Design and performance assessment of aortic heart valve for tissue engineering

Current artificial heart valves are classified as mechanical and bioprosthetic. An appealing pathway that promises to overcome the shortcomings of commercially available heart valves is offered by the interdisciplinary approach of cardiovascular tissue engineering. However, the mechanical properties of the Tissue Engineering Heart Valves (TEHV) are limited and generally fail in the long-term use. To meet this performance challenge novel biodegradable triblock copolymer poly(ethylene oxide)-polypropylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO or F108) crosslinked to Silk Fibroin (F108-SilkC) to be used as tri-leaflet heart valve material was investigated. ^ Synthesis of ten polymers with varying concentration and thickness (55 µm, 75 µm and 100 µm) was achieved via a covalent crosslinking scheme using bifunctional polyethylene glycol diglycidyl ether (PEGDE). Static and fatigue testing were used to assess mechanical properties of films, and hydrodynamic testing was performed to determine performance under a simulated left ventricular flow regime. The crosslinked copolymer (F108-Silk C) showed greater flexibility and resilience, but inferior ultimate tensile strength, by increasing concentration of PEGDE. Concentration molar ratio of 80:1 (F108: Silk) and thickness of 75 µm showed longer fatigue life for both tension-tension and bending fatigue tests. Four valves out of twelve designed satisfactorily complied with minimum performance requirement ISO 5840, 2005. ^ In conclusion, it was demonstrated that the applicability of a degradable polymer in conjugation with silk fibroin for tissue engineering cardiovascular use, specifically for aortic valve leaflet design, met the performance demands. Thinner thicknesses (t<75 µm) in conjunction with stiffness lower than 320 MPa (80:1, F108: Silk) are essential for the correct functionality of proposed heart valve biomaterial F108-SilkC. Fatigue tests were demonstrated to be a useful tool to characterize biomaterials that undergo cyclic loading. ^

An investigation of the relationships between selected characteristics and leadership outcomes of Athletic Training Education Program directors

There is currently no evidence describing what characteristics make an Athletic Training Program Director (PD) an effective leader. An influx of accredited programs resulted in a rapid increase in the demand for PDs, yet training and preparation for these positions has failed to evolve. Although Certified Athletic Trainers (ATs) are trained in specific content areas, they may not always be prepared for the administrative and leadership responsibilities associated with the role of PD (Leone, 2008). This dissertation examined the relationships between selected characteristics and leadership outcomes of Athletic Training Program Directors. Each PD participants (n=27) completed a demographic questionnaire to obtain the leader's academic preparation, accreditation experience and leadership training history. Each participant also completed the Multifactor Leadership Questionnaire (MLQ) to obtain leadership styles, behaviors, and outcomes. Overall, the PDs reported utilizing transformational leadership most often and passive avoidant leadership least often. There was no significant difference between PDs with master's and doctorate degrees on overall leadership outcome. However, participants with a doctorate degree scored significantly different on the effectiveness component of the leadership outcome compared with participants with a master's degree. Those participants who have completed academic coursework on leadership scored significantly different on the leadership outcome compared to those who have not completed academic coursework on leadership. Findings from this study indicate that changes to the current requirements for the role of PD may be warranted. Consideration should be given to increasing the minimum degree requirement and requiring academic coursework on leadership. Future research may be useful in determining specific degree guidelines and types and amounts of leadership training that would be beneficial to Athletic Training PDs.