RESUMO
MnAs epilayers grown on GaAs are used as a model system to study the effects of strain and epitaxial constraints on the dynamics of structural domains following 150 fs pulse pumping. Optical diffraction over 7 orders of magnitude of time is used to probe the evolution of the domains that are spatially periodic between 10 and 42 °C because of misfit strain and substrate mediated periodic elastic strain. Following excitation of 150 and 190 nm thick films, the domain fractions and the elastic strain oscillate with an ~400 ps period while the average low temperature phase fraction decreases monotonically for ~2 ns reflecting MnAs heat diffusion. Equilibrium structures are restored in 100 ns-2 µs via substrate heat diffusion. Excitation of transient periodic domains from the homogeneous low temperature phase can occur for temperatures as low as 4 °C but only after ~20 ns during film cooling.
RESUMO
We have examined the neuroprotective efficacy of the mitochondrial uncoupler 2,4-dinitrophenol (DNP) in animals receiving striatal injections of the neurotoxin quinolinic acid. Animals administered DNP either 1 h before or 3 h following QA infusion developed lesions that were 25% smaller than control animals. Animals treated with the DNP analogue 2,4,6-trinitrophenol, which does not possess uncoupling activity in intact mitochondria, showed no neuroprotection. These results indicate that DNP, and other compounds that diminish the mitochondrial membrane potential, might provide a novel approach to the treatment of acute neurological injury.
