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The vacuolar-type H+-translocating ATPase (V-ATPase) is the major proton pump for intraorganellar acidification. Therefore, the integrity of the V-ATPase is closely associated with cellular homeostasis, and mutations in genes encoding V-ATPase components and assembly factors have been reported in certain types of diseases. For instance, the recurrent mutations of ATP6AP1, a gene encoding a V-ATPase accessory protein, have been associated with cancers and immunodeficiency. With the aim of studying V-ATPase-related mutations using the yeast model system, we report that Big1 is another homologue of ATP6AP1 in yeast cells, and we characterize the role of Big1 in maintaining a fully functional V-ATPase. In addition to its role in acidifying the vacuole or lysosome, our data support the concept that the V-ATPase may function as part of a signaling pathway to regulate macroautophagy/autophagy through a mechanism that is independent from Tor/MTOR.
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Autofagia , Lisosomas , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , ATPasas de Translocación de Protón Vacuolares , Vacuolas , ATPasas de Translocación de Protón Vacuolares/metabolismo , ATPasas de Translocación de Protón Vacuolares/genética , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Lisosomas/metabolismo , Vacuolas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Mutación/genética , Transducción de Señal , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
WRKY transcription factors play key roles in plant resistance to various stresses, but their roles in fruit ripening remain largely unknown. Here, we report a WRKY gene PpWRKY14 involved in the regulation of fruit ripening in peach. The expression of PpWRKY14 showed an increasing trend throughout fruit development. PpWRKY14 was a target gene of PpNAC1, a master regulator of peach fruit ripening. PpWRKY14 could directly bind to the promoters of PpACS1 and PpACO1 to induce their expression, and this induction was greatly enhanced when PpWRKY14 formed a dimer with PpNAC1. However, the transcription of PpNAC1 could be directly suppressed by two EIN3/EIL1 genes, PpEIL2 and PpEIL3. The PpEIL2/3 genes were highly expressed at the early stages of fruit development, but their expression was programmed to decrease significantly during the ripening stage, thus derepressing the expression of PpNAC1. These results suggested a PpEIL2/3-PpNAC1-PpWRKY14 module that regulates fruit ripening by modulating ethylene production in peach. Our results provided an insight into the regulatory roles of EIN3/EIL1 and WRKY genes in fruit ripening.
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Peach fruit is an important natural source of phenolic compounds that are well-known to have health benefits, but their metabolic basis remain elusive. Here, we report on phenolic compounds accumulation and antioxidant activity of ripe fruits in peach. A considerable variation in phenolic compounds content was observed among peach germplasm, with significantly higher levels detected in red-fleshed peaches compared to non-red-fleshed peaches. Antioxidant activity of crude extracts from ripe fruits showed significant differences among peach germplasm, with red-fleshed peaches having the strongest antioxidant activity. Intriguingly, it was observed that total phenolics instead of anthocyanins were strongly associated with antioxidant activity. Phenolic compounds content and antioxidant activity showed dynamic changes throughout fruit development, and these were much higher in the peel than in the flesh. Metabolomic analysis unveiled a coordinated accumulation of anthocyanins as well as key components of flavonoids and phenolic acids, which endows red-fleshed peaches with superior antioxidant activity.
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The plateau phase transition in quantum anomalous Hall (QAH) insulators corresponds to a quantum state wherein a single magnetic domain gives way to multiple domains and then reconverges back to a single magnetic domain. The layer structure of the sample provides an external knob for adjusting the Chern number C of the QAH insulators. Here, we employ molecular beam epitaxy to grow magnetic topological insulator multilayers and realize the magnetic field-driven plateau phase transition between two QAH states with odd Chern number change ΔC. We find that critical exponents extracted for the plateau phase transitions with ΔC = 1 and ΔC = 3 in QAH insulators are nearly identical. We construct a four-layer Chalker-Coddington network model to understand the consistent critical exponents for the plateau phase transitions with ΔC = 1 and ΔC = 3. This work will motivate further investigations into the critical behaviors of plateau phase transitions with different ΔC in QAH insulators.
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Daphne genkwa, as a traditional medicine, is widely distributed in China, Korea and Vietnam. In China, the dried flower buds of this plant are named "Yuanhua". It has the ability to effectively promote urination, eliminate phlegm and alleviate cough, eliminate parasites and cure of scabies, with a broad spectrum of pharmacological effects and considerable clinical efficacy. This paper provides a summary and classification of the main chemical constituents of D. genkwa based on a review of relevant domestic and foreign literature. It also outlines the current research status of traditional clinical usage, pharmacological effects, and toxicity of D. genkwa. The aim is to provide a theoretical basis for further study of D. genkwa and its potential new clinical applications.
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Daphne , Etnofarmacología , Fitoquímicos , Daphne/química , Fitoquímicos/farmacología , Fitoquímicos/aislamiento & purificación , Humanos , Medicina Tradicional China , Estructura Molecular , China , Flores/química , Animales , VietnamRESUMEN
OBJECTIVE: Benign childhood epilepsy with centrotemporal spikes (BECTS) affects brain network hierarchy and cognitive function; however, itremainsunclearhowhierarchical changeaffectscognition in patients with BECTS. A major aim of this study was to examine changes in the macro-network function hierarchy in BECTS and its potential contribution to cognitive function. METHODS: Overall, the study included 50 children with BECTS and 69 healthy controls. Connectome gradient analysis was used to determine the brain network hierarchy of each group. By comparing gradient scores at each voxel level and network between groups, we assessed changes in whole-brain voxel-level and network hierarchy. Functional connectivity was used to detect the functional reorganization of epilepsy caused by these abnormal brain regions based on these aberrant gradients. Lastly, we explored the relationships between the change gradient and functional connectivity values and clinical variables and further predicted the cognitive function associated with BECTS gradient changes. RESULTS: In children with BECTS, the gradient was extended at different network and voxel levels. The gradient scores frontoparietal network was increased in the principal gradient of patients with BECTS. The left precentral gyrus (PCG) and right angular gyrus gradient scores were significantly increased in the principal gradient of children with BECTS. Moreover, in regions of the brain with abnormal principal gradients, functional connectivity was disrupted. The left PCG gradient score of children with BECTS was correlated with the verbal intelligence quotient (VIQ), and the disruption of functional connectivity in brain regions with abnormal principal gradients was closely related to cognitive function. VIQ was significantly predicted by the principal gradient map of patients. SIGNIFICANCE: The results indicate connectome gradient disruption in children with BECTS and its relationship to cognitive function, thereby increasing our understanding of the functional connectome hierarchy and providing potential biomarkers for cognitive function of children with BECTS.
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Cognición , Conectoma , Epilepsia Rolándica , Imagen por Resonancia Magnética , Humanos , Niño , Epilepsia Rolándica/fisiopatología , Epilepsia Rolándica/diagnóstico por imagen , Masculino , Conectoma/métodos , Femenino , Cognición/fisiología , Red Nerviosa/diagnóstico por imagen , Red Nerviosa/fisiopatología , Encéfalo/fisiopatología , Encéfalo/diagnóstico por imagen , AdolescenteRESUMEN
Contralateral tension pneumothorax is a rare but fatal complication of one-lung ventilation. The life-saving decompression of pleural space was frequently delayed by the difficult confirmation of diagnosis because of general anesthesia that masks specific clinical presentations when the patient is alert. We reported a case of tension pneumothorax in a patient who underwent thoracic spine instrumentation. There were no contralateral tension pneumothorax cases on file from the search of the Anesthesia Quality Institute Closed Claims Database from 2001 to 2017. We systematically searched PubMed, Ovid MEDLINE, Embase, and Google Scholar. Over the past 30 years, there were 21 single case reports and two case series were retrieved. It was a consensus that difficult confirmation of the diagnosis of contralateral tension pneumothorax is the culprit of delayed life-saving intervention. Difficulty of oxygenation with increasing inspiratory pressure was usually the first sign suggesting contralateral pneumothorax; however, earlier presentations of cardiovascular system failure than respiratory failure have significantly increased the incidence of cardiac arrest and death. It is paramount to maintain a high suspicion of tension pneumothorax. The application of esophageal stethoscope, lung ultrasound, and simulator training may improve the chance of early diagnosis and patient outcome.
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Objective: To test the psychometric properties of the Chinese version of the biological rhythms interview of assessment in neuropsychiatry (C-BRIAN) in a group of young adults with and without depressive symptoms. Methods: Three hundred and seventy-eight university students were recruited as participants. Based on the scores from Center for Epidemiological Survey Depression Scale (CES-D), students were divided into the depressed group and healthy group. Explorative factor analysis was applied to assess the construct validity of the C-BRIAN. The Pittsburgh Sleep Quality Index (PSQI) and CES-D were compared with the C-BRIAN to test the convergent validity. The internal consistency of the C-BRIAN was also examined. Results: Three factors were extracted (activities, eating patterns, and sleep factors) explaining 63.9% of the total variance. The internal consistencies were very good with a coefficient of 0.94 (overall) and 0.89-0.91 for three factors. The domains of activities, eating patterns, and sleep were moderately correlated with PSQI (r=0.579) and CES-D (r=0.559) (ps<0.01). Conclusion: Our findings suggest that C-BRIAN has good validity and reliability which can be used to assess the biological rhythm in the young adult population with depressive symptoms. C-BRIAN would be a reliable tool to detect depressive symptoms for timely prevention and intervention in the community.
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BACKGROUND: Polycystic ovary syndrome (PCOS) is a gynecological endocrine disease and could be considered a metabolic disease because it is often accompanied by obesity and insulin resistance. Brown adipose tissue (BAT) transplantation has been shown to be effective in treating PCOS rats. RESULTS: The study demonstrated that BAT successfully recovered the reproductive and metabolic phenotype of PCOS rats. The disorder estrous cycle, abnormal hyperglycemia and the expression of liver factors were improved. Differentially expressed metabolites were analyzed, among them, arachidonic acid may play a role in inhibiting cell proliferation, enhancing oxidative stress reaction, promoting estrogen expression, and reducing progesterone level in KGN cells. CONCLUSION: Our findings suggest that BAT transplantation may be a therapeutic strategy for PCOS by changing the expression of some cytokines and metabolites. Differentially expressed metabolites might be crucially important for the pathogenesis of PCOS.
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Síndrome del Ovario Poliquístico , Humanos , Femenino , Ratas , Animales , Ácido Araquidónico/metabolismo , Ácido Araquidónico/farmacología , Síndrome del Ovario Poliquístico/metabolismo , Células de la Granulosa/metabolismo , Hígado/metabolismo , Obesidad/metabolismoRESUMEN
The interface between two different materials can show unexpected quantum phenomena. In this study, we used molecular beam epitaxy to synthesize heterostructures formed by stacking together two magnetic materials, a ferromagnetic topological insulator (TI) and an antiferromagnetic iron chalcogenide (FeTe). We observed emergent interface-induced superconductivity in these heterostructures and demonstrated the co-occurrence of superconductivity, ferromagnetism, and topological band structure in the magnetic TI layer-the three essential ingredients of chiral topological superconductivity (TSC). The unusual coexistence of ferromagnetism and superconductivity is accompanied by a high upper critical magnetic field that exceeds the Pauli paramagnetic limit for conventional superconductors at low temperatures. These magnetic TI/FeTe heterostructures with robust superconductivity and atomically sharp interfaces provide an ideal wafer-scale platform for the exploration of chiral TSC and Majorana physics.
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Hydrogel materials have proven valuable in wound healing, but improving the safety of these hydrogels is still challenging. Therefore, designing multifunctional natural polymeric-based hydrogels with excellent mechanical properties to replace toxic or potentially risky, refractory chemical polymer-based hydrogels such as polyacrylamide and polyethylene glycol is of particular significance. Here, a green starch-based hydrogel (Starch@Ca/CGC hydrogel) with injectability, self-healing, and instant adhesion was constructed by coordination interaction, electrostatic interaction, and intramolecular and intermolecular hydrogen bonds. Therein, natural bioactive small molecules gallic acid (GA) and carvacrol (CA) were coordinated with metal ions by the ultrasonic-triggered self-assembly and ionic cross-linking codriven strategy to prepare Cu-gallic acid-carvacrol nanospheres (CGC NPs), which conferred the hydrogel with near-infrared light (NIR)-controlled CA release and photothermal synergistic sterilization properties, as well as antioxidant and anti-infection capabilities. More importantly, the multifunctional hydrogel platforms could completely cover an irregular wound shape to prevent secondary injury and significantly accelerate wound healing under NIR with more skin appendages like hair follicles and blood vessels appearing. Therefore, it is expected that this starch-based hydrogel could serve as a competitive multifunctional dressing in the biomedical field, including bacteria-derived wound infection and other tissue repair.
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Antibacterianos , Cimenos , Cicatrización de Heridas , Humanos , Adherencias Tisulares , Antibacterianos/farmacología , Ácido Gálico , Hidrogeles/farmacologíaRESUMEN
Colorectal cancer is a prevalent cancer type in the United States, affecting both genders and influenced by genetics and environmental factors. The role of the gut microbiome in colorectal cancer development and therapy response is a burgeoning field of study. A recent study uncovered that trans-3-indoleacrylic acid (IDA), a microbial metabolite from P. anaerobius, promotes colorectal cancer by inhibiting ferroptosis, a type of nonapoptotic cell death driven by unrestricted lipid peroxidation and subsequent membrane damage. IDA activates aryl hydrocarbon receptor (AHR), a nuclear transcription factor, leading to the expression of aldehyde dehydrogenase 1 family member A3 (ALDH1A3). ALDH1A3, known for aldehyde detoxification, also contributes to ferroptosis resistance by generating reduced nicotinamide adenine dinucleotide (NADH), critical for the synthesis of reduced coenzyme Q10 (COQH10), by apoptosis-inducing factor mitochondria-associated 2 (AIFM2, also known as FSP1). Knocking out AHR, AIFM2, or ALDH1A3 reverses the inhibitory effect of IDA on ferroptosis and IDA-mediated tumor growth. Significantly, P. anaerobius is enriched in patients with colorectal cancer, and supplementing IDA or P. anaerobius accelerates colorectal cancer progression in spontaneous or orthotopic mouse models. Taken together, these findings suggest that targeting P. anaerobius-mediated ferroptosis resistance emerges as a promising strategy to combat colorectal cancer development.
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Neoplasias Colorrectales , Ferroptosis , Microbioma Gastrointestinal , Animales , Ratones , Humanos , Masculino , Femenino , Muerte Celular , Peroxidación de Lípido , Neoplasias Colorrectales/patologíaRESUMEN
STUDY OBJECTIVES: To evaluate the efficacy and safety of Dimdazenil, a positive allosteric modulator with selectivity for α1, α5 subunit-containing GABAA receptors, on sleep variables in patients with insomnia disorder. METHODS: In this randomized, double-blind, placebo-controlled trial, adults (18-65 years) with insomnia disorder were randomized (1:1:1:1 to receive daily oral placebo, Dimdazenil (1.5, 2.5, or 5 mg) for 14 days. The primary efficacy outcome was the total sleep time (TST) on day 1/2 and day 13/14, measured by polysomnography. The secondary outcome measures included (1) latency to persistent sleep (LPS), sleep efficiency (SE), wake after sleep onset (WASO) and number of awakenings (NAW) on days 1/2 and day 13/14, and (2) the average subjective sleep latency (sSL), total sleep time (sTST), wake after sleep onset (sWASO) and number of awakenings (sNAW) recorded in sleep diary and sleep questionnaire, and the evaluation of insomnia severity index. Rebound insomnia, withdrawal, and treatment-emergent adverse events were also assessed. RESULTS: Of 569 patients screened, 288 (76.4% female) were randomized and received one dose. For the primary outcomes, TST was significantly improved in the Dimdazenil 1.5, 2.5, and 5 mg group compared with the placebo group at day 1/2, and significantly improved in the Dimdazenil 2.5 and 5 mg groups compared with the placebo group at day 13/14. The Least Squares Means (standard errors) and 95% Confidence Intervals for the three active doses compared to placebo are 25.5 (8.31), (9.16, 41.89) for the 1.5 mg dose; 17.4 (8.19), (1.29, 33.55) for the 2.5 mg dose; 22.8 (8.15), (6.72, 38.80) for the 5 mg dose on day 1/2. Corresponding data on day 13/14 are 7.6 (8.07), (-8.24, 23.53) and 19.3 (8.06), (3.43, 35.17) and 18.2 (7.95), (2.49, 33.80). LPS was significantly reduced in the Dimdazenil 5 mg group compared with the placebo group on day 1/2. SE was significantly improved in the Dimdazenil 1.5 and 5 mg group compared with the placebo group at day 1/2. In the subjective sleep parameters, sSL on average was significantly lower in the Dimdazenil 1.5, 2.5, and 5 mg groups compared with the placebo group. sTST on average was significantly higher in the Dimdazenil 1.5, 2.5, and 5 mg groups compared with the placebo group. The most common TEAEs were dizziness, vertigo, and weakness with no clinically relevant treatment-related serious adverse events. CONCLUSIONS: Dimdazenil of 1.5, 2.5, and 5 mg improved certain objective and subjective sleep outcomes in people with insomnia disorder, with a favorable safety profile. These findings suggested that Dimdazenil may represent a promising new treatment for insomnia disorder, a prevalent condition with limited effective and safe treatments available. CLINICAL TRIAL INFORMATION: A multicenter, randomized, double-blind, multidose, placebo parallel controlled phase II clinical study of EVT201 in the treatment of insomnia disorders (http://www.chinadrugtrials.org), with the number of CTR20150664.
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Trastornos del Inicio y del Mantenimiento del Sueño , Adulto , Femenino , Humanos , Masculino , Método Doble Ciego , Hipnóticos y Sedantes/efectos adversos , Polisomnografía , Sueño , Trastornos del Inicio y del Mantenimiento del Sueño/tratamiento farmacológico , Resultado del Tratamiento , Adolescente , Adulto Joven , Persona de Mediana Edad , AncianoRESUMEN
STUDY OBJECTIVES: To evaluate the efficacy and safety of Dimdazenil, a novel partial positive allosteric modulator for GABAA receptor in adults with insomnia disorder. METHODS: This was a 2-week, multicenter, randomized, double-blind, placebo-controlled, parallel-group phase III study of Dimdazenil. The primary efficacy outcome was total sleep time (TST) analyzed by polysomnography (PSG) on day 13/14. Latency to persistent sleep (LPS), sleep efficiency (SE), and wake after sleep onset (WASO) were analyzed in the same way by polysomnography (PSG). The other secondary outcomes including the average subjective sleep latency (sSL), subjective TST (sTST), subjective SE (sSE), subjective WASO (sWASO), and subjective number of awakenings (sNAW) were analyzed from sleep diary data, and the insomnia severity index (ISI) was also assessed. Treatment-emergent adverse events (TEAEs) were monitored throughout the study. RESULTS: A total of 546 participants with insomnia (ageâ ≥18 years) were randomized (2:1), received treatment with an oral dose of Dimdazenil (2.5 mg) or placebo, and analyzed. Compared to baseline and placebo, Dimdazenil demonstrated significant improvements in PSG measures, increased TST (71.09, 31.68 minutes, respectively; both pâ <â 0.001), increased SE (13.26%, 5.55%, respectively; bothâ <â 0.001), reduced WASO (49.67, 20.16 minutes, respectively; both pâ <â 0.001), and reduced LPS (21.65 minutes, pâ <â 0.001; 6.46 minutes, pâ =â 0.023). Compared to placebo, Dimdazenil also improved key self-reported measures of sTST (18.33 minutes, pâ <â 0.001), sWASO (14.60 minutes, pâ <â 0.001), sSL (4.23 minutes, pâ <â 0.001), sSE (2.97%, pâ <â 0.001), and sNAW (0.29, pâ <â 0.001). Participants treated with Dimdazenil reported a significant improvement in ISI. Dimdazenil was well tolerated. The majority of TEAEs were mild or moderate. There were no clinically relevant treatment-related serious AEs and no deaths. CONCLUSIONS: Dimdazenil of 2.5 mg provided significant benefit on sleep maintenance and sleep onset in individuals with insomnia disorder versus placebo, with a favorable safety profile and was well tolerated. CLINICAL TRIAL INFORMATION: A multicenter, randomized, double-blind phase III clinical study evaluating the efficacy and safety of EVT201 capsules compared to placebo in patients with insomnia disorders (http://www.chinadrugtrials.org), with the number of CTR20201068.
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Trastornos del Inicio y del Mantenimiento del Sueño , Adulto , Humanos , Método Doble Ciego , Lipopolisacáridos , Polisomnografía , Sueño , Trastornos del Inicio y del Mantenimiento del Sueño/tratamiento farmacológico , Resultado del TratamientoRESUMEN
A quantum anomalous Hall (QAH) insulator is a topological phase in which the interior is insulating but electrical current flows along the edges of the sample in either a clockwise or counterclockwise direction, as dictated by the spontaneous magnetization orientation. Such a chiral edge current eliminates any backscattering, giving rise to quantized Hall resistance and zero longitudinal resistance. Here we fabricate mesoscopic QAH sandwich Hall bar devices and succeed in switching the edge current chirality through thermally assisted spin-orbit torque (SOT). The well-quantized QAH states before and after SOT switching with opposite edge current chiralities are demonstrated through four- and three-terminal measurements. We show that the SOT responsible for magnetization switching can be generated by both surface and bulk carriers. Our results further our understanding of the interplay between magnetism and topological states and usher in an easy and instantaneous method to manipulate the QAH state.
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Although maturity date (MD) is an essential factor affecting fresh fruit marketing and has a pleiotropic effect on fruit taste qualities, the underlying mechanisms remain largely unclear. In this study, we functionally characterized two adjacent NAM-ATAF1/2-CUC2 (NAC) transcription factors (TFs), PpNAC1 and PpNAC5, both of which were associated with fruit MD in peach. PpNAC1 and PpNAC5 were found capable of activating transcription of genes associated with cell elongation, cell wall degradation and ethylene biosynthesis, suggesting their regulatory roles in fruit enlargement and ripening. Furthermore, PpNAC1 and PpNAC5 had pleiotropic effects on fruit taste due to their ability to activate transcription of genes for sugar accumulation and organic acid degradation. Interestingly, both PpNAC1 and PpNAC5 orthologues were found in fruit-producing angiosperms and adjacently arranged in all 91 tested dicots but absent in fruitless gymnosperms, suggesting their important roles in fruit development. Our results provide insight into the regulatory roles of NAC TFs in MD and fruit taste.
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Prunus persica , Factores de Transcripción , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Prunus persica/genética , Frutas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Regulación de la Expresión Génica de las PlantasRESUMEN
Magnetic topological states refer to a class of exotic phases in magnetic materials with the non-trivial topological property determined by magnetic spin configurations. An example of such states is the quantum anomalous Hall (QAH) state, which is a zero magnetic field manifestation of the quantum Hall effect. Current research in this direction focuses on QAH insulators with a thickness of less than 10 nm. Here, molecular beam epitaxy (MBE) is employed to synthesize magnetic TI trilayers with a thickness of up to ≈106 nm. It is found that these samples exhibit well-quantized Hall resistance and vanishing longitudinal resistance at zero magnetic field. By varying the magnetic dopants, gate voltages, temperature, and external magnetic fields, the properties of these thick QAH insulators are examined and the robustness of the 3D QAH effect is demonstrated. The realization of the well-quantized 3D QAH effect indicates that the nonchiral side surface states of the thick magnetic TI trilayers are gapped and thus do not affect the QAH quantization. The 3D QAH insulators of hundred-nanometer thickness provide a promising platform for the exploration of fundamental physics, including axion physics and image magnetic monopole, and the advancement of electronic and spintronic devices to circumvent Moore's law.
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Over the last decade, the possibility of realizing topological superconductivity (TSC) has generated much excitement. TSC can be created in electronic systems where the topological and superconducting orders coexist, motivating the continued exploration of candidate material platforms to this end. Here, we use molecular beam epitaxy (MBE) to synthesize heterostructures that host emergent interfacial superconductivity when a non-superconducting antiferromagnet (FeTe) is interfaced with a topological insulator (TI) (Bi, Sb)2Te3. By performing in-vacuo angle-resolved photoemission spectroscopy (ARPES) and ex-situ electrical transport measurements, we find that the superconducting transition temperature and the upper critical magnetic field are suppressed when the chemical potential approaches the Dirac point. We provide evidence to show that the observed interfacial superconductivity and its chemical potential dependence is the result of the competition between the Ruderman-Kittel-Kasuya-Yosida-type ferromagnetic coupling mediated by Dirac surface states and antiferromagnetic exchange couplings that generate the bicollinear antiferromagnetic order in the FeTe layer.
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An axion insulator is a three-dimensional (3D) topological insulator (TI), in which the bulk maintains the time-reversal symmetry or inversion symmetry but the surface states are gapped by surface magnetization. The axion insulator state has been observed in molecular beam epitaxy (MBE)-grown magnetically doped TI sandwiches and exfoliated intrinsic magnetic TI MnBi2Te4 flakes with an even number layer. All these samples have a thickness of ~ 10 nm, near the 2D-to-3D boundary. The coupling between the top and bottom surface states in thin samples may hinder the observation of quantized topological magnetoelectric response. Here, we employ MBE to synthesize magnetic TI sandwich heterostructures and find that the axion insulator state persists in a 3D sample with a thickness of ~ 106 nm. Our transport results show that the axion insulator state starts to emerge when the thickness of the middle undoped TI layer is greater than ~ 3 nm. The 3D hundred-nanometer-thick axion insulator provides a promising platform for the exploration of the topological magnetoelectric effect and other emergent magnetic topological states, such as the high-order TI phase.