This paper presents a low power non-recursive compensated modified comb decimation structure. A new simple wideband compensator for a modified comb is proposed. The compensator has only three coefficients, presented in a Signed Power of Two (SPT) form, which can be implemented by adders and shifts. As a result, we get a multiplierless compensator. Since the modified comb is a multiplierless filter, the overall filter is, like a comb filter, also a multiplierless filter. The compensated modified comb decreases comb-filter passband droop and improves its alias rejection. The benefits of the compensated modified comb are proven by the comparisons with the state of the art.

Conference - IEEE Latin American Symposium on Circuits and Systems LASCAS 2021

This work describes Electrical Stimulations (ES) assays on stem cells. The neuroblastoma (N2A) cell linage was submitted to several electrical fields to enable and enhance its differentiation toward neurons. Both Direct Current (DC) and Alternated Current (AC) time dependent electric field protocols were applied to N2A cell culture under differentiation conditions, obtaining different responses. Control and electrically excited samples’ number of differentiated cells and neurite lengths were measure after differentiation. Results showed that DC fields have a strong influence on N2A differentiation since the percentage of differentiated cells and the neurites lengths were the highest. In addition, a significant alignment of neurites measured with the applied electrical field has been detected, which demonstrates the high sensitivity of differentiation processes to electrical field polarity.

Conference - International Conference on Biomedical Electronics and Devices BIODEVICES 2021

In this paper, we present results of processing Dynamic Vision Sensor (DVS) recordings of visual patterns with a retinal model based on foveal-pit inspired Difference of Gaussian (DoG) filters. A DVS sensor was stimulated with varying number of vertical white and black bars of different spatial frequencies moving horizontally at a constant velocity. The output spikes generated by the DVS sensor were applied as input to a set of DoG filters inspired by the receptive field structure of the primate visual pathway. In particular, these filters mimic the receptive fields of the midget and parasol ganglion cells (spiking neurons of the retina) that sub-serve the photo-receptors of the fovealpit. The features extracted with the foveal-pit model are used for further classification using a spiking convolutional neural network trained with a backpropagation variant adapted for spiking neural networks.

Conference - Annual Conference on Information Sciences and Systems CISS 2021

Nano-oscillators based on phase-transition materials are being explored for the implementation of different non-conventional computing paradigms. In particular, vanadium dioxide (VO ₂) devices are used to design autonomous non-linear oscillators from which oscillatory neural networks (ONNs) can be developed. In this work, we propose a new architecture for ONNs in which sub-harmonic injection locking (SHIL) is exploited to ensure that the phase information encoded in each neuron can only take two values. In this sense, the implementation of ONNs from neurons that inherently encode information with two-phase values has advantages in terms of robustness and tolerance to variability present in VO₂ devices. Unlike conventional interconnection schemes, in which the sign of the weights is coded in the value of the resistances, in our proposal the negative (positive) weights are coded using static inverting (non-inverting) logic at the output of the oscillator. The operation of the proposed architecture is shown for pattern recognition applications.

Journal Paper - Frontiers in Neuroscience, vol. 15, article 655823, 2021 FRONTIERS MEDIA
DOI: 10.3389/fnins.2021.655823    ISSN: 1662-453X    » doi

High-intensity focused ultrasound (HIFU) has been used in different medical applications in the last years. In this work, we present for the first time the use of HIFU in the field of cryopreservation, the preservation of biological material at low temperatures. An HIFU system has been designed with the objective of achieving a fast and uniform rewarming in organs, key to overcome the critical problem of devitrification. The finite-element simulations have been carried out using COMSOL Multiphysics software. An array of 26 ultrasonic transducers was simulated, achieving an HIFU focal area in the order of magnitude of a model organ (ovary). A parametric study of the warming rate and temperature gradients, as a function of the frequency and power of ultrasonic waves, was performed. An optimal value for these parameters was found. The results validate the appropriateness of the technique, which is of utmost importance for the future creation of cryopreserved organ banks.

Journal Paper - IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, vol. 68, no. 3, pp 599-607, 2021 IEEE
DOI: 10.1109/TUFFC.2020.3016950    ISSN: 0885-3010    » doi