arXiv subjects

Alexandra Pinto Castellanos

Publications and source records attributed to Alexandra Pinto Castellanos.

3 recordsLinked to original sources

arXiv2019

Stochastic Resonance in Neural Network, Noise Color Effects

Some systems cannot be predicted by classical theories and it is required the development of combined deterministic and stochastic theories that make used of noise for dynamical prediction. Noise is not always an interfering signal which perturbs the system. On the contrary, noise signal can enhance the performance of some non-linear systems. The advantage of noise is observed in Stochastic Resonance (SR) where noise is used for amplification and subsequent detection of small signals. To detect this phenomena it is necessary that the system have a bistable potential barrier that creates a threshold, the input of the system should be a weak periodic signal which amplitude is below threshold together with an stochastic signal. In this way, the SR is detected when there are weak periodic signals that are added to different noise colors in order to be amplified and optimised. The interactions between the two signals transform the potential of the system precisely at the frequency of the weak periodic signal that is added to the system. The behaviour of the SR is detected in a neural network and it is study under noise color variations. Here I found that Pink noise amplified the sub-threshold input signal twenty times more in comparison to white noise. This is evidence of the functionality of background noise in the brain, where neurons are naturally embedded in pink noise.

nlin.AO↗

arXiv2019

Simulation and Experimental Verification of DNA Damage Due to X-Rays Interaction

This paper describes the model for DNA in MATLAB taking into account all of component atoms. In this model, it is possible to generate sequences with length 10000 basis pairs available for introducing all types of sequences. Once the strands are generated, it is studied the DNA damage in the single strand and double strand. The damage are outcomes of ionising radiation of X-rays when interacting with the DNA immersed in water. This is a theoretical and experimental in-vitro study that quantifies the single strand and double strand damage for different doses of radiation. This can be useful to predict the exact risks of expositions to radiations. In simulations, it is taken into account the damage caused by free electrons generated by the effect of the interaction with the water molecules, this is different to the effect considered in radiobiology, where indirect damages are due to chemical reactions. The spatial distribution of the electrons is obtained from Geant4 and here this distribution is used for the creation of rays as three-dimensional random trajectories through Monte Carlo simulations. It is also presented the experimental DNA damage through radiating DNA samples immersed in water with a X-rays unit with Molybdenum target. The damage level is quantified through Atomic Force Microscopy (AFM). It is possible to conclude a direct relation between the damage and the radiation doses with the experimental results.

physics.med-ph↗

arXiv2018

Wave to pulse generation. From oscillatory synapse to train of action potentials

Neurons have the capability of transforming information from a digital signal at the dendrites of the presynaptic termi- nal to an analogous wave at the synaptic cleft and back to a digital pulse when they achieve the required voltage for the generation of an action potential at the postsynaptic neuron. The main question of this research is what processes are generating the oscillatory wave signal at the synaptic cleft and what is the best model for this phenomenon. Here, it is proposed a model of the synapse as an oscillatory system capable of synchronization taking into account conservation of information and consequently of frequency at the interior of the synaptic cleft. Trains of action potentials certainly encode and transmit information along the nervous system but most of the time neurons are not transmitting action potentials, 99 percent of their time neurons are in the sub threshold regime were only small signals without the energy to emanate an action potential are carrying the majority of information. The proposed model for a synapse, smooths the train of action potential and keeps its frequency. Synapses are presented here as a system composed of an input wave that is transformed through interferometry. The collective synaptic interference pattern of waves will reflect the points of maximum amplitude for the density wave synaptic function were the location of the "particle" in our case action potential, has its highest probability.

physics.bio-ph↗