Ignition and Extinction Behavior of Fuels in a Microcombustor
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Shock Tube Test Time Limitation Due to Turbulent-Wall Boundary Layer
Shock tube test time limitation due to the premature arrival of the contact surface is analytically investigated for wholly turbulent-wall boundary layers The results are compared with those for wholly laminar-wall boundary layers It is found that, for a given shock Mach number Ms, the maximum possible test time (in a long shock tube) varies as d 6//4p co1/4 and d2p CD for the turbulent and laminar cases, respectively (d = tube diameter, p oo = initial pressure) For 3 ^ 5, whereas the laminar theory applies, roughly, for dpm ~ 1 (d is in inches; pm is in centimeters of mercury) When dp » 5, turbulent theory for both air and argon indicates test times of about one-half to one-fourth the ideal value for xs/d = 45 to 150, respectively (xs = length of low-pressure section) Higher values of dp » result in more test time When dpm ~ 0 5, laminar theory indicates about one-half ideal test time for xs/d ~ 100 Lower dpm reduces test time Working curves are presented for more accurate estimates of test time in specific cases Boundary-layer closure occurs, in long shock tubes, when Ms < 1 2 and Ms < 3 for laminar and turbulent boundary layers, respectively
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.