Near-net-shape fabrication of continuous Ag-clad Bi-based superconductors
We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors. This alternative to the powder-in-tube process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. The powder is rolled into an Ag channel, a cap is applied, and the assembly is lightly rolled. To minimize distortion during heat treatment, it is especially important that the Bi-2212 powder be nearly free of volatile species such as carbon. A vacuum-calcination process was developed to control CO/sub 2/ evolution during heating. Superconducting properties are discussed.
Commercialization of ceramic superconductor composite wires
Recent advances in the development of high-temperature superconductor (HTS) composite wires demonstrate an increasingly realistic potential for commercial applications, such as power transmission cables, motors, and superconducting magnetic energy storage (SMES) systems. Successful commercialization requires the development of manufacturing technologies that can produce high-performance, low-cost HTS wires. The achievement of this goal has been occurring through an understanding of the basic relationships between the processing, properties, and microstructures of complex ceramic superconductors. Remarkable results have already been demonstrated with the oxide-powder-in-tube (OPIT) process. The purpose of this paper is to review the recent progress of OPIT-processed HTS composite wires and prototype products fabricated from these wires.
Influence of inducers and inhibitors on the metabolism in vitro and neurochemical effects in vivo of MDMA.
(S)-(+)- and (R)-(-)-3,4-methylenedioxymethamphetamine (MDMA) were metabolized in vitro by rat liver microsomes via N-demethylation to 3,4-methylenedioxyamphetamine (MDA). Whereas no difference was found in the biotransformation of the two enantiomers in the male rat or in the phenobarbital (PB) treated animals of either sex, more than twice as much MDA was formed from (S)-(+)- than from (R)-(-)-MDMA in the untreated female rat. Although 3-methylcholanthrene (3MC) pretreated rat liver microsomes were less active than those from the untreated rats of the same sex, they formed more MDA from (+)- than from (-)-MDMA. The enantioselective metabolism thus appears to be associated with the relative abundance of individual cytochrome P-450 isozymes. (S)-(+)- and (R)-(-)-MDMA.HCl (20 mg/kg) were about equipotent in depleting serotonin (5-HT) levels in the frontal cortex at 3 hrs and 1 wk following oral administration to female rats. Pretreatment of rats with SKF-525A attenuated and that with PB enhanced the 5-HT depleting potential of either isomer at 3 hrs. The 5-HT depleting potency of (+)-MDMA was significantly greater than that of its (-)-antipode at 3 hr in PB pretreated, but not in SKF-525A pretreated animals. The results suggest that the neurochemical effects of MDMA are caused by the formation of an active metabolite in vivo, and since both enantiomers were N-demethylated in vitro to approximately the same extent by PB pretreated rat liver microsomes, the active metabolite may be other than MDA.