《自然》（20200910出版）一周论文导读

编译 | 李言

Nature, 10 September 2020, Volume 585 Issue 7824

《自然》2020年9月10日，第585卷，7824期

天文学Astronomy

The Magellanic Corona as the key to the formation of the Magellanic Stream

麦哲伦日冕是麦哲伦星流形成的关键

▲ 作者：S. Lucchini, E. D’Onghia, A. J. Fox, C. Bustard, J. Bland-Hawthorn & E. Zweibel

▲ 链接：https://www.nature.com/articles/s41586-020-2663-4

▲ 摘要

星系晕中主要的气体结构是麦哲伦星流。

最近几项发现——包括与麦哲伦星群相关的矮星系的发现、LMC高质量的测定、LMC中恒星附近高度电离气体的探测以及宇宙学模拟预测——都支持在LMC（麦哲伦日冕）附近有一圈温暖的（约500,000 k）电离气体存在。

在这里我们报告，通过在水动力学模拟麦哲伦云落在银河系的麦哲伦日冕，我们可以重现麦哲伦星流和它的主导臂。我们的模拟解释了麦哲伦星流的丝状结构、空间范围、径向速度梯度和总电离气体质量。

我们预测，在LMC附近的背景类星体紫外光谱的高电离吸收线中，麦哲伦日冕将是明确可见的。

▲ Abstract

The dominant gaseous structure in the Galactic halo is the Magellanic Stream. Several recent developments—including the discovery of dwarf galaxies associated with the Magellanic group, determination of the high mass of the LMC, detection of highly ionized gas near stars in the LMC and predictions of cosmological simulations —support the existence of a halo of warm (roughly 500,000 kelvin) ionized gas around the LMC (the ‘Magellanic Corona’). Here we report that, by including this Magellanic Corona in hydrodynamic simulations of the Magellanic Clouds falling onto the Milky Way, we can reproduce the Magellanic Stream and its leading arm. Our simulations explain the filamentary structure, spatial extent, radial-velocity gradient and total ionized-gas mass of the Magellanic Stream. We predict that the Magellanic Corona will be unambiguously observable via high-ionization absorption lines in the ultraviolet spectra of background quasars lying near the LMC.

量子物理Quantum Physics

Experimental deterministic correction of qubit loss

量子位丢失的实验确定校正

▲ 作者：Roman Stricker, Davide Vodola, Alexander Erhard, Lukas Postler, Michael Meth, Martin Ringbauer, et al.

▲ 链接：https://www.nature.com/articles/s41586-020-2667-0

▲ 摘要

量子计算机的成功运行依赖于保护量子位不受退相干和噪声的影响，如果不进行校正，这些噪声将导致错误的结果。

在此，我们实现了一个全周期的量子丢失检测和校正的拓扑表面代码的最小实例在捕获离子量子处理器。

用于校正的关键技术是通过辅助量子位元执行的量子非破坏测量，它充当了一个最小侵入探针，检测缺失的量子位元，同时将最小的量子力学可能的干扰传递给剩余的量子位元。

一旦检测到量子位丢失，一个恢复程序就会被实时触发，该程序将逻辑信息映射到剩余量子位上的新编码上。

虽然目前的演示是在一个截留离子量子处理器中进行的，但该协议适用于其他量子计算架构和纠错码，包括领先的二维和三维拓扑码。

▲ Abstract

The successful operation of quantum computers relies on protecting qubits from decoherence and noise, which—if uncorrected—will lead to erroneous results. Here we experimentally implement a full cycle of qubit loss detection and correction on a minimal instance of a topological surface code in a trapped-ion quantum processor. The key technique used for this correction is a quantum non-demolition measurement performed via an ancillary qubit, which acts as a minimally invasive probe that detects absent qubits while imparting the smallest quantum mechanically possible disturbance to the remaining qubits. Upon detecting qubit loss, a recovery procedure is triggered in real time that maps the logical information onto a new encoding on the remaining qubits. Although the current demonstration is performed in a trapped-ion quantum processor, the protocol is applicable to other quantum computing architectures and error correcting codes, including leading two- and three-dimensional topological codes.

材料科学Material Science

Co-designing electronics with microfluidics for more sustainable cooling

与微流体协同设计电子器件，实现更可持续的冷却

▲ 作者：Remco van Erp, Reza Soleimanzadeh, Luca Nela, Georgios Kampitsis & Elison Matioli

▲ 链接：https://www.nature.com/articles/s41586-020-2666-1

▲ 摘要

将液体冷却直接嵌入芯片内部是一种很有前途的更有效的热管理方法。然而，即使在最先进的方法，电子和冷却分开处理，留下充分的节能潜力的嵌入式冷却未开发。

在这里，我们表明，通过在同一半导体衬底内共同设计微流体和电子元件，我们可以生产一个整体集成的流形微通道冷却结构，其效率超过目前可用的。我们的结果表明，超过1.7千瓦每平方厘米的热流可以提取仅使用0.57瓦每平方厘米的泵送功率。

我们观察到，对于每平方厘米超过1千瓦的热通量的单相水冷却具有前所未有的性能系数（超过10,000），对应于直线微通道50倍的增长，以及非常高的平均努塞尔数16。

▲ Abstract

Embedding liquid cooling directly inside the chip is a promising approach for more efficient thermal management. However, even in state-of-the-art approaches, the electronics and cooling are treated separately, leaving the full energy-saving potential of embedded cooling untapped. Here we show that by co-designing microfluidics and electronics within the same semiconductor substrate we can produce a monolithically integrated manifold microchannel cooling structure with efficiency beyond what is currently available. Our results show that heat fluxes exceeding 1.7 kilowatts per square centimetre can be extracted using only 0.57 watts per square centimetre of pumping power. We observed an unprecedented coefficient of performance (exceeding 10,000) for single-phase water-cooling of heat fluxes exceeding 1 kilowatt per square centimetre, corresponding to a 50-fold increase compared to straight microchannels, as well as a very high average Nusselt number of 16.

化学Chemstry

Evidence for supercritical behaviour of high-pressure liquid hydrogen

高压液氢的超临界行为的证据

▲ 作者：Bingqing Cheng, Guglielmo Mazzola, Chris J. Pickard & Michele Ceriotti

▲ 链接：https://www.nature.com/articles/s41586-020-2677-y

▲ 摘要

氢是宇宙中最简单、最丰富的元素，在压缩过程中会表现出非常复杂的特性。

在这里，我们提出了一个理论研究的相图的致密氢使用机器学习从参考计算中“学习”势能表面和原子间的力，然后预测他们在低计算成本、克服长度和时间尺度的限制。我们重现了重入熔点的行为和固相的多态性。

使用基于机器学习的电势的模拟为液体中连续的分子到原子转变提供了证据，在熔融线上没有观察到一级转变。这表明，在巨大的气体行星中，绝缘层和金属层之间存在着平稳的过渡，同时也调和了实验中存在的超临界现象的差异。

▲ Abstract

Hydrogen, the simplest and most abundant element in the Universe, develops a remarkably complex behaviour upon compression. Here we present a theoretical study of the phase diagram of dense hydrogen that uses machine learning to ‘learn’ potential-energy surfaces and interatomic forces from reference calculations and then predict them at low computational cost, overcoming length- and timescale limitations. We reproduce both the re-entrant melting behaviour and the polymorphism of the solid phase. Simulations using our machine-learning-based potentials provide evidence for a continuous molecular-to-atomic transition in the liquid, with no first-order transition observed above the melting line. This suggests a smooth transition between insulating and metallic layers in giant gas planets, and reconciles existing discrepancies between experiments as a manifestation of supercritical behaviour.

Rare-earth–platinum alloy nanoparticles in mesoporous zeolite for catalysis

稀土-铂合金纳米颗粒在介孔沸石中的催化作用

▲ 作者：Ryong Ryoo, Jaeheon Kim, Changbum Jo, Seung Won Han, Jeong-Chul Kim, Hongjun Park, Jongho Han, et al.

▲ 链接：https://www.nature.com/articles/s41586-020-2671-4

▲ 摘要

在石油化工过程中，铂是一种常用的催化剂，通常与其他金属混合以提高催化活性、选择性和使用寿命。

这里我们使用了一种具有孔壁表面框架缺陷的介孔沸石（称为“硅醇巢”）作为支撑，表明沸石使铂和稀土元素之间形成合金。我们发现硅醇巢使稀土元素以比大块氧化物高得多的化学势以单原子形式存在，使它们有可能扩散到铂上。

高分辨率的透射电子显微镜和氢化学吸附测量表明，负载在介孔沸石上的双金属纳米颗粒是金属间化合物，我们发现它是丙烷脱氢反应的稳定、高活性和选择性催化剂。

当与=过渡金属一起使用时，同样的制备策略可以产生含有大量第二金属的铂合金催化剂，对于铂碳合金，在H2中优先氧化一氧化碳时表现出高的催化活性和选择性。

▲ Abstract

Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity. Here we use as support a mesoporous zeolite that has pore walls with surface framework defects (called ‘silanol nests’) and show that the zeolite enables alloy formation between Pt and rare-earth elements. We find that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt. High-resolution transmission electron microscopy and hydrogen chemisorption measurements indicate that the resultant bimetallic nanoparticles supported on the mesoporous zeolite are intermetallic compounds, which we find to be stable, highly active and selective catalysts for the propane dehydrogenation reaction. When used with late transition metals, the same preparation strategy produces Pt alloy catalysts that incorporate an unusually large amount of the second metal and, in the case of the PtCo alloy, show high catalytic activity and selectivity in the preferential oxidation of carbon monoxide in H2.

地球科学Geoscience

Satellite isoprene retrievals constrain emissions and atmospheric oxidation

卫星异戊二烯回收装置限制了排放和大气氧化

▲ 作者：Kelley C. Wells, Dylan B. Millet, Vivienne H. Payne, M. Julian Deventer, Kelvin H. Bates, Joost A. de Gouw, et al.

▲ 链接：https://www.nature.com/articles/s41586-020-2664-3

▲ 摘要

异戊二烯是排放到大气中的主要非甲烷有机化合物。它驱动臭氧和气溶胶的产生，调节大气氧化，并与全球氮循环相互作用。

这里我们展示了全球异戊二烯的测量从空间使用交叉跟踪红外探测器。连同对甲醛（一种异戊二烯氧化产物）的观察，这些测量提供了对异戊二烯排放和大气氧化的限制。

我们发现，从空间测量的异戊二烯-甲醛关系与目前对异戊二烯- OH化学的理解大致一致，没有迹象表明在低氮氧化物浓度下缺失OH循环。我们分析了全球四个异戊二烯热点数据集与模型预测的关系，并根据卫星对异戊二烯本身的测量结果，给出了对异戊二烯排放量的量化分析。

亚马逊地区出现了一个重大差异，在那里，目前对自然氮氧化物排放的低估偏向模拟了OH和异戊二烯。在非洲南部，我们发现一个显著的异戊二烯热点在自下而上的预测中消失了。

▲ Abstract

Isoprene is the dominant non-methane organic compound emitted to the atmosphere. It drives ozone and aerosol production, modulates atmospheric oxidation and interacts with the global nitrogen cycle. Here we present global isoprene measurements taken from space using the Cross-track Infrared Sounder. Together with observations of formaldehyde, an isoprene oxidation product, these measurements provide constraints on isoprene emissions and atmospheric oxidation. We find that the isoprene–formaldehyde relationships measured from space are broadly consistent with the current understanding of isoprene–OH chemistry, with no indication of missing OH recycling at low nitrogen oxide concentrations. We analyse these datasets over four global isoprene hotspots in relation to model predictions, and present a quantification of isoprene emissions based directly on satellite measurements of isoprene itself. A major discrepancy emerges over Amazonia, where current underestimates of natural nitrogen oxide emissions bias modelled OH and hence isoprene. Over southern Africa, we find that a prominent isoprene hotspot is missing from bottom-up predictions.

The lithospheric-to-lower-mantle carbon cycle recorded in superdeep diamonds

超深金刚石记录的岩石圈到下地幔的碳循环

▲ 作者：M. E. Regier, D. G. Pearson, T. Stachel, R. W. Luth, R. A. Stern & J. W. Harris

▲ 链接：https://www.nature.com/articles/s41586-020-2676-z

▲ 摘要

碳进入地幔是地球碳循环的重要途径，影响着气候和地表和地幔的氧化还原条件。在此，我们展示了对来自几内亚的金刚石中的矿物包裹体的氧同位素测量，这些包裹体来自于从岩石圈延伸至下地幔的深度（超过660公里）。

结合金刚石的碳和氮同位素含量，这些数据表明，在俯冲到岩石圈深处和过渡带深处（小于660公里）的板块中，碳酸化的火成岩海洋壳，而不是沉积物，是主要的含碳储层。

在这个深度范围内，亚岩石圈包裹体相对于从地壳原岩中衍生出来的发育岩石圈包裹体的氧同位素明显富集。这些亚岩石圈包裹体氧同位素含量的增加是由于富含碳酸盐的俯冲洋壳熔融结晶所致。

相比之下，下地幔矿物包裹体及其宿主金刚石（深度超过660公里）的同位素值范围很窄，这是很少或没有发生地壳相互作用的地幔的典型特征。

由于碳赋存在金属中，而不是金刚石中，在还原的、挥发性差的下地幔中，碳必须被动员和集中以形成下地幔金刚石。

我们的数据支持了一个模型，在这个模型中，俯冲的海洋岩石圈使上下层地幔的水合作用使含碳金属不稳定，从而形成金刚石，而不干扰中地幔稳定同位素特征。这种从过渡带碳酸盐岩板融化到下地幔板脱水的转变为碳俯冲提供了下地幔屏障。

▲ Abstract

The transport of carbon into Earth’s mantle is a critical pathway in Earth’s carbon cycle, affecting both the climate and the redox conditions of the surface and mantle. Here we present oxygen isotope measurements of mineral inclusions within diamonds from Kankan, Guinea that are derived from depths extending from the lithosphere to the lower mantle (greater than 660 kilometres). These data, combined with the carbon and nitrogen isotope contents of the diamonds, indicate that carbonated igneous oceanic crust, not sediment, is the primary carbon-bearing reservoir in slabs subducted to deep-lithospheric and transition-zone depths (less than 660 kilometres). Within this depth regime, sublithospheric inclusions are distinctly enriched in 18O relative to eclogitic lithospheric inclusions derived from crustal protoliths. The increased 18O content of these sublithospheric inclusions results from their crystallization from melts of carbonate-rich subducted oceanic crust. In contrast, lower-mantle mineral inclusions and their host diamonds (deeper than 660 kilometres) have a narrow range of isotopic values that are typical of mantle that has experienced little or no crustal interaction. Because carbon is hosted in metals, rather than in diamond, in the reduced, volatile-poor lower mantle, carbon must be mobilized and concentrated to form lower-mantle diamonds. Our data support a model in which the hydration of the uppermost lower mantle by subducted oceanic lithosphere destabilizes carbon-bearing metals to form diamond, without disturbing the ambient-mantle stable-isotope signatures. This transition from carbonate slab melting in the transition zone to slab dehydration in the lower mantle supports a lower-mantle barrier for carbon subduction.