《自然》（20211028出版）一周论文导读

编译｜冯维维

Nature, 28 October 2021, Volume 598 Issue 7882

《自然》2021年10月28日，第598卷，7882期

物理学Physics

A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere

炙热木星大气中的太阳碳氧比和亚太阳金属丰度

▲ 链接：

https://www.nature.com/articles/s41586-021-03912-6

▲ 摘要

测量炙热木星大气中碳（C）和氧（O）相对于氢（H）的变化，有助于了解其形成位置和随后的轨道迁移。热木星形成于主要挥发性（H2O/CO/CO2）冰线之外，随后在星盘消散后迁移，据预测其大气碳氧比（C/O）接近1，并存在亚太阳金属，而那些在消散之前通过星盘迁移的行星，预计会受到坠落的富含O的冰状星子的严重污染，导致C/O小于 0.5和超级太阳金属含量。

▲ 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

原子双层中的强相关激子绝缘体

▲ 链接：

https://www.nature.com/articles/s41586-021-03947-9

▲ 摘要

激子绝缘体（EIs）产生于半导体中束缚电子-空穴对（激子）的形成，为量子多玻色子物理提供了一个固态平台。强激子斥力通过抑制密度和相的波动来稳定凝聚的超流体和结晶相。虽然科学家已经 道了EI的光谱特征，但强烈相关EI状态的确凿证据仍然难以捉摸。

▲ 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.

化学Chemistry

Multicomponent alkene azidoarylation by anion-mediated dual catalysis

阴离子双催化多组分烯烃叠氮化

▲ 链接：

https://www.nature.com/articles/s41586-021-03980-8

▲ 摘要

在可见光的驱动下，两个分散的铜催化剂协调芳基自由基的形成和叠氮基转移，支撑烯烃叠氮芳基化过程。该方法在烯烃和芳基组分中具有广阔的应用范围，叠氮化物阴离子在氮源和通过球内电子转移介导氧化还原中性双催化中发挥着多方面的作用。

这种阴离子介导的烯烃功能化过程的合成能力很可能在各种药物相关和更广泛的合成应用中使用。

▲ 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

利用太阳能从空气中收集饮用水的全球潜力

▲ 链接：

https://www.nature.com/articles/s41586-021-03900-w

▲ 摘要

▲ 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.

地球物理学Geophysics

Indo-Pacific Walker circulation drove Pleistocene African aridification

印度-太平洋沃克环流驱动更新世非洲干旱化

▲ 链接：

https://www.nature.com/articles/s41586-021-03896-3

▲ 摘要

今天，东非的水文气候与纬向大气沃克环流的波动紧密相关。越来越多的证据表明，随着大约220 万- 200万年前太平洋沃克环流的发展，这种环流在更长的冰期-间冰期时间尺度上塑造了印度洋地区的水文气候条件。然而，没有连续的长期记录来确定印度洋受太平洋影响的气候转变的时间和机制。

▲ 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考古学

Dairying enabled Early Bronze Age Yamnaya steppe expansions

乳业使青铜器时代早期的亚姆那亚草原得以扩张

▲ 链接：

https://www.nature.com/articles/s41586-021-03798-4

▲ 摘要

在青铜器时代早期，欧亚大陆西部大草原的人口扩展到欧亚大陆北部的广阔地区。结合考古学和遗传学证据，支持了早期青铜时代大量人口从庞特-里海草原迁移出去，导致了长距离的基因流动，将斯堪的纳维亚地区的亚姆那亚牧民与遥远东方阿尔泰山脉和蒙古地区的牧民联系起来。

虽然一些模型认为，这种扩张是一种新的流动畜牧经济的结果，其特征是马牵引、散装马车运输、以及对肉类和牛奶的定期饮食依赖，但这些经济特征的确凿证据尚未发现。

▲ 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.