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Secret in the eye of the chicken 

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Research over the past 15 years shows that materials exhibiting a so-called disordered hyperuniform state have unique properties involving transmission and control of light waves.

Hyperuniform disordered solids (HUDS) are non-crystalline materials that transmit light without affecting the motion of photons, as happens with crystals. This lack of interference offers potential applications in the photonics industry. HUDS are similar to crystals in exhibiting disorder over small distances, but they keep their particle density consistent over large distances. They are also like liquids in that they have the same physical properties in all directions.

Researchers at Princeton University and Washington University in St Louis studying cone cells in the eyes of chickens have described disordered hyperuniformity in a biological setting for the first time. As well as possessing cones for detecting red, green and blue light, like humans, hens and other birds possess two other types of cone cell, one for detecting violet light, and a double cone for detecting movement.

During evolutionary history most birds, unlike mammals, have never had a period as nocturnal creatures, and so have evolved eyes with a greater percentage and variety of cone cells, which are only sensitive in conditions of good light. The different types of cone cells vary in size and at first glance appear to be packed into the retina in a random fashion.

However, computer analysis has shown that each type of cone cell is in fact arranged in a uniform fashion compared with others of the same type, with an exclusion zone from similar cones, to avoid interference. However, they are disordered when compared with other cone types.

It is thought that this arrangement of cones allows for optimum sampling of incoming light, and gives birds extra sensitivity to a greater range of colours and movement — essential for finding food, mates, and avoiding predators.

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From: Beyond pharmacy blog

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