Fine control over the physicochemical structures of carbon electrocatalysts is important for improving the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable ...Zn–air batteries. Covalent organic frameworks (COFs) are considered good candidate carbon materials because their structures can be precisely controlled. However, it remains a challenge to impart bifunctional electrocatalytic activities for both the ORR and OER to COFs. Herein, a pyridine‐linked triazine covalent organic framework (PTCOF) with well‐defined active sites and pores is readily prepared under mild conditions, and its electronic structure is modulated by incorporating Co nanoparticles (CoNP‐PTCOF) to induce bifunctional electrocatalytic activities for the ORR and OER. The CoNP‐PTCOF exhibits lower overpotentials for both ORR and OER with outstanding stability. Computational simulations find that the p‐band center of CoNP‐PTCOF down‐shifted by charge transfer, compared to pristine PTCOF, facilitate the adsorption and desorption of oxygen intermediates on the pyridinic carbon active sites during the reactions. The Zn–air battery assembled with bifunctional CoNP‐PTCOF exhibits a small voltage gap of 0.83 V and superior durability for 720 cycles as compared with a battery containing commercial Pt/C and RuO2. This strategy for modulating COF electrocatalytic activities can be extended for designing diverse carbon electrocatalysts.
Pyridine‐linked triazine covalent organic framework (PTCOF) with well‐defined carbon active sites and pores is readily prepared, and its electronic structure is effectively modulated by incorporating Co nanoparticles into the framework (CoNP‐PTCOF) to improve the bifunctional electrocatalytic activity for the oxygen reduction reaction and oxygen evolution reaction in Zn–air batteries. A rechargeable Zn–air battery with bifunctional CoNP‐PTCOF exhibits outstanding performance with superior durability.
In this paper, we propose an adaptive quantization method that can easily transfer the weights, which are trained in software network with floating point operation, to the real synaptic devices in ...hardware-based neural networks and maintain high performance. An n-type gated Schottky diode is investigated as a synaptic device, and the conductance behavior of this device is modeled successfully. Max value normalization and <inline-formula> <tex-math notation="LaTeX">3\sigma </tex-math></inline-formula> normalization are applied to the weights trained with an accuracy of 98.29% on fully connected neural network (<inline-formula> <tex-math notation="LaTeX">784\times 256\times10 </tex-math></inline-formula>) using software network. Then, the weights are quantized using the adaptive quantization method and can be transferred by adjusting the number of identical pulses applied to the synaptic devices. After applying the adaptive quantization method, accuracy rates of 98.09% and 97.20% in MNIST classification are obtained for both max value normalization and <inline-formula> <tex-math notation="LaTeX">3\sigma </tex-math></inline-formula> normalization, respectively. The proposed quantization method works well even when there is nonideality of synaptic devices such as nonlinearity of conductance behavior, limited conductance levels, and variation of conductance.
Background and Aims The efficacy of palliative biliary drainage by using bilateral or unilateral self-expandable metal stents (SEMSs) for a malignant hilar biliary stricture (MHS) remains ...controversial. This prospective, randomized, multicenter study investigated whether bilateral drainage by using SEMSs is superior to unilateral drainage in patients with inoperable MHSs. Methods Patients with inoperable high-grade MHSs who underwent palliative endoscopic insertion of bilateral or unilateral SEMSs were enrolled. The main outcome measurements were the rate of primary reintervention for malfunction after successful placement of SEMSs, stent patency, technical and clinical success rates, adverse events, and survival duration. Results A total of 133 pathology-diagnosed patients were randomized to the bilateral group (n = 67) or the unilateral group (n = 66). The primary technical success rates were 95.5% (64/67) and 100% (66/66) in the bilateral and unilateral groups, respectively ( P = .244). The clinical success rates were 95.3% (61/64) and 84.9% (56/66), respectively ( P = .047). The primary reintervention rates based on the per-protocol analysis were 42.6% (26/61) in the bilateral group and 60.3% (38/63) in the unilateral group ( P = .049). The median cumulative stent patency duration was 252 days in the bilateral group and 139 days in the unilateral group. The risk of stent patency failure was significantly higher in the unilateral group (log-rank test; P < .01). In a multivariate Cox proportional hazard model to assess stent patency, bilateral SEMS placement was a favorable factor (adjusted hazard ratio 0.30, 95% confidence interval, 0.172-0.521; P < .001). Survival probability and late adverse events were not different between the 2 groups. Conclusions Unilateral and bilateral drainage strategies by using SEMSs had similar technical success rates, but bilateral drainage resulted in fewer reinterventions and more durable stent patency in patients with inoperable high-grade MHSs. (Clinical trial registration number: NCT02166970.)
In this work, the low-frequency noise (LFN) characteristics of hafnium-zirconium oxide (HZO) ferroelectric field-effect transistors (FeFETs) with and without high-pressure forming gas annealing (HPA) ...treatment are investigated. The origin of <inline-formula> <tex-math notation="LaTeX">1/ {f} </tex-math></inline-formula> noise in the FeFET without HPA is changed from carrier number fluctuation to Hooge's mobility fluctuation after wake-up due to the remote phonon scattering from the polarized HZO. Also, Hooge's parameter is increased by the program/erase (P/E) cycling-induced stress. On the contrary, only the correlated mobility fluctuation is increased after the wake-up in the FeFET with HPA. Furthermore, the LFN of the FeFET with HPA shows robustness to P/E cycling-induced stress after the wake-up, showing superb endurance performance.
Organic solid electrolytes offer an effective route for safe and high‐energy‐density all‐solid‐state Li metal batteries. However, it remains a challenge to devise a new strategy to promote the ...dissociation of strong ion pairs and the transport of ionic components in organic solid electrolytes. Herein, a zwitterionic covalent organic framework (Zwitt‐COF) with well‐defined chemical and pore structures is prepared as a solid electrolyte capable of accelerating the dissociation and transport of Li ions. The Zwitt‐COF solid electrolyte exhibits a high room‐temperature ionic conductivity of 1.65 × 10−4 S cm−1 with a wide electrochemical stability window. Besides, the Zwitt‐COF solid electrolyte displays stable Li plating/stripping behavior via effective inhibition of the formation of Li dendrites and dead Li, leading to superior long‐term cycle performance with retention of 99% discharge capacity and 98% Coulombic efficiency in an all‐solid‐state Li‐metal battery. Theoretical simulations reveal that the incorporation of zwitterionic groups into COF can facilitate the dissociation of strong ion pairs and reconstruct the AA‐stacking configuration by dissociative adsorption of Li+ ions on Zwitt‐COF producing linear hexagonal ion channels in the Zwitt‐COF solid electrolyte. This strategy based on Zwitt‐COF can provide an alternative way to construct various solid‐state Li batteries.
A zwitterionic covalent organic framework (Zwitt‐COF) is developed as a solid electrolyte for all‐solid‐state Li‐metal batteries. The Zwitt‐COF solid electrolyte exhibits a high room‐temperature ionic conductivity with a wide electrochemical window, leading to superior long‐term cycle performance in the battery. Theoretical simulations reveal that Zwitt‐COF promotes the dissociation of Li‐ion pairs and provides ion channels for effective Li+ transport.
Precise control over doping of photocatalysts is required to modulate their photocatalytic activity in visible light‐driven reactions. Here, a single precursor‐employing bottom‐up approach is ...developed to produce different heteroatom‐doped graphene quantum dots (GQDs) with unique photocatalytic activities. The solvothermal reaction of a norepinephrine precursor with redox active and condensable moieties effectively produces both nitrogen/sulfur codoped GQDs (NS‐GQDs) and nitrogen‐doped GQDs (N‐GQDs) by simply varying solvents (from dimethyl sulfoxide to water) under microwave irradiation. As‐prepared NS‐GQDs and N‐GQDs show similar lateral sizes (3–4 nm) and heights (1–2 nm), but they include different dopant types and doping constitution and content, which lead to changes in photocatalytic activity in aerobic oxidative coupling reactions of various amines. NS‐GQDs exhibit much higher photocatalytic activity in reactions under visible light than N‐GQDs and oxygen‐doped GQDs (O‐GQDs). The mechanism responsible for the outstanding photocatalytic activity of NS‐GQDs in visible light‐driven oxidative coupling reactions of amines is also fully investigated.
Modulation of the photocatalytic activity of heteroatom‐doped graphene quantum dots (GQDs) is reported. A single precursor, norepinephrine, is used to effectively produce N,S‐co‐doped GQDs and N‐doped GQDs under microwave irradiation. Tailoring dopant types, constitution, and content imparts much higher photocatalytic activity to N,S‐codoped GQDs than N‐doped GQDs and O‐doped GQDs in the visible‐light‐driven oxidative coupling reaction of various amines.
Abstract
Current technological advances in the organic light‐emitting diode panel design of foldable smartphones demand advanced adhesives with UV‐blocking abilities, beyond their conventional roles ...of bonding objects and relieving deformation stress. However, optically clear adhesives (OCAs) with UV‐blocking ability cannot be prepared using conventional UV‐curing methods relying on a photoinitiator. Herein, a new acrylic resin that can be efficiently cured using visible light without oxygen removal is presented, which may be used to develop UV‐blocking OCAs for use in current flexible displays. A novel photocatalyst and a specific combination of additives facilitate sufficiently rapid curing under visible light in the presence of UV‐absorbers. Only a very small amount of the highly active photocatalyst is required to prepare UV‐blocking OCA films with very high transparency in the visible region. Using this system, a UV‐blocking OCA that nearly meets the specifications of an OCA used in commercialized foldable smartphones is realized. This technology can also be utilized in other applications that require highly efficient visible light curing, such as optically clear resins, dental resins, and 3D/4D‐printable materials.
An AND-type flash synaptic array is cointegrated with CMOS circuits using a novel fabrication method. Electrical characteristics of the basic circuit blocks required for neural network operation are ...verified. By reducing the number of masks and fabrication steps required, the proposed fabrication method successfully integrates synaptic array and CMOS peripheral circuits, including integrate-and-fire (I&F) circuits and passive devices, on a single wafer. The proposed fabrication method provides a methodology for the efficient implementation of hardware-based neural networks as well as verification of excellent compatibility of the proposed synaptic array with CMOS technology.
Background A lumen-apposing stent can be used effectively under endosonographic guidance. Objective To evaluate a newly designed, fully covered self-expandable metal stent with folding anchoring ...flanges for lumen apposition assembled on a conventional delivery system. Design Retrospective case series and animal study. Setting Tertiary care academic medical centers. Subjects Six pigs for animal study and 7 patients, 3 of whom underwent endoscopic drainage for acute cholecystitis (AC) and 4 for pancreatic fluid collection (PFC). Intervention Stent deployment under EUS guidance after puncturing, passage of an endoscope through the stent into the gallbladder (GB), or PFC with conventional endoscopic procedures. Main Outcome Measurements Technical and clinical success, adverse events, and removability. Results In the animal study, the stent was successfully inserted and deployed in the GB via a transgastric approach under EUS guidance without adverse events in all 6 pigs. Contrast injection demonstrated the absence of leakage. Cholecystoscopy with enhanced endoscopy was performed successfully in all animals after stent placement. All stents were intact and were removed successfully at 4 weeks. GB firmly adhered to the stomach with an intact cholecystogastric tract on necropsy and histopathology. The stents were successfully deployed without adverse effects in 7 patients. AC or PFC was resolved after stent placement in all patients. Endoscopic procedures were possible through the stent. Stent migration was not observed. The stent was successfully removed from the 4 patients with PFC after complete resolution. Limitations Small sample size, retrospective study. Conclusions Transenteric drainage and endoscopic intervention by using a novel fully covered self-expandable metal stent for lumen apposition under EUS guidance is feasible for the management of AC and PFC. Further study is warranted.
We demonstrate a novel ferroelectric-gate field effect transistor with recessed channel (R-FeFET) to improve memory window (MW), program/erase speed, long-time retention, and endurance ...simultaneously. Based on technology computer-aided design (TCAD) simulations including calibrated ferroelectric material (FE) parameters, it is revealed that the polarization is enhanced by the larger electric field (e-field) across the FE compared to a conventional planar FeFET, resulting in the wider MW and the faster program/erase speed. Moreover, the endurance/retention of the R-FeFET is expected to be improved as the e-field across the SiO 2 interlayer is significantly reduced.
