1,001 research outputs found
All-sky Relative Opacity Mapping Using Night Time Panoramic Images
An all-sky cloud monitoring system that generates relative opacity maps over
many of the world's premier astronomical observatories is described.
Photometric measurements of numerous background stars are combined with
simultaneous sky brightness measurements to differentiate thin clouds from sky
glow sources such as air glow and zodiacal light. The system takes a continuous
pipeline of all-sky images, and compares them to canonical images taken on
other nights at the same sidereal time. Data interpolation then yields
transmission maps covering almost the entire sky. An implementation of this
system is currently operating through the Night Sky Live network of CONCAM3s
located at Cerro Pachon (Chile), Mauna Kea (Hawaii), Haleakala (Hawaii), SALT
(South Africa) and the Canary Islands (Northwestern Africa).Comment: Accepted for publication in PAS
The Quiet-Sun Photosphere and Chromosphere
The overall structure and the fine structure of the solar photosphere outside
active regions are largely understood, except possibly important roles of a
turbulent near-surface dynamo at its bottom, internal gravity waves at its top,
and small-scale vorticity. Classical 1D static radiation-escape modelling has
been replaced by 3D time-dependent MHD simulations that come closer to reality.
The solar chromosphere, in contrast, remains ill-understood although its
pivotal role in coronal mass and energy loading makes it a principal research
area. Its fine structure defines its overall structure, so that hard-to-observe
and hard-to-model small-scale dynamical processes are the key to understanding.
However, both chromospheric observation and chromospheric simulation presently
mature towards the required sophistication. The open-field features seem of
greater interest than the easier-to-see closed-field features.Comment: Accepted for special issue "Astrophysical Processes on the Sun" of
Phil. Trans. Royal Soc. A, ed. C. Parnell. Note: clicking on the year in a
citation opens the corresponding ADS abstract page in the browse
56Ni dredge-up in the type IIp Supernova 1995V
We present contemporary infrared and optical spectra of the plateau type II
SN 1995V in NGC 1087 covering four epochs, approximately 22 to 84 days after
shock breakout. The data show, for the first time, the infrared spectroscopic
evolution during the plateau phase of a typical type II event. In the optical
region P Cygni lines of the Balmer series and of metals lines were identified.
The infrared (IR) spectra were largely dominated by the continuum, but P Cygni
Paschen lines and Brackett gamma lines were also clearly seen. The other
prominent IR features are confined to wavelengths blueward of 11000 \AA and
include Sr II 10327, Fe II 10547, C I 10695 and He I 10830 \AA. We demonstrate
the presence of He I 10830 \AA on days 69 and 85. The presence of this line at
such late times implies re-ionisation. A likely re-ionising mechanism is
gamma-ray deposition following the radioactive decay of 56Ni. We examine this
mechanism by constructing a spectral model for the He I 10830 \AA line based on
explosion model s15s7b2f of Weaver & Woosley (1993). We find that this does not
generate the observed line owing to the confinement of the 56Ni to the central
zones of the ejecta. In order to reproduce the He I line, it was necessary to
introduce additional upward mixing of the 56Ni, with 10^{-5} of the total
nickel mass reaching above the helium photosphere. In addition, we argue that
the He I line-formation region is likely to have been in the form of pure
helium clumps in the hydrogen envelope.Comment: Accepted for publication in MNRAS, 32 pages including 11 figures
(uses psfig.sty - included
HST Observations of Chromospheres in Metal Deficient Field Giants
HST high resolution spectra of metal-deficient field giants more than double
the stars in previous studies, span about 3 magnitudes on the red giant branch,
and sample an abundance range [Fe/H]= -1 to -3. These stars, in spite of their
age and low metallicity, possess chromospheric fluxes of Mg II (2800 Angstrom)
that are within a factor of 4 of Population I stars, and give signs of a
dependence on the metal abundance at the lowest metallicities. The Mg II k-line
widths depend on luminosity and correlate with metallicity. Line profile
asymmetries reveal outflows that occur at lower luminosities (M_V = -0.8) than
detected in Ca K and H-alpha lines in metal-poor giants, suggesting mass
outflow occurs over a larger span of the red giant branch than previously
thought, and confirming that the Mg II lines are good wind diagnostics. These
results do not support a magnetically dominated chromosphere, but appear more
consistent with some sort of hydrodynamic, or acoustic heating of the outer
atmospheres.Comment: 36 pages, 12 figures, 7 tables, and accepted for publication in The
Astronomical Journa
A quantitative comparison of cognitive performance and patient-reported symptoms in preoperative lower-grade glioma patients from two Dutch Hospitals
Background Protocols for assessment of (neuro)psychological outcomes in lower-grade glioma patients vary between hospitals. This potentially complicates generalization of these outcomes. We compared standardized scores on tests of two frequently impaired cognitive domains (attention and executive functioning (EF)), and two relevant patient-reported outcomes (PROs; depression and fatigue) of two neuro-oncological hospitals that use different measurement instruments. Material and Methods Data were used from preoperative assessments of patients with (IDH-mut) WHO grade II/III glioma tested between 2007 and 2021 at Amsterdam UMC (AMS) or at Elisabeth-Tweesteden Hospital Tilburg (ETZ). AMS patients were referred for (neuro)psychological assessment based on physician and patient preference (paper and pencil tests), whereas all ETZ patients routinely undergo screening (computerized tests). To compare scores of the different attention and EF tests we converted patients’ performances to z-scores based on normative data. For cognitive performance, we compared scores of different cognitive flexibility tests (CST vs SAT), processing speed tests (SDC vs LDMT), and Stroop tests (Stroop I and Stroop III). PROs included the CES-D vs HADS-D and the CIS-fatigue vs MVI-general fatigue (AMS vs ETZ, resp.). Differences were tested using Fisher's, χ 2, and Mann-Whitney U tests. Results Assessments were done median 4 weeks (AMS, n=97, range 19-0 weeks) and 1 day (ETZ, n=106; range 14-0 days) preoperatively. Age, sex, tumor location and histology were comparable between cohorts (p>0.05), but the AMS cohort showed significantly more grade III tumors (36% vs 16%) and more awake surgeries (84% vs 46%). Z-scores measuring attention and EF (n=94 and n=95, AMS vs ETZ) were not significantly different (CST vs SAT, percentage with a disorder (z <-1.5SD) 15% vs 13%; SDC vs LDMT 13% vs 14%; Stroop I 11% vs 18%; Stroop III 13% vs 16% at AMS and ETZ, resp.). Percentages of patients with possible depression (CES-D≥16, n=88 and HADS-D≥8, n=106) did not differ significantly between hospitals (28% vs 26%), nor did percentages of patients with severe fatigue (CIS-fatigue≥35, n=88 and MVI-general fatigue (z <-1.5SD), n=38, 42% vs 24% at AMS and ETZ, resp.). Conclusion Standardized scores of glioma patients on cognitive domains (attention and EF) and PROs (depression and fatigue) did not differ between two centers with slightly different samples using different testing protocols. This cautiously suggests that study findings on cognitive functioning and symptoms could be generalized. For research purposes, conjoint use of pooled populations for outcome evaluation could be explored with different samples from other centers using different instruments
Infrared Properties of Cataclysmic Variables from 2MASS: Results from the 2nd Incremental Data Release
Because accretion-generated luminosity dominates the radiated energy of most
cataclysmic variables, they have been ``traditionally'' observed primarily at
short wavelengths. Infrared observations of cataclysmic variables contribute to
the understanding of key system components that are expected to radiate at
these wavelengths, such as the cool outer disk, accretion stream, and secondary
star. We have compiled the J, H, and Ks photometry of all cataclysmic variables
located in the sky coverage of the 2 Micron All Sky Survey (2MASS) 2nd
Incremental Data Release. This data comprises 251 systems with reliably
identified near-IR counterparts and S/N > 10 photometry in one or more of the
three near-IR bands.Comment: 2 pages, including 1 figure. To appear in the proceedings of The
Physics of Cataclysmic Variables and Related Objects, Goettingen, Germany.
For our followup ApJ paper (in press), also see
http://www.ctio.noao.edu/~hoard/research/2mass/index.htm
Lumbar spine segmentation in MR images: a dataset and a public benchmark
This paper presents a large publicly available multi-center lumbar spine
magnetic resonance imaging (MRI) dataset with reference segmentations of
vertebrae, intervertebral discs (IVDs), and spinal canal. The dataset includes
447 sagittal T1 and T2 MRI series from 218 patients with a history of low back
pain. It was collected from four different hospitals and was divided into a
training (179 patients) and validation (39 patients) set. An iterative data
annotation approach was used by training a segmentation algorithm on a small
part of the dataset, enabling semi-automatic segmentation of the remaining
images. The algorithm provided an initial segmentation, which was subsequently
reviewed, manually corrected, and added to the training data. We provide
reference performance values for this baseline algorithm and nnU-Net, which
performed comparably. We set up a continuous segmentation challenge to allow
for a fair comparison of different segmentation algorithms. This study may
encourage wider collaboration in the field of spine segmentation, and improve
the diagnostic value of lumbar spine MRI
GJ 900: A new hierarchical system with low-mass components
Speckle interferometric observations made with the 6 m telescope of the
Special Astrophysical Observatory of the Russian Academy of Sciences in 2000
revealed the triple nature of the nearby ( mas)
low-mass young ( Myr) star GJ 900. The configuration of the triple
system allowed it to be dynamically unstable. Differential photometry performed
from 2000 through 2004 yielded - and -band absolute magnitudes and
spectral types for the components to be =6.660.08,
=9.150.11, =10.080.26, =4.840.08,
=6.760.20, =7.390.31, K5--K7,
M3--M4, M5--M6. The ``mass--luminosity''
relation is used to estimate the individual masses of the components:
,
,
. From the observations of the
components relative motion in the period 2000--2006, we conclude that GJ 900 is
a hierarchical triple star with the possible orbital periods
P80 yrs and P20 yrs. An analysis of the 2MASS
images of the region around GJ 900 leads us to suggest that the system can
include other very-low-mass components.Comment: 7 pages, 5 figure
Irradiation of the secondary star in X-ray Nova Scorpii 1994 (=GRO J1655--40)
We have obtained intermediate resolution optical spectra of the black-hole
candidate Nova Sco 1994 in June 1996, when the source was in an X-ray/optical
active state (R~15.05). We measure the radial velocity curve of the secondary
star and obtain a semi-amplitude of 279+/-10 km/s; a value which is 30 per cent
larger than the value obtained when the source is in quiescence. Our large
value for K_2 is consistent with 60 +9,-7 per cent of the secondary star's
surface being heated; compared to 35 per cent, which is what one would expect
if only the inner face of the secondary star were irradiated. Effects such as
irradiation-induced flows on the secondary star may be important in explaining
the observed large value for K_2.Comment: 5 pages, 2 figures, accepted by MNRA
Systematic analysis of relationships between plasma branched-chain amino acid concentrations and cardiometabolic parameters:an association and Mendelian randomization study
Abstract Background Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are essential amino acids that are associated with an increased risk of cardiometabolic diseases (CMD). However, there are still only limited insights into potential direct associations between BCAAs and a wide range of CMD parameters, especially those remaining after correcting for covariates and underlying causal relationships. Methods To shed light on these relationships, we systematically characterized the associations between plasma BCAA concentrations and a large panel of 537 CMD parameters (including atherosclerosis-related parameters, fat distribution, plasma cytokine concentrations and cell counts, circulating concentrations of cardiovascular-related proteins and plasma metabolites) in 1400 individuals from the Dutch population cohort LifeLines DEEP and 294 overweight individuals from the 300OB cohort. After correcting for age, sex, and BMI, we assessed associations between individual BCAAs and CMD parameters. We further assessed the underlying causality using Mendelian randomization. Results A total of 838 significant associations were detected for 409 CMD parameters. BCAAs showed both common and specific associations, with the most specific associations being detected for isoleucine. Further, we found that obesity status substantially affected the strength and direction of associations for valine, which cannot be corrected for using BMI as a covariate. Subsequent univariable Mendelian randomization (UVMR), after removing BMI-associated SNPs, identified seven significant causal relationships from four CMD traits to BCAA levels, mostly for diabetes-related parameters. However, no causal effects of BCAAs on CMD parameters were supported. Conclusions Our cross-sectional association study reports a large number of associations between BCAAs and CMD parameters. Our results highlight some specific associations for isoleucine, as well as obesity-specific effects for valine. MR-based causality analysis suggests that altered BCAA levels can be a consequence of diabetes and alteration in lipid metabolism. We found no MR evidence to support a causal role for BCAAs in CMD. These findings provide evidence to (re)evaluate the clinical importance of individual BCAAs in CMD diagnosis, prevention, and treatment
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