695 research outputs found
Massive gas gangrene secondary to occult colon carcinoma
AbstractGas gangrene is a rare but often fatal soft-tissue infection. Because it is uncommon and the classic symptom of crepitus does not appear until the infection is advanced, prompt diagnosis requires a high index of suspicion. We present a case report of a middle-aged man who presented with acute onset lower-extremity pain that was initially thought to be due to deep vein thrombosis. After undergoing workup for pulmonary embolism, he was found to have massive gas gangrene of the lower extremity secondary to an occult colon adenocarcinoma and died within hours of presentation from multisystem organ failure
A Simple Approach for State-Action Abstraction using a Learned MDP Homomorphism
Animals are able to rapidly infer from limited experience when sets of state
action pairs have equivalent reward and transition dynamics. On the other hand,
modern reinforcement learning systems must painstakingly learn through trial
and error that sets of state action pairs are value equivalent -- requiring an
often prohibitively large amount of samples from their environment. MDP
homomorphisms have been proposed that reduce the observed MDP of an environment
to an abstract MDP, which can enable more sample efficient policy learning.
Consequently, impressive improvements in sample efficiency have been achieved
when a suitable MDP homomorphism can be constructed a priori -- usually by
exploiting a practioner's knowledge of environment symmetries. We propose a
novel approach to constructing a homomorphism in discrete action spaces, which
uses a partial model of environment dynamics to infer which state action pairs
lead to the same state -- reducing the size of the state-action space by a
factor equal to the cardinality of the action space. We call this method
equivalent effect abstraction. In a gridworld setting, we demonstrate
empirically that equivalent effect abstraction can improve sample efficiency in
a model-free setting and planning efficiency for modelbased approaches.
Furthermore, we show on cartpole that our approach outperforms an existing
method for learning homomorphisms, while using 33x less training data.Comment: Previously Presented at the Multi-disciplinary Conference on
Reinforcement Learning and Decision Making (RLDM) 202
Predicting the response of a submillimeter bolometer to cosmic rays
Bolometers designed to detect. submillimeter radiation also respond to cosmic, gamma, and x rays. Because detectors cannot be fully shielded from such energy sources, it is necessary to understand the effect of a photon or cosmic-ray particle being absorbed. The resulting signal (known as a glitch) can then be removed from raw data. We present measurements using an Americium-241 gamma radiation source to irradiate a prototype bolometer for the High Frequency Instrument in the Planck Surveyor satellite. Our measurements showed no variation in response depending on where the radiation was absorbed, demonstrating that the bolometer absorber and thermistor thermalize quickly. The bolometer has previously been fully characterized both electrically and optically. We find that using optically measured time constants underestimates the time taken for the detector to recover from a radiation absorption event. However, a full thermal model for the bolometer, with parameters taken from electrical and optical measurements, provides accurate time constants. Slight deviations from the model were seen at high energies; these can be accounted for by use of an extended model
A Bright Submillimeter Source in the Bullet Cluster (1E0657--56) Field Detected with BLAST
We present the 250, 350, and 500 micron detection of bright submillimeter
emission in the direction of the Bullet Cluster measured by the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST). The 500 micron centroid is
coincident with an AzTEC 1.1 mm point-source detection at a position close to
the peak lensing magnification produced by the cluster. However, the 250 micron
and 350 micron centroids are elongated and shifted toward the south with a
differential shift between bands that cannot be explained by pointing
uncertainties. We therefore conclude that the BLAST detection is likely
contaminated by emission from foreground galaxies associated with the Bullet
Cluster. The submillimeter redshift estimate based on 250-1100 micron
photometry at the position of the AzTEC source is z_phot = 2.9 (+0.6 -0.3),
consistent with the infrared color redshift estimation of the most likely IRAC
counterpart. These flux densities indicate an apparent far-infrared luminosity
of L_FIR = 2E13 Lsun. When the amplification due to the gravitational lensing
of the cluster is removed, the intrinsic far-infrared luminosity of the source
is found to be L_FIR <= 10^12 Lsun, consistent with typical luminous infrared
galaxies.Comment: Accepted for publication in the Astrophysical Journal. Maps are
available at http://blastexperiment.info
Inhibition of IRE1 alpha RNase activity reduces NLRP3 inflammasome assembly and processing of pro-IL1 beta
The inflammasome is a multiprotein complex assembled in response to Pathogen Associated Molecular Patterns (PAMPs) and Danger Associated Molecular Patterns (DAMPS). Inflammasome activation occurs through a two-step mechanism, with the first signal facilitating priming of inflammasome components while the second signal triggers complex assembly. Once assembled, the inflammasome recruits and activates pro-caspase-1, which in turn processes pro-interleukin (IL)-18 and pro-IL-1 beta into their bio-active forms. Owing to its key role in the regulation of innate immune responses, the inflammasome has emerged as a therapeutic target for the treatment of inflammatory conditions. In this study we demonstrate that IRE1 alpha, a key component of the Unfolded Protein Response, contributes to assembly of the NLRP3 inflammasome. Blockade of IRE1 alpha RNase signaling lowered NLRP3 inflammasome assembly, caspase-1 activation and pro-IL-1 beta processing. These results underscore both the importance and potential therapeutic relevance of targeting IRE1 alpha signaling in conditions of excessive inflammasome formation
Over half of the far-infrared background light comes from galaxies at z >= 1.2
Submillimetre surveys during the past decade have discovered a population of
luminous, high-redshift, dusty starburst galaxies. In the redshift range 1 <= z
<= 4, these massive submillimetre galaxies go through a phase characterized by
optically obscured star formation at rates several hundred times that in the
local Universe. Half of the starlight from this highly energetic process is
absorbed and thermally re-radiated by clouds of dust at temperatures near 30 K
with spectral energy distributions peaking at 100 microns in the rest frame. At
1 <= z <= 4, the peak is redshifted to wavelengths between 200 and 500 microns.
The cumulative effect of these galaxies is to yield extragalactic optical and
far-infrared backgrounds with approximately equal energy densities. Since the
initial detection of the far-infrared background (FIRB), higher-resolution
experiments have sought to decompose this integrated radiation into the
contributions from individual galaxies. Here we report the results of an
extragalactic survey at 250, 350 and 500 microns. Combining our results at 500
microns with those at 24 microns, we determine that all of the FIRB comes from
individual galaxies, with galaxies at z >= 1.2 accounting for 70 per cent of
it. As expected, at the longest wavelengths the signal is dominated by
ultraluminous galaxies at z > 1.Comment: Accepted to Nature. Maps available at http://blastexperiment.info
Atmospheric transmission at submillimetre wavelengths from Mauna Kea
The submillimetre atmospheric transmission spectrum above Mauna Kea has been measured at a resolution of 0.005 cmâ1 (150 MHz) with a Fourier transform spectrometer at the James Clerk Maxwell Telescope, using the Sun as a source. Column abundances of O2, H2O and O3 determined from these spectra are found to be in excellent agreement with independent measurements. The derived column abundances have been used as inputs to the atmospheric spectral modelling program fascod. The synthetic transmission spectrum is found to be in excellent agreement with the measured spectrum, and provides a template for submillimetre observations from the JCMT
Third-Party Allogeneic Mesenchymal Stromal Cells Prevent Rejection in a Pre-sensitized High-Risk Model of Corneal Transplantation
High-risk cornea transplant recipients represent a patient population with significant un-met medical need for more effective therapies to prevent immunological graft rejection due to heightened anti-donor immune response. In this study, a rat model of pre-existing anti-donor immunity was developed in which corneal allografts were rejected earlier than in non-pre-sensitized recipients. In this model, third-party (non-donor, non-recipient strain) allogeneic mesenchymal stromal cells (allo-MSC) were administered intravenously 7 and 1 days prior to transplantation. Rejection-free graft survival to 30 days post-transplant improved from 0 to 63.6% in MSC-treated compared to vehicle-treated control animals (p = < 0.0001). Pre-sensitized animals that received third-party allo-MSC prior to transplantation had significantly higher proportions of CD45+CD11b+ B220+ monocytes in the lungs 24 h after the second MSC injection and significantly higher proportions of CD4+ FoxP3+ regulatory T cells in the graft-draining lymph nodes at the average day of rejection of control animals. In in vitro experiments, third-party allo-MSC polarized primary lung-derived CD11b/c+ myeloid cells to a more anti-inflammatory phenotype, as determined by cytokine profile and conferred them with the capacity to suppress T cell activation via prostaglandin E2 and TGFÎČ1. In experiments designed to further validate the clinical potential of the protocol, thawed cryopreserved, third-party allo-MSC were shown to be similarly potent at prolonging rejection-free corneal allograft survival as their freshly-cultured counterparts in the pre-sensitized high-risk model. Furthermore, thawed cryopreserved third-party allo-MSC could be co-administered with mycophenolate mofetil without adversely affecting their immunomodulatory function. In conclusion, a clinically-relevant protocol consisting of two intravenous infusions of third-party allo-MSC during the week prior to transplantation, exerts a potent anti-rejection effect in a pre-sensitized rat model of high-risk corneal allo-transplantation. This immune regulatory effect is likely to be mediated in the immediate post-transplant period through the promotion, by allo-MSC, of alternatively-activated macrophages in the lung and, later, by enhanced regulatory T-cell numbers
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