Search results for " Color"

There is more to accommodation of the eye than simply minimizing retinal blur

2017

Eyes of children and young adults change their optical power to focus nearby objects at the retina. But does accommodation function by trial and error to minimize blur and maximize contrast as is generally accepted? Three experiments in monocular and monochromatic vision were performed under two conditions while aberrations were being corrected. In the first condition, feedback was available to the eye from both optical vergence and optical blur. In the second, feedback was only available from target blur. Accommodation was less precise for the second condition, suggesting that it is more than a trial-and-error function. Optical vergence itself seems to be an important cue for accommodation.

Pigment patterns in mutants affecting the biosynthesis of pteridines and xanthommatin in Drosophila melanogaster.

1986

Eye-color mutants of Drosophila melanogaster have been analyzed for their pigment content and related metabolites. Xanthommatin and dihydroxanthommatin (pigments causing brown eye color) were measured after selective extraction in acidified butanol. Pteridines (pigments causing red eye color) were quantitated after separation of 28 spots by thin-layer chromatography, most of which are pteridines and a few of which are fluorescent metabolites from the xanthommatin pathway. Pigment patterns have been studied in 45 loci. The pteridine pathway ramifies into two double branches giving rise to isoxanthopterin, “drosopterins,” and biopterin as final products. The regulatory relationship among the …

Color stimuli perception in presence of light scattering.

2006

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresp…

Stable polymorphism for mutant eye colour geues in populations of Drosophila melanogaster in two different media

1988

In previous work analyzing variability of eye colour alleles existing in natural populations of D. melanogaster, it was observed that the number of females heterozygous for some eye colour alleles was greater in a wine cellar population than in populations outside this cellar. In order to determine which mechanisms caused these eye colour alleles to be favored in the heterozygotes, the changes in the frequency of four eye colour alleles frequently seen in the cellar population (se77o, sf77m, cd77o and multichromosomal 77o) was studied in artificial populations. Two different culture media, one supplemented with 10% ethanol and the other without ethanol were used. It was found that each of t…

RGB imaging of laser-excited skin autofluorescence bleaching rates

2010

In-vivo skin photo-bleaching (intensity decrease during irradiation) has been investigated at 405 nm cw laser excitation. Digital RGB photo-camera was used for studies of the bleaching features by analysis of fluorescent images at separated R, G and B spectral bands. Diagnostic potential based on correlations between skin pigmentation and bleaching rates is discussed.

The functional significance of colour polymorphism in the European common wall lizard (Podarcis muralis)

2021

Colour polymorphisms, the coexistence of two or more colour morphs of a species within a population, have long fascinated evolutionary biologists interested in the mechanisms generating and maintaining phenotypic variation in nature. The functional significance of colour polymorphisms (i.e. their adaptive value) is often linked to the selective mechanisms responsible for their maintenance over time. In lizards, the hypothesis that colour morphs may reflect alternative reproductive strategies involving differential sociosexual behaviour and/or alternative reproductive strategies has come to dominate the field. Wall lizards (family Lacertidae, genus Podarcis), with several geographically dist…

Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review

2010

AbstractWe review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli - factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early …

Spatiocolorimetric neighborhood hypergraph and Image Processing Applications : Noise Removal and Edge Detection.

2004

In this document, we are interested in image modeling by the means of the hypergraph theory. Our contribution is essentially centered on the determination of the properties resulting from this theory and on the analysis from their adequacy with image problems, particularly edge and noise detection.First, we study the image spatiocolorimetric neighborhood hypergraph representation. Three representations are respectively presented incorporating global properties, local properties and similarity functions. Then, we use the hypergraph properties generated by the representation in order to define the structural models of noise and edge. This enables us to deduce the algorithms of noise suppressi…

IONOGEL DA SALI DI IMIDAZOLIO PER LA RIMOZIONE DI COLORANTI DA ACQUE

Sociolinguistic upsets and people of color in social media performances

2022

Abstract Particularly since the refugee “reception crisis” in 2015, Finland has started transforming into a more diverse and multicultural society. These societal changes have also been accompanied by sociolinguistic change, as well as language ideological debates and tensions, often manifesting in explicitly racist and xenophobic bursts of upset. In this article, our focus is on social media as a space where such societal and sociolinguistic upsets are articulated and re-worked. Drawing on recent sociolinguistic and discourse analytic work on transformative and critical popular cultural practices in social media, and studies on rap and belonging, we discuss how, in a mediatized society suc…