编译 冯维维
Nature, Volume 625 Issue 7993, 4 January 2024
《自然》第625卷，7993期，2024年1月4日
行星科学Planetary science
SO2 , silicate clouds, but no CH4 detected in a warm Neptune
类海王星存在二氧化硫、硅酸盐云
▲ 作者：Achrène Dyrek, Michiel Min, Leen Decin, Jeroen Bouwman, Nicolas Crouzet, Paul Mollière, Pierre-Olivier Lagage, Thomas Konings, Pascal Tremblin, Manuel Güdel, John Pye, Rens waters, Thomas Henning, Gillian Wright Show authors, etc.
▲ 链接：
https://www.nature.com/articles/s41586-023-06790-2
▲ 摘要：
WASP-107b是一颗温暖的（约740K）凌日行星，质量与海王星相似，约为30.5 M地球体积，半径与木星相似，约为0.94RJ，其大气层正在被侵蚀。此前的观测表明，在WASP-107b的大气中存在水蒸气和厚厚的高空凝结水层。
最近，通过4.05微米附近的透射光谱，在一颗热土星质量行星的大气中检测到光化学产生的二氧化硫（SO2），但在低于1000 K的温度下，预计硫更容易形成硫同素异物而不是SO2。研究者报道了韦布望远镜红外仪器（MIRI）对WASP-107b透射光谱中7.35微米和8.69微米两个SO2基本振动波段的9σ探测。
这一发现确立了WASP-107b是第二颗被证实具有光化学反应的系外行星，将探测到光化学反应的系外行星的温度范围从约1200K扩展到约740K。该光谱分析揭示了硅酸盐云的存在，它们比更简单的云结构更受青睐。此外，研究还探测到水，但没有探测到甲烷。这些发现表明其具有超太阳金属丰度的动态活跃大气。
▲ Abstract：
WASP-107b is a warm (approximately 740K) transiting planet with a Neptune-like mass of roughly 30.5 M and Jupiter-like radius of about 0.94RJ, whose extended atmosphere is eroding3. Previous observations showed evidence for water vapour and a thick, high-altitude condensate layer in the atmosphere of WASP-107b. Recently, photochemically produced sulfur dioxide (SO2) was detected in the atmosphere of a hot (about 1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 μm, but for temperatures below about 1,000 K, sulfur is predicted to preferably form sulfur allotropes instead of SO2. Here we report the 9σ detection of two fundamental vibration bands of SO2, at 7.35 μm and 8.69 μm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from about 1,200K down to about 740 K. Furthermore, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (around 7σ) over simpler cloud set-ups. Furthermore, water is detected (around 12σ) but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity.
A probable Keplerian disk feeding an optically revealed massive young star
开普勒盘或为大质量年轻恒星提供食物
▲ 作者：Anna F. McLeod, Pamela D. Klaassen, Megan Reiter, Jonathan Henshaw, Rolf Kuiper & Adam Ginsburg
▲ 链接：
https://www.nature.com/articles/s41586-023-06790-2
▲ 摘要：
恒星形成的经典图像涉及盘状星云介导的吸积，开普勒吸积盘和相关的双极射流主要在附近的低质量年轻恒星物体（YSO）中观察到。
最近，在几个大质量（M>8M太阳质量）YSOs（MYSOs）周围发现了旋转的气体结构和开普勒盘，包括几个圆盘射流系统。已知的MYSO系统都在银河系中，并且都镶嵌在它们的原始物质中。
研究者报告称在大麦哲伦星云的星系外MYSO周围发现了一个旋转的气体结构。气体运动表明，有一种物质的径向流从较大的尺度落在中心的圆盘状结构上。后者表现出开普勒旋转的迹象，因此有一个旋转的环面为吸积盘提供食物，从而促进了中央恒星的生长。
这个系统几乎在所有方面都可以与银河系的高质量YSO相媲美，这些YSO是从开普勒盘吸积气体的。这个源与银河系对应源之间的关键区别在于，它是在光学上显露出来的，而不是像人们预期的那样，在如此巨大的年轻恒星中被深深嵌入到它的出生物质中。
研究者认为这是恒星在低金属丰度和低尘埃含量环境中形成的结果。这些结果为大质量恒星及其星周盘的形成和演化模型提供了重要的约束。
▲ Abstract：
The canonical picture of star formation involves disk-mediated accretion, with Keplerian accretion disks and associated bipolar jets primarily observed in nearby, low-mass young stellar objects (YSOs). Recently, rotating gaseous structures and Keplerian disks have been detected around several massive (M>8M⊙) YSOs (MYSOs), including several disk-jet systems. All the known MYSO systems are in the Milky Way, and all are embedded in their natal material. Here we report the detection of a rotating gaseous structure around an extragalactic MYSO in the Large Magellanic Cloud. The gas motion indicates that there is a radial flow of material falling from larger scales onto a central disk-like structure. The latter exhibits signs of Keplerian rotation, so that there is a rotating toroid feeding an accretion disk and thus the growth of the central star. The system is in almost all aspects comparable to Milky Way high-mass YSOs accreting gas from a Keplerian disk. The key difference between this source and its Galactic counterparts is that it is optically revealed rather than being deeply embedded in its natal material as is expected of such a massive young star. We suggest that this is the consequence of the star having formed in a low-metallicity and low-dust content environment. Thus, these results provide important constraints for models of the formation and evolution of massive stars and their circumstellar disks.
物理学PhySiCs
Ultrahigh-mobility semiconducting epitaxial graphene on silicon carbide
碳化硅上的超高迁移率半导体外延石墨烯
▲ 作者：Jian Zhao, Peixuan Ji, Yaqi Li, Rui Li, Kaimin Zhang, Hao Tian, Kaicheng Yu, Boyue Bian, Luzhen Hao, Xue Xiao, Will Griffin, Noel Dudeck, Ramiro Moro, Lei Ma & Walt A. de Heer
▲ 链接：
https://www.nature.com/articles/s41586-023-06811-0
▲ 摘要：
由于石墨烯缺乏固有带隙，半导体石墨烯在石墨烯纳米电子学中起着重要的作用。过去二十年，通过量子限制或化学官能化来改变带隙的尝试都未能产生可行的半导体石墨烯。
这项研究表明，单晶硅衬底上的半导体层石烯（SEG）具有0.6eV的带隙和超过5000cm2V-1s-1的室温迁移率，是硅的10倍，是其他二维半导体的20倍。众所周知，当硅从碳化硅晶体表面蒸发时，富含碳的表面结晶生成多层石墨烯。
在碳化硅的硅端面上形成的第一层石墨层是与碳化硅表面部分共价键合的绝缘石墨烯层。该缓冲层的光谱测量显示出半导体特征，但由于无序性，该层的可移动性受到限制。
研究者展示了一种准平衡退火方法，可以在宏观原子平坦的梯田上产生SEG（即有序的缓冲层）。SEG晶格与SiC衬底对齐。它具有化学、机械和热稳定性，可以使用传统的半导体制造技术进行图像化和无缝连接到半金属石。这些基本特性使SEG适用于纳米电子学。
▲ Abstract：
Semiconducting graphene plays an important part in graphene nanoelectronics because of the lack of an intrinsic bandgap in graphene1. In the past two decades, attempts to modify the bandgap either by quantum confinement or by chemical functionalization failed to produce viable semiconducting graphene. Here we demonstrate that semiconducting epigraphene (SEG) on single-crystal silicon carbide substrates has a band gap of 0.6 eV and room temperature mobilities exceeding 5,000 cm2 V-1s-1, which is 10 times larger than that of silicon and 20 times larger than that of the other two-dimensional semiconductors. It is well known that when silicon evaporates from silicon carbide crystal surfaces, the carbon-rich surface crystallizes to produce graphene multilayers. The first graphitic layer to form on the silicon-terminated face of SiC is an insulating epigraphene layer that is partially covalently bonded to the SiC surface3. Spectroscopic measurements of this buffer layer4 demonstrated semiconducting signatures4, but the mobilities of this layer were limited because of disorder5. Here we demonstrate a quasi-equilibrium annealing method that produces SEG (that is, a well-ordered buffer layer) on macroscopic atomically flat terraces. The SEG lattice is aligned with the SiC substrate. It is chemically, mechanically and thermally robust and can be patterned and seamlessly connected to semimetallic epigraphene using conventional semiconductor fabrication techniques. These essential properties make SEG suitable for nanoelectronics.
Disordered enthalpyentropy descriptor for high-entropy ceramics discovery
高熵陶瓷发现的无序焓熵描述符
▲ 作者：Simon Divilov, Hagen Eckert, David Hicks, Corey Oses, Cormac Toher, Rico Friedrich, Marco Esters, Michael J. Mehl, Adam C. Zettel, Yoav Lederer, Eva Zurek, Jon-Paul Maria, Donald W. Brenner, Xiomara Campilongo, Suzana Filipovi, William G. Fahrenholtz, Caillin J. Ryan, Christopher M. DeSalle, Ryan J. Crealese, Douglas E. Wolfe, Arrigo Calzolari & Stefano Curtarolo
▲ 链接：
https://www.nature.com/articles/s41586-023-06786-y
▲ 摘要：
对在极端环境下改进功能的需求正在激发人们对高熵陶瓷的兴趣。除了利用熵形成能力描述符（熵-形成能力描述符）计算发现高熵碳化物，大多数创新都是通过实验手段缓慢推动的。
因此，该领域的进步需要更多的理论贡献。新研究引入无序焓熵描述符（DEED），一个描述符捕获熵增益和焓成本之间的平衡，允许正确分类多组分陶瓷的功能合成能力，而不考虑化学和结构。为了使相关计算成为可能，研究者开发了一种卷积算法，它大大减少了计算资源。
此外，DEED还指导了新的单相高熵碳氮化物和硼化物的实验发现。这项工作被集成到AFLOW计算生态系统，提供了一系列潜在的实验发现。
▲ Abstract：
The need for improved functionalities in extreme environments is fuelling interest in high-entropy ceramics. Except for the computational discovery of high-entropy carbides, performed with the entropy-forming-ability descriptor, most innovation has been slowly driven by experimental means. Hence, advancement in the field needs more theoretical contributions. Here we introduce disordered enthalpyentropy descriptor (DEED), a descriptor that captures the balance between entropy gains and enthalpy costs, allowing the correct classification of functional synthesizability of multicomponent ceramics, regardless of chemistry and structure. To make our calculations possible, we have developed a convolutional algorithm that drastically reduces computational resources. Moreover, DEED guides the experimental discovery of new single-phase high-entropy carbonitrides and borides. This work, integrated into the AFLOW computational ecosystem, provides an array of potential new candidates, ripe for experimental discoveries.
生态Ecology
A unified explanation for the morphology of raised peatlands
泥炭地形态的统一解释
▲ 作者：Alexander R. Cobb, René Dommain, Kimberly Yeap, Hannan Cao, Nathan C. Dadap, Bodo Bookhagen, Paul H. Glaser & Charles F. Harvey
▲ 链接：
https://www.nature.com/articles/s41586-023-06807-w
▲ 摘要：
凸起的泥炭地或沼泽是一种完全由有机物组成的温和的丘状地貌，是陆地生态系统中单位面积储存碳最多的地形。沼泽的形状至关重要，它们的圆顶形态决定了沼泽储存的大部分碳，并决定了其对人为排水后阻止温室气体排放和火灾的干预措施的反应。
然而，目前还缺乏一种推断沼泽形态的通用理论。研究者展示了一个基于沼泽普遍过程的方程，解释了它们在生物群落中的形态，从阿拉斯加到热带，再到新西兰。早期的沼泽形态模型只试图描述长期的平衡形状，因此不适用于大多数沼泽，与之相反，新方法没有这样的假设，并且可以从海拔样本中推断沼泽的完整形状，例如单个海拔样带。
研究结果为定量推断地球历史上沼泽的形态、水文和碳储量提供了基础，并为通过重新湿润世界各地受损的沼泽来规划自然气候解决方案提供了基础。
▲ Abstract：
Raised peatlands, or bogs, are gently mounded landforms that are composed entirely of organic matter and store the most carbon per area of any terrestrial ecosystem. The shapes of bogs are critically important because their domed morphology accounts for much of the carbon that bogs store and determines how they will respond to interventions to stop greenhouse gas emissions and fires after anthropogenic drainage. However, a general theory to infer the morphology of bogs is still lacking. Here we show that an equation based on the processes universal to bogs explains their morphology across biomes, from Alaska, through the tropics, to New Zealand. In contrast to earlier models of bog morphology that attempted to describe only long-term equilibrium shapes and were, therefore, inapplicable to most bog, our approach makes no such assumption and makes it possible to infer full shapes of bogs from a sample of elevations, such as a single elevation transect. Our findings provide a foundation for quantitative inference about the morphology, hydrology and carbon storage of bogs through Earths history, as well as a basis for planning natural climate solutions by rewetting damaged bogs around the world.
Satellite mapping reveals extensive industrial activity at sea
卫星制图显示海上广泛工业活动
▲ 作者：Fernando Paolo, David Kroodsma, Jennifer Raynor, Tim Hochberg, Pete Davis, Jesse Cleary, Luca Marsaglia, Sara Orofino, Christian Thomas & Patrick Halpin
▲ 链接：
https://www.nature.com/articles/s41586-023-06825-8
▲ 摘要：
世界人口越来越依赖海洋获得食物、能源生产和全球贸易，但人类在海洋的活动尚未得到很好的量化。研究者结合卫星图像、船舶GPS数据和深度学习模型，绘制了2017年至2021年全球沿海水域工业船舶活动和海上能源基础设施的地图。
他们发现，世界上72%~76%的工业渔船没有被公开追踪，其中大部分捕鱼发生在南亚、东南亚和非洲附近。研究还发现，21%~30%的运输和能源船只活动在公共跟踪系统中缺失。2020年新冠病毒病大流行爆发时，全球捕鱼量下降了12±1%，到2021年仍未恢复到大流行前的水平。
相比之下，运输和能源船活动在同一时期相对未受影响。海上风电正在迅速发展，大多数风力涡轮机仅限于海洋的小区域，但到2021年将超过石油结构的数量。这一海洋工业化地图揭示了海洋上最广泛和经济上最重要的人类活动的变化。
▲ Abstract：
The worlds population increasingly relies on the ocean for food, energy production and global trade, yet human activities at sea are not well quantified. We combine satellite imagery, vessel GPS data and deep-learning models to map industrial vessel activities and offshore energy infrastructure across the worlds coastal waters from 2017 to 2021. We find that 7276% of the worlds industrial fishing vessels are not publicly tracked, with much of that fishing taking place around South Asia, Southeast Asia and Africa. We also find that 2130% of transport and energy vessel activity is missing from public tracking systems. Globally, fishing decreased by 12±1% at the onset of the COVID-19 pandemic in 2020 and had not recovered to pre-pandemic levels by 2021. By contrast, transport and energy vessel activities were relatively unaffected during the same period. Offshore wind is growing rapidly, with most wind turbines confined to small areas of the ocean but surpassing the number of oil structures in 2021. Our map of ocean industrialization reveals changes in some of the most extensive and economically important human activities at sea..
