Realization of monolayer ZrTe5 topological insulators with wide band gaps.

Two-dimensional topological insulators hosting the quantum spin Hall effect have application potential in dissipationless electronics. To observe the quantum spin Hall effect at elevated temperatures, a wide band gap is indispensable to efficiently suppress bulk conduction. Yet, most candidate materials exhibit narrow or even negative band gaps. Here, via elegant control of van der Waals epitaxy, we have successfully grown monolayer ZrTe5 on a bilayer graphene/SiC substrate. The epitaxial ZrTe5 monolayer crystalizes in two allotrope isomers with different intralayer alignments of ZrTe3 prisms. Our scanning tunneling microscopy/spectroscopy characterization unveils an intrinsic full band gap as large as 254 meV and one-dimensional edge states localized along the periphery of the ZrTe5 monolayer. First-principles calculations further confirm that the large band gap originates from strong spin-orbit coupling, and the edge states are topologically nontrivial. These findings thus provide a highly desirable material platform for the exploration of the high-temperature quantum spin Hall effect.

The dysfunction of CD8+ T cells triggered by endometriotic stromal cells promotes the immune survival of endometriosis.

Endometriosis is defined as an oestrogen-dependent and inflammatory gynaecological disease of which the pathogenesis remains unclear. This study aimed to investigate the cellular heterogeneity and reveal the effect of CD8+ T cells on the progress of endometriosis. Three ovarian endometriosis patients were collected, and single-cell RNA sequencing (scRNA-seq) progressed and delineated the cellular landscape of endometriosis containing five cell clusters. The endometrial cells (EMCs) were the major component, of which the mesenchymal cells were preponderant and characterized with increased inflammation and oestrogen synthesis in endometriosis. The proportion of T cells, mainly CD8+ T cells rather than CD4+, was reduced in endometriotic lesions, and the cytokines and cytotoxicity of ectopic T cells were depressed. CD8+ T cells depressed the proliferation of ESCs through inhibiting CDK1/CCNB1 pathway to arrest the cell cycle and triggered inflammation through activating STAT1 pathway. Correspondingly, the coculture with ESCs resulted in the dysfunction of CD8+ T cells through upregulating STAT1/PDCD1 pathway and glycolysis-promoted metabolism reprogramming. The endometriotic lesions were larger in nude mouse models with T-cell deficiency than the normal mouse models. The inhibition of T cells via CD90.2 or CD8A antibody increased the endometriotic lesions in mouse models, and the supplement of T cells to nude mouse models diminished the lesion sizes. In conclusion, this study revealed the global cellular variation of endometriosis among which the cellular count and physiology of EMCs and T cells were significantly changed. The depressed cytotoxicity and aberrant metabolism of CD8+ T cells were induced by ESCs with the activation of STAT1/PDCD1 pathway resulting in immune survival to promote endometriosis.

Iron Vacancy Tunable Superconductor-Insulator Transition in FeSe/SrTiO_{3} Monolayer.

The Fe_{4}Se_{5} with a sqrt[5]×sqrt[5] Fe vacancy order is suggested to be a Mott insulator and the parent state of bulk FeSe superconductor. The iron vacancy ordered state has been considered as a Mott insulator and the parent compound of bulk FeSe-based superconductors. However, for the superconducting FeSe/SrTiO_{3} monolayer (FeSe/STO) with an interface-enhanced high transition temperature (T_{c}), the electronic evolution from its Fe vacancy ordered parent phase to the superconducting state, has not been explored due to the challenge to realize an Fe vacancy order in the FeSe/STO monolayer, even though important to the understanding of superconductivity mechanism. In this study, we developed a new method to generate Fe vacancies within the FeSe/STO monolayer in a tunable fashion, with the assistance of atomic hydrogen. As a consequence, an insulating sqrt[5]×sqrt[5] Fe vacancy ordered monolayer is realized as the parent state. By using scanning tunneling microscopy and scanning tunneling spectroscopy, the spectral evolution from superconductivity to insulator is fully characterized. Surprisingly, a prominent spectral weight transfer occurs, thus implying a strong electron correlation effect. Moreover, the Fe vacancy induced insulating gap exhibits no Mott gap-like features. This work provides new insights in understanding the high-T_{c} superconductivity in FeSe/STO monolayer.

Moderating Effects of Religious Tourism Activities on Environmental Risk, Leisure Satisfaction, Physical and Mental Health and Well-Being among the Elderly in the Context of COVID-19.

The purpose of this study is to explore whether religious tourism activities can create a safe leisure environment and improve the well-being of the elderly during the COVID-19 pandemic, with the participants in the Baishatun Mazu pilgrimage in Taiwan as the subjects of this study. A mixed research method was used. First, statistical software and the Pearson product-moment correlation coefficient were used to analyze the data. Then the respondents' opinions were collected. Finally, a multivariate analysis method was used to discuss the results of analysis. The findings showed that the elderly respondents thought that the epidemic prevention information and leisure space planning for the pilgrimage made them feel secure. The elderly believed the scenery, religious atmosphere, and commodities en route could reduce the perception of environmental risks to tourists, relieve pressure on the brain, and increase social opportunities. Therefore, the friendlier the leisure environment around the pilgrimage, the greater the leisure satisfaction among the elderly respondents. The happier the elderly felt, the less they considered the concentration of airborne contaminants, including viruses. The better their physical and mental health was, the less likely they were to want to ask for religious goods.

Direct Oxygen Transfer from H2 O to Cyclooctene over Electron-Rich RuO2 Nanocrystals for Epoxidation and Hydrogen Evolution.

Production of more than 20 million tons of epoxides per year from olefins suffers from low atom economy due to the use of oxidants and complex catalysts with unsatisfactory selectivity, leading to huge environmental and economic costs. We present a proof-of-concept application of electron-rich RuO2 nanocrystals to boost the highly selective epoxidation of cyclooctene via direct oxygen transfer from water as the sole oxygen source under mild conditions. The enhanced electron enrichment of RuO2 nanocrystals via the Schottky effect with nitrogen-doped carbons largely promotes the capture and activation of cyclooctene to give a high turnover frequency (260 h-1 ) of cyclooctene oxide, far surpassing the reported values (<20 h-1 ) of benchmarked catalysts at room temperature with oxidants. Our electron-rich RuO2 electrocatalysts enable efficient and durable hydrogen production (Faradaic efficiency >90 %) on the cathode without impacting on the selectivity to epoxide (>99 %) on the anode.

Facilitating Hot Electron Injection from Graphene to Semiconductor by Rectifying Contact for Vis-NIR-Driven H2 O2 Production.

Solar-driven production of hydrogen peroxide (H2 O2 ), as an important industrial chemical oxidant with an extensive range of applications, from oxygen reduction is a sustainable alternative to mainstream anthraquinone oxidation and direct hydrogenation of dioxygen methods. The efficiency of solar to hydrogen peroxide over semiconductor-based photocatalysts is still largely limited by the narrow light absorption to visible light. Here, the authors proposed and demonstrate the proof-of-concept application of light-generated hot electrons in a graphene/semiconductor (exemplified with widely used TiO2 ) dyad to largely extend visible light spectra up to 800 nm for efficient H2 O2 production. The well-designed graphene/semiconductor heterojunction has a rectifying interface with a zero barrier for the hot electron injection, largely boosting excited hot electrons with an average lifetime of ≈0.5 ps into charge carriers with a long fluorescent lifetime (4.0 ns) for subsequent H2 O2 production. The optimized dyadic photocatalyst can provide an H2 O2 yield of 0.67 mm g-1  h-1 under visible light irradiation (λ ≥ 400 nm), which is 20 times of the state-of-the-art noble-metal-free titanium oxide-based photocatalyst, and even achieves an H2 O2 yield of 0.14 mm g-1  h-1 upon photoexcitation by near-infrared-region light (≈800 nm).

Boosting Mass Exchange between Pd/NC and MoC/NC Dual Junctions via Electron Exchange for Cascade CO2 Fixation.

Merging existing catalysts together as a cascade catalyst may achieve "one-pot" synthesis of complex but functional molecules by simplifying multistep reactions, which is the blueprint of sustainable chemistry with low pollutant emission and consumption of energy and materials only when the smooth mass exchange between different catalysts is ensured. Effective strategies to facilitate the mass exchange between different active centers, which may dominate the final activity of various cascade catalysts, have not been reached until now, even though charged interfaces due to work function driven electron exchange have been widely observed. Here, we successfully constructed mass (reactants and intermediates) exchange paths between Pd/N-doped carbon and MoC/N-doped carbon induced by interfacial electron exchange to trigger the mild and cascade methylation of amines using CO2 and H2. Theoretical and experimental results have demonstrated that the mass exchange between electron-rich MoC and electron-deficient Pd could prominently improve the production of N,N-dimethyl tertiary amine, which results in a remarkably high turnover frequency value under mild conditions, outperforming the state-of-the-art catalysts in the literature by a factor of 5.9.

Moiré enhanced charge density wave state in twisted 1T-TiTe2/1T-TiSe2 heterostructures.

Nanoscale periodic moiré patterns, for example those formed at the interface of a twisted bilayer of two-dimensional materials, provide opportunities for engineering the electronic properties of van der Waals heterostructures1-11. In this work, we synthesized the epitaxial heterostructure of 1T-TiTe2/1T-TiSe2 with various twist angles using molecular beam epitaxy and investigated the moiré pattern induced/enhanced charge density wave (CDW) states with scanning tunnelling microscopy. When the twist angle is near zero degrees, 2 × 2 CDW domains are formed in 1T-TiTe2, separated by 1 × 1 normal state domains, and trapped in the moiré pattern. The formation of the moiré-trapped CDW state is ascribed to the local strain variation due to atomic reconstruction. Furthermore, this CDW state persists at room temperature, suggesting its potential for future CDW-based applications. Such moiré-trapped CDW patterns were not observed at larger twist angles. Our study paves the way for constructing metallic twist van der Waals bilayers and tuning many-body effects via moiré engineering.

Heterojunction-Based Electron Donators to Stabilize and Activate Ultrafine Pt Nanoparticles for Efficient Hydrogen Atom Dissociation and Gas Evolution.

Platinum (Pt) is the most effective bench-marked catalyst for producing renewable and clean hydrogen energy by electrochemical water splitting. There is demand for high HER catalytic activity to achieve efficient utilization and minimize the loading of Pt in catalysts. In this work, we significantly boost the HER mass activity of Pt nanoparticles in Ptx /Co to 8.3 times higher than that of commercial Pt/C by using Co/NC heterojunctions as a heterogeneous version of electron donors. The highly coupled interfaces between Co/NC and Pt metal enrich the electron density of Pt nanoparticles to facilitate the adsorption of H+ , the dissociation of Pt-H bonds and H2 release, giving the lowest HER overpotential of 6.9 mV vs. RHE at 10 mA cm-2 in acid among reported HER electrocatalysts. Given the easy scale-up synthesis due to the stabilization of ultrafine Pt nanoparticles by Co/NC solid ligands, Ptx /Co can even be a promising substitute for commercial Pt/C for practical applications.

Direct Growth of van der Waals Tin Diiodide Monolayers.

Two-dimensional (2D) van der Waals (vdW) materials have garnered considerable attention for their unique properties and potentials in a wide range of fields, which include nano-electronics/optoelectronics, solar energy, and catalysis. Meanwhile, challenges in the approaches toward achieving high-performance devices still inspire the search for new 2D vdW materials with precious properties. In this study, via molecular beam epitaxy, for the first time, the vdW SnI2 monolayer is successfully fabricated with a new structure. Scanning tunneling microscopy/spectroscopy characterization, as corroborated by the density functional theory calculation, indicates that this SnI2 monolayer exhibits a band gap of ≈2.9 eV in the visible purple range, and an indirect- to direct-band gap transition occurs in the SnI2 bilayer. This study provides a new semiconducting 2D material that is promising as a building block in future electronics/optoelectronics.

Schottky Barrier-Induced Surface Electric Field Boosts Universal Reduction of NOx - in Water to Ammonia.

NOx - reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3 ) is an excellent energy carrier and the most valuable product among all the products of NOx - reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple-electron NOx - -to-NH3 process. Here, we utilize the Schottky barrier-induced surface electric field, by the construction of high density of electron-deficient Ni nanoparticles inside nitrogen-rich carbons, to facilitate the enrichment and fixation of all NOx - anions on the electrode surface, including NO3 - and NO2 - , and thus ensure the final selectivity to NH3 . Both theoretical and experimental results demonstrate that NOx - anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3 - and NO2 - reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h-1 cm-2 in electrocatalytic NO2 - reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx - pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology.

Erratum: Realization of a Metallic State in 1T-TaS_{2} with Persisting Long-Range Order of a Charge Density Wave [Phys. Rev. Lett. 123, 206405 (2019)].

This corrects the article DOI: 10.1103/PhysRevLett.123.206405.

Realization of a Metallic State in 1T-TaS_{2} with Persisting Long-Range Order of a Charge Density Wave.

Metallization of 1T-TaS_{2} is generally initiated at the domain boundary of a charge density wave (CDW), at the expense of its long-range order. However, we demonstrate in this study that the metallization of 1T-TaS_{2} can be also realized without breaking the long-range CDW order upon surface alkali doping. By using scanning tunneling microscopy, we find the long-range CDW order is always persisting, and the metallization is instead associated with additional in-gap excitations. Interestingly, the in-gap excitation is near the top of the lower Hubbard band, in contrast to a conventional electron-doped Mott insulator where it is beneath the upper Hubbard band. In combination with the numerical calculations, we suggest that the appearance of the in-gap excitations near the lower Hubbard band is mainly due to the effectively reduced on-site Coulomb energy by the adsorbed alkali ions.

Superconductivity in Potassium-Intercalated T d-WTe2.

To realize a topological superconductor is one of the most attracting topics because of its great potential in quantum computation. In this study, we successfully intercalate potassium (K) into the van der Waals gap of type II Weyl semimetal WTe2 and discover the superconducting state in K xWTe2 through both electrical transport and scanning tunneling spectroscopy measurements. The superconductivity exhibits an evident anisotropic behavior. Moreover, we also uncover the coexistence of superconductivity and the positive magnetoresistance state. Structural analysis substantiates the negligible lattice expansion induced by the intercalation, therefore suggesting K-intercalated WTe2 still hosts the topological nontrivial state. These results indicate that the K-intercalated WTe2 may be a promising candidate to explore the topological superconductor.

Effects of particulate matter on allergic respiratory diseases.

The health impact of airborne particulate matter (PM) has long been a concern to clinicians, biologists, and the general public. With many epidemiological studies confirming the association of PM with allergic respiratory diseases, an increasing number of follow-up empirical studies are being conducted to investigate the mechanisms underlying the toxic effects of PM on asthma and allergic rhinitis. In this review, we have briefly introduced the characteristics of PM and discussed its effects on public health. Subsequently, we have focused on recent studies to elucidate the association between PM and the allergic symptoms of human respiratory diseases. Specifically, we have discussed the mechanism of action of PM in allergic respiratory diseases according to different subtypes: coarse PM (PM2.5-10), fine PM (PM2.5), and ultrafine PM.

Transcription profiling and identification of infection-related genes in Phytophthora cactorum.

Phytophthora cactorum, an oomycete pathogen, infects more than 200 plant species within several plant families. To gain insight into the repertoire of the infection-related genes of P. cactorum, Illumina RNA-Seq was used to perform a global transcriptome analysis of three life cycle stages of the pathogen, mycelia (MY), zoospores (ZO) and germinating cysts with germ tubes (GC). From over 9.8 million Illumina reads for each library, 18,402, 18,569 and 19,443 distinct genes were identified for MY, ZO and GC libraries, respectively. Furthermore, the transcriptome difference among MY, ZO and GC stages was investigated. Gene ontology (GO) and KEGG pathway enrichment analyses revealed diverse biological functions and processes. Comparative analysis identified a large number of genes that are associated with specific stages and pathogenicity, including 166 effector genes. Of them, most of RXLR and NLP genes showed induction while the majority of CRN genes were down-regulated in GC, the important pre-infection stage, compared to either MY or ZO. And 14 genes encoding small cysteine-rich (SCR) secretory proteins showed differential expression during the developmental stages and in planta. Ectopic expression in the Solanaceae indicated that SCR113 and one elicitin PcINF1 can trigger cell death on Nicotiana benthamiana, tobacco (N. tabacum) and tomato (Solanum lycopersicum) leaves. Neither conserved domain nor homologues of SCR113 in other organisms can be identified. Collectively, our study provides a comprehensive examination of gene expression across three P. cactorum developmental stages and describes pathogenicity-related genes, all of which will help elucidate the pathogenicity mechanism of this destructive pathogen.

SCR96, a small cysteine-rich secretory protein of Phytophthora cactorum, can trigger cell death in the Solanaceae and is important for pathogenicity and oxidative stress tolerance.

Peptides and small molecules produced by both the plant pathogen Phytophthora and host plants in the apoplastic space mediate the relationship between the interplaying organisms. Various Phytophthora apoplastic effectors, including small cysteine-rich (SCR) secretory proteins, have been identified, but their roles during interaction remain to be determined. Here, we identified an SCR effector encoded by scr96, one of three novel genes encoding SCR proteins in P. cactorum with similarity to the P. cactorum phytotoxic protein PcF. Together with the other two genes, scr96 was transcriptionally induced throughout the developmental and infection stages of the pathogen. These genes triggered plant cell death (PCD) in the Solanaceae, including Nicotiana benthamiana and tomato. The scr96 gene did not show single nucleotide polymorphisms in a collection of P. cactorum isolates from different countries and host plants, suggesting that its role is essential and non-redundant during infection. Homologues of SCR96 were identified only in oomycetes, but not in fungi and other organisms. A stable protoplast transformation protocol was adapted for P. cactorum using green fluorescent protein as a marker. The silencing of scr96 in P. cactorum caused gene-silenced transformants to lose their pathogenicity on host plants and these transformants were significantly more sensitive to oxidative stress. Transient expression of scr96 partially recovered the virulence of gene-silenced transformants on plants. Overall, our results indicate that the P. cactorum scr96 gene encodes an important virulence factor that not only causes PCD in host plants, but is also important for pathogenicity and oxidative stress tolerance.

Transcriptomic analysis of the phytopathogenic oomycete Phytophthora cactorum provides insights into infection-related effectors.

BACKGROUND: Phytophthora cactorum, a hemibiotrophic oomycete pathogen, can cause destructive diseases on numerous crops worldwide, leading to essential economic losses every year. However, little has been known about its molecular pathogenicity mechanisms. To gain insight into its repertoire of effectors, the P. cactorum transcriptome was investigated using Illumina RNA-seq. RESULTS: We first demonstrated an in vitro inoculation method that can be used to mimic natural cyst germination on host plants. Over 28 million cDNA reads were obtained for five life cycle stages (mycelium, sporangium, zoospore, cyst and germinating cyst) and de novo assembled into 21,662 unique genes. By comparisons with 11 public databases, 88.99% of the unique genes were annotated, including 15,845 mapped to the gene models of the annotated relative Phytophthora infestans. Using TribeMCL, 5,538 gene families conserved across P. cactorum and other three completely sequenced Phytophthora pathogen species were determined. In silico analyses revealed that 620 P. cactorum effector homologues including 94 RXLR effector candidates matched known or putative virulence genes in other oomycetes. About half of the RXLR effector candidates were predicted to share a conserved structure unit, termed the WY-domain fold. A subset of the effector genes were checked and validated by PCR amplification. Transcriptional experiments indicated that effector genes were differentially expressed during the life cycle and host infection stages of P. cactorum. Ectopic expression in Nicotiana benthamiana revealed that RXLR, elicitin and NLP effectors can trigger plant cell death. These effectors are highly conserved across oomycete species. Single nucleotide polymorphisms for RXLR effectors were detected in a collection of P. cactorum isolates from different countries and hosts. CONCLUSIONS: This study demonstrates the comprehensive sequencing, de novo assembly, and analyses of the transcriptome of P. cactorum life cycle stages. In the absence of genome sequence, transcriptome data is important for infection-related gene discovery in P. cactorum, as demonstrated here for the effector genes. The first look at the transcriptome and effector arsenal of P. cactorum provides valuable data to elucidate the pathogenicity basis of this broad-host-range pathogen.