Experimental study of artificial neural networks using a digital memristor simulator

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a fully digital implementation of a memristor hardware simulator, as the core of an emulator, based on a behavioral model of voltage-controlled threshold-type bipolar memristors. Compared to other analog solutions, the proposed digital design is compact, easily reconfigurable, demonstrates very good matching with the mathematical model on which it is based, and complies with all the required features for memristor emulators. We validated its functionality using Altera Quartus II and ModelSim tools targeting low-cost yet powerful field programmable gate array (FPGA) families. We tested its suitability for complex memristive circuits as well as its synapse functioning in artificial neural networks (ANNs), implementing examples of associative memory and unsupervised learning of spatio-temporal correlations in parallel input streams using a simplified STDP. We provide the full circuit schematics of all our digital circuit designs and comment on the required hardware resources and their scaling trends, thus presenting a design framework for applications based on our hardware simulator.Peer ReviewedPostprint (author's final draft

El paradigma de la sociedad de sospecha en Chile: análisis crítico de una política criminal basada en el estado de policía

Treballs Finals del Màster de Criminologia, Política Criminal i Sociologia Juridicopenal, Facultat de Dret, Universitat de Barcelona, Curs: 2014-2015, Tutors: Antonio Madrid Pérez i Alejandro GoldbergEn este trabajo examinamos y analizamos la existencia de un estatus jurídico de sospechoso, a partir del cual se propone una política criminal basada en la selectividad y exclusión de ciertos sectores e individuos de la sociedad. Dicha política criminal se implementa en el contexto de un permanente discurso securitario que propone la producción de un Derecho penal de características autoritarias, muchas veces basada en el derecho penal de autor (y no del hecho), que crea categorías de delitos que se estructuran a partir de una presunción de culpa, y que la doctrina denomina “delitos de sospecha”, normas que son abiertamente inconstitucionales por poner en juego derechos fundamentales, como la presunción de inocencia. El foco de atención de nuestro análisis está puesto en el caso chileno. Este discurso, y esta política –en definitiva– permea hacia los juzgados y las policías quienes llevan a cabo acciones que, a través de interpretaciones extensivas de ciertas instituciones del Derecho penal, reviven prácticas que se creían superadas, como lo es la detención por sospecha. En este contexto se funda –a nuestro juicio– el paradigma de la sociedad de sospecha, el cual estigmatiza a comunidades y grupos de la sociedad, en constante lucha por recuperar sus derechos, que terminan sucumbiendo frente a una sociedad que sospecha de ellos permanentemente

Las compras públicas de tecnología e innovación como un elemento central de las políticas públicas del siglo XXI

The following essay describes the main problems and opportunities regarding the procurement of new technologies and innovative solutions by the government. Accordingly, basic concepts, such as public innovation, and public procurement of innovation, are analyzed, as well as the digital government’s current situation in Chile. Moreover, both Chilean public measures and academic approaches on this matter are critically examined. Finally, special procedures used for procuring innovation are also studied.Este artículo tiene por objeto describir los principales problemas y oportunidades que existen para que el Estado pueda adquirir nuevas tecnologías y soluciones innovadoras. En este sentido, se analizan conceptos básicos en la materia como gobierno digital, innovación pública, y compra pública de innovación. Además, se hace una revisión crítica de las iniciativas públicas realizadas en Chile y de los enfoques académicos en la materia

Resistive switching behavior seen from the energy point of view

The technology of Resistive Switching (RS) devices (memristors) is continuously maturing on its way towards viable commercial establishment. So far, the change of resistance has been identified as a function of the applied pulse characteristics, such as amplitude and duration. However, parameter variability holds back any universal approach based on these two magnitudes, making also difficult even the qualitative comparison between different RS material compounds. On the contrary, there is a relevant magnitude which is much less affected by device variability; the energy. In this direction, we doubt anyone so far has ever wondered 'what is the quantitative effect of the injected energy on the device state?' Interestingly, a first step was made recently towards the definition of performance parameters for this emerging device technology, using as fundamental parameter the energy. In this work, we further elaborate on such ideas, proving experimentally that the 'resistance change per energy unit' (dR/dE) can be considered a significant magnitude in analog operation of bipolar memristors, being a key performance parameter worth of timely disclosure.Peer ReviewedPostprint (author's final draft

Host response mechanisms in periodontal diseases

Periodontal diseases usually refer to common inflammatory disorders known as gingivitis and periodontitis, which are caused by a pathogenic microbiota in the subgingival biofilm, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola that trigger innate, inflammatory, and adaptive immune responses. These processes result in the destruction of the tissues surrounding and supporting the teeth, and eventually in tissue, bone and finally, tooth loss. The innate immune response constitutes a homeostatic system, which is the first line of defense, and is able to recognize invading microorganisms as non-self, triggering immune responses to eliminate them. In addition to the innate immunity, adaptive immunity cells and characteristic cytokines have been described as important players in the periodontal disease pathogenesis scenario, with a special attention to CD4+ T-cells (T-helper cells). Interestingly, the T cell-mediated adaptive immunity development is highly dependent on innate immunity-associated antigen presenting cells, which after antigen capture undergo into a maturation process and migrate towards the lymph nodes, where they produce distinct patterns of cytokines that will contribute to the subsequent polarization and activation of specific T CD4+ lymphocytes. Skeletal homeostasis depends on a dynamic balance between the activities of the bone-forming osteoblasts (OBLs) and bone-resorbing osteoclasts (OCLs). This balance is tightly controlled by various regulatory systems, such as the endocrine system, and is influenced by the immune system, an osteoimmunological regulation depending on lymphocyte- and macrophage-derived cytokines. All these cytokines and inflammatory mediators are capable of acting alone or in concert, to stimulate periodontal breakdown and collagen destruction via tissue-derived matrix metalloproteinases, a characterization of the progression of periodontitis as a stage that presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors

Exploring the “resistance change per energy unit” as universal performance parameter for resistive switching devices

© Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Resistive switching (RS) device (memristor) technology is continuously maturing towards industrial establishment. There are RS devices that demonstrate an “incremental” (analog) switching behavior, whereas others change their state in a binary form. The final achieved resistance is generally a function of the applied pulse characteristics, i.e. amplitude and duration. However, variability —both from device to device but also from cycle to cycle— and the stochastic nature of internal RS phenomena, still hold back any universal tuning approach based solely on these two magnitudes, making also difficult the qualitative comparison between devices with different material compounds owing to the required SET/RESET voltages being dependent on the biasing conditions. In this work we demonstrate experimentally using commercial RS devices from Knowm Inc. that the switching energy is very insensitive to the biasing conditions. We explored experimentally the SET-RESET behavior of bipolar RS devices from the energy point of view. We figured out the quantitative effect of the injected energy to the resistive state of the devices, and proposed an analytical model to explain our observations in the energy consumed by the device during the switching process. Our results lay the foundations for the definition of “resistance change per energy unit” as a performance parameter for this emerging device technology.Peer ReviewedPostprint (author's final draft