编译 | 未玖

Science, 31 MAY 2024, VOL 384, ISSUE 6699

《科学》2024年5月31日，第384卷，6699期

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材料科学Materials Science

Molecular templating of layered halide perovskite nanowires

层状卤化物钙钛矿纳米线的分子模板

▲ 作者：WENHAO SHAO, JEONG HUI KIM, JEFFREY SIMON, ZHICHEN NIAN, SUNG-DOO BAEK, YUAN LU, ET AL.

▲ 链接：

https://www.science.org/doi/10.1126/science.adl0920

▲ 摘要：

层状金属卤化物钙钛矿或二维钙钛矿可以在溶液中合成，并可通过改变组成来调节其光学和电子性质。

研究组报道了一种分子模板方法，限制了沿除[110]以外所有晶体方向的晶体生长，从而促进了一维生长。该方法广泛适用于合成一系列具有大纵横比和可调有机-无机化学组成的高质量层状钙钛矿纳米线。

这些纳米线形成了非常清晰和灵活的空腔，表现出超越传统钙钛矿纳米线的一系列不同寻常的光学特性。研究组观察到各向异性发射偏振、低损耗波导（低于3分贝/毫米）和有效的低阈值光放大（低于20微焦耳/平方厘米）。

▲ Abstract：

Layered metal-halide perovskites, or two-dimensional perovskites, can be synthesized in solution, and their optical and electronic properties can be tuned by changing their composition. We report a molecular templating method that restricted crystal growth along all crystallographic directions except for [110] and promoted one-dimensional growth. Our approach is widely applicable to synthesize a range of high-quality layered perovskite nanowires with large aspect ratios and tunable organic-inorganic chemical compositions. These nanowires form exceptionally well-defined and flexible cavities that exhibited a wide range of unusual optical properties beyond those of conventional perovskite nanowires. We observed anisotropic emission polarization, low-loss waveguiding (below 3 decibels per millimeter), and efficient low-threshold light amplification (below 20 microjoules per square centimeter).

A three-dimensionally architected electronic skin mimicking human mechanosensation

模拟人类机械感知的三维结构电子皮肤

▲ 作者：ZHI LIU, XIAONAN HU, RENHENG BO, YOUZHOU YANG, XU CHENG, WENBO PANG, ET AL.

▲ 链接：

https://www.science.org/doi/10.1126/science.adk5556

▲ 摘要：

人体皮肤对机械刺激的感知源于将外力转化为电信号的机械感受器的传导。虽然模仿这些机械感受器的空间分布可使电子皮肤的发展能够解耦传感法向力/剪切力和应变，但其仍难以捉摸。

研究组报道了一种三维（3D）结构的电子皮肤（称为3DAE皮肤），其力和应变传感组件以3D布局排列，模仿人类皮肤中的默克尔细胞和鲁菲尼氏小体。

这种3DAE皮肤具有优异的法向力、剪切力和应变解耦传感性能，可用于开发触觉系统，通过触摸同时测量物体的模量/曲率。演示包括对各种形状和新鲜度的水果、面包和蛋糕进行快速模量测量。

▲ Abstract：

Human skin sensing of mechanical stimuli originates from transduction of mechanoreceptors that converts external forces into electrical signals. Although imitating the spatial distribution of those mechanoreceptors can enable developments of electronic skins capable of decoupled sensing of normal/shear forces and strains, it remains elusive. We report a three-dimensionally (3D) architected electronic skin (denoted as 3DAE-Skin) with force and strain sensing components arranged in a 3D layout that mimics that of Merkel cells and Ruffini endings in human skin. This 3DAE-Skin shows excellent decoupled sensing performances of normal force, shear force, and strain and enables development of a tactile system for simultaneous modulus/curvature measurements of an object through touch. Demonstrations include rapid modulus measurements of fruits, bread, and cake with various shapes and degrees of freshness.

Spontaneous weathering of natural minerals in charged water microdroplets forms nanomaterials

天然矿物质在带电水微滴中自然风化形成纳米材料

▲ 作者：B. K. SPOORTHI, KOYENDRILA DEBNATH, PALLAB BASURI, ANKIT NAGAR, UMESH V. WAGHMARE AND THALAPPIL PRADEEP

▲ 链接：

https://www.science.org/doi/10.1126/science.adl3364

▲ 摘要：

在这项工作中，研究组展示了常见矿物质颗粒在几毫秒内自发分解，在带电的水微滴中形成纳米颗粒。他们将石英和红宝石等微米级天然矿物整合到通过电喷雾产生的水性微滴中，将其转化为5至10纳米的颗粒。将液滴沉积在基底上，从而实现纳米颗粒表征。

研究组通过模拟确定，石英经历了质子诱导滑移，特别是当尺寸缩小并暴露在电场中时。这导致颗粒分裂和硅酸盐碎片的形成，质谱分析证实了这一点。考虑到大气中带电气溶胶的普遍存在，这种快速风化过程可能对土壤形成至关重要。

▲ Abstract：

In this work, we show that particles of common minerals break down spontaneously to form nanoparticles in charged water microdroplets within milliseconds. We transformed micron-sized natural minerals like quartz and ruby into 5- to 10-nanometer particles when integrated into aqueous microdroplets generated via electrospray. We deposited the droplets on a substrate, which allowed nanoparticle characterization. We determined through simulations that quartz undergoes proton-induced slip, especially when reduced in size and exposed to an electric field. This leads to particle scission and the formation of silicate fragments, which we confirmed with mass spectrometry. This rapid weathering process may be important for soil formation, given the prevalence of charged aerosols in the atmosphere.

Shearing brittle intermetallics enhances cryogenic strength and ductility of steels

剪切脆性金属间化合物提高钢的低温强度和塑性

▲ 作者：FENG WANG, MIAO SONG, MOHAMED N. ELKOT, NING YAO, BINHAN SUN, MIN SONG, ET AL.

▲ 链接：

https://www.science.org/doi/10.1126/science.ado2919

▲ 摘要：

沉淀物对于制造机械强度高的金属材料至关重要。在这项工作中，研究组报道了B2相（有序体心立方）纳米沉淀（通常被认为是不可剪切的金属间化合物）在低温拉伸载荷过程中在轻质复合钢中的位错切割。

由于亚纳米尺度局部化学有序区的显著强化和基体中多主元素明显的固溶强化，奥氏体基体中位错滑移的高强度水平实现了剪切。这种机制不仅利用了原本难以穿透的脆性纳米沉淀物所提供的强烈强化和应变硬化，而且还通过其连续剪切和持续变形引入了塑性。

因此，这种钢材展示了超高的低温拉伸强度，高达2吉帕，拉伸伸长率达到34%。这项研究揭示了一种设计高性能结构材料的新策略。

▲ Abstract：

Precipitates are crucial for crafting mechanically strong metallic materials. In this work, we report the dislocation cutting of B2 (ordered body-centered cubic) nanoprecipitates, typically considered nonshearable intermetallics, in a lightweight compositionally complex steel during cryogenic tensile loading. Shearing is enabled by the high strength level for dislocation glide within the austenitic matrix, attributed to the substantial strengthening from subnanoscale local chemical ordering zones and the pronounced solid solution strengthening from the multiprincipal elements in the matrix. This mechanism not only harnesses the intense strengthening and strain hardening provided by otherwise impenetrable brittle nanoprecipitates but also introduces ductility through their sequential shearing with ongoing deformation. Our steel thus showcases ultrahigh cryogenic tensile strength up to 2 gigapascal at a remarkable tensile elongation of 34%. This study reveals a new strategy for designing high-performance structural materials.

地球科学Earth Science

Heinrich event ice discharge and the fate of the Atlantic Meridional Overturning Circulation

海因里希事件冰排放与大西洋经向翻转环流的命运

▲ 作者：YUXIN ZHOU AND JERRY F. MCMANUS

▲ 链接：

https://www.science.org/doi/10.1126/science.adh8369

▲ 摘要：

在海因里希事件期间，巨大的冰山“舰队”偶尔淹没北大西洋，削弱了翻转环流。这些事件的冰排放限制了翻转环流对冰山融化的敏感性。

研究组重建了海因里希事件4期间的这些冰排放，发现其高达0.13 Sv（1 Sv = 100万立方米每秒），而在所有事件中平均值仅为0.029 Sv。如今格陵兰冰盖的冰山崩解与中等规模海因里希事件相当。

随着未来格陵兰冰盖从海洋终点出口消退，仅冰山崩解尚不足以对大西洋翻转环流造成灾难性破坏，其可能不会持续足够长的时间，尽管加速的格陵兰径流和持续的全球变暖仍然威胁着环流的稳定性。

▲ Abstract：

During Heinrich events, great armadas of icebergs episodically flooded the North Atlantic Ocean and weakened overturning circulation. The ice discharges of these episodes constrain the sensitivity of overturning circulation to iceberg melting. We reconstructed these ice discharges to be as high as 0.13 sverdrup (Sv) (1 Sv = 1 million cubic meters per second) during Heinrich event 4 and to average 0.029 Sv over all episodes. The present-day Greenland Ice Sheet calving of icebergs is comparable to that of a mid-range Heinrich event. As the future Greenland Ice Sheet recedes from marine-terminating outlets, its iceberg calving likely will not persist long enough for icebergs alone to cause catastrophic disruption to the Atlantic overturning circulation, although the accelerating Greenland runoff and continued global warming remain threats to the circulation stability.

社会学Sociology

Supersharers of fake news on Twitter

推特上的假新闻超级分享者

▲ 作者：SAHAR BARIBI-BARTOV, BRIONY SWIRE-THOMPSON AND NIR GRINBERG

▲ 链接：

https://www.science.org/doi/10.1126/science.adl4435

▲ 摘要：

政府或许有能力让假新闻充斥社交媒体，但普通选民如何使用这些泛滥的假新闻却鲜为人知。

在这项工作中，研究组确定了2107名登记的美国选民，2020年美国总统大选期间，他们在由664391名选民组成的整个群组中在Twitter上分享了80%的假新闻。结果发现超级分享者是该网络的重要成员，在该平台注册选民中占比高达5.2%。

超级分享者中女性、老年人和注册共和党人的比例明显过高。超级分享者的巨大流量似乎并非自动产生，而是通过人工和持续转发产生的。这些发现凸显了社交媒体对民主的脆弱性，在社交媒体上，一小群人歪曲了许多人的政治现实。

▲ Abstract：

Governments may have the capacity to flood social media with fake news, but little is known about the use of flooding by ordinary voters. In this work, we identify 2107 registered US voters who account for 80% of the fake news shared on Twitter during the 2020 US presidential election by an entire panel of 664391 voters. We found that supersharers were important members of the network, reaching a sizable 5.2% of registered voters on the platform. Supersharers had a significant overrepresentation of women, older adults, and registered Republicans. Supersharers’ massive volume did not seem automated but was rather generated through manual and persistent retweeting. These findings highlight a vulnerability of social media for democracy, where a small group of people distort the political reality for many.