63 research outputs found
Discrete and fuzzy dynamical genetic programming in the XCSF learning classifier system
A number of representation schemes have been presented for use within
learning classifier systems, ranging from binary encodings to neural networks.
This paper presents results from an investigation into using discrete and fuzzy
dynamical system representations within the XCSF learning classifier system. In
particular, asynchronous random Boolean networks are used to represent the
traditional condition-action production system rules in the discrete case and
asynchronous fuzzy logic networks in the continuous-valued case. It is shown
possible to use self-adaptive, open-ended evolution to design an ensemble of
such dynamical systems within XCSF to solve a number of well-known test
problems
Radial velocities in the globular cluster omega Centauri
We have used the ARGUS multi-object spectrometer at the CTIO 4m Blanco
telescope to obtain 2756 radial velocity measurements for 1966 individual stars
in the globular cluster omega Centauri brighter than blue photographic
magnitude of about 16.5. Of these, 1589 stars are cluster members. A comparison
with two independent radial velocity studies, carried out by Suntzeff & Kraft
and by Mayor et al., demonstrates that the median error of our measurements is
below 2 km/s for the stars brighter than B-magnitude 15, which constitute the
bulk of the sample. The observed velocity dispersion decreases from about 15
km/s in the inner few arcmin to about 6 km/s at a radius of 25 arcmin. The
cluster shows significant rotation, with a maximum amplitude of about 6 km/s in
the radial zone between 6 and 10 arcmin. In a companion paper by van de Ven et
al., we correct these radial velocities for the perspective rotation caused by
the space motion of the cluster, and combine them with the internal proper
motions of nearly 8000 cluster members measured by van Leeuwen et al., to
construct a detailed dynamical model of omega Centauri and to measure its
distance.Comment: 10 pages (7 figures), accepted for publication in A&
Quantum Cryptography
Quantum cryptography could well be the first application of quantum mechanics
at the individual quanta level. The very fast progress in both theory and
experiments over the recent years are reviewed, with emphasis on open questions
and technological issues.Comment: 55 pages, 32 figures; to appear in Reviews of Modern Physic
Ubiquitous molecular substrates for associative learning and activity-dependent neuronal facilitation.
Recent evidence suggests that many of the molecular cascades and substrates that contribute to learning-related forms of neuronal plasticity may be conserved across ostensibly disparate model systems. Notably, the facilitation of neuronal excitability and synaptic transmission that contribute to associative learning in Aplysia and Hermissenda, as well as associative LTP in hippocampal CA1 cells, all require (or are enhanced by) the convergence of a transient elevation in intracellular Ca2+ with transmitter binding to metabotropic cell-surface receptors. This temporal convergence of Ca2+ and G-protein-stimulated second-messenger cascades synergistically stimulates several classes of serine/threonine protein kinases, which in turn modulate receptor function or cell excitability through the phosphorylation of ion channels. We present a summary of the biophysical and molecular constituents of neuronal and synaptic facilitation in each of these three model systems. Although specific components of the underlying molecular cascades differ across these three systems, fundamental aspects of these cascades are widely conserved, leading to the conclusion that the conceptual semblance of these superficially disparate systems is far greater than is generally acknowledged. We suggest that the elucidation of mechanistic similarities between different systems will ultimately fulfill the goal of the model systems approach, that is, the description of critical and ubiquitous features of neuronal and synaptic events that contribute to memory induction
Comparing Synchronous and Asynchronous Cellular Genetic Algorithms
This paper presents a comparative study of several asynchronous policies for updating the population in a cellular genetic algorithm (cGA). Cellular GA's are regular GA's with the important exception that individuals are placed in a given geographical distribution (usually a 2-d grid). Operators are applied locally on a set made of each individual and the surrounding neighbors, thus promoting intraneighborhood exploitation and inter-neighborhood exploration of the search space. Here, we analyze the respective advantages and drawbacks of dealing with this decentralized population in the traditional synchronous manner or in several possible asynchronous update policies
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