High-efficiency Algorithm for the Most Unfavourable Load Case Combinations of Multilayered Frame-Type Wharf Structure

The wharf, which was built in the Three Gorges Reservoir of China, is constructed as a layered frame-type structure for adapting to large water level fluctuations that exceed 30 m. These large fluctuations cause the frame-type structure to exhibit a considerably higher number of load case combinations than traditional marine high-piled wharfs. To estimate the most adverse combined internal force and the corresponding unfavourable load case combinations of significant components for multilayered frame-type wharf structures in the Three Gorges Reservoir of China, a high-efficiency algorithm is developed in this study. This algorithm can skilfully transform the computational mode of load case combinations into a matrix operations process by computer programming. By applying the proposed algorithm, the number of load case combinations for eight significant components of frame-type wharf, including piles, columns, beams, braces and berthing components, are resolved to a total of 21 from the original quantity of more than six billion. This high-efficiency algorithm can provide powerful technical support for evaluating the bearing capability of multilayered frame-type wharfs in the Three Gorges Reservoir of China

Low-energy spin excitations in optimally doped CaFe0.88_{0.88}Co0.12_{0.12}AsF superconductor studied with inelastic neutron scattering

There are few inelastic neutron scattering (INS) reports on the superconducting single crystals of FeAs-1111 system, even though it was first discovered in 2008, due to the extreme difficulty in large single crystal growth. In this paper, we have studied the low-energy spin excitations in the optimally electron-doped CaFe$_{0.88}$Co$_{0.12}$AsF single crystals with $T_\mathrm{c}$ = 21 K by INS. The resonance energy of the superconducting spin resonant mode with $E_\mathrm{r}$ = 12 meV amounts to 6.6 $k_\mathrm{B}$$T_\mathrm{c}$, which constitutes the largest $E_\mathrm{r}$/$k_\mathrm{B}$$T_\mathrm{c}$ ratio among iron-based superconductors reported to date. The large ratio implies a strong coupling between conduction electrons and magnetic excitations in CaFe$_{0.88}$Co$_{0.12}$AsF. The resonance possesses a magnonlike upward dispersion along transverse direction due to the anisotropy of spin-spin correlation length within $ab$ plane in the normal-state, which points to a spin fluctuation mediated sign-reversed ${s}\mathbf\pm$ wave pairing in CaFe$_{0.88}$Co$_{0.12}$AsF

Cdc42 is essential for the polarized movement and adhesion of human dental pulp stem cells

Objective: Stem cell-based tissue repair and regeneration require the regulation of cell migration and adhesion. As a regulator of cell polarization, Cdc42 (cell division control protein 42) plays a basic role at the initial stage of cell migration and adhesion. This study explores the effect of Cdc42 on the polarized migration and adhesion of hDPSCs (human dental pulp stem cells). Design: HDPSCs were isolated from extracted third molars and transfected with siRNA targeted against Cdc42. Scratch wound assays and transwell assays were performed to detect the migration of human dental pulp stem cells. Polarization assays were applied to explore the polarized movement of Golgi bodies and nuclei. Western blot was used to examine the expression of related proteins. Results: The expression of Cdc42 was knocked down by siRNA transfection, which inhibited the migration of hDPSCs in both the scratch wound assays and transwell assays. Meanwhile, the proportion of polarized hDPSCs during migration was also decreased, and the adhesion ability of hDPSCs was downregulated. Western blot demonstrated that these effects were dependent on FAK (focal adhesion kinase), β-catenin and GSK3β (Glycogen synthase kinase-3β). Conclusion Our study demonstrates that Cdc42 plays an essential role during the polarized movement and adhesion of hDPSCs

Strong Interplay between Stripe Spin Fluctuations, Nematicity and Superconductivity in FeSe

Elucidating the microscopic origin of nematic order in iron-based superconducting materials is important because the interactions that drive nematic order may also mediate the Cooper pairing. Nematic order breaks fourfold rotational symmetry in the iron plane, which is believed to be driven by either orbital or spin degrees of freedom. However, as the nematic phase often develops at a temperature just above or coincides with a stripe magnetic phase transition, experimentally determining the dominant driving force of nematic order is difficult. Here, we use neutron scattering to study structurally the simplest iron-based superconductor FeSe, which displays a nematic (orthorhombic) phase transition at $T_s=90$ K, but does not order antiferromagnetically. Our data reveal substantial stripe spin fluctuations, which are coupled with orthorhombicity and are enhanced abruptly on cooling to below $T_s$. Moreover, a sharp spin resonance develops in the superconducting state, whose energy (~4 meV) is consistent with an electron boson coupling mode revealed by scanning tunneling spectroscopy, thereby suggesting a spin fluctuation-mediated sign-changing pairing symmetry. By normalizing the dynamic susceptibility into absolute units, we show that the magnetic spectral weight in FeSe is comparable to that of the iron arsenides. Our findings support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations.Comment: 19 pages, 8 figure

Cu doping effects on the electronic structure of Fe1-xCuxSe

Using angle-resolved photoemission spectroscopy (ARPES), we studied the evolution of the electronic structure of Fe1-xCuxSe from x = 0 to 0.10. We found that the Cu dopant introduces extra electron carriers. The hole bands near the gamma point are observed to steadily shift downward with increasing doping and completely sink down below the Fermi level (EF) for x > 0.05. Meanwhile, the electron pocket near the M point becomes larger but loses the spectral weight near EF. We also observed that effective mass of the electron band near the M point increases with doping. Our result explains why superconductivity disappears and metal insulator transition (MIT) like behavior occurs upon Cu doping in terms of electronic structure, and provide insight into emergent magnetic fluctuation in Fe1-xCuxSe