1,331 research outputs found
Statistical physics of neural systems with non-additive dendritic coupling
How neurons process their inputs crucially determines the dynamics of
biological and artificial neural networks. In such neural and neural-like
systems, synaptic input is typically considered to be merely transmitted
linearly or sublinearly by the dendritic compartments. Yet, single-neuron
experiments report pronounced supralinear dendritic summation of sufficiently
synchronous and spatially close-by inputs. Here, we provide a statistical
physics approach to study the impact of such non-additive dendritic processing
on single neuron responses and the performance of associative memory tasks in
artificial neural networks. First, we compute the effect of random input to a
neuron incorporating nonlinear dendrites. This approach is independent of the
details of the neuronal dynamics. Second, we use those results to study the
impact of dendritic nonlinearities on the network dynamics in a paradigmatic
model for associative memory, both numerically and analytically. We find that
dendritic nonlinearities maintain network convergence and increase the
robustness of memory performance against noise. Interestingly, an intermediate
number of dendritic branches is optimal for memory functionality
Enumerating Colorings, Tensions and Flows in Cell Complexes
We study quasipolynomials enumerating proper colorings, nowhere-zero
tensions, and nowhere-zero flows in an arbitrary CW-complex , generalizing
the chromatic, tension and flow polynomials of a graph. Our colorings, tensions
and flows may be either modular (with values in for
some ) or integral (with values in ). We obtain
deletion-contraction recurrences and closed formulas for the chromatic, tension
and flow quasipolynomials, assuming certain unimodularity conditions. We use
geometric methods, specifically Ehrhart theory and inside-out polytopes, to
obtain reciprocity theorems for all of the aforementioned quasipolynomials,
giving combinatorial interpretations of their values at negative integers as
well as formulas for the numbers of acyclic and totally cyclic orientations of
.Comment: 28 pages, 3 figures. Final version, to appear in J. Combin. Theory
Series
Study of structure and composition of micro arc lantanum-siliconincorporated calcium phosphate coatings
The lanthanum- silicon-incorporated calcium phosphate coatings on the titanium have porous X-Ray amorphous structure. The increase of the process voltage leads to the growth of thickness and structural elements and to the formation in the coatings of crystalline phases CaHPO4 and β-Ca2P2O7
Bloch-Redfield equations for modeling light-harvesting complexes
We challenge the misconception that Bloch-Redfield equations are a less
powerful tool than phenomenological Lindblad equations for modeling exciton
transport in photosynthetic complexes. This view predominantly originates from
an indiscriminate use of the secular approximation. We provide a detailed
description of how to model both coherent oscillations and several types of
noise, giving explicit examples. All issues with non-positivity are overcome by
a consistent straightforward physical noise model. Herein also lies the
strength of the Bloch-Redfield approach because it facilitates the analysis of
noise-effects by linking them back to physical parameters of the noise
environment. This includes temporal and spatial correlations and the strength
and type of interaction between the noise and the system of interest. Finally
we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson
(FMO) complex in regards to spatial correlation length of the noise, noise
strength, temperature and their connection to the transfer time and transfer
Polaron Physics in Optical Lattices
We investigate the effects of a nearly uniform Bose-Einstein condensate (BEC)
on the properties of immersed trapped impurity atoms. Using a weak-coupling
expansion in the BEC-impurity interaction strength, we derive a model
describing polarons, i.e., impurities dressed by a coherent state of Bogoliubov
phonons, and apply it to ultracold bosonic atoms in an optical lattice. We show
that, with increasing BEC temperature, the transport properties of the
impurities change from coherent to diffusive. Furthermore, stable polaron
clusters are formed via a phonon-mediated off-site attraction.Comment: 4 pages, 4 figure
THE ROLE OF ACCOUNTING PROCEDURES IN WRITING/IMPLEMENTING EUROPEAN PROJECTS
This paper focuses on aspects of accounting procedures in general accounting procedures specific to those projects with European funding within public institutions in particular. Given the great emphasis placed by the legislator on the development and implementation of accounting procedures, we consider that the theme is a nowadays one that can be used by accounting specialists who work as accountants and financial managers in European projects. We will also focuses on the attributes of the persons responsible for implementing the accounting procedures in a project but also on the importance of their proper professional training in the field. In preparing this paper we started from the legislative provisions in the field, and the results of the study aim to present the work procedures required for accounting organization within a project, and to present the accounting notes used for economic and financial operations specific for European Regional Development Fund funded projects which beneficiary is a public institution
Subharmonic Generation in Quantum Systems
We show how the classical-quantum correspondence permits long-lived
subharmonic motion in a quantum system driven by a periodic force.
Exponentially small deviations from exact subharmonicity are due to coherent
tunneling between quantized vortex tubes which surround classical elliptic
periodic orbits.Comment: 11 pages + 5 figures (available upon request), Revtex 3.0,
NSF-ITP-93-4
Aufbau eines Standardmess-verfahrens zum Nachweis des Sequestrierungspotenzials von Biokohlen durch 13CO2-Emission
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