《自然》（20181213出版）一周論文導讀

Nature, 13 December 2018, Volume 564 Issue 7735

《自然》2018年12月13日第7735期564卷

封面圖片來源：MuraliKrishna/IQOQI

物理學Physics

Anentanglement-based wavelength-multiplexed quantum communication network

基於糾纏的波長復用量子通信網路

作者：S?ren Wengerowsky, SiddarthKoduru Joshi, Fabian Steinlechner, et al.

鏈接：

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

摘要：

量子密匙分配達到的成熟度已能滿足應用於現實場景的要求。這裡，我們展示了一種完全連接的量子網路架構。

在該架構中，單個糾纏光子源向很多用戶分發量子狀態，同時使每個用戶所需的資源最小化。更重要的是，和兩方通信方案相比，最新架構並未犧牲安全性或者功能性。

我們利用單一來源的雙向偏振糾纏證實了該方法的合理性。這種糾纏被複用成12個波長通道。隨後，在一個完全連接的圖像中，6種狀態在4個用戶之間成功分發，而每個用戶僅利用了1根光纖和1個偏振分析模塊。

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

實驗實現晶元上拓撲納機電超材料

作者：Jinwoong Cha, KunWoo Kim & Chiara Daraio

鏈接：

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

摘要：

引導波通過穩定的物理信道對於可靠的信息傳輸非常重要。

不過，由於反向散射和損失，高頻機械系統比如信號處理應用中的能量傳送對缺陷和急轉彎非常敏感。凝聚態系統中的拓撲現象表現出對缺陷的「免疫性」和單向能量傳播。

這裡，我們在試驗中實現了拓撲納機電超材料。其含有在高頻率下（10~20兆赫茲）下運行的二維列陣獨立氮化硅納米膜。

我們通過實驗展示了邊緣態的存在，並且描述了其定位和類似於狄拉克椎的頻率分散的特徵。

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.

化學Chemistry

Reversiblesuperdense ordering of lithium between two graphene sheets

兩個石墨烯片之間鋰的可逆超緻密排序

作者：Matthias Kühne, FelixB?rrnert, Sven Fecher, et al

鏈接：

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

摘要：

很多碳的同素異形體能充當可逆鋰吸收的主體材料，因此為現有和未來的電化學能量儲存奠定了基礎。

不過，關於鋰如何在這些主體材料內排列的理解很難從工作系統中獲得。

這裡，我們通過現場低壓透射電鏡，研究了鋰在雙層石墨烯中的可逆嵌入。這個過程中，我們利用了球差和色差矯正，以增強所需水平的對比度和解析度。

顯微鏡檢查得到了電子能量損失能譜法和密度泛函理論計算的支撐。

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

通過可見光敏化激活使手性丙二烯催化去外消旋

作者：AlenaH?lzl-Hobmeier, Andreas Bauer, Alexandre Vieira Silva, et al.

鏈接：

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

摘要：

手性化合物作為彼此的不重疊鏡像的對映異構物存在。

由於對映體純手性化合物的重要性，比如作為藥物活性成分，外消旋酒石酸鹽（對映異構體的1:1混合物）的分離被廣泛實施。

這裡，我們證實，在（催化量為2.5克分子百分比）手性敏化劑的作用下，可以利用可見光（波長為420納米）照射，通過光化學手段使擁有高對映選擇性的手性化合物去外消旋化。

我們將17個手性外消旋丙二烯陣列轉化成各自的單一對映體。對映體過量百分數達到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.

氣候科學Climate Science

Increased variability of eastern Pacific ElNi?o under greenhouse warming

溫室氣體增溫背景下太平洋東部厄爾尼諾變化性增加

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

鏈接：

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

摘要：

厄爾尼諾—南方濤動（ENSO）是地球上佔主導地位且影響最深遠的氣候變化。其特徵是在厄爾尼諾發生期間赤道太平洋海面溫度（SSTs）上升，在拉尼娜現象出現時溫度下降。

ENSO事件往往有一個中心，和最大SST異常的位置相對應——在赤道太平洋中部（北緯5°~南緯5°、東經160° ~西經150° ），或者赤道太平洋東部（南緯5°~北緯5°、西經150° ~西經90°）。

這兩種不同的ENSO事件分別被稱為CP-ENSO和EP-ENSO。

這裡，我們發現，在模擬兩種不同ENSO事件的CMIP5氣候模型中，未來EP-ENSOSST的變化性明顯增加。

我們證實，EP-ENSO SST異常模式及其中心在不同模型間差異很大，因此無法被觀測中心單一的SST指數充分體現。

不過，儘管異常中心的位置在每個模型中不同，但我們發現，在涉及的大多數模型中，每個異常中心的SST變化性明顯增加。

Abstract

The ElNi?o–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 Ni?o phase and cooling during the LaNi?a 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.

Widespreadbut heterogeneousresponses of Andean forests to climate change

安第斯山脈森林對氣候變化作出普遍但多樣化的響應

作者：Belén Fadrique, SeleneBáez, álvaro Duque, et al.

鏈接：

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

摘要：

全球變暖正在迫使很多物種向上平移其生存範圍，導致特定位置的物種組成隨之變化。這一預測很大程度上未在熱帶森林中得到驗證。

這裡，我們利用一個關於近200個安第斯森林地塊的資料庫證實，熱帶和亞熱帶森林群落在組成上正經歷方向性改變，即來自海拔較低、更溫暖地域的物種相對丰度增加。

這些地塊分布在超過33.5個緯度（從南緯26.8°到北緯7.1°）和海拔相差3000米（從超過海平面360米到3360米）的範圍內。

儘管這一現象在安第斯山脈很常見，但物種組成改變的速率在不同海拔間並不統一。

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.

生物學Biology

A circuit fromhippocampal CA2 to lateral septum disinhibits social aggression

從海馬體CA2到側間隔的迴路使社會性攻擊擺脫抑制

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

鏈接：

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

摘要：

儘管海馬體已知對陳述性記憶很重要，但海馬體輸出如何調控社會性攻擊等動機行為仍不太明確。

這裡，我們報告稱，海馬體CA2區域中對社會記憶非常重要的椎體神經元，會促進小鼠的社會性攻擊。這一行為取決於來自CA2的輸出向即將發起攻擊前選擇性得到增強的側間隔傳遞。

CA2對椎體神經元的激活招募了一個使已知觸發攻擊的腹內側下丘腦亞核團擺脫抑制的迴路。

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 mappingof lineage and identity in direct reprogramming

直接重編程中對譜系和身份的單細胞描繪

作者：Brent A. Biddy, WenjunKong, Kenji Kamimoto, et al.

鏈接：

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

摘要：

直接譜系重編程涉及細胞身份的轉換。單細胞技術可用於解構譜系轉換期間出現的大量異質性。這裡，我們展示了CellTagging技術。

這是一種組合的細胞標引方法，使並行捕獲克隆歷史和細胞身份成為可能。在這個過程中，連續的一輪輪細胞標記使多層次譜系樹的建構成為可能。

從纖維原細胞的CellTagging和縱向跟蹤到誘導內皮祖細胞重編程揭示了兩種不同的路徑：一種帶來了成功編程的細胞，另一種則導致「死胡同」狀態，路徑在譜系轉換的最早期階段便已決定。

我們發現，一種假定的甲基轉移酶Mettl7a1的表達同成功的重編程路徑存在關聯。向重編程因子混合物中加入Mettl7a1，增加了誘導內皮祖細胞的產出。

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.

（宗華）

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