X-ray Anomalous Scattering of Diluted Magnetic Oxide Semiconductors: Possible Evidence of Lattice Deformation for High Temperature Ferromagnetism

We have examined whether the Co ions crystallographically substitute on the Ti sites in rutile and anatase Ti_{1-x}$Co$_{x}$O$_{2-delta}$thin films that exhibit room-temperature ferromagnetism. Intensities of the x-ray Bragg reflection from the films were measured around the$K$-absorption-edge of Co. If the Co ions randomly substitute on the Ti sites, the intensity should exhibit an anomaly due to the anomalous dispersion of the atomic scattering factor of Co. However, none of the anatase and rutile samples did exhibit an anomaly, unambiguously showing that the Co ions in Ti$_{1-x}$Co$_{x}$O$_{2-delta}$are not exactly located at the Ti sites of TiO$_2$. The absence of the anomaly is probably caused by a significant deformation of the local structure around Co due to the oxygen vacancy. We have applied the same method to paramagnetic Zn$_{1-x}$Co$_{x}$O thin films and obtained direct evidence that the Co ions are indeed substituted on the Zn sites.Comment: 5 pages, 4 figures, accepted in PR

Ultra-high-purity iron is a novel and very compatible biomaterial

Metals and alloys are used widely in bone prosthetic materials, stents and dental tissue reconstructions. The most common materials are stainless steels and cobalt-chromium-nickel and titanium alloys. These alloys can be easily deformed but are hard to break. However, their affinity for cells and tissues is very low. In addition, they can sometimes provoke unexpected metal allergies. Iron is an abundant trace element essential for humans. However, excess amounts in particular of Fe2+ ions are toxic. We previously succeeded in obtaining 99.9996% ultra-high-purity iron (ABIKO iron). The chemical properties of ABIKO iron are completely different from that of conventional pure iron. For example, the reaction rate in hydrochloric acid is very slow and there is barely any corrosion. Here, we found that, in the absence of any type of coating, mammalian cells could easily attach to, and normally proliferate and differentiate on, ABIKO iron. On the other hand, cell densities and proliferation rate of the surfaces of plates made from Co–Cr–Mo or Ti–6Al–4V were significantly reduced. In addition, several stress and iron response genes, HSP70, SOD1, ATM and IRP2 did not change in the cells on ABIKO iron, while these genes were induced with exogenous application of FeSO4. Cells also secreted and fastened some organics on ABIKO iron. In vitro collagen binding assay showed that ABIKO iron binds higher amount of collagens. These findings highlight ABIKO iron as a novel biocompatible prosthetic material

Successive Magnetic Phase Transitions of Component Orderings in DyB4

The successive magnetic phase transitions in DyB4 have been studied in detail by microscopic measurements using resonant X-ray diffraction and neutron scattering. It is shown that the ab-plane component of the magnetic moment is short-range-ordered in the intermediate phase where the c-axis component is long-range-ordered. It is estimated that this short-range order is dynamically fluctuating with a time scale between ~ 10−8 to ~ 10−11s. Crystal field excitation has also been investigated by inelastic neutron scattering. To qualitatively understand the phase-transition phenomenon, we have studied a simple two-sublattice model with an antiferromagnetic interaction by mean-field calculation. The calculation, though without a quadrupolar interaction, successfully explains the occurrence of double phase transition, magnetic specific heat and entropy, magnetic susceptibility, and the huge elastic softening in the intermediate phase. The general success of the mean-field calculation, except for the shortrange order, suggests that there is little effect of geometrical frustration on the macroscopic properties at zero magnetic field.This work was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS) and also by the 21st century COE program of Tohoku University

Transplantation of a human induced pluripotent stem cell-derived airway epithelial cell sheet into the middle ear of rats

[Introduction] Early postoperative regeneration of the middle ear mucosa is essential for the prevention of postoperative refractory otitis media and recurrent cholesteatoma. As a means for intractable otitis media management, we focused on human induced pluripotent stem cell (hiPSC)-derived airway epithelial cells (AECs), which have been used in upper airway mucosal regeneration and transplantation therapy. In this study, we transplanted hiPSC-derived AECs into the middle ear of immunodeficient rats. [Methods] Following the preparation of AEC sheets from hiPSCs, the bilateral middle ear mucosa of X-linked severe combined immunodeficient rats was scraped, and the AEC sheets were transplanted in the ears unilaterally. [Results] Human nuclear antigen (HNA)-positive ciliated cells were observed on the transplanted side of the middle ear cavity surface in three of six rats in the 1-week postoperative group and in three of eight rats in the 2-week postoperative group. No HNA-positive cells were found on the control side. The percentage of HNA-positive ciliated cells in the transplanted areas increased in the 2-week postoperative group compared with the 1-week group, suggesting survival of hiPSC-derived AECs. Additionally, HNA-positive ciliated cells were mainly located at sites where the original ciliated cells were localized. Immunohistochemical analysis showed that the transplanted AECs contained cytokeratin 5- and mucin 5AC-positive cells, indicating that both basal cells and goblet cells had regenerated within the middle ear cavity. [Conclusions] The results of this study are an important first step in the establishment of a novel transplantation therapy for chronic otitis media