Gate-tunable heavy fermions in a moiré Kondo lattice.

The Kondo lattice-a matrix of local magnetic moments coupled through spin-exchange interactions to itinerant conduction electrons-is a prototype of strongly correlated quantum matter1-4. Usually, Kondo lattices are realized in intermetallic compounds containing lanthanide or actinide1,2. The complex electronic structure and limited tunability of both the electron density and exchange interactions in these bulk materials pose considerable challenges to studying Kondo lattice physics. Here we report the realization of a synthetic Kondo lattice in AB-stacked MoTe2/WSe2 moiré bilayers, in which the MoTe2 layer is tuned to a Mott insulating state, supporting a triangular moiré lattice of local moments, and the WSe2 layer is doped with itinerant conduction carriers. We observe heavy fermions with a large Fermi surface below the Kondo temperature. We also observe the destruction of the heavy fermions by an external magnetic field with an abrupt decrease in the Fermi surface size and quasi-particle mass. We further demonstrate widely and continuously gate-tunable Kondo temperatures through either the itinerant carrier density or the Kondo interaction. Our study opens the possibility of in situ access to the phase diagram of the Kondo lattice with exotic quantum criticalities in a single device based on semiconductor moiré materials2-9.

Quantum anomalous Hall effect from intertwined moiré bands.

Electron correlation and topology are two central threads of modern condensed matter physics. Semiconductor moiré materials provide a highly tuneable platform for studies of electron correlation1-12. Correlation-driven phenomena, including the Mott insulator2-5, generalized Wigner crystals2,6,9, stripe phases10 and continuous Mott transition11,12, have been demonstrated. However, non-trivial band topology has remained unclear. Here we report the observation of a quantum anomalous Hall effect in AB-stacked MoTe2 /WSe2 moiré heterobilayers. Unlike in the AA-stacked heterobilayers11, an out-of-plane electric field not only controls the bandwidth but also the band topology by intertwining moiré bands centred at different layers. At half band filling, corresponding to one particle per moiré unit cell, we observe quantized Hall resistance, h/e2 (with h and e denoting the Planck's constant and electron charge, respectively), and vanishing longitudinal resistance at zero magnetic field. The electric-field-induced topological phase transition from a Mott insulator to a quantum anomalous Hall insulator precedes an insulator-to-metal transition. Contrary to most known topological phase transitions13, it is not accompanied by a bulk charge gap closure. Our study paves the way for discovery of emergent phenomena arising from the combined influence of strong correlation and topology in semiconductor moiré materials.

Long-term monitoring chlorophyll-a concentration using HJ-1 A/B imagery and machine learning algorithms in typical lakes, a cold semi-arid region.

Chlorophyll a (Chl-a) in lakes serves as an effective marker for assessing algal biomass and the nutritional level of lakes, and its observation is feasible through remote sensing methods. HJ-1 (Huanjing-1) satellite, deployed in 2008, incorporates a CCD capable of a 30 m resolution and has a revisit interval of 2 days, rendering it a superb choice or supplemental sensor for monitoring trophic state of lakes. For effective long-term and regional-scale mapping, both the imagery and the evaluation of machine learning algorithms are essential. The several typical machine learning algorithms, i.e., Support Vector Regression (SVR), Gradient Boosting Decision Trees (GBDT), XGBoost (XGB), Random Forest (RF), K-Nearest Neighbor (KNN), Kernel Ridge Regression (KRR), and Multi-Layer Perception Network (MLP), were developed using our in-situ measured Chl-a. A cross-validation grid to identify the most effective hyperparameter combinations for each algorithm was used, as well as the selected optimal superparameter combinations. In Chl-a mapping of three typical lakes, the R2 of GBDT, XGB, RF, and KRR all reached 0.90, while XGB algorithm also exhibited stable performance with the smallest error (RMSE = 3.11 µg/L). Adjustments were made to align the Chl-a spatial-temporal patterns with past data, utilizing HJ1-A/B CCD images mapping through XGB algorithm, which demonstrates its stability. Our results highlight the considerable effectiveness and utility of HJ-1 A/B CCD imagery for evaluation and monitoring trophic state of lakes in a cold arid region, providing the application cases contribute to the ongoing efforts to monitor water qualities.

Stripe phases in WSe2/WS2 moiré superlattices.

Stripe phases, in which the rotational symmetry of charge density is spontaneously broken, occur in many strongly correlated systems with competing interactions1-11. However, identifying and studying such stripe phases remains challenging. Here we uncover stripe phases in WSe2/WS2 moiré superlattices by combining optical anisotropy and electronic compressibility measurements. We find strong electronic anisotropy over a large doping range peaked at 1/2 filling of the moiré superlattice. The 1/2 state is incompressible and assigned to an insulating stripe crystal phase. Wide-field imaging reveals domain configurations with a preferential alignment along the high-symmetry axes of the moiré superlattice. Away from 1/2 filling, we observe additional stripe crystals at commensurate filling 1/4, 2/5 and 3/5, and compressible electronic liquid crystal states at incommensurate fillings. Our results demonstrate that two-dimensional semiconductor moiré superlattices are a highly tunable platform from which to study the stripe phases and their interplay with other symmetry breaking ground states.

Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides.

We conduct a comprehensive study of three different magnetic semiconductors, CrI3, CrBr3, and CrCl3, by incorporating both few-layer and bilayer samples in van der Waals tunnel junctions. We find that the interlayer magnetic ordering, exchange gap, magnetic anisotropy, and magnon excitations evolve systematically with changing halogen atom. By fitting to a spin wave theory that accounts for nearest-neighbor exchange interactions, we are able to further determine a simple spin Hamiltonian describing all three systems. These results extend the 2D magnetism platform to Ising, Heisenberg, and XY spin classes in a single material family. Using magneto-optical measurements, we additionally demonstrate that ferromagnetism can be stabilized down to monolayer in more isotropic CrBr3, with transition temperature still close to that of the bulk.

Imaging and control of critical fluctuations in two-dimensional magnets.

Strong magnetization fluctuations are expected near the thermodynamic critical point of a continuous magnetic phase transition. Such critical fluctuations are highly correlated and in principle can occur at any time and length scales1; they govern critical phenomena and potentially can drive new phases2,3. Although critical phenomena in magnetic materials have been studied using neutron scattering, magnetic a.c. susceptibility and other techniques4-6, direct real-time imaging of critical magnetization fluctuations remains elusive. Here we develop a fast and sensitive magneto-optical imaging microscope to achieve wide-field, real-time monitoring of critical magnetization fluctuations in single-layer ferromagnetic insulator CrBr3. We track the critical phenomena directly from the fluctuation correlations and observe both slowing-down dynamics and enhanced correlation length. Through real-time feedback control of the critical fluctuations, we further achieve switching of magnetic states solely by electrostatic gating. The ability to directly image and control critical fluctuations in 2D magnets opens up exciting opportunities to explore critical phenomena and develop applications in nanoscale engines and information science.

A colorimetric aptamer-based method for detection of cadmium using the enhanced peroxidase-like activity of Au-MoS2 nanocomposites.

In this work, a colorimetric aptamer-based method for detection of cadmium using gold nanoparticles modified MoS2 nanocomposites as enzyme mimic is established. In short, biotinylated Cd2+ aptamers are immobilized by biotin-avidin binding on the bottoms of the microplate, the complementary strands of Cd2+ aptamers are connected to the Au-MoS2 nanocomposites which have the function of enhanced peroxidase-like activity. The csDNA-Au-MoS2 signal probe and target Cd2+ compete for binding Cd2+ aptamer, the color change can be observed by addition of chromogenic substrate, thereby realizing visual detection of Cd2+. The absorbance of the solution at 450 nm has a clear linear relationship with the Cd2+ concentration. The linear range is 1-500 ng/mL, and the limit of detection is 0.7 ng/mL. The assay was used to test white wine samples, the results are consistent with those of atomic absorption spectrometry; which prove that this method can be used for detection of Cd2+ in real samples.

Lin28b stimulates the reprogramming of rat Müller glia to retinal progenitors.

In lower-order vertebrates, Müller glia exhibit characteristics of retinal progenitor cells, while in higher vertebrates, such as mammals, the regenerative capacity of Müller glia is limited. Recently, we reported that Lin28b promoted the trans-differentiation of Müller cells to rod photoreceptor and bipolar cells in the retina of retinitis pigmentosa rat model, whereas it is unclear whether Lin28b can stimulate the reprogramming of Müller glia in vitro for transplantation into a damaged retina. In the present study, Long-Evens rat Müller glia were infected with Adeno-Lin28b or Adeno-GFP. Over-expression of Lin28b in isolated rat Müller glia resulted in the suppression of GFAP expression, enhancement of cell proliferation and a significant increase of the expression of retinal progenitor markers 5 days after infection. Moreover, Lin28b caused a significant reduction of the Let-7 family of microRNAs. Following sub-retinal space transplantation, Müller glia-derived retinal progenitors improved b-wave amplification of 30d Royal College of Surgeons retinitis pigmentosa model (RCS-P+) rats, as detected by electroretinography (ERG) recordings. Taken together, these data suggest that the up-regulation of Lin28b expression facilitated the reprogramming of Müller cells toward characteristics of retinal progenitors.

Laboratory Rearing of Thitarodes armoricanus and Thitarodes jianchuanensis (Lepidoptera: Hepialidae), Hosts of the Chinese Medicinal Fungus Ophiocordyceps sinensis (Hypocreales: Ophiocordycipitaceae).

Ophiocordyceps sinensis (Ophiocordycipitaceae) is an entomopathogenic fungus endemic to the Tibetan Plateau, at elevations ranging between 3,000 and 5,000 m. The fungus-insect complex is useful in healthcare but limited in the field, so there is an urgent need to develop an artificial rearing system of both the fungus and its insect hosts. Large-scale artificial rearing of the Thitarodes insect hosts is crucial. This paper reports results of the artificial cultivation and complete life tables of two host species of O. sinensis, Thitarodes armoricanus and Thitarodes jianchuanensis (Lepidoptera: Hepialidae), under low-altitude laboratory conditions. The larvae were reared on carrots in plastic containers at 9­13°C and 50­80% RH. Both experimental insect species had long and unusual life cycle; it took 263­494 and 443­780 d for T. jianchuanensis and T. armoricanus, respectively, to complete a developmental cycle, including egg, larval instars L1-L9, pupa, and adult. The larvae did develop into pupae from the L7, L8, or L9 instar larvae. Although the total survival rates of both insect species were low (12.0% for T. jianchuanensis and 1.6% for T. armoricanus), the experimental populations successfully developed into the next generation owing to high egg production by fertilized females (averages of 703 and 355 eggs per female in the Yunnan and Sichuan species, respectively). Successful artificial rearing of host insect species for O. sinensis under low temperature conditions will allow the cultivation of this important fungus-insect complex to ensure its protection as a bio-resource and for commercial supply.

Error-Triggered Adaptive Sparse Identification for Predictive Control and Its Application to Multiple Operating Conditions Processes.

With the digital transformation of process manufacturing, identifying the system model from process data and then applying to predictive control has become the most dominant approach in process control. However, the controlled plant often operates under changing operating conditions. What is more, there are often unknown operating conditions such as first appearance operating conditions, which make traditional predictive control methods based on identified model difficult to adapt to changing operating conditions. Moreover, the control accuracy is low during operating condition switching. To solve these problems, this article proposes an error-triggered adaptive sparse identification for predictive control (ETASI4PC) method. Specifically, an initial model is established based on sparse identification. Then, a prediction error-triggered mechanism is proposed to monitor operating condition changes in real time. Next, the previously identified model is updated with the fewest modifications by identifying parameter change, structural change, and combination of changes in the dynamical equations, thus achieving precise control to multiple operating conditions. Considering the problem of low control accuracy during the operating condition switching, a novel elastic feedback correction strategy is proposed to significantly improve the control accuracy in the transition period and ensure accurate control under full operating conditions. To verify the superiority of the proposed method, a numerical simulation case and a continuous stirred tank reactor (CSTR) case are designed. Compared with some state-of-the-art methods, the proposed method can rapidly adapt to frequent changes in operating conditions, and it can achieve real-time control effects even for unknown operating conditions such as first appearance operating conditions.

Identifying Hmga2 preserving visual function by promoting a shift of Müller glia cell fate in mice with acute retinal injury.

BACKGROUND: Unlike in lower vertebrates, Müller glia (MG) in adult mammalian retinas lack the ability to reprogram into neurons after retinal injury or degeneration and exhibit reactive gliosis instead. Whether a transition in MG cell fate from gliosis to reprogramming would help preserve photoreceptors is still under exploration. METHODS: A mouse model of retinitis pigmentosa (RP) was established using MG cell lineage tracing mice by intraperitoneal injection of sodium iodate (SI). The critical time point for the fate determination of MG gliosis was determined through immunohistochemical staining methods. Then, bulk-RNA and single-cell RNA seq techniques were used to elucidate the changes in RNA transcription of the retina and MG at that time point, and new genes that may determine the fate transition of MG were screened. Finally, the selected gene was specifically overexpressed in MG cells through adeno-associated viruses (AAV) in the mouse RP model. Bulk-RNA seq technique, immunohistochemical staining methods, and visual function testing were used to elucidate and validate the mechanism of new genes function on MG cell fate transition and retinal function. RESULTS: Here, we found the critical time point for MG gliosis fate determination was 3 days post SI injection. Hmga2 was screened out as a candidate regulator for the cell fate transition of MG. After retinal injury caused by SI, the Hmga2 protein is temporarily and lowly expressed in MG cells. Overexpression of Hmga2 in MG down-regulated glial cell related genes and up-regulated photoreceptor related genes. Besides, overexpressing Hmga2 exclusively to MG reduced MG gliosis, made MG obtain cone's marker, and retained visual function in mice with acute retinal injury. CONCLUSION: Our results suggested the unique reprogramming properties of Hmga2 in regulating the fate transition of MG and neuroprotective effects on the retina with acute injury. This work uncovers the reprogramming ability of epigenetic factors in MG.

Giant spin Hall effect in AB-stacked MoTe2/WSe2 bilayers.

The spin Hall effect (SHE), in which an electrical current generates a transverse spin current, plays an important role in spintronics for the generation and manipulation of spin-polarized electrons. The phenomenon originates from spin-orbit coupling. In general, stronger spin-orbit coupling favours larger SHEs but shorter spin relaxation times and diffusion lengths. However, correlated magnetic materials often do not support large SHEs. Achieving large SHEs, long-range spin transport and magnetism simultaneously in a single material is attractive for spintronics applications but has remained a challenge. Here we demonstrate a giant intrinsic SHE coexisting with ferromagnetism in AB-stacked MoTe2/WSe2 moiré bilayers by direct magneto-optical imaging. Under moderate electrical currents with density <1 A m-1, we observe spin accumulation on transverse sample edges that nearly saturates the spin density. We also demonstrate long-range spin Hall transport and efficient non-local spin accumulation that is limited only by the device size (about 10 µm). The gate dependence shows that the giant SHE occurs only near the interaction-driven Chern insulating state. At low temperatures, it emerges after the quantum anomalous Hall breakdown. Our results demonstrate moiré engineering of Berry curvature and electronic correlation for potential spintronics applications.

Adaptive Multimode Process Monitoring Based on Mode-Matching and Similarity-Preserving Dictionary Learning.

In real industrial processes, factors, such as the change in manufacturing strategy and production technology lead to the creation of multimode industrial processes and the continuous emergence of new modes. Although the industrial SCADA system has accumulated a large amount of historical data, which can be used for modeling and monitoring multimode processes to a certain extent, it is difficult for the model learned from historical data to adapt to emerging modes, resulting in the model mismatch. On the other hand, updating the model with data from new modes allows the model to continuously match the new modes, but it may cause the model to lose the ability to represent the historical modes, resulting in "catastrophic forgetting." To address these problems, this article proposed a jointly mode-matching and similarity-preserving dictionary learning (JMSDL) method, which updated the model by learning the data of new modes, so that the model can adaptively match the newly emerged modes. At the same time, a similarity metric was put forward to guarantee the representation ability of the proposed method for historical data. A numerical simulation experiment, the CSTH process experiment, and an industrial roasting process experiment indicated that the proposed JMSDL method can match new modes while maintaining its performance on the historical modes accurately. In addition, the proposed method significantly outperforms the state-of-the-art methods in terms of fault detection and false alarm rate.

Repopulated retinal microglia promote Müller glia reprogramming and preserve visual function in retinal degenerative mice.

Rationale: Müller glia (MG) play a key role in maintaining homeostasis of the retinal microenvironment. In zebrafish, MG reprogram into retinal progenitors and repair the injured retina, while this MG regenerative capability is suppressed in mammals. It has been revealed that microglia in zebrafish contribute to MG reprogramming, whereas those in mammals are over-activated during retinal injury or degeneration, causing chronic inflammation, acceleration of photoreceptor apoptosis, and gliosis of MG. Therefore, how to modulate the phenotype of microglia to enhance MG reprogramming rather than gliosis is critical. Methods: PLX3397, a colony-stimulating factor 1 receptor inhibitor, was applied to deplete microglia in the retinas of retinal degeneration 10 (rd10) mice, and withdrawal of PLX3397 was used to induce the repopulated microglia (Rep-MiG). The protective roles of the Rep-MiG on the degenerative retina were assessed using a light/dark transition test, and scotopic electroretinogram recordings. Immunofluorescence, western blot, transcriptomic sequencing, and bioinformatics analysis were performed to investigate the effects and mechanisms of microglia on MG reprogramming. Results: Following PLX3397 withdrawal, Rep-MiG replenished the entire retina with a ramified morphology and significantly improved the retinal outer nuclear layer structure, the electroretinography response, and the visual behavior of rd10 mice. Coincidentally, MG were activated, de-differentiated, and showed properties of retina progenitors in a spatial correlation with Rep-MiG. Morphological and transcriptomic analyses revealed Rep-MiG significantly enhanced protease inhibitor activity and suppressed extracellular matrix (ECM) levels during retinal degeneration. Conclusions: It suggested that Rep-MiG with the homeostasis characteristic stimulated the progenitor cell-like properties of MG, probably through regulating ECM remodeling, which protected photoreceptors and improved visual function of rd10 mice. It might be a potential protocol to reprogram MG and delay mammal retinal degeneration.

Fullerol rescues the light-induced retinal damage by modulating Müller glia cell fate.

Excessive light exposure can damage photoreceptors and lead to blindness. Oxidative stress serves a key role in photo-induced retinal damage. Free radical scavengers have been proven to protect against photo-damaged retinal degeneration. Fullerol, a potent antioxidant, has the potential to protect against ultraviolet-B (UVB)-induced cornea injury by activating the endogenous stem cells. However, its effects on cell fate determination of Müller glia (MG) between gliosis and de-differentiation remain unclear. Therefore, we established a MG lineage-tracing mouse model of light-induced retinal damage to examine the therapeutic effects of fullerol. Fullerol exhibited superior protection against light-induced retinal injury compared to glutathione (GSH) and reduced oxidative stress levels, inhibited gliosis by suppressing the TGF-ß pathway, and enhanced the de-differentiation of MG cells. RNA sequencing revealed that transcription candidate pathways, including Nrf2 and Wnt10a pathways, were involved in fullerol-induced neuroprotection. Fullerol-mediated transcriptional changes were validated by qPCR, Western blotting, and immunostaining using mouse retinas and human-derived Müller cell lines MIO-M1 cells, confirming that fullerol possibly modulated the Nrf2, Wnt10a, and TGF-ß pathways in MG, which suppressed gliosis and promoted the de-differentiation of MG in light-induced retinal degeneration, indicating its potential in treating retinal diseases.

Chinese Soil Moisture Observation Network and Time Series Data Set for High Resolution Satellite Applications.

High-quality ground observation networks are an important basis for scientific research. Here, an automatic soil observation network for high-resolution satellite applications in China (SONTE-China) was established to measure both pixel- and multilayer-based soil moisture and temperature. SONTE-China is distributed across 17 field observation stations with a variety of ecosystems, covering both dry and wet zones. In this paper, the average root mean squared error (RMSE) of station-based soil moisture for well-characterized SONTE-China sites is 0.027 m3/m3 (0.014~0.057 m3/m3) following calibration for specific soil properties. The temporal and spatial characteristics of the observed soil moisture and temperature in SONTE-China conform to the geographical location, seasonality and rainfall of each station. The time series Sentinel-1 C-band radar signal and soil moisture show strong correlations, and the RMSE of the estimated soil moisture from radar data was lower than 0.05 m3/m3 for the Guyuan and Minqin stations. SONTE-China is a soil moisture retrieval algorithm that can validate soil moisture products and provide basic data for weather forecasting, flood forecasting, agricultural drought monitoring and water resource management.

Disease-associated microglial activation prevents photoreceptor degeneration by suppressing the accumulation of cell debris and neutrophils in degenerating rat retinas.

Retinitis pigmentosa initially presents as night blindness owing to defects in rods, and the secondary degeneration of cones ultimately leads to blindness. Previous studies have identified active roles of microglia in the pathogenesis of photoreceptor degeneration in RP. However, the contribution of microglia to photoreceptor degeneration remains controversial, partly due to limited knowledge of microglial phenotypes during RP. Rationale: In this study, we investigated the pathways of microglial activation and its contribution to photoreceptor degeneration in RP. Methods: A classic RP model, Royal College of Surgeons rat, was used to explore the process of microglial activation during the development of RP. An inhibitor of colony-stimulating factor 1 receptor (PLX3397) was fed to RCS rats for sustained ablation of microglia. Immunohistochemistry, flow cytometry, RT-qPCR, electroretinography and RNA-Seq were used to investigate the mechanisms by which activated microglia influenced photoreceptor degeneration. Results: Microglia were gradually activated to disease-associated microglia in the photoreceptor layers of RCS rats. Sustained treatment with PLX3397 ablated most of the disease-associated microglia and aggravated photoreceptor degeneration, including the secondary degeneration of cones, by downregulating the expression of genes associated with photoreceptor function and components and exacerbating the impairment of photoreceptor cell function. Disease-associated microglial activation promoted microglia to engulf apoptotic photoreceptor cell debris and suppressed the increase of infiltrated neutrophils by increasing engulfment and inhibiting CXCL1 secretion by Müller cells, which provided a healthier microenvironment for photoreceptor survival. Conclusions: Our data highlight a key role of disease-associated microglia activation in the suppression of rod and cone degeneration, which reduces secondary damage caused by the accumulation of dead cells and infiltrated neutrophils in the degenerating retina.

A significant enhancement of bulk charge separation in photoelectrocatalysis by ferroelectric polarization induced in CdS/BaTiO3 nanowires.

Efficient charge separation, in particular bulk charge separation (BCS), is one of the most critical factors in determining the performance of photoelectrochemical (PEC) water-splitting. The BCS enhancement of CdS/BaTiO3 (CdS/BTO) nanowires (NWs) in photoelectrocatalysis has rarely been reported. This paper describes a remarkable PEC properties promotion of the CdS/BTO NWs, which is confirmed to be a result of the enhanced BCS efficiency induced by the ferroelectric polarization. The vertical arrays of BTO NWs endow fast transfer of carriers. Meanwhile, CdS is decorated uniformly on the surface of BTO NWs, which ensures a wide range of light absorption. After two negative polarizations, the CdS/BTO NWs have successfully obtained a remarkable photocurrent density, achieving 459.53 µA cm-2 at 1.2 V(vs.RHE), which is 2.86 times that of the unpolarized sample. However, after two positive polarizations, the photocurrent density dramatically decreases to 40.18 µA cm-2 at 1.2 V(vs.RHE), which is merely 0.25 times the original value. More importantly, the photocurrent density reaches up to a prominent value of -71.09 mA cm-2 at -0.8 V(vs.RHE) after two successive negative polarizations, which is a 40.87 mA cm-2 enhancement with respect to the sample without poling. Significantly, at -0.8 V(vs.RHE), the BCS efficiency of the CdS/BTO NWs is as high as 91.87% after two negative polarizations. The effects of ferroelectric polarization on the PEC performance of CdS/BTO NWs have been systematically studied. The results demonstrate that ferroelectric polarization, especially negative polarization, results in an internal electric field to tune band bending of CdS/BTO NWs, thus prominently enhancing the PEC performance.

Air-Stable and Layer-Dependent Ferromagnetism in Atomically Thin van der Waals CrPS4.

Ferromagnetism in two-dimensional materials presents a promising platform for the development of ultrathin spintronic devices with advanced functionalities. Recently discovered ferromagnetic van der Waals crystals such as CrI3, readily isolated two-dimensional crystals, are highly tunable through external fields or structural modifications. However, there remains a challenge because of material instability under air exposure. Here, we report the observation of an air-stable and layer-dependent ferromagnetic (FM) van der Waals crystal, CrPS4, using magneto-optic Kerr effect microscopy. In contrast to the antiferromagnetic (AFM) bulk, the FM out-of-plane spin orientation is found in the monolayer crystal. Furthermore, alternating AFM and FM properties observed in even and odd layers suggest robust antiferromagnetic exchange interactions between layers. The observed ferromagnetism in these crystals remains resilient even after the air exposure of about a day, providing possibilities for the practical applications of van der Waals spintronics.

Competitive HRP-Linked Colorimetric Aptasensor for the Detection of Fumonisin B1 in Food based on Dual Biotin-Streptavidin Interaction.

Fumonisin B1 (FB1) is the most prevalent and toxic form among fumonisin homologues which are produced by fusarium species and it contaminates various types of food products, posing serious health hazards for humans and animals. In this work, a colorimetric assay for the detection of FB1 has been developed based on competitive horseradish peroxidase (HRP)-linked aptamer and dual biotin-streptavidin interaction. In short, a biotinylated aptamer of FB1 was immobilized on the microplate by biotin-streptavidin binding; the complementary strand (csDNA) of the aptamer was ligated with HRP by biotin-streptavidin binding again to form a csDNA-HRP sensing probe, competing with FB1 to bind to the aptamer. The color change can be observed after the addition of chromogenic and stop solution, thereby realizing the visual detection of FB1. Under optimal conditions, good linearity was observed within the concentration range of 0.5 to 300 ng/mL, with a detection of limit of 0.3 ng/mL. This assay is further validated by spike recovery tests towards beer and corn samples, it provides a simple, sensitive and reliable method for the screening of FB1 in food samples and may be potentially used as an alternative to conventional assays.