編譯|李言
Nature, 16 January 2025, Volume 637 Issue 8046
《自然》2025年1月16日，第637卷，8046期
材料科學Material Sciences
Janus graphene nanoribbons with localized states on a single zigzag edge
單之字形邊緣局域態的Janus石墨烯納米帶
▲ 作者：Shaotang Song, Yu Teng et al.
▲鏈接：
https://www.nature.com/articles/s41586-024-08296-x
▲摘要：
在此，我們報告設計和制造具有兩種不同邊緣結構的雅努斯石墨烯納米帶（JGNRs）的方法。在Lieb定理和拓撲分類理論的指導下，我們在一個鋸齒形邊緣不對稱地引入苯基序的拓撲缺陷陣列，同時另一條之字形邊緣不變，設計出兩種JGNRs。這打破了結構對稱性，并在每個晶胞內產生子晶格不平衡，引發自旋對稱性破缺。
我們設計了三個之字形前驅體，用于制造母本之字形石墨烯納米帶和兩條具有最優缺陷陣列晶格間距的JGNRs，以完全淬滅“缺陷”邊緣的磁邊緣態。通過掃描探針顯微鏡和光譜學以及第一性原理密度泛函理論的表征，我們成功制造了JGNRs，其鐵磁基態沿未受干擾的之字形邊緣局域。
▲ Abstract：
Here we report a general approach for designing and fabricating such ferromagnetic GNRs in the form of Janus GNRs (JGNRs) with two distinct edge configurations. Guided by Lieb’s theorem and topological classification theory, we devised two JGNRs by asymmetrically introducing a topological defect array of benzene motifs to one zigzag edge, while keeping the opposing zigzag edge unchanged. This breaks the structural symmetry and creates a sublattice imbalance within each unit cell, initiating a spin-symmetry breaking. Three Z-shaped precursors are designed to fabricate one parent ZGNR and two JGNRs with an optimal lattice spacing of the defect array for a complete quench of the magnetic edge states at the ‘defective’ edge. Characterization by scanning probe microscopy and spectroscopy and first-principles density functional theory confirms the successful fabrication of JGNRs with a ferromagnetic ground-state localized along the pristine zigzag edge.
地球科學Earth Science
Sulfide-rich continental roots at cratonic margins formed by carbonated melts
碳酸鹽熔體在克拉通邊緣形成的富含硫化物的大陸根
▲ 作者：Chunfei Chen, Michael W. F?rster et al.
▲鏈接：
https://www.nature.com/articles/s41586-024-08316-w
▲摘要：
在此，我們整理了全球克拉通橄欖巖的硫和銅含量，確定了克拉通邊緣深度160—190公里的富硫化物和富銅大陸根。新的高壓實驗表明，源自軟流圈的碳酸硅酸鹽熔體在與巖石圈橄欖巖的反應過程中失去了硅酸鹽成分，演化為碳酸鹽巖熔體，并集中在克拉通邊緣。
這一過程中，隨著熔體SiO2含量的降低，硫在熔體中的溶解度大幅降低，迫使硫化物沉淀，并在地幔巖石圈底部形成富硫化物的大陸根。碳酸化熔體向克拉通邊緣的遷移為那里的大陸根補充了硫，解釋了巖漿金屬礦床與靠近克拉通邊緣的碳酸鹽巖共存的原因。
這些發現突出了碳酸化熔體在成礦作用中的重要作用，為金屬礦勘查提供了潛在途徑。
▲ Abstract：
Here we compile sulfur and copper contents of global cratonic peridotites, identifying sulfide-rich and copper-rich continental roots at depths of 160–190?km at cratonic margins. Our new high-pressure experiments show that carbonated silicate melts originating from the asthenosphere lose silicate components during reaction with lithospheric peridotite, evolving to carbonatite melts that become concentrated at cratonic margins. Sulfur solubility in melts substantially decreases as the SiO2content of melts decreases during this process, forcing sulfide precipitation and the formation of sulfide-rich continental roots at the base of the mantle lithosphere. The migration of carbonated melts towards cratonic margins replenishes the continental roots there with sulfur, explaining the co-location of magmatic metal deposits with carbonatites close to cratonic margins. These findings highlight the notable role of carbonated melts in metallogenesis and provide a potential platform for metal ore exploration.
Diversity and biogeography of the bacterial microbiome in glacier-fed streams
冰川補給河流中細菌微生物群的多樣性和生物地理學
▲ 作者：Le?la Ezzat, Hannes Peter et al.
▲鏈接：
https://www.nature.com/articles/s41586-024-08313-z
▲摘要：
在此，通過利用元條形碼和宏基因組學，我們對地球主要山脈的152個冰川補給河流（GFSs）的底棲微生物群細菌進行了全面調查。我們發現GFS細菌微生物組在分類和功能上與其他冰凍圈微生物組不同。
GFS細菌種類繁多，其中一半以上是某些山脈特有的，一些是單一GFS所特有的，還有一些是世界性的，含菌量眾多。我們展示了地理隔離和環境選擇如何塑造其生物地理，其特征是在山脈和半球之間具有獨特的組成模式。系統發育分析進一步揭示了環境選擇導致的微多樣性分支，可能促進了功能恢復能力，并有助于GFS細菌多樣性和生物地理學。
氣候導致的冰川消融使這種獨特的微生物群處于危險之中。我們的研究為未來可能消失的GFS生態系統上開展氣候變化微生物學研究提供了全球性的參考。
▲ Abstract：
Here, by leveraging metabarcoding and metagenomics, we provide a comprehensive survey of bacteria in the benthic microbiome across 152? Glacier-fed streams (GFSs) draining the Earth’s major mountain ranges. We find that the GFS bacterial microbiome is taxonomically and functionally distinct from other cryospheric microbiomes. GFS bacteria are diverse, with more than half being specific to a given mountain range, some unique to single GFSs and a few cosmopolitan and abundant. We show how geographic isolation and environmental selection shape their biogeography, which is characterized by distinct compositional patterns between mountain ranges and hemispheres. Phylogenetic analyses furthermore uncovered microdiverse clades resulting from environmental selection, probably promoting functional resilience and contributing to GFS bacterial biodiversity and biogeography. Climate-induced glacier shrinkage puts this unique microbiome at risk. Our study provides a global reference for future climate-change microbiology studies on the vanishing GFS ecosystem.
生物學Biology
A combinatorial neural code for long-term motor memory
長期運動記憶的組合神經代碼
▲ 作者：Jae-Hyun Kim, Kayvon Daie & Nuo Li
▲鏈接：
https://www.nature.com/articles/s41586-024-08193-3
▲摘要：
在此，我們追蹤了老鼠生命周期中學習到的動作的神經表征，并表明學習到的動作在與環境的結合中被穩定地保留，這保護了現有的記憶在新的運動學習中不被抹去。我們建立了一個持續的學習范式。
在這個范式中，老鼠學會了在不同的任務背景下進行定向舔舐。同時我們使用雙光子成像跟蹤了老鼠長達六個月的運動皮層活動。在相同的任務背景下，驅動定向舔舐的活動隨著時間的推移是穩定的，幾乎沒有代表性漂移。當學習新的任務情境時，新的準備活動出現以驅動相同的舔舐動作。學習創造了新的運動記憶，而不是修改現有的表征。甚至幾個月后，在之前的任務環境中重新學習做出同樣的動作，也會重新激活之前的準備活動。
對新任務背景的持續學習不斷創造新的準備活動模式。正如我們在運動系統中觀察到的那樣，情境特定記憶可能在持續學習過程中為穩定的記憶存儲提供了一種解決方案。
▲ Abstract：
Here we tracked neural representation of learned actions throughout a significant portion of the lifespan of a mouse and show that learned actions are stably retained in combination with context, which protects existing memories from erasure during new motor learning. We established a continual learning paradigm in which mice learned to perform directional licking in different task contexts while we tracked motor cortex activity for up to six months using two-photon imaging. Within the same task context, activity driving directional licking was stable over time with little representational drift. When learning new task contexts, new preparatory activity emerged to drive the same licking actions. Learning created parallel new motor memories instead of modifying existing representations. Re-learning to make the same actions in the previous task context re-activated the previous preparatory activity, even months later. Continual learning of new task contexts kept creating new preparatory activity patterns. Context-specific memories, as we observed in the motor system, may provide a solution for stable memory storage throughout continual learning.
Diatom phytochromes integrate the underwater light spectrum to sense depth
硅藻光敏色素整合水下光譜來感知深度
▲ 作者：Carole Duchêne, Jean-Pierre Bouly et al.
▲鏈接：
https://www.nature.com/articles/s41586-024-08301-3
▲摘要：
在此，通過對硅藻光敏色素（DPH）介導的光譜變化進行體內劑量響應分析，我們發現DPH可以在整個光譜中觸發光可逆反應，導致DPH光平衡隨深度的變化。通過在硅藻Thalassiosira pseudonana中產生DPH突變體，我們還證明了在模擬海洋深度的低藍光條件下，DPH調節光合作用適應，從而將光學深度檢測與功能響應聯系起來。
從永久分層區到季節混合區含DPH硅藻的緯度分布表明，DPH功能在應對水體垂直位移方面具有一定的適應性。通過將DPH作為光學深度探測器，我們的研究提供了一種新的視角，即嵌入在水下光場的信息如何被硅藻利用以調節其在光區的生理作用。
▲ Abstract：
Here, by developing an in vivo dose–response assay to light spectral variations mediated by DPH, we show that DPH can trigger photoreversible responses across the entire light spectrum, resulting in a change in DPH photoequilibrium with depth. By generating dph mutants in the diatom Thalassiosira pseudonana, we also demonstrate that under simulated low-blue-light conditions of ocean depth, DPH regulates photosynthesis acclimation, thus linking optical depth detection with a functional response. The latitudinal distribution of DPH-containing diatoms from permanently stratified regions to seasonally mixed regions suggests an adaptive value of DPH functions in coping with vertical displacements in the water column. By establishing DPH as a detector of optical depth, this study provides a new view of how information embedded in the underwater light field can be exploited by diatoms to modulate their physiology throughout the photic zone.
古生物學Paleontology
New Silurian aculiferan fossils reveal complex early history of Mollusca
新志留紀甲殼綱化石揭示了軟體動物復雜的早期歷史
▲ 作者：Mark D. Sutton, Julia D. Sigwart et al.
▲鏈接：
https://www.nature.com/articles/s41586-024-08312-0
▲摘要：
在此，我們描述了兩種新的三維保存的甲殼綱物種，它們來自志留紀的赫里福德郡，大大擴展了該分支的形態和生態范圍。系統發育分析表明它們在一個復雜的類群關系中的位置，顯示基本特征狀態會發生逆轉，如瓣膜的存在和腳的性質。
與先前的形態保守性假設相反，早期甲殼綱物種的進化產生了大量不尋常的形式，與其他冠類軟體動物的多樣化相當。
▲ Abstract：
Here we describe two new three-dimensionally preserved aculiferan species from the Silurian Herefordshire Lagerst?tte, which substantially extend the morphological and ecological range of the clade. Phylogenetic analyses indicate positions within a complex nexus of taxa and suggest reversals in the states of fundamental characters such as the presence of valves and the nature of the foot. In contrast to previous hypotheses of morphological conservatism, evolution in early aculiferans generated a profusion of unusual forms comparable to the diversification of other crown-group molluscs.
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