Insect wing veins are biological composites of chitin and protein arranged in a complex lamellar configuration. Although these hierarchical structures are found in many ‘venous wings' of insects, very little is known about their physical and mechanical characteristics. For the first time, we carried out a systematic comparative study to gain a better understanding of the influence of microstructure on the mechanical characteristics and damping behaviour of the veins. Morphological data have been used to develop a series of three-dimensional numerical models with different material properties and geometries. Finite-element analysis has been employed to simulate the mechanical response of the models under different loading conditions. The modelling strategy used in this study enabled us to determine the effects selectively induced by resilin, friction between layers, shape of the cross section, material composition and layered structure on the stiffness and damping characteristics of wing veins. Numerical simulations suggest that although the presence of the resilin-dominated endocuticle layer results in a much higher flexibility of wing veins, the dumbbell-shaped cross section increases their bending rigidity. Our study further shows that the rubber-like cuticle, friction between layers and material gradient-based design contribute to the higher damping capacity of veins. The results of this study can serve as a reference for the design of novel bioinspired composite structures.
Dragonflies are fast and manoeuvrable fliers and this ability is reflected in their unique wing morphology. Due to the specific lightweight structure, with the crossing veins joined by rubber-like resilin patches, wings possess strong deformability but can resist high forces and large deformations during aerial collisions. The computational results demonstrate the strong influence of resilin-containing vein joints on the stress distribution within the wing. The presence of flexible resilin in the contact region of the veins prevents excessive bending of the cross veins and significantly reduces the stress concentration in the joint.
Background:Diabetes has become the next most widespread disease after cancer. Recent studies have found that diabetes and moderate to severe vitamin D deficiency are associated with reduced bone mineral content; therefore administration of vitamin D may correct these conditions. The purpose of this research is to compare the effect of vitamin D administration on bone to implant contact in diabetic rats with control group.Materials and Methods:In this randomized placebo-controlled trial, 48 Wistar rats were rendered diabetic (130≤ blood sugar ≤200 mg/dl) by IV injection of 35 mg/kg Alloxan. Implants were inserted in tibial bone; Then rats were divided into study and control groups and received oral vitamin D3 (160 IU) or placebo respectively for one week. Bone to implant contact value was measured under light microscope at 3 and 6 weeks.Results:Analysis of data indicated that vitamin D had no significant effect on bone to implant contact (BIC). At 3 weeks, the control group (n = 5) reported BIC level at 44 ± 19 and study group (n = 7) at 57 ± 20. At 6 weeks, the control group (n = 5) reported BIC level at 70 ± 29, and study group (n = 10) at 65 ± 22. Twenty one samples were missed because of death or incorrect lab processes.Conclusion:It seems that vitamin D supplement has no significant effect on BIC in 130 mg/dL ≤ blood sugar ≤200 mg/dL (P = 0.703) andwas also not time dependent (P = 0.074).
Although wings of insects show a large variation in morphology, they are all made from a network of irregular veins interconnected through membranous areas. Depending on their shape, size, and position, wing veins are usually divided into three different groups: longitudinal veins, cross-veins and ambient veins. The veins together with the membrane and some other elements such as spines, nodus and pterostigma can be considered as the wing’s “constructional elements”. In spite of rather extensive literature on dragonfly wing structure, the role of each of these elements in determining the wing’s function remains mostly unknown. As this question is difficult to answer in vivo using biomechanical experiments on actual wings, this study was undertaken to reveal the effects of the constructional elements on the mechanical behaviour of dragonfly wings by applying numerical simulations. An image processing technique was used to develop 12 finite element models of the insect wings with different constructional elements. The mechanical behaviour of these models was then simulated under normal and shear stresses due to tension, bending and torsion. A free vibration analysis was also performed to determine the resonant frequencies and the mode shapes of the models. For the first time, a quantitative comparison was carried out between the mechanical effects selectively caused by different elements. Our results suggest that the complex interactions of veins, membranes and corrugations may considerably affect the dynamic deformation of the insect wings during flight
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.