53 research outputs found
JWST/MIRI Spectroscopy of the Disk of the Young Eruptive Star EX Lup in Quiescence
EX Lup is a low-mass pre-main sequence star that occasionally shows
accretion-related outbursts. Here, we present JWST/MIRI medium resolution
spectroscopy obtained for EX Lup fourteen years after its powerful outburst. EX
Lup is now in quiescence and displays a Class II spectrum. We detect a forest
of emission lines from molecules previously identified in infrared spectra of
classical T Tauri disks: H2O, OH, H2, HCN, C2H2, and CO2. The detection of
organic molecules demonstrates that they are back after disappearing during the
large outburst. Spectral lines from water and OH are for the first time
de-blended and will provide a much improved characterization of their
distribution and density in the inner disk. The spectrum also shows broad
emission bands from warm, sub-micron size amorphous silicate grains at 10 and
18 um. During the outburst, in 2008, crystalline forsterite grains were
annealed in the inner disk within 1 au, but their spectral signatures in the 10
um silicate band later disappeared. With JWST we re-discovered these crystals
via their 19.0, 20.0, and 23.5 um emission, whose strength implies that the
particles are at ~3 au from the star. This suggests that crystalline grains
formed in 2008 were transported outwards and now approach the water snowline,
where they may be incorporated into planetesimals. Containing several key
tracers of planetesimal and planet formation, EX Lup is an ideal laboratory to
study the effects of variable luminosity on the planet-forming material and may
provide explanation for the observed high crystalline fraction in solar system
comets.Comment: 9 pages, 4 figures, accepted for publication in ApJL. JWST/MIRI
spectrum is available for download at https://tinyurl.com/spexodisksJWS
Science with an ngVLA: Resolving the Radio Complexity of EXor and FUor-type Systems with the ngVLA
Episodic accretion may be a common occurrence in the evolution of young
pre-main sequence stars and has important implications for our understanding of
star and planet formation. Many fundamental aspects of what drives the
accretion physics, however, are still unknown. The ngVLA will be a key tool in
understanding the nature of these events. The high spatial resolution, broad
spectral coverage, and unprecedented sensitivity will allow for the detailed
analysis of outburst systems. The proposed frequency range of the ngVLA allows
for observations of the gas, dust, and non-thermal emission from the star and
disk.Comment: 8 pages, 1 figure, To be published in the ASP Monograph Series,
"Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco,
CA
Genome-wide association analysis of susceptibility and clinical phenotype in multiple sclerosis
Multiple sclerosis (MS), a chronic disorder of the central nervous system and common cause of neurological disability in young adults, is characterized by moderate but complex risk heritability. Here we report the results of a genome-wide association study performed in a 1000 prospective case series of well-characterized individuals with MS and group-matched controls using the Sentrix® HumanHap550 BeadChip platform from Illumina. After stringent quality control data filtering, we compared allele frequencies for 551 642 SNPs in 978 cases and 883 controls and assessed genotypic influences on susceptibility, age of onset, disease severity, as well as brain lesion load and normalized brain volume from magnetic resonance imaging exams. A multi-analytical strategy identified 242 susceptibility SNPs exceeding established thresholds of significance, including 65 within the MHC locus in chromosome 6p21.3. Independent replication confirms a role for GPC5, a heparan sulfate proteoglycan, in disease risk. Gene ontology-based analysis shows a functional dichotomy between genes involved in the susceptibility pathway and those affecting the clinical phenotyp
Resolving the Radio Complexity of EXor and FUor-type Systems with the ngVLA
Episodic accretion may be a common occurrence in the evolution of young pre-main sequence stars and has important implications for our understanding of star and planet formation. Many fundamental aspects of what drives the accretion physics, however, are still unknown. The ngVLA will be a key tool in understanding the nature of these events. The high spatial resolution, broad spectral coverage, and unprecedented sensitivity will allow for detailed analysis of outburst systems. The proposed frequency range of the ngVLA allows for observations of the gas, dust, and non-thermal emission from the star and disk
Integrated analysis for a carbon- and water-constrained future: an assessment of drip irrigation in a lettuce production system in eastern Australia
The Australian Government is meeting the challenge of water scarcity and climate change through significant on-farm infrastructure investment to increase water use efficiency and productivity, and secure longer term water supplies. However, it is likely that on-farm infrastructure investment will alter energy consumption and therefore generate considerable greenhouse gas (GHG) emissions, suggesting potential conflicts in terms of mitigation and adaptation policies. In particular, the introduction of a price on carbon may influence the extent to which new irrigation technologies are adopted.
This study evaluated trade-offs between water savings, GHG emissions and economic gain associated with the conversion of a sprinkler (hand shift) irrigation system to a drip (trickle) irrigation system for a lettuce production system in the Lockyer Valley, one of the major vegetable producing regions in Australia. Surprisingly, instead of trade-offs, this study found positive synergies e a win-win situation.
The conversion of the old hand-shift sprinkler irrigation system to a drip irrigation system resulted in significant water savings of almost 2 ML/ha, as well as an overall reduction in GHG emissions. Economic modelling, at a carbon price of 4620/ML/year.
We suggest priority should be given, in the implementation of on-farm infrastructure investment policy, to replacing older inefficient and energy-intensive sprinkler irrigation systems such as hand shift and roll-line. The findings of the study support the use of an integrated approach to avoid possible conflicts in designing national climate change mitigation and adaptation policies, both of which are being developed in Australia
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