《自然》（20230907出版）一周論文導讀

原文地址：http://news.sciencenet.cn/htmlnews/2023/9/508185.shtm

編譯 | 未玖

Nature, 7 September 2023, VOL 621, ISSUE 7977

《自然》2023年9月7日，第621卷，7977期

物理學Physics

Turbulence suppression by cardiac-cycle-inspired driving of pipe flow

心動周期啟發的驅動管流湍流抑制

▲ 作者：D. Scarselli, J. M. Lopez, A. Varshney & B. Hof

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06399-5

▲ 摘要：

在實踐中，管道和通道中的流動幾乎總是湍流，而多尺度渦流運動是所遇到的摩擦損失和泵送成本的主要原因。相反，對于脈動流，特別是主動脈血流，盡管峰值速度相對較大，但湍流水平仍然很低。對于主動脈血流，高湍流水平是無法忍受的，因為其會損傷剪切敏感的內皮細胞層。

研究組表明，如果以脈動模式驅動流體，并結合心臟波形的所有關鍵特征，那么普通管道流中的湍流就會減少。當雷諾數與主動脈血流的雷諾數相當時，湍流在很大程度上被抑制，而在更高的速度下，湍流阻力減少了25%以上。

與穩定驅動相比，這種特定的運行模式更高效，有望應用于從加熱回路到水、天然氣和石油管道幾乎所有流體輸送過程。

▲ 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.

天文學Astronomy

Formation of the methyl cation by photochemistry in a protoplanetary disk

原行星盤中甲基陽離子的光化學形成

▲ 作者：Olivier Berné, Marie-Aline Martin-Drumel, Ilane Schroetter, Javier R. Goicoechea, Ugo Jacovella, Bérenger Gans, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06307-x

▲ 摘要：

40年前，有人提出星際介質中的氣相有機化學可由甲基陽離子CH3+引發，但迄今為止尚未在太陽系外觀測到。目前人們已經啟用了涉及晶粒表面處理的替代路線。

研究組報道了詹姆斯·韋伯太空望遠鏡在獵戶座恒星形成區域的原行星盤中觀測到CH3+，并發現氣相有機化學在紫外線照射下被激活。

▲ 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.

材料科學Materials Science

Adsorbate motors for unidirectional translation and transport

用于單向轉化和輸送的吸附物馬達

▲ 作者：Grant J. Simpson, Mats Persson & Leonhard Grill

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06384-y

▲ 摘要：

人工分子馬達被設計為以單向運動的形式將外部能量轉化為有用功，主要在溶液中進行研究，但有時也在固體表面進行，固體表面提供了固定參考點，以實現跟蹤分子馬達的運動。

然而，這些分子需要復雜的設計和合成，因為馬達功能必須印跡到化學結構中，且與溶液中相比，在固體表面上顯示出較少的功能。另一方面，DNA助行器具有高度方向性，因其將表面作為運動功能的一部分，但需要化學表面圖案化和順序溶劑修飾來激活馬達。

研究組展示了高效分子馬達如何在沒有任何液體的均勻金屬表面上以更小的長度尺度運行。這通過將表面與一個簡單分子結合來實現，該分子本身不包含任何馬達單元。

研究組在單分子水平上跟蹤該運動，由分子內質子轉移引發，并對勢能面進行相應調制。每個分子沿著原子定義的直線100%單向性移動。

通過控制單個一氧化碳分子的輸送，研究組證明了該分子馬達可執行有意義的工作。這種簡單化的概念為原子尺度上納米結構可控的自下而上組裝奠定了基礎。

▲ 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.

化學Chemistry

Visualizing interfacial collective reaction behaviour of Li–S batteries

鋰硫電池界面集體反應行為的可視化

▲ 作者：Shiyuan Zhou, Jie Shi, Sangui Liu, Gen Li, Fei Pei, Youhu Chen, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06326-8

▲ 摘要：

得益于高能量密度（2600 Wh kg?1）和低成本的鋰硫（Li-S）電池被認為是先進儲能系統頗有潛力的候選者。盡管人們在抑制多硫化物鋰長期存在的穿梭效應方面做出了巨大努力，但對多硫化鋰在納米尺度上界面反應的理解仍難以捉摸。

這主要是因為原位表征工具在高時空分辨率下追蹤不穩定多硫化鋰的液固轉化方面存在局限性。目前迫切需要理解鋰硫電池內部的耦合現象，特別是多硫化鋰的動態分布、聚集、沉積和溶解。

通過使用原位液體電池電化學透射電子顯微鏡，研究組在原子尺度上直接觀測到多硫化鋰在在電極表面的轉化。值得注意的是，他們在納米簇活性中心固定化表面上捕獲了多硫化鋰意外聚集誘導的集體電荷轉移，其進一步誘導了非平衡態Li2S納米晶體從多硫化鋰的富集液相中瞬時沉積。

在沒有活性中心介導的情況下，反應遵循經典的單分子途徑，多硫化鋰逐步轉化為Li2S2和Li2S。分子動力學模擬表明，活性中心與多硫化鋰之間的長程靜電相互作用促進了由Li+和Sn2?（2<n≤6）組成的致密相的形成，并通過從頭算分子動力學模擬進一步驗證了致密相中的集體電荷轉移。集體界面反應途徑揭示了一種新型轉化機制，加深了對鋰硫電池的基本理解。

▲ 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

通過有機小分子制備具有催化活性的振蕩器

▲ 作者：Matthijs ter Harmsel, Oliver R. Maguire, Sofiya A. Runikhina, Albert S. Y. Wong, Wilhelm T. S. Huck & Syuzanna R. Harutyunyan

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06310-2

▲ 摘要：

振蕩系統調節許多生物過程，包括如代謝和細胞分裂等關鍵細胞功能，以及如晝夜節律和心跳等更大規模的過程。最初在無機系統中發現的非生物化學振蕩激發了各種合成振蕩器的發展，用作分析化學、材料化學和生物醫學領域的自主計時系統。

通過讓合成化學振蕩器周期性地驅動輔助功能，可將其用途擴展到起搏器之外，將使它們成為更強大的工具。但這不容小覷，因為振蕩器組件在輔助功能中的參與可能危及其計時能力。

研究組報道了一種小分子振蕩器，可以在原位催化獨立化學反應而不損害其振蕩特性。在流動體系中，振蕩器的催化活性產物濃度呈現持續振蕩，且催化反應僅在濃度達到峰值時才會加速。

具有周期性催化作用的合成振蕩器的增強實現了復雜系統的構建，這些系統在未來有望應用于自動化合成、系統和聚合化學以及周期性藥物遞送。

▲ 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.

地球科學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.

▲ 鏈接：

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匯或交織的地方。WUI是人類-環境沖突和風險集中的區域，包括野火造成的房屋和生命損失、棲息地喪失和碎片化以及人畜共患疾病的傳播。然而，缺乏對WUI的全球分析。

研究組基于建筑面積和荒地植被的遙感衍生數據集，采用全球一致且經過驗證的方法，繪制了2020年WUI的10米分辨率全球地圖。他們表明WUI是一個全球性的現象，確定了許多以前未記載的WUI熱點，并強調了全球WUI不同地區的人口密度、土地覆蓋類型和生物量水平的廣泛差異。

WUI僅占陸地面積的4.7%，但居住著近一半的人口（35億）。WUI在歐洲（占陸地面積的15%）和溫帶闊葉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（4億）中，三分之二居住在WUI，其中大多數在非洲（1.5億）。

鑒于預計許多地區的野火活動將因氣候變化而增加，作為WUI變化的驅動因素，亟需理解住房增長情況和植被模式。

▲ Abstract：