A Multiple Radiation Effects Facility for the Study of Structural and Flexible Materials Exposed to the Space Environment
A radiation effects facility is described which utilizes multiple radiation sources, vacuum chambers and thermal control to simulate the space environment. Use of the facility for eight months' continuous testing of thin film flexible materials is discussed and summary results, primarily from in-situ testing, are presented.
Effect of Neutron and Proton Irradiation on Some Properties of Kapton
Photoacoustic, dielectric and surface-morphological properties of Kapton* were studied after exposing sheets (25 μm thick) separately to fast reactor neutrons (E>0.1 MeV) and to 250 keV protons up to doses 1.2×1018 (maximum)and 7.0×1015 cm−2, respectively. The photoacoustic spectrum (PAS) of the maximum neutron dose irradiated sample shows the red-shift of the absorption peak from 450 nm to 470 nm, whereas in the proton irradiated (7×1015 cm−2) sample, a new flattened absorption peak appears at λ ≃ 515 nm. There is a net enhancement in the D.C. dielectric constant of about 13% after the maximum neutron dose. It is attributed to the enhanced water absorptivity of the material due to neutron induced radiation damage.
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.