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发布日期：2024-10-15 作者：华体会
编译 | 未玖
Nature, 26 September 2024, Volume 633, Issue 8031
《天然》，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暖和超等木星图象
▲ 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，年夜约25颗直接成像的行星的春秋都小在500 Myr。除6颗外，其他行星的春秋都小在100 Myr。Eps Ind A（HD209100，HIP108870）是一颗K5V型恒星，与太阳春秋（比来推算为3.7-5.7 Gyr和3.5+0.8-1.3 Gyr）年夜致相当。持久的径向速度趋向和天体丈量加快度致使了一颗庞大行星环绕四周恒星（3.6384±0.0013 pc）运行的假说。
研究组报导了日冕图象，揭露了一颗庞大的系外行星。它与这些径向和天体丈量成果一致，但与先前宣称的行星特征纷歧致。这颗新行星的温度约为275K，在10.65和15.50μm处很是敞亮。但在3.5~5.0μm之间未检测到，暗示年夜气中存在未知的不透明源，或注解这是一颗金属品貌高、碳氧比高的行星。
行星的最好拟合温度与理论热演变模子一致，这些模子在该温度规模内未经测试。上述数据注解，这多是该系统中独一的巨行星，是以将其称为b，虽然其轨道特征与之前宣称的行星b有很年夜分歧。
▲ 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
轴突样有源旌旗灯号传输
▲ 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：
因为金属的自然电阻，在金属导体中传布的任何电旌旗灯号城市掉去振幅。要抵偿这类消耗，今朝需要频频断启发体，并插入接收和再生旌旗灯号的放年夜器。这类延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机能。
研究组提出了一种基在半不变浑沌边沿（EOC）的迥然分歧的原始手艺，这是一种持久理论化但尝试难以捉摸的机制，也是生物轴突中自动（自放年夜）传输的根本。经由过程电进入LaCoO3中的自旋交叉，研究组分手出半不变的EOC，其特点是小旌旗灯号负电阻和扰动放年夜。在EOC偏置介质顶部的金属线中，一真个旌旗灯号输入在另外一端分开后放年夜，而欠亨过零丁的放年夜组件。
固然概况上近似在超导，有源传输在常温常压下供给可控放年夜的时变小旌旗灯号传布，但需要带电的EOC介质。动态原位热谱揭露了EOC介质的放年夜—偏置能量机制，部门用在放年夜金属线中的旌旗灯号，而不是完全作为热量耗散，从而实现空间持续有源传输，这有望改变复杂电子芯片的设计和机能。
▲ 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！从氧化物到可延续年夜块合金
▲ 作者：Shaolou Wei, Yan Ma Dierk Raabe
▲链接：
https://www.nature.com/articles/s41586-024-07932-w
▲摘要：
传统的冶金出产包罗三个步调：从矿石中提取金属，经由过程液体加工和热机械加工将其夹杂成合金，以取得所需的微不雅布局。因为对可延续经济的火急需求，这类自青铜器时期就最先实施的挨次方式至今已达极限：几近10%的温室气体排放归因在利用化石还原剂和高温冶金加工。
研究组提出了一种基在H2的氧化还原合成和压塑方式，经由过程将金属提取、合金化和热机械加工归并到一个单一固态操作中，改革了传统的合金制造策略。他们提出了一个热力学指点原则和一个通用的动力学概念，以消弭萃取冶金和物理冶金之间的经典边界，从而释放出极年夜的可延续年夜块合金设计机缘。
铁—镍因瓦块体合金是最吸惹人的铁材料之一，但出产起来最“脏”：因瓦表示出怪异的低热膨胀，实现了从周详仪器到低温部件的要害利用。但是该工艺污名昭著地不环保，出产每千克镍酿成的二氧化碳排放量是铁的10倍以上，使得这类合金种别成为完善的示范案例。
该可延续方式将氧化物直接转化为块体绿色合金，颇具利用价值，所有这些都在远低在块体熔点的温度下取得，同时连结零二氧化碳萍踪。
▲ 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 traditi华体会体育apponal 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
基在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：
微核电池操纵放射性同位素的放射性衰变发生的能量进行小范围发电，凡是在纳瓦或微瓦规模内。与化学电池分歧，微核电池的寿命与所用放射性同位素的半衰期有关，其利用寿命可长达数十年。另外，放射性衰变不受温度、压力和磁场等情况身分的影响，这使得微核电池在传统电池被证实不切现实或难以改换的环境下成为持久靠得住的电源。
镅的常见放射性同位素（241Am和243Am）是α-衰变发射体，半衰期跨越数百年。传统微核电池布局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辟带来了挑战。
研究组提出了一种微核电池布局，此中包罗一个经由过程将243Am掺入发光镧系配位聚合物的聚能传感器。这类方式将放射性同位素与份子程度上的能量传感器耦合在一路，与传统布局比拟，从α衰变能量到延续自觉光的能量转换效力提高了8000倍。
当与将自觉光转化为电能的光伏电池连系利用时，研究组取得了一种新型的放射性光伏微核电池，其总功率转换效力为0.889%，单元勾当功率为139 μW Ci-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 Ci-1) is obtained.
地球科学Earth Science
Forest fire size amplifies postfire land surface warming
丛林火警范围放年夜了火警后地表升温
▲ 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：
天气变暖致使极端火警气候遍及增添，使丛林火警延续时候更长，范围更年夜。近几十年来，加拿年夜、美国和Australia的平均丛林火警范围翻了一番乃至三倍。反过来，丛林火警经由过程调理陆地—年夜气中的碳、氮、气溶胶、能量和水的通量来反馈天气。但是，愈来愈年夜的火警对地表天气的影响和其对地盘治理的影响仍有待肯定。
研究组操纵卫星不雅测注解，在北半球温带和北方丛林中，火警范围延续放年夜了夏日每单元偏激面积长达十年的火警后地表升温。跟着阔叶树品貌的增添，升温和其随火警范围的放年夜都削弱，这与阔叶树种比针叶树种更低的火警懦弱性相一致。
火警范围加强的升温可能会影响火警后林分更新的成功和构成和永远冻土退化，对将来天气和火警动态表示出此前被轻忽的额外反馈效应。鉴在北方丛林火警范围估计会增添，天气智能型林业应致力在减轻年夜火的天气风险，或可经由过程恰当增添阔叶树的比例，并避免莳植活跃的焦生植物。
▲ 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年加拿年夜野火的碳排放量
▲ 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年加拿年夜丛林年夜火在范围和强度上都很极端，年平均销毁面积是曩昔40年的7倍多。
研究组基在卫星一氧化碳不雅测的反演模子，量化了2023年5月至9月这些火警的碳排放量。成果发现碳排放量的范围为647 TgC（570-727 TgC），与排放年夜国的年化石燃料排放量相当，仅次在印度、中国和美国。
研究组发现，年夜规模的干热气候是火警舒展的首要驱动身分，2023年是最少自1980年以来最暖和、最干燥的一年。虽然2023年温度相对汗青记实颇极端，但天气猜测注解，即便在暖和的天气减缓情形下（配合社会经济路子，SSP 2-4.5），该温度在2050年月也多是典型的。
这类环境可能会致使火警勾当增添，按捺加拿年夜丛林的碳接收，加重人们对这些丛林作为碳汇的持久持久性的耽忧。
▲ 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.
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