167 research outputs found
Strategy for Dynamic Wisp Removal in James Webb Space Telescope NIRCam Images
The James Webb Space Telescope (JWST) near-infrared camera (NIRCam) has been
found to exhibit serious wisp-like structures in four of its eight
short-wavelength detectors. The exact structure and strength of these wisps is
highly variable with the position and orientation of JWST, so the use of static
templates is non-optimal. Here we investigate a dynamic strategy to mitigate
these wisps using long-wavelength reference images. Based on a suite of
experiments where we embed a worst-case scenario median-stacked wisp into
wisp-free images, we define suitable parameters for our wisp removal strategy.
Using this setup we re-process wisp-affected public Prime Extragalactic Areas
for Reionization and Lensing Science (PEARLS) data in the North Ecliptic Pole
Time Domain Field (NEP-TDF) field, resulting in significant visual improvement
in our detector frames and reduced noise in the final stacked images.Comment: 16 pages, 10 figures, submitted to PASP, comments welcom
Turbulent Erosion of Magnetic Flux Tubes
Results from a numerical and analytical investigation of the solution of a
nonlinear axially symmetric diffusion equation for the magnetic field are
presented for the case when the nonlinear dependence of the diffusivity nu(B)
on the magnetic field satisfies basic physical requirements. We find that for
sufficiently strong nonlinearity (i.e. for sufficiently strong reduction of nu
inside the tube) a current sheet is spontaneously formed around the tube within
one diffusion timescale. This sheet propagates inwards with a velocity
inversely proportional to the ratio of the field strength just inside the
current sheet to the equipartition field strength B0/Be, so the lifetime of a
tube with constant internal flux density is increased approximately by a factor
not exceeding B0/Be, even for infinitely effective inhibition of turbulence
inside the tube. Among the applications of these results we point out that
toroidal flux tubes in the solar convective zone are subject to significant
flux loss owing to turbulent erosion on a timescale of about 1 month, and that
turbulent erosion may be responsible for the formation of a current sheet
around a sunspot. It is further proposed that, despite the simplifying
assumptions involved, our solutions correctly reflect the essential features of
the sunspot decay process.Comment: 17 pages, 11 figure
Training for a First-Time Marathon Reverses Age-Related Aortic Stiffening.
BACKGROUND: Aging increases aortic stiffness, contributing to cardiovascular risk even in healthy individuals. Aortic stiffness is reduced through supervised training programs, but these are not easily generalizable. OBJECTIVES: The purpose of this study was to determine whether real-world exercise training for a first-time marathon can reverse age-related aortic stiffening. METHODS: Untrained healthy individuals underwent 6 months of training for the London Marathon. Assessment pre-training and 2 weeks post-marathon included central (aortic) blood pressure and aortic stiffness using cardiovascular magnetic resonance distensibility. Biological "aortic age" was calculated from the baseline chronological age-stiffness relationship. Change in stiffness was assessed at the ascending (Ao-A) and descending aorta at the pulmonary artery bifurcation (Ao-P) and diaphragm (Ao-D). Data are mean changes (95% confidence intervals [CIs]). RESULTS: A total of 138 first-time marathon completers (age 21 to 69 years, 49% male) were assessed, with an estimated training schedule of 6 to 13 miles/week. At baseline, a decade of chronological aging correlated with a decrease in Ao-A, Ao-P, and Ao-D distensibility by 2.3, 1.9, and 3.1 à 10-3 mm Hg-1, respectively (p < 0.05 for all). Training decreased systolic and diastolic central (aortic) blood pressure by 4 mm Hg (95% CI: 2.8 to 5.5 mm Hg) and 3 mm Hg (95% CI: 1.6 to 3.5 mm Hg). Descending aortic distensibility increased (Ao-P: 9%; p = 0.009; Ao-D: 16%; p = 0.002), while remaining unchanged in the Ao-A. These translated to a reduction in "aortic age" by 3.9 years (95% CI: 1.1 to 7.6 years) and 4.0 years (95% CI: 1.7 to 8.0 years) (Ao-P and Ao-D, respectively). Benefit was greater in older, male participants with slower running times (p < 0.05 for all). CONCLUSIONS: Training for and completing a marathon even at relatively low exercise intensity reduces central blood pressure and aortic stiffness-equivalent to a âŒ4-year reduction in vascular age. Greater rejuvenation was observed in older, slower individuals
The case for a distributed solar dynamo shaped by near-surface shear
Arguments for and against the widely accepted picture of a solar dynamo being
seated in the tachocline are reviewed and alternative ideas concerning dynamos
operating in the bulk of the convection zone, or perhaps even in the
near-surface shear layer, are discussed. Based on the angular velocities of
magnetic tracers it is argued that the observations are compatible with a
distributed dynamo that may be strongly shaped by the near-surface shear layer.
Direct simulations of dynamo action in a slab with turbulence and shear are
presented to discuss filling factor and tilt angles of bipolar regions in such
a model.Comment: 10 pages, 6 figures, Astrophys. J. 625 (scheduled for the 1 June 2005
issue
Spectroscopy of the Supernova H0pe Host Galaxy at Redshift 1.78
Supernova (SN) H0pe was discovered as a new transient in James Webb Space
Telescope (JWST) NIRCam images of the galaxy cluster PLCK G165.7+67.0 taken as
part of the "Prime Extragalactic Areas for Reionization and Lensing Science"
(PEARLS) JWST GTO program (# 1176) on 2023 March 30 (AstroNote 2023-96; Frye et
al. 2023). The transient is a compact source associated with a background
galaxy that is stretched and triply-imaged by the cluster's strong
gravitational lensing. This paper reports spectra in the 950-1370 nm observer
frame of two of the galaxy's images obtained with Large Binocular Telescope
(LBT) Utility Camera in the Infrared (LUCI) in longslit mode two weeks after
the \JWST\ observations. The individual average spectra show the [OII] doublet
and the Balmer and 4000 Angstrom breaks at redshift z=1.783+/-0.002. The CIGALE
best-fit model of the spectral energy distribution indicates that SN H0pe's
host galaxy is massive (Mstar~6x10^10 Msun after correcting for a magnification
factor ~7) with a predominant intermediate age (~2 Gyr) stellar population,
moderate extinction, and a magnification-corrected star formation rate ~13
Msun/yr, consistent with being below the main sequence of star formation. These
properties suggest that H0pe might be a type Ia SN. Additional observations of
SN H0pe and its host recently carried out with JWST (JWST-DD-4446; PI: B. Frye)
will be able to both determine the SN classification and confirm its
association with the galaxy analyzed in this work.Comment: 6 pages, 4 figures, Letter accepted for publication in Astronomy &
Astrophysic
PEARLS: A Potentially Isolated Quiescent Dwarf Galaxy with a TRGB Distance of 31 Mpc
A wealth of observations have long suggested that the vast majority of
isolated classical dwarf galaxies (- M) are currently
star-forming. However, recent observations of the large abundance of
"Ultra-Diffuse Galaxies" beyond the reach of previous large spectroscopic
surveys suggest that our understanding of the dwarf galaxy population may be
incomplete. Here we report the serendipitous discovery of an isolated quiescent
dwarf galaxy in the nearby Universe, which was imaged as part of the PEARLS GTO
program. Remarkably, individual red-giant branch stars are visible in this
near-IR imaging, suggesting a distance of Mpc, and a wealth of archival
photometry point to an sSFR of yr. Spectra obtained
with the Lowell Discovery Telescope find a recessional velocity consistent with
the Hubble Flow and km/s separated from the nearest massive galaxy in
SDSS, suggesting that this galaxy was either quenched from internal mechanisms
or had a very high-velocity interaction with a nearby massive galaxy in the
past. This analysis highlights the possibility that many nearby quiescent dwarf
galaxies are waiting to be discovered and that JWST has the potential to
identify them.Comment: Submitted to ApJ Letters. Comments welcome
Diagnostic yield and financial implications of a nationwide electrocardiographic screening programme to detect cardiac disease in the young.
AIMS: There is limited information on the role of screening with electrocardiography (ECG) for identifying cardiovascular diseases associated with sudden cardiac death (SCD) in a non-select group of adolescents and young adults in the general population. METHODS AND RESULTS: Between 2012 and 2014, 26â900 young individuals (aged 14-35âyears) were prospectively evaluated with a health questionnaire and ECG. Individuals with abnormal results underwent secondary investigations, the costs of which were being based on the UK National Health Service tariffs. Six hundred and seventy-five (2.5%) individuals required further investigation for an abnormal health questionnaire, 2175 (8.1%) for an abnormal ECG, and 114 (0.5%) for both. Diseases associated with young SCD were identified in 88 (0.3%) individuals of which 15 (17%) were detected with the health questionnaire, 72 (81%) with ECG and 2 (2%) with both. Forty-nine (56%) of these individuals received medical intervention beyond lifestyle modification advice in the follow-up period of 24âmonths. The overall cost of the evaluation process was âŹ97 per person screened, âŹ17â834 per cardiovascular disease detected, and âŹ29â588 per cardiovascular disease associated with SCD detected. Inclusion of ECG was associated with a 36% cost reduction per diagnosis of diseases associated with SCD compared with the health questionnaire alone. CONCLUSION: The inclusion of an ECG to a health questionnaire is associated with a five-fold increase in the ability to detect disease associated with SCD in young individuals and is more cost effective for detecting serious disease compared with screening with a health questionnaire alone
EPOCHS VII: Discovery of high redshift () AGN candidates in JWST ERO and PEARLS data
We present an analysis of a sample of robust high redshift galaxies selected
photometrically from the `blank' fields of the Prime Extragalactic Areas for
Reionization Science (PEARLS) survey and Early Release Observations (ERO) data
of the James Webb Space Telescope (JWST) with the aim of selecting candidate
high redshift active galactic nuclei (AGN). Sources were identified from the
parent sample using a threefold selection procedure, which includes spectral
energy distribution (SED) fitting to identify sources that are best fitted by
AGN SED templates, a further selection based on the relative performance of AGN
and non-AGN models, and finally morphological fitting to identify compact
sources of emission, resulting in a purity-oriented procedure. Using this
procedure, we identify a sample of nine AGN candidates at , from
which we constrain their physical properties as well as measure a lower bound
on the AGN fraction in this redshift range of \%. As this is an
extreme lower limit due to our focus on purity and our SEDs being calibrated
for unobscured Type 1 AGN, this demonstrates that AGN are perhaps quite common
at this early epoch. The rest-frame UV colors of our candidate objects suggest
that these systems are potentially candidate obese black hole galaxies (OBG),
or AGN with very little galaxy component. We also investigate emission from our
sample sources from fields overlapping with Chandra and VLA surveys, allowing
us to place X-ray and 3 GHz radio detection limits on our candidates. Of note
is a candidate source exhibiting an abrupt morphological shift in
the reddest band as compared to the bluer bands, indicating a potential merger
or an unusually strong outflow.Comment: Submitted to MNRAS, 12 pages, 11 figures, typos correcte
Novel germline variants identified in the inner mitochondrial membrane transporter TIMM44 and their role in predisposition to oncocytic thyroid carcinomas
Familial Non-Medullary Thyroid Carcinoma (fNMTC) represents 3â7% of all thyroid tumours and is associated with some of the highest familial risks among all cancers, with an inheritance pattern compatible with an autosomal dominant model with reduced penetrance. We previously mapped a predisposing locus, TCO (Thyroid tumour with Cell Oxyphilia) on chromosome 19p13.2, for a particular form of thyroid tumour characterised by cells with an abnormal proliferation of mitochondria (oxyphilic or oncocytic cells). In the present work, we report the systematic screening of 14 candidate genes mapping to the region of linkage in affected TCO members, that led us to identify two novel variants respectively in exon 9 and exon 13 of TIMM44, a mitochondrial inner membrane translocase for the import in the mitochondria of nuclear-encoded proteins. These variants were co-segregating with the TCO phenotype, were not present in a large group of controls and were predicted to negatively affect the protein (exon 9 change) or the transcript (exon 13 change). Functional analysis was performed in vitro for both changes and although no dramatic loss of function effects were identified for the mutant alleles, subtler effects might still be present that could alter Timm44 function and thus promote oncocytic tumour development. Thus we suggest that TIMM44 should be considered for further studies in independent samples of affected individuals with TCO
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