We examine the validity of pulse count of snapping shrimps for sea environmental monitoring. Snapping shrimps, which make a peculiar pulse sound, are found everywhere in the world. Pulse count can be achieved merely by recording their sounds for a few minutes by using a hydrophone without special biological knowledge. From field surveys and laboratory experiments, we found that the pulse count depends on water temperature when sea environment is normal, and it falls due to the occurrence of oxygen-deficient water. The results show that this method can be a useful index of the effect of water pollution on benthic animals in fixed-point observation.
The effect of visible light exposing on the ortho-positronium formation in polyethylene was studied. Lifetime spectra of positrons in polyethylene were measured in the temperature range between 50 K and 370 K. It was observed that the visible light quenches the enhancement of ortho-positronium intensity (I3) at lower temperature than ca. 250 K -the glass transition temperature of polyethylene. On the other hand, the lifetime of ortho-positronium component (T3) was not affected by the presence of the visible light.
polyquasicrystalline icosahedral quasicrystals. As-grown and plastically deformed single quasicrystals of Al 70.6 Pd 21.1 Mn 8.3 were also studied. In every sample the lifetime spectrum consists of a single component with the lifetime of 206 6 4 ps. The results indicate that icosahedral quasicrystalline AlPdMn contains a dense distribution of vacancy-type sites. These trapping sites seem to remain unaltered during plastic deformation at high temperature. [S0031-9007 (97)04002-7]
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