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Biomechanics of the Pericellular Matrix: Roles in Cartilage Development and Osteoarthritis
No full textPost-traumatic osteoarthritis is caused by joint injuries leading to progressive degeneration of articular cartilage. PTOA is prevalent in young adults and acute symptoms include swelling, severe pain and synovial effusion. Currently, PTOA is not clinically diagnosed until the onset of the symptomatic phase and there are no effective pharmacological treatments that slows or halts disease progression. This is because the pathogenesis of PTOA is still not well understood, despite advances in research. Although PTOA is considered a whole joint disease, the irreversible breakdown of articular cartilage is considered the key hallmark of PTOA. Articular cartilage is a smooth, white highly-specialized tissue that lines diathrodial joints. It is comprised of a dense extracellular matrix (ECM) with a sparse distribution of cells called chondrocytes. During PTOA, there is a disturbance in the homeostasis of the anabolic-catabolic activities of chondrocytes leading to disruption of cell-ECM interplay. This renders it important to understand the immediate microenvironment of the chondrocytes, the pericellular matrix (PCM). The PCM is a narrow 3-5 m thick tissue surrounding the chondrocytes in articular cartilage. The PCM of normal cartilage surrounds the chondrocytes, separating the cell from the ECM and has distinctive mechanical and structural properties from the ECM. Because the PCM surrounds each cell, any biochemical or biophysical signal the chondrocyte perceives is likely to be influenced, and potentially regulated, by the properties of the PCM. Furthermore, enzymes and growth factors released by the chondrocytes must first be passed through the PCM, where they may be preserved or altered. In PTOA, the PCM undergoes structural changes as well as significant loss of its' biomechanical properties. Additionally, the PCM has been shown to soften and expand during the development of PTOA. Thus, studying the PCM during PTOA and development could provide a basis for therapeutic interventions and better understanding of cellular stress and strain. This study will generate new knowledge on the biomechanics and structure of the PCM and chondrocyte mechanotransduction in articular cartilage during the progression of PTOA and articular cartilage development. First, since murine model provides a unique tool to study OA pathogenesis in vivo, we will for the first time, quantify the structure and mechanical properties of the PCM during the progression of OA in wild-type articular cartilage using our destabilization of medial meniscus mice model. This will provide a basis for understanding whether PCM can serve as a potential target for early OA detection. Second, we will study the effects of decorin on the structure and mechanical properties of murine articular cartilage at the fetal, juvenile and adult ages. This will provide a molecular benchmark for understanding the governing effects of decorin on articular cartilage PCM during post-natal development.Ph.D., Biomedical Science -- Drexel University, 201
Developing the High-Resolution Electrohydrodynamic (EHD) 3D Jet Printing System for Thermoplastic Materials
No full textThree-Dimensional Printing (3DP) is a versatile method that has been quickly developed within the past few decades to become a robust tool widely applied in many fields such as prototyping, constructions, food industry, electronic industry, biomedical applications and modeling for casting. 3DP simplifies the manufacturing process allowing production of complex shaped parts. Several types of 3DP methods exist one of which is electrohydrodynamic (EHD) 3DP. This method can have applications in both the electronic and biomedical industry as it can meet the needs of these industries due to its high-resolution printing capabilities. The high voltage applied in EHD 3DP results in sub 10 μm printing for each printed line allowing for overall high resolution in the final printed product. In EHD 3DP either pneumatic or mechanic pressure can be applied to the syringe to deposit a continuous flow of droplets out from the nozzle. In this work, using the EHD 3DP method, we do not apply any back pressure to our material tube where the only force applied is an electric field force originating from the applied high voltage. In this thesis, the mechanical properties and axial movement capabilities of the High Resolution EHD 3D Jet Printer were developed and improved. Furthermore, the relationship between printing parameters (velocity of the moving platform, temperature of the heating control unit and applied high voltage causing the electric field) and resolution of printing were analyzed in order to define the ideal printing parameters for the desired printing model of a polycaprolactone (PCL) thermoplastic. Finally, results of the tests are given within their corresponding tables and graphs along with a conclusion of the effect of printing parameters.M.S., Mechanical Engineering and Mechanics -- Drexel University, 201
How will the rise of the Millennial generation affect nonprofit fundraising?
No full textThe characteristics of particular generations have a significant impact on how nonprofit organizations identify and cultivate potential donors. The Millennial generation has been compared to Baby Boomers in many ways, particularly in regards to financial and philanthropic habits. As Millennials enter the workforce and become the largest population, outgrowing Baby Boomers, nonprofit organizations must adapt fundraising methods to accommodate the characteristics of this particular generation. These methods include the use of technology, cultivation strategies targeting Millennials, and establishing patterns for long term donor development. By focusing on the characteristics of Millennials, these methods will prove to be effective for long term success.M.S., Arts Administration -- Drexel University, 201
Distributed Generation Dispatch in Islanded Distribution Systems: Imbalance and Slack Bus Modeling Studies
No full textDistribution systems have evolved into a complex participant in the overall power infrastructure. Both nationally and internationally, a push for increasing distributed energy resources has been made through economic policies for their environmental favorability and promise of service reliability. This, in turn, has led consumers and power system planners to consider partitioning larger networks into smaller, self-serviced subsystems, or microgrids, especially in cases of larger grid (e.g. transmission system) outages. Thus, traditional methods of distribution system planning and analysis need to be reevaluated. This thesis looks at the challenges associated with operating islanded distribution systems with a variety of distributed generation (DG) sources available. With fewer means of control, unbalanced loading, and the introduction of single-phase sources, such as photovoltaics and batteries, maintaining system balance needs to be considered. In addition, because of limited generating capacity, the impact of the slack bus model and its location in power flow analyses is studied. Emphasis is then placed on determining the commitment and economic dispatch of available DG, and how these can be used to regulate imbalance levels. This work presents modeling of distributed energy resources and imbalance metrics, a comprehensive cost minimization formulation, and a method for finding feasible dispatch schemes. Simulation results were obtained on a 64-bus islanded distribution network. Multiple sets of simulations were performed to see the effects different DG types and levels of penetration have on overall microgrid operation. The results show how different slack bus locations and corresponding dispatch decisions can improve or worsen operating costs and system-wide imbalance levels.M.S., Electrical Engineering -- Drexel University, 201
Formation and Early Evolution of Stellar Clusters
No full textWe describe a novel numerical method for the studying the formation and evolution of stellar clusters, Torch. This method combines the magnetohydrodynamics code Flash with the Astrophysical Multipurpose Software Environment, AMUSE. Once embedded into AMUSE, we combine Flash with the stellar evolution code SeBa, the N-body dynamics code ph4 and the multiple star system evolution module multiples to create a unique method for tracing the detailed evolution of stellar clusters through time. We then add units for radiation, stellar winds and supernovae, as well as a new star by star formation prescription to Flash that allows for star formation and stellar feedback to create and destroy star clusters and the interstellar gas they form from. The result is the most detailed star cluster formation code to date. We then demonstrate the use of these methods for studying binary star formation and the effects of stellar feedback. We find that massive dynamical binaries created in our simulations are consistent with observations. Further, we observe that wide dynamical binaries tighten due to gas dynamical friction, losing cluster energy to the natal gas, after which they are disrupted by stellar encounters. This supports theoretical predictions that embedded clusters may contract due to the interactions of gas and stars. We also find that while stellar feedback is effective at expelling gas from natal clusters, the clusters themselves remain bound even as they expand due to the loss of the binding potential of the gas. Finally, stellar clusters formed in our simulations mass segregate before the expulsion of their natal gas clouds, as expected from observations of young clusters in the Milky Way.Ph.D., Physics -- Drexel University, 201
The State of Sports Television: How to Create the Ultimate Sports Network in the Ever-Changing Television Landscape
No full textIn the fast evolving television landscape, many networks and executives are looking towards the future to see how they can ensure success moving forward. For cable and broadcast networks, it is crucial to explore innovative strategies and decisions that help draw audiences and stay competitive in a landscape inundated with options for consumers to choose from. With more money spent in sports television than ever before, this research will explore how this money can be spent most cost effectively. This research examines the sports television industry to see what has worked, what hasn’t worked, and how these ideas can be evolved to thrive in the future. A case study was conducted, featuring a survey administered through Qualtrics to 169 individuals, interviews and articles featuring industry titans, and the collection of Nielsen ratings, arranged using Microsoft Excel, to answer the following research questions: (1) What is causing the recent proliferation of sports networks and what is its effect? (2) How do major sports networks fare with audiences and against competitors? (3) Are rising cable subscription fees causing subscribers to drop sports networks? (4) What are the current and future costs of live sports contracts and what is the right balance between live and original programming? The results of this case study provided insights and actionable strategies for the sports television industry. Ratings, Shares, Universe Estimates, and Median Age averages all contributed to the results of the case study. Interviews featuring current and former sports television executives gave more clarity to the sports industry and its inner workings while observed industry publications showed how the industry is received on a more widespread level.M.S., Television Management -- Drexel University, 201
Social Competence in Youth with Neurofibromatosis Type 1
No full textBackground Children and adolescents with neurofibromatosis type 1 (NF1) experience significant difficulties with social adjustment (SA), adversely impacting quality of life across the lifespan. SA refers to the quality of the child’s social relationships and their attainment of developmentally appropriate goals. Youth with NF1 also experience clinically significant impairments across a variety of neuropsychological domains including global intelligence, attention, and executive function. Despite evidence that neurocognitive weaknesses and family-systems factors contribute to worse SA in other pediatric neurological populations, few studies have examined these associations in children with NF1. A greater understanding of processes underlying psychosocial deficits in this population will allow providers to identify those youth at greatest risk for social difficulties, and inform novel, targeted intervention strategies aimed at improving functional and quality of life outcomes. Aims The current study applied a developmental model of social competence in childhood brain disorder to identify aspects of social information processing (SIP) underlying social interaction (SI) and SA difficulties in youth with NF1. SIP encompasses domains such as executive functions and social-affective processing, including theory of mind (ToM). The specific aims of the current study were to 1) compare youth with NF1 and healthy controls (HC) across domains of social competence; 2) establish associations among SIP, SI, and SA constructs in youth with NF1, and 3) determine the potential mediating role of family functioning in youth’s social behaviors and adjustment. Methods Participants diagnosed with NF1, and typically-developing HC youth, between the ages of 10 and 15 years were recruited prospectively from the Children’s Hospital of Philadelphia. Participants completed a brief neuropsychological battery assessing global intellectual functioning (WASI-II), cognitive processing speed and working memory (WISC-V), performance- (TEA-Ch) and caregiver-reported (BRIEF-2) executive functioning, ToM (Jack & Jill Task), relationship quality (NRI-RQV), and perceived peer acceptance (PROMIS). Caregiver perceptions of peer acceptance (PROMIS) and family functioning (FAD) were also collected, and ratings of social interaction styles were assessed via teacher-report (BASC-3). The final sample consisted of 20 youth diagnosed with NF1 (M age = 12.55 years; SD = 1.67) and 14 HC (M age = 12.66 years; SD = 1.75) participants. MANOVAs were conducted to examine group differences across SIP, SI, and SA constructs. Serial parallel mediation analyses were used to evaluate relationships among social competence constructs and moderation analyses evaluated the conditional effects of family functioning on SA within the NF1 group. Results One-way MANOVA revealed significant group differences across all SIP variables. Compared to the HC group, youth with NF1 exhibited significantly worse TEA-Ch EF Composite performance, F(1, 32) = 6.29, p = .017, [eta]p2 = .164, higher caregiver-rated executive dysfunction on the BRIEF-2 GEC, F(1, 32) = 11.25, p = .002, [eta]p2 = .260, and lower accuracy on key ToM trials of the J&J Task, F(1, 32) = 5.97, p = .020, [eta]p2 = .157. Groups also differed on caregiver-reported PROMIS ratings, F(1, 32) = 9.79, p = .004, [eta]p2 = .234, but not on other SA variables of interest (ps > .05) . No significant differences were observed across teacher-reported SI variables (ps > .05). No significant indirect effects of SIP or SI were observed on the relationship between NF1 status and caregiver-reported peer acceptance (PROMIS). Within the NF1 group, family functioning (FAD) significantly moderated the relationship between TEA-Ch EF Composite performance and teacher-reported affiliative SI style (BASC-3 Social Skills; p = .049), and caregiver-reported PROMIS ratings (p = .040). FAD ratings also moderated the relationship between BRIEF-2 GEC scores and teacher-reported social withdrawal (BASC-3 Withdrawal; p = .020), and caregiver PROMIS ratings (p = .036), as well as the relationship between ToM performance (J&J) and teacher-reported aggression (BASC-3 Aggression; p = .039). Discussion Results of the current study suggest that youth with NF1 experience deficits in underlying SIP skills, including executive functioning and ToM, as well as lower caregiver-reported peer acceptance relative to their typically-developing peers. Although no significant indirect effects of underlying SIP skills and/or SI tendencies on the relationship between NF1 and SA were observed, these factors may play an important role in determining social competence outcomes in this population. Importantly, findings suggest that family functioning may play a significant role in moderating the relationships among these aspects of social competence. Results of the present study can inform the development of evidence-based interventions designed to improve SA in this population.Ph.D., Psychology -- Drexel University, 201
A Phenomenological Study: Exploring Academic Equity In Elementary Virtual Classrooms Of A Pennsylvania Cyber Charter School
No full textCyber schools have experienced exponential increases in enrollment across the United States in recent years. While research shows the potential for academic equity in cyber schools to educate students who may have faced struggles in a traditional school setting, we lack a clear understanding of the factors that contribute to that potential equity. The purpose of this phenomenological research study was to describe the lived experiences of elementary cyber school teachers to explore their perceptions, conceptualization, development, and implementation of academic equity in their elementary virtual classrooms. This study explored the experiences of four elementary virtual classroom teachers of a single cyber charter school in Southeastern Pennsylvania to grasp the essence of their perceptions, conceptualization, development, and implementation of academic equity in their virtual classroom setting. The data gathered was comprised of semi-structured interviews, observations, and artifact review. First cycle In Vivo coding and second cycle Descriptive coding revealed five emergent themes, producing key findings. Results and interpretations revealed the following: (a) Families seek alternative learning environments for their children in order for students facing challenges in traditional classroom settings to feel safe and supported according to their individual needs; (b) The parent(s)/guardian must be an integral part of the K-5 virtual classroom experience in order for students to engage and fully access the equitable opportunities offered in the virtual classroom; (c) Leveraging relationships between and among students, parents, and faculty is critical in order to maintain engagement of the family and to improve the capacity of the teachers' equitable instruction; (d) Flexibility in schedule and approach is an indispensable component of a successful virtual program in order for teachers to prioritize collaboration and extensive differentiated planning; (e) Differentiating instruction is a necessary part of the planning and delivery of virtual classroom instruction in order to meet the needs of the diverse students. Conclusions rendered insights to the four research questions. Recommendations to enhance and increase equitable access and opportunity in cyber charter schools were included and comprised of the following: (a) recommendations to the Cyber Charter School; (b) recommendations to cyber charter schools overall; and (c) recommendations for practice and recommendations for additional research.Ed.D., Educational Leadership and Management -- Drexel University, 201
Experimental Technique to Investigate Compliance of Fish Fin During Natural Swimming
No full textThe compliance of a fish fin and how it contributes to swimming has gained extensive attention in the biology and engineering research and design communities. Many studies have hypothesized that fish can actively control the stiffness of their fin rays and fins during swimming to optimize propulsion, but such active controls have not been confirmed through experiments with live fish during natural swimming. This is partly because there are no experimental devices or methodologies that can facilitate controlled experiments during natural swimming to investigate the compliance of the fish fins. It is proposed, through this research, that the compliance of a fish fin can be investigated by applying an external perturbation, like a vortex ring, to the fin while it is being used in locomotion and by measuring the displacement of the fin from its natural swimming motion. To that end, the goal of this thesis was to develop and validate a perturbation device (vortex generator) and a technique to investigate compliance of fins during natural swimming. Experiments were conducted to understand how the vortex formation, size and speed could be altered by tuning the design features on the vortex generator. The evaluation of the vortex generator, the development of the experimental protocol, and the investigation of compliance changes in a fish fin at different swimming speeds were done by conducting experiments with live bluegill sunfish at different steady-swimming speeds and with flexible foils of known flexural rigidities. The evaluation of the technique was conducted by building an engineered system with tunable compliance and estimating the compliance using the perturbation technique proposed herein. The results from the experiments showed that (a) the vortex generator was able to produce an adequate range of vortex rings that could be used to perturb the fins during natural swimming, (b) the fish at slower swimming speed responded similarly to a compliant foil, while the fish at higher swimming speeds responded similarly to a stiffer foil, suggesting a stiffer fin at higher swimming speeds, (c) we can successfully predict changes in the compliance of a system by comparing the maximum deflection and rate of deflection from the unperturbed state to the maximum deflection of a system. Perturbation of fins is a key technique to uncover not only compliance but also behavioral responses that cannot be understood through the study of normal locomotion alone. The outcomes of this research will continue to advance the understanding of fish swimming as fish continue to be one of the greatest inspirations for advanced underwater vehicles.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Rank in Matrix Analysis: On the Preservers of Maximally Entangled States and Fractional Minimal Rank
No full textFor Hilbert spaces \s X, \s Y, the set of maximally entangled states, \MES_{\s X, \s Y}, is a set of rank-1 positive semidefinite operators over the space \s X \otimes \s Y. In this thesis, we consider the problem of classifying the linear maps that take maximally entangled states to maximally entangled states in the case of finite dimensional spaces \s X, \s Y. After classifying these linear maps in the case where \dim \s X divides \dim \s Y, we consider possible avenues of extending these results and consider the set \WMES_{\s X, \s Y}, which is a set of low-rank positive semidefinite operators over \s X \otimes \s Y. We then discuss the "fractional minimal rank", a fractional parameter assigned to partial matrices. We compute the fractional minimal rank for partial matrices whose pattern of knowns is a "minimal cycle", which is the family of the smallest cases for which it is known that the ''minimal rank'' and ''triangular minimal ranks'' differ in general.Ph.D., Mathematics -- Drexel University, 201