Biomedical subjects

R Erichsen

Publications and source records attributed to R Erichsen.

5 recordsLinked to original sources

PubMed2003

Time evolution of the extremely diluted Blume-Emery-Griffiths neural network.

A study of the time evolution and a stability analysis of the phases in the extremely diluted Blume-Emery-Griffiths neural network model are shown to yield new phase diagrams in which fluctuation retrieval may drive pattern retrieval. It is shown that saddle-point solutions associated with fluctuation overlaps slow down the flow of the network states towards the retrieval fixed points. A comparison of the performance with other three-state networks is also presented.

Biophysical Phenomena↗

PubMed2001

Retrieval behavior and thermodynamic properties of symmetrically diluted Q-Ising neural networks.

The retrieval behavior and thermodynamic properties of symmetrically diluted Q-Ising neural networks are derived and studied in replica-symmetric mean-field theory generalizing earlier works on either the fully connected or the symmetrical extremely diluted network. Capacity-gain parameter phase diagrams are obtained for the Q=3, Q=4, and Q=infinity state networks with uniformly distributed patterns of low activity in order to search for the effects of a gradual dilution of the synapses. It is shown that enlarged regions of continuous changeover into a region of optimal performance are obtained for finite stochastic noise and small but finite connectivity. The de Almeida-Thouless lines of stability are obtained for arbitrary connectivity, and the resulting phase diagrams are used to draw conclusions on the behavior of symmetrically diluted networks with other pattern distributions of either high or low activity.

Animals↗

PubMed1999

Coupling of low-frequency modes with the complex Ginzburg-Landau equation: Generalized Zakharov equations.

In this paper we introduce and examine a generalization of the complex Ginzburg-Landau equation (CGLE) where the self-interaction contained in the cubic term is replaced by a coupling involving the original field and a low-frequency one. New instabilities arise and a radically new asymptotic dynamical behavior emerges displaying defect turbulence over wide regions of the parameter space.

Journal Article↗

PubMed1999

Categorization in fully connected multistate neural network models.

The categorization ability of fully connected neural network models, with either discrete or continuous Q-state units, is studied in this work in replica symmetric mean-field theory. Hierarchically correlated multistate patterns in a two level structure of ancestors and descendents (examples) are embedded in the network and the categorization task consists in recognizing the ancestors when the network is trained exclusively with their descendents. Explicit results for the dependence of the equilibrium properties of a Q=3-state model and a Q=infinity-state model are obtained in the form of phase diagrams and categorization curves. A strong improvement of the categorization ability is found when the network is trained with examples of low activity. The categorization ability is found to be robust to finite threshold and synaptic noise. The Almeida-Thouless lines that limit the validity of the replica-symmetric results, are also obtained.

Learning↗

PubMed1996

[Not Available].

After 1933 many scientists and university teachers were obliged to relinquish their posts in the universities of Germany because of national-socialist laws. Organizations-in-aid like the Academic Assistance Council in Great Britain tried to 'defend science and learning' raising funds and finding new openings for the expelled academics. But as immigration laws were tight and jobs were scarce in the host countries the AAC and the other organizations had to select the most qualified from among the applicants for support. -- The questions the article tries to answer are: What kind of criteria were applied in this selection? Who were the experts? How were the placements made? How did the applicants react to the decisions? Taking for example the AAC, it examines measures to assist a group of scientists who, having tried to settle down in England, finally emigrated to Turkey.

Economics↗