scholarly journals The golden age of arthropods: ancient mechanisms of colour production in body scales

2019 ◽  
Vol 16 (159) ◽  
pp. 20190366 ◽  
Author(s):  
Liliana D'Alba ◽  
Bo Wang ◽  
Bram Vanthournout ◽  
Matthew D. Shawkey
Keyword(s):  
Electron Microscopy ◽  
Diffraction Grating ◽  
Selection Pressure ◽  
Zero Order ◽  
Finite Domain ◽  
Colour Measurement ◽  
Optical Modelling ◽  
Considerable Research ◽  
Fossil Material ◽  
Early Origin

Insect colour is extremely diverse and produced by a large number of pigmentary and nanostructural mechanisms. Considerable research has been dedicated to these optical mechanisms, with most of it focused on chromatic colours, such as blues and greens, and less on achromatic colours like white and gold. Moreover, studies on the evolution of these colours are less common and largely limited to inferences from extant organisms, in part because of the limited amount and types of available fossil material. Here, we directly compare nanostructure and colour of extant and amber-preserved (approx. 15 and 99 Myr old, respectively) gold-coloured representatives of micromoths (Lepidoptera: Micropterigidae) and springtails (Collembola: Tomoceridae). Using electron microscopy, microspectrophotometry and finite domain time difference optical modelling, we show that golden coloration in the extant micromoth is produced by nanometre-scale crossribs that function as zero-order diffraction gratings and in the springtail by a diffraction grating without crossribs. Surprisingly, nanostructure and thus predicted colour of the amber-preserved specimens were nearly identical to those of their extant counterparts. Removal of amber enabled direct colour measurement of the fossil micromoth and further revealed that its colour matched both that of the extant specimen and the predicted colour, providing further support for our optical models. Our data thus clearly show an early origin and striking conservation of scale nanostructures and golden coloration, suggesting strong selection pressure either on the colour itself or on the mechanisms that produce the colour. Furthermore, we show the thus-far untapped potential for the use of amber-preserved specimens in studies on the evolution of organismal coloration.

scholarly journals Sexual dichromatism of the Blue-throated Starfrontlet, Coeligena helianthea, hummingbird plumage

2019 ◽  
Vol 161 (1) ◽  
pp. 289-296 ◽  
Author(s):  
Juliana Sosa ◽  
Juan L. Parra ◽  
Doekele G. Stavenga ◽  
Marco A. Giraldo
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Spectral Data ◽  
Reflectance Spectra ◽  
Structural Basis ◽  
Sexual Dichromatism ◽  
Male And Female ◽  
Optical Modelling ◽  
The Many

Abstract Among the many richly coloured birds, hummingbirds with their brilliant colouration are outstanding. We studied the plumage of male and female Blue-throated Starfrontlet, Coeligena helianthea, which exhibits a marked sexual dichromatism. The wide diversity of coloured feathers (blue, purple, golden, green, red) makes it an attractive species to investigate the structural basis of the colouration and to study the connection between the displayed colours and the perception by conspecifics. We analysed the optical properties of the feather barbules, applying spectrophotometry, scatterometry, and electron microscopy. Using the anatomical results, the spectral data can be interpreted by optical modelling. The reflectance spectra of the feathers of male C. helianthea strikingly overlap with the spectral sensitivities of bird photoreceptors, which suggests that the feather and photoreceptor spectra are tuned.

scholarly journals Splendid coloration of the peacock spider Maratus splendens

2016 ◽  
Vol 13 (121) ◽  
pp. 20160437 ◽  
Author(s):  
Doekele G. Stavenga ◽  
Jürgen C. Otto ◽  
Bodo D. Wilts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Optical Properties ◽  
Air Gap ◽  
The Body ◽  
Structural Coloration ◽  
Optical Modelling ◽  
Jumping Spiders ◽  
Blue Coloration ◽  
Scanning Electron

Jumping spiders are well known for their acute vision and often bright colours. The male peacock spider Maratus splendens is richly coloured by scales that cover the body. The colours of the white, cream and red scales, which have an elaborate shape with numerous spines, are pigmentary. Blue scales are unpigmented and have a structural colour, created by an intricate photonic system consisting of two chitinous layers with ridges, separated by an air gap, with on the inner sides of the chitin layers an array of filaments. We have characterized the optical properties of the scales by microspectrophotometry, imaging scatterometry and light and scanning electron microscopy. Optical modelling revealed that the filament array constitutes a novel structural coloration system, which subtly fine tunes the scale reflectance to the observed blue coloration.

A Display Based On Switchable Zero Order Diffraction Grating Light Valves

1985 ◽  
Author(s):  
Josephine A. Steir ◽  
Jan A. Rajchman ◽  
John Melngailis ◽  
Deborah A. Summa
Keyword(s):  
Diffraction Grating ◽  
Zero Order ◽  
Order Diffraction

scholarly journals A Constrained Many-objective Optimization Evolutionary Algorithm with Enhanced Mating and Environmental Selections

2021 ◽  
Author(s):  
Fei Ming
Keyword(s):  
Evolutionary Algorithms ◽  
Evolutionary Algorithm ◽  
Density Estimation ◽  
Real World ◽  
Selection Pressure ◽  
Optimization Problems ◽  
Variable Number ◽  
Objective Functions ◽  
Considerable Research ◽  
Real World Applications

<div>Unlike the considerable research on solving many objective optimization problems with evolutionary algorithms, there has been much less research on constrained many-objective optimization problems (CMaOPs). Generally, to effectively solve CMaOPs, an algorithm needs to balance feasibility, convergence, and diversity simultaneously. It is essential for handling CMaOPs yet most of the existing research encounters difficulties. This paper proposes a novel constrained many-objective optimization evolutionary algorithm with enhanced mating and environmental selections, namely CMME. The main features are: i) two ranking strategies are proposed and applied in the mating and environmental selections to enrich feasibility and convergence; ii) an individual density estimation is designed, and crowding distance is integrated to promote diversity; and iii) the ?-dominance is used to strengthen the selection pressure on both the convergence and diversity. The synergy of these components can achieve the goal of balancing feasibility, convergence, and diversity for solving CMaOPs. The proposed CMME algorithm is evaluated on 10 CMaOPs with different features and a variable number of objective functions. Experimental results on three benchmark CMOPs and three real-world applications demonstrate that CMME shows superiority or competitiveness over nine related algorithms.</div>

scholarly journals INVESTIGATION OF THE METHOD OF DIRECT LASER WRITING OF OPTICAL ELEMENTS WITH BINARY HIGH-CONTRAST AMPLITUDE-PHASE TRANSMISSION

2021 ◽  
Vol 8 ◽  
pp. 236-240
Author(s):  
Victor P. Korolkov ◽  
Andrey G. Sedukhin ◽  
Nikita A. Gurin ◽  
Anatoliy I. Malyshev
Keyword(s):  
Diffraction Grating ◽  
Optical Transmittance ◽  
Zero Order ◽  
Minimum Size ◽  
Two Dimensional ◽  
High Contrast ◽  
Contrast Structure ◽  
Chromium Film ◽  
Order Diffraction ◽  
Direct Laser

A method is proposed for formation on one substrate of two superimposed optical structures - a binary phase structure and an analog high-contrast amplitude structure made on a thick chromium film in the form of a regular two-dimensional zero-order diffraction grating with a variable fill-factor of cells. A numerical and experimental study of this method is carried out as applied to an optical transparency for generating the structure of a gamma-coupled laser beam. The quality of a high-contrast structure, suitable for practical application, was experimentally achieved, with an optical density of a chromium film of about 4.3, when measured at a wavelength of 532 nm, and with a minimum size of transparent and opaque windows of the order of 1x1 μm. This method can be used to synthesize amplitude-phase transparencies with a large alternating range of change in the amplitude optical transmittance, with a relatively slow (smooth) change in the transmittance (with the carrier spatial frequency of the amplitude modulation determined by the period of the above two-dimensional zero-order diffraction grating).

scholarly journals A Constrained Many-objective Optimization Evolutionary Algorithm with Enhanced Mating and Environmental Selections

2021 ◽  
Author(s):  
Fei Ming
Keyword(s):  
Evolutionary Algorithms ◽  
Evolutionary Algorithm ◽  
Density Estimation ◽  
Real World ◽  
Selection Pressure ◽  
Optimization Problems ◽  
Variable Number ◽  
Objective Functions ◽  
Considerable Research ◽  
Real World Applications

<div>Unlike the considerable research on solving many objective optimization problems with evolutionary algorithms, there has been much less research on constrained many-objective optimization problems (CMaOPs). Generally, to effectively solve CMaOPs, an algorithm needs to balance feasibility, convergence, and diversity simultaneously. It is essential for handling CMaOPs yet most of the existing research encounters difficulties. This paper proposes a novel constrained many-objective optimization evolutionary algorithm with enhanced mating and environmental selections, namely CMME. The main features are: i) two ranking strategies are proposed and applied in the mating and environmental selections to enrich feasibility and convergence; ii) an individual density estimation is designed, and crowding distance is integrated to promote diversity; and iii) the ?-dominance is used to strengthen the selection pressure on both the convergence and diversity. The synergy of these components can achieve the goal of balancing feasibility, convergence, and diversity for solving CMaOPs. The proposed CMME algorithm is evaluated on 10 CMaOPs with different features and a variable number of objective functions. Experimental results on three benchmark CMOPs and three real-world applications demonstrate that CMME shows superiority or competitiveness over nine related algorithms.</div>

scholarly journals Investigation of hole-free phase plate performance in transmission electron microscopy under different operation conditions by experiments and simulations

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Rebecca Pretzsch ◽  
Manuel Dries ◽  
Simon Hettler ◽  
Martin Spiecker ◽  
Martin Obermair ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Shift ◽  
Zero Order ◽  
Phase Shifting ◽  
Negative Phase ◽  
Phase Plate ◽  
Microscopy Imaging ◽  
Transmission Electron ◽  
Phase Plates

Abstract Hole-free phase plates (HFPPs), also known as Volta phase plates, were already demonstrated to be well suited for in-focus transmission electron microscopy imaging of organic objects. However, the underlying physical processes have not been fully understood yet. To further elucidate the imaging properties of HFPPs, phase shift measurements were carried out under different experimental conditions. Both positive and negative phase shifts occur depending on the diameter of the zero-order electron beam and the HFPP film temperature. The analysis of Thon ring patterns of an amorphous carbon test sample reveals that the phase-shifting patch can be significantly larger than the size of the zero-order beam on the HFPP film. An HFPP was used for in-focus phase contrast imaging of carbon nanotube (CNT) bundles under positive and negative phase-shifting conditions. The comparison of experimental and simulated images of CNT bundles gives detailed information on the phase shift profile, which depends on the spatial frequency in the vicinity of the zero-order beam. The shape of the phase shift profile also explains halo-like image artifacts that surround the imaged objects.

scholarly journals A dynamic broadband reflector built from microscopic silica spheres in the ‘disco’ clam Ctenoides ales

2014 ◽  
Vol 11 (98) ◽  
pp. 20140407 ◽  
Author(s):  
Lindsey F. Dougherty ◽  
Sönke Johnsen ◽  
Roy L. Caldwell ◽  
N. Justin Marshall
Keyword(s):  
Electron Microscopy ◽  
Visible Light ◽  
High Speed ◽  
Scattered Light ◽  
Strong Absorption ◽  
Silica Spheres ◽  
Optical Effect ◽  
Optical Modelling ◽  
High Speed Video ◽  
Two Sides

The ‘disco’ or ‘electric’ clam Ctenoides ales (Limidae) is the only species of bivalve known to have a behaviourally mediated photic display. This display is so vivid that it has been repeatedly confused for bioluminescence, but it is actually the result of scattered light. The flashing occurs on the mantle lip, where electron microscopy revealed two distinct tissue sides: one highly scattering side that contains dense aggregations of spheres composed of silica, and one highly absorbing side that does not. High-speed video confirmed that the two sides act in concert to alternate between vivid broadband reflectance and strong absorption in the blue region of the spectrum. Optical modelling suggests that the diameter of the spheres is nearly optimal for scattering visible light, especially at shorter wavelengths which predominate in their environment. This simple mechanism produces a striking optical effect that may function as a signal.

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