Showing papers by "Federico Morán published in 1999"

Designing a Simulation Model of a Self-Maintaining Cellular System

Abstract: This paper deals with the problem of finding a suitable framework for designing computer simulations that could help us determine the minimal requirements (both material and organizational) for the origin of the first full-fledged autonomous systems. The design of a particular model that takes into account some fundamental thermodynamic requirements is offered and discussed. Behind this work, there is a belief that Artificial Life models can inform biology on several fundamental questions (such as the origin and definition of life) but only provided that they assume more realistic and grounded premises to lead us to more conclusive results.

Transit Time Distribution for Biochemical Networks Far from Equilibrium: Amplification of the Probability of Net Transformation Due to Multiple Reflections

Abstract: We investigate a nonequilibrium biochemical network described in terms of transit time distributions. We assume that the network is made up of two subsystems which are connected to each other as well as to the environment. We evaluate the probability distribution of the time necessary for a molecular species to cross the system, i.e., the distribution of the time that elapses from the moment the species enters one subsystem and leaves it by passing through the second subsystem. For this process the total probability of crossing the system is at the same time the probability of net transformation of a chemical in a desired product. The analysis leads to the surprising result that the probability of crossing the system increases with the average time spent by the species in one subsystem. A physical explanation of this apparent paradox is given by taking into account the multiple reflections occurring within the system. The escape from the system takes place after a random number of forward and backward tra...

A Self-Organizing Model for the Development of Ocular Dominance and Orientation Columns in the Virtual Cortex

Abstract: A binocular model describing the ontogenetic development in the visual nervous system is presented. It consists of a set of deterministic differential equations which have been derived from an statistical approach. The evolution of the solution is led by the spontaneous generation of input activity, characterized in this model by its spatial and temporal decorrelation. The development of a connection depends on the output activity of both connected neurons; for this purpose, Hebbian and anti-Hebbian learning have been used. The model can explain some properties observed in natural brains such as the appearance of ocular domains and orientation selectivity in the V1 visual cortex development.