Nature, 21 March 2024, VOL 627, ISSUE 8004

《自然》2024年3月21日，第627卷，8004期

天文学Astronomy

At least one in a dozen stars shows evidence of planetary ingestion

至少1成恒星显示出吞噬行星的证据

▲ 作者：Fan Liu, Yuan-Sen Ting, David Yong, Bertram Bitsch, Amanda Karakas, Michael T. Murphy, et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07091-y

▲ 摘要：

恒星的化学成分可通过吸积行星物质和/或行星形成物而改变，这将从原恒星盘中移除难熔物质。这些“行星特征”表现为元素丰度差异与尘埃凝结温度之间的相关性。然而，由于未知发生率、较小振幅和恒星年龄差异较大的异质恒星样本，探测这些行星的特征颇具挑战性。

因此，共同诞生（即共生）的恒星具有相同的成分，这有助于探测行星特征。虽然此前光谱研究仅限于少数双星，但盖亚卫星有望在确认为共生的共动恒星对中探测行星的恒星化学特征。

研究组用一个明确的选择函数报告了91对共生双星系统的均匀样本的高精度化学丰度，并确定了至少7个吞噬行星的实例，对应于8%的发生率。他们确定了一个独立贝叶斯指标，可以有效地将行星特征与其他因素（如随机丰度变化和原子扩散）区分开来。

该研究提供了行星特征的证据，并通过提供对行星吞噬、形成和演化机制的观测约束，促进了对恒星-行星-化学联系的更深入理解。

▲ Abstract：

Stellar chemical compositions can be altered by ingestion of planetary material and/or planet formation, which removes refractory material from the protostellar disk. These ‘planet signatures’ appear as correlations between elemental abundance differences and the dust condensation temperature. Detecting these planet signatures, however, is challenging owing to unknown occurrence rates, small amplitudes and heterogeneous star samples with large differences in stellar ages. Therefore, stars born together (that is, co-natal) with identical compositions can facilitate the detection of planet signatures. Although previous spectroscopic studies have been limited to a small number of binary stars, the Gaia satellite provides opportunities for detecting stellar chemical signatures of planets among co-moving pairs of stars confirmed to be co-natal. Here we report high-precision chemical abundances for a homogeneous sample of ninety-one co-natal pairs of stars with a well defined selection function and identify at least seven instances of planetary ingestion, corresponding to an occurrence rate of eight per cent. An independent Bayesian indicator is deployed, which can effectively disentangle the planet signatures from other factors, such as random abundance variation and atomic diffusion. Our study provides evidence of planet signatures and facilitates a deeper understanding of the star–planet–chemistry connection by providing observational constraints on the mechanisms of planet engulfment, formation and evolution.

物理学Physics

Penning micro-trap for quantum computing

潘宁微阱助力量子计算

▲ 作者：Shreyans Jain, Tobias Sägesser, Pavel Hrmo, Celeste Torkzaban, Martin Stadler, Robin Oswald, et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07111-x

▲ 摘要：

由于高保真量子门和长相干时间，在射频阱中捕获离子是实现量子计算机的主要方法之一。然而，射频的使用对缩放提出了几个挑战，包括要求芯片与高电压的兼容性、管理功耗以及限制离子的传输和放置。

研究组实现了一个微型制造的潘宁离子阱，通过用3T磁场代替射频场来突破这些限制。他们展示了在该设置下对离子的完全量子控制，以及在芯片上方的捕获平面中任意传输离子的能力。

潘宁微阱方法的这一独特功能改进了量子电荷耦合器件架构，提高了连接性和灵活性，助力大规模捕获离子量子计算、量子模拟和量子传感的实现。

▲ Abstract：

Trapped ions in radio-frequency traps are among the leading approaches for realizing quantum computers, because of high-fidelity quantum gates and long coherence times. However, the use of radio-frequencies presents several challenges to scaling, including requiring compatibility of chips with high voltages, managing power dissipation and restricting transport and placement of ions. Here we realize a micro-fabricated Penning ion trap that removes these restrictions by replacing the radio-frequency field with a 3 T magnetic field. We demonstrate full quantum control of an ion in this setting, as well as the ability to transport the ion arbitrarily in the trapping plane above the chip. This unique feature of the Penning micro-trap approach opens up a modification of the quantum charge-coupled device architecture with improved connectivity and flexibility, facilitating the realization of large-scale trapped-ion quantum computing, quantum simulation and quantum sensing.

Pattern formation by turbulent cascades

湍流级联导致模式形成

▲ 作者：Xander M. de Wit, Michel Fruchart, Tali Khain, Federico Toschi & Vincenzo Vitelli

▲ 链接：

https://www.nature.com/articles/s41586-024-07074-z

▲ 摘要：

充分发展的湍流是一种普遍且尺度不变的混沌状态，其特征是从大尺度到小尺度的能量级联，能量级联最终因耗散而停滞。

研究组展示了如何利用这些看似无结构的湍流级联来生成模式。模式形成需要一个波长选择的过程，这通常可追溯到均匀状态的线性不稳定性。与此相反，研究组提出的机制是完全非线性的。它由湍流级联的非耗散停滞而触发：能量在中间尺度堆积，该尺度既不是系统尺度，也不是通常能量耗散的最小尺度。

利用理论和大规模模拟的结合，研究组表明这些级联诱导模式的可调波长可通过称为“奇粘度”的非耗散传输系数来设置，奇粘度在从生物活性到量子系统的手性流体中普遍存在。奇粘度作为一种尺度依赖的类科里奥利力，在小尺度上导致流体二维化，与旋转流体在大尺度上发生二维化相反。

除奇粘度流体外，研究组还讨论了级联诱导模式如何在自然系统中出现，包括大气流动、恒星等离子体（如太阳风），或质量而非能量级联的物体或液滴的粉碎和凝结。

▲ Abstract：

Fully developed turbulence is a universal and scale-invariant chaotic state characterized by an energy cascade from large to small scales at which the cascade is eventually arrested by dissipation. Here we show how to harness these seemingly structureless turbulent cascades to generate patterns. Pattern formation entails a process of wavelength selection, which can usually be traced to the linear instability of a homogeneous state. By contrast, the mechanism we propose here is fully nonlinear. It is triggered by the non-dissipative arrest of turbulent cascades: energy piles up at an intermediate scale, which is neither the system size nor the smallest scales at which energy is usually dissipated. Using a combination of theory and large-scale simulations, we show that the tunable wavelength of these cascade-induced patterns can be set by a non-dissipative transport coefficient called odd viscosity, ubiquitous in chiral fluids ranging from bioactive to quantum systems. Odd viscosity, which acts as a scale-dependent Coriolis-like force, leads to a two-dimensionalization of the flow at small scales, in contrast with rotating fluids in which a two-dimensionalization occurs at large scales. Apart from odd viscosity fluids, we discuss how cascade-induced patterns can arise in natural systems, including atmospheric flows, stellar plasma such as the solar wind, or the pulverization and coagulation of objects or droplets in which mass rather than energy cascades.

Photonic chip-based low-noise microwave oscillator

基于光子芯片的低噪声微波振荡器

▲ 作者：Igor Kudelin, William Groman, Qing-Xin Ji, Joel Guo, Megan L. Kelleher, Dahyeon Lee, et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07058-z

▲ 摘要：

许多现代技术都依赖于微波信号的低相位噪声和精确时序稳定性。人们在微波光子学领域已取得了重大进展，利用频率梳对超稳定光基准进行下变频，以产生低噪声微波信号。然而，这样的系统是由块体或光纤构成的，很难进一步减小尺寸和功耗。

在这项工作中，研究组基于集成光子学的进展，通过两点光分频产生低噪声微波来解决这一挑战。将窄线宽自注入锁定集成激光器稳定在一个微型法布里-珀罗腔中，并用高效暗孤子频率梳来划分激光器之间的频率间隙。

微梳稳定输出的光检测产生20 GHz的微波信号，在100 Hz偏移频率下相位噪声为-96 dBc Hz^-1，在10 kHz偏移频率下降至-135 dBc Hz^-1，该值对于集成光子系统而言前所未有。所有光子元件都可以异质集成在单个芯片上，这为光子学在高精度导航、通信和计时系统中的应用奠定了基础。

▲ Abstract：

Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb. Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division. Narrow-linewidth self-injection-locked integrated lasers are stabilized to a miniature Fabry–Pérot cavity, and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb. The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of 96 dBc Hz^-1 at 100 Hz offset frequency that decreases to 135 dBc Hz^-1 at 10 kHz offset—values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems.

化学Chemistry

Oxidative cyclization reagents reveal tryptophan cation–π interactions

氧化环化试剂揭示色氨酸阳离子-π相互作用

▲ 作者：Xiao Xie, Patrick J. Moon, Steven W. M. Crossley, Amanda J. Bischoff, Dan He, Gen Li, et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07140-6

▲ 摘要：

蛋白质上氨基酸的选择性共价修饰方法可实现从蛋白质功能探针和调节剂到蛋白质组学的一系列应用。半胱氨酸和赖氨酸残基因其高亲核性，是通过酸碱反应性进行蛋白质生物偶联化学反应中最常见的附着点。

研究组报道了一种基于氧化还原的色氨酸（最稀有的氨基酸）生物偶联策略，使用氧氮丙啶试剂模拟吲哚类生物碱生物合成途径中的氧化环化反应，以实现高效和特异性的色氨酸标记。

他们展示了这种被称为色氨酸环化化学连接（Trp-CLiC）方法的广泛应用，用于选择性地将有效载荷附加到肽和蛋白质的色氨酸残基上，其反应速率可与传统的点击反应相媲美，并实现在整个蛋白质组中对高反应性色氨酸位点进行全局分析。

值得注意的是，这些试剂揭示了参与阳离子-π相互作用的色氨酸残基的系统图谱，包括可调节蛋白质介导相分离过程的功能位点。

▲ Abstract：

Methods for selective covalent modification of amino acids on proteins can enable a diverse array of applications, spanning probes and modulators of protein function to proteomics. Owing to their high nucleophilicity, cysteine and lysine residues are the most common points of attachment for protein bioconjugation chemistry through acid–base reactivity. Here we report a redox-based strategy for bioconjugation of tryptophan, the rarest amino acid, using oxaziridine reagents that mimic oxidative cyclization reactions in indole-based alkaloid biosynthetic pathways to achieve highly efficient and specific tryptophan labelling. We establish the broad use of this method, termed tryptophan chemical ligation by cyclization (Trp-CLiC), for selectively appending payloads to tryptophan residues on peptides and proteins with reaction rates that rival traditional click reactions and enabling global profiling of hyper-reactive tryptophan sites across whole proteomes. Notably, these reagents reveal a systematic map of tryptophan residues that participate in cation–π interactions, including functional sites that can regulate protein-mediated phase-separation processes.

地球科学One Earth

Global prediction of extreme floods in ungauged watersheds

未测量流域极端洪水的全球预测

▲ 作者：Grey Nearing, Deborah Cohen, Vusumuzi Dube, Martin Gauch, Oren Gilon, Shaun Harrigan, et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07145-1

▲ 摘要：

洪水是最常见的自然灾害之一，对通常缺乏密集流量测量网络的发展中国家构成了巨大威胁。准确及时的预警对于减轻洪水风险至关重要，但水文模拟模型通常必须根据每个流域的长期数据记录进行校准。

研究组展示了人工智能预警在长达五天的提前期内预测未测量流域极端河流事件方面的可靠性，可与当前最先进全球模型系统（哥白尼应急管理服务全球洪水预警系统）实时预报（零日提前期）的可靠性相媲美。此外，在五年以上回归期事件中实现的精度优于当前一年以上回归期事件的精度。

这意味着人工智能可在未测量流域更大、更有影响力的事件中更早地提供洪水预警。该开发模型被纳入一个可操作的早期预警系统，该系统在80多个国家提供公开（免费和开放）的实时预报。这项工作强调了增加水文数据可用性的必要性，以持续改善全球获得可靠洪水预警的机会。

▲ Abstract：

Floods are one of the most common natural disasters, with a disproportionate impact in developing countries that often lack dense streamflow gauge networks. Accurate and timely warnings are critical for mitigating flood risks, but hydrological simulation models typically must be calibrated to long data records in each watershed. Here we show that artificial intelligence-based forecasting achieves reliability in predicting extreme riverine events in ungauged watersheds at up to a five-day lead time that is similar to or better than the reliability of nowcasts (zero-day lead time) from a current state-of-the-art global modelling system (the Copernicus Emergency Management Service Global Flood Awareness System). In addition, we achieve accuracies over five-year return period events that are similar to or better than current accuracies over one-year return period events. This means that artificial intelligence can provide flood warnings earlier and over larger and more impactful events in ungauged basins. The model developed here was incorporated into an operational early warning system that produces publicly available (free and open) forecasts in real time in over 80 countries. This work highlights a need for increasing the availability of hydrological data to continue to improve global access to reliable flood warnings.