An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet.

Broad absorption signatures from alkali metals, such as the sodium (Na I) and potassium (K I) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets1-3. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles4-6. Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances7-9. Here we report an optical transmission spectrum for the 'hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logεNa = [Formula: see text], and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Zp/Zʘ = [Formula: see text]). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets10-12.

An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b.

The 'hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only approximately 0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94 days and a mass of ten Jupiter masses (10 M(Jup)), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 10(6), as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.

Positive predictive value of cardiac fluoroscopy in asymptomatic U.S. Army aviators.

The primary aim of this study was to determine the positive predictive value (PPV) of cardiac fluoroscopy in U.S. Army aviators. Cardiac fluoroscopy is one of the non-invasive tests used to screen for coronary artery disease (CAD) in the U.S. Army Cardiovascular Screening Program. The secondary objective is to determine the positive predictive value (PPV) of the combination of the aeromedical graded exercise test (GXT) and cardiac fluoroscopy. The results of these two screening tests are used to determine the need for coronary angiography. Records of 220 male aviators (mean age--42.3) who underwent coronary angiography from 1990-95 were obtained from the Aviation Epidemiology Data Register (AEDR) at Ft. Rucker, AL. These records contained results from the screening tests (GXT, cardiac fluoroscopy, and thallium scintigraphy) and coronary angiography. Significant CAD (SCAD) was present in 47 (21%), while 83 (38%) had minimal CAD (MCAD). The PPV of cardiac fluoroscopy was 81% for all CAD (34% for SCAD). GXT and thallium scintigraphy had a PPV of 62 and 67% for all CAD (23 and 45% for SCAD), respectively. The PPV's of the screening tests were not statistically different at the 95% confidence interval level. The combination of GXT and cardiac fluoroscopy had a PPV of 64% (21% for SCAD).

Cancer mortality in a human isolate.

Cancer mortality (1965--77) among 12,652 members of an inbred human religious isolate, the Hutterites, was compared with expectations based on mortality rates for the U.S. white population in 1970. Overall, Hutterites had significantly fewer deaths from cancer than expected (P < 0.01), due primarily to fewer lung cancers among males. Smoking is prohibited for this religious group. The most frequent types of cancers were leukemia and cancers of the digestive system, the prostate gland, and the female breast. Preliminary results suggest an association between recessive alleles and childhood leukemia. More stomach and rectal cancers were observed than expected, but differences were generally not significant. Familial aggregates of cancers of the stomach and breast are being investigated. The low frequency of cervical cancer is consistent with current evidence for an association of cervical cancer with early age at first intercourse and promiscuity, neither of which is characteristic of this population.