An adaptive Metropolis-Hastings scheme: sampling and optimization

We propose an adaptive Metropolis-Hastings algorithm in which sampled data are used to update the proposal distribution. We use the samples found by the algorithm at a particular step to form the information-theoretically optimal mean-field approximation to the target distribution, and update the proposal distribution to be that approximatio. We employ our algorithm to sample the energy distribution for several spin-glasses and we demonstrate the superiority of our algorithm to the conventional MH algorithm in sampling and in annealing optimization.Comment: To appear in Europhysics Letter

Collective Intelligence for Control of Distributed Dynamical Systems

We consider the El Farol bar problem, also known as the minority game (W. B. Arthur, ``The American Economic Review'', 84(2): 406--411 (1994), D. Challet and Y.C. Zhang, ``Physica A'', 256:514 (1998)). We view it as an instance of the general problem of how to configure the nodal elements of a distributed dynamical system so that they do not ``work at cross purposes'', in that their collective dynamics avoids frustration and thereby achieves a provided global goal. We summarize a mathematical theory for such configuration applicable when (as in the bar problem) the global goal can be expressed as minimizing a global energy function and the nodes can be expressed as minimizers of local free energy functions. We show that a system designed with that theory performs nearly optimally for the bar problem.Comment: 8 page

A low-energy solar cosmic ray experiment for OGO-F

Instrumentation data for low energy solar cosmic ray measurements using OGO-F satellit

Pattern Formation by Boundary Forcing in Convectively Unstable, Oscillatory Media With and Without Differential Transport

Motivated by recent experiments and models of biological segmentation, we analyze the exicitation of pattern-forming instabilities of convectively unstable reaction-diffusion-advection (RDA) systems, occuring by means of constant or periodic forcing at the upstream boundary. Such boundary-controlled pattern selection is a generalization of the flow-distributed oscillation (FDO) mechanism that can include Turing or differential flow instability (DIFI) modes. Our goal is to clarify the relationships among these mechanisms in the general case where there is differential flow as well as differential diffusion. We do so by analyzing the dispersion relation for linear perturbations and showing how its solutions are affected by differential transport. We find a close relationship between DIFI and FDO, while the Turing mechanism gives rise to a distinct set of unstable modes. Finally, we illustrate the relevance of the dispersion relations using nonlinear simulations and we discuss the experimental implications of our results.Comment: Revised version with added content (new section and figures added), changes to wording and organizatio

Measuring what matters to patients: Using goal content to inform measure choice and development

Introduction: Personalised care requires personalised outcomes and ways of feeding back clinically useful information to clinicians and practitioners, but it is not clear how to best personalise outcome measurement and feedback using existing standardised outcome measures. / Method: The constant comparison method of grounded theory was used to compare goal themes derived from goals set at the outset of therapy for 180 children aged between 4 and 17 years, visiting eight child and adolescent mental health services, to existing standardised outcome measures used as part of common national datasets. / Results: In all, 20 out of 27 goal themes corresponded to items on at least one commonly used outcome measure. Discussion: Consideration of goal themes helped to identify potential relevant outcome measures. However, there were several goal themes that were not captured by items on standardised outcome measures. These seemed to be related to existential factors such as understanding, thinking about oneself and future planning. / Conclusion: This presents a powerful framework for how clinicians can use goals to help select a standardised outcome measure (where this is helpful) in addition to the use of a goal-based outcome measure and personalise choices. There may be areas not captured by standardised outcome measures that may be important for children and young people and which may only be currently captured in goal measurement. There is an indication that we may not be measuring what is important to children and young people. We may need to develop or look for new measures that capture these areas

Multi-Agent Complex Systems and Many-Body Physics

Multi-agent complex systems comprising populations of decision-making particles, have many potential applications across the biological, informational and social sciences. We show that the time-averaged dynamics in such systems bear a striking resemblance to conventional many-body physics. For the specific example of the Minority Game, this analogy enables us to obtain analytic expressions which are in excellent agreement with numerical simulations.Comment: Accepted for publication in Europhysics Letter

Algebraic-geometrical formulation of two-dimensional quantum gravity

We find a volume form on moduli space of double punctured Riemann surfaces whose integral satisfies the Painlev\'e I recursion relations of the genus expansion of the specific heat of 2D gravity. This allows us to express the asymptotic expansion of the specific heat as an integral on an infinite dimensional moduli space in the spirit of Friedan-Shenker approach. We outline a conjectural derivation of such recursion relations using the Duistermaat-Heckman theorem.Comment: 10 pages, Latex fil

Patient reported outcome measures in child and adolescent mental health services: associations between clinician demographic characteristics, attitudes and efficacy

BACKGROUND: Policy recommends using patient reported outcome measures (PROMs), yet their use is persistently low. Our aim was to examine the association between PROM use and clinician demographic characteristics, attitudes and efficacy. METHOD: A sample of N = 109 clinicians completed an online survey. RESULTS: Clinicians who reported higher levels of use of cognitive behaviour or humanistic approaches had higher levels of PROM use than clinicians who reported lower levels of use of these approaches. Clinicians who reported having received training had higher levels of self-efficacy regarding PROMs than clinicians who reported not having received training, but the effects of training on PROM attitudes and use were not significant. Still, clinicians with more positive attitudes or self-efficacy regarding PROMs had higher levels of PROM use than clinicians with less positive attitudes or self-efficacy regarding PROMs. CONCLUSION: Clinicians should be supported to have the knowledge, skills and confidence to effectively use PROMs in their clinical practice

A systematic review of shared decision making interventions in child and youth mental health: synthesising the use of theory, intervention functions, and behaviour change techniques

Reviews around interventions to improve shared decision making (SDM) for child and youth mental health have produced inconclusive findings on what approaches increase participation. Importantly, the previous reviews did not explore the use of theory, as well as mechanisms of change (intervention functions) and active units of change (behaviour change techniques). The aim of this review was to explore these factors and ascertain how, if at all, these contribute to SDM. Five databases were searched up until April 2020. Studies met inclusion criteria if they were: (a) an intervention to facilitate SDM; (b) aimed at children, adolescence, or young people aged up to 25, with a mental health difficulty, or their parents/guardians; and (c) included a control group. Data were extracted on patient characteristics, study design, intervention, theoretical background, intervention functions, behaviour change techniques, and SDM. Quality assessment of the studies was undertaken using the Effective Public Health Practice Project (EPHPP) quality assessment tool. Eight different interventions met inclusion criteria. The role of theory to increase SDM remains unclear. Specific intervention functions, such as 'education' on SDM and treatment options and 'environmental restructuring' using decision aids, are being used in SDM interventions, as well as 'training' for clinicians. Similarly, behaviour change techniques linked to these, such as 'adding objects to the environment', 'discussing pros/cons', and clinicians engaging in 'behavioural practice/rehearsal'. However, as most studies scored low on the quality assessment criteria, as well as a small number of studies included and a low number of behaviour change techniques utilised, links between behaviour change techniques, intervention functions and increased participation remain tentative. Intervention developers and clinicians may wish to consider specific intervention functions and behaviour change techniques to facilitate SDM

Robust formation of morphogen gradients

We discuss the formation of graded morphogen profiles in a cell layer by nonlinear transport phenomena, important for patterning developing organisms. We focus on a process termed transcytosis, where morphogen transport results from binding of ligands to receptors on the cell surface, incorporation into the cell and subsequent externalization. Starting from a microscopic model, we derive effective transport equations. We show that, in contrast to morphogen transport by extracellular diffusion, transcytosis leads to robust ligand profiles which are insensitive to the rate of ligand production