The Ever Changing Circumstellar Nebula Around UW Centauri

We present new images of the reflection nebula surrounding the R Coronae Borealis Star, UW Cen. This nebula, first detected in 1990, has changed its appearance significantly. At the estimated distance of UW Cen, this nebula is approximately 0.6 ly in radius so the nebula cannot have physically altered in only 8 years. Instead, the morphology of the nebula appears to change as different parts are illuminated by light from the central star modulated by shifting thick dust clouds near its surface. These dust clouds form and dissipate at irregular intervals causing the well-known declines in the R Coronae Borealis (RCB) stars. In this way, the central star acts like a lighthouse shining through holes in the dust clouds and lighting up different portions of the nebula. The existence of this nebula provides clues to the evolutionary history of RCB stars possibly linking them to the Planetary Nebulae and the final helium shell flash stars.Comment: To be published in ApJ Letters. 5 pages, 3 figures (2 in color

AN EVALUATION OF THE EFFECTIVENESS OF THE FLORIDA COOPERATIVE'S SEASONAL PRICING PLAN ON SEASONAL PRODUCTION VARIABILITY

From 1993 - 1995, Florida dairy cooperatives implemented a seasonal pricing plan in an attempt to decrease the variability in seasonal production. Farmers that participated in the seasonal pricing plan were able to reduce seasonality in each year when compared to 1992 by as much as 20 percent. For farmers that did not participate, seasonality increased in each year by as much as 32 percent. Overall, the seasonal pricing plan was effective in reducing seasonality for those farmers that chose to participate in the plan and that its limited short-run success was the result of seasonality increases by non-participating farms.amplitude, seasonal pricing plan, seasonality, Livestock Production/Industries,

Conceptualizing, Embracing, and Measuring Failure in Social Marketing Practice

Background: While failure in social marketing practice represents an emerging research agenda, the discipline has not yet considered this concept systematically or cohesively. This lack of a clear conceptualization of failure in social marketing to aid practice thus presents a significant research gap. Focus: This study aimed to conceptualize failures in social marketing practice. Methods: A qualitative survey was conducted using purposive sampling to solicit expert views of well-established social marketing academics and practitioners. Participants were asked to discuss failures in social marketing practice based on their experience in the field. A total of 49 participants provided their input to the survey. Thematic analysis was used to develop four themes addressing the research question. Importance: It is widely acknowledged that reflecting and learning from past failures to promote future best practices is desirable for any discipline. As an empirically based social change discipline, social marketing would benefit from the elevation of failure within its broader research agenda. Results: Four themes were identified: 1) Failures occur when the target behaviors are not achieved, 2) Tactics used to measure failures, 3) Process failure, and 4) Failures either not measured or reframed as lessons learned. A conceptual framework was created to characterize the nature of failures in social marketing practice, representing a feedback loop deemed problematic for the discipline. Recommendations: We call for social marketers to explicitly acknowledge and address failures when describing and reporting on their work and project outcomes. Efforts should be made to adopt a reflexive stance and examine and address internal and external factors affecting the program's failures

Companion problems in quasispin and isospin

We note that the same mathematical results apply to problems involving quasispin and isospin, but the problems per se are different. In the quasispin case, one deals with a system of identical fermions (e.g. neutrons) and address the problem of how many seniority conserving interactions there are. In the isospin case, one deals with a system of both neutrons and protons and the problem in question is the number of neutron-proton pairs with a given total angular momentum. Other companion problems are also discussed.Comment: 12 pages, Latex; some additions in section II and a brief summary at the en

One step multiderivative methods for first order ordinary differential equations

A family of one-step multiderivative methods based on Padé approximants to the exponential function is developed. The methods are extrapolated and analysed for use in PECE mode. Error constants and stability intervals are calculated and the combinations compared with well known linear multi-step combinations and combinations using high accuracy Newton-Cotes quadrature formulas as correctors. w926020

The ion motion in self-modulated plasma wakefield accelerators

The effects of plasma ion motion in self-modulated plasma based accelerators is examined. An analytical model describing ion motion in the narrow beam limit is developed, and confirmed through multi-dimensional particle-in-cell simulations. It is shown that the ion motion can lead to the early saturation of the self-modulation instability, and to the suppression of the accelerating gradients. This can reduce the total energy that can be transformed into kinetic energy of accelerated particles. For the parameters of future proton-driven plasma accelerator experiments, the ion dynamics can have a strong impact. Possible methods to mitigate the effects of the ion motion in future experiments are demonstrated.Comment: 11 pages, 3 figures, accepted for publication in Phys. Rev. Let