天文学Astronomy Lense Thirring precession after a supermassive black hole disrupts a star 超年夜质量黑洞粉碎恒星后的兰斯-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： https://www.nature.com/articles/s41586-024-07433-w ▲ 摘要： 超年夜质量黑洞粉碎一颗恒星后，在其四周构成的吸积盘最初可能与黑洞的赤道面错位。这类错位引发了吸积盘上的相对论力矩（兰斯-蒂林效应），致使吸积盘在初期进动，而在后期与黑洞对齐，进动终止。 研究组报导，利用高节拍的X射线监测不雅测潮汐中止事务（TDE），发现了强烈、准周期性的X射线通量和温度调制。这些X射线调制年夜约距离15天，在TDE的初期阶段延续约130天。 吸积流的兰斯-蒂林进动可发生这类X射线转变，但不克不及解除其他物理机制，如辐射压力不不变性。假定典型的TDE参数，即一颗类太阳恒星的吸积盘最多延长到所谓圆化半径，而且盘面以刚体情势进动，研究组将黑洞的扰动无量纲自旋参数束缚为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 经由过程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： https://www.nature.com/articles/s41586-024-07406-z ▲ 摘要： 二维（2D）半导体因其概况无悬空键和可以或许集成到各类基底上而不受传统晶格匹配束缚，从而在单片三维（M3D）集成方面显示出庞大潜力。但是，因其原子薄的体厚，2D半导体与微电子范畴的各类高能工艺不兼容，此中多个2D电路层的M3D集成颇具挑战性。 研究组报导了一种替换的低温M3D集成方式，即经由过程范德华（vdW）层压全部预制电路层，此中加工温度节制在120℃。经由过程进一步逐层反复vdW层压工艺，在垂直标的目的上实现了10个电路层的M3D集成系统，降服了先前的热预算限制。 具体的电气特征注解，在顶部反复层压vdW电路层后，底部2D晶体管不会遭到影响。另外，经由过程vdW层间通孔垂直毗连分歧层内的器件，可实现所需系统功能的各类逻辑和异构布局。研究组的演示为制备层数增添的M3D电路供给了低温路子。 ▲ 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. 材料科学Materials Science Experiment-free exoskeleton assistance via learning in simulation 经由过程仿真进修实现无尝试外骨骼辅助 ▲ 作者：Shuzhen Luo, Menghan Jiang, Sainan Zhang, Junxi Zhu, Shuangyue Yu, Israel Dominguez Silva, et al. ▲ 链接： https://www.nature.com/articles/s41586-024-07382-4 ▲ 摘要： 外骨骼在改良人类活动机能方面具有庞大潜力。但是，其成长和普遍传布遭到长时候人体测试和手工节制法则的限制。 研究组展现了一种在仿真中进修通用节制策略的无尝试方式。该仿真进修框架操纵动力学感知的肌肉骨骼和外骨骼模子和数据驱动的强化进修，在没有人体尝试的环境下弥合摹拟与实际之间的差距。 进修节制器安装在定制的髋关节外骨骼上，可在分歧的勾当中主动生成辅助，步行、跑步和爬楼梯的代谢率别离下降24.3%、13.1%和15.4%。该框架为身体健全和步履未便的小我快速开辟和普遍采取各类辅助机械人供给了一种可推行和可扩大的策略。 ▲ 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. Ou开云体育appr 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： https://www.nature.com/articles/s41586-024-07408-x ▲ 摘要： 虽然玻璃具有没有序的类液体布局，但亦表示出类固体的机械机能。玻璃质材料的构成经由过程玻璃化进行，避免结晶和增进无定形布局。因为其怪异的光学、化学和机械机能和耐用性、多功能性和情况可延续性，玻璃是材料科学各个范畴的根本。但是，在不影响其机能的环境下工程设计玻璃材料颇具挑战性。 研究组报导了一种由短芬芳三肽YYY与布局水非共价交联激发的自觉自组织构成的超份子无定形玻璃，其怪异地连系了常常彼此矛盾的多种属性，高度刚性但可在室温下进行完全的自修复。 另外，超份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规模内是透明的。研究组在由自然氨基酸构成的简单生物有机肽玻璃中不雅察到了这类非凡特征，这代表了一种多功能材料，可助力科学和工程中的各类利用。 ▲ 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 用原子分辩率成像冰Ih的概况布局和预熔化 ▲ 作者：Jiani Hong, Ye Tian, Tiancheng Liang, Xinmeng Liu, Yizhi Song, Dong Guan, et al. ▲ 链接： https://www.nature.com/articles/s41586-024-07427-8 ▲ 摘要： 冰概况与很多物理和化学性质紧密亲密相干，如熔化、冻结、磨擦、气体接收和年夜气反映。虽然进行了年夜量的尝试和理论研究，但因为懦弱的氢键收集和复杂的预熔化进程，冰界面简直切原子布局仍难以捉摸。 研究组操纵基在qPlus的具有一氧化碳功能化尖真个低温原子力显微镜，实现了六方水冰（冰Ih）的根本（0001）概况布局的原子分辩率成像。成果发现晶体冰-Ih概况由Ih和立方（Ic）堆叠的夹杂纳米畴构成，构成 19 19的周期性超布局。 密度泛函理论注解，经由过程最小化悬空OH键之间的静电排挤，这类重构概况在抱负冰概况上连结不变。研究组还不雅察到，跟着温度的升高（跨越120 K），冰概况逐步变得无序，这注解预熔化进程的最先。 概况预熔化产生在Ih和Ic畴之间的缺点鸿沟处，并可经由过程构成平面局部布局来增进。这些成果竣事了持久以来关在冰概况布局的争辩，并揭露了冰预熔化的份子发源，或致使对冰物理和化学理解的范式改变。 ▲ 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. 化学Chemistry Selective lignin arylation for biomass fractionation and benign bisphenols 选择性木质素芳基化助力生物资分馏和情况友爱双酚 ▲ 作者：Ning Li, Kexin Yan, Thanya Rukkijakan, Jiefeng Liang, Yuting Liu, Zhipeng Wang, et al. ▲ 链接： https://www.nature.com/articles/s41586-024-07446-5 ▲ 摘要： 木质纤维素首要由疏水木质素和亲水多糖聚合物构成，是绿色生物精辟不成或缺的碳资本。当化学处置时，木质素因阻碍下流进程的有害份子内和份子间交联而遭到侵害。今朝的增值范式旨在经由过程阻断或不变木质素的懦弱部门来避免构成新的C-C键，即自缩合。 虽然人们已尽力经由过程引入酚类添加剂来提高生物资的操纵率，但还没有证实操纵木质素的缩合偏向可将木质素和碳水化合物都增值为高价值产物。 研究组经由过程高亲核性木质素衍生酚在催化芳基化路子中指导C-C键构成来充实操纵这类缩合偏向。选择性缩合的木质素以接近定量的产量分手，同时保存其优良的可裂解 -醚单位，可在触及芳基迁徙和转移氢化的串连催化进程中解聚。是以，木材中的木质素被转化为情况友爱的双酚（34-48 wt%），代表了其化石基同类物资的机能优势替换品。 源自纤维素的脱木质素纸浆和源自木聚糖的木糖配合出产纺织纤维和可再生化学品。这类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式相辅相成的要害进展，这些方式均针对有价值的平台化学品和材料，从而有助在整体生物资增值。 ▲ 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 -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.特殊声明：本文转载仅仅是出在传布信息的需要，其实不意味着代表本网站不雅点或证实其内容的真实性；如其他媒体、网站或小我从本网站转载利用，须保存本网站注明的“来历”，并自大版权等法令责任；作者假如不但愿被转载或联系转载稿费等事宜，请与我们联系。
