翻译 | 宗华

Nature，12 September 2019，Volume 573 Issue 7773

《自然》 2019年9月12日，第573卷，7773期

材料Materials

Electrochemically reconfigurable architected materials

电化学可重构的结构化材料

结构化材料可以通过改变几何形状，实现对机械力、水合作用、磁场等外部刺激的积极响应，从而实现新的功能。

在此，我们开发了三维硅包覆的四方微晶格。该微晶格在电化学驱动的硅锂合金化反应中，通过协同梁屈曲转变为正弦模式。

原位显微技术揭示了一种可控的、非挥发性的电脑、可逆的结构转变。这种转变形成了多个有序的屈曲区域。这些区域被扭曲的区域边界所分隔。

通过化学—力学建模和统计力学分析，我们研究了单个屈曲梁的力学动力学、相邻梁之间的协同耦合以及与锂化率有关的区域尺寸分布。

我们的结果强调了缺陷和能量波动在结构化材料动态响应中的重要作用。

Architected materials can actively respond to external stimuli—such as mechanical forces, hydration and magnetic fields—by changing their geometries and thereby achieve novel functionalities. Here we develop three-dimensional silicon-coated tetragonal microlattices that transform into sinusoidal patterns via cooperative beam buckling in response to an electrochemically driven silicon-lithium alloying reaction. In situ microscopy reveals a controllable, non-volatile and reversible structural transformation that forms multiple ordered buckling domains separated by distorted domain boundaries. We investigate the mechanical dynamics of individual buckling beams, cooperative coupling among 电脑 neighbouring beams, and lithiation-rate-dependent distributions of domain sizes through chemo-mechanical modelling and statistical mechanics analysis. Our results highlight the critical role of defects and energy fluctuations in the dynamic response of architected materials.

Position and momentum mapping of vibrations in graphene nanostructures

石墨烯纳米结构振动的位置和动量图

传播的原子振动波—声子—决定了材料的重要热、机械、光电和输运特性。

因此，对于声子色散（即振动能量对动量的依赖）的了解是我们理解和优化材料行为的关键部分。

这里，我们提供了一种新的途径——通过绘制大动量转移的不同振动模式，确定单个独立石墨烯单层的声子色散。

我们利用密度泛函微扰理论对测量到的散射强度进行了精确的再现和解释。

此外，利用石墨烯纳米带结构对选定的动量分辨振动模式进行纳米尺度映射，使我们能够在空间上分离体、边缘和表面振动。

Propagating atomic vibrational waves—phonons—determine important thermal, mechanical, optoelectronic and transport characteristics of materials. Thus a knowledge of phonon dispersion (that is, the dependence of vibrational energy on momentum) is a key part of our understanding and optimization of a material’s behaviour. Here we provide a new pathway to determine phonon dispersions down to the scale of an individual free-standing graphene monolayer by mapping the distinct vibrational modes for a large momentum transfer. The measured scattering intensities are accurately reproduced and interpreted with density functional perturbation theory. Additionally, a nanometre-scale mapping of selected momentum-resolved vibrational modes using graphene nanoribbon structures has enabled us to spatially disentangle bulk, edge and surface vibrations.

古人类学Paleoanthropology

A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia

来自埃塞俄比亚Woranso-Mille的380万年前古人类头盖骨

在南方古猿属中，已知最早的古人类的颅骨形态仍不清楚。

这一属中最古老的物种（湖畔南方古猿，其标本可追溯到420万至390万年前）主要通过颌骨和牙齿得以确认，而较年轻的物种（年代可追溯到350万至200万年前）通常由多个头骨代表。

这里，我们描述了一个来自埃塞俄比亚Woranso-Mille地区的几乎完整的古人类头盖骨。

我们将其追溯至380万年前。根据犬齿、上颌骨和颞骨的分类和系统发育信息形态学，我们将该头盖骨归为湖畔南方古猿。

因此，该标本提供了对已知最早的南方古猿属成员的整个颅面形态的首次一瞥。

The cranial morphology of the earliest known hominins in the genus Australopithecus remains unclear. The oldest species in this genus (Australopithecus anamensis, specimens of which have been dated to 4.2–3.9 million years ago) is known primarily from jaws and teeth, whereas younger species (dated to 3.5–2.0 million years ago) are typically represented by multiple skulls. Here we describe a nearly complete hominin cranium from Woranso-Mille (Ethiopia) that we date to 3.8 million years ago. We assign this cranium to A. anamensis on the basis of the taxonomically and phylogenetically informative morphology of the canine, maxilla and temporal bone. This specimen thus provides the first glimpse of the entire craniofacial morphology of the earliest known members of the genus Australopithecus.

Age and context of mid-Pliocene hominin cranium from Woranso-Mille, Ethiopia

来自埃塞俄比亚Woranso-Mille上新世中期古人类头盖骨的年龄和背景

一块古人类头盖骨化石在埃塞俄比亚西北部Woranso-Mille研究区Godaya山谷上新世三角洲地层中被发现。

这里，我们通过分析化学相关火山层和古地磁地层学，同时结合贝叶斯造型过时凝灰岩，产生了一个针对该三角洲地层及其所包含化石的年龄范围——3.804±0.013到3.777±001.4万年前（平均±1σ）。

我们还记录了三角洲层序下一个常年湖泊的沉积物。

与头盖骨相关的哺乳动物化石代表了当时广泛分布的类群，而来自植物遗迹的数据表明，湖泊和三角洲流域的植被主要是干灌木丛，其中草原、湿地和河岸森林的比例各不相同。

A fossil hominin cranium was discovered in mid-Pliocene deltaic strata in the Godaya Valley of the northwestern Woranso-Mille study area in Ethiopia. Here we show that analyses of chemically correlated volcanic layers and the palaeomagnetic stratigraphy, combined with Bayesian modelling of dated tuffs, yield an age range of 3.804 ± 0.013 to 3.777 ± 0.014 million years old (mean ± 1σ) for the deltaic strata and the fossils that they contain. We also document deposits of a perennial lake beneath the deltaic sequence. Mammalian fossils associated with the cranium represent taxa that were widespread at the time and data from botanical remains indicate that the vegetation in the lake and delta catchment was predominantly dry shrubland with varying proportions of grassland, wetland and riparian forest.

古气候学Paleoclimatology

Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years

过去136万年地中海冬季降水与非洲季风同期

地中海气候的特点是在干燥的夏季和潮湿的冬季之间形成强烈的季节对比。

这里，我们证实，过去136万年里，地中海中北部潮湿的冬季往往与当地季节性日照和强烈的非洲夏季风形成高反差。

来自巴尔干半岛奥赫里德湖的时间序列加上78.4万年短暂气候模型追算表明，海洋表面温度增加放大了当地气旋发展，并为北大西洋低压系统补充能量，使其在大陆冰量较低和大气温室气体浓度较高期间进入地中海。

与现代再分析数据的比较表明，目前地中海地区降雨量的驱动因素与那些驱动重建降水增加的因素有一些相似之处。

Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation.

社会学Sociology

Hidden resilience and adaptive dynamics of the global online hate ecology

全球网络仇恨生态的隐藏复原力和自适应动力学

网上的仇恨和极端主义言论与现实世界中令人憎恶的事件存在关联。社交媒体平台似乎正在输掉与网络仇恨的战斗，并且迫切需要新的洞见。

这里，我们证实，理解网络仇恨复原力的关键在于它的全球网络动力学。相互关联的仇恨集群形成了全球性的“仇恨高速公路”。

在集体网络自适应的助力下，这些“仇恨高速公路”可以跨越社交媒体平台，有时甚至在被禁之后还会使用“后门”，并且跨越国家、大洲和语言。

我们的数学模型预测，在单一平台内进行监管可能会使情况变得更糟，并最终产生全球性的“黑池”，其中网络仇恨将会泛滥。

我们观察到，当前的憎恨网络在受到攻击时，会在微观层面迅速地“重新布线”和自我修复，这与化学中共价键的形成过程类似。

Online hate and extremist narratives have been linked to abhorrent real-world events. Social media platforms seem to be losing the battle against online hate and urgently need new insights. Here we show that the key to understanding the resilience of online hate lies in its global network-of-network dynamics. Interconnected hate clusters form global ‘hate highways’ that—assisted by collective online adaptations—cross social media platforms, sometimes using ‘back doors’ even after being banned, as well as jumping between countries, continents and languages. Our mathematical model predicts that policing within a single platform (such as Facebook) can make matters worse, and will eventually generate global ‘dark pools’ in which online hate will flourish. We observe the current hate network rapidly rewiring and self-repairing at the micro level when attacked, in a way that mimics the formation of covalent bonds in chemistry.

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