Optical Light Curves of Supernovae

Photometry is the most easily acquired information about supernovae. The light curves constructed from regular imaging provide signatures not only for the energy input, the radiation escape, the local environment and the progenitor stars, but also for the intervening dust. They are the main tool for the use of supernovae as distance indicators through the determination of the luminosity. The light curve of SN 1987A still is the richest and longest observed example for a core-collapse supernova. Despite the peculiar nature of this object, as explosion of a blue supergiant, it displayed all the characteristics of Type II supernovae. The light curves of Type Ib/c supernovae are more homogeneous, but still display the signatures of explosions in massive stars, among them early interaction with their circumstellar material. Wrinkles in the near-uniform appearance of thermonuclear (Type Ia) supernovae have emerged during the past decade. Subtle differences have been observed especially at near-infrared wavelengths. Interestingly, the light curve shapes appear to correlate with a variety of other characteristics of these supernovae. The construction of bolometric light curves provides the most direct link to theoretical predictions and can yield sorely needed constraints for the models. First steps in this direction have been already made.Comment: To be published in:"Supernovae and Gamma Ray Bursters", Lecture Notes in Physics (http://link.springer.de/series/lnpp

Building consensus in strategic decision-making : system dynamics as a group support system

Contains fulltext : 28724.pdf (publisher's version ) (Open Access)System dynamics was originally founded as a method for modeling and simulating the behavior of industrial systems. In recent years it is increasingly employed as a Group Support System for strategic decision-making groups. The model is constructed in direct interaction with a management team, and the procedure is generally referred to as group model-building. The model can be conceptual (qualitative) or a full-blown (quantitative) computer simulation model. In this article, a case is described in which a qualitative system dynamics model was built to support strategic decision making in a Dutch government agency. Since people from different departments held strongly opposite viewpoints on the strategy, the agency had discussed its strategic problem for more than a year, but was obviously not able to reach consensus. The application of group model-building was successful in integrating opposite points of view, as well as in fostering consensus and creating commitment. The purpose of the article is twofold: first, to illustrate the process of group model-building with system dynamics; second, to evaluate why it was successful. Evaluation results reveal the importance of both systemic thinking through model-building and the role of the facilitator in catalyzing the strategic decision-making process

Smoking cessation at the workplace. Results of a randomised controlled intervention study

OBJECTIVES—To compare the effects of a worksite intervention by the occupational physician offering simple advice of smoking cessation with a more active strategy of advice including a "quit date" and extra support.
POPULATION—Employees of an electrical and gas company seen at the annual visit by their occupational physicians.
CRITERIA END POINTS—Smoking point prevalence defined as the percentage of smokers who were non-smokers at one year. Secondary criteria were the percentage of smokers who stopped smoking for more than six months and the difference in prevalence of smoking in both groups.
METHODS—Randomised controlled trial. The unit of randomisation was the work site physician and a random sample of the employees of whom he or she was in charge. The length of the follow up was one year. Each of 30 work site physicians included in the study 100 to 150( )employees.
RESULTS—Among 504 subjects classified as smokers at baseline receiving simple advice (group A) and 591 the more active programme (group B), 68 (13.5%) in group A and 109 (18.4%) were non-smokers one year later (p=0.03; p=0.01 taking the occupational physician as the statistical unit and using a non-parametric test). Twenty three subjects (4.6%) in group A and 36 (6.1%) in group B (p=0.26) declared abstinence of six months or more. Among non-smokers at baseline, 3.4% in both groups were smokers after one year follow up. The prevalence of smokers did not differ significantly at baseline (32.9% and 32.4%, p=0.75). After the intervention the prevalence of smoking was 30.8% in group A and 28.7% in group B (p=0.19). An increase of the mean symptoms score for depression in those who quit was observed during this period.
CONCLUSIONS—A simple cessation intervention strategy during a mandatory annual examination, targeting a population of smokers independently of their motivation to stop smoking or their health status, showed a 36% relative increase of the proportion of smokers who quit smoking as compared with what can be achieved through simple advice.


Keywords: tobacco smoking; smoking cessation; randomised controlled trial; work sit