Geometric aspects of nonlinear and nonequilibrium phenomena

We review recent developments in the research of nonlinear and nonequilibrium phenomena in solids focusing on their geometrical aspects. We start with introducing the basic concepts of geometrical phases of Bloch electrons and Floquet theory for periodically driven systems. Then we review recent attempts to engineer topological phases in nonequilibrium matters such as graphene, magnets, and superconductors irradiated with circularly polarized light. We next review a bulk photovoltaic effect of inversion broken materials focusing on the shift current response. The shift current is described with Berry connections and has a close relationship to the modern theory of polarization. We further review recent extensions of the shift current to correlated electron systems. Finally, we explain the geometric diabatic time evolution in the Zener tunneling process and its consequences on nonreciprocal transport.Comment: 22 pages, 13 figures; a review paper submitted to J. Phys. Soc. Jp

Effects of Ca substitution on the local structure and oxide–ion behavior of layered perovskite lanthanum nickelate

La2NiO4+δ-based materials with a layered perovskite structure have attracted significant attention as air–electrode materials for use in solid oxide fuel cells. In particular, Ca-substituted materials, La2-xCaxNiO4+δ, have been investigated, as the partial substitution of La with Ca can improve oxide–ion conduction in crystals. However, the local structures around the conducting oxide ion and Ca dopant are not been well understood because their distributions cannot be characterized by a general structure analysis only using Bragg peaks. Therefore, we examine the atomic structure of La1.75Ca0.25NiO4+δ by a combination of molecular dynamics simulations and a reverse Monte Carlo modeling using the Faber–Ziman structure factor, real-space function, and the Bragg profile simultaneously. The results indicate that conducting oxide ions are introduced into rocksalt layers in the crystal and are present around La but not Ca. Furthermore, it is found that ionic diffusion is accompanied by a change in the rocksalt layer volume, which can be suppressed by the partial substitution with Ca. This can be regarded as a major reason why Ca substitution improves oxide–ion diffusion in the La2NiO4+δ layered perovskite

Modeling and emergence of flapping flight of butterfly based on experimental measurements

The objective of this paper is to clarify the principle of stabilization in flapping-of-wing flight of a butterfly, which is a rhythmic and cyclic motion. For this purpose, a dynamics model of a butterfly is derived by Lagrange’s method, where the butterfly is considered as a rigid multi-body system. For the aerodynamic forces, a panel method is applied. Validity of the mathematical models is shown by an agreement of the numerical result with the measured data. Then, periodic orbits of flapping-of-wing flights are searched in order to fly the butterfly models. Almost periodic orbits are obtained, but the model in the searched flapping-of-wing flight is unstable. This research, then, studies how the wake-induced flow and the flexibly torsional wing’s effect on the flight stability. Numerical simulations demonstrate that both the wake-induced flow and the flexible torsion reduces the flight instability. Because the obtained periodic flapping-of-wing flight is unstable, a feedback control system is designed, and a stable flight is realized

Dentin Materials as Biological Scaffolds for Tissue Engineering

Vital tooth-derived demineralized dentin matrix (DDM) has a bone-inductive ability, while non-vital tooth-derived DDM lost it. Acid treatment for dentin provides the increase of surface area, the release of matrix-binding growth factors such as BMPs, and the decrease of the infection risk. Human autograft of vital tooth-derived DDM was achieved first in Japan 2002, while first bone autograft was noted in Italy 1820. This paper introduced dentin/bone biology and a unique clinical case, combined with two types of non-vital tooth-derived DDM (roots, granules) for lateral bone augmentation. A 63-year-old woman revealed highly atrophic mandible in 2015. Three non-vital teeth were extracted, changed in shape, demineralized in 2% HNO3, were rinsed, and were grafted immediately. The CT images at 3 months after the graft showed remarkable lateral augmentation. DDM scaffolds were received to host, and two fixtures were placed into the DDM-augmented bone. The patient was successfully restored with their own DDM scaffolds and implant surgery

Signalling via the osteopontin and high mobility group box-1 axis drives the fibrogenic response to liver injury

Objective: Liver fibrosis is associated with significant collagen-I deposition largely produced by activated hepatic stellate cells (HSCs); yet, the link between hepatocyte damage and the HSC profibrogenic response remains unclear. Here we show significant induction of osteopontin (OPN) and high-mobility group box-1 (HMGB1) in liver fibrosis. Since OPN was identified as upstream of HMGB1, we hypothesised that OPN could participate in the pathogenesis of liver fibrosis by increasing HMGB1 to upregulate collagen-I expression. Design and results: Patients with long-term hepatitis C virus (HCV) progressing in disease stage displayed enhanced hepatic OPN and HMGB1 immunostaining, which correlated with fibrosis stage, whereas it remained similar in non-progressors. Hepatocyte cytoplasmic OPN and HMGB1 expression was significant while loss of nuclear HMGB1 occurred in patients with HCV-induced fibrosis compared with healthy explants. Well-established liver fibrosis along with marked induction of HMGB1 occurred in CCl4-injected OpnHep transgenic yet it was less in wild type and almost absent in Opn−/− mice. Hmgb1 ablation in hepatocytes (Hmgb1ΔHep) protected mice from CCl4-induced liver fibrosis. Coculture with hepatocytes that secrete OPN plus HMGB1 and challenge with recombinant OPN (rOPN) or HMGB1 (rHMGB1) enhanced collagen-I expression in HSCs, which was blunted by neutralising antibodies (Abs) and by Opn or Hmgb1 ablation. rOPN induced acetylation of HMGB1 in HSCs due to increased NADPH oxidase activity and the associated decrease in histone deacetylases 1/2 leading to upregulation of collagen-I. Last, rHMGB1 signalled via receptor for advanced glycation end-products and activated the PI3K–pAkt1/2/ 3 pathway to upregulate collagen-I