Strain-induced ferroelectric polarization reversal without undergoing geometric inversion in blue SiSe monolayer.

Ferroelectricity in two-dimensional (2D) systems generally arises from phonons and has been widely investigated. On the contrary, electronic ferroelectricity in 2D systems has been rarely studied. Using first-principles calculations, the ferroelectric behavior of the buckled blue SiSe monolayer under strain are explored. It is found that the direction of the out-of-plane ferroelectric polarization can be reversed by applying an in-plane strain. And such polarization switching is realized without undergoing geometric inversion. Besides, the strain-triggered polarization reversal emerges in both biaxial and uniaxial strain cases, indicating it is an intrinsic feature of such a system. Further analysis shows that the polarization switching is the result of the reversal of the magnitudes of the positive and negative charge center vectors. And the variation of buckling is found to play an important role, which results in the switch. Moreover, a non-monotonic variation of band gap with strain is revealed. Our findings throws light on the investigation of novel electronic ferroelectric systems.

Tuning charge transport by manipulating concentration dependent single-molecule absorption configurations.

Understanding and tuning charge transport in molecular junctions is pivotal for crafting molecular devices with tailored functionalities. Here, we report a novel approach to manipulate the absorption configuration within a 4,4'-bipyridine (4,4'-BPY) molecular junction, utilizing the scanning tunneling microscope break junction technique in a concentration-dependent manner. Single-molecule conductance measurements demonstrate that the molecular junctions exhibit a significant concentration dependence, with a transition from high conductance (HC) to low conductance (LC) states as the concentration decreases. Moreover, we identified an additional conductance state in the molecular junctions besides already known HC and LC states. Flicker noise analysis and theoretical calculations provided valuable insights into the underlying charge transport mechanisms and single-molecule absorption configurations concerning varying concentrations. These findings contribute to a fundamental comprehension of charge transport in concentration-dependent molecular junctions. Furthermore, they offer promising prospects for controlling single-molecule adsorption configurations, thereby paving the way for future molecular devices.

Frontiers in all electrical control of magnetization by spin orbit torque.

Achieving all electrical control of magnetism without assistance of an external magnetic field has been highly pursued for spintronic applications. In recent years, the manipulation of magnetic states through spin-orbit torque (SOT) has emerged as a promising avenue for realizing energy-efficient spintronic memory and logic devices. Here, we provide a review of the rapidly evolving research frontiers in all electrical control of magnetization by SOT. The first part introduces the SOT mechanisms and SOT devices with different configurations. In the second part, the developments in all electrical SOT control of magnetization enabled by spin current engineering are introduced, which include the approaches of lateral symmetry breaking, crystalline structure engineering of spin source material, antiferromagnetic order and interface-generated spin current. The third part introduces all electrical SOT switching enabled by magnetization engineering of the ferromagnet, such as the interface/interlayer exchange coupling and tuning of anisotropy or magnetization. At last, we provide a summary and future perspectives for all electrical control of magnetization by SOT.

Sliding ferroelectricity and the moiré effect in Janus bilayer MoSSe.

Two-dimensional van der Waals layered materials have attracted extensive attention in the field of low-dimensional ferroelectricity, on account of their readily delaminated structure and high-density information storage advantages. Here, we report the sliding ferroelectricity and moiré effects on the ferroelectricity in Janus bilayer MoSSe based on first-principles calculations. We focus on the changes of in-plane and out-of-plane polarizations due to sliding, and the calculations demonstrate that the in-plane and out-of-plane polarizations can be switched simultaneously by sliding. In addition, in moiré-twisted bilayer MoSSe, the complex stacking pattern and significant interlayer distance suppress the interlayer charge transfer, and the ferroelectric polarization is effectively suppressed. The polarization in the large-angle twisted structure is small but its direction can be adjusted by changing the twist angle. Our results emphasize the importance of low-dimensional ferroelectrics in van der Waals structures and pave a way for the search of sliding ferroelectric materials, as well as enriching the research on the ferroelectricity of large-angle twisted structures.

Comprehensive insights into the mechanism of keratin degradation and exploitation of keratinase to enhance the bioaccessibility of soybean protein.

Keratin is a recalcitrant protein and can be decomposed in nature. However, the mechanism of keratin degradation is still not well understood. In this study, Bacillus sp. 8A6 can completely degrade the feather in 20 h, which is an efficient keratin degrader reported so far. Comprehensive transcriptome analysis continuously tracks the metabolism of Bacillus sp. 8A6 throughout its growth in feather medium. It reveals for the first time how the strain can acquire nutrients and energy in an oligotrophic feather medium for proliferation in the early stage. Then, the degradation of the outer lipid layer of feather can expose the internal keratin structure for disulfide bonds reduction by sulfite from the newly identified sulfite metabolic pathway, disulfide reductases and iron uptake. The resulting weakened keratin has been further proposedly de-assembled by the S9 protease and hydrolyzed by synergistic effects of the endo, exo and oligo-proteases from S1, S8, M3, M14, M20, M24, M42, M84 and T3 families. Finally, bioaccessible peptides and amino acids are generated and transported for strain growth. The keratinase has been applied for soybean hydrolysis, which generates 2234 peptides and 559.93 mg/L17 amino acids. Therefore, the keratinases, inducing from the poultry waste, have great potential to be further applied for producing bioaccessible peptides and amino acids for feed industry.

Modulation of edge defects on dual-spin filtering in zigzag ß-SiC7 nanoribbons.

The unique edge states of the zigzag ß-SiC7 nanoribbons aroused our attention, and therefore, based on first-principles calculations, we investigated their spin-dependent electronic transport properties by constructing controllable defects to modulate these special edge states. Interestingly, by introducing rectangular edge defects in the SiSi and SiC edge-terminated systems, not only the spin-unpolarized is successfully converted to completely spin-polarized, but also the direction of polarization can be switched, thus enabling a dual spin filter. The analyses further reveal that the two transmission channels with opposite spins are spatially separated and that the transmission eigenstates are highly concentrated at the relative edges. The specific edge defect introduced only suppresses the transmission channel at the same edge but reserves the transmission channel at the other edge. In addition, for the CSi and CC edge-terminated systems, an additional spin-down band exists due to spin splitting in the spin-up band at EF, so that besides the original spatially separated two spin-opposite channels, an extra spin channel is distributed at the upper edge, resulting in unidirectional fully spin-polarized transport. The peculiar spatially separated edge states and excellent spin filtering properties could open up further possibilities for ß-SiC7-based electronic devices in spintronics applications.

Bacteroides fragilis strain ZY-312 facilitates colonic mucosa regeneration in colitis via motivating STAT3 signaling pathway induced by IL-22 from ILC3 secretion.

Introduction: Probiotics play critical roles in relieving inflammatory bowel disease (IBD). However, the underlying mechanism of Bacteroides fragilis strain ZY-312 (B. fragilis) for colonic mucosa regeneration in IBD remains unclear. Methods: The weight loss, disease activity index (DAI), colon length, and histopathology-associated index (HAI) were evaluated the therapeutic effects of B. fragilis in a DSS-induced colitis mouse model. Colonic mucosa proliferation and apoptosis level, and mucus density were detected by histological stain. Gut microbiota was sequenced by 16srRNA analysis. The expression of signal transducer and activator of transcription 3 (STAT3) phosphorylation in colonic mucosa was detected in B. fragilis-treated mice in colitis. B. fragilis-regulated immunity factors of motivating downstream STAT3 phosphorylation were screened by ELISA and flow cytometry. Lastly, B. fragilis-mediated colonic mucosa regeneration effects were verified though the knockout of STAT3 (Stat3 △IEC) and IL-22 (IL-22-/-) in mice, and inhibitor of STAT3 and IL-22 in co-culture model. Results: B. fragilis alleviated DSS-induced colitis in mice with less weight loss, DAI, colon length shortening, and HAI. Further the results showed that B. fragilis motivated STAT3 phosphorylation in colonic mucosa with the upregulation of proliferation index Ki-67 and mucus density, the downregulation of apoptosis level, and the modulation of gut microbiota through a Stat3 △IEC mice model and STAT3 inhibitor-added model in vitro. Meanhwhile we found that B. fragilis promoted IL-22 production, and increased the percentage of IL-22-secreting type 3 innate lymphocytes (ILC3) in colitis. Consequently, We identified that B. fragilis did not increase the expression of pSTAT3, either proliferation level, mucus density, or alter gut microbiota in IL-22 -/- mice. Discussion: B. fragilis may indirectly motivate ILC3 to secrete IL-22, followed by IL-22-induced STAT3 phosphorylation, hence promoting colonic mucosa regeneration in colitis. It indicates that B. fragilis has the potential to be a biological agent for IBD therapy.

Correction: Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain.

Correction for 'Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain' by Hui-Min Ni et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d2cp05066h.

Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain.

Among many modulation methods, strain engineering is often chosen for nanomaterials to produce tunable band gaps continuously. Inspired by the recently reported two-dimensional material PC3, we explore the tuning of strain on the spin-dependent transport properties of PC3 nanoribbons using the first-principle approach. Surprisingly, strain regulation achieves uninterrupted completely dual-spin polarization over a wide energy range near EF. Analysis reveals that the peculiar transmission spectra arise from the interesting evolution of the band structure, in which strain induces bands to shift and broaden/flatten. This results in triggering the transition of PC3NRs from bandgap-tunable bipolar magnetic semiconductors to spin-gapless semiconductors to ferromagnetic metals or half-metal magnets. Their unique performance demonstrates great potential in spintronics, and our study is expected to provide ideas and theoretical support for the design and application of novel PC3-based spintronic devices in the future.

SuperFast: 200× Video Frame Interpolation via Event Camera.

Traditional frame-based video frame interpolation (VFI) methods rely on the linear motion assumption and brightness invariance assumption, which may lead to fatal errors confronting the scenarios with high-speed motions. To tackle the above challenge, inspired by the advantages of event cameras on asynchronously recording brightness changes at each pixel, we propose a Fast-Slow joint synthesis framework for event-enhanced high-speed video frame interpolation, named SuperFast, in this paper, which can generate high frame rate (5000 FPS, 200× faster) video from the input low frame rate (25 FPS) video and the corresponding event stream. In our framework, the task is divided into two sub-tasks, i.e., video frame interpolation for the contents with and without high-speed motions, which are tackled by two corresponding branches, i.e., the fast synthesis pathway and the slow synthesis pathway. The fast synthesis pathway leverages a spiking neural network to encode the input event stream, and combines boundary frames to generate intermediate results through synthesis and refinement, targeting on contents with high-speed motions. The slow synthesis pathway stacks the two input boundary frames and the event stream to synthesize intermediate results, focusing on relatively slow-motion contents. Finally, a fusion module with a comparison loss is utilized to generate the final video frame interpolation results. We also build a hybrid visual acquisition system containing an event camera and a high frame rate camera, and collect the first 5000 FPS High-Speed Event-enhanced Video frame Interpolation (THU[Formula: see text]) dataset. To evaluate the performance of our proposed framework, we have conducted experiments on our THU[Formula: see text] dataset and the existing HS-ERGB dataset. Experimental results demonstrate that our proposed framework can achieve state-of-the-art 200× video frame interpolation performance under high-speed motion scenarios.

Electrically modulated reversible dual-spin filter in zigzag ß-SiC7 nanoribbons.

Compared with traditional magnetic approaches, electrical modulation of spin-polarized current can greatly reduce the energy consumption and scale of nanodevices and improve their operating speed, which has become a promising research field in spintronics. Motivated by the latest reported novel two-dimensional material ß-SiC7, we employ first-principles calculations to investigate its spin-dependent electron transport with diverse edge configurations. By introducing a gate voltage, the three-terminal device can not only switch between spin-unpolarized and fully spin-polarized states, but also easily change the polarization direction, behaving as an excellent electrically modulated reversible dual-spin filter. Surprisingly, an arbitrary proportion of spin-up and spin-down electron numbers is achieved, enabling precise control of spin polarization. Analysis reveals that it is attributed to the peculiar transmission spectrum, where two broad peaks with opposite spins are located around the Fermi level and respond differently to gate voltage. They belong to the spatially separated edge states originating from the p orbitals of the edge atoms. This feature is robust to different edge configurations of ß-SiC7 nanoribbons, indicating that this may be an intrinsic property of such systems, showing great potential for applications.

A robust spin-dependent Seebeck effect and remarkable spin thermoelectric performance in graphether nanoribbons.

The generation of spin currents is a significant issue in spintronics. A spin current can be induced by a temperature gradient in the spin-dependent Seebeck effect, which has attracted growing interest over recent years. Herein we propose spin caloritronic devices based on magnetic graphether nanoribbons and investigate the spin thermoelectric properties by first-principles calculations. Owing to the symmetrical spin-resolved transmission spectra, our devices exhibit a robust spin-dependent Seebeck effect and could generate a pure spin current. Moreover, they manifest a high spin Seebeck coefficient and a giant spin figure of merit. Our findings demonstrate that graphether-nanoribbon-based devices possess remarkable spin thermoelectric performance, and might be promising candidates for spin caloritronics.

Metallic-semiconducting transition and spin polarized-unpolarized transition in a single molecule with a negative Poisson's ratio.

Different from conventional materials, structures with a negative Poisson's ratio (NPR) contract/expand laterally under a longitudinal compressive/tensile strain, usually exhibiting peculiar features. Through first-principles calculations, we investigate the electronic and transport properties of Pd9B16 molecules. Its Poisson's ratio is found to be negative under uniaxial strain along a specific direction. By contacting with Au nanowires, atomic Au chains and atomic C chain electrodes, two kinds of transitions for transmission states could be realized by the modulation of the strain and the contacting site, i.e., metallic-semiconducting transition and spin polarized-unpolarized transition. Further analysis shows that it is the suppression and shifting of density of states, caused by the strain or contacting electrodes, that trigger the transitions. Those findings combine NPR and spintronics at the single-molecule level, which may throw light on the development of nanoelectronic devices.

Switchable Interlayer Magnetic Coupling of Bilayer CrI3.

Due to the weak van der Waals (vdW) interlayer interaction, interfacial geometry of two-dimensional (2D) magnetic vdW materials can be freely assembled, and the stacking order between layers can be readily controlled, such as laterally shifting or rotating, which may trigger the variation of magnetic order. We investigate the H-type bilayer CrI3 where the two layers are aligned in anti-parallel directions. Based on first-principles calculations, we propose two states with different interlayer magnetic couplings, i.e., ferromagnetic and antiferromagnetic, and analyze the superexchange mechanism inside. It is found that the two magnetic coupling states are stacking-dependent, and could be switched by applying out-of-plane axial strain and electron doping. Our findings show great application potential in the design of heterostructural and spintronic devices based on 2D magnetic vdW materials.

Electrically controlled spin reversal and spin polarization of electronic transport in nanoporous graphene nanoribbons.

Based on first-principles calculations, the spin-dependent electronic transport of nanoporous graphene nanoribbons is investigated. A three-terminal configuration is proposed, which can electronically control the spin polarization of transmission, instead of magnetic methods. By modulating the gate voltage, not only could the transmission be switched between completely spin up and spin down polarized states to realize a dual-spin filter, but also the spin polarization could be finely tuned between 100% and -100%. Any ratio of spin up to spin down transport electrons can be realized, providing more possibilities for the design of nanoelectronic devices. Further analysis shows that the transmission spectra, with two distinct transmission peaks with opposite spins around EF, are the key point, which are contributed by p orbitals. And such a phenomenon is robust to the width and length of the nanoporous graphene nanoribbons, suggesting that it is an intrinsic feature of these systems. The electrical control on spin polarization is realized in pure-carbon systems, showing great application potential.

3D CNN classification model for accurate diagnosis of coronavirus disease 2019 using computed tomography images.

Purpose: The coronavirus disease (COVID-19) has been spreading rapidly around the world. As of August 25, 2020, 23.719 million people have been infected in many countries. The cumulative death toll exceeds 812,000. Early detection of COVID-19 is essential to provide patients with appropriate medical care and protecting uninfected people. Approach: Leveraging a large computed tomography (CT) database from 1112 patients provided by China Consortium of Chest CT Image Investigation (CC-CCII), we investigated multiple solutions in detecting COVID-19 and distinguished it from other common pneumonia (CP) and normal controls. We also compared the performance of different models for complete and segmented CT slices. In particular, we studied the effects of CT-superimposition depths into volumes on the performance of our models. Results: The results show that the optimal model can identify the COVID-19 slices with 99.76% accuracy (99.96% recall, 99.35% precision, and 99.65% F 1 -score). The overall performance for three-way classification obtained 99.24% accuracy and a macroaverage area under the receiver operating characteristic curve (macro-AUROC) of 0.9998. To the best of our knowledge, our method achieves the highest accuracy and recall with the largest public available COVID-19 CT dataset. Conclusions: Our model can help radiologists and physicians perform rapid diagnosis, especially when the healthcare system is overloaded.

Graphether: a reversible and high-capacity anode material for sodium-ion batteries with ultrafast directional Na-ion diffusion.

Sodium-ion batteries (SIBs) have been attracting great attention as the most promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage. However, the absence of suitable anode materials is the main bottleneck for the commercial application of SIBs. Herein, the adsorption and diffusion behaviors of Na on graphether are predicted by first-principles density functional calculations. Our results show that Na atoms can be adsorbed on graphether forming a uniform and stable coverage on both sides. Even at low intercalated Na concentrations, the semiconducting graphether can be changed to a metallic state, ensuring good electrical conductivity. Due to the structural anisotropy of graphether, the Na+ ions show a remarkable one-dimensional diffusion with an ultralow energy barrier of 0.04 eV, suggesting ultrafast charge/discharge characteristics. The graphether monolayer has a high theoretical specific capacity of 670 mA h g-1, which is much higher than commercial graphite anode materials. Furthermore, the average voltage is 1.58 V, comparable with that of commercial TiO2 anode materials for LIBs (1.5 V). During the charge/discharge process, graphether could mostly preserve the structural integrity upon the adsorption of Na even at the maximum concentration, suggesting its good reversibility. All these results show that graphether is a promising anode material for high-performance SIBs.

Metallic two-dimensional BP2: a high-performance electrode material for Li- and Na-ion batteries.

Searching for high-performance electrode materials is an important topic in rechargeable batteries. Using first-principles calculations, we systematically explore the potential application of a two-dimensional BP2 monolayer as a cathode material for Li-ion and Na-ion batteries. The pristine BP2 monolayer exhibits metallic characteristics, which facilitate the transportation of electrons. The Li and Na atoms bind strongly to the BP2 monolayer, indicating a good structural stability. Furthermore, the geometrical structure of BP2 is well maintained during the adsorption process. The Li and Na ions prefer to move along the zigzag direction with relatively low energy barriers. Especially, the ultralow Na diffusion barrier (0.03 eV) implies that monolayer BP2 has an excellent charge/discharge capability. The specific capacity and average electrode potential of Li (Na) are 619.45 (279.93) mA h g-1 and 2.89 (2.49) V, respectively. These results reveal that the BP2 monolayer is an appealing cathode material for alkali-metal batteries.

The dynamic behavior and intrinsic mechanism of CO2 absorption by amino acid ionic liquids.

Reducing carbon dioxide emissions is one of the possible solutions to prevent global climate change, which is urgently needed for the sustainable development of our society. In this work, easily available, biodegradable amino acid ionic liquids (AAILs) with great potential for CO2 absorption in the manned closed space such as spacecraft, submarines and other manned devices are used as the basic material. Molecular dynamics simulations and ab initio calculations were performed for 12 AAILs ([P4444][X] and [P66614][X], [X] = X = [GLy]-, [Im]-, [Pro]-, [Suc]-, [Lys]-, [Asp]2-), and the dynamic characteristics and the internal mechanism of AAILs to improve CO2 absorption capacity were clarified. Based on structural analysis and the analysis of interaction energy including van der Waals and electrostatic interaction energy, it was revealed that the anion of ionic liquids dominates the interaction between CO2 and AAILs. At the same time, the CO2 absorption capacity of AAILs increases in the order [Asp]2- < [Suc]- < [Lys]- < [Pro]- < [Im]- < [Gly]-. Meanwhile, the synergistic absorption of CO2 by multiple-sites of amino and carboxyl groups in the anion was proved by DFT calculations. These findings show that the anion of AAILs can be an effective factor to regulate the CO2 absorption process, which can also provide guidance for the rational and targeted molecular design of AAILs for CO2 capture, especially in the manned closed space.

Clinical and endoscopic features of esophageal tuberculosis: a 20-year retrospective study.

BACKGROUND: Tuberculosis of the esophagus is a rare clinical entity. There is a paucity of data on esophageal tuberculosis. This study aims to analyze the clinical and endoscopic features of esophageal tuberculosis over the last 20 years. METHODS: We retrospectively analyzed the data of 14 patients with esophageal tuberculosis between January 1999 to January 2019 at Nanfang Hospital. Tuberculosis was considered diagnostic if histopathological results showing epithelioid granuloma with or without caseous necrosis. Records of clinical features, imaging findings, endoscopic features and outcome of antitubercular treatment were evaluated. RESULTS: A total of 14 patients with definite esophageal tuberculosis were included. 7 patients (50%) presented with dysphagia, followed by 6 patients (42.86%) had retrosternal pain and another had cough (7.14%). On endoscopy, involvement of esophagus was observed at mid-segment mostly and findings included bulging lesions in 10 patients (71.43%), ulcer in 3 patients (21.43%), and tracheoesophageal fistula in 1 patient (7.14%). Endoscopic ultrasound showed a heterogeneous hypoechoic lesion with indistinct margins or interruption of the five layers structure of esophageal wall. Endoscopic ultrasound demonstrated mediastinal lymphadenopathy adjacent to esophageal pathology in 7/11(63.64%). Antitubercular treatment resulted in a good response with complete remission in all patients. CONCLUSIONS: Esophageal tuberculosis is rare and frequently misdiagnosed due to the lack of diagnostic signs. There needs to be a high index of clinical suspicion among patients with dysphagia or retrosternal pain. Endoscopic biopsy and endoscopic ultrasound-guided FNA can help in achieving the correct diagnosis in esophageal tuberculosis.