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 $X$, generalizing the chromatic, tension and flow polynomials of a graph. Our colorings, tensions and flows may be either modular (with values in $\mathbb{Z}/k\mathbb{Z}$ for some $k$) or integral (with values in $\{-k+1,\dots,k-1\}$). 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 $X$.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