675 research outputs found
Thermodynamic properties of extremely diluted symmetric Q-Ising neural networks
Using the replica-symmetric mean-field theory approach the thermodynamic and
retrieval properties of extremely diluted {\it symmetric} -Ising neural
networks are studied. In particular, capacity-gain parameter and
capacity-temperature phase diagrams are derived for and .
The zero-temperature results are compared with those obtained from a study of
the dynamics of the model. Furthermore, the de Almeida-Thouless line is
determined. Where appropriate, the difference with other -Ising
architectures is outlined.Comment: 16 pages Latex including 6 eps-figures. Corrections, also in most of
the figures have been mad
A qualitative study of the impact on the counsellor of engagement in long term empathic relationships with survivors of childhood sexual abuse
This dissertation is a qualitative study of the impact on the counsellor of engagement in long term relationship with survivors of childhood sexual abuse. Five counsellors, experienced in working with adult survivors, were interviewed. Discussion focused on questioning their training and preparation for working with the particular needs of adult clients seriously damaged by traumatic child abuse; the counsellor's experiencing of long term empathic engagement; the quality and availability of supervision and other means of supporting the counsellor; the impact on counsellors exceeding their emotional and physical limitations; and changes caused by the nature of this work in the counsellor's perceptions of the world, their feelings, and the impact on their domestic, social and spiritual life. The study examines the particular nature of childhood abuse and the circumstances that arise working with survivors which may put the counsellor at risk. The results of the study indicate that careful preparation and appropriate training are required for counsellors who wish to be involved in this work, and that constant awareness of the potential dangers combined with self-care and experienced support will help the counsellor to avoid or lessen the risks involved
Neotypification and redescription of Amanita preissii (Basidiomycota), and reconsideration of the status of A. griseibrunnea
Amanita preissii (Fr.) Sacc. is redescribed. Re-examination of collections of
A. griseibrunnea O.K.Mill. show that they do not differ significantly from A. preissii and the two
species are combined. This species is common in the Perth IBRA subregion. Sequence data from the
nuclear ribosomal internal transcribed spacer (ITS) region, 28S nuclear ribosomal large subunit rRNA
(28S) region, RNA polymerase II (RPB2) region, β-tubulin region and translation elongation factor
1-α (EF1-α) region have been deposited in GenBank
On the center of mass of Ising vectors
We show that the center of mass of Ising vectors that obey some simple
constraints, is again an Ising vector.Comment: 8 pages, 3 figures, LaTeX; Claims in connection with disordered
systems have been withdrawn; More detailed description of the simulations;
Inset added to figure
Statistical Mechanics of Learning in the Presence of Outliers
Using methods of statistical mechanics, we analyse the effect of outliers on
the supervised learning of a classification problem. The learning strategy aims
at selecting informative examples and discarding outliers. We compare two
algorithms which perform the selection either in a soft or a hard way. When the
fraction of outliers grows large, the estimation errors undergo a first order
phase transition.Comment: 24 pages, 7 figures (minor extensions added
Correlated patterns in non-monotonic graded-response perceptrons
The optimal capacity of graded-response perceptrons storing biased and
spatially correlated patterns with non-monotonic input-output relations is
studied. It is shown that only the structure of the output patterns is
important for the overall performance of the perceptrons.Comment: 4 pages, 4 figure
A Hebbian approach to complex network generation
Through a redefinition of patterns in an Hopfield-like model, we introduce
and develop an approach to model discrete systems made up of many, interacting
components with inner degrees of freedom. Our approach clarifies the intrinsic
connection between the kind of interactions among components and the emergent
topology describing the system itself; also, it allows to effectively address
the statistical mechanics on the resulting networks. Indeed, a wide class of
analytically treatable, weighted random graphs with a tunable level of
correlation can be recovered and controlled. We especially focus on the case of
imitative couplings among components endowed with similar patterns (i.e.
attributes), which, as we show, naturally and without any a-priori assumption,
gives rise to small-world effects. We also solve the thermodynamics (at a
replica symmetric level) by extending the double stochastic stability
technique: free energy, self consistency relations and fluctuation analysis for
a picture of criticality are obtained
Activation of the IκB Kinase Complex and Nuclear Factor-κB Contributes to Mutant Huntingtin Neurotoxicity
Transcriptional dysregulation by mutant huntingtin (Htt) protein has been implicated in the pathogenesis of Huntington's disease (HD). We find that cultured cells expressing mutant Htt and striatal cells from HD transgenic mice have elevated nuclear factor-κB (NF-κB) activity. Furthermore, NF-κB is concentrated in the nucleus of neurons in the brains of HD transgenic mice. In inducible PC12 cells and in HD transgenic mice, mutant Htt activates the IκB kinase complex (IKK), a key regulator of NF-κB. Activation of IKK is likely mediated by direct interaction with mutant Htt, because the expanded polyglutamine stretch and adjacent proline-rich motifs in mutant Htt interact with IKKγ, a regulatory subunit of IKK. Activation of IKK may also influence the toxicity of mutant Htt, because expression of IKKγ promotes aggregation and nuclear localization of mutant Htt exon-1. Moreover, in acute striatal slice cultures, inhibition of IKK activity with an N-terminally truncated form of IKKγ blocks mutant Htt-induced toxicity in medium-sized spiny neurons (MSNs). In addition, blocking degradation of NF-κB inhibitors with a dominant-negative ubiquitin ligase β-transducin repeat-containing protein also reduces the toxicity of mutant Htt in MSNs. Therefore, aberrant NF-κB activation may contribute to the neurodegeneration induced by mutant Htt
Fixed Points of Hopfield Type Neural Networks
The set of the fixed points of the Hopfield type network is under
investigation. The connection matrix of the network is constructed according to
the Hebb rule from the set of memorized patterns which are treated as distorted
copies of the standard-vector. It is found that the dependence of the set of
the fixed points on the value of the distortion parameter can be described
analytically. The obtained results are interpreted in the terms of neural
networks and the Ising model.Comment: RevTEX, 19 pages, 2 Postscript figures, the full version of the
earler brief report (cond-mat/9901251
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