Clusters in the Luminous Giant HII Regions in M101

(Abridged) We have obtained HST WFPC2 observations of three very luminous but morphologically different giant HII regions (GHRs) in M101, NGC5461, NGC5462, and NGC5471, in order to study cluster formation in GHRs. The measured (M_F547M - M_F675W) colors and M_F547M magnitudes are used to determine the ages and masses of the cluster candidates with M_F547M <= -9.0. NGC5461 is dominated by a very luminous core, and has been suggested to host a super-star cluster (SSC). Our observations show that it contains three R136-class clusters superposed on a bright stellar background in a small region. This tight group of clusters may dynamically evolve into an SSC in the future, and may appear unresolved and be identified as an SSC at large distances, but at present NGC5461 has no SSCs. NGC5462 has loosely distributed HII regions and clusters without a prominent core. It has the largest number of cluster candidates among the three GHRs, but most of them are faint and older than 10 Myr. NGC5471 has multiple bright HII regions, and contains a large number of faint clusters younger than 5 Myr. Two of the clusters in NGC5471 are older than R136, but just as luminous; they may be the most massive clusters in the three GHRs. The fraction of stars formed in massive clusters is estimated from the clusters' contribution to the total stellar continuum emission and a comparison of the ionizing power of the clusters to the ionizing requirement of the associated HII regions. Both estimates show that <~ 50% of massive stars are formed in massive clusters. The cluster luminosity functions (CLFs) of the three GHRs show different slopes. NGC5462 has the steepest CLF and the most loosely distributed interstellar gas, qualitatively consistent with the hypothesis that massive clusters are formed in high-pressure interstellar environments.Comment: 36 pages (figures not included), 16 figures (3 of them are color figures). Figures are in JPEG or GIF format with a lower resolution due to the size limit of the file. For a higher resolution version of the paper, please download from http://www.astro.uiuc.edu/~c-chen/clusters.pdf. accepted for ApJ (scheduled for the ApJ 2005 February issue

Biofortification of UK food crops with selenium

Se is an essential element for animals. In man low dietary Se intakes are associated with health disorders including oxidative stress-related conditions, reduced fertility and immune functions and an increased risk of cancers. Although the reference nutrient intakes for adult females and males in the UK are 60 and 75 μg Se/d respectively, dietary Se intakes in the UK have declined from >60 μg Se/d in the 1970s to 35 μg Se/d in the 1990s, with a concomitant decline in human Se status. This decline in Se intake and status has been attributed primarily to the replacement of milling wheat having high levels of grain Se and grown on high-Se soils in North America with UK-sourced wheat having low levels of grain Se and grown on low-Se soils. An immediate solution to low dietary Se intake and status is to enrich UK-grown food crops using Se fertilisers (agronomic biofortification). Such a strategy has been adopted with success in Finland. It may also be possible to enrich food crops in the longer term by selecting or breeding crop varieties with enhanced Se-accumulation characteristics (genetic biofortification). The present paper will review the potential for biofortification of UK food crops with Se

Cassini VIMS observations of H3+ emission on the nightside of Jupiter

We present the first detailed analysis of H3+ nightside emission from Jupiter, using Visual and Infrared Mapping Spectrometer (VIMS) data from the Cassini flyby in 2000–2001, producing the first Jovian maps of nightside H3+ emission, temperature, and column density. Using these, we identify and characterize regions of H3+ nightside emission, compared against past observations of H3+ emission on the dayside. We focus our investigation on the region previously described as “mid-to-low latitude emission,” the source for which has been controversial. We find that the brightest of this emission is generated at Jovigraphic latitudes similar to the most equatorward extent of the main auroral emission but concentrated at longitudes eastward of this emission. The emission is produced by enhanced H3+ density, with temperatures dropping away in this region. This emission has a loose association with the predicted location of diffuse aurora produced by pitch angle scattering in the north, but not in the south. This emission also lays in the path of subrotating winds flowing from the aurora, suggesting a transport origin. Some differences are seen between dayside and nightside subauroral emissions, with dayside emission extending more equatorward, perhaps caused by the lack of sunlight ionization on the nightside, and unmeasured changes in temperature. Ionospheric temperatures are hotter in the polar region (~1100–1500 K), dropping away toward the equator (as low as 750 K), broadly similar to values on the dayside, highlighting the dominance of auroral effects in the polar region. No equatorial emission is observed, suggesting that very little particle precipitation occurs away from the polar regions

Qualitative study of the impact of an authentic electronic portfolio in undergraduate medical education

Background Portfolios are increasingly used in undergraduate and postgraduate medical education. Four medical schools have collaborated with an established NHS electronic portfolio provider to develop and implement an authentic professional electronic portfolio for undergraduate students. We hypothesized that using an authentic portfolio would have significant advantages for students, particularly in familiarizing them with the tool many will continue to use for years after graduation. This paper describes the early evaluation of this undergraduate portfolio at two participating medical schools. Methods To gather data, a questionnaire survey with extensive free text comments was used at School 1, and three focus groups were held at School 2. This paper reports thematic analysis of students’ opinions expressed in the free text comments and focus groups. Results Five main themes, common across both schools were identified. These concerned the purpose, use and acceptability of the portfolio, advantages of and barriers to the use of the portfolio, and the impacts on both learning and professional identity. Conclusions An authentic portfolio mitigated some of the negative aspects of using a portfolio, and had a positive effect on students’ perception of themselves as becoming past of the profession. However, significant barriers to portfolio use remained, including a lack of understanding of the purpose of a portfolio and a perceived damaging effect on feedback

The risk and nature of flares in juvenile idiopathic arthritis: Results from the ReACCh-Out cohort

Objective To describe probabilities and characteristics of disease flares in children with juvenile idiopathic arthritis ( JIA) and to identify clinical features associated with an increased risk of flare. Methods We studied children in the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) prospective inception cohort. A flare was defined as a recurrence of disease manifestations after attaining inactive disease and was called significant if it required intensification of treatment. Probability of first flare was calculated with Kaplan-Meier methods, and associated features were identified using Cox regression. Results 1146 children were followed up a median of 24 months after attaining inactive disease. We observed 627 first flares (54.7% of patients) with median active joint count of 1, physician global assessment (PGA) of 12 mm and duration of 27 weeks. Within a year after attaining inactive disease, the probability of flare was 42.5% (95% CI 39% to 46%) for any flare and 26.6% (24% to 30%) for a significant flare. Within a year after stopping treatment, it was 31.7% (28% to 36%) and 25.0% (21% to 29%), respectively. A maximum PGA \u3e30 mm, maximum active joint count \u3e4, rheumatoid factor (RF)-positive polyarthritis, antinuclear antibodies (ANA) and receiving disease-modifying antirheumatic drugs (DMARDs) or biological agents before attaining inactive disease were associated with increased risk of flare. Systemic JIA was associated with the lowest risk of flare. Conclusions In this real-practice JIA cohort, flares were frequent, usually involved a few swollen joints for an average of 6 months and 60% led to treatment intensification. Children with a severe disease course had an increased risk of flare