4,406 research outputs found
Relative Value Iteration for Stochastic Differential Games
We study zero-sum stochastic differential games with player dynamics governed
by a nondegenerate controlled diffusion process. Under the assumption of
uniform stability, we establish the existence of a solution to the Isaac's
equation for the ergodic game and characterize the optimal stationary
strategies. The data is not assumed to be bounded, nor do we assume geometric
ergodicity. Thus our results extend previous work in the literature. We also
study a relative value iteration scheme that takes the form of a parabolic
Isaac's equation. Under the hypothesis of geometric ergodicity we show that the
relative value iteration converges to the elliptic Isaac's equation as time
goes to infinity. We use these results to establish convergence of the relative
value iteration for risk-sensitive control problems under an asymptotic
flatness assumption
Why don't the British eat locally harvested shellfish? The role of misconceptions and knowledge gaps
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record Although the UK consumes a substantial amount of shellfish, most is imported (e.g. prawns), while locally harvested molluscs and crustaceans (e.g. mussels, crab) tend to be exported. This study aimed to investigate whether a low rate of local shellfish consumption in the UK is due to misunderstandings or knowledge gaps about the potential health and environmental risks and benefits of consumption. Following the Mental Models Approach, the present paper reveals: 1) qualitative results from 26 stakeholder/public interviews which identified 10 key misunderstandings and knowledge gaps, including incorrect beliefs about health risks and a lack of knowledge about the relative environmental benefits compared to other foods (key misunderstandings included some parts of a crab are poisonous if eaten, and the majority of UK shellfish is farmed), and 2) quantitative results from a survey (n = 1,433) that explored the degree to which these misunderstandings and knowledge gaps may influence consumption intentions in the wider UK population. Survey results suggested the number of misunderstandings and knowledge gaps significantly predicted shellfish consumption intentions even after controlling for demographics, food related values, and past consumption behaviour. Path analyses revealed their impact on intentions was partially mediated via Theory of Planned Behaviour variables. Results could inform information campaigns supporting consumers to make more informed decisions regarding a group of foods that are potentially both healthy and relatively environmentally friendly.European Regional Development Fund ProgrammeEuropean Social Fund Convergence Programme for Cornwall and the Isles of Scill
Consensus statement on the use of high sensitivity cardiac troponins
The increased sensitivity of high sensitivity cardiac troponin assays comes at a cost of decreased specificity, and “false positive” diagnosis of acute coronary syndromes has made clinicians wary of their use, fearing unnecessary hospitalisations, angiography and revascularisation. The Ethics and Guidelines Standing Committee of SA Heart Association convened a meeting of cardiologists, chemical pathologists, emergency medicine specialists and industry representatives to discuss the role of high sensitivity troponin (hsTn) testing. An international expert provided guidance, and this Consensus Statement is the product of that meeting. It is recommended that hsTn assays be widely adopted as the preferred biomarker for diagnosis of myocardial infarction. Pathology laboratories will standardise the units of measurement and the reporting of results. Rules for interpretation of results and algorithms for their application are provided. Separate algorithms apply to troponin T and troponin I, and the several troponin I assays on the market each have different numerical values. Use of high sensitivity troponin assays will result in earlier diagnosis of myocardial infarction, more reliable ruling out of myocardial infarction, and shortening of chest pain triage (to 4 hours), compared to former assays
Light-cone-like spreading of correlations in a quantum many-body system
How fast can correlations spread in a quantum many-body system? Based on the
seminal work by Lieb and Robinson, it has recently been shown that several
interacting many-body systems exhibit an effective light cone that bounds the
propagation speed of correlations. The existence of such a "speed of light" has
profound implications for condensed matter physics and quantum information, but
has never been observed experimentally. Here we report on the time-resolved
detection of propagating correlations in an interacting quantum many-body
system. By quenching a one-dimensional quantum gas in an optical lattice, we
reveal how quasiparticle pairs transport correlations with a finite velocity
across the system, resulting in an effective light cone for the quantum
dynamics. Our results open important perspectives for understanding relaxation
of closed quantum systems far from equilibrium as well as for engineering
efficient quantum channels necessary for fast quantum computations.Comment: 7 pages, 5 figures, 2 table
Simple, Fast and Accurate Implementation of the Diffusion Approximation Algorithm for Stochastic Ion Channels with Multiple States
The phenomena that emerge from the interaction of the stochastic opening and
closing of ion channels (channel noise) with the non-linear neural dynamics are
essential to our understanding of the operation of the nervous system. The
effects that channel noise can have on neural dynamics are generally studied
using numerical simulations of stochastic models. Algorithms based on discrete
Markov Chains (MC) seem to be the most reliable and trustworthy, but even
optimized algorithms come with a non-negligible computational cost. Diffusion
Approximation (DA) methods use Stochastic Differential Equations (SDE) to
approximate the behavior of a number of MCs, considerably speeding up
simulation times. However, model comparisons have suggested that DA methods did
not lead to the same results as in MC modeling in terms of channel noise
statistics and effects on excitability. Recently, it was shown that the
difference arose because MCs were modeled with coupled activation subunits,
while the DA was modeled using uncoupled activation subunits. Implementations
of DA with coupled subunits, in the context of a specific kinetic scheme,
yielded similar results to MC. However, it remained unclear how to generalize
these implementations to different kinetic schemes, or whether they were faster
than MC algorithms. Additionally, a steady state approximation was used for the
stochastic terms, which, as we show here, can introduce significant
inaccuracies. We derived the SDE explicitly for any given ion channel kinetic
scheme. The resulting generic equations were surprisingly simple and
interpretable - allowing an easy and efficient DA implementation. The algorithm
was tested in a voltage clamp simulation and in two different current clamp
simulations, yielding the same results as MC modeling. Also, the simulation
efficiency of this DA method demonstrated considerable superiority over MC
methods.Comment: 32 text pages, 10 figures, 1 supplementary text + figur
Cancer and thrombosis: Managing the risks and approaches to thromboprophylaxis
Patients with cancer are at increased risk of venous thromboembolism (VTE) compared with patients without cancer. This results from both the prothrombotic effects of the cancer itself and iatrogenic factors, such as chemotherapy, radiotherapy, indwelling central venous devices and surgery, that further increase the risk of VTE. Although cancer-associated thrombosis remains an important cause of morbidity and mortality, it is often underdiagnosed and undertreated. However, evidence is accumulating to support the use of low-molecular-weight heparins (LMWHs) in the secondary prevention of VTE in patients with cancer. Not only have LMWHs been shown to be at least as effective as coumarin derivatives in this setting, but they have a lower incidence of complications, including bleeding, and are not associated with the practical problems of warfarin therapy. Furthermore, a growing number of studies indicate that LMWHs may improve survival among patients with cancer due to a possible antitumor effect. Current evidence suggests that LMWHs should increasingly be considered for the long-term management of VTE in patients with cancer
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The combined diabetes and renal control trial (C-DIRECT) - a feasibility randomised controlled trial to evaluate outcomes in multi-morbid patients with diabetes and on dialysis using a mixed methods approach
Background: This cluster randomised controlled trial set out to investigate the feasibility and acceptability of the “Combined Diabetes and Renal Control Trial” (C-DIRECT) intervention, a nurse-led intervention based on motivational interviewing and self-management in patients with coexisting end stage renal diseases and diabetes mellitus (DM ESRD). Its efficacy to improve glycaemic control, as well as psychosocial and self-care outcomes were also evaluated as secondary outcomes.
Methods: An assessor-blinded, clustered randomised-controlled trial was conducted with 44 haemodialysis patients with DM ESRD and ≥ 8% glycated haemoglobin (HbA1c), in dialysis centres across Singapore. Patients were randomised according to dialysis shifts. 20 patients were assigned to intervention and 24 were in usual care. The C-DIRECT intervention consisted of three weekly chair-side sessions delivered by diabetes specialist nurses. Data on recruitment, randomisation, and retention, and secondary outcomes such as clinical endpoints, emotional distress, adherence, and self-management skills measures were obtained at baseline and at 12 weeks follow-up. A qualitative evaluation using interviews was conducted at the end of the trial.
Results: Of the 44 recruited at baseline, 42 patients were evaluated at follow-up. One patient died, and one discontinued the study due to deteriorating health. Recruitment, retention, and acceptability rates of C-DIRECT were generally satisfactory HbA1c levels decreased in both groups, but C-DIRECT had more participants with HbA1c < 8% at follow up compared to usual care. Significant improvements in role limitations due to physical health were noted for C-DIRECT whereas levels remained stable in usual care. No statistically significant differences between groups were observed for other clinical markers and other patient-reported outcomes. There were no adverse effects.
Conclusions: The trial demonstrated satisfactory feasibility. A brief intervention delivered on bedside as part of routine dialysis care showed some benefits in glycaemic control and on QOL domain compared with usual care, although no effect was observed in other secondary outcomes. Further research is needed to design and assess interventions to promote diabetes self-management in socially vulnerable patients
The what and where of adding channel noise to the Hodgkin-Huxley equations
One of the most celebrated successes in computational biology is the
Hodgkin-Huxley framework for modeling electrically active cells. This
framework, expressed through a set of differential equations, synthesizes the
impact of ionic currents on a cell's voltage -- and the highly nonlinear impact
of that voltage back on the currents themselves -- into the rapid push and pull
of the action potential. Latter studies confirmed that these cellular dynamics
are orchestrated by individual ion channels, whose conformational changes
regulate the conductance of each ionic current. Thus, kinetic equations
familiar from physical chemistry are the natural setting for describing
conductances; for small-to-moderate numbers of channels, these will predict
fluctuations in conductances and stochasticity in the resulting action
potentials. At first glance, the kinetic equations provide a far more complex
(and higher-dimensional) description than the original Hodgkin-Huxley
equations. This has prompted more than a decade of efforts to capture channel
fluctuations with noise terms added to the Hodgkin-Huxley equations. Many of
these approaches, while intuitively appealing, produce quantitative errors when
compared to kinetic equations; others, as only very recently demonstrated, are
both accurate and relatively simple. We review what works, what doesn't, and
why, seeking to build a bridge to well-established results for the
deterministic Hodgkin-Huxley equations. As such, we hope that this review will
speed emerging studies of how channel noise modulates electrophysiological
dynamics and function. We supply user-friendly Matlab simulation code of these
stochastic versions of the Hodgkin-Huxley equations on the ModelDB website
(accession number 138950) and
http://www.amath.washington.edu/~etsb/tutorials.html.Comment: 14 pages, 3 figures, review articl
Services just for men? Insights from a national study of the well men services pilots.
Men continue to have a lower life expectancy in most countries compared to women. Explanations of this gendered health inequality tend to focus on male risk taking, unhealthy lifestyle choices and resistance to seeking help from health services. In the period 2005-2008 the Scottish Government funded a nationwide community health promotion programme aimed at improving men's health, called Well Men Service Pilots (henceforth WMS)
Existence of Integral -Varifolds minimizing and , , in Riemannian Manifolds
We prove existence and partial regularity of integral rectifiable
-dimensional varifolds minimizing functionals of the type and
in a given Riemannian -dimensional manifold , , under suitable assumptions on (in the end of the paper we
give many examples of such ambient manifolds). To this aim we introduce the
following new tools: some monotonicity formulas for varifolds in
involving , to avoid degeneracy of the minimizer, and a sort of
isoperimetric inequality to bound the mass in terms of the mentioned
functionals.Comment: 33 pages; this second submission corresponds to the published version
of the paper, minor typos are fixe
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