The presence of oxygen in tumours has substantial impact on treatment outcome; relative to anoxic regions, well-oxygenated cells respond better to radiotherapy by a factor 2.5–3. This increased radioresponse is known as the oxygen enhancement ratio. The oxygen effect ismost commonly explained by the oxygen fixation hypothesis, which postulates that radical-inducedDNAdamage can be permanently ‘f...

Throughout this paper, k denotes a field of characteristic 0. We write E8 for the split simple algebraic group with Killing-Cartan type E8. The Galois cohomology set H (k, E8) classifies simple algebraic groups of type E8 over k. One of the goals of the theory of algebraic groups over arbitrary fields is to understand the groups of type E8, equivalently, understand the set H(k, E8). The main to...