Quantitative assessment of carcinogenic risks associated with 'hot particles'.

We have examined the hot particle problem in terms of the number of irradiated cells and the doses to which they are subjected, assuming both linear and nonlinear dose-response functions typical of those reported in the radiobiological literature. We assess the risk associated with point sources of alpha, beta and gamma activity compared with uniform irradiation, as well as the effects of fractionation of a single particle, and the change in risk if the particle moves. Finally, although the biological data are insufficient for firm estimates, we have tentatively attributed absolute carcinogenic risks in these various situations.     

The long shadow of childhood: associations between parental social class and own social class, educational attainment and timing of first birth; results from the ONS Longitudinal Study

In September 2004, linked data from the 2001 Census was made available in the Office for National Statistics (ONS) Longitudinal Study (a 1 per cent sample of the population of England and Wales). The study now includes information from four censuses on sample members and the people they lived with. The availability of this new information, the length of follow-up and other features of the study (such as records of births and deaths to sample members) provide new opportunities for analysing change--both over the life course, between time periods, and between generations. This article illustrates the potential for analysis of continuity and change with new results on intergenerational social mobility, and on parental social class and age at first birth.     

An Earth-like correspondence between Saturn's auroral features and radio emission

Saturn is a source of intense kilometre-wavelength radio emissions that are believed to be associated with its polar aurorae, and which provide an important remote diagnostic of its magnetospheric activity. Previous observations implied that the radio emission originated in the polar regions, and indicated a strong correlation with solar wind dynamic pressure. The radio source also appeared to be fixed near local noon and at the latitude of the ultraviolet aurora. There have, however, been no observations relating the radio emissions to detailed auroral structures. Here we report measurements of the radio emissions, which, along with high-resolution images of Saturn's ultraviolet auroral emissions, suggest that although there are differences in the global morphology of the aurorae, Saturn's radio emissions exhibit an Earth-like correspondence between bright auroral features and the radio emissions. This demonstrates the universality of the mechanism that results in emissions near the electron cyclotron frequency narrowly beamed at large angles to the magnetic field.     

Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter

It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven, and those of Jupiter, where processes are driven by a large source of internal plasma. But this view is based on information about Saturn that is far inferior to what is now available. Here we report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind and Saturn kilometric radio emission, demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter. Saturn's auroral emissions vary slowly; some features appear in partial corotation whereas others are fixed to the solar wind direction; the auroral oval shifts quickly in latitude; and the aurora is often not centred on the magnetic pole nor closed on itself. In response to a large increase in solar wind dynamic pressure Saturn's aurora brightened dramatically, the brightest auroral emissions moved to higher latitudes, and the dawn side polar regions were filled with intense emissions. The brightening is reminiscent of terrestrial aurorae, but the other two variations are not. Rather than being intermediate between the Earth and Jupiter, Saturn's auroral emissions behave fundamentally differently from those at the other planets.     

A possible correlation between reverse mutation and complementation

Résumé Les mutants présentant la complémentation intra-allélique sont probablement susceptibles aussi de mutation reversé vraie sous l'effet de l'acide nitreux.