The feather aerofoil is unequalled in nature. It is comprised of a central rachis, serial paired branches or barbs, from which arise further branches, the barbules. Barbs and barbules arise from the significantly thinner lateral walls (the epicortex) of the rachis and barbs respectively, as opposed to the thicker dorsal and ventral walls (the cortex). We hypothesized a microstructural design of the epicortex that would resist the vertical or shearing stresses. The microstructures of the cortex and epicortex of the rachis and barbs were investigated in several bird species by microbe-assisted selective disassembly and conventional methods via scanning electron microscopy. We report, preeminent of the finds, a novel system of crossed fibres (ranging from ∼100–800 nm in diameter), oppositely oriented in alternate layers of the epicortex in the rachis and barbs. It represents the first cross-fibre microstructure, not only for the feather but in keratin per se. The cortex of the barbs is comprised of syncitial barbule cells, definitive structural units shown in the rachidial cortex in a related study. The structural connection between the cortex of the rachis and barbs appears uninterrupted. A new model on feather microstructure incorporating the findings here and in the related study is presented. The helical fibre system found in the integument of a diverse range of invertebrates and vertebrates has been implicated in profound functional strategies, perhaps none more so potentially than in the aerofoil microstructure of the feather here, which is central to one of the marvels of nature, bird flight.

No abstract

The radical increase in consumption of acidic (sour) candies amongst children and teenagers is considered a significant public health concern. The purpose of this study was to evaluate the erosive potential of sour candy in comparison with their regular counterparts at different exposure times. Sixteen prepared tooth samples were randomly assigned into four groups, namely: sour candy (n=8), regular candy (n=8); each of these was prepared to have protected (unexposed) and exposed surfaces in respective candy solutions for 15 min and 2 h (n=4). An Atomic Force Microscope (AFM) was used to measure the surface roughness (Ra) between the exposed and unexposed enamel surfaces for each sample group. The mean Ra measured was used for statistical analysis whilst the elemental loss was assessed using Energy Dispersive Spectroscopy (EDX). The findings showed that sour candy significantly eroded the exposed enamel samples (P<0.01). Overall, the samples exposed to the sour candy for 2 h had the highest eroded Ra values. The study suggests that frequent and long-time consumption of sour candies may pose a negative impact on the tooth as they are found to be highly erosive.

No abstract

No abstract

No abstract

No abstract

This study aimed to evaluate the erosive potential of sour candy at a different time of exposure within a laboratory-based setting. Fifty human anterior tooth samples were randomly assigned into three groups, namely: sour candy, regular candy A, and deionized water (n=15). Each tooth sample was exposed to a solution containing the sample groups at different time intervals. Vickers hardness tester was used to measure the surface hardness pre- and postexposure. The mean surface hardness value measured was compared using a paired sample test (α =.05). Raman spectroscopy was used to study the change in the enamel structure in all sample groups. A significant difference in the surface hardness value was measured pre and post-exposure in all the sample groups (P<0.01). The samples exposed to sour candy had the highest tooth surface loss. In terms of the time of exposure, it was found that prolonged exposure had a significant effect on the surface hardness (P<0.01). The Raman intensity change confirmed that samples exposed to sour candy, after 2 hrs of exposure, had the highest loss of structural integrity. The study conclude that sour candies are very erosive and its impact enhances with time.