Nature, 20 July 2023, Volume 619 Issue 7970

《自然》2023年7月20日，第619卷，7970期

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天文学Astronomy

A long-period radio transient active for three decades

活跃了30年的长周期无线电瞬变

▲ 作者：N. Hurley-Walker, N. Rea, S. J. McSweeney et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06202-5

▲ 摘要：

在此，我们报告了针对一个长达21分钟的无线电瞬变观测结果，我们将其标记为GPM J1839–10。其脉冲的亮度在两个数量级间变化，持续时间在30到300秒之间，且具有准周期子结构。

这些观测促使我们对该无线电进行了搜索，我们发现它至少从1988年开始就一直在重复。数据发现周期导数小于3.6?×?10?13?s?s?1，这正是任何预测孤立中子星偶极射电发射的经典理论模型的极限。

▲ Abstract：

Here we report observations of a long-period (21?min) radio transient, which we have labelled GPM J1839–10. The pulses vary in brightness by two orders of magnitude, last between 30 and 300?s and have quasiperiodic substructure. The observations prompted a search of radio archives and we found that the source has been repeating since at least 1988. The archival data enabled constraint of the period derivative to <3.6?×?10?13?s?s?1, which is at the very limit of any classical theoretical model that predicts dipolar radio emission from an isolated neutron star.

化学Chemistry

Hydration solids

水合固体

▲ 作者：Steven G. Harrellson, Michael S. DeLay et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06144-y

▲ 摘要：

在此，我们报告了原子力显微镜对一种常见土壤细菌的吸湿性孢子的测量，并发展了一种理论。

该理论描述了观测到的平衡、非平衡和水反应性机械行为，我们发现这些都是由水合力控制的。我们基于水合力的理论解释了水传输的极度慢速，并成功地预测了强非线性弹性和不同于玻璃和孔隙弹性行为的机械性能的转变。

这些结果表明，水不仅赋予生物物质流动性，而且可以通过水合力控制其宏观性质，形成具有特殊性质的“水合固体”。很多生物物质可能属于这种独特的固体物质。

▲ Abstract：

Here we report atomic force microscopy measurements on the hygroscopic spores of a common soil bacterium and develop a theory that captures the observed equilibrium, non-equilibrium and water-responsive mechanical behaviours, finding that these are controlled by the hydration force. Our theory based on the hydration force explains an extreme slowdown of water transport and successfully predicts a strong nonlinear elasticity and a transition in mechanical properties that differs from glassy and poroelastic behaviours. These results indicate that water not only endows biological matter with fluidity but also can—through the hydration force—control macroscopic properties and give rise to a ‘hydration solid’ with unusual properties. A large fraction of biological matter could belong to this distinct class of solid matter.

Regioselective aliphatic C–H functionalization using frustrated radical pairs

使用受挫自由基对的区域选择性脂肪族C-H键的功能化

▲ 作者：Zhipeng Lu, Minsoo Ju et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06131-3

▲ 摘要：

在此，我们证明了C(sp3)–H键的功能化可以用二硅叠氮化物供体和N-氧铵受体生成的一类FRP来完成。这些物质共同经历单电子转移，产生瞬时且持久的自由基对，能够裂解未活化的C-H键以提供氨基化产物。

通过调整给体的结构，可以控制区域选择性和对叔键、仲键或伯C-H键的反应性。机理研究为自由基对在靶反应中的形成和参与提供了有力支持。

▲ Abstract：

Here we demonstrate that the functionalization of C(sp3)–H bonds can be accomplished using a class of FRPs generated from disilazide donors and an N-oxoammonium acceptor. Together, these species undergo single-electron transfer to generate a transient and persistent radical pair capable of cleaving unactivated C–H bonds to furnish aminoxylated products. By tuning the structure of the donor, it is possible to control regioselectivity and tailor reactivity towards tertiary, secondary or primary C–H bonds. Mechanistic studies lend strong support for the formation and involvement of radical pairs in the target reaction.

生态学Ecology

Assembly of functional diversity in an oceanic island flora

海洋岛屿植物群功能多样性的集合

▲ 作者：Martha Paola Barajas Barbosa, Dylan Craven et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06305-z

▲ 摘要：

在此，通过广泛的野外和实验室测量，我们描述了一个海洋岛屿（西班牙特内里费岛）本地植物群的功能性状空间，并将其与生态策略中的全球平衡联系起来。

我们发现，岛屿性状空间具有显著的功能丰富性，但大多数植物集中在以灌木为主的热点周围，其生存历史策略较为保守。

通过生物地理分布和多样化历史将岛屿植物群划分为不同的物种群，我们的研究结果还表明，长距离扩散的殖民化以及岛屿间扩散和群岛水平物种形成过程之间的相互作用，驱动了功能分化和性状空间扩展。

与我们的预期相反，通过分枝进化形成的物种导致了功能趋同，因此，灌木周围密集的性状空间对功能多样性的贡献非常小。通过结合生物地理学、生态学和进化，我们的方法为了解扩散、物种形成和持久性如何塑造整个原生岛屿植物群的组合的见解开拓了新途径。

▲ Abstract：

Here we describe the functional trait space of the native flora of an oceanic island (Tenerife, Canary Islands, Spain) using extensive field and laboratory measurements, and relate it to global trade-offs in ecological strategies. We find that the island trait space exhibits a remarkable functional richness but that most plants are concentrated around a functional hotspot dominated by shrubs with a conservative life-history strategy. By dividing the island flora into species groups associated with distinct biogeographical distributions and diversification histories, our results also suggest that colonization via long-distance dispersal and the interplay between inter-island dispersal and archipelago-level speciation processes drive functional divergence and trait space expansion. Contrary to our expectations, speciation via cladogenesis has led to functional convergence, and therefore only contributes marginally to functional diversity by densely packing trait space around shrubs. By combining biogeography, ecology and evolution, our approach opens new avenues for trait-based insights into how dispersal, speciation and persistence shape the assembly of entire native island floras.

地理学Geography

Accurate medium-range global weather forecasting with 3D neural networks

三维神经网络用于精准中期全球天气预报

▲ 作者：Kaifeng Bi, Lingxi Xie et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06185-3

▲ 摘要：

在此，我们介绍了一种可用于准确中期全球天气预报的人工智能方法。我们展示了，配备了地球特定先验的三维深度网络在处理天气数据中的复杂模式方面是有效的，并且分层时间聚合策略减少了中期预报的累积误差。

与欧洲中期天气预报中心（ECMWF）的全球综合预报系统NWP系统相比，我们的盘古气象大模型在使用39年的全球数据训练后，在所有测试变量的再分析数据上获得了更强的确定性预报结果。

我们的方法也适用于极端天气预报和集合预报。通过初始化再分析数据，我们对热带气旋的跟踪精度也高于ECMWF-HRES。

▲ Abstract：

Here we introduce an artificial-intelligence-based method for accurate, medium-range global weather forecasting. We show that three-dimensional deep networks equipped with Earth-specific priors are effective at dealing with complex patterns in weather data, and that a hierarchical temporal aggregation strategy reduces accumulation errors in medium-range forecasting. Trained on 39?years of global data, our program, Pangu-Weather, obtains stronger deterministic forecast results on reanalysis data in all tested variables when compared with the world’s best NWP system, the operational integrated forecasting system of the European Centre for Medium-Range Weather Forecasts (ECMWF). Our method also works well with extreme weather forecasts and ensemble forecasts. When initialized with reanalysis data, the accuracy of tracking tropical cyclones is also higher than that of ECMWF-HRES.

Global climate-change trends detected in indicators of ocean ecology

从海洋生态指标中检测到的全球气候变化趋势

▲ 作者：B. B. Cael, Kelsey Bisson et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06321-z

▲ 摘要：

在此，我们发现气候变化趋势在海洋颜色（遥感反射率，Rrs）中出现得更快，因为Rrs是多变量的，且一些波段具有较低的年际变率。

我们分析了Aqua卫星上的中分辨率成像光谱仪(MODIS)的20年遥感反射率时间序列，发现56%的全球表面海洋的遥感反射率有显著的趋势，尤其是40°向赤道方向。

在最先进的生态系统模型中，遥感反射率中的气候变化信号是在20年后在覆盖海洋相似部分的类似区域出现的，这表明我们观察到的趋势显示，海洋颜色以及延伸到海洋表面生态系统的变化，都是由气候变化驱动的。总体来说，过去的20年中，低纬度的海洋变得更绿了。

▲ Abstract：

Here we show that climate-change trends emerge more rapidly in ocean colour (remote-sensing reflectance, Rrs), because Rrs is multivariate and some wavebands have low interannual variability. We analyse a 20-year Rrs time series from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, and find significant trends in Rrs for 56% of the global surface ocean, mainly equatorward of 40°. The climate-change signal in Rrs emerges after 20 years in similar regions covering a similar fraction of the ocean in a state-of-the-art ecosystem model, which suggests that our observed trends indicate shifts in ocean colour—and, by extension, in surface-ocean ecosystems—that are driven by climate change. On the whole, low-latitude oceans have become greener in the past 20 years.