819 research outputs found
Hierarchy and Polysynchrony in an adaptive network
We describe a simple adaptive network of coupled chaotic maps. The network
reaches a stationary state (frozen topology) for all values of the coupling
parameter, although the dynamics of the maps at the nodes of the network can be
non-trivial. The structure of the network shows interesting hierarchical
properties and in certain parameter regions the dynamics is polysynchronous:
nodes can be divided in differently synchronized classes but contrary to
cluster synchronization, nodes in the same class need not be connected to each
other. These complicated synchrony patterns have been conjectured to play roles
in systems biology and circuits. The adaptive system we study describes ways
whereby this behaviour can evolve from undifferentiated nodes.Comment: 13 pages, 17 figure
Individual Budgets : Lessons from Early Users' Experiences
Within the context of modernization, there has been a trend towards 'cash-for-care' schemes designed to bring choice and control closer to the service user. In England, Individual Budgets (IBs) are being piloted, with the aim of promoting personalized support for disabled people and other users of social care services. This paper reports on the experiences and outcomes of early IB users two to three months after first being offered an IB. The users included adults with physical/sensory impairments, learning difficulties, mental health problems and older people. Semi-structured interviews were carried out with nine service users and five proxies. The findings suggest that IBs have the potential to be innovative and life-enhancing. However, achieving this potential in practice depends on a range of other factors, including changes in the routine practices and organizational culture of adult social care services and ensuring users have access to appropriate documentation and support. Any conclusions drawn from the experiences of these early IB users must be treated with caution. The findings nevertheless indicate some of the issues that will need to be addressed as IBs are implemented more widely to replace conventional forms of adult social care provision
Multistability and nonsmooth bifurcations in the quasiperiodically forced circle map
It is well-known that the dynamics of the Arnold circle map is phase-locked
in regions of the parameter space called Arnold tongues. If the map is
invertible, the only possible dynamics is either quasiperiodic motion, or
phase-locked behavior with a unique attracting periodic orbit. Under the
influence of quasiperiodic forcing the dynamics of the map changes
dramatically. Inside the Arnold tongues open regions of multistability exist,
and the parameter dependency of the dynamics becomes rather complex. This paper
discusses the bifurcation structure inside the Arnold tongue with zero rotation
number and includes a study of nonsmooth bifurcations that happen for large
nonlinearity in the region with strange nonchaotic attractors.Comment: 25 pages, 22 colored figures in reduced quality, submitted to Int. J.
of Bifurcation and Chaos, a supplementary website
(http://www.mpipks-dresden.mpg.de/eprint/jwiersig/0004003/) is provide
Families of piecewise linear maps with constant Lyapunov exponent
We consider families of piecewise linear maps in which the moduli of the two
slopes take different values. In some parameter regions, despite the variations
in the dynamics, the Lyapunov exponent and the topological entropy remain
constant. We provide numerical evidence of this fact and we prove it
analytically for some special cases. The mechanism is very different from that
of the logistic map and we conjecture that the Lyapunov plateaus reflect
arithmetic relations between the slopes.Comment: 26 pages, 13 figure
Mechanisms of intermittent state transitions in a coupled heterogeneous oscillator model of epilepsy
This is the final version of the article. Available from BioMed Central/SpringerOpen via the DOI in this record.We investigate the dynamic mechanisms underlying intermittent state transitions in a recently proposed neural mass model of epilepsy. A low dimensional model is constructed, which preserves two key features of the neural mass model, namely (i) coupling between oscillators and (ii) heterogeneous proximity of these oscillators to a bifurcation between distinct limit cycles. We demonstrate that state transitions due to intermittency occur in the abstract model. This suggests that there is a general bifurcation mechanism responsible for this behaviour and that this is independent of the precise form of the evolution equations. Such abstractions of neural mass models allow a deeper insight into underlying dynamic and physiological mechanisms, and also allow the more efficient exploration of large scale brain dynamics in disease.MG acknowledges funding from the EPSRC through a postdoctoral prize fellowship
Imperfect Homoclinic Bifurcations
Experimental observations of an almost symmetric electronic circuit show
complicated sequences of bifurcations. These results are discussed in the light
of a theory of imperfect global bifurcations. It is shown that much of the
dynamics observed in the circuit can be understood by reference to imperfect
homoclinic bifurcations without constructing an explicit mathematical model of
the system.Comment: 8 pages, 11 figures, submitted to PR
Simulating soil carbon sequestration from long term fertilizer and manure additions under continuous wheat using the DailyDayCent model
Bangabandhu Fellowship on Science and ICT project, Ministry of Science and Technology, People’s Republic of Bangladesh. Open Access via Springer Compact AgreementPeer reviewedPublisher PD
Emergence of hierarchical networks and polysynchronous behaviour in simple adaptive systems
We describe the dynamics of a simple adaptive network. The network
architecture evolves to a number of disconnected components on which the
dynamics is characterized by the possibility of differently synchronized nodes
within the same network (polysynchronous states). These systems may have
implications for the evolutionary emergence of polysynchrony and hierarchical
networks in physical or biological systems modeled by adaptive networks.Comment: 4 pages, 4 figure
Evaluating postgraduate students' perceptions of activity led learning: Findings from a longitudinal study
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