Toxicity and Larvicidal Activity of Podophyllum-Based Lignans Against Aedes aegypti (Diptera: Culicidae).

Aedes aegypti L. (Diptera: Culicidae) is a mosquito species that has adapted to urban environments and is the main vector of dengue viruses. Because of the increasing incidence of dengue, a more environmentally acceptable insecticide needs to be found.

Relative effects of gaussian and poisson noise on subjective image quality.

Photographic transparencies were prepared with precisely determined quantities of gaussian (signal-independent) and Poisson (signal-dependent) noise and submitted to observers for subjective ranking of image quality. Average values of noise and signal-to-noise ratio, based upon the relative variance of the signal, were calculated for the imagery: (a) assuming equal a priori probabilities of allowed signal levels; (b) using a normalized probability density function for signal levels derived from scene statistics. Best correlation with the results of subjective quality ranking was obtained with an average signal-to-noise ratio based upon the normalized probability density function.