118 research outputs found
Related Enteric Viruses Have Different Requirements for Host Microbiota in Mice
Accumulating evidence suggests that intestinal bacteria promote enteric virus infection in mice. For example, previous work demonstrated that antibiotic treatment of mice prior to oral infection with poliovirus reduced viral replication and pathogenesis. Here, we examined the effect of antibiotic treatment on infection with coxsackievirus B3 (CVB3), a picornavirus closely related to poliovirus. We treated mice with a mixture of five antibiotics to deplete host microbiota and examined CVB3 replication and pathogenesis following oral inoculation. We found that, as seen with poliovirus, CVB3 shedding and pathogenesis were reduced in antibiotic-treated mice. While treatment with just two antibiotics, vancomycin and ampicillin, was sufficient to reduce CVB3 replication and pathogenesis, this treatment had no effect on poliovirus. The quantity and composition of bacterial communities were altered by treatment with the five-antibiotic cocktail and by treatment with vancomycin and ampicillin. To determine whether more-subtle changes in bacterial populations impact viral replication, we examined viral infection in mice treated with milder antibiotic regimens. Mice treated with one-tenth the standard concentration of the normal antibiotic cocktail supported replication of poliovirus but not CVB3. Importantly, a single dose of one antibiotic, streptomycin, was sufficient to reduce CVB3 shedding and pathogenesis while having no effect on poliovirus shedding and pathogenesis. Overall, replication and pathogenesis of CVB3 are more sensitive to antibiotic treatment than poliovirus, indicating that closely related viruses may differ with respect to their reliance on microbiota.
IMPORTANCE Recent data indicate that intestinal bacteria promote intestinal infection of several enteric viruses. Here, we show that coxsackievirus, an enteric virus in the picornavirus family, also relies on microbiota for intestinal replication and pathogenesis. Relatively minor depletion of the microbiota was sufficient to decrease coxsackievirus infection, while poliovirus infection was unaffected. Surprisingly, a single dose of one antibiotic was sufficient to reduce coxsackievirus infection. Therefore, these data indicate that closely related viruses may differ with respect to their reliance on microbiota
A Library of Self-Consistent Simulated Exoplanet Atmospheres
We present a publicly available library of model atmospheres with
radiative-convective equilibrium Pressure-Temperature (-) profiles fully
consistent with equilibrium chemical abundances, and the corresponding emission
and transmission spectrum with R5000 at 0.2 m decreasing to
R35 at 30 m, for 89 hot Jupiter exoplanets, for four re-circulation
factors, six metallicities and six C/O ratios. We find the choice of
condensation process (local/rainout) alters the - profile and thereby the
spectrum substantially, potentially detectable by JWST. We find H opacity
can contribute to form a strong temperature inversion in ultra-hot Jupiters for
C/O ratios 1 and can make transmission spectra features flat in the
optical, alongside altering the entire emission spectra. We highlight how
adopting different model choices such as thermal ionisation, opacities,
line-wing profiles and the methodology of varying the C/O ratio, effects the
- structure and the spectrum. We show the role of Fe opacity to form
primary/secondary inversion in the atmosphere. We use WASP-17b and WASP-121b as
test cases to demonstrate the effect of grid parameters across their full
range, while highlighting some important findings, concerning the overall
atmospheric structure, chemical transition regimes and their observables.
Finally, we apply this library to the current transmission and emission spectra
observations of WASP-121b, which shows HO and tentative evidence for VO at
the limb, and HO emission feature indicative of inversion on the dayside,
with very low energy redistribution, thereby demonstrating the applicability of
library for planning and interpreting observations of transmission and emission
spectrum.Comment: 26 pages, 19 figures in the main paper. 13 pages, 6 figures, 3 tables
in the supplementary material attached with the main paper here. Accepted for
Publication in MNRAS. Full grid of model P-T profiles, chemical abundances,
transmission and emission spectra, contribution functions are available here,
https://drive.google.com/drive/folders/1zCCe6HICuK2nLgnYJFal7W4lyunjU4J
The Hubble PanCET program: The near-ultraviolet transmission spectrum of WASP-79b
We present Hubble Space Telescope (HST) transit observations of the
Hot-Jupiter WASP-79b acquired with the Space Telescope Imaging Spectrograph
(STIS) in the near ultraviolet (NUV). Two transit observations, part of the
PanCET program, are used to obtain the transmission spectra of the planet
between 2280 and 3070{\AA}. We correct for systematic effects in the raw data
using the jitter engineering parameters and polynomial modelling to fit the
white light curves of the two transits. We observe an increase in the
planet-to-star radius ratio at short wavelengths, but no spectrally resolved
absorption lines. The difference between the radius ratios at 2400 and
3000{\AA} reaches (4.5). Although the NUV
transmission spectrum does not show evidence of hydrodynamical escape, the
strong atmospheric features are likely due to species at very high altitudes.
We performed a 1D simulation of the temperature and composition of WASP-79b
using Exo-REM. The temperature pressure profile crosses condensation curves of
radiatively active clouds, particularly MnS, MgSiO, Fe, and
AlO. Still, none of these species produces the level of observed
absorption at short wavelengths and can explain the observed increase in the
planet's radius. WASP-79b's transit depth reaches 23 scale height, making it
one of the largest spectral features observed in an exoplanet at this
temperature (1700 K). The comparison of WASP-79b's transmission spectrum
with three warmer hot Jupiters shows a similar level of absorption to WASP-178b
and WASP-121b between 0.2 and 0.3m, while HAT-P-41b's spectrum is flat.
The features could be explained by SiO absorption.Comment: Accepted for publication January 31, 2023 in the Journal Astronomy &
Astrophysic
A JWST NIRSpec Phase Curve for WASP-121b: Dayside Emission Strongest Eastward of the Substellar Point and Nightside Conditions Conducive to Cloud Formation
We present the first exoplanet phase curve measurement made with the JWST
NIRSpec instrument, highlighting the exceptional stability of this
newly-commissioned observatory for exoplanet climate studies. The target,
WASP-121b, is an ultrahot Jupiter with an orbital period of 30.6 hr. We analyze
two broadband light curves generated for the NRS1 and NRS2 detectors, covering
wavelength ranges of 2.70-3.72 micron and 3.82-5.15 micron, respectively. Both
light curves exhibit minimal systematics, with approximately linear drifts in
the baseline flux level of 30 ppm/hr (NRS1) and 10 ppm/hr (NRS2). Assuming a
simple brightness map for the planet described by a low-order spherical
harmonic dipole, our light curve fits suggest that the phase curve peaks
coincide with orbital phases deg (NRS1) and deg
(NRS2) prior to mid-eclipse. This is consistent with the strongest dayside
emission emanating from eastward of the substellar point. We measure
planet-to-star emission ratios of ppm (NRS1) and
ppm (NRS2) for the dayside hemisphere, and ppm (NRS1) and ppm (NRS2) for the nightside hemisphere. The latter nightside emission
ratios translate to planetary brightness temperatures of K (NRS1)
and K (NRS2), which are low enough for a wide range of
refractory condensates to form, including enstatite and forsterite. A nightside
cloud deck may be blocking emission from deeper, hotter layers of the
atmosphere, potentially helping to explain why cloud-free 3D general
circulation model simulations systematically over-predict the nightside
emission for WASP-121b.Comment: Accepted for publication in Astrophysical Journal Letters on December
29, 202
The Hubble PanCET program: Long-term chromospheric evolution and flaring activity of the M dwarf host GJ 3470
Neptune-size exoplanets seem particularly sensitive to atmospheric
evaporation, making it essential to characterize the stellar high-energy
radiation that drives this mechanism. This is particularly important with M
dwarfs, which emit a large and variable fraction of their luminosity in the UV
and can display strong flaring behavior. The warm Neptune GJ3470b, hosted by an
M2 dwarf, was found to harbor a giant hydrogen exosphere thanks to 3 transits
observed with the HST/STIS. Here we report on 3 additional transit observations
from the PanCET program, obtained with the HST/COS. These data confirm the
absorption signature from GJ3470b's exosphere in the stellar Ly-alpha line and
demonstrate its stability over time. No planetary signatures are detected in
other lines, setting a 3sigma limit on GJ3470b's FUV radius at 1.3x its Roche
lobe radius. We detect 3 flares from GJ3470. They show different spectral
energy distributions but peak consistently in the Si III line, which traces
intermediate-temperature layers in the transition region. These layers appear
to play a particular role in GJ3470's activity as emission lines that form at
lower or higher temperatures than Si III evolved differently over the long
term. Based on the measured emission lines, we derive synthetic XUV spectra for
the 6 observed quiescent phases, covering one year, as well as for the 3
flaring episodes. Our results suggest that most of GJ3470's quiescent
high-energy emission comes from the EUV domain, with flares amplifying the FUV
emission more strongly. The hydrogen photoionization lifetimes and mass loss
derived for GJ3470b show little variation over the epochs, in agreement with
the stability of the exosphere. Simulations informed by our XUV spectra are
required to understand the atmospheric structure and evolution of GJ3470b and
the role played by evaporation in the formation of the hot-Neptune desert.Comment: 21 pages, 18 figures, accepted in A&
Abundance measurements of H<sub>2</sub>O and carbon-bearing species in the atmosphere of WASP-127b confirm its super-solar metallicity
The chemical abundances of exoplanet atmospheres may provide valuable information about the bulk compositions, formation pathways, and evolutionary histories of planets. Exoplanets with large, relatively cloud-free atmospheres, and which orbit bright stars provide the best opportunities for accurate abundance measurements. For this reason, we measured the transmission spectrum of the bright (V∼10.2), large (), sub-Saturn mass () exoplanet WASP-127b across the near-UV to near-infrared wavelength range (0.3–5 μm), using the Hubble and Spitzer Space Telescopes. Our results show a feature-rich transmission spectrum, with absorption from Na, , and , and wavelength-dependent scattering from small-particle condensates. We ran two types of atmospheric retrieval models: one enforcing chemical equilibrium, and the other which fit the abundances freely. Our retrieved abundances at chemical equilibrium for Na, O and C are all super-solar, with abundances relative to solar values of , , and respectively. Despite giving conflicting C/O ratios, both retrievals gave super-solar volume mixing ratios, which adds to the likelihood that WASP-127b’s bulk metallicity is super-solar, since abundance is highly sensitive to atmospheric metallicity. We detect water at a significance of 13.7 σ. Our detection of Na is in agreement with previous ground-based detections, though we find a much lower abundance, and we also do not find evidence for Li or K despite increased sensitivity. In the future, spectroscopy with JWST will be able to constrain WASP-127b’s C/O ratio, and may reveal the formation history of this metal-enriched, highly observable exoplanet
A JWST NIRSpec Phase Curve for WASP-121b: Dayside Emission Strongest Eastward of the Substellar Point and Nightside Conditions Conducive to Cloud Formation
We present the first exoplanet phase-curve measurement made with the JWST NIRSpec instrument, highlighting the exceptional stability of this newly commissioned observatory for exoplanet climate studies. The target, WASP-121b, is an ultrahot Jupiter with an orbital period of 30.6 hr. We analyze two broadband light curves generated for the NRS1 and NRS2 detectors, covering wavelength ranges of 2.70–3.72 μm and 3.82–5.15 μm, respectively. Both light curves exhibit minimal systematics, with approximately linear drifts in the baseline flux level of 30 ppm hr−1 (NRS1) and 10 ppm hr−1 (NRS2). Assuming a simple brightness map for the planet described by a low-order spherical harmonic dipole, our light-curve light curve fits suggest that the phase curve peaks coincide with orbital phases 3.°36 ± 0.°11 (NRS1) and 2.°66 ± 0.°12 (NRS2) prior to mideclipse. This is consistent with the strongest dayside emission emanating from eastward of the substellar point. We measure planet-to-star emission ratios of 3924 ± 7 ppm (NRS1) and 4924 ± 9 ppm (NRS2) for the dayside hemisphere and 136 ± 8 ppm (NRS1) and 630 ± 10 ppm (NRS2) for the nightside hemisphere. The latter nightside emission ratios translate to planetary brightness temperatures of 926 ± 12 K (NRS1) and 1122 ± 10 K (NRS2), which are low enough for a wide range of refractory condensates to form, including enstatite and forsterite. A nightside cloud deck may be blocking emission from deeper, hotter layers of the atmosphere, potentially helping to explain why cloud-free 3D general circulation model simulations systematically overpredict the nightside emission for WASP-121b
Participant Perceptions of Twitter Research Ethics
Social computing systems such as Twitter present new research sites that have provided billions of data points to researchers. However, the availability of public social media data has also presented ethical challenges. As the research community works to create ethical norms, we should be considering users’ concerns as well. With this in mind, we report on an exploratory survey of Twitter users’ perceptions of the use of tweets in research. Within our survey sample, few users were previously aware that their public tweets could be used by researchers, and the majority felt that researchers should not be able to use tweets without consent. However, we find that these attitudes are highly contextual, depending on factors such as how the research is conducted or disseminated, who is conducting it, and what the study is about. The findings of this study point to potential best practices for researchers conducting observation and analysis of public data
Identification of carbon dioxide in an exoplanet atmosphere
Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called 'metallicity')1-3, and thus the formation processes of the primary atmospheres of hot gas giants4-6. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets7-9. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification10-12. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme13,14. The data used in this study span 3.0-5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative-convective-thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models
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