《自然》（20181213出版）一周论文导读

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《自然》（20181213出版）一周论文导读

2018 年 12 月 16 日 科学网

Nature, 13 December 2018, Volume 564 Issue 7735

《自然》2018年12月13日第7735期564卷

封面图片来源：MuraliKrishna/IQOQI

物理学Physics

An entanglement-based wavelength-multiplexed quantum communication network

基于纠缠的波长复用量子通信网络

▲ 作者：Sören Wengerowsky, Siddarth Koduru Joshi, Fabian Steinlechner, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0766-y

▲ 摘要：

量子密匙分配达到的成熟度已能满足应用于现实场景的要求。这里，我们展示了一种完全连接的量子网络架构。

在该架构中，单个纠缠光子源向很多用户分发量子状态，同时使每个用户所需的资源最小化。更重要的是，和两方通信方案相比，最新架构并未牺牲安全性或者功能性。

我们利用单一来源的双向偏振纠缠证实了该方法的合理性。这种纠缠被复用成12个波长通道。随后，在一个完全连接的图像中，6种状态在4个用户之间成功分发，而每个用户仅利用了1根光纤和1个偏振分析模块。

▲ Abstract

Quantum key distribution has reached the level of maturity required for deployment in real-world scenarios2,3,4,5,6. Here we present a fully connected quantum network architecture in which a single entangled photon source distributes quantum states to many users while minimizing the resources required for each. Further, it does so without sacrificing security or functionality relative to two-party communication schemes. We demonstrate the feasibility of our approach using a single source of bipartite polarization entanglement, which is multiplexed into 12 wavelength channels. Six states are then distributed between four users in a fully connected graph using only one fibre and one polarization analysis module per user.

Experimental realization of on-chip topological nanoelectromechanical metamaterials

实验实现芯片上拓扑纳机电超材料

▲ 作者：Jinwoong Cha, KunWoo Kim & Chiara Daraio

▲ 链接：

https://www.nature.com/articles/s41586-018-0764-0

▲ 摘要：

引导波通过稳定的物理信道对于可靠的信息传输非常重要。

不过，由于反向散射和损失，高频机械系统比如信号处理应用中的能量传送对缺陷和急转弯非常敏感。凝聚态系统中的拓扑现象表现出对缺陷的“免疫性”和单向能量传播。

这里，我们在试验中实现了拓扑纳机电超材料。其含有在高频率下（10~20兆赫兹）下运行的二维列阵独立氮化硅纳米膜。

我们通过实验展示了边缘态的存在，并且描述了其定位和类似于狄拉克椎的频率分散的特征。

▲ Abstract

Guiding waves through a stable physical channel is essential for reliable information transport. However, energy transport in high-frequency mechanical systems, such as in signal-processing applications, is particularly sensitive to defects and sharp turns because of back-scattering and losses. Topological phenomena in condensed matter systems have shown immunity to defects and unidirectional energy propagation. Here we report the experimental realization of topological nanoelectromechanical metamaterials, consisting of two-dimensional arrays of free-standing silicon nitride nanomembranes that operate at high frequencies(10–20 megahertz). We experimentally demonstrate the presence of edge states, and characterize their localization and Dirac-cone-like frequency dispersion.

化学Chemistry

Reversible superdense ordering of lithium between two graphene sheets

两个石墨烯片之间锂的可逆超致密排序

▲ 作者：Matthias Kühne, Felix Börrnert, Sven Fecher, et al

▲ 链接：

https://www.nature.com/articles/s41586-018-0754-2

▲ 摘要：

很多碳的同素异形体能充当可逆锂吸收的主体材料，因此为现有和未来的电化学能量储存奠定了基础。

不过，关于锂如何在这些主体材料内排列的理解很难从工作系统中获得。

这里，我们通过现场低压透射电镜，研究了锂在双层石墨烯中的可逆嵌入。这个过程中，我们利用了球差和色差矫正，以增强所需水平的对比度和分辨率。

显微镜检查得到了电子能量损失能谱法和密度泛函理论计算的支撑。

▲ Abstract

Many carbon allotropes can act as host materials for reversible lithium uptake, thereby laying the foundations for existing and future electrochemical energy storage. However, insight into how lithium is arranged within these hosts is difficult to obtain from a working system. Here we study the reversible intercalation of lithium into bilayer graphene by in situ low-voltage transmission electron microscopy, using both spherical and chromatic aberration correction9 to enhance contrast and resolution to the required levels. The microscopy is supported by electron energy-loss spectroscopy and density functional theory calculations.

Catalytic deracemization of chiral allenes by sensitized excitation with visible light

通过可见光敏化激活使手性丙二烯催化去外消旋

▲ 作者：AlenaHölzl-Hobmeier, Andreas Bauer, Alexandre Vieira Silva, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0755-1

▲ 摘要：

手性化合物作为彼此的不重叠镜像的对映异构物存在。

由于对映体纯手性化合物的重要性，比如作为药物活性成分，外消旋酒石酸盐（对映异构体的1:1混合物）的分离被广泛实施。

这里，我们证实，在（催化量为2.5克分子百分比）手性敏化剂的作用下，可以利用可见光（波长为420纳米）照射，通过光化学手段使拥有高对映选择性的手性化合物去外消旋化。

我们将17个手性外消旋丙二烯阵列转化成各自的单一对映体。对映体过量百分数达到89%~97%。

▲ Abstract

Chiral compounds exist as enantiomers that are non-superimposable mirror images of each other. Owing to the importance of enantiomerically pure chiral compounds—for example, as active pharmaceutical ingredients—separation of racemates (1:1 mixtures of enantiomers) is extensively performed. Here we show that it is possible to photo chemically deracemize chiral compounds with high enantioselectivity using irradiation with visible light (wavelength of 420 nanometres) in the presence of catalytic quantities (2.5 mole per cent) of a chiral sensitizer. We converted an array of 17 chiral racemic allenes into the respective single enantiomers with 89 to 97 percent enantiomeric excess.

气候科学Climate Science

Increased variability of eastern Pacific ElNiño under greenhouse warming

温室气体增温背景下太平洋东部厄尔尼诺变化性增加

▲ 作者：Wenju Cai, Guojian Wang, Boris Dewitte, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0776-9

▲ 摘要：

厄尔尼诺—南方涛动（ENSO）是地球上占主导地位且影响最深远的气候变化。其特征是在厄尔尼诺发生期间赤道太平洋海面温度（SSTs）上升，在拉尼娜现象出现时温度下降。

ENSO事件往往有一个中心，和最大SST异常的位置相对应——在赤道太平洋中部（北纬5°~南纬5°、东经160° ~西经150° ），或者赤道太平洋东部（南纬5°~北纬5°、西经150° ~西经90°）。

这两种不同的ENSO事件分别被称为CP-ENSO和EP-ENSO。

这里，我们发现，在模拟两种不同ENSO事件的CMIP5气候模型中，未来EP-ENSOSST的变化性明显增加。

我们证实，EP-ENSO SST异常模式及其中心在不同模型间差异很大，因此无法被观测中心单一的SST指数充分体现。

不过，尽管异常中心的位置在每个模型中不同，但我们发现，在涉及的大多数模型中，每个异常中心的SST变化性明显增加。

▲ Abstract

The ElNiño–Southern Oscillation (ENSO) is the dominant and most consequential climate variation on Earth, and is characterized by warming of equatorial Pacific sea surface temperatures (SSTs) during the El Niño phase and cooling during the LaNiña phase. ENSO events tend to have a centre—corresponding to the location of the maximum SST anomaly—in either the central equatorial Pacific (5° S–5° N, 160° E–150° W) or the eastern equatorial Pacific (5° S–5° N, 150°–90° W); these two distinct types of ENSO event are referred to as the CP-ENSO and EP-ENSO regimes, respectively. Here we find a robust increase in future EP-ENSO SST variability among CMIP5 climate models that simulate the two distinct ENSO regimes. We show that the EP-ENSO SST anomaly pattern and its centre differ greatly from one model to another, and therefore cannot be well represented by a single SST ‘index’ at the observed centre. However, although the locations of the anomaly centres differ in each model, we find a robust increase in SST variability at each anomaly centre across the majority of models considered.

Widespread but heterogeneous responses of Andean forests to climate change

安第斯山脉森林对气候变化作出普遍但多样化的响应

▲ 作者：Belén Fadrique, Selene Báez, Álvaro Duque, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0715-9

▲ 摘要：

全球变暖正在迫使很多物种向上平移其生存范围，导致特定位置的物种组成随之变化。这一预测很大程度上未在热带森林中得到验证。

这里，我们利用一个关于近200个安第斯森林地块的数据库证实，热带和亚热带森林群落在组成上正经历方向性改变，即来自海拔较低、更温暖地域的物种相对丰度增加。

这些地块分布在超过33.5个纬度（从南纬26.8°到北纬7.1°）和海拔相差3000米（从超过海平面360米到3360米）的范围内。

尽管这一现象在安第斯山脉很常见，但物种组成改变的速率在不同海拔间并不统一。

▲ Abstract

Global warming is forcing many species to shift their distributions upward, causing consequent changes in the compositions of species that occur at specific locations. This prediction remains largely untested for tropical trees. Here we show, using a database of nearly 200 Andean forest plot inventories spread across more than 33.5° latitude (from 26.8° S to 7.1° N) and 3,000-m elevation (from 360 to3,360 m above sea level), that tropical and subtropical tree communities are experiencing directional shifts in composition towards having greater relative abundances of species from lower, warmer elevations. Although this phenomenon of ‘thermophilization’ is widespread throughout the Andes, the rates of compositional change are not uniform across elevations.

生物学Biology

A circuit fromhippocampal CA2 to lateral septum disinhibits social aggression

从海马体CA2到侧间隔的回路使社会性攻击摆脱抑制

▲ 作者：Felix Leroy, JungPark, Arun Asok, David H. Brann, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0772-0

▲ 摘要：

尽管海马体已知对陈述性记忆很重要，但海马体输出如何调控社会性攻击等动机行为仍不太明确。

这里，我们报告称，海马体CA2区域中对社会记忆非常重要的椎体神经元，会促进小鼠的社会性攻击。这一行为取决于来自CA2的输出向即将发起攻击前选择性得到增强的侧间隔传递。

CA2对椎体神经元的激活招募了一个使已知触发攻击的腹内侧下丘脑亚核团摆脱抑制的回路。

▲ Abstract

Although the hippocampus is known to be important for declarative memory, it is less clear how hippocampal output regulates motivated behaviours, such as social aggression. Here we report that pyramidal neurons in the CA2 region of the hippocampus, which are important for social memory, promote social aggression in mice. This action depends on output from CA2 to the lateral septum, which is selectively enhanced immediately before an attack. Activation of the lateral septum by CA2 recruits a circuit that disinhibits a subnucleus of the ventromedial hypothalamus that is known to trigger attack.

Single-cell mapping of lineage and identity in direct reprogramming

直接重编程中对谱系和身份的单细胞描绘

▲ 作者：Brent A. Biddy, Wenjun Kong, Kenji Kamimoto, et al.

▲ 链接：

https://www.nature.com/articles/s41586-018-0744-4

▲ 摘要：

直接谱系重编程涉及细胞身份的转换。单细胞技术可用于解构谱系转换期间出现的大量异质性。这里，我们展示了CellTagging技术。

这是一种组合的细胞标引方法，使并行捕获克隆历史和细胞身份成为可能。在这个过程中，连续的一轮轮细胞标记使多层次谱系树的建构成为可能。

从纤维原细胞的CellTagging和纵向跟踪到诱导内皮祖细胞重编程揭示了两种不同的路径：一种带来了成功编程的细胞，另一种则导致“死胡同”状态，路径在谱系转换的最早期阶段便已决定。

我们发现，一种假定的甲基转移酶Mettl7a1的表达同成功的重编程路径存在关联。向重编程因子混合物中加入Mettl7a1，增加了诱导内皮祖细胞的产出。

▲ Abstract

Direct lineage reprogramming involves the conversion of cellular identity. Single-cell technologies are useful for deconstructing the considerable heterogeneity that emerges during lineage conversion. Here we present ‘CellTagging’, a combinatorial cell-indexing methodology that enables parallel capture of clonal history and cell identity, in which sequential rounds of cell labelling enable the construction of multi-level lineage trees. CellTagging and longitudinal tracking of fibroblast to induced endoderm progenitor reprogramming reveals two distinct trajectories: one leading to successfully reprogrammed cells, and one leading to a ‘dead-end’ state, paths determined in the earliest stages of lineage conversion. We find that expression of a putative methyltransferase, Mettl7a1, is associated with the successful reprogramming trajectory; addingMettl7a1 to the reprogramming cocktail increases the yield of induced endoderm progenitors.