994 resultados para 148


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Climate change over the past ,30 years has produced numerous shifts in the distributions and abundances of species1,2 and has been implicated in one species-level extinction3. Using projections of species’ distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth’s terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a powerlaw relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15–37% of species in our sample of regions and taxa will be ‘committed to extinction’. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction (,18%) than mid-range (,24%) and maximum change (,35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse

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Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (> 2 MJ). Aims: Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long term radial velocity variability indicating the presence of other bodies in the system. Methods: For transiting planets, the Rossiter-McLaughlin effect allows the measurement of the sky-projected angle ß between the stellar rotation axis and a planet's orbital axis. Using the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six transiting hot Jupiters found by the WASP consortium. We combine these with long term radial velocity measurements obtained with CORALIE. We used a combined analysis of photometry and radial velocities, fitting model parameters with the Markov Chain Monte Carlo method. After obtaining ß we attempt to statistically determine the distribution of the real spin-orbit angle ?. Results: We found that three of our targets have ß above 90°: WASP-2b: ß = 153°+11-15, WASP-15b: ß = 139.6°+5.2-4.3 and WASP-17b: ß = 148.5°+5.1-4.2; the other three (WASP-4b, WASP-5b and WASP-18b) have angles compatible with 0°. We find no dependence between the misaligned angle and planet mass nor with any other planetary parameter. All six orbits are close to circular, with only one firm detection of eccentricity e = 0.00848+0.00085-0.00095 in WASP-18b. No long-term radial acceleration was detected for any of the targets. Combining all previous 20 measurements of ß and our six and transforming them into a distribution of ? we find that between about 45 and 85% of hot Jupiters have ? > 30°. Conclusions: Most hot Jupiters are misaligned, with a large variety of spin-orbit angles. We find observations and predictions using the Kozai mechanism match well. If these observational facts are confirmed in the future, we may then conclude that most hot Jupiters are formed from a dynamical and tidal origin without the necessity to use type I or II migration. At present, standard disc migration cannot explain the observations without invoking at least another additional process.

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We investigate the simplicial cohomology of certain Banach operator algebras. The two main examples considered are the Banach algebra of all bounded operators on a Banach space and its ideal of approximable operators. Sufficient conditions will be given forcing Banach algebras of this kind to be simplicially trivial.

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Objectives: To explore the views and perspectives of children on the unlicensed/off-label use of medicines in children and on the participation of children in clinical trials. Methods: Focus-group discussions, involving school children, were carried out in a range of primary and secondary schools in Northern Ireland. A purposeful sample was chosen to facilitate representation of various socioeconomic groupings. Results: A total of 123 pupils, aged from 10 to 16 years, from six schools, participated in 16 focus groups. In general, pupils viewed the unlicensed/off-label use of medicines in children as unsafe and unethical and felt it is necessary to test medicines in children to improve the availability of licensed products. The majority felt that older children should be told, and that parents should be told, about the unlicensed/off-label use of medicines in children, yet they recognised some implications of this, such as potential medication non-adherence. Conclusions: This is the first study to explore the views of healthy children on unlicensed medicine use in children. Children were able to recognise potential risks associated with the unlicensed use of medicines and felt it is necessary to test and license more medicines in children. Practice implications Health care professionals should consider the views of children in decisions that affect their health.

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This article deals with Paul Celans relation to Europe and his version of the 'souci de soi' (Foucault).

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