Strain-tunable skyrmions in two-dimensional monolayer Janus magnets.

The Dzyaloshinskii-Moriya interaction (DMI), which only exists in noncentrosymmetric systems, plays an important role in the formation of exotic chiral magnetic states. However, the absence of the DMI occurs in most two-dimensional (2D) magnetic materials due to their intrinsic inversion symmetry. Here, by using first-principles calculations, we demonstrate that a significant DMI can be obtained in a series of Janus monolayers of dichalcogenides XSeTe (X = Nb, Re) in which the difference between Se and Te on the opposite sides of X breaks the inversion symmetry. Remarkably, the DMI amplitudes of NbSeTe (1.78 meV) and ReSeTe (4.82 meV) are larger than the experimental value of Co/graphene (0.16 meV), and NbSeTe and ReSeTe monolayers have a high Curie temperature of 1023 K and 689 K, respectively. Through the micromagnetic simulation of XSeTe (X= Nb, Re) simulations, we also find that the ReSeTe monolayer can performance for skyrmion states by applying an external magnetic field, and importantly, the skyrmion states can be regulated and controlled under external strain. The findings pave the way for device concepts using chiral magnetic structures in specially designed 2D ferromagnetic materials.

High excellent hydrogen evolution characteristics and novel mechanism of two-dimensional tetra-phase OsN2 and ReN2.

It is essential to find a kind of electrocatalyst for hydrogen evolution reduction (HER) comparable with a noble metal that has good conductivity and abundant active sites. Based on systematic searches by first-principles calculations, we discovered two-dimensional transition-metal nitrides, tetra-phase OsN2 and ReN2 monolayers, as potential HER electrocatalysts with superior thermodynamic and kinetic stability. They exhibited excellent catalytic activity due to the presence of multiple active sites with a density of 8 × 1015 site per cm2 and an overpotential close to 0. In addition, we also found that the synergistic effect of strain and coverage makes them have a good hydrogen evolution activity. The ΔGH of the OsN2 monolayer at 1% tensile strain under 3/4 hydrogen coverage is 0.02 eV, and that of ReN2 at 1/2 hydrogen coverage could decrease to 0.001 eV. Different from other common transition metal nitrides, we found that the active sites of OsN2 and ReN2 monolayers are both at nitrogen atoms, which could be further understood by the crystal orbital Hamiltonian population analysis between N and metal atoms. All these interesting findings not only provide new excellent candidates but also provide new insights into the mechanism of hydrogen evolution of nitrides.

Magnetic anisotropy and ferroelectric-driven magnetic phase transition in monolayer Cr2Ge2Te6.

Monolayer Cr2Ge2Te6 (ML-CGT) has attracted broad interest due to its novel electronic and magnetic properties. However, there are still controversies on the origin of its intrinsic magnetism. Here, by exploring the electronic and magnetic properties of ML-CGT, we find that the magnetic shape anisotropy (MSA) is vital for establishing the long-range ferromagnetism, except for the contribution from magnetocrystalline anisotropy energy (MCA). Electronic band analysis, combined with atomic- and orbital-resolved magnetic anisotropy from a second-order perturbation theory, further reveals that the MCA of ML-CGT is mainly originated from hybridized Te-py and -pz orbitals. The MSA from magnetic Cr atoms in ML-CGT is larger than MCA, resulting in an in-plane magnetic anisotropy. Noticeably, by constructing a heterostructure (HTS) with ferroelectric Sc2CO2, CGT undergoes an in-plane to out-of-plane spin reorientation via ferroelectric polarization switching, accompanied with an electronic property transition from semiconductor to half-metal. The Curie temperature of CGT/Sc2CO2 HTS can be enhanced to 92.4 K under the ferroelectric polarization, which is much higher than that of pristine ML-CGT (34.7 K). These results not only clarify the contradiction of magnetic mechanism of ML-CGT in previous experimental and theoretical works, but also open the door for realizing nonvolatile magnetic memory devices based on a multifunctional ferromagnetic/ferroelectric HTS.

Two-dimensional Weyl semi-half-metallic NiCS3 with a band structure controllable by the direction of magnetization.

Two-dimensional (2D) Weyl semi-half-metals (WSHMs) have attracted tremendous interest for their fascinating properties combining half-metallic ferromagnetism and Weyl fermions. In this work, we present a NiCS3 monolayer as a new 2D WSHM material using systematic first-principles calculations. It has 12 fully spin-polarized Weyl nodal points in one spin channel with a Fermi velocity of 3.18 × 105 m s-1 and a fully gapped band structure in the other spin channel. It exhibits good mechanical and thermodynamic stabilities and the Curie temperature is estimated to be 403 K. The Weyl points are protected by vertical mirror plane symmetry along Γ-K, and each of them remains gapless even under spin-orbit coupling when the direction of spin is perpendicular to the Γ-K line including the Weyl point, which makes it possible to control the opening and closing of Weyl points by applying and rotating external magnetic fields. Our work not only provides a promising 2D WSHM material to explore the fundamental physics of symmetry protected ferromagnetic Weyl fermions, but also reveals a potential mechanism of band engineering of 2D WSHM materials in spintronics.

Half-Dirac semimetals and the quantum anomalous Hall effect in Kagome Cd2N3 lattices.

Half-Dirac semimetals (HDSs), which possess 100% spin-polarizations for Dirac materials, are highly desirable for exploring various topological phases of matter as low-dimensionality opens unprecedented opportunities for manipulating the quantum state of low-cost electronic nanodevices. The search for high-temperature HDSs is still a current hotspot and yet challenging experimentally. Herein based on first-principles calculations, we propose the realization of Half Dirac semimetals (HDS) in two-dimensional (2D) Kagome transition-metal nitride Cd2N3, which is robust against strain engineering. Monte Carlo simulations reveal that Cd2N3 possesses a Curie temperature reaching up to T C = 225 K, which is much higher than that of the reported monolayers CrI3 (T C = 45 K) and Cr2Ge2Te6 (T C = 20 K). The band crossings in Cd2N3 are gapped out by the spin-orbit coupling, which brings about the quantum anomalous Hall (QAH) effect with a sizeable band gap of E g = 4.9 meV, characterized by the nonzero Chern number (C = 1) and chiral edge states. A tight-binding model is further used to clarify the origin of HDSs and nontrivial electronic properties. The results suggest monolayer transition-metal nitrides as a promising platform to explore fascinating physical phenomena associated with novel 2D emergent HDSs and QAH insulators toward realistic spintronics devices, thus stimulating experimental interest.

SnxPy Monolayers: a New Type of Two-Dimensional Materials with High Stability, Carrier Mobility, and Magnetic Properties.

Searching for two-dimensional (2D) group V materials with ferromagnetism, elastic anisotropy, and carrier mobility and tunable band structure is one key to developing constantly developing nanodevices. The 2D monolayers SnxPy with x/y (1/1, 1/2, 1/3, and so on) coordination number are studied based on the particle-swarm optimization technique combined with the density functional theory optimization. Its thermal stability can be confirmed by molecular dynamics at 70K and 300K, indicating that the novel 2D materials have a stable existence. The electronic band structures of four stable structures suggest that all the monolayers of SnxPy are fully adjustable and flexible tunable band gaps semiconductors under the biaxial strain. The monolayer of P[Formula: see text]m-SnP2 with unique valence band structure can go from nonmagnetic to ferromagnetic by the hole doping because of the "Stoner criterion," and Pmc21-SnP2 is a direct-like gap semiconductor with in-plane elastic anisotropy to possess a high electron mobility as high as 800 cm2V-1 s-1 along the kb direction, which is much higher than that of MoS2 (∼ 200 cm2V-1 s-1). The optical absorption peak of the material is in the ultraviolet region. These discoveries expand the potential applications of the emerging field of 2D SnxPy structures in nanoelectronics.

A critical role for miR­135a­5p­mediated regulation of SLC24A2 in neuropathic pain.

Neuropathic pain (NP) is a refractory and long­lasting disease caused mostly by peripheral nerve injury. Currently, the mechanism of NP is yet to be elucidated. Intracellular calcium homeostasis is critical for some physiological functions, including the occurrence of NP. NCKX2, encoded by the solute carrier family 4 member 2 (SLC24A2) gene, is an important K+­dependent Na+­Ca2+ exchanger that mediates Ca2+ extrusion. The role of NCKX2 in the development of NP is unknown. For this purpose, a sciatic nerve chronic constriction injury (CCI) model was established and it was revealed that the expression levels of SLC24A2 and its encoded protein NCKX2 were both downregulated in the posterior horn of the spinal cord. Overexpression of SLC24A2 reduced both mechanical and thermal hyperalgesia and decreased the expression of inflammatory cytokines [interleukin (IL)­1ß, IL­6 and tumor necrosis factor­α] in CCI rats. Using bioinformatics analyses, luciferase reporter assays, and a series of behavioral tests, it was demonstrated that the decrease in SLC24A2 after CCI treatment was directly regulated by increased microRNA (miR)­135a­5p in the spinal cord. Moreover, the effects of miR­135a­5p on NP were SLC24A2­dependent. In conclusion, the present results highlighted the suppressive role of NCKX2 in NP, which is mainly regulated by miR­135a­5p and mediates the release of inflammatory cytokines in the dorsal horn of the spinal cord. These findings deepen our understanding of the development of NP and provide novel candidates for NP treatment.

Germanene/GaGeTe heterostructure: a promising electric-field induced data storage device with high carrier mobility.

Opening up a band gap without lowering high carrier mobility in germanene and finding suitable substrate materials to form van der Waals heterostructures have recently emerged as an intriguing way of designing a new type of electronic devices. By using first-principles calculations, here, we systematically investigate the effect of the GaGeTe substrate on the electronic properties of monolayer germanene. Linear dichroism of the Dirac-cone like band dispersion and higher carrier mobility (9.7 × 103 cm2 V-1 s-1) in the Ge/GaGeTe heterostructure (HTS) are found to be preserved compared to that of free-standing germanene. Remarkably, the band structure of HTS can be flexibly modulated by applying bias voltage or strain. A prototype data storage device FET based on Ge/GaGeTe HTS is proposed, which presents a promising high performance platform with a tunable band gap and high carrier mobility.

Intrinsic ferromagnetism with high temperature, strong anisotropy and controllable magnetization in the CrX (X = P, As) monolayer.

2D ferromagnetic (FM) materials with high temperature, large magnetocrystalline anisotropic energy (MAE), and controllable magnetization are highly desirable for novel nanoscale spintronic applications. Herein by using DFT and Monte Carlo simulations, we demonstrate the possibility of realizing intrinsic ferromagnetism in 2D monolayer CrX (X = P, As), which are stable and can be exfoliated from their bulk phase with a van der Waals layered structure. Following the Goodenough-Kanamori-Anderson (GKA) rule, the long-range ferromagnetism of CrX is caused via a 90° superexchange interaction along Cr-P(As)-Cr bonds. The Curie temperature of CrP is predicted to be 232 K based on a Heisenberg Hamiltonian model, while the Berezinskii-Kosterlitz-Thouless transition temperature of CrAs is as high as 855 K. In contrast to other 2D magnetic materials, the CrP monolayer exhibits a significant uniaxial MAE of 217 µeV per Cr atom originating from spin-orbit coupling. Analysis of MAE reveals that CrP favors easy out-of-plane magnetization, while CrAs prefers easy in-plane magnetization. Remarkably, hole and electron doping can switch the magnetization axis in between the in-plane and out-of-plane direction, allowing for the effective control of spin injection/detection in 2D structures. Our results offer an ideal platform for realizing 2D magnetoelectric devices such as spin-FETs in spintronics.

Emergence of a spin-valley Dirac semimetal in a strained group-VA monolayer.

The combination of Dirac and Valley physics in one single-layer system is a very interesting topic and has received widespread attention in materials science and condensed matter physics. Using density-functional theoretical calculations, we predict that a two-dimensional (2D) cyanided group-VA monolayer, MAs(CN)2 (M = Sb, Bi), can turn into the spin-valley Dirac point (svDP) state under external strains. In sharp contrast to the symmetry protected 2D Dirac semimetal (DSM), the Dirac Fermions in svDP materials are spin non-degenerate due to strong spin-splitting under SOC. Remarkably, the Dirac fermions in inequivalent valleys can host opposite Berry curvature and spin moment, leading to the Dirac spin-valley Hall effect with dissipationless transport. We also find that the svDP of MAs(CN)2 is a critical state of topological phase transition between the trivial and nontrivial states. An effective tight-binding model is used to unveil the physics of svDP and topological phase transition under strain. These results will provide a route towards the integration of spin-valley indexes in 2D Dirac materials and design multipurpose and controllable devices in valleytronics.

Glide Mirror Plane Protected Nodal-Loop in an Anisotropic Half-Metallic MnNF Monolayer.

Two-dimensional (2D) nodal-loop (NL) semimetals have attracted tremendous attention for their abundant physics and potential device applications, whereas the realization of gapless NL semimetals robust against spin-orbit coupling (SOC) remains a big challenge. Recently, breakthroughs have been made with the realization of gapless NL semimetals in 2D half-metallic materials, where NLs were protected by a horizontal mirror plane symmetry. Here we first propose an alternative nonsymmorphic horizontal glide mirror plane symmetry which could protect the NLs in 2D materials. On the basis of comprehensive first-principles calculations and symmetry analysis, we found that the glide mirror symmetry together with intrinsic out-of-plane spin polarization can protect the NL against SOC in a half-metallic semimetal, namely, the MnNF monolayer. Moreover, we predict that the MnNF monolayer has strong anisotropic characteristics, tunable band structure by changing the magnetization direction, and 100% spin-polarized transport properties. Our work not only provides a novel 2D half-metallic semimetal with strong anisotropy but also broadens the scope of 2D nodal-loop materials.

Eosinopenia is a predictive factor for the severity of acute ischemic stroke.

Previous data have revealed an association between eosinopenia and mortality of acute ischemic stroke. However, the relationship of eosinopenia with infarct volume, infection rate, and poor outcome of acute ischemic stroke is still unknown. The retrospective study included 421 patients (273 males, 65%; mean age, 68.0 ± 13.0 years) with first acute ischemic stroke who were hospitalized in the Second Affiliated Hospital of Soochow University, China, from January 2017 to February 2018. Laboratory data, neuroimaging results, and modified Rankin Scale scores were collected. Patients were divided into four groups according to their eosinophil percentage level (< 0.4%, 0.4-1.1%, 1.1-2.3%, ≥ 2.3%). Spearman's correlation analysis showed that the percentage of eosinophils was negatively correlated with infarct volume (rs = -0.514, P < 0.001). Receiver operating characteristic analysis demonstrated that eosinopenia predicted a large infarct volume more accurately than neutrophilia; the area under curve was 0.906 and 0.876, respectively; a large infarct was considered as that with a diameter larger than 3 cm and involving more than two major arterial blood supply areas. Logistic regression analysis revealed that eosinophil percentage was an independent risk factor for acute ischemic stroke (P = 0.002). Moreover, eosinophil percentage was significantly associated with large infarct volume, high infection rate (pulmonary and urinary tract infections), and poor outcome (modified Rankin Scale score > 3) after adjusting for potential confounding factors (P-trend < 0.001). These findings suggest that eosinopenia has the potential to predict the severity of acute ischemic stroke. This study was approved by the Ethics Committee of the Second Affiliated Hospital of Soochow University, China (approval number: K10) on November 10, 2015.

[Analysis on mechanisms and medication rules of herbal prescriptions for nonalcoholic fatty liver disease based on methods of data mining and biological information].

To explore the medication rules of herbal prescriptions for nonalcoholic fatty liver disease,and analyze the possible drug targets and interactions,in order to explore the mechanisms of the herbs. Randomized controlled trials of herbal prescriptions for treating nonalcoholic fatty liver disease were collected from CNKI,Wan Fang,VIP,Sino Med and PubMed databases. The properties,flavors and meridian tropism of herbs were analyzed by using systematic cluster analysis method with SPSS 19. 0 software. Subsequently,the association rules of herbs were analyzed by using Clementine 12. 0 software. Finally,the interactions between targets and relevant signaling pathways were analyzed by Traditional Chinese Medicine Systems Pharmacology Database(TCMSP),Search Tool for the Retrieval of Interacting Genes/Proteins(STRING) and Kyoto Encyclopedia of Genes and Genomes(KEGG). In the 88 prescriptions screened out,the commonly used herbs were Salvia miltiorrhiza,Bupleurum chinense,Alisma orientale,and Crataegus pinnatifida,and the potential signaling pathways were PPAR signaling pathway and calcium signaling pathway. The results showed that the main effects of herbal prescriptions were to improve blood flow/clear blood stasis,clear heatiness/dampness,promote digestion and strengthen spleen. And its mechanism of action may be achieved through the regulation of PPAR signaling pathway and calcium signaling pathway.

EP1 receptor is involved in prostaglandin E2-induced osteosarcoma growth.

Recent studies showed that the activation of prostaglandin (PG) receptor EP1 promotes cell migration and invasion in different cancers. The aim of this study was to investigate the role of EP1 in the proliferation of osteosarcoma (OS) cells in vitro and in vivo. EP1 mRNA and protein levels were analyzed by real-time RT-PCR and Western blot, respectively in human OS cell lines MG63, OS732, U-2OS, and 143B compared to human fetal osteoblastic hFOB 1.19 cells. MG63 cells were treated with PGE2, EP1 specific agonist 17-PT-PGE2, 17-PT-PGE2 + EP1 specific antagonist SC51089, or DMSO (control). EP1R-siRNA or a non-silencing irrelevant RNA duplex (negative control) were used for the transfection of MG63 cells, followed by PGE2 treatment. Nude mice carrying MG63 xenografts were treated with SC51089 (2 mg/kg/day). MG63 cells/xenografts were analyzed by MTT assay, TUNEL assay, PKC enzyme activity assay, and Western blot (EP1 and apoptotic proteins), and tumor growth/volume was evaluated in mice. EP1 levels were significantly higher in OS cells compared to osteoblasts. PGE2 or 17-PT-PGE2 treatment increased the proliferation and decreased the apoptosis of MG63 cells. Inhibition of EP1 by SC51089 or siRNA markedly decreased the viability of MG63 cells. Similarly, SC51089 treatment significantly inhibited MG63 cell proliferation and promoted apoptosis in vivo. The silencing of EP1 receptor by siRNA or blockade of EP1 signaling by SC51089 activated extrinsic and intrinsic apoptotic pathways both in vivo and in vitro, as evidenced by increased levels of Bax, cyt c, cleaved caspase-3, caspase-8 and caspase-9. EP1 appears to be involved in PGE2-induced proliferative activity of MG63 cells. Antagonizing EP1 may provide a novel therapeutic approach to the treatment of OS.

Two-dimensional honeycomb-kagome Ta2S3: a promising single-spin Dirac fermion and quantum anomalous hall insulator with half-metallic edge states.

Recent experimental success in the realization of two-dimensional (2D) magnetism has invigorated the search for new 2D magnetic materials with a large magnetocrystalline anisotropy, high Curie temperature, and high carrier mobility. Using first-principles calculations, here we predict a novel class of single-spin Dirac fermion states in a 2D Ta2S3 monolayer, characterized by a band structure with a large gap in one spin channel and a Dirac cone in the other with carrier mobility comparable to that of graphene. Ta2S3 is dynamically and thermodynamically stable under ambient conditions, and possesses a large out-of-plane magnetic anisotropy energy and a high Curie temperature (TC = 445 K) predicted from the spin-wave theory. When the spin and orbital degrees of freedom are allowed to couple, the Ta2S3 monolayer becomes a Chern insulator with a fully spin-polarized half-metallic edge state. An effective four-band tight-binding model is constructed to clarify the origin of a semi-Dirac cone in a spin-up channel and nontrivial band topology, which can be well maintained on a semiconducting substrate. The combination of these unique single-spin Dirac fermion and quantum anomalous Hall states renders the 2D Ta2S3 lattice a promising platform for applications in topologically high fidelity data storage and energy-efficient spintronic devices.

Discovery of a ferroelastic topological insulator in a two-dimensional tetragonal lattice.

Ferroelasticity and band topology are two intriguing yet distinct quantum states of condensed matter materials. Their coexistence in a single two-dimensional (2D) lattice, however, has never been observed. Here, we found that the 2D tetragonal HfC monolayer allowed simultaneous presence of ferroelastic and topological orders. By using first-principles calculations, we found that it could allow a low switching barrier with reversible strain of 17.4%, indicating that the anisotropic properties are achievable experimentally for a 2D tetragonal lattice. More interestingly, the tuning of topological behaviors with strain led to spin-separated and gapless edge states, that is, the quantum spin Hall effect. These findings from the coupling of two quantum orders offer insights into ferroelastic control over topological edge states for achieving multifunctional properties in next-generation 2D nanodevices.

Novel graphene-like two-dimensional bilayer germanene dioxide: electronic structure and optical properties.

Using ab initio calculations, we present a two-dimensional (2D) α-2D-germanene dioxide material with an ideal sp3 bonding network which possesses a large band gap up to 2.50 eV. The phonon dispersion curves and molecular dynamics (MD) simulation under the chosen parameters suggest that the novel 2D structure is stable. The dielectric function and absorption spectrum also show the consistent band gap within the electronic structure diagram, suggesting possible application as an ultraviolet light optical detector. The calculated carrier mobility of 4.09 × 103 cm2 V-1 s-1 can be observed along the x direction, which is much higher than that of MoS2 (∼3.0 cm2 V-1 s-1). Finally, we found that α-2D-germanene dioxide could potentially act as an ideal monolayer insulator in so-called van der Waals (vdW) heterostructure devices. These findings expand the potential applications of the emerging field of 2D α-2D-germanene dioxide materials in nanoelectronics.

Discovery of a novel spin-polarized nodal ring in a two-dimensional HK lattice.

Nodal-ring materials with a spin-polarized feature have attracted intensive interest recently due to their exotic properties and potential applications in spintronics. However, such a type of two-dimensional (2D) lattice is rather rare and difficult to realize experimentally. Here, we identify the first 2D Honeycomb-Kagome (HK) lattice, Mn-Cyanogen, as a new single-spin nodal-ring material by using first-principles calculations. Mn-Cyanogen shows gapless and semiconducting properties in spin-up and spin-down orientations, respectively, indicating a spin-gapless semiconductor nature. Remarkably, a spin-polarized nodal ring induced by px,y/pz band inversion is captured from the 3D band structure, which is irrelevant to spin-orbit coupling. The origin of the single-spin nodal-ring can be further clarified by the effective tight-binding (TB) model. These results open a new avenue to achieving spin-polarized nodal-ring materials with promising applications in spintronic devices.

Strain-Tuned Topological Insulator and Rashba-Induced Anisotropic Momentum-Locked Dirac Cones in Two-Dimensional SeTe Monolayers.

Rashba spin-orbit coupling (SOC) in topological insulators (TIs) is a very interesting phenomenon and has received extensive attention in two-dimensional (2D) materials. However, the coexistence of Rashba SOC and band topology, especially for materials with a square lattice, is still lacking. Here, by using first-principles calculations, we propose for the first time a SeTe monolayer as a 2D candidate with these novel properties. We find that the square lattice exhibits anisotropic band dispersions near the Fermi level and a Rashba effect related to large SOC and inversion asymmetry, which leads to a Dirac semimetal state. Another prominent feature is that SeTe can achieve a topological state under a tensile strain of only 1%, characterized by the Z2 invariant and helical edge states. Our findings demonstrate that SeTe is a promising material for novel electronic and spintronics applications.

Prediction of high-temperature Chern insulator with half-metallic edge states in asymmetry-functionalized stanene.

A great obstacle for the practical applications of the quantum anomalous Hall (QAH) effect is the lack of suitable two-dimensional (2D) materials with a sizable nontrivial band gap, high Curie temperature, and high carrier mobility. Based on first-principles calculations, here, we propose the realizations of these intriguing properties in asymmetry-functionalized 2D SnHN and SnOH lattices. Spin-polarized band structures reveal that SnOH monolayer exhibits a spin gapless semiconductor (SGS) feature, whereas SnNH is converted to SGS under compressive strain. The Curie temperature of SnOH reaches 266 K, as predicted by Monte Carlo simulation, and it is comparable to the room temperature. When the spin and orbital degrees of freedom are allowed to couple, both systems become large-gap QAH insulators with fully spin-polarized half-metallic edge states and higher Fermi velocity of 4.9 × 105 m s-1. These results pave a new way for designing topological field transistors in group-IV honeycomb lattices.