Feather Rachis Research Articles

Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications.

Traditional medical soft matrix used in a surgical treatment or in wound management was not good enough in both the structural support and interconnectivity to be applied in tissue engineering as a scaffold. Avian skeleton and feather rachises might be good reference objects to mimic in designing a scaffold material with good structural support and high interconnectivity because of its structural foam-wall microarchitectures and structural pneumaticity. In this study, a biomimetic airstream pore-foaming process was built up and the corresponding new medical soft matrix derived from polyvinyl alcohol matrix (PVAM) with air cavities inspired by avian skeleton and feather rachises was prepared. Furthermore, the resulting medical soft matrix and bovine Achilles tendon type I collagen could be employed to prepare a new collagen-containing composite matrix. Characterization, thermal stability and cell morphology of the bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix with open-cell foam-wall microarchitectures were studied for evaluation of potential tissue engineering applications. TGA, DTG, DSC, SEM and FTIR results of new bioinspired PVA matrix were employed to build up the effective system identification approach for biomimetic structure, stability, purity, and safety of target soft matrix. The bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix would be conductive to human hepatoblastoma HepG2 cell proliferation, migration, and expression which might serve as a promising liver cell culture carrier to be used in the biological artificial liver reactor.

Analysis and comparison of protein secondary structures in the rachis of avian flight feathers.

Avians have evolved many different modes of flying as well as various types of feathers for adapting to varied environments. However, the protein content and ratio of protein secondary structures (PSSs) in mature flight feathers are less understood. Further research is needed to understand the proportions of PSSs in feather shafts adapted to various flight modes in different avian species. Flight feathers were analyzed in chicken, mallard, sacred ibis, crested goshawk, collared scops owl, budgie, and zebra finch to investigate the PSSs that have evolved in the feather cortex and medulla by using nondestructive attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). In addition, synchrotron radiation-based, Fourier transform infrared microspectroscopy (SR-FTIRM) was utilized to measure and analyze cross-sections of the feather shafts of seven bird species at a high lateral resolution to resolve the composition of proteins distributed within the sampled area of interest. In this study, significant amounts of α-keratin and collagen components were observed in flight feather shafts, suggesting that these proteins play significant roles in the mechanical strength of flight feathers. This investigation increases our understanding of adaptations to flight by elucidating the structural and mechanistic basis of the feather composition.

Creative Contributions of the Methods of a Biomimetic Inventive Design of Novel Medical Drainage Materials Derived From Polyvinyl Alcohol Foam with Air Cavities Bioinspired by Avian Skeleton and Feather Rachises

Traditional drainage materials used in a surgical treatment or in wound management are not good enough in both the effectiveness and efficiency because they may cause infection due to their characteristics. Therefore, a novel drainage material should be essential and designed to solve the problem. Avian skeleton and feather rachises may be good reference objects to mimic in designing a novel drainage material because its good cell structure which support a bird to fly safe and efficient. The term “nature-Bioinspired” is associated with a sequence of efforts to understand, synthesize and imitate any natural object or phenomenon either in a tangible or intangible form, which allows us to obtain improved insights into nature. Such inspirations can come through materials, processes, or designs. In this study, a new medical matrix derived from polyvinyl alcohol foam with air cavities inspired by avian skeleton and feather rachises for drainage medical treatments was designed, prepared, and characterized. Establishment of biomimetic biomedical inventive principles and a bio-inspired design-thinking method for innovative design of biomimetic medical devices and biomaterials were achieved. Also, the medical device (MD) unified problem-driven bioinspired evaluating approach was established to guide biomimetic design of biomaterials and the corresponding medical devices for various clinic applications.

Study on the structural features and geometric parameters affecting the axial mechanical properties of the primary feather rachis.

The seagull feather shaft is an important part of the feather, which provides a good mechanical support for the excellent flight performance of seagull, and has the characteristics of lightweight and high strength. In this paper, the microstructure of the seagull feather rachis was observed firstly. Then, based on the structure of feather rachis, combined with the cortex that plays the main load-bearing role, a model with the characteristics of the cortex was proposed and its finite element model was established. Through analyzing the simulation, the effect of section shape of cortex on mechanical properties of feathers under axial impact was revealed. And the conclusion that the section shape with groove structure and non-equal wall thickness could have different effects on mechanical properties was drawn. Then, parameterized cortical models were studied, including different impact velocities and different cortical heights, to reveal the differences in mechanical properties of cortical models.

Stability and Sensitivity Analysis of Bird Flapping Flight

This paper investigates stability analysis of flapping flight. Due to time-varying aerodynamic forces, such systems do not display fixed points of equilibrium. The problem is therefore approached via a limit cycle analysis based on Floquet theory. Stability is assessed from the eigenvalues of the Jacobian matrix associated to the limit cycle, also known as the Floquet multipliers. We developed this framework to analyze the flapping flight equations of motion of a bird in the longitudinal plane. Such a system is known to be not only non-linear and time-dependent, but also driven by state-dependent forcing aerodynamic forces. A model accounting for wing morphing under prescribed kinematics is developed for generating realistic state-dependent aerodynamic forces. The morphing wing geometry results from the envelope of continuously articulated rigid bodies, modeling bones and feather rachises, and capturing biologically relevant degrees of freedom. A sensitivity analysis is carried out which allows studying several flight configurations in trimmed state. Our numerical results show that in such a system one instability mode is ubiquitous, thus suggesting the importance of sensory feedback to achieve steady-state flapping flight in birds. The effect of wingbeat amplitude, governed by the shoulder joint, is found to be crucial in tuning the gait towards level flight, but marginally affects stability. In contrast, the relative position between the wing and the center of mass is found to significantly affect the values of Floquet multipliers, suggesting that the distribution of pitching moment plays a very important role in flapping flight stability.

Morphological Characterization of Chicken Feather Rachis, Neem Sawdust, and High Density Polyethylene (HDPE) Reinforced Composite Material

In this paper research was expanded on waste that can be recycled. There are so many different types of waste products available in our country that would ruin the environment. Three different products are considered to reduce some of the problems among them two are fibers and the other is polyethylene. Chicken feather rachis and Neem sawdust are the two different fibers and the reinforced material is high density polyethylene (HDPE). These materials are made as seven different compositions to find the ability of the sample in different characterizations. The seven compositions are 80H-10CF-10SD, 80H-5CF-15SD, 80H-15CF-5SD, 80H-20CF, 70H-30CF, 70H-30SD, 80H-20SD, and these compositions are made in CIPET, Hyderabad by using single screw extruder& strand pelletizer. These granules are prepared with the help of Injection moulding, the samples are examined by various testing to prove the ability, strength, structure of materials in individual, and combination forms. The testing conducted for the samples is that the Morphology of the sample was characterized using FESEM, XRD. It is examined that the ratios are light weight with high strength by using the testings and it gives perfect images without any cracks on the surface and no more defects among these ratios.

Mid-Cretaceous amber inclusions reveal morphogenesis of extinct rachis-dominated feathers

We describe three-dimensionally preserved feathers in mid-Cretaceous Burmese amber that share macro-morphological similarities (e.g., proportionally wide rachis with a “medial stripe”) with lithic, two-dimensionally preserved rachis-dominated feathers, first recognized in the Jehol Biota. These feathers in amber reveal a unique ventrally concave and dorsoventrally thin rachis, and a dorsal groove (sometimes pigmented) that we identify as the “medial stripe” visible in many rachis-dominated rectrices of Mesozoic birds. The distally pennaceous portion of these feathers shows differentiated proximal and distal barbules, the latter with hooklets forming interlocking barbs. Micro-CT scans and transverse sections demonstrate the absence of histodifferentiated cortex and medullary pith of the rachis and barb rami. The highly differentiated barbules combined with the lack of obvious histodifferentiation of the barb rami or rachis suggests that these feathers could have been formed without the full suite and developmental interplay of intermediate filament alpha keratins and corneous beta-proteins that is employed in the cornification process of modern feathers. This study thus highlights how the development of these feathers might have differed from that of their modern counterparts, namely in the morphogenesis of the ventral components of the rachis and barb rami. We suggest that the concave ventral surface of the rachis of these Cretaceous feathers is not homologous with the ventral groove of modern rachises. Our study of these Burmese feathers also confirms previous claims, based on two-dimensional fossils, that they correspond to an extinct morphotype and it cautions about the common practice of extrapolating developmental aspects (and mechanical attributes) of modern feathers to those of stem birds (and their dinosaurian outgroups) because the latter need not to have developed through identical pathways.

An engineering perspective on the microstructure and compression properties of the seagull Larus argentatus feather rachis

The feathers of the seagull Larus argentatus are lightweight but can withstand high alternating stresses and exhibit excellent stiffness and strength. The shaft is an important part of the feather, with the functions of body protection and supporting flight. In this study, the microstructure properties of L. argentatus feather rachis were analysed by scanning electron microscopy (SEM). These analysis methods enabled the configuration, structure and compression properties of the rachis to be investigated. The results indicated that the rachis was composed of the outer cortex and the inner medulla. The cortex had a continuous layered nano-fibre composite structure, which bears, transmits, absorbs and disperses the compression force. The medulla had bubble-like cells with a porous-fibre structure, which rapidly absorbs, transmits and consumes compression force and is a suitably lightweight material for flight. Axial compression tests showed that the rachis from primary feathers had the best energy absorption and that from secondary feathers had the best compressive strength. The compressive strength might have something to do with the ratio of cortical area to medullary area. When the moisture content in the rachis increased, the compressive strength of feather rachis in different parts would decrease. These results indicate that the L. argentatus feather rachis have excellent compression resistance properties, deriving from structural factor.

Chicken feather rachis: An improvement over feather fiber derived electrocatalyst for oxygen electroreduction

Heteroatom doped carbon structures are widely recognized as efficient catalysts for oxygen reduction reaction (ORR). Herein, chicken feather rachis (FR), a poultry industry biowaste is explored as a novel precursor for ORR catalysis. This study comprises the effect of pyrolysis temperature on the structural characteristics and electrocatalytic performance of prepared electrocatalysts. N-doped carbon (NC) synthesized at 950 °C is further activated using KOH, ZnCl2, and H3PO4 at different temperatures. Poultry feather fiber (FF) derived samples were also prepared for comparison. KOH activated NCA-900 (NCA-K-900) exhibits the superior electrochemical performance in terms of onset potential (−0.02 V vs Ag/AgCl) in comparison to similar catalysts previously reported and prepared from feather fiber, which exhibits ~ −0.2 V vs Ag/AgCl. This is attributed to the mesoporous structure and increased ORR active CN sites in FR derived samples as confirmed by adsorption isotherm and XPS analysis, respectively. In addition, it shows 96% current stability in chronoamperometric measurements for 15 h. It is better than the previously reported electrocatalyst prepared from coconut shell (90%, 13 h) and egg yolk (91%, 9 h) respectively. Hence, this study presents an improved environment friendly substitute for ORR catalysis.

Biowaste derived activated carbon electrocatalyst for oxygen reduction reaction: Effect of chemical activation

Conversion of bio-wastes to useful doped carbon materials for various energy applications is emerging as a cost-effective strategy. A novel activated carbon electrocatalyst derived from chicken feather rachis (RCF), a poultry industry bio-waste is explored for oxygen reduction reaction (ORR) catalysis. The rachis is the central stem from which the fibrous ramus is completely removed and it is more crystalline compared to feather ramus. Nitrogen doped activated carbon (CNAx) electrocatalyst is prepared by chemical activation coupled pyrolysis. The chemical activators used include potassium hydroxide (KOH), phosphoric acid (H3PO4) and zinc chloride (ZnCl2) followed by pyrolysis at 500, 700 and 900 °C. Electrochemical performance has been evaluated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) using a rotating disk electrode (RDE). KOH activated electrocatalyst exhibits remarkable improvement in surface area favouring improved onset potential (−0.02 V vs Ag/AgCl). This increased activity is due to increase in number of well-exposed ORR active sites on activation. The effect of chemical activators on the structure and morphology of the activated carbons are discussed using Raman spectroscopy, adsorption-desorption isotherm study, electron microscopic techniques, atomic force microscopy (AFM), and XPS studies. KOH activated CNAx-900 exhibits best combination of properties and confirms its feasibility to be a suitable electrocatalyst for PEMFC. Hence, RCF derived electrocatalysts are propitious alternates for ORR catalysis.

Development and characterization of chicken feather rachis, sawdust and HDPE hybrid composite material

Development and characterization of chicken feather rachis, sawdust and HDPE hybrid composite material

Comparison of turbulence modelling approaches in simulation of a feather shuttle: a porous conical bluff body

The aerodynamics of a feather shuttlecock, a porous conical bluff body, are unique in comparison to other sports projectiles. Experimental wind tunnel studies have been published that present values of drag coefficient (Cd) for traditional feather shuttles that vary widely (0.48 < Cd < 0.74). It is difficult to compare published experimental data, due to a lack of clarity concerning experimental apparatus. All studies have used traditional sting mounts inserted aft of the shuttle base, and it is believed this has a strong influence on Cd, as significant air movement is known to occur in this region. Flow passes through gaps formed by individual feather shafts, or rachis, inserted into the shuttle base. The use of computational fluid dynamic (CFD) simulation in the analysis of shuttles has great potential as analysis can be performed without the need of an experimental sting. This study presents the first CFD simulations of a geometrically realistic feather shuttle. Careful consideration must be given to applied grids, numeric, and turbulence models (unsteady RANS vs scale resolving) if results obtained are to be reliable. CFD results present detailed insights of shuttle aerodynamics, and the significance of flow passage between the feather rachis and internal to the shuttle. The study raises significant concerns regarding the appropriateness of rear sting mounts in shuttle wind tunnel experiments.

A Millimeter Scale Flexural Testing System for Measuring the Mechanical Properties of Marine Sponge Spicules.

Many load bearing biological structures (LBBSs)-such as feather rachises and spicules-are small (<1 mm) but not microscopic. Measuring the flexural behavior of these LBBSs is important for understanding the origins of their remarkable mechanical functions. We describe a protocol for performing three-point bending tests using a custom-built mechanical testing device that can measure forces ranging from 10-5 to 101 N and displacements ranging from 10-7 to 10-2 m. The primary advantage of this mechanical testing device is that the force and displacement capacities can be easily adjusted for different LBBSs. The device's operating principle is similar to that of an atomic force microscope. Namely, force is applied to the LBBS by a load point that is attached to the end of a cantilever. The load point displacement is measured by a fiber optic displacement sensor and converted into a force using the measured cantilever stiffness. The device's force range can be adjusted by using cantilevers of different stiffnesses. The device's capabilities are demonstrated by performing three-point bending tests on the skeletal elements of the marine sponge Euplectella aspergillum. The skeletal elements-known as spicules-are silica fibers that are approximately 50 µm in diameter. We describe the procedures for calibrating the mechanical testing device, mounting the spicules on a three-point bending fixture with a ≈1.3 mm span, and performing a bending test. The force applied to the spicule and its deflection at the location of the applied force are measured.

Microstructural tissue-engineering in the rachis and barbs of bird feathers

Feathers do not have to be especially strong but they do need to be stiff and at the same time resilient and to have a high work of fracture. Syncitial barbule fibres are the highest size-class of continuous filaments in the cortex of the rachis of the feather. However, the rachis can be treated as a generalized cone of rapidly diminishing volume. This means that hundreds of syncitial barbule fibres of the rachis may have to be terminated before reaching the tip – creating potentially thousands of inherently fatal crack-like defects. Here I report a new microstructural architecture of the feather cortex in which most syncitial barbule fibres deviate to the right and left edges of the feather rachis from far within its borders and extend into the barbs, side branches of the rachis, as continuous filaments. This novel morphology adds significantly to knowledge of β-keratin self-assembly in the feather and helps solve the potential problem of fatal crack-like defects in the rachidial cortex. Furthermore, this new complexity, consistent with biology’s robust multi-functionality, solves two biomechanical problems at a stroke. Feather barbs deeply ‘rooted’ within the rachis are also able to better withstand the aerodynamic forces to which they are subjected.

Rachis morphology cannot accurately predict the mechanical performance of primary feathers in extant (and therefore fossil) feathered flyers.

It was previously suggested that the flight ability of feathered fossils could be hypothesized from the diameter of their feather rachises. Central to the idea is the unvalidated assumption that the strength of a primary flight feather (i.e. its material and structural properties) may be consistently calculated from the external diameter of the feather rachis, which is the only dimension that is likely to relate to structural properties available from fossils. Here, using three-point bending tests, the relationship between feather structural properties (maximum bending moment, Mmax and Young's modulus, Ebend) and external morphological parameters (primary feather rachis length, diameter and second moment of area at the calamus) in 180 primary feathers from four species of bird of differing flight style was investigated. Intraspecifically, both Ebend and Mmax were strongly correlated with morphology, decreasing and increasing, respectively, with all three morphological measures. Without accounting for species, however, external morphology was a poor predictor of rachis structural properties, meaning that precise determination of aerial performance in extinct, feathered species from external rachis dimensions alone is not possible. Even if it were possible to calculate the second moment of area of the rachis, our data suggest that feather strength could still not be reliably estimated.

Light Like a Feather: A Fibrous Natural Composite with a Shape Changing from Round to Square.

Only seldom are square/rectangular shapes found in nature. One notable exception is the bird feather rachis, which raises the question: why is the proximal base round but the distal end square? Herein, it is uncovered that, given the same area, square cross sections show higher bending rigidity and are superior in maintaining the original shape, whereas circular sections ovalize upon flexing. This circular‐to‐square shape change increases the ability of the flight feathers to resist flexure while minimizes the weight along the shaft length. The walls are themselves a heterogeneous composite with the fiber arrangements adjusted to the local stress requirements: the dorsal and ventral regions are composed of longitudinal and circumferential fibers, while lateral walls consist of crossed fibers. This natural avian design is ready to be reproduced, and it is anticipated that the knowledge gained from this work will inspire new materials and structures for, e.g., manned/unmanned aerial vehicles.

Elemental composition in feathers of a migratory passerine for differentiation of sex, age, and molting areas.

The bulk analysis of single feathers of 263 feathers belonging to 238 individuals of a migratory passerine (collared flycatcher, Ficedula albicollis, originating from a breeding population in the Pilis-Visegrád Mountains in Hungary) by inductively coupled plasma sector field mass spectrometry (ICP-SF-MS) for determination of elements after proper dissolution allowed the quantitative determination of 38 elements. Calcium, Mg, Mn, Fe, and Zn were found to have a quantitative determination frequency larger than 80% and a concentration greater than 100μg/g. Among ecotoxicologically relevant elements, Ni, Cd, Hg, and Pb could be determined in more than 55% of the tail feather samples. The concentration of Hg with a quantification limit of 0.006μg/g and Pb with that of 0.015μg/g was higher than 1 and 10μg/g, respectively, in more than 80% of the investigated samples, but generally lower than levels that could cause adverse behavioral effects. The principal component analyses of elemental concentration data followed by the application of general linear models revealed that, for male collared flycatchers, the concentration of Sn, Pb, Ni, Sr, Mg, Zn, Ba, and Sc differed significantly in the wing and tail feathers collected from the same individuals. With females, only the Ca and Sc concentration showed a significant difference between wing and tail feathers. Moreover, the concentration of rare earth elements, V, Fe, Sr, Mg, Mn, Zn, Pb, and Ba in tail feathers allowed differentiation between sexes while the concentration of Se, Bi, and Sc between yearling and adult male individuals. At the same time, Sc differentiated age categories in females. Distribution of major elements along the rachis of feathers could be monitored by laser ablation ICP-SF-MS after normalization of the intensities to either 13C or 34S signals.

Expression levels of GSTA2 and APOD genes might be associated with carotenoid coloration in golden pheasant (Chrysolophus pictus) plumage.

Carotenoids, which generate yellow, orange, and red colors, are crucial pigments in avian plumage. Investigations into genes associated with carotenoidbased coloration in avian species are important; however, such research is difficult because carotenoids cannot be synthetized in vertebrates as they are only derived from dietary sources. Here, the golden pheasant (Chrysolophus pictus) was used as a model in analysis of candidate gene expression profiles implicated in carotenoid binding and deposition. Using mass and Raman spectrometry to confirm the presence of carotenoids in golden pheasant feathers, we found C40H54O and C40H56O2 in feathers with yellow to red colors, and in the rachis of iridescent feathers. The global gene expression profiles in golden pheasant skins were analyzed by RNA-seq and all six carotenoid binding candidate genes sequenced were studied by realtime PCR. StAR4, GSTA2, Scarb1, and APOD in feather follicles showed different expressions in red breast and orange nape feathers compared with that of iridescent mantle feathers. Further comparison of golden pheasant yellow rump and Lady Amherst's pheasant (Chrysolophus amherstiae) white nape feathers suggested that GSTA2 and APOD played a potential role in carotenoid-based coloration in golden pheasant.

Morphological Variations of Leading-Edge Serrations in Owls (Strigiformes).

BackgroundOwls have developed serrations, comb-like structures, along the leading edge of their wings. Serrations were investigated from a morphological and a mechanical point of view, but were not yet quantitatively compared for different species. Such a comparative investigation of serrations from species of different sizes and activity patterns may provide new information about the function of the serrations.ResultsSerrations on complete wings and on tenth primary remiges of seven owl species were investigated. Small, middle-sized, and large owl species were investigated as well as species being more active during the day and owls being more active during the night. Serrations occurred at the outer parts of the wings, predominantly at tenth primary remiges, but also on further wing feathers in most species. Serration tips were oriented away from the feather rachis so that they faced into the air stream during flight. The serrations of nocturnal owl species were higher developed as demonstrated by a larger inclination angle (the angle between the base of the barb and the rachis), a larger tip displacement angle (the angle between the tip of the serration and the base of the serration) and a longer length. Putting the measured data into a clustering algorithm yielded dendrograms that suggested a strong influence of activity pattern, but only a weak influence of size on the development of the serrations.ConclusionsSerrations are supposed to be involved in noise reduction during flight and also depend on the aerodynamic properties that in turn depend on body size. Since especially nocturnal owls have to rely on hearing during prey capture, the more pronounced serrations of nocturnal species lend further support to the notion that serrations have an important function in noise reduction. The differences in shape of the serrations investigated indicate that a silent flight requires well-developed serrations.

Quantifying variation in δ 13C and δ 15N isotopes within and between feathers and individuals: Is one sample enough?

Studies of avian migration increasingly use stable isotope analysis to provide vital trophic and spatial markers. However, when interpreting differences in stable isotope values of feathers, many studies are forced to make assumptions about the timing of moult. A fundamental question remains about the consistency of these values within and between feathers from the same individual. In this study, we examine variation in carbon and nitrogen isotopes by sub-sampling feathers collected from the wings of adults of two small congeneric petrel species, the broad-billed Pachyptila vittata and Antarctic prion P. desolata. Broad-billed prion feather vane material was enriched in 15N compared to feather rachis material, but there was no detectable difference in δ 13C. Comparison of multiple samples taken from Antarctic prion feathers indicated subtle difference in isotopes; rachis material was enriched in 13C compared to vane material, and there were differences along the length of the feather, with samples from the middle and tip of the feather depleted in 15N compared to those from the base. While the greatest proportion of model variance was explained by differences between feathers and individuals, the magnitude of these within-feather differences was up to 0.5 ‰ in δ 15N and 0.8 ‰ in δ 13C. We discuss the potential drivers of these differences, linking isotopic variation to individual-level dietary differences, movement patterns and temporal dietary shifts. A novel result is that within-feather differences in δ 13C may be attributed to differences in keratin structure within feathers, suggesting further work is required to understand the role of different amino acids. Our results highlight the importance of multiple sampling regimes that consider both within- and between-feather variation in studies using stable isotopes. Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-015-2618-8) contains supplementary material, which is available to authorized users.