An antenatal emotional self-management training that may lower the risk of developing postnatal depression among Chinese women is recommended.

The biological visual system encodes optical information into spikes and processes them by the neural network, which enables the perception with high throughput of visual processing with ultralow energy budget. This has inspired a wide spectrum of devices to imitate such neural process, while precise mimicking such procedure is still highly required. Here, a highly bio‐realistic photoelectric spiking neuron for visual depth perception is presented. The firing spikes generated by the TaOX memristive spiking encoders have a biologically similar frequency range of 1–200 Hz and sub‐micro watts power. Such spiking encoder is integrated with a photodetector and a network of neuromorphic transistors, for information collection and recognition tasks, respectively. The distance‐dependent response and eye fatigue of biological visual systems have been mimicked based on such photoelectric spiking neuron. The simulated depth perception shows a recognition improvement by adapting to sights at different distances. The results can advance the technologies in bioinspired or robotic systems that may be endowed with depth perception and power efficiency at the same time.

Emerging polymer memory devices with resistive switching are promising alternatives to existing conventional random access memory technology due to their ability of information storage and process. [1-4] An effective strategy to realize resistive switching for memory effect is organicinorganic hybrid design in polymer device, with the merits of tailorable components, tunable properties, solution process and low-cost manufacturing. [5-8] In the organicinorganic hybrid systems, insulating or semiconducting polymers are widely used as active matrix, low dimensional inorganic materials including zero dimensional (0D) nanodots, [9,10] 1D nanotubes [11,12] and 2D nanosheets [13,14] are introduced into polymer matrix as charge trapping to trigger the resistive switching. Among these nanomaterials, quantum dots (QDs) have attracted much attention because of outstanding quantum confinement for charge trapping and well dispersion in matrix for high reproducibility as well as operation stability. Recently, a series of novel QDs derived from 2D materials have been successfully synthesized and applied into polymer memories, such as graphene QDs, [15,16] black phosphorus QDs, [17,18] and transition-metal dichalcogenide (TMD) QDs, [19] with the function of nonvolatile write once read many times (WORM) and Flash memory effect. [20,21] More recently, MXene nanosheets, referring to a new class of 2D materials, [22,23] have aroused extensive attention owing to their metallic conductivity, abundant active sites, and hydrophilic surface. Compared to intrinsic 2D MXene nanosheets, the smallsized MXene with a diameter of less than 10 nm, referred as MXene quantum dots (MQDs), [24,25] shows stronger quantum confinement, edge effect, and hydrophilic properties, making them very promising to disperse in water soluble polymer and act as charge trapping center. [26,27] Therefore, constructing MQDs-polymer hybrid architecture will provide the feasibility of memory achievement for data storage and extend their application in information fields. [28] Herein, for the first time, we report the controllable resistive switching and nonvolatile memory behaviors in MQDs and PVP hybrid composite films. By modulating MQDs doping

Building transient and flexible memristors is a promising strategy for developing emerging memory technologies. Here, a transient and flexible memristor based on a polymer nanocomposite, with a configuration of silver nanowire (AgNW)/citric acid quantum dot (CA QD)-polyvinyl pyrrolidone (PVP)/AgNW, is fabricated using a full-solution process method. The obtained device exhibits reversible resistive switching behavior and a dynamic random access memory (DRAM) storage feature, with the significant merits of a high ON/OFF ratio, low switching voltage, excellent reproducibility and desirable high flexibility, indicating outstanding memory characteristics such as low misreading, low power operation and low cost potential. Moreover, an operating mechanism of charge trapping/de-trapping of the quantum dots in the polymer matrix has been proposed. Importantly, the memristor can be disintegrated in water within 30 minutes, showing that it is a promising candidate for transient memories. This work paves a new way for potential use of this material in transient electronics, implanted electronics, data storage security and flexible electronic systems.

Aim: To study the sleep and mental health of chronic insomnia patients in China during coronavirus disease in 2019 (COVID-19) epidemic. Methods: A total of 764 patients with chronic insomnia were included in this study. From 17 January 2020 to 24 January 2020, insomnia, anxiety and physical symptoms were evaluated online, and they were followed up for 4 and 8 weeks. Main outcomes and indicators were assessed using the Pittsburgh Sleep Quality Index (PSQI) and each factor score, the General Anxiety Disorder-7 (GAD-7) and the Patient Health Questionnaire-15 (PHQ-15), respectively. In addition, insomnia, anxiety and physical symptoms were assessed at baseline and at the end of fourth and eighth weeks. Wilcoxon signed rank test was used to compare the changes in patients’ scale scores at different time points. Results: Among the 764 participants, there were 755 and 738 evaluators who completed the fourth and eighth weeks, respectively, and the questionnaire completion rates were 98.82% and 96.60%, respectively. Among them, there are 459 (60.0%) aged 41–60 years old, 546 (71.5%) women, 218 (28.5%) men and 313 (41%) college degrees. After 8 weeks of follow-up, the differences in sleep status, anxiety symptoms and physical symptoms were statistically significant. Among the factors of PSQI, there were differences in subjective sleep quality, sleep latency, sleep duration, sleep disturbance (disorder), sleep efficiency and daytime function. At 4 weeks of follow-up, there was a statistically significant difference in the use of hypnotic drugs; at 8 weeks of follow-up, there was no statistically significant difference in the use of hypnotic drugs. Conclusion: Under the influence of the COVID-19, the sleep status and anxiety of patients with chronic insomnia are affected by the epidemic.

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MXenes, an emerging class of two-dimensional (2D) transition-metal carbide materials, have received increasing attention for their interesting physiochemical properties. For not only MXenes but also other 2D materials, delamination is a requisite step for the exploitation of their unique properties. In this work, a facile method for exfoliating Ti 3 C 2 T x MXene to nanosheets of small size with the aid of poly-(vinylpyrrolidone) (PVP) is designed, which has never been reported to our knowledge. Since both hydrophobic methylene groups and hydrophilic amide groups are provided with PVP, this method is applicable in a wide range of solvents, such as ethanol, water, and chloroform. Considering the charge detrapping and trapping behavior of 2D transitionmetal materials in PVP dielectric, a memory device with the configuration of reduced graphene oxide (rGO)/Ti 3 C 2 T x -PVP/Au is directly fabricated with these well-dispersed Ti 3 C 2 T x −PVP composites by the solution process technique. Interestingly, the resultant device exhibits a typical bistable electrical switching, ultralow switching voltage (∼0.9 V), and a nonvolatile rewritable memory effect with the function of flash. This work might pave the way of using MXenes for future data storage, which is an indispensable field nowadays. KEYWORDS: nonvolatile memory, Ti 3 C 2 T x −MXene nanosheets, poly(vinylpyrrolidone), flash, delamination

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