Leukaemia and non-Hodgkin's lymphoma in young persons resident in small areas of West Cumbria in relation to paternal preconceptional irradiation.

The results of a previous study suggested that an association between childhood leukaemia and the radiation dose received occupationally by a father before the conception of his child might provide the explanation for the marked excess of childhood leukaemia and non-Hodgkin's lymphoma in the village of Seascale, West Cumbria. The present study identifies other small areas (electoral wards) in West Cumbria where excess cases of leukaemia and non-Hodgkin's lymphoma in young people have occurred and determines whether a recorded dose of radiation was received occupationally by the father before the conception of each of the affected individuals. Forty-one cases of leukaemia and non-Hodgkin's lymphoma were diagnosed during 1968-85 in young people under 25 years of age resident in the 49 electoral wards lying within the boundary of West Cumbria and the adjacent ward of Broughton. Raised incidence rate ratios (two-sided P<0.01) were found for acute lymphoblastic leukaemia among those aged 0-14 years (concentrated among those aged 0-4 years) in Seascale ward and among those aged 0-24 years (also concentrated among those aged 0-4 years) in Egremont North ward, for acute myeloid leukaemia among those aged 0-14 years in Sandwith ward, for all leukaemias among those aged 0-14 years in Broughton ward (South Lakeland) and for non-Hodgkin's lymphoma among those aged 0-14 years in Seascale ward. For West Cumbria as a whole, incidence rates were not usual. Apart from Seascale, for none of these electoral wards has a father of an affected child been linked definitely to an occupational dose of radiation recorded before the conception of the child. Particularly striking are the excesses of acute lymphoblastic leukaemia cases among young children living in the wards of Seascale and Egremont North, situated 11 km apart. The cases in Egremont North are not associated with recorded doses of radiation received occupationally by fathers before the conception of the affected children, even though the total numbers of children associated with such doses born in Seascale and Egremont North wards are similar. This finding is further evidence against a causal role for paternal preconceptional radiation exposure in the cases of childhood leukaemia in Seascale

Cross-comparison of MRCGP & MRCP(UK) in a database linkage study of 2,284 candidates taking both examinations: assessment of validity and differential performance by ethnicity.

MRCGP and MRCP(UK) are the main entry qualifications for UK doctors entering general [family] practice or hospital [internal] medicine. The performance of MRCP(UK) candidates who subsequently take MRCGP allows validation of each assessment. In the UK, underperformance of ethnic minority doctors taking MRCGP has had a high political profile, with a Judicial Review in the High Court in April 2014 for alleged racial discrimination. Although the legal challenge was dismissed, substantial performance differences between white and BME (Black and Minority Ethnic) doctors undoubtedly exist. Understanding ethnic differences can be helped by comparing the performance of doctors who take both MRCGP and MRCP(UK)

Marginalising instrument systematics in HST WFC3 transit lightcurves

Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7$\mu$m probe primarily the H$_2$O absorption band at 1.4$\mu$m, and has provided low resolution transmission spectra for a wide range of exoplanets. We present the application of marginalisation based on Gibson (2014) to analyse exoplanet transit lightcurves obtained from HST WFC3, to better determine important transit parameters such as R$_p$/R$_*$, important for accurate detections of H$_2$O. We approximate the evidence, often referred to as the marginal likelihood, for a grid of systematic models using the Akaike Information Criterion (AIC). We then calculate the evidence-based weight assigned to each systematic model and use the information from all tested models to calculate the final marginalised transit parameters for both the band-integrated, and spectroscopic lightcurves to construct the transmission spectrum. We find that a majority of the highest weight models contain a correction for a linear trend in time, as well as corrections related to HST orbital phase. We additionally test the dependence on the shift in spectral wavelength position over the course of the observations and find that spectroscopic wavelength shifts $\delta_\lambda(\lambda)$, best describe the associated systematic in the spectroscopic lightcurves for most targets, while fast scan rate observations of bright targets require an additional level of processing to produce a robust transmission spectrum. The use of marginalisation allows for transparent interpretation and understanding of the instrument and the impact of each systematic evaluated statistically for each dataset, expanding the ability to make true and comprehensive comparisons between exoplanet atmospheres.Comment: 19 pages, 13 figures, 8 tables, Accepted to Ap

Limits on Clouds and Hazes for the TRAPPIST-1 Planets

The TRAPPIST-1 planetary system is an excellent candidate for study of the evolution and habitability of M-dwarf planets. Transmission spectroscopy observations performed with the Hubble Space Telescope (HST) suggest the innermost five planets do not possess clear hydrogen atmospheres. Here we reassess these conclusions with recently updated mass constraints and expand the analysis to include limits on metallicity, cloud top pressure, and the strength of haze scattering. We connect recent laboratory results of particle size and production rate for exoplanet hazes to a one-dimensional atmospheric model for TRAPPIST-1 transmission spectra. Doing so, we obtain a physically-based estimate of haze scattering cross sections. We find haze scattering cross sections on the order of 1e-26 to 1e-19 cm squared are needed in hydrogen-rich atmospheres for TRAPPIST-1 d, e, and f to match the HST data. For TRAPPIST-1 g, we cannot rule out a clear hydrogen-rich atmosphere. We also modeled the effects an opaque cloud deck and substantial heavy element content have on the transmission spectra. We determine that hydrogen-rich atmospheres with high altitude clouds, at pressures of 12mbar and lower, are consistent with the HST observations for TRAPPIST-1 d and e. For TRAPPIST-1 f and g, we cannot rule out clear hydrogen-rich cases to high confidence. We demonstrate that metallicities of at least 60xsolar with tropospheric (0.1 bar) clouds agree with observations. Additionally, we provide estimates of the precision necessary for future observations to disentangle degeneracies in cloud top pressure and metallicity. Our results suggest secondary, volatile-rich atmospheres for the outer TRAPPIST-1 planets d, e, and f.Comment: 15 pages, 3 figures, 2 tables, accepted in the Astronomical Journa

The Importance of Optical Wavelength Data on Atmospheric Retrievals of Exoplanet Transmission Spectra

Exoplanet transmission spectra provide rich information about the chemical composition, clouds and temperature structure of exoplanet atmospheres. Most exoplanet transmission spectra only span infrared wavelengths ($\gtrsim$ 1 $\rm{\mu m}$), which can preclude crucial atmospheric information from shorter wavelengths. Here, we explore how retrieved atmospheric parameters from exoplanet transmission spectra change with the addition of optical data. From a sample of 14 giant planets with transit spectra from 0.3-4.5 $\rm{\mu m}$, primarily from the Hubble and Spitzer space telescopes, we apply a free chemistry retrieval to planetary spectra for wavelength ranges of 0.3-4.5 $\rm{\mu m}$, 0.6-4.5 $\rm{\mu m}$, and 1.1-4.5 $\rm{\mu m}$. We analyse the posterior distributions of these retrievals and perform an information content analysis, finding wavelengths below 0.6 $\rm{\mu m}$ are necessary to constrain cloud scattering slope parameters ($\log{a}$ and $\gamma$) and alkali species Na and K. There is limited improvement in the constraints on the remaining atmospheric parameters. Across the population, we find limb temperatures are retrieved colder than planetary equilibrium temperatures but have an overall good agreement with Global Circulation Models. As JWST extends to a minimum wavelength of 0.6 $\rm{\mu m}$, we demonstrate that exploration into complementing JWST observations with optical HST data is important to further our understanding of aerosol properties and alkali abundances in exoplanet atmospheres.Comment: 26 pages, 12 figures. Accepted for publication in the Astronomical Journa

Aerosols are not Spherical Cows: Using Discrete Dipole Approximation to Model the Properties of Fractal Particles

The optical properties of particulate-matter aerosols, within the context of exoplanet and brown dwarf atmospheres, are compared using three different models: Mie theory, Modified Mean Field (MMF) Theory, and Discrete Dipole Approximation (DDA). Previous results have demonstrated that fractal haze particles (MMF and DDA) absorb much less long-wavelength radiation than their spherical counterparts (Mie), however it is shown here that the opposite can also be true if a more varying refractive index profile is used. Additionally, it is demonstrated that absorption and scattering cross-sections, as well as the asymmetry parameter, are underestimated if Mie theory is used. Although DDA can be used to obtain more accurate results, it is known to be much more computationally intensive; to avoid this, the use of low-resolution aerosol models is explored, which could dramatically speed up the process of obtaining accurate computations of optical cross-sections within a certain parameter space. The validity of DDA is probed for wavelengths of interest for observations of aerosols within exoplanet and brown dwarf atmospheres (0.2 to 15 micrometres). Finally, novel code is presented to compare the results of Mie, MMF and DDA theories (CORAL: Comparison Of Radiative AnaLyses), as well as to increase and decrease the resolution of DDA shape files accordingly (SPHERIFY). Both codes can be applied to a range of other interesting astrophysical environments in addition to exoplanet atmospheres, for example dust grains within protoplanetary disks.Comment: 24 pages, 23 figures, accepted for publication in "Monthly Notices of the Royal Astronomical Society

High temperature condensate clouds in super-hot Jupiter atmospheres

Deciphering the role of clouds is central to our understanding of exoplanet atmospheres, as they have a direct impact on the temperature and pressure structure, and observational properties of the planet. Super-hot Jupiters occupy a temperature regime similar to low mass M-dwarfs, where minimal cloud condensation is expected. However, observations of exoplanets such as WASP-12b (Teq ~ 2500 K) result in a transmission spectrum indicative of a cloudy atmosphere. We re-examine the temperature and pressure space occupied by these super-hot Jupiter atmospheres, to explore the role of the initial Al- and Ti-bearing condensates as the main source of cloud material. Due to the high temperatures a majority of the more common refractory material is not depleted into deeper layers and would remain in the vapor phase. The lack of depletion into deeper layers means that these materials with relatively low cloud masses can become significant absorbers in the upper atmosphere. We provide condensation curves for the initial Al- and Ti-bearing condensates that may be used to provide quantitative estimates of the effect of metallicity on cloud masses, as planets with metal-rich hosts potentially form more opaque clouds because more mass is available for condensation. Increased metallicity also pushes the point of condensation to hotter, deeper layers in the planetary atmosphere further increasing the density of the cloud. We suggest that planets around metal-rich hosts are more likely to have thick refractory clouds, and discuss the implication on the observed spectra of WASP-12b.Comment: Accepted for publication in MNRAS, 10 pages, 1 table, 5 figure

PLAB and UK graduates' performance on MRCP(UK) and MRCGP examinations: data linkage study

OBJECTIVES: To assess whether international medical graduates passing the two examinations set by the Professional and Linguistic Assessments Board (PLAB1 and PLAB2) of the General Medical Council (GMC) are equivalent to UK graduates at the end of the first foundation year of medical training (F1), as the GMC requires, and if not, to assess what changes in the PLAB pass marks might produce equivalence. DESIGN: Data linkage of GMC PLAB performance data with data from the Royal Colleges of Physicians and the Royal College of General Practitioners on performance of PLAB graduates and UK graduates at the MRCP(UK) and MRCGP examinations. SETTING: Doctors in training for internal medicine or general practice in the United Kingdom. PARTICIPANTS: 7829, 5135, and 4387 PLAB graduates on their first attempt at MRCP(UK) Part 1, Part 2, and PACES assessments from 2001 to 2012 compared with 18,532, 14,094, and 14,376 UK graduates taking the same assessments; 3160 PLAB1 graduates making their first attempt at the MRCGP AKT during 2007-12 compared with 14,235 UK graduates; and 1411 PLAB2 graduates making their first attempt at the MRCGP CSA during 2010-12 compared with 6935 UK graduates. MAIN OUTCOME MEASURES: Performance at MRCP(UK) Part 1, Part 2, and PACES assessments, and MRCGP AKT and CSA assessments in relation to performance on PLAB1 and PLAB2 assessments, as well as to International English Language Testing System (IELTS) scores. MRCP(UK), MRCGP, and PLAB results were analysed as marks relative to the pass mark at the first attempt. RESULTS: PLAB1 marks were a valid predictor of MRCP(UK) Part 1, MRCP(UK) Part 2, and MRCGP AKT (r=0.521, 0.390, and 0.490; all P<0.001). PLAB2 marks correlated with MRCP(UK) PACES and MRCGP CSA (r=0.274, 0.321; both P<0.001). PLAB graduates had significantly lower MRCP(UK) and MRCGP assessments (Glass's Δ=0.94, 0.91, 1.40, 1.01, and 1.82 for MRCP(UK) Part 1, Part 2, and PACES and MRCGP AKT and CSA), and were more likely to fail assessments and to progress more slowly than UK medical graduates. IELTS scores correlated significantly with later performance, multiple regression showing that the effect of PLAB1 (β=0.496) was much stronger than the effect of IELTS (β=0.086). Changes to PLAB pass marks that would result in international medical graduate and UK medical graduate equivalence were assessed in two ways. Method 1 adjusted PLAB pass marks to equate median performance of PLAB and UK graduates. Method 2 divided PLAB graduates into 12 equally spaced groups according to PLAB performance, and compared these with mean performance of graduates from individual UK medical schools, assessing which PLAB groups were equivalent in MRCP(UK) and MRCGP performance to UK graduates. The two methods produced similar results. To produce equivalent performance on the MRCP and MRGP examinations, the pass mark for PLAB1 would require raising by about 27 marks (13%) and for PLAB2 by about 15-16 marks (20%) above the present standard. CONCLUSIONS: PLAB is a valid assessment of medical knowledge and clinical skills, correlating well with performance at MRCP(UK) and MRCGP. PLAB graduates' knowledge and skills at MRCP(UK) and MRCGP are over one standard deviation below those of UK graduates, although differences in training quality cannot be taken into account. Equivalent performance in MRCGP(UK) and MRCGP would occur if the pass marks of PLAB1 and PLAB2 were raised considerably, but that would also reduce the pass rate, with implications for medical workforce planning. Increasing IELTS requirements would have less impact on equivalence than raising PLAB pass marks