Origin and Evolution of Saturn's Ring System

The origin and long-term evolution of Saturn's rings is still an unsolved problem in modern planetary science. In this chapter we review the current state of our knowledge on this long-standing question for the main rings (A, Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During the Voyager era, models of evolutionary processes affecting the rings on long time scales (erosion, viscous spreading, accretion, ballistic transport, etc.) had suggested that Saturn's rings are not older than 100 My. In addition, Saturn's large system of diffuse rings has been thought to be the result of material loss from one or more of Saturn's satellites. In the Cassini era, high spatial and spectral resolution data have allowed progress to be made on some of these questions. Discoveries such as the ''propellers'' in the A ring, the shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume provide new constraints on evolutionary processes in Saturn's rings. At the same time, advances in numerical simulations over the last 20 years have opened the way to realistic models of the rings's fine scale structure, and progress in our understanding of the formation of the Solar System provides a better-defined historical context in which to understand ring formation. All these elements have important implications for the origin and long-term evolution of Saturn's rings. They strengthen the idea that Saturn's rings are very dynamical and rapidly evolving, while new arguments suggest that the rings could be older than previously believed, provided that they are regularly renewed. Key evolutionary processes, timescales and possible scenarios for the rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009) 537-57

Asthma Programme in Finland: Did the use of secondary care resources become more rational?

SummaryObjectivesThe aims were to evaluate the profile of newly diagnosed adult asthma cases and the approach adopted to the secondary care management at the launch of the Finnish asthma programme in 1994 and seven years later, in 2001.MethodsA retrospective medical record audit was made of non-acutely referred patients with asthma in 1994 (n=165) and in 2001 (n=133). Clinical profile data, numbers of out-patient visits and periods of in-patient care before and after asthma diagnosis were gathered from referral letters and secondary care records.ResultsThe newly diagnosed asthma patients in 2001 were older, more obese and had more co-morbidities. The main asthma symptoms, such as dyspnoea, wheezing and cough, occurred equally in both years but were more often periodic than daily in 2001. Wheezing during auscultation was significantly less common in 2001. The diagnostic process was associated to a history of asthma in first-degree relatives (OR 5.34, 95% CI 1.12–24.49) in 1994 and a visit to a nurse prior to that to a physician (OR 3.13, 95% CI 1.17–8.37) in 2001. Secondary care visits per new case of asthma (7.3 in 1994 vs. 5.4 in 2001) and days in hospital (3.6 in 1994 vs. 0.95 in 2001) decreased significantly.ConclusionsThe profile of asthma diagnosed in secondary care indicates milder disease with more co-morbidities in 2001 than in 1994.Trends towards assigning a more active role on the part of primary care physicians and more rational use of secondary care resources in the management of asthma were found