Statistical properties of classical gravitating particles in (2+1) dimensions

We report the statistical properties of classical particles in (2+1) gravity as resulting from numerical simulations. Only particle momenta have been taken into account. In the range of total momentum where thermal equilibrium is reached, the distribution function and the corresponding Boltzmann entropy are computed. In the presence of large gravity effects, different extensions of the temperature turn out to be inequivalent, the distribution function has a power law high-energy tail and the entropy as a function of the internal energy presents a flex. When the energy approaches the open universe limit, the entropy and the mean value of the particle kinetic energy seem to diverge.Comment: Latex2e (amssymb) file, 17 page

Non-Perturbative Particle Dynamics

We construct a non-perturbative, single-valued solution for the metric and the motion of two interacting particles in ($2+1$)-Gravity, by using a Coulomb gauge of conformal type. The method provides the mapping from multivalued ( minkowskian ) coordinates to single-valued ones, which solves the non-abelian monodromies due to particles's momenta and can be applied also to the general N-body case.Comment: 11 pages, LaTeX, no figure

The 5-kW arcjet power electronics

The initial design and evaluation of a 5 kW arcjet power electronics breadboard which as been integrated with a modified 1 kW design laboratory arcjet is presented. A single stage, 5 kW full bridge, pulse width modulated (PWM), power converter was developed which was phase shift regulated. The converter used metal oxide semiconductor field effect transistor (MOSFET) power switches and incorporated current mode control and an integral arcjet pulse ignition circuit. The unoptimized power efficiency was 93.5 and 93.9 percent at 5 kW and 50A output at input voltages of 130 and 150V, respectively. Line and load current regulation at 50A output was within one percent. The converter provided up to 6.6 kW to the arcjet with simulated ammonia used as a propellant

What is the cost of palliative care in the UK? A systematic review

OBJECTIVES: Little is known about the cost of a palliative care approach in the UK, and there is an absence of robust activity and unit cost data. The aim of this study was to review evidence on the costs of specialist and generalist palliative care in the UK, and to explore different approaches used for capturing activity and unit cost data. METHODS: A systematic review with narrative synthesis. Four electronic databases were searched for empirical literature on the costs of a palliative care approach in the UK, and a narrative method was used to synthesise the data. RESULTS: Ten papers met our inclusion criteria. The studies displayed significant variation in their estimates of the cost of palliative care, therefore it was not possible to present an accurate aggregate cost of palliative care in the UK. The majority of studies explored costs from a National Health Service perspective and only two studies included informal care costs. Approaches to estimating activity and costs varied. Particular challenges were noted with capturing activity and cost data for hospice and informal care. CONCLUSION: The data are limited, and the heterogeneity is such that it is not possible to provide an aggregate cost of palliative care in the UK. It is notable that the costs of hospice care and informal care are often neglected in economic studies. Further work is needed to address methodological and practical challenges in order to gain a more complete understanding of the costs of palliative care

(2+1)-Gravity with Moving Particles in an Instantaneous Gauge

By defining a regular gauge which is conformal-like and provides instantaneous field propagation, we investigate classical solutions of (2+1)-Gravity coupled to arbitrarily moving point-like particles. We show how to separate field equations from self-consistent motion and we provide a solution for the metric and the motion in the two-body case with arbitrary speed, up to second order in the mass parameters.Comment: 16 pages, LaTeX, no figure

Exploring the transition from curative care to palliative care: a systematic review of the literature.

BACKGROUND: UK policy guidance on treatment and care towards the end of life identifies a need to better recognise patients who are likely to be in the last 12 months of life. Health and social care professionals have a key role in initiating and managing a patient's transition from 'curative care' to palliative care. The aim of this paper is to provide a systematic review of evidence relating to the transition from curative care to palliative care within UK settings. METHOD: Four electronic databases were searched for studies published between 1975 and March 2010. Inclusion criteria were all UK studies relating to the transition from curative care to palliative care in adults over the age of 18. Selected studies were independently reviewed, data were extracted, quality was assessed and data were synthesised using a descriptive thematic approach. RESULTS: Of the 1464 articles initially identified, 12 papers met the criteria for inclusion. Four themes emerged from the literature: (1) patient and carer experiences of transitions; (2) recognition and identification of the transition phase; (3) optimising and improving transitions; and (4) defining and conceptualising transitions. CONCLUSIONS: The literature suggests that little is known about the potentially complex transition to palliative care. Evidence suggests that continuity of care and multidisciplinary collaboration are crucial in order to improve the experience of patients making the transition. An important role is outlined for generalist providers of palliative care. Incorporating palliative care earlier in the disease trajectory and implementing a phased transition appear key components of optimum care

Varying c cosmology and Planck value constraints

It has been suggested that by increasing the speed of light during the early universe various cosmological problems of standard big bang cosmology can be overcome, without requiring an inflationary phase. However, we find that as the Planck length and Planck time are then made correspondingly smaller, and together with the need that the universe should not re-enter a Planck epoch, the higher $c$ models have very limited ability to resolve such problems. For a constantly decreasing $c$ the universe will quickly becomes quantum gravitationally dominated as time increases: the opposite to standard cosmology where quantum behaviour is only ascribed to early times.Comment: extended versio

Exact Relativistic Two-Body Motion in Lineal Gravity

We consider the N-body problem in (1+1) dimensional lineal gravity. For 2 point masses (N=2) we obtain an exact solution for the relativistic motion. In the equal mass case we obtain an explicit expression for their proper separation as a function of their mutual proper time. Our solution gives the exact Hamiltonian to infinite order in the gravitational coupling constant.Comment: latex, 11 pages, 2 figures, final version to appear in Phys. Rev. Let

Self-Gravitating Strings In 2+1 Dimensions

We present a family of classical spacetimes in 2+1 dimensions. Such a spacetime is produced by a Nambu-Goto self-gravitating string. Due to the special properties of three-dimensional gravity, the metric is completely described as a Minkowski space with two identified worldsheets. In the flat limit, the standard string is recovered. The formalism is developed for an open string with massive endpoints, but applies to other boundary conditions as well. We consider another limit, where the string tension vanishes in geometrical units but the end-masses produce finite deficit angles. In this limit, our open string reduces to the free-masses solution of Gott, which possesses closed timelike curves when the relative motion of the two masses is sufficiently rapid. We discuss the possible causal structures of our spacetimes in other regimes. It is shown that the induced worldsheet Liouville mode obeys ({\it classically}) a differential equation, similar to the Liouville equation and reducing to it in the flat limit. A quadratic action formulation of this system is presented. The possibility and significance of quantizing the self-gravitating string, is discussed.Comment: 55 page

Cosmological constant influence on cosmic string spacetime

We investigate the line element of spacetime around a linear cosmic string in the presence of a cosmological constant. We obtain the metric and argue that it should be discarded because of asymptotic considerations. Then a time dependent and consistent form of the metric is obtained and its properties are discussed.Comment: 3 page