferenced historic aerial photographs were analyzed for changes in shoreline position, aerial extent of overwash, and number and areas of extensive building damage caused by the storm. For these analyses, the Delaware Atlantic Coastshoreline between Cape Henlopen to the Delaware-Maryland was divided into twelve zones, each approximately 3.7 km (2.3 mi) in length. To quantify erosion due to the storm, the landward displacement of the Delaware shoreline between 1960 (pre-storm) and 1962 (post-storm) was measured at 500 m (1,640 ft) intervals along its length and the maximum amount of landward displacement within each of the zones was determined. The maximum amount of erosion as a result of the storm was 150 m (490 ft) in the zone located within the Delaware Seashore State Park, just north of the Indian River Inlet. Significant amounts (100-130 m (330-430 ft)) of shoreline erosion occurred in the northern portion of Delaware Seashore State Park and near South Bethany and Fenwick Island. The zones with the greatest amounts of maximum erosion as a result of the 1962 Northeaster coincide with the areas of significant longer-term erosion identified by Honeycutt (2003). Areas of overwash due to the storm were digitized on the 1962 post-storm aerial photographs. The total extent of overwash in the study area was 8.34 km2 (3.2 mi2) with the most visibly pronounced areas along the bay barrier portion of the shoreline south of Dewey Beach, Delaware. Maximum and minimum lateral (landward) displacement of overwash sand was measured for each zone. The maximum amount of lateral displacement, ~650 m (2150 ft), was found to be located just south of Bush Island in Delaware Seashore State Park. The least amount of lateral overwash, ~45 m (150 ft), occurred near Rehoboth Beach.Buildings present in the 1960, 1962, and 2002 aerial photographs were digitized as GIS point shapefiles. The 1962 post-storm aerial photographs indicated that the destruction of buildings was highly correlative to the areas of overwash from the storm. As shown by the 2002 aerial photographs, a great deal of residential development took place along the Delaware Atlantic shoreline. For example, in the area of Bethany Beach the increase in structures was as high as 812%. In order to assess the potential effects of another storm of this magnitude on the modern coastline, elevation maps based on LiDAR were used to show areas most at risk due to a 2.9 m (10 ft) storm surge, equivalent to that determined for the 1962 storm. As with the 1962 Northeaster, these high risk areas include the vast majority of the coastline. The effect of 6-9 m (20-30 ft) wave heights, similar to that observed during the 1962 storm, on top of the storm surge was also considered. For example in the areas of greatest development near Bethany Beach, where major overwash and flooding occurred during the 1962 storm, it would be predicted that large-scale erosion of the dune barrier systems with subsequent overwash could occur followed by flooding with levels of inundation approaching 12 m (36 ft). Although modern building codes are much improved from 1962, one could still expect that a future coastal storm of the magnitude of the 1962 Northeaster would have significant impact on Delaware‟s coastal communities.
- ItemUse of a novel magnetic resonance imaging based modeling technique to investigate differences in tibiofemoral articular cartilage contact area In subjects with moderate knee osteoarthritis(University of Delaware, 2009) Henderson, ChristopherKnee osteoarthritis (OA) detrimentally impacts the lives of millions of older Americans through pain and decreased functional ability. Unfortunately, the pathomechanics and associated changes that OA patients experience are not well understood. Mechanical stress in the knee joint may play an essential role in OA; however existing literature in this area is limited. Purpose: The purpose of this study was two-fold. First, we wanted to evaluate an existing magnetic resonance imaging (MRI) based modeling method’s estimation of articular cartilage contact area in vivo. Secondly, we wanted to apply this method to a cohort of subjects with moderate knee OA and compare their medial compartment articular cartilage contact area estimates with healthy, age matched controls. Methods: In order to establish confidence in the modeling method’s ability to estimate articular cartilage contact area, imaging data on a single, healthy subject were collected and compared to existing contact area estimates in the literature. Intra-observer reliability and sensitivity studies were also performed in an attempt to further establish confidence in the method. In the second half of this study, MRIs of the knee at 0°, 15°, and 30° flexion were collected during partial-weightbearing in subjects with moderate knee OA (n = 11) and healthy, age matched controls (n = 11). Articular cartilage contact area estimates were normalized to an approximation of the surface area of the tibial plateau in order to account for joint size differences between subjects. The relationship between medial compartment articular cartilage contact area and knee flexion was investigated in each group. Results: The single healthy subject was found to have articular cartilage contact areaestimates similar to those reported in the literature. The method was found to be sensitive to changes in the cartilage tracings on the peripheries of the compartment and demonstrated an intra-observer reliability of 0.95 when assessed using Pearson’s correlation coefficient. In the second half of the study, medial compartment articular cartilage contact area in the healthy controls was found to be significantly correlated with knee flexion angle (p ≤ 0.01), while no such correlation was found in the moderate OA subjects (p = 0.34). Linear regression analysis found that the moderate knee OA subjects had higher articular cartilage contact areas than their healthy, control counterparts across all flexion angles considered. Conclusions: Confidence was established in the MRI based knee modeling method’s ability to estimate articular cartilage contact area through a series of assessments and comparison with existing literature on healthy subjects. Healthy subjects were found to have a significant correlation between medial compartment articular cartilage contact area and knee flexion, which agreed with the literature. The moderate OA subjects did not show the same relationship between medial compartment articular cartilage contact area and knee flexion. Regression analysis found that they had higher medial compartment articular cartilage contact area estimates in all instances when compared with healthy controls. Increased contact area may be a biomechanical adaptation in response to OA in order to decrease the mechanical stress applied across the painful joint.