Measurement of the cross section for diphoton production in 1.8 TeV proton-antiproton collisions

Thesis (Ph. D. in Science)--University of Tsukuba, (B), no. 1348, 1998.1.3

A Cross-Whiskers Junction as a Novel Fabrication Process for Intrinsic Josephson Junction

A Bi2Sr2CaCu2O8+d cross-whiskers junction has been successfully discovered as a novel intrinsic Josephson junction without using any technique for micro-fabrication. Two Bi2Sr2CaCu2O8+d whisker crystals were placed crosswise on a MgO substrate and heated at 850C for 30 min. They were electrically connected at their c-planes. The measurement terminals were made at the four ends of the whiskers. The I-V characteristics of the cross-whiskers junction at 5K were found to show a clear multiple-branch structure with a spacing of approximately 15 mV that is a feature of the intrinsic Josephson junction. The critical current density Jc was estimated to be 1170 A/cm2. The branch-structure was strongly suppressed by the magnetic field above 1kOe.Comment: 4 pages, PDF fil

Hierarchical nanophase-separated structures created by precisely-designed polymers with complexity

AbstractThis review paper summarizes recent advances in self-assembly of complex polymers, focusing on three characteristic polymeric systems. The first is star-branched polymers of the ABC type, the second one consists of multiblock terpolymers with different chain lengths, while the third comprises supramacromolecular assembly systems with hydrogen and ionic bonding interactions between different polymer species. A quasicrystalline tiling structure with mesoscopic length scale has been found for the first star polymer system as well as the periodic Archimedean tiling structures, and moreover three-dimensional Zincblende network structure has been discovered. Furthermore the hierarchical structures having two length scales have been also found for the ABC star molecules whose chain length ratios, that is, A/B and/or A/C are larger than approximately five. Hierarchical structures with double periodicity have been observed for the hexablock and undecablock terpolymers and it has been revealed that their morphology changes systematically depending on composition of polymeric species. Poly(4-hydroxystyrene) (H) homopolymer was found to be dissolved into microdomain of poly(2-vinylpyridine) formed by poly(styrene-b-2-vinylpyridine) due to hydrogen bonding interaction, resulting in the origin of morphological transitions depending on the composition of H homopolymer added. Hierarchical structures possessing double periodicity have been found for poly(isoprene-b-2-vinylpyridine)/poly(styrene-b-4-hydroxystyrene) blends depending on both volume fractions of component polymers and blend ratio. Blends of different homopolymers with several complementary nucleotides or acid/base moieties on chain ends have been confirmed to show nanophase-separated structures as a result of successful formation of “supramacromolecules”

Fabrication of Bi2212 Cross Whiskers Junction

An intrinsic Josephson junction has been successfully fabricated without any micro-fabrication technique. Two Bi2212 whiskers were crossed with one another and joined by post-annealing. The inter-whisker electrical transport properties were measured by the four-probe method. The temperature dependence of resistance exhibited metallic behavior above TC. The resistance decreased to zero around 80K, corresponding to the superconducting transition. The current-voltage characteristics at 5K exhibited a small hysteresis and voltage jump, which can be explained by the intrinsic Josephson effect.Comment: 3 page PDF fil