Preserving the Sounds of the South

Joint paper delivered by Sean Street and David Lee, Director of the Wessex Film and sound Archive about the joint project, funded by the AHRC, to digitize and put online the Central Southern England Commercial Radio Archiv

Magnetic helicity in magnetohydrodynamic turbulence with a mean magnetic field

A computational investigation of magnetic helicity of the fluctuatingmagnetic fieldHm in ideal and freely decaying three‐dimensional (3‐D) magnetohydrodynamics (MHD) in the presence of a uniform mean magnetic field is performed. It is shown that for ideal 3‐D MHDHm, which is a rugged invariant in the absence of a mean magnetic field [Frisch et al., J. Fluid Mech. 77, 796 (1975)], decays from its initial value and proceeds to oscillate about zero. The decay of Hm is shown to result from the presence of a new ‘‘generalized’’ helicity invariant, which includes contributions from the uniform magnetic field. The loss of invariance of Hm will diminish the effects of inverse transfer of Hm on freely decaying turbulence. This is demonstrated in a discussion of the selective decay relaxation process

Flavored Quantum Boltzmann Equations

We derive from first principles, using non-equilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading non-trivial order in ratios of relevant time scales, we study in detail a toy model for weak scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a non-trivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.Comment: 41 pages, 7 figures. v2: references added, minor corrections and clarification

Dilatonic wormholes: construction, operation, maintenance and collapse to black holes

The CGHS two-dimensional dilaton gravity model is generalized to include a ghost Klein-Gordon field, i.e. with negative gravitational coupling. This exotic radiation supports the existence of static traversible wormhole solutions, analogous to Morris-Thorne wormholes. Since the field equations are explicitly integrable, concrete examples can be given of various dynamic wormhole processes, as follows. (i) Static wormholes are constructed by irradiating an initially static black hole with the ghost field. (ii) The operation of a wormhole to transport matter or radiation between the two universes is described, including the back-reaction on the wormhole, which is found to exhibit a type of neutral stability. (iii) It is shown how to maintain an operating wormhole in a static state, or return it to its original state, by turning up the ghost field. (iv) If the ghost field is turned off, either instantaneously or gradually, the wormhole collapses into a black hole.Comment: 9 pages, 7 figure

Planting the Seed : Perceived Benefits of and Strategies for Discussing Long-Term Prognosis with Older Adults

OBJECTIVES: To characterize the goals and approaches of clinicians with experience discussing long-term prognostic information with older adults. DESIGN: We used a semistructured interview guide containing 2 domains of perceived benefits and strategies to explore why and how clinicians choose to discuss long-term prognosis, defined as life expectancy on the scale of years, with patients. SETTING: Clinicians from home-based primary care practices, community-based clinics, and academic medical centers across San Francisco. PARTICIPANTS: Fourteen physicians, including 11 geriatricians and 1 geriatric nurse practitioner, with a mean age of 40 and a mean 9 years in practice. MEASUREMENTS: Clinician responses were analyzed qualitatively using the constant comparisons approach. RESULTS: Perceived benefits of discussing long-term prognosis included establishing realistic expectations for patients, encouraging conversations about future planning, and promoting shared decision-making through understanding of patient goals of care. Communication strategies included adapting discussions to individual patient preferences and engaging in multiple conversations over time. Clinicians preferred to communicate prognosis in words and with a visual aid, although most did not know of a suitable visual aid. CONCLUSION: Engaging in customized longitudinal discussions of long-term prognosis aids clinicians in anchoring conversations about future planning and preparing patients for the end of life