65 research outputs found
Opening a new window to other worlds with spectropolarimetry
A high level of diversity has already been observed among the planets of our
own Solar System. As such, one expects extrasolar planets to present a wide
range of distinctive features, therefore the characterisation of Earth- and
super Earth-like planets is becoming of key importance in scientific research.
The SEARCH (Spectropolarimetric Exoplanet AtmospheRe CHaracerisation) mission
proposal of this paper represents one possible approach to realising these
objectives. The mission goals of SEARCH include the detailed characterisation
of a wide variety of exoplanets, ranging from terrestrial planets to gas
giants. More specifically, SEARCH will determine atmospheric properties such as
cloud coverage, surface pressure and atmospheric composition, and may also be
capable of identifying basic surface features. To resolve a planet with a semi
major axis of down to 1.4AU and 30pc distant SEARCH will have a mirror system
consisting of two segments, with elliptical rim, cut out of a parabolic mirror.
This will yield an effective diameter of 9 meters along one axis. A phase mask
coronagraph along with an integral spectrograph will be used to overcome the
contrast ratio of star to planet light. Such a mission would provide invaluable
data on the diversity present in extrasolar planetary systems and much more
could be learned from the similarities and differences compared to our own
Solar System. This would allow our theories of planetary formation, atmospheric
accretion and evolution to be tested, and our understanding of regions such as
the outer limit of the Habitable Zone to be further improved.Comment: 23 pages, accepted for publication in Experimental Astronom
A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
Exoplanets orbiting close to their parent stars could lose some fraction of
their atmospheres because of the extreme irradiation. Atmospheric mass loss
primarily affects low-mass exoplanets, leading to suggest that hot rocky
planets might have begun as Neptune-like, but subsequently lost all of their
atmospheres; however, no confident measurements have hitherto been available.
The signature of this loss could be observed in the ultraviolet spectrum, when
the planet and its escaping atmosphere transit the star, giving rise to deeper
and longer transit signatures than in the optical spectrum. Here we report that
in the ultraviolet the Neptune-mass exoplanet GJ 436b (also known as Gliese
436b) has transit depths of 56.3 +/- 3.5% (1 sigma), far beyond the 0.69%
optical transit depth. The ultraviolet transits repeatedly start ~2 h before,
and end >3 h after the ~1 h optical transit, which is substantially different
from one previous claim (based on an inaccurate ephemeris). We infer from this
that the planet is surrounded and trailed by a large exospheric cloud composed
mainly of hydrogen atoms. We estimate a mass-loss rate in the range of
~10^8-10^9 g/s, which today is far too small to deplete the atmosphere of a
Neptune-like planet in the lifetime of the parent star, but would have been
much greater in the past.Comment: Published in Nature on 25 June 2015. Preprint is 28 pages, 12
figures, 2 table
High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)
(abridged) A complete census of planetary systems around a volume-limited
sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform
sensitivity down to Earth-mass planets within their Habitable Zones out to
several AUs would be a major milestone in extrasolar planets astrophysics. This
fundamental goal can be achieved with a mission concept such as NEAT - the
Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne
extremely-high-precision astrometric measurements sufficient to detect
dynamical effects due to orbiting planets of mass even lower than Earth's
around the nearest stars. Such a survey mission would provide the actual
planetary masses and the full orbital geometry for all the components of the
detected planetary systems down to the Earth-mass limit. The NEAT performance
limits can be achieved by carrying out differential astrometry between the
targets and a set of suitable reference stars in the field. The NEAT instrument
design consists of an off-axis parabola single-mirror telescope, a detector
with a large field of view made of small movable CCDs located around a fixed
central CCD, and an interferometric calibration system originating from
metrology fibers located at the primary mirror. The proposed mission
architecture relies on the use of two satellites operating at L2 for 5 years,
flying in formation and offering a capability of more than 20,000
reconfigurations (alternative option uses deployable boom). The NEAT primary
science program will encompass an astrometric survey of our 200 closest F-, G-
and K-type stellar neighbors, with an average of 50 visits. The remaining time
might be allocated to improve the characterization of the architecture of
selected planetary systems around nearby targets of specific interest (low-mass
stars, young stars, etc.) discovered by Gaia, ground-based high-precision
radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member
list of the NEAT proposal and the news about the project are available at
http://neat.obs.ujf-grenoble.fr. The final publication is available at
http://www.springerlink.co
Antimicrobial Use and Antimicrobial Resistance IndicatorsâIntegration of Farm-Level Surveillance Data From Broiler Chickens and Turkeys in British Columbia, Canada
Using data from the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS), we aimed to describe trends in antimicrobial use (AMU) in broiler chickens and turkeys, to compare AMU across species, to compare with trends in antimicrobial resistance (AMR), and to assess the effects of various AMU/AMR units of measurement (metrics and indicators) on data integration. Data on AMU and AMR in enteric bacteria, collected from 2013 to 2017 from broiler chickens (n = 143 flocks) and turkeys (n = 145) were used. In broiler chickens, the total AMU in milligrams/population correction unit (mg/PCUBr) decreased by 6%, the number (n) of defined daily doses for animals using Canadian standards (nDDDvetCA) per 1,000 broiler chicken-days decreased by 12%, and nDDDvetCA/PCU decreased by 6%. In turkeys, the mg/PCUTk decreased by 1%, whereas the nDDDvetCA/1,000 turkey-days and the nDDDvetCA/PCU increased by 1 and 5%, respectively. The types of antimicrobial classes used in both species were similar. Using the frequency of flocks reporting use (i.e., number of flocks reporting use/number of flocks participating) as a measurement, the use of certain antimicrobials changed over time (e.g., Broilers, decreased cephalosporin use, virginiamycin use, emerging use of lincomycin-spectinomycin, and avilamycin; Turkeys: increased trimethoprim-sulfonamides and macrolide use). The trends in resistance to specific antimicrobials paralleled the frequency and quantity of use (e.g., ceftriaxone use decreasedâceftriaxone resistance decreased, and gentamicin use increasedâgentamicin resistance increased) in some situations, but not others (decreased fluoroquinolone useâincreased ciprofloxacin resistance). AMR data were summarized using the AMR indicator index (AMR Ix). The most notable AMR Ix trend was the decrease in ceftriaxone AMR Ix among Escherichia coli (0.19 to 0.07); indicative of the success of the poultry industry action to eliminate the preventive use of third generation cephalosporins. Other trends observed were the increase in ciprofloxacin AMR Ix among Campylobacter from 0.23 to 0.41 and gentamicin AMR Ix among E. coli from 0.11 to 0.22, suggestive of the persistence/emergence of resistance related to previous and current AMU not captured in our surveillance timeframe. These data highlight the necessity of multiple AMU and AMR indicators for monitoring the impact of stewardship activities and interventions
A chemical survey of exoplanets with ARIEL
Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planetâs birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25â7.8 ÎŒm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10â100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed â using conservative estimates of mission performance and a full model of all significant noise sources in the measurement â using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL â in line with the stated mission objectives â will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio
Independent and combined influence of healthy lifestyle factors on academic performance in adolescents: DADOS Study
BACKGROUND. Few studies have analyzed the combined effect of lifestyle factors
on academic performance (AP) in adolescents. The aim of this study was to analyze the
independent and combined effects of weight status, screen time, sleep quality, daily
meal frequency, cardiorespiratory fitness and physical activity (PA) on AP in
adolescents.
METHODS. A total of 262 adolescents (13.9±0.3 years) from the DADOS study were
included in the analysis. Weight status was assessed through body mass index (kg/m 2 ).
Participants completed questionnaires to evaluate screen time, sleep quality and daily
meal frequency. Cardiorespiratory fitness was assessed by the 20-m shuttle run test. PA
was evaluated by a wrist-worn GENEActiv accelerometer. AP was assessed through the
final academic grades and a validated questionnaire.
RESULTS. Non-overweight status, low screen time, good sleep quality and proper
meal frequency showed independent, positive influence on AP. Moreover, adolescents
achieving at least 3 healthy lifestyles were more likely to be in the high-performance
group for academic grades than those achieving †1 (math OR: 3.02-9.51, language OR:
3.51-6.76 and grade point average OR: 4.22-9.36).
CONCLUSIONS. Although individual healthy lifestyles are independently and
positively associated with AP, the cumulative effect of multiple healthy lifestyles have a
stronger impact
A super-Earth transiting a nearby low-mass star
A decade ago, the detection of the first transiting extrasolar planet
provided a direct constraint on its composition and opened the door to
spectroscopic investigations of extrasolar planetary atmospheres. As such
characterization studies are feasible only for transiting systems that are both
nearby and for which the planet-to-star radius ratio is relatively large,
nearby small stars have been surveyed intensively. Doppler studies and
microlensing have uncovered a population of planets with minimum masses of
1.9-10 times the Earth's mass (M_Earth), called super-Earths. The first
constraint on the bulk composition of this novel class of planets was afforded
by CoRoT-7b, but the distance and size of its star preclude atmospheric studies
in the foreseeable future. Here we report observations of the transiting planet
GJ 1214b, which has a mass of 6.55 M_Earth and a radius 2.68 times Earth's
radius (R_Earth), indicating that it is intermediate in stature between Earth
and the ice giants of the Solar System. We find that the planetary mass and
radius are consistent with a composition of primarily water enshrouded by a
hydrogen-helium envelope that is only 0.05% of the mass of the planet. The
atmosphere is probably escaping hydrodynamically, indicating that it has
undergone significant evolution during its history. As the star is small and
only 13 parsecs away, the planetary atmosphere is amenable to study with
current observatories.Comment: 13 pages, 3 figures, published in Natur
Isokinetic knee muscle strength of soccer players according to their position
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