Nature, 6 February 2025, Volume 638 Issue 8049

《自然》2025年2月6日，第638卷，8049期

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材料科学Material Sciences

Degradable thermosets via orthogonal polymerizations of a single monomer

通过单一单体的正交聚合制备可降解热固性塑料

▲ 作者：Reagan J. Dreiling, Kathleen Huynh & Brett P. Fors

▲ 链接：https://www.nature.com/articles/s41586-024-08386-w

▲ 摘要：在此，我们提出了一种具有可降解热固性的一次性合成模块。它来自商业上可行的、生物来源的单体2,3-二氢呋喃（DHF）。在钌催化剂和光酸发生器的存在下，DHF进行缓慢开环复分解聚合，得到软聚合物；然后，暴露在光线下后触发强酸生成，促进同一DHF单体的阳离子聚合，从而产生空间交联，增加材料强度。通过操纵催化剂负载和光照，我们可以获得具有跨越数量级的物理性质的材料，并实现空间分辨率的材料域。

重要的是，基于DHF的热固性材料经过刺激可以逐渐降解，通过温和加热进行回收。在单一官能团上使用两种不同的聚合机制，可以合成具有精确控制性能的可降解和可回收的热固性材料。

▲ Abstract：Here we present a modular, one-pot synthesis of degradable thermosets from the commercially available, biosourced monomer 2,3-dihydrofuran (DHF). In the presence of a ruthenium catalyst and photoacid generator, DHF undergoes slow ring-opening metathesis polymerization to give a soft polymer; then, exposure to light triggers strong acid generation and promotes the cationic polymerization of the same DHF monomer to spatially crosslink and strengthen the material. By manipulating catalyst loading and light exposure, we can access materials with physical properties spanning orders of magnitude and achieve spatially resolved material domains. Importantly, the DHF-based thermosets undergo stimuli-selective degradation and can be recycled to the monomer under mild heating. The use of two distinct polymerization mechanisms on a single functional group allows the synthesis of degradable and recyclable thermoset materials with precisely controlled properties.

物理学Physics

Quantum coarsening and collective dynamics on a programmable simulator

可编程模拟器上的量子粗化和集体动力学

▲ 作者：Tom Manovitz, Sophie H. Li et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08353-5

▲摘要：在此，我们使用一个基于里德伯原子阵列的可编程量子模拟器来实验研究（2+1）维伊辛量子相变的集体动力学。越过量子临界点后，我们观察到反铁磁有序畴的粗化导致相关逐渐增长。

通过预备和跟踪有序畴的演化，我们发现粗化是由畴边界的曲率驱动的，并且动力学随着量子临界点的接近而加速。我们定量地探索了这些现象，并进一步观察了顺序参数的长期振荡，响应振幅（“希格斯”）模式。这些观察结果为强相关量子系统和非平衡量子过程中的涌现集体动力学提供了一个视角。

▲ Abstract：Here we use a programmable quantum simulator based on Rydberg atom arrays to experimentally study collective dynamics across a (2+1)-dimensional Ising quantum phase transition. After crossing the quantum critical point, we observe a gradual growth of correlations through coarsening of antiferromagnetically ordered domains. By deterministically preparing and following the evolution of ordered domains, we show that the coarsening is driven by the curvature of domain boundaries, and find that the dynamics accelerate with proximity to the quantum critical point. We quantitatively explore these phenomena and further observe long-lived oscillations of the order parameter, corresponding to an amplitude (‘Higgs’) mode. These observations offer a viewpoint into emergent collective dynamics in strongly correlated quantum systems and non-equilibrium quantum processes.

Emergence of collective oscillations in massive human crowds

在大量人群中出现的集体振荡

▲ 作者：Fran?ois Gu, Benjamin Guiselin, Nicolas Bain, Iker Zuriguel & Denis Bartolo

▲ 链接：https://www.nature.com/articles/s41586-024-08514-6

▲摘要：在此，我们分析了在西班牙圣费尔明节上聚集的上千人的动力学，并推断出密集人群在行动受限情况下的物理理论。我们的测量表明，密集的群体可以自组织成宏观手性振子，在没有外部引导的情况下协调数百个个体的轨道运动。在这些测量和对称原理的指导下，我们构建了密集人群运动的力学模型。

我们的模型表明，突现的奇摩擦力驱动了非互反的相位转变向集体手性振荡，契合我们所有的观察结果。为了测试研究结果的稳健性，我们证明了类似的手性动力学在2010年爱情游行灾难开始时出现，并提出了一个可以帮助预测这些先前不可预测的动力学的方案。

▲ Abstract：Here we analyse the dynamics of thousands of densely packed individuals at the San Fermín festival (Spain) and infer a physical theory of dense crowds in confinement. Our measurements reveal that dense crowds can self-organize into macroscopic chiral oscillators, coordinating the orbital motion of hundreds of individuals without external guidance. Guided by these measurements and symmetry principles, we construct a mechanical model of dense-crowd motion. Our model demonstrates that emergent odd frictional forces drive a non-reciprocal phase transition towards collective chiral oscillations, capturing all our experimental observations. To test the robustness of our findings, we show that similar chiral dynamics emerged at the onset of the 2010 Love Parade disaster and propose a protocol that could help anticipate these previously unpredictable dynamics.

古生物学Paleontology

Cretaceous Antarctic bird skull elucidates early avian ecological diversity

白垩纪南极鸟类头骨揭示早期鸟类生态多样性

▲ 作者：Christopher R. Torres, Julia A. Clarke et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08390-0

▲摘要：在此，我们报告一个几乎完整的维加鸟新头骨。它为这种鸟类的摄食生态学研究提供了新的见解，并展示了冠群鸟类中水禽的形态学。维加鸟有典型的鸟类的喙（没有牙齿和缩小的上颌骨）和大脑形状（过度膨胀的大脑和腹侧移位的视叶）。

颞窝扩张明显，表明这只鸟有肥大的下颌肌肉组织。喙窄而尖，下颌骨缺乏关节后突。综上，这些特征组成了一种进食结构。它不同于任何其他已知的反形动物，但与其他现存的在水下捕获猎物的鸟类的进食结构相似。

▲ Abstract：Here we report a new, nearly complete skull of Vegavis that provides new insight into its feeding ecology and exhibits morphologies that support placement among waterfowl within crown-group birds. Vegavis has an avian beak (absence of teeth and reduced maxilla) and brain shape (hyperinflated cerebrum and ventrally shifted optic lobes). The temporal fossa is well excavated and expansive, indicating that this bird had hypertrophied jaw musculature. The beak is narrow and pointed, and the mandible lacks retroarticular processes. Together, these features comprise a feeding apparatus unlike that of any other known anseriform but like that of other extant birds that capture prey underwater (for example, grebes and loons).

生态学Ecology

One-quarter of freshwater fauna threatened with extinction

四分之一的淡水动物面临灭绝风险

▲ 作者：Catherine A. Sayer, Eresha Fernando et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08375-z

▲摘要：在此，我们提供对世界自然保护联盟濒危物种红色名录的全球淡水动物的多分类评估结果。该项结果涵盖23496种十足甲壳类、鱼类和蜻蜓目昆虫，其中四分之一面临灭绝的威胁。普遍存在的威胁包括污染、水坝和取水、农业和入侵物种，过度捕捞也将导致物种灭绝。

我们还研究了受威胁的四足动物和淡水非生物因子（水分胁迫和氮）对受威胁淡水物种的替代程度。濒危四足动物在优先栖息地以最大化稀缺性加权丰富度时是很好的替代指标，但在从最受范围限制的物种角度出发进行选择时则效果较差。然而，它们是比非生物因素更好的替代指标，非生物因素的表现比随机因素差。

因此，尽管确定的全球四足动物保护优先区域大致反映了淡水动物群的优先区域，但鉴于主要威胁和栖息地的差异，不能认为满足四足动物的需求就能在局部尺度上保护淡水物种。

▲ Abstract：Here we present the results of a multi-taxon global freshwater fauna assessment for The IUCN Red List of Threatened Species covering 23,496 decapod crustaceans, fishes and odonates, finding that one-quarter are threatened with extinction. Prevalent threats include pollution, dams and water extraction, agriculture and invasive species, with overharvesting also driving extinctions. We also examined the degree of surrogacy of both threatened tetrapods and freshwater abiotic factors (water stress and nitrogen) for threatened freshwater species. Threatened tetrapods are good surrogates when prioritizing sites to maximize rarity-weighted richness, but poorer when prioritizing based on the most range-restricted species. However, they are much better surrogates than abiotic factors, which perform worse than random. Thus, although global priority regions identified for tetrapod conservation are broadly reflective of those for freshwater faunas, given differences in key threats and habitats, meeting the needs of tetrapods cannot be assumed sufficient to conserve freshwater species at local scales.

地球科学Earth Science

The Ronne Ice Shelf survived the last interglacial

罗纳冰架在末次间冰期中幸存

▲ 作者：Eric W. Wolff, Robert Mulvaney et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08394-w

▲ 摘要：在此，我们使用了来自Skytrain ice Rise的冰芯海盐数据。该冰芯位于西南极冰盖（WAIS）附近，表明在末次间冰期（LIG）的大部分时间里，罗纳冰架仍然存在，并且接近其当前的范围。水同位素数据与WAIS的退缩一致，但似乎与WAIS和大型南极冰架都消失的更剧烈的模式实现不一致。

这一新的限制要求重新评估LIG海平面预算的其他要素。这一结果还削弱了促使模式模拟预测未来海平面上升速度至2300年及以后的最高预测值的观测基础。

▲ Abstract：Here we use sea salt data from an ice core from Skytrain Ice Rise, adjacent to WAIS, to show that, during most of the LIG, the Ronne Ice Shelf was still in place, and close to its current extent. Water isotope data are consistent with a retreat of WAIS, but seem inconsistent with more dramatic model realizations in which both WAIS and the large Antarctic ice shelves were lost. This new constraint calls for a reappraisal of other elements of the LIG sea-level budget. It also weakens the observational basis that motivated model simulations projecting the highest end of projections for future rates of sea-level rise to 2300 and beyond.