29,261 research outputs found
Statistical Mechanics Characterization of Neuronal Mosaics
The spatial distribution of neuronal cells is an important requirement for
achieving proper neuronal function in several parts of the nervous system of
most animals. For instance, specific distribution of photoreceptors and related
neuronal cells, particularly the ganglion cells, in mammal's retina is required
in order to properly sample the projected scene. This work presents how two
concepts from the areas of statistical mechanics and complex systems, namely
the \emph{lacunarity} and the \emph{multiscale entropy} (i.e. the entropy
calculated over progressively diffused representations of the cell mosaic),
have allowed effective characterization of the spatial distribution of retinal
cells.Comment: 3 pages, 1 figure, The following article has been submitted to
Applied Physics Letters. If it is published, it will be found online at
http://apl.aip.org
On quasi-Jacobi and Jacobi-quasi bialgebroids
We study quasi-Jacobi and Jacobi-quasi bialgebroids and their relationships
with twisted Jacobi and quasi Jacobi manifolds. We show that we can construct
quasi-Lie bialgebroids from quasi-Jacobi bialgebroids, and conversely, and also
that the structures induced on their base manifolds are related via a quasi
Poissonization
Effects of Random Biquadratic Couplings in a Spin-1 Spin-Glass Model
A spin-1 model, appropriated to study the competition between bilinear
(J_{ij}S_{i}S_{j}) and biquadratic (K_{ij}S_{i}^{2}S_{j}^{2}) random
interactions, both of them with zero mean, is investigated. The interactions
are infinite-ranged and the replica method is employed. Within the
replica-symmetric assumption, the system presents two phases, namely,
paramagnetic and spin-glass, separated by a continuous transition line. The
stability analysis of the replica-symmetric solution yields, besides the usual
instability associated with the spin-glass ordering, a new phase due to the
random biquadratic couplings between the spins.Comment: 16 pages plus 2 ps figure
Arbitrary bi-dimensional finite strain crack propagation
In the past two decades numerous numerical procedures for crack propagation have been developed. Lately,
enrichment methods (either local, such as SDA or global, such as XFEM) have been applied with success to simple
problems, typically involving some intersections. For arbitrary finite strain propagation, numerous difficulties are
encountered: modeling of intersection and coalescence, step size dependence and the presence of distorted finite
elements. In order to overcome these difficulties, an approach fully capable of dealing with multiple advancing
cracks and self-contact is presented (see Fig.1). This approach makes use of a coupled Arbitrary Lagrangian-Eulerian
method (ALE) and local tip remeshing. This is substantially less costly than a full remeshing while retaining its full
versatility. Compared to full remeshing, angle measures and crack paths are superior. A consistent continuationbased
linear control is used to force the critical tip to be exactly critical, while moving around the candidate set.
The critical crack front is identified and propagated when one of the following criteria reaches a material limiting
value: (i) the stress intensity factor; or (ii) the element-ahead tip stress. These are the control equations.
The ability to solve crack intersection and coalescence problems is shown. Additionally, the independence from
crack tip and step size and the absence of blade and dagger-shaped finite elements is observed. Classic benchmarks
are computed leading to excellent crack path and load-deflection results, where convergence rate is quadratic
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