3,153 research outputs found
Localization of response functions of spiral waves in the FitzHugh-Nagumo system
Dynamics of spiral waves in perturbed, e. g. slightly inhomogeneous or
subject to a small periodic external force, two-dimensional autowave media can
be described asymptotically in terms of Aristotelean dynamics, so that the
velocities of the spiral wave drift in space and time are proportional to the
forces caused by the perturbation. The forces are defined as a convolution of
the perturbation with the spiral's Response Functions, which are eigenfunctions
of the adjoint linearised problem. In this paper we find numerically the
Response Functions of a spiral wave solution in the classic excitable
FitzHugh-Nagumo model, and show that they are effectively localised in the
vicinity of the spiral core.Comment: 11 pages, 2 figure
Soliton-like phenomena in one-dimensional cross-diffusion systems: a predator-prey pursuit and evasion example
We have studied properties of nonlinear waves in a mathematical model of a
predator-prey system with pursuit and evasion. We demonstrate a new type of
propagating wave in this system. The mechanism of propagation of these waves
essentially depends on the ``taxis'', represented by nonlinear
``cross-diffusion'' terms in the mathematical formulation. We have shown that
the dependence of the velocity of wave propagation on the taxis has two
distinct forms, ``parabolic'' and ``linear''. Transition from one form to the
other correlates with changes in the shape of the wave profile. Dependence of
the propagation velocity on diffusion in this system differs from the
square-root dependence typical of reaction-diffusion waves. We demonstrate also
that, for systems with negative and positive taxis, for example, pursuit and
evasion, there typically exists a large region in the parameter space, where
the waves demonstrate quasisoliton interaction: colliding waves can penetrate
through each other, and waves can also reflect from impermeable boundaries.Comment: 15 pages, 18 figures, submitted to Physica
Pursuit-evasion predator-prey waves in two spatial dimensions
We consider a spatially distributed population dynamics model with excitable
predator-prey dynamics, where species propagate in space due to their taxis
with respect to each other's gradient in addition to, or instead of, their
diffusive spread. Earlier, we have described new phenomena in this model in one
spatial dimension, not found in analogous systems without taxis: reflecting and
self-splitting waves. Here we identify new phenomena in two spatial dimensions:
unusual patterns of meander of spirals, partial reflection of waves, swelling
wavetips, attachment of free wave ends to wave backs, and as a result, a novel
mechanism of self-supporting complicated spatio-temporal activity, unknown in
reaction-diffusion population models.Comment: 15 pages, 15 figures, submitted to Chao
Localization of response functions of spiral waves in the FitzHugh-Nagumo system
Preprint of an article submitted for consideration and subsequently published in International Journal of Bifurcation and Chaos © 2005 copyright World Scientific Publishing Company. http://www.worldscientific.com/worldscinet/ijbcDynamics of spiral waves in perturbed, e. g. slightly inhomogeneous or subject to a small periodic external force, two-dimensional autowave media can be described asymptotically in terms of Aristotelean dynamics, so that the velocities of the spiral wave drift in space and time are proportional to the forces caused by the perturbation. The forces are defined as a convolution of the perturbation with the spiral's Response Functions, which are eigenfunctions of the adjoint linearised problem. In this paper we find numerically the Response Functions of a spiral wave solution in the classic excitable FitzHugh-Nagumo model, and show that they are effectively localised in the vicinity of the spiral core
In-Plane Spectral Weight Shift of Charge Carriers in
The temperature dependent redistribution of the spectral weight of the
plane derived conduction band of the high
temperature superconductor (T_c = 92.7 K) was studied with wide-band (from 0.01
to 5.6 eV) spectroscopic ellipsometry. A superconductivity - induced transfer
of the spectral weight involving a high energy scale in excess of 1 eV was
observed. Correspondingly, the charge carrier spectral weight was shown to
decrease in the superconducting state. The ellipsometric data also provide
detailed information about the evolution of the optical self-energy in the
normal and superconducting states
Anomalous oxygen isotope effect on the in-plane FIR conductivity of detwinned YBa2Cu3O
We observe an anomalous oxygen isotope effect on the a-axis component of the
far-infrared electronic response of detwinned YBa2Cu3O. For
O a pronounced low-energy electronic mode (LEM) appears around 240
cm. This a-axis LEM exhibits a clear aging effect, after one year it is
shifted to 190 cm. For O we cannot resolve a corresponding a-axis
LEM above 120 cm. We interpret the LEM in terms of a collective
electronic mode that is pinned by `isotopic defects', i.e. by the residual
O in the matrix of O.Comment: 10 pages, 2 figure
Striving to practice what we preach: academics reflecting on teaching reflective practice.
That reflection is part of the HRD academics’ continuing professional development is a powerful rhetoric. But to what extent are we guilty of hypocrisy? Inspired by the title and theme of the conference ‘HRD: Reflecting upon the Past, Shaping the Future’ this paper seeks to make a critically reflective statement on our own practice as HRD academics teaching and researching reflective practice. Researching ‘practising what we preach’, in the context of reflective practice, raises difficult questions but offers the potential for valuable insight into the HRD academics’ professional practice
From reflective learning to reflective practice: assessing transfer
A key attribute of reflective practice is its capacity for on-going purposeful learning in relation to changing and demanding professional work. The teaching of reflective learning techniques in management education is intended to promote deep-level learning and the application of critical thinking to oneself, personal experience and the work environment. However, we lack empirical evidence that the teaching of reflective learning leads to enhanced reflective practice in professional work. This study provides an examination of reflection in work post formal education. It reports on interviews with 18 Human Resource professionals. Reflection does not get ‘left behind’ on completion of formal teaching but there is not an even or simple process of transfer to a work context. Likewise, there was not a slavish adherence to reflective techniques but rather some evidence that students were able to translate their learning into something meaningful for their practice. © 2016 Society for Research into Higher Educatio
Reflective practice: is there transfer from classroom to workplace?
Does HE based teaching of reflective practice transfer into management practice in the workplace? This paper reports on research addressing this question. Initially the research is set in context. Extensive theorising, conceptual debate and discussion on a problematic curriculum have not been matched with empirical data about reflection as part of managing. Interviews with eighteen HR professionals provide the data upon which initial findings are drawn. Management practice is influenced by their professional programme and, in the main, reflection is an important element of perceived change. For some transfer appears restricted to instrumental practice. For others, however, a more complex picture emerges; one where glimpses of criticality are evident but where the link to the formal teaching of reflection is less straightforward. This, together with factors influencing the reflective landscape observed, warrant further analysis as a precursor to consideration of curriculum implication
- …