157 research outputs found
Measuring Dislocation Density in Aluminum with Resonant Ultrasound Spectroscopy
Dislocations in a material will, when present in enough numbers, change the
speed of propagation of elastic waves. Consequently, two material samples,
differing only in dislocation density, will have different elastic constants, a
quantity that can be measured using Resonant Ultrasound Spectroscopy.
Measurements of this effect on aluminum samples are reported. They compare well
with the predictions of the theory.Comment: 4 pages, 2 figure
Characterizing the Near-infrared Spectra of Flares from TRAPPIST-1 During JWST Transit Spectroscopy Observations
We present the first analysis of JWST near-infrared spectroscopy of stellar
flares from TRAPPIST-1 during transits of rocky exoplanets. Four flares were
observed from 0.6--2.8 m with NIRISS and 0.6--3.5 m with NIRSpec
during transits of TRAPPIST-1b, f, and g. We discover P and Br
line emission and characterize flare continuum at wavelengths from 1--3.5
m for the first time. Observed lines include H,
P-P, Br, He I 0.7062m, two Ca II
infrared triplet (IRT) lines, and the He I IRT. We observe a reversed Paschen
decrement from P-P alongside changes in the light curve shapes
of these lines. The continuum of all four flares is well-described by blackbody
emission with an effective temperature below 5300 K, lower than temperatures
typically observed at optical wavelengths. The 0.6--1 m spectra were
convolved with the TESS response, enabling us to measure the flare rate of
TRAPPIST-1 in the TESS bandpass. We find flares of 10 erg large enough
to impact transit spectra occur at a rate of 3.6 flare
d, 10 higher than previous predictions from K2. We measure
the amount of flare contamination at 2 m for the TRAPPIST-1b and f
transits to be 500450 and 2100400 ppm, respectively. We find up to
80% of flare contamination can be removed, with mitigation most effective from
1.0--2.4 m. These results suggest transits affected by flares may still be
useful for atmospheric characterization efforts.Comment: 29 pages, 17 figures, 3 tables, accepted to The Astrophysical Journa
Transcriptome profiling of grapevine seedless segregants during berry development reveals candidate genes associated with berry weight
Indexación: Web of Science; PubMedBackground
Berry size is considered as one of the main selection criteria in table grape breeding programs. However, this is a quantitative and polygenic trait, and its genetic determination is still poorly understood. Considering its economic importance, it is relevant to determine its genetic architecture and elucidate the mechanisms involved in its expression. To approach this issue, an RNA-Seq experiment based on Illumina platform was performed (14 libraries), including seedless segregants with contrasting phenotypes for berry weight at fruit setting (FST) and 6–8 mm berries (B68) phenological stages.
Results
A group of 526 differentially expressed (DE) genes were identified, by comparing seedless segregants with contrasting phenotypes for berry weight: 101 genes from the FST stage and 463 from the B68 stage. Also, we integrated differential expression, principal components analysis (PCA), correlations and network co-expression analyses to characterize the transcriptome profiling observed in segregants with contrasting phenotypes for berry weight. After this, 68 DE genes were selected as candidate genes, and seven candidate genes were validated by real time-PCR, confirming their expression profiles.
Conclusions
We have carried out the first transcriptome analysis focused on table grape seedless segregants with contrasting phenotypes for berry weight. Our findings contributed to the understanding of the mechanisms involved in berry weight determination. Also, this comparative transcriptome profiling revealed candidate genes for berry weight which could be evaluated as selection tools in table grape breeding programs.http://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-016-0789-
ATOCA: an algorithm to treat order contamination. Application to the NIRISS SOSS mode
After a successful launch, the James Webb Space Telescope is preparing to
undertake one of its principal missions, the characterization of the
atmospheres of exoplanets. The Single Object Slitless Spectroscopy (SOSS) mode
of the Near Infrared Imager and Slitless Spectrograph (NIRISS) is the only
observing mode that has been specifically designed for this objective. It
features a wide simultaneous spectral range (0.6--2.8\,\micron) through two
spectral diffraction orders. However, due to mechanical constraints, these two
orders overlap slightly over a short range, potentially introducing a
``contamination'' signal in the extracted spectrum. We show that for a typical
box extraction, this contaminating signal amounts to 1\% or less over the
1.6--2.8\,\micron\ range (order 1), and up to 1\% over the 0.85--0.95\,\micron\
range (order 2). For observations of exoplanet atmospheres (transits, eclipses
or phase curves) where only temporal variations in flux matter, the
contamination signal typically biases the results by order of 1\% of the
planetary atmosphere spectral features strength. To address this problem, we
developed the Algorithm to Treat Order ContAmination (ATOCA). By constructing a
linear model of each pixel on the detector, treating the underlying incident
spectrum as a free variable, ATOCA is able to perform a simultaneous extraction
of both orders. We show that, given appropriate estimates of the spatial trace
profiles, the throughputs, the wavelength solutions, as well as the spectral
resolution kernels for each order, it is possible to obtain an extracted
spectrum accurate to within 10\,ppm over the full spectral range.Comment: Submitted to PASP. 22 pages, 12 figure
Awesome SOSS: Transmission Spectroscopy of WASP-96b with NIRISS/SOSS
The future is now - after its long-awaited launch in December 2021, JWST
began science operations in July 2022 and is already revolutionizing exoplanet
astronomy. The Early Release Observations (ERO) program was designed to provide
the first images and spectra from JWST, covering a multitude of science cases
and using multiple modes of each on-board instrument. Here, we present
transmission spectroscopy observations of the hot-Saturn WASP-96b with the
Single Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and
Slitless Spectrograph, observed as part of the ERO program. As the SOSS mode
presents some unique data reduction challenges, we provide an in-depth
walk-through of the major steps necessary for the reduction of SOSS data:
including background subtraction, correction of 1/f noise, and treatment of the
trace order overlap. We furthermore offer potential routes to correct for field
star contamination, which can occur due to the SOSS mode's slitless nature. By
comparing our extracted transmission spectrum with grids of atmosphere models,
we find an atmosphere metallicity between 1x and 5x solar, and a solar
carbon-to-oxygen ratio. Moreover, our models indicate that no grey cloud deck
is required to fit WASP-96b's transmission spectrum, but find evidence for a
slope shortward of 0.9m, which could either be caused by enhanced Rayleigh
scattering or the red wing of a pressure-broadened Na feature. Our work
demonstrates the unique capabilities of the SOSS mode for exoplanet
transmission spectroscopy and presents a step-by-step reduction guide for this
new and exciting instrument.Comment: MNRAS, in press. Updated to reflect published versio
Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis
BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London
Recommended from our members
A protocol for an intercomparison of biodiversity and ecosystem services models using harmonized land-use and climate scenarios
To support the assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the IPBES Expert Group on Scenarios and Models is carrying out an intercomparison of biodiversity and ecosystem services models using harmonized scenarios (BES-SIM). The goals of BES-SIM are (1) to project the global impacts of land-use and climate change on biodiversity and ecosystem services (i.e., nature's contributions to people) over the coming decades, compared to the 20th century, using a set of common metrics at multiple scales, and (2) to identify model uncertainties and research gaps through the comparisons of projected biodiversity and ecosystem services across models. BES-SIM uses three scenarios combining specific Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs)-SSP1xRCP2.6, SSP3xRCP6.0, SSP5xRCP8.6-to explore a wide range of land-use change and climate change futures. This paper describes the rationale for scenario selection, the process of harmonizing input data for land use, based on the second phase of the Land Use Harmonization Project (LUH2), and climate, the biodiversity and ecosystem services models used, the core simulations carried out, the harmonization of the model output metrics, and the treatment of uncertainty. The results of this collaborative modeling project will support the ongoing global assessment of IPBES, strengthen ties between IPBES and the Intergovernmental Panel on Climate Change (IPCC) scenarios and modeling processes, advise the Convention on Biological Diversity (CBD) on its development of a post-2020 strategic plans and conservation goals, and inform the development of a new generation of nature-centred scenarios
A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot
Jupiters'') have been the subject of extensive efforts to determine their
atmospheric properties using thermal emission measurements from the Hubble and
Spitzer Space Telescopes. However, previous studies have yielded inconsistent
results because the small sizes of the spectral features and the limited
information content of the data resulted in high sensitivity to the varying
assumptions made in the treatment of instrument systematics and the atmospheric
retrieval analysis. Here we present a dayside thermal emission spectrum of the
ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on JWST. The
data span 0.85 to 2.85 m in wavelength at an average resolving power of
400 and exhibit minimal systematics. The spectrum shows three water emission
features (at 6 confidence) and evidence for optical opacity,
possibly due to H, TiO, and VO (combined significance of 3.8).
Models that fit the data require a thermal inversion, molecular dissociation as
predicted by chemical equilibrium, a solar heavy element abundance
(''metallicity'', M/H = 1.03 solar), and a
carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside
brightness temperature map, which shows a peak in temperature near the
sub-stellar point that decreases steeply and symmetrically with longitude
toward the terminators.Comment: JWST ERS bright star observations. Uploaded to inform JWST Cycle 2
proposals. Manuscript under review. 50 pages, 14 figures, 2 table
- …