《自然》（20240613出版）一周論文導讀

編譯 | 未玖

Nature, 13 June 2024, VOL 630, ISSUE 8016

《自然》2024年6月13日，第630卷，8016期

天文學Astronomy

Lense–Thirring precession after a supermassive black hole disrupts a star

超大質量黑洞破壞恒星后的蘭斯-蒂林進動

▲ 作者：Dheeraj R. Pasham, Michal Zaja?ek, C. J. Nixon, Eric R. Coughlin, Marzena ?niegowska, Agnieszka Janiuk, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07433-w

▲ 摘要：

超大質量黑洞破壞一顆恒星后，在其周圍形成的吸積盤最初可能與黑洞的赤道面錯位。這種錯位引起了吸積盤上的相對論力矩（蘭斯-蒂林效應），導致吸積盤在早期進動，而在后期與黑洞對齊，進動終止。

研究組報道，使用高節奏的X射線監測觀測潮汐中斷事件（TDE），發現了強烈、準周期性的X射線通量和溫度調制。這些X射線調制大約間隔15天，在TDE的早期階段持續約130天。

吸積流的蘭斯-蒂林進動可產生這種X射線變化，但不能排除其他物理機制，如輻射壓力不穩定性。假設典型的TDE參數，即一顆類太陽恒星的吸積盤最多延伸到所謂圓化半徑，并且盤面以剛體形式進動，研究組將黑洞的擾動無量綱自旋參數約束為0.05?∣a∣?0.5。

▲ Abstract：

An accretion disk formed around a supermassive black hole after it disrupts a star is expected to be initially misaligned with respect to the equatorial plane of the black hole. This misalignment induces relativistic torques (the Lense–Thirring effect) on the disk, causing the disk to precess at early times, whereas at late times the disk aligns with the black hole and precession terminates. Here we report, using high-cadence X-ray monitoring observations of a tidal disruption event (TDE), the discovery of strong, quasi-periodic X-ray flux and temperature modulations. These X-ray modulations are separated by roughly 15 days and persist for about 130 days during the early phase of the TDE. Lense–Thirring precession of the accretion flow can produce this X-ray variability, but other physical mechanisms, such as the radiation-pressure instability, cannot be ruled out. Assuming typical TDE parameters, that is, a solar-like star with the resulting disk extending at most to the so-called circularization radius, and that the disk precesses as a rigid body, we constrain the disrupting dimensionless spin parameter of the black hole to be 0.05?∣a∣?0.5.

物理學Physics

Monolithic three-dimensional tier-by-tier integration via van der Waals lamination

通過范德華層壓實現單片三維逐層集成

▲ 作者：Donglin Lu, Yang Chen, Zheyi Lu, Likuan Ma, Quanyang Tao, Zhiwei Li, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07406-z

▲ 摘要：

二維（2D）半導體因其表面無懸空鍵和能夠集成到各種基底上而不受傳統晶格匹配約束，從而在單片三維（M3D）集成方面顯示出巨大潛力。然而，因其原子薄的體厚，2D半導體與微電子領域的各種高能工藝不兼容，其中多個2D電路層的M3D集成頗具挑戰性。

研究組報道了一種替代的低溫M3D集成方法，即通過范德華（vdW）層壓整個預制電路層，其中加工溫度控制在120℃。通過進一步逐層重復vdW層壓工藝，在垂直方向上實現了10個電路層的M3D集成系統，克服了先前的熱預算限制。

詳細的電氣特性表明，在頂部重復層壓vdW電路層后，底部2D晶體管不會受到影響。此外，通過vdW層間通孔垂直連接不同層內的器件，可實現所需系統功能的各種邏輯和異構結構。研究組的演示為制備層數增加的M3D電路提供了低溫途徑。

▲ Abstract：

Two-dimensional (2D) semiconductors have shown great potential for monolithic three-dimensional (M3D) integration due to their dangling-bonds-free surface and the ability to integrate to various substrates without the conventional constraint of lattice matching. However, with atomically thin body thickness, 2D semiconductors are not compatible with various high-energy processes in microelectronics, where the M3D integration of multiple 2D circuit tiers is challenging. Here we report an alternative low-temperature M3D integration approach by van der Waals (vdW) lamination of entire prefabricated circuit tiers, where the processing temperature is controlled to 120°C. By further repeating the vdW lamination process tier by tier, an M3D integrated system is achieved with 10 circuit tiers in the vertical direction, overcoming previous thermal budget limitations. Detailed electrical characterization demonstrates the bottom 2D transistor is not impacted after repetitively laminating vdW circuit tiers on top. Furthermore, by vertically connecting devices within different tiers through vdW inter-tier vias, various logic and heterogeneous structures are realized with desired system functions. Our demonstration provides a low-temperature route towards fabricating M3D circuits with increased numbers of tiers.

材料科學Materials Science

Experiment-free exoskeleton assistance via learning in simulation

通過仿真學習實現無實驗外骨骼輔助

▲ 作者：Shuzhen Luo, Menghan Jiang, Sainan Zhang, Junxi Zhu, Shuangyue Yu, Israel Dominguez Silva, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07382-4

▲ 摘要：

外骨骼在改善人類運動性能方面具有巨大潛力。然而，其發展和廣泛傳播受到長時間人體測試和手工控制規則的限制。

研究組展示了一種在仿真中學習通用控制策略的無實驗方法。該仿真學習框架利用動力學感知的肌肉骨骼和外骨骼模型以及數據驅動的強化學習，在沒有人體實驗的情況下彌合模擬與現實之間的差距。

學習控制器安裝在定制的髖關節外骨骼上，可在不同的活動中自動生成輔助，步行、跑步和爬樓梯的代謝率分別降低24.3%、13.1%和15.4%。該框架為身體健全和行動不便的個人快速開發和廣泛采用各種輔助機器人提供了一種可推廣和可擴展的策略。

▲ Abstract：

Exoskeletons have enormous potential to improve human locomotive performance. However, their development and broad dissemination are limited by the requirement for lengthy human tests and handcrafted control laws. Here we show an experiment-free method to learn a versatile control policy in simulation. Our learning-in-simulation framework leverages dynamics-aware musculoskeletal and exoskeleton models and data-driven reinforcement learning to bridge the gap between simulation and reality without human experiments. The learned controller is deployed on a custom hip exoskeleton that automatically generates assistance across different activities with reduced metabolic rates by 24.3%, 13.1% and 15.4% for walking, running and stair climbing, respectively. Our framework may offer a generalizable and scalable strategy for the rapid development and widespread adoption of a variety of assistive robots for both able-bodied and mobility-impaired individuals.

A self-healing multispectral transparent adhesive peptide glass

一種自修復的多光譜透明膠肽玻璃

▲ 作者：Gal Finkelstein-Zuta, Zohar A. Arnon, Thangavel Vijayakanth, Or Messer, Orr Simon Lusky, Avital Wagner, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07408-x

▲ 摘要：

盡管玻璃具有無序的類液體結構，但亦表現出類固體的機械性能。玻璃質材料的形成通過玻璃化進行，防止結晶和促進無定形結構。由于其獨特的光學、化學和機械性能以及耐用性、多功能性和環境可持續性，玻璃是材料科學各個領域的基礎。然而，在不影響其性能的情況下工程設計玻璃材料頗具挑戰性。

研究組報道了一種由短芳香三肽YYY與結構水非共價交聯引發的自發自組織形成的超分子無定形玻璃，其獨特地結合了經常相互矛盾的多種屬性，高度剛性但可在室溫下進行完全的自修復。

此外，超分子玻璃是一種極強的粘合劑，但其在從可見光到中紅外的寬光譜范圍內是透明的。研究組在由天然氨基酸組成的簡單生物有機肽玻璃中觀察到了這種特殊特性，這代表了一種多功能材料，可助力科學和工程中的各種應用。

▲ Abstract：

Despite its disordered liquid-like structure, glass exhibits solid-like mechanical properties. The formation of glassy material occurs by vitrification, preventing crystallization and promoting an amorphous structure. Glass is fundamental in diverse fields of materials science, owing to its unique optical, chemical and mechanical properties as well as durability, versatility and environmental sustainability. However, engineering a glassy material without compromising its properties is challenging. Here we report the discovery of a supramolecular amorphous glass formed by the spontaneous self-organization of the short aromatic tripeptide YYY initiated by non-covalent cross-linking with structural water. This system uniquely combines often contradictory sets of properties; it is highly rigid yet can undergo complete self-healing at room temperature. Moreover, the supramolecular glass is an extremely strong adhesive yet it is transparent in a wide spectral range from visible to mid-infrared. This exceptional set of characteristics is observed in a simple bioorganic peptide glass composed of natural amino acids, presenting a multi-functional material that could be highly advantageous for various applications in science and engineering.

Imaging surface structure and premelting of ice Ih with atomic resolution

用原子分辨率成像冰Ih的表面結構和預融化

▲ 作者：Jiani Hong, Ye Tian, Tiancheng Liang, Xinmeng Liu, Yizhi Song, Dong Guan, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07427-8

▲ 摘要：

冰表面與許多物理和化學性質密切相關，如融化、凍結、摩擦、氣體吸收和大氣反應。盡管進行了大量的實驗和理論研究，但由于脆弱的氫鍵網絡和復雜的預融化過程，冰界面的確切原子結構仍難以捉摸。

研究組利用基于qPlus的具有一氧化碳功能化尖端的低溫原子力顯微鏡，實現了六方水冰（冰Ih）的基礎（0001）表面結構的原子分辨率成像。結果發現晶體冰-Ih表面由Ih和立方（Ic）堆疊的混合納米疇組成，形成√19×√19的周期性超結構。

密度泛函理論表明，通過最小化懸空OH鍵之間的靜電排斥，這種重構表面在理想冰表面上保持穩定。研究組還觀察到，隨著溫度的升高（超過120 K），冰表面逐漸變得無序，這表明預融化過程的開始。

表面預融化發生在Ih和Ic疇之間的缺陷邊界處，并可通過形成平面局部結構來促進。這些結果結束了長期以來關于冰表面結構的爭論，并揭示了冰預融化的分子起源，或導致對冰物理和化學理解的范式轉變。

▲ Abstract：

Ice surfaces are closely relevant to many physical and chemical properties, such as melting, freezing, friction, gas uptake and atmospheric reaction. Despite extensive experimental and theoretical investigations, the exact atomic structures of ice interfaces remain elusive owing to the vulnerable hydrogen-bonding network and the complicated premelting process. Here we realize atomic-resolution imaging of the basal (0001) surface structure of hexagonal water ice (ice Ih) by using qPlus-based cryogenic atomic force microscopy with a carbon monoxide-functionalized tip. We find that the crystalline ice-Ih surface consists of mixed Ih- and cubic (Ic)-stacking nanodomains, forming √19×√19 periodic superstructures. Density functional theory reveals that this reconstructed surface is stabilized over the ideal ice surface mainly by minimizing the electrostatic repulsion between dangling OH bonds. Moreover, we observe that the ice surface gradually becomes disordered with increasing temperature (above 120Kelvin), indicating the onset of the premelting process. The surface premelting occurs from the defective boundaries between the Ih and Ic domains and can be promoted by the formation of a planar local structure. These results put an end to the longstanding debate on ice surface structures and shed light on the molecular origin of ice premelting, which may lead to a paradigm shift in the understanding of ice physics and chemistry.

化學Chemistry

Selective lignin arylation for biomass fractionation and benign bisphenols

選擇性木質素芳基化助力生物質分餾和環境友好雙酚

▲ 作者：Ning Li, Kexin Yan, Thanya Rukkijakan, Jiefeng Liang, Yuting Liu, Zhipeng Wang, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-024-07446-5

▲ 摘要：

木質纖維素主要由疏水木質素和親水多糖聚合物組成，是綠色生物精煉不可或缺的碳資源。當化學處理時，木質素因阻礙下游過程的有害分子內和分子間交聯而受到損害。目前的增值范式旨在通過阻斷或穩定木質素的脆弱部分來避免形成新的C-C鍵，即自縮合。

盡管人們已經努力通過引入酚類添加劑來提高生物質的利用率，但尚未證實利用木質素的縮合傾向可將木質素和碳水化合物都增值為高價值產品。

研究組通過高親核性木質素衍生酚在催化芳基化途徑中引導C-C鍵形成來充分利用這種縮合傾向。選擇性縮合的木質素以接近定量的產量分離，同時保留其優異的可裂解β-醚單元，可在涉及芳基遷移和轉移氫化的串聯催化過程中解聚。因此，木材中的木質素被轉化為環境友好的雙酚（34-48 wt%），代表了其化石基同類物質的性能優勢替代品。

源自纖維素的脫木質素紙漿和源自木聚糖的木糖共同生產紡織纖維和可再生化學品。這種縮合驅動的策略代表了一項與其他頗具前景的單酚導向方法相輔相成的關鍵進展，這些方法均針對有價值的平臺化學品和材料，從而有助于整體生物質增值。

▲ Abstract：

Lignocellulose is mainly composed of hydrophobic lignin and hydrophilic polysaccharide polymers, contributing to an indispensable carbon resource for green biorefineries. When chemically treated, lignin is compromised owing to detrimental intra- and intermolecular crosslinking that hampers downstream process. The current valorization paradigms aim to avoid the formation of new C–C bonds, referred to as condensation, by blocking or stabilizing the vulnerable moieties of lignin. Although there have been efforts to enhance biomass utilization through the incorporation of phenolic additives, exploiting lignin’s proclivity towards condensation remains unproven for valorizing both lignin and carbohydrates to high-value products. Here we leverage the proclivity by directing the C–C bond formation in a catalytic arylation pathway using lignin-derived phenols with high nucleophilicity. The selectively condensed lignin, isolated in near-quantitative yields while preserving its prominent cleavable β-ether units, can be unlocked in a tandem catalytic process involving aryl migration and transfer hydrogenation. Lignin in wood is thereby converted to benign bisphenols (34–48 wt%) that represent performance-advantaged replacements for their fossil-based counterparts. Delignified pulp from cellulose and xylose from xylan are co-produced for textile fibres and renewable chemicals. This condensation-driven strategy represents a key advancement complementary to other promising monophenol-oriented approaches targeting valuable platform chemicals and materials, thereby contributing to holistic biomass valorization.