Ultra-luminous X-ray sources and neutron-star-black-hole mergers from very massive close binaries at low metallicity

Gravitational waves from the binary black hole (BH) merger GW150914 may enlighten our understanding of ultra-luminous X-ray sources (ULXs), as BHs>30Msun can reach luminosities>4x10^39 erg s^-1 without exceeding their Eddington limit. It is then important to study variations of evolutionary channels for merging BHs, which might instead form accreting BHs and become ULXs. It was recently shown that massive binaries with mass ratios close to unity and tight orbits can undergo efficient rotational mixing and evolve chemically homogeneously, resulting in a compact BH binary. We study similar systems by computing ~120000 detailed binary models with the MESA code covering a wide range of initial parameters. For initial mass ratios M2/M1~0.1-0.4, primaries >40Msun can evolve chemically homogeneously, remaining compact and forming a BH without undergoing Roche-lobe overflow. The secondary then expands and transfers mass to the BH, initiating a ULX phase. We predict that ~1 out of 10^4 massive stars evolves this way, and that in the local universe 0.13 ULXs per Msun yr^-1 of star-formation rate are observable, with a strong preference for low-metallicities. At metallicities log Z>-3, BH masses in ULXs are limited to 60Msun due to the occurrence of pair-instability supernovae which leave no remnant, resulting in an X-ray luminosity cut-off. At lower metallicities, very massive stars can avoid exploding as pair-instability supernovae and instead form BHs with masses above 130Msun, producing a gap in the ULX luminosity distribution. After the ULX phase, neutron-star-BH binaries that merge in less than a Hubble time are produced with a formation rate <0.2 Gpc^-3 yr^-1. We expect that upcoming X-ray observatories will test these predictions, which together with additional gravitational wave detections will provide strict constraints on the origin of the most massive BHs that can be produced by stars.Comment: Accepted for publication in A&A. 19 Pages plus 16 pages of appendices. Abstract abridge

Effects of Attentional Strategies on Novice Dart Throwing, Quiet Eye Duration and Pupillary Responses

This study examined the effects of focus ofattention (FOA) instructions on learning a dart throwing task,quiet eye duration (QED) and pupillary responses. Thirty-sixnovices (M age ¼ 33.6, SD ¼ 19.7) learned using either (a)internal-focus (arm movement), (b) external-focus (target/dart)or (c) control instructions before completing retention andtransfer tests 10 days later. FOA strategies did not significantlybenefit dart throwing learning or performance. QED was associated with performance in the transfer task, and pupillary constriction occurred during the QED. The content of FOAinstructions may have limited anticipated performance benefitsand reduced the FOA influence on QED. Pupillary constrictionreflected increased cognitive effort during QED, suggesting animportant feature of future precision aiming research

The use of OPTIMAL Instructions and Feedback in Physical Education Settings

In physical education (PE), the use of instruction and feedback are central to children’s motor skill learning. Recently, it has been identified that instruction and feedback which promote OPTIMAL theory motor learning factors (e.g., an external focus of attention, enhanced expectancies and autonomy support) can enhance children’s motor learning. However, it is unclear how PE teachers use OPTIMAL instructional approaches and therefore, was examined in the present study. Verbal statements (n = 5765) from seven PE teachers (Mean age: 39.29 ± 7.19yrs) over 10 PE lessons were collected and thematically analysed. Results indicate that PE teachers use more externally focused (25%) vs internally focused (10%) instructional behaviours. Moreover, PE teachers used instructional approaches that enhanced (35%) as compared to diminished expectancies (8%) in addition to statements which supported (35%) rather than thwarted (23%) autonomy. Overall, PE teachers appear to use instructional behaviours which support OPTIMAL motor learning however, more efforts are needed to improve the provision of optimised instructional behaviours. Additionally, the findings indicate that OPTIMAL instructions and feedback are rarely delivered in isolation and may be influenced by the contextual factors of PE and sometimes conflict in their delivery (i.e., externally focused and autonomy thwarting)

Detection and characterisation of genetic associations with canine skull shape and disease

The brachycephalic head conformation is a morphological trait under human selection across many popular breeds such as the Pug. The conformation is characterised by the concurrent rostrocaudal shortening and mediolateral widening of the skull. Overwhelming evidence suggests this skull conformation predisposes breeds to a respiratory morbidity, Brachycephalic Obstructive Airway Syndrome (BOAS) which restricts airflow. This is a major welfare concern. To date, very little is known regarding the genetic factors underpinning canine craniofacial variation or how such factors may influence BOAS aetiology. This project utilised computer tomography scans of 560 dogs to generate high resolution three-dimensional reconstructions of the skull. Geometric morphometric analysis permitted the separation of the confounding influence of size on shape (allometry) at an individual-level – a study design never previously utilised in dogs. Genome-wide association studies (GWAS) using viscerocranial shape changes identified a QTL on chromosome 1 associated with canine brachycephaly. Haplotype mapping refined the critical interval to encompass the SPARC-related modular calcium-binding protein 2 (SMOC2) gene. Leveraging haplotype mapping and whole-genome sequencing, a long interspersed nuclear element (LINE-1) was discovered within intron eight of SMOC2. Transcriptomic analysis revealed the presence of alternative SMOC2 transcripts containing premature stop codons and a downregulation of the gene among brachycephalic carriers of the LINE-1. Models of phenotypic effect predicted that this structural variant explains up to 36% of the total craniofacial variation in the dog. Despite many brachycephalic dogs being fixed for the SMOC2 LINE-1 mutation, heterogeneity in BOAS presentation suggests additional genetic factors contribute to disease risk and presentation. To address this, a respiratory distress syndrome with remarkable similarities to BOAS was assessed in the Norwich Terrier. Endoscopic examinations of 233 Norwich Terriers graded and characterised the respiratory syndrome for the use in a GWAS. A single QTL on chromosome 13 was associated with changes in the structure of the laryngeal saccules and cartilage of affected dogs. The underlying disease-associated haplotype encompassed the disintegrin and metalloproteinase with thrombospondin motifs 3 (ADAMTS3) gene which was observed to harbour a missense mutation in severely affected dogs. Screening for the variant across 89 diverse dog breeds revealed it was enriched in brachycephalic breeds, suggesting that the brachycephalic conformation alone does not completely explain the presentation of BOAS in these breeds. Together, these results provide the opportunity to improve animal welfare by offering genetic screening tests and further our understanding of the condition which is driven by both skeletal and non-skeletal factors

Label-checking strategies to adapt behaviour to design

Despite robust quality control procedures, labelling errors on fresh produce are estimated to cost the UK supermarket industry approximately £50million pounds per year in product recalls and wastage. Changing the format of the labels themselves is not a viable option. Instead, the challenge is to change or guide human operatives' behaviour so that label printing errors do not go undetected during quality control procedures. To this end, a simulated label checking task was presented to naïve participants to compare more systematic and strategic methods of label checking. Two conditions in which behaviour was computer-led were compared with a control condition in which checkers adopted their own idiosyncratic checking method. The data indicate that the two computer-led approaches resulted in improved levels of accuracy. Pushing label checkers towards a more systematic approach would appear to be effective in reducing undetected label errors, and could lead potentially to significant financial savings and reduced environmental wastage in the fresh produce industry