Literature data for visual pigment spectra are formally treated by assuming that the spectra consist of a summation of absorbance bands, that the shape of the bands is invariant according to the Mansfield-MacNichol transform and that this shape is described by simple exponential functions. A new template for constructing visual pigment spectra from peak wavelengths is derived.
The colors of butterfly wings are determined by the structural as well as pigmentary properties of the wing scales. Reflectance spectra of the wings of a number of pierid butterfly species, specifically the small white, Pieris rapae, show that the long-wavelength reflectance of the scales in situ, on the wing, is distinctly higher than that of single, isolated scales. An optical model explains that this is due to multiple scattering on overlapping scales by treating the layers of scales on both sides of the wing as a stack of incoherently scattering plates. The model sheds new light on the adaptive significance and evolution of butterfly wing patterns.
Quasi-normal-modes description of transmission properties for photonic bandgap structures Settimi, A.; Severini, S.; Hoenders, B. J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We use the "quasi-normal-modes" (QNM) approach for discussing the transmission properties of double-side opened optical cavities: in particular, this approach is specified for one-dimensional (1D) "photonic bandgap" (PBG) structures. Moreover, we conjecture that the density of the modes is a dynamical variable that has the flexibility of varying with respect to the boundary conditions as well as the initial conditions; in fact, the electromagnetic (e.m.) field generated by two monochromatic counterpropagating pump waves leads to interference effects inside a quarter-wave symmetric 1D-PBG structure. Finally, here, for the first time to the best of our knowledge, a large number of theoretical assumptions on QNM metrics for an open cavity, never discussed in literature, are proved, and a simple and direct method to calculate the QNM norm for a 1D-PBG structure is reported.
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