Developing noniridescent structural color on flexible substrates with high bending resistance

Nanostructured materials producing structural colors have great potential in replacing toxic metals or organic pigments. Electrophoretic deposition (EPD) is a promising method for producing these materials on a large scale, but it requires improvements in brightness, saturation, and mechanical stability. Herein, we use EPD assembly to codeposit silica (SiO2) particles with precursors of synthetic melanin, polydopamine (PDA), to produce mechanically robust, wide-angle structurally colored coatings. We use spectrophotometry to show that PDA precursors enhance the saturation of structural colors and nanoscratch testing to demonstrate that they stabilize particles within the EPD coatings. Stabilization by PDA precursors allows us to coat flexible substrates that can sustain bending stresses, opening an avenue for electroprinting on flexible materials

Manakins can produce iridescent and bright feather colours without melanosomes

Males of many species often use colourful and conspicuous ornaments to attract females. Among these, male manakins (family: Pipridae) provide classic examples of sexual selection favouring the evolution of bright and colourful plumage coloration. The highly iridescent feather colours of birds are most commonly produced by the periodic arrangement of melanin-containing organelles (melanosomes) within barbules. Melanin increases the saturation of iridescent colours seen from optimal viewing angles by absorbing back-scattered light; however, this may reduce the wide-angle brightness of these signals, contributing to a dark background appearance. We examined the nanostructure of four manakin species (Lepidothrix isidorei, L. iris, L. nattereri and L. coeruleocapilla) to identify how they produce their bright plumage colours. Feather barbs of all four species were characterized by dense and fibrous internal spongy matrices that likely increase scattering of light within the barb. The iridescent, yet pale or whitish colours of L. iris and L. nattereri feathers were produced not by periodically arranged melanosomes within barbules, but by periodic matrices of air and beta-keratin within barbs. Lepidothrix iris crown feathers were able to produce a dazzling display of colours with small shifts in viewing geometry, likely because of a periodic nanostructure, a flattened barb morphology and disorder at a microstructural level. We hypothesize that iridescent plumage ornaments of male L. iris and L. nattereri are under selection to increase brightness or luminance across wide viewing angles, which may potentially increase their detectability by females during dynamic and fast-paced courtship displays in dim light environments

Specular and diffuse reflectance of phase-separated polymer blend films

Diffuse reflectors have various applications in devices ranging from liquid crystal displays to light emitting diodes, to coatings. Herein, specular and diffuse reflectance from controlled phase separation of polymer blend films, a well-known self-organization process, are studied. Temperature-induced spinodal phase separation of polymer blend films in which one of the components is selectively extracted is shown to exhibit enhanced surface roughness as compared to unextracted films, leading to a notable increase of diffuse reflectance. Diffuse reflectance of UV-visible light from such selectively leached phase-separated blend films is determined by a synergy of varying lateral scale of phase separation (approximate to 200 nm to 1 mu m) and blend film surface roughness (0-40 nm). These critical parameters are controlled by tuning annealing time (0.5-3 h) and temperature (140, 150, 160 degrees C) of phase separation. Angle-resolved diffuse reflection studies show that the surface-roughened polymer films exhibit diffuse reflectance up to 40 degrees from normal incident light in contrast to optically uniform as-cast films that exhibit largely specular reflectance. Furthermore, the intensity of the diffusively reflected light can be enhanced (300-700 nm) or reduced (220-300 nm) significantly by coating the leached phase-separated films with a thin silver over layer

Exploring the use of unprocessed waste chicken eggshells for UV-protective applications

Photodegradation causes a steady loss of the useful physical, mechanical and optical properties of materials, necessitating their replacement over time. Because UV (Ultraviolet) light is most harmful in this regard, many materials now contain UV-protective additives. However, these additives are not always effective and durable, can be expensive, and their natural extraction or synthetic production can be harmful to the environment. Here, we investigated the use of unprocessed chicken eggshells in providing UV protection to two commonly used synthetic polymers: polystyrene and nylon. We show that unprocessed chicken eggshells provide a durable and effective UV protection. Our data sets the stage for future research to find a practical way to use the large amounts of unprocessed chicken eggshell waste as novel, economically appealing and environmentally friendly UV-protective additives

Manakins can produce iridescent and bright feather colours without melanosomes

Males of many species often use colourful and conspicuous ornaments to attract females. Among these, male manakins (family: Pipridae) provide classic examples of sexual selection favouring the evolution of bright and colourful plumage coloration. The highly iridescent feather colours of birds are most commonly produced by the periodic arrangement of melanin-containing organelles (melanosomes) within barbules. Melanin increases the saturation of iridescent colours seen from optimal viewing angles by absorbing back-scattered light; however, this may reduce the wide-angle brightness of these signals, contributing to a dark background appearance. We examined the nanostructure of four manakin species (Lepidothrix isidorei, L. iris, L. nattereri and L. coeruleocapilla) to identify how they produce their bright plumage colours. Feather barbs of all four species were characterized by dense and fibrous internal spongy matrices that likely increase scattering of light within the barb. The iridescent, yet pale or whitish colours of L. iris and L. nattereri feathers were produced not by periodically arranged melanosomes within barbules, but by periodic matrices of air and β-keratin within barbs. Lepidothrix iris crown feathers were able to produce a dazzling display of colours with small shifts in viewing geometry, likely because of a periodic nanostructure, a flattened barb morphology and disorder at a microstructural level. We hypothesize that iridescent plumage ornaments of male L. iris and L. nattereri are under selection to increase brightness or luminance across wide viewing angles, which may potentially increase their detectability by females during dynamic and fast-paced courtship displays in dim light environments

Experimental and theoretical evidence for molecular forces driving surface segregation in photonic colloidal assemblies

Surface segregation in binary colloidal mixtures offers a simple way to control both surface and bulk properties without affecting their bulk composition. Here, we combine experiments and coarse-grained molecular dynamics (CG-MD) simulations to delineate the effects of particle chemistry and size on surface segregation in photonic colloidal assemblies from binary mixtures of melanin and silica particles of size ratio (Dlarge/Dsmall) ranging from 1.0 to similar to 2.2. We find that melanin and/or smaller particles segregate at the surface of micrometer-sized colloidal assemblies (supraballs) prepared by an emulsion process. Conversely, no such surface segregation occurs in films prepared by evaporative assembly. CG-MD simulations explain the experimental observations by showing that particles with the larger contact angle (melanin) are enriched at the supraball surface regardless of the relative strength of particle-interface interactions, a result with implications for the broad understanding and design of colloidal particle assemblies

Biofunctional molecules from Citrullus colocynthis: An HPLC/MS analysis in correlation to antimicrobial and anticancer activities

Background: Citrullus colocynthis belongs to Family Cucurbitaceae. It grows widely in Egypt and Sudan and it has been used in folk medicine of Sudan and many other African countries as anti inflammatory, anti diabetic, and antioxidant agent. Objectives: To evaluate the antibacterial, antifungal, antiviral, anticancer activities of ethanolic crude extracts of the fruits, leaves, seeds and roots of this plant, as well as identifying them HPLC/MS. Materials and Methods: Dried fruits, seeds, leaves and roots of C. colocynthis were powdered and passed through a 40- mesh, then, the powders were extracted with 95% ethanol in a soxhlet apparatus. The residues were dried under reduced pressure in rotary evaporator. Crude extract from different plant parts were evaluated biologically and phytochemically. Results: All extracts showed good antifungal activities with inhibition zone ranges between 15.1 ± 0.32 to 25.6 ± 0.16 mm. In terms of plant organ, fruits were the most active. In term of fungal strain Aspergillus fumigatus and Geotricum candidum were the most sensitive. Against tested Gram +ve, all extracts showed good activities except roots, while antibacterial activity against Gram –ve showed that the fruits extract have good activity as it was the sole extract with activity against Pseudomonas aeruginosa. Test for antiviral activities showed moderate to weak inhibitions of cytopathic effect (CPE). Anticancer activities of different crude extracts showed that fruits had significant antitumor activities against all tested cell lines, the IC50 values were 24.6, 16, 18.5 and 19.7 µg /ml for HCT-116, MCF-7, Hep-G2 and Caco-2 respectively. Seeds extract was only active on HCT-116 and Hep G2 with IC50 =21.2 µg/ml for HCT-116 and 22.4 µg/ml for Hep G2. Leaves extract was only active against Hep G2 cancer cell line with IC50 19.7 µg/ml. Roots extract show weak antitumor activity on tested cell lines (IC50 values > 30µg/ml). HPLC/MS qualitative and quantitative analysis of different organs extracts revealed the presence of 21 compounds identified as fourteen cucurbitacins, three flavonoids, three tannins, and one sterol. The presence of cucurbitacins can explain most of the biological activities. Conclusion: The biological activities of colocynth different parts are due to the presence of secondary metabolites mainly cucurbitacins in addition to flavonoids and tannins.  These activities prove the use of this plant in folk medicine and deserve much more future exploration targeting their discovery in unexplored sources and their derivatives for improving their anticancer and antimicrobial abilities. Keywords: Citrullus colocynthis, crude extracts, antifungal, antibacterial, antiviral, anticancer, HPLC/M

Demonstration of a Thermally Coupled Row-Column SNSPD Imaging Array

While single-pixel superconducting nanowire single photon detectors (SNSPDs) have demonstrated remarkable efficiency and timing performance from the UV to near-IR, scaling these devices to large imaging arrays remains challenging. Here, we propose a new SNSPD multiplexing system using thermal coupling and detection correlations between two photosensitive layers of an array. Using this architecture with the channels of one layer oriented in rows and the second layer in columns, we demonstrate imaging capability in 16-pixel arrays with accurate spot tracking at the few-photon level. We also explore the performance trade-offs of orienting the top layer nanowires parallel and perpendicular to the bottom layer. The thermally coupled row-column scheme is readily able to scale to the kilopixel size with existing readout systems and, when combined with other multiplexing architectures, has the potential to enable megapixel scale SNSPD imaging arrays

الخبّاز في مصر القديمة The Baker in Ancient Egypt

{AR} يتناول هذا البحث إحدى المهن الاقتصادية المهمة في مصر القديمة وهي مهنة الخبّاز، وقد ذُكر الخبّازون في النصوص المصرية القديمة منذ أقدم العصور، وتتطورت مهنة الخبّاز عبر العصور حتى أنه في عصر الدولة الحديثة كانت هناك مصطلحات تعبر بصورة واضحة عن الخبّازين المتخصصين بأنواع بعينها من المخبوزات، ويستهدف البحث إظهار ما جاء عن هذه المهنة من مفردات في اللغة المصرية القديمة وكل ما يتعلق بهذه المهنة من حيث دور الخبّاز وأجره في صناعة الخبز وإشراف الدولة عليه ومرتبته بين المهن الأخرى وأسماء بعض الخبّازين الذين وردت أسماؤهم في النصوص المصرية القديمة . {EN} This article investigates the baker's profession, an essential economic profession. The article shed light on the vocabulary of the profession and its social status based on titles, wages, and supervision conditions. Moreover, the writer attempts to rank the baker among other professions and mentions the names of some bakers in ancient Egypt texts

Blue reflectance in tarantulas is evolutionarily conserved despite nanostructural diversity

Slight shifts in arrangement within biological photonic nanostructures can produce large color differences, and sexual selection often leads to high color diversity in clades with structural colors. We use phylogenetic reconstruction, electron microscopy, spectrophotometry, and opticalmodeling to showan opposing pattern of nanostructural diversification accompanied by unusual conservation of blue color in tarantulas (Araneae: Theraphosidae). In contrast to other clades, blue coloration in phylogenetically distant tarantulas peaks within a narrow 20-nm region around 450 nm. Both quasi-ordered and multilayer nanostructures found in different tarantulas produce this blue color. Thus, even within monophyletic lineages, tarantulas have evolved strikingly similar blue coloration through divergent mechanisms. The poor color perception and lack of conspicuous display during courtship of tarantulas argue that these colors are not sexually selected. Therefore, our data contrast with sexual selection that typically produces a diverse array of colors with a single structuralmechanismby showing that natural selection on structural color in tarantulas resulted in convergence on similar color through diverse structural mechanisms