Search

A new synthetic method for the synthesis of C-substituted [RC(O)CH2-CB11H11]− carborate anions has been developed. The reaction of [closo-B11H11]2− with terminal alkynes in the presence of a copper catalyst leads to insertion into the boron cluster, and C-substituted [RC(O)CH2-CB11H11]− carborate anions are formed. These reactions are strongly dependent on the reaction conditions, the solvents, and the alkynes used. The alkynes HCCCO2Et, HCCCO2Me, and HCCCONH2 lead to the formation of [NH2C(O)CH2-CB11H11]− as the final product in aqueous ammonia solution. In contrast, the reaction using the alkyne HCCCOMe yields [MeC(O)CH2-CB11H11]−. The products have been fully characterized by multinuclear NMR and IR spectroscopy as well as mass spectrometry. The crystal structures of K[NH2C(O)CH2-CB11H11] and [NEt3CH2Cl][NH2C(O)CH2-CB11H11] have been determined.

A new synthetic method for the synthesis of C-substituted [RC(O)CH2-CB11H11]− carborate anions has been developed. The reaction of [closo-B11H11]2− with terminal alkynes in the presence of a copper catalyst leads to insertion into the boron cluster, and C-substituted [RC(O)CH2-CB11H11]− carborate anions are formed. These reactions are strongly dependent on the reaction conditions, the solvents, and the alkynes used. The alkynes HCCCO2Et, HCCCO2Me, and HCCCONH2 lead to the formation of [NH2C(O)CH2-CB11H11]− as the final product in aqueous ammonia solution. In contrast, the reaction using the alkyne HCCCOMe yields [MeC(O)CH2-CB11H11]−. The products have been fully characterized by multinuclear NMR and IR spectroscopy as well as mass spectrometry. The crystal structures of K[NH2C(O)CH2-CB11H11] and [NEt3CH2Cl][NH2C(O)CH2-CB11H11] have been determined. [ABSTRACT FROM AUTHOR]

We studied the complete set of elastic constants Cij and internal frictions tensor Qij-1 of anisotropic decagonal Al72Ni18Co8 single quasicrystal by electromagnetic acoustic resonance at low temperatures, to 5 K. Most Cij(T) showed usual stiffening upon cooling and their temperature behaviors are well characterized by an Einstein-lattice-vibration model. The average Grüneisen parameter estimated from the bulk modulus is 2.4, almost identical to crystalline Al. Ambient temperature Qij-1 show a linear relationship to the elastic-constants temperature derivatives |dCij/dT|/Cij with a slope of 1.28 K-1, suggesting that lattice anharmonicity plays a dominant role for Qij-1. The longitudinal modulus for the decagonal axis C33 and corresponding internal friction Q33-1, however, showed significant deviation from such ideal behavior, suggesting additional low-frequency phonon-excitation modes along the decagonal axis. [ABSTRACT FROM AUTHOR]

The electromagnetic acoustic resonance approach is employed to determine the complete elastic constants and internal fricitions of the decagonal [Al.sub.72][Ni.sub.18][Co.sub.8] single quasicrystal at low temperatures. The elastic constants are shown to get stiffened upon cooling.

Background and study aims Colorectal premalignant polyps and hemorrhoids are important findings in colonoscopy; however, the association between them is unclear. Therefore, we investigated the association between the presence and severity of hemorrhoids and the detection of precancerous colorectal polyps on colonoscopy.

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our research, we have developed novel bioplastics called “cell-plastics”, in which a unicellular green algal cell serves as a fundamental resource. The production of the cell-plastics would be expected to reduce environmental impact due to the usage of a natural product. Herein, to overcome the mechanical strength of cell-plastics, we used thermosetting epoxy and urethane resins containing Chlorella sp. as the green algae. We successfully fabricated thermosetting resins with a Chlorella sp. content of approximately 70 wt% or more. IR measurements revealed that the chemical structure of an epoxide or isocyanate monomer mixed with Chlorella sp. was modified, which suggests that the resins were hardened by the chemical reaction. In addition, we investigated the effect of thermosetting conditions such as temperature and compression for curing both resins. It was revealed that the Young’s moduli and tensile strengths were controlled by thermosetting temperature and compression, whereas the elongation ratios of the resins were constant at low values regardless of the conditions.