"About half that dose, or 5 Gy, is fatal if the entire body is exposed to it," he said.
The value was comparable with the doses obtained by other techniques applied to non-biological samples, such as measurement of the luminescence of quartz grains present in brick and roof tile fragments found at the bomb sites.
Basic physics has also evolved to the extent that you can simulate and manipulate the signal from the sample using computational techniques." Thanks to these advances, he added, in the new study, it was possible to separate the signal corresponding to the radiation dose absorbed during the nuclear attack from the so-called background signal, a kind of noise scientists suspect may have resulted from superheating of the material during the explosion.
The investigation was conducted during the postdoctoral research of Angela Kinoshita, currently a professor at Universidade do Sagrado Coração in Bauru, São Paulo State."We then constructed a curve and extrapolated from that the initial dose, when the signal was presumably zero.This calibration method enabled us to measure different samples, as each bone and each part of the same bone has a different sensitivity to radiation, depending on its composition." Thanks to this combination of techniques, they were able to measure a dose of approximately 9.46 grays (Gy), which is high in Baffa's view."They gave me a jawbone, and I decided to measure the radiation right there, at Hiroshima University," he said."I needed to prove experimentally that my discovery was genuine." Mascarenhas succeeded in demonstrating that a dosimetric signal could be obtained from the sample even though the technology was still rudimentary and there were no computers to help process the results.The bombing of the Japanese cities Hiroshima and Nagasaki by the United States in 1945 was the first and only use of nuclear weapons against civilian targets.A series of studies began in its aftermath to measure the impact of the fallout, in terms of both the radiation dose to which the victims were exposed and the effects of this exposure on DNA and health in general.Techniques like this can help identify who has been exposed to radioactive fallout and needs treatment." As Kinoshita explained, the study is unique insofar as it used samples of human tissue from victims of the bomb dropped on Hiroshima."There were serious doubts about the feasibility of using this methodology to determine the radiation dose deposited in these samples, because of the processes involved in the episode," she said.According to the authors, it was also close to the results of biological measurement techniques applied in long-term studies using alterations in survivors' DNA as a parameter."The measurement we obtained in this latest study is more reliable and up to date than the preliminary finding, but I'm currently evaluating a methodology that's about a thousand times more sensitive than spin resonance.