自然期刊阅读（自然20221020出版一周论文导读）

编译 | 未玖

Nature, 20 October 2022, VOL 610, ISSUE 7932

《自然》2022年10月20日，第610卷，7932期

天文学Astronomy

A dense 0.1-solar-mass star in a 51-minute-orbital-period eclipsing binary

0.1太阳质量恒星、轨道周期为51分钟的食双星

▲ 作者：Kevin B. Burdge, Kareem El-Badry, Thomas R. Marsh, Saul Rappaport, Warren R. Brown, Ilaria Caiazzo, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05195-x

▲ 摘要：

在一千多个已知的激变变星（CVs）中，白矮星从富氢恒星吸积，只有十几个轨道周期低于75分钟。实现这种短周期的一种方法是，供体恒星在与白矮星相互作用之前，必须经历实质性的核演化，预计CVs将过渡至氦吸积。

这些过渡CVs被认为是氦CVs的前身。然而，已知的过渡CV无法达到一个足够短的轨道周期来解释大部分氦CV群，这使得该进化路径的作用尚不明确。

研究组报道了ZTF J1813 4251的观测结果，这是一个51分钟轨道周期的完全食双星系统，由一颗温度与太阳相当，但由于成分富氦，密度是太阳100倍的恒星，吸积至另一颗白矮星上。

相分辨光谱、多波段光曲线和宽带光谱能量分布使研究组能够获得对该食双星的质量、半径和温度的精确而稳健的约束。进化模型显示，ZTF J1813 4251注定会成为氦CV双星，轨道周期在20分钟以内，ZTF J1813 4251填补了氦CV双星和富氢CV双星之间此前缺失的一环。

▲ Abstract：

Of more than a thousand known cataclysmic variables (CVs), where a white dwarf is accreting from a hydrogen-rich star, only a dozen have orbital periods below 75 minutes. One way to achieve these short periods requires the donor star to have undergone substantial nuclear evolution before interacting with the white dwarf, and it is expected that these objects will transition to helium accretion. These transitional CVs have been proposed as progenitors of helium CVs. However, no known transitional CV is expected to reach an orbital period short enough to account for most of the helium CV population, leaving the role of this evolutionary pathway unclear. Here we report observations of ZTF J1813 4251, a 51-minute-orbital-period, fully eclipsing binary system consisting of a star with a temperature comparable to that of the Sun but a density 100 times greater owing to its helium-rich composition, accreting onto a white dwarf. Phase-resolved spectra, multi-band light curves and the broadband spectral energy distribution allow us to obtain precise and robust constraints on the masses, radii and temperatures of both components. Evolutionary modelling shows that ZTF J1813 4251 is destined to become a helium CV binary, reaching an orbital period under 20 minutes, rendering ZTF J1813 4251 a previously missing link between helium CV binaries and hydrogen-rich CVs.

物理学Physics

Enhanced interactions of interlayer excitons in free-standing heterobilayers

独立异质双层中层间激子的增强相互作用

▲ 作者：Xueqian Sun, Yi Zhu, Hao Qin, Boqing Liu, Yilin Tang, Tieyu Lü, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05193-z

▲ 摘要：

层间激子（IXs）之间强长程偶极-偶极相互作用可产生新型多粒子关联机制，驱动系统进入不同的量子和经典相，包括偶极液体、晶体和超流体。人们在理论上已预测了半导体双层中IXs间的排斥和吸引偶极-偶极相互作用，但迄今为止只有排斥相互作用的实验报道。

课题组研究了独立、扭曲的（51°、53°、45°）二硒化钨/二硫化钨（WSe2/WS2）异质双层，在其中观察到IXs间的偶极相互作用性质从排斥转变为吸引。这是由量子交换相关效应引起的，导致出现了一个稳健的层间双激子相（由两个IXs形成），这在理论上已预测过，但此前从未在实验中观察到。

独立异质双层中介电屏蔽的降低不仅大大提高了IXs的形成效率，还极大增强了偶极-偶极相互作用，从而能够在二维量子极限下实验观察到原始IXs的多体关联。此外，研究组首次在室温下排列良好、独立的WSe2/WS2异质双层中观察到莫尔阱IXs的几个发射峰。该发现为探索具有非线性光学应用潜力的新量子相开辟了道路。

▲ Abstract：

Strong, long-range dipole–dipole interactions between interlayer excitons (IXs) can lead to new multiparticle correlation regimes, which drive the system into distinct quantum and classical phases, including dipolar liquids, crystals and superfluids. Both repulsive and attractive dipole–dipole interactions have been theoretically predicted between IXs in a semiconductor bilayer, but only repulsive interactions have been reported experimentally so far. This study investigated free-standing, twisted (51°, 53°, 45°) tungsten diselenide/tungsten disulfide (WSe2/WS2) heterobilayers, in which we observed a transition in the nature of dipolar interactions among IXs, from repulsive to attractive. This was caused by quantum-exchange-correlation effects, leading to the appearance of a robust interlayer biexciton phase (formed by two IXs), which has been theoretically predicted but never observed before in experiments. The reduced dielectric screening in a free-standing heterobilayer not only resulted in a much higher formation efficiency of IXs, but also led to strongly enhanced dipole–dipole interactions, which enabled us to observe the many-body correlations of pristine IXs at the two-dimensional quantum limit. In addition, we firstly observed several emission peaks from moiré-trapped IXs at room temperature in a well-aligned, free-standing WSe2/WS2 heterobilayer. Our findings open avenues for exploring new quantum phases with potential for applications in non-linear optics.

材料科学Materials Science

Self-assembly of emulsion droplets through programmable folding

通过可编程折叠实现乳液液滴自组装

▲ 作者：Angus McMullen, Maitane Muñoz Basagoiti, Zorana Zeravcic & Jasna Brujic

▲ 链接：

https://www.nature.com/articles/s41586-022-05198-8

▲ 摘要：

在粒子自组装领域，如果所有单元都不同，则有望构建出几乎任意结构，但迄今为止，含有较少种类构建块的系统仅限于奇异晶体的组装。

研究组介绍了一种胶体液滴链的最小模型系统，具有可编程的DNA相互作用，引导它们向下折叠成特定的几何形状。液滴在真实时空中观测，揭示了折叠规则。结合实验、模拟和理论，研究组表明，控制相互作用的开启顺序可直接将胶体液滴折叠成独特的结构，并将其称之为胶体折叠体。

最多13个液滴的最简单交替序列（ABAB…）产生了11个二维折叠体和1个三维折叠体。通过优化液滴序列和添加额外种类，可对619个可能的二维几何图形中的多半进行独特编程。由至少13个液滴组成的折叠体显示有孔的开放结构，可提供多孔设计。数值模拟表明，这些折叠体可进一步相互作用，形成复杂的超胶体结构，如二聚体、带状体和镶嵌体。

该研究结果与动力学无关，因此适用于所有长度尺度上具有层级相互作用的聚合物材料，从有机分子一直到“魔尺”。该工具箱使大规模设计编码短聚合物序列成为可能，将折叠设计置于材料自组装的前沿。

▲ Abstract：

In the realm of particle self-assembly, it is possible to reliably construct nearly arbitrary structures if all the pieces are distinct, but systems with fewer flavours of building blocks have so far been limited to the assembly of exotic crystals. Here we introduce a minimal model system of colloidal droplet chains, with programmable DNA interactions that guide their downhill folding into specific geometries. Droplets are observed in real space and time, unravelling the rules of folding. Combining experiments, simulations and theory, we show that controlling the order in which interactions are switched on directs folding into unique structures, which we call colloidal foldamers. The simplest alternating sequences (ABAB...) of up to 13 droplets yield 11 foldamers in two dimensions and one in three dimensions. Optimizing the droplet sequence and adding an extra flavour uniquely encodes more than half of the 619 possible two-dimensional geometries. Foldamers consisting of at least 13 droplets exhibit open structures with holes, offering porous design. Numerical simulations show that foldamers can further interact to make complex supracolloidal architectures, such as dimers, ribbons and mosaics. Our results are independent of the dynamics and therefore apply to polymeric materials with hierarchical interactions on all length scales, from organic molecules all the way to Rubik’s Snakes. This toolbox enables the encoding of large-scale design into sequences of short polymers, placing folding at the forefront of materials self-assembly.

Low-hysteresis shape-memory ceramics designed by multimode modelling

多模态建模设计低滞回形状记忆陶瓷

▲ 作者：Edward L. Pang, Gregory B. Olson & Christopher A. Schuh

▲ 链接：

https://www.nature.com/articles/s41586-022-05210-1

▲ 摘要：

氧化锆陶瓷表现出马氏体相变，能产生高达10%的大应变，使其在高温下具有形状记忆和超弹性的应用前景。与其他马氏体材料类似，这种相变应变可通过精确合金化来设计，以产生减少滞回（加热和冷却时的相变温度差异）的更相称相变。

然而，氧化锆中的这种“晶格工程”由于附加的物理约束而变得复杂：其次需要管理较大的相变体积变化，并实现足够高的相变温度以避免动力学障碍。

研究组提出了一种将晶格工程方法扩展到马氏体设计的方法，以解决这些额外的约束，结合现代计算热力学和数据科学工具，跨越数据空白的复杂多组分空间。结果得到一种新的氧化锆组分，具有15K的低滞回记录，相变滞回比典型值低约10倍（比目前报道的最佳值低约5倍）。

这一发现表明，氧化锆陶瓷表现出可与广泛应用的形状记忆合金相媲美的滞回值，有望应用于可行的高温形状记忆材料。

▲ Abstract：

Zirconia ceramics exhibit a martensitic phase transformation that enables large strains of order 10%, making them prospects for shape-memory and superelastic applications at high temperature. Similarly to other martensitic materials, this transformation strain can be engineered by carefully alloying to produce a more commensurate transformation with reduced hysteresis (difference in transformation temperature on heating and cooling). However, such ‘lattice engineering’ in zirconia is complicated by additional physical constraints: there is a secondary need to manage a large transformation volume change, and to achieve transformation temperatures high enough to avoid kinetic barriers. Here we present a method of augmenting the lattice engineering approach to martensite design to address these additional constraints, incorporating modern computational thermodynamics and data science tools to span complex multicomponent spaces for which no data yet exist. The result is a new zirconia composition with record low hysteresis of 15 K, which is about ten times less transformation hysteresis compared to typical values (and approximately five times less than the best values reported so far). This finding demonstrates that zirconia ceramics can exhibit hysteresis values of the order of those of widely deployed shape-memory alloys, paving the way for their use as viable high-temperature shape-memory materials.

仿生学Bionics

Accommodating unobservability to control flight attitude with optic flow

利用光流调节不可观测性以控制飞行姿势

▲ 作者：Guido C. H. E. de Croon, Julien J. G. Dupeyroux, Christophe De Wagter, Abhishek Chatterjee, Diana A. Olejnik & Franck Ruffier

▲ 链接：

https://www.nature.com/articles/s41586-022-05182-2

▲ 摘要：

姿势控制是一种基本的飞行能力。飞行机器人通常依靠加速度计来估计姿势，而飞行昆虫缺乏明确的重力感。尽管人们已确定了几种感觉器官在姿势稳定中的作用，但飞行昆虫估计内部重力方向的依赖性仍不清楚。

研究组展示了当结合一个将姿势与加速度方向联系起来的运动模型时，如何从光流中提取姿势。虽然存在诸如悬停等姿势不可观测的状况，但研究组证明了后续控制系统仍然稳定，且不断地进出这些状况。

飞行机器人实验证实，以这种方式调节不可观测性导致稳定但略有振荡的姿势控制。此外，一个仿生扑翼机器人的实验表明，扑翼运动产生的残留高频姿势振荡提高了可观测性。

该方法为机器人技术带来了希望，无加速度计的自动驾驶仪为昆虫级自主飞行机器人铺平了道路。该研究形成了昆虫姿势估计和控制的假设，有望为已知生物现象提供进一步见解，并产生新的预测，如在更高飞行速度下头部和身体的姿势变化减小。

▲ Abstract：

Attitude control is an essential flight capability. Whereas flying robots commonly rely on accelerometers for estimating attitude, flying insects lack an unambiguous sense of gravity. Despite the established role of several sense organs in attitude stabilization, the dependence of flying insects on an internal gravity direction estimate remains unclear. Here we show how attitude can be extracted from optic flow when combined with a motion model that relates attitude to acceleration direction. Although there are conditions such as hover in which the attitude is unobservable, we prove that the ensuing control system is still stable, continuously moving into and out of these conditions. Flying robot experiments confirm that accommodating unobservability in this manner leads to stable, but slightly oscillatory, attitude control. Moreover, experiments with a bio-inspired flapping-wing robot show that residual, high-frequency attitude oscillations from flapping motion improve observability. The presented approach holds a promise for robotics, with accelerometer-less autopilots paving the road for insect-scale autonomous flying robots. Finally, it forms a hypothesis on insect attitude estimation and control, with the potential to provide further insight into known biological phenomena and to generate new predictions such as reduced head and body attitude variance at higher flight speeds.

地球科学Earth Science

A function-based typology for Earth’s ecosystems

基于功能的地球生态系统类型学

▲ 作者：David A. Keith, José R. Ferrer-Paris, Emily Nicholson, Melanie J. Bishop, Beth A. Polidoro, Eva Ramirez-Llodra, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05318-4

▲ 摘要：

随着联合国为《生物多样性公约》制定2020年后全球生物多样性框架，人们聚集生态系统保护的新目标和指标如何服务于“与自然和谐共处”的愿景。推进保护生物多样性和维持生态系统服务的双重任务，需要对生态系统对环境变化与管理的响应做出可靠而有弹性的概括和预测。

生态系统在其生物群、服务提供和相对风险暴露方面各不相同，但缺乏全球一致的生态系统分类，以反映对变化和管理的功能响应。这阻碍了在制定保护目标和可持续性目标方面取得进展。

研究组提出了国际自然保护联盟（IUCN）的全球生态系统类型学，这是一种概念稳健、可扩展、空间明确的方法，用于概括和预测整个生物圈的功能、生物群、风险和管理补救措施。该新框架是一项重大跨学科合作的成果，它将地球上所有的生态系统置于一个统一的理论背景中，以指导生态系统政策和管理从全球到地方的转变。

这一新的信息基础设施将支持在特定生态系统的管理和恢复、全球标准化的生态系统风险评估、自然资本核算以及2020年后全球生物多样性框架进展方面的知识转让。

▲ Abstract：

As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of ‘living in harmony with nature’. Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management. Ecosystems vary in their biota, service provision and relative exposure to risks, yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earth’s ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework.

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