Quantum geometry quadrupole-induced third-order nonlinear transport in antiferromagnetic topological insulator MnBi2Te4.

The study of quantum geometry effects in materials has been one of the most important research directions in recent decades. The quantum geometry of a material is characterized by the quantum geometric tensor of the Bloch states. The imaginary part of the quantum geometry tensor gives rise to the Berry curvature while the real part gives rise to the quantum metric. While Berry curvature has been well studied in the past decades, the experimental investigation on the quantum metric effects is only at its infancy stage. In this work, we measure the nonlinear transport of bulk MnBi2Te4, which is a topological anti-ferromagnet. We found that the second order nonlinear responses are negligible as required by inversion symmetry, the third-order nonlinear responses are finite. The measured third-harmonic longitudinal ( V x x 3 ω ) and transverse ( V x y 3 ω ) voltages with frequency 3 ω , driven by an a.c. current with frequency ω , show an intimate connection with magnetic transitions of MnBi2Te4 flakes. Their magnitudes change abruptly as MnBi2Te4 flakes go through magnetic transitions from an antiferromagnetic state to a canted antiferromagnetic state and to a ferromagnetic state. In addition, the measured V x x 3 ω is an even function of the applied magnetic field B while V x y 3 ω is odd in B. Amazingly, the field dependence of the third-order responses as a function of the magnetic field suggests that V x x 3 ω is induced by the quantum metric quadrupole and V x y 3 ω is induced by the Berry curvature quadrupole. Therefore, the quadrupoles of both the real and the imaginary part of the quantum geometry tensor of bulk MnBi2Te4 are revealed through the third order nonlinear transport measurements. This work greatly advanced our understanding on the connections between the higher order moments of quantum geometry and nonlinear transport.

Nonlinear optical diode effect in a magnetic Weyl semimetal.

Diode effects are of great interest for both fundamental physics and modern technologies. Electrical diode effects (nonreciprocal transport) have been observed in Weyl systems. Optical diode effects arising from the Weyl fermions have been theoretically considered but not probed experimentally. Here, we report the observation of a nonlinear optical diode effect (NODE) in the magnetic Weyl semimetal CeAlSi, where the magnetization introduces a pronounced directionality in the nonlinear optical second-harmonic generation (SHG). We demonstrate a six-fold change of the measured SHG intensity between opposite propagation directions over a bandwidth exceeding 250 meV. Supported by density-functional theory, we establish the linearly dispersive bands emerging from Weyl nodes as the origin of this broadband effect. We further demonstrate current-induced magnetization switching and thus electrical control of the NODE. Our results advance ongoing research to identify novel nonlinear optical/transport phenomena in magnetic topological materials and further opens new pathways for the unidirectional manipulation of light.

An investigation into the effects of various processing methods on the characteristic compounds of highland barley using a widely targeted metabolomics approach.

This study explored the influence of diverse processing methods (cooking (CO), extrusion puffing (EX), and steam explosion puffing (SE), stir-frying (SF) and fermentation (FE)) on highland barley (Qingke) chemical composition using UHPLC-MS/MS based widely targeted metabolomics. Overall, 827 metabolites were identified and categorized into 16 classes, encompassing secondary metabolites, amino acids, nucleotides, lipids, etc. There 43, 85, 131, 51 and 98 differential metabolites were respectively selected from five comparative groups (raw materials (RM) vs CO/EX/SE/SF/FE), mainly involved in amino acids, nucleotides, flavonoids, and alkaloids. Compared to other treated groups, FE group possessed the higher content of crude protein (15.12 g/100 g DW), and the relative levels of free amino acids (1.32 %), key polyphenols and arachidonic acid (0.01 %). EX group had the higher content of anthocyanins (4.22 mg/100 g DW), and the relative levels of free amino acids (2.02 %) and key polyphenols. SE group showed the higher relative levels of phenolic acids (0.14 %), flavonoids (0.20 %) and alkaloids (1.17 %), but the lowest free amino acids (0.75 %). Different processing methods all decreased Qingke's antioxidant capacity, with the iron reduction capacity (988.93 µmol/100 g DW) in SE group was the lowest. On the whole, FE and EX were alleged in improving Qingke's nutritional value. CO and SF were also suitable for Qingke processing since fewer differential metabolites were identified in CO vs RM and SF vs RM groups. Differential metabolites were connected to 14 metabolic pathways, with alanine, aspartate, and glutamate metabolism being central. This study contributed theoretical groundwork for the scientific processing and quality control of Qingke products.

Nonlinear transport and radio frequency rectification in BiTeBr at room temperature.

Materials showing second-order nonlinear transport under time reversal symmetry can be used for Radio Frequency (RF) rectification, but practical application demands room temperature operation and sensitivity to microwatts level RF signals in the ambient. In this study, we demonstrate that BiTeBr exhibits a giant nonlinear response which persists up to 350 K. Through scaling and symmetry analysis, we show that skew scattering is the dominant mechanism. Additionally, the sign of the nonlinear response can be electrically switched by tuning the Fermi energy. Theoretical analysis suggests that the large Rashba spin-orbit interactions (SOI), which gives rise to the chirality of the Bloch electrons, provide the microscopic origin of the observed nonlinear response. Our BiTeBr rectifier is capable of rectifying radiation within the frequency range of 0.2 to 6 gigahertz at room temperature, even at extremely low power levels of -15 dBm, and without the need for external biasing. Our work highlights that materials exhibiting large Rashba SOI have the potential to exhibit nonlinear responses at room temperature, making them promising candidates for harvesting high-frequency and low-power ambient electromagnetic energy.

Black rice regulates lipid metabolism, liver injury, oxidative stress and adipose accumulation in high-fat/cholesterol diet mice based on gut microbiota and untargeted metabonomics.

Black rice displays a series of properties including regulating lipid metabolism and attenuating liver injury. Our study aimed to investigate the effect of Zixiangnuo black rice (ZG), peeled rice (ZPG), rice bran (ZBG) on lipid metabolism, liver inflammation, gut microbiota and metabolite profiles in high-fat/cholesterol (HFCD) diet mice. A total of five treatment groups were fed a normal control diet or a HFCD with or without Highland barley (HB) supplementation for 10 weeks. The results showed that ZBG significantly improved lipid parameters, liver function and injury and blood glucose indexes related to hyperlipidemia compared with HFCD group. ZBG recovered the disorder of gut microbiota by increasing Bacteroidetes/Firmicutes ratio and Lactobacillus abundance, and decreasing Proteobacteria abundance. ZBG enhanced the levels of six short chain fatty acids. Fecal metabolomics analysis showed that the important differential metabolites between ZBG and HFCD group were Deoxycholic acid and Myclobutanil, and metabolic pathways were Arachidonic acid metabolism and ABC transporters. Results suggested that BR or bran were effective dietary candidates to ameliorate hyperlipidemia.

Substitution Effects on the Reactivity and Thermostability of Five-Membered Ring Fluorides.

Recently, five-membered ring fluorides (c-C5Fs) have been significantly desirable in green chlorofluorocarbon substitutes due to their practically flexible application in various fields and environmental friendliness. Detailed knowledge regarding different substitution effects on their environmental properties and thermal stability is very limited due to their high-cost experiments. Here, comprehensive density functional theory and ab initio molecular dynamics calculations were performed to explore the relative electrophilic and nucleophilic reactivity and thermostability of c-C5F chemicals. The electronic properties induced by substitution effects of c-C5Fs were first explored. The environmental friendliness of c-C5Fs including 1,1,2,2,3,3-hexafluorocyclopentane (F6A), 1,1,2,2,3,3,4-heptafluorocyclopentane (F7A), cis-1,1,2,2,3,3,4,5-octafluorocyclopentane (F8A), 3,3,4,4,5,5-hexafluorocyclopentene (F6E), 1,3,3,4,4,5,5-heptafluorocyclopentene (F7E), octafluorocyclopentene (F8E), 1-chloro-3,3,4,4,5,5-hexafluorocyclopent-1-ene (F6-1), and 1-chloro-2,3,3,4,4,5,5-heptafluorocyclopent-1-ene (F7-1) was validly confirmed. Besides, their thermal stabilities at 600 K temperature were concluded due to their flexible carbon skeletons, where both in-plane stability and slight aromaticity of F6E were in peculiar found to contribute substantially. We also would like to stress the future application of F6-1 due to its significant out-plane stability. This study may pave the way for the development of chlorofluorocarbon substitutes.

Modified highland barley regulates lipid metabolism, liver inflammation and gut microbiota in high-fat/cholesterol diet mice as revealed by LC-MS based metabonomics.

Highland barley (HB) displays a series of properties including regulation of lipid metabolism and attenuation of liver injury. Our study aimed to investigate the effect of modified highland barley (MHB) including fluidized highland barley (HB-1), extruded and puffed highland barley (HB-2), and ultrafine pulverized highland barley (HB-3) on lipid metabolism, liver inflammation, gut microbiota and metabolite profiles in mice fed with a high-fat/cholesterol diet (HFCD). 6 treatment groups were fed a normal control diet or an HFCD with or without MHB supplementation for 10 weeks. Results showed that MHB significantly improved lipid parameters, liver function and injury and blood glucose indexes related to hyperlipidemia compared with the HFCD group. In addition, MHB recovered the disorder of gut microbiota by increasing the Bacteroidetes/Firmicutes ratio and Lactobacillus and Allobaculum abundances and decreasing Proteobacteria abundance related to lipid metabolism bacteria. MHB reversed the decrease of short-chain fatty acid levels caused by the HFCD. Fecal metabolomics analysis showed that the important differential metabolites between HB-1 and HFCD were deoxycholic acid, myclobutanil and dibutyl phthalate, and the important differential metabolic pathways were arachidonic acid metabolism, ABC transporters and biosynthesis of unsaturated fatty acids. Results suggested that MHB especially HB-1 were better effective dietary intervention candidates to ameliorate hyperlipidemia compared with HB.

Valley-Polarized Quantum Anomalous Hall State in Moiré MoTe_{2}/WSe_{2} Heterobilayers.

Moiré heterobilayer transition metal dichalcogenides (TMDs) emerge as an ideal system for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Nevertheless, the moiré bands in heterobilayer TMDs were believed to be topologically trivial. Recently, it was reported that both a quantum valley Hall insulating state at filling ν=2 (two holes per moiré unit cell) and a valley-polarized quantum anomalous Hall state at filling ν=1 were observed in AB stacked moiré MoTe_{2}/WSe_{2} heterobilayers. However, how the topologically nontrivial states emerge is not known. In this Letter, we propose that the pseudomagnetic fields induced by lattice relaxation in moiré MoTe_{2}/WSe_{2} heterobilayers could naturally give rise to moiré bands with finite Chern numbers. We show that a time-reversal invariant quantum valley Hall insulator is formed at full filling ν=2, when two moiré bands with opposite Chern numbers are filled. At half filling ν=1, the Coulomb interaction lifts the valley degeneracy and results in a valley-polarized quantum anomalous Hall state, as observed in the experiment. Our theory identifies a new way to achieve topologically nontrivial states in heterobilayer TMD materials.

Kramers nodal line metals.

Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.

The Relationship between Parenting Styles and Adolescents' Social Anxiety in Migrant Families: A Study in Guangdong, China.

Previous studies indicated that parenting styles were important influencing factors for the development of children's well-being. It is known that mass migration to the cities in China will affect family relations. However, few studies focused on the relationship between parenting styles and adolescents' mental health in migrant families. Thus, this study aimed to investigate how parenting styles could affect adolescent's social anxiety in migrant families. A total number of 1,345 adolescents in migrant families from four non-government-funded junior middle schools in Guangdong province formed the research sample. Parenting styles were measured using short-form of the Egna Minnen Beträffande Uppfostran, and social anxiety was evaluated using Social Anxiety Subscale of Self-Consciousness Scale. The results showed that emotional warmth, overprotection and rejection were significantly more often perceived from mothers than from fathers. Significant group differences between high social anxiety group and low social anxiety group were found in both father's rearing styles and mother's rearing styles. Furthermore, in migrant families, paternal emotional warmth could decrease adolescents' social anxiety, whereas maternal overprotection could increase it.

Surface-Enhanced Raman Scattering Active Gold Nanoparticles with Enzyme-Mimicking Activities for Measuring Glucose and Lactate in Living Tissues.

Gold nanoparticles (AuNPs) with simultaneous plasmonic and biocatalytic properties provide a promising approach to developing versatile bioassays. However, the combination of AuNPs' intrinsic enzyme-mimicking properties with their surface-enhanced Raman scattering (SERS) activities has yet to be explored. Here we designed a peroxidase-mimicking nanozyme by in situ growing AuNPs into a highly porous and thermally stable metal-organic framework called MIL-101. The obtained AuNPs@MIL-101 nanozymes acted as peroxidase mimics to oxidize Raman-inactive reporter leucomalachite green into the active malachite green (MG) with hydrogen peroxide and simultaneously as the SERS substrates to enhance the Raman signals of the as-produced MG. We then assembled glucose oxidase (GOx) and lactate oxidase (LOx) onto AuNPs@MIL-101 to form AuNPs@MIL-101@GOx and AuNPs@MIL-101@LOx integrative nanozymes for in vitro detection of glucose and lactate via SERS. Moreover, the integrative nanozymes were further explored for monitoring the change of glucose and lactate in living brains, which are associated with ischemic stroke. The integrative nanozymes were then used to evaluate the therapeutic efficacy of potential drugs (such as astaxanthin for alleviating cerebral ischemic injuries) in living rats. They were also employed to determine glucose and lactate metabolism in tumors. This study not only demonstrated the great promise of combining AuNPs' multiple functionalities for versatile bioassays but also provided an interesting approach to designing nanozymes for biomedical and catalytic applications.

Microscopic phase-shifting profilometry based on digital micromirror device technology.

A microscopic three-dimensional (3-D) shape measurement system based on digital fringe projection has been developed and experimentally investigated. A Digital Micromirror Device along with its illumination optics is integrated into a stereomicroscope, which projects computer-generated fringe patterns with a sinusoidal intensity profile through the microscope objective onto the object surface being measured. The fringe patterns deformed by the object surface are recorded by a CCD camera. The microscopic 3-D shape of the object surface is measured and reconstructed by use of a phase-shifting technique. We discuss design considerations and error analysis of the system. Experimental results successfully demonstrate the capability of this technique for surface profile measurement of rough surfaces at the micrometer level.