Point singularities and suprathreshold stochastic resonance in optimal coding

Motivated by recent studies of population coding in theoretical neuroscience, we examine the optimality of a recently described form of stochastic resonance known as suprathreshold stochastic resonance, which occurs in populations of noisy threshold devices such as models of sensory neurons. Using the mutual information measure, it is shown numerically that for a random input signal, the optimal threshold distribution contains singularities. For large enough noise, this distribution consists of a single point and hence the optimal encoding is realized by the suprathreshold stochastic resonance effect. Furthermore, it is shown that a bifurcational pattern appears in the optimal threshold settings as the noise intensity increases. Fisher information is used to examine the behavior of the optimal threshold distribution as the population size approaches infinity.Comment: 11 pages, 3 figures, RevTe

Ab-initio spin dynamics applied to nanoparticles: canted magnetism of a finite Co chain along a Pt(111) surface step edge

In order to search for the magnetic ground state of surface nanostructures we extended first principles adiabatic spin dynamics to the case of fully relativistic electron scattering. Our method relies on a constrained density functional theory whereby the evolution of the orientations of the spin-moments results from a semi-classical Landau-Lifshitz equation. This approach is applied to a study of the ground state of a finite Co chain placed along a step edge of a Pt(111) surface. As far as the ground state spin orientation is concerned we obtain excellent agreement with the experiment. Furthermore we observe noncollinearity of the atom-resolved spin and orbital moments. In terms of magnetic force theorem calculations we also demonstrate how a reduction of symmetry leads to the existence of canted magnetic states.Comment: 4 pages, ReVTeX + 3 figures (Encapsulated Postscript), submitted to PR

Stochastic resonance in electrical circuits—II: Nonconventional stochastic resonance.

Stochastic resonance (SR), in which a periodic signal in a nonlinear system can be amplified by added noise, is discussed. The application of circuit modeling techniques to the conventional form of SR, which occurs in static bistable potentials, was considered in a companion paper. Here, the investigation of nonconventional forms of SR in part using similar electronic techniques is described. In the small-signal limit, the results are well described in terms of linear response theory. Some other phenomena of topical interest, closely related to SR, are also treate

A Raid on the Inarticulate: The Problem of Language in the Poetry of W.S. Merwin

In this paper, I hope to examine Merwin\u27s ultimately successful quest for such a language and such a myth. Beginning with a brief description of his early work, in which the problem of language becomes a seemingly insuperable barrier to an understanding of the world, I wish to demonstrate his gradual evolution of a poetic voice which is both contemporary and universal. Of course, a study of this length will inevitably be marred by a certain amount of over-generalization and simplification. Merwin\u27s struggle with language has been a long and arduous one, and he has explored many byways on the journey which we will simply not be able to investigate. However, I trust that this summary of the major stages of Merwin\u27s poetic development, with a special concentration on the poems which mark its fruition, will provide a cogent introduction to his response to the unique poetic problems of his time, as well as offer some insights as to the achievement of his work

A Raid on the Inarticulate: The Problem of Language in the Poetry of W.S. Merwin

In this paper, I hope to examine Merwin\u27s ultimately successful quest for such a language and such a myth. Beginning with a brief description of his early work, in which the problem of language becomes a seemingly insuperable barrier to an understanding of the world, I wish to demonstrate his gradual evolution of a poetic voice which is both contemporary and universal. Of course, a study of this length will inevitably be marred by a certain amount of over-generalization and simplification. Merwin\u27s struggle with language has been a long and arduous one, and he has explored many byways on the journey which we will simply not be able to investigate. However, I trust that this summary of the major stages of Merwin\u27s poetic development, with a special concentration on the poems which mark its fruition, will provide a cogent introduction to his response to the unique poetic problems of his time, as well as offer some insights as to the achievement of his work

Stochastic resonance in electrical circuits—I: Conventional stochastic resonance.

Stochastic resonance (SR), a phenomenon in which a periodic signal in a nonlinear system can be amplified by added noise, is introduced and discussed. Techniques for investigating SR using electronic circuits are described in practical terms. The physical nature of SR, and the explanation of weak-noise SR as a linear response phenomenon, are considered. Conventional SR, for systems characterized by static bistable potentials, is described together with examples of the data obtainable from the circuit models used to test the theory