Simulations of Evolving or Outbursting Molecular Protostellar Jets

The kinematic and radiative power of molecular jets is expected to change as a protostar undergoes permanent or episodal changes in the rate at which it accretes. We study here the consequences of evolving jet power on the spatial and velocity structure, as well as the fluxes, of molecular emission from the bipolar outflow. We consider a jet of rapidly increasing density and a jet in which the mass input is abruptly cut off. We perform three dimensional hydrodynamic simulations with atomic and molecular cooling and chemistry. In this work, highly collimated and sheared jets are assumed. We find that position-velocity diagrams, velocity-channel maps and the relative H$_2$ and CO fluxes are potentially the best indicators of the evolutionary stage. In particular, the velocity width of the CO lines may prove most reliable although the often-quoted mass-velocity power-law index is probably not. We demonstrate how the relative H$_2$ 1--0 S(1) and CO J=1--0 fluxes evolve and apply this to interpret the phase of several outflows.Comment: 13 pages, 15 figures, Accepted for publication in MNRA

The end [programme]

Inspired by the stage direction from The Winter’s Tale, ‘Exit pursued by a bear’, The End explores endings and exits and asks why we perform and how we will know when to stop. Developed at The Junction (Cambridge), Brighton Dome and Festival, New Art Exchange and Lakeside Arts Centre (Nottingham). Commissioned by Chester Performs. Supported by the National Lottery through Arts Council England. Selected for the British Council’s Edinburgh Showcase 2011

Graph-theoretical conditions for inscribability and Delaunay realizability

We present new graph-theoretical conditions for inscribable polyhedra and Delaunay triangulations. We establish several sufficient conditions of the following general form: if a polyhedron has a sufficiently rich collection of Hamiltonian subgraphs, then it is inscribable. These results have several consequences:All 4-connected polyhedra are inscribable.All simplical polyhedra in which all vertex degrees are between 4 and 6, inclusive, are inscribable.All triangulations without chords or nonfacial triangles are realizable as Delaunay triangulations.We also strengthen some earlier results about matchings in inscribable polyhedra. Specifically, we show that any nonbipartite inscribable polyhedron has a perfect matching containing any specified edge, and that any bipartite inscribable polyhedron has a perfect matching containing any two specified disjoint edges. We give examples showing that these results are best possible

The beginning [programme]

Inspired by A Midsummer Night’s Dream, The Beginning is the second in a trilogy of works deconstructing Shakespearean stage directions. The Beginning was developed at Lakeside Arts Centre (Nottingham), Leeds Met Studio Theatre, Loughborough University and The Junction (Cambridge). Supported by the National Lottery through Arts Council England and commissioned by the World Event Young Artists 2012. Selected for the British Council's Edinburgh Showcase 2013

Anticipated and Actual Bequests

This paper uses data on anticipated bequests from two waves of the Health and Retirement Study and the Asset and Health Dynamics of the Oldest Old (AHEAD), and on actual bequests from AHEAD. Actual bequests were measured in exit interviews given by proxy respondents for 774 AHEAD respondents who died between waves 1 and 2. Because the exit interview is representative of the elderly population, the distribution of estate values is quite different from that obtained from estate records, which represent just a wealthy subset of the population. Anticipated bequests were measured by the subjective probability of leaving bequests. Between waves 1 and 2, increases in bequest probabilities were associated with increases in the subjective probability of surviving, increments in household wealth, and widowing while out-of-pocket medical expenses reduced the likelihood of a bequest. By comparing bequest probabilities with baseline wealth we were able to test a main prediction of the life-cycle model, that individuals will dissave at advanced old-age. The AHEAD respondents anticipate substantial dissaving before they die.

The distribution of shock waves in driven supersonic turbulence

Supersonic turbulence generates distributions of shock waves. Here, we analyse the shock waves in three-dimensional numerical simulations of uniformly driven supersonic turbulence, with and without magnetohydrodynamics and self-gravity. We can identify the nature of the turbulence by measuring the distribution of the shock strengths. We find that uniformly driven turbulence possesses a power law distribution of fast shocks with the number of shocks inversely proportional to the square root of the shock jump speed. A tail of high speed shocks steeper than Gaussian results from the random superposition of driving waves which decay rapidly. The energy is dissipated by a small range of fast shocks. These results contrast with the exponential distribution and slow shock dissipation associated with decaying turbulence. A strong magnetic field enhances the shock number transverse to the field direction at the expense of parallel shocks. A simulation with self-gravity demonstrates the development of a number of highly dissipative accretion shocks. Finally, we examine the dynamics to demonstrate how the power-law behaviour arises.Comment: accepted to Astron. & Astrophys.; ten page