Effects of doping with nanoscale Co3O4 particles on the superconducting properties of powder-in-tube processed MgB2 tapes

Nanoscale Co₃O₄ particles were doped into MgB₂ tapes with the aim of developing superconducting wires with high-current-carrying capacity. Fe-sheathed MgB₂ tapes with a mono-core were prepared using the in situ powder-in-tube (PIT) process with the addition of 0.2–1.0 mol% Co₃O₄. The critical temperature decreased monotonically with an increasing amount of doped Co₃O₄ particles for all heat-treatment temperatures from 600 to 900 °C. However, the transport critical current density (J_c) at 4.2 K varied with the heat-treatment temperatures. The J_c values in magnetic fields ranging from 7 to 12 T decreased monotonically with increasing Co₃O₄ doping level for a heat-treatment temperature of 600 °C. In contrast, some improvements on the J_c values of the Co₃O₄ doped tapes were observed in the magnetic fields below 10 T for 700 and 800 °C. Furthermore, J_c values in all the fields measured increased as the Co₃O₄ doping level increase from 0 to 1 mol% for 900 °C. This heat-treatment temperature dependence of the J_c values could be explained in terms of the heat-treatment temperature dependence of the irreversibility field with Co₃O₄ doping.     

Synthesis and potential central nervous system stimulant activity of 5,8‐methanoquinazolines and bornano‐triazines fused with imidazole and pyrimidine

Starting from 3‐chloro‐5,8‐methanoquinazoline 1 and 3‐chloro‐bornano[1,2,4]triazine 7 , the novel 5,8‐methanoquinazolines 5a‐b and bornano[1,2,4]triazines 10a‐b fused with imidazole and pyrimidine were prepared. None of these compounds showed any satisfactory central nervous system stimulant activities.     

Spectrophotometric determination of iron(III) with o-hydroxyhydroquinonephthalein after preconcentration on a membrane filter

Application of xanthene derivatives in analytical chemistry. Part LXXXVIII. Part LXXXVII see ref. [1]     

Synthesis of the Tricyclic Skeleton of Cyathins Using Brook Rearrangement-Mediated

The tricyclic core of cyathins has been synthesized using a Brook rearrangement-mediated [3 + 4] annulation that we previously developed.     

Synthesis of polyolefins with unique properties by using metallocene-type catalysts

Copolymerization of ethylene and 1,5-hexadiene (HD) by zirconocene catalysts proceeded via cyclization-addition mechanism to form 1,3-didsubstituted cyclopentane structure in the polyethylene chain. The 1,3-cyclopentane structure was found to be taken in the crystalline structure of polyethylene (isomorphism) by partially chainging the trans zigzag chain into gauche conformation, thereby, inducing a transformation of orthorhombic crystal to pseudohexagonal crystal. Copolymerization of ethylene and cyclopentene (CPE) by zirconocene catalysts yielded copolymers having 1,2-disubstituted cyclopentane structure in the polyethylene chain. The 1,2-cyclopentane structure was not taken into the crystalline structure of polyethylene. The melting point (T_m) and the crystallinity (X_c) of polyethylene decreased by copolymerization of HD or CPE, and the T_m- and X_c-decreasing effect of CPE was stronger than HD. For copolymers of propylene and HD or CPE obtained with isospecific zirconocene catalyst, the isomorphism was not ovserved.