2,118 research outputs found
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
Hybrid Local-Order Mechanism for Inversion Symmetry Breaking
Using classical Monte Carlo simulations, we study a simple statistical
mechanical model of relevance to the emergence of polarisation from local
displacements on the square and cubic lattices. Our model contains two key
ingredients: a Kitaev-like orientation-dependent interaction between nearest
neighbours, and a steric term that acts between next-nearest neighbours. Taken
by themselves, each of these two ingredients is incapable of driving long-range
symmetry breaking, despite the presence of a broad feature in the corresponding
heat capacity functions. Instead each component results in a "hidden"
transition on cooling to a manifold of degenerate states, the two manifolds are
different in the sense that they reflect distinct types of local order.
Remarkably, their intersection---\emph{i.e.} the ground state when both
interaction terms are included in the Hamiltonian---supports a spontaneous
polarisation. In this way, our study demonstrates how local ordering mechanisms
might be combined to break global inversion symmetry in a manner conceptually
similar to that operating in the "hybrid" improper ferroelectrics. We discuss
the relevance of our analysis to the emergence of spontaneous polarisation in
well-studied ferroelectrics such as BaTiO and KNbO.Comment: 8 pages, 8 figure
Sensory motor systems of artificial and natural hands
The surgeon Ambroise ParƩ designed an anthropomorphic hand for wounded soldiers in the 16th century. Since that time, there have been advances in technology through the use of computer-aided design, modern materials, electronic controllers and sensors to realise artificial hands which have good functionality and reliability. Data from touch, object slip, finger position and temperature sensors, mounted in the fingers and on the palm, can be used in feedback loops to automatically hold objects. A study of the natural neuromuscular systems reveals a complexity which can only in part be realised today with technology. Highlights of the parallels and differences between natural and artificial hands are discussed with reference to the Southampton Hand. The anatomical structure of parts of the natural systems can be made artificially such as the antagonist muscles using tendons. Theses solutions look promising as they are based on the natural form but in practice lack the desired physical specification. However, concepts of the lower spinal loops can be mimicked in principle. Some future devices will require greater skills from the surgeon to create the interface between the natural system and an artificial device. Such developments may offer a more natural control with ease of use for the limb deficient person
Child- and school-level predictors of children's bullying behavior: A multilevel analysis in 648 primary schools
Ā© 2017 American Psychological Association. A great deal of bullying behavior takes place at school, however, existing literature has predominantly focused on individual characteristics of children associated with bullying with less attention on schoollevel factors. The current study, comprising 23,215 children (51% boys) recruited from Year 4 or Year 5 (M = 9.06 years, SD = .56 years) from 648 primary schools in England, aimed to examine the independent and combined influence of child- and school-level predictors on bullying behavior in primary school. Children provided information on bullying behavior and school climate. Demographic characteristics of children were obtained from the National Pupil Database, and demographic characteristics of schools were drawn from EduBase. Multilevel logistic regression models showed that individual child gender, ethnicity, deprivation and special educational needs status all predicted bullying behavior. Of the school-level predictors, only overall school deprivation and school climate were predictive of bullying behavior once child-level predictors were taken into account. There was a significant interaction between child- and school-level deprivation; high-deprivation schools were a risk factor for bullying only for children that came from nondeprived backgrounds, whereas deprived children reported engaging in bullying behavior irrespective of school-level deprivation. Given the independent and combined role of child- and school-level factors for bullying behavior, the current study has implications for targeted school interventions to tackle bullying behavior, both in terms of identifying high-risk children and identifying high-risk schools
Systematic review of approaches to using patient experience data for quality improvement in healthcare settings
Objectives: Explore how patient-reported experience measures (PREMs) are collected, communicated and used to inform quality improvement (QI) across healthcare settings.
Design: Systematic review.
Setting: Various primary and secondary care settings, including general practice, and acute and chronic care hospitals.
Participants: A full range of patient populations from (children through to the elderly) and staff (from healthcare practitioners to senior managers).
Methods: Scientific databases were searched (CINAHL, PsycINFO, MEDLINE and Cochrane Libraries) as was grey literature. Qualitative and quantitative studies describing collection of PREM data and subsequent QI actions in any healthcare setting were included. Risk of bias was assessed using established criteria. Of 5312 initial hits, 32 full texts were screened, and 11 were included.
Results: Patient experience data were most commonly collected through surveys and used to identify small areas of incremental change to services that do not require a change to clinician behaviour (eg, changes to admission processes and producing educational materials). While staff in most studies reported having made effective improvements, authors struggled to identify what those changes were or the impact they had.
Conclusions: Findings suggest there is no single best way to collect or use PREM data for QI, but they do suggest some key points to consider when planning such an approach. For instance, formal training is recommended, as a lack of expertise in QI and confidence in interpreting patient experience data effectively may continue to be a barrier to a successful shift towards a more patient-centred healthcare service. In the context of QI, more attention is required on how patient experience data will be used to inform changes to practice and, in turn, measure any impact these changes may have on patient experience
When is Sessional Monitoring More Likely in Child and Adolescent Mental Health Services?
Sessional monitoring of patient progress or experience of therapy is an evidence-based intervention recommended by healthcare systems internationally. It is being rolled out across child and adolescent mental health services (CAMHS) in England to inform clinical practice and service evaluation. We explored whether patient demographic and case characteristics were associated with the likelihood of using sessional monitoring. Multilevel regressions were conducted on NĀ =Ā 2609 youths from a routinely collected dataset from 10 CAMHS. Girls (odds ratio, OR 1.26), older youths (OR 1.10), White youths (OR 1.35), and youths presenting with mood (OR 1.46) or anxiety problems (OR 1.59) were more likely to have sessional monitoring. In contrast, youths under state care (OR 0.20) or in need of social service input (OR 0.39) were less likely to have sessional monitoring. Findings of the present research may suggest that sessional monitoring is more likely with common problems such as mood and anxiety problems but less likely with more complex cases, such as those involving youths under state care or those in need of social service input
Finding the center reliably: robust patterns of developmental gene expression
We investigate a mechanism for the robust identification of the center of a
developing biological system. We assume the existence of two morphogen
gradients, an activator emanating from the anterior, and a co-repressor from
the posterior. The co-repressor inhibits the action of the activator in
switching on target genes. We apply this system to Drosophila embryos, where we
predict the existence of a hitherto undetected posterior co-repressor. Using
mathematical modelling, we show that a symmetric activator-co-repressor model
can quantitatively explain the precise mid-embryo expression boundary of the
hunchback gene, and the scaling of this pattern with embryo size.Comment: 4 pages, 3 figure
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