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Nature, 13 June 2024, VOL 630, ISSUE 8016

《自然》2024年6月13日，第630卷，8016期

天文学Astronomy

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

超大质量黑洞破坏恒星后的兰斯-蒂林进动

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

▲ 链接：

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

▲ 摘要：

超大质量黑洞破坏一颗恒星后，在其周围形成的吸积盘最初可能与黑洞的赤道面错位。这种错位引起了吸积盘上的相对论力矩（兰斯-蒂林效应），导致吸积盘在早期进动，而在后期与黑洞对齐，进动终止。

研究组报道，使用高节奏的X射线监测观测潮汐中断事件（TDE），发现了强烈、准周期性的X射线通量和温度调制。这些X射线调制大约间隔15天，在TDE的早期阶段持续约130天。

吸积流的兰斯-蒂林进动可产生这种X射线变化，但不能排除其他物理机制，如辐射压力不稳定性。假设典型的TDE参数，即一颗类太阳恒星的吸积盘最多延伸到所谓圆化半径，并且盘面以刚体形式进动，研究组将黑洞的扰动无量纲自旋参数约束为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.

物理学Physics

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

通过范德华层压实现单片三维逐层集成

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

▲ 链接：

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

▲ 摘要：

二维（2D）半导体因其表面无悬空键和能够集成到各种基底上而不受传统晶格匹配约束，从而在单片三维（M3D）集成方面显示出巨大潜力。然而，因其原子薄的体厚，2D半导体与微电子领域的各种高能工艺不兼容，其中多个2D电路层的M3D集成颇具挑战性。

研究组报道了一种替代的低温M3D集成方法，即通过范德华（vdW）层压整个预制电路层，其中加工温度控制在120℃。通过进一步逐层重复vdW层压工艺，在垂直方向上实现了10个电路层的M3D集成系统，克服了先前的热预算限制。

详细的电气特性表明，在顶部重复层压vdW电路层后，底部2D晶体管不会受到影响。此外，通过vdW层间通孔垂直连接不同层内的器件，可实现所需系统功能的各种逻辑和异构结构。研究组的演示为制备层数增加的M3D电路提供了低温途径。

▲ 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.

材料明升体育appMaterials Science

Experiment-free exoskeleton assistance via learning in simulation

通过仿真学习实现无实验外骨骼辅助

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

▲ 链接：

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

▲ 摘要：

外骨骼在改善人类运动性能方面具有巨大潜力。然而，其发展和广泛传播受到长时间人体测试和手工控制规则的限制。

研究组展示了一种在仿真中学习通用控制策略的无实验方法。该仿真学习框架利用动力学感知的肌肉骨骼和外骨骼模型以及数据驱动的强明升手机习，在没有人体实验的情况下弥合模拟与现实之间的差距。

学习控制器安装在定制的髋关节外骨骼上，可在不同的活动中自动生成辅助，步行、跑步和爬楼梯的代谢率分别降低24.3%、13.1%和15.4%。该框架为身体健全和行动不便的个人快速开发和广泛采用各种辅助机器人提供了一种可推广和可扩展的策略。

▲ 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

一种自修复的多光谱透明胶肽玻璃

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

▲ 链接：

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

▲ 摘要：

尽管玻璃具有无序的类液体结构，但亦表现出类固体的机械性能。玻璃质材料的形成通过玻璃化进行，防止结晶和促进无定形结构。由于其独特的光学、明升手机和机械性能以及耐用性、多功能性和环境可持续性，玻璃是材料明升体育app各个领域的基础。然而，在不影响其性能的情况下工程设计玻璃材料颇具挑战性。

研究组报道了一种由短芳香三肽YYY与结构水非共价交联引发的自发自组织形成的超分子无定形玻璃，其独特地结合了经常相互矛盾的多种属性，高度刚性但可在室温下进行完全的自修复。

此外，超分子玻璃是一种极强的粘合剂，但其在从可见光到中红外的宽光谱范围内是透明的。研究组在由天然氨基酸组成的简单生物有机肽玻璃中观察到了这种特殊特性，这代表了一种多功能材料，可助力明升体育app和工程中的各种应用。

▲ 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的表面结构和预融化

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

▲ 链接：

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

▲ 摘要：

冰表面与许多物理和明升手机性质密切相关，如融化、冻结、摩擦、气体吸收和大气反应。尽管进行了大量的实验和理论研究，但由于脆弱的氢键网络和复杂的预融化过程，冰界面的确切原子结构仍难以捉摸。

研究组利用基于qPlus的具有一氧化碳功能化尖端的低温原子力显微镜，实现了六方水冰（冰Ih）的基础（0001）表面结构的原子分辨率成像。结果发现晶体冰-Ih表面由Ih和立方（Ic）堆叠的混合纳米畴组成，形成√19×√19的周期性超结构。

密度泛函理论表明，通过最小化悬空OH键之间的静电排斥，这种重构表面在理想冰表面上保持稳定。研究组还观察到，随着温度的升高（超过120 K），冰表面逐渐变得无序，这表明预融化过程的开始。

表面预融化发生在Ih和Ic畴之间的缺陷边界处，并可通过形成平面局部结构来促进。这些结果结束了长期以来关于冰表面结构的争论，并揭示了冰预融化的分子起源，或导致对冰物理和明升手机理解的范式转变。

▲ 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.

明升手机Chemistry

Selective lignin arylation for biomass fractionation and benign bisphenols

选择性木质素芳基化助力生物质分馏和环境友好双酚

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

▲ 链接：

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

▲ 摘要：

木质纤维素主要由疏水木质素和亲水多糖聚合物组成，是绿色生物精炼不可或缺的碳资源。当明升手机处理时，木质素因阻碍下游过程的有害分子内和分子间交联而受到损害。目前的增值范式旨在通过阻断或稳定木质素的脆弱部分来避免形成新的C-C键，即自缩合。

尽管人们已经努力通过引入酚类添加剂来提高生物质的利用率，但尚未证实利用木质素的缩合倾向可将木质素和碳水化合物都增值为高价值产品。

研究组通过高亲核性木质素衍生酚在催化芳基化途径中引导C-C键形成来充分利用这种缩合倾向。选择性缩合的木质素以接近定量的产量分离，同时保留其优异的可裂解β-醚单元，可在涉及芳基迁移和转移氢化的串联催化过程中解聚。因此，木材中的木质素被转化为环境友好的双酚（34-48 wt%），代表了其化石基同类物质的性能优势替代品。

源自纤维素的脱木质素纸浆和源自木聚糖的木糖共同生产纺织纤维和可再生明升手机品。这种缩合驱动的策略代表了一项与其他颇具前景的单酚导向方法相辅相成的关键进展，这些方法均针对有价值的平台明升手机品和材料，从而有助于整体生物质增值。

▲ 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.