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1. The psychophysical technique of selective adaptation to stationary sine-wave gratings of varying spatial frequency and orientation was used to investigate the central processing of spatial information in the visual system of the complete achromat. 2. For adapting spatial frequencies of 1 and 2 cycles/deg, the spatial frequency and orientation selectivity(More)
Mechanisms underlying rod temporal contrast sensitivity have been considered in terms of a fast retinal signal predominating at mesopic levels and a slower retinal signal predominating at scotopic levels. Here we use a small signal masking method, which has previously been used to delineate the cone-mediated cortical temporal channels, to investigate their(More)
The flicker sensitivity (temporal modulation transfer function) of a rod monochromat was measured at luminances in the range of 8 to 782 scotopic td. The results could be fitted by a single curve shifted vertically, suggesting that rod saturation is independent of the temporal properties of the stimulus. This is consistent with the hypothesis that rod(More)
The sensitivity to sine-wave flicker of a rod monochromat was compared with that of a normal subject at photopic and scotopic levels of luminance. The sensitivity of the rod monochromat in the low-frequency region (below 3 Hz at scotopic levels and below 12 to 14 Hz at photopic levels) was found to be superior to that of the control. This superiority was(More)
The objective of our experiments was to study the persistence and dissemination of orally administered Salmonella in smoltified Atlantic salmon. In experiment 1, salmon kept at 15 degrees C were fed for 1 week with feed contaminated with 96 most-probable-number units of Salmonella Agona per 100 g of feed and then starved for 2 weeks. Samples were taken from(More)
The molecular epidemiology of 98 isolates of Salmonella serovar Agona (n = 27), S. Montevideo (n = 42) and S. Senftenberg (n = 29) from wild-living gulls, fish-meal factories, feed factories, humans and domestic animals was investigated using pulsed-field gel electrophoresis (PFGE) and computerized numerical analysis. Two of the S. Agona profiles were(More)