RESUMEN
We study the magnetic relaxation rate Γ of the single-molecule magnet Mn(12)-tBuAc as a function of the magnetic field component H(T) transverse to the molecule's easy axis. When the spin is near a magnetic quantum tunneling resonance, we find that Γ increases abruptly at certain values of H(T). These increases are observed just beyond values of H(T) at which a geometric-phase interference effect suppresses tunneling between two excited energy levels. The effect is washed out by rotating H(T) away from the spin's hard axis, thereby suppressing the interference effect. Detailed numerical calculations of Γ using the known spin Hamiltonian accurately reproduce the observed behavior. These results are the first experimental evidence for geometric-phase interference in a single-molecule magnet with true fourfold symmetry.
RESUMEN
A health-specific locus-of-control (HLC) questionnaire was constructed to measure beliefs about Self-Control Over Health, Provider Control Over Health, Chance Health Outcomes and General Health Threat. A factor analysis of items confirmed these dimensions, and corresponding scales were shown to be reliable. A factor analysis of HLC scales and other measures was used to evaluate construct validity. Persons believing in provider control over health outcomes tended to have strong favorable attitudes toward the quality of medical care. Chance Health Outcomes was associated with more general chance and controllability measures. General Health Threat seemed to tap susceptibility to disease and beliefs that doctors are unable to diagnose those diseases. People who believe in Self-Control Over Health tended to reject the role of chance and health threat in determining health outcomes and to believe in the efficacy of doctors, although they view them as inaccessible. Results are compared with those of previous studies, and some applications of the questionnaire are discussed.