RESUMO
The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne(8+) ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations.
RESUMO
Phenytoin has a beneficial effect on wound healing and on the healing of bone fractures, while beta-aminopropionitrile (BAPN) has an adverse effect on both. BAPN causes what appears to be a repair response in the periosteum at sites of muscle attachment, but phenytoin does not alter that response. The effect of phenytoin and/or BAPN on the repair of a surgically induced periosteal wound at the insertion of the adductor longus and pectineus muscles was studied in rats at 7 days post-wounding. Phenytoin facilitated and BAPN exacerbated the repair process, as indicated by the size of the periosteal response. Phenytoin increased the percentage of bone present in the responses, and both phenytoin and BAPN reduced the amount of cartilage present. The possible role of inflammation in obtaining the beneficial effects of phenytoin in wound healing is discussed.
