Anomalous open orbits in Hofstadter spectrum of Chern insulator

The nontrivial band topology can influence the Hofstadter spectrum. We investigate the Hofstadter spectrum for various models of Chern insulators under a rational flux $\frac{\phi_{0}}{q}$, here $\phi_{0}=\frac{h}{e}$ and $q$ being an integer. We find two major features. First, the number of splitting subbands is $|q-C|$ with Chern number $C$. Second, the anomalous open-orbit subbands with Chern numbers $q-1$ and $-q-1$ emerge, which are beyond the parameter window $(-q/2,q/2)$ of the Diophantine equation studied by Thouless-Kohmoto-Nightingale-den Nijs [Phys. Rev. Lett. \textbf{49}, 405 (1982)]. These two findings are explained by semiclassical dynamics. We propose that the number of splitting subbands can be utilized to determine Chern number in cold atom systems, and the open-orbit subbands can provide routes to study exotic features beyond the Landau level physics

Disorder effects on quantum transport and quantum phase transition in low-dimensional superconducting and topological systems

Disorder effects inevitably exist in realistic samples, manifesting in various physical properties. In this paper, we review the recent progress in understanding the disorder effects on quantum transport and quantum phase transition properties in low-dimensional superconducting and topological systems. As a consequence of the pronounced quantum fluctuation in low-dimensional systems, rare events drastically change the physical characteristics and underlying microscopic transport process in these systems, which are beyond the traditional paradigms. Associating with recent experimental observations, we emphasize the microscopic mechanism for disordered Ising superconductivity, the quantum Griffiths singularity of superconductor metal transition and the discrete scale invariance in topological materials

Nature of support plays vital roles in H2O promoted CO oxidation over Pt catalysts

Pt nanoparticle catalysts supported on a series of TiO2-SiO2 composites with different molar ratios were prepared, characterized, and their CO oxidation activities were evaluated under dry and humid condi-tions. Among the catalysts, Pt/1Ti-3Si showed the best performance under both conditions and potentials for future industrial applications. H218O experiments were designed and the CO2 composition was calcu-lated to quantify the promotion effect of H2O, which was highly correlated with the concentration of H2O and Ti-Si ratio. The XRD, XPS and BET results revealed that the defects on the supports inhibited phase transformation and lattice growth for anatase TiO2. These defects also led to an increase in the number of acid sites on Pt/TiO2-SiO2. The TEM, EDS mapping, and CO chemosorption results indicated that metal-lic Pt0 particles were formed, which was beneficial for CO oxidation during reaction. It was found that the generation of OH from H2O dissociation and the desorption of OH on TiO2 were much easier than those on SiO2, illustrating that the H2O promotion effect could be controlled by regulating the nature of support. The mechanism of H2O promotion was proposed by experimental and theoretical methods, which con-firmed the carboxyl intermediate pathway rather than the formate pathway.(c) 2022 Elsevier Inc. All rights reserved

UAV Autonomous Tracking and Landing Based on Deep Reinforcement Learning Strategy

Unmanned aerial vehicle (UAV) autonomous tracking and landing is playing an increasingly important role in military and civil applications. In particular, machine learning has been successfully introduced to robotics-related tasks. A novel UAV autonomous tracking and landing approach based on a deep reinforcement learning strategy is presented in this paper, with the aim of dealing with the UAV motion control problem in an unpredictable and harsh environment. Instead of building a prior model and inferring the landing actions based on heuristic rules, a model-free method based on a partially observable Markov decision process (POMDP) is proposed. In the POMDP model, the UAV automatically learns the landing maneuver by an end-to-end neural network, which combines the Deep Deterministic Policy Gradients (DDPG) algorithm and heuristic rules. A Modular Open Robots Simulation Engine (MORSE)-based reinforcement learning framework is designed and validated with a continuous UAV tracking and landing task on a randomly moving platform in high sensor noise and intermittent measurements. The simulation results show that when the moving platform is moving in different trajectories, the average landing success rate of the proposed algorithm is about 10% higher than that of the Proportional-Integral-Derivative (PID) method. As an indirect result, a state-of-the-art deep reinforcement learning-based UAV control method is validated, where the UAV can learn the optimal strategy of a continuously autonomous landing and perform properly in a simulation environment

Nature of support plays vital roles in H2O promoted CO oxidation over Pt catalysts

Pt nanoparticle catalysts supported on a series of TiO2-SiO2 composites with different molar ratios were prepared, characterized, and their CO oxidation activities were evaluated under dry and humid condi-tions. Among the catalysts, Pt/1Ti-3Si showed the best performance under both conditions and potentials for future industrial applications. H218O experiments were designed and the CO2 composition was calcu-lated to quantify the promotion effect of H2O, which was highly correlated with the concentration of H2O and Ti-Si ratio. The XRD, XPS and BET results revealed that the defects on the supports inhibited phase transformation and lattice growth for anatase TiO2. These defects also led to an increase in the number of acid sites on Pt/TiO2-SiO2. The TEM, EDS mapping, and CO chemosorption results indicated that metal-lic Pt0 particles were formed, which was beneficial for CO oxidation during reaction. It was found that the generation of OH from H2O dissociation and the desorption of OH on TiO2 were much easier than those on SiO2, illustrating that the H2O promotion effect could be controlled by regulating the nature of support. The mechanism of H2O promotion was proposed by experimental and theoretical methods, which con-firmed the carboxyl intermediate pathway rather than the formate pathway.(c) 2022 Elsevier Inc. All rights reserved

(111)-Oriented crystalline plane MnO loaded by biomass carbon separator to facilitate sulfur redox kinetics in lithium–sulfur batteries

Lithium-sulfur batteries have gained widespread attention due to their high theoretical energy density. However, the insulating properties of the charge–discharge products and slow kinetic transformation result in poor rate performance of these batteries. To address this issue, a study utilized Density-functional theory calculations to predict the formation of MnO on biochar derived from Phragmites australis. Additionally, the study investigated the adsorption energy and catalytic ability of MnO with different crystal planes for lithium polysulfide. Notably, the MnO (111) crystal plane exhibited the highest chemical adsorption energy. The study also analyzed the anchoring and catalytic method of lithium polysulfides. Furthermore, advanced analytical methods were employed to examine the structure and morphology of biomass carbon loaded with MnO, and a separator made from MnO-loaded biomass carbon was developed for use in Li-S batteries. The findings indicate that the separator substantially enhances the kinetic reaction, resulting in exceptional rate performance

The Relationship between Oxygen Permeability and Phase Separation Morphology of the Multicomponent Silicone Hydrogels

In this article, the multicomponent copolymers were prepared by the copolymerization of two hydrophobic silicon-containing monomers bis­(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris­(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers 2-hydroxyethyl methacrylate, <i>N</i>-vinylpyrrolidone, and <i>N</i>,<i>N</i>-dimethyl acrylamide. The copolymers were hydrated to form transparent silicone hydrogels. The oxygen permeability coefficients (Dk) of hydrogels were measured, and their relationships with the equilibrium water contents (EWC) and the types and contents of silicon containing monomers as well as the phase separation structures of silicone hydrogels were analyzed in detail. The results showed that the EWC decreased as the increase of SiMA content. The relationship between Dk and SiMA content, as well as that between Dk and EWC, showed inverted bell curve distributions, which meant two main factors, i.e., silicon–oxygen bond in silicone and water in hydrogel, contributed to oxygen permeation and followed a mutual inhibition competition mechanism. The internal morphologies of the hydrogels were observed by transmission electron microscope, and the results showed that the hydrogels presented two different phase separation structures depending on the types of the silicon-containing monomers. The silicone phase in SiMA containing hydrogel presented to be a granular texture, while the silicone phase in TRIS containing hydrogel formed a fibrous texture which resulted in a higher Dk value. These results could help to design a silicone hydrogel with better properties and wider application

Lattice distortion SnS2 piezoelectric self-Fenton system for efficient degradation and detoxification of pollutants

Abstract Both piezoelectricity and self-Fenton catalysis are effective ways to degrade water pollution, but little research has combined them to construct a more efficient water pollution treatment method. Here, a Fe-doped SnS2 (Sn1-xFexS2) piezoelectric self-Fenton system was constructed, which shows superior water treatment performance. The best piezoelectric properties of the Sn0.97Fe0.03S2 system were verified by degrading rhodamine B (RhB). The toxicity analysis of degradation intermediates and solutions confirmed that the toxicity of RhB decreased after degradation. In addition, Kelvin probe force microscopy and photoelectrochemical analysis confirmed the better piezoelectric properties of Sn0.97Fe0.03S2. It has demonstrated the enhancement of systematic piezoelectricity by Fe lattice defects and the formation of self-Fenton by Fe as an active center in the degradation of RhB. In this work, an efficient piezoelectric and self-Fenton technology is constructed to remove organic pollutants from water, which is significant for developing water treatment technology

Causal effects of gut microbiome on HIV infection: a two-sample mendelian randomization analysis

Abstract Background The causal association between gut microbiome and HIV infection remains to be elucidated. We conducted a two-sample mendelian randomization analysis to estimate the causality between gut microbiome and HIV infection. Methods Publicly released genome-wide association studies summary data were collected to perform the mendelian analysis. The GWAS summary data of gut microbiome was retrieved from the MiBioGen consortium, which contains 18 340 samples from 24 cohorts. GWAS summary data of HIV infection was collected from the R5 release of FinnGen consortium, including 357 HIV infected cases and 218 435 controls. The SNPs were selected as instrumental variables according to our selection rules. And SNPs with a F-statistics less than ten were regarded as weak instrumental variables and excluded. Mendelian randomization analysis was conducted by five methods, including inverse variance weighted (IVW), MR-Egger, weighted median, weighted mode, and simple mode. The Cochran’s Q test and MR-Egger intercept test were performed to identify heterogeneity and pleiotropy. Leave-one-out analysis were used to test the sensitivity of the results. Results Fifteen gut microbiota taxa showed causal effects on HIV infection according to the MR methods. Four taxa were observed to increase the risk of HIV infection, including Ruminococcaceae (OR: 2.468[1.043, 5.842], P: 0.039), Ruminococcaceae UCG005 (OR: 2.051[1.048, 4.011], P: 0.036), Subdoligranulum (OR: 3.957[1.762, 8.887], P < 0.001) and Victivallis (OR: 1.605[1.012, 2.547], P=0.044). Erysipelotrichaceae was protective factor of HIV infection (OR: 0.278[0.106, 0.731], P < 0.001) and Methanobrevibacter was also found to be associated with reduced risk of HIV infection (OR: 0.509[0.265, 0.980], P=0.043). Horizontal pleiotropy was found for Fusicatenibacter (P<0.05) according to the MR-Egger regression intercept analysis. No heterogeneity was detected. Conclusion Our results demonstrate significant causal effects of gut microbiome on HIV infection. These findings facilitate future studies to develop better strategies for HIV prophylaxis through gut microbiome regulation. Further explorations are also warranted to dissect the mechanism of how gut microbiome affects HIV susceptibility

Catalytic deoxygenation of carboxyl compounds in the hydrothermal liquefaction crude bio-oil via in-situ hydrogen supply by CuO-CeO2/gamma-Al2O3 catalyst

Hydrothermal liquefaction (HTL) has drawn great attention as a potential method to produce bio-oil from biomass waste. However, bio-crude from HTL shows undesired high-oxygen content and needs further deoxygenation upgrading. Herein, stearic acids as a model carboxylic compounds in HTL bio-crude was employed to investigate catalytic deoxygenation performance. Results showed that (CuO)(10)-CeO2/gamma-Al2O3 had the most superior catalytic deoxygenation performance for the stearic acids. The maximum stearic acid conversion rate (96.36%) and total hydrocarbon yield (88.79%) were obtained at 300 degrees C, 12 h, ratio of stearic acid to water 1 : 4. The main catalytic deoxygenation pathways were proposed: carbon monoxide generation (decarbonylation) - in-situ hydrogen generation (water-gas shift) - short-chain fatty acid generation (hydrogenolysis) - n-alkanes generation (decarboxylation, hydrodeoxygenation and hydrogenation). DFT calculation elucidated that CuO-CeO2 reduced the activation energy from 24.8 kcal mol(-1) (vacuum) to 15.0 kcal mol(-1) (catalytic). Thus, deoxygenation via CuO-CeO2/gamma-Al2O3 would be an effective method for upgrading HTL bio-crude