9,650 research outputs found
Learning Dynamic Boltzmann Distributions as Reduced Models of Spatial Chemical Kinetics
Finding reduced models of spatially-distributed chemical reaction networks
requires an estimation of which effective dynamics are relevant. We propose a
machine learning approach to this coarse graining problem, where a maximum
entropy approximation is constructed that evolves slowly in time. The dynamical
model governing the approximation is expressed as a functional, allowing a
general treatment of spatial interactions. In contrast to typical machine
learning approaches which estimate the interaction parameters of a graphical
model, we derive Boltzmann-machine like learning algorithms to estimate
directly the functionals dictating the time evolution of these parameters. By
incorporating analytic solutions from simple reaction motifs, an efficient
simulation method is demonstrated for systems ranging from toy problems to
basic biologically relevant networks. The broadly applicable nature of our
approach to learning spatial dynamics suggests promising applications to
multiscale methods for spatial networks, as well as to further problems in
machine learning
Tracking and Tracing in Food Networks: The Case of the Feed Industry
This paper discusses an organisational framework for Tracking & Tracing and quality management in the agriculture and food network and thus providing increased transparency therein. The legal and market environments that especially European companies of the compound feeds sector face today is being analyzed with respect to resulting recent and present requirements. A technological solution for companies and supply chains that helps dealing with these requirements is presented with an organisational glance inside the QM-G system.Tracking & Tracing, Feed Industry, Inter-Organizational Information System QM-G, Agribusiness, Industrial Organization,
Thinking territory historically.
BACKGROUND:
While the randomised controlled trial (RCT) is generally regarded as the design of
choice for assessing the effects of health care, within the social sciences there is
considerable debate about the relative suitability of RCTs and non-randomised
studies (NRSs) for evaluating public policy interventions.
// OBJECTIVES:
To determine whether RCTs lead to the same effect size and variance as NRSs of
similar policy interventions; and whether these findings can be explained by other
factors associated with the interventions or their evaluation.
// METHODS:
Analyses of methodological studies, empirical reviews, and individual health and
social services studies investigated the relationship between randomisation and
effect size of policy interventions by:
1) Comparing controlled trials that are identical in all respects other than the use of
randomisation by 'breaking' the randomisation in a trial to create non-randomised
trials (re-sampling studies).
2) Comparing randomised and non-randomised arms of controlled trials mounted
simultaneously in the field (replication studies).
3) Comparing similar controlled trials drawn from systematic reviews that include
both randomised and non-randomised studies (structured narrative reviews and
sensitivity analyses within meta-analyses).
4) Investigating associations between randomisation and effect size using a pool of
more diverse RCTs and NRSs within broadly similar areas (meta-epidemiology).
// RESULTS:
Prior methodological reviews and meta-analyses of existing reviews comparing
effects from RCTs and nRCTs suggested that effect sizes from RCTs and nRCTs
may indeed differ in some circumstances and that these differences may well be
associated with factors confounded with design.
Re-sampling studies offer no evidence that the absence of randomisation directly
influences the effect size of policy interventions in a systematic way. No consistent
explanations were found for randomisation being associated with changes in effect
sizes of policy interventions in field trials
Pericenter passage of the gas cloud G2 in the Galactic Center
We have further followed the evolution of the orbital and physical properties
of G2, the object currently falling toward the massive black hole in the
Galactic Center on a near-radial orbit. New, very sensitive data were taken in
April 2013 with NACO and SINFONI at the ESO VLT . The 'head' of G2 continues to
be stretched ever further along the orbit in position-velocity space. A
fraction of its emission appears to be already emerging on the blue-shifted
side of the orbit, past pericenter approach. Ionized gas in the head is now
stretched over more than 15,000 Schwarzschild radii RS around the pericenter of
the orbit, at ~ 2000 RS ~ 20 light hours from the black hole. The pericenter
passage of G2 will be a process stretching over a period of at least one year.
The Brackett-{\gamma} luminosity of the head has been constant over the past 9
years, to within +- 25%, as have the line ratios Brackett-{\gamma} /
Paschen-{\alpha} and Brackett-{\gamma} / Helium-I. We do not see any
significant evidence for deviations of G2's dynamical evolution, due to
hydrodynamical interactions with the hot gas around the black hole, from a
ballistic orbit of an initially compact cloud with moderate velocity
dispersion. The constant luminosity and the increasingly stretched appearance
of the head of G2 in the position-velocity plane, without a central peak, is
not consistent with several proposed models with continuous gas release from an
initially bound zone around a faint star on the same orbit as G2.Comment: 10 figures, submitted to Ap
'It's a Form of Freedom': The experiences of people with disabilities within equestrian sport
This paper explores the embodied, gendered experiences of disabled horseâriders. Drawing on data from five inâdepth interviews with paradressage riders, the ways in which their involvement in elite disability sport impacts upon their sense of identity and confidence are explored, as well as the considerable health and social benefits that this involvement brings. Social models of disability are employed and the shortcomings of such models, when applied to disability sport, are highlighted. The data presented here demonstrates the necessity of seeing disability sport as an embodied experience and acknowledging the importance of impairment to the experiences of disabled athletes. Living within an impaired body is also a gendered experience and the implications of this when applied to elite disability sport are considered
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Ecological traps for large-scale invasive species control: predicting settling rules by recolonising American mink post-culling
1. Management programs worldwide seeking to reduce the density of invasive species must overcome compensatory processes, such as recolonisation by dispersers from non- or partially-controlled areas. However, the scale and drivers of dispersal in such context are poorly known.
2. We investigated the dispersal patterns of American mink reinvading 20,000 km2 of their non-native range following a culling programme led by citizen conservationists. Using multinomial models, we estimated the contributions of density dependence, proxies for patch quality and distance from the natal patch on mink settlement.
3. Seventy seven percent of mink dispersed and settled in non-natal patches. Dispersal distances were large with settlement probabilities only reduced by half at ~60 km, and 20% of mink dispersing > 80 km.
4. Females were more attracted to patches of high quality mostly found at low altitudes. Males favoured patches with intermediate current densities and consistently high quality.
Synthesis and applications. Predicting post-culling recolonisation by a non-native mobile carnivore over large spatial scale could was using information on relative densities obtained during management interventions largely implemented by citizen conservationists. This was made possible by a monitoring component designed to feed into the adaptive management process implemented in this project. High mink mobility dictates management should take place on very large spatial scales to minimise reinvasion from un-controlled areas. Both males and females were attracted to patches that were previously consistently occupied, providing a degree of predictability to patterns of recolonisation. Targeting control to patches attractive to immigrant mink requires knowledge of current mink density. Creating so-called ecological traps in the face of ongoing immigration from peripheral areas provides a promising tool to effectively control mobile invasive species
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