《自然》（20240926出版）一周论文导读

 

编译 | 未玖

Nature, 26 September 2024, Volume 633, Issue 8031

《自然》，2024年9月26日，第633卷，8031期

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天文学Astronomy

A temperate super-Jupiter imaged with JWST in the mid-infrared

JWST在中红外波段成像的温和超级木星图像

▲ 作者：E. C. Matthews, A. L. Carter, P. Pathak, C. V. Morley, M. W. Phillips, S. Krishanth P. M., et al.

▲链接：

https://www.nature.com/articles/s41586-024-07837-8

▲摘要：

迄今为止，大约25颗直接成像的行星的年龄都小于500 Myr。除6颗外，其他行星的年龄都小于100 Myr。Eps Ind A（HD209100，HIP108870）是一颗K5V型恒星，与太阳年龄（最近推算为3.7-5.7 Gyr和3.5+^0.8_-1.3 Gyr）大致相当。长期的径向速度趋势和天体测量加速度导致了一颗巨大行星围绕附近恒星（3.6384±0.0013 pc）运行的假说。

研究组报道了日冕图像，揭示了一颗巨大的系外行星。它与这些径向和天体测量结果一致，但与先前声称的行星特性不一致。这颗新行星的温度约为275K，在10.65和15.50μm处非常明亮。但在3.5~5.0μm之间未检测到，暗示大气中存在未知的不透明源，或表明这是一颗金属丰度高、碳氧比高的行星。

行星的最佳拟合温度与理论热演化模型一致，这些模型在该温度范围内未经测试。上述数据表明，这可能是该系统中唯一的巨行星，因此将其称为b，尽管其轨道特性与之前声称的行星b有很大不同。

▲ Abstract：

Of the approximately 25 directly imaged planets to date, all are younger than 500 Myr, and all but six are younger than 100 Myr. Eps Ind A (HD209100, HIP108870) is a K5V star of roughly solar age (recently derived as 3.7–5.7 Gyr and 3.5+^0.8_-1.3 Gyr). A long-term radial-velocity trend and an astrometric acceleration led to claims of a giant planet orbiting the nearby star (3.6384 ± 0.0013 pc). Here we report JWST coronagraphic images which reveal a giant exoplanet that is consistent with these radial and astrometric measurements but inconsistent with the previously claimed planet properties. The new planet has a temperature of approximately 275 K and is remarkably bright at 10.65 and 15.50 μm. Non-detections between 3.5 and 5.0 μm indicate an unknown opacity source in the atmosphere, possibly suggesting a high-metallicity, high carbon-to-oxygen ratio planet. The best-fitting temperature of the planet is consistent with theoretical thermal evolution models, which were previously untested at this temperature range. The data indicate that this is probably the only giant planet in the system, and therefore we refer to it as b, despite it having significantly different orbital properties than the previously claimed planet b.

物理学Physics

Axon-like active signal transmission

轴突样有源信号传输

▲ 作者：Timothy D. Brown, Alan Zhang, Frederick U. Nitta, Elliot D. Grant, Jenny L. Chong, Jacklyn Zhu, et al.

▲链接：

https://www.nature.com/articles/s41586-024-07921-z

▲摘要：

由于金属的天然电阻，在金属导体中传播的任何电信号都会失去振幅。要补偿这种损耗，目前需要反复断开导体，并插入吸收和再生信号的放大器。这种持续百年的原始策略严重限制了现代互连密集芯片的设计和性能。

研究组提出了一种基于半稳定混沌边缘（EOC）的迥然不同的原始技术，这是一种长期理论化但实验难以捉摸的机制，也是生物轴突中主动（自放大）传输的基础。通过电进入LaCoO₃中的自旋交叉，研究组分离出半稳定的EOC，其特征是小信号负电阻和扰动放大。在EOC偏置介质顶部的金属线中，一端的信号输入在另一端离开后放大，而不通过单独的放大组件。

虽然表面上类似于超导，有源传输在常温常压下提供可控放大的时变小信号传播，但需要带电的EOC介质。动态原位热谱揭示了EOC介质的放大—偏置能量机制，部分用于放大金属线中的信号，而不是完全作为热量耗散，从而实现空间连续有源传输，这有望改变复杂电子芯片的设计和性能。

▲ Abstract：

Any electrical signal propagating in a metallic conductor loses amplitude due to the natural resistance of the metal. Compensating for such losses presently requires repeatedly breaking the conductor and interposing amplifiers that consume and regenerate the signal. This century-old primitive severely constrains the design and performance of modern interconnect-dense chips. Here we present a fundamentally different primitive based on semi-stable edge of chaos (EOC), a long-theorized but experimentally elusive regime that underlies active (self-amplifying) transmission in biological axons. By electrically accessing the spin crossover in LaCoO₃, we isolate semi-stable EOC, characterized by small-signal negative resistance and amplification of perturbations. In a metallic line atop a medium biased at EOC, a signal input at one end exits the other end amplified, without passing through a separate amplifying component. While superficially resembling superconductivity, active transmission offers controllably amplified time-varying small-signal propagation at normal temperature and pressure, but requires an electrically energized EOC medium. Operando thermal mapping reveals the mechanism of amplification—bias energy of the EOC medium, instead of fully dissipating as heat, is partly used to amplify signals in the metallic line, thereby enabling spatially continuous active transmission, which could transform the design and performance of complex electronic chips.

材料科学Materials Science

One step from oxides to sustainable bulk alloys

只需一步！从氧化物到可持续大块合金

▲ 作者：Shaolou Wei, Yan Ma & Dierk Raabe

▲链接：

https://www.nature.com/articles/s41586-024-07932-w

▲摘要：

传统的冶金生产包括三个步骤：从矿石中提取金属，通过液体加工和热机械加工将其混合成合金，以获得所需的微观结构。由于对可持续经济的迫切需求，这种自青铜器时代就开始实行的顺序方法至今已达极限：几乎10%的温室气体排放归因于使用化石还原剂和高温冶金加工。

研究组提出了一种基于H₂的氧化还原合成和压塑方法，通过将金属提取、合金化和热机械加工合并到一个单一固态操作中，革新了传统的合金制造策略。他们提出了一个热力学指导原则和一个通用的动力学概念，以消除萃取冶金和物理冶金之间的经典界限，从而释放出极大的可持续大块合金设计机遇。

铁—镍因瓦块体合金是最吸引人的铁材料之一，但生产起来最“脏”：因瓦表现出独特的低热膨胀，实现了从精密仪器到低温部件的关键应用。然而该工艺臭名昭著地不环保，生产每公斤镍造成的二氧化碳排放量是铁的10倍以上，使得这种合金类别成为完美的示范案例。

该可持续方法将氧化物直接转化为块体绿色合金，颇具应用价值，所有这些都在远低于块体熔点的温度下获得，同时保持零二氧化碳足迹。

▲ Abstract：

Metallurgical production traditionally involves three steps: extracting metals from ores, mixing them into alloys by liquid processing and thermomechanical processing to achieve the desired microstructures. This sequential approach, practised since the Bronze Age, reaches its limit today because of the urgent demand for a sustainable economy: almost 10% of all greenhouse gas emissions are because of the use of fossil reductants and high-temperature metallurgical processing. Here we present a H₂-based redox synthesis and compaction approach that reforms traditional alloy-making by merging metal extraction, alloying and thermomechanical processing into one single solid-state operation. We propose a thermodynamically informed guideline and a general kinetic conception to dissolve the classical boundaries between extractive and physical metallurgy, unlocking tremendous sustainable bulk alloy design opportunities. We exemplify this approach for the case of Fe–Ni invar bulk alloys, one of the most appealing ferrous materials but the dirtiest to produce: invar shows uniquely low thermal expansion, enabling key applications spanning from precision instruments to cryogenic components. Yet, it is notoriously eco-unfriendly, with Ni causing more than 10 times higher CO2 emission than Fe per kilogram production, qualifying this alloy class as a perfect demonstrator case. Our sustainable method turns oxides directly into green alloys in bulk forms, with application-worthy properties, all obtained at temperatures far below the bulk melting point, while maintaining a zero CO2 footprint.

能源科学Energy Science

Micronuclear battery based on a coalescent energy transducer

基于聚能传感器的微核电池

▲ 作者：Kai Li, Congchong Yan, Junren Wang, Kun Zhu, Junjun Guo, Yugang Zhang, et al.

▲链接：

https://www.nature.com/articles/s41586-024-07933-9

▲摘要：

微核电池利用放射性同位素的放射性衰变产生的能量进行小规模发电，通常在纳瓦或微瓦范围内。与化学电池不同，微核电池的寿命与所用放射性同位素的半衰期有关，其使用寿命可长达数十年。此外，放射性衰变不受温度、压力和磁场等环境因素的影响，这使得微核电池在传统电池被证明不切实际或难以更换的情况下成为持久可靠的电源。

镅的常见放射性同位素（²⁴¹Am和²⁴³Am）是α-衰变发射体，半衰期超过数百年。传统微核电池结构中的严重自吸附阻碍了α-衰变能量的高效转换，为α-放射性同位素微核电池的开发带来了挑战。

研究组提出了一种微核电池结构，其中包括一个通过将²⁴³Am掺入发光镧系配位聚合物的聚能传感器。这种方法将放射性同位素与分子水平上的能量传感器耦合在一起，与传统结构相比，从α衰变能量到持续自发光的能量转换效率提高了8000倍。

当与将自发光转化为电能的光伏电池结合使用时，研究组获得了一种新型的放射性光伏微核电池，其总功率转换效率为0.889%，单位活动功率为139 μW C_i-1。

▲ Abstract：

Micronuclear batteries harness energy from the radioactive decay of radioisotopes to generate electricity on a small scale, typically in the nanowatt or microwatt range. Contrary to chemical batteries, the longevity of a micronuclear battery is tied to the half-life of the used radioisotope, enabling operational lifetimes that can span several decades. Furthermore, the radioactive decay remains unaffected by environmental factors such as temperature, pressure and magnetic fields, making the micronuclear battery an enduring and reliable power source in scenarios in which conventional batteries prove impractical or challenging to replace. Common radioisotopes of americium (²⁴¹Am and ²⁴³Am) are α-decay emitters with half-lives longer than hundreds of years. Severe self-adsorption in traditional architectures of micronuclear batteries impedes high-efficiency α-decay energy conversion, making the development of α-radioisotope micronuclear batteries challenging. Here we propose a micronuclear battery architecture that includes a coalescent energy transducer by incorporating ²⁴³Am into a luminescent lanthanide coordination polymer. This couples radioisotopes with energy transducers at the molecular level, resulting in an 8,000-fold enhancement in energy conversion efficiency from α decay energy to sustained autoluminescence compared with that of conventional architectures. When implemented in conjunction with a photovoltaic cell that translates autoluminescence into electricity, a new type of radiophotovoltaic micronuclear battery with a total power conversion efficiency of 0.889% and a power per activity of 139 microwatts per curie (μW C_i-1) is obtained.

地球科学Earth Science

Forest fire size amplifies postfire land surface warming

森林火灾规模放大了火灾后地表升温

▲ 作者：Jie Zhao, Chao Yue, Jiaming Wang, Stijn Hantson, Xianli Wang, Binbin He, et al.

▲链接：

https://www.nature.com/articles/s41586-024-07918-8

▲摘要：

气候变暖导致极端火灾天气普遍增加，使森林火灾持续时间更长，规模更大。近几十年来，加拿大、美国和澳大利亚的平均森林火灾规模翻了一番甚至三倍。反过来，森林火灾通过调节陆地—大气中的碳、氮、气溶胶、能量和水的通量来反馈气候。然而，越来越大的火灾对地表气候的影响及其对土地管理的影响仍有待确定。

研究组利用卫星观测表明，在北半球温带和北方森林中，火灾规模持续放大了夏季每单位过火面积长达十年的火灾后地表升温。随着阔叶树丰度的增加，升温及其随火灾规模的放大都减弱，这与阔叶树种比针叶树种更低的火灾脆弱性相一致。

火灾规模增强的升温可能会影响火灾后林分更新的成功和组成以及永久冻土退化，对未来气候和火灾动态表现出此前被忽视的额外反馈效应。鉴于北方森林火灾规模预计会增加，气候智能型林业应致力于减轻大火的气候风险，或可通过适当增加阔叶树的比例，并避免种植活跃的焦生植物。

▲ Abstract：

Climate warming has caused a widespread increase in extreme fire weather, making forest fires longer-lived and larger. The average forest fire size in Canada, the USA and Australia has doubled or even tripled in recent decades. In return, forest fires feed back to climate by modulating land–atmospheric carbon, nitrogen, aerosol, energy and water fluxes. However, the surface climate impacts of increasingly large fires and their implications for land management remain to be established. Here we use satellite observations to show that in temperate and boreal forests in the Northern Hemisphere, fire size persistently amplified decade-long postfire land surface warming in summer per unit burnt area. Both warming and its amplification with fire size were found to diminish with an increasing abundance of broadleaf trees, consistent with their lower fire vulnerability compared with coniferous species. Fire-size-enhanced warming may affect the success and composition of postfire stand regeneration as well as permafrost degradation, presenting previously overlooked, additional feedback effects to future climate and fire dynamics. Given the projected increase in fire size in northern forests, climate-smart forestry should aim to mitigate the climate risks of large fires, possibly by increasing the share of broadleaf trees, where appropriate, and avoiding active pyrophytes.

Carbon emissions from the 2023 Canadian wildfires

2023年加拿大野火的碳排放量

▲ 作者：Brendan Byrne, Junjie Liu, Kevin W. Bowman, Madeleine Pascolini-Campbell, Abhishek Chatterjee, Sudhanshu Pandey, et al.

▲链接：

https://www.nature.com/articles/s41586-024-07878-z

▲摘要：

2023年加拿大森林大火在规模和强度上都很极端，年平均烧毁面积是过去40年的7倍多。

研究组基于卫星一氧化碳观测的反演模型，量化了2023年5月至9月这些火灾的碳排放量。结果发现碳排放量的规模为647 TgC（570-727 TgC），与排放大国的年化石燃料排放量相当，仅次于印度、中国和美国。

研究组发现，大范围的干热天气是火灾蔓延的主要驱动因素，2023年是至少自1980年以来最温暖、最干燥的一年。尽管2023年温度相对于历史记录颇极端，但气候预测表明，即使在温和的气候缓解情景下（共同社会经济途径，SSP 2-4.5），该温度在2050年代也可能是典型的。

这种情况可能会导致火灾活动增加，抑制加拿大森林的碳吸收，加剧人们对这些森林作为碳汇的长期持久性的担忧。

▲ Abstract：

The 2023 Canadian forest fires have been extreme in scale and intensity with more than seven times the average annual area burned compared to the previous four decades. Here, we quantify the carbon emissions from these fires from May to September 2023 on the basis of inverse modelling of satellite carbon monoxide observations. We find that the magnitude of the carbon emissions is 647?TgC (570–727?TgC), comparable to the annual fossil fuel emissions of large nations, with only India, China and the USA releasing more carbon per year. We find that widespread hot–dry weather was a principal driver of fire spread, with 2023 being the warmest and driest year since at least 1980. Although temperatures were extreme relative to the historical record, climate projections indicate that these temperatures are likely to be typical during the 2050s, even under a moderate climate mitigation scenario (shared socioeconomic pathway, SSP?2–4.5). Such conditions are likely to drive increased fire activity and suppress carbon uptake by Canadian forests, adding to concerns about the long-term durability of these forests as a carbon sink.