RESUMO
The concept of grain-oriented fabrication in ceramics, which utilizes anisotropy either in morphology or some specific property of the particle, is reviewed. A fabrication method, which maximizes the grain orientation, is described for Bi(4)Ti(3)O(12 ). The process utilized plate-like morphology of Bi(4)Ti (3)O(12) particles and yielded a ceramic with an X-ray density of 95.4% and an unprecedented value of 100% for Lotgering's orientation factor in the direction of orientation. The dielectric and piezoelectric properties of this ceramic are described and compared to single crystal values. Complex impedance analysis of the ceramics was used to explain the dielectric relaxations at elevated temperatures. The use of grain-oriented fabrication as a practical technique for making polycrystalline ceramics with electrical properties close to those of single crystals (in the direction of orientation) is emphasized. The use of grain-oriented Bi(4)Ti(3)O(12) ceramics as a high-temperature piezoelectric transducer is suggested.
RESUMO
Incremental feeding of nutrients was found to be beneficial in mass cultivation of R. leguminosarum. Similarly, semi-continuous fermentation of R. leguminosarum up to 4 days was also found to be useful in maintaining the viable number of cells.
Assuntos
Técnicas Bacteriológicas , Rhizobium/crescimento & desenvolvimento , Técnicas Bacteriológicas/economia , Meios de Cultura , Fermentação , Manitol/metabolismo , Rhizobium/metabolismo , Saccharomyces cerevisiaeRESUMO
Several different methods of performing susceptibility tests on six clinical isolates of Aspergillus are described. Some of the conditions that affected the level of susceptibility to drugs were: the type of media used, temperature and time of incubation, and the initial inoculum size. For amphotericin B susceptibility testing, the effectiveness of the polyene antibiotic as measured by visual growth was equivalent to the effectiveness as measured by inhibition of ribonucleic acid synthesis and dry-weight increase. For 5-fluorocytosine and rifampin, the visual-turbidity method gave minimum inhibitory concentrations that were much higher than those determined by effects on ribonucleic acid synthesis and dry weight. The reason for these discrepancies in susceptibility testing with 5-fluorocytosine and rifampin are unknown. We conclude that the most relevant test of this fungus to antifungal agents will have to be determined by the correlation of in vitro data with animal experiments and clinical results.
Assuntos
Anfotericina B/farmacologia , Aspergillus/efeitos dos fármacos , Aspergillus/metabolismo , Aspergillus flavus/efeitos dos fármacos , Aspergillus fumigatus/efeitos dos fármacos , Meios de Cultura , Testes de Sensibilidade Microbiana , RNA/isolamento & purificação , Temperatura , Fatores de TempoRESUMO
Amphotericin B in combination with 5-fluorocytosine was synergistic against three clinical isolates of Aspergillus fumigatus and one of three clinical isolates of A. flavus. Amphotericin B in combination with rifampin was synergistic against all six clinical isolates of Aspergillus tested. The levels of 5-fluorocytosine and rifampin required for synergism were higher than clinically achievable concentrations when measurements of synergism were based on visual turbidity; but when the effects of the drugs were measured by inhibition of ribonucleic acid synthesis or dry-weight increase, much lower concentrations were effective.