Cryogenic masers

Various factors affecting the frequency stability of hydrogen masers are described and related to maser design parameters. The long-term frequency stability of a hydrogen maser is limited by the mechanical stability of the cavity, and the magnitudes of the wall relaxation, spin exchange, and recombination rates which affect the Q of the line. Magnetic resonance studies of hydrogen atoms at temperatures below 1 K and in containers coated with liquid helium films demonstrated that cryogenic masers may allow substantial improvements in all of these parameters. In particular the thermal expansion coefficients of most materials are negligible at 1 K. Spin exchange broadening is three orders of magnitude smaller at 1 K than at room temperature, and the recombination and wall relaxation rates are negligible at 0.52 K where the frequency shift due to the 4 He-coated walls of the container has a broad minimum as a function of temperature. Other advantages of the helium-cooled maser result from the high purity, homogeneity, and resilence of helium-film-coated walls and the natural compatibility of the apparatus with helium-cooled amplifiers

Impurity scattering and localization in dd-wave superconductors

Strong evidence is presented for the localization of low energy quasiparticle states in disordered $d$-wave superconductors. Within the framework of the Bogoliubov-de Gennes (BdG) theory applied to the extended Hubbard model with a finite concentration of non-magnetic impurities, we carry out a fully self-consistent numerical diagonalization of the BdG equations on finite clusters containing up to $50\times 50$ sites. Localized states are identified by probing their sensitivity to the boundary conditions and by analyzing the finite size dependence of inverse participation ratios.Comment: 4 pages REVTeX with 2 embedded .ps figures; submitted to PRB as Rapid Communicatio

Building Blocks for the Development of a Chronic Care Lung Cancer Model

Lung cancer, is the leading cause of cancer death in the United States for both men and women, and as such, represents a tremendous burden on the healthcare system. Survival rates have remained relatively unchanged over the past forty years, yet we seem to be on the verge of a paradigm shift as a result of advances in early screening, diagnosis and better treatment modalities. Lung cancer is different from all other cancers in that 90% of lung cancer cases can be attributed to the conscious behavioral risk factor of smoking, either currently or previously engaged in by the patient. Funding and research has been limited in terms of identifying the unique characteristics and needs of these patients, their physicians and their caregivers. If survival rates improve dramatically, these patients will be managed chronically rather than acutely in the near future. When this occurs, a lung cancer treatment model for the future must be developed in order to more successfully prepare the market place for adapting to these unique patients and their providers who will be operating in a chronic rather than acute care environment. Prior to the development of such a model, the need exists to first develop a comprehensive information map identifying knowledge and knowledge gaps with regards to these patients and providers and their healthcare interactions and individualized needs. Productive patient provider interactions are critical for successful chronic disease management, and therefore several questions must be answered as they relate to treating lung cancer in a more chronic versus acute environment