IRF4 affects the protective effect of regulatory T cells on the pulmonary vasculature of a bronchopulmonary dysplasia mouse model by regulating FOXP3.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in preterm infants, characterised by compromised alveolar development and pulmonary vascular abnormalities. Emerging evidence suggests that regulatory T cells (Tregs) may confer protective effects on the vasculature. Knockdown of their transcription factor, interferon regulatory factor 4 (IRF4), has been shown to promote vascular endothelial hyperplasia. However, the involvement of Tregs and IRF4 in the BPD pathogenesis remains unclear. This study aimed to investigate the regulation of Tregs by IRF4 and elucidate its potential role in pulmonary vasculature development in a BPD mouse model. METHODS: The BPD model was established using 85% hyperoxia exposure, with air exposure as the normal control. Lung tissues were collected after 7 or 14 days of air or hyperoxia exposure, respectively. Haematoxylin-eosin staining was performed to assess lung tissue pathology. Immunohistochemistry was used to measure platelet endothelial cell adhesion molecule-1 (PECAM-1) level, flow cytometry to quantify Treg numbers, and Western blot to assess vascular endothelial growth factor (VEGFA), angiopoietin-1 (Ang-1), forkhead box protein P3 (FOXP3), and IRF4 protein levels. We also examined the co-expression of IRF4 and FOXP3 proteins using immunoprecipitation and immunofluorescence double staining. Furthermore, we employed CRISPR/Cas9 technology to knock down the IRF4 gene and observed changes in the aforementioned indicators to validate its effect on pulmonary vasculature development in mice. RESULTS: Elevated IRF4 levels in BPD model mice led to FOXP3 downregulation, reduced Treg numbers, and impaired pulmonary vascular development. Knockdown of IRF4 resulted in improved pulmonary vascular development and upregulated FOXP3 level. CONCLUSION: IRF4 may affect the protective role of Tregs in the proliferation of pulmonary vascular endothelial cells and pulmonary vascular development in BPD model mice by inhibiting the FOXP3 level.

Blocking the ATR-SerRS-VEGFA pathway targets angiogenesis for UV-induced cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma (cSCC) is the second most prevalent form of skin cancer, with an escalating incidence rate and a notable potential (up to 5%) for metastasis. Ultraviolet radiation (UVA and UVB) exposure is the primary risk factor for cSCC carcinogenesis, with literature suggesting ultraviolet radiation (UVR) promotes vascular endothelial growth factor A (VEGFA) expression. This study aims to investigate UVR-induced upregulation of VEGFA and explore combination therapeutic strategies. The skin squamous cell carcinoma cell line A431 was exposed to specific durations of ultraviolet radiation. The effect of emodin on ATR/SerRS/VEGFA pathway was observed. The cell masses were also transplanted subcutaneously into mice (n = 8). ATR inhibitor combined with emodin was used to observe the growth and angiogenesis of the xenografts. The results showed that UV treatment significantly enhanced the phosphorylation of SerRS and the expression level of VEGFA in A431 cells (p < 0.05). Treatment with emodin significantly inhibited this expression (p < 0.05), and the combination of emodin and ATR inhibitor further enhanced the inhibitory effect (p < 0.05). This phenomenon was further confirmed in the xenograft model, which showed that the combination of ATR inhibitor and emodin significantly inhibited the expression of VEGFA to inhibit angiogenesis (p < 0.05), thus showing an inhibitory effect on cSCC. This study innovatively reveals the molecular mechanism of UV-induced angiogenesis in cSCC and confirms SerRS as a novel target to inhibit cSCC angiogenesis and progression in vitro and in vivo studies.

Superconductivity in Ca-intercalated bilayer graphene: C2CaC2.

The deposition and intercalation of metal atoms can induce superconductivity in monolayer and bilayer graphenes. For example, it has been experimentally proved that Li-deposited graphene is a superconductor with critical temperature Tc of 5.9 K, Ca-intercalated bilayer graphene C6CaC6 and K-intercalated epitaxial bilayer graphene C8KC8 are superconductors with Tc of 2-4 K and 3.6 K, respectively. However, the Tc of them are relatively low. To obtain higher Tc in graphene-based superconductors, here we predict a new Ca-intercalated bilayer graphene C2CaC2, which shows higher Ca concentration than the C6CaC6. It is proved to be thermodynamically and dynamically stable. The electronic structure, electron-phonon coupling (EPC) and superconductivity of C2CaC2 are investigated based on first-principles calculations. The EPC of C2CaC2 mainly comes from the coupling between the electrons of C-pz orbital and the high- and low-frequency vibration modes of C atoms. The calculated EPC constant λ of C2CaC2 is 0.75, and the superconducting Tc is 18.9 K, which is much higher than other metal-intercalated bilayer graphenes. By further applying -4% biaxial compressive strain to C2CaC2, the Tc can be boosted to 26.6 K. Thus, the predicted C2CaC2 provides a new platform for realizing superconductivity with the highest Tc in bilayer graphenes.

First-principles prediction of superconducting properties of monolayer 1T'-WS2 under biaxial tensile strain.

High-purity 1T'-WS2 film has been experimentally synthesized [Nature Materials, 20, 1113-1120 (2021)] and theoretically predicted to be a two-dimensional (2D) superconducting material with Dirac cones [arXiv:2301.11425]. In the present work, we further study the superconducting properties of monolayer 1T'-WS2 by applying biaxial tensile strain. It is shown that the superconducting critical temperature Tc firstly increases and then decreases with respect to tensile strains, with the highest superconducting critical temperature Tc of 7.25 K under the biaxial tensile strain of 3%. In particular, we find that Dirac cones also exist in several tensile strained cases. Our studies show that monolayer 1T'-WS2 may provide a good platform for understanding the superconductivity of 2D Dirac materials.

Unraveling the mediation role of frailty and depression in the relationship between social support and self-management among Chinese elderly COPD patients: a cross-sectional study.

BACKGROUND: Self-management (SM) is the key factor in controlling the progression of chronic obstructive pulmonary disease (COPD). Previous studies have reported that majority of COPD patients later presented with frailty and mental health diseases, which affect self-management. This study attempted to explore the mediation role of depression and frailty between social support and self-management in elderly COPD population. METHODS: Six hundred twenty-seven stable elderly COPD patients admitted to 5 public hospitals in Ningxia, China were selected as study subjects by convenience sampling method. Self-management, frailty, depression and social support were assessed using the COPD Self-management Scale (COPD-SMS), Frail Scale (FS), 15-item Geriatric Depression Scale (GDS-15), and Social Support Rating Scale (SSRS) respectively. The Pearson correlation analysis was used to assess the correlation between variables. Additionally, SPSS25.0 PROCESS plugin Model 6 was used to explore the mediating effects of frailty and depression in the relationship between social support and self-management. RESULTS: The mean participant age was 72.87 ± 7.03 years, 60.4% of participants were male. The mean total score of the COPD-SMS was 156.99 ± 25.15. Scores for the SSRS, FS, and GDS-15 were significantly correlated with COPD-SMS (p < 0.05). The analysis of the mediation effect demonstrated that social support has a direct predictive effect on self- management (ß = 1.687, 95%CI: 1.359 to 2.318). Additionally, social support can also predict self- management indirectly through the mediation of depression (ß = 0.290, 95%CI: 0.161 to 0.436) and frailty-depression (ß = 0.040, 95%CI: 0.010 to 0.081). However, the mediation effect of frailty alone was not found to be statistically significant (ß =-0.010, 95%CI: -0.061 to 0.036). The direct effect accounted for 84.06% of the total effect, while the indirect effect accounted for 15.94% of the total effect. CONCLUSION: Self-management among elderly COPD patients was relatively moderate to low. Furthermore, frailty and depression were found to have a partially mediation role in the relationship between social support and self-management. Therefore, healthcare professionals need to comprehensively consider the frailty and depression status of patients, and implement targeted intervention measures as part of their care, which can improve the self-management of elderly COPD patients.

Epidermolysis Bullosa: Two rare case reports of COL7A1 and EBS-GEN SEV KRT14 variants with review of literature.

EPIDERMOLYSIS: Bullosa is a rare hereditary skin condition that causes blisters. Genes encoding structural proteins at or near the dermal-epidermal junction are mutated recessively or dominantly, and this is the primary cause of EB. Herein, two Chinese boys were diagnosed with the condition, each with a different variant in a gene that serves as a reference for EB genetic counseling. Skincare significantly impacted their prognosis and quality of life. CASE PRESENTATION: Two Chinese boys, with phenotypically normal parents, have been diagnosed with distinct blister symptoms, one with Dominant Dystrophic Epidermolysis Bullosa and the other with a severe form of Epidermolysis Bullosa Simplex. The first patient had a G-to-A variant in the COL7A1 allele, at nucleotide position 6163 which was named "G2055A". The proband is heterozygous for Dystrophic Epidermolysis Bullosa due to a COL7A1 allele with a glycine substitution at the triple helix domain. A similar variant has been discovered in his mother, indicating its potential transmission to future generations. Another patient had severe Epidermolysis Bullosa Simplex with a rare c.377T > A  variant resulting in substitution of amino acid p.Leu126Arg (NM_000526.5 (c.377T > G, p.Leu126Arg) in the Keratin 14 gene. In prior literature, Keratin 14 has been associated with an excellent prognosis. However, our patient with this infrequent variant tragically died from sepsis at 21 days old. There has been a reported occurrence of the variant only once. CONCLUSION: Our study reveals that Epidermolysis Bullosa patients with COL7A1 c.6163G > A and KRT14 c.377T>A variants have different clinical presentations, with dominant forms of Dystrophic EB having milder phenotypes than recessive ones. Thus, the better prognosis in the c.6163G > A patient. Furthermore, c.377T>A patient was more prone to infection than the patient with c.6163G>A gene variant. Genetic testing is crucial for identifying the specific variant responsible and improving treatment options.

[Efficacy and safety of dust mite subcutaneous immunotherapy in children with allergic asthma： a prospective randomized controlled study]. / å°˜èž¨çš®ä¸‹å ç–«æ²»ç–—åº”ç”¨äºŽå„¿ç«¥è¿‡æ•æ€§å“®å–˜ç–—æ•ˆä¸Žå®‰å ¨æ€§çš„å‰çž»æ€§éšæœºå¯¹ç §ç ”ç©¶.

OBJECTIVES: To investigate the efficacy and safety of subcutaneous immunotherapy (SCIT) using dust mites in children with allergic asthma. METHODS: In a prospective randomized controlled study, 98 children with dust mite-induced allergic asthma were randomly divided into a control group (n=49) and an SCIT group (n=49). The control group received inhaled corticosteroid treatment, while the SCIT group additionally received a standardized three-year SCIT regimen. The two groups were compared based on peripheral blood eosinophil percentage, visual analogue score (VAS), total medication score, Asthma Control Test/Childhood Asthma Control Test scores, fractional exhaled nitric oxide (FeNO), and lung function before treatment, and at 6 months, 1 year, 2 years, and 3 years after treatment. Adverse reactions were recorded post-injection to evaluate the safety of SCIT. RESULTS: Compared with pre-treatment levels, the SCIT group showed a significant reduction in the percentage of peripheral blood eosinophils, VAS, total medication score, and FeNO, while lung function significantly improved, and asthma control levels were better 3 years after treatment (P<0.05). Compared with the control group, the SCIT group showed more significant improvement in all evaluated indicators 3 years after treatment (P<0.05). A total of 2 744 injections were administered, resulting in 157 cases (5.72%) of local adverse reactions and 4 cases (0.15%) of systemic adverse reactions, with no severe systemic adverse events. CONCLUSIONS: SCIT is an effective and safe treatment for allergic asthma in children.

IL-33-ST2 pathway regulates AECII transdifferentiation by targeting alveolar macrophage in a bronchopulmonary dysplasia mouse model.

Evidence points to the indispensable function of alveolar macrophages (AMs) in normal lung development and tissue homeostasis. However, the importance of AMs in bronchopulmonary dysplasia (BPD) has not been elucidated. Here, we identified a significant role of abnormal AM proliferation and polarization in alveolar dysplasia during BPD, which is closely related to the activation of the IL-33-ST2 pathway. Compared with the control BPD group, AMs depletion partially abolished the epithelialmesenchymal transition process of AECII and alleviated pulmonary differentiation arrest. In addition, IL-33 or ST2 knockdown has protective effects against lung injury after hyperoxia, which is associated with reduced AM polarization and proliferation. The protective effect disappeared following reconstitution of AMs in injured IL-33 knockdown mice, and the differentiation of lung epithelium was blocked again. In conclusion, the IL-33-ST2 pathway regulates AECII transdifferentiation by targeting AMs proliferation and polarization in BPD, which shows a novel strategy for manipulating the IL-33-ST2-AMs axis for the diagnosis and intervention of BPD.

Break-induced replication plays a prominent role in long-range repeat-mediated deletion.

Repetitive DNA sequences are often associated with chromosomal rearrangements in cancers. Conventionally, single-strand annealing (SSA) is thought to mediate homology-directed repair of double-strand breaks (DSBs) between two repeats, causing repeat-mediated deletion (RMD). In this report, we demonstrate that break-induced replication (BIR) is used predominantly over SSA in mammalian cells for mediating RMD, especially when repeats are far apart. We show that SSA becomes inefficient in mammalian cells when the distance between the DSBs and the repeats is increased to the 1-2 kb range, while BIR-mediated RMD (BIR/RMD) can act over a long distance (e.g., ~ 100-200 kb) when the DSB is close to one repeat. Importantly, oncogene expression potentiates BIR/RMD but not SSA, and BIR/RMD is used more frequently at single-ended DSBs formed at collapsed replication forks than at double-ended DSBs. In contrast to short-range SSA, H2AX is required for long-range BIR/RMD, and sequence divergence strongly suppresses BIR/RMD in a manner partially dependent on MSH2. Our finding that BIR/RMD has a more important role than SSA in mammalian cells has a significant impact on the understanding of repeat-mediated rearrangements associated with oncogenesis.

Immunogenicity and safety of inactivated SARS-CoV-2 vaccines in people living with HIV: A longitudinal cohort study.

To clarify the characteristics in immunogenicity and safety of inactivated SARS-Cov-2 vaccines among HIV-infected individuals, a longitudinal cohort study was performed on HIV-infected and HIV-uninfected participants with no history of COVID-19 infection and COVID-19 vaccine inoculation. Participants information and adverse events were collected. Blood samples were collected on the same day before vaccination, 21 days after the first shot, 28 days after the second shot, 6 months after the second vaccination and 14 days after the third dose to test anti-receptor-binding domain IgG antibody, viral load, CD4+, CD8+ T cell count. Our result showed that although HIV-infected adults with low nadir CD4+ T cell count ≤ 350 cells/mm3 generate significantly lower immune response after three shots of vaccine compared with HIV-negative controls, 100% of all the HIV-infected and healthy controls were seroconverted after the third shot. Seroconversion ratio and antibody level of 190 days after two shots of vaccination for HIV-infected with nadir CD4+ T cell count ≤ 350 were significantly lower than that of healthy controls. No significant difference was found in viral load among blood samples collected at each time points. CD4 and CD4/CD8 ratio value were found increased greatly after each shot of inoculation in HIV-infected individuals with nadir CD4+ T cell count ≤ 350. Multiple logistic regression analysis showed that among HIV-infected individuals, PLWH with CD4+ T cell count ≤ 350 were less likely experience seroconversion 21 days after the first shot, and less likely maintained antibody immunity 6 months post 2nd dose. Adverse events after each inoculation were not serious and recovered within 1 week. In conclusion, inactivated COVID-19 vaccine was safe and effective in people living with HIV after three shots of vaccination. HIV-infected individuals with low nadir CD4+ T cell count ≤ 350 was associated with a nonoptimal antibody response. Further vaccination strategies could be developed for those with low CD4+ T cell counts.

Advanced Covalent Organic Frameworks for Multi-Valent Metal Ion Batteries.

Covalent organic frameworks (COFs) have received increased interest in recent years as an advanced class of materials. By virtue of the available monomers, multiple conformations and various linkages, COFs offer a wide range of opportunities for complex structural design and specific functional development of materials, which has facilitated the widespread application in many fields, including multi-valent metal ion batteries (MVMIBs), described as the attractive candidate replacing lithium-ion batteries (LIBs). With their robust skeletons, diverse pores, flexible structures and abundant functional groups, COFs are expected to help realize a high performance MVMIBs. In this review, we present an overview of COFs, describe advances in topology design and synthetic reactions, and study the application of COFs in MVMIBs, as well as discuss challenges and solutions in the preparation of COFs electrodes, in the hope of providing constructive insights into the future direction of COFs.

Comparison of gut viral communities in children under 5 years old and newborns.

OBJECTIVES: The gut virome of humans is mainly composed of bacteriophages and their role in shaping the gut microbiome and influencing human health is increasingly recognized. However, little is known about the dynamic changes of the gut virome in children and its role in growth and development. In this study, we collected fecal samples from newborns and children under 5 years old from the same area during the same time period to investigate the gut viral community using viral metagenomic technique. METHODS: We used viral metagenomics to compare the gut bacteriophage composition between newborns and children under 5 years of age. We collected fecal samples from 45 newborns who were born at the Affiliated Hospital of Jiangsu University and 45 healthy children who were examined at the same hospital. The two groups were classified as the newborn group and the children group. RESULTS: Our sequencing analysis showed that the number of seqeunce reads of the children group were more than that of the newborn group. The results of alpha diversity and beta diversity both indicated that the diversity of the children group was significantly higher than that of the newborn group and the children group is different from the newborn group. The abundance of gut virome in the children group was also higher than that in the newborn group. The analysis of the genetic characteristics of the viruses showed that the phage genome was scattered and clustered with specificity. CONCLUSION: Our findings indicate that the gut bacteriophage communities undergo changes over time, presenting diversity and dynamic characteristics. We characterized the composition of gut virome in children and newborns in this region. However, further research is needed to investigate the function of bacteriophages in the ecology of the gastrointestinal tract.

Effect of PI3K/AKT/mTOR signaling pathway-based clustered nursing care combined with papaverine injection on vascular inflammation and vascular crisis after replantation of severed fingers.

This research aimed to investigate the effect of PI3K (phosphatidylinositol 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target protein of rapamycin) signaling pathway-based clustering care combined with papaverine injection on vascular inflammation and vascular crisis after finger amputation and replantation. 100 patients admitted in General Hospital of Ningxia Medical University from April 2022 to December 2022 for replantation of severed fingers were selected and divided into a control group (n = 50) and an observation group (n = 50) using the randomized grouping principle. The control group received a papaverine injection and general nursing care, the observation group received a papaverine injection and clustered care. The pain score; constipation incidence; replantation finger survival rate; physician, nurse, and patient satisfaction; serum inflammatory factors; vascular crisis parameters; and occurrence of adverse reactions were compared between the two patient groups. Enzyme-linked immunosorbent assay was performed to detect PI3K, AKT, and mTOR protein concentrations in the venous blood of the two groups, and statistical analysis of the data was performed. On postoperative day 7, the pain score and incidence of constipation in the observation group were lower than those in the control group (P < 0.05); the survival rate of reimplanted fingers in the observation group was 88.00%, which was higher than that in the control group 80.00% (P < 0.05); the satisfaction of doctors, nurses, and patients in the observation group was higher than that in the control group; the concentrations of interleukin-1 (IL-1), tumor necrosis factor (TNF-α), blood flow resistance index (RI), and arterial pulsatility index (PI) in the observation group were lower than those in the control group, while the concentration of interleukin-10 (IL-10), vascular diameter, and Vm (mean blood flow velocity) were higher in the observation group than those in the control group; the differences were statistically significant (P < 0.05). The difference in the incidence of adverse reactions between the two groups was not statistically significant (P > 0.05). The concentrations of PI3K, AKT, and mTOR proteins in the observation group were higher than those in the control group (P < 0.05). The concentrations of PI3K, AKT, and mTOR proteins in the observation group were higher than those in the control group (P < 0.05). Overall, these findings suggest that clustered care combined with papaverine injection reduces vascular inflammatory symptoms and vascular crisis in the treatment of severed finger replantation through the PI3K/AKT/mTOR signaling pathway.

Polar Bismuth Selenite Iodate Oxide BiSeIO6 with Three Types of Lone Pair Cations in One Structure.

Novel bismuth selenite iodate oxide BiSeIO6 was synthesized in a mild hydrothermal condition. BiSeIO6 was crystallized in the polar space group Pna21 of an orthorhombic system. The crystal structure features a three-dimensional framework composed of three types of lone pair cations with distorted BiO7 polyhedra, SeO3 pyramids, and IO3 pyramids in one structure. Interestingly, BiSeIO6 exhibits a strong and phase-matchable second-harmonic generation (SHG) of ∼6 times that of KH2PO4 (KDP). Dipole moment analysis shows that all three local acentric groups of BiO7, SeO3, and IO3 cooperatively contribute to the large macroscopic polarization and thereby strong SHG efficiency of BiSeIO6. In addition, BiSeIO6 has a broad transparency range from 0.35 to 11 µm, indicating its promising nonlinear optical applications from visible to mid-infrared bands.

Nanodesigns for Na3V2(PO4)3-based cathode in sodium-ion batteries: a topical review.

With the rapid development of sodium-ion batteries (SIBs), it is urgent to exploit the cathode materials with good rate capability, attractive high energy density and considerable long cycle performance. Na3V2(PO4)3(NVP), as a NASICON-type electrode material, is one of the cathode materials with great potential for application because of its good thermal stability and stable. However, NVP has the inherent problem of low electronic conductivity, and various strategies are proposed to improve it, moreover, nanotechnology or nanostructure are involved in these strategies, the construction of nanostructured active particles and nanocomposites with conductive carbon networks have been shown to be effective in improving the electrical conductivity of NVP. Herein, we review the research progress of NVP performance improvement strategies from the perspective of nanostructures and classifies the prepared nanomaterials according to their different nano-dimension. In addition, NVP nanocomposites are reviewed in terms of both preparation methods and promotion effects, and examples of NVP nanocomposites at different nano-dimension are given. Finally, some personal views are presented to provide reasonable guidance for the research and design of high-performance polyanionic cathode materials of SIBs.

Genetic characteristics of a novel HIV-1 recombinant lineage (CRF103_01B) and its prevalence in northern China.

During the routine surveillance of HIV-1 pretreatment drug resistance in Beijing, five men who have sex with men (MSM) and a woman were observed to get infected by newly identified CRF103_01B strain. To elucidate the genetic characteristics, the near full-length genome (NFLG) was obtained. Phylogenetic inference indicated that CRF103_01B NFLG was composed of six mosaic segments. Segments IV and V of CRF103_01B were located among the clusters subtype B and CRF01_AE (group 5), respectively. The CRF103_01B strain was deduced to originate from Beijing MSM population around 2002.3-2006.4 and continued to spread among MSM population at a low level, then to the general population via heterosexual contact in northern China. Molecular epidemiology surveillance of CRF103_01B should be reinforced.

A novel internet sampling for HIV surveillance: feasibility of self-sampling and preparation of DBS for delivery detection of HIV total nucleic acid and complementarity to sentinel surveillance.

BACKGROUND: To propose a new mode of HIV test and surveillance among population of men who have sex with men (MSM): Internet-based Self-sampling at home plus Laboratory testing of HIV total nucleic acid (TNA) in dried blood spot (DBS) (ISL of DBS TNA). Feasibility of ISL of DBS TNA was studied. Characteristics of the new mode and that of conventional surveillance mode at HIV voluntary counseling and testing clinic (VCT) were compared. METHODS: A non-governmental organization (NGO) published the recruitment information on the WeChat public account. MSM filled in the questionnaire online, applied for self-sampling service package, and mailed the self made DBS to professional laboratory. The laboratory performed HIV TNA test and submitted the test results to online platform. Participants queried test results online with their unique ID. Center for Disease Control and Prevention (CDC) followed up participants with positive nucleic acid results using IDs and contact information. Rates were compared by using the Chi-Square test or Fisher's exact test. RESULTS: Four hundred twenty-three questionnaires were completed. 423 self-sampling service packages were sent out and 340 DBSs were returned to professional laboratory within one month with qualified rate of sampling as high as 95.0% (323/340). Seven samples were found to be TNA positive. Comparing ISL of DBS TNA with sentinel surveillance, it was found that there was a significant difference in the composition ratio of the two modes of surveillance population (P < 0.05). HIV prevalence of ISL of DBS as 2.17% was significantly lower than sentinel site as 8.96% (χ2 = 14.953, P = 0.000 < 0.05). CONCLUSIONS: ISL of DBS TNA proposed is feasible and has a high self-sampling qualification rate, good confidentiality. It is an effective supplement to routine sentinel surveillance and has important promotion value.

Exploring electronic and valley properties of single-layer SMSiN2 (M = Mo, W): a first-principles study on two-dimensional Janus materials.

In this study, we employ first-principles calculations to explore the electronic and valleytronic properties of single-layer (SL) SMSiN2 (M = Mo, W), which are two-dimensional Janus materials with strong spin-orbit coupling. Our findings indicate that SL SMoSiN2/SWSiN2 possess a direct/indirect band gap, where the valence band maximum is situated at the K/K' point, giving rise to the formation of degenerate valleys. When considering spin-orbit coupling, SMoSiN2 and SWSiN2 demonstrate intriguing valley spin splitting in their valleys, with a maximum splitting of up to 0.14/0.39 eV in the valence bands. By implementing magnetic doping with V and Cr, we provide a demonstration that valley polarization could be realized in SL SMSiN2. Moreover, the findings reveal high carrier mobility in SL SMSiN2, notably in SWSiN2, where hole carriers can achieve a remarkable mobility of up to 7.98 × 103 cm2 V-1 s-1 along the zigzag direction. Furthermore, our observations suggest that strain can be effectively utilized to manipulate the character and magnitude of the band gap, as well as the valley spin splitting in these materials.

Hydrogenation induced high-temperature superconductivity in two-dimensional W2C3.

The discovery of highly crystalline two-dimensional (2D) superconductors provides a new alluring branch for exploring the fundamental significances. Based on first-principles calculations, we predict a new kind of 2D stable material W2C3, which is a semimetal but not a superconductor because of the weak electron-phonon coupling (EPC) strength. After hydrogenation, W2C3H2 possesses the intrinsic metallic properties with a large density of states (DOS) at the Fermi energy (EF). More interestingly, the EPC strength is greatly enhanced after hydrogenation and the calculated critical temperature (Tc) is 40.5 K. Furthermore, the compressive strain can obviously soften the low-frequency phonons and enhance the EPC strength. Then, the Tc of W2C3H2 can be increased from 40.5 K to 49.1 K with -4% compressive strain. This work paves the way for providing a new platform for 2D superconductivity.

Superconductivity of monolayer functionalized biphenylene with Dirac cones.

Monolayer biphenylene is a new two-dimensional (2D) carbon allotrope, which has been experimentally synthesized and theoretically predicted to show superconductivity. In this work, we investigate functionalized biphenylene with the adsorption of Li. The superconducting critical temperature (Tc) can be pushed from 0.59 K up to 3.91 K after Li adsorption. Our calculations confirm that the adsorption pushes the peak showing a high electronic density of states closer to the Fermi level, which usually leads to a larger Tc. Furthermore, the application of biaxial tensile strain can soften phonons and further enhance the Tc up to 15.86 K in Li-deposited biphenylene. Interestingly, a pair of type-II Dirac cones below the Fermi level has been observed, expanding the range of Dirac materials. It suggests that monolayer biphenylene deposited with Li may be a material with potential applications and improves the understanding of Dirac-type superconductors.