翻译 | 宗华

Nature, 10 October 2019, Volume 574 Issue 7777

《自然》2019年10月10日 第574卷 7777期

化学Chemistry

Tuning element distribution, structure and properties by composition in high-entropy alloys

通过成分调整高熵合金中的元素分布、结构和性能

作者：Qingqing Ding, Yin Zhang, Xiao Chen, et al

链接：

https://www.nature.com/articles/s41586-019-1617-1

摘要：

高熵合金是一类含有5种或5种以上元素的物质。其中，这些元素的原子比例几乎相等。高熵合金的非常规成分和化学结构有望实现前所未有的机械性能组合。

这里，我们利用原子分辨率化学映射，揭示了被广泛研究的面心立方CrMnFeCoNi Cantor合金和一种新的面心立方合金CrFeCoNiPd的元素分布。

在Cantor合金中，5种成分元素的分布是相对随机和均匀的。相反，在CrFeCoNiPd合金中，均匀性明显下降。其中，钯原子的原子尺寸和电负性明显不同于其他元素。

所有这5种元素都倾向于表现出更大的聚合，且初始浓度波的波长最小为1到3纳米。

Abstract

High-entropy alloys are a class of materials that contain five or more elements in near-equiatomic proportions. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical properties. Here we use atomic-resolution chemical mapping to reveal the element distribution of the widely studied face-centred cubic CrMnFeCoNi Cantor alloy and of a new face-centred cubic alloy, CrFeCoNiPd. In the Cantor alloy, the distribution of the five constituent elements is relatively random and uniform. By contrast, in the CrFeCoNiPd alloy, in which the palladium atoms have a markedly different atomic size and electronegativity from the other elements, the homogeneity decreases considerably; all five elements tend to show greater aggregation, with a wavelength of incipient concentration waves as small as 1 to 3 nanometres.

Analogue quantum chemistry simulation

量子化学模拟的相似体

作者：Javier Argüello-Luengo, Alejandro González-Tudela, Tao Shi, et al

链接：

https://www.nature.com/articles/s41586-019-1614-4

摘要：

高精度计算分子的电子结构是量子化学领域的一个核心挑战。

尽管近似方法取得了成功，但在传统计算机上精确地解决这个问题仍是一项艰巨的任务。

这里，我们提出了一种模拟方法来模拟量子化学问题。

它依赖于两种技术的精心组合：光学晶格中的超冷原子和腔量子电动力学。

在该模拟器中，在光电势中跳跃的费米原子扮演了电子的角色，附加的光电势提供原子核的吸引力，同时莫特绝缘体中的单自旋激发利用空腔模式调节电子库仑斥力。我们确定了模拟器的运行条件，并利用一个简单的分子进行了测试。

Abstract

Computing the electronic structure of molecules with high precision is a central challenge in the field of quantum chemistry. Despite the success of approximate methods, tackling this problem exactly with conventional computers remains a formidable task. Here we present an analogue approach to the simulation of quantum chemistry problems that relies on the careful combination of two technologies: ultracold atoms in optical lattices and cavity quantum electrodynamics. In the proposed simulator, fermionic atoms hopping in an optical potential play the role of electrons, additional optical potentials provide the nuclear attraction, and a single-spin excitation in a Mott insulator mediates the electronic Coulomb repulsion with the help of a cavity mode. We determine the operational conditions of the simulator and test it using a simple molecule.

古气候学Paleoclimatology

Constraints on global mean sea level during Pliocene warmth

上新世温暖期全球平均海平面的制约因素

作者：Oana A. Dumitru, Jacqueline Austermann, Victor J. Polyak, et al

链接：

https://www.nature.com/articles/s41586-019-1543-2

摘要：

重建海平面在过去较温暖时期（如上新世）的演变，有助于深入了解海平面和冰盖对长期变暖的反应。

尽管在此期间对全球平均海平面（GMSL）的估测确实存在，但它们相差几十米。这阻碍了对过去和未来冰盖稳定性的评估。

这里，我们证实，在温度比工业化前平均高出两到三摄氏度的中新世暖期，由于全球冰量的变化，GMSL比今天高出16.2米。当海洋热膨胀被包括在内时，要高出约17.4米。

我们的结果表明，在更温暖的上新世气候最适宜期（大约比工业化前的温度高4摄氏度），GMSL比现在的水平高23.5米，同时热膨胀额外增加了1.6米。数据表明，冰盖对气候变暖非常敏感，从而为未来的冰盖模型提供了重要的校准指标。

Abstract

Reconstructing the evolution of sea level during past warmer epochs such as the Pliocene provides insight into the response of sea level and ice sheets to prolonged warming. Although estimates of the global mean sea level (GMSL) during this time do exist, they vary by several tens of metres, hindering the assessment of past and future ice-sheet stability. Here we show that during the mid-Piacenzian Warm Period, which was on average two to three degrees Celsius warmer than the pre-industrial period5, the GMSL was about 16.2 metres higher than today owing to global ice-volume changes, and around 17.4 metres when thermal expansion of the oceans is included. During the even warmer Pliocene Climatic Optimum (about four degrees Celsius warmer than pre-industrial levels), our results show that the GMSL was 23.5 metres above the present level, with an additional 1.6 metres from thermal expansion. Our data indicate that ice sheets are very sensitive to warming and provide important calibration targets for future ice-sheet models.

The amplitude and origin of sea-level variability during the Pliocene epoch

上新世海平面变化幅度及其成因

作者：G. R. Grant, T. R. Naish, G. B. Dunbar, et al

链接：

https://www.nature.com/articles/s41586-019-1619-z

摘要：

当下的地球气候越来越像超过300万年（Ma）前的中新世温暖期。当时，大气二氧化碳浓度约为百万分之400，因响应轨道驱动和全球平均海平面（GMSL）达到峰值而振荡的全球海平面可能比今年的平均值高出约20米。

然而，在冰期—间冰期循环内，海平面变化的相对幅度仍然很有限。

我们校准了现代波浪输沙与水深之间的理论关系，然后将该技术应用于新西兰旺加努伊盆地800米厚上新世浅海沉积层序列的粒度。

通过这种方法得到的水深变化，经构造沉降修正后，得到循环相对海平面（RSL）变化。我们证实，在上新世中后期（约3.3-2.5 Ma），海平面在冰期—间冰期循环期间平均变化了13±5米。

Abstract

Earth is heading towards a climate that last existed more than three million years ago (Ma) during the ‘mid-Pliocene warm period’, when atmospheric carbon dioxide concentrations were about 400 parts per million, global sea level oscillated in response to orbital forcing and peak global-mean sea level (GMSL) may have reached about 20 metres above the present-day value. Yet the relative amplitude of sea-level variations within glacial–interglacial cycles remains poorly constrained. To address this, we calibrate a theoretical relationship between modern sediment transport by waves and water depth, and then apply the technique to grain size in a continuous 800-metre-thick Pliocene sequence of shallow-marine sediments from Whanganui Basin, New Zealand. Water-depth variations obtained in this way, after corrections for tectonic subsidence, yield cyclic relative sea-level (RSL) variations. Here we show that sea level varied on average by 13 ± 5 metres over glacial–interglacial cycles during the middle-to-late Pliocene (about 3.3–2.5 Ma).

地质学/天文学Geology/Astronomy

Real-time discrimination of earthquake foreshocks and aftershocks

实时识别地震前震和余震

作者：Laura Gulia & Stefan Wiemer

链接：

https://www.nature.com/articles/s41586-019-1606-4

摘要：

在一次大地震之后，公众和决策者提出的主要问题是：这是主震还是一次更强烈地震的前震。

这里，我们分析了最近几年发生的意大利Amatrice–Norcia地震序列和日本熊本地震序列的余震平均大小分布。

我们认为，在很多情况下，有可能区分一次正在进行的地震序列是正在衰减的余震序列还是即将到来的大地震的前震。

据此，我们提出了一种简单的红绿灯分类法。它可以实时评估对后续更大地震的关注程度，并对58个地震序列进行测试，实现了95%的分类准确率。

Abstract

Immediately after a large earthquake, the main question asked by the public and decision-makers is whether it was the mainshock or a foreshock to an even stronger event yet to come. Here we analyse the average size distribution of aftershocks of the recent Amatrice–Norcia and Kumamoto earthquake sequences, and we suggest that in many cases it may be possible to discriminate whether an ongoing sequence represents a decaying aftershock sequence or foreshocks to an upcoming large event. We propose a simple traffic light classification to assess in real time the level of concern about a subsequent larger event and test it against 58 sequences, achieving a classification accuracy of 95 per cent.

Stellar mergers as the origin of magnetic massive stars

恒星合并作为磁性大质量恒星的起源

作者：Fabian R. N. Schneider, Sebastian T. Ohlmann, Philipp Podsiadlowski, et al

链接：

https://www.nature.com/articles/s41586-019-1621-5

摘要：

约10%的“大质量”恒星（质量大于1.5倍太阳质量的恒星）拥有强烈的、大规模的表面磁场。

这里，我们报告了对两颗大质量恒星合并的三维磁铃动力学模拟结果，并跟踪了合并产物的演化。在模拟中产生了强大的磁场，同时合并后的恒星变得年轻，比其他同时期的恒星看起来更年轻、更蓝。

这可以解释天蝎座上部组中磁性“蓝离散星”τ Sco的性质。根据观察推断，τ Sco拥有明显小于500万岁的年龄，不到其诞生的天蝎座上部组年龄的一半。

Abstract

About ten per cent of ‘massive’ stars (those of more than 1.5 solar masses) have strong, large-scale surface magnetic fields. Here we report three-dimensional magnetohydrodynamical simulations of the coalescence of two massive stars and follow the evolution of the merged product. Strong magnetic fields are produced in the simulations, and the merged star rejuvenates such that it appears younger and bluer than other coeval stars. This can explain the properties of the magnetic ‘blue straggler’ star τ Sco in the Upper Scorpius association that has an observationally inferred, apparent age of less than five million years, which is less than half the age of its birth association.

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