A Coupled Quantum Otto Cycle

We study the 1-d isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A new domain of parameter values is pointed out which was not feasible in the interaction-free model. Locally, each spin seems to effect the flow of heat in a direction opposite to the global temperature gradient. This seeming contradiction to the second law can be resolved in terms of local effective temperature of the spins

Neither Fear Nor Favour, Affection Or Ill Will: Modernisation of care proceedings and the use and value of independent social work expertise to senior judges

This is part two of an evaluation of the work of independent social work experts (ISWs) in care proceedings (stage I was published in April 2012). It takes forward findings from stage I exploring further the evidential base for views put to the Family Justice Review about the practice of courts. It examines the views, experiences and practices of a sample of senior judges in commissioning ISW assessments, placing these in the context of the timing, format and value of local authority assessments. Finally, judges? views about the implications of the modernisation programme for use of ISWs are explored - in the light of a need for earlier completion of cases, without loss of quality in assessments, and with regard to issues of fairness, justice and transparency in judicial decision making. In the report each section is followed by a summary of findings reflecting the key issue for policy and practice. The study is based on interviews with 23 senior judges (20 DFJs, 3 Circuit Judges) in 20/43 county courts in England and Wales. Interviews were held between February and April 2013. They include representation from all circuits, and courts with small and high volume case loads (less than 115, 251 - 900 applications in 12 months). They hear applications from just over half of authorities in England (59%) and just over one third (36%) in Wales

Universal efficiency at optimal work with Bayesian statistics

If the work per cycle of a quantum heat engine is averaged over an appropriate prior distribution for an external parameter $a$, the work becomes optimal at Curzon-Ahlborn efficiency. More general priors of the form $\Pi(a) \propto 1/a^{\gamma}$ yield optimal work at an efficiency which stays close to CA value, in particular near equilibrium the efficiency scales as one-half of the Carnot value. This feature is analogous to the one recently observed in literature for certain models of finite-time thermodynamics. Further, the use of Bayes' theorem implies that the work estimated with posterior probabilities also bears close analogy with the classical formula. These findings suggest that the notion of prior information can be used to reveal thermodynamic features in quantum systems, thus pointing to a new connection between thermodynamic behavior and the concept of information.Comment: revtex4, 5 pages, abstract changed and presentation improved; results unchanged. New result with Bayes Theorem adde

The contribution of experts in care proceedings : evaluation of independent social work reports on care proceedings

Several concerns surround the use of independent social work (ISW) assessments in care proceedings. Some result from the exclusion of this work from a review of legal aid for expert assessments in this field, a cap on ISW fees, and fears about a resulting reduction in the availability of ISWs. At the same time, submissions to the Family Justice Review (FJR) claimed that ISWs cause delay, simply duplicate existing local authority assessments, add nothing new and undermine confidence in social work assessments. It was also said that ISW reports result from parents utilising human rights claims to gain a second opinion of a local authority assessment ? and to which courts too readily accede. ... But while strong views have been expressed about the use of independent social work assessments, there is little hard evidence. This evaluation, commissioned following submissions to the FJR, begins to address that lack. It is based on 65 cases concerning 121 children and 82 reports for courts in England and Wales. The sample was drawn from the records of three independent agencies providing ISWs

Ignorance based inference of optimality in thermodynamic processes

We derive ignorance based prior distribution to quantify incomplete information and show its use to estimate the optimal work characteristics of a heat engine.Comment: Latex, 10 pages, 3 figure

(How) does productivity matter in the foundational economy?

Academics and policy makers have increasingly recognised the importance of mundane economic activities – variously termed foundational or everyday – by academics and policy makers. The foundational or everyday economy is now featuring in local industrial strategy and economic action plans, because the desirable high-tech sectors on the ‘frontier’ cannot diffuse prosperity within and between regions. This paper aims to distinguish between several different approaches to the foundational or everyday economy and argues that a constructive approach needs to break with the preoccupation about improving productivity. This argument is developed in three stages. First, we distinguish between a social approach and a more technical economic approach to delimiting this other mundane economy; the defining feature of the foundational in the social approach is contribution to wellbeing and in the technical economic approach it is low productivity. The second section presents and explores productivity evidence on output per worker hour across a range of foundational activities and by region. Drawing out the implications of observed diversity and heterogeneity, the third section develops an argument about how productivity has limited relevance as measure and target in foundational activitie

Coupling theory for counterion distributions based in Tsallis statistics

It is well known that the Poisson-Boltzmann (PB) equation yields the exact counterion density around charged objects in the weak coupling limit. In this paper we generalize the PB approach to account for coupling of arbitrary strength by making use of Tsallis q-exponential distributions. Both the weak coupling and the strong coupling limits are reproduced. For arbitrary coupling we also provide simple analytical expressions which are compared to recent Monte Carlo simulations by A. G. Moreira and R. R. Netz [Europhys. Lett. 52 (2000) 705]. Excellent agreement with these is obtained.Comment: 17 pages, 2 figures, 1 table. Final version, accepted for publication in Physica

Barnett-Pegg formalism of angle operators, revivals, and flux lines

We use the Barnett-Pegg formalism of angle operators to study a rotating particle with and without a flux line. Requiring a finite dimensional version of the Wigner function to be well defined we find a natural time quantization that leads to classical maps from which the arithmetical basis of quantum revivals is seen. The flux line, that fundamentally alters the quantum statistics, forces this time quantum to be increased by a factor of a winding number and determines the homotopy class of the path. The value of the flux is restricted to the rational numbers, a feature that persists in the infinite dimensional limit.Comment: 5 pages, 0 figures, Revte

5 year follow up of a hydroxyapatite coated short stem femoral component for hip arthroplasty: a prospective multicentre study

Short stem, uncemented femoral implants for hip arthroplasty are bone conserving achieving stability through initial metaphyseal press-fit and biological fixation. This study aimed to evaluate the survivorship, mid-term function and health related quality of life outcomes in patients who have undergone total hip arthroplasty (THA) with a fully hydroxyapatite coated straight short stem femoral component with up to 5 years follow-up. 668 patients were recruited to a multicentre study investigating the performance of the cementless Furlong Evolution® stem for THA. 137 patients withdrew at various time points. The mean follow-up was 49 months. Clinical (Harris Hip Score (HHS), radiographic and patient-reported outcome measures—Oxford Hip Score (OHS) and EuroQol 5D (EQ-5D), were recorded pre-operatively and at 6 weeks, 6 months, 1 year, 3 year and 5 year follow ups. At 5-year follow-up, 12 patients underwent revision surgery, representing a cumulative revision rate of 1.8%. Median OHS, HHS and EQ5D scores improved significantly: OHS improved from a pre-operative median of 21 (IQR 14–26) to 47 (IQR 44–48) (p < 0.001). HHS improved from 52 (IQR 40–63) to 98 (IQR 92–100) (p < 0.001) and EQ5D improved from 70 (IQR 50–80) to 85 (IQR 75–95) (p < 0.001). This fully HA-coated straight short femoral stem implant demonstrated acceptable mid-term survivorship and delivered substantial improvements in function and quality of life after THA