The Chemical Composition of Red Giants, AGB Stars and Planetary Nebulae

The determinations of element abundances in red-giant stars and in particular in AGB stars are reviewed and the resulting abundances are compared with those obtained for planetary nebulae in the Galaxy and in nearby galaxies. The problems, possibilities and implications of such comparisons when estimating yields from low-mass and intermediate-mass stars are illustrated and commented on.Comment: 8 pages, 1 figure, to appear in proceedings of IAU Symposium 234, "Planetary Nebulae in Our Galaxy and Beyond," eds. R. Mendez & M. Barlo

Thresholds for the Dust Driven Mass Loss from C-rich AGB Stars

It is well established that mass loss from AGB stars due to dust driven winds cannot be arbitrarily low. We model the mass loss from carbon rich AGB stars using detailed frequency-dependent radiation hydrodynamics including dust formation. We present a study of the thresholds for the mass loss rate as a function of stellar parameters based on a subset of a larger grid of such models and compare these results to previous observational and theoretical work. Furthermore, we demonstrate the impact of the pulsation mechanism and dust formation for the creation of a stellar wind and how it affects these thresholds and briefly discuss the consequences for stellar evolution.Comment: 2 pages, 1 figure. To be published in the proceedings of IAU Symp. 241 on Stellar Populations as Building Blocks of Galaxies, ed. A. Vazdekis et al. (2007). Replaced to match edited versio

Do-not-resuscitate orders Ethical aspects on decision making and communication among physicians, nurses, patients and relatives

The purpose was to describe ethical aspects on how do-not-resuscitate (DNR) deci-sions are made, established, and communicated between physicians, nurses, patients and relatives. A random sample of 220 physicians and nurses answered a questionnaire about their attitudes to and experiences of the making and communication of a DNR decision. The re-sponse rate was 73%. Twenty seriously ill patients, and 21 relatives of patients who died with a DNR order, were interviewed. The literature on medical futility was searched for conditions for futility and moral consequences. The results showed that many physicians and nurses are uncertain about the rules and ethics of DNR orders. There are discrepancies between guidelines and attitudes regarding DNR orders, as well as between attitudes and behaviour. Seriously ill patients estimate open and straightforward conversations about treatments in the end of life. Relatives seem to get acceptable information and counselling. Conditions and consequences of medical futility may be approached in a new clinical way. There are numerous possible ethical conflicts within and between the principles of autonomy, non-maleficence, beneficence, and the virtues and ideals of the profession. Start a dialogue about end-of-life support with chronically ill and elderly patients, and their relatives, while they still are capable of understanding and authorisation. The clinical conversation model may make it easier. All involved should understand why certain deci-sions are made. Conditions and consequences of futility should be ascertained together with the patients, the relatives and the staff, after which a joint decision can be reached

Investigating Reading Behavior and Inference-making in Advanced L2 Reading Comprehension Assessment Tasks

Despite the ubiquity of reading comprehension tasks in English language proficiency tests (or sections of tests), the constructs underlying successful reading comprehension in English as a second/additional language at the advanced academic level are still not completely understood. Part of the reason for this gap in the current state of knowledge comes from how existing models of second language reading neglect higher-order reading skills. Many reading assessments overly target language proficiency skills and assume the transfer of first language literacy skills, leaving unexamined the higher-order skills of language learners who become skilled academic readers in their second or additional language. This study seeks to address the dearth of research on higher-order reading skills in advanced second language reading comprehension by examining the activation of these skills in realistic L2 reading comprehension tasks. A reading comprehension test with three different tasks (MC questions, cloze, and summary) was developed and administered to 102 second language English and multilingual undergraduate and graduate students studying at a university in the US. Eye-movement behavior was recorded during these tasks, and each reading task was followed by a sentence verification task to measure activation of inferencing. Eye-movement behavior and inferencing are compared across the reading tasks, and additionally compared to language proficiency and reading comprehension scores. The tasks each elicited distinct patterns of reading behavior: the cloze task elicited careful local reading, the MC task elicited expeditious linear reading, and the summary task elicited both careful global reading and expeditious strategies. Cloze scores were closely related to language proficiency, but also related to reasoning ability and processing efficiency. MC scores were unrelated to proficiency. They were instead related more to reasoning ability and were predicted by readers’ ability to efficiently process the MC questions. Inferencing ability was only predictive of score in the summary task. Summary scores were additionally influenced by global attention to the text, processing efficiency, reading motivation, and language proficiency. Implications for the use of each task as L2 reading assessment are discussed, as well as implications for the teaching of second language reading

Dust driven mass loss from carbon stars as a function of stellar parameters - I. A grid of Solar-metallicity wind models

[Abridged] We have computed a grid of 900 numeric dynamic model atmospheres (DMAs) using a well-tested computer code. This grid of models covers most of the expected combinations of stellar parameters, which are made up of the stellar temperature, the stellar luminosity, the stellar mass, the abundance of condensible carbon, and the velocity amplitude of the pulsation. The resultant mass-loss rates and wind speeds are clearly affected by the choice of stellar temperature, mass, luminosity and the abundance of available carbon. In certain parts of the parameter space there is also an inevitable mass-loss threshold, below which a dust-driven wind is not possible. Contrary to some previous studies, we find a strong dependence on the abundance of free carbon, which turns out to be a critical parameter. Furthermore, we have found that the dust grains that form in the atmosphere may grow too large for the commonly used small particle approximation of the dust opacity to be strictly valid. This may have some bearing on the wind properties, although further study of this problem is needed before quantitative conclusions can be drawn. The wind properties show relatively simple dependences on stellar parameters above the mass-loss threshold, while the threshold itself is of a more complicated nature. Hence, we chose not to derive any simplistic mass-loss formula, but rather provide a mass-loss prescription in the form of an easy-to-use FORTRAN routine. Since this mass-loss routine is based on data coming from an essentially self-consistent model of mass loss, it may therefore serve as a better mass-loss prescription for stellar evolution calculations than empirical formulae. Furthermore, we conclude that there are still some issues that need to be investigated, such as the role of grain-sizes.Comment: 27 pages, 11 figures, to appear in Astronomy & Astrophysics. Corrections by language editor included in this new versio