原文地址：http://news.sciencenet.cn/htmlnews/2023/9/508185.shtm
编译 | 未玖
Nature, 7 September 2023, VOL 621, ISSUE 7977
《自然》2023年9月7日，第621卷，7977期
物理学Physics
Turbulence suppression by cardiac-cycle-inspired driving of pipe flow
心动周期启发的驱动管流湍流抑制
▲ 作者：D. Scarselli, J. M. Lopez, A. Varshney & B. Hof
▲ 链接：
https://www.nature.com/articles/s41586-023-06399-5
▲ 摘要：
在实践中，管道和通道中的流动几乎总是湍流，而多尺度涡流运动是所遇到的摩擦损失和泵送成本的主要原因。相反，对于脉动流，特别是主动脉血流，尽管峰值速度相对较大，但湍流水平仍然很低。对于主动脉血流，高湍流水平是无法忍受的，因为其会损伤剪切敏感的内皮细胞层。
研究组表明，如果以脉动模式驱动流体，并结合心脏波形的所有关键特征，那么普通管道流中的湍流就会减少。当雷诺数与主动脉血流的雷诺数相当时，湍流在很大程度上被抑制，而在更高的速度下，湍流阻力减少了25%以上。
与稳定驱动相比，这种特定的运行模式更高效，有望应用于从加热回路到水、天然气和石油管道几乎所有流体输送过程。
▲ Abstract：
Flows through pipes and channels are, in practice, almost always turbulent, and the multiscale eddying motion is responsible for a major part of the encountered friction losses and pumping costs. Conversely, for pulsatile flows, in particular for aortic blood flow, turbulence levels remain low despite relatively large peak velocities. For aortic blood flow, high turbulence levels are intolerable as they would damage the shear-sensitive endothelial cell layer. Here we show that turbulence in ordinary pipe flow is diminished if the flow is driven in a pulsatile mode that incorporates all the key features of the cardiac waveform. At Reynolds numbers comparable to those of aortic blood flow, turbulence is largely inhibited, whereas at much higher speeds, the turbulent drag is reduced by more than 25%. This specific operation mode is more efficient when compared with steady driving, which is the present situation for virtually all fluid transport processes ranging from heating circuits to water, gas and oil pipelines.
天文学Astronomy
Formation of the methyl cation by photochemistry in a protoplanetary disk
原行星盘中甲基阳离子的光化学形成
▲ 作者：Olivier Berné, Marie-Aline Martin-Drumel, Ilane Schroetter, Javier R. Goicoechea, Ugo Jacovella, Bérenger Gans, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06307-x
▲ 摘要：
40年前，有人提出星际介质中的气相有机化学可由甲基阳离子CH3+引发，但迄今为止尚未在太阳系外观测到。目前人们已经启用了涉及晶粒表面处理的替代路线。
研究组报道了詹姆斯·韦伯太空望远镜在猎户座恒星形成区域的原行星盘中观测到CH3+，并发现气相有机化学在紫外线照射下被激活。
▲ Abstract：
Forty years ago, it was proposed that gas-phase organic chemistry in the interstellar medium can be initiated by the methyl cation CH3+, but so far it has not been observed outside the Solar System. Alternative routes involving processes on grain surfaces have been invoked. Here we report James Webb Space Telescope observations of CH3+ in a protoplanetary disk in the Orion star-forming region. We find that gas-phase organic chemistry is activated by ultraviolet irradiation.
材料科学Materials Science
Adsorbate motors for unidirectional translation and transport
用于单向转化和输送的吸附物马达
▲ 作者：Grant J. Simpson, Mats Persson & Leonhard Grill
▲ 链接：
https://www.nature.com/articles/s41586-023-06384-y
▲ 摘要：
人工分子马达被设计为以单向运动的形式将外部能量转化为有用功，主要在溶液中进行研究，但有时也在固体表面进行，固体表面提供了固定参考点，以实现跟踪分子马达的运动。
然而，这些分子需要复杂的设计和合成，因为马达功能必须印迹到化学结构中，且与溶液中相比，在固体表面上显示出较少的功能。另一方面，DNA助行器具有高度方向性，因其将表面作为运动功能的一部分，但需要化学表面图案化和顺序溶剂修饰来激活马达。
研究组展示了高效分子马达如何在没有任何液体的均匀金属表面上以更小的长度尺度运行。这通过将表面与一个简单分子结合来实现，该分子本身不包含任何马达单元。
研究组在单分子水平上跟踪该运动，由分子内质子转移引发，并对势能面进行相应调制。每个分子沿着原子定义的直线100%单向性移动。
通过控制单个一氧化碳分子的输送，研究组证明了该分子马达可执行有意义的工作。这种简单化的概念为原子尺度上纳米结构可控的自下而上组装奠定了基础。
▲ Abstract：
Artificial molecular motors are designed to transform external energy into useful work in the form of unidirectional motion. They have been studied mainly in solution, but also on solid surfaces, which provide fixed reference points, allowing for tracking of their movement. However, these molecules require sophisticated design and synthesis, because the motor function must be imprinted into the chemical structure, and show reduced functionality on surfaces compared with in solution. DNA walkers, on the other hand, impart high directionality as they include the surface as part of the motor function, but they require chemical surface patterning and sequential solvent modification for motor activation. Here we show how efficient motors can operate at much smaller length scales on a homogeneous metal surface without any liquid. This is realized by combining a surface with a simple molecule, which, by itself, does not contain any motor unit. The motion, which is tracked at the single-molecule level, is triggered by intramolecular proton transfer with a corresponding modulation of the potential energy surface. Each molecule moves with 100 percent unidirectionality along an atomically defined straight line. Proof of the motor performing meaningful work is shown by controlled transport of single carbon monoxide molecules. This simplistic concept could form the basis for the controlled bottom-up assembly of nanostructures at the atomic scale.
化学Chemistry
Visualizing interfacial collective reaction behaviour of Li–S batteries
锂硫电池界面集体反应行为的可视化
▲ 作者：Shiyuan Zhou, Jie Shi, Sangui Liu, Gen Li, Fei Pei, Youhu Chen, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06326-8
▲ 摘要：
得益于高能量密度（2600 Wh kg?1）和低成本的锂硫（Li-S）电池被认为是先进储能系统颇有潜力的候选者。尽管人们在抑制多硫化物锂长期存在的穿梭效应方面做出了巨大努力，但对多硫化锂在纳米尺度上界面反应的理解仍难以捉摸。
这主要是因为原位表征工具在高时空分辨率下追踪不稳定多硫化锂的液固转化方面存在局限性。目前迫切需要理解锂硫电池内部的耦合现象，特别是多硫化锂的动态分布、聚集、沉积和溶解。
通过使用原位液体电池电化学透射电子显微镜，研究组在原子尺度上直接观测到多硫化锂在在电极表面的转化。值得注意的是，他们在纳米簇活性中心固定化表面上捕获了多硫化锂意外聚集诱导的集体电荷转移，其进一步诱导了非平衡态Li2S纳米晶体从多硫化锂的富集液相中瞬时沉积。
在没有活性中心介导的情况下，反应遵循经典的单分子途径，多硫化锂逐步转化为Li2S2和Li2S。分子动力学模拟表明，活性中心与多硫化锂之间的长程静电相互作用促进了由Li+和Sn2?（2<n≤6）组成的致密相的形成，并通过从头算分子动力学模拟进一步验证了致密相中的集体电荷转移。集体界面反应途径揭示了一种新型转化机制，加深了对锂硫电池的基本理解。
▲ Abstract：
Benefiting from high energy density (2,600 Wh kg?1) and low cost, lithium–sulfur (Li–S) batteries are considered promising candidates for advanced energy-storage systems. Despite tremendous efforts in suppressing the long-standing shuttle effect of lithium polysulfides, understanding of the interfacial reactions of lithium polysulfides at the nanoscale remains elusive. This is mainly because of the limitations of in situ characterization tools in tracing the liquid–solid conversion of unstable lithium polysulfides at high temporal–spatial resolution. There is an urgent need to understand the coupled phenomena inside Li–S batteries, specifically, the dynamic distribution, aggregation, deposition and dissolution of lithium polysulfides. Here, by using in situ liquid-cell electrochemical transmission electron microscopy, we directly visualized the transformation of lithium polysulfides over electrode surfaces at the atomic scale. Notably, an unexpected gathering-induced collective charge transfer of lithium polysulfides was captured on the nanocluster active-centre-immobilized surface. It further induced an instantaneous deposition of nonequilibrium Li2S nanocrystals from the dense liquid phase of lithium polysulfides. Without mediation of active centres, the reactions followed a classical single-molecule pathway, lithium polysulfides transforming into Li2S2 and Lii2S step by step. Molecular dynamics simulations indicated that the long-range electrostatic interaction between active centres and lithium polysulfides promoted the formation of a dense phase consisting of Li+ and Sn2? (2<n≤6), and the collective charge transfer in the dense phase was further verified by ab initio molecular dynamics simulations. The collective interfacial reaction pathway unveils a new transformation mechanism and deepens the fundamental understanding of Li–S batteries.
A catalytically active oscillator made from small organic molecules
通过有机小分子制备具有催化活性的振荡器
▲ 作者：Matthijs ter Harmsel, Oliver R. Maguire, Sofiya A. Runikhina, Albert S. Y. Wong, Wilhelm T. S. Huck & Syuzanna R. Harutyunyan
▲ 链接：
https://www.nature.com/articles/s41586-023-06310-2
▲ 摘要：
振荡系统调节许多生物过程，包括如代谢和细胞分裂等关键细胞功能，以及如昼夜节律和心跳等更大规模的过程。最初在无机系统中发现的非生物化学振荡激发了各种合成振荡器的发展，用作分析化学、材料化学和生物医学领域的自主计时系统。
通过让合成化学振荡器周期性地驱动辅助功能，可将其用途扩展到起搏器之外，将使它们成为更强大的工具。但这不容小觑，因为振荡器组件在辅助功能中的参与可能危及其计时能力。
研究组报道了一种小分子振荡器，可以在原位催化独立化学反应而不损害其振荡特性。在流动体系中，振荡器的催化活性产物浓度呈现持续振荡，且催化反应仅在浓度达到峰值时才会加速。
具有周期性催化作用的合成振荡器的增强实现了复杂系统的构建，这些系统在未来有望应用于自动化合成、系统和聚合化学以及周期性药物递送。
▲ Abstract：
Oscillatory systems regulate many biological processes, including key cellular functions such as metabolism and cell division, as well as larger-scale processes such as circadian rhythm and heartbeat. Abiotic chemical oscillations, discovered originally in inorganic systems, inspired the development of various synthetic oscillators for application as autonomous time-keeping systems in analytical chemistry, materials chemistry and the biomedical field. Expanding their role beyond that of a pacemaker by having synthetic chemical oscillators periodically drive a secondary function would turn them into significantly more powerful tools. However, this is not trivial because the participation of components of the oscillator in the secondary function might jeopardize its time-keeping ability. We now report a small molecule oscillator that can catalyse an independent chemical reaction in situ without impairing its oscillating properties. In a flow system, the concentration of the catalytically active product of the oscillator shows sustained oscillations and the catalysed reaction is accelerated only during concentration peaks. Augmentation of synthetic oscillators with periodic catalytic action allows the construction of complex systems that, in the future, may benefit applications in automated synthesis, systems and polymerization chemistry and periodic drug delivery.
地球科学Earth Science
The global wildland–urban interface
全球荒地-城市界面
▲ 作者：Franz Schug, Avi Bar-Massada, Amanda R. Carlson, Heather Cox, Todd J. Hawbaker, David Helmers, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06320-0
▲ 摘要：
荒地-城市界面（WUI）是建筑物和荒地植被交汇或交织的地方。WUI是人类-环境冲突和风险集中的区域，包括野火造成的房屋和生命损失、栖息地丧失和碎片化以及人畜共患疾病的传播。然而，缺乏对WUI的全球分析。
研究组基于建筑面积和荒地植被的遥感衍生数据集，采用全球一致且经过验证的方法，绘制了2020年WUI的10米分辨率全球地图。他们表明WUI是一个全球性的现象，确定了许多以前未记载的WUI热点，并强调了全球WUI不同地区的人口密度、土地覆盖类型和生物量水平的广泛差异。
WUI仅占陆地面积的4.7%，但居住着近一半的人口（35亿）。WUI在欧洲（占陆地面积的15%）和温带阔叶林和混交林生物群落（18%）中尤其普遍。在2003~2020年野火附近居住的所有人（4亿）中，三分之二居住在WUI，其中大多数在非洲（1.5亿）。
鉴于预计许多地区的野火活动将因气候变化而增加，作为WUI变化的驱动因素，亟需理解住房增长情况和植被模式。
▲ Abstract：
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