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Schwannomatosis of the Spinal Accessory Nerve: A Case Report.
Schwannomatosis is a distinct syndrome characterized by multiple peripheral nerve schwannomas that can be sporadic or familial in nature. Cases affecting the lower cranial nerves are infrequent. Here, the authors present a rare case of schwannomatosis affecting the left spinal accessory nerve. Upon genetic screening, an in-frame insertion at codon p.R177 of the Sox 10 gene was observed. There were no identifiable alterations in NF1, NF2, LZTR1, and SMARCB1. This case demonstrates a rare clinical presentation of schwannomatosis in addition to a genetic aberration that has not been previously reported in this disease context
On the Insignificance of Photochemical Hydrocarbon Aerosols in the Atmospheres of Close-in Extrasolar Giant Planets
The close-in extrasolar giant planets (CEGPs) reside in irradiated
environments much more intense than that of the giant planets in our solar
system. The high UV irradiance strongly influences their photochemistry and the
general current view believed that this high UV flux will greatly enhance
photochemical production of hydrocarbon aerosols. In this letter, we
investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find
that the abundances of hydrocarbons in the atmospheres of CEGPs are
significantly less than that of Jupiter except for models in which the CH
abundance is unreasonably high (as high as CO) for the hot (effective
temperatures K) atmospheres. Moreover, the hydrocarbons will be
condensed out to form aerosols only when the temperature-pressure profiles of
the species intersect with the saturation profiles--a case almost certainly not
realized in the hot CEGPs atmospheres. Hence our models show that photochemical
hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In
contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon
aerosols in their atmospheres which are responsible for strong absorption
shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon
aerosols in the atmospheres of CEGPs rules out one class of models with low
albedos and featureless spectra shortward of 600 nm.Comment: ApJL accepte
Photochemical modeling of CH_3 abundances in the outer solar system
Recent measurements of methyl radicals (CH_3) in the upper atmospheres of Saturn and Neptune by the Infrared Space Observatory (ISO) provide new constraints to photochemical models of hydrocarbon chemistry in the outer solar system. The derived column abundances of CH_3 on Saturn above 10 mbar and Neptune above the 0.2 mbar pressure level are (2.5–6.0) × 10^(13) cm^(−2) and (0.7–2.8) × 10^(13) cm^(−2), respectively. We use the updated Caltech/Jet Propulsion Laboratory photochemical model, which incorporates hydrocarbon photochemistry, vertical molecular and bulk atmospheric eddy diffusion, and realistic radiative transfer modeling, to study the CH_3 abundances in the upper atmosphere of the giant planets and Titan. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M → C_2H_6 + M. We evaluate and extrapolate the three-body rate constant of this reaction to the low-temperature limit (1.8×10^(−16) T^(−3.75) e^(−300/T), T<300 K) and compare methyl radical abundances in five atmospheres: Jupiter, Saturn, Uranus, Neptune, and Titan. The sensitivity of our models to the rate coefficients for the reactions H + CH_3 + M → CH_4 + M, H + C_2H_3 → C_2H_2 + H_2, ^1CH_2 + H_2 → CH_3 + H, and H + C_2H_5 → 2 CH_3, the branching ratios of CH_4 photolysis, vertical mixing in the five atmospheres, and Lyman α photon enhancement at the orbit of Neptune have all been tested. The results of our model CH_3 abundances for both Saturn (5.1×10^(13) cm^(−2)) and Neptune (2.2×10^(13) cm^(−2)) show good agreement with ISO Short Wavelength Spectrometer measurements. Using the same chemical reaction set, our calculations also successfully generate vertical profiles of stable hydrocarbons consistent with Voyager and ground-based measurements in these outer solar system atmospheres. Predictions of CH_3 column concentrations (for p≤0.2 mbar) in the atmospheres of Jupiter (3.3×10^(13) cm^(−2)), Uranus (2.5×10^(12) cm^(−2)), and Titan (1.9×10^(15) cm^(−2)) may be checked by future observations
Accelerated Cardiac Diffusion Tensor Imaging Using Joint Low-Rank and Sparsity Constraints
Objective: The purpose of this manuscript is to accelerate cardiac diffusion
tensor imaging (CDTI) by integrating low-rankness and compressed sensing.
Methods: Diffusion-weighted images exhibit both transform sparsity and
low-rankness. These properties can jointly be exploited to accelerate CDTI,
especially when a phase map is applied to correct for the phase inconsistency
across diffusion directions, thereby enhancing low-rankness. The proposed
method is evaluated both ex vivo and in vivo, and is compared to methods using
either a low-rank or sparsity constraint alone. Results: Compared to using a
low-rank or sparsity constraint alone, the proposed method preserves more
accurate helix angle features, the transmural continuum across the myocardium
wall, and mean diffusivity at higher acceleration, while yielding significantly
lower bias and higher intraclass correlation coefficient. Conclusion:
Low-rankness and compressed sensing together facilitate acceleration for both
ex vivo and in vivo CDTI, improving reconstruction accuracy compared to
employing either constraint alone. Significance: Compared to previous methods
for accelerating CDTI, the proposed method has the potential to reach higher
acceleration while preserving myofiber architecture features which may allow
more spatial coverage, higher spatial resolution and shorter temporal footprint
in the future.Comment: 11 pages, 16 figures, published on IEEE Transactions on Biomedical
Engineerin
Meridional Transport in the Stratosphere of Jupiter
The Cassini measurements of CH and CH at 5 mbar provide
a constraint on meridional transport in the stratosphere of Jupiter. We
performed a two-dimensional photochemical calculation coupled with mass
transport due to vertical and meridional mixing. The modeled profile of
CH at latitudes less than 70 follows the latitude dependence of
the solar insolation, while that of CH shows little latitude
dependence, consistent with the measurements. In general, our model study
suggests that the meridional transport timescale above 5-10 mbar altitude level
is 1000 years and the time could be as short as 10 years below 10 mbar
level, in order to fit the Cassini measurements. The derived meridional
transport timescale above the 5 mbar level is a hundred times longer than that
obtained from the spreading of gas-phase molecules deposited after the impact
of Shoemaker-Levy 9 comet. There is no explanation at this time for this
discrepancy.Comment: 11 pages, 3 figures, 1 table. ApJL in pres
The Diversity of Diffuse Ly Nebulae around Star-Forming Galaxies at High Redshift
We report the detection of diffuse Ly emission, or Ly halos
(LAHs), around star-forming galaxies at and in the NOAO
Deep Wide-Field Survey Bo\"otes field. Our samples consist of a total of
1400 galaxies, within two separate regions containing spectroscopically
confirmed galaxy overdensities. They provide a unique opportunity to
investigate how the LAH characteristics vary with host galaxy large-scale
environment and physical properties. We stack Ly images of different
samples defined by these properties and measure their median LAH sizes by
decomposing the stacked Ly radial profile into a compact galaxy-like
and an extended halo-like component. We find that the exponential scale-length
of LAHs depends on UV continuum and Ly luminosities, but not on
Ly equivalent widths or galaxy overdensity parameters. The full
samples, which are dominated by low UV-continuum luminosity Ly emitters
(), exhibit LAH sizes of 5kpc. However, the
most UV- or Ly-luminous galaxies have more extended halos with
scale-lengths of 7kpc. The stacked Ly radial profiles decline
more steeply than recent theoretical predictions that include the contributions
from gravitational cooling of infalling gas and from low-level star formation
in satellites. On the other hand, the LAH extent matches what one would expect
for photons produced in the galaxy and then resonantly scattered by gas in an
outflowing envelope. The observed trends of LAH sizes with host galaxy
properties suggest that the physical conditions of the circumgalactic medium
(covering fraction, HI column density, and outflow velocity) change with halo
mass and/or star-formation rates.Comment: published in ApJ, minor proof corrections applie
Unstable Nonradial Oscillations on Helium Burning Neutron Stars
Material accreted onto a neutron star can stably burn in steady state only
when the accretion rate is high (typically super-Eddington) or if a large flux
from the neutron star crust permeates the outer atmosphere. For such situations
we have analyzed the stability of nonradial oscillations, finding one unstable
mode for pure helium accretion. This is a shallow surface wave which resides in
the helium atmosphere above the heavier ashes of the ocean. It is excited by
the increase in the nuclear reaction rate during the oscillations, and it grows
on the timescale of a second. For a slowly rotating star, this mode has a
frequency of approximately 20-30 Hz (for l=1), and we calculate the full
spectrum that a rapidly rotating (>>30 Hz) neutron star would support. The
short period X-ray binary 4U 1820--30 is accreting helium rich material and is
the system most likely to show this unstable mode,especially when it is not
exhibiting X-ray bursts. Our discovery of an unstable mode in a thermally
stable atmosphere shows that nonradial perturbations have a different stability
criterion than the spherically symmetric thermal perturbations that generate
type I X-ray bursts.Comment: Accepted for publication in Astrophysical Journal, 22 pages, 14
figure
Enhancement of deuterated ethane on Jupiter
We report laboratory measurements of cross sections of CH_3D and C_2H_5D in the extreme ultraviolet. The results are incorporated in a photochemical model for the deuterated hydrocarbons up to C_2 in the upper atmosphere of Jupiter, taking into account the fast reactions for exchanging H and D atoms between H_2 and CH_4, H + HD ↔ D + H_2, CH_3 + D ↔ CH_2D + H. Since there is no reliable kinetics measurement for the reaction, CH_2D + H → CH_3 + D, we use Yung et al.'s estimate for its rate constant. The strong temperature dependence for this reaction leads to large isotopic fractionation for CH_3D and C_2H_5D in the upper atmosphere of Jupiter, where their production rates depend on the abundance of deuterated methyl radical. The model predicts that the D/H ratio in deuterated ethane is about 15 times that of the bulk atmosphere. A confirmation of this result would provide a sensitive test of the photochemistry of hydrocarbons in the atmosphere of Jupiter
Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere
Atmospheric heavy ozone is enriched in the isotopes ^(18)O and ^(17)O. The magnitude of this enhancement, of the order of 100‰, is very large compared with that commonly known in atmospheric chemistry and geochemistry. The heavy oxygen atom in heavy ozone is therefore useful as a tracer of chemical species and pathways that involve ozone or its derived products. As a test of the isotopic exchange reactions, we successfully carry out a series of numerical experiments to simulate the results of the laboratory experiments performed by Wen and Thiemens [1993] on ozone and CO_2. A small discrepancy between the experimental and the model values for ^(17)O exchange is also revealed. The results are used to compute the magnitude of isotopic exchange between ozone and carbon dioxide via the excited atom O(^1D) in the middle atmosphere. The model for ^(18)O is in good agreement with the observed values
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