Atsushi Ishihara

Regulation of Platelet-derived Growth Factor-A Chain by Krüppel-like Factor 5 NEW PATHWAY OF COOPERATIVE ACTIVATION WITH NUCLEAR FACTOR-κB

The transcription factor Krüppel-like factor 5 (KLF5) and its genetically downstream target gene platelet-derived growth factor-A (PDGF-A) chain are key factors in regulation of cardiovascular remodeling in response to stress. We show that KLF5 mediates a novel distinct delayed persistent induction of PDGF-A chain in response to the model agonist, phorbol ester, through a cis-element previously shown to mediate phorbol ester induction on to PDGF-A chain through the early growth response factor (Egr-1). Interestingly, the nuclear factor-κB (NF-κB) p50 subunit further cooperatively activates PDGF-A chain through protein-protein interaction with KLF5 but not Egr-1. RNA interference analysis confirmed that KLF5 and p50 are important for induction of PDGF-A chain. Collectively, we identify a novel regulatory pathway in which PDGF-A chain gene expression, under the control of KLF5, is cooperatively activated by the NF-κB p50 subunit and a pathophysiological stimulus.

Tri-axial Grain Orientation of Y2Ba4Cu7Oy Achieved by the Magneto-science Method

Tri-axial orientation of orthorhombic and twin-free Y2Ba4Cu7Oy (Y247) powders was attempted using a rotating magnetic field with modulated rate. Although magnetic anisotropy of paramagnetic Y247 originated only from the two-dimensional CuO2 and one-dimensional Cu–O chain structures are small, strong tri-axial grain orientation with misorientation angles below 1.5° was successfully achieved during the solidification process of epoxy resin. Our present results indicate the possibility of fabrication of tri- or bi-axial grain-oriented bulk and thick films without applying epitaxial methods, such as melt-solidification or thin film deposition, and that the modulated-rotation magnetic field is applicable not only to RE247 compounds but also to orthorhombic high critical temperature cuprate superconductors, including practical REBa2Cu3Oy, in principle.

Magnetic orientation and magnetic anisotropy in paramagnetic layered oxides containing rare-earth ions

Abstract The magnetic anisotropies and easy axes of magnetization at room temperature were determined, and the effects of rare-earth (RE) ions were clarified for RE-based cuprates, RE-doped bismuth-based cuprates and RE-doped Bi-based cobaltite regarding the grain orientation by magnetic field. The easy axis, determined from the powder orientation in a static field of 10 T, depended qualitatively on the type of RE ion for all three systems. On the other hand, the magnetization measurement of the c-axis oriented powders, aligned in static or rotating fields, revealed that the type of RE ion strongly affected not only the directions of the easy axis but also the absolute value of magnetic anisotropy, and an appropriate choice of RE ion is required to minimize the magnetic field used for grain orientation. We also studied the possibility of triaxial grain orientation in high-critical-temperature superconductors by a modulated oval magnetic field. In particular, triaxial orientation was attempted in a high-oxygen-pressure phase of orthorhombic RE-based cuprates Y2Ba4Cu7Oy. Although the experiment was performed in epoxy resin, which is not practical, in-plane alignment within 3° was achieved.

Rare-Earth-Dependent Magnetic Anisotropy in REBa2Cu3Oy

We report magnetic anisotropies (Δχ) depending on rare earth (RE) element in the paramagnetic REBa2Cu3Oy (RE123) system as an important finding of magneto-scientific grain-orientation. The c-axis-oriented RE123 powder samples using static or rotating magnetic fields were fabricated at room temperature to clarify Δχ. Their easy axes of magnetization were mainly dominated by second-order Stevens factors, whereas |Δχ| largely depended on y and RE elements. Especially for heavy RE elements, |Δχ| reached the order of 10-4, indicating that appropriate choice of RE directly leads to a drastic reduction of required magnetic fields for grain-orientation of RE123.

3-Dimensional Grain Orientation of RE-Ba-Cu-O Superconductors Using a Modulated Oval Magnetic Field

Tri-axial orientation of twin-free powders of RE2Ba4Cu7O15-delta (RE247, RE = Y, Dy, Ho, Er) was attempted by modulated rotating magnetic fields. The c -axis orientation was almost completely achieved for all the four RE247 compounds, whereas the degrees of in-plane orientation depended on RE element. Especially for Y247, the degrees of in-plane and c-axis orientation were determined to be ~ 2.5degand < 2deg, respectively, by the phi-scanning and rocking curve measurements. This excellent in-plane orientation is comparable or superior to those for coated conductors ( ~ 4deg) and melt-solidified bulks ( ~ 8deg) of REBa2Cu3O7-delta. Magnetic field dependence of Lotgering factors revealed that the degrees of in-plane orientation were sensitive to the applied magnetic field. The required magnetic field for the tri-axial orientation is determined by the in-plane magnetic anisotropy rather than the magnetic anisotropy between in-plane and out-of-plane directions.

Superior homogeneity of trapped magnetic field in superconducting MgB2 bulk magnets

Homogeneity of trapped magnetic field in radial and circumferential directions of high temperature superconducting bulk magnets, MgB2 (T c ~38.3 K) and YBa2Cu3O y (T c ~91.5 K), have been measured. In polycrystalline MgB2 bulks, the circularity of trapped magnetic field in a cylindrical disk is over 97% at 20–32.5 K, while that of YBa2Cu3O y was ~87% at 77 K. Magnetic field distribution of MgB2 bulk was satisfactorily homogeneous and these measurements suggest MgB2 bulks with highly efficient cryocoolers should be very useful for novel high field permanent magnet applications.

Elucidation of Crystal-Chemical Determination Factor of Magnetic Anisotropy in HTSC

Easy axes of magnetization at room temperature in REBa₂Cu₃O_y (RE: rare earth) and Bi₂Sr₂Ca_1-xRE_xCu₂O_y were clarified using their powders oriented in a static magnetic field. The easy axes clearly depended on the type of RE which could be mainly explained in terms of second-order Stevens factors and magnetic anisotropy of the CuO₂ plane. Furthermore, we found the difference in magnetic effects of Er³⁺ for orientation through systematic evaluations of Er-doped Y123 and Bi2212 powders. This result means that magnetic anisotropies of RE³⁺ ions are sensitive to not only the type of RE but also local structure of oxygen ions surrounding RE³⁺ ions.