6,185 research outputs found
Heteroclinic Chaos, Chaotic Itinerancy and Neutral Attractors in Symmetrical Replicator Equations with Mutations
A replicator equation with mutation processes is numerically studied.
Without any mutations, two characteristics of the replicator dynamics are
known: an exponential divergence of the dominance period, and hierarchical
orderings of the attractors. A mutation introduces some new aspects: the
emergence of structurally stable attractors, and chaotic itinerant behavior. In
addition, it is reported that a neutral attractor can exist in the mutataion
rate -> +0 region.Comment: 4 pages, 9 figure
Altruistic Contents of Quantum Prisoner's Dilemma
We examine the classical contents of quantum games. It is shown that a
quantum strategy can be interpreted as a classical strategies with effective
density-dependent game matrices composed of transposed matrix elements. In
particular, successful quantum strategies in dilemma games are interpreted in
terms of a symmetrized game matrix that corresponds to an altruistic game plan.Comment: Revised according to publisher's request: 4 pgs, 2 fgs, ReVTeX4. For
more info, go to http://www.mech.kochi-tech.ac.jp/cheon
The Wehl family of South Australia and their botanical connections with “Dear Uncle” Baron Ferdinand von Mueller
Dr Eduard Wehl and Clara Wehl (née Mueller) and their children hold a unique position in the history of South Australian botany because of their association with Clara’s brother and the children’s uncle, Baron Ferdinand von Mueller, Australia’s most significant botanist of the nineteenth century. Both Wehl parents and six of their twelve surviving children collected botanical specimens for Mueller and about 1200 herbarium specimens have been located with most being held in the National Herbarium of Victoria. The majority of specimens were collected in the vicinity of Mount Gambier and Lake Bonney, South Australia. As well as collecting botanical specimens, two daughters, Marie Magdalene Wehl and Henrietta Jane Wehl, illustrated plants and fungi. About 300 illustrations have survived. Of these, about 240 are of flowering plants and contained in three sketchbooks, two of which are at the National Herbarium of Victoria and one at the State Herbarium of South Australia. Marie made a speciality of illustrating fungi, and 36 illustrations are included in an album in the Natural History Museum, London, and 25 others are held as either loose illustrations or associated with herbarium specimens in the National Herbarium of Victoria. Specimens collected by the Wehls have been used in the typification of at least 23 species names. The family is commemorated in three taxa: Clara Wehl in the marine alga Gigartina wehliae Sond.; Eduard and Clara Wehl jointly in the plant genus Wehlia F.Muell. [= Homalocalyx F.Muell.]; and Marie Wehl in the fungus Agaricus wehlianus F.Muell. ex Cooke [=Pluteus wehlianus (F.Muell. ex Cooke) Sacc.]. In this paper we provide a brief history of the Wehl family in South Australia. We assess the herbarium specimens collected by them, examine their illustrations and determine the connections between them and their current importance for typification. Underlying this, we consider the contribution made by the Wehl family toward the botanical work of Baron Ferdinand von Mueller
Better Nonlinear Models from Noisy Data: Attractors with Maximum Likelihood
A new approach to nonlinear modelling is presented which, by incorporating
the global behaviour of the model, lifts shortcomings of both least squares and
total least squares parameter estimates. Although ubiquitous in practice, a
least squares approach is fundamentally flawed in that it assumes independent,
normally distributed (IND) forecast errors: nonlinear models will not yield IND
errors even if the noise is IND. A new cost function is obtained via the
maximum likelihood principle; superior results are illustrated both for small
data sets and infinitely long data streams.Comment: RevTex, 11 pages, 4 figure
Fucosylation inhibitor development for producing afucosylated antibodies
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Fluctuations and Correlations in Lattice Models for Predator-Prey Interaction
Including spatial structure and stochastic noise invalidates the classical
Lotka-Volterra picture of stable regular population cycles emerging in models
for predator-prey interactions. Growth-limiting terms for the prey induce a
continuous extinction threshold for the predator population whose critical
properties are in the directed percolation universality class. Here, we discuss
the robustness of this scenario by considering an ecologically inspired
stochastic lattice predator-prey model variant where the predation process
includes next-nearest-neighbor interactions. We find that the corresponding
stochastic model reproduces the above scenario in dimensions 1< d \leq 4, in
contrast with mean-field theory which predicts a first-order phase transition.
However, the mean-field features are recovered upon allowing for
nearest-neighbor particle exchange processes, provided these are sufficiently
fast.Comment: 5 pages, 4 figures, 2-column revtex4 format. Emphasis on the lattice
predator-prey model with next-nearest-neighbor interaction (Rapid
Communication in PRE
Do institutional arrangements make a difference to transport policy and implementation? Lessons for Britain
This paper describes local government decision-making in transport in three areas of the UK, London, West Yorkshire and Edinburgh, in which major changes in local government decision-making structures have taken place over the last decade, and between which arrangements are now very different. The research discusses whether institutional change has had a beneficial or adverse effect, and whether any of the current structures provides a more effective framework for policy development and implementation. The results show that although the sites share a broadly common set of objectives there are differences in devolved responsibilities and in the extent to which various policy options are within the control of the bodies charged with transport policy delivery. The existence of several tiers of government, coupled with the many interactions required between these public sector bodies and the predominantly private sector public transport operators appears to create extra transactional barriers and impedes the implementation of the most effective measures for cutting congestion. There is, however, a compelling argument for the presence of an overarching tier of government to organise travel over a spatial scale compatible with that of major commuter patterns. The extent to which such arrangements currently appear to work is a function of the range of powers and the funding levels afforded to the co-ordinating organisation
Parametrization of C-shocks. Evolution of the Sputtering of Grains
Context: The detection of narrow SiO lines toward the young shocks of the
L1448-mm outflow has been interpreted as a signature of the magnetic precursor
of C-shocks. In contrast with the low SiO abundances (<10E-12) in the ambient
gas, the narrow SiO emission at almost ambient velocities reveals enhanced SiO
abundances of 10E-11. This enhancement has been proposed to be produced by the
sputtering of the grain mantles at the first stages of C-shocks. However,
modelling of the sputtering of grains has usually averaged the SiO abundances
over the dissipation region of C-shocks, which cannot explain the recent
observations. Aims: To model the evolution of the gas phase abundances of SiO,
CH3OH and H2O, produced by the sputtering of grains as the shock propagates
through the ambient gas. Methods: We propose a parametric model to describe the
physical structure of C-shocks as a function of time. Using the known
sputtering yields for water mantles (with minor constituents like silicon and
CH3OH) and olivine cores by collisions with H2, He, C, O, Si, Fe and CO, we
follow the evolution of the abundances of silicon, CH3OH and H2O ejected from
grains. Results: The evolution of these abundances shows that CO seems to be
the most efficient sputtering agent in low velocity shocks. The velocity
threshold for the sputtering of silicon from the grain mantles is reduced by
5-10 km s-1 by CO compared to other models. The sputtering by CO can generate
SiO abundances of 10E-11 at the early stages of low velocity shocks, consistent
with those observed in the magnetic precursor of L1448-mm. Our model also
satisfactorily reproduce the progressive enhancement of SiO, CH3OH and H2O
observed in this outflow by the coexistence of two shocks with vs=30 and
60kms-1 within the same region.Comment: 12 pages, 7 figures, accepted for publication in A&
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