A quantitative model of implicit masking, with a front-end low-pass filter, a retinal local compressive nonlinearity described by a modified Naka-Rushton equation, a cortical representation of the image in the Fourier domain, and a frequency-dependent compressive nonlinearity, was developed to simulate visual image processing. The model algorithm was used to estimate contrast sensitivity functi...

REFERENCES 1 Pierse N, Rushton L, Harris RS, et al. Locally generated particulate pollution and respiratory symptoms in young children. Thorax 2006; 61: 216–220. 2 Andersen ZJ, Loft S, Ketzel M, et al. Ambient air pollution triggers wheezing symptoms in infants. Thorax 2008; 63: 710–716. 3 Nordling E, Berglind N, Melen E, et al. Traffic-related air pollution and childhood respiratory symptoms, ...

The functional and electrophysiological similarities in the changes in the electroretinogram (ERG) of man and cat affected by hereditary retinal degenerative disease were studied. The results of a series of log intensity-amplitude studies in a group of young affected Abyssinian cats were fitted to the Naka-Rushton relationship by means of a mathematical package on the University of London mainf...

The dipper effect for contrast discrimination provides strong evidence that the underlying neural response is accelerating at low contrasts and saturating at high contrasts. The contrast-response functions of V1 neurons do have this sigmoidal shape, but individual neurons do not generally have a dynamic range wide enough to account for the dipper effect. This paper presents a Bayesian model of ...

To examine how the mechanisms of light adaptation affect spatial pattern vision, contrast detection thresholds were measured for sinusoidal (increment-Gabor) probes on flashed backgrounds in the presence of steady adapting backgrounds. The thresholds for all spatial frequencies (1-12 c/deg), flashed-background intensities (dark to 4 log td) and adapting-background intensities (dark to 4 log td)...

The gas holdup and flow dynamics in a laboratory scale Rushton-turbine flotation tank were simulated using the dispersed k- turbulence model and Eulerian-Eulerian multiphase modelling approach. The inherent uncertainties in the CFD predictions were quantified by examining the model and numerical (i.e., discretization) uncertainties. The contribution of model uncertainty was explored by conside...

The advantage of using paddle dryers (PD) in the production of sugars and 2nd generation ethanol from pretreated wheat straw was investigated. This machinery was employed in order to detoxify steam-exploded substrates and to mix different slurries in the hydrolysis step. The obtained hydrolysate was fermented by the yeast Saccharomyces cerevisiae. Acetic acid and furfural were reduced up to 11 ...

Streptomyces griseus was cultured in three different bioreactors in a medium containing chitin flakes. When a conventional bioreactor stirred by two sets of Rushton impellers and operated at high speed was used, the yield of streptomycin (3.1mg/l) was the highest observed and occurred at approximately 500 h. Cultivation of S. griseus in a bioreactor stirred at low speed by a U-shaped paddle res...

Double- to single-loop pattern transition and a significant reduction in the power number with decrease clearance of Rushton turbine impeller baffled reactor was elucidated earlier research works. The present work investigates physical reasons behind these phenomena using computational fluid dynamics approach. Reynolds Averaged Navier–Stokes equations standard turbulence model closure were used...

Experiments Most publications of velocity measurements in stirred tanks concern measurements in single-phase flows. An excellent review of these studies was made by Ranade and Joshi (1990a). Literature concerning velocity measurements in aerated stirred tanks is scarcer however. An overview of literature is given in Table 1. Lu and Ju (1987) used constant temperature anemometry (CTA) in order t...