Star clusters near and far; tracing star formation across cosmic time

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00690-x.Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e.\ detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.Peer reviewedFinal Accepted Versio

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe

The use of spatial manipulation to examine goalkeepers' anticipation

This study investigated whether anticipation and search strategies of goalkeepers are influenced by temporally and spatially manipulated video of a penalty. Participants were clustered into three groups depending on skill: goalkeepers (n = 17), field players (n = 20) and control group (n = 20). An eye tracker was worn whilst watching 40 videos of a striker kicking to four corners of a goal in random order. All 40 videos were temporally occluded at foot-to-ball contact, and the non-kicking leg of 20 videos was spatially manipulated. Results showed that goalkeepers had significantly better predictions than the two groups with no differences between the two testing conditions. According to effect size, the percentage of fixation location and viewing time of the kicking leg and ball were greater for the goalkeepers and field players group than the control group irrespective of testing conditions. The fixations on the kicking leg and ball in conjunction with comparable predictions between spatially manipulated and control conditions suggest that goalkeepers may not rely on the non-kicking leg. Furthermore, goalkeepers appear to use a global perceptual approach by anchoring on a distal fixation point/s of the penalty taker whilst using peripheral vision to obtain additional information

The role of video manipulation in skill acquisition

Introduction: The use of temporal and spatial occlusion are well established methods to obtain visual information and subsequent mechanisms underlying sport skills when comparing athlete levels and progression of learning. Although temporal occlusion may meet ecological validity, the use of spatial occlusion in research (Panchuk & Vickers, 2009; Williams & David, 1998) where sections of the body are no longer visible may cause concerns for poor ecological validity. Therefore, the aim of this abstract is to discuss the use of video manipulation as a tool for analysing anticipation. \ud \ud Methods: This abstract involves data taken from a previous study by the authors where video of a striker kicking a penalty kick was digitally manipulated by changing the standing leg depending on direction. Three groups depending on skill where used, goalkeepers (n = 17), field players (n = 20) and control group (n = 20). An eye tracker was worn whilst watching 40 videos of a striker kicking at the goal in randomised placement order (left or right and high or low). All 40 videos were temporally occluded at foot-to-ball contact and the non-kicking leg of 20 videos were spatially manipulated. \ud \ud Results: As shown in Tamara et al., (2015), the results of using a video spatial manipulation method for the football penalty kick showed similar effects as previous research (Savelsbergh et al. 2002) for predominately final fixations occurring at the stance foot (37.6%) and the ball (33.7%). There was no significant difference for goalkeepers' prediction the direction of the ball in either the manipulated or controlled condition. \ud \ud Discussion: This is the first time that video spatial manipulation has been used and it appears that the results mimic previous research with spatial occlusion. However, it has been shown that once the stance leg is occluded performance decreases, this was not the case when the video was manipulated. Future research should look at comparing the methods to determine which would be more useful from an ecological point of view

Association of Fetal Growth Restriction With Neurocognitive Function After Repeated Antenatal Betamethasone Treatment vs Placebo:Secondary Analysis of the ACTORDS Randomized Clinical Trial

Published: February 1, 2019Importance: Repeated doses of antenatal betamethasone are recommended for women at less than 32 weeks' gestation with ongoing risk of preterm birth. However, concern that this therapy may be associated with adverse neurocognitive effects in children with fetal growth restriction (FGR) remains. Objective: To determine the influence of FGR on the effects of repeated doses of antenatal betamethasone on neurocognitive function in midchildhood. Design, Setting, and Participants: This preplanned secondary analysis of data from the multicenter Australasian Collaborative Trial of Repeat Doses of Corticosteroids (ACTORDS) included women at less than 32 weeks' gestation with ongoing risk of preterm birth (<32 weeks) at least 7 days after an initial course of antenatal corticosteroids who were treated at 23 hospitals across Australia and New Zealand from April 1, 1998, through July 20, 2004. Participants were randomized to intramuscular betamethasone or saline placebo; treatment could be repeated weekly if the woman was judged to be at continued risk of preterm birth. All surviving children were invited to a midchildhood outcome study. Data for this study were collected from October 27, 2006, through March 18, 2011, and analyzed from June 1 through 30, 2018. Interventions: At 6 to 8 years of corrected age, children were assessed by a pediatrician and psychologist for neurosensory and cognitive function, and parents completed standardized questionnaires. Main Outcomes and Measures: The prespecified primary outcomes were survival free of any disability and death or survival with moderate to severe disability. Results:Of 1059 eligible children, 988 (55.0% male; mean [SD] age at follow-up, 7.5 [1.1] years) were assessed at midchildhood. The FGR rate was 139 of 493 children (28.2%) in the repeated betamethasone treatment group and 122 of 495 (24.6%) in the placebo group (P = .20). Primary outcome rates were similar between treatment groups for the FGR and non-FGR subgroups, with no evidence of an interaction effect for survival free of any disability (FGR group, 108 of 144 [75.0%] for repeated betamethasone treatment vs 91 of 126 [72.2%] for placebo groups [odds ratio [OR], 1.1; 95% CI, 0.6-1.9]; non-FGR group, 267 of 335 [79.7%] for repeated betamethasone vs 283 of 358 [79.0%] for placebo groups [OR, 1.0; 95% CI, 0.7-1.5]; P = .77) and death or moderate to severe disability (FGR group, 21 of 144 [14.6%] for repeated betamethasone treatment vs 20 of 126 [15.9%] for placebo groups [OR, 0.9; 95% CI, 0.4-1.9]; non-FGR group, 29 of 335 [8.6%] for repeated betamethasone vs 36 of 358 [10.0%] for placebo [OR, 0.8; 95% CI, 0.4-1.3]; P = .84). Conclusions and Relevance: In this study, repeated antenatal betamethasone treatment compared with placebo was not associated with adverse effects on neurocognitive function at 6 to 8 years of age, even in the presence of FGR. Physicians should use repeated doses of antenatal corticosteroids when indicated before preterm birth, regardless of FGR, in view of the associated neonatal benefits and absence of later adverse effects. Trial Registration: anzctr.org.au Identifier: ACTRN12606000318583.Robert D. Cartwright, Caroline A. Crowther, Peter J. Anderson, Jane E. Harding, Lex W. Doyle, Christopher J. D. McKinla

Noble Gas Evolution of the Martian Atmosphere in the last 4 Gyr Recorded by Regolith Breccia NWA 8114

The martian meteorite Northwest Africa (NWA) 8114 is a regolith breccia grouped with the NWA 7034 (‘Black Beauty’) stone and others. The meteorite, with its complex rock and mineral load, records over 4.4 billion years of martian geological and atmospheric history. In this work we present new analyses of noble gases in NWA 8114, and consider the constraints they impose on the evolution of the martian atmosphere over the past 4 billion years. We also report a petrographic overview, halogen abundances, and an argon isotope age, which provide context for interpreting the noble gas data. The krypton and xenon elemental signature of NWA 8114 is elementally fractionated with respect to the present-day martian atmosphere as measured in shergottite glasses; there is no requirement for a contribution from the ancient martian atmosphere in our data. The xenon isotopic composition incorporates (i) a component enriched in 129Xe (maximum 129Xe/132Xe = 2.450 ± 0.045 compared with a solar ratio of ∼ 1), which is similar to the present day martian atmosphere, (ii) a cosmic-ray spallation component dominated by production from barium, and (iii) a fission component. We estimate a cosmic ray exposure (CRE) age of 5.7 ± 1.3 Myr from cosmogenic 21Ne and 38Ar. Understanding how the martian atmosphere has changed through the planet’s history is a key part of understanding the planet’s geological history and evolution. We develop a model for the evolution of the martian atmosphere constrained by the amount of spallation-derived xenon in the atmosphere today and the evolution of the 129Xe/132Xe ratio over time. A baseline model in which the early atmosphere collapsed 3.7 Gyr ago (and assuming no further loss) requires a constant degassing of the crustal budget of spallation xenon of 0.034 % Myr−1 to accumulate sufficient spallation-derived xenon in the atmosphere. Combining constraints imposed by the 129Xe/132Xe ratio with the spallation budget requires loss of xenon from the martian atmosphere over the last 3.7 Gyr, with the present day budget being as little as 20 % of that at the start of this period.ISSN:0016-7037ISSN:1872-953