NLTE analysis of Sr lines in spectra of late-type stars with new R-matrix atomic data

We investigate statistical equilibrium of neutral and singly-ionized strontium in late-type stellar atmospheres. Particular attention is given to the completeness of the model atom, which includes new energy levels, transition probabilities, photoionization and electron-impact excitation cross-sections computed with the R-matrix method. The NLTE model is applied to the analysis of Sr I and Sr II lines in the spectra of the Sun, Procyon, Arcturus, and HD 122563, showing a significant improvement in the ionization balance compared to LTE line formation calculations, which predict abundance discrepancies of up to 0.5 dex. The solar Sr abundance is log A = 2.93 \pm 0.04 dex, in agreement with the meteorites. A grid of NLTE abundance corrections for Sr I and Sr II lines covering a large range of stellar parameters is presented.Comment: 11 pages, 7 figures, accepted for publication in Astronomy & Astrophysic

Time Resolution and Linearity Measurements for a Scintillating Fiber Detector Instrumented with VLPC's

The time resolution for a charged particle detection is reported for a typical scintillating fiber detector instrumented with Rockwell HISTE-IV Visible Light Photon Counters. The resolution measurements are shown to agree with a simple Monte Carlo model, and the model is used to make recomendations for improved performance. In addition, the gain linearity of a sample of VLPC devices was measured. The gain is shown to be linear for incident light intensities which produce up to approximately 600 photoelectrons per event.Comment: 18 pages, 14 figures; Submitted to Nucl. Instr & Meth. in Phys. Res. A; Please direct correspondence to [email protected]

Athlete learning in Olympic sport

High-performance sport impacts athletes beyond the physical. Coaches and coaching practice are particularly influential in shaping this learning and development. This article examines the learning identified through an inductive content analysis of eight former Olympic athletes’ career narratives. Three phases of learning could be identified across the cohort: ‘Growing into high-performance sport’, ‘Making sense of high-performance sport’, and ‘(Re)shaping high-performance sport’. A cultural perspective of learning, in particular the metaphor of ‘becoming’, is employed to interpret the Olympians’ learning experiences. The findings of this research indicate that athlete learning is bound by particular high-performance sporting contexts and career phases, yet impacted by the athletes’ individual backgrounds and dispositions. Further, data indicate that athletes’ personal development reflexively intertwines with athletic performance and performance enhancement. Implications for coaches are to: (1) involve athletes in co-constructing their sporting cultures and training contexts; and (2) provide possibilities and support for athletes to develop personally

Non-local Thermodynamic Equilibrium Stellar Spectroscopy with 1D and 〈3D〉 Models. II. Chemical Properties of the Galactic Metal-poor Disk and the Halo

From exploratory studies and theoretical expectations it is known that simplifying approximations in spectroscopic analysis (local thermodynamic equilibrium (LTE), 1D) lead to systematic biases of stellar parameters and abundances. These biases depend strongly on surface gravity, temperature and, in particular, for LTE versus non-LTE (NLTE), on metallicity of the stars. Here we analyze the [Mg/Fe] and [Fe/H] plane of a sample of 326 stars, comparing LTE and NLTE results obtained using 1D hydrostatic models and averaged $\langle 3{\rm{D}}\rangle$ models. We show that compared to the $\langle 3{\rm{D}}\rangle$ NLTE benchmark, the other three methods display increasing biases toward lower metallicities, resulting in false trends of [Mg/Fe] against [Fe/H], which have profound implications for interpretations by chemical evolution models. In our best $\langle 3{\rm{D}}\rangle$ NLTE model, the halo and disk stars show a clearer behavior in the [Mg/Fe]–[Fe/H] plane, from the knee in abundance space down to the lowest metallicities. Our sample has a large fraction of thick disk stars and this population extends down to at least [Fe/H] ~ −1.6 dex, further than previously proven. The thick disk stars display a constant [Mg/Fe] ≈ 0.3 dex, with a small intrinsic dispersion in [Mg/Fe] that suggests that a fast SN Ia channel is not relevant for the disk formation. The halo stars reach higher [Mg/Fe] ratios and display a net trend of [Mg/Fe] at low metallicities, paired with a large dispersion in [Mg/Fe]. These indicate the diverse origin of halo stars from accreted low-mass systems to stochastic/inhomogeneous chemical evolution in the Galactic halo

A High-resolution Scintillating Fiber Tracker With Silicon Photomultiplier Array Readout

We present prototype modules for a tracking detector consisting of multiple layers of 0.25 mm diameter scintillating fibers that are read out by linear arrays of silicon photomultipliers. The module production process is described and measurements of the key properties for both the fibers and the readout devices are shown. Five modules have been subjected to a 12 GeV/c proton/pion testbeam at CERN. A spatial resolution of 0.05 mm and light yields exceeding 20 detected photons per minimum ionizing particle have been achieved, at a tracking efficiency of more than 98.5%. Possible techniques for further improvement of the spatial resolution are discussed.Comment: 31 pages, 27 figures, pre-print version of an article published in Nuclear Instruments and Methods in Physics Research Section A, Vol. 62

The RAVE Survey: Constraining the Local Galactic Escape Speed

We report new constraints on the local escape speed of our Galaxy. Our analysis is based on a sample of high velocity stars from the RAVE survey and two previously published datasets. We use cosmological simulations of disk galaxy formation to motivate our assumptions on the shape of the velocity distribution, allowing for a significantly more precise measurement of the escape velocity compared to previous studies. We find that the escape velocity lies within the range 498\kms < \ve < 608 \kms (90 per cent confidence), with a median likelihood of 544\kms. The fact that \ve^2 is significantly greater than 2\vc^2 (where \vc=220\kms is the local circular velocity) implies that there must be a significant amount of mass exterior to the Solar circle, i.e. this convincingly demonstrates the presence of a dark halo in the Galaxy. For a simple isothermal halo, one can calculate that the minimum radial extent is $\sim58$ kpc. We use our constraints on \ve to determine the mass of the Milky Way halo for three halo profiles. For example, an adiabatically contracted NFW halo model results in a virial mass of $1.42^{+1.14}_{-0.54}\times10^{12}M_\odot$ and virial radius of $305^{+66}_{-45}$ kpc (90 per cent confidence). For this model the circular velocity at the virial radius is 142^{+31}_{-21}\kms. Although our halo masses are model dependent, we find that they are in good agreement with each other.Comment: 19 pages, 9 figures, MNRAS (accepted). v2 incorporates minor cosmetic revisions which have no effect on the results or conclusion

The Gaia-ESO Survey: a quiescent Milky Way with no significant dark/stellar accreted disc

According to our current cosmological model, galaxies like the Milky Way are expected to experience many mergers over their lifetimes. The most massive of the merging galaxies will be dragged towards the disc-plane, depositing stars and dark matter into an accreted disc structure. In this work, we utilize the chemo-dynamical template developed in Ruchti et al. to hunt for accreted stars. We apply the template to a sample of 4,675 stars in the third internal data release from the Gaia-ESO Spectroscopic Survey. We find a significant component of accreted halo stars, but find no evidence of an accreted disc component. This suggests that the Milky Way has had a rather quiescent merger history since its disc formed some 8-10 billion years ago and therefore possesses no significant dark matter disc.Comment: 15 pages, 11 figures, accepted for publication in MNRA

Circulating calprotectin levels four months after severe and non-severe COVID-19.

BACKGROUND Calprotectin is an inflammatory marker mainly released by activated neutrophils that is increased in acute severe COVID-19. After initial recovery, some patients have persistent respiratory impairment with reduced diffusion capacity of the lungs for carbon monoxide (DLCO) months after infection. Underlying causes of this persistent impairment are unclear. We aimed to investigate the correlation between circulating calprotectin, persistent lung functional impairment and intensive care unit (ICU) stay after COVID-19 in two university hospital centres in Switzerland. METHODS Calprotectin levels were measured in serum from 124 patients (50% male) from the Bern cohort (post-ICU and non-ICU patients) and 68 (76% male) from the Lausanne cohort (only post-ICU patients) four months after COVID-19. Calprotectin was correlated with clinical parameters. Multivariate linear regression (MLR) was performed to evaluate the independent association of calprotectin in different models. RESULTS Overall, we found that post-ICU patients, compared to non-ICU, were significantly older (age 59.4 ± 13.6 (Bern), 60.5 ± 12.0 (Lausanne) vs. 48.8 ± 13.4 years) and more obese (BMI 28.6 ± 4.5 and 29.1 ± 5.3 vs. 25.2 ± 6.0 kg/m2, respectively). 48% of patients from Lausanne and 44% of the post-ICU Bern cohort had arterial hypertension as a pre-existing comorbidity vs. only 10% in non-ICU patients. Four months after COVID-19 infection, DLCO was lower in post-ICU patients (75.96 ± 19.05% predicted Bern, 71.11 ± 18.50% Lausanne) compared to non-ICU (97.79 ± 21.70% predicted, p < 0.01). The post-ICU cohort in Lausanne had similar calprotectin levels when compared to the cohort in Bern (Bern 2.74 ± 1.15 µg/ml, Lausanne 2.49 ± 1.13 µg/ml vs. non-ICU 1.86 ± 1.02 µg/ml; p-value < 0.01). Calprotectin correlated negatively with DLCO (r= -0.290, p < 0.001) and the forced vital capacity (FVC) (r= -0.311, p < 0.001). CONCLUSIONS Serum calprotectin is elevated in post-ICU patients in two independent cohorts and higher compared to non-ICU patients four months after COVID-19. In addition, there is a negative correlation between calprotectin levels and DLCO or FVC. The relationship between inflammation and lung functional impairment needs further investigations. TRIAL REGISTRATION NCT04581135