999 research outputs found
Constraining the Variability and Binary Fraction of Galactic Center Young Stars
We present constraints on the variability and binarity of young stars in the
central 10 arcseconds (~0.4 pc) of the Milky Way Galactic Center (GC) using
Keck Adaptive Optics data over a 12 year baseline. Given our experiment's
photometric uncertainties, at least 36% of our sample's known early-type stars
are variable. We identified eclipsing binary systems by searching for periodic
variability. In our sample of spectroscopically confirmed and likely early-type
stars, we detected the two previously discovered GC eclipsing binary systems.
We derived the likely binary fraction of main sequence, early-type stars at the
GC via Monte Carlo simulations of eclipsing binary systems, and find that it is
at least 32% with 90% confidence.Comment: Accepted for publication in Proceedings of IAU Symposium 322: The
Multi-Messenger Astrophysics of the Galactic Centre, 2 pages, 1 figur
The effect of training intensity on implicit learning rates in schizophrenia
Cognitive impairments in learning and memory are core symptoms of schizophrenia, associated with reduced self-reported quality of life. The most effective treatment of cognitive impairments is drill and practice cognitive training. Still, to date no study has investigated the effect of varying the frequency of training on cognitive outcomes. Here we utilized a verbal memory based language learning task, tapping into implicit cognitive processes, to investigate the role of training intensity on learning rates in individuals with schizophrenia. Data from 47 participants across two studies was utilized, one with a daily training regimen over 5 days and the other with a more intensive schedule of 5 sessions delivered over 2 days. The primary outcome measure was the change in implicit learning performance across five sessions, quantified with the Matthews Correlation Coefficient (MCC). Participants in the daily training group showed improved performance compared to the intensive group only at session 4. This is the first study to show that implicit learning rates are influenced by training intensity, with daily sessions outperforming a more intensive regimen; a period of consolidation overnight may be necessary to optimize cognitive training for individuals with schizophrenia
Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole
We present improved relative astrometry for stars within the central half parsec of our Galactic Center (GC) based on data obtained with the 10 m W. M. Keck Observatory from 1995 to 2017. The new methods used to improve the astrometric precision and accuracy include correcting for local astrometric distortions, applying a magnitude-dependent additive error, and more carefully removing instances of stellar confusion. Additionally, we adopt jackknife methods to calculate velocity and acceleration uncertainties. The resulting median proper motion uncertainty is 0.05 mas yr^(â1) for our complete sample of 1184 stars in the central 10'' (0.4 pc). We have detected 24 accelerating sources, 2.6 times more than the number of previously published accelerating sources, which extend out to 4'' (0.16 pc) from the black hole. Based on S0-2's orbit, our new astrometric analysis has reduced the systematic error of the supermassive black hole (SMBH) by a factor of 2. The linear drift in our astrometric reference frame is also reduced in the northâsouth direction by a factor of 4. We also find the first potential astrometric binary candidate S0-27 in the GC. These astrometric improvements provide a foundation for future studies of the origin and dynamics of the young stars around the SMBH, the structure and dynamics of the old nuclear star cluster, the SMBH's properties derived from orbits, and tests of general relativity in a strong gravitational field
Stellar Populations in the Central 0.5 pc of Our Galaxy III: The Dynamical Sub-structures
We measure the 3D kinematic structures of the young stars within the central
0.5 parsec of our Galactic Center using the 10 m telescopes of the W.~M.~Keck
Observatory over a time span of 25 years. Using high-precision measurements of
positions on the sky, and proper motions and radial velocities from new
observations and the literature, we constrain the orbital parameters for each
young star. Our results show two statistically significant sub-structures: a
clockwise stellar disk with 18 candidate stars, as has been proposed before,
but with an improved disk membership; a second, almost edge-on plane of 10
candidate stars oriented East-West on the sky that includes at least one IRS 13
star. We estimate the eccentricity distribution of each sub-structure and find
that the clockwise disk has = 0.39 and the edge-on plane has =
0.68. We also perform simulations of each disk/plane with incompleteness and
spatially-variable extinction to search for asymmetry. Our results show that
the clockwise stellar disk is consistent with a uniform azimuthal distribution
within the disk. The edge-on plane has an asymmetry that cannot be explained by
variable extinction or incompleteness in the field. The orientation, asymmetric
stellar distribution, and high eccentricity of the edge-on plane members
suggest that this structure may be a stream associated with the IRS 13 group.
The complex dynamical structure of the young nuclear cluster indicates that the
star formation process involved complex gas structures and dynamics and is
inconsistent with a single massive gaseous disk.Comment: 41 pages, 26 figures, 13 tables, 2 appendices. Accepted for
publication in Ap
Keck Observations Confirm a Super-Jupiter Planet Orbiting M Dwarf OGLE-2005-BLG-071L
We present adaptive optics imaging from the NIRC2 instrument on the Keck II telescope that resolves the exoplanet host (and lens) star as it separates from the brighter source star. These observations yield the K-band brightness of the lens and planetary host star, as well as the lens-source relative proper motion, ”_(rel,H), in the heliocentric reference frame. The ”_(rel,H) measurement allows for the determination of the microlensing parallax vector, Ï_E, which had only a single component determined by the microlensing light curve. The combined measurements of ”_(rel,H) and K L provide the masses of the host star, M_(host) = 0.426 ± 0.037 Mâ, and planet, m_p = 3.27 ± 0.32M_(Jupiter) with a projected separation of 3.4 ± 0.5 au. This confirms the tentative conclusion of a previous paper that this super-Jupiter mass planet, OGLE-2005-BLG-071Lb, orbits an M dwarf. Such planets are predicted to be rare by the core accretion theory and have been difficult to find with other methods, but there are two such planets with firm mass measurements from microlensing, and an additional 11 planetary microlens events with host mass estimates <0.
0.5Mâ and planet mass estimates >2 Jupiter masses that could be confirmed by high angular follow-up observations. We also point out that OGLE-2005-BLG-071L has separated far enough from its host star that it should be possible to measure the host-star metallicity with spectra from a high angular resolution telescope such as Keck, the Very Large Telescope, the Hubble Space Telescope, or the James Webb Space Telescope
Adaptive Optics Imaging Breaks the Central Caustic Cusp Approach Degeneracy in High Magnification Microlensing Events
We report new results for the gravitational microlensing target
OGLE-2011-BLG-0950 from adaptive optics (AO) images using the Keck observatory.
The original analysis by Choi et al. 2012 reports degenerate solutions between
planetary and stellar binary lens systems. This is due to a degeneracy in high
magnification events where the shape of the light curve peak can be explained
by a source approach to two different cusp geometries with different source
radius crossing times. This particular case is the most important type of
degeneracy for exoplanet demographics, because the distinction between a
planetary mass or stellar binary companion has direct consequences for
microlensing exoplanet statistics. The 8 and 10-year baselines between the
event and the Keck observations allow us to directly measure a relative proper
motion of mas/yr, which confirms the detection of the lens star
system and directly rules out the planetary companion models that predict a
smaller relative proper motion. The combination of the lens
brightness and close stellar binary light curve parameters yield primary and
secondary star masses of and at a distance of kpc, and a primary-secondary projected separation of
AU. Since this degeneracy is likely to be common, the
high resolution imaging method described here will be used to disentangle the
central caustic cusp approach degeneracy for events observed by the
\textit{Roman} exoplanet microlensing survey using the \textit{Roman} images
taken near the beginning or end of the survey.Comment: Revised version, 19 pages, 8 figures. AJ, 164, 21
Uropathogenic Escherichia coli infection-induced epithelial trained immunity impacts urinary tract disease outcome
Previous urinary tract infections (UTIs) can predispose one to future infections; however, the underlying mechanisms affecting recurrence are poorly understood. We previously found that UTIs in mice cause differential bladder epithelial (urothelial) remodelling, depending on disease outcome, that impacts susceptibility to recurrent UTI. Here we compared urothelial stem cell (USC) lines isolated from mice with a history of either resolved or chronic uropathogenic Escherichia coli (UPEC) infection, elucidating evidence of molecular imprinting that involved epigenetic changes, including differences in chromatin accessibility, DNA methylation and histone modification. Epigenetic marks in USCs from chronically infected mice enhanced caspase-1-mediated cell death upon UPEC infection, promoting bacterial clearance. Increased Ptgs2os2 expression also occurred, potentially contributing to sustained cyclooxygenase-2 expression, bladder inflammation and mucosal wounding-responses associated with severe recurrent cystitis. Thus, UPEC infection acts as an epi-mutagen reprogramming the urothelial epigenome, leading to urothelial-intrinsic remodelling and training of the innate response to subsequent infection
Clinical risk factors and atherosclerotic plaque extent to define risk for major events in patients without obstructive coronary artery disease: the long-term coronary computed tomography angiography CONFIRM registry.
AimsIn patients without obstructive coronary artery disease (CAD), we examined the prognostic value of risk factors and atherosclerotic extent.Methods and resultsPatients from the long-term CONFIRM registry without prior CAD and without obstructive (â„50%) stenosis were included. Within the groups of normal coronary computed tomography angiography (CCTA) (Nâ=â1849) and non-obstructive CAD (Nâ=â1698), the prognostic value of traditional clinical risk factors and atherosclerotic extent (segment involvement score, SIS) was assessed with Cox models. Major adverse cardiac events (MACE) were defined as all-cause mortality, non-fatal myocardial infarction, or late revascularization. In total, 3547 patients were included (age 57.9â±â12.1âyears, 57.8% male), experiencing 460 MACE during 5.4âyears of follow-up. Age, body mass index, hypertension, and diabetes were the clinical variables associated with increased MACE risk, but the magnitude of risk was higher for CCTA defined atherosclerotic extent; adjusted hazard ratio (HR) for SIS >5 was 3.4 (95% confidence interval [CI] 2.3-4.9) while HR for diabetes and hypertension were 1.7 (95% CI 1.3-2.2) and 1.4 (95% CI 1.1-1.7), respectively. Exclusion of revascularization as endpoint did not modify the results. In normal CCTA, presence of â„1 traditional risk factors did not worsen prognosis (log-rank Pâ=â0.248), while it did in non-obstructive CAD (log-rank Pâ=â0.025). Adjusted for SIS, hypertension and diabetes predicted MACE risk in non-obstructive CAD, while diabetes did not increase risk in absence of CAD (P-interactionâ=â0.004).ConclusionAmong patients without obstructive CAD, the extent of CAD provides more prognostic information for MACE than traditional cardiovascular risk factors. An interaction was observed between risk factors and CAD burden, suggesting synergistic effects of both
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Coronary atherosclerosis scoring with semiquantitative CCTA risk scores for prediction of major adverse cardiac events: Propensity score-based analysis of diabetic and non-diabetic patients.
AIMS:We aimed to compare semiquantitative coronary computed tomography angiography (CCTA) risk scores - which score presence, extent, composition, stenosis and/or location of coronary artery disease (CAD) - and their prognostic value between patients with and without diabetes mellitus (DM). Risk scores derived from general chest-pain populations are often challenging to apply in DM patients, because of numerous confounders. METHODS:Out of a combined cohort from the Leiden University Medical Center and the CONFIRM registry with 5-year follow-up data, we performed a secondary analysis in diabetic patients with suspected CAD who were clinically referred for CCTA. A total of 732 DM patients was 1:1 propensity-matched with 732 non-DM patients by age, sex and cardiovascular risk factors. A subset of 7 semiquantitative CCTA risk scores was compared between groups: 1) any stenosis â„50%, 2) any stenosis â„70%, 3) stenosis-severity component of the coronary artery disease-reporting and data system (CAD-RADS), 4) segment involvement score (SIS), 5) segment stenosis score (SSS), 6) CT-adapted Leaman score (CT-LeSc), and 7) Leiden CCTA risk score. Cox-regression analysis was performed to assess the association between the scores and the primary endpoint of all-cause death and non-fatal myocardial infarction. Also, area under the receiver-operating characteristics curves were compared to evaluate discriminatory ability. RESULTS:A total of 1,464 DM and non-DM patients (mean age 58 ± 12 years, 40% women) underwent CCTA and 155 (11%) events were documented after median follow-up of 5.1 years. In DM patients, the 7 semiquantitative CCTA risk scores were significantly more prevalent or higher as compared to non-DM patients (p â€Â 0.022). All scores were independently associated with the primary endpoint in both patients with and without DM (p â€Â 0.020), with non-significant interaction between the scores and diabetes (interaction p â„ 0.109). Discriminatory ability of the Leiden CCTA risk score in DM patients was significantly better than any stenosis â„50% and â„70% (p = 0.003 and p = 0.007, respectively), but comparable to the CAD-RADS, SIS, SSS and CT-LeSc that also focus on the extent of CAD (p â„ 0.265). CONCLUSION:Coronary atherosclerosis scoring with semiquantitative CCTA risk scores incorporating the total extent of CAD discriminate major adverse cardiac events well, and might be useful for risk stratification of patients with DM beyond the binary evaluation of obstructive stenosis alone
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