BackgroundRecruitment of young people for health research by traditional methods has become more expensive and challenging over recent decades. The Internet presents an opportunity for innovative recruitment modalities.ObjectiveTo assess the feasibility of recruiting young females using targeted advertising on the social networking site Facebook.MethodsWe placed an advertisement on Facebook from May to September 2010, inviting 16- to 25-year-old females from Victoria, Australia, to participate in a health study. Those who clicked on the advertisement were redirected to the study website and were able to express interest by submitting their contact details online. They were contacted by a researcher who assessed eligibility and invited them to complete a health-related survey, which they could do confidentially and securely either at the study site or remotely online.ResultsA total of 551 females responded to the advertisement, of whom 426 agreed to participate, with 278 completing the survey (139 at the study site and 139 remotely). Respondents’ age distribution was representative of the target population, while 18- to 25-year-olds were more likely to be enrolled in the study and complete the survey than 16- to 17-year-olds (prevalence ratio = 1.37, 95% confidence interval 1.05–1.78, P = .02). The broad geographic distribution (major city, inner regional, and outer regional/remote) and socioeconomic profile of participants matched the target population. Predictors of participation were older age, higher education level, and higher body mass index. Average cost in advertising fees per compliant participant was US $20, making this highly cost effective.ConclusionsResults demonstrate the potential of using modern information and communication technologies to engage young women in health research and penetrate into nonurban communities. The success of this method has implications for future medical and population research in this and other demographics.

We modeled the evolution of the Milky Way to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.As we learn more about the Milky Way Galaxy, extrasolar planets and the evolution of life on Earth, qualitative discussions of the prerequisites for life in a Galactic context can become more quantitative (1-3). The Galactic habitable zone (GHZ) (4), analogous to the concept of the circumstellar habitable zone (5), is an annular region lying in the plane of the Galactic disk possessing the heavy elements necessary to form terrestrial planets and a sufficiently clement environment over several billion years to allow the biological evolution of complex multicellular life. In order to more quantitatively estimate the position, size and time evolution of the GHZ, we combined an updated model of the evolution of the Galaxy (6) with metallicity constraints derived from extrasolar planet data (7).Of the factors that determine the location of the GHZ, the abundance of elements heavier than hydrogen and helium (metallicity) is particularly crucial because these 1

A self‐consistent model of the chemical evolution of the globular cluster NGC 6752 is presented to test a popular theory that observed abundance anomalies are due to ‘internal pollution’ from intermediate‐mass asymptotic giant branch stars. We simulated the chemical evolution of the intracluster medium under the assumption that the products of Type II supernovae are completely expelled from the globular cluster, whereas the material ejected from stars with m≲ 7  M⊙ is retained, due to their weak stellar winds. By tracing the chemical evolution of the intracluster gas we have tested an internal pollution scenario, in which the Na‐ and Al‐enhanced ejecta from intermediate‐mass stars is either accreted on to the surfaces of other stars, or goes toward forming new stars. The observed spread in Na and Al was reproduced, but not the O–Na and Mg–Al anticorrelations. In particular, neither O nor Mg are sufficiently depleted to account for the observations. We predict that the Mg content of Na‐rich cluster stars should be overwhelmingly dominated by the 25,26Mg isotopes, whereas the latest data show only a mild 26Mg enhancement and no correlation with 25Mg. Furthermore, stars bearing the imprint of intermediate‐mass stellar ejecta are predicted to be strongly enhanced in both C and N, in conflict with the empirical data. We show that the NGC 6752 data are not matched by a model incorporating detailed nucleosynthetic yields from asymptotic giant branch stars. Although these stars do show the hot hydrogen burning that seems to be required to explain the observations, this is accompanied by helium burning, producing primary C, N, Mg and Na (via hot‐bottom burning) which do not match the observations. Based on current theories of intermediate‐mass stellar nucleosynthesis, we conclude that these stars are not responsible for most of the observed globular cluster abundance anomalies.

The main astrophysical factories of fluorine (19F) are thought to be Type II supernovae, Wolf-Rayet stars, and the asymptotic giant branch (AGB) of intermediate mass stars. We present a model for the chemical evolution of fluorine in the Milky Way using a semi-analytic multi-zone chemical evolution model. For the first time, we demonstrate quantitatively the impact of fluorine nucleosynthesis in Wolf-Rayet and AGB stars. The inclusion of these latter two fluorine production sites provides a possible solution to the long-standing discrepancy between model predictions and the fluorine abundances observed in Milky Way giants. Finally, fluorine is discussed as a possible probe of the role of supernovae and intermediate mass stars in the chemical evolution history of the globular cluster omega Centauri.Comment: 7 pages, 4 figures. MNRAS in pres