Electrical and thermal transport properties of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals
This work presents measurements of the electrical resistivity (ρ), Seebeck coefficient, and thermal conductivity (κ) of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals from 10to300K. A series of quasicrystals was prepared with x=0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, and 1.0 to systematically study the effect of substitution. The electrical resistivity increases as the temperature decreases, suggesting a semiconductinglike behavior in these alloys. The room-temperature values of the Seebeck coefficient vary from −5μV∕K to +65μV∕K, showing a significant dependence on the value of x. However, κ exhibits a rather weak composition dependence in the temperature range investigated. The room-temperature dimensionless thermoelectric figure of merit (ZT) of this system is optimized at x=0.1. With further appropriate heat treatments, high ZT is presumably available at elevated temperatures in the Al70Pd22.5(Re0.9Mn0.1)7.5 sample.
Generalization of the Mooij correlation to quasicrystals
The Mooij correlation has been generalized to include quasicrystals. The average temperature dependence of the electrical resistivity ρ(T), as estimated from the difference ρ4.2 K–ρ295 K, was found to be correlated with ρ295 K over seven orders of magnitude. This relation remains robust for modifications of the samples such as approximants, single grain samples, and samples with properties that vary strongly with annealing. An interesting subset of data is metallic alloys of the type Al–Cu–M (M=Li, Li(Mg), Cu Ru, Os), where ρ4.2 K–ρ295 K ∼ [ρ295 K]2.
Immunization with Brucella melitensis Rev 1 against Brucella ovis infection of rams.
The efficacy of Brucella Melitensis Rev 1 vaccine (Rev 1) for the prophylaxis of Brucella ovis ram epididymitis was evaluated. Twenty-nine 3-month-old rams were vaccinated with 2 X 10(9) Rev 1 and 14 were revaccinated with 5 X 10(8) at 14 months of age. Six rams remained unvaccinated as a control group. All rams were challenged with 5 X 10(8) B. ovis at 21 months of age. Before being slaughtered 8 weeks later, only one vaccinated ram developed epididymitis while four of the six control rams developed testicular alterations. Genital and selected extragenital organs and lymph nodes were removed at slaughter and inoculated on selective media. B. ovis was isolated from 26.6% of the vaccinated rams, 21.4% of the revaccinated rams and 100% of control rams. Portions of epididymis, testes and vesicular glands were also used for pathological studies. More severe lesions were observed in control rams than in vaccinated ones. In conclusion, these results show that vaccination of young lambs, followed or not by revaccination, is a suitable method for the prophylaxis of B. ovis infection of rams.