Shear-free, Irrotational, Geodesic, Anisotropic Fluid Cosmologies

General relativistic anisotropic fluid models whose fluid flow lines form a shear-free, irrotational, geodesic timelike congruence are examined. These models are of Petrov type D, and are assumed to have zero heat flux and an anisotropic stress tensor that possesses two distinct non-zero eigenvalues. Some general results concerning the form of the metric and the stress-tensor for these models are established. Furthermore, if the energy density and the isotropic pressure, as measured by a comoving observer, satisfy an equation of state of the form $p = p(\mu)$, with $\frac{dp}{d\mu} \neq -\frac{1}{3}$, then these spacetimes admit a foliation by spacelike hypersurfaces of constant Ricci scalar. In addition, models for which both the energy density and the anisotropic pressures only depend on time are investigated; both spatially homogeneous and spatially inhomogeneous models are found. A classification of these models is undertaken. Also, a particular class of anisotropic fluid models which are simple generalizations of the homogeneous isotropic cosmological models is studied.Comment: 13 pages LaTe

The specialty choices of graduates from Brighton and Sussex Medical School: a longitudinal cohort study

BACKGROUND Since 2007 junior doctors in the UK have had to make major career decisions at a point when previously many had not yet chosen a specialty. This study examined when doctors in this new system make specialty choices, which factors influence choices, and whether doctors who choose a specialty they were interested in at medical school are more confident in their choice than those doctors whose interests change post-graduation. METHODS Two cohorts of students in their penultimate year at one medical school (n = 227/239) were asked which specialty interested them as a career. Two years later, 210/227 were sent a questionnaire measuring actual specialty chosen, confidence, influence of perceptions of the specialty and experiences on choice, satisfaction with medicine, personality, self-efficacy, and demographics. Medical school and post-graduation choices in the same category were deemed 'stable'. Predictors of stability, and of not having chosen a specialty, were calculated using bootstrapped logistic regression. Differences between specialties on questionnaire factors were analysed. RESULTS 50% responded (n = 105/277; 44% of the 239 Year 4 students). 65% specialty choices were 'stable'. Factors univariately associated with stability were specialty chosen, having enjoyed the specialty at medical school or since starting work, having first considered the specialty earlier. A regression found doctors who chose psychiatry were more likely to have changed choice than those who chose general practice. Confidence in the choice was not associated with stability. Those who chose general practice valued lifestyle factors. A psychiatry choice was associated with needing a job and using one's intellect to help others. The decision to choose surgical training tended to be made early. Not having applied for specialty training was associated with being lower on agreeableness and conscientiousness. CONCLUSION Medical school experiences are important in specialty choice but experiences post-graduation remain significant, particularly in some specialties (psychiatry in our sample). Career guidance is important at medical school and should be continued post-graduation, with senior clinicians supported in advising juniors. Careers advice in the first year post-graduation may be particularly important, especially for specialties which have difficulty recruiting or are poorly represented at medical school

An assessment of the torrefaction of North American pine and life cycle greenhouse gas emissions

Bioenergy is increasingly being used to meet EU objectives for renewable energy generation and reducing greenhouse gas (GHG) emissions. Problems with using biomass however include high moisture contents, lower calorific value and poor grindability when compared to fossil fuels. Torrefaction is a pre-treatment process that aims to address these issues. In this paper four torrefaction treatments of pine were performed and a mass-energy balance calculated. Using experimental data, a pellet production supply chain incorporating torrefaction was modelled and compared to an existing wood pellet system to determine life-cycle GHG emissions. Two utility fuels, wood chips and natural gas, were considered to provide process heat in addition to volatile gases released during torrefaction (torgas). Experimental results show that torrefaction reduces the moisture content and increases the calorific value of the fuels. Increasing torrefaction temperature and residence time results in lower mass and energy yields. GHG emissions reduce with increasing torrefaction severity. Emissions from drying &amp; torrefaction and shipping are the highest GHG contributors to the supply chain. All 4 torrefaction conditions assessed outperformed traditional wood pellet supply chain emissions but more land is required which increases with temperature and residence time. Sensitivity analysis results show that emissions increase significantly where natural gas is used for utility fuel and no torgas is utilised.</p

The Formation of non-Keplerian Rings of Matter about Compact Stars

The formation of energetic rings of matter in a Kerr spacetime with an outward pointing acceleration field does not appear to have previously been noted as a relativistic effect. In this paper we show that such rings are a gravimagneto effect with no Newtonian analog, and that they do not occur in the static limit. The energy efficiency of these rings can, depending of the strength of the acceleration field, be much greater than that of Keplerian disks. The rings rotate in a direction opposite to that of compact star about which they form. The size and energy efficiency of the rings depend on the fundamental parameters of the spacetime as well as the strength the acceleration field.Comment: 19 pages, 7 figures, 1 diagram. Figures are included in the text using the "graphicx" package. If you do not have this package you can use epsfig, or another package as long as you alter the tex file appropriately. Alternatively you could print the figures out seperatel

The Application of the Newman-Janis Algorithm in Obtaining Interior Solutions of the Kerr Metric

In this paper we present a class of metrics to be considered as new possible sources for the Kerr metric. These new solutions are generated by applying the Newman-Janis algorithm (NJA) to any static spherically symmetric (SSS) ``seed'' metric. The continuity conditions for joining any two of these new metrics is presented. A specific analysis of the joining of interior solutions to the Kerr exterior is made. The boundary conditions used are those first developed by Dormois and Israel. We find that the NJA can be used to generate new physically allowable interior solutions. These new solutions can be matched smoothly to the Kerr metric. We present a general method for finding such solutions with oblate spheroidal boundary surfaces. Finally a trial solution is found and presented.Comment: 11 pages, Latex, 4 postscript figures. To be published in Classical and Quantum Gravity. Title and abstract are now on the same pag

Effectiveness of current policing-related mental health interventions in England and Wales and Crisis Intervention Teams as a future potential model: a systematic review

Background Experiencing mental ill health adds a layer of complexity for individuals in touch with the justice system and for those responsible for working in the justice service with these individuals, such as frontline police officers. In England and Wales, there are three commonly used but not necessarily commonly designed or operated, mental health interventions associated with policing, Liaison and Diversion, Street Triage and specialist staff embedded in Police Contact Control Rooms. A fourth US designed model, Crisis Intervention Teams (CITs), is now attracting some interest in England and Wales, and these four are to be considered in this review. A fifth intervention, Mental Health Courts, was trialed but has now been abandoned in England and Wales and so has been excluded, but remains in use elsewhere. In recent years, there has been an increase in the level of investment related to these intervention options. This has largely been without an evidence base being available to aid design, structure, and consistency of approach. The review will address this gap and provide a systematic review of each of these options. This will provide a baseline of research evidence for those who commission and provide services for individuals experiencing mental ill health and who are in contact with the justice system. Methods Twenty-nine relevant databases and sources have been selected which will be systematically searched to locate relevant studies. These studies have to meet the set inclusion criteria which require them to report an objective outcome measure(s) in respect of offending or mental health outcomes and to have an experimental or quasi-experimental design including a comparator group(s) or a pre/post comparison. The review will exclude PhD theses, papers in non-English languages and papers published prior to 1980. Keywords have been collected through canvassing experts’ opinion, literature review, controlled vocabulary and reviewing the results of a primary scoping review carried out to aid the development of the PICO, composed of Population/Participants, Intervention/Indicator, Comparator/Control, and Outcomes. For the proposed review, the key elements of the PICO are the following: persons with mental health problems, symptoms or diagnoses who come into contact with the police; interventions involving partnership working between police and mental health nurses and related professionals to divert those with mental health problems away from criminal justice processes; comparisons with control groups or areas where such interventions have not been introduced; and outcomes concerning criminal justice and health outcomes. The results of the searches will be screened using the set criteria and the selected papers reviewed and analysed to allow findings regarding these interventions to be reported. Discussion The objectives of the review are firstly to identify and report research on the relevant interventions, nationally and internationally and then secondly to consider, when possible, which interventions or aspects of those interventions are effective. This is judged with regard to changes in mental health status or service use and future offending behaviour. The approaches to be considered have gained a good deal of support and funding over recent years, and this review will provide a systematic review of the underpinning research evidence to inform future commissioning, service design and investment decisions