منابع مشابه
Coloration strategies in peacock feathers.
We report the mechanism of color production in peacock feathers. We find that the cortex in differently colored barbules, which contains a 2D photonic-crystal structure, is responsible for coloration. Simulations reveal that the photonic-crystal structure possesses a partial photonic bandgap along the direction normal to the cortex surface, for frequencies within which light is strongly reflect...
متن کاملUnzipping bird feathers.
The bird feather vane can be separated into two parts by pulling the barbs apart. The original state can be re-established easily by lightly stroking through the feather. Hooklets responsible for holding vane barbs together are not damaged by multiple zipping and unzipping cycles. Because numerous microhooks keep the integrity of the feather, their properties are of great interest for understan...
متن کاملThickness of Feathers
Briefly, a feather is a semigroup derivation diagram with the labels on the edges removed. In this paper, we are concerned with possible definitions for the thickness of a feather. A major open problem is whether the word problem is solvable for semigroup presentations with one defining relation. It is known that word problems for semigroup presentations are solvable if the number of regions in...
متن کاملAxioms for Thickness of Feathers
We approach thickness of feathers from an axiomatic point of view. We show that our axioms are independent and we use our axioms to establish general properties for arbitrary definitions of thickness which satisfy these axioms. 1. Axioms for Thickness Informally, a feather is a semigroup derivation diagram with the labels on the edges removed. See [2] for a discussion of semigroup derivation di...
متن کاملAir transmissivity of feathers
The flight feathers and their coverts of a European kestrel Falco tinnunculus have been tested for their air transmissivity. The transmissivity was measured in both directions, i.e. from ventral to dorsal and vice versa; the mean difference between the two directions was less than 10 %. However, the transmissivity of the inner versus outer vanes of the remiges and coverts differed significantly...
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ژورنال
عنوان ژورنال: Nature
سال: 2000
ISSN: 0028-0836,1476-4687
DOI: 10.1038/35016735