Simple threshold rules solve explore/exploit trade‐offs in a resource accumulation search task

How, and how well, do people switch between exploration and exploitation to search for and accumulate resources? We study the decision processes underlying such exploration/exploitation trade‐offs using a novel card selection task that captures the common situation of searching among multiple resources (e.g., jobs) that can be exploited without depleting. With experience, participants learn to switch appropriately between exploration and exploitation and approach optimal performance. We model participants' behavior on this task with random, threshold, and sampling strategies, and find that a linear decreasing threshold rule best fits participants' results. Further evidence that participants use decreasing threshold‐based strategies comes from reaction time differences between exploration and exploitation; however, participants themselves report non‐decreasing thresholds. Decreasing threshold strategies that “front‐load” exploration and switch quickly to exploitation are particularly effective in resource accumulation tasks, in contrast to optimal stopping problems like the Secretary Problem requiring longer exploration

Exploring equity in uptake of the NHS Health Check and a nested physical activity intervention trial.

BACKGROUND: Socio-demographic factors characterizing disadvantage may influence uptake of preventative health interventions such as the NHS Health Check and research trials informing their content. METHODS: A cross-sectional study examining socio-demographic characteristics of participants and non-participants to the NHS Health Check and a nested trial of very brief physical activity interventions within this context. Age, gender, Index of Multiple Deprivation (IMD) and ethnicity were extracted from patient records of four General Practices (GP) in England. RESULTS: In multivariate analyses controlling for GP surgery, the odds of participation in the Health Check were higher for older patients (OR 1.05, 95% CI 1.04-1.07) and lower from areas of greater deprivation (IMD Quintiles 4 versus 1, OR 0.37, 95% CI 0.18-0.76, 5 versus 1 OR 0.42, 95% CI 0.20-0.88). Older patients were more likely to participate in the physical activity trial (OR 1.04, 95% CI 1.02-1.06). CONCLUSIONS: Younger patients and those living in areas of greater deprivation may be at risk of non-participation in the NHS Health Check, while younger age also predicted non-participation in a nested research trial. The role that GP-surgery-specific factors play in influencing participation across different socio-demographic groups requires further exploration.The work was undertaken by the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence. Funding from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research, and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. This paper presents independent research funded by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research Programme (Grant Reference Number RP-PG-0608-10079)This is the final published version. It first appeared at http://jpubhealth.oxfordjournals.org/content/early/2015/06/01/pubmed.fdv070.full

A Model for Phase Transition based on Statistical Disassembly of Nuclei at Intermediate Energies

Consider a model of particles (nucleons) which has a two-body interaction which leads to bound composites with saturation properties. These properties are : all composites have the same density and the ground state energies of composites with k nucleons are given by -kW+\sigma k^{2/3} where W and \sigma are positive constants. W represents a volume term and \sigma a surface tension term. These values are taken from nuclear physics. We show that in the large N limit where N is the number of particles such an assembly in a large enclosure at finite temperature shows properties of liquid-gas phase transition. We do not use the two-body interaction but the gross properties of the composites only. We show that (a) the p-\rho isotherms show a region where pressure does not change as $\rho$ changes just as in Maxwell construction of a Van der Waals gas, (b) in this region the chemical potential does not change and (c) the model obeys the celebrated Clausius-Clapeyron relations. A scaling law for the yields of composites emerges. For a finite number of particles N (upto some thousands) the problem can be easily solved on a computer. This allows us to study finite particle number effects which modify phase transition effects. The model is calculationally simple. Monte-Carlo simulations are not needed.Comment: RevTex file, 21 pages, 5 figure

Life on a low income in austere times

Following the ‘credit crunch’ 2007-2008, the UK entered the deepest recessionary conditions in living memory. As the liquidity from the financial services sector came to an abrupt halt, the investment ‘life blood’ of the economy in short supply, numerous companies, including long established high street businesses, ceased trading and consequently, unemployment rates rose to the highest levels since the 1980s. After the initial ‘bailout’ of the banking sector, political attention turned to the growing public deficit and the spectre of public sector austerity came to dominate the policy agenda. This agenda swiftly moved from how best to regulate the financial services industry to the question of the ‘welfare bill’ and the growing problem of ‘worklessness’. From this point, particularly as the Universal Credit Scheme passed through parliament and came to be implemented in various phases, much was said in political and policy debates about the lives of the ‘poor’ and many ‘common sense’ assumptions informed these discussions. However as is often the case, omitted from these discussions were the voices of those people living of low income. To redress this imbalance, the report aims to document the reality of life on a low income during this period, by affording primacy to the ‘voices’ of those living in poverty

Large-Scale Image Processing with the ROTSE Pipeline for Follow-Up of Gravitational Wave Events

Electromagnetic (EM) observations of gravitational-wave (GW) sources would bring unique insights into a source which are not available from either channel alone. However EM follow-up of GW events presents new challenges. GW events will have large sky error regions, on the order of 10-100 square degrees, which can be made up of many disjoint patches. When searching such large areas there is potential contamination by EM transients unrelated to the GW event. Furthermore, the characteristics of possible EM counterparts to GW events are also uncertain. It is therefore desirable to be able to assess the statistical significance of a candidate EM counterpart, which can only be done by performing background studies of large data sets. Current image processing pipelines such as that used by ROTSE are not usually optimised for large-scale processing. We have automated the ROTSE image analysis, and supplemented it with a post-processing unit for candidate validation and classification. We also propose a simple ad hoc statistic for ranking candidates as more likely to be associated with the GW trigger. We demonstrate the performance of the automated pipeline and ranking statistic using archival ROTSE data. EM candidates from a randomly selected set of images are compared to a background estimated from the analysis of 102 additional sets of archival images. The pipeline's detection efficiency is computed empirically by re-analysis of the images after adding simulated optical transients that follow typical light curves for gamma-ray burst afterglows and kilonovae. We show that the automated pipeline rejects most background events and is sensitive to simulated transients to limiting magnitudes consistent with the limiting magnitude of the images

Iron redox systematics of martian magmas.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日（金） 国立国語研究所 2階講

Iron Redox Systematics of Martian Magmas

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite [1]. Morris et al. [1] propose that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks [2,3]. Magnetite stability in terrestrial magmas is well understood, as are the stability of FeO and Fe2O3 in terrestrial magmas [4,5]. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas we have undertaken an experimental study with two emphases. First we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition. Second, we determine the FeO and Fe2O3 contents of the same shergottite bulk composition at 1 bar and variable fO2 at 1250 C, and at variable pressure. These two goals will help define not only magnetite stability, but pyroxene-melt equilibria that are also dependent upon fO2

Review of the Laguerre-Gauss mode technology research program at Birmingham

Gravitational wave detectors from the advanced generation onwards are expected to be limited in sensitivity by thermal noise of the optics, making the reduction of this noise a key factor in the success of such detectors. A proposed method for reducing the impact of this noise is to use higher-order Laguerre-Gauss (LG) modes for the readout beam, as opposed to the currently used fundamental mode. We present here a synopsis of the research program undertaken by the University of Birmingham into the suitability of LG mode technology for future gravitational wave detectors. This will cover our previous and current work on this topic, from initial simulations and table-top LG mode experiments up to implementation in a prototype scale suspended cavity and high-power laser bench

Acute ischaemic stroke patients - direct admission to a specialist centre or initial treatment in a local hospital? A systematic review

Objectives To assess the clinical effectiveness, in acute ischaemic stroke patients, of bypassing non-specialist centres in preference for a specialist stroke centre to receive the time-critical intervention of thrombolysis. Methods Systematic review and meta-analysis using: MEDLINE; MEDLINE In-Process; EMBASE; CINAHL; Cochrane Library including Cochrane Database of Systematic Reviews, Cochrane CENTRAL Controlled Trials Register, DARE, NHS EED and HTA databases. Studies were included if they compared acute ischaemic stroke patients directly triaged to a specialist centre versus those initially triaged to a non-specialist centre with some or all later transferred to a specialist centre. Studies were excluded if they compared patients ever treated in a specialist centre versus those never treated in such a centre, since the aim was to assess the optimum initial triage route rather than the optimum location for overall management. The assumption being, based on previous research, that management in a specialist centre leads to better patient outcomes. Results Fourteen studies investigating 2790 patients were identified. Studies comparing commencement of thrombolysis in non-specialist centres versus the specialist centres (n=1394) showed no significant difference in unadjusted mortality (OR = 0.89; 95% CI = 0.61–1.30) or morbidity (favourable modified Rankin Score, n = 899) (OR = 1.16; 95% CI = 0.85–1.59) among thrombolysed patients. In studies where thrombolysis could only be administered in a specialist centre, data for patients arriving within the therapeutic window (n = 140) revealed significantly higher mortality for those initially admitted to a non-specialist centre compared to directly admitted to a specialist centre (OR = 6.62; 95% CI = 2.60–16.82); morbidity data also favoured direct admission to a specialist centre, although not consistently. Conclusions For ischaemic stroke patients, the location of initial thrombolysis treatment does not affect outcomes. However, if thrombolysis is only available at a specialist centre, outcomes are considerably better for those patients admitted directly. However, these conclusions are based on poor quality data with small sample populations, significant heterogeneity and subject to confounding