50 research outputs found
It Sounds like It Feels: Preliminary Exploration of an Aeroacoustic Diagnostic Protocol for Singers
To date, no established protocol exists for measuring functional voice changes in singers with subclinical singing-voice complaints. Hence, these may go undiagnosed until they progress into greater severity. This exploratory study sought to (1) determine which scale items in the self-perceptual Evaluation of Ability to Sing Easily (EASE) are associated with instrumental voice measures, and (2) construct as proof-of-concept an instrumental index related to singers’ perceptions of their vocal function and health status. Eighteen classical singers were acoustically recorded in a controlled environment singing an /a/ vowel using soft phonation. Aerodynamic data were collected during a softly sung /papapapapapapa/ task with the KayPENTAX Phonatory Aerodynamic System. Using multi and univariate linear regression techniques, CPPS, vibrato jitter, vibrato shimmer, and an efficiency ratio (SPL/PSub) were included in a significant model (p < 0.001) explaining 62.4% of variance in participants’ composite scores of three scale items related to vocal fatigue. The instrumental index showed a significant association (p = 0.001) with the EASE vocal fatigue subscale overall. Findings illustrate that an aeroacoustic instrumental index may be useful for monitoring functional changes in the singing voice as part of a multidimensional diagnostic approach to preventative and rehabilitative voice healthcare for professional singing-voice users
Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data
The formation and evolution pathway for the directly-imaged multi-planetary
system HR 8799 remains mysterious. Accurate constraints on the chemical
composition of the planetary atmosphere(s) are key to solving the mystery. We
perform a detailed atmospheric retrieval on HR 8799~c to infer the chemical
abundances and abundance ratios using a combination of photometric data along
with low- and high-resolution spectroscopic data (R20-35,000). We
specifically retrieve [C/H], [O/H], and C/O and find them to be
0.55, 0.47, and 0.67 at
68\% confidence. The super-stellar C and O abundances, yet a stellar C/O ratio,
reveal a potential formation pathway for HR 8799~c. Planet c, and likely the
other gas giant planets in the system, formed early on (likely within 1
Myr), followed by further atmospheric enrichment in C and O through the
accretion of solids beyond the CO iceline. The enrichment either preceded or
took place during the early phase of the inward migration to the planet current
locations.Comment: 19 pages, 6 figures, 3 tables, accepted to AAS journal
Retrieving the C and O Abundances of HR 7672~AB: a Solar-Type Primary Star with a Benchmark Brown Dwarf
A benchmark brown dwarf (BD) is a BD whose properties (e.g., mass and
chemical composition) are precisely and independently measured. Benchmark BDs
are valuable in testing theoretical evolutionary tracks, spectral synthesis,
and atmospheric retrievals for sub-stellar objects. Here, we report results of
atmospheric retrieval on a synthetic spectrum and a benchmark BD -- HR 7672~B
-- with \petit. First, we test the retrieval framework on a synthetic PHOENIX
BT-Settl spectrum with a solar composition. We show that the retrieved C and O
abundances are consistent with solar values, but the retrieved C/O is
overestimated by 0.13-0.18, which is 4 times higher than the formal error
bar. Second, we perform retrieval on HR 7672~B using high spectral resolution
data (R=35,000) from the Keck Planet Imager and Characterizer (KPIC) and near
infrared photometry. We retrieve [C/H], [O/H], and C/O to be ,
, and . These values are consistent with those of HR
7672~A within 1.5-. As such, HR 7672~B is among only a few benchmark
BDs (along with Gl 570~D and HD 3651~B) that have been demonstrated to have
consistent elemental abundances with their primary stars. Our work provides a
practical procedure of testing and performing atmospheric retrieval, and sheds
light on potential systematics of future retrievals using high- and
low-resolution data.Comment: 29 pages, 17 figures, 5 tables, resubmitted to AAS journals after
first revisio
A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy
Direct imaging studies have mainly used low-resolution spectroscopy
() to study the atmospheres of giant exoplanets and brown dwarf
companions, but the presence of clouds has often led to degeneracies in the
retrieved atmospheric abundances (e.g. C/O, metallicity). This precludes clear
insights into the formation mechanisms of these companions. The Keck Planet
Imager and Characterizer (KPIC) uses adaptive optics and single-mode fibers to
transport light into NIRSPEC ( in band), and aims to address
these challenges with high-resolution spectroscopy. Using an atmospheric
retrieval framework based on petitRADTRANS, we analyze KPIC high-resolution
spectrum (m) and archival low-resolution spectrum (m)
of the benchmark brown dwarf HD 4747 B (,
au, K). We find that our measured C/O
and metallicity for the companion from the KPIC high-resolution spectrum agree
with that of its host star within . The retrieved parameters from
the band high-resolution spectrum are also independent of our choice of
cloud model. In contrast, the retrieved parameters from the low-resolution
spectrum are highly sensitive to our chosen cloud model. Finally, we detect CO,
HO, and CH (volume mixing ratio of log(CH)=) in this
L/T transition companion with the KPIC data. The relative molecular abundances
allow us to constrain the degree of chemical disequilibrium in the atmosphere
of HD 4747 B, and infer a vertical diffusion coefficient that is at the upper
limit predicted from mixing length theory.Comment: 33 pages, 16 figures, Accepted to Ap
Structural and functional basis for RNA cleavage by Ire1
BACKGROUND: The unfolded protein response (UPR) controls the protein folding capacity of the endoplasmic reticulum (ER). Central to this signaling pathway is the ER-resident bifunctional transmembrane kinase/endoribonuclease Ire1. The endoribonuclease (RNase) domain of Ire1 initiates a non-conventional mRNA splicing reaction, leading to the production of a transcription factor that controls UPR target genes. The mRNA splicing reaction is an obligatory step of Ire1 signaling, yet its mechanism has remained poorly understood due to the absence of substrate-bound crystal structures of Ire1, the lack of structural similarity between Ire1 and other RNases, and a scarcity of quantitative enzymological data. Here, we experimentally define the active site of Ire1 RNase and quantitatively evaluate the contribution of the key active site residues to catalysis.
RESULTS: This analysis and two new crystal structures suggest that Ire1 RNase uses histidine H1061 and tyrosine Y1043 as the general acid-general base pair contributing \u3e/=7.6 kcal/mol and 1.4 kcal/mol to transition state stabilization, respectively, and asparagine N1057 and arginine R1056 for coordination of the scissile phosphate. Investigation of the stem-loop recognition revealed that additionally to the stem-loops derived from the classic Ire1 substrates HAC1 and Xbp1 mRNA, Ire1 can site-specifically and rapidly cleave anticodon stem-loop (ASL) of unmodified tRNAPhe, extending known substrate specificity of Ire1 RNase.
CONCLUSIONS: Our data define the catalytic center of Ire1 RNase and suggest a mechanism of RNA cleavage: each RNase monomer apparently contains a separate catalytic apparatus for RNA cleavage, whereas two RNase subunits contribute to RNA stem-loop docking. Conservation of the key residues among Ire1 homologues suggests that the mechanism elucidated here for yeast Ire1 applies to Ire1 in metazoan cells, and to the only known Ire1 homologue RNase L
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure