《自然》（20190606出版）一周论文导读

翻译 | 宗华

Nature, 6 June 2019, Volume 570 Issue 7759

《自然》2019年6月6日，第7759期570卷

地质学Geology

 

Surface erosion events controlled the evolution of plate tectonics on Earth

地表侵蚀事件控制地球板块构造的演化

▲ 作者：Stephan V. Sobolev & Michael Brown

▲ 链接：

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

▲ 摘要：

板块构造是地球上最重要的地质过程之一，但其产生和演化至今仍不清楚。

这里，我们将现在的板块构造模型外推到过去，并且提出，从约30亿年前起，大陆的隆起以及沉积物在大陆边缘和海沟的积累提供了稳定俯冲的润滑作用，同时在地球板块构造的发展中扮演了至关重要的角色。

我们得出这样的结论：两次最大的表面侵蚀和俯冲润滑事件分别发生在古元古代全球休伦冰期（24.5亿~22亿年前）之后，导致哥伦比亚超大陆的形成，以及在新元古代“雪球”地球冰期（7.5亿~ 6.3亿年前）之后。

▲ 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

地幔过渡带深部冷俯冲板块的磁性

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

▲ 链接：

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

▲ 摘要：

地球的壳—幔边界，即莫霍维奇不连续面，传统上被认为是磁性地壳和非磁性地幔之间的交界面。

然而，这一假设受到地球物理观测结果的质疑，幔源包体中磁性剩余物的识别——表明地幔有磁性来源——也对此提出了挑战。

这里，我们将同步加速器穆斯堡尔源光谱技术应用于激光加热的金刚石压砧中，研究了在压力和温度分别高达90吉帕和1300开尔文的情况下，三氧化二铁同质多形体的磁跃迁和临界温度。

结果表明，赤铁矿在冷俯冲或极冷俯冲地温作用下，在地幔过渡带深部仍具有磁性，并且形成了西太平洋地区的深磁化岩系。

▲ Abstract

The Earth’s crust–mantle boundary, the Mohorovičić 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 Mössbauer source spectroscopy in laser-heated diamond anvil cells to investigate the magnetic transitions and critical temperatures in Fe₂O₃ polymorphs 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.

 

生物学Biology

Predator-induced collapse of niche structure and species coexistence

捕食者诱导的生态位结构与物种共存的崩溃

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

▲ 链接：

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

▲ 摘要：

生物入侵既是一个紧迫的环境挑战，也是一个研究基本生态过程的机会，比如顶级捕食者在调节生物多样性和食物网结构中的作用。

在以沙氏变色蜥为当地顶级捕食者的加勒比小岛的全生态系统操作中，我们实验性地引入沙氏变色蜥的竞争对手——绿安乐蜥和/或新的顶级捕食者——卷尾蜥蜴的入侵。研究发现，卷尾蜥蜴破坏了相互竞争的猎物物种共存的稳定性，这与经典的梯形捕食理论相反。

恐惧驱动的对捕食者的逃避破坏了原本稳定共存的空间和饮食生态位结构，加剧了无捕食者庇护所内的种间竞争，导致两个岛屿上的绿安乐蜥种群灭绝。

▲ 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

追踪成体肠干细胞的起源

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

▲ 链接：

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

▲ 摘要：

成体肠干细胞位于李培昆氏腺窝的底部。在那里，它们表达LGR5等标记物，促进肠上皮细胞的持续补充。

虽然胎儿的LGR5表达细胞可产生成体肠干细胞，但目前尚不清楚这些在模式上皮细胞中的细胞群是否代表独特的肠干细胞前体。

这里，利用无偏差定量谱系追踪方法、生物物理建模和肠移植，我们证实小鼠肠上皮的所有细胞——和它们的位置以及在胎儿肠道管LGR5表达模式无关——主动为成体干细胞池作贡献。

利用三维成像，我们发现在胎儿发育过程中绒毛经历了总体重塑和分裂。这使得上皮细胞从非增生性绒毛进入增生性绒毛间区，从而为成体干细胞生态位的形成作出贡献。

▲ 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.

 

物理学Physics

Freestanding crystalline oxide perovskites down to the monolayer limit

独立的晶体氧化物钙钛矿降至单层极限

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

▲ 链接：

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

▲ 摘要：

二维材料如石墨烯和过渡金属双卤代烷，揭示了当大块晶体被还原为单层时所出现的电子相。

过渡金属氧化物钙钛矿含有多种相关的电子相，因此基于过渡金属氧化物钙钛矿的单层材料的类似行为将为尚未被探索的丰富的奇异二维相关相谱打开大门。

这里，我们报告了独立钙钛矿薄膜的制作。这种薄膜的高晶体质量几乎降至单个晶胞。

采用近年发展起来的以水溶性Sr₃Al₂O₆为牺牲性缓冲层的方法，我们通过反应分子束外延法合成了SrTiO₃和BiFeO₃薄膜，并将它们转移到不同的衬底上，特别是晶体硅片和多孔碳薄膜上。

▲ 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 BiFeO₃ ultrathin 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

晶格锚定稳定经溶液处理的半导体

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

▲ 链接：

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

▲ 摘要：

经溶液处理的半导体的稳定性仍然是其向更广泛应用方向改进的重要领域。

无机铯卤化铅钙钛矿具有非常适合串列太阳能电池的带隙，但在室温附近会发生不希望发生的相变。胶体量子点（CQDs）是一种结构坚固的材料，因其尺寸可调的带隙而备受赞誉。

这里，我们报告了一种将铯卤化铅钙钛矿和铅的硫属化合物CQDs结合在一起的“晶格锚定”杂化材料。其中，两种材料之间的晶格匹配有助于其稳定性超过组分的稳定性。

我们发现，CQDs使钙钛矿保持在期望的立方相，并且抑制了向不期望的晶格错配相的转变。

▲ 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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