古埃及人类进化断层怎么发现的（科学一周论文导读南非南方古猿）

翻译 | 李言

Science, 03 APRIL 2020, VOL 368, ISSUE 6486

《科学》2020年4月3日，第368卷，6486期

物理学Physics

Critical differences in 3D atomic structure of individual ligand-protected nanocrystals in solution

溶液中单个配体保护的纳米晶体3D原子结构的关键差异

▲ 作者：Byung Hyo Kim, Junyoung Heo, Sungin Kim, Cyril F. Reboul, Hoje Chun,et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/60

▲ 摘要：

准确地确定纳米晶体的三维原子结构是了解和预测纳米晶体物理性质的前提。来自同一合成批次的纳米晶体通常被认为是微小的，但可能在尺寸、晶格畸变和缺陷方面有重要的差异，这只能通过高空间三维分辨率的结构表征来理解。

我们通过发展原子分辨率的三维液体细胞电子显微镜来解决单个胶体铂纳米晶体的结构，以揭示配体保护的铂纳米晶体在溶液中的关键内在异质性，包括结构简并度、晶格参数偏差、内部缺陷和应变。

这些结构上的差异导致对自由能的大量贡献，其结果足以使它们在任何关于纳米晶体基本性质或应用的讨论中都必须加以考虑。

▲ Abstract

Precise three-dimensional (3D) atomic structure determination of individual nanocrystals is a prerequisite for understanding and predicting their physical properties. Nanocrystals from the same synthesis batch display what are often presumed to be small but possibly important differences in size, lattice distortions, and defects, which can only be understood by structural characterization with high spatial 3D resolution. We solved the structures of individual colloidal platinum nanocrystals by developing atomic-resolution 3D liquid-cell electron micROScopy to reveal critical intrinsic heterogeneity of ligand-protected platinum nanocrystals in solution, including structural degeneracies, lattice parameter deviations, internal defects, and strain. These differences in structure lead to substantial contributions to free energies, consequential enough that they must be considered in any discussion of fundamental nanocrystal properties or applications.

天文学Astronomy

An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime

对小行星（162173）龙宫的人为撞击形成了一个以重力为主的陨石坑

▲ 作者：M. Arakawa, T. Saiki, K. Wada, K. Ogawa, T. Kadono, et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/67

▲ 摘要

隼鸟2号对小行星龙宫进行了探测，龙宫有一个碎石堆结构。我们描述了利用隼鸟2号的小型携带撞击器在龙宫上进行的撞击实验。

这次撞击产生了一个直径大于10米的人工陨石坑，它有一个半圆形，边缘凸起，中心有个坑。分离相机记录了撞击和产生的喷出物图像，持续时间长于8分钟，显示了喷出物幕（喷出物的外边缘）的生长和喷出物在表面的沉积。

喷出物幕是不对称和不均匀的，它从来没有完全脱离表面。陨石坑形成于重力主导的区域；换句话说，陨石坑的生长受到重力而不是表面的强度的限制。我们讨论了龙宫地表年龄的影响。

▲ Abstract

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2’s Small Carry-on Impactor. The impact produced an artificial crater with a diameter>10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu’s surface age.

材料科学Material Science

Extreme tensile strain states in La0.7Ca0.3MnO3 membranes

La0.7Ca0.3MnO3薄膜的极端拉伸应变状态

▲ 作者：Seung Sae Hong, Mingqiang Gu, Manish Verma, et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/71

▲ 摘要

复合氧化物中呈展现象的一个显著特征是基态之间的竞争与合作。在锰氧化物中，金属相和绝缘相之间的平衡可以通过晶格来调节；扩展点阵控制的范围将增强访问其他相的能力。

我们在纳米级La0.7Ca0.3MnO3 薄膜中稳定了均匀的极端拉伸应变，单轴超过8%，双轴超过5%。单轴和双轴应变抑制了明显不同的应变值的铁磁金属，使其变成可以被磁场转换的绝缘体。

电子结构计算表明，绝缘子由电荷有序Mn4 和Mn3 构成，并在平面内具有交错应变增强的姜—泰勒畸变。这种高度可调的应变膜方法为设计和处理相关电子态提供了机会。

▲ Abstract

A defining feature of emergent phenomena in complex oxides is the competition and cooperation between ground states. In manganites, the balance between metallic and insulating phases can be tuned by the lattice; extending the range of lattice control would enhance the ability to access other phases. We stabilized uniform extreme tensile strain in nanoscaleLa0.7Ca0.3MnO3 membranes, exceeding 8% uniaxially and 5% biaxially. Uniaxial and biaxialstrain suppresses the ferromagnetic metal at distinctly different strain values, inducing an insulator that can be extinguished by a magnetic field. Electronic structure calculations indicate that the insulator consists of charge-ordered Mn4 and Mn3 with staggered strain-enhanced Jahn-Teller distortions within the plane. This highly tunable strained membrane approach provides a broad opportunity to design and manipulate correlated electron states.

地理学Geography

A slip law for glaciers on deformable beds

冰川在变形床层上的滑动定律

▲ 作者：Lucas K. Zoet, Neal R. Iverson

▲ 链接：

https://science.sciencemag.org/content/368/6486/76

▲ 摘要

南极西部冰盖导致海平面上升，大部分是由于海洋终端冰流在可变形冰碛床上的滑动造成的。其他地方的冰原和倾斜层状冰川的流动模型需要一条与床层的滑动阻力、滑动速度和水压相关的定律。

本文介绍了加压冰在饱和水床上滑动的实验结果。由于冰在床层上的滑动，稳态的滑动阻力随滑动速度的增加而增大，但大于临界速度，直到达到与速度无关的库仑强度。

这些结果为结合了硬层滑动和床层变形过程的冰川流模型提供了一个广义滑动定律。

▲ Abstract

Slip of marine-terminating ice streams over beds of deformable till is responsible for most of the contribution of the West Antarctic Ice Sheet to sea level rise. Flow models of the ice sheet and till-bedded glaciers elsewhere require a law that relates slip resistance, slip velocity, and water pressure at the bed. We present results of experiments in which pressurized ice at its melting temperature is slid over a water-saturated till bed. Steady-state slip resistance increases with slip velocity owing to sliding of ice across the bed, but above a threshold velocity, till shears at its rate-independent Coulomb strength. These results motivate a generalized slip law for glacier-flow models that combines processes of hard-bedded sliding and bed deformation.

古人类学Paleoanthropology

Contemporaneity of Australopithecus, Paranthropus, and earlyHomo erectus in South Africa

南非南方古猿、傍人和早期直立人的同时期性

▲ 作者：Andy I. R. Herries, Jesse M. Martin, A. B. Leece, et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/eaaw7293

▲ 摘要

对南非南方古猿的灭绝和傍人及人属起源的了解一直受到人们所认为的古人类化石的复杂地质环境、较差的年代分辨率以及缺乏保存完好的早期人属标本的阻碍。

我们描述了在南非的Drimolen Main Quarry发现两个人头颅的过程，并确定了它们的年代。DNH 152诞生约204 ~ 195万年前，是最早出现的罗百氏傍人，而DNH 134则是最早出现的与直立人有明显亲缘关系的头盖骨。

这些化石还表明，直立人、傍人和南方古猿在大约200万年前是同时期的。这种高度的分类学多样性也反映在非人族的物种中，并为在气候变化时期特有的进化和扩散提供了证据。

▲ Abstract

Understanding the extinction of Australopithecus and origins of Paranthropusand Homo in South Africa has been hampered by the perceived complex geological context of hominin fossils, poor chronological resolution, and a lack of well-preserved early Homo specimens. We describe, date, and contextualize the discovery of two hominin crania from Drimolen Main Quarry in South Africa. At ~2.04 million to 1.95 million years old, DNH 152 represents the earliest definitive occurrence of Paranthropus robustus, and DNH 134 represents the earliest occurrence of a cranium with clear affinities to Homo erectus. These crania also show that Homo, Paranthropus, andAustralopithecus were contemporaneous at ~2 million years ago. This high taxonomic diversity is also reflected in non-hominin species and provides evidence of endemic evolution and dispersal during a period of climatic variability.

医学Medical Science

Maintenance of neural stem cell positional identity by mixed-lineage leukemia 1

MLL1对神经干细胞定位识别的维持

▲ 作者：Ryan N. Delgado, Benjamin Mansky, Sajad Hamid Ahanger, et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/48

▲ 摘要

发育中的大脑和出生后的大脑中的神经干细胞（NSCs）具有不同的位置特征，这些特征决定了它们产生的神经元的类型。

虽然形态形成学最初在神经管中建立了NSC的位置识别，但随着前脑越来越大、解剖结构越来越复杂，这种差异是如何维持的还不清楚。

我们发现，维持NSC在小鼠大脑中的定位需要MLL1依赖的表观遗传记忆系统。在音猬因子建立后，腹侧的NSC独立于这一形态。即使是短暂的MLL1抑制也会导致持续性的腹侧特征丧失，导致体内产生具有背侧NSCs特征的神经元。

因此，形态形成所提供的空间信息可以转化为表观遗传机制，在前脑中维持区域上不同的发育程序。

▲ Abstract

Neural stem cells (NSCs) in the developing and postnatal brain have distinct positional identities that dictate the types of neurons they generate. Although morphogens initially establish NSC positional identity in the neural tube, it is unclear how such regional differences are maintained as the forebrain grows much largerand more anatomically complex. We found that the maintenance of NSC positional identity in the murine brain requires a mixed-lineage leukemia 1 (Mll1)–dependent epigenetic memory system. After establishment by sonic hedgehog, ventral NSC identity became independent of this morphogen. Even transient MLL1 inhibition caused a durable loss of ventral identity, resulting in the generation of neurons with the characteristics of dorsal NSCs in vivo. Thus, spatial information provided by morphogens can be transitioned to epigenetic mechanisms that maintain regionally distinct developmental programs in the forebrain.

Cysteine depletion induces pancreatic tumor ferroptosis in mice

半胱氨酸缺失诱导小鼠胰腺肿瘤铁死亡

▲ 作者：Michael A. Badgley, Daniel M. Kremer, H. Carlo Maurer, et al.

▲ 链接：

https://science.sciencemag.org/content/368/6486/85

▲ 摘要

铁死亡是细胞死亡的一种形式，是由脂质活性氧（ROS）的灾难性积累引起的。致癌信号提高了许多肿瘤类型的脂质ROS的生成，并被来自氨基酸半胱氨酸的代谢物抵消。

在这项研究中，我们发现氧化半胱氨酸（cystine）通过xC- 系统输入是胰腺导管腺癌（PDAC）的一个重要依赖项，是导致癌症死亡的主要原因。PDAC细胞利用半胱氨酸合成谷胱甘肽和辅酶A，两者共同下调铁死亡。

通过对基因改造小鼠的研究，我们发现xC- 亚基Slc7a11的缺失，诱导了肿瘤选择性铁死亡，抑制了PDAC的生长。

▲ Abstract

Ferroptosis is a form of cell death that results from the catastrophic accumulation of lipid reactive oxygen species (ROS). Oncogenic signaling elevates lipid ROS production in many tumor types and is counteracted by metabolites that are derived from the amino acid cysteine. In this work, we show that the import of oxidized cysteine (cystine) via system xC- is a critical dependency of pancreatic ductal adenocarcinoma (PDAC), which is a leading cause of cancer mortality. PDAC cells used cysteine to synthesize glutathione and coenzyme A, which, together, down-regulated ferroptosis. Studying genetically engineered mice, we found that the deletion of a system xC-subunit, Slc7a11, induced tumor-selective ferroptosis and inhibited PDAC growth.

,