Nature, 25 May 2023, VOL 617, ISSUE 7962
《自然》2023年5月25日，第617卷，7962期
天文学Astronomy
The lunar solid inner core and the mantle overturn
月球固体内核和月幔翻转
▲ 作者：Arthur Briaud, Clément Ganino, Agnès Fienga, Anthony Mémin & Nicolas Rambaux
▲ 链接：
https://www.nature.com/articles/s41586-023-05935-7
▲ 摘要：
阿波罗任务的月震模型首次记录了月球内核-月幔边界地震波速度下降的内部结构。这些记录的分辨率阻碍了对假定的月球固体内核的严格检测，且人们对月球最低部分月幔翻转的影响仍未有定论。
研究组将蒙特卡洛勘探的地球物理和测地线约束与不同月球内部结构的热力学模拟相结合，表明只有富含钛铁矿低粘度带和内核的模型才具有从热力学约束推断出的密度，且与潮汐变形推导出的密度一致。
因此，研究组获得了支持月幔翻转假说的有力证据，并在此背景下证明了月球内核的存在，其半径为258±40 km，密度为7,822±1,615 kg m−3。该研究结果对月球磁场的演化提出了质疑，因其证明了月球内核的存在，并支持一个全月球月幔翻转的场景，这为太阳系最初十亿年月球轰炸期时间线带来了实质性的见解。
▲ Abstract：
Seismological models from Apollo missions provided the first records of the Moon inner structure with a decrease in seismic wave velocities at the core–mantle boundary. The resolution of these records prevents a strict detection of a putative lunar solid inner core and the impact of the lunar mantle overturn in the lowest part of the Moon is still discussed. Here we combine geophysical and geodesic constraints from Monte Carlo exploration and thermodynamical simulations for different Moon internal structures to show that only models with a low viscosity zone enriched in ilmenite and an inner core present densities deduced from thermodynamic constraints compatible with densities deduced from tidal deformations. We thus obtain strong indications in favour of the lunar mantle overturn scenario and, in this context, demonstrate the existence of the lunar inner core with a radius of 258?± 40 km and density 7,822 ± 1,615 kg m−3. Our results question the evolution of the Moon magnetic field thanks to its demonstration of the existence of the inner core and support a global mantle overturn scenario that brings substantial insights on the timeline of the lunar bombardment in the first billion years of the Solar System.
材料科学Materials Science
Flexible solar cells based on foldable silicon wafers with blunted edges
基于边缘钝化可折叠硅片的柔性太阳能电池
▲ 作者：Wenzhu Liu, Yujing Liu, Ziqiang Yang, Changqing Xu, Xiaodong Li, Shenglei Huang, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05921-z
▲ 摘要：
柔性太阳能电池具有重量轻、防震和自供电的特点，因此在集成到建筑和可穿戴电子产品的光伏应用方面具有很大的市场潜力。硅太阳能电池已成功应用于大型发电厂。然而，尽管付出了50多年的努力，但柔性硅太阳能电池的发展因其刚性缺陷一直未取得显著进展。
研究组报道了一种组装大规模可折叠硅片和制造柔性太阳能电池的策略。织构化的晶体硅晶片总是在晶片边缘区域表面棱锥间的尖锐通道处开始破裂。这一事实表明可通过钝化边缘区域的棱锥结构来提高硅片的柔韧性。
这种边缘钝化技术使大规模（>240 cm2）、高效（>24%）的硅太阳能电池能够商业化生产，这种电池可以像一张纸那样卷起来，且在1000次左右弯曲循环后仍能保持100%的功率转换效率。
在组装成大型（>10000 cm2）柔性组件后，这种硅太阳能电池在-70℃至85℃之间热循环120小时后仍能保持99.62%的功率。此外，当该电池连接到软气囊（模拟猛烈风暴中的风），在气流中暴露20分钟后，仍能保持96.03%的功率。
▲ Abstract：
Flexible solar cells have a lot of market potential for application in photovoltaics integrated into buildings and wearable electronics because they are lightweight, shockproof and self-powered. Silicon solar cells have been successfully used in large power plants. However, despite the efforts made for more than 50?years, there has been no notable progress in the development of flexible silicon solar cells because of their rigidity. Here we provide a strategy for fabricating large-scale, foldable silicon wafers and manufacturing flexible solar cells. A textured crystalline silicon wafer always starts to crack at the sharp channels between surface pyramids in the marginal region of the wafer. This fact enabled us to improve the flexibility of silicon wafers by blunting the pyramidal structure in the marginal regions. This edge-blunting technique enables commercial production of large-scale (>240 cm2), high-efficiency (>24%) silicon solar cells that can be rolled similarly to a sheet of paper. The cells retain 100% of their power conversion efficiency after 1,000 side-to-side bending cycles. After being assembled into large (>10,000 cm2) flexible modules, these cells retain 99.62% of their power after thermal cycling between 70 °C and 85 °C for 120 h. Furthermore, they retain 96.03% of their power after 20 min of exposure to air flow when attached to a soft gasbag, which models wind blowing during a violent storm.
仪器分析Instrumental Analysis
Ångström-resolution fluorescence microscopy
埃级分辨率荧光显微镜
▲ 作者：Susanne C. M. Reinhardt, Luciano A. Masullo, Isabelle Baudrexel, Philipp R. Steen, Rafal Kowalewski, Alexandra S. Eklund, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05925-9
▲ 摘要：
荧光显微镜因其分子特异性，是生命科学中用于了解复杂生物系统的主要表征方法之一。超分辨率方法可实现15至20 nm范围的细胞内分辨率，但单个生物分子之间的相互作用发生在10 nm以下的长度尺度上，分子内结构的表征需要埃级分辨率。
最先进的超分辨率实现已经证明，在某些体外条件下空间分辨率可低至5纳米，定位精度为1纳米。然而，这种分辨率不能直接转化为细胞中的实验，埃级分辨率迄今尚未得到证明。
研究组介绍了一种DNA条形码方法，通过序列成像分辨率增强（RESI）技术，使用现成的荧光显微镜硬件和试剂将荧光显微镜的分辨率提高到埃级。通过以>15 nm的中等空间分辨率对稀疏目标亚群进行序列成像，证明了可在整个完整细胞中对生物分子实现单蛋白分辨率。
此外，研究组用埃级分辨率实验解析了DNA折纸中单个碱基的DNA主链距离。在原理验证演示中，使用该方法在未处理和药物处理的细胞中原位绘制免疫治疗靶点CD20的分子排列，这为评估靶向免疫治疗的分子机制开辟了可能性。
这些观察结果表明，通过在环境条件下对整个完整细胞进行分子内成像，RESI缩小了超分辨率显微镜和结构生物学研究之间的差距，从而提供了理解复杂生物系统的关键信息。
▲ Abstract：
Fluorescence microscopy, with its molecular specificity, is one of the major characterization methods used in the life sciences to understand complex biological systems. Super-resolution approaches can achieve resolution in cells in the range of 15 to 20 nm, but interactions between individual biomolecules occur at length scales below 10 nm and characterization of intramolecular structure requires Ångström resolution. State-of-the-art super-resolution implementations have demonstrated spatial resolutions down to 5 nm and localization precisions of 1 nm under certain in vitro conditions. However, such resolutions do not directly translate to experiments in cells, and ?ngstr?m resolution has not been demonstrated to date. Here we introdue a DNA-barcoding method, resolution enhancement by sequential imaging (RESI), that improves the resolution of fluorescence microscopy down to the ?ngstr?m scale using off-the-shelf fluorescence microscopy hardware and reagents. By sequentially imaging sparse target subsets at moderate spatial resolutions of >15 nm, we demonstrate that single-protein resolution can be achieved for biomolecules in whole intact cells. Furthermore, we experimentally resolve the DNA backbone distance of single bases in DNA origami with Ångström resolution. We use our method in a proof-of-principle demonstration to map the molecular arrangement of the immunotherapy target CD20 in situ in untreated and drug-treated cells, which opens possibilities for assessing the molecular mechanisms of targeted immunotherapy. These observations demonstrate that, by enabling intramolecular imaging under ambient conditions in whole intact cells, RESI closes the gap between super-resolution microscopy and structural biology studies and thus delivers information key to understanding complex biological systems.
化学Chemistry
Constrained C2adsorbate orientation enables CO-to-acetate electroreduction
受限C2吸附物取向助力CO电还原合成乙酸盐
▲ 作者：Jian Jin, Joshua Wicks, Qiuhong Min, Jun Li, Yongfeng Hu, Jingyuan Ma, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05918-8
▲ 摘要：
当使用低碳电力供电时，二氧化碳和一氧化碳的电还原反应为化学制造脱碳提供了途径。如今，依赖于铜（Cu）催化的碳-碳耦合可产生十多种C2+化学物质的混合物：一个长期存在的挑战在于实现对单一主要C2+产物的选择性。乙酸盐就是这样一种C2化合物，正走向庞大但化石来源居多的乙酸市场。
研究组致力于将低浓度的Cu原子分散在主体金属中，从而促进以单齿方式结合到电催化剂上的乙烯酮-化学中间体的稳定性。他们合成了Cu-in-Ag稀释（约为Cu的1原子%）合金材料，发现在高*CO覆盖率、10个标准大气压下，从CO电合成乙酸盐具有高度选择性。
原位X射线吸收光谱表明，原位生成的由少于4个原子组成的Cu簇可作为活性位点。相对于从一氧化碳电还原反应中观察到的所有其他产物，乙酸盐的选择性为12：1，与此前最佳报道相比增加了一个数量级。
结合催化剂设计和反应器工程，研究组实现了CO合成乙酸的法拉第效率为91%，并在运行820小时后法拉第效率仍保持85%。高选择性有利于所有碳基电化学转化的能量效率和下游分离，突出了最大化法拉第效率对单一C2+产物的的重要性。
▲ Abstract：
The carbon dioxide and carbon monoxide electroreduction reactions, when powered using low-carbon electricity, offer pathways to the decarbonization of chemical manufacture. Copper (Cu) is relied on today for carbon–carbon coupling, in which it produces mixtures of more than ten C2+chemicals: a long-standing challenge lies in achieving selectivity to a single principalC2+ product. Acetate is one such C2 compound on the path to the large but fossil-derived acetic acid market. Here we pursued dispersing a low concentration of Cu atoms in a host metal to favour the stabilization of ketenes—chemical intermediates that are bound in monodentate fashion to the electrocatalyst. We synthesize Cu-in-Ag dilute (about 1 atomic per cent of Cu) alloy materials that we find to be highly selective for acetate electrosynthesis from CO at high *CO coverage, implemented at 10?atm pressure. Operando X-ray absorption spectroscopy indicates in situ-generated Cu clusters consisting of <4 atoms as active sites. We report a 12:1 ratio, an order of magnitude increase compared to the best previous reports, in the selectivity for acetate relative to all other products observed from the carbon monoxide electroreduction reaction. Combining catalyst design and reactor engineering, we achieve a CO-to-acetate Faradaic efficiency of 91% and report a Faradaic efficiency of 85% with an 820-h operating time. High selectivity benefits energy efficiency and downstream separation across all carbon-based electrochemical transformations, highlighting the importance of maximizing the Faradaic efficiency towards a single C2+ product.
Catalytic disconnection of C–O bonds in epoxy resins and composites
环氧树脂和复合材料中C-O键的催化断裂
▲ 作者：Alexander Ahrens, Andreas Bonde, Hongwei Sun, Nina Kølln Wittig, Hans Christian D. Hammershøj, Gabriel Martins Ferreira Batista, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05944-6
▲ 摘要：
纤维增强环氧复合材料因其重量轻、耐用性高，在航空航天、汽车和风力发电行业的承重应用中得到了很好的应用。这些复合材料是基于嵌入玻璃或碳纤维的热固性树脂。
风力涡轮机叶片等使用结束的复合材料结构通常会被填埋，以替代可行的回收策略。由于塑料垃圾对环境的负面影响，人们对塑料循环经济的需求变得更加迫切。然而，回收热固性塑料并非易事。
研究组报道了一种过渡金属催化策略，用于从环氧复合材料中回收聚合物构建块双酚A和完整的纤维。钌催化的脱氢/键合、裂解/还原级联反应实现了聚合物中最常见的C（烷基）-O键断裂。
研究组展示了该方法在相关未改性胺固化环氧树脂以及商业复合材料中的应用，包括风力涡轮机叶片的外壳。研究结果表明，热固性环氧树脂和复合材料的化学回收方法有望实现。
▲ Abstract：
Fibre-reinforced epoxy composites are well established in regard to load-bearing applications in the aerospace, automotive and wind power industries, owing to their light weight and high durability. These composites are based on thermoset resins embedding glass or carbon fibres. In lieu of viable recycling strategies, end-of-use composite-based structures such as wind turbine blades are commonly landfilled. Because of the negative environmental impact of plastic waste, the need for circular economies of plastics has become more pressing. However, recycling thermoset plastics is no trivial matter. Here we report a transition-metal-catalysed protocol for recovery of the polymer building block bisphenol?A and intact fibres from epoxy composites. A Ru-catalysed, dehydrogenation/bond, cleavage/reduction cascade disconnects the C(alkyl)–O bonds of the most common linkages of the polymer. We showcase the application of this methodology to relevant unmodified amine-cured epoxy resins as well as commercial composites, including the shell of a wind turbine blade. Our results demonstrate that chemical recycling approaches for thermoset epoxy resins and composites are achievable.
地球科学Earth Science
Increased heat risk in wet climate induced by urban humid heat
城市湿热导致潮湿气候的热风险增加
▲ 作者：Keer Zhang, Chang Cao, Haoran Chu, Lei Zhao, Jiayu Zhao & Xuhui Lee
▲ 链接：
https://www.nature.com/articles/s41586-023-05911-1
▲ 摘要：
城市通常比邻近的农村地区更温暖，这种现象被称为城市热岛（UHI）。通常伴随着热岛效应的是另一种被称为城市干岛（UDI）的现象，即城市土地的湿度低于周围农村土地的湿度。
UHI加剧了城市居民的热应激，而UDI反而可缓解这种应激，因为人体可通过排汗在较低湿度环境中更好地应对高温条件。UHI和UDI之间的相对平衡是城市气候中人类热应激的一个关键但很大程度上未知的决定因素，这种相对平衡通过湿球温度（Tw）的变化来测量。
研究组发现Tw在干燥和中度潮湿气候的城市中减少，此时UDI超过并抵消了UHI，但在潮湿气候（夏季降水超过570毫米）中增加。该结果源于对世界各地城市和农村气象站数据的分析以及城市气候模型的计算。
在潮湿气候中，夏季城市白天的Tw比农村高0.17±0.14℃（平均值±1标准差），主要是由于城市空气的动态混合较弱。这一Tw增量很小，但由于潮湿气候下的高背景Tw，在当前气候条件下，这足以使城市居民每年夏季多出2至6个危险的热应激日。预计未来极端湿热的风险将会增加，而这些城市效应可能会进一步放大该风险。
▲ Abstract：
Cities are generally warmer than their adjacent rural land, a phenomenon known as the urban heat island (UHI). Often accompanying the UHI effect is another phenomenon called the urban dry island (UDI), whereby the humidity of urban land is lower than that of the surrounding rural land. The UHI exacerbates heat stress on urban residents, whereas the UDI may instead provide relief because the human body can cope with hot conditions better at lower humidity through perspiration. The relative balance between the UHI and the UDI—as measured by changes in the wet-bulb temperature (Tw)—is a key yet largely unknown determinant of human heat stress in urban climates. Here we show that Tw is reduced in cities in dry and moderately wet climates, where the UDI more than offsets the UHI, but increased in wet climates (summer precipitation of more than 570?millimetres). Our results arise from analysis of urban and rural weather station data across the world and calculations with an urban climate model. In wet climates, the urban daytime Tw is 0.17 ± 0.14 degrees Celsius (mean ± 1 standard deviation) higher than rural Tw in the summer, primarily because of a weaker dynamic mixing in urban air. This Tw increment is small, but because of the high background Tw in wet climates, it is enough to cause two to six extra dangerous heat-stress days per summer for urban residents under current climate conditions. The risk of extreme humid heat is projected to increase in the future, and these urban effects may further amplify the risk.
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