Memristive tonotopic mapping with volatile resistive switching memory devices

: To reach the energy efficiency and the computing capability of biological neural networks, novel hardware systems and paradigms are required where the information needs to be processed in both spatial and temporal domains. Resistive switching memory (RRAM) devices appear as key enablers for the implementation of large-scale neuromorphic computing systems with high energy efficiency and extended scalability. Demonstrating a full set of spatiotemporal primitives with RRAM-based circuits remains an open challenge. By taking inspiration from the neurobiological processes in the human auditory systems, we develop neuromorphic circuits for memristive tonotopic mapping via volatile RRAM devices. Based on a generalized stochastic device-level approach, we demonstrate the main features of signal processing of cochlea, namely logarithmic integration and tonotopic mapping of signals. We also show that our tonotopic classification is suitable for speech recognition. These results support memristive devices for physical processing of temporal signals, thus paving the way for energy efficient, high density neuromorphic systems

Le procès de Giordano Bruno par l’Inquisition

This article focuses on Giordano Bruno’s trial, pointing out the main legal and theological foundations of the Holy Office’s procedures, and the Pope’s role in Counterreformation’s Church and in the Inquisition as well. New light is thrown on the fact that the Pope, as he was the Praefectus (Chairman) of the tribunal, created during the trial a doctrinal assessment about some Bruno’s cosmological views. That assessment was unprecedented, because the Church had never considered before the infinity of worlds and the heliocentric theory as heretical. Reflecting opinions not yet shared by the theological schools, censors and inquisitors unanimously, the Pope created a new juridical truth. Nevertheless, this side of Bruno’s trial, a secondary one as it was, compared to the prevailing theological and metaphysical matters of the case (for instance, the concept of Holy Trinity, and the nature of human soul), was not evoked during Galileo’s trial, and seems that it did not constitute a precedent in the tribunal’s memory. New cosmological subjects will be perceived as embarrassing challenges by the Holy Office and the Roman Church even when they were later dropped by Galileo, in a very different way and context

Campanella, Botero e gli infedeli

Accused to be leading a plot against the Spanish government in Calabria in 1599, supposedly supported by a Turkish fleet, Campanella was almost labeled as a renegade. On the contrary, while in jail, he deepened his prophetic interpretation of the history, and of the future of the world, offered theological and political confutation of Islam, and began shaping a wider idea of the role of this religion in the ‘apocalyptic’ times. Not focusing on the Turkish menace only, he tries to integrate some of the Muslim kingdoms in his appeal to the universal recognition of the Christian revelation as ‘natural reason’. In his main work about this topic, Quod reminiscentur, completed in 1618, but published only in the 20th Century, Campanella presents different strategies of conversion of Islamic peoples, depending on the various historical features of Islam, and adapted to the diverse societies involved. Giovanni Botero’s Relationi universali was a very important source of Campanella’s historical and geographic information about Islam, but the philosopher developed an original prophetic and political vision of Church, conversion and apocalypse, alternative to that dominating in the Counter Reformation

Decision Making by a Neuromorphic Network of Volatile Resistive Switching Memories

The necessity of having an electronic device working in relevant biological time scales with a small footprint boosted the research of a new class of emerging memories. Ag-based volatile resistive switching memories (RRAMs) feature a spontaneous change of device conductance with a similarity to biological mechanisms. They rely on the formation and self-disruption of a metallic conductive filament through an oxide layer, with a retention time ranging from a few milliseconds to several seconds, greatly tunable according to the maximum current which is flowing through the device. Here we prove a neuromorphic system based on volatile-RRAMs able to mimic the principles of biological decision-making behavior and tackle the Two-Alternative Forced Choice problem, where a subject is asked to make a choice between two possible alternatives not relying on a precise knowledge of the problem, rather on noisy perceptions

The unintended consequences of the launch of the single supervisory mechanism in Europe

The launch of the Single Supervisory Mechanism (SSM) was an historic event. Beginning in Nov. 2014, the most significant banks came under the direct supervision of the European Central Bank, while national supervisory authorities maintained direct supervision of the remaining banks. Thus, supervision is conducted on two levels, which could cause inconsistency problems. Did the behavior of the significant banks differ from that of the less significant banks during the SSM launch? We find that the significant banks reduced their lending activity more than the less significant banks did in order to shrink their balance sheets and increase their capitalization

Memtransistor Devices Based on MoS 2 Multilayers with Volatile Switching due to Ag Cation Migration

In the recent years, the need for fast, robust, and scalable memory devices have spurred the exploration of advanced materials with unique electrical properties. Among these materials, 2D semiconductors are promising candidates as they combine atomically thin size, semiconductor behavior, and complementary metal-oxide-semiconductor compatibility. Here a three-terminal memtransistor device, based on multilayer MoS2 with ultrashort channel length, that combines the usual transistor behavior of 2D semiconductors with resistive switching memory operation is presented. The volatile switching behavior is explained by the Ag cation migration along the channel surface. An extensive physical and electrical characterization to investigate the fundamental properties of the device, is presented. Finally, a chain-type memory array architecture similar to a NAND flash structure consisting of memtransistors is demonstrated, where the individual memory devices can be selected for write and read, paving the way for high-density, 3D memories based on 2D semiconductors

Reservoir Computing with Charge-Trap Memory Based on a MoS2 Channel for Neuromorphic Engineering

Novel memory devices are essential for developing low power, fast, and accurate in-memory computing and neuromorphic engineering concepts that can compete with the conventional complementary metal-oxide-semiconductor (CMOS) digital processors. 2D semiconductors provide a novel platform for advanced semiconductors with atomic thickness, low-current operation, and capability of 3D integration. This work presents a charge-trap memory (CTM) device with a MoS2 channel where memory operation arises, thanks to electron trapping/detrapping at interface states. Transistor operation, memory characteristics, and synaptic potentiation/depression for neuromorphic applications are demonstrated. The CTM device shows outstanding linearity of the potentiation by applied drain pulses of equal amplitude. Finally, pattern recognition is demonstrated by reservoir computing where the input pattern is applied as a stimulation of the MoS2-based CTMs, while the output current after stimulation is processed by a feedforward readout network. The good accuracy, the low current operation, and the robustness to input random bit flip makes the CTM device a promising technology for future high-density neuromorphic computing concepts

Volatile and Nonvolatile Dual‐Mode Switching Operations in an Ag‐Ag2S Core‐Shell Nanoparticle Atomic Switch Network

This paper proposes a nanoparticle-based atomic switch network memristive device, capable of both volatile and nonvolatile switching operations, which have not been previously reported for this material. The operational modes can be determined by altering the compliance current, demonstrating high stability over 100 cycles. Analysis of the conduction mechanism using I-V curves reveals switching characteristics consistent with space-charge-limited current conduction during the set process and ohmic behavior in the reset state. Furthermore, this study analyzes these dual-operational modes in devices with varying electrode spacings. The results indicate that a wider spacing necessitated a higher compliance current for the volatile-to-nonvolatile transition, underscoring the significance of interconnection. These findings facilitate the integration of neuron and synapse functions within a single atomic switch network device, thereby advancing neuromorphic systems

Whole-brain functional imaging to highlight differences between the diurnal and nocturnal neuronal activity in zebrafish larvae

Most living organisms show highly conserved physiological changes following a 24-hour cycle which goes by the name of circadian rhythm. Among experimental models, the effects of light-dark cycle have been recently investigated in the larval zebrafish. Owing to its small size and transparency, this vertebrate enables optical access to the entire brain. Indeed, the combination of this organism with light-sheet imaging grants high spatio-temporal resolution volumetric recording of neuronal activity. This imaging technique, in its multiphoton variant, allows functional investigations without unwanted visual stimulation. Here, we employed a custom two-photon light-sheet microscope to study whole-brain differences in neuronal activity between diurnal and nocturnal periods in larval zebrafish. We describe for the first time an activity increase in the low frequency domain of the pretectum and a frequency-localised activity decrease of the anterior rhombencephalic turning region during the nocturnal period. Moreover, our data confirm a nocturnal reduction in habenular activity. Furthermore, whole-brain detrended fluctuation analysis revealed a nocturnal decrease in the self-affinity of the neuronal signals in parts of the dorsal thalamus and the medulla oblongata. Our data show that whole-brain nonlinear light-sheet imaging represents a useful tool to investigate circadian rhythm effects on neuronal activity.Comment: 18 pages, 6 figure

Surprised or not surprised? The investors' reaction to the comprehensive assessment preceding the launch of the banking union

Did the Comprehensive Assessment (CA), preceding the Single Supervisory Mechanism (SSM) launch in Europe, achieve its aims of producing new valuable information for the market? We show that the CA achieved the goal of increasing transparency: investors were able to detect weak banks at the announce- ment of the procedure (23rd October 2013), but gained full information on the amount of the capital shortfall only at the disclosure of the results (26th October 2014). Furthermore, at the official launch of the SSM (4th November 2014), banks under direct European Central Bank (ECB) supervision registered a more negative market reaction with respect to banks maintaining their national supervisors. Using a regression model including possible confounders and allowing for treatment effect heterogeneity, this negative reaction is confirmed. These findings suggest that, at least in the short run, investors penalized banks subject to direct ECB supervision, probably because of the fear of regulatory inconsistencies