Fractional quantum anomalous Hall effect in multilayer graphene.

The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect1 at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking2-6. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation7-9. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2 (refs. 10-13). Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. Here we report the observation of integer and fractional QAH effects in a rhombohedral pentalayer graphene-hBN moiré superlattice. At zero magnetic field, we observed plateaus of quantized Hall resistance [Formula: see text] at v = 1, 2/3, 3/5, 4/7, 4/9, 3/7 and 2/5 of the moiré superlattice, respectively, accompanied by clear dips in the longitudinal resistance Rxx. Rxy equals [Formula: see text] at v = 1/2 and varies linearly with v, similar to the composite Fermi liquid in the half-filled lowest Landau level at high magnetic fields14-16. By tuning the gate-displacement field D and v, we observed phase transitions from composite Fermi liquid and FQAH states to other correlated electron states. Our system provides an ideal platform for exploring charge fractionalization and (non-Abelian) anyonic braiding at zero magnetic field7-9,17-19, especially considering a lateral junction between FQAHE and superconducting regions in the same device20-22.

Orbital multiferroicity in pentalayer rhombohedral graphene.

Ferroic orders describe spontaneous polarization of spin, charge and lattice degrees of freedom in materials. Materials exhibiting multiple ferroic orders, known as multiferroics, have important parts in multifunctional electrical and magnetic device applications1-4. Two-dimensional materials with honeycomb lattices offer opportunities to engineer unconventional multiferroicity, in which the ferroic orders are driven purely by the orbital degrees of freedom and not by electron spin. These include ferro-valleytricity corresponding to the electron valley5 and ferro-orbital-magnetism6 supported by quantum geometric effects. These orbital multiferroics could offer strong valley-magnetic couplings and large responses to external fields-enabling device applications such as multiple-state memory elements and electric control of the valley and magnetic states. Here we report orbital multiferroicity in pentalayer rhombohedral graphene using low-temperature magneto-transport measurements. We observed anomalous Hall signals Rxy with an exceptionally large Hall angle (tanΘH > 0.6) and orbital magnetic hysteresis at hole doping. There are four such states with different valley polarizations and orbital magnetizations, forming a valley-magnetic quartet. By sweeping the gate electric field E, we observed a butterfly-shaped hysteresis of Rxy connecting the quartet. This hysteresis indicates a ferro-valleytronic order that couples to the composite field E · B (where B is the magnetic field), but not to the individual fields. Tuning E would switch each ferroic order independently and achieve non-volatile switching of them together. Our observations demonstrate a previously unknown type of multiferroics and point to electrically tunable ultralow-power valleytronic and magnetic devices.

Cascaded compression of size distribution of nanopores in monolayer graphene.

Monolayer graphene with nanometre-scale pores, atomically thin thickness and remarkable mechanical properties provides wide-ranging opportunities for applications in ion and molecular separations1, energy storage2 and electronics3. Because the performance of these applications relies heavily on the size of the nanopores, it is desirable to design and engineer with precision a suitable nanopore size with narrow size distributions. However, conventional top-down processes often yield log-normal distributions with long tails, particularly at the sub-nanometre scale4. Moreover, the size distribution and density of the nanopores are often intrinsically intercorrelated, leading to a trade-off between the two that substantially limits their applications5-9. Here we report a cascaded compression approach to narrowing the size distribution of nanopores with left skewness and ultrasmall tail deviation, while keeping the density of nanopores increasing at each compression cycle. The formation of nanopores is split into many small steps, in each of which the size distribution of all the existing nanopores is compressed by a combination of shrinkage and expansion and, at the same time as expansion, a new batch of nanopores is created, leading to increased nanopore density by each cycle. As a result, high-density nanopores in monolayer graphene with a left-skewed, short-tail size distribution are obtained that show ultrafast and ångström-size-tunable selective transport of ions and molecules, breaking the limitation of the conventional log-normal size distribution9,10. This method allows for independent control of several metrics of the generated nanopores, including the density, mean diameter, standard deviation and skewness of the size distribution, which will lead to the next leap in nanotechnology.

Rapid synthesis of BaMoO4 :Eu3+ red phosphors using microwave irradiation.

This study synthesized BaMoO4:Eu3+ red phosphors using the microwave method. In addition, the phase composition, morphology, and luminescence properties of the red phosphors were characterized using X-ray diffraction, field-scanning electron microscopy, and photoluminescence spectroscopy. The results revealed that doping red phosphors with different concentrations of Eu3+ does not change the crystal structure of the matrix material. The BaMoO4 :Eu3+ phosphors exhibited micron-scale irregular polyhedra, which could be excited by ultraviolet light with a wavelength of 395 nm to induce red-light emission. The optimal dosage of Eu3+ was 0.08, and the chromaticity coordinates of BaMoO4 :0.08Eu3+ phosphors were (0.5869, 0.3099). White light-emitting diode (w-LED) devices manufactured by using a combination of BaMoO4 :0.08Eu3+ phosphor and commercially available phosphors exhibited good white-light emission under the excitation of an ultraviolet chip. The BaMoO4 :0.08Eu3+ red phosphors that rapidly synthesized under the microwave field are expected to be used in w-LED devices.

Medial Plantar Fasciocutaneous Flap Reconstruction for Load-Bearing Foot Defects in Patients With Acral Melanoma.

BACKGROUND: Acral lentiginous melanoma (ALM) is a rare subtype of malignant melanoma that usually involves the weight-bearing plantar area. Plantar defect reconstruction has traditionally been performed with skin grafts or free flaps. This study examined the efficacy and safety of a medial plantar artery perforator flap (MPAPF) for plantar defect reconstruction after wide excision of an ALM. METHOD: Twenty-five patients who underwent reconstruction with a MPAPF between 2011 and 2021 were enrolled in this study. The defects were classified into 6 plantar zones. Demographic and clinical data were retrospectively analyzed. RESULTS: Reconstruction with medial plantar fasciocutaneous island flaps was performed in all cases, except for 4 patients who had lesions in forefoot, which required free medial plantar flaps. Defects in lateral and posterior heel were more likely to present with venous congestion and require longer healing times and revision surgery (P < 0.05). The average follow-up period was 49 months. Four and 5 patients developed local recurrence and distant metastasis, respectively. Four cases of hyperkeratosis and paresthesia were documented, but there were no cases of ulceration or wound dehiscence. None of the cases required secondary debulking procedures. CONCLUSIONS: The MPAPF is safe and effective for plantar defect reconstruction among patients with ALM. Meticulous dissection and adequate tunneling are needed, particularly for defects in the lateral and posterior heel, to minimize flap congestion and revision operations.

[Efficacy Evaluation of Three Endoscopic Therapies of Isolated Gastric Varices with Modified Tissue Adhesive].

Objective: To evaluate the efficacy of three endoscopic therapies of isolated gastric varices (IGV) with modified tissue adhesive. Methods: A retrospective analysis was conducted with the clinical data of 73 IGV patients who were treated between January 2008 and December 2019 at Beijing Ditan Hospital. Patient clinical data on age, sex, etiology, biochemistry findings, Child-Pugh classification, the type of spontaneous shunt, preoperative bleeding history, and the presence or absence of liver cancer were collected. The three therapies evaluated were endoscopic intravenous injection of tissue glue combined with lauromacrogol, endoscopic clip-assisted intravenous injection of tissue glue combined with lauromacrogol, and endoscopic clip and LOOP-assisted intravenous injection of tissue glue combined with lauromacrogol. Their respective clinical treatment outcomes, including ectopic embolism rate, survival rate, rebleeding rate, amount of lauromacrogol and tissue glue used, the number of endoscopic clips used, and the number of times of the procedure the patient underwent, were evaluated. Results: In the patient baseline data, Child-Pugh grade, preoperative thrombus formation, and the presence or absence of liver cancer, showed significant difference between the three therapies ( P<0.05). There was no significant difference in the rates of ectopic embolism among the three methods ( P>0.05), but no ectopic embolism occurred after endoscopic clip-assisted intravenous injection of tissue glue combined with lauromacrogol, or after endoscopic clip and LOOP-assisted intravenous injection of tissue glue combined with lauromacrogol. There was no significant difference in the survival rate, the rebleeding rate, amount of lauromacrogol and tissue glue used for the three therapies, but there was significant difference in the number of endoscopic clips used and the number of times the procedure was conducted within one year ( P<0.05). Conclusion: The two endoscopic therapies of intravenous injection of modified tissue glue, one assisted by clip and the other assisted by clip and LOOP, can help reduce the number of procedures IGV patients undergo within one year.

Accurate Measurement of the Gap of Graphene/h-BN Moiré Superlattice through Photocurrent Spectroscopy.

Monolayer graphene aligned with hexagonal boron nitride (h-BN) develops a gap at the charge neutrality point (CNP). This gap has previously been extensively studied by electrical transport through thermal activation measurements. Here, we report the determination of the gap size at the CNP of graphene/h-BN superlattice through photocurrent spectroscopy study. We demonstrate two distinct measurement approaches to extract the gap size. A maximum of ∼14 meV gap is observed for devices with a twist angle of less than 1°. This value is significantly smaller than that obtained from thermal activation measurements, yet larger than the theoretically predicted single-particle gap. Our results suggest that lattice relaxation and moderate electron-electron interaction effects may enhance the CNP gap in graphene/h-BN superlattice.

Topological valley transport at bilayer graphene domain walls.

Electron valley, a degree of freedom that is analogous to spin, can lead to novel topological phases in bilayer graphene. A tunable bandgap can be induced in bilayer graphene by an external electric field, and such gapped bilayer graphene is predicted to be a topological insulating phase protected by no-valley mixing symmetry, featuring quantum valley Hall effects and chiral edge states. Observation of such chiral edge states, however, is challenging because inter-valley scattering is induced by atomic-scale defects at real bilayer graphene edges. Recent theoretical work has shown that domain walls between AB- and BA-stacked bilayer graphene can support protected chiral edge states of quantum valley Hall insulators. Here we report an experimental observation of ballistic (that is, with no scattering of electrons) conducting channels at bilayer graphene domain walls. We employ near-field infrared nanometre-scale microscopy (nanoscopy) to image in situ bilayer graphene layer-stacking domain walls on device substrates, and we fabricate dual-gated field effect transistors based on the domain walls. Unlike single-domain bilayer graphene, which shows gapped insulating behaviour under a vertical electrical field, bilayer graphene domain walls feature one-dimensional valley-polarized conducting channels with a ballistic length of about 400 nanometres at 4 kelvin. Such topologically protected one-dimensional chiral states at bilayer graphene domain walls open up opportunities for exploring unique topological phases and valley physics in graphene.

[Effect of calcium on ion contents and expression of photosynthetic related genes in honeysuckle under salt stress].

Exogenous calcium can enhance the resistance of certain plants to abiotic stress. Research have demonstrated that exogenous calcium could enhances the resistance of honeysuckle under salt stress by promoting the transmission of photosynthetic electrons.The aim of this study was to investigate the effects of exogenous calcium on the contents of Na~+,K~+,Ca~(2+),Mg~(2+)and the expression of photosynthetic related genes Cab and rbc L. In this study,we used ICP-OES to analysis ion contents and used qRT-PCR to analysis the expression patterns of Cab and rbc L. The results showed that CaCl_2 significantly enhanced the K~+-Na~+,Ca~(2+)-Na~+,Mg~(2+)-Na+ratio of honeysuckle treated with 50 and 100 mmol·L~(-1) NaCl. Meanwhile,Cab and rbc L were significantly up-regulated under short-term salt stress,and CaCl_2 promoted this trend. From the two gene expression patterns,rbc L rapidly up-regulated on the first day of stress and then decreased,and was more sensitive to environmental changes. In summary,exogenous calcium could alleviate salt stress and increase plant development by increasing intracellular K~+-Na~+,Ca~(2+)-Na~+,Mg~(2+)-Na+ratio,and the transient overexpression of Cab and rbc L.

Soliton-dependent plasmon reflection at bilayer graphene domain walls.

Layer-stacking domain walls in bilayer graphene are emerging as a fascinating one-dimensional system that features stacking solitons structurally and quantum valley Hall boundary states electronically. The interactions between electrons in the 2D graphene domains and the one-dimensional domain-wall solitons can lead to further new quantum phenomena. Domain-wall solitons of varied local structures exist along different crystallographic orientations, which can exhibit distinct electrical, mechanical and optical properties. Here we report soliton-dependent 2D graphene plasmon reflection at different 1D domain-wall solitons in bilayer graphene using near-field infrared nanoscopy. We observe various domain-wall structures in mechanically exfoliated graphene bilayers, including network-forming triangular lattices, individual straight or bent lines, and even closed circles. The near-field infrared contrast of domain-wall solitons arises from plasmon reflection at domain walls, and exhibits markedly different behaviours at the tensile- and shear-type domain-wall solitons. In addition, the plasmon reflection at domain walls exhibits a peculiar dependence on electrostatic gating. Our study demonstrates the unusual and tunable coupling between 2D graphene plasmons and domain-wall solitons.

A graphene-based broadband optical modulator.

Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm(2), which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

Nanoscale Control of Rewriteable Doping Patterns in Pristine Graphene/Boron Nitride Heterostructures.

Nanoscale control of charge doping in two-dimensional (2D) materials permits the realization of electronic analogs of optical phenomena, relativistic physics at low energies, and technologically promising nanoelectronics. Electrostatic gating and chemical doping are the two most common methods to achieve local control of such doping. However, these approaches suffer from complicated fabrication processes that introduce contamination, change material properties irreversibly, and lack flexible pattern control. Here we demonstrate a clean, simple, and reversible technique that permits writing, reading, and erasing of doping patterns for 2D materials at the nanometer scale. We accomplish this by employing a graphene/boron nitride heterostructure that is equipped with a bottom gate electrode. By using electron transport and scanning tunneling microscopy (STM), we demonstrate that spatial control of charge doping can be realized with the application of either light or STM tip voltage excitations in conjunction with a gate electric field. Our straightforward and novel technique provides a new path toward on-demand graphene p-n junctions and ultrathin memory devices.

Switching individual quantum dot emission through electrically controlling resonant energy transfer to graphene.

Electrically controlling resonant energy transfer of optical emitters provides a novel mechanism to switch nanoscale light sources on and off individually for optoelectronic applications. Graphene's optical transitions are tunable through electrostatic gating over a broad wavelength spectrum, making it possible to modulate energy transfer from a variety of nanoemitters to graphene at room temperature. We demonstrate photoluminescence switching of individual colloidal quantum dots by electrically tuning their energy transfer to graphene. The gate dependence of energy transfer modulation confirms that the transition occurs when the Fermi level is shifted over half the emitter's excitation energy. The modulation magnitude decreases rapidly with increasing emitter-graphene distance (d), following the 1/d(4) rate trend unique to the energy transfer process to two-dimensional materials.

[Correlation of FOXA1 with the malignancy and progression of prostate cancer].

OBJECTIVE: To study the relationship of the expression of FOXA1 in the prostate cancer (PCa) tissue with the Gleason score and clinical staging of PCa and with castration-resistant PCa (CRPC). METHODS: Using the immunohistochemical method, we detected the expressions of FOXA1 and Ki-67 in the pathological sections of 35 cases of PCa and 21 cases of benign prostatic hyperplasia (BPH). Then we analyzed their correlation with the Gleason score and TNM staging of PCa and that with CRPC. RESULTS: The positive expression of FOXA1 was significantly higher in the PCa than in the BPH tissue (P < 0.001) and was positively correlated with that of Ki-67 (P < 0.001) as well as with the Gleason score (P = 0.027) and clinical staging of PCa (P = 0.002), but showed no correlation with CRPC (P = 0.391). CONCLUSION: The positive expression of FOXA1 is increased in PCa, most significantly in the advanced stage of the tumor.

Wingless gene cloning and its role in manipulating the wing dimorphism in the white-backed planthopper, Sogatella furcifera.

BACKGROUND: Wingless gene (Wg) plays a fundamental role in regulating the segment polarity and wing imaginal discs of insects. The rice planthoppers have an obvious wing dimorphism, and the long- and short-winged forms exist normally in natural populations. However, the molecular characteristics and functions of Wg in rice planthoppers are poorly understood, and the relationship between expression level of Wg and wing dimorphism has not been clarified. RESULTS: In this study, wingless gene (Wg) was cloned from three species of rice planthopper, Sogatella furcifera, Laodelphgax striatellus and Nilaparvata lugens, and its characteristics and role in determining the wing dimorphism of S. furcifera were explored. The results showed that only three different amino acid residuals encoded by Wg were found between S. furcifera and L. striatellus, but more than 10 residuals in N. lugens were different with L. striatellus and S. furcifera. The sequences of amino acids encoded by Wg showed a high degree of identity between these three species of rice planthopper that belong to the same family, Delphacidae. The macropterous and brachypterous lineages of S. furcifera were established by selection experiment. The Wg mRNA expression levels in nymphs were significantly higher in the macropterous lineage than in the brachypterous lineage of S. furcifera. In macropterous adults, the Wg was expressed mainly in wings and legs, and less in body segments. Ingestion of 100 ng/µL double-stranded RNA of Wg from second instar nymphs led to a significant decrease of expression level of Wg during nymphal stage and of body weight of subsequent adults. Moreover, RNAi of Wg resulted in significantly shorter and deformative wings, including shrunken and unfolded wings. CONCLUSION: Wg has high degree of identity among three species of rice planthopper. Wg is involved in the development and growth of wings in S. furcifera. Expression level of Wg during the nymphal stage manipulates the size and pattern of wings in S. furcifera.

Chromosomal insertions in the Lactobacillus casei upp gene that are useful for vaccine expression.

To develop a stable and marker-free Lactobacillus strain useful for the expression of vaccines, we developed a temperature-sensitive suicide plasmid with expression cassettes containing an HCE promoter, a PgsA anchor, the alpha-toxin gene, and an rrnB T1T2 terminator (PPαT) that uses a 5-fluorouracil (5-FU) counterselectable marker for Lactobacillus casei. Three strains containing the correct PPαT expression cassettes were produced via the selective pressure of 5-FU screening. We confirmed that the upp gene was deleted and that the PPαT expression cassettes were inserted into the upp site of L. casei ATCC 393 by genomic PCR amplification and sequencing. 5-FU resistance in recombinant bacteria could be stably inherited for as long as 40 generations following insertion. However, bacteria containing the integrated DNA grew more slowly than wild-type L. casei. An indirect enzyme-linked immunosorbent assay (ELISA) analysis demonstrated that the alpha-toxin gene was expressed. Also, we visualized expression of the protein on the surface of L. casei cells using laser confocal microscopy. These results taken together demonstrate that these recombinant bacteria should provide a safe tool for effective vaccine production.

Large hexagonal bi- and trilayer graphene single crystals with varied interlayer rotations.

Bi- and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high-quality large-size bi- and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 µm pyramid-like hexagonal bi- and trilayer graphene single-crystal domains on Cu foils using chemical vapor deposition is reported. The as-produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier-transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first-principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations.

Implementation of contact line motion based on the phase-field lattice Boltzmann method.

This paper proposes a strategy to implement the free-energy-based wetting boundary condition within the phase-field lattice Boltzmann method. The greatest advantage of the proposed method is that the implementation of contact line motion can be significantly simplified while still maintaining good accuracy. For this purpose, the liquid-solid free energy is treated as a part of the chemical potential instead of the boundary condition, thus avoiding complicated interpolations with irregular geometries. Several numerical testing cases, including droplet spreading processes on the idea flat, inclined, and curved boundaries, are conducted, and the results demonstrate that the proposed method has good ability and satisfactory accuracy to simulate contact line motions.

Correlated insulator and Chern insulators in pentalayer rhombohedral-stacked graphene.

Rhombohedral-stacked multilayer graphene hosts a pair of flat bands touching at zero energy, which should give rise to correlated electron phenomena that can be tuned further by an electric field. Moreover, when electron correlation breaks the isospin symmetry, the valley-dependent Berry phase at zero energy may give rise to topologically non-trivial states. Here we measure electron transport through hexagonal boron nitride-encapsulated pentalayer graphene down to 100 mK. We observed a correlated insulating state with resistance at the megaohm level or greater at charge density n = 0 and displacement field D = 0. Tight-binding calculations predict a metallic ground state under these conditions. By increasing D, we observed a Chern insulator state with C = -5 and two other states with C = -3 at a magnetic field of around 1 T. At high D and n, we observed isospin-polarized quarter- and half-metals. Hence, rhombohedral pentalayer graphene exhibits two different types of Fermi-surface instability, one driven by a pair of flat bands touching at zero energy, and one induced by the Stoner mechanism in a single flat band. Our results establish rhombohedral multilayer graphene as a suitable system for exploring intertwined electron correlation and topology phenomena in natural graphitic materials without the need for moiré superlattice engineering.