The Theory of Brown Dwarfs and Extrasolar Giant Planets

Straddling the traditional realms of the planets and the stars, objects below the edge of the main sequence have such unique properties, and are being discovered in such quantities, that one can rightly claim that a new field at the interface of planetary science and and astronomy is being born. In this review, we explore the essential elements of the theory of brown dwarfs and giant planets, as well as of the new spectroscopic classes L and T. To this end, we describe their evolution, spectra, atmospheric compositions, chemistry, physics, and nuclear phases and explain the basic systematics of substellar-mass objects across three orders of magnitude in both mass and age and a factor of 30 in effective temperature. Moreover, we discuss the distinctive features of those extrasolar giant planets that are irradiated by a central primary, in particular their reflection spectra, albedos, and transits. Aspects of the latest theory of Jupiter and Saturn are also presented. Throughout, we highlight the effects of condensates, clouds, molecular abundances, and molecular/atomic opacities in brown dwarf and giant planet atmospheres and summarize the resulting spectral diagnostics. Where possible, the theory is put in its current observational context.Comment: 67 pages (including 36 figures), RMP RevTeX LaTeX, accepted for publication in the Reviews of Modern Physics. 30 figures are color. Most of the figures are in GIF format to reduce the overall size. The full version with figures can also be found at: http://jupiter.as.arizona.edu/~burrows/papers/rm

On the origin and evolution of the material in 67P/Churyumov-Gerasimenko

International audiencePrimitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth- and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices and thus indicate that common processes and conditions were involved in their formation. The samples returned by the Stardust mission to comet Wild 2 showed that the bulk refractory material was processed by high temperatures in the vicinity of the early sun. The recent Rosetta mission acquired a wealth of new data on the composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) and complemented earlier observations of other comets. The isotopic, elemental, and molecular abundances of the volatile, semi-volatile, and refractory phases brought many new insights into the origin and processing of the incorporated material. The emerging picture after Rosetta is that at least part of the volatile material was formed before the solar system and that cometary nuclei agglomerated over a wide range of heliocentric distances, different from where they are found today. Deviations from bulk solar system abundances indicate that the material was not fully homogenized at the location of comet formation, despite the radial mixing implied by the Stardust results. Post-formation evolution of the material might play an important role, which further complicates the picture. This paper discusses these major findings of the Rosetta mission with respect to the origin of the material and puts them in the context of what we know from other comets and solar system objects

Assessing children's emotional responses to surgery: a multidimensional approach

Aim. This paper reports a study to assess the interrelationships between physiological measures of children's heart rates and blood pressure, subjective measures of children's level of anxiety, and direct behavioural observations in children's emotional responses to surgery. Background. Psychological upset has been described as a multidimensional phenomenon which includes behavioural, subjective, and physiological components. However, a majority of previous studies have employed only one or two measures of psychological upset. Most importantly, the interrelationships among these three components of psychological upset have seldom been explored. Methods. A cross-sectional design was employed, and 106 Chinese children admitted for day surgery during the summer of 2004 were invited to participate in the study. They were asked to respond to the Chinese version of the State Anxiety Scale for Children. Their mean arterial blood pressure and heart rates were recorded in the operating theatre after being transferred to the operating table but before anaesthesia induction. A research nurse used the Children's Emotional Manifestation Scale to document the children's emotional behaviours during anaesthesia induction. The data were collected in 2004. Results. Children with high preoperative anxiety levels manifested more negative emotional behaviour during anaesthesia induction. Those with more negative emotional behaviour or high levels of state anxiety also had faster heart rates and higher mean arterial blood pressure. Conclusion. A child's response to stressful medical procedures can be varied. The emotional responses of children to surgery need to be understood as a multidimensional phenomenon. To gain a more comprehensive understanding of the effects of surgery on children, it is recommended that assessment strategies used should reflect the multidimensional phenomenon of the emotional upset. © 2006 Blackwell Publishing Ltd.postprin