RESUMO
A technique for accurate measurement of the linear electro-optic coefficient(s) in crystals that are simultaneously optically active and birefringent is described. It is shown that this technique provides a direct method of measuring field-induced birefringence and so can form the basis of a Bi(12)SiO(20) (or Bi(12)GeO(20)) sensor arrangement. The high degree of accuracy obtained in the measurements of the linear electro-optic coefficient in Bi(12)SiO(20) and Bi(12)GeO(20) crystals indicates the particular suitability of these materials in electric-field and voltage-sensor systems with a high dynamic range and for possible waveguiding applications.
RESUMO
Excavations into the Australian swamp of Lancefield show that a bone bed dated at 26,000 years ago contains perhaps 10,000 giant extinct animals. Associated artifacts suggest that humans were in the area, but the direct cause of death of the animals is, on present evidence, not explicable. Such a recent date for the classic megafauna shows that it was living together with humans for at least 7000 years in southeast Australia. This enduring association argues against a catastrophic and rapid overkill in the Australian Pleistocene.
