編譯｜馮維維
Nature, 28 October 2021, Volume 598 Issue 7882
《自然》2021年10月28日，第598卷，7882期
物理學Physics
A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere
炙熱木星大氣中的太陽碳氧比和亞太陽金屬丰度
▲ 作者：Michael R. Line, Matteo Brogi, Jacob L. Bean, Siddharth Gandhi, Joseph Zalesky, Vivien Parmentier, Peter Smith, Gregory N. Mace, Megan Mansfield, Eliza M.-R. Kempton, Jonathan J. Fortney, Evgenya Shkolnik, Jennifer Patience, Emily Rauscher, Jean-Michel Désert & Joost P. Wardenier
▲ 連結：
https://www.nature.com/articles/s41586-021-03912-6
▲ 摘要
測量炙熱木星大氣中碳（C）和氧（O）相對於氫（H）的變化，有助於瞭解其形成位置和隨後的軌道遷移。熱木星形成於主要揮發性（H2O/CO/CO2）冰線之外，隨後在星盤消散後遷移，據預測其大氣碳氧比（C/O）接近1，並存在亞太陽金屬，而那些在消散之前透過星盤遷移的行星，預計會受到墜落的富含O的冰狀星子的嚴重汙染，導致C/O小於 0.5和超級太陽金屬含量。
作者確定了大氣氣體體積混合比對H2O和CO的約束條件（分別為9.5 × 10−5-1.5 × 10−4和1.2 × 10−4 - 2.6 × 10−4）。根據這些有界約束條件，可以得到大氣C/H和O/H的丰度以及相應的大氣碳氧比。亞太陽（C+O）/H表明，相對於類木行星而言，大氣中金屬含量較低，而接近太陽的C/O值排除了無盤遷移/富含C的大氣情景。
▲ Abstract
Measurements of the atmospheric carbon (C) and oxygen (O) relative to hydrogen (H) in hot Jupiters (relative to their host stars) provide insight into their formation location and subsequent orbital migration. Hot Jupiters that form beyond the major volatile (H2O/CO/CO2) ice lines and subsequently migrate post disk-dissipation are predicted have atmospheric carbon-to-oxygen ratios (C/O) near 1 and subsolar metallicities, whereas planets that migrate through the disk before dissipation are predicted to be heavily polluted by infalling O-rich icy planetesimals, resulting in C/O < 0.5 and super-solar metallicities. Here we report spectroscopic observations of a typical transiting hot Jupiter, WASP-77Ab. From these, we determine the atmospheric gas volume mixing ratio constraints on both H2O and CO (9.5 × 10−5–1.5 × 10−4 and 1.2 × 10−4–2.6 × 10−4, respectively). From these bounded constraints, we are able to derive the atmospheric C/H and O/H abundances and the corresponding atmospheric carbon-to-oxygen ratio (C/O = 0.59 ± 0.08; the solar value is 0.55). The sub-solar (C+O)/H is suggestive of a metal-depleted atmosphere relative to what is expected for Jovian-like planets1 while the near solar value of C/O rules out the disk-free migration/C-rich atmosphere scenario.
Strongly correlated excitonic insulator in atomic double layers
原子雙層中的強相關激子絕緣體
▲ 作者：Liguo Ma, Phuong X. Nguyen, Zefang Wang, Yongxin Zeng, Kenji Watanabe, Takashi Taniguchi, Allan H. MacDonald, Kin Fai Mak & Jie Shan
▲ 連結：
https://www.nature.com/articles/s41586-021-03947-9
▲ 摘要
激子絕緣體（EIs）產生於半導體中束縛電子-空穴對（激子）的形成，為量子多玻色子物理提供了一個固態平臺。強激子斥力透過抑制密度和相的波動來穩定凝聚的超流體和結晶相。雖然科學家已經報道了EI的光譜特徵，但強烈相關EI狀態的確鑿證據仍然難以捉摸。
作者演示了過渡金屬二鹵族（TMD）半導體雙層中形成的一個強相關的二維EI基態。當施加在兩個電隔離TMD層之間的偏置電壓被調諧到一個範圍，該範圍會填充束縛電子-空穴對，而不是自由電子或空穴時，就會產生準平衡空間間接激子流體。電容測量表明流體是激可壓縮但電荷不可壓縮的，這是EI的直接熱力學證據。
流體也與超過10的無因次激子耦合常數密切相關。他們構建了一個激子相圖，揭示了莫特躍遷和相互作用穩定的準凝聚。作者表示，該實驗為實現奇異的激子量子相位以及多端激子電路的應用鋪平了道路。
▲ Abstract
Excitonic insulators (EIs) arise from the formation of bound electron–hole pairs (excitons) in semiconductors and provide a solid-state platform for quantum many-boson physics. Strong exciton–exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations. Although spectroscopic signatures of EIs have been reported, conclusive evidence for strongly correlated EI states has remained elusive. Here we demonstrate a strongly correlated two-dimensional (2D) EI ground state formed in transition metal dichalcogenide (TMD) semiconductor double layers. A quasi-equilibrium spatially indirect exciton fluid is created when the bias voltage applied between the two electrically isolated TMD layers is tuned to a range that populates bound electron–hole pairs, but not free electrons or holes. Capacitance measurements show that the fluid is exciton-compressible but charge-incompressible—direct thermodynamic evidence of the EI. The fluid is also strongly correlated with a dimensionless exciton coupling constant exceeding 10. We construct an exciton phase diagram that reveals both the Mott transition and interaction-stabilized quasi-condensation. Our experiment paves the path for realizing exotic quantum phases of excitons, as well as multi-terminal exciton circuitry for applications.
化學Chemistry
Multicomponent alkene azidoarylation by anion-mediated dual catalysis
陰離子雙催化多組分烯烴疊氮化
▲ 作者：Ala Bunescu, Yusra Abdelhamid & Matthew J. Gaunt
▲ 連結：
https://www.nature.com/articles/s41586-021-03980-8
▲ 摘要
含有β-芳基乙胺基序的分子在疼痛調節、神經系統疾病的治療和阿片類藥物成癮的管理等方面都有應用，使其成為藥物發現的一個重要支架。作者報告了一個雙催化平臺的發展，使烯烴、芳基親電試劑和簡單的氮親核試劑的多組分偶聯，提供了一步合成多功能和功能多樣性的β-芳基乙胺。
在可見光的驅動下，兩個分散的銅催化劑協調芳基自由基的形成和疊氮基轉移，支撐烯烴疊氮芳基化過程。該方法在烯烴和芳基組分中具有廣闊的應用範圍，疊氮化物陰離子在氮源和透過球內電子轉移介導氧化還原中性雙催化中發揮著多方面的作用。
這種陰離子介導的烯烴功能化過程的合成能力很可能在各種藥物相關和更廣泛的合成應用中使用。
▲ Abstract
Molecules that contain the β-arylethylamine motif have applications in the modulation of pain, treatment of neurological disorders and management of opioid addiction, among others, making it a privileged scaffold in drug discovery. Synthetic invention can drive the investigation of the chemical space around this scaffold to further expand its capabilities in biology. Here we report the development of a dual catalysis platform that enables a multicomponent coupling of alkenes, aryl electrophiles and a simple nitrogen nucleophile, providing single-step access to synthetically versatile and functionally diverse β-arylethylamines. Driven by visible light, two discrete copper catalysts orchestrate aryl-radical formation and azido-group transfer, which underpin an alkene azidoarylation process. The process shows broad scope in alkene and aryl components and an azide anion performs a multifaceted role both as a nitrogen source and in mediating the redox-neutral dual catalysis via inner-sphere electron transfer. The synthetic capabilities of this anion-mediated alkene functionalization process are likely to be of use in a variety of pharmaceutically relevant and wider synthetic applications.
Global potential for harvesting drinking water from air using solar energy
利用太陽能從空氣中收集飲用水的全球潛力
▲ 作者：Jackson Lord, Ashley Thomas, Neil Treat, Matthew Forkin, Robert Bain, Pierre Dulac, Cyrus H. Behroozi, Tilek Mamutov, Jillia Fongheiser, Nicole Kobilansky, Shane Washburn, Claudia Truesdell, Clare Lee & Philipp H. Schmaelzle
▲ 連結：
https://www.nature.com/articles/s41586-021-03900-w
▲ 摘要
獲得安全管理的飲用水仍然是一項全球性挑戰，影響著22億人。太陽能驅動的連續迴圈大氣水收集（AWH）裝置可透過分散從空氣中提取水來加速進展，但低的比產量（SY）和低的白天相對溼度（RH）對它們的效能提出了挑戰（以每天輸出升水為單位）。作者展示了AWH可以為10億人提供安全管理的飲用水。
作者使用谷歌地球進行了評估，他們引入了一個假設1平方米的裝置，在30%至90% RH下，SY剖面分別為0.2至2.5升/千瓦時（對於2米平方的裝置，SY剖面為0.1至1.25升/千瓦時）。這種裝置可以達到每人每天平均5升飲用水的目標。他們繪製了現有裝置和新的吸附劑類別的影響潛力，這表明這些目標可以透過持續的技術發展，並在熱力學限制內實現。
事實上，這些效能目標已經在吸附劑材料的實驗演示中得到了實現。作者表示該工具可以為全球影響最大化的大氣水收集裝置的設計權衡提供資訊，同時還可為利用現有技術實現可持續發展目標的持續努力提供資訊。
▲ Abstract
Access to safely managed drinking water (SMDW) remains a global challenge, and affects 2.2 billion people. Solar-driven atmospheric water harvesting (AWH) devices with continuous cycling may accelerate progress by enabling decentralized extraction of water from air, but low specific yields (SY) and low daytime relative humidity (RH) have raised questions about their performance (in litres of water output per day). However, to our knowledge, no analysis has mapped the global potential of AWH despite favourable conditions in tropical regions, where two-thirds of people without SMDW live. Here we show that AWH could provide SMDW for a billion people. Our assessment—using Google Earth Engine—introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatt-hour (0.1 to 1.25 litres per kilowatt-hour for a 2-metre-square device) at 30% to 90% RH, respectively. Such a device could meet a target average daily drinking water requirement of 5 litres per day per person. We plot the impact potential of existing devices and new sorbent classes, which suggests that these targets could be met with continued technological development, and well within thermodynamic limits. Indeed, these performance targets have been achieved experimentally in demonstrations of sorbent materials. Our tools can inform design trade-offs for atmospheric water harvesting devices that maximize global impact, alongside ongoing efforts to meet Sustainable Development Goals (SDGs) with existing technologies.
地球物理學Geophysics
Indo-Pacific Walker circulation drove Pleistocene African aridification
印度-太平洋沃克環流驅動更新世非洲乾旱化
▲ 作者：H. J. L. van der Lubbe, I. R. Hall, S. Barker, S. R. Hemming, T. F. Baars, A. Starr, J. Just, B. C. Backeberg & J. C. A. Joordens
▲ 連結：
https://www.nature.com/articles/s41586-021-03896-3
▲ 摘要
今天，東非的水文氣候與緯向大氣沃克環流的波動緊密相關。越來越多的證據表明，隨著大約220 萬- 200萬年前太平洋沃克環流的發展，這種環流在更長的冰期-間冰期時間尺度上塑造了印度洋地區的水文氣候條件。然而，沒有連續的長期記錄來確定印度洋受太平洋影響的氣候轉變的時間和機制。
作者展示了熱帶印度洋的風驅動環流長達700萬年的記錄，記錄於莫三比克海峽透過流（MCT）的流速變化。他們發現MCT的流速相對較弱且穩定，直到210萬年（±10萬年），當它開始增加時，與太平洋沃克環流的增強相一致。冰期有強烈的增加，在中更新世轉世（0.9-0.64百萬年），在間冰期被弱流速打斷。
作者提供了一種機制，解釋了MCT流速的增加反映了促進非洲乾旱化的印度-太平洋沃克單元的同步發展。研究結果表明，大約210萬年之後，乾旱加劇被明顯的溼潤間冰期打斷。這一記錄將有助於檢驗古人類進化和傳播的氣候-環境驅動假說。
▲ Abstract
Today, the eastern African hydroclimate is tightly linked to fluctuations in the zonal atmospheric Walker circulation. A growing body of evidence indicates that this circulation shaped hydroclimatic conditions in the Indian Ocean region also on much longer, glacial–interglacial timescales, following the development of Pacific Walker circulation around 2.2–2.0 million years ago (Ma). However, continuous long-term records to determine the timing and mechanisms of Pacific-influenced climate transitions in the Indian Ocean have been unavailable. Here we present a seven-million-year-long record of wind-driven circulation of the tropical Indian Ocean, as recorded in Mozambique Channel Throughflow (MCT) flow-speed variations. We show that the MCT flow speed was relatively weak and steady until 2.1 ± 0.1 Ma, when it began to increase, coincident with the intensification of the Pacific Walker circulation. Strong increases during glacial periods, which reached maxima after the Mid-Pleistocene Transition (0.9–0.64 Ma; ref. 8), were punctuated by weak flow speeds during interglacial periods. We provide a mechanism explaining that increasing MCT flow speeds reflect synchronous development of the Indo-Pacific Walker cells that promote aridification in Africa. Our results suggest that after about 2.1 Ma, the increasing aridification is punctuated by pronounced humid interglacial periods. This record will facilitate testing of hypotheses of climate–environmental drivers for hominin evolution and dispersal.
Archeology考古學
Dairying enabled Early Bronze Age Yamnaya steppe expansions
乳業使青銅器時代早期的亞姆那亞草原得以擴張
▲ 作者：Shevan Wilkin, Alicia Ventresca Miller, Ricardo Fernandes, Robert Spengler, William T.-T. Taylor, Dorcas R. Brown, David Reich, Douglas J. Kennett, Brendan J. Culleton, Laura Kunz, Claudia Fortes, Aleksandra Kitova, Pavel Kuznetsov, Andrey Epimakhov, Victor F. Zaibert, Alan K. Outram, Egor Kitov, Aleksandr Khokhlov, David Anthony & Nicole Boivin
▲ 連結：
https://www.nature.com/articles/s41586-021-03798-4
▲ 摘要
在青銅器時代早期，歐亞大陸西部大草原的人口擴充套件到歐亞大陸北部的廣闊地區。結合考古學和遺傳學證據，支援了早期青銅時代大量人口從龐特-裡海草原遷移出去，導致了長距離的基因流動，將斯堪的納維亞地區的亞姆那亞牧民與遙遠東方阿爾泰山脈和蒙古地區的牧民聯絡起來。
雖然一些模型認為，這種擴張是一種新的流動畜牧經濟的結果，其特徵是馬牽引、散裝馬車運輸、以及對肉類和牛奶的定期飲食依賴，但這些經濟特徵的確鑿證據尚未發現。
作者利用蛋白質組學分析了來自歐亞西部草原的個體的牙石，以證明在青銅時代開始時，乳品業發生了重大轉變。在已知草原種群開始分散的時間點上，無所不在的擠奶業迅速興起，為了解草原流動性的關鍵催化劑提供了關鍵的見解。對馬奶蛋白的鑑定也表明，早在青銅器時代就有人馴養了馬，這為馬在草原擴散中的作用提供了支援。
作者表示，該研究結果認為到公元前3000年龐特-裡海草原可能是馬馴化的一箇中心，並有力地支援了一種觀點，即次級動物產品的新開發是早期青銅器時代歐亞草原牧民擴張的關鍵驅動因素。
▲ Abstract
During the Early Bronze Age, populations of the western Eurasian steppe expanded across an immense area of northern Eurasia. Combined archaeological and genetic evidence supports widespread Early Bronze Age population movements out of the Pontic–Caspian steppe that resulted in gene flow across vast distances, linking populations of Yamnaya pastoralists in Scandinavia with pastoral populations (known as the Afanasievo) far to the east in the Altai Mountains and Mongolia. Although some models hold that this expansion was the outcome of a newly mobile pastoral economy characterized by horse traction, bulk wagon transport and regular dietary dependence on meat and milk, hard evidence for these economic features has not been found. Here we draw on proteomic analysis of dental calculus from individuals from the western Eurasian steppe to demonstrate a major transition in dairying at the start of the Bronze Age. The rapid onset of ubiquitous dairying at a point in time when steppe populations are known to have begun dispersing offers critical insight into a key catalyst of steppe mobility. The identification of horse milk proteins also indicates horse domestication by the Early Bronze Age, which provides support for its role in steppe dispersals. Our results point to a potential epicentre for horse domestication in the Pontic–Caspian steppe by the third millennium BC, and offer strong support for the notion that the novel exploitation of secondary animal products was a key driver of the expansions of Eurasian steppe pastoralists by the Early Bronze Age.
