Research roundup: 6 cool science stories we almost missed
Research roundup: 6 cool science stories we almost missed
研究综述：6个我们差点错过的酷炫科学故事
It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across. So every month, we highlight a handful of the best stories that nearly slipped through the cracks. April’s list includes tracking Roman ship repairs, the discovery that mushrooms can detect human urine, crushing soda cans for science, and the physics of why dolphins can swim so fast. 令人遗憾的是，我们总是没有足够的时间来报道所有遇到的有趣科学故事。因此，每个月我们都会精选出一些差点被遗漏的精彩报道。四月份的名单包括：追踪罗马船只的维修记录、蘑菇能探测人类尿液的发现、为了科学而压扁汽水罐，以及海豚为何能游得如此之快的物理学原理。
Physics of why dolphins swim so fast
海豚为何游得如此之快的物理学原理
Dolphins are very good swimmers but the exact mechanisms by which they achieve their impressive speed and agility in water have remained murky. Japanese scientists from the University of Osaka ran multiple supercomputer simulations to learn more about how dolphins optimize their propulsion and found it has to do with the vortices, or eddies, produced by dolphin kicks, according to a paper published in the journal Physical Review Fluids. 海豚是游泳健将，但它们在水中实现惊人速度和敏捷性的确切机制一直不甚明朗。根据发表在《物理评论流体》（Physical Review Fluids）期刊上的一篇论文，日本大阪大学的科学家们进行了多次超级计算机模拟，以深入了解海豚如何优化其推进力，结果发现这与海豚摆动尾部时产生的涡流（vortices）有关。
Per the authors, when dolphins flap their tails up and down, the kicking motion pushes water backward and produces swirling currents of varying sizes. The computer simulations enabled the team to break down those different sizes, revealing that the initial tail oscillations produce large vortex rings that generate thrust, and those larger ones then produce many more smaller vortices. However, the smaller ones don’t contribute to the forward motion. 作者指出，当海豚上下摆动尾部时，这种踢水动作会将水向后推，并产生大小不一的旋流。计算机模拟使研究团队能够解析这些不同尺寸的涡流，揭示了最初的尾部摆动会产生巨大的涡环以提供推力，而这些较大的涡环随后会产生更多较小的涡流。然而，这些较小的涡流对前进动力并无贡献。
In short, “Our results show that the hierarchy of vortices in turbulence is crucial for understanding dolphin swimming,” said co-author Susumu Goto. “The largest vortices are responsible for most of the propulsion, while the smaller ones are mainly byproducts of turbulent flow.” The team hopes to apply these insights into the mechanics of underwater propulsion to the design of faster and more efficient underwater robots. 简而言之，合著者后藤进（Susumu Goto）表示：“我们的研究结果表明，湍流中涡流的层级结构对于理解海豚的游泳方式至关重要。最大的涡流负责大部分推进力，而较小的涡流主要是湍流的副产品。”该团队希望将这些关于水下推进机制的见解应用于设计更快、更高效的水下机器人。
Tracking Roman shipwreck repairs
追踪罗马沉船的维修记录
Back in 2016, archaeologists discovered a shipwreck from the Roman Republic, the Ilovik–Paržine 1. The wreck has been the subject of much study of the actual ship, enabling scientists to determine it was constructed in what is now Brindisi on Italy’s south-eastern coast. Most recently, analysis of pollen trapped in the ship’s waterproofing layers have yielded insight into repairs made successively in other locations throughout the Adriatic Sea, according to a paper published in the journal Frontiers in Materials. 早在2016年，考古学家发现了一艘罗马共和国时期的沉船“Ilovik–Paržine 1号”。这艘沉船一直是深入研究的对象，科学家们得以确定它是在现今意大利东南海岸的布林迪西（Brindisi）建造的。根据发表在《材料前沿》（Frontiers in Materials）期刊上的一篇论文，最近对船体防水层中残留花粉的分析，揭示了该船在亚得里亚海沿岸其他地点进行的一系列维修记录。
Per the authors, prior research had largely ignored studying non-wooden materials like seawater-resistant coatings, so they used mass spectrometry and similar methods to examine the molecular makeup of ten coating samples. The results showed that pine tree resin or tar (pitch) was the main component. But one sample was a combination of beeswax and tar, a mixture unique to Greek shipbuilders known as zopissa. The combination makes the coating easier to apply when heated and also makes the pitch adhesive more flexible. 作者指出，先前的研究大多忽略了对耐海水涂层等非木质材料的研究，因此他们利用质谱分析法及类似方法检查了十个涂层样本的分子构成。结果显示，松树树脂或焦油（沥青）是主要成分。但其中一个样本是蜂蜡和焦油的混合物，这是一种希腊造船者特有的混合物，被称为“zopissa”。这种组合使涂层在加热时更容易涂抹，也使沥青粘合剂更具柔韧性。
Because pitch’s adhesive nature easily traps and preserve pollen, the researchers were also able to identify which plants had been present when the coating was applied, so they could in turn identify the regions where the pitch had been produced. They found pollen from a wide range of environments, such as forests of holly oak, pine, and matorral, all typical of the Mediterranean and Adriatic coastal regions. Other samples contained alder and ash, more common to rivers, as well as fir and beech more typical of the mountain regions of Istria and Dalmatia. This provides concrete proof of mid-voyage repairs to the ship. 由于沥青的粘性容易捕获并保存花粉，研究人员得以识别出涂层施工时周围存在哪些植物，从而推断出沥青的产地。他们发现了来自多种环境的花粉，如冬青栎、松树和灌木丛林，这些都是地中海和亚得里亚海沿岸的典型植被。其他样本中还含有桤木和白蜡树（常见于河流地带），以及伊斯特拉和达尔马提亚山区典型的冷杉和山毛榉。这为该船在航行途中进行的维修提供了确凿证据。
Crushing soda cans for science
为了科学而压扁汽水罐
Who doesn’t love to watch those YouTube videos of people using hydraulics to crush a variety of objects? That includes physicists at the University of Manchester, who were intrigued by the difference between crushing an empty soda can versus one that is full of liquid. An empty can collapsed immediately; a full can collapses gradually in a series of circular rings. The Manchester physicists wanted to know why a full can behaves this way. They investigated via a combination of mathematical modeling and laboratory crushing experiments, describing their findings in a paper published in the journal Communications Physics. 谁不喜欢看那些用液压机压碎各种物体的YouTube视频呢？曼彻斯特大学的物理学家们也对此很感兴趣，他们想探究压扁空汽水罐和装满液体的汽水罐之间有何不同。空罐子会立即坍塌；而装满液体的罐子则会以一系列环状结构逐渐坍塌。曼彻斯特的物理学家们想知道为什么装满液体的罐子会有这种表现。他们通过数学建模和实验室压碎实验相结合的方式进行了研究，并将研究结果发表在《通讯-物理》（Communications Physics）期刊上。
It turns out that how a full can buckles isn’t random and that the liquid inside actually alters how the can responds to force. The buckling may start in the middle, and minor variations in a given can’s shape and size might affect when the first ring emerges. But then, the authors say, the physics takes over in a highly predictable process. The rings arise because the metal softens as the can compresses, then stiffens, then compresses and stiffens again, repeating the pattern until the compression is complete—akin to something called homoclinic snaking. 事实证明，装满液体的罐子如何屈曲并非随机，内部的液体确实改变了罐子对力的反应方式。屈曲可能从中间开始，罐子形状和尺寸的微小差异可能会影响第一个环出现的时间。但作者表示，随后物理规律会接管这一过程，使其变得高度可预测。环的出现是因为金属在压缩时会变软，然后变硬，接着再次压缩和变硬，这种模式不断重复直到压缩完成——这类似于一种被称为“同宿蛇形”（homoclinic snaking）的现象。
This seems to be a fundamental property of liquid-filled cylinders, which are common in such industries as industrial storage transportation, construction, energy systems, and rocket parts. So this work could help engineers detect early signs of failure in such structures. 这似乎是充液圆柱体的一个基本属性，这种结构常见于工业仓储运输、建筑、能源系统和火箭部件等行业。因此，这项研究可以帮助工程师检测此类结构中早期的失效迹象。