The reversible and fast phase transitions induced by picosecond electrical pulses are observed in the nanostructured GeSbTe materials, which provide opportunities in the application of high speed nonvolatile random access memory devices. The mechanisms for fast phase transition are discussed based on the investigation of the correlation between phase transition speed and material size. With the shrinkage of material dimensions, the size effects play increasingly important roles in enabling the ultrafast phase transition under electrical activation. The understanding of how the size effects contribute to the phase transition speed is of great importance for ultrafast phenomena and applications.

and high density. [4][5][6][7] Moreover, memristors with analog switching behaviors can faithfully resemble biological computational elements in both structure and switching dynamics. With the intrinsic biomimetic features, memristors could act as the basic computational element in artificial neural networks and have been demonstrated with the capability of solving cognitive computing tasks with spatiotemporal complexity without complex peripheral circuits. [7] Among various material systems, 2D materials recently demonstrated memristive switching behaviors that possess biologically comparable energy consumption compared with the traditional memristors based on oxide materials. [8][9][10][11] Thanks to their atomically thin layers and planar configurations, 2D material based memristors have provided an intriguing window into the motions of ions and opportunities to achieve outstanding electrical performances. [12][13][14] It has been reported that vertical synapses built in 2D MoS 2 push the switching threshold voltages to an extremely low value of 0.1 V. [14] More recently, multiterminal memtransistor consisting of hybrid memristor and transistor were fabricated using 2D materials to realize gate-tunable heterosynaptic functionality, which could not be achieved with transitional materials. [4,15,16] In addition, the rapid development of chemical vapor deposition (CVD) technology enables wafer scale production of 2D material, paving the way for large scale integration of 2D devices. Therefore, dimensionality reduction from 3D to 2D provides an innovative way for further advancing memristor devices in both scalability and electrical performance.Despite enormous efforts have been devoted in investigating 2D material based memristors, progresses are only made on emulating various synaptic functions. Neuromorphic networks comprise layers of artificial neurons that receive, process and transmit signals, and synapses that connect the neurons and evolve to alter the connection patterns during learning. [17,18] Although artificial neurons based on traditional oxide and phase change materials have been implemented, 2D materials have their distinct advantages. [19,20] For instance, the physical properties of 2D materials can easily be modulated by multi factors, such as doping and interface engineering, 2D material based memristors have exhibited superior performance as artificial synapses for neuromorphic computing. However, 2D artificial neurons as have note been exploited as an indispensable computational element owing to the rich dynamics of neurons, which impede the construction of a 2D neuromorphic network. A methodology is developed by introducing ionic migration dynamics and electrochemical reaction into monolayer MoS 2 single crystal and a 2D artificial neuron is realized. The sophisticated electrophysiology process of leaky integrate-and-fire (LIF) is emulated by the injection and extraction of Ag + ions under an e-field in a monolayer MoS 2 device with fine-tuned channel length. Moreover, the fire frequency and ...

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The prevalence of tandem repeats in eukaryotic genomes and their association with a number of genetic diseases has raised considerable interest in locating these repeats. Over the last 10-15 years, numerous tools have been developed for searching tandem repeats, but differences in the search algorithms adopted and difficulties with parameter settings have confounded many users resulting in widely varying results. In this review, we have systematically separated the algorithmic aspect of the search tools from the influence of the parameter settings. We hope that this will give a better understanding of how the tools differ in algorithmic performance, their inherent constraints and how one should approach in evaluating and selecting them.

Physically transient electronics have attracted increasing attention recently due to their potential as the basis for building “green” electronics and biomedical devices. In the development of transient devices for biomedical applications, however, the dilemma between the strictly required biodegradability and device performance has brought great difficulties to the material selection. In this paper, we introduced silk fibroin as dielectric layer to fabricate biodegradable resistive memory devices. Comprising a W/silk fibroin/Mg sandwich structure, stable bipolar resistive switching behavior with good repeatability and device variability was obtained, surpassing most organic resistive memory and comparable to inorganic resistive memory. The carrier-transport evolution process was carefully examined to reveal the mechanism behind resistive switching. A switching model regarding the formation of metallic conductive filament was proposed by considering both the nature of silk fibroin dielectric layer and the key role of active metal electrode. Furthermore, the solubility test in phosphate-buffered saline indicates the device exhibiting physically transient behavior and good biodegradability. Good mechanical property and flexibility were also demonstrated through electrical testing under different bending conditions. These results suggest that our device is a promising memory element candidate for constructing transient electronic system, especially for biomedical applications.