冬季恋歌

Scientists Unveil Mystery Surrounding 500 Million-Year-Old Critter Without Anus_我的网站

A |     　　武汉8月24日电(葛利龙 余哲)随着最后一根猫道承重索精准下放至桥面，由湖北交投投资、中交二航局承建的湖北燕矶长江大桥猫道拆除工程23日全部完成，标志着这座世界最大跨径四主缆悬索桥全面进入上部结构施工收尾阶段，正全力冲刺年底建成通车目标。    Researchers from China and the UK have solved the mystery surrounding Saccorhytus coronaries – a millimeter-long spiny creature that was found in 2017 and believed to have inhabited oceans 500 million years ago. The veil of mystery over the critter persisted for years, as the scientists could not locate the creature’s anus. Turns out – they should not have even tried.,The critter was originally determined to be a member of a deuterostomes group of animals - the ancestors to the modern vertebrates (including humans). However, scientists' latest research suggests that it actually belongs to another group called ecdysozoans – the predecessors of the modern spiders and various insects. As it turned out, the whole mishap happened over the creature's anus – or rather lack thereof.,Ecdysozoans normally have an anus and hence the critter was initially ruled not to belong to them. But, upon closer discovery using x-rays, scientists saw it resembles ecdysozoans internally more than the ancestors of the vertebrates.,Like them, Saccorhytus has a large mouth and also features tiny holes around it that served as bases for spines that kept the critter anchored in one place. Those holes also served as a source of confusion as they were originally believed to be gills – another mark of the proto-vertebrates.,'Ugliest I've Ever Seen': Fisherman Shares Pic of Mysterious Creature He Found in Australia29 June, 13:17 GMT,As to Saccorhytus' absence of anus, scientists are yet to find out what happened to it. One theory suggests that there was an even earlier representative of ecdysozoans that has not been discovered, but did not have an anus.,Another theory goes that Saccorhytus did not actually need one.,"It could be that it lost it during its own evolution - perhaps it didn't need one because it could just sit in one spot with one opening for everything," Emily Carlisle, one of the researchers, said.。图为猫道全部拆除完成的燕矶长江大桥。

B | 　(无人机照片) 葛利龙 摄　　燕矶长江大桥横跨鄂州与黄冈两地，采用一跨过江设计，主跨达1860米，项目全长约26公里。上层为六车道高速公路，设计时速100公里；下层为四车道城市快速路，设计时速80公里。作为串接鄂州和黄冈沿江发展轴、对接湖北国际物流核心枢纽机场的重大交通工程，大桥建成后将打通沿线交通瓶颈，强化两市经济联系，极大完善区域“公、铁、水、空”综合交通运输体系。　　猫道是悬索桥施工中不可或缺的临时高空作业通道，平行布设于主缆下方，主缆索股牵引、紧缆压实、索夹与吊索安装、主缆防腐涂装等全部关键工序均依托猫道展开。燕矶长江大桥采用独特的四主缆设计，内外主缆下方各设一条猫道，将南北两岸主塔相连。

C | 单条猫道宽3.45米，长约3公里，四条猫道总长达12公里，是目前世界上最长的猫道。图为猫道全部拆除完成的燕矶长江大桥。　(无人机照片) 葛利龙 摄　　此次拆除面临极高风险与巨大挑战。

D | 大桥横跨长江主航道，猫道承重索采用直径60毫米高强度钢丝绳，抗拉强度达2160兆帕，为国内之最，拆除安全风险高、施工难度大。

E | 而外缆猫道拆除更是难上加难，受双层钢桁梁结构限制，猫道挤在钢梁外侧与上层桥面下方，作业空间局促犹如“高空夹缝”。施工团队需先将猫道承重索整体向上提举、翻越外主缆后再平稳下放，对姿态控制精度要求极高。　　为此，中交二航局项目建设团队为猫道量身定制了“翻缆方案”。

F | 通过增设辅助导向轮对索体进行限位导向，实时监测两侧高差变化，动态调整提吊参数，有效避免承重索在翻越过程中发生扭转或滑移，防止与主体结构发生磕碰损伤。针对绳索直径大、自身索力高等难题，团队优化卷扬机配置，设计多级滑轮组牵引系统，成功化解大直径钢丝绳平稳下放的技术瓶颈。

G | 图为猫道全部拆除完成的燕矶长江大桥桥面。　(无人机照片) 葛利龙 摄　　随着猫道全部拆除完成，燕矶长江大桥施工进入最后冲刺阶段。下一步，建设团队将有序推进桥塔涂装等附属工程施工、荷载试验及交工验收等工作，全力冲刺年底建成通车。

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