Tight asteroseismic constraints on core overshooting and diffusive mixing in the slowly rotating pulsating B8.3V star KIC 10526294

KIC 10526294 is a very slowly rotating and slowly pulsating late B-type star. Its 19 consecutive dipole gravity modes constitute a series with almost constant period spacing. This unique collection of identified modes probes the near-core environment of this star and holds the potential to reveal the size and structure of the overshooting zone on top of the convective core, as well as the mixing properties of the star. We pursue forward seismic modelling based on adiabatic eigenfrequencies of equilibrium models for eight extensive evolutionary grids tuned to KIC 10526294, by varying the initial mass, metallicity, chemical mixture, and the extent of the overshooting layer on top of the convective core. We examine models for both OP and OPAL opacities and test the occurrence of extra diffusive mixing. We find a tight mass, metallicity relation within the ranges $M$ ~ 3.13 to 3.25 Msun and $Z$ ~ 0.014 to 0.028. We deduce that an exponentially decaying diffusive core overshooting prescription describes the seismic data better than a step function formulation and derive a value of $f_{ov}$ between 0.017 and 0.018. Moreover, the inclusion of extra diffusive mixing with a value of $\log D_{\rm mix}$ between 1.75 and 2.00 dex (with $D_{\rm mix}$ in cm^2/sec) improves the goodness-of-fit based on the observed and modelled frequencies with a factor 11 compared to the case where no extra mixing is considered, irrespective of the $(M,Z)$ combination within the allowed seismic range. The inclusion of diffusive mixing in addition to core overshooting is essential to explain the structure in the observed period spacing pattern of this star. Moreover, we deduce that an exponentially decaying prescription for the core overshooting is to be preferred over a step function. Our best models for KIC 10526294 approach the seismic data to a level that they can serve future inversion of its stellar structure.Comment: 13 pages, 4 tables, 12 figures, accepted for publication in Astronomy & Astrophyic

New instantons in the double-well potential

A new instanton solution is found in the quantum-mechanical double-well potential with a four-fermion term. The solution has finite action and depends on four fermionic collective coordinates. We explain why in general the instanton action can depend on collective coordinates.Comment: 10 pages, clarifications and references adde

CubeSpec, A Mission Overview

CubeSpec is an in-orbit demonstration CubeSat mission in the ESA technology programme, developed and funded in Belgium. The goal of the mission is to demonstrate high-spectral-resolution astronomical spectroscopy from a 6-unit CubeSat. The prime science demonstration case for the in-orbit demonstration mission is to unravel the interior of massive stars using asteroseismology by high-cadance monitoring of the variations in spectral line profiles during a few months. The technological challenges are numerous. The 10x20cm aperture telescope and echelle spectrometer have been designed to fit in a 10x10x20cm volume. Under low-Earth orbit thermal variations, maintaining the fast telescope focus and spectrometer alignment is achieved via an athermal design. Straylight rejection and thermal shielding from the Sun and Earth infrared flux is achieved via deploying Earth and Sunshades. The narrow spectrometer slit requires arcsecond-level pointing stability using a performant 3-axis wheel stabilised attitude control system with star tracker augmented with a fine beam steering mechanism controlled in closed loop with a guiding sensor. The high cadence, long-term monitoring requirement of the mission poses specific requirements on the orbit and operational scenarios to enable the required sky visibility. CubeSpec is starting the implementation phase, with a planned launch early 2024

The number of patients simultaneously present at the emergency department as an indicator of unsafe waiting times: A receiver operated curve-based evaluation

BACKGROUND: Emergency department (ED) crowding and prolonged waiting times have been associated with adverse consequences towards quality and patient safety. OBJECTIVE: This study investigates whether the number of patients simultaneously present at the ED might be an indicator of unsafe waiting and at what threshold hospital-wide measures to improve patient outflow could be justified. METHODS: Data were retrospectively collected during a 1-year period; all ED patients aged ≥16 years, and triaged as ESI-1 or ESI-2 were eligible for inclusion. The number of patients simultaneously present was used as occupancy rate. Waiting time was considered unsafe if it was longer than 10 min for ESI-1 patients, or longer than 30 min for ESI-2 patients. Differences in waiting time and occupancy between patients with safe and unsafe waiting times were analysed using the Mann-Whitney U test. The ability of the occupancy rate to discriminate unsafe waiting times was analysed using a receiver operating characteristic curve. RESULTS: The overall median waiting time was 5 min (IQR=4-8) for ESI-1, and 12 min (IQR=6-24) for ESI-2 patients. Unsafe waiting times occurred in 16.0% of ESI-1 patients (median waiting time=17 min, IQR=13-23), and in 18.9% of ESI-2 patients (median waiting time=48 min, IQR=37-68). The occupancy rate was a weak indicator for unsafe waiting times in ESI-1 patients (AUC=0.625, 95%CI 0.537-0.713) but a fair indicator for unsafe waiting times in ESI-2 patients (AUC=0.740, 95%CI 0.727-0.753) for which the threshold to predict unsafe waiting times with 90% sensitivity was 51 patients. CONCLUSION: The number of patients simultaneously present is a moderate indicator of unsafe waiting times. Future initiatives to improve safe waiting times should not focus solely on occupancy, and expand their focus towards other factors affecting waiting time.publisher: Elsevier articletitle: The number of patients simultaneously present at the emergency department as an indicator of unsafe waiting times: A receiver operated curve-based evaluation journaltitle: International Emergency Nursing articlelink: http://dx.doi.org/10.1016/j.ienj.2014.01.002 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe

The number of patients simultaneously present at the emergency department as an indicator of unsafe waiting times: a receiver operated curve-based evaluation

status: publishe