tion of Liquid-Metal Jets as the Conductor in a ated, Exploding-Fuse Opening Switc
A repetitive, high-power opening switch technique for use in pulsed power applications using inductive energy storage is presented, along with data which demonstrate performance characteristics. This technique uses jets of a liquid conductor to replace the solid metal fuses in exploding-fuse opening-switch designs. High-power switching characteristics such as interrupt current, holdoff voltage, and resistance change are presented, along with information on how these characteristics change as jet length and circuit parameters are varied. A simulated load is used to demonstrate that exploding liquid-metal jets are feasible replacements for solid-fuse conductors in realistic applications. Likewise, the switching facility has been rep-rated in a two-pulse scenario to show its primary advantage over solid-fuse switches. The use of a highspeed camera to monitor the expansion of the mercury column upon vaporization is also described. Radial expansion velocities have been extracted from the images and are correlated with the electrical data.
Characteristics of a Magnetic Energy Storage System Using Exploding Foils
A capacitor bank operating at 15 kV and 34 kJ is used to energize an inductive system of 40 nH. Interrupting the current of ∼800 kA, by means of an exploding copper foil fuse, produces voltages across the fuse of the order of 80 kV. The opening time of the fuse, as well as the characteristics of the voltage developed across the fuse are examined as a function of the fuse dimensions. If transfer of the current into a matching inductive load is to take place at the time of peak voltage, energy transfer efficiency is of the order of 8% with I's of the order of 2×1012 A/sec.
Genotypic diversity in field isolates of Babesia bovis from cattle with babesiosis after vaccination.
OBJECTIVE
To determine whether particular genotypes of Babesia bovis were common to field isolates obtained from cattle properties in Queensland where the B bovis vaccine had apparently failed.


DESIGN
A comparative study of polymerase chain reaction genotypes in different populations of B bovis.


PROCEDURE
Two polymerase chain reaction assays were applied to analyse DNA extracts of B bovis vaccine (K, T and Dixie strains) and 27 field isolates from 24 properties where disease outbreaks had occurred despite the use of the vaccine. To evaluate the stability of the genotypes identified, 11 of the field isolates were inoculated into experimental cattle that had either been previously vaccinated with T strain or not vaccinated.


RESULTS
No particular genotype of B bovis was responsible for the problems observed in previously vaccinated herds. None of the isolates had genotypes identical to the vaccine strains used. No geographic trends among the genotypes were observed. Isolates that originated from the same property also had different genotypes. Blood passage of the 11 field isolates in either previously vaccinated or nonvaccinated cattle did not alter the original genotype.


CONCLUSION
No particular genotypes identified by the Bv80 and BvVA1 polymerase chain reaction assays could be associated with vaccine failures.