383 research outputs found
First Record of \u3ci\u3eAgonostomus monticola\u3c/i\u3e (Family: Mugilidae) in Mississippi Freshwaters with Notes of its Distribution in the Southern United States
An individual of Agonostomus monticola (Mountain Mullet) was collected in southern Mississippi while conducting a series of community surveys on 7 November 2007. This is the first documented report of Mountain Mullet in Mississippi freshwaters, even though there are reports of three specimens collected in Mississippi estuarine waters in 1937. Given its life history and difficulties in sampling, it is likely that Mountain Mullet has a broader distribution and more frequently occurs in Gulf Coast drainages in the southern US than was previously thought
On the Origin of HD149026b
The high density of the close-in extrasolar planet HD149026b suggests the
presence of a huge core in the planet, which challenges planet formation
theory. We first derive constraints on the amount of heavy elements and
hydrogen/helium present in the planet: We find that preferred values of the
core mass are between 50 and 80 M_E. We then investigate the possibility of
subcritical core accretion as envisioned for Uranus and Neptune and find that
the subcritical accretion scenario is unlikely in the case of HD149026b for at
least two reasons: (i) Subcritical planets are such that the ratio of their
core mass to their total mass is above ~0.7, in contradiction with constraints
for all but the most extreme interior models of HD149026b; (ii) High accretion
rates and large isolation mass required for the formation of a subcritical core
of 30 M_E are possible only at specific orbital distances in a disk with a
surface density of dust equal to at least 10 times that of the minimum mass
solar nebula. This value climbs to 30 when considering a 50 M_E core. These
facts point toward two main routes for the formation of this planet: (i) Gas
accretion that is limited by a slow viscous inflow of gas in an evaporating
disk; (ii) A significant modification of the composition of the planet after as
accretion has stopped. These two routes are not mutually exclusive.
Illustrating the second route, we show that for a wide range of impact
parameters, giant impacts lead to a loss of the gas component of the planet and
thus may lead to planets that are highly enriched in heavy elements. In the
giant impact scenario, we expect an outer giant planet to be present.
Observational studies by imaging, astrometry and long term interferometry of
this system are needed to better narrow down the ensemble of possibilities.Comment: 29 pages, 8 figures, to appear in the 10 October 2006 issue of Ap
ESPRESSO Mass determination of TOI-263b: An extreme inhabitant of the brown dwarf desert
The TESS mission has reported a wealth of new planetary systems around bright
and nearby stars amenable for detailed characterization of the planet
properties and their atmospheres. However, not all interesting TESS planets
orbit around bright host stars. TOI-263b is a validated ultra-short period
substellar object in a 0.56-day orbit around a faint (V=18.97) M3.5 dwarf star.
The substellar nature of TOI-263b was explored using multi-color photometry,
which determined a true radius of 0.87+-0.21 Rj, establishing TOI-263b's nature
ranging from an inflated Neptune to a brown dwarf. The orbital period-radius
parameter space occupied by TOI-263b is quite unique, which prompted a further
characterization of its true nature. Here, we report radial velocity
measurements of TOI-263 obtained with 3 VLT units and the ESPRESSO spectrograph
to retrieve the mass of TOI-263b. We find that TOI-263b is a brown dwarf with a
mass of 61.6+-4.0 Mj. Additionally, the orbital period of the brown dwarf is
found to be synchronized with the rotation period of the host star, and the
system is found to be relatively active, possibly revealing a star--brown dwarf
interaction. All these findings suggest that the system's formation history
might be explained via disc fragmentation and later migration to close-in
orbits. If the system is found to be unstable, TOI-263 is an excellent target
to test the migration mechanisms before the brown dwarf becomes engulfed by its
parent star.Comment: Accepted for Publication in Astronomy and Astrophysic
Artificial Neural Networks Predicted the Overall Survival and Molecular Subtypes of Diffuse Large B-Cell Lymphoma Using a Pancancer Immune-Oncology Panel
Diffuse large B-cell lymphoma (DLBCL) is one of the most frequent subtypes of non-Hodgkin lymphomas. We used artificial neural networks (multilayer perceptron and radial basis function), machine learning, and conventional bioinformatics to predict the overall survival and molecular subtypes of DLBCL. The series included 106 cases and 730 genes of a pancancer immune oncology panel (nCounter) as predictors. The multilayer perceptron predicted the outcome with high accuracy, with an area under the curve (AUC) of 0.98, and ranked all the genes according to their importance. In a multivariate analysis, ARG1, TNFSF12, REL, and NRP1 correlated with favorable survival (hazard risks: 0.3–0.5), and IFNA8, CASP1, and CTSG, with poor survival (hazard risks = 1.0–2.1). Gene set enrichment analysis (GSEA) showed enrichment toward poor prognosis. These high-risk genes were also associated with the gene expression of M2-like tumor-associated macrophages (CD163), and MYD88 expression. The prognostic relevance of this set of 7 genes was also confirmed within the IPI and MYC translocation strata, the EBER-negative cases, the DLBCL not-otherwise specified (NOS) (High-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements excluded), and an independent series of 414 cases of DLBCL in Europe and North America (GSE10846). The perceptron analysis also predicted molecular subtypes (based on the Lymph2Cx assay) with high accuracy (AUC = 1). STAT6, TREM2, and REL were associated with the germinal center B-cell (GCB) subtype, and CD37, GNLY, CD46, and IL17B were associated with the activated B-cell (ABC)/unspecified subtype. The GSEA had a sinusoidal-like plot with association to both molecular subtypes, and immunohistochemistry analysis confirmed the correlation of MAPK3 with the GCB subtype in another series of 96 cases (notably, MAPK3 also correlated with LMO2, but not with M2-like tumor-associated macrophage markers CD163, CSF1R, TNFAIP8, CASP8, PD-L1, PTX3, and IL-10). Finally, survival and molecular subtypes were successfully modeled using other machine learning techniques including logistic regression, discriminant analysis, SVM, CHAID, C5, C&R trees, KNN algorithm, and Bayesian network. In conclusion, prognoses and molecular subtypes were predicted with high accuracy using neural networks, and relevant genes were highlighted
Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to 3D equivalents using weight bearing CT
Exploring the Ability of HST WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres Through a Homogeneous Transmission Survey of 70 Gaseous Planets
We present the analysis of the atmospheres of 70 gaseous extrasolar planets
via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over
half of these, we statistically detect spectral modulation which our retrievals
attribute to molecular species. Among these, we use Bayesian Hierarchical
Modelling to search for chemical trends with bulk parameters. We use the
extracted water abundance to infer the atmospheric metallicity and compare it
to the planet's mass. We also run chemical equilibrium retrievals, fitting for
the atmospheric metallicity directly. However, although previous studies have
found evidence of a mass-metallicity trend, we find no such relation within our
data. For the hotter planets within our sample, we find evidence for thermal
dissociation of dihydrogen and water via the H opacity. We suggest that the
general lack of trends seen across this population study could be due to i) the
insufficient spectral coverage offered by HST WFC3 G141, ii) the lack of a
simple trend across the whole population, iii) the essentially random nature of
the target selection for this study or iv) a combination of all the above. We
set out how we can learn from this vast dataset going forward in an attempt to
ensure comparative planetology can be undertaken in the future with facilities
such as JWST, Twinkle and Ariel. We conclude that a wider simultaneous spectral
coverage is required as well as a more structured approach to target selection.Comment: Accepted for publication in ApJ
Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets
We present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble’s Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet’s mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass–metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H− opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope’s WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection
The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet
Kepler-10b was the first rocky planet detected by the Kepler satellite and
con- firmed with radial velocity follow-up observations from Keck-HIRES. The
mass of the planet was measured with a precision of around 30%, which was
insufficient to constrain models of its internal structure and composition in
detail. In addition to Kepler-10b, a second planet transiting the same star
with a period of 45 days was sta- tistically validated, but the radial
velocities were only good enough to set an upper limit of 20 Mearth for the
mass of Kepler-10c. To improve the precision on the mass for planet b, the
HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N
spectrograph on the Telescopio Nazionale Galileo on La Palma. In to- tal, 148
high-quality radial-velocity measurements were obtained over two observing
seasons. These new data allow us to improve the precision of the mass
determina- tion for Kepler-10b to 15%. With a mass of 3.33 +/- 0.49 Mearth and
an updated radius of 1.47 +0.03 -0.02 Rearth, Kepler-10b has a density of 5.8
+/- 0.8 g cm-3, very close to the value -0.02 predicted by models with the same
internal structure and composition as the Earth. We were also able to determine
a mass for the 45-day period planet Kepler-10c, with an even better precision
of 11%. With a mass of 17.2 +/- 1.9 Mearth and radius of 2.35 +0.09 -0.04
Rearth, -0.04 Kepler-10c has a density of 7.1 +/- 1.0 g cm-3. Kepler-10c
appears to be the first strong evidence of a class of more massive solid
planets with longer orbital periods.Comment: 44 pages, 8 figures, accepted for publication in Ap
Bulk composition of the transiting hot Neptune around GJ 436
The hot Neptune orbiting around GJ 436 is a unique example of an intermediate
mass planet. Its close-in orbit suggests that the planet has undergone
migration and its study is fundamental to understanding planet formation and
evolution. As it transits its parent star, it is the only Neptune-mass
extrasolar planet of known mass and radius, being slightly larger and more
massive than Neptune (M=22.6 M_Earth, R=4.19R_Earth). In this regime, several
bulk compositions are possible: from an Earth-like core with a thick hydrogen
envelope to a water-rich planet with a thin hydrogen envelope comprising a
Neptune-like structure. We combine planet-structure modeling with an advanced
planet-formation model to assess the likelihood of the different possible bulk
compositions of GJ 436 b. We find that both an envelope-free water planet
("Ocean planet") as well as a diminute version of a gaseous giant planet are
excluded. Consisting of a rocky core with a thick hydrogen/helium envelope, a
"dry" composition produces not only too small a radius but is also a very
unlikely outcome of planet formation around such a low-mass star. We conclude
that GJ 436 b is probably of much higher rock content than Neptune (more than
45% in mass), with a small H-He envelope (10 - 20% in mass). This is the
expected outcome of the gathering of materials during the migration process in
the inner disk, creating a population of which the hot Neptune is
representative.Comment: (7 pages, 2 figures, already published in Astronomy and Astrophysics
Debris disks as signposts of terrestrial planet formation. II Dependence of exoplanet architectures on giant planet and disk properties
We present models for the formation of terrestrial planets, and the
collisional evolution of debris disks, in planetary systems that contain
multiple unstable gas giants. We previously showed that the dynamics of the
giant planets introduces a correlation between the presence of terrestrial
planets and debris disks. Here we present new simulations that show that this
connection is qualitatively robust to changes in: the mass distribution of the
giant planets, the width and mass distribution of the outer planetesimal disk,
and the presence of gas in the disk. We discuss how variations in these
parameters affect the evolution. Systems with equal-mass giant planets undergo
the most violent instabilities, and these destroy both terrestrial planets and
the outer planetesimal disks that produce debris disks. In contrast, systems
with low-mass giant planets efficiently produce both terrestrial planets and
debris disks. A large fraction of systems with low-mass outermost giant planets
have stable gaps between these planets that are frequently populated by
planetesimals. Planetesimal belts between outer giant planets may affect debris
disk SEDs. If Earth-mass seeds are present in outer planetesimal disks, the
disks radially spread to colder temperatures. We argue that this may explain
the very low frequency of > 1 Gyr-old solar-type stars with observed 24 micron
excesses. Among the (limited) set of configurations explored, the best
candidates for hosting terrestrial planets at ~1 AU are stars older than 0.1-1
Gyr with bright debris disks at 70 micron but with no currently-known giant
planets. These systems combine evidence for rocky building blocks, with giant
planet properties least likely to undergo destructive dynamical evolution. We
predict an anti-correlation between debris disks and eccentric giant planets,
and a positive correlation between debris disks and terrestrial planets.Comment: Astronomy and Astrophysics, in press. Movies from simulations are at
http://www.obs.u-bordeaux1.fr/e3arths/raymond/movies_debris.htm
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