編譯 | 未玖
Nature , 21 March 2024, VOL 627, ISSUE 8004
【自然】 2024年3月21日，第627卷，8004期
天文學 Astronomy
At least one in a dozen stars shows evidence of planetary ingestion
至少1成恒星顯示出吞噬行星的證據
▲ 作者：Fan Liu, Yuan-Sen Ting, David Yong, Bertram Bitsch, Amanda Karakas, Michael T. Murphy, et al.
▲ 連結：
https://www.nature.com/articles/s41586-024-07091-y
▲ 摘要：
恒星的化學成分可透過吸積行星物質和/或行星形成物而改變，這將從原恒星盤中移除難熔物質。這些「行星特征」表現為元素豐度差異與塵埃凝結溫度之間的相關性。然而，由於未知發生率、較小振幅和恒星年齡差異較大的異質恒星樣本，探測這些行星的特征頗具挑戰性。
因此，共同誕生（即共生）的恒星具有相同的成分，這有助於探測行星特征。雖然此前光譜研究僅限於少數雙星，但蓋亞衛星有望在確認為共生的共動恒星對中探測行星的恒星化學特征。
研究組用一個明確的選擇函式報告了91對共生雙星系統的均勻樣本的高精度化學豐度，並確定了至少7個吞噬行星的例項，對應於8%的發生率。他們確定了一個獨立貝葉斯指標，可以有效地將行星特征與其他因素（如隨機豐度變化和原子擴散）區分開來。
該研究提供了行星特征的證據，並透過提供對行星吞噬、形成和演化機制的觀測約束，促進了對恒星-行星-化學聯系的更深入理解。
▲ 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.
物理學 Physics
Penning micro-trap for quantum computing
潘寧微阱助力量子計算
▲ 作者：Shreyans Jain, Tobias Sägesser, Pavel Hrmo, Celeste Torkzaban, Martin Stadler, Robin Oswald, et al.
▲ 連結：
https://www.nature.com/articles/s41586-024-07111-x
▲ 摘要：
由於高保真量子門和長相幹時間，在射頻阱中捕獲離子是實作量子電腦的主要方法之一。然而，射頻的使用對縮放提出了幾個挑戰，包括要求芯片與高電壓的相容性、管理功耗以及限制離子的傳輸和放置。
研究組實作了一個微型制造的潘寧離子阱，透過用3T磁場代替射頻場來突破這些限制。他們展示了在該設定下對離子的完全量子控制，以及在芯片上方的捕獲平面中任意傳輸離子的能力。
潘寧微阱方法的這一獨特功能改進了量子電荷耦合器件架構，提高了連線性和靈活性，助力大規模捕獲離子量子計算、量子模擬和量子傳感的實作。
▲ 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
亂流級聯導致模式形成
▲ 作者：Xander M. de Wit, Michel Fruchart, Tali Khain, Federico Toschi & Vincenzo Vitelli
▲ 連結：
https://www.nature.com/articles/s41586-024-07074-z
▲ 摘要：
充分發展的亂流是一種普遍且尺度不變的混沌狀態，其特征是從大尺度到小尺度的能量級聯，能量級聯最終因耗散而停滯。
研究組展示了如何利用這些看似無結構的亂流級聯來生成模式。模式形成需要一個波長選擇的過程，這通常可追溯到均勻狀態的線性不穩定性。與此相反，研究組提出的機制是完全非線性的。它由亂流級聯的非耗散停滯而觸發：能量在中間尺度堆積，該尺度既不是系統尺度，也不是通常能量耗散的最小尺度。
利用理論和大規模模擬的結合，研究組表明這些級聯誘導模式的可調波長可透過稱為「奇粘度」的非耗散傳輸系數來設定，奇粘度在從生物活性到量子系統的手性流體中普遍存在。奇粘度作為一種尺度依賴的類科裏奧利力，在小尺度上導致流體二維化，與旋轉流體在大尺度上發生二維化相反。
除奇粘度流體外，研究組還討論了級聯誘導模式如何在自然系統中出現，包括大氣流動、恒星電漿（如太陽風），或品質而非能量級聯的物體或液滴的粉碎和凝結。
▲ 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
基於光子芯片的低雜訊微波振蕩器
▲ 作者：Igor Kudelin, William Groman, Qing-Xin Ji, Joel Guo, Megan L. Kelleher, Dahyeon Lee, et al.
▲ 連結：
https://www.nature.com/articles/s41586-024-07058-z
▲ 摘要：
許多現代技術都依賴於微波訊號的低相位雜訊和精確時序穩定性。人們在微波光子學領域已取得了重大進展，利用頻率梳對超穩定光基準進行下變頻，以產生低雜訊微波訊號。然而，這樣的系統是由塊體或光纖構成的，很難進一步減小尺寸和功耗。
在這項工作中，研究組基於整合光子學的進展，透過兩點光分頻產生低雜訊微波來解決這一挑戰。將窄線寬自註入釘選整合雷射器穩定在一個微型法布立-培若腔中，並用高效暗孤子頻率梳來劃分雷射器之間的頻率間隙。
微梳穩定輸出的光檢測產生20 GHz的微波訊號，在100 Hz偏移頻率下相位雜訊為-96 dBc Hz-1，在10 kHz偏移頻率下降至-135 dBc Hz-1，該值對於整合光子系統而言前所未有。所有光子元件都可以異質整合在單個芯片上，這為光子學在高精度導航、通訊和計時系統中的套用奠定了基礎。
▲ 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.
化學 Chemistry
Oxidative cyclization reagents reveal tryptophan cation–π interactions
氧化環化試劑揭示色胺酸陽離子-π交互作用
▲ 作者：Xiao Xie, Patrick J. Moon, Steven W. M. Crossley, Amanda J. Bischoff, Dan He, Gen Li, et al.
▲ 連結：
https://www.nature.com/articles/s41586-024-07140-6
▲ 摘要：
蛋白質上胺基酸的選擇性共價修飾方法可實作從蛋白質功能探針和調節劑到蛋白質組學的一系列套用。半胱胺酸和賴胺酸殘基因其高親核性，是透過酸堿反應性進行蛋白質生物偶聯化學反應中最常見的附著點。
研究組報道了一種基於氧化還原的色胺酸（最稀有的胺基酸）生物偶聯策略，使用氧氮丙啶試劑模擬吲哚類生物堿生物合成途徑中的氧化環化反應，以實作高效和特異性的色胺酸標記。
他們展示了這種被稱為色胺酸環化化學連線（Trp-CLiC）方法的廣泛套用，用於選擇性地將有效載荷附加到肽和蛋白質的色胺酸殘基上，其反應速率可與傳統的點選反應相媲美，並實作在整個蛋白質組中對高反應性色胺酸位元點進行全域分析。
值得註意的是，這些試劑揭示了參與陽離子-π交互作用的色胺酸殘基的系統圖譜，包括可調節蛋白質介導相分離過程的功能位點。
▲ 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.
地球科學 One Earth
Global prediction of extreme floods in ungauged watersheds
未測量流域極端洪水的全球預測
▲ 作者：Grey Nearing, Deborah Cohen, Vusumuzi Dube, Martin Gauch, Oren Gilon, Shaun Harrigan, et al.
▲ 連結：
https://www.nature.com/articles/s41586-024-07145-1
▲ 摘要：
洪水是最常見的自然災害之一，對通常缺乏密集流量測量網路的開發中國家構成了巨大威脅。準確及時的預警對於減輕洪水風險至關重要，但水文模擬模型通常必須根據每個流域的長期數據記錄進行校準。
研究組展示了人工智慧預警在長達五天的提前期內預測未測量流域極端河流事件方面的可靠性，可與當前最先進全球模型系統（哥白尼應急管理服務全球洪水預警系統）即時預報（零日提前期）的可靠性相媲美。此外，在五年以上回歸期事件中實作的精度優於當前一年以上回歸期事件的精度。
這意味著人工智慧可在未測量流域更大、更有影響力的事件中更早地提供洪水預警。該開發模型被納入一個可操作的早期預警系統，該系統在80多個國家提供公開（免費和開放）的即時預報。這項工作強調了增加水文數據可用性的必要性，以持續改善全球獲得可靠洪水預警的機會。
▲ 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.
