原文地址：http://news.sciencenet.cn/htmlnews/2023/8/506086.shtm
Nature, Volume 620 Issue 7972, 3 August 2023
《自然》第620卷，7972期，2023年8月3日
物理學Physics
A rotating white dwarf shows different compositions on its opposite faces
一顆旋轉白矮星相對面呈現不同成分
▲ 作者：Ilaria Caiazzo, Kevin B. Burdge, Dayal Wickramasinghe, Vikram S. Dhillon, Stuart P. Littlefair, James Munday, Ingrid Pelisoli, Daniel Perley, Dave I. Sahman
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06171-9
▲ 摘要：
白矮星是大多數恒星死亡后留下的密度極高的殘留物，其質量與太陽質量相當，可壓縮成類地行星大小。
研究者報告了對ZTF J203349.8+322901.1的觀測，這是一顆過渡白矮星，有兩個面：其大氣層一面由氫主導，另一面由氦主導。這種特殊性質可能是由一個小磁場的存在引起的，在其表面上造成了溫度、壓力或混合強度的不均勻性。
ZTF J203349.8+322901.1可能是一類磁性過渡白矮星中最極端的成員，與其類似的還有白矮星GD 323，后者顯示出與此相似但更微妙的變化。這類白矮星有助于揭示白矮星光譜演化背后的物理機制。
▲ Abstract：
White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterized by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. Here we report observations of ZTF?J203349.8+322901.1, a transitioning white dwarf with two faces: one side of its atmosphere is dominated by hydrogen and the other one by helium. This peculiar nature is probably caused by the presence of a small magnetic field, which creates an inhomogeneity in temperature, pressure or mixing strength over the surface. ZTF?J203349.8+322901.1 might be the most extreme member of a class of magnetic, transitioning white dwarfs—together with GD?323, a white dwarf that shows similar but much more subtle variations. This class of white dwarfs could help shed light on the physical mechanisms behind the spectral evolution of white dwarfs.
3D integration enables ultralow-noise isolator-free lasers in silicon photonics
3D集成讓硅光子學中超低噪聲無隔離器激光器成為可能
▲ 作者：Chao Xiang, Warren Jin, Osama Terra, Bozhang Dong, Heming Wang, Lue Wu, Joel Guo, Theodore J. Morin, Eamonn Hughes, Jonathan Peters, Qing-Xin Ji, Avi Feshali, Mario Paniccia, Kerry J. Vahala & John E. Bowers
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06251-w
▲ 摘要：
光子集成電路廣泛應用于電信和數據中心互連等領域。然而，在諸如微波合成器、光學陀螺儀和原子鐘等光學系統中，光子集成電路盡管在尺寸、重量、功耗和成本方面具有優勢，但仍被認為是次等的解決方案。
這種高精度和高度相干的應用有利于超低噪聲激光源與其他光子元件以緊湊而堅固的排列形式集成在一起——即在單個芯片上——用于光子集成電路，以取代大塊的光學和光纖。有兩個主要問題阻礙了這種設想的光子集成電路的實現：半導體激光器的高相位噪聲和在芯片上直接集成光隔離器的困難。
研究者通過利用三維集成來挑戰這種慣例，從而產生具有無隔離器操作的硅光子學超低噪聲激光器。由于超高質量因子腔，研究所演示的光子集成電路進入了一種不需要光隔離器而產生超低噪聲激光器和微波合成器的狀態。
這種光子集成電路還為復雜功能和批量生產提供了優越的可擴展性，并隨著時間的推移提高了穩定性和可靠性。超低損耗光子集成電路的三維集成標志著向硅基復雜系統和網絡邁出了關鍵的一步。
▲ Abstract：
Photonic integrated circuits are widely used in applications such as telecommunications and data-centre interconnects. However, in optical systems such as microwave synthesizers, optical gyroscopes and atomic clocks, photonic integrated circuits are still considered inferior solutions despite their advantages in size, weight, power consumption and cost. Such high-precision and highly coherent applications favour ultralow-noise laser sources to be integrated with other photonic components in a compact and robustly aligned format—that is, on a single chip—for photonic integrated circuits to replace bulk optics and fibres. There are two major issues preventing the realization of such envisioned photonic integrated circuits: the high phase noise of semiconductor lasers and the difficulty of integrating optical isolators directly on-chip. Here we challenge this convention by leveraging three-dimensional integration that results in ultralow-noise lasers with isolator-free operation for silicon photonics. Through multiple monolithic and heterogeneous processing sequences, direct on-chip integration of III–V gain medium and ultralow-loss silicon nitride waveguides with optical loss around 0.5?decibels per metre are demonstrated. Consequently, the demonstrated photonic integrated circuit enters a regime that gives rise to ultralow-noise lasers and microwave synthesizers without the need for optical isolators, owing to the ultrahigh-quality-factor cavity. Such photonic integrated circuits also offer superior scalability for complex functionalities and volume production, as well as improved stability and reliability over time. The three-dimensional integration on ultralow-loss photonic integrated circuits thus marks a critical step towards complex systems and networks on silicon.
化學Chemistry
Ultrafast deposition of faceted lithium polyhedra by outpacing SEI formation
鋰多面體的超快沉積
▲ 作者：Xintong Yuan, Bo Liu, Matthew Mecklenburg & Yuzhang Li
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06235-w
▲ 摘要：
電沉積鋰（Li）金屬對高能電池至關重要。然而，同時形成的表面腐蝕膜——固體電解質界面（SEI）使沉積過程復雜化，這使得對鋰金屬電沉積的理解很差。研究者通過在超快沉積電流密度下超越SEI形成，同時避免質量輸運限制，將這兩個交織在一起的過程解耦。
通過使用低溫電子顯微鏡，研究者發現金屬鋰的內在沉積形態是一個菱形十二面體，這是令人驚訝的獨立于電解質化學或電流集電極襯底。
在硬幣電池結構中，這些菱形十二面體與電流收集器表現出接近點接觸的連接，這可以加速非活性鋰的形成。研究者提出了一種脈沖電流方案，通過利用鋰菱形十二面體作為成核種子來克服這種失效模式，使致密鋰的后續生長與基線相比提高了電池性能。
雖然在過去的研究中，鋰沉積和SEI形成一直緊密相連，但新實驗方法為從根本上理解這些相互分離的過程提供了新的機會，并為設計更好的電池帶來了新的見解。
▲ Abstract：
Electrodeposition of lithium (Li) metal is critical for high-energy batteries. However, the simultaneous formation of a surface corrosion film termed the solid electrolyte interphase (SEI) complicates the deposition process, which underpins our poor understanding of Li metal electrodeposition. Here we decouple these two intertwined processes by outpacing SEI formation at ultrafast deposition current densities while also avoiding mass transport limitations. By using cryogenic electron microscopy, we discover the intrinsic deposition morphology of metallic Li to be that of a rhombic dodecahedron, which is surprisingly independent of electrolyte chemistry or current collector substrate. In a coin cell architecture, these rhombic dodecahedra exhibit near point-contact connectivity with the current collector, which can accelerate inactive Li formation8. We propose a pulse-current protocol that overcomes this failure mode by leveraging Li rhombic dodecahedra as nucleation seeds, enabling the subsequent growth of dense Li that improves battery performance compared with a baseline. While Li deposition and SEI formation have always been tightly linked in past studies, our experimental approach enables new opportunities to fundamentally understand these processes decoupled from each other and bring about new insights to engineer better batteries.
Synthesis and properties of cyclic sandwich compounds
環狀夾層化合物的合成及性質
▲ 作者：Luca Münzfeld, Sebastian Gillhuber, Adrian Hauser, Sergei Lebedkin, Pauline H?dinger, Nicolai D. Kn?fel, Christina Zovko, Michael T. Gamer, Florian Weigend, Manfred M. Kappes & Peter W. Roesky
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06192-4
▲ 摘要：
狀納米夾層配合物由單個構建塊組裝而成。研究者展示了設計、合成和表征一個同構系列的圓形夾心化合物，其術語為“環茂烯”。這些環烯烴由18個重復單元組成，在固體狀態下形成幾乎理想的圓形封閉環。
量子化學計算認為，離子金屬-配體鍵之間的獨特相互作用，配體系統的體積和環閉合時的能量增益，這是由色散相互作用的關鍵影響，促進了這些循環系統的形成。
到目前為止，只有線性一維多層夾層化合物被研究用于納米線等潛在應用。這個教科書式的環狀夾層化合物的例子有望為進一步創新新的功能有機金屬材料打開大門。
▲ Abstract：
Cyclic nanometre-scale sandwich complexes assembled from individual building blocks were synthesized.Here we show the design, synthesis and characterization of an isomorphous series of circular sandwich compounds, for which the term ‘cyclocenes’ is suggested. These cyclocenes consist of 18 repeating units, forming almost ideally circular, closed rings in the solid state, that can be described by the general formula . Quantum chemical calculations lead to the conclusion that a unique interplay between the ionic metal-to-ligand bonds, the bulkiness of the ligand system and the energy gain on ring closure, which is crucially influenced by dispersion interactions, facilitate the formation of these cyclic systems. Up to now, only linear one-dimensional multidecker sandwich compounds have been investigated for possible applications such as nanowires. This textbook example of cyclic sandwich compounds is expected to open the door for further innovations towards new functional organometallic materials.
地質和氣候Climate & Geology
Remote detection of a lunar granitic batholith at Compton–Belkovich
月球花崗巖基的遠程探測
▲ 作者：Matthew A. Siegler, Jianqing Feng, Katelyn Lehman-Franco, Jeffery C. Andrews-Hanna, Rita C. Economos, Michael St. Clair, Chase Million, James W. Head, Timothy D. Glotch & Mackenzie N. White
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06183-5
▲ 摘要：
除了地球，太陽系中幾乎沒有花崗巖。在巖漿系統中獲得花崗巖組成需要多階段的熔融和分選，這也增加了放射性成因元素的濃度。地球上豐富的水和板塊構造促進了這些過程，幫助重新融化。
雖然在月球上沒有這些驅動因素，但已經發現了小的花崗巖樣本，但它們的起源和它們所代表的系統規模的細節是未知的。研究者報告了一個異常熱地熱源的微波波長測量，最好的解釋是在富釷的遠側特征康普頓-貝爾科維奇下面存在一個直徑約50公里的花崗巖系統。被動微波輻射測量對多個波長深度的綜合熱梯度很敏感。
嫦娥一號和嫦娥二號微波儀器的3 - 37千兆赫天線溫度能夠測量到每平方米約180毫瓦的峰值熱通量，這大約是月球高地平均熱通量的20倍。這一驚人的規模和地理范圍表明，在月球上，特別是在Procellarum地區之外，存在一個類似地球的、進化的花崗巖系統，其規模比人們認為的要大得多。
此外，這些方法是可推廣的：類似被動輻射測量數據的使用可以極大地擴展我們對月球和其他行星上地熱過程的認識。
▲ Abstract：
Granites are nearly absent in the Solar System outside of Earth. Achieving granitic compositions in magmatic systems requires multi-stage melting and fractionation, which also increases the concentration of radiogenic elements. Abundant water and plate tectonics facilitate these processes on Earth, aiding in remelting. Although these drivers are absent on the Moon, small granite samples have been found, but details of their origin and the scale of systems they represent are unknown. Here we report microwave-wavelength measurements of an anomalously hot geothermal source that is best explained by the presence of an approximately 50-kilometre-diameter granitic system below the thorium-rich farside feature known as Compton–Belkovich. Passive microwave radiometry is sensitive to the integrated thermal gradient to several wavelengths depth. The 3–37-gigahertz antenna temperatures of the Chang’e-1 and Chang’e-2 microwave instruments allow us to measure a peak heat flux of about 180?milliwatts per square metre, which is about 20 times higher than that of the average lunar highlands3,4. The surprising magnitude and geographic extent of this feature imply an Earth-like, evolved granitic system larger than believed possible on the Moon, especially outside of the Procellarum region5. Furthermore, these methods are generalizable: similar uses of passive radiometric data could vastly expand our knowledge of geothermal processes on the Moon and other planetary bodies.
Fennoscandian tree-ring anatomy shows a warmer modern than medieval climate
樹木年輪解剖顯示，現代氣候比中世紀氣候更溫暖
▲ 作者：Jesper Bj?rklund, Kristina Seftigen, Markus Stoffel, Marina V. Fonti, Sven Kottlow, David C. Frank, Jan Esper, Patrick Fonti, Hugues Goosse, H?kan Grudd, Bj?rn E. Gunnarson, Daniel Nievergelt, Elena Pellizzari, Marco Carrer & Georg von Arx
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06176-4
▲ 摘要：
地球系統模型和各種氣候代理來源表明，全球變暖至少在公元前是前所未有的。研究利用樹木年輪發現，芬諾斯坎迪亞半島當前的氣候比中世紀時期的氣候要溫暖得多。這突出了即使在區域尺度上，人為強迫在氣候變暖中的主導作用，從而調和了重建和模式模擬之間的不一致。
研究者使用每年解決1170年的樹木年輪記錄，該記錄完全依賴于松樹的管狀解剖測量，提供了溫暖季節儀器溫度變化的高保真測量。
因此，他們呼吁建立更多這樣的千年記錄，以進一步提高對歷史和未來氣候變化的認識，減少區域間乃至全球尺度上的不確定性。
▲ Abstract：
Earth system models and various climate proxy sources indicate global warming is unprecedented during at least the Common Era. Here we show that the current climate of the Fennoscandian Peninsula is substantially warmer than that of the medieval period. This highlights the dominant role of anthropogenic forcing in climate warming even at the regional scale, thereby reconciling inconsistencies between reconstructions and model simulations. We used an annually resolved 1,170-year-long tree-ring record that relies exclusively on tracheid anatomical measurements from Pinus sylvestris trees, providing high-fidelity measurements of instrumental temperature variability during the warm season. We therefore call for the construction of more such millennia-long records to further improve our understanding and reduce uncertainties around historical and future climate change at inter-regional and eventually global scales.