This work reports the discovery of cycle-to-cycle modulated spectral line and atmospheric velocity gradient variability in long-period Cepheids based on 925 high-resolution optical spectra of l ...Carinae (P ~ 35.5 d) recorded during three heavy duty-cycle monitoring campaigns (in 2014, 2015, and 2016). Spectral line variability is investigated via cross-correlation functions (CCFs) computed using three sets of spectral lines (weak, solar, strong). A metallic line velocity gradient, ...(t), is computed as the difference between weak and strong-line radial velocities (RVs). CCF shape indicators bisector inverse span (BIS) (asymmetry), full width at half-maximum, and depth all exhibit clear phase-dependent variability patterns that differ from one pulsation cycle to the next. Weak-line CCFs exhibit these effects more clearly than strong-line CCFs. BIS exhibits the most peculiar modulated variability and can be used to identify the presence of cycle-to-cycle modulated line profile variations. ...(t) clearly exhibits cycle-to-cycle differences that correlate very closely with modulated BIS variability, suggesting perturbations of the atmospheric velocity field as the cause for modulated spectral line variability. These perturbations are most significant during contraction and are not in phase with the pulsation, transmitting information between consecutive pulsation cycles. This work shows RV curve modulation to be a consequence of atmospheric velocity gradient perturbations. Possible origins of these perturbations and their impact on Cepheid RV measurements as well as the projection factor used in Baade-Wesselink-type distance determinations are discussed. (ProQuest: ... denotes formulae/symbols omitted.)
We have estimated relativistic corrections for cosmic distance estimates based on stellar standard candles such as classical Cepheids and stars near the tip of the red giant branch (TRGB stars) with ...the goal of enabling a future unbiased 1% measurement of Hubble’s constant,
H
0
. We considered four effects: K corrections, time dilation, the apparent change of host dust extinction due to non-comoving reference frames, and the change of observed color due to redshift. Using stellar model atmospheres, we computed extinction-dependent K corrections for a wide range of effective temperatures, between 3500 and 6000 K, iron abundances between Fe/H = −2.0 and 0.5, surface gravity between log
g
= 2.0 and 0.0, and host reddening (up to
E
(
B
−
V
)
host
= 0.5) for a range of redshifts corresponding to distances of ∼20−120 Mpc (
z
between 0.005 and 0.03) in several HST, JWST, and 2MASS filters. The optical-near-infrared (NIR) Wesenheit function applied by the Cepheid distance ladder is particularly useful for limiting the magnitude of K corrections and for mitigating complications arising from host dust extinction. Missing host extinction corrections related to the circumgalactic medium and circumstellar environments arising from stellar mass loss are discussed as potential systematics of TRGB distance measurements. However, their effect is estimated to be insufficient to explain differences in
H
0
values based on Cepheids or TRGB supernova calibrations. All stellar standard candle observations require relativistic corrections in order to achieve an unbiased 1%
H
0
measurement in the future. Applying the K correction, the redshift-Leavitt bias correction, and a correction for the Wesenheit slope redshift dependence, the Cepheid-based
H
0
measurement increases by 0.45 ± 0.05 km s
−1
Mpc
−1
to
H
0
SH0ES
= 73.65 ± 1.30 km s
−1
Mpc
−1
, raising the tension with the early-Universe value reported by the Planck Collaboration from 4.2
σ
to 4.4
σ
. For TRGB-based
H
0
measurements, we estimate a ∼0.5% upward correction for the methodology employed by Freedman et al. (
H
0
CCHP
= 70.2 ± 1.7 km s
−1
Mpc
−1
) and an even smaller −0.15% downward correction for the methodology employed by Anand et al. (
H
0
EDD
= 71.4 ± 1.8 km s
−1
Mpc
−1
). The opposite sign of these corrections is related to different reddening systematics and reduces the difference between the studies by ∼0.46 km s
−1
Mpc
−1
. The optical-NIR Wesenheit function is particularly attractive for accurate distance measurements because it advantageously combines measurements in filters where K corrections have opposite signs. The JWST/NIRCAM
F
277
W
filter is of particular interest for TRGB stars thanks to its insensitivity to (weak) host reddening and K corrections below the level of 1% at Coma cluster distances.
We present Hubble Space Telescope (HST) photometry of a selected sample of 50 long-period, low-extinction Milky Way Cepheids measured on the same WFC3 F555W-, F814W-, and F160W-band photometric ...system as extragalactic Cepheids in Type Ia supernova host galaxies. These bright Cepheids were observed with the WFC3 spatial scanning mode in the optical and near-infrared to mitigate saturation and reduce pixel-to-pixel calibration errors to reach a mean photometric error of 5 mmag per observation. We use the new Gaia DR2 parallaxes and HST photometry to simultaneously constrain the cosmic distance scale and to measure the DR2 parallax zeropoint offset appropriate for Cepheids. We find the latter to be −46 13 as or 6 as for a fixed distance scale, higher than found from quasars, as expected for these brighter and redder sources. The precision of the distance scale from DR2 has been reduced by a factor of 2.5 because of the need to independently determine the parallax offset. The best-fit distance scale is 1.006 0.033, relative to the scale from Riess et al. with H0 = 73.24 km s−1 Mpc−1 used to predict the parallaxes photometrically, and is inconsistent with the scale needed to match the Planck 2016 cosmic microwave background data combined with ΛCDM at the 2.9 confidence level (99.6%). At 96.5% confidence we find that the formal DR2 errors may be underestimated as indicated. We identify additional errors associated with the use of augmented Cepheid samples utilizing ground-based photometry and discuss their likely origins. Including the DR2 parallaxes with all prior distance-ladder data raises the current tension between the late and early universe route to the Hubble constant to 3.8 (99.99%). With the final expected precision from Gaia, the sample of 50 Cepheids with HST photometry will limit to 0.5% the contribution of the first rung of the distance ladder to the uncertainty in H0.
Integrin-dependent adhesions are mechanosensitive structures in which talin mediates a linkage to actin filaments either directly or indirectly by recruiting vinculin. Here, we report the development ...and validation of a talin tension sensor. We find that talin in focal adhesions is under tension, which is higher in peripheral than central adhesions. Tension on talin is increased by vinculin and depends mainly on actin-binding site 2 (ABS2) within the middle of the rod domain, rather than ABS3 at the far C terminus. Unlike vinculin, talin is under lower tension on soft substrates. The difference between central and peripheral adhesions requires ABS3 but not vinculin or ABS2. However, differential stiffness sensing by talin requires ABS2 but not vinculin or ABS3. These results indicate that central versus peripheral adhesions must be organized and regulated differently, and that ABS2 and ABS3 have distinct functions in spatial variations and stiffness sensing. Overall, these results shed new light on talin function and constrain models for cellular mechanosensing.
Marine phytoplankton generate half of global primary production, making them essential to ecosystem functioning and biogeochemical cycling. Though phytoplankton are phylogenetically diverse, studies ...rarely designate unique thermal traits to different taxa, resulting in coarse representations of phytoplankton thermal responses. Here we assessed phytoplankton functional responses to temperature using empirically derived thermal growth rates from four principal contributors to marine productivity: diatoms, dinoflagellates, cyanobacteria, and coccolithophores. Using modeled sea surface temperatures for 1950-1970 and 2080-2100, we explored potential alterations to each group's growth rates and geographical distribution under a future climate change scenario. Contrary to the commonly applied Eppley formulation, our data suggest phytoplankton functional types may be characterized by different temperature coefficients (Q
), growth maxima thermal dependencies, and thermal ranges which would drive dissimilar responses to each degree of temperature change. These differences, when applied in response to global simulations of future temperature, result in taxon-specific projections of growth and geographic distribution, with low-latitude coccolithophores facing considerable decreases and cyanobacteria substantial increases in growth rates. These results suggest that the singular effect of changing temperature may alter phytoplankton global community structure, owing to the significant variability in thermal response between phytoplankton functional types.
State-of-the-art photometric measurements of extragalactic Cepheids account for the mean additional light due to chance superposition of Cepheids on crowded backgrounds through the use of artificial ...star measurements. However, light from stars physically associated with Cepheids may bias relative distance measurements if the changing spatial resolution along the distance ladder significantly alters the amount of associated blending. We have identified two regimes where this phenomenon may occur: Cepheids in wide binaries and in open clusters. We estimate stellar association bias using the photometric passbands and reddening-free Wesenheit magnitudes used to set up the distance scale. For wide binaries, we rely on Geneva stellar evolution models in conjunction with detailed statistics on intermediate-mass binary stars. For the impact of cluster stars, we have compiled information on the clustered Cepheid fraction and measured the typical cluster contribution in M31 via deep Hubble Space Telescope imaging provided by the Panchromatic Hubble Andromeda Treasury project. We find that the dominant effect on the distance scale comes from Cepheids in clusters, even though cluster Cepheids are a relatively rare phenomenon. Wide binaries have a negligible effect of 0.004% on H0 for long-period Cepheids observed in the near-infrared or when considering Wesenheit magnitudes. We estimate that blending due to cluster populations has previously resulted in a 0.23% overestimate of H0. Correcting for this bias, we obtain , which remains in 3.3 tension with the Planck value. We conclude that stellar association bias does not constitute a limit for measuring H0 with an accuracy of 1%.
Emergency laparotomy: time to improve? Anderson, I. D.
ANZ journal of surgery,
December 2021, 2021-12-00, 20211201, Letnik:
91, Številka:
12
Journal Article
Reduced hippocampal volume has been reported in depression and may be involved in the aetiology of depressive symptoms and vulnerability to depressive relapse. Neuroplasticity following ...antidepressant drug treatment in the hippocampus has been demonstrated in animal models but adaptive changes after such treatment have not been shown in humans. In this study, we determined whether grey matter loss in the hippocampus in depression (1) is present in medication-free depressed (2) changes in response to antidepressant treatment and (3) is present as a stable trait in medication-free remitted patients. Sixty-four medication-free unipolar depressed patients: 39 currently depressed and 25 in remission, and 66 healthy controls (HC) underwent structural magnetic resonance imaging in a cross-sectional and longitudinal design. Thirty-two currently depressed participants were then treated with the antidepressant citalopram for 8 weeks. Adherence to treatment was evaluated by measuring plasma citalopram concentration. We measured regional variation in grey matter concentration by using voxel-based morphometry-Diffeomorphic Anatomical Registration Through Exponentiated Lie algebra. Patients with current depression had bilaterally reduced grey matter in the hippocampus compared with HC and untreated patients in stable remission with the latter groups not differing. An increase in grey matter was observed in the hippocampus following treatment with citalopram in currently depressed patients. Grey matter reduction in the hippocampus appears specific to the depressed state and is a potential biomarker for a depressive episode.
Assessing the significance and implications of the recently established Hubble tension requires the comprehensive identification, quantification, and mitigation of uncertainties and/or biases ...affecting H0 measurements. Here, we investigate the previously overlooked distance scale bias resulting from the interplay between redshift and Leavitt laws in an expanding Universe: Redshift-Leavitt bias (RLB). Redshift dilates oscillation periods of pulsating stars residing in supernova-host galaxies relative to periods of identical stars residing in nearby (anchor) galaxies. Multiplying dilated log P with Leavitt Law slopes leads to underestimated absolute magnitudes, overestimated distance moduli, and a systematic error on H0. Emulating the SH0ES distance ladder, we estimate an associated H0 bias of (0.27 ± 0.01)% and obtain a corrected H0 = 73.70 ± 1.40 km s−1 Mpc−1. RLB becomes increasingly relevant as distance ladder calibrations pursue greater numbers of ever more distant galaxies hosting both Cepheids (or Miras) and type-Ia supernovae. The measured periods of oscillating stars can readily be corrected for heliocentric redshift (e.g. of their host galaxies) in order to ensure H0 measurements free of RLB.
The Integrated Microbial Genomes (IMG) system serves as a community resource for comparative analysis of publicly available genomes in a comprehensive integrated context. IMG integrates publicly ...available draft and complete genomes from all three domains of life with a large number of plasmids and viruses. IMG provides tools and viewers for analyzing and reviewing the annotations of genes and genomes in a comparative context. IMG's data content and analytical capabilities have been continuously extended through regular updates since its first release in March 2005. IMG is available at http://img.jgi.doe.gov. Companion IMG systems provide support for expert review of genome annotations (IMG/ER: http://img.jgi.doe.gov/er), teaching courses and training in microbial genome analysis (IMG/EDU: http://img.jgi.doe.gov/edu) and analysis of genomes related to the Human Microbiome Project (IMG/HMP: http://www.hmpdacc-resources.org/img_hmp).
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