Chirality-selective topological magnon phase transition induced by interplay of anisotropic exchange interactions in honeycomb ferromagnet.

A variety of distinct anisotropic exchange interactions commonly exist in one magnetic material due to complex crystal, magnetic and orbital symmetries. Here we investigate the effects of multiple anisotropic exchange interactions on topological magnon in a honeycomb ferromagnet, and find a chirality-selective topological magnon phase transition induced by a complicated interplay of Dzyaloshinsky-Moriya interaction and pseudo-dipolar interaction, accompanied by the bulk gap close and reopen with chiral inversion. Moreover, this novel topological phase transition involves band inversion at high symmetry pointsKandK', which can be regarded as a pseudo-orbital reversal, i.e. magnon valley degree of freedom, implying a new manipulation corresponding to a sign change of the magnon thermal Hall conductivity. Indeed, it can be realized in 4dor 5dcorrelated materials with both spin-orbit coupling and orbital localized states, such as iridates and ruthenates,etc.This novel regulation may have potential applications on magnon devices and topological magnonics.

High-temperature magnetically topological candidate material Mn3Bi2Te6.

The Mn-Bi-Te family displaying magnetism and non-trivial topological properties has received extensive attention. Here, we predict that the antiferromagnetic structure of Mn3Bi2Te6with three MnTe layers is energetically stable and the magnetic energy difference of Mn-Mn is enhanced four times compared with that in the single MnTe layer of MnBi2Te4. The predicted Néel transition point is raised to 102.5 K, surpassing the temperature of liquid nitrogen. The topological properties show that with the variation of the MnTe layer from a single layer to three layers, the system transforms from a non-trivial topological phase to a trivial topological phase. Interestingly, the ferromagnetic state of Mn3Bi2Te6is a topological semimetal and it exhibits a topological transition from trivial to non-trivial induced by the magnetic transition. Our results enrich the Mn-Bi-Te family system, offer a new platform for studying topological phase transitions, and pave a new way to improve the working temperature of magnetically topological devices.

Role of Lanthanides and Bilayer Fe2As2 in the Electronic Properties of RbLn2Fe4As4O2 (Ln = Gd, Tb, and Dy) Superconductors.

The superconducting transition temperatures (Tc) of RbGd2Fe4As4O2, RbTb2Fe4As4O2, and RbDy2Fe4As4O2 are 35 K, 34.7 K, and 34.3 K without doping, respectively. For the first time, we have studied the high-temperature nonmagnetic state and the low-temperature magnetic ground state of 12442 materials, RbTb2Fe4As4O2 and RbDy2Fe4As4O2, using first principles calculations and comparing them with RbGd2Fe4As4O2. We also performed a detailed study of the effects of lanthanides and bilayer Fe2As2. We predict that the ground state of RbLn2Fe4As4O2 (Ln = Gd, Tb, and Dy) is spin-density-wave-type, in-plane, striped antiferromagnets, and the magnetic moment around each Fe atom is about 2 µB. We also found that the structural differences caused by the simple ionic radius have little effect on the properties of these three materials. Different lanthanide elements themselves play a major role in the electronic properties of the materials. It can be confirmed that the effect of Gd on RbLn2Fe4As4O2 is indeed different from that of Tb and Dy, and the presence of Gd is more conducive to interlayer electron transfer. This means that Gd can transfer more electrons from the GdO layer to the FeAs layer compared to Tb and Dy. Therefore, RbGd2Fe4As4O2 has a stronger internal coupling strength of the bilayer Fe2As2 layer. This can explain why the Tc of RbGd2Fe4As4O2 is slightly higher than that of RbTb2Fe4As4O2 and RbDy2Fe4As4O2.

Role of Doping Effect and Chemical Pressure Effect Introduced by Alkali Metal Substitution on 1144 Iron-Based Superconductors.

CaAFe4As4 with A = K, Rb, and Cs are close to the doped 122 system, and the parent material can reach a superconducting transition temperature of 31-36 K without doping. To study the role of alkali metals, we investigated the induced hole doping and chemical pressure effects as a result of the introduction of alkali metals using density-functional-based methods. These two effects can affect the superconducting transition temperature by changing the number of electrons and the structure of the FeAs conductive layer, respectively. Our study shows that the dxz and dyz orbitals, which are degenerate in CaFe2As2, become nondegenerate in CaAFe4As4 due to two nonequivalent arsenic atoms (As1 and As2). The unusual oblate ellipsoid hole pocket at Γ point in CaAFe4As4 results from a divalent cation Ca2+ replaced by a monovalent cation A+. It shows one of the main differences in fermiology compared to a particular form of CaFe2As2 with reduced 1144 symmetry, due to the enhancement of As2-Fe hybridization. The unusual band appears in CaFe2As2 (1144) and gradually disappears in the change of K to Cs. Further analysis shows that this band is contributed by As1 and has strong dispersion perpendicular to the FeAs layer, suggesting that it is related to the peculiar van Hove singularity below the Fermi level. In addition, various aspects of CaFe2As2 (1144) and CaAFe4As4 in the ground state are discussed in terms of the influence of hole doping and chemical pressure.

Topological magnons in one-dimensional ferromagnetic Su-Schrieffer-Heeger model with anisotropic interaction.

Topological magnons in a one-dimensional (1D) ferromagnetic Su-Schrieffer-Heeger (SSH) model with anisotropic exchange interactions are investigated. Apart from the intercellular isotropic Heisenberg interaction, the intercellular anisotropic exchange interactions, i.e. Dzyaloshinskii-Moriya interaction and pseudo-dipolar interaction, also can induce the emergence of the non-trivial phase with two degenerate in-gap edge states separately localized at the two ends of the 1D chain, while the intracellular interactions instead unfavors the topological phase. The interplay among them has synergistic effects on the topological phase transition, very different from that in the two-dimensional (2D) ferromagnet. These results demonstrate that the 1D magnons possess rich topological phase diagrams distinctly different from the electronic version of the SSH model and even the 2D magnons. Due to the low dimensional structural characteristics of this 1D topological magnonic system, the magnonic crystals can be constructed from bottom to top, which has important potential applications in the design of novel magnonic devices.

Investigation on the interlayer coupling and bonding in layered nitride-halides ThNF and ThNCl.

Motivated by recent experimental observation [N. Z. Wang, et al., Inorg. Chem., 2019, 58, 9897], we investigated the electronic properties and chemical bonding in layered nitride-halide compounds ThNF and ThNCl using first-principles calculations to illustrate the interlayer interaction. The energy gaps and chemical valences of both compounds are in agreement with experimental data. The crystal orbital Hamiltonian population (COHP) and charge density differential analysis show that interlayer chemical bonding plays a more important role than that van der Waals interactions in ThNF and ThNCl, in contrast to isostructural ZrNCl and HfNCl. These results explain why it is difficult to intercalate ThNF and ThNCl with charged particles, as observed in experiments.

IGFBP2 upregulates ZEB1 expression and promotes hepatocellular carcinoma progression through NF-κB signaling pathway.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most lethal cancers owing to the high metastasis rate. The molecular mechanism underlying HCC progression remains unclear. AIMS: We aimed to explore the function and mechanism of action of insulin-like growth factor binding protein 2 (IGFBP2) in HCC. METHODS: Expression of IGFBP2 was evaluated with western blotting and reverse transcription polymerase chain reaction (RT-PCR). Loss- and gain-function assays were conducted to evaluate the effects of IGFBP2 on HCC cell proliferation, migration, and invasion. Signaling pathways were screened with a dual-fluorescein reporting system, and levels of epithelial and mesenchymal markers were measured after altering IGFBP2 expression. Cell fractionation analysis was conducted to evaluate the nuclear translocation of p65. RESULTS: IGFBP2 expression was upregulated in HCC tissues, predicted worse prognosis, and was associated with strong metastatic potentials. IGFBP2 depletion significantly inhibited HCC cell proliferation, migration, and invasion, whereas IGFBP2 overexpression showed reverse phenotypes. The underlying mechanism involved IGFBP2-mediated nuclear localization of p65, which activated nuclear factor kappa B (NF-κB) and zinc finger E-Box binding homeobox 1 (ZEB1) transcription via binding to the gene promoter. CONCLUSION: This study for the first time identifies IGFBP2 as a novel therapeutic target in HCC that activates the NF-κB-ZEB1 signaling axis and promotes HCC tumorigenesis.

Treatment for Thoracic Ossification of Posterior Longitudinal Ligament with Posterior Circumferential Decompression.

OBJECTIVE: To report the results of the posterior approach for thoracic ossification of posterior longitudinal ligament (TOPLL) by using a special "L" osteotome. METHODS: The present study enrolled 16 consecutive patients (9 men and 7 women) between May 2009 and September 2013. All patients underwent a posterior circumferential decompression osteotomy and segmental instrumentation with interbody fusion. The mean age at surgery was 57.3 years (range, 37-68 years). Patients' data, clinical manifestation, blood loss, length of surgery, complications, visual analog scale (VAS), Japanese Orthopedic Association (JOA), and Frankel grading system before and after surgery were collected and evaluated, retrospectively. RESULTS: The average follow-up period was 30 ± 19 months (range, 12-50 months). All patients were successfully treated with posterior compression and segmental instrumentation with interbody fusion. The average operation time was 261.6 ± 51.3 min (range, 190-310 min). The mean blood loss was 980.3 ± 370.5 mL (range, 600-2100 mL). All patients had subjective improvement of motor power and gait. Average preoperative and postoperative JOA scores were 4.2 ± 1.7 and 7.8 ± 2.5 points, respectively. Differences in the overall JOA scores showed significant postoperative improvement. At the last follow-up, all patients improved either by one or two Frankel grades. There was a significant difference between preoperative VAS scores and those 3 months after surgery (P < 0.05). No significant difference was observed between the 3-month and 12-month results (P > 0.05). Cerebrospinal fluid (CSF) leakage occurred in 3 patients. Acute neurological deterioration was encountered postoperatively in 1 patient. CONCLUSION: Treatment with posterior transpedicular osteotomy and circumferential decompression was found to be safe, effective, reliable, and technically feasible, and keeping the thoracic cavity intact avoids many shortcomings of anterior surgery and results in a satisfactory spinal decompression.

Surgical Treatment for Central Calcified Thoracic Disk Herniation: A Novel L-Shaped Osteotome.

Few reports are available on the posterior transfacet approach for the treatment of central calcified thoracic disk herniation (TDH). The objective of this study was to assess outcomes and complications in a consecutive series of patients with TDH who underwent posterior transfacet decompression and diskectomy with segmental instrumentation and fusion. The data for 27 patients (16 males and 11 females) were retrospectively reviewed and analyzed, including clinical presentation, blood loss, operative time, pre- and postoperative complications, visual analog scale, Japanese Orthopedic Association (JOA) score, and Frankel grade. All patients underwent trans-facet decompression and segmental instrumentation with interbody fusion. Mean patient age at surgery was 55.2 years (range, 21-81 years). Average follow-up was 30±19 months (range, 12-50 months). All patients were successfully treated with posterior decompression and segmental instrumentation with interbody fusion. Average operative time was 124±58 minutes (range, 87-180 minutes). Mean blood loss was 439±225 mL (range, 300-1500 mL). Average pre- and postoperative JOA scores were 4.12±0.87 and 8.01±0.97 points, respectively. Overall JOA scores showed a significant postoperative improvement. Overall recovery rates were excellent in 12 patients, good in 6, fair in 5, and unchanged in 1. No patient was classified as worse. The results suggest that the posterior approach using a special L-shaped osteotome is feasible. No major complications occurred while achieving adequate decompression for central calcified TDH.

Band filling and correlation controlling electronic properties and magnetism in K(x)Fe(2-y)Se2: a slave boson study.

We investigate the electronic and magnetic properties of K(x)Fe(2-y)Se2 materials at different band fillings utilizing the multi-orbital Kotliar-Ruckenstein slave boson mean-field approach. We find that the ground state of KFe2Se2 is a paramagnetic (PM) bad metal with intermediate correlation, in contrast with the previous antiferromagnetic (AFM) results obtained by the local density approximation. Our PM metallic ground state suggests that KFe2Se2 is the parent phase of superconducting K(x)Fe(2-y)Se2, supporting a recent scanning tunneling spectroscopy experiment. For pure Fe2+-based systems, the ground state is a striped AFM (SAFM) metal with a spin density wave gap partially opened near the Fermi level. In comparison, for Fe3+-based compounds, besides SAFM, a Néel AFM metal without orbital ordering is observed, and an orbital selective Mott phase (OSMP) accompanied by an intermediate-spin to high-spin transition is also found, giving a possible scenario of an OSMP in K(x)Fe(2-y)Se2. These results demonstrate that the band filling and correlation control the Fermi surface topology, electronic state and magnetism in K(x)Fe(2-y)Se2.

Influence of electronic correlations on orbital polarizations in the parent and doped iron pnictides.

Orbital polarization and electronic correlation are two essential aspects in understanding the normal-state and superconducting properties of multi-orbital FeAs-based superconductors. In this paper, we present a systematic study on the orbital polarization of iron pnictides from weak to strong Coulomb correlations within the Kotliar-Ruckenstein slave boson approach. The magnetic phase diagram of the two-orbital model for LaFeAsO clearly shows that a striped antiferromagnetic metallic phase with orbital polarization exists over a wide doping range, in addition to the Slater-type insulator, Mott insulator and paramagnetic phases. A reversal of the orbital polarization occurs in the intermediate correlation regime in the absence of the crystal field splitting; however, a small crystal field splitting considerably enhances the orbital polarization, and stabilizes the xz-type orbital order. We argue that the ferro-orbital polarization is characteristic of a density wave, and leads to a pseudogap-like behavior in the density of states.

Poly[[[silver(I)-µ-1,4-bis-[(imidazol-1-yl)meth-yl]benzene-κN:N-silver(I)-µ-1,4-bis-[(imidazol-1-yl)meth-yl]benzene-κN:N] 4,4'-diazenediyldibenzoate] dihydrate].

In the title compound, [Ag(2)(C(14)H(14)N(4))(2)](C(14)H(8)N(2)O(4))·2H(2)O, each of the two unique Ag(+) ions is two-coordinated by two N atoms from two different 1,4-bis-[(imidazol-1-yl)meth-yl]benzene ligands in an almost linear fashion [N-Ag-N = 170.34 (10) and 160.25 (10)°]. The 4,4'-diazenediyldibenzoate anions do not coordinate to Ag. O-H⋯O hydrogen bonds stabilize the crystal structure.

2-Chloro-N'-(2-hy-droxy-3,5-diiodo-benzyl-idene)benzohydrazide.

In the title compound, C(14)H(9)ClI(2)N(2)O(2), the dihedral angle between the benzene rings is 65.9 (2)° and an intra-molecular O-H⋯N hydrogen bond generates an S(6) ring. The mol-ecule has an E conformation about the C=N bond. In the crystal, mol-ecules are linked into C(4) chains propagating in [001] by N-H⋯O hydrogen bonds.

(E)-N'-(2-Bromo-benzyl-idene)-2-fluoro-benzohydrazide.

The title compound, C(14)H(10)BrFN(2)O, adopts an E geometry about the C=N bond. The dihedral angle between the mean planes of the two benzene rings is 81.5 (6)°. In the crystal, mol-ecules are linked through inter-molecular N-H⋯O hydrogen bonds, forming chains running along the b axis.

Human dental pulp stem cell is a promising autologous seed cell for bone tissue engineering.

BACKGROUND: The seed cell is a core problem in bone tissue engineering research. Recent research indicates that human dental pulp stem cells (hDPSCs) can differentiate into osteoblasts in vitro, which suggests that they may become a new kind of seed cells for bone tissue engineering. The aim of this study was to evaluate the osteogenic differentiation of hDPSCs in vitro and bone-like tissue formation when transplanted with three-dimensional gelatin scaffolds in vivo, and hDPSCs may become appropriate seed cells for bone tissue engineering. METHODS: We have utilized enzymatic digestion to obtain hDPSCs from dental pulp tissue extracted during orthodontic treatment. After culturing and expansion to three passages, the cells were seeded in 6-well plates or on three-dimensional gelatin scaffolds and cultured in osteogenic medium. After 14 days in culture, the three-dimensional gelatin scaffolds were implanted subcutaneously in nude mice for 4 weeks. In 6-well plate culture, osteogenesis was assessed by alkaline phosphatase staining, Von Kossa staining, and reverse transcription-polymerase chain reaction (RT-PCR) analysis of the osteogenesis-specific genes type I collagen (COL I), bone sialoprotein (BSP), osteocalcin (OCN), RUNX2, and osterix (OSX). In three-dimensional gelatin scaffold culture, X-rays, hematoxylin/eosin staining, and immunohistochemical staining were used to examine bone formation. RESULTS: In vitro studies revealed that hDPSCs do possess osteogenic differentiation potential. In vivo studies revealed that hDPSCs seeded on gelatin scaffolds can form bone structures in heterotopic sites of nude mice. CONCLUSIONS: These findings suggested that hDPSCs may be valuable as seed cells for bone tissue engineering. As a special stem cell source, hDPSCs may blaze a new path for bone tissue engineering.

Orbital polarizations and superconducting phase diagrams in two-orbital asymmetric t-J models.

We present the zero-temperature superconducting (SC) phase diagrams of the two-orbital asymmetric t-J model on a square lattice by means of the auxiliary-boson approach. Besides the two-gap SC and normal phases, we find an orbital dependent intermediate SC phase, in which one orbit is fully SC and another orbit is exponentially vanishing gapped SC. Such an intermediate phase is stable only for sufficient asymmetry in orbital space and doping concentration. The implication of the present scenario on the iron-based and other multi-orbital superconductors is discussed.

Anharmonic effect on lattice distortion, orbital ordering and magnetic properties in Cs(2)AgF(4).

We develop the cluster self-consistent field method incorporating both electronic and lattice degrees of freedom to study the origin of ferromagnetism in Cs(2)AgF(4). After self-consistently determining the harmonic and anharmonic Jahn-Teller distortions, we show that the anharmonic distortion stabilizes the staggered x(2)-z(2)/y(2)-z(2) orbital and ferromagnetic ground state, rather than the antiferromagnetic one. The amplitudes of lattice distortions, Q(2) and Q(3), the magnetic coupling strengths, J(x,y), and the magnetic moment are in good agreement with the experimental observations.

Temporal expression of estrogen receptor alpha in rat bone marrow mesenchymal stem cells.

Estrogen responsiveness of bone formation is mediated by the estrogen receptor alpha (ERalpha) in osteoblastic lineage. As osteoblasts arise from the multipotent bone marrow stromal (mesenchymal) cells, this study was undertaken to observe the ERalpha in primary female adult rat bone marrow mesenchymal stem cells (BMSCs). The ERalpha was localized using immunocytochemical analysis in identified primary BMSCs. Then, using real-time PCR analysis, we measured the expression of ERalpha messenger RNA (mRNA) in BMSCs. ERalpha transcripts showed different trends between untreated cultures (control group) and osteogenic-induced cultures (treated group). In the control group, ERalpha mRNA climbed at peak levels at a confluence stage and decreased until day 20, whereas, in the treated group, the ERalpha mRNA kept climbing from a low level until day 20. Thus, the observed developmental expression of ERalpha mRNA correlates with progressive BMSCs growth and osteogenic differentiation and BMSCs may be a primary target cell for estrogen in maintaining bone formation.

Expression and purification of recombinant bone morphogenetic protein-2 in E.coli.

OBJECTIVE: To explore the method for producing human bone morphogenetic protein-2 (hBMP-2) by gene engineering techniques. METHODS: E.coli BL21 was transformed with recombinant plasmid pYR (pBV220-hBMP-2) under different conditions, and SDS-PAGE analysis was conducted to observe the effects of the activation status and induction time of the bacterium on the target protein expression. The inclusion bodies obtained from E.coli were purified by anion exchange chromatography DEAE and molecular sieve S-300, and the recombinant protein was renatured by dialyse. RESULTS: SDS-PAGE analysis showed a conspicuous band after induction signifying a new foreign protein with relative molecular mass of approximately 13 000. After activation of the bacteria when D600 was about 0.45, most efficient expression of rhBMP-2 was achieved which reached the peak 4 h after induction with heat. Implantation of the purified recombinant hBMP-2 resulted in proliferation of mesenchymal cells and new cartilage and bone formation, as shown by histological analysis 4 weeks after implantation. CONCLUSION: hBMP-2 produced by gene engineering techniques possesses the biological capacity of ectopic bone formation.

Changes in content of macrophage migration inhibitory factor secreted by Schwann cells after peripheral nerve injury.

OBJECTIVE: To investigate whether Schwann cells can secrete macrophage migration inhibitory factor (MIF) after peripheral nerve injury. METHODS: Two kinds of infant rat Schwann cells(which were derived from intact and injured nerves respectively) were cultured in 10% newborn calf serum (NCS) DMEM/F12 medium for 72 h. Then the level of MIF in the conditioned media was determined by an enzyme-linked immunoadsordent assay (ELISA). As control,MIF level was also determined in 10% NCS DMEM/F12 medium without any cells. RESULTS: The concentration of MIF in the conditioned medium of Schwann cells derived from injured nerves was significantly higher than that of control samples (P<0.05), while the concentration of MIF in the conditioned medium of Schwann cells from intact nerves was not elevated. CONCLUSION: After peripheral nerve injury, Schwann cells can secrete MIF which may play an important role as an immunomodulatory cytokine for macrophage activation, inflammatory reactions and immune responses.