《自然》（20190606出版）一周論文導讀

翻譯 | 宗華

Nature, 6 June 2019, Volume 570 Issue 7759

《自然》2019年6月6日，第7759期570卷

地質學Geology

Surface erosion events controlled the evolution of plate tectonics on Earth

地表侵蝕事件控制地球板塊構造的演化

作者：Stephan V. Sobolev & Michael Brown

鏈接：

https://www.nature.com/articles/s41586-019-1258-4

摘要：

板塊構造是地球上最重要的地質過程之一，但其產生和演化至今仍不清楚。

這裡，我們將現在的板塊構造模型外推到過去，並且提出，從約30億年前起，大陸的隆起以及沉積物在大陸邊緣和海溝的積累提供了穩定俯衝的潤滑作用，同時在地球板塊構造的發展中扮演了至關重要的角色。

我們得出這樣的結論：兩次最大的表面侵蝕和俯衝潤滑事件分別發生在古元古代全球休倫冰期（24.5億~22億年前）之後，導致哥倫比亞超大陸的形成，以及在新元古代「雪球」地球冰期（7.5億~ 6.3億年前）之後。

Abstract

Plate tectonics is among the most important geological processes on Earth, but its emergence and evolution remain unclear. Here we extrapolate models of present-day plate tectonics to the past and propose that since about three billion years ago the rise of continents and the accumulation of sediments at continental edges and in trenches has provided lubrication for the stabilization of subduction and has been crucial in the development of plate tectonics on Earth. We conclude that the two largest surface erosion and subduction lubrication events occurred after the Palaeoproterozoic Huronian global glaciations (2.45 to 2.2 billion years ago), leading to the formation of the Columbia super continent, and after the Neoproterozoic 『snowball』 Earth glaciations (0.75 to 0.63 billion years ago).

Magnetism in cold subducting slabs at mantle transition zone depths

地幔過渡帶深部冷俯衝板塊的磁性

作者：I. Kupenko, G. Aprilis, D. M. Vasiukov, C. McCammon, et al

鏈接：

https://www.nature.com/articles/s41586-019-1254-8

摘要：

地球的殼—幔邊界，即莫霍維奇不連續面，傳統上被認為是磁性地殼和非磁性地幔之間的交界面。

然而，這一假設受到地球物理觀測結果的質疑，幔源包體中磁性剩餘物的識別——表明地幔有磁性來源——也對此提出了挑戰。

這裡，我們將同步加速器穆斯堡爾源光譜技術應用於激光加熱的金剛石壓砧中，研究了在壓力和溫度分別高達90吉帕和1300開爾文的情況下，三氧化二鐵同質多形體的磁躍遷和臨界溫度。

結果表明，赤鐵礦在冷俯衝或極冷俯衝地溫作用下，在地幔過渡帶深部仍具有磁性，並且形成了西太平洋地區的深磁化岩系。

Abstract

The Earth』s crust–mantle boundary, the Mohorovi?i? discontinuity, has been traditionally considered to be the interface between the magnetic crust and the non-magnetic mantle. However, this assumption has been questioned by geophysical observations and by the identification of magnetic remanence in mantle xenoliths, which suggest mantle magnetic sources. Here we apply synchrotron M?ssbauer source spectroscopy in laser-heated diamond anvil cells to investigate the magnetic transitions and critical temperatures in Fe₂O₃polymorphs at pressures and temperatures of up to 90 gigapascals and 1,300 kelvin, respectively. Ourresults show that haematite remains magnetic at the depth of the transition zone in the Earth』s mantle in cold or very cold subduction geotherms, forming a frame of deep magnetized rocks in the West Pacific region.

生物學Biology

Predator-induced collapse of niche structure and species coexistence

捕食者誘導的生態位結構與物種共存的崩潰

作者：Robert M. Pringle, Tyler R. Kartzinel, Todd M. Palmer, et al

鏈接：

https://www.nature.com/articles/s41586-019-1264-6

摘要：

生物入侵既是一個緊迫的環境挑戰，也是一個研究基本生態過程的機會，比如頂級捕食者在調節生物多樣性和食物網結構中的作用。

在以沙氏變色蜥為當地頂級捕食者的加勒比小島的全生態系統操作中，我們實驗性地引入沙氏變色蜥的競爭對手——綠安樂蜥和/或新的頂級捕食者——卷尾蜥蜴的入侵。研究發現，卷尾蜥蜴破壞了相互競爭的獵物物種共存的穩定性，這與經典的梯形捕食理論相反。

恐懼驅動的對捕食者的逃避破壞了原本穩定共存的空間和飲食生態位結構，加劇了無捕食者庇護所內的種間競爭，導致兩個島嶼上的綠安樂蜥種群滅絕。

Abstract

Biological invasions are both a pressing environmental challenge and an opportunity to investigate fundamental ecological processes, such as the role of top predators in regulating biodiversity and food-web structure. In whole-ecosystem manipulations of small Caribbean islands on which brown anole lizards (Anolis sagrei) were the nativetop predator, we experimentally staged invasions by competitors (green anoles, Anolis smaragdinus) and/or new top predators (curly-tailed lizards, Leiocephalus carinatus). We show that curly-tailed lizards destabilized the coexistence of competing prey species, contrary to the classic idea of key stonepredation. Fear-driven avoidance of predators collapsed the spatial and dietary niche structure that otherwise stabilized coexistence, which intensified interspecific competition within predator-free refuges and contributed to the extinction of green-anole populations on two islands.

Tracing the origin of adult intestinal stem cells

追蹤成體腸幹細胞的起源

作者：Jordi Guiu, Edouard Hannezo, Shiro Yui, et al

鏈接：

https://www.nature.com/articles/s41586-019-1212-5

摘要：

成體腸幹細胞位於李培昆氏腺窩的底部。在那裡，它們表達LGR5等標記物，促進腸上皮細胞的持續補充。

雖然胎兒的LGR5表達細胞可產生成體腸幹細胞，但目前尚不清楚這些在模式上皮細胞中的細胞群是否代表獨特的腸幹細胞前體。

這裡，利用無偏差定量譜系追蹤方法、生物物理建模和腸移植，我們證實小鼠腸上皮的所有細胞——和它們的位置以及在胎兒腸道管LGR5表達模式無關——主動為成體幹細胞池作貢獻。

利用三維成像，我們發現在胎兒發育過程中絨毛經歷了總體重塑和分裂。這使得上皮細胞從非增生性絨毛進入增生性絨毛間區，從而為成體幹細胞生態位的形成作出貢獻。

Abstract

Adult intestinal stem cells are located atthe bottom of crypts of Lieberkühn, where they express markers such as LGR5 and fuel the constant replenishment of the intestinal epithelium. Although fetal LGR5-expressing cells can give rise to adult intestinal stem cells, it remains unclear whether this population in the patterned epithelium represents unique intestinal stem-cell precursors. Here we show, using unbiased quantitative lineage-tracing approaches, biophysical modelling and intestinal transplantation, that all cells of the mouse intestinal epithelium—irrespective of their location and pattern of LGR5 expression in the fetal guttube—contribute actively to the adult intestinal stem cell pool. Using 3D imaging, we find that during fetal development the villus undergoes gross remodelling and fission. This brings epithelial cells from the non-proliferative villus into the proliferative intervillus region, which enables them to contribute to the adult stem-cell niche.

物理學Physics

Freestanding crystalline oxide perovskites down to the monolayer limit

獨立的晶體氧化物鈣鈦礦降至單層極限

作者：Dianxiang Ji, Songhua Cai, Tula R. Paudel, et al

鏈接：

https://www.nature.com/articles/s41586-019-1255-7

摘要：

二維材料如石墨烯和過渡金屬雙鹵代烷，揭示了當大塊晶體被還原為單層時所出現的電子相。

過渡金屬氧化物鈣鈦礦含有多種相關的電子相，因此基於過渡金屬氧化物鈣鈦礦的單層材料的類似行為將為尚未被探索的豐富的奇異二維相關相譜打開大門。

這裡，我們報告了獨立鈣鈦礦薄膜的製作。這種薄膜的高晶體質量幾乎降至單個晶胞。

採用近年發展起來的以水溶性Sr₃Al₂O₆為犧牲性緩衝層的方法，我們通過反應分子束外延法合成了SrTiO₃和BiFeO₃薄膜，並將它們轉移到不同的襯底上，特別是晶體矽片和多孔碳薄膜上。

Abstract

Two-dimensional materials such as graphene and transition-metal dichalcogenides reveal the electronic phases that emerge when a bulk crystal is reduced to a monolayer. Transition-metal oxide perovskites host a variety of correlated electronic phases, so similar behaviour in monolayer materials based on transition-metal oxide perovskites would open the door to a rich spectrum of exotic 2D correlated phases that have not yet been explored. Here we report the fabrication of freestanding perovskite films with high crystalline quality almost down to a single unitcell. Using a recently developed method based on water-soluble Sr₃Al₂O₆ as the sacrificial buffer layer we synthesize freestanding SrTiO₃ and BiFeO₃ultrathin films by reactive molecular beam epitaxy and transfer them to diverse substrates, in particular crystalline silicon wafers and holey carbon films.

Lattice anchoring stabilizes solution-processed semiconductors

晶格錨定穩定經溶液處理的半導體

作者：Mengxia Liu, Yuelang Chen, Chih-Shan Tan, et al

鏈接：

https://www.nature.com/articles/s41586-019-1239-7

摘要：

經溶液處理的半導體的穩定性仍然是其向更廣泛應用方向改進的重要領域。

無機銫鹵化鉛鈣鈦礦具有非常適合串列太陽能電池的帶隙，但在室溫附近會發生不希望發生的相變。膠體量子點（CQDs）是一種結構堅固的材料，因其尺寸可調的帶隙而備受讚譽。

這裡，我們報告了一種將銫鹵化鉛鈣鈦礦和鉛的硫屬化合物CQDs結合在一起的「晶格錨定」雜化材料。其中，兩種材料之間的晶格匹配有助於其穩定性超過組分的穩定性。

我們發現，CQDs使鈣鈦礦保持在期望的立方相，並且抑制了向不期望的晶格錯配相的轉變。

Abstract

The stability of solution-processed semiconductors remains an important area for improvement on their path to wider deployment. Inorganic caesium lead halide perovskites have a bandgap well suited to tandem solar cells but suffer from an undesired phase transition near room temperature. Colloidal quantum dots (CQDs) are structurally robust materials prized for their size-tunable bandgap. Here we report『lattice-anchored』 hybrid materials that combine caesium lead halide perovskites with lead chalcogenide CQDs, in which lattice matching between the two materials contributes to a stability exceeding that of the constituents. We find that CQDs keep the perovskite in its desired cubic phase, suppressing the transition to the undesired lattice-mismatched phases.

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