84 research outputs found
Localization of the corticotropin-releasing hormone receptor gene on mouse Chromosome 11
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47014/1/335_2004_Article_BF00350896.pd
NIMBUS: The Near-Infrared Multi-Band Ultraprecise Spectroimager for SOFIA
We present a new and innovative near-infrared multi-band ultraprecise
spectroimager (NIMBUS) for SOFIA. This design is capable of characterizing a
large sample of extrasolar planet atmospheres by measuring elemental and
molecular abundances during primary transit and occultation. This wide-field
spectroimager would also provide new insights into Trans-Neptunian Objects
(TNO), Solar System occultations, brown dwarf atmospheres, carbon chemistry in
globular clusters, chemical gradients in nearby galaxies, and galaxy
photometric redshifts. NIMBUS would be the premier ultraprecise spectroimager
by taking advantage of the SOFIA observatory and state of the art infrared
technologies.
This optical design splits the beam into eight separate spectral bandpasses,
centered around key molecular bands from 1 to 4 microns. Each spectral channel
has a wide field of view for simultaneous observations of a reference star that
can decorrelate time-variable atmospheric and optical assembly effects,
allowing the instrument to achieve ultraprecise calibration for imaging and
photometry for a wide variety of astrophysical sources. NIMBUS produces the
same data products as a low-resolution integral field spectrograph over a large
spectral bandpass, but this design obviates many of the problems that preclude
high-precision measurements with traditional slit and integral field
spectrographs. This instrument concept is currently not funded for development.Comment: 14 pages, 9 figures, SPIE Astronomical Telescopes and Instrumentation
201
Infrared Transmission Spectroscopy of the Exoplanets HD209458b and XO-1b Using the Wide Field Camera-3 on the Hubble Space Telescope
Exoplanetary transmission spectroscopy in the near-infrared using the Hubble Space Telescope (HST) NICMOS is currently ambiguous because different observational groups claim different results from the same data, depending on their analysis methodologies. Spatial scanning with HST/WFC3 provides an opportunity to resolve this ambiguity. We here report WFC3 spectroscopy of the giant planets HD 209458b and XO-1b in transit, using spatial scanning mode for maximum photon-collecting efficiency. We introduce an analysis technique that derives the exoplanetary transmission spectrum without the necessity of explicitly decorrelating instrumental effects, and achieves nearly photon-limited precision even at the high flux levels collected in spatial scan mode. Our errors are within 6% (XO-1) and 26% (HD 209458b) of the photon-limit at a resolving power of λ/δλ ~ 70, and are better than 0.01% per spectral channel. Both planets exhibit water absorption of approximately 200 ppm at the water peak near 1.38 μm. Our result for XO-1b contradicts the much larger absorption derived from NICMOS spectroscopy. The weak water absorption we measure for HD 209458b is reminiscent of the weakness of sodium absorption in the first transmission spectroscopy of an exoplanet atmosphere by Charbonneau et al. Model atmospheres having uniformly distributed extra opacity of 0.012 cm2 g−1 account approximately for both our water measurement and the sodium absorption. Our results for HD 209458b support the picture advocated by Pont et al. in which weak molecular absorptions are superposed on a transmission spectrum that is dominated by continuous opacity due to haze and/or dust. However, the extra opacity needed for HD 209458b is grayer than for HD 189733b, with a weaker Rayleigh component
Incidence of Resident Mistreatment in the Learning Environment Across Three Institutions
Introduction: Mistreatment in the learning environment is associated with negative outcomes for trainees. While the Association of American Medical Colleges (AAMC) annual Graduation Questionnaire (GQ) has collected medical student reports of mistreatment for a decade, there is not a similar nationally benchmarked survey for residents. The objective of this study is to explore the prevalence of resident experiences with mistreatment.
Methods: Residents at three academic institutions were surveyed using questions similar to the GQ in 2018. Quantitative data were analyzed based on frequency and Mann-Whitney U tests to detect gender differences.
Results: Nine hundred ninety-six of 2682 residents (37.1%) responded to the survey. Thirty-nine percent of residents reported experiencing at least one incident of mistreatment. The highest reported incidents were public humiliation (23.7%) and subject to offensive sexist remarks/comments (16.0%). Female residents indicated experiencing significantly more incidents of: public embarrassment, public humiliation, offensive sexist remarks, lower evaluations based on gender, denied opportunities for training or rewards, and unwanted sexual advances. Faculty were the most frequent instigators of mistreatment (66.4%). Of trainees who reported experiencing mistreatment, less than one-quarter reported the behavior.
Conclusion: Mistreatment in the academic learning environment is a concern in residency programs. There is increased frequency among female residents
A Spitzer Transmission Spectrum for the Exoplanet GJ 436b, Evidence for Stellar Variability, and Constraints on Dayside Flux Variations
In this paper we describe a uniform analysis of eight transits and eleven
secondary eclipses of the extrasolar planet GJ 436b obtained in the 3.6, 4.5,
and 8.0 micron bands using the IRAC instrument on the Spitzer Space Telescope
between UT 2007 June 29 and UT 2009 Feb 4. We find that the best-fit transit
depths for visits in the same bandpass can vary by as much as 8% of the total
(4.7 sigma significance) from one epoch to the next. Although we cannot
entirely rule out residual detector effects or a time-varying, high-altitude
cloud layer in the planet's atmosphere as the cause of these variations, we
consider the occultation of active regions on the star in a subset of the
transit observations to be the most likely explanation. We reconcile the
presence of magnetically active regions with the lack of significant visible or
infrared flux variations from the star by proposing that the star's spin axis
is tilted with respect to our line of sight, and that the planet's orbit is
therefore likely to be misaligned. These observations serve to illustrate the
challenges associated with transmission spectroscopy of planets orbiting
late-type stars; we expect that other systems, such as GJ 1214, may display
comparably variable transit depths. Our measured 8 micron secondary eclipse
depths are consistent with a constant value, and we place a 1 sigma upper limit
of 17% on changes in the planet's dayside flux in this band. Averaging over the
eleven visits gives us an improved estimate of 0.0452% +/- 0.0027% for the
secondary eclipse depth. We combine timing information from our observations
with previously published data to produce a refined orbital ephemeris, and
determine that the best-fit transit and eclipse times are consistent with a
constant orbital period. [ABRIDGED]Comment: 26 pages, 18 figures, 7 tables in emulateapj format. Accepted for
publication in Ap
Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
The James Webb Space Telescope will revolutionize transiting exoplanet
atmospheric science due to its capability for continuous, long-duration
observations and its larger collecting area, spectral coverage, and spectral
resolution compared to existing space-based facilities. However, it is unclear
precisely how well JWST will perform and which of its myriad instruments and
observing modes will be best suited for transiting exoplanet studies. In this
article, we describe a prefatory JWST Early Release Science (ERS) program that
focuses on testing specific observing modes to quickly give the community the
data and experience it needs to plan more efficient and successful future
transiting exoplanet characterization programs. We propose a multi-pronged
approach wherein one aspect of the program focuses on observing transits of a
single target with all of the recommended observing modes to identify and
understand potential systematics, compare transmission spectra at overlapping
and neighboring wavelength regions, confirm throughputs, and determine overall
performances. In our search for transiting exoplanets that are well suited to
achieving these goals, we identify 12 objects (dubbed "community targets") that
meet our defined criteria. Currently, the most favorable target is WASP-62b
because of its large predicted signal size, relatively bright host star, and
location in JWST's continuous viewing zone. Since most of the community targets
do not have well-characterized atmospheres, we recommend initiating preparatory
observing programs to determine the presence of obscuring clouds/hazes within
their atmospheres. Measurable spectroscopic features are needed to establish
the optimal resolution and wavelength regions for exoplanet characterization.
Other initiatives from our proposed ERS program include testing the instrument
brightness limits and performing phase-curve observations.(Abridged)Comment: This is a white paper that originated from an open discussion at the
Enabling Transiting Exoplanet Science with JWST workshop held November 16 -
18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted
for publication in PAS
Atmospheric retrieval of exoplanets
Exoplanetary atmospheric retrieval refers to the inference of atmospheric
properties of an exoplanet given an observed spectrum. The atmospheric
properties include the chemical compositions, temperature profiles,
clouds/hazes, and energy circulation. These properties, in turn, can provide
key insights into the atmospheric physicochemical processes of exoplanets as
well as their formation mechanisms. Major advancements in atmospheric retrieval
have been made in the last decade, thanks to a combination of state-of-the-art
spectroscopic observations and advanced atmospheric modeling and statistical
inference methods. These developments have already resulted in key constraints
on the atmospheric H2O abundances, temperature profiles, and other properties
for several exoplanets. Upcoming facilities such as the JWST will further
advance this area. The present chapter is a pedagogical review of this exciting
frontier of exoplanetary science. The principles of atmospheric retrievals of
exoplanets are discussed in detail, including parametric models and statistical
inference methods, along with a review of key results in the field. Some of the
main challenges in retrievals with current observations are discussed along
with new directions and the future landscape
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A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
Thousands of transiting exoplanets have been discovered, but spectral analysis of their atmospheres has so far been dominated by a small number of exoplanets and data spanning relatively narrow wavelength ranges (such as 1.1–1.7 micrometres). Recent studies show that some hot-Jupiter exoplanets have much weaker water absorption features in their near-infrared spectra than predicted. The low amplitude of water signatures could be explained by very low water abundances, which may be a sign that water was depleted in the protoplanetary disk at the planet’s formation location, but it is unclear whether this level of depletion can actually occur. Alternatively, these weak signals could be the result of obscuration by clouds or hazes, as found in some optical spectra. Here we report results from a comparative study of ten hot Jupiters covering the wavelength range 0.3–5 micrometres, which allows us to resolve both the optical scattering and infrared molecular absorption spectroscopically. Our results reveal a diverse group of hot Jupiters that exhibit a continuum from clear to cloudy atmospheres. We find that the difference between the planetary radius measured at optical and infrared wavelengths is an effective metric for distinguishing different atmosphere types. The difference correlates with the spectral strength of water, so that strong water absorption lines are seen in clear-atmosphere planets and the weakest features are associated with clouds and hazes. This result strongly suggests that primordial water depletion during formation is unlikely and that clouds and hazes are the cause of weaker spectral signatures
Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.
BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700
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