452 research outputs found
Passive turbulent flamelet propagation
We analyze results of a premixed constant density flame propagating in three-dimensional turbulence, where a flame model developed by Kerstein, et al. (1988) has been used. Simulations with constant and evolving velocity fields are used, where peculiar results were obtained from the constant velocity field runs. Data from the evolving flow runs with various flame speeds are used to determine two-point correlations of the fluctuating scalar field and implications for flamelet modeling are discussed
General Aviation Trends in the European Market Memorandum Report
In 1969, as western Europe was becoming a common market, significant economic growth was projected. His Highness, The Aga Kahn requested that Economics Research Associates (ERA) perform a memorandum report and forecast the trends for private aviation potentials in Europe over the decade of the 1970s. The resulting report by ERA reviews the history of European aviation, current and future economic trends in the common European market area as these pertain to the growth of private aviation, advantages and disadvantages involved in noncommercial flying, and future trends in private aviation. Data was gathered from such sources as aviation publications, interviews with persons connected with private aviation, and market studies and projections of commercial organizations. The report includes the following sections: 1) introduction, 2) summary and conclusions, 3) the western European economy, 4) general aviation, 5) general aviation and future trends in aviation design, 6) impact of general aviation on tourism. The report includes four tables
KOI-3890: A high mass-ratio asteroseismic red-giantM-dwarf eclipsing binary undergoing heartbeat tidal interactions
KOI-3890 is a highly eccentric, 153-day period eclipsing, single-lined
spectroscopic binary system containing a red-giant star showing solar-like
oscillations alongside tidal interactions. The combination of transit
photometry, radial velocity observations, and asteroseismology have enabled the
detailed characterisation of both the red-giant primary and the M-dwarf
companion, along with the tidal interaction and the geometry of the system. The
stellar parameters of the red-giant primary are determined through the use of
asteroseismology and grid-based modelling to give a mass and radius of
and
respectively. When combined with
transit photometry the M-dwarf companion is found to have a mass and radius of
and
. Moreover, through
asteroseismology we constrain the age of the system through the red-giant
primary to be . This provides a constraint on
the age of the M-dwarf secondary, which is difficult to do for other M-dwarf
binary systems. In addition, the asteroseismic analysis yields an estimate of
the inclination angle of the rotation axis of the red-giant star of
degrees. The obliquity of the system\textemdash the
angle between the stellar rotation axis and the angle normal to the orbital
plane\textemdash is also derived to give degrees
showing that the system is consistent with alignment. We observe no radius
inflation in the M-dwarf companion when compared to current low-mass stellar
models.Comment: 11 pages, 5 figures, accepted for publication in MNRA
Asteroseismology of the Hyades with K2: first detection of main-sequence solar-like oscillations in an open cluster
The Hyades open cluster was targeted during Campaign 4 (C4) of the NASA K2
mission, and short-cadence data were collected on a number of cool
main-sequence stars. Here, we report results on two F-type stars that show
detectable oscillations of a quality that allows asteroseismic analyses to be
performed. These are the first ever detections of solar-like oscillations in
main-sequence stars in an open cluster.Comment: 12 pages, 8 figures, 2 tables; accepted for publication in MNRA
Synchronous deficits in cumulative muscle protein synthesis and ribosomal biogenesis underlie age-related anabolic resistance to exercise in humans
Ageing is associated with impaired hypertrophic responses to resistance exercise training (RET). Here we investigated the aetiology of ‘anabolic resistance’ in older humans. Twenty healthy male individuals, 10 younger (Y; 23 ± 1 years) and 10 older (O; 69 ± 3 years), performed 6 weeks unilateral RET (6 × 8 repetitions, 75% of one repetition maximum (1-RM), 3 times per week). After baseline bilateral vastus lateralis (VL) muscle biopsies, subjects consumed 150 ml D2O (70 atom%; thereafter 50 ml week−1), further bilateral VL muscle biopsies were taken at 3 and 6 weeks to quantify muscle protein synthesis (MPS) via gas chromatography–pyrolysis–isotope ratio mass spectrometry. After RET, 1-RM increased in Y (+35 ± 4%) and O (+25 ± 3%; P < 0.01), while MVC increased in Y (+21 ± 5%; P < 0.01) but not O (+6 ± 3%; not significant (NS)). In comparison to Y, O displayed blunted RET-induced increases in muscle thickness (at 3 and 6 weeks, respectively, Y: +8 ± 1% and +11 ± 2%, P < 0.01; O: +2.6 ± 1% and +3.5 ± 2%, NS). While ‘basal’ longer term MPS was identical between Y and O (∼1.35 ± 0.1% day−1), MPS increased in response to RET only in Y (3 weeks, Y: 1.61 ± 0.1% day−1; O: 1.49 ± 0.1% day−1). Consistent with this, O exhibited inferior ribosomal biogenesis (RNA:DNA ratio and c-MYC induction: Y: +4 ± 2 fold change; O: +1.9 ± 1 fold change), translational efficiency (S6K1 phosphorylation, Y: +10 ± 4 fold change; O: +4 ± 2 fold change) and anabolic hormone milieu (testosterone, Y: 367 ± 19; O: 274 ± 19 ng dl−1 (all P < 0.05). Anabolic resistance is thus multifactorial
Kepler-93b: A Terrestrial World Measured to within 120 km, and a Test Case for a New Spitzer Observing Mode
We present the characterization of the Kepler-93 exoplanetary system, based
on three years of photometry gathered by the Kepler spacecraft. The duration
and cadence of the Kepler observations, in tandem with the brightness of the
star, enable unusually precise constraints on both the planet and its host. We
conduct an asteroseismic analysis of the Kepler photometry and conclude that
the star has an average density of 1.652+/-0.006 g/cm^3. Its mass of
0.911+/-0.033 M_Sun renders it one of the lowest-mass subjects of asteroseismic
study. An analysis of the transit signature produced by the planet Kepler-93b,
which appears with a period of 4.72673978+/-9.7x10^-7 days, returns a
consistent but less precise measurement of the stellar density, 1.72+0.02-0.28
g/cm^3. The agreement of these two values lends credence to the planetary
interpretation of the transit signal. The achromatic transit depth, as compared
between Kepler and the Spitzer Space Telescope, supports the same conclusion.
We observed seven transits of Kepler-93b with Spitzer, three of which we
conducted in a new observing mode. The pointing strategy we employed to gather
this subset of observations halved our uncertainty on the transit radius ratio
R_p/R_star. We find, after folding together the stellar radius measurement of
0.919+/-0.011 R_Sun with the transit depth, a best-fit value for the planetary
radius of 1.481+/-0.019 R_Earth. The uncertainty of 120 km on our measurement
of the planet's size currently renders it one of the most precisely measured
planetary radii outside of the Solar System. Together with the radius, the
planetary mass of 3.8+/-1.5 M_Earth corresponds to a rocky density of 6.3+/-2.6
g/cm^3. After applying a prior on the plausible maximum densities of
similarly-sized worlds between 1--1.5 R_Earth, we find that Kepler-93b
possesses an average density within this group.Comment: 20 pages, 9 figures, accepted for publication in Ap
Kepler-68: Three Planets, One With a Density Between That of Earth and Ice Giants
NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68.
Follow-up Doppler measurements have established the mass of the innermost
planet and revealed a third jovian-mass planet orbiting beyond the two
transiting planets. Kepler-68b, in a 5.4 day orbit has mass 8.3 +/- 2.3 Earth,
radius 2.31 +/- 0.07 Earth radii, and a density of 3.32 +/- 0.92 (cgs), giving
Kepler-68b a density intermediate between that of the ice giants and Earth.
Kepler-68c is Earth-sized with a radius of 0.953 Earth and transits on a 9.6
day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an
orbital period of 580 +/- 15 days and minimum mass of Msin(i) = 0.947 Jupiter.
Power spectra of the Kepler photometry at 1-minute cadence exhibit a rich and
strong set of asteroseismic pulsation modes enabling detailed analysis of the
stellar interior. Spectroscopy of the star coupled with asteroseismic modeling
of the multiple pulsation modes yield precise measurements of stellar
properties, notably Teff = 5793 +/- 74 K, M = 1.079 +/- 0.051 Msun, R = 1.243
+/- 0.019 Rsun, and density 0.7903 +/- 0.0054 (cgs), all measured with
fractional uncertainties of only a few percent. Models of Kepler-68b suggest it
is likely composed of rock and water, or has a H and He envelope to yield its
density of about 3 (cgs).Comment: 32 pages, 13 figures, Accepted to Ap
Kepler-432: a red giant interacting with one of its two long period giant planets
We report the discovery of Kepler-432b, a giant planet ()
transiting an evolved star with an orbital period of days. Radial velocities (RVs) reveal that
Kepler-432b orbits its parent star with an eccentricity of , which we also measure independently with
asterodensity profiling (AP; ), thereby confirming
the validity of AP on this particular evolved star. The well-determined
planetary properties and unusually large mass also make this planet an
important benchmark for theoretical models of super-Jupiter formation.
Long-term RV monitoring detected the presence of a non-transiting outer planet
(Kepler-432c; days), and adaptive optics imaging revealed a nearby
(0\farcs87), faint companion (Kepler-432B) that is a physically bound M dwarf.
The host star exhibits high signal-to-noise asteroseismic oscillations, which
enable precise measurements of the stellar mass, radius and age. Analysis of
the rotational splitting of the oscillation modes additionally reveals the
stellar spin axis to be nearly edge-on, which suggests that the stellar spin is
likely well-aligned with the orbit of the transiting planet. Despite its long
period, the obliquity of the 52.5-day orbit may have been shaped by star-planet
interaction in a manner similar to hot Jupiter systems, and we present
observational and theoretical evidence to support this scenario. Finally, as a
short-period outlier among giant planets orbiting giant stars, study of
Kepler-432b may help explain the distribution of massive planets orbiting giant
stars interior to 1 AU.Comment: 22 pages, 19 figures, 5 tables. Accepted to ApJ on Jan 24, 2015
(submitted Nov 11, 2014). Updated with minor changes to match published
versio
Stellar Spin-Orbit Misalignment in a Multiplanet System
Stars hosting hot Jupiters are often observed to have high obliquities,
whereas stars with multiple co-planar planets have been seen to have low
obliquities. This has been interpreted as evidence that hot-Jupiter formation
is linked to dynamical disruption, as opposed to planet migration through a
protoplanetary disk. We used asteroseismology to measure a large obliquity for
Kepler-56, a red giant star hosting two transiting co-planar planets. These
observations show that spin-orbit misalignments are not confined to hot-Jupiter
systems. Misalignments in a broader class of systems had been predicted as a
consequence of torques from wide-orbiting companions, and indeed
radial-velocity measurements revealed a third companion in a wide orbit in the
Kepler-56 system.Comment: Accepted for publication in Science, published online on October 17
2013; PDF includes main article and supplementary materials (65 pages, 27
figures, 7 tables); v2: small correction to author lis
Fundamental Properties of Kepler Planet-Candidate Host Stars using Asteroseismology
We have used asteroseismology to determine fundamental properties for 66
Kepler planet-candidate host stars, with typical uncertainties of 3% and 7% in
radius and mass, respectively. The results include new asteroseismic solutions
for four host stars with confirmed planets (Kepler-4, Kepler-14, Kepler-23 and
Kepler-25) and increase the total number of Kepler host stars with
asteroseismic solutions to 77. A comparison with stellar properties in the
planet-candidate catalog by Batalha et al. shows that radii for subgiants and
giants obtained from spectroscopic follow-up are systematically too low by up
to a factor of 1.5, while the properties for unevolved stars are in good
agreement. We furthermore apply asteroseismology to confirm that a large
majority of cool main-sequence hosts are indeed dwarfs and not misclassified
giants. Using the revised stellar properties, we recalculate the radii for 107
planet candidates in our sample, and comment on candidates for which the radii
change from a previously giant-planet/brown-dwarf/stellar regime to a
sub-Jupiter size, or vice versa. A comparison of stellar densities from
asteroseismology with densities derived from transit models in Batalha et al.
assuming circular orbits shows significant disagreement for more than half of
the sample due to systematics in the modeled impact parameters, or due to
planet candidates which may be in eccentric orbits. Finally, we investigate
tentative correlations between host-star masses and planet candidate radii,
orbital periods, and multiplicity, but caution that these results may be
influenced by the small sample size and detection biases.Comment: 19 pages, 10 figures, 4 tables; accepted for publication in ApJ;
machine-readable versions of tables 1-3 are available as ancillary files or
in the source code; v2: minor changes to match published versio
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