Magnetic behavior of current-carrying Type-II superconducting cylinders

The theoretical magnetic behavior of current-carrying superconducting cylinders in the presence of applied axial fields is investigated. An attempt is made to systematize the complex behavior by carefully accounting for critical current, surface pinning, and surface pitch angle, and by stressing the importance of the magnetic history of the sample. A differential equation is developed relating the thermodynamic field H(B) to the cylinder radius rho. This equation, is readily integrated numerically using a Runge-Kutta technique. The resultant flux profiles are further integrated numerically to obtain the mean magnetization of the cylinder. Careful distinction is maintained between the magnetic flux density B and the magnetic field H inside the cylinder. Results are displayed using a phase-diagrammatic technique, which shows the relative amounts of axial and azimuthal field needed to produce a given field within the cylinder, as a function of the bulk pinning strength and the surface pitch angle. In order to incorporate the magnetic history of a sample, a pair of simultaneous differential equations is developed, relating the field H and time, and the radius rho and the time, in a quasistatic manner. When simultaneously integrated, these equations yield a flux profile H(rho) which accounts for any arbitrary variations in the current and axial field experienced by the sample in progressing from the virgin state to the final flux configuration, provided the surface magnetic field increases with time. This should enable certain laboratory sequences in the application of current and field to be modeled analytically

Toward a 21st-century health care system: Recommendations for health care reform

The coverage, cost, and quality problems of the U.S. health care system are evident. Sustainable health care reform must go beyond financing expanded access to care to substantially changing the organization and delivery of care. The FRESH-Thinking Project (www.fresh-thinking.org) held a series of workshops during which physicians, health policy experts, health insurance executives, business leaders, hospital administrators, economists, and others who represent diverse perspectives came together. This group agreed that the following 8 recommendations are fundamental to successful reform: 1. Replace the current fee-for-service payment system with a payment system that encourages and rewards innovation in the efficient delivery of quality care. The new payment system should invest in the development of outcome measures to guide payment. 2. Establish a securely funded, independent agency to sponsor and evaluate research on the comparative effectiveness of drugs, devices, and other medical interventions. 3. Simplify and rationalize federal and state laws and regulations to facilitate organizational innovation, support care coordination, and streamline financial and administrative functions. 4. Develop a health information technology infrastructure with national standards of interoperability to promote data exchange. 5. Create a national health database with the participation of all payers, delivery systems, and others who own health care data. Agree on methods to make de-identified information from this database on clinical interventions, patient outcomes, and costs available to researchers. 6. Identify revenue sources, including a cap on the tax exclusion of employer-based health insurance, to subsidize health care coverage with the goal of insuring all Americans. 7. Create state or regional insurance exchanges to pool risk, so that Americans without access to employer-based or other group insurance could obtain a standard benefits package through these exchanges. Employers should also be allowed to participate in these exchanges for their employees' coverage. 8. Create a health coverage board with broad stakeholder representation to determine and periodically update the affordable standard benefit package available through state or regional insurance exchanges