编译 | 冯维维

Nature,  Volume 628 Issue 8008, 18 April 2024

《自然》,第628卷，8008期，2024年4月18日

物理学Physics

Methane emission from a cool brown dwarf

一颗低温褐矮星释放出的甲烷

▲ 作者：Jacqueline K. Faherty, Ben Burningham, Jonathan Gagné, Genaro Suárez, Johanna M. Vos, Sherelyn Alejandro Merchan, Caroline V. Morley, Melanie Rowland, Brianna Lacy, Rocio Kiman, Dan Caselden, J. Davy Kirkpatrick, Aaron Meisner, Adam C. Schneider, Marc Jason Kuchner, Daniella Carolina Bardalez Gagliuffi, Charles Beichman, Peter Eisenhardt, Christopher R. Gelino, Ehsan Gharib-Nezhad, Eileen Gonzales, Federico Marocco, Austin James Rothermich & Niall Whiteford

▲ 链接：

https://www.nature.com/articles/s41586-024-07190-w

▲ 摘要：

在太阳系之外，极光是从对孤立的褐矮星的无线电观测中推断出来的。在太阳系中，巨大的行星在电磁波谱上有极光发射的特征，包括H3+和甲烷的红外发射。科学家尝试在无线电中寻找具有极光特征的孤立的褐矮星，以寻找相应的红外特征，但只报道了无效探测。CWISEP j193518.59 - 154620.3.（简称W1935）是一颗孤立的褐矮星，温度约为482 K。

研究者报告了詹姆斯·韦布太空望远镜观测到W1935在3.326 μm波段强烈的甲烷排放。大气模拟得出的结论表示，以1-10毫巴为中心的大约300 K的逆温重复了这一特征。这代表了没有主星辐射的类木星大气的大气温度反演。

强逆温的一个合理解释是由极光过程加热，尽管不能排除其他内部和外部动力过程。最合适的模型排除了H3+的贡献，这在太阳系气体巨星中很突出。然而，这与H3+在W1935发射源的较高压力下的快速破坏是一致的。

▲ Abstract：

Beyond our Solar System, aurorae have been inferred from radio observations of isolated brown dwarfs. Within our Solar System, giant planets have auroral emission with signatures across the electromagnetic spectrum including infrared emission of H3+ and methane. Isolated brown dwarfs with auroral signatures in the radio have been searched for corresponding infrared features, but only null detections have been reported. CWISEP J193518.59-154620.3. (W1935 for short) is an isolated brown dwarf with a temperature of approximately 482?K. Here we report James Webb Space Telescope observations of strong methane emission from W1935 at 3.326?μm. Atmospheric modelling leads us to conclude that a temperature inversion of approximately 300?K centred at 1–10?mbar replicates the feature. This represents an atmospheric temperature inversion for a Jupiter-like atmosphere without irradiation from a host star. A plausible explanation for the strong inversion is heating by auroral processes, although other internal and external dynamical processes cannot be ruled out. The best-fitting model rules out the contribution of H3+ emission, which is prominent in Solar System gas giants. However, this is consistent with rapid destruction of H3+ at the higher pressure where the W1935 emission originates.

A hybrid topological quantum state in an elemental solid

单质固体中的混合拓扑量子态

▲ 作者：Md Shafayat Hossain, Frank Schindler, Rajibul Islam, Zahir Muhammad, Yu-Xiao Jiang, Zi-Jia Cheng, Qi Zhang, Tao Hou, Hongyu Chen, Maksim Litskevich, Brian Casas, Jia-Xin Yin, Tyler A. Cochran, Mohammad Yahyavi, Xian P. Yang, Luis Balicas, Guoqing Chang, Weisheng Zhao, Titus Neupert & M. Zahid Hasan

▲ 链接：

https://www.nature.com/articles/s41586-024-07203-8

▲ 摘要：

拓扑学和相互作用是现代量子物质理解中的基本概念。它们之间的联系产生了三个重要的研究方向：

（1）不同相互作用之间的竞争，如在几个相互交织的相中；（2）相互作用和拓扑之间的相互作用驱动扭曲层状材料和拓扑磁体中的现象；（3）几个拓扑顺序的合并产生不同的新相。前两个例子已经发展成为主要的研究领域，尽管最后一个例子仍未被探索，主要是因为缺乏实验研究的材料平台。

研究者使用隧道显微镜、光电发射光谱和理论分析，揭示了简单元素-固体砷中物质的“混合”拓扑相。通过独特的体积-表面-边缘对应，他们发现砷具有连接强的高阶拓扑结构，稳定了混合拓扑相。虽然动量-空间光谱测量显示了拓扑表面状态的迹象，但实空间显微镜测量揭示了表面上各种天然纳米结构上拓扑诱导的阶梯边缘传导通道的独特几何形状。

利用理论模型，他们证明了砷中无间隙阶边态的存在依赖于非平凡强Z2不变量和非平凡高阶拓扑不变量的同时存在，这为混合拓扑的存在提供了实验证据。研究强调了在工程量子或纳米器件中探索不同带拓扑的相互作用和利用相关拓扑传导通道的途径。

▲ Abstract：

Topology and interactions are foundational concepts in the modern understanding of quantum matter. Their nexus yields three important research directions: (1) the competition between distinct interactions, as in several intertwined phases, (2) the interplay between interactions and topology that drives the phenomena in twisted layered materials and topological magnets, and (3) the coalescence of several topological orders to generate distinct novel phases. The first two examples have grown into major areas of research, although the last example remains mostly unexplored, mainly because of the lack of a material platform for experimental studies. Here, using tunnelling microscopy, photoemission spectroscopy and a theoretical analysis, we unveil a ‘hybrid’ topological phase of matter in the simple elemental-solid arsenic. Through a unique bulk-surface-edge correspondence, we uncover that arsenic features a conjoined strong and higher-order topology that stabilizes a hybrid topological phase. Although momentum-space spectroscopy measurements show signs of topological surface states, real-space microscopy measurements unravel a unique geometry of topologically induced step-edge conduction channels revealed on various natural nanostructures on the surface. Using theoretical models, we show that the existence of gapless step-edge states in arsenic relies on the simultaneous presence of both a non-trivial strong Z2 invariant and a non-trivial higher-order topological invariant, which provide experimental evidence for hybrid topology. Our study highlights pathways for exploring the interplay of different band topologies and harnessing the associated topological conduction channels in engineered quantum or nano-devices.

Phononic switching of magnetization by the ultrafast Barnett effect

利用超快巴尼特效应实现磁化的声子开关

▲ 作者：C. S. Davies, F. G. N. Fennema, A. Tsukamoto, I. Razdolski, A. V. Kimel & A. Kirilyuk

▲ 链接：

https://www.nature.com/articles/s41586-024-07200-x

▲ 摘要：

历史上的巴内特效应描述了一个净磁矩为零的惯性体如何在机械旋转时获得自发磁化。最近的突破性实验表明，超短激光脉冲在数百飞秒内破坏有序铁磁体的磁化，自旋失去角动量，成为圆偏振光学声子，这是超快爱因斯坦-德哈斯效应的一部分。

然而，利用这种晶格的高频振动来在附近的磁性介质中往复切换磁化的前景尚未得到实验探索。

研究者证明了通过超快巴尼特效应获得的自发磁化，通过顺磁性衬底中的圆极化光学声子的共振激发，可以用来永久地逆转安装在所述衬底上的异质结构的磁性状态。由于声子的手性控制磁开关的方向，超快巴尼特效应为对磁有序进行超快非局部控制提供了一种选择性和潜在的通用方法。

▲ Abstract：

The historic Barnett effect describes how an inertial body with otherwise zero net magnetic moment acquires spontaneous magnetization when mechanically spinning. Breakthrough experiments have recently shown that an ultrashort laser pulse destroys the magnetization of an ordered ferromagnet within hundreds of femtoseconds, with the spins losing angular momentum to circularly polarized optical phonons as part of the ultrafast Einstein–de Haas effect. However, the prospect of using such high-frequency vibrations of the lattice to reciprocally switch magnetization in a nearby magnetic medium has not yet been experimentally explored. Here we show that the spontaneous magnetization gained temporarily by means of the ultrafast Barnett effect, through the resonant excitation of circularly polarized optical phonons in a paramagnetic substrate, can be used to permanently reverse the magnetic state of a heterostructure mounted atop the said substrate. With the handedness of the phonons steering the direction of magnetic switching, the ultrafast Barnett effect offers a selective and potentially universal method for exercising ultrafast non-local control over magnetic order.

气候和生态Climate & Ecology

The economic commitment of climate change

气候变化让全球收入减少

▲ 作者：Maximilian Kotz, Anders Levermann & Leonie Wenz

▲ 链接：https://www.nature.com/articles/s41586-024-07219-0

▲ 摘要：

宏观经济气候变化损害的全球预测，通常会考虑长期平均年和全国气温的影响。研究者利用过去40年全球1600多个地区的最新实证研究结果，预测了温度和降水造成的次国家损害，包括日变率和极端事件。

通过实证方法，他们发现世界经济将在未来26年内减少19%的收入，而不受未来排放选择的影响（相对于不受气候影响的基线，考虑到物理气候和经验不确定性，可能范围为11%~29%）。

在这个短期框架内，这些损失已经超过了将全球变暖限制在2℃以内所需的减缓成本的6倍，并且此后会因排放选择而出现很大差异。造成的损害主要是通过平均温度的变化引起的，但考虑到进一步的气候因素，估计结果将提高约50%，并导致更强的区域异质性。

除极高纬度地区外，预计所有地区都将出现承诺损失，在极高纬度地区，温度变率的减少会带来好处。最大的损失发生在历史累积排放量较低和当前收入较低的低纬度地区。

▲ Abstract：

Global projections of macroeconomic climate-change damages typically consider impacts from average annual and national temperatures over long time horizons. Here we use recent empirical findings from more than 1,600 regions worldwide over the past 40?years to project sub-national damages from temperature and precipitation, including daily variability and extremes. Using an empirical approach that provides a robust lower bound on the persistence of impacts on economic growth, we find that the world economy is committed to an income reduction of 19% within the next 26?years independent of future emission choices (relative to a baseline without climate impacts, likely range of 11–29% accounting for physical climate and empirical uncertainty). These damages already outweigh the mitigation costs required to limit global warming to 2?°C by sixfold over this near-term time frame and thereafter diverge strongly dependent on emission choices. Committed damages arise predominantly through changes in average temperature, but accounting for further climatic components raises estimates by approximately 50% and leads to stronger regional heterogeneity. Committed losses are projected for all regions except those at very high latitudes, at which reductions in temperature variability bring benefits. The largest losses are committed at lower latitudes in regions with lower cumulative historical emissions and lower present-day income.

FSC-certified forest management benefits large mammals compared to non-FSC

FSC森林有利于保护大型哺乳动物

▲ 作者：Joeri A. Zwerts, E. H. M. Sterck, Pita A. Verweij, Fiona Maisels, Jaap van der Waarde, Emma A. M. Geelen, Georges Belmond Tchoumba, Hermann Frankie Donfouet Zebaze & Marijke van Kuijk

▲ 链接：

https://www.nature.com/articles/s41586-024-07257-8

▲ 摘要：

世界上超过四分之一的热带森林被用来采伐木材。伐木影响了这些生态系统的生物多样性，主要是通过开辟森林道路，方便在广大地区狩猎野生动物。森林管理委员会（FSC）等森林管理认证计划有望减轻对生物多样性的影响，但由于研究设计方面的挑战，主要是样本量有限，迄今为止对FSC认证的有效性知之甚少。

研究者通过在西赤道非洲的14个伐木区使用130万张相机陷阱拍摄的55种哺乳动物的照片来提供这一证据。他们观察到，在FSC认证的伐木特许权中，遇到哺乳动物的比率高于非FSC伐木特许权。

对于体重超过10公斤的物种和高度保护的物种，如极度濒危的森林象和西部低地大猩猩，这种影响最为明显。在整个哺乳动物群落中，与FSC认证的特许权相比，非FSC特许权含有FC碰碰胡老虎机法典-提高赢钱机率的下注技巧的啮齿动物和其他小物种。

物种保护的首要任务应该是通过有效的执法来维持未采伐的森林，但对于采伐的森林，研究结果提供了令人信服的数据，即FSC认证的森林管理对哺乳动物群落的损害小于非FSC森林管理。这项研究提供了强有力的证据，证明FSC认证的森林管理或同等严格的要求和控制机制应该成为木材开采的规范，以避免由啮齿动物和其他小物种主导的半空森林。

▲ Abstract：

More than a quarter of the world’s tropical forests are exploited for timber. Logging impacts biodiversity in these ecosystems, primarily through the creation of forest roads that facilitate hunting for wildlife over extensive areas. Forest management certification schemes such as the Forest Stewardship Council (FSC) are expected to mitigate impacts on biodiversity, but so far very little is known about the effectiveness of FSC certification because of research design challenges, predominantly limited sample sizes. Here we provide this evidence by using 1.3?million camera-trap photos of 55 mammal species in 14 logging concessions in western equatorial Africa. We observed higher mammal encounter rates in FSC-certified than in non-FSC logging concessions. The effect was most pronounced for species weighing more than 10?kg and for species of high conservation priority such as the critically endangered forest elephant and western lowland gorilla. Across the whole mammal community, non-FSC concessions contained proportionally more rodents and other small species than did FSC-certified concessions. The first priority for species protection should be to maintain unlogged forests with effective law enforcement, but for logged forests our findings provide convincing data that FSC-certified forest management is less damaging to the mammal community than is non-FSC forest management. This study provides strong evidence that FSC-certified forest management or equivalently stringent requirements and controlling mechanisms should become the norm for timber extraction to avoid half-empty forests dominated by rodents and other small species.

古生物学Paleontology

Jurassic shuotheriids show earliest dental diversification of mammaliaforms

侏罗纪shuotheriids显示哺乳动物中最早的牙齿多样化

▲ 作者：Fangyuan Mao, Zhiyu Li, Zhili Wang, Chi Zhang, Thomas Rich, Patricia Vickers-Rich & Jin Meng

▲ 链接：

https://www.nature.com/articles/s41586-024-07258-7

▲ 摘要：

侏罗纪时期的类哺乳动物Shuotheriids因其独特的牙齿特征而困扰着科学家。shuotheriids有所谓的“假摩擦牙”，在下臼齿的三角状体前面有一个“假爪状体”（一种盆状结构），这与目前在哺乳动物中看到的摩擦牙不同，爪状体位于三角状体后面。这种独特的牙齿模式阻碍了人们对shuotheriid关系的理解以及哺乳动物物种进化的第一步。

研究小组使用先进的技术发现了侏罗纪shuotheriids的新标本，其中一些具有完整的骨骼，从而能够彻底检查它们的“假摩擦”牙齿。在对这种新材料的分析中，研究人员能够使用各种分析方法更全面地分析牙齿结构，这表明shuotheriid牙齿结构似乎与docodontans的牙齿结构非常相似。

这项研究表明，shuotheriids在它们的底部牙齿中没有真正的三角体，这表明它们与docodontans的关系比以前认为的更近。对牙齿结构的重新评估不仅解决了未解决的解释，还引发了对哺乳动物形态进化关系的重新思考。

▲ Abstract：

Shuotheriids are Jurassic mammaliaforms that possess pseudotribosphenic teeth in which a pseudotalonid is anterior to the trigonid in the lower molar, contrasting with the tribosphenic pattern of therian mammals (placentals, marsupials and kin) in which the talonid is posterior to the trigonid. The origin of the pseudotribosphenic teeth remains unclear, obscuring our perception of shuotheriid affinities and the early evolution of mammaliaforms. Here we report a new Jurassic shuotheriid represented by two skeletal specimens. Their complete pseudotribosphenic dentitions allow reidentification of dental structures using serial homology and the tooth occlusal relationship. Contrary to the conventional view, our findings show that dental structures of shuotheriids can be homologized to those of docodontans and partly support homologous statements for some dental structures between docodontans and other mammaliaforms. The phylogenetic analysis based on new evidence removes shuotheriids from the tribosphenic ausktribosphenids (including monotremes) and clusters them with docodontans to form a new clade, Docodontiformes, that is characterized by pseudotribosphenic features. In the phylogeny, docodontiforms and ‘holotherians’ (Kuehneotherium, monotremes and therians)13 evolve independently from a Morganucodon-like ancestor with triconodont molars by labio-lingual widening their posterior teeth for more efficient food processing. The pseudotribosphenic pattern passed a cusp semitriangulation stage9, whereas the tribosphenic pattern and its precursor went through a stage of cusp triangulation. The two different processes resulted in complex tooth structures and occlusal patterns that elucidate the earliest diversification of mammaliaforms.

Fossils document evolutionary changes of jaw joint to mammalian middle ear

化石记录了哺乳动物下颌关节到中耳的进化变化

▲ 作者：Fangyuan Mao, Chi Zhang, Jicheng Ren, Tao Wang, Guofu Wang, Fakui Zhang, Thomas Rich, Patricia Vickers-Rich & Jin Meng

▲ 链接：

https://www.nature.com/articles/s41586-024-07235-0

▲ 摘要：

长齿鲨双颌关节由牙鳞关节外侧和关节-方关节内侧组成。关节-方关节及其相关的牙后骨构成哺乳动物中耳的前体。记录从这种前体到哺乳动物中耳过渡的化石很少，导致对哺乳动物进化最早阶段这一标志性器官的解释不一致。

研究者报告了两种侏罗纪哺乳动物的下颌中耳：一种新的morganucodondon 样种和一种Shuotheriid水生动物。Morganucodonan样种显示出许多以前未知的后牙状骨形态，并显示出其关节-方关节丧失承重功能的特征。Shuotheriid的中耳接近哺乳动物的状态，因为它的特征只适合于听觉功能，尽管后牙骨仍然附着在牙上。

随着下颌关节骨的缩小，两种哺乳动物的方骨相对于关节有不同程度的内移。这些变化提供了证据，证明关节-方颚关节的承重功能逐渐丧失，这是哺乳动物进化过程中牙髓后骨脱离牙髓和Meckel软骨最终破裂的先决条件。

▲ Abstract：

The dual jaw joint of Morganucodon consists of the dentary–squamosal joint laterally and the articular–quadrate one medially. The articular–quadrate joint and its associated post-dentary bones constitute the precursor of the mammalian middle ear. Fossils documenting the transition from such a precursor to the mammalian middle ear are poor, resulting in inconsistent interpretations of this hallmark apparatus in the earliest stage of mammaliaform evolution. Here we report mandibular middle ears from two Jurassic mammaliaforms: a new morganucodontan-like species and a pseudotribosphenic shuotheriid species. The morganucodontan-like species shows many previously unknown post-dentary bone morphologies and exhibits features that suggest a loss of load-bearing function in its articular–quadrate joint. The middle ear of the shuotheriid approaches the mammalian condition in that it has features that are suitable for an exclusively auditory function, although the post-dentary bones are still attached to the dentary. With size reduction of the jaw-joint bones, the quadrate shifts medially at different degrees in relation to the articular in the two mammaliaforms. These changes provide evidence of a gradual loss of load-bearing function in the articular–quadrate jaw joint—a prerequisite for the detachment of the post-dentary bones from the dentary and the eventual breakdown of the Meckel’s cartilage during the evolution of mammaliaforms.