575 research outputs found
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)
Space-weighted seismic attenuation mapping of the aseismic source of Campi Flegrei 1983-84 unrest
Peer reviewedPublisher PD
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
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
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Fisheries Buyouts: An Appropriate Solution to Conservation?
Various buyout or retirement schemes are used, primarily to reduce fishing effort and capacity. Buyouts are used to provide economic aid in cases of natural disaster and to reduce the numbers of vessels, licenses, and gear in a fishery, i.e., capacity reduction. This paper is part of a larger internship report conducted at the National Audubon Society's Living Oceans Program, Islip, New York. The report was the final requirement for an M.A. in Marine Affairs and Policy at the University of Miami, Florida. In this paper I briefly outline two case studies, The Texas shrimp license buyout and the Florida net ban. I also illustrate the complexities when discussing multiple buyout programs such as New England and Canada Atlantic groundfish. The impetus of this research project was to examine the case study of Atlantic swordfish and its pelagic longline fishery including the pros and cons of the management tech-niques of conservation and buyouts. In conclusion, I discuss the salient points of buyouts and provide recommendations for future buyouts
High Temperature Condensate Clouds in Super-Hot Jupiter Atmospheres
Deciphering the role of clouds is central to our understanding of exoplanet atmo- spheres, 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
A comparative study of WASP-67b and HAT-P-38b from WFC3 data
Atmospheric temperature and planetary gravity are thought to be the main
parameters affecting cloud formation in giant exoplanet atmospheres. Recent
attempts to understand cloud formation have explored wide regions of the
equilibrium temperature-gravity parameter space. In this study, we instead
compare the case of two giant planets with nearly identical equilibrium
temperature ( ) and gravity (. During Cycle 23, we collected WFC3/G141
observations of the two planets, WASP-67 b and HAT-P-38 b. HAT-P-38 b, with
mass 0.42 M and radius 1.4 , exhibits a relatively
clear atmosphere with a clear detection of water. We refine the orbital period
of this planet with new observations, obtaining . WASP-67 b, with mass 0.27 M and radius 0.83
, shows a more muted water absorption feature than that of
HAT-P-38 b, indicating either a higher cloud deck in the atmosphere or a more
metal-rich composition. The difference in the spectra supports the hypothesis
that giant exoplanet atmospheres carry traces of their formation history.
Future observations in the visible and mid-infrared are needed to probe the
aerosol properties and constrain the evolutionary scenario of these planets.Comment: 16 pages, 17 figures, 8 tables, accepted for publication in The
Astronomical Journa
Assessing the reliability of dose coefficients for exposure to radioiodine by members of the public, accounting for dosimetric and risk model uncertainties
Assessments of risk to a specific population group resulting from internal exposure to a particular radionuclide can be used to assess the reliability of the appropriate International Commission on Radiological Protection (ICRP) dose coefficients used as a radiation protection device for the specified exposure pathway. An estimate of the uncertainty on the associated risk is important for informing judgments on reliability; a derived uncertainty factor, UF, is an estimate of the 95% probable geometric difference between the best risk estimate and the nominal risk and is a useful tool for making this assessment. This paper describes the application of parameter uncertainty analysis to quantify uncertainties resulting from internal exposures to radioiodine by members of the public, specifically 1, 10 and 20-year old females from the population of England and Wales. Best estimates of thyroid cancer incidence risk (lifetime attributable risk) are calculated for ingestion or inhalation of 129I and 131I, accounting for uncertainties in biokinetic model and cancer risk model parameter values. These estimates are compared with the equivalent ICRP derived nominal age-, sex- and population-averaged estimates of excess thyroid cancer incidence to obtain UFs. Derived UF values for ingestion or inhalation of 131I for 1 year, 10-year and 20-year olds are around 28, 12 and 6, respectively, when compared with ICRP Publication 103 nominal values, and 9, 7 and 14, respectively, when compared with ICRP Publication 60 values. Broadly similar results were obtained for 129I. The uncertainties on risk estimates are largely determined by uncertainties on risk model parameters rather than uncertainties on biokinetic model parameters. An examination of the sensitivity of the results to the risk models and populations used in the calculations show variations in the central estimates of risk of a factor of around 2–3. It is assumed that the direct proportionality of excess thyroid cancer risk and dose observed at low to moderate acute doses and incorporated in the risk models also applies to very small doses received at very low dose rates; the uncertainty in this assumption is considerable, but largely unquantifiable. The UF values illustrate the need for an informed approach to the use of ICRP dose and risk coefficients
HST hot-Jupiter transmission spectral survey: Haze in the atmosphere of WASP-6b
We report Hubble Space Telescope (HST) optical to near-infrared transmission
spectroscopy of the hot Jupiter WASP-6b, measured with the Space Telescope
Imaging Spectrograph (STIS) and Spitzer's InfraRed Array Camera (IRAC). The
resulting spectrum covers the range m. We find evidence for
modest stellar activity of WASP-6b and take it into account in the transmission
spectrum. The overall main characteristic of the spectrum is an increasing
radius as a function of decreasing wavelength corresponding to a change of
from 0.33 to m. The spectrum suggests
an effective extinction cross-section with a power law of index consistent with
Rayleigh scattering, with temperatures of K at the planetary
terminator. We compare the transmission spectrum with hot-Jupiter atmospheric
models including condensate-free and aerosol-dominated models incorporating Mie
theory. While none of the clear-atmosphere models is found to be in good
agreement with the data, we find that the complete spectrum can be described by
models that include significant opacity from aerosols including Fe-poor
MgSiO, MgSiO, KCl and NaS dust condensates. WASP-6b is the
second planet after HD189733b which has equilibrium temperatures near
K and shows prominent atmospheric scattering in the optical.Comment: 18 pages, 15 figures, 7 table
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