The edge engineering of topological Bi(111) bilayer

A topological insulator is a novel quantum state, characterized by symmetry-protected non-trivial edge/surface states. Our first-principle simulations show the significant effects of the chemical decoration on edge states of topological Bi(111) bilayer nanoribbon, which remove the trivial edge state and recover the Dirac linear dispersion of topological edge state. By comparing the edge states with and without chemical decoration, the Bi(111) bilayer nanoribbon offers a simple system for assessing conductance fluctuation of edge states. The chemical decoration can also modify the penetration depth and the spin texture of edge states. A low-energy effective model is proposed to explain the distinctive spin texture of Bi(111) bilayer nanoribbon, which breaks the spin-momentum orthogonality along the armchair edge.Comment: 5 pages, 5 figure

Treatment and Recycling of the Process Water in Iron Ore Flotation of Yuanjiacun Iron Mine

Coagulating sedimentation and oxidation treatment of process water in iron ore flotation of Yuanjiacun iron mine had been studied. The process water of this mine carried residual polyacrylamide (PAM), poly(diallyldimethylammonium chloride) (PDADMAC), and Ca2+ from the flotation and caused decrease of the iron flotation recovery or grade of the concentrate. The studies on high-intensity magnetic separation (HIMS) tailings for coagulating sedimentation showed that the settling performance of coagulant (named CYH) was better than that of PDADMAC. The analyses of FTIR spectra and zeta potential demonstrated that CYH is adsorbed mainly through electrostatic attraction onto HIMS tailings. Sodium hypochlorite was adopted to oxidize the residual organics in tailings wastewater. When sodium hypochlorite is at the dosage of 1.0 g/L, reaction temperature is of 20°C, and reaction time is of 30 minutes, the removal rates of PAM, COD, and Ca2+ were 90.48%, 83.97%, and 85.00%, respectively. Bench-scale flotation studies on the treated tailings wastewater indicated that the iron recovery and grade of concentrate were close to those of freshwater

Synchronization and Pinning Control in Complex Networks with Interval Time-Varying Delay

The problems on synchronization and pinning control for complex dynamical networks with interval time-varying delay are investigated and two less conservative criteria are established based on reciprocal convex technique. Pinning control strategies are designed to make the complex networks synchronized. Moreover, the problem of designing controllers can be converted into solving a series of NMIs (nonlinear matrix inequalities) and LMIs (linear matrix inequalities), which reduces the computation complexity when comparing with those present results. Finally, numerical simulations can verify the effectiveness of the derived methods

Bis(2-amino-6-methyl­pyridinium) tetra­chloridocuprate(II)

The title compound, (C6H9N2)2[CuCl4], contains a distorted tetra­hedral [CuCl4]2− anion and two protonated amino­pyridinium cations. The geometries of the protonated amino­pyridinium cations reveal amine–imine tautomerism. The crystal packing is influenced by N—H⋯Cl and C—H⋯Cl hydrogen bonds and π–π stacking inter­actions [centroid–centroid distances = 3.635 (4) and 3.642 (4)°]

2-Amino-3-methyl­pyridinium 2-amino-5-methyl­pyridinium sulfate monohydrate

The asymmetric unit of the title compound, 2C6H9N2 +·SO4 2−·H2O, contains two isomeric protonated amino­methyl­pyridine cations, a sulfate anion and a solvent water mol­ecule. The cations are in the iminium tautomeric form. In the crystal structure, inter­molecular O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen bonds link the components into a three-dimensional network. Additional stabilization is provided by weak π–π stacking inter­actions, with centroid–centroid distances of 3.758 (2) and 3.774 (1) Å

Observation of a phononic higher-order Weyl semimetal

Weyl semimetals are extraordinary systems where exotic phenomena such as Fermi arcs, pseudo-gauge fields and quantum anomalies arise from topological band degeneracy in crystalline solids for electrons and metamaterials for photons and phonons. On the other hand, higher-order topological insulators unveil intriguing multidimensional topological physics beyond the conventional bulk-edge correspondences. However, it is unclear whether higher-order topology can emerge in Weyl semimetals. Here, we report the experimental discovery of higher-order Weyl semimetals in its phononic analog which exhibit topologically-protected boundary states in multiple dimensions. We create the physical realization of the higher-order Weyl semimetal in a chiral phononic crystal with uniaxial screw symmetry. Using near-field spectroscopies, we observe the chiral Fermi arcs on the surfaces and a new type of hinge arc states on the hinge boundaries. These topological boundary arc states link the projections of Weyl points in different dimensions and directions, and hence demonstrate higher-order multidimensional topological physics in Weyl semimetals. Our study establishes the fundamental connection between higher-order topology and Weyl physics in crystalline materials and unveils a new horizon of higher-order topological semimetals where unprecedented materials such as higher-order topological nodal-lines may emerge

Is Floppy Eyelid Syndrome More Prevalent in Obstructive Sleep Apnea Syndrome Patients?

Controversial findings are reported about the relationship between floppy eyelid syndrome (FES) and obstructive sleep apnea syndrome (OSAS). The main goal of this study was to evaluate whether FES is more prevalent in OSAS patients by performing a meta-analysis. A comprehensive literature search of Pubmed, Embase, and Cochrane databases was performed. Only studies related to the prevalence of FES in OSAS were included in the meta-analysis. We estimated a pooled odds ratio (OR) for the prevalence of FES in OSAS. In total, 6 studies with 767 participants met the inclusion criteria. Using a fixed-effects model, the pooled OR was 4.12. The test for the overall effect revealed that FES was statistically prevalent in OSAS patients when compared with that in non-OSAS subjects (Z=4.98, p<0.00001). In the subgroup analysis by OSAS severity, the incidence of FES in OSAS increased with severity of OSAS as indicated with increased OR values (OR = 2.56, 4.62, and 7.64 for mild, moderate, and severe OSAS). In conclusion, the results indicate that FES is more prevalent in OSAS patients. However, this result was based only on unadjusted estimates. Prospective cohort studies are needed to determine whether OSAS is an independent risk factor for FES

Investigation of ultra-thin Al₂O₃ film as Cu diffusion barrier on low-k (k=2.5) dielectrics

Ultrathin Al(2)O(3) films were deposited by PEALD as Cu diffusion barrier on low-k (k=2.5) material. The thermal stability and electrical properties of the Cu/low k system with Al(2)O(3) layers with different thickness were studied after annealing. The AES, TEM and EDX results revealed that the ultrathin Al(2)O(3) films are thermally stable and have excellent Cu diffusion barrier performance. The electrical measurements of dielectric breakdown and TDDB tests further confirmed that the ultrathin Al(2)O(3) film is a potential Cu diffusion barrier in the Cu/low-k interconnects system