A dual weighted residual method applied to complex periodic gratings

An extension of the dual weighted residual (DWR) method to the analysis of electromagnetic waves in a periodic diffraction grating is presented. Using the α,0-quasi-periodic transformation, an upper bound for the a posteriori error estimate is derived. This is then used to solve adaptively the associated Helmholtz problem. The goal is to achieve an acceptable accuracy in the computed diffraction efficiency while keeping the computational mesh relatively coarse. Numerical results are presented to illustrate the advantage of using DWR over the global a posteriori error estimate approach. The application of the method in biomimetic, to address the complex diffraction geometry of the Morpho butterfly wing is also discussed

Far field scattering pattern of differently structured butterfly scales

The angular and spectral reflectance of single scales of five different butterfly species was measured and related to the scale anatomy. The scales of the pierids Pieris rapae and Delias nigrina scatter white light randomly, in close agreement with Lambert’s cosine law, which can be well understood from the randomly organized beads on the scale crossribs. The reflectance of the iridescent blue scales of Morpho aega is determined by multilayer structures in the scale ridges, causing diffraction in approximately a plane. The purple scales in the dorsal wing tips of the male Colotis regina act similarly as the Morpho scale in the blue, due to multilayers in the ridges, but the scattering in the red occurs as in the Pieris scale, because the scales contain beads with pigment that does not absorb in the red wavelength range. The green–yellow scales of Urania fulgens backscatter light in a narrow spatial angle, because of a multilayer structure in the scale body

Quasi-ordered photonic structures colour the bluespotted ribbontail ray

Due to the scarcity of blue colour exhibited by natural organisms, highlighting the underlying this colour mechanisms is always very impactful for the understanding of the natural world. In this research, the colour of the blue rounded spots occurring in the skin of Taeniura lymma stingray was unveiled by a combination of experimental and numerical techniques. Our results demonstrated that this blue colour arises from coherent scattering in quasi-ordered photonic structures occurring in the skin of this stingray.</p

Quasi-ordered photonic structures colour the bluespotted ribbontail ray

Due to the scarcity of blue colour exhibited by natural organisms, highlighting the underlying this colour mechanisms is always very impactful for the understanding of the natural world. In this research, the colour of the blue rounded spots occurring in the skin of Taeniura lymma stingray was unveiled by a combination of experimental and numerical techniques. Our results demonstrated that this blue colour arises from coherent scattering in quasi-ordered photonic structures occurring in the skin of this stingray.</p

Spectral reflectance properties of iridescent pierid butterfly wings

The wings of most pierid butterflies exhibit a main, pigmentary colouration: white, yellow or orange. The males of many species have in restricted areas of the wing upper sides a distinct structural colouration, which is created by stacks of lamellae in the ridges of the wing scales, resulting in iridescence. The amplitude of the reflectance is proportional to the number of lamellae in the ridge stacks. The angle-dependent peak wavelength of the observed iridescence is in agreement with classical multilayer theory. The iridescence is virtually always in the ultraviolet wavelength range, but some species have a blue-peaking iridescence. The spectral properties of the pigmentary and structural colourations are presumably tuned to the spectral sensitivities of the butterflies’ photoreceptors

Fossilized Biophotonic Nanostructures Reveal the Original Colors of 47-Million-Year-Old Moths

Original structural colors reconstructed in fossil moths had a dual defensive function and illuminate the evolution of communication strategies in insects

Circularly polarized colour reflection from helicoidal structures in the beetle Plusiotis boucardi

Copyright © 2007 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. This is the published version of an article published in New Journal of Physics Vol. 9, article 99. DOI: 10.1088/1367-2630/9/4/099A detailed optical study of the iridescent outer-shell of the beetle Plusiotis boucardi has revealed a novel microstructure which controls both the polarization and wavelength of reflected light. A previously unreported hexagonal array across the integument of the beetle exhibits highly localized regions of reflection of only red and green left-handed circularly-polarized light. Optical and transmission electron microscopy (TEM) imaging reveals the origin of this effect as an array of 'bowl-shaped' recesses on the elytra that are formed from a dual-pitch helicoidal layer. Reflectivity spectra collected from the beetle are compared to theoretical data produced using a multi-layer optics model for modelling chiral, optically anisotropic media such as cholesteric liquid crystals. Excellent agreement is obtained between data and theory produced using a model that incorporates an upper isotropic layer (of cuticular wax), followed by a short pitch (310 (± 1) nm) overlying a longer pitch (370 (±1) nm) helicoidal layer of optically anisotropic material. These layers are backed by an absorbing underlayer. Synthetic replication of this form of structure may provide a route to the fabrication of tuneable micro-mirrors for optical applications

Meanings of being received and met by others as experienced by women with MS

In order to elucidate meanings of being received and met by others as experienced by women with multiple sclerosis (MS) we conducted a qualitative inquiry. We interviewed 15 women with MS and analysed the interviews with a phenomenological hermeneutic interpretation. The findings were presented in two themes: experiencing oneself as a valuable person and experiencing oneself as diminished. Meanings of being received and met by others, as experienced by women with MS, can be understood as containing two dimensions where treatment from others can mean recognising oneself through confirmation, as well as being ignored due to missing togetherness with others

Mechanical metamaterials at the theoretical limit of isotropic elastic stiffness

Acknowledgements H.N.G.W. is grateful for support for this work by the ONR (grant number N00014-15-1-2933), managed by D. Shifler, and the DARPA MCMA programme (grant number W91CRB-10-1-005), managed by J. Goldwasser.Peer reviewedPostprintPostprintPostprintPostprin

UV-Green Iridescence Predicts Male Quality during Jumping Spider Contests

10.1371/journal.pone.0059774PLoS ONE84