Modern microtechnology is enabling the channel count of neural recording integrated circuits to scale exponentially. However, the raw data bandwidth of these systems is increasing proportionately, presenting major challenges in terms of power consumption and data transmission (especially for wireless systems). This paper presents a system that exploits the sparse nature of neural signals to address these challenges and provides a reconfigurable low-bandwidth event-driven output. Specifically, we present a novel 64-channel low-noise (2.1 V), low-power (23  W per analogue channel) neural recording system-on-chip (SoC). This features individually configurable channels, 10-bit analogue-to-digital conversion, digital filtering, spike detection, and an event-driven output. Each channel's gain, bandwidth, and sampling rate settings can be independently configured to extract local field potentials at a low data-rate and/or action potentials (APs) at a higher data rate. The sampled data are streamed through an SRAM buffer that supports additional on-chip processing such as digital filtering and spike detection. Real-time spike detection can achieve 2 orders of magnitude data reduction, by using a dual polarity simple threshold to enable an event driven output for neural spikes (16-sample window). The SoC additionally features a latency-encoded asynchronous output that is critical if used as part of a closed-loop system. This has been specifically developed to complement a separate on-node spike sorting coprocessor to provide a real-time (low latency) output. The system has been implemented in a commercially available 0.35-m CMOS technology occupying a silicon area of 19.1 mm (0.3 mm gross per channel), demonstrating a low-power and efficient architecture that could be further optimized by aggressive technology and supply voltage scaling.

This paper investigated the high-temperature mechanical properties of nano-steel fibre-reinforced concrete (NSFC), steel fibre-reinforced concrete (SFRC) and normal concrete. The mechanical properties were compressive strength, splitting tensile strength and flexural strength. The microstructure and interfacial transition zone of steel fibre at different temperatures were also examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties of NSFC are found to be better than those of SFRC and normal concrete at all test temperatures, particularly at 4008C, where the maximum values are reached. Compared with normal concrete, the compressive, splitting tensile and flexural strengths of NSFC increase by 27 . 0%, 63 . 3% and 54 . 1%, respectively, at room temperature, and by 35 . 1%, 84 . 6% and 87 . 2%, respectively at 4008C. SEM and XRD analysis show the existence of a permeable diffusion layer on the steel fibre surface because of the solid-state reaction in the interfacial transition zone of steel fibre and concrete. This layer is white, bright and serrated, and mainly consists of iron disilicide (FeSi 2 ) as well as the complex hydrated calcium silicate. The compounds of this layer change the interfacial transition zone structure, enhance the bonding capacity of the steel fibre and matrix, and also increase the hightemperature mechanical properties of concrete. IntroductionIn recent years, frequent fire accidents have inflicted damage to the stability and safety of buildings. Thus, many researchers are focusing on the loss of mechanical properties of ordinary concrete at high temperatures (Long and Carino, 1998;Schneider, 1988;Zhang et al., 2000). The application of nanotechnology in concrete has enabled improvements in its performance and multifunctionality. Given the unique effects of nanomaterials (e.g. small-size, quantum, surface and interface effects), there are many distinctive features in structure, physical and chemical properties (Xu, 2004). Several studies (Senff et al., 2010;Ye et al., 2007) on the mechanical properties of nanoconcrete at normal temperature have obtained interesting results. For example, mixing 1-3% nano-silica (nano-SiO 2 ) noticeably improves the compressive and splitting strengths of concrete at the early period, reduces the amount of calcium hydroxide (Ca(OH) 2 ) on the interface between the cement paste and aggregate, results in grain refinement and also improves the microstructure of concrete. The influence of lithium silicate sol mixed with nano-silica particles on the later period of concrete hydration has also been studied (Guo et al., 2010). Adding nano-silica particles to the lithium silicate sol doubles the number of pores between C-S-H gel layers. Consequently, the number of pores is greatly reduced and concrete hydration in the later period becomes more noticeable. However, the mechanical properties of nano-steel fibre-reinforced concrete (NSFC) at high temperatures has not been reported. Therefore, this paper investigates the mecha...

This paper investigates continuous-time (CT) signal acquisition as an activity-dependent and nonuniform sampling alternative to conventional fixed-rate digitisation. We demonstrate the applicability to biosignal representation by quantifying the achievable bandwidth saving by nonuniform quantisation to commonly recorded biological signal fragments allowing a compression ratio of 5 and 26 when applied to electrocardiogram and extracellular action potential signals, respectively. We describe several desirable properties of CT sampling, including bandwidth reduction, elimination/reduction of quantisation error, and describe its impact on aliasing. This is followed by demonstration of a resource-efficient hardware implementation. We propose a novel circuit topology for a charge-based CT analogue-to-digital converter that has been optimized for the acquisition of neural signals. This has been implemented in a commercially available 0.35  CMOS technology occupying a compact footprint of 0.12 mm. Silicon verified measurements demonstrate an 8-bit resolution and a 4 kHz bandwidth with static power consumption of 3.75  W from a 1.5 V supply. The dynamic power dissipation is completely activity-dependent, requiring 1.39 pJ energy per conversion.

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Article impact statement: Species distribution pattern and connectivity change call for transboundary conservation on China's borders with Myanmar, Laos, and Vietnam.

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In this study, the collective dynamical behavior of two unidirectionally, linearly coupled neurons was investigated. Our investigation illustrates that, depending on the coupling strength, the internal stochastic resonance (ISR) effect observed in one of the two neurons could be amplified or sustained by the other. The amplification of ISR is enhanced as the coupling strength is increased from 0. However, when the coupling strength is increased above a certain level, the amplification of ISR is reduced, implicating that there exists an optimal coupling strength for the information flow between two neurons. As the coupling strength is increased further, i.e., above the critical level, synchronization of the two subsystems is achieved, yet the two subsystems exhibit the same magnitude response to the external noise, suggesting that the information transmission among coupled subunits could not be improved by further enhancing their coupling strength. And similar phenomena could also be obtained for the nonidentical case.