In vertebrate embryos, formation of anterior neural structures requires suppression of Wnt signals emanating from the paraxial mesoderm and midbrain territory. In Six3 −/− mice, the prosencephalon was severely truncated, and the expression of Wnt1 was rostrally expanded, a finding that indicates that the mutant head was posteriorized. Ectopic expression of Six3 in chick and fish embryos, together with the use of in vivo and in vitro DNA-binding assays, allowed us to determine that Six3 is a direct negative regulator of Wnt1 expression. These results, together with those of phenotypic rescue of headless/tcf3 zebrafish mutants by mouse Six3, demonstrate that regionalization of the vertebrate forebrain involves repression of Wnt1 expression by Six3 within the anterior neuroectoderm. Furthermore, these results support the hypothesis that a Wnt signal gradient specifies posterior fates in the anterior neural plate.

We demonstrate the generation of alternating spin current (SC) via spin-rotation coupling (SRC) using a surface acoustic wave (SAW) in a Cu film. Ferromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO_{2} film into the interface. The intensity of the resonance depended on the angle between the wave vector of the SAW and the magnetization of the Ni-Fe film. This angular dependence is explicable in terms of the presence of spin transfer torque from a SC generated via SRC.

We have studied the electronic structure of epitaxially grown thin films of La1−xSrxFeO3 by insitu photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS) measurements. The Fe 2p and valence-band PES spectra and the O 1s XAS spectra of LaFeO3 have been successfully reproduced by configuration-interaction cluster-model calculation and, except for the satellite structure, by band-structure calculation. From the shift of the binding energies of core levels, the chemical potential was found to be shifted downward as x was increased. Among the three peaks in the valence-band spectra of La1−xSrxFeO3, the peak nearest to the Fermi level (EF ), due to the "eg band", was found to move toward EF and became weaker as x was increased, whereas the intensity of the peak just above EF in the O 1s XAS spectra increased with x. The gap or pseudogap at EF was seen for all values of x. These results indicate that changes in the spectral line shape around EF are dominated by spectral weight transfer from below to above EF across the gap and are therefore highly non-rigid-band-like.

We have examined the thermal stability of TiO2-terminated SrTiO3(100) surfaces obtained by buffered HF etching and widely used as substrates for oxide film growth. In situ coaxial impact-collision ion scattering spectroscopy was used to measure the composition of the terminating atomic layer at temperatures up to 1000°C, simulating a broad range of thin-film growth conditions. The TiO2 termination of a nonannealed but HF-etched surface was found to start collapsing at temperatures as low as 300°C regardless of atmosphere, showing thermal instability of the chemically cleaved surface. Here, we introduce an alternative way to prepare a stabilized SrTiO3 surface, which maintains a perfect TiO2 termination up to 700°C, ideal for the growth of atomically sharp oxide heterointerfaces.

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The effects of soft X-ray exposure on structures of CH3NH3PbI3 perovskite were investigated using an X-ray photoelectron spectroscopy (XPS) time-dependent measurement method. A crystalline sample was fabricated with the inverse-temperature crystallization method. The time evolutions of the core-level and valence-band spectra were recorded to determine the compositional ratios and valence band electronic structure of the sample, respectively. In addition, first-principles calculations were conducted to evaluate the valence band XPS spectra. The in situ XPS analysis combined with theoretical calculations demonstrated a degradation of the surface of CH3NH3PbI3 perovskite into PbI2 owing to the evaporation of methylammonium iodide.

The chemical properties and electronic structures of atomically flat SrTiO3(001) substrates with various surface treatments have been investigated by high-resolution synchrotron-radiation photoemission spectroscopy. We have found that an annealing process causes the segregation of Sr oxides at the TiO2-terminated surface and that the TiO2-terminated surface is more stable than the SrO terminated one. We demonstrate that the use of chemical etching process is effective as a removal technique for Sr oxides accumulating on TiO2-terminated surfaces and that the adding of a reetching process after annealing in an O2 environment is one of the best methods to obtain well defined and nearly perfect substrate surface.