Perturbations induced by a molecular cloud on the young stellar disc in the Galactic Centre

The Galactic centre (GC) is a crowded environment: observations have revealed the presence of (molecular, atomic and ionized) gas, of a cusp of late-type stars, and of ~100 early-type stars, about half of which lying in one or possibly two discs. In this paper, we study the perturbations exerted on a thin stellar disc (with outer radius ~0.4 pc) by a molecular cloud that falls towards the GC and is disrupted by the supermassive black hole (SMBH). The initial conditions for the stellar disc were drawn from the results of previous simulations of molecular cloud infall and disruption in the SMBH potential. We find that most of the gas from the disrupted molecular cloud settles into a dense and irregular disc surrounding the SMBH. If the gas disc and the stellar disc are slightly misaligned (~5-20 deg), the precession of the stellar orbits induced by the gas disc significantly increases the inclinations of the stellar orbits (by a factor of ~3-5 in 1.5 Myr) with respect to the normal vector to the disc. Furthermore, the distribution of orbit inclinations becomes significantly broader. These results might be the clue to explain the broad distribution of observed inclinations of the early-type stars with respect to the normal vector of the main disc. We discuss the implications for the possibility that fresh gas was accreted by the GC after the formation of the disc(s) of early-type stars.Comment: 12 pages, 12 figures, 2 tables, accepted for publication in MNRA

Nonparametric Econometrics: The np Package

We describe the R np package via a series of applications that may be of interest to applied econometricians. The np package implements a variety of nonparametric and semiparametric kernel-based estimators that are popular among econometricians. There are also procedures for nonparametric tests of significance and consistent model specification tests for parametric mean regression models and parametric quantile regression models, among others. The np package focuses on kernel methods appropriate for the mix of continuous, discrete, and categorical data often found in applied settings. Data-driven methods of bandwidth selection are emphasized throughout, though we caution the user that data-driven bandwidth selection methods can be computationally demanding.

'Never judge a book by its cover?': students' understandings of lesbian, gay and bisexual appearance

This research aimed to explore (predominantly heterosexual) students' perceptions of sexuality and appearance. A short qualitative survey, which contained questions about the 'typical appearance' of lesbians, gay men, bisexual and heterosexual people, was completed by 36 university students. Previous research on dress and appearance in relation to sexuality has mainly focused on lesbian, gay or 'queer' individuals and communities. Minimal research has considered whether heterosexual people recognise non-heterosexuality through the dress and appearance of lesbians, gay men and bisexual people, and it would seem that previous studies have not explicitly considered the notion that heterosexuality might also be recognisable through appearance. Data were analysed using thematic analysis. Findings indicated that while students were able to provide appearance norms for lesbians and gay men (which conformed to those identified in previous research), they were also reluctant to give credence to (what they perceived as) 'stereotypes' of sexuality and appearance. They described heterosexual men and women in ways that conformed to 'traditional' gender norms, but were less able to identify any appearance norms for bisexual people, reflecting the invisibility of bisexuality within Western culture. © 2013 Copyright Taylor and Francis Group, LLC

SPHS: smoothed particle hydrodynamics with a higher order dissipation switch

We present a novel implementation of smoothed particle hydrodynamics that uses the spatial derivative of the velocity divergence as a higher order dissipation switch. Our switch - which is second order accurate - detects flow convergence before it occurs. If particle trajectories are going to cross, we switch on the usual SPH artificial viscosity, as well as conservative dissipation in all advected fluid quantities (e.g. the entropy). The viscosity and dissipation terms (that are numerical errors) are designed to ensure that all fluid quantities remain single valued as particles approach one another, to respect conservation laws, and to vanish on a given physical scale as the resolution is increased. SPHS alleviates a number of known problems with ‘classic' SPH, successfully resolving mixing, and recovering numerical convergence with increasing resolution. An additional key advantage is that - treating the particle mass similarly to the entropy - we are able to use multimass particles, giving significantly improved control over the refinement strategy. We present a wide range of code tests including the Sod shock tube, Sedov-Taylor blast wave, Kelvin-Helmholtz Instability, the ‘blob test' and some convergence tests. Our method performs well on all tests, giving good agreement with analytic expectation

Reflecting on bisexual identities and relationships: Nikki Hayfield in conversation with Annukka Lahti

Annukka Lahti is a Doctoral Student (Gender Studies) in the Department of Social Sciences and Philosophy at the University of Jyväskylä, Finland . Before starting her doctoral studies, she taught psychology at The Open University of the University of Jyväskylä. In her Doctoral studies, she explores how bisexuality – which is persistently culturally associated with temporariness, multiple partners and promiscuity - fits, fights and expands the normative cultural understandings of relationships. Her research specifically examines how a sample of Finnish bisexual women and their (ex-)partners of various genders negotiate bisexuality in their relationships, as psychosocial subjects. She considers how intersecting cultural constructions of relationships, genders and (bi)sexualities shape those negotiations and analyses her interview data through a psychosocial lens. Her analysis shows that negotiations around bisexuality and relationships are made not only through discursive regulation, but are also shaped in interaction with affective, non-rational psychic dimensions of being in a relationship. She has recently published on bisexual women’s and their partners’ relationships in Feminism & Psychology and has a number of papers under review. She is currently finishing her dissertation and plans to start her post-doctoral research project focusing on the separation experiences of LGBTIQ persons. Nikki Hayfield had an email discussion with Annukka over the summer to find out more about her research and interest in bisexuality

Editorial: Bisexualities and non-binary sexualities: Reflecting on invisibility, erasure and marginalisation

Editorial: Bisexualities and non-binary sexualities: Reflecting on invisibility, erasure and marginalisation

Looking heteronormatively good! Combining story completion with Bitstrips to explore understandings of sexuality and appearance

© 2019, © 2019 Taylor & Francis Group, LLC. This study sought to develop knowledge about understandings of sexuality and appearance by using a story completion task combined with an innovative visual methodology. Fifty-four (mainly female) participants were randomly assigned to complete a story about a fictional bisexual, lesbian, or heterosexual character who is going on a date, and then asked to build a Bitstrips online avatar of their character. Our social constructionist thematic analysis identified that looking good was a common feature of the stories and that this was understood in largely heteronormative terms. This imperative was also clear in stories of the date, which relied on traditional notions of gender and heterosexuality. Finally, individuality and authenticity were rewarded in participants’ stories, yet this was simultaneously constrained by (dominant) heteronormative narratives. We conclude that combining story completion with visual methods enabled deeper insights into representations of appearance, dating, and relationships, than a textual method alone