Recent studies of public school choice programs in the United States suggest that choice benefits not only students participating in choice programs, but all the students in a choice district. This paper tests whether choice influences the behavior of public school teachers, arguably the link between policy and outcome. The results suggest that one form of choice-intradistrict choice-leads teachers to work more diligently.
This paper is of two parts: a review of the experience of the T58 in an erosive environment, and a review of the design considerations, development testing and field experience in the T64 program relative to operation in a sand environment. Combat operation of various T58-powered helicopters showed erosion to be the major cause of engine premature removals. A description is given of problems encountered and of the design improvements and maintenance procedures implemented to minimize erosion effects. Field experience and redesign effort established general guidelines applicable to future turbine engine design and installations for helicopter and V/STOL aircraft. Mechanical and aerodynamic design requirements for sand environment operation are discussed as applicable to the T64, including the test experience obtained during the development program. Results are presented of the flight test program to evaluate the effectiveness of the inertial separator installed on the Sikorsky CH-53. Relative engine conditions are reviewed and compared to SEA field experience.
Educational institutions sponsoring competitive athletics may use an athletics model, academic model, or medical model for delivery of sports medicine to student-athletes. Four types of legal risk are considered for these 3 models: litigation, contract, regulatory, and structural. The athletics model presents the greatest legal risk to institutions, whereas the medical model presents the least legal risk. Institutional administrators should consider these risks when selecting or maintaining a delivery model for sports medicine.
The issue of concussions 1 in football has risen to prominence in recent years, thanks in no small part to the efforts of intrepid investigative journalists at the New York Times. 2 As media attention brought new interest to this topic, a variety of research institutions launched or accelerated efforts to understand the scientific aspects of brain injury. 3 Concern about the long-term consequences of concussions has prompted notable rule changes and modifications, including greater "emphasis" on certain existing rules in college and professional football. 4 Even at a lower level of competition, the link between concussions and football has prompted schools and leagues to change their *
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