Recent progress on fabrication and flat-band physics in 2D transition metal dichalcogenides moiré superlattices

Moiré superlattices are formed when overlaying two materials with a slight mismatch in twist angle or lattice constant. They provide a novel platform for the study of strong electronic correlations and non-trivial band topology, where emergent phenomena such as correlated insulating states, unconventional superconductivity, and quantum anomalous Hall effect are discovered. In this review, we focus on the semiconducting transition metal dichalcogenides(TMDs) based moiré systems that host intriguing flat-band physics. We first review the exfoliation methods of two-dimensional materials and the fabrication technique of their moiré structures. Secondly, we overview the progress of the optically excited moiré excitons, which render the main discovery in the early experiments on TMD moiré systems. We then introduce the formation mechanism of flat bands and their potential in the quantum simulation of the Hubbard model with tunable doping, degeneracies, and correlation strength. Finally, we briefly discuss the challenges and future perspectives of this field.

Hydration Characteristics and Mechanical Properties of Cement-Based Materials Modified by Calcined Zeolite and Montmorillonite

Montmorillonite and clinoptilolite zeolite were used as representative materials to prepare calcined clay-cement binary cementitious materials in order to study the effect of calcination treatment on the activation of clay minerals and the activity difference between layered and framed clays in this research.The influence of different calcined clay content(2%,4%,6%,8%,10%)on the fluidity,compressive strength,microstructure,phase change,and hydration heat of cement-based materials were analyzed.The calcined clay improves the fluidity of cement-based materials as compared with the uncalcined group.The addition of calcined montmorillonite(CMT)improves the development of mechanical strength,and the optimal compressive strength reaches 85 MPa at 28 days with 8%CMT.However,the activity of calcined clinoptilolite zeolite(CZL)is weak with few reaction sites,which slightly reduced the mechanical strength as compared to the blank sample.The addition of CMT changes the microscopic morphology of hydration products such as C-S-H and C-A-H,leading to the formation and transformation of ettringite in the early stage.It promotes the gradual polymerization of Si-O bonds into Si-O-Si bonds simultaneously,which accelerates the early hydration process.However,CZL acts mainly as a filling function in the cementitious system.In brief,CMT as an admixture can improve the mechanical properties of cement,but CZL has little effect.This work provides a guideline for the applications of calcined clay in cement,considering the influence of clay type on workability and mechanical strength.

Evaluation Model of Rural Drinking Water Project Based on Entropy Weight and Fuzzy Comprehensive Evaluation Method

Based on Measures for Assessment of Rural Drinking Water Standard Raising Action in Zhejiang Province,this study established an evaluation system for rural drinking water project in Zhejiang Province,covering three primary indicators of project construction,project management and project performance,and 18 secondary indicators.It proposed an evaluation model based on entropy weight and fuzzy evaluation method.It solved the problems of the objectivity of the indicator weight and the quantification of the indicators,and can well achieve the coordination and unity of fuzziness and accuracy.Using this model,it evaluated a rural drinking water project in a county and concluded that both accuracy and feasibility of the model are high.

保卫细胞中ABA信号调控机制研究进展

脱落酸(ABA)具有调节植物快速响应逆境的重要功能。植物细胞中ABA核心信号通路由ABA受体PYR1/PYLs/RCARs、A类碱性蛋白磷酸酶PP2Cs和Snf1相关蛋白激酶SnRK2s组成。活性氧(ROS)和Ca^(2+)是保卫细胞中的重要第二信使,调控ABA诱导的气孔关闭。该文对保卫细胞中核心ABA信号蛋白的调控以及ROS和Ca^(2+)介导的ABA信号转导等最新研究成果进行综述,旨在阐明保卫细胞中ABA信号调控机制。

Dietary ferulic acid and vanillic acid on inflammation,gut barrier function and growth performance in lipopolysaccharide-challenged piglets

Ferulic acid(FA)and vanillic acid(VA)are considered as major phenolic metabolites of cyanidin 3-glucoside,a polyphenol that widely exists in plants that possess a protective effect against oxidative stress and inflammation in our previous study.This study aimed to investigate the effect of FA and VA on inflammation,gut barrier function,and growth performance in a weaned piglet model challenged with lipopolysaccharide(LPS).Thirty-six piglets(PIC 337×C48,28 d of age)were randomly allocated into 3 treatments with 6 replicate pens(2 piglets per pen).They were fed with a basal diet or a diet containing 4,000 mg/kg of FA or VA.Dietary supplementation of VA significantly increased average daily gain(ADG)(P<0.05).Both FA and VA decreased serum levels of thiobarbituric acid reactive substances(TBARS),interlukin(IL)-1β,IL-2,IL-6,and tumor necrosis factor(TNF)-α(P<0.05),and enhanced the expression of tight junction protein oclaudin(P<0.05).Analysis of gut microbiota indicated that both FA and VA increased the Firmicutes/Bacteroidetes ratio alongside reducing the relative abundance of the Prevotellaceae family including Prevotella 9 and Prevotella 2 genera,but enriched the Lachoiraceaea family including the Lachnospiraceae FCS020 group(P<0.05).Moreover,VA reduced the relative abundance of Prevotella 7 and Prevotella 1 but enriched Lachnospira,Eubacterium eligens group,and Eubacterium xylanophilum group(P<0.05),while FA showed a limited effect on these genera.The results demonstrated that both VA and FA could alleviate inflammation and oxidative stress,but only VA has a significant positive effect on the growth performance of LPS-challenged piglets potentially through modulating gut microbiota.

Short-term Transmission Maintenance Scheduling Considering Network Topology Optimization

With the increasing penetration of renewable energy sources,transmission maintenance scheduling(TMS)will have a larger impact on the accommodation of wind power.Meanwhile,the more flexible transmission network topology owing to the network topology optimization(NTO)technique can ensure the secure and economic operation of power systems.This paper proposes a TMS model considering NTO to decrease the wind curtailment without adding control devices.The problem is formulated as a two-stage stochastic mixed-integer programming model.The first stage arranges the maintenance periods of transmission lines.The second stage optimizes the transmission network topology to minimize the maintenance cost and system operation in different wind speed scenarios.The proposed model cannot be solved efficiently with off-theshelf solvers due to the binary variables in both stages.Therefore,the progressive hedging algorithm is applied.The results on the modified IEEE RTS-79 system show that the proposed method can reduce the negative impact of transmission maintenance on wind accommodation by 65.49%,which proves its effectiveness.

InSe/hBN/graphite heterostructure for high-performance 2D electronics and flexible electronics

Two-dimensional(2D)materials as channel materials provide a promising alternative route for future electronics and flexible electronics,but the device performance is affected by the quality of interface between the 2D-material channel and the gate dielectric.Here we demonstrate an indium selenide(lnSe)/hexagonal boron nitride(hBN)/graphite heterostructure as a 2D field-effect transistor(FET),with InSe as channel material,hBN as dielectric,and graphite as gate.The fabricated FETs feature high electron mobility up to 1,146 cm2·V^-1·s^-1 at room temperature and on/off ratio up to 1010 due to the atomically flat gate dielectric.Integrated digital inverters based on InSe/hBN/graphite heterostructures are constructed by local gating modulation and an ultrahigh voltage gain up to 93.4 is obtained.Taking advantages of the mechanical flexibility of these materials,we integrated the heterostructured InSe FET on a flexible substrate,exhibiting little modification of device performance at a high strain level of up to 2%.Such high-performance heterostructured device configuration based on 2D materials provides a new way for future electronics and flexible electronics.

设计二维有序原子微晶结构构建离子筛分通道

具有原子级厚度的物质选择传输固态通道可广泛应用于分离于能量转换过程.决定这种通道选择性的几个关键因素有通道的密度、高度、间距以及边界结构.然而,目前这种拥有原子级精度的微小限域通道仅限于微型二维晶体条带构建的概念原型器件中.本文报道了一种通过化学气相沉积法设计制备大面积、高有序的单层石墨烯微晶阵列结构.通过一种改进的各向异性刻蚀过程,可以大面积控制石墨烯微晶阵列的尺寸、形貌、间距以及边界结构.这种阵列结构可以作为支柱支撑起平滑的单晶石墨烯薄膜,从而构筑连续的埃米级(3.4A)通道.该通道能选择性通过水分子并阻挡水合离子的通过,在离子筛分和纳米过滤方面具有应用潜力.

Generating scattering dark states through the Fano interference between excitons and an individual silicon nanogroove

Effective interactions between excitons and resonating nanocavities are important for many emerging applications in nanophotonics.Although plasmonic nanocavities are considered promising substitutes for diffraction-limited dielectric microcavities,their practical applications are hindered by large ohmic loss and Joule heating.Other than plasmonic materials,highrefractive-index dielectric nanocavities is a new way to trap light in subwavelength scales.However,studies on the interaction between dielectric nanocavities and excitons are still scarce.Here,for the first time,we demonstrate that the Fano interference between molecular excitons and an individual silicon nanogroove can generate scattering dark modes.By placing J-aggregate excitons into a silicon nanogroove,the leaky magnetic resonant modes filling in the groove can tailor their scattering directivity and reduce the uncoupled radiation decay in a specific direction.This unidirectional‘dark state’brings a new approach to tailor the interaction between excitons and nanocavities without large near-field enhancement.By adjusting the resonant modes,the scattering spectra can change from a Fano asymmetric line shape to a significantly suppressed scattering dip.These findings indicate that silicon nanogrooves can provide a platform for integrated on-chip silicon–exciton hybrid optical systems in the future.