Brown dwarf formation by gravitational fragmentation of massive, extended protostellar discs

We suggest that low-mass hydrogen-burning stars like the Sun should sometimes form with massive extended discs; and we show, by means of radiation hydrodynamic simulations, that the outer parts of such discs (R>100 AU) are likely to fragment on a dynamical timescale (10^3 to $10^4 yr), forming low-mass companions: principally brown dwarfs (BDs), but also very low-mass hydrogen-burning stars and planetary-mass objects. A few of the BDs formed in this way remain attached to the primary star, orbiting at large radii. The majority are released into the field, by interactions amongst themselves; in so doing they acquire only a low velocity dispersion (<2 km/s), and therefore they usually retain small discs, capable of registering an infrared excess and sustaining accretion. Some BDs form close BD/BD binaries, and these binaries can survive ejection into the field. This BD formation mechanism appears to avoid some of the problems associated with the `embryo ejection' scenario, and to answer some of the questions not yet answered by the `turbulent fragmentation' scenario.Comment: 5 pages, accepted for publication in MNRAS Letter

Episodic accretion, radiative feedback, and their role in low-mass star formation

It is speculated that the accretion of material onto young protostars is episodic. We present a computational method to include the effects of episodic accretion in radiation hydrodynamic simulations of star formation. We find that during accretion events protostars are "switched on", heating and stabilising the discs around them. However, these events typically last only a few hundred years, whereas the intervals in between them may last for a few thousand years. During these intervals the protostars are effectively "switched off", allowing gravitational instabilities to develop in their discs and induce fragmentation. Thus, episodic accretion promotes disc frag- mentation, enabling the formation of low-mass stars, brown dwarfs and planetary-mass objects. The frequency and the duration of episodic accretion events may be responsible for the low-mass end of the IMF, i.e. for more than 60% of all stars.Comment: To appear in the proceedings of the 9th Pacific Rim Conference of Stellar Astrophysics, Lijiang, China, 201

Diegetic wounds : the representation of individual and collective trauma in found footage horror films

The type of horror film known as “found footage” was prominent in the 2000s and early 2010s. The term refers to films that aim to scare their audience, and which are primarily shot diegetically, with handheld and surveillance cameras that exist within the world of the film. The thesis identifies conceptual, aesthetic, and thematic links between found footage horror films and psychological trauma theory. For example, in each film the premise of the characters and viewers finding footage of a frightening event evokes the victim’s belated recollection of a traumatic experience. Additionally, the often-frantic cinematography and ambiguous formulation of the monster evokes the shocked and disoriented cognition of the trauma victim in the wake of their experience. Finally, the experience and effect of trauma on society is a recurring theme of found footage horror films. By examining 14 films, this thesis aims to answer the question: how do found footage horror films represent the relationship between individual and collective trauma? It theorises that individual trauma is conveyed through the films’ point-of-view (POV) aesthetic, while collective trauma is conveyed through their narrative themes. The thesis groups the films into four categories, each of which addresses a different aspect of trauma theory. Firstly, Remote found footage horror films, such as The Blair Witch Project (Myrick and Sánchez 1999), are examined as depictions of national historical traumas. Secondly, Urban found footage horror films, such as Cloverfield (Reeves 2008), are read as depictions of contemporary global traumas. Thirdly, Domestic found footage horror films, such as Paranormal Activity (Peli 2009), are framed as depictions of systemic domestic trauma. Fourthly, Perpetrator found footage horror films, such as Man Bites Dog (Belvaux, Bonzel and Poelvoorde 1992), are examined as depictions of perpetrator trauma. The thesis disputes the claim made by numerous critics and theorists that found footage horror films do not constitute a subgenre, but merely a cinematographic style or marketing gimmick. By demonstrating their aesthetic and thematic consistency, and the manifold ways that found footage horror can be read as representing trauma, the thesis argues that the films constitute a specific subgenre of horror cinema. The thesis makes significant contributions to knowledge by identifying, testing and demonstrating links between horror film theory, genre theory, spectator theory, and psychological and collective trauma theory. It conducts a broad survey of a recent subgenre of horror films that has, thus far, only received sporadic and insubstantial academic attention. It also presents an original theory that explains the psychological and sociological subtext of the subgenre, and the cultural insights that the films provide.Doctor of Philosoph

The role of representation in teaching and learning ideas about matter

The research described in this paper is designed around the notion that learning involves the recognition and development of students&rsquo; representational resources. This paper describes a classroom sequence in Ideas about Matter that focuses on representations and their negotiation, and reports on the effectiveness of this perspective in guiding teaching, and in providing further insight into student learning. Classroom sequences involving two experienced teachers (2008, Year 8 students) and an inexperienced teacher (2010, Year 7 students) were videotaped using a combined focus on the teacher and groups of students. Video analysis software was used to code the variety of representations used teachers and students, and sequences of representational negotiation. The paper reports on the effect of this approach on teacher pedagogy and on student learning of Ideas about Matter. The paper will present data from video of classroom activities, students&rsquo; work samples, student and teacher interviews and pre and post-unit testing, to explore what a representational focus might entail in teaching Ideas about Matter, and the role of representations in learning and reasoning and exploring scientific ideas.<br /