ZnO nanowire optoelectronic synapse for neuromorphic computing

Artificial synapses that integrate functions of sensing, memory and computing are highly desired for developing brain-inspired neuromorphic hardware. In this work, an optoelectronic synapse based on the ZnO nanowire (NW) transistor is achieved, which can be used to emulate both the short-term and long-term synaptic plasticity. Synaptic potentiation is present when the device is stimulated by light pulses, arising from the light-induced O₂desorption and the persistent photoconductivity behavior of the ZnO NW. On the other hand, synaptic depression occurs when the device is stimulated by electrical pulses in dark, which is realized by introducing a charge trapping layer in the gate dielectric to trap carriers. Simulation of a neural network utilizing the ZnO NW synapses is carried out, demonstrating a high recognition accuracy over 90% after only 20 training epochs for recognizing the Modified National Institute of Standards and Technology digits. The present nanoscale optoelectronic synapse has great potential in the development of neuromorphic visual systems.

[Epidemiology and etiology of bacillary dysentery in Xinjiang Uigur Autonomous Region, 2004-2014]

Objective: To understand the epidemiological and etiological characteristics of bacillary dysentery in Xinjiang Uigur Autonomous Region (Xinjiang) during 2004-2014, and provide evidence for the prevention and control of bacillary dysentery. Methods: Descriptive epidemiological analysis was conducted by using the incidence data of bacillary dysentery in Xinjiang during 2004-2014 and the serotyping and the antibiotic susceptibility test of the pathogens isolated were performed. Results: A total of 123 238 cases of bacillary dysentery were reported in Xinjiang from 2004 to 2014. The average annual incidence of bacillary dysentery ranged from 25.91 per 100 000 to 76.04 per 100 000 and the average annual mortality ranged from 0.00 to 46.90 per 100 000. The incidence of bacillary dysentery was higher in eastern Xinjiang than other areas. The incidence peak was during July-September. The incidence of bacillary dysentery in males was higher than that in females. The incidence was highest in infants and young children under five years old. Most cases were children outside child care settings, farmers and students. Shigella flexneri was the predominant pathogen and F2a was the most frequently detected subtype. The isolated strains were highly resistant to streptomycin, penicillin, doxycycline and tetracycline. The resistant rates to penicillin, tetracycline, doxycycline and streptomycin increased with year. Up to 71.43% of the strains were resistant to more than five antibiotics. Conclusion: The incidence of bacillary dysentery was in decrease in Xinjiang from 2004 to 2014, but in some area, the incidence of bacterial dysentery was higher than national average level. It is necessary to strengthen the surveillance and conduct targeted prevention and control in areas and population at high risk and in season with high incidence. The serious drug resistance and multi drug resistance of the pathogens have posed challenge to the prevention and treatment of bacillary dysentery in Xinjiang.

Ta2O5-TiO2 Composite Charge-trapping Dielectric for the Application of the Nonvolatile Memory

The charge-trapping memory devices with a structure Pt/Al₂O₃/(Ta₂O₅) _x (TiO₂) _1-x /Al₂O₃/p-Si (x = 0.9, 0.75, 0.5, 0.25) were fabricated by using rf-sputtering and atomic layer deposition techniques. A special band alignment between (Ta₂O₅) _x (TiO₂) _1-x and Si substrate was designed to enhance the memory performance by controlling the composition and dielectric constant of the charge-trapping layer and reducing the difference of the potentials at the bottom of the conduction band between (Ta₂O₅) _x (TiO₂) _1-x and Si substrate. The memory device with a composite charge storage layer (Ta₂O₅) _0.5 (TiO₂) _0.5 shows a density of trapped charges 3.84 × 10¹³/cm² at ± 12 V, a programming/erasing speed of 1 µs at ± 10 V, a 8% degradation of the memory window at ± 10 V after 10⁴ programming/erasing cycles and a 32% losing of trapped charges after ten years. The difference among the activation energies of the trapped electrons in (Ta₂O₅) _x (TiO₂) _1-x CTM devices indicates that the retention characteristics are dominated by the difference of energy level for the trap sites in each TTO CTM device.

Towards an all-in fiber photodetector by directly bonding few-layer molybdenum disulfide to a fiber facet

Although photodetectors based on two dimensional (2D) materials have been intensively studied, there are few reports of optical fiber compatible devices. Herein we successfully fabricated an all-in fiber photodetector (FPD) based on an end-face bonded with few-layer molybdenum disulfide (MoS₂). Our FPD has a considerably high photo-responsivity of ∼0.6 A W^-1 at a bias voltage of 4 V and 0.01 A W^-1 under the bias-free conditions. We believe that the proposed platform may provide a new strategy for the integration of 2D materials in fibers and realization of optoelectronic and sensing applications.