scholarly journals On the colour of wing scales in butterflies: iridescence and preferred orientation of single gyroid photonic crystals

2017 ◽  
Vol 7 (4) ◽  
pp. 20160154 ◽  
Author(s):  
Robert W. Corkery ◽  
Eric C. Tyrode
Keyword(s):  
Band Gap ◽  
Cone Angle ◽  
Green Light ◽  
Optimal Solution ◽  
Visible Spectrum ◽  
Critical Cone ◽  
Optical Images ◽  
Highly Correlated ◽  
Preferential Alignment ◽  
Wing Scales

Lycaenid butterflies from the genera Callophrys , Cyanophrys and Thecla have evolved remarkable biophotonic gyroid nanostructures within their wing scales that have only recently been replicated by nanoscale additive manufacturing. These nanostructures selectively reflect parts of the visible spectrum to give their characteristic non-iridescent, matte-green appearance, despite a distinct blue–green–yellow iridescence predicted for individual crystals from theory. It has been hypothesized that the organism must achieve its uniform appearance by growing crystals with some restrictions on the possible distribution of orientations, yet preferential orientation observed in Callophrys rubi confirms that this distribution need not be uniform. By analysing scanning electron microscope and optical images of 912 crystals in three wing scales, we find no preference for their rotational alignment in the plane of the scales. However, crystal orientation normal to the scale was highly correlated to their colour at low (conical) angles of view and illumination. This correlation enabled the use of optical images, each containing up to 10 4 –10 5 crystals, for concluding the preferential alignment seen along the at the level of single scales, appears ubiquitous. By contrast, orientations were found to occur at no greater rate than that expected by chance. Above a critical cone angle, all crystals reflected bright green light indicating the dominant light scattering is due to the predicted band gap along the direction, independent of the domain orientation. Together with the natural variation in scale and wing shapes, we can readily understand the detailed mechanism of uniform colour production and iridescence suppression in these butterflies. It appears that the combination of preferential alignment normal to the wing scale, and uniform distribution within the plane is a near optimal solution for homogenizing the angular distribution of the band gap relative to the wings. Finally, the distributions of orientations, shapes, sizes and degree of order of crystals within single scales provide useful insights for understanding the mechanisms at play in the formation of these biophotonic nanostructures.

Visible Light Emission from Erbium Doped Yttria Stabilized Zirconia

2003 ◽  
Vol 789 ◽  
Author(s):  
Michael Cross ◽  
Walter Varhue
Keyword(s):  
Band Gap ◽  
Light Emission ◽  
Green Light ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Rare Earth Ion ◽  
Device Structure ◽  
Insulating Layer ◽  
Light Emitting ◽  
Erbium Doped

ABSTRACT: One of the major shortcomings of silicon (Si) as a semiconductor material is its inability to yield efficient light emission. There has been a continued interest in adding rare earth ion impurities such as erbium (Er) to the Si lattice to act as light emitting centers. The low band gap of Si however has complicated this practice by quenching and absorbing this possible emission. Increasing the band gap of the host has been successfully tried in the case of gallium nitride (GaN) [1] and Si-rich oxide (SRO) [2] alloys. A similar approach has been tried here, where Er oxide (ErOx) nanocrystals have been formed in a yttria stabilized zirconia (YSZ) host deposited on a Si (100) substrate. The YSZ is deposited as a heteroepitaxial, insulating layer on the Si substrate by a reactive sputtering technique. The Er is also incorporated by a sputtering process from a metallic target and its placement in the YSZ host can be easily controlled. The device structure formed is a simple metal contact/insulator/phosphor sandwich. The device has been found to emit visible green light at low bias voltages. The advantage of this material is that it is much more structured than SiO2 which can theoretically lead to higher emission intensity.

scholarly journals Numerical and Experimental Investigation of Computed Tomography of Chemiluminescence for Hydrogen-Air Premixed Laminar Flames

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Liang Lv ◽  
Jianguo Tan ◽  
Yue Hu
Keyword(s):  
Computed Tomography ◽  
Cone Angle ◽  
Reconstruction Algorithm ◽  
Laminar Flames ◽  
Iccd Camera ◽  
Critical Cone ◽  
Premixed Laminar Flames ◽  
Flame Structures ◽  
Premixed Laminar ◽  
Flow Velocities

Computed tomography of chemiluminescence (CTC) is a promising technique for combustion diagnostics, providing instantaneous 3D information of flame structures, especially in harsh circumstance. This work focuses on assessing the feasibility of CTC and investigating structures of hydrogen-air premixed laminar flames using CTC. A numerical phantom study was performed to assess the accuracy of the reconstruction algorithm. A well-designed burner was used to generate stable hydrogen-air premixed laminar flames. TheOH⁎chemiluminescence intensity field reconstructed from 37 views using CTC was compared to theOH⁎chemiluminescence distributions recorded directly by a single ICCD camera from the side view. The flame structures in different flow velocities and equivalence ratios were analyzed using the reconstructions. The results show that the CTC technique can effectively indicate real distributions of the flame chemiluminescence. The height of the flame becomes larger with increasing flow velocities, whereas it decreases with increasing equivalence ratios (no larger than 1). The increasing flow velocities gradually lift the flame reaction zones. A critical cone angle of 4.76 degrees is obtained to avoid blow-off. These results set up a foundation for next studies and the methods can be further developed to reconstruct 3D structures of flames.

scholarly journals Ant Colony Optimization for Real Time Traffic Lights Control on a Single Intersection

2020 ◽  
Vol 14 (02) ◽  
pp. 196 ◽  
Author(s):  
Nouha Rida ◽  
Mohammed Ouadoud ◽  
Aberrahim Hasbi
Keyword(s):  
Road Traffic ◽  
Green Light ◽  
Optimal Solution ◽  
Ant Colony ◽  
Traffic Data ◽  
Traffic Light ◽  
Traffic Lights ◽  
The Road ◽  
Real Time Traffic ◽  
On The Road

In this paper, we present a new scheme to intelligently control the cycles and phases of traffic lights by exploiting the road traffic data collected by a wireless sensor network installed on the road. The traffic light controller determines the next phase of traffic lights by applying the Ant Colony Optimazation metaheuristics to the information collected by WSN. The objective of this system is to find an optimal solution that gives the best possible results in terms of reducing the waiting time of vehicles and maximizing the flow crossing the intersection during the green light. The results of simulations by the SUMO traffic simulator confirm the preference of the developed algorithm over the predefined time controller and other dynamic controllers.

scholarly journals THE SENSIBILITY OF THE NOCTURNAL LONG-EARED OWL IN THE SPECTRUM

1940 ◽  
Vol 23 (6) ◽  
pp. 709-717 ◽  
Author(s):  
Selig Hecht ◽  
Maurice Henri Pirenne
Keyword(s):  
Infrared Radiation ◽  
Energy Content ◽  
Green Light ◽  
Visible Spectrum ◽  
Low Light ◽  
Light Intensities ◽  
Different Parts

Infrared radiation (750–1500 mµ) produces no iris contraction in the typically nocturnal long-eared owl even when the energy content is millions of times greater than that of green light which easily elicits a pupil change. The energies in different parts of the visible spectrum required for a minimal iris response yield a spectral visibility curve for the owl which is the same as the human visibility curve at low light intensities. Functionally, the owl's vision thus corresponds to the predominantly rod structure of its retina, and the idea that nocturnal owls have a special type of vision sensitive to infrared radiation for seeing in the woods at night is erroneous.

scholarly journals Iridescence and spectral filtering of the gyroid-type photonic crystals in Parides sesostris wing scales

2011 ◽  
Vol 2 (5) ◽  
pp. 681-687 ◽  
Author(s):  
Bodo D. Wilts ◽  
Kristel Michielsen ◽  
Hans De Raedt ◽  
Doekele G. Stavenga
Keyword(s):  
Spatial Distribution ◽  
Photonic Crystals ◽  
Reflectance Spectrum ◽  
Green Light ◽  
Wing Pattern ◽  
Photonic Band Structure ◽  
Spectral Filtering ◽  
Pass Filter ◽  
Photonic Band ◽  
Wing Scales

The cover scales on the wing of the Emerald-patched Cattleheart butterfly, Parides sesostris , contain gyroid-type biological photonic crystals that brightly reflect green light. A pigment, which absorbs maximally at approximately 395 nm, is immersed predominantly throughout the elaborate upper lamina. This pigment acts as a long-pass filter shaping the reflectance spectrum of the underlying photonic crystals. The additional effect of the filtering is that the spatial distribution of the scale reflectance is approximately angle-independent, leading to a stable wing pattern contrast. The spectral tuning of the original reflectance is verified by photonic band structure modelling.

Band-Gap Modulation in Single Bi3+-Doped Yttrium–Scandium–Niobium Vanadates for Color Tuning over the Whole Visible Spectrum

2016 ◽  
Vol 28 (8) ◽  
pp. 2692-2703 ◽  
Author(s):  
Fengwen Kang ◽  
Haishan Zhang ◽  
Lothar Wondraczek ◽  
Xiaobao Yang ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Band Gap ◽  
Visible Spectrum ◽  
Color Tuning ◽  
Band Gap Modulation

scholarly journals New chromophores based on combination of ethylenedioxythiophene and carbazole fragments: synthesis and optoelectronic properties

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
A.N. Bakiev ◽  
O.A. Mayorova ◽  
A.A. Gorbunov ◽  
I.V. Lunegov ◽  
E.V. Shklyaeva ◽  
...  
Keyword(s):  
Band Gap ◽  
Visible Spectrum ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Good Solubility ◽  
Film Forming ◽  
Photovoltaic Applications ◽  
Key Steps ◽  
Homo Lumo ◽  
Stokes Shifts

AbstractTwo new D-π-A chromophores composed of an electron-donating carbazole unit linked through π- bridges, bearing 3,4-ethylenedioxythiophene (EDOT) moiety, with an electron withdrawing dicyanovinyl group (DCV) were successfully synthesized involving Suzuki or Heck cross-coupling and Knöevenagel reactions as the key steps. The obtained compounds absorb light over a broad spectral range, including the visible spectrum. The HOMO/LUMO energies and band gap energy values (Eg) were calculated on the basis of the experimental optical and electrochemical data: HOMO, LUMO, Eg (eV), −5.51, −3.14, 2.37 (4), −5.34, −3.14, 2.20 (7). The presence of the HC=CH unit in compound 7 resulted in the increase of the HOMO energy level, the decrease of a band gap value and red shifts of the absorption and emission bands in comparison with those of 4. Large Stokes shifts and broadband luminescence inherent to both chromophores suggest their use as materials for luminescent solar collectors (LSCs). The obtained compounds demonstrated good solubility and suitable thin-film forming properties. For this reason, they may be suitable for solution-processable photovoltaic applications.

Behavioral response of adult caddisflies (Trichoptera) to blue and green light-emitting diode lamps

Zoosymposia ◽  
2019 ◽  
Vol 14 (1) ◽  
pp. 59-62
Author(s):  
GORO KIMURA ◽  
GORO TAJIKA ◽  
TOSHIHIRO KUSAMA ◽  
TSUTOMU TANIKAWA
Keyword(s):  
Uv Light ◽  
Diversity Index ◽  
Light Emitting Diode ◽  
Broad Band ◽  
Green Light ◽  
Visible Spectrum ◽  
Ultraviolet Spectrum ◽  
White Led ◽  
Light Emitting ◽  
Wiener Diversity Index

To clarify the effect of the visible spectrum, we collected Trichoptera adults using blue, green, and white light-emitting diode (LED) lamps and black light (BL) lamps. Except for white LED lamps, all lamps emitted broad-band wavelengths in the ultraviolet spectrum. A total of 212 adult Trichoptera were trapped. The most individuals were attracted by BL (96), followed blue (74), green (32), and white (10). Hydroptilidae spp. was the most abundant taxa among the lamps (183 individuals, 86.3%), followed by Cheumatopsyche brevilineata (23 individuals, 10.8%). Only Hydroptilidae spp. was common to all lamps. The Shannon–Wiener diversity index (H’) was highest at 0.96 for BL, followed by green (0.53), and blue (0.28). Trichoptera were attracted to both UV light and visible light. These results suggest that BL is the most useful for faunistic investigations of Trichoptera.

scholarly journals Measurement of rotatory dispersive power in the visible and ultra-violet regions of the spectrum

1908 ◽  
Vol 81 (550) ◽  
pp. 472-474 ◽  
Keyword(s):  
Photographic Plate ◽  
Monochromatic Light ◽  
Green Light ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Narrow Strip ◽  
In Series ◽  
Limited Scale ◽  
Dispersive Power ◽  
Constant Deviation

The following is a brief preliminary account of improvements effected in the method of determining rotatory dispersive power which have made it possible to observe accurately not only in the bright regions of the visible spectrum, but throughout the scale from the region of the lithium red line into that commanded by the photographic plate. Two methods have generally been used for the purpose, namely, (1) Broch’s method, in which a spectroscope is arranged in series with the polarimeter and a narrow strip of a continuous spectrum is picked out for observation—a method which is much improved by using a constant-deviation spectroscope in place of one of the variable-deviation type, and .(2) Landolt’s method, in which a white light is reduced by means of filters to approximate homogeneity in the red, green, light-blue, or dark-blue parts of the spectrum. Neither method fulfils the fundamental condition that the field of the polarimeter shall be uniformly lighted with monochromatic light—many of the measurements that have been made, therefore, possess only a qualitative value. A much better method is due to the late Sir William Perkin, who introduced the use of a spectroscope-eyepiece as a means of purifying the sodium light, and used it on a limited scale for measuring rotatory dispersive power in the red (lithium), yellow (sodium), and green, thallium) parts of the spectrum.

Optoelectronic Analysis of CdGa2X4 (X= S, Se): A Promising Material for Solar Cells

2017 ◽  
Vol 900 ◽  
pp. 69-73 ◽  
Author(s):  
Pancham Kumar ◽  
Jagrati Sahariya ◽  
Amit Soni ◽  
K.C. Bhamu
Keyword(s):  
Solar Cell ◽  
Band Gap ◽  
Density Of States ◽  
Density Functional ◽  
Visible Spectrum ◽  
Full Potential ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Direct Band Gap ◽  
Direct Band

In this paper, the optoelectronic nature of the CdGa2X4 (X = S, Se) solar cell materials are examined using full potential linear augmented plane wave (FP-LAPW) method as embodied in WIEN2K code. In present computation, we have used most suitable modified Backe-Johnson (mBJ) potential under the framework of density functional theory (DFT). The calculated electronic properties like energy band structure and density of states spectra show that these materials exhibit a direct band gap (Γ–Γ) result of 3.22 eV and 2.36 eV for CdGa2S4 and CdGa2Se4 compounds, respectively. Absorption spectra for CdGa2X4 (X = S, Se) compounds have been studied and it has been found that above the band gap, absorption are taking place and it covers wide visible spectrum energy range. On the basis of calculated band gap, density of states and absorption coefficient spectra, it is found that these compounds can be suitably applicable in optoelectronic devices such as solar cell. The evaluated properties pose well agreement with available experimental data.

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