Multi-walled carbon nanotubes (MWNTs) and singlewall carbon nanotubes (SWNTs) are produced by do arc discharge evaporation. In the case of MWNTs, hydrogen arc discharge was effective to make highly crystallised ones and with the thinnest inner tubes. In Raman spectra of MWNTs, radial breathing modes corresponding to the thinnest inner tube were observed. Mass production of SWNTs by arc discharge evaporation was carried out by arc plasma jet method. Hydrogen gas or addition of 1 % H2S gas also was effective to prepare SWNTs by arc discharge.
Recently, bright long-lasting phosphorescence has been observed for newly discovered crystals with tridymite and melilite structures. We report the optical properties of the longlasting phosphorescence produced by UV or near infrared excitation in the Eu2+ and Dy3+codoped tridymite and Ce3+ doped melilite crystals. We also propose the mechanisms of the long-lasting phosphorescence in these crystals.
Spinet-type Si3N4 has been synthesized under high pressures and high temperature conditions. Some structural characteristics have been investigated. Recent results are reviewed and compared with those of compounds containing six-fold coordinated Si. Some perspective will be given.
In mammals, heme is degraded to biliverdin by heme oxygenase (HO) and subsequently, the biliverdin is reduced to bilirubin by biliverdin reductase (BVR) . The metabolic waste product, bilirubin is now becoming recognized as having functional importance. It appears to play a key role in oxidative stress defense in vivo. Thus, heme degradation pathway has seen renewed interest in its biosynthesis. Recently, the X-ray crystal structures of HO and BVR were determined. Based on the structures, new insights into the mechanism of the heme degradation and bilirubin synthesis are discussed.