67 research outputs found
Deep z-band observations of the coolest y dwarf
Taisiya G. Kopytova, et al., “Deep z-band observations of the coolest y dwarf”, The Astrophysical Journal, Vol. 797(1), November 2014. © 2014. The American Astronomical Society.WISE J085510.83-071442.5 (hereafter, WISE 0855-07) is the coolest Y dwarf known to date and is located at a distance of 2.31 ± 0.08 pc, giving it the fourth largest parallax of any known star or brown dwarf system. We report deep z-band observations of WISE 0855-07 using FORS2 on UT1/Very Large Telescope. We do not detect any counterpart to WISE 0855-07 in our z-band images and estimate a brightness upper limit of AB mag > 24.8 (F ν <0.45 μJy) at 910 ± 65 nm with 3σ confidence. We combine our z-band upper limit with previous near- and mid-infrared photometry to place constraints on the atmospheric properties of WISE 0855-07 via comparison to models which implement water clouds in the atmospheres of T eff <300 K substellar objects. We find that none of the available models that implement water clouds can completely reproduce the observed spectral energy distribution of WISE 0855-07. Every model significantly disagrees with the (3.6 μm/4.5 μm) flux ratio and at least one other bandpass. Since methane is predicted to be the dominant absorber at 3-4 μm, these mismatches might point to an incorrect or incomplete treatment of methane in current models. We conclude that (a) WISE0855-07 has T eff 200-250 K, (b)Peer reviewe
Conspiracy theories: why they are believed and how they can be challenged
The current study aimed: (i) to identify personal characteristics associated with endorsing conspiracy theories; and (ii) to investigate methods for dispelling conspiracy beliefs. Participants were shown a single conspiracy theory and they also completed questionnaires about their reasoning skills, types of information processing (System 1 vs. System 2), endorsement of paranormal beliefs, locus of control and pattern perception. To challenge the endorsement of the conspiracy, participants read either: (i) neutral information; (ii) a critical analysis of the vignette; (iii) a critical analysis of the vignette with discussion of realistic consequences; or (iv) a critical analysis of the vignette with “feeling of control” priming. Only addressing the consequences of the conspiracy theory decreased its endorsement. Furthermore, only type of information processing and belief in paranormal phenomena, were associated with endorsement of the conspiracy. These findings are discussed in relation to previous studies and theories of conspiratorial ideation
A systematic review and meta-analysis of the effect of dispatcher-assisted CPR on outcomes from sudden cardiac arrest in adults and children
Background: Dispatcher-assisted cardiopulmonary resuscitation (DA-CPR) has been reported in individual studies to significantly increase the rate of bystander CPR and survival from cardiac arrest. Methods: We undertook a systematic review and meta-analysis to evaluate the impact of DA-CPR programs on key clinical outcomes following out-of-hospital cardiac arrest. We searched the PubMED, EMBASE, CINAHL, ERIC and Cochrane Central Register of Controlled Trials databases from inception until July 2018. Eligible studies compared systems with and without dispatcher-assisted CPR programs. The results of included studies were classified into 3 categories for the purposes of more accurate analysis: comparison of outcomes in systems with DA-CPR programs, case-based comparison of DA-CPR to bystander CPR, and case-based comparisons of DA-CPR to no CPR before EMS arrival. The GRADE system was used to assess certainty of evidence at an outcome level. We used random-effects models to produce summary effect sizes across all outcomes. Results: Of 5531 citations screened, 33 studies were eligible for inclusion. All included studies were observational. Evidence certainty across all outcomes was assessed as low or very low. In system-level and patient-level comparisons, the provision of DA-CPR compared with no DA-CPR was consistently associated with improved outcome across all analyses. Comparison of DA-CPR to bystander CPR produced conflicting results. Findings were consistent across sensitivity analyses and the pediatric sub-group. Conclusion: These results support the recommendation that dispatchers provide CPR instructions to callers for adults and children with suspected OHCA. Review registration: PROSPERO- CRD42018091427
Transport of Explosive Residue Surrogates in Saturated Porous Media
Department of Defense operational ranges may become contaminated by particles of explosives residues (ER) as a result of low-order detonations of munitions. The goal of this study was to determine the extent to which particles of ER could migrate through columns of sandy sediment, representing model aquifer materials. Transport experiments were conducted in saturated columns (2 × 20 cm) packed with different grain sizes of clean sand or glass beads. Fine particles (approximately 2 to 50 μm) of 2,6-dinitrotoluene (DNT) were used as a surrogate for ER. DNT particles were applied to the top 1 cm of sand or beads in the columns, and the columns were subsequently leached with artificial groundwater solutions. DNT migration occurred as both dissolved and particulate phases. Concentration differences between unfiltered and filtered samples indicate that particulate DNT accounted for up to 41% of the mass recovered in effluent samples. Proportionally, more particulate than dissolved DNT was recovered in effluent solutions from columns with larger grain sizes, while total concentrations of DNT in effluent were inversely related to grain size. Of the total DNT mass applied to the uppermost layer of the column, <3% was recovered in the effluent with the bulk remaining in the top 2 cm of the column. Our results suggest there is some potential for subsurface migration of ER particles and that most of the particles will be retained over relatively short transport distances
Generalized interpolation and definability
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32849/1/0000225.pd
Listening to patients: using verbal data in the validation of the Aberdeen Measures of Impairment, Activity Limitation and Participation Restriction (Ab-IAP)
Peer reviewedPublisher PD
The JWST Early-Release Science Program for Direct Observations of Exoplanetary Systems Ii: A 1 To 20 Μm Spectrum of the Planetary-Mass Companion Vhs 1256-1257 B
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a (∼8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color-magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST\u27s NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20 μm at resolutions of ∼1000-3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion
Variability of Brown Dwarfs
Brown dwarfs constitute a missing link between low-mass stars and giant
planets. Their atmospheres display chemical species typical of planets, and one
could wonder whether they also have weather-like patterns. While brown dwarf
surface features cannot be directly resolved, the photometric and spectroscopic
modulations induced by these features, as they rotate in and out of view,
provide a wealth of information on the evolution of their atmosphere. A review
of brown dwarfs variability through the L, T and Y spectral types sequence is
presented, as well as the constraints that they set on the nature of
weather-like patterns on their surface.Comment: Accepted chapter in the "Handbook of Exoplanets"; Springe
A Giant Planet Candidate Transiting a White Dwarf
Astronomers have discovered thousands of planets outside the solar system,
most of which orbit stars that will eventually evolve into red giants and then
into white dwarfs. During the red giant phase, any close-orbiting planets will
be engulfed by the star, but more distant planets can survive this phase and
remain in orbit around the white dwarf. Some white dwarfs show evidence for
rocky material floating in their atmospheres, in warm debris disks, or orbiting
very closely, which has been interpreted as the debris of rocky planets that
were scattered inward and tidally disrupted. Recently, the discovery of a
gaseous debris disk with a composition similar to ice giant planets
demonstrated that massive planets might also find their way into tight orbits
around white dwarfs, but it is unclear whether the planets can survive the
journey. So far, the detection of intact planets in close orbits around white
dwarfs has remained elusive. Here, we report the discovery of a giant planet
candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4
days. The planet candidate is roughly the same size as Jupiter and is no more
than 14 times as massive (with 95% confidence). Other cases of white dwarfs
with close brown dwarf or stellar companions are explained as the consequence
of common-envelope evolution, wherein the original orbit is enveloped during
the red-giant phase and shrinks due to friction. In this case, though, the low
mass and relatively long orbital period of the planet candidate make
common-envelope evolution less likely. Instead, the WD 1856+534 system seems to
demonstrate that giant planets can be scattered into tight orbits without being
tidally disrupted, and motivates searches for smaller transiting planets around
white dwarfs.Comment: 50 pages, 12 figures, 2 tables. Published in Nature on Sept. 17,
2020. The final authenticated version is available online at:
https://www.nature.com/articles/s41586-020-2713-
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