404 research outputs found
Detectability of Rocky-Vapour atmospheres on super-Earths with Ariel
Ariel will mark the dawn of a new era as the first large-scale survey characterising exoplanetary atmospheres with science objectives to address fundamental questions about planetary composition, evolution and formation. In this study, we explore the detectability of atmospheres vaporised from magma oceans on dry, rocky Super-Earths orbiting very close to their host stars. The detection of such atmospheres would provide a definitive piece of evidence for rocky planets but are challenging measurements with currently available instruments due to their small spectral signatures. However, some of the hottest planets are believed to have atmospheres composed of vaporised rock, such as Na and SiO, with spectral signatures bright enough to be detected through eclipse observations with planned space-based telescopes. In this study, we find that rocky super-Earths with a irradiation temperature of 3000 K and a distance from Earth of up to 20 pc, as well as planets hotter than 3500 K and closer than 50 pc, have SiO features which are potentially detectable in eclipse spectra observed with Ariel
Farnesyl diphosphate synthase may determine the accumulation level of (â)-rotundone in 'Syrah' grapes
(â)-Rotundone is an oxygenated sesquiterpene responsible for the peppery aroma in grapes, wines, herbs, and spices, and it was first identified in 'Syrah' wine from Australia. In this study, we demonstrated the expression profiles of genes related to (â)-rotundone biosynthesis during the maturation of 'Syrah' grapes from two different vineyards, namely, the Iwaimura and Johnohira vineyards in Japan. The α-guaiene and (â)-rotundone accumulation levels in the grape exocarp from the Johnohira vineyard, which has a cool climatic condition located at a high altitude, were extremely higher than those from the Iwaimura vineyard. Among the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway genes, the transcript levels of 1-deoxy-D-xylulose-5-phosphate synthase gene (DXS) in the grape exocarp from the Johnohira vineyard were higher than those from the Iwaimura vineyard after vĂ©raison. The expression levels of the mevalonate pathway genes, Vitis vinifera terpene synthase gene (VvTPS24) and cytochrome P450 gene (CYP71BE5) in the final step of (â)-rotundone biosynthesis were not significantly different between samples from the two vineyards during grape maturation. In contrast, the farnesyl diphosphate synthase gene (FPPS) expression level was considerably higher in the grape exocarp from the Johnohira vineyard than in that from the Iwaimura vineyard. Consistent with these observations, FPPS was constantly expressed at higher level in 'Syrah' grape exocarp compared with 'Merlot' grape which is a low-rotundone cultivar. These findings suggest that FPPS may play a key role in determining the accumulation level of (â)-rotundone, which can provide abundant substrates for VvTPS24 catalysis to produce α-guaiene as a precursor of (â)-rotundone. In addition, among the MEP pathway genes, DXS may have a regulatory role for a precursor supply from the plastids to (â)-rotundone biosynthesis
Origin of the Different Architectures of the Jovian and Saturnian Satellite Systems
The Jovian regular satellite system mainly consists of four Galilean
satellites that have similar masses and are trapped in mutual mean motion
resonances except for the outer satellite, Callisto. On the other hand, the
Saturnian regular satellite system has only one big icy body, Titan, and a
population of much smaller icy moons. We have investigated the origin of these
major differences between the Jovian and Saturnian satellite systems by
semi-analytically simulating the growth and orbital migration of
proto-satellites in an accreting proto-satellite disk. We set up two different
disk evolution/structure models that correspond to Jovian and Saturnian
systems, by building upon previously developed models of an actively-supplied
proto-satellite disk, the formation of gas giants, and observations of young
stars. Our simulations extend previous models by including the (1) different
termination timescales of gas infall onto the proto-satellite disk and (2)
different evolution of a cavity in the disk, between the Jovian and Saturnian
systems. We have performed Monte Carlo simulations and show that in the case of
the Jovian systems, four to five similar-mass satellites are likely to remain
trapped in mean motion resonances. This orbital configuration is formed by type
I migration, temporal stopping of the migration near the disk inner edge, and
quick truncation of gas infall caused by Jupiter opening a gap in the Solar
nebula. The Saturnian systems tend to end up with one dominant body in the
outer regions caused by the slower decay of gas infall associated with global
depletion of the Solar nebula. The total mass and compositional zoning of the
predicted Jovian and Saturnian satellite systems are consistent with the
observed satellite systems.Comment: Accepted to ApJ, 33pages, 6figures, 2table
Forming Jupiter, Saturn, Uranus and Neptune in Few Million Years by Core Accretion
Giant planet formation process is still not completely understood. The
current most accepted paradigm, the core instability model, explains several
observed properties of the solar system's giant planets but, to date, has faced
difficulties to account for a formation time shorter than the observational
estimates of protoplanetary disks' lifetimes, especially for the cases of
Uranus and Neptune. In the context of this model, and considering a recently
proposed primordial solar system orbital structure, we performed numerical
calculations of giant planet formation. Our results show that if accreted
planetesimals follow a size distribution in which most of the mass lies in
30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed
according to the nucleated instability scenario. The formation of each planet
occurs within the time constraints and they end up with core masses in good
agreement with present estimations.Comment: 11 pages, 3 figures, in press (Icarus
TRPV1-expressing primary afferents generate behavioral responses to pruritogens via multiple mechanisms
The mechanisms that generate itch are poorly understood at both the molecular and cellular levels despite its clinical importance. To explore the peripheral neuronal mechanisms underlying itch, we assessed the behavioral responses (scratching) produced by s.c. injection of various pruritogens in PLCÎČ3- or TRPV1-deficient mice. We provide evidence that at least 3 different molecular pathways contribute to the transduction of itch responses to different pruritogens: 1) histamine requires the function of both PLCÎČ3 and the TRPV1 channel; 2) serotonin, or a selective agonist, α-methyl-serotonin (α-Me-5-HT), requires the presence of PLCÎČ3 but not TRPV1, and 3) endothelin-1 (ET-1) does not require either PLCÎČ3 or TRPV1. To determine whether the activity of these molecules is represented in a particular subpopulation of sensory neurons, we examined the behavioral consequences of selectively eliminating 2 nonoverlapping subsets of nociceptors. The genetic ablation of MrgprD^+ neurons that represent â90% of cutaneous nonpeptidergic neurons did not affect the scratching responses to a number of pruritogens. In contrast, chemical ablation of the central branch of TRPV1+ nociceptors led to a significant behavioral deficit for pruritogens, including α-Me-5-HT and ET-1, that is, the TRPV1-expressing nociceptor was required, whether or not TRPV1 itself was essential. Thus, TRPV1 neurons are equipped with multiple signaling mechanisms that respond to different pruritogens. Some of these require TRPV1 function; others use alternate signal transduction pathways
Towards Reliable Colorectal Cancer Polyps Classification via Vision Based Tactile Sensing and Confidence-Calibrated Neural Networks
In this study, toward addressing the over-confident outputs of existing
artificial intelligence-based colorectal cancer (CRC) polyp classification
techniques, we propose a confidence-calibrated residual neural network.
Utilizing a novel vision-based tactile sensing (VS-TS) system and unique CRC
polyp phantoms, we demonstrate that traditional metrics such as accuracy and
precision are not sufficient to encapsulate model performance for handling a
sensitive CRC polyp diagnosis. To this end, we develop a residual neural
network classifier and address its over-confident outputs for CRC polyps
classification via the post-processing method of temperature scaling. To
evaluate the proposed method, we introduce noise and blur to the obtained
textural images of the VS-TS and test the model's reliability for non-ideal
inputs through reliability diagrams and other statistical metrics
Structure and evolution of super-Earth to super-Jupiter exoplanets: I. heavy element enrichment in the interior
We examine the uncertainties in current planetary models and we quantify
their impact on the planet cooling histories and mass-radius relationships.
These uncertainties include (i) the differences between the various equations
of state used to characterize the heavy material thermodynamical properties,
(ii) the distribution of heavy elements within planetary interiors, (iii) their
chemical composition and (iv) their thermal contribution to the planet
evolution. Our models, which include a gaseous H/He envelope, are compared with
models of solid, gasless Earth-like planets in order to examine the impact of a
gaseous envelope on the cooling and the resulting radius. We find that for a
fraction of heavy material larger than 20% of the planet mass, the distribution
of the heavy elements in the planet's interior affects substantially the
evolution and thus the radius at a given age. For planets with large core mass
fractions (\simgr 50%), such as the Neptune-mass transiting planet GJ436b,
the contribution of the gravitational and thermal energy from the core to the
planet cooling history is not negligible, yielding a 10% effect on the
radius after 1 Gyr. We show that the present mass and radius determinations of
the massive planet Hat-P-2b require at least 200 \mearth of heavy material in
the interior, at the edge of what is currently predicted by the core-accretion
model for planet formation. We show that if planets as massive as 25
\mjup can form, as predicted by improved core-accretion models, deuterium is
able to burn in the H/He layers above the core, even for core masses as large
as 100 \mearth. We provide extensive grids of planetary evolution
models from 10 \mearth to 10 M, with various fractions of heavy
elements.Comment: 20 pages, 12 figures. Accepted for publication in Astronomy and
Astrophysic
The Hydrogen Evolution and Oxidation Kinetics during Overdischarging of Sealed Nickel-Metal Hydride Batteries
Analysis of new high-precision transit light curves of WASP-10 b: starspot occultations, small planetary radius, and high metallicity
The WASP-10 planetary system is intriguing because different values of radius
have been reported for its transiting exoplanet. The host star exhibits
activity in terms of photometric variability, which is caused by the rotational
modulation of the spots. Moreover, a periodic modulation has been discovered in
transit timing of WASP-10 b, which could be a sign of an additional body
perturbing the orbital motion of the transiting planet. We attempt to refine
the physical parameters of the system, in particular the planetary radius,
which is crucial for studying the internal structure of the transiting planet.
We also determine new mid-transit times to confirm or refute observed anomalies
in transit timing. We acquired high-precision light curves for four transits of
WASP-10 b in 2010. Assuming various limb-darkening laws, we generated best-fit
models and redetermined parameters of the system. The prayer-bead method and
Monte Carlo simulations were used to derive error estimates. Three transit
light curves exhibit signatures of the occultations of dark spots by the planet
during its passage across the stellar disk. The influence of stellar activity
on transit depth is taken into account while determining system parameters. The
radius of WASP-10 b is found to be no greater than 1.03 Jupiter radii, a value
significantly smaller than most previous studies indicate. We calculate
interior structure models of the planet, assuming a two-layer structure with
one homogeneous envelope atop a rock core. The high value of the WASP-10 b's
mean density allows one to consider the planet's internal structure including
270 to 450 Earth masses of heavy elements. Our new mid-transit times confirm
that transit timing cannot be explained by a constant period if all literature
data points are considered. They are consistent with the ephemeris assuming a
periodic variation of transit timing...Comment: Accepted for publication in A&
Giant Planet Formation: A First Classification of Isothermal Protoplanetary Equilibria
We present a model for the equilibrium of solid planetary cores embedded in a
gaseous nebula. From this model we are able to extract an idealized roadmap of
all hydrostatic states of the isothermal protoplanets. The complete
classification of the isothermal protoplanetary equilibria should improve the
understanding of the general problem of giant planet formation, within the
framework of the nucleated instability hypothesis. We approximate the
protoplanet as a spherically symmetric, isothermal, self-gravitating classical
ideal gas envelope in equilibrium, around a rigid body of given mass and
density, with the gaseous envelope required to fill the Hill-sphere. Starting
only with a core of given mass and an envelope gas density at the core surface,
the equilibria are calculated without prescribing the total protoplanetary mass
or nebula density. The static critical core masses of the protoplanets for the
typical orbits of 1, 5.2, and 30 AU, around a parent star of 1 solar mass are
found to be 0.1524, 0.0948, and 0.0335 Earth masses, respectively, for standard
nebula conditions (Kusaka et al. 1970). These values are much lower than
currently admitted ones primarily because our model is isothermal and the
envelope is in thermal equilibrium with the nebula. For a given core, multiple
solutions (at least two) are found to fit into the same nebula. We extend the
concept of the static critical core mass to the local and global critical core
mass. We conclude that the 'global static critical core mass' marks the meeting
point of all four qualitatively different envelope regions.Comment: 13 pages, 15 figure
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