149 research outputs found
Total Pancreatectomy with Islet Autologous Transplantation: The Cure for Chronic Pancreatitis?
Chronic pancreatitis (CP) is a debilitating disease that leads to varying degrees of pancreatic endocrine and exocrine dysfunction. One of the most difficult symptoms of CP is severe abdominal pain, which is often challenging to control with available analgesics and therapies. In the last decade, total pancreatectomy with autologous islet cell transplantation has emerged as a promising treatment for the refractory pain of CP and is currently performed at approximately a dozen centers in the United States. While total pancreatectomy is not a new procedure, the endocrine function-preserving autologous islet cell isolation and re-implantation have made the prospect of total pancreatectomy more acceptable to patients and clinicians. This review will focus on the current status of total pancreatectomy with autologous islet cell transplant including patient selection, technical considerations, and outcomes. As the procedure is performed at an increasing number of centers, this review will highlight opportunities for quality improvement and outcome optimization
Resolving chemical gradients in exoplanet atmospheres with high-resolution spectroscopy
Laboratory astrophysics and astrochemistryStars and planetary system
Mapping weather on WASP-76b with high-resolution transmission spectroscopy
Stars and planetary system
The puzzling atmospheres of low-mass stars, brown dwarfs and exoplanets revealed by the Discovery Channel Telescope
The Large Monolithic Imager (LMI) on the Discovery Channel Telescope (DCT) enables high-precision photometry with a scriptable interface and rapid cycling between photometric bands, all while guiding off-axis. Using LMI, scientists at Boston University have undertaken a number of investigations into low-mass stars, brown dwarfs and extrasolar planets. We will report on recent results from these investigations, including (1) measurements of transiting asteroids orbiting a white dwarf, (2) refined ephemerides for long-period transiting exoplanets, (3) investigations revealing biases in space-based exoplanet light curves, (4) investigations of the nature of activity in low-mass stars and brown dwarfs and (5) investigations of low-mass eclipsing binary stars. We will also propose future studies of low-mass stars, brown dwarfs and exoplanets using current and future DCT instrumentation.http://adsabs.harvard.edu/abs/2017AAS...22912607MPublished versio
Harmonic Analysis of Boolean Networks: Determinative Power and Perturbations
Consider a large Boolean network with a feed forward structure. Given a
probability distribution on the inputs, can one find, possibly small,
collections of input nodes that determine the states of most other nodes in the
network? To answer this question, a notion that quantifies the determinative
power of an input over the states of the nodes in the network is needed. We
argue that the mutual information (MI) between a given subset of the inputs X =
{X_1, ..., X_n} of some node i and its associated function f_i(X) quantifies
the determinative power of this set of inputs over node i. We compare the
determinative power of a set of inputs to the sensitivity to perturbations to
these inputs, and find that, maybe surprisingly, an input that has large
sensitivity to perturbations does not necessarily have large determinative
power. However, for unate functions, which play an important role in genetic
regulatory networks, we find a direct relation between MI and sensitivity to
perturbations. As an application of our results, we analyze the large-scale
regulatory network of Escherichia coli. We identify the most determinative
nodes and show that a small subset of those reduces the overall uncertainty of
the network state significantly. Furthermore, the network is found to be
tolerant to perturbations of its inputs
A Search for FeH in Hot-Jupiter Atmospheres with High-Dispersion Spectroscopy
Most of the molecules detected thus far in exoplanet atmospheres, such as
water and CO, are present for a large range of pressures and temperatures. In
contrast, metal hydrides exist in much more specific regimes of parameter
space, and so can be used as probes of atmospheric conditions. Iron hydride
(FeH) is a dominant source of opacity in low-mass stars and brown dwarfs, and
evidence for its existence in exoplanets has recently been observed at low
resolution. We performed a systematic search of archival CARMENES near-infrared
data for signatures of FeH during transits of 12 exoplanets. These planets span
a large range of equilibrium temperatures (600
4000K) and surface gravities (2.5 3.5). We
did not find a statistically significant FeH signal in any of the atmospheres,
but obtained potential low-confidence signals (SNR3) in two planets,
WASP-33b and MASCARA-2b. Previous modeling of exoplanet atmospheres indicate
that the highest volume mixing ratios (VMRs) of 10 to 10 are
expected for temperatures between 1800 and 3000K and log . The two
planets for which we find low-confidence signals are in the regime where strong
FeH absorption is expected. We performed injection and recovery tests for each
planet and determined that FeH would be detected in every planet for VMRs , and could be detected in some planets for VMRs as low as 10.
Additional observations are necessary to conclusively detect FeH and assess its
role in the temperature structures of hot Jupiter atmospheres.Comment: Accepted to AAS journal
Detection of OH in the ultra-hot Jupiter WASP-76b
Stars and planetary system
Spatial characterization of the trailing and leading limbs of WASP-76b: detection of H2O and HCN at high-resolution
Stars and planetary system
Detection of OH at the evening terminator of the ultra-hot Jupiter WASP-76b
Stars and planetary system
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