THE COLOR BLUE IN MORPHO BUTTERFLIES
The Morpho butterfly is a species native to the rain forests of South America that have attracted the interest of researchers all over the world due to its unique appearance.
The metallic blue hues of its wings have come to be one of the most studied examples of structural colors while also illustrating nature’s ingenuity in adapting the bodies of living organisms for the ongoing survival race.
Morpho Butterfly Wing via Science Source
Despite the magnificent iridescent blue color of the Morpho butterflies, their wings contain no blue pigments. Their coloration is given instead by the actual shape of their wings or, more precisely, through the interaction of light waves within the nanometric structures on each individual scale.
Photograph by Raoul Gonzales
On closer inspection, scientists discovered that the tiny scales on the Morpho butterfly wings present Christmas tree-shaped ridges made of chitin and air pockets. These translucent structures act like a microscopic light filter and directly influence how light waves interfere with each other.
Butterfly Wing Nanostructure via Science Source
After a light beam hits the first branch of one of those tree structures (lamellae), it then passes through every layer. The light with the right wavelength—in this case, the blue color— will be reinforced and reflected (constructive interference) while the others will be destroyed (destructive interference).
Intensifying screen
At the time the article was created Ayush Goel had no recorded disclosures.
Last revised:
9 Oct 2023, Raymond Chieng ◉
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At the time the article was last revised Raymond Chieng had no financial relationships to ineligible companies to disclose.
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17 times, by 11 contributors – see full revision history and disclosures
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- Intensifying screens
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Intensifying screens are used in the x-ray cassette to intensify the effect of the x-ray photon by producing a larger number of light photons. It decreases the mAs required to produce a particular density and hence decreases the patient dose significantly. It also reduces motion blur and x-ray tube loading by reducing exposure time.
In cassettes, which use double emulsion films, two screens are used, mounted on both sides of the cassette. In mammography, however, a single screen on the back side and a single emulsion film is used.
The thickness of an intensifying screen is about 0.4 mm. The thickness of the screen affects the screen speed and spatial resolution: thicker screen improves speed but reduces spatial resolution (increased diffusion of light before image formation).
The intensity factor is a measure of efficiency of intensifying screen, and is the ratio photon exposures with and without intensifying screen to achieve a designated film density 4,5 . The absorption and conversion efficiency of the screen affect the intensity factor.
Film-screen combination typically used for chest radiography has a limiting resolution of 6 line pairs per mm, which is two times better than a typical digital radiography of 3 line pairs per mm 6 .
Layers
- base
- reflecting layer/absorptive layer
- luminiscent layer – absorbs the x-ray photon and converts it to visible light that is recorded by the film. Contains fluorescent materials called ‘phosphors’:
- calcium tungstate (CaWO4): blue light
- lanthanum oxybromide (LaOBr): blue light
- gadolinium oxysulfide (Gd2O2S): green light
Rare earth elements are used in present-day screens as they are faster and have higher absorption and conversion efficiency:
- gadolinium: green light
- lanthanum: blue light
- yttrium
Spectral matching
It is important to note that the color of the light emitted (wavelength) must match the light sensitivity of the film used. This is known as spectral matching:
- conventional films: sensitive to ultraviolet and blue lights
- orthochromatic films: sensitive to ultraviolet, blue and green lights
If the wavelength of light emitted by the screen is not in the sensitive range of the film, it will not be absorbed by the film.
Blue Light Ingredients and Research Intensify in Cosmetics R&D
A two-part review article published in the Journal of Cosmetic Dermatology highlights the cosmetic industry’s heightened interest in blue/visible light. Part one defines blue light and identifies its effects on skin, whereas part two takes inventory of cosmetic ingredients to mitigate these effects and test methods to substantiate related claims.
According to the University of Toledo authors, blue or visible light falls within the wavelengths of 400 to 500 nm and is primarily emitted by the sun as well as digital devices, light‐emitting diodes and fluorescent lighting. Concerns over blue light’s effects on skin emerged more than a decade ago but have surged in recent years due in part to increased screen time from tablets, smart phones, etc.
Based on Google Scholar literature searches, the authors found that shorter exposure times to low energy blue light can actually prevent skin diseases, whereas longer exposures to high energy blue light can increase photoaging and skin barrier damage, among other effects.
Furthermore, as is well-known, the industry has launched many ingredients for blue light protection including algae derivatives, UV filters, botanical extracts, antioxidants and vitamins, etc. And while no formal test method has been established to measure their efficacy, spectrophotometers, imaging devices and visual observation, along with measurements of oxidative stress endpoints, have been implemented.
The authors concluded, based on these observations, that industry interest in this area will continue to rise, especially as new test methods uncover additional insights that further the development of ingredients for blue light protection.
“Consumer concerns about blue light and its potentially damaging effects on the skin have been growing as more scientific results are published about this topic,” writes Gabriella Baki, Ph.D., director of cosmetic science and formulation design major at the University of Toledo, and co-author on the study. “Blue light protection is important, and in my opinion, we will see more ingredients and products—including moisturizers, sunscreens and even makeup products, with blue light protection claims in the near future.”
