Accretion Disk Assembly During Common Envelope Evolution: Implications for Feedback and LIGO Binary Black Hole Formation

During a common envelope episode in a binary system, the engulfed companion spirals to tighter orbital separations under the influence of drag from the surrounding envelope material. As this object sweeps through material with a steep radial gradient of density, net angular momentum is introduced into the flow, potentially leading to the formation of an accretion disk. The presence of a disk would have dramatic consequences for the outcome of the interaction because accretion might be accompanied by strong, polar outflows with enough energy to unbind the entire envelope. Without a detailed understanding of the necessary conditions for disk formation during common envelope, therefore, it is difficult to accurately predict the population of merging compact binaries. This paper examines the conditions for disk formation around objects embedded within common envelopes using the `wind tunnel' formalism developed by MacLeod et al. (2017). We find that the formation of disks is highly dependent on the compressibility of the envelope material. Disks form only in the most compressible of stellar envelope gas, found in envelopes' outer layers in zones of partial ionization. These zones are largest in low-mass stellar envelopes, but comprise small portions of the envelope mass and radius in all cases. We conclude that disk formation and associated accretion feedback in common envelope is rare, and if it occurs, transitory. The implication for LIGO black hole binary assembly is that by avoiding strong accretion feedback, common envelope interactions should still result in the substantial orbital tightening needed to produce merging binaries.Comment: 12 pages, 10 figures, submitted to Ap

Core intended learning outcomes for tackling health inequalities in undergraduate medicine Curriculum development

© 2015 Williamson et al.; licensee BioMed Central. Background: Despite there being a concerted effort in recent years to influence what doctors can do to tackle health inequalities in the UK, there has been limited policy focus on what undergraduate students need to learn at medical school in preparation for this. This project led by members of the Health Inequalities Group of the Royal College of General Practitioners in collaboration with the Institute of Health Equity, University College London sought to fill this gap. Discussion: We conducted a Delphi poll using our teaching and stakeholder networks. We identified 5 areas for learning focusing on key knowledge and skills. These were population concepts, health systems, marginalised patient groups, cultural diversity and ethics. Summary: These intended learning outcomes about health inequalities represent the best available evidence to date for colleagues seeking to develop core undergraduate medical curricula on the topic

“Determined to succeed”: perceptions of success from autistic adults

This qualitative study employed a participatory approach to consult with sixteen autistic students on their experiences of success. Participants were students at five different UK higher education institutions. Using Interpretative Phenomenological Analysis, the research explored how they defined their successes and made sense of them in relation to their autism diagnoses. A flexible, multi-staged interview process was used. Evaluations indicated that the methodology enabled participation on both practical and theoretical levels. Participants became co-analysts of their data and demonstrated commitment to the project. The students described a wide range of successes, from the academic to the deeply personal, providing powerful counter-narratives to the dominant deficit-based interpretation of autism. The encouragement of one key individual (professional, family member or friend) had often been greatly influential to their achievements. Findings indicated the need for participants to both resist essentialist discourses regarding autism and to make themselves ‘extra-visible’ as an autistic person in order to assert their rights, with the autism diagnosis perceived as both an aid to self-understanding and a cause of additional barriers. In raising awareness of their own needs, participants contributed to broader understandings of autism, becoming educators and role models. The research demonstrates the importance of insights from autistic individuals, in particular showing how making sense of the autism label relates to perceptions of success. Implications for post-diagnostic support are discussed

Modelling vocabulary development among multilingual children prior to and following the transition to school entry

Differences between monolingual and multilingual vocabulary development have been observed but few studies provide a longitudinal perspective on vocabulary development before and following school entry. This study compares vocabulary growth profiles of 106 multilingual children to 211 monolingual peers before and after school entry to examine whether: (1) school entry coincides with different rates of vocabulary growth compared to prior to school entry, (2) compared to monolingual peers, multilingual children show different vocabulary sizes or rates of vocabulary growth, (3) the age of onset of second-language acquisition for multilingual children is associated with vocabulary size or rate of vocabulary growth, and (4) the sociolinguistic context of the languages spoken by multilingual children is associated with vocabulary size or rate of vocabulary growth. Results showed increases in vocabulary size across time for all children, with a steeper increase prior to school entry. A significant difference between monolingual and multilingual children who speak a minority language was observed with regards to vocabulary size at school entry and vocabulary growth prior to school entry, but growth rate differences were no longer present following school entry. Taken together, results suggest that which languages children speak may matter more than being multilingual per se