A nickel sulfide mini-bead technique to preconcentrate noble metals has been developed. Following this technique, several types of geological, environmental and international reference samples have been fused successfully. The recovery of the noble metals from 10g of reference material with only 0.25g Ni has been found to be as good as that achieved by larger amounts of nickel. The homogeneous distribution of noble metals within the bead was confirmed by laser ablation ICP-MS analysis. Chemical composition of flux suitable for different types of samples was established.
Bulk glassy alloys with thicknesses up to 75mm and a wide supercooled liquid region reaching 127K before crystallization were found to be fabricated in a number of multicomponent systems which satisfy the three empirical rules for the achievement of large glass-forming ability, i.e., (1) multicomponent alloy systems consisting of more than three constituent elements, (2) significantly different atomic size ratios above 12%, and (3) negative heats of mixing. The scientific significance of the rules has been proved based on a number of experimental data as well as on the kinetic theories of the nucleation and growth of a crystalline phase. By choosing appropriate compositions which satisfy the empirical rules, bulk glassy alloys in Mg-, lanthanide metal-, Zr-, Pd-, Fe- and Co-based systems were produced in cylindrical and sheet forms by various solidification processes. The bulk glassy alloys exhibit high tensile strength, good ductility, high elastic energy, high impact fracture energy and high corrosion resistance for Zr-based system and good soft magnetic properties for Fe-based system. Furthermore, their glassy alloys heated in the supercooled liquid region can be deformed into various shapes through viscous flow. The ideal Newtonian flow has been achieved in the supercooled liquid. The utilization of the ideal superplasticity enabled the achievement of an extremely large elongation exceeding 15000%. These excellent data allow us to expect that the bulk glassy alloys develop as a new type of engineering material.
Ca2+ channel blockers from two different chemical classes, nifedipine and varapamil, were compared in rats for their ability to inhibit the wet-dog shakes behavior and limbic seizures induced by kainic acid which binds to a subtype of glutamate receptors in the brain. Pretreatment for 30 minutes with nicardipine or verapamil suppressed slightly kainic acid-induced wet-dog shakes independent of the dose 1-4mg/kg. In the rats treated with 5mg/kg of nicardipine or verapamil, however, the frequency of wet-dog shakes decreased to 50-60% of controls. In contrast, nicardipine accelerated the onset time and frequency of limbic seizures, resulting in increased mortality by kainic acid in the dose-dependent manner. Occurrence of limbic seizures in verapamil-treated rats was similar to that in the controls and the mortality in this group was smaller than in the nicardipine-treated group. Pretreatment with diazepam alone prevented the kainic acid-induced limbic seizures. However, in the rats pretreated with diazepam and nicardipine simultaneously, anticonvulsive effect of diazepam was not shown and the mortality in this group was the similar to that in the nicardipine pretreated group. Both nicardipine and verapamil did not enhance the picrotoxin-induced convulsions. The mechanism of the apparent enhancement of the mortality of kainic acid by even low doses of nicardipine is not clear. This might be, at least in part, correlated with their different mechanism of channel blocking action.
DMSO reductase from Rhodobacter sphaeroides f. sp. denitrificans was crystallized by the hanging-drop vapor diffusion method, using ammonium sulfate as a precipitant. The space group of the crystal was P21212, with unit-cell dimensions of a=76.1Å, b=203.4Å, and c=62.2Å. Assuming one protein molecule per asymmetric unit, the solvent content was estimated to be 56%.