Abstract
Topological superconductors (TSCs) are unconventional superconductors with bulk superconducting gap and in-gap Majorana states on the boundary that may be used as topological qubits for ...quantum computation. Despite their importance in both fundamental research and applications, natural TSCs are very rare. Here, combining state of the art synchrotron and laser-based angle-resolved photoemission spectroscopy, we investigated a stoichiometric transition metal dichalcogenide (TMD), 2M-WS
2
with a superconducting transition temperature of 8.8 K (the highest among all TMDs in the natural form up to date) and observed distinctive topological surface states (TSSs). Furthermore, in the superconducting state, we found that the TSSs acquired a nodeless superconducting gap with similar magnitude as that of the bulk states. These discoveries not only evidence 2M-WS
2
as an intrinsic TSC without the need of sensitive composition tuning or sophisticated heterostructures fabrication, but also provide an ideal platform for device applications thanks to its van der Waals layered structure.
The as-extruded AZ91D magnesium alloy processed by conventional extrusion exhibits a yield strength of 320 MPa, an ultimate tensile strength of 382 MPa and a fracture elongation of 13.8%, superior ...than most AZ91D alloys reported so far, which is mainly attributed to ultra-fine grains, sub-micron precipitates, and strong texture.
A new phenomenon of tensile yielding plateau in the fine-grained age-type Mg-14Gd-2Ag-0.5Zr alloy is reported, which is closely related to the activation of mobile pinned-dislocations. The yielding ...plateau contributes ~6% strain in the peak-aged sample, while it contributes only ~2% strain in the extruded sample.
T helper (Th)-17 is a recently identified subtype of Th response that has been implicated in host defense and autoimmunity. We investigated whether there is evidence for a Th-17 response in human and ...experimental murine dry eye (DE). Gene expression in the human DE conjunctiva showed increased levels of the Th-17 inducers, interleukin (IL)-23, IL-17A, and interferon-gamma (IFN-gamma). In the murine model, we found that desiccating stress increased matrix metalloproteinase-9, Th-17-associated genes (IL-6, IL-23, transforming growth factor-beta1 and -2, IL-23R, IL-17R, IL-17A, retinoid-related orphan receptor-gammat, and CC chemokine attractant ligand-20) and IFN-gamma in cornea and conjunctiva. Furthermore, we found a significantly increased concentration of IL-17 in tears and number of IL-17-producing cells on the ocular surface. Antibody neutralization of IL-17 ameliorated experimental DE-induced corneal epithelial barrier dysfunction and decreased the expression of matrix metalloproteinases 3 and 9. Taken together, these findings suggest that IL-17 has a role in corneal epithelial barrier disruption in DE.
An extruded Mg-5Zn-2.5Y-1Ce-0.5Mn alloy with uniform fine α-Mg grains, dispersed W-phase and T-phase and weak basal texture was prepared by the semi-continuous casting and one-pass extrusion methods. ...The deformation behaviors of the extruded alloy were tested at a temperature range from room temperature (RT) to 350 °C and a strain rate range from 1×10−2s−1 to 4×10−4s−1. The results and relevant mechanisms were analyzed by using the measured data of the strain rate sensitivity (m) and the activation energy (Q) and the observations of the morphologies of deformation and fracture surfaces. It was demonstrated that the tensile strengths decrease, while the elongation to failure tends to increase with increasing temperature or decreasing strain rate. The variation in mechanical properties with increasing temperature mainly arises from a change in opening deformation mechanisms from the dislocation slip at RT to the dislocation climb at 250 °C to the grain boundary (GB) sliding at 350 °C. At RT, the slightly decreased tensile strengths and slightly increased elongation to failure with decreasing strain rate are mainly attributed to the weak sensitivity of the dislocation slip to strain rate. At 250 °C, the lower tensile strengths and the larger elongation to failure at 4×10−4s−1 than that at 1×10−2s−1 are mainly attributed to the occurrence of the dynamic recrystallization (DRX) at lower strain rate, while such DRX does not occur at higher strain rate. At 350 °C, the lower tensile strengths and the much larger elongation to failure at 4×10−4s−1 than that at 1×10−2s−1 are attributed to the GB sliding accommodated by the lattice diffusion at lower strain rate, while the GB sliding at higher strain rate is accommodated by the GB diffusion.
The augmented finite element method (A-FEM) is used to study the fundamental composite failure problem of delamination and associated damage events spreading from a stress concentrator during tensile ...loading. The solution exploits the ability of A-FEM to account for coupled multiple crack types that are not predetermined in shape or number. The nonlinear processes of each fracture mode are represented by a cohesive model, which provides a unified description of crack initiation and propagation and can also describe crack coalescence and bifurcation. The study problem is an orthogonal double-notched tension specimen, in which delaminations interact with transverse ply cracks, intra-ply splitting cracks, non-localized fine-scale matrix shear deformation, and fiber breaks. Cohesive laws and constitutive laws for matrix shear deformation are calibrated using literature data from independent tests. The calibrated simulations are mesh independent and correctly reproduce all qualitative aspects of the coupled damage evolution processes. They also correctly predict delamination sizes and shapes, the density of transverse ply cracks, the growth rate of splitting cracks, softening of the global stress–strain curve, and the ultimate strength. A sensitivity analysis relates variability in cohesive law parameters to predicted deviance in engineering properties. Given the known variability in cohesive law parameters, the predicted deviance in ultimate strength agrees with that in experimental data. The importance of including the interactions between different crack systems and non-localized shear deformation is demonstrated by suppressing the presence of separate mechanisms; the predicted delamination shapes, splitting crack growth rate, and the stress–displacement relationship fall into significant error.
We present electronic band structure, Gibbs free energy of formation, and electric field modulation calculations for silicane nanoribbons (NRs), i.e., completely hydrogenated or fluorinated silicene ...NRs, using density functional theory. We find that although the completely hydrogenated silicene (H-silicane) sheet in the chair-like configuration is an indirect-band-gap semiconductor, a direct band gap can be achieved in the zigzag H-silicane NRs by using Brillouin-zone folding. Compared to H-silicane NRs, the band gaps of completely fluorinated silicene (F-silicane) NRs reduce at least by half. For all silicane NRs considered here, the Gibbs free energy of formation is negative but shows different trends by changing the ribbon width for H-silicane NRs and F-silicane NRs. Furthermore, by analyzing the effect of transverse electric fields on the electronic properties of silicane NRs, we show that an external electric field can make the electrons and holes states spatially separated and even render silicane NRs self-doped. The tunable electronic properties of silicane NRs make them suitable for nanotechnology application.
The effect of Zr, Mn and Mn
+
Sc additions on the grain size of Mg–10Gd alloy has been investigated and the grain refinement mechanisms are also suggested. The results reveal that the addition of Zr ...results in a significant grain refinement of as-cast Mg–10Gd alloy by generating nucleants. However, it cannot restrict grain growth during homogenization treatment at 520
°C, and completely loss the grain refining effect for extruded alloy sample. Mn has a negligible effect on grain size of as-cast Mg–10Gd alloy, but α-Mn particles precipitate during homogenization treatment, which helps to refine the grains of extruded alloy sample due to α-Mn particles restricting recrystallization grain growth during extrusion. Successful grain refinement can be obtained by the addition of Mn
+
Sc. It is effective to refine microstructure of as-cast Mg–10Gd alloy, inhibit grain growth during homogenization treatment and also have a significant grain refining effect on extruded Mg–10Gd alloy sample, which are ascribed to the precipitation of a large number of Mn
2Sc particles.
The aim of this study was to explore the role of micro ribonucleic acid (miR)-15b in steroid-induced osteonecrosis of the femoral head (SONFH) and its potential mechanism.
Bone marrow tissues were ...collected from 5 patients with glucocorticoid (GC)-induced ONFH (GC-ONFH, GC group) and 5 patients with secondary ONFH (control group) undergoing total hip replacement in our hospital from July 2016 to August 2017. Subsequently, bone marrow mesenchymal stem cells (BMSCs) were separated from bone marrow extracted and cultured in vitro. Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) assay was used to detect differentially expressed miRNAs in BMSCs of patients in GC group and control group. BMSCs were treated with different concentrations of GC. Next, the effect of GC on tmiR-15b expression level was detected via qRT-PCR. Alizarin red staining assay was performed to evaluate the effect of miR-15b on osteogenic differentiation of BMSCs. Meanwhile, the potential targets of miR-15b were predicted using bioinformatics software and validated through luciferase reporter gene assay, respectively. Additionally, Western blotting was conducted to determine the effect of miR-15b on the protein expression of the transforming growth factor beta (TGF-β) signaling pathway.
Flow cytometry demonstrated that the proportion of cluster of differentiation 44 (CD44)-positive cells was 99.7%, while that of CD45-positive cells was only 0.17% in cultured BMSCs. This suggested that the purity of BMSCs was relatively high. QRT-PCR assay indicated that the expression level of miR-15b declined significantly in BMSCs of GC group when compared with control group (p<0.01). The osteogenic differentiation capacity of BMSCs was significantly strengthened in GC group compared with control group (p<0.01). Subsequent qRT-PCR assay revealed that GC down-regulated the expression level of miR-15b in a dose-dependent manner. Besides, the osteogenic differentiation capacity of cells was remarkably strengthened in miR-15b mimic treatment group when compared with control group (p<0.01). Bioinformatics software (TargetScan) predicted that drosophila mothers against decapentaplegic protein 7 (Smad7) might be a potential target of miR-15b, which was indicated by luciferase reporter gene assay. In comparison with control group, miR-15b mimic treatment group exhibited significantly down-regulated protein expression level of Smad7, increased expression level of phosphorylated (p)-Smad2/3 and up-regulated messenger RNA (mRNA) expression level of runt-related transcription factor 2 (Runx2). However, the protein expression level of Smad7 and p-Smad2/3 and the mRNA expression level of Runx2 exhibited opposite trends in miR-15b inhibitor treatment group.
MiR-15b relieves SONFH by targeting Smad7 and repressing osteogenic differentiation of BMSCs.
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