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Fabrication of Artificial Melanin-Based Structural Color Materials through Biomimetic Design
Published in Akihiro Miyauchi, Masatsugu Shimomura, Biomimetics, 2023
Natural colors are mainly classified into two types: pigment colors and structural colors. A pigment color is a remaining color that is visible by absorbing light of a specific wavelength. In contrast, a structural color is a color that appears when light hits a submicron-sized periodic structure. Familiar examples include soap bubbles and rainbow colors on a back of compact disc. In each case, there is no inherent color of materials. The former is a color derived from thin-film interference caused by the difference in the refractive index between the air and the thin film of the soap bubble, and the latter is a diffraction grating formed in fine irregularities on the surface. Pigment colors are easily discolored by the decomposition of dyes through ultraviolet irradiation. On the other hand, a structural color does not fade as long as the structure is maintained. The most prominent example is the color of fossil bird feathers. Fossils formed by replacing tissue with minerals are usually colorless, but, very rarely, colored fossils have been found [1]. The color of these fossils has been reported to be a structural color due to the microstructure formed inside the wing feathers.
Principles of Penetrants
Published in Don E. Bray, Roderic K. Stanley, Nondestructive Evaluation, 2018
Don E. Bray, Roderic K. Stanley
The physics of the surface forces exerted by a fluid film are described thoroughly in standard textbooks on physics and fluid mechanics, e.g., Refs. [2–5]. For a fluid, a large soap bubble blown from a small ring may demonstrate some of the principles of surface physics. As shown in Fig. 34-2, a small ring has been dipped in a soap solution so that a single two-sided film of soap is contained within the ring. Skillful blowing through the ring, however, can produce a bubble with a surface area many times larger than the surface in the ring. While the fluid would prefer to revert to the initial, smaller size of the ring, i.e., a smaller surface area, the pressure of the air in the bubble prevents this from occurring. Thus, the nonequilibrium fluid state of the bubble is being supported by the surface forces originating from the internal air pressure. These surface forces of the internal air are counteracted by the opposing surface forces of the fluid film of the soap solution. If the bubble were to be pierced, the fluid ideally would revert to its lowest energy state, i.e., a spherical liquid drop. In this lowest energy state, the surface forces constraining the fluid clearly are lower than those constraining the original bubble.
Capillary Forces in Fluid Flow in Porous Solids (Shale Formations)
Published in K.S. Birdi, Surface Chemistry and Geochemistry of Hydraulic Fracturing, 2016
The iridescent colors of the soap bubble arise from the interference of reflected light waves. The reflected light from the outer surface and the inner layer give rise to this interference effect. The rainbow colors are observed as the bubble thickness decreases due to the evaporation of water. Thicker films reflect more red light, and therefore, one observes blue-green colors. Thinner films cancel out the yellow wavelengths, and a blue color is observed. As the thickness approaches the wavelength of light, all colors are cancelled out, and a so-called black (or gray) film is observed. This corresponds to 25 nm (250 Å) (Scheludko, 1966; Birdi, 2016). The transmitted light, Itr, is related to the incident, Iin, and the reflected intensity, Ire: () Itr=Iin−Itr
Particle size measurement of electronic cigarette aerosol with a cascade impactor
Published in Aerosol Science and Technology, 2021
To operate the sampling system, after all the flows have been set, an EC is inserted into the EC port. To take a puff, the puff flow (B) is switched to the exhaust port of the solenoid valve for the duration of the puff. When flow B is stopped the sampling system will draw air through the EC port and flow A is generated to maintain the 2 L/min into the impactor. Since flows C and D are controlled by mass flow controllers flow A will of necessity be equal to flow B. This creates a puff on the EC that lasts until the solenoid valve is switched back. In practice the solenoid valve is controlled by a lab timer (Model 451, Gralab, Centerville, OH, USA). During the initial setup and testing of the sampling system the flow rate through the EC port was observed to be steady by watching the movement of the soap bubble in the soap bubble flow meter. The flow rates from the mass flow controllers into (C) and out of (D) the system were monitored with the MSK software and were found to remain steady through the experiment. This suggests that the flow through the impactor was not disrupted by puffing on the EC.
Spatial trends, health risk assessment and ozone formation potential linked to BTEX
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Hassan Mojarrad, Reza Fouladi Fard, Mostafa Rezaali, Hamidreza Heidari, Hassan Izanloo, Abolfazl Mohammadbeigi, Amir Mohammadi, Armin Sorooshian
The apparatus used for sampling was an SKC™ pump (model: TX44-244, made in the USA) with an inlet flow rate capacity of 0.2 L min−1. The pump was continually calibrated using a soap bubble solution and a graduated cylinder. The SKC™ (model: 22601, made in the USA, mesh size: 50) activated coconut charcoal tube was used as an absorbing media to capture VOCs in ambient air. Right after the sampling process, each of the sampling tubes was capped and kept at 0 °C (NIOSH 2003). To ensure the quality of the sampling process, 10% of the total number of the samples were repeated. Also, some basic meteorological variables such as temperature, pressure, and humidity were recorded using a PHB-318 apparatus (made in Taiwan; Lutron Electronic Enterprise Co 2019), while the other variables including wind speed and wind direction were obtained from Iran Meteorological Organization (IRIMO 2019).
Preparation of silver nanowire/expanded polytetrafluoroethylene and polypropylene nanocomposites via all solution process method for antibacterial applications
Published in The Journal of The Textile Institute, 2020
S. H. Mirjalili, Mohammad Reza Nateghi, F. Kalantari-Fotooh
The filtering performance test was employed in this study to evaluate the air permeability of the filters. A picture of the test device is shown in Figure 1. As can be seen, this setup consisted of a vacuum pump (Airchek Sampler, SKC, model 224-PCXR8, USA) and a soap bubble flow meter (TIS 500 CC, Iran). At first, when there was no filter inside the cell test, the pump suction flow was set at 1.7 L per min (i.e. human air flow). Then each of the pristine and modified filters was located in a cell test where air suction was performed by Airchek Sampler. Finally, the resulting air flow was measured by a soap bubble flow meter. Each test on fabricated filters was repeated for three times.