Ryutaro Sato

Formation of an Fe–H complex anion in YFe2: adjustment of imbalanced charge by using additional Li as an electron donor

The novel complex hydride YLiFeH6 with the Fe–H complex anion ([FeH6]4−) was synthesized by hydrogenation of YFe2 together with additional Li. Li adjusts the original imbalanced charge between Y3+ and [FeH6]4− by donating an electron to convert into Li+ during the hydrogenation, resulting in the formation of the well charge-balanced state of Y3+Li+[FeH6]4−.

Formation process of perovskite-type hydride LiNiH3: In situ synchrotron radiation X-ray diffraction study

The formation process of perovskite-type hydride LiNiH3 was investigated using in situ synchrotron X-ray diffraction measurements. A mixture of LiH and Ni was hydrogenated at 873 K and 3 GPa, and the structural changes associated with hydrogenation were observed. Time-resolved diffraction profiles showed a three-step reaction: hydrogenation of Ni to NiHx, formation of LiyNi1–yH solid solution, and conversion to perovskite-type hydride LiNiH3. The solid solution, which has never been reported, plays the role of the precursor in the perovskite formation and its presence is apparently critical for synthesizing perovskite-type hydrides.

Histamine reduces susceptibility to natural killer cells via down-regulation of NKG2D ligands on human monocytic leukaemia THP-1 cells

Natural killer (NK) group 2D (NKG2D) is a key activating receptor expressed on NK cells, whose interaction with ligands on target cells plays an important role in tumorigenesis. However, the effect of histamine on NKG2D ligands on tumour cells is unclear. Here we showed that human monocytic leukaemia THP‐1 cells constitutively express MHC class I‐related chain A (MICA) and UL16‐binding protein 1 on their surface, and incubation with histamine reduced the expression in a dose‐dependent and time‐dependent manner as assessed by flow cytometry. Interferon‐γ augmented the surface expression of the NKG2D ligands, and this augmentation was significantly attenuated by histamine. The histamine H1 receptor (H1R) agonist 2‐pyridylethylamine and H2R agonist dimaprit down‐regulated the expression of NKG2D ligands, and activation of H1R and H2R signalling by A23187 and forskolin, respectively, had the same effect, indicating that the histamine‐induced down‐regulation of NKG2D ligands is mediated by H1R and H2R. Quantitative reverse transcription‐PCR showed that mRNA levels of the NKG2D ligands and relevant microRNAs were not significantly changed by histamine. Histamine down‐regulated the surface expression of endoplasmic reticulum protein 5, and inhibition of matrix metalloproteinases did not impair this down‐regulation, indicating that proteolytic shedding was not involved. Instead, pharmacological inhibition of protein transport and proteasome abrogated it, and histamine enhanced ubiquitination of MICA. Furthermore, histamine treatment significantly reduced susceptibility to NK cell‐mediated cytotoxicity. These results suggest that histamine down‐regulates NKG2D ligands through the activation of an H1R‐ and H2R‐mediated ubiquitin–proteasome pathway and consequently reduces susceptibility to NK cells.

Bethe Ansatz Calculations for Quantum Spin Chains with Partial Integrability

We study the S matrix of a spin- s quantum spin chain which can be interpreted as a multicomponent quantum lattice gas. We show that this system contains integrable subsystems where the Bethe ansatz method is applicable. We demonstrate that for some ranges of parameters of a spin-1 model, the ground states and low-lying excited states are exactly given by those of integrable subsystems; exact calculation is possible even if the system is not strictly integrable as a whole. We also analyze the magnetization curves for the spin chain, with exact saturation fields.

Formation of Hydrides in (Ti1−xZrx)Co2.00 (0 < x < 1) Pseudobinary Alloys

The exposure of (Ti(1-x)Zr(x))Co(2.00) intermetallic alloys to hydrogen at high pressure caused (Ti(1-x)Zr(x))Co(2.00) (x = 0.50-0.90) hydrides in the alloy. The crystalline structural, electronic, and magnetic properties of parent alloys and of their hydrides were determined by using XRD (X-ray powder diffraction) and XAS (X-ray absorption spectrometry) and by the use of SQUID (a superconducting quantum interference device). Hydrogenation did not alter the crystal structure of the parent alloy, but it did increase the volume of the unit cell. An in situ Co K-edge XAS study of the hydride revealed that the valence state of Co increased during discharge (which is the release of hydrogen from the hydride). Hydrogenation of the parent alloy also reduced the magnetic moment. A possible mechanism of discharge for the hydride is also proposed.

Multi-Phonon Excitations in Fe 2p RIXS on Mg2FeH6

Multi-phonon excitations, indicating a strong electron–phonon coupling, were observed by soft X-ray resonant inelastic X-ray scattering of Mg2FeH6 and Mg2FeD6. The Fe–H/D stretch and bend modes are selectively activated by the tuned electron excitation to eg brach of Fe 3d states in octahedral symmetry. The energy deviation with the factor of \( {\sim} \sqrt{2} \) due to the isotope effect was clearly observed.