Silver Nanowire Networks with Moisture-Enhanced Learning Ability.

The human brain possesses a remarkable ability to memorize information with the assistance of a specific external environment. Therefore, mimicking the human brain's environment-enhanced learning abilities in artificial electronic devices is essential but remains a considerable challenge. Here, a network of Ag nanowires with a moisture-enhanced learning ability, which can mimic long-term potentiation (LTP) synaptic plasticity at an ultralow operating voltage as low as 0.01 V, is presented. To realize a moisture-enhanced learning ability and to adjust the aggregations of Ag ions, we introduced a thin polyvinylpyrrolidone (PVP) coating layer with moisture-sensitive properties to the surfaces of the Ag nanowires of Ag ions. That Ag nanowire network was shown to exhibit, in response to the humidity of its operating environment, different learning speeds during the LTP process. In high-humidity environments, the synaptic plasticity was significantly strengthened with a higher learning speed compared with that in relatively low-humidity environments. Based on experimental and simulation results, we attribute this enhancement to the higher electric mobility of the Ag ions in the water-absorbed PVP layer. Finally, we demonstrated by simulation that the moisture-enhanced synaptic plasticity enabled the device to adjust connection weights and delivery modes based on various input patterns. The recognition rate of a handwritten data set reached 94.5% with fewer epochs in a high-humidity environment. This work shows the feasibility of building our electronic device to achieve artificial adaptive learning abilities.

Electron Oscillation-Induced Splitting Electroluminescence from Nano-LEDs for Device-Level Encryption.

Data security is a major concern in digital age, which generally relies on algorithm-based mathematical encryption. Recently, encryption techniques based on physical principles are emerging and being developed, leading to the new generation of encryption moving from mathematics to the intersection of mathematics and physics. Here, device-level encryption with ideal security is ingeniously achieved using modulation of the electron-hole radiative recombination in a GaN-light-emitting diode (LED). When a nano-LED is driven in the non-carrier injection mode, the oscillation of confined electrons can split what should be a single light pulse into multiple pulses. The morphology (amplitude, shape, and pulse number) of those history-dependent multiple pulses that act as carriers for transmitted digital information depends highly on the parameters of the driving signals, which makes those signals mathematically uncrackable and can increase the volume and security of transmitted information. Moreover, a hardware and software platform are designed to demonstrate the encrypted data transmission based on the device-level encryption method, enabling recognition of the entire ASCII code table. The device-level encryption based on splitting electroluminescence provides an encryption method during the conversion process of digital signals to optical signals and can improve the security of LED-based communication.

In-Well Ionization from Monolayer Quantum Dots for Non-Carrier-Injection Electroluminescence.

Quantum dot (QD) light-emitting devices operating in non-carrier-injection (NCI) mode have attracted intense interest. Revealing the source of carriers that support the periodic electroluminescence is important because there is no injection of carriers from the external electrode. Electrons/holes generated by well-to-well multiple ionization in adjacent QDs are generally recognized as the carrier source for electroluminescence, and the stacked QD layers are necessary. In this work, NCI electroluminescence (NCI-EL) from monolayer QDs is successfully demonstrated, which cannot be properly explained by the previously proposed mechanism of multiple ionization. A working mechanism related to periodic in-well ionization is proposed, in which electrons tunnel directly from the valence band of QDs to the conduction band to form free electrons and holes. The effects of driving voltage amplitude, frequency, and QD size on the NCI-EL performance are investigated. Finite element simulation is used to clarify the ionization process. We believe this work can extend the working mechanism model of NCI-EL from QDs and provide guidance for promoting QD-based light-emitting device performance.

Omnidirectional Triboelectric Nanogenerator for Wide-Speed-Range Wind Energy Harvesting.

The environmentally friendly harvesting of wind energy is an effective technique for achieving carbon neutrality and a green economy. In this work, a core-shell triboelectric nanogenerator (CS-TENG) for harvesting wind energy is demonstrated and the device structure parameters are optimized. The core-shell structure enables the CS-TENG to respond sensitively to wind from any direction and generate electrical output on the basis of the vertical contact-separation mode. A single device can generate a maximum power density of 0.14 W/m3 and can power 124 light-emitting diodes. In addition, wind energy can be harvested even at a wind speed as low as 2.3 m/s by paralleling CS-TENGs of different sizes. Finally, a self-powered water quality testing system that uses the CS-TENG as its power supply is built. The CS-TENG exhibits the advantages of a simple structure, environmentally friendly materials, low cost, and simple fabrication process. These features are of considerable significance for the development of green energy harvesting devices.

Low-voltage driving high-resistance liquid crystal micro-lens with electrically tunable depth of field for the light field imaging system.

Light field imaging (LFI) based on Liquid crystal microlens array (LC MLAs) are emerging as a significant area for 3D imaging technology in the field of upcoming Internet of things and artificial intelligence era. However, in scenes of LFI through conventional MLAs, such as biological imaging and medicine imaging, the quality of imaging reconstruction will be severely reduced due to the limited depth of field. Here, we are proposed a low-voltage driving LC MLAs with electrically tunable depth of field (DOF) for the LFI system. An aluminum-doped zinc oxide (AZO) film was deposited on the top of the hole-patterned driven-electrode arrays and used as a high resistance (Hi-R) layer, a uniform gradient electric field was obtained across the sandwiched LC cell. Experimental results confirm that the proposed LC MLAs possess high-quality interference rings and tunable focal length at a lower working voltage. In addition, the focal lengths are tunable from 3.93 to 2.62 mm and the DOF are adjustable from 15.60 to 1.23 mm. The experiments demonstrated that the LFI system based on the proposed structure can clearly capture 3D information of the insets with enlarged depths by changing the working voltage and driving frequency, which indicates that the tunable DOF LC MLAs have a potential application prospects for the biological and medical imaging.

Novel fabrication of bi-metal oxide hybrid nanocomposites for synergetic enhancement of in vivo healing and wound care after caesarean section surgery.

In the current study, bi-metal oxide hybrid nanocomposites prepared by cerium oxide (CeO2 ) nanoparticles are included into chitosan-ZnO composites for developing the potential materials of dressing the wound. The wound healing effect of prepared hybrid nanocomposites was evaluated regarding the surface morphology, functional groups, thermal degradation and composite size. The antimicrobial activity of chitosan-ZnO/CeO2 hybrid nano composites was tested against the pathogens of Staphylococcus aureus and Escherichia coli. The hybrid nanocomposites containing CeO2 -based chitosan and ZnO nanoparticles were taken for optimum dressing included in the vivo studies on the excisional wounds in wistar rats. After 2 weeks, it is seen that the wound treated with CS-ZnO/CeO2 hybrid nano composites consists of the significant dressing of nearly 100% compared with control which showed nearly 65% of wound closure. Finally, our reported results gave the proof in supporting the availability of CS-ZnO/CeO2 hybrid nanocomposites contains the dressing of the wounds for the treatment.

Working Mechanisms of Nanoscale Light-Emitting Diodes Operating in Non-Electrical Contact and Non-Carrier Injection Mode: Modeling and Simulation.

Non-electrical contact and non-carrier injection (NEC&NCI) mode is an emerging driving mode for nanoscale light-emitting diodes (LEDs), aiming for applications in nano-pixel light-emitting displays (NLEDs). However, the working mechanism of nano-LED operating in NEC&NCI mode is not clear yet. In particular, the questions comes down to how the inherent holes and electrons in the LED can support sufficient radiation recombination, which lacks a direct physical picture. In this work, a finite element simulation was used to study the working process of the nano-LED operating in the NEC&NCI mode to explore the working mechanisms. The energy band variation, carrier concentration redistribution, emission rate, emission spectrum, and current-voltage characteristics are studied. Moreover, the effect of the thickness of insulating layer that plays a key role on device performance is demonstrated. We believe this work can provide simulation guidance for a follow-up study of NEC&NCI-LED.

Hybrid Device of Blue GaN Light-Emitting Diodes and Organic Light-Emitting Diodes with Color Tunability for Smart Lighting Sources.

A lighting device with a wide color-tunable range is still a challenge for lighting based on either organic light-emitting diodes (OLEDs) or inorganic LEDs. In this work, we first proposed a novel hybrid device of organic LEDs and inorganic blue GaN LEDs to achieve full white and other colors. Organic LEDs were stacked with green and red emissive layers and connected with blue GaN LEDs in parallel but in opposite polarity voltage. Under the alternate-current (AC) driving, the hybrid structure can be controlled independently by applying timing variable opposite voltages to emit the light from either blue LEDs or the stacked OLEDs for forming mixed colors. The hybrid device can generate white light, varying in a wide range by changing the amplitude and duty ratio (DR) of AC-driving signals, from cold white to standard white and to warm white (3668-11 833 K). When an AC voltage of (4.80 V, -2.45 V) was applied, the device has a high color gamut of 95.24% National Television System Committee (NTSC) and a high color rendering index (R a) of 92.4%. The novel hybrid device with the blue LED and OLED in opposite polarity exhibits potential applications in smart solid-state lighting, display, and light communication.

Design and fabrication of hybrid MLAs/gratings for the enhancement of light extraction efficiency and distribution uniformity of OLEDs.

Extracting light from organic light-emitting diodes (OLEDs) and improving the angular distribution are essential for their commercial applications in illumination and displays. In this work, hybrid microlens arrays (MLAs) and gratings with periods and depths in the scale of submicron have been designed and incorporated on the lighting surface of OLEDs for simultaneous enhancement of light outcoupling efficiency and angular distribution improvement. It is found that the augmentation of light extraction efficiency is mainly attributed to the MLAs, while the gratings can improve the viewing angle by increasing the angular distribution uniformity. A novel approach was proposed by combining photoresist thermal reflow, soft-lithography and plasma treatments on polydimethylsiloxane (PDMS) surfaces synergistically to realize gratings on the wavy surface of MLAs. It has been proved that with the hybrid MLAs/gratings, the external quantum efficiency (EQE) of the OLED can reach up to 22.8%, which increased by 24% compared to that of bare OLED. Moreover, the OLED with the hybrid MLAs/gratings showed an obvious lateral enhancement at wider viewing angle.

Spontaneous Formation of Random Wrinkles by Atomic Layer Infiltration for Anticounterfeiting.

Continuous developments of innovative anticounterfeiting strategies are vital to restrain the fast-growing counterfeit markets. Physical unclonable function (PUF)-based taggants allow for a practical solution to provide irreproducible codes for strong authentication. Herein, an advanced anticounterfeiting strategy with multiple security levels was successfully developed using screen printing and atomic layer infiltration (ALI) techniques. Macroscale poly(dimethylsiloxane) (PDMS) patterns were fabricated for primary verification. Spontaneous formation of random wrinkles with size in the micrometer scale was achieved on the top surface of screen-printed PDMS patterns due to the anisotropic relief and redistribution of extra compressive stress after Al2O3 infiltration, which can be used for senior authentication by image identification using the artificial intelligence (AI) technique. Furthermore, the complexity and security level of a code, which are proportional to the minutia density, can be adjusted by the morphology of the wrinkles in terms of amplitude and wavelength via the degree of Al2O3 permeation depending on ALI conditions. These spontaneously formed random wrinkles were demonstrated for validation and decoding with AI, exhibiting the merits of being unclonable, nondestructive, universally adaptable, environmentally stable, and mass-producible, and sufficiently adaptable for an industry-suitable authentication strategy.

Knowledge, Attitudes, and Practices of Urban Residents Toward COVID-19 in Shaanxi During the Post-lockdown Period.

Background: The coronavirus disease 2019 (COVID-19) pandemic in China is essentially under control. Under global scrutiny, China has started reviving the social, cultural, and working lives of its inhabitants. However, localized outbreaks of COVID-19 are occurring, indicating that the country still needs to follow disease prevention and control measures. Previous studies have assessed the knowledge, attitudes, and behaviors of the general public in China regarding COVID-19 during the pandemic. However, little is known about knowledge, attitudes, and practices (KAP) of Chinese residents regarding COVID-19 after periods of lockdown. Therefore, this study was conducted to identify the KAP and other factors among the residents of Shaanxi Province during the post-lockdown period. Methods: A cross-sectional, network questionnaire survey was conducted in Shaanxi Province from October 1-30, 2020. A total of 1,175 urban residents were interviewed via Wen Juan Xing, an online questionnaire tool. A self-developed online KAP COVID-19 questionnaire was developed in this study. The questionnaire consisted of four parts: general information, knowledge, attitude, and practice. Descriptive statistics and binomial logistic regression analysis were used in the statistical analysis. Results: The majority of the participants were knowledgeable about COVID-19. They had optimistic attitudes and behaved appropriately toward COVID-19. Education was an associated factor for the knowledge of residents and the knowledge of COVID-19 was high among people with high academic qualifications. Attitudes were more positive in residents who lived with elderly people, women, and children. The score of practice was higher in residents with positive attitudes and high academic qualifications. There was a positive correlation between age and practice. Conclusion: We found that the KAP of residents in Shaanxi was at a relatively high level during the post-lockdown period. Although the lockdown was lifted, the epidemic is not over. Thus, it is necessary to develop targeted health education programs for residents with different demographic characteristics in Shaanxi.

Nurses' turnover intention in secondary hospitals in China: A structural equation modelling approach.

AIM: To identify the factors affecting nurses' turnover intention. BACKGROUND: The shortage of nurses has been a great challenge worldwide, and nurses' turnover may exacerbate the situation. METHODS: A cross-sectional study was conducted among nurses in six secondary hospitals in China. A model was constructed, and structured questionnaires were adopted to measure model variables. Structural equation modelling was used to verify the model. RESULTS: Totally, 594 valid questionnaires were collected. The final model showed an acceptable fit, and 35.0% of the total variation was explained. Nine of the ten pathways were statistically significant. The model verified the contribution of professional value, nursing practice, job stress and social support to turnover intention and their effects were mediated by job satisfaction and organisational commitment. As hypothesized, there existed a significant effect between job satisfaction and organisational commitment. Unexpectedly, job stress had a greater direct effect on turnover intention than job satisfaction and organisational commitment. CONCLUSIONS: The structural model provided a feasible model that could explain nurses' turnover intention in China. IMPLICATIONS FOR NURSING MANAGEMENT: To prevent the turnover of nurses, administrators and managers should advisably prioritize the effect of job stress, especially in hospitals with similar medical context.

Emerging Nanopixel Light-Emitting Displays: Significance, Challenges, and Prospects.

The requirement for increased resolution has created the concept of displays with nanoscale pixels; that is, each subpixel consists of multiple or even a single nanolight source, which is considered the ultimate light source for light field, near-eye, and implantable displays. However, related research is still at an early stage, and further insights into this future display concept should be provided. In this Perspective, we provide our proposed term for this future display, namely, nanopixel light-emitting display (NLED). We present an overview of nanolight-emitting diodes, which are considered the core component of NLEDs. Then, a roadmap to realize NLEDs from the view of material design is provided. Finally, we introduce our proposed operation mode (nonelectrical contact and noncarrier injection mode) for NLEDs and recommend possible nanopixel-level drive approaches. We hope that this Perspective will be helpful in designing innovative display technologies.

Susceptibility to chronic immobilization stress-induced depressive-like behaviour in middle-aged female mice and accompanying changes in dopamine D1 and GABAA receptors in related brain regions.

BACKGROUND: Middle-aged females, especially perimenopausal females, are vulnerable to depression, but the potential mechanism remains unclear. Dopaminergic and GABAergic system dysfunction is involved in the pathophysiology of depression. In the current study, we used 2-month-old and 11-month-old C57BL/6 mice as young and middle-aged mice, respectively. Chronic immobilization stress (CIS) was used to induce depressive-like behaviour, and the sucrose preference test (SPT), tail suspension test (TST) and forced swim test (FST) were used to assess these behaviours. We then measured the mRNA levels of dopamine receptor D1 (DRD1) and the GABAA receptors GABRA1, GABRB2 and GABRG2 in the nucleus accumbens (NAc) and prefrontal cortex (PFC). RESULTS: We found that immobility time in the FST was significantly increased in the middle-aged mice compared with the middle-aged control mice and the young mice. In addition, the preference for sucrose water was reduced in the middle-aged mice compared with the middle-aged control mice. However, CIS did not induce obvious changes in the performance of the young mice in our behavioural tests. Moreover, the middle-aged mice exhibited equal immobility times as the young mice in the absence of stress. Decreases in the mRNA levels of DRD1, GABRA1, and GABRB2 but not GABRG2 were found in the NAc and PFC in the middle-aged mice in the absence of stress. Further decreases in the mRNA levels of DRD1 in the NAc and GABRG2 in the NAc and PFC were found in the middle-aged mice subjected to CIS. CONCLUSIONS: Our results suggested that ageing could not directly induce depression in the absence of stress. However, ageing could induce susceptibility to depression in middle-aged mice in the presence of stress. CIS-induced decreases in DRD1 and GABRG2 levels might be involved in the increase in susceptibility to depression in this context.

Psychometric analysis of a Chinese version of the Sleep Hygiene Index in nursing students in China: a cross-sectional study.

OBJECTIVE: The aim of the study had two stages. One was to examine the psychometric quality of the Sleep Hygiene Index (SHI) in Chinese version and its predicted function for the prevalence of insomnia. The other was to describe the prevalence of poor sleep hygiene habits and associated factors of sleep hygiene habits in Chinese nursing students. METHOD: According to Brislin translation model, the English version of SHI was translated into Chinese. And a pilot-survey was carried out to measure psychometric quality of the Chinese version of SHI with 260 nursing students by convenient sampling. Then a cross-sectional survey was conducted. 659 undergraduates were recruited by simple random sampling in a medical university in China. Data collection instruments consisted of a demographic questionnaire, the Sleep Hygiene Index (SHI), the Insomnia Severity Index (ISI) and the Brief Insomnia Questionnaire (BIQ). Data were analyzed by SPSS 24.0 and Amos 24.0 with P = 0.05 as the significant test value. RESULTS: The internal consistency reliability of SHI in Chinese version was more than 0.60 (α = 0.62, ω = 0.63). The concurrent validity presented significantly (r = 0.25, P < 0.001). Exploratory factor analysis found that a six component model explained 63.06% of total variance and confirmatory factor analysis showed good fitness (χ2/df=2.14, RMSEA = 0.04). ROC analysis showed that the cut-off value predicting for insomnia was 5.50 (52.90% sensitivity and 75.80% specificity). The area under the ROC curve was 0.66 (95% confidence interval = 0.61-0.71). 199 (30.20%) participant had poor sleep hygiene habits, especially in the aspects of staying too longer in bed (65.25%) and irregular sleep schedule. Multiple linear regression analysis showed health condition, academic difficulties and gender were more common associated factors of sleep hygiene. CONCLUSIONS: The Chinese version of the Sleep Hygiene Index demonstrates satisfactory psychometric qualities and has higher sensitivity and specificity to predict for insomnia. So SHI could be used in Chinese nursing students and detect high levels of insomnia. The status of sleep hygiene of nursing students in China should be concerned. Sleep hygiene education should be carried out in nursing students with different gender, health condition, and academic performance.

Fabrication of a micro-lens array for improving depth-of-field of integral imaging 3D display.

In this paper, we present a new, to the best of our knowledge, structure of double pinhole/micro-lens array (DP/MLA) with two center-depth planes, used for improving the depth-of-field (DOF) of integral imaging (II), which can be fabricated by a combination of lithography and inkjet printing. The results show that a black circular groove array prepared by lithography can be used for micro-lens location and reduce the stray light for II. By controlling the parameters of the inkjet printing system, DP/MLA with high precision, high alignment, and good focusing ability can be achieved. When the fabricated DP/MLA is applied in the II system, the reconstructed image has a better three-dimensional (3D) image with higher DOF than that by traditional MLA and higher quality than that by ordinary double-layer MLA.

Large-scale microlens arrays on flexible substrate with improved numerical aperture for curved integral imaging 3D display.

Curved integral imaging 3D display could provide enhanced 3D sense of immersion and wider viewing angle, and is gaining increasing interest among discerning users. In this work, large scale microlens arrays (MLAs) on flexible PMMA substrate were achieved based on screen printing method. Meanwhile, an inverted reflowing configuration as well as optimization of UV resin's viscosity and substrate's surface wettability were implemented to improved the numerical aperture (NA) of microlenses. The results showed that the NA values of MLAs could be increased effectively by adopting inverted reflowing manner with appropriate reflowing time. With decreasing the substrate's wettability, the NA values could be increased from 0.036 to 0.096, when the UV resin contact angles increased from 60.1° to 88.7°. For demonstration, the fabricated MLAs was combined to a curved 2D monitor to realize a 31-inch curved integral imaging 3D display system, exhibiting wider viewing angle than flat integral imaging 3D display system.

Electroluminescence from µLED without external charge injection.

Stable electroluminescence from micro-pixelated light-emitting diode (µLED) occurs when electrons and holes are continuously injected from external electrodes. Different from the general recognition, in this work, µLED works in an operation mode, namely, non-electrical contact and non-carrier injection mode, and can be 'wirelessly' lit up without external charge injection, which is different from the general recognition. Inherent holes and electrons in µLEDs can provide sufficient carriers for radiative recombination under alternating-current electric field. A possible model related to the diffusion of majority carrier and the drift of minority carrier in µLED was proposed, which is further confirmed by the employment of a 'carrier pump'. Finally, the intrinsic characteristics of the device-in-capacitor, namely, self-protection against electrical breakdown, were discussed. This work demonstrates a new device configuration and an alternative operating mode for µLED and provides a research manner to obtain advanced µLED-based technology.

Binary Electronic Synapses for Integrating Digital and Neuromorphic Computation in a Single Physical Platform.

As a promising advanced computation technology, the integration of digital computation with neuromorphic computation into a single physical platform holds the advantage of a precise, deterministic, fast data process as well as the advantage of a flexible, paralleled, fault-tolerant data process. Even though two-terminal memristive devices have been respectively proved as leading electronic elements for digital computation and neuromorphic computation, it is difficult to steadily maintain both sudden-state-change and gradual-state-change in a single device due to the entirely different operating mechanisms. In this work, we developed a digital-analog compatible memristive device, namely, binary electronic synapse, through realizing controllable cation drift in a memristive layer. The devices feature nonvolatile binary memory as well as artificial neuromorphic plasticity with high operation endurance. With strong nonlinearity in switching dynamics, binary switching, neuromorphic plasticity, two-dimension information store, and trainable memory can be implemented by a single device.

Decreased expression of CD200 and CD200R1 by human decidual tissues in spontaneous early abortion.

Objective: To examine the cellular distribution and the expression of CD200 and its receptor 1 (CD200R1) in human deciduas in first-trimester pregnant women with spontaneous early abortion (SEA) and normal pregnancy, and to explore their role in the etiology of SEA.Subjects and methods: Thirty-five women at 6-10-week gestation with SA and 30 women of similar gestational age with a healthy pregnancy were recruited. Expression of CD200 and CD200R1 in the deciduas was determined using immunohistochemistry, confocal laser scanning microscope, Western blot, and real-time PCR (RT-PCR).Results: The decidual stromal cells, glandular epithelial cells, and vessel endothelial cells during the first trimester of pregnancy express both CD200 and CD200R1 proteins. During this period, the expression of CD200 in glandular epithelial cells and vessel endothelial cells is significantly higher in normal pregnancy than that in women with SEA (0.3079 ± 0.0674 versus 0.2735 ± 0.0515; 0.4077 ± 0.1366 versus 0.3249 ± 0.0993); the expression of CD200R1 in stromal cells, decidual stromal cells, glandular epithelial cells is significantly higher during normal pregnancy than SEA (0.2574 ± 0.0588 versus 0.2292 ± 0.0415; 0.3617 ± 0.1046 versus 0.2804 ± 0.0640). Western blot analysis showed an approximately 44% decrease in CD200R1expression in decidua in the SEA versus the controls. Finally, in decidua, the expression of both CD200 protein and CD200R1 transcript are significantly higher in healthy first-trimester pregnancy than in SEA (CD200: 2.2089 ± 1.2754 versus 0.7241 ± 0.2143; CD200R1: 15.7843 ± 10.7085 versus 7.3381 ± 5.8529).Conclusions: Women with SEA have a lower level of CD200 and CD200R1 expression in deciduas compared with normal pregnant women suggesting that under physiological conditions, CD200 and CD200R1 expression by deciduas is important to prevent fetal loss ensure a successful pregnancy.