Radionuclides of caesium are environmentally important since they are formed as significant high yield fission products ( 135 Cs and 137 Cs) and activation products ( 134 Cs and 136 Cs) during nuclear fission. They originate from a range of nuclear activities such as weapons testing, nuclear reprocessing and nuclear fuel cycle discharges and nuclear accidents. Whilst 137 Cs, 134 Cs and 136 Cs are routinely measurable at high sensitivity by gamma spectrometry, routine detection of long-lived 135 Cs by radiometric methods is challenging. This measurement is, however, important given its significance in long-term nuclear waste storage and disposal. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPTseparation using an ICP-MS equipped with a reaction cell. The removal of the peak tailing interference is dependent on the instrument used for final measurement. This review summarizes and compares the analytical procedures developed for determination of 135 Cs/ 137 Cs, with particular focus on ICP-MS detection and the methods applied to interference separation. Sources and properties of caesium isotopesHigh yield fission products 135 Cs and 137 Cs (Table 1) are present in environmental samples as a result of releases from nuclear power plants and reprocessing sites, nuclear accidents, and fallout from atmospheric weapons testing [1]. Caesium-137 is established as an important radionuclide in radiation protection, environmental monitoring, sediment dating, land erosion and waste disposal [2]. By comparison, 135 Cs is a long-lived radioisotope with a comparatively low radiation risk; however it is a significant contributor to the long term radiological risk associated with deep geological disposal [3]. Furthermore, the 135Cs/ 137 Cs ratio varies with reactor, weapon and fuel type, and therefore can be used as a forensic tool to identify the source of radioactive contamination [1,[4][5][6]. Other isotopes of caesium include the activation products ( 134 Cs and 136 Cs, Table 1). These shorter-lived activation products (2.06 years and 13.2 days, respectively) provide information on fuel irradiation history and have importance in health physics terms but are not considered further here.( Table 1) Caesium-137 decays by beta emission to short-lived metastable isomer Cs is therefore achievable using beta counting or gamma spectrometry. Gamma spectrometry is generally favoured because it exploits the high gamma intensity of the 662 keV energy that is not susceptible to significant absorption. The ability to directly count most samples without the need for any chemical separation is also beneficial, and a high-purity germanium (HPGe)well detector can readily achieve a detection limit of ~2.5 mBq g -1 (for a 20 g sample counted for half a day), which is suitable for many environmental samples [3]. By comparison, 137 Cs measurement by beta counting in environmental samples requires chemical separation from other beta-emitting nuclides prior to measurement.Caesium-135 decays with a maximum beta particle energy of 2...

Background Objectively structured clinical examinations (OSCEs) are a stressful experience for many health care students and professionals in training. Mock OSCEs have been shown to be beneficial for student OSCE preparation. However, due to their expense and administrative burden students may only get a few opportunities to partake in these. To address this gap in student preparation a series of regularly run totally peer led multi-role practice OSCEs (PrOSCEs) was developed. Methods Fifteen PrOSCEs were run over five-months. A total of 32 second year medical students took part, all of whom were enrolled on the graduate-entry programme at the University of Southampton. In each PrOSCE, 18 participants rotated through the roles of ‘student’, ‘examiner’ and ‘patient’ in six simulated stations designed by their peers. Peer feedback was provided after each station. At the end of the series of PrOSCEs students were asked to fill in an anonymous online feedback survey to assess the usefulness of the PrOSCEs in exam preparation. Results Twenty-two students responded to the survey. 100% of respondents deemed routine participation either ‘very useful’ or ‘useful’ in preparing for their exam. PrOSCEs were found to improve confidence (mean = 7.9/10, 95% CI 7.4–8.3), expected performance (mean = 7.5/10, 95% CI 6.8–8.2) and help guide revision (mean = 8.3/10, 95% CI 7.6–9.0). Self-perceived teaching performance and confidence in providing feedback was also positively associated with participation. The most beneficial roles were ‘student’ and ‘station creator’. Free-text feedback suggests that the informal setting and regular practice were particularly beneficial. Conclusion The peer-led nature of the PrOSCEs allows for a low cost, low administrative burden and easy to replicate adjunct or alternative to large scale mock OSCEs. In addition the multi-role aspect of this approach could enhance exam preparation and may also improve aptitude as a clinical teacher. Further studies are required to understand if repeated practice has beneficial implications on OSCE performance.

Arctic primary production is sensitive to reductions in sea ice cover, and will likely increase into the future. Whether this increased primary production (PP) will translate into increased export of particulate organic carbon (POC) is currently unclear. Here we report on the POC export efficiency during summer 2012 in the Atlantic sector of the Arctic Ocean. We coupled 234‐thorium based estimates of the export flux of POC to onboard incubation‐based estimates of PP. Export efficiency (defined as the fraction of PP that is exported below 100 m depth: ThE‐ratio) showed large variability (0.09 ± 0.19–1.3 ± 0.3). The highest ThE‐ratio (1.3 ± 0.3) was recorded in a mono‐specific bloom of Phaeocystis pouchetii located in the ice edge. Blooming diatom dominated areas also had high ThE‐ratios (0.1 ± 0.1–0.5 ± 0.2), while mixed and/or prebloom communities showed lower ThE‐ratios (0.10 ± 0.03–0.19 ± 0.05). Furthermore, using oxygen saturation, bacterial abundance, bacterial production, and zooplankton oxygen demand, we also investigated spatial variability in the degree to which this sinking material may be remineralized in the upper mesopelagic (<300 m). Our results suggest that blooming diatoms and P. pouchetii can export a significant fraction of their biomass below the surface layer (100 m) in the open Arctic Ocean. Also, we show evidence that the material sinking from a P. pouchetii bloom may be remineralized (>100 m) at a similar rate as the material sinking from diatom blooms in the upper mesopelagic, contrary to previous findings.