An extreme critical space-time: echoing and black-hole perturbations

A homothetic, static, spherically symmetric solution to the massless Einstein- Klein-Gordon equations is described. There is a curvature singularity which is central, null, bifurcate and marginally trapped. The space-time is therefore extreme in the sense of lying at the threshold between black holes and naked singularities, just avoiding both. A linear perturbation analysis reveals two types of dominant mode. One breaks the continuous self-similarity by periodic terms reminiscent of discrete self-similarity, with echoing period within a few percent of the value observed numerically in near-critical gravitational collapse. The other dominant mode explicitly produces a black hole, white hole, eternally naked singularity or regular dispersal, the latter indicating that the background is critical. The black hole is not static but has constant area, the corresponding mass being linear in the perturbation amplitudes, explicitly determining a unit critical exponent. It is argued that a central null singularity may be a feature of critical gravitational collapse.Comment: 6 revtex pages, 6 eps figure

Pilot evaluation of a brief training video aimed at reducing mental health stigma amongst emergency first responders (the ENHANcE II study)

Background First responders (i.e. police and ambulance staff) have increasingly become part of the mental health care system, often being the first port of call for those experiencing a crisis. Despite their frequent involvement in supporting those with mental health problems, there is evidence that mental health stigma is high amongst first responders. Aims The aim of the present study was to evaluate a brief training video aimed at reducing mental health stigma amongst first responders. Methods First responders watched a training video based on the cognitive behavioural model of mental health stigma, and involved contributions from people with lived experience, and first responders. Measures of mental health stigma were collected before and after viewing the training. Results The training video produced small but significant improvements in mental health stigma, and these effects did not differ between police and ambulance staff. We were unable to determine what psychological constructs mediated this change in stigma. The feedback on the training video was generally positive, but also indicated some key areas for future development. Conclusions The present study provides encouraging evidence that levels of mental health stigma can be improved using a resource-light training intervention

Advanced Industrial Robot Control Systems

The objective of this research is to extend the flexibility a,hd . \u27usefulness. of current industrial robots by the integration of robot motion control directly into a. general purpose programming language, the development of force feedback and its integration into the language, the formulation of a high-level task description language RTM, and by the investigation of both off-line collision-free path planning and on-line collision avoidance

Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission

We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-$L\star$ starburst, and $L\star$ galaxies with different propagation models, including advection, isotropic and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two moment method. We forward-model and compare to observations of $\gamma$-ray emission from nearby and starburst galaxies. We reproduce the $\gamma$-ray observations of dwarf and $L\star$ galaxies with constant isotropic diffusion coefficient $\kappa \sim 3\times 10^{29}\,{\rm cm^{2}\,s^{-1}}$. Advection-only and streaming-only models produce order-of-magnitude too large $\gamma$-ray luminosities in dwarf and $L\star$ galaxies. We show that in models that match the $\gamma$-ray observations, most CRs escape low-gas-density galaxies (e.g.\ dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for $\gamma$-ray emissivities. Models where CRs are ``trapped'' in the star-forming disk have lower star formation efficiency, but these models are ruled out by $\gamma$-ray observations. For models with constant $\kappa$ that match the $\gamma$-ray observations, CRs form extended halos with scale heights of several kpc to several tens of kpc.Comment: 31 pages, 26 figures, accepted for publication in MNRA

Classification of spacelike surfaces in spacetime

A classification of 2-dimensional surfaces imbedded in spacetime is presented, according to the algebraic properties of their shape tensor. The classification has five levels, and provides among other things a refinement of the concepts of trapped, umbilical and extremal surfaces, which split into several different classes. The classification raises new important questions and opens many possible new lines of research. These, together with some applications and examples, are briefly considered.Comment: 42 pages, 10 tables, many diagram

Quasi-spherical approximation for rotating black holes

We numerically implement a quasi-spherical approximation scheme for computing gravitational waveforms for coalescing black holes, testing it against angular momentum by applying it to Kerr black holes. As error measures, we take the conformal strain and specific energy due to spurious gravitational radiation. The strain is found to be monotonic rather than wavelike. The specific energy is found to be at least an order of magnitude smaller than the 1% level expected from typical black-hole collisions, for angular momentum up to at least 70% of the maximum, for an initial surface as close as $r=3m$.Comment: revised version, 8 pages, RevTeX, 8 figures, epsf.sty, psfrag.sty, graphicx.st

Enhancing mental health awareness in emergency services (the ENHANcE I project): cross-sectional survey on mental health stigma among emergency services staff

Background The number of mental health-related 999 calls to emergency services has increased in recent years. However, emergency services staff have an unfavourable reputation when it comes to supporting people experiencing mental health problems. Aims To assess the levels of explicit and implicit mental health stigma among accident and emergency, ambulance and police staff, and draw comparisons with the general population. Additional analyses sought to identify which variables predict mental health stigma among emergency services staff. Method A cross-sectional survey of 1837 participants, comprising four independent groups (accident and emergency, ambulance and police staff, and the general population). Results Levels of mental health stigma across all four groups were lower than those reported in recent surveys of the general population by the ‘Time to Change’ campaign. Within this study, explicit levels of mental health stigma were lower among the general population compared with emergency services staff. There was no difference between emergency service professions, nor were there any between-group differences in terms of implicit mental health stigma. The only consistent predictors of mental health stigma were attitudes and future behavioural intentions, whereby increased stigma was predicted by increased fear, reduced sympathy and greater intended discrimination. Conclusions Our findings suggest that levels of mental health stigma have improved over time, but there is room for improvement in emergency services staff. Interventions to improve mental health stigma may be most effective if, in line with the cognitive–behavioural model of stigma, they target attitudes and behavioural intentions

Deciphering interplay between Salmonella invasion effectors

Bacterial pathogens have evolved a specialized type III secretion system (T3SS) to translocate virulence effector proteins directly into eukaryotic target cells. Salmonellae deploy effectors that trigger localized actin reorganization to force their own entry into non-phagocytic host cells. Six effectors (SipC, SipA, SopE/2, SopB, SptP) can individually manipulate actin dynamics at the plasma membrane, which acts as a ‘signaling hub’ during Salmonella invasion. The extent of crosstalk between these spatially coincident effectors remains unknown. Here we describe trans and cis binary entry effector interplay (BENEFIT) screens that systematically examine functional associations between effectors following their delivery into the host cell. The results reveal extensive ordered synergistic and antagonistic relationships and their relative potency, and illuminate an unexpectedly sophisticated signaling network evolved through longstanding pathogen–host interaction

Hawking radiation as tunneling and the unified first law of thermodynamics at the apparent horizon in the FRW universe

Relations between the tunneling rate and the unified first law of thermodynamics at the apparent horizon of the FRW universe are investigated. The tunneling rate arises as a consequence of the unified first law of thermodynamics in such a dynamical system. The analysis shows obviously how the tunneling is intimately connected with the unified first law of thermodynamics through the principle of conservation of energy.Comment: Latex, 9 pages, no figur

Hamiltonians for Reduced Gravity

A generalised canonical formulation of gravity is devised for foliations of spacetime with codimension $n\ge1$. The new formalism retains n-dimensional covariance and is especially suited to 2+2 decompositions of spacetime. It is also possible to use the generalised formalism to obtain boundary contributions to the 3+1 Hamiltonian.Comment: 18 pages, revtex, 3 postscript figures include