Woodpeckers are well able to resist head injury during repeated high speed impacts at 6-7 m s-1 with decelerations up to 1000 g.This study was designed to compare the mechanical properties,microstructures and composit...Woodpeckers are well able to resist head injury during repeated high speed impacts at 6-7 m s-1 with decelerations up to 1000 g.This study was designed to compare the mechanical properties,microstructures and compositions of cranial bone and beak bone of great spotted woodpecker(Dendrocopos major) and the Mongolian sky lark(Melanocorypha mongolica).Microstructures were observed using micro-computed tomography and scanning electron microscopy and their compositions were characterized by X-ray powder diffraction and Fourier-transform infrared spectroscopy.Under high stress,the cranial bone and the beak of the woodpecker exhibited distinctive mechanical features,which were associated with differences in micro-structure and composition,compared with those of the lark.Evolutionary optimization of bone micro-structure has enabled functional adaptation to the woodpecker's specific lifestyle.Its characteristic micro-structure efficiently avoids head impact injury and may provide potential clues to the prevention of brain injury using bio-inspired designs of shock-absorbing materials.展开更多
珀西·比希·雪莱(Percy Bysshe Shelley)创作于1820年的《给云雀》(To a Skylark),是广为流传的浪漫主义代表作。该诗开篇盛赞云雀飞行的姿态与歌声,接着试图将其与尘世中的种种美好相比较,但始终无法找到能够与之媲美的事物,...珀西·比希·雪莱(Percy Bysshe Shelley)创作于1820年的《给云雀》(To a Skylark),是广为流传的浪漫主义代表作。该诗开篇盛赞云雀飞行的姿态与歌声,接着试图将其与尘世中的种种美好相比较,但始终无法找到能够与之媲美的事物,诗篇最后则祈求云雀教会诗人那“熟知的欢欣”。诗中勾勒出的浪漫主义诗人的形象,和入云而去的云雀一般,令人无限崇拜与神往。但诗人始终不可能与云雀一样,到达真正纯粹的欢乐和自由。云雀所象征的一切,终究可望不可即。这实在是人类悲剧的宿命之一。毫无疑问,《给云雀》的精神实质是浪漫主义的。对自然的崇敬、对孤独形象的描绘、对个体心灵的沉思、自然与人性的比较,以及对诗人身份的追问,都是浪漫主义时期核心的诗学议题。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10925208 and 11120101001)
文摘Woodpeckers are well able to resist head injury during repeated high speed impacts at 6-7 m s-1 with decelerations up to 1000 g.This study was designed to compare the mechanical properties,microstructures and compositions of cranial bone and beak bone of great spotted woodpecker(Dendrocopos major) and the Mongolian sky lark(Melanocorypha mongolica).Microstructures were observed using micro-computed tomography and scanning electron microscopy and their compositions were characterized by X-ray powder diffraction and Fourier-transform infrared spectroscopy.Under high stress,the cranial bone and the beak of the woodpecker exhibited distinctive mechanical features,which were associated with differences in micro-structure and composition,compared with those of the lark.Evolutionary optimization of bone micro-structure has enabled functional adaptation to the woodpecker's specific lifestyle.Its characteristic micro-structure efficiently avoids head impact injury and may provide potential clues to the prevention of brain injury using bio-inspired designs of shock-absorbing materials.
文摘珀西·比希·雪莱(Percy Bysshe Shelley)创作于1820年的《给云雀》(To a Skylark),是广为流传的浪漫主义代表作。该诗开篇盛赞云雀飞行的姿态与歌声,接着试图将其与尘世中的种种美好相比较,但始终无法找到能够与之媲美的事物,诗篇最后则祈求云雀教会诗人那“熟知的欢欣”。诗中勾勒出的浪漫主义诗人的形象,和入云而去的云雀一般,令人无限崇拜与神往。但诗人始终不可能与云雀一样,到达真正纯粹的欢乐和自由。云雀所象征的一切,终究可望不可即。这实在是人类悲剧的宿命之一。毫无疑问,《给云雀》的精神实质是浪漫主义的。对自然的崇敬、对孤独形象的描绘、对个体心灵的沉思、自然与人性的比较,以及对诗人身份的追问,都是浪漫主义时期核心的诗学议题。
