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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天文學Astronomy

A long-period radio transient active for three decades

活躍了30年的長周期無線電瞬變

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

▲ 鏈接：

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

▲ 摘要：

在此，我們報告了針對一個長達21分鐘的無線電瞬變觀測結果，我們將其標記為GPM J1839–10。其脈沖的亮度在兩個數量級間變化，持續時間在30到300秒之間，且具有準周期子結構。

這些觀測促使我們對該無線電進行了搜索，我們發現它至少從1988年開始就一直在重復。數據發現周期導數小于3.6?×?10?13?s?s?1，這正是任何預測孤立中子星偶極射電發射的經典理論模型的極限。

▲ 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.

化學Chemistry

Hydration solids

水合固體

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

▲ 鏈接：

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

▲ 摘要：

在此，我們報告了原子力顯微鏡對一種常見土壤細菌的吸濕性孢子的測量，并發展了一種理論。

該理論描述了觀測到的平衡、非平衡和水反應性機械行為，我們發現這些都是由水合力控制的。我們基于水合力的理論解釋了水傳輸的極度慢速，并成功地預測了強非線性彈性和不同于玻璃和孔隙彈性行為的機械性能的轉變。

這些結果表明，水不僅賦予生物物質流動性，而且可以通過水合力控制其宏觀性質，形成具有特殊性質的“水合固體”。很多生物物質可能屬于這種獨特的固體物質。

▲ 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

使用受挫自由基對的區域選擇性脂肪族C-H鍵的功能化

▲ 作者：Zhipeng Lu, Minsoo Ju et al.

▲ 鏈接：

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

▲ 摘要：

在此，我們證明了C(sp3)–H鍵的功能化可以用二硅疊氮化物供體和N-氧銨受體生成的一類FRP來完成。這些物質共同經歷單電子轉移，產生瞬時且持久的自由基對，能夠裂解未活化的C-H鍵以提供氨基化產物。

通過調整給體的結構，可以控制區域選擇性和對叔鍵、仲鍵或伯C-H鍵的反應性。機理研究為自由基對在靶反應中的形成和參與提供了有力支持。

▲ 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.

生態學Ecology

Assembly of functional diversity in an oceanic island flora

海洋島嶼植物群功能多樣性的集合

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

▲ 鏈接：

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

▲ 摘要：

在此，通過廣泛的野外和實驗室測量，我們描述了一個海洋島嶼（西班牙特內里費島）本地植物群的功能性狀空間，并將其與生態策略中的全球平衡聯系起來。

我們發現，島嶼性狀空間具有顯著的功能豐富性，但大多數植物集中在以灌木為主的熱點周圍，其生存歷史策略較為保守。

通過生物地理分布和多樣化歷史將島嶼植物群劃分為不同的物種群，我們的研究結果還表明，長距離擴散的殖民化以及島嶼間擴散和群島水平物種形成過程之間的相互作用，驅動了功能分化和性狀空間擴展。

與我們的預期相反，通過分枝進化形成的物種導致了功能趨同，因此，灌木周圍密集的性狀空間對功能多樣性的貢獻非常小。通過結合生物地理學、生態學和進化，我們的方法為了解擴散、物種形成和持久性如何塑造整個原生島嶼植物群的組合的見解開拓了新途徑。

▲ 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.

地理學Geography

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

三維神經網絡用于精準中期全球天氣預報

▲ 作者：Kaifeng Bi, Lingxi Xie et al.

▲ 鏈接：

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

▲ 摘要：

在此，我們介紹了一種可用于準確中期全球天氣預報的人工智能方法。我們展示了，配備了地球特定先驗的三維深度網絡在處理天氣數據中的復雜模式方面是有效的，并且分層時間聚合策略減少了中期預報的累積誤差。

與歐洲中期天氣預報中心（ECMWF）的全球綜合預報系統NWP系統相比，我們的盤古氣象大模型在使用39年的全球數據訓練后，在所有測試變量的再分析數據上獲得了更強的確定性預報結果。

我們的方法也適用于極端天氣預報和集合預報。通過初始化再分析數據，我們對熱帶氣旋的跟蹤精度也高于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

從海洋生態指標中檢測到的全球氣候變化趨勢

▲ 作者：B. B. Cael, Kelsey Bisson et al.

▲ 鏈接：

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

▲ 摘要：

在此，我們發現氣候變化趨勢在海洋顏色（遙感反射率，Rrs）中出現得更快，因為Rrs是多變量的，且一些波段具有較低的年際變率。

我們分析了Aqua衛星上的中分辨率成像光譜儀(MODIS)的20年遙感反射率時間序列，發現56%的全球表面海洋的遙感反射率有顯著的趨勢，尤其是40°向赤道方向。

在最先進的生態系統模型中，遙感反射率中的氣候變化信號是在20年后在覆蓋海洋相似部分的類似區域出現的，這表明我們觀察到的趨勢顯示，海洋顏色以及延伸到海洋表面生態系統的變化，都是由氣候變化驅動的。總體來說，過去的20年中，低緯度的海洋變得更綠了。

▲ 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.