《科學》（20210521出版）一周論文導讀
編譯 馮維維
Science , 21 May 2021, Volume 372 Issue 6544
《科學》 2021年5月21日，第372卷，6544期
物理學 Physics
Electron ptychography achieves atomic-resolution limits set by lattice vibrations
電子疊層成像實現(xiàn)晶格振動規(guī)定的原子分辨率極限
作者：Zhen Chen, Yi Jiang, Yu-Tsun Shao, David A. Muller, etc.
鏈接：
https://science.sciencemag.org/content/372/6544/826
摘要
限制電子顯微鏡圖像分辨率和解釋的兩個主要問題是透鏡像差和多次散射。
作者利用疊層成像——一種使用相干散射和多個重疊照明點從遠場衍射模式重建圖像的技術，克服了這些問題。這種方法的分辨率不是受光學的限制，而是受樣品散射強度的限制，所以它可以更好地用于較厚的樣品。
作者獲得了比PrScO3樣品中原子的熱振動更好的最終橫向分辨率，表明在理論上可以識別單個摻雜原子。
Abstract
Two major problems that limit the resolution and interpretation of electron microscopy images are lens aberrations and multiple scattering. Chen et al. overcame these issues with ptychography, a technique that uses coherent scattering and multiple overlapping illumination spots to reconstruct an image from far-field diffraction patterns. This method works at a resolution that is limited, not by optics, but rather by the scattering strength of the sample, so it can work better with thicker samples. The authors achieved ultimate lateral resolution better than the thermal vibration of atoms in a PrScO3 sample and showed that it is theoretically possible to identify single dopant atoms.
Observation of superfluidity in a strongly correlated two-dimensional Fermi gas
二維費米氣體中的超流體現(xiàn)象
作者：Lennart Sobirey, Niclas Luick, Markus Bohlen, Hauke Biss, Henning Moritz, VThomas Lompe
鏈接：
https://science.sciencemag.org/content/372/6544/844
摘要
理解緊密相關的二維系統(tǒng)如何在高溫下產生非常規(guī)超導性是凝聚態(tài)物理中尚未解決的主要問題之一。
超冷的二維費米氣體作為干凈和可控的模型系統(tǒng)出現(xiàn)，用于研究強相關性和降維的相互作用，但這些系統(tǒng)中超流體的直接證據(jù)一直缺失。
作者通過在系統(tǒng)中移動一個周期勢，并觀察到在臨界速度VC以下沒有耗散，來證明在超冷二維費米氣體中的超流體性。
他們將VC 作為相互作用強度的函數(shù)進行了測量，并在玻色子超流和費米超流的交叉域中找到一個極大值。作者表示，該測量使系統(tǒng)地研究降維對費米超流的影響成為可能。
Abstract
Understanding how strongly correlated two-dimensional (2D) systems can give rise to unconventional superconductivity with high critical temperatures is one of the major unsolved problems in condensed matter physics. Ultracold 2D Fermi gases have emerged as clean and controllable model systems to study the interplay of strong correlations and reduced dimensionality, but direct evidence of superfluidity in these systems has been missing. We demonstrate superfluidity in an ultracold 2D Fermi gas by moving a periodic potential through the system and observing no dissipation below a critical velocity vc. We measure vc as a function of interaction strength and find a maximum in the crossover regime between bosonic and fermionic superfluidity. Our measurements enable systematic studies of the influence of reduced dimensionality on fermionic superfluidity.
化學 Chemistry
Reversible ketone hydrogenation and dehydrogenation for aqueous organic redox flow batteries
有機水相氧化還原流電池酮可逆氫化和脫氫
作者：Ruozhu Feng, Xin Zhang, Vijayakumar Murugesan, Aaron Hollas, Ying Chen, Yuyan Shao, Eric Walter, Nadeesha P. N. Wellala, Litao Yan, Kevin M. Rosso, Wei Wang
鏈接：
https://science.sciencemag.org/content/372/6544/836
摘要
在液流電池中，陰極液和陽極液被存儲在單獨的槽中，泵被用于將液體循環(huán)到由薄膜隔開的電極堆中。這種電池是大規(guī)模電網(wǎng)存儲應用的理想選擇；然而，合適的氧化還原分子目前仍然有限。
作者利用“分子工程”對廉價的前體（9-芴酮）進行修飾，作為有機氧化還原流電池的基礎。他們在一個氧化還原流電池中測試了一系列不同的分子，其中的反應涉及可逆的酮在水電解質中氫化和脫氫。這些反應具有雙電子氧化還原和在空氣、高溫（50 ）下操作等優(yōu)點，更適合于實際應用。
Abstract
In a flow battery, catholyte and anolyte are stored in separate tanks, and pumps are used to circulate the fluids into a stack with electrodes separated by a thin membrane. Such batteries are ideal for large-scale grid storage applications; however, suitable redox molecules are currently limited. Feng et al. used “molecular engineering” to modify an inexpensive precursor (9-fluorenone) as the basis for an organic-based redox flow battery. The authors tested a series of variant molecules in a redox flow battery in which the reactions involve reversible ketone hydrogenation and dehydrogenation in an aqueous electrolyte. These reactions have advantageous features, including two-electron redox and operation in air and at elevated temperatures (50 C), that are more suitable for real-world applications.
Biphenylene network: A nonbenzenoid carbon allotrope
聯(lián)苯網(wǎng)絡:一種非苯類碳同素異形體
作者：Qitang Fan, Linghao Yan, Matthias W. Tripp, Ondrej Krejcí, Stavrina Dimosthenous, Stefan R. Kachel, Mengyi Chen, Adam S. Foster, Ulrich Koert, Peter Liljeroth, J. Michael Gottfried
鏈接：
https://science.sciencemag.org/content/372/6544/852
摘要
雖然石墨烯形成了二維的碳片，但其他排列的碳環(huán)也可以組裝成平面的薄片。
作者在金表面上合成了一種由 sp2 雜化碳原子組成的四元、六元和八元環(huán)的聯(lián)苯碳片。吸附的鹵代三苯分子經(jīng)過兩步互聚脫氫氟化聚合，通過碳-碳鍵形成四元環(huán)和八元環(huán)。
掃描隧道光譜顯示，該碳同素異形體是金屬的，而不是電介質。作者期望這種互聚體HF-zip方法能夠補充其他非苯類碳同素異形體的合成工具箱。
Abstract
Although graphene forms two-dimensional carbon sheets, other arrangements of carbon rings could also assemble as flat sheers. Fan et al. synthesized an ultraflat biphenylene carbon sheet consisting of sp2 -hybridized carbon atoms forming four-, six-, and eight-membered rings on a gold surface. An adsorbed halogenated terphenyl molecule undergoes a two-step interpolymer dehydrofluorination polymerization that creates the four- and eight-membered rings through carbon–carbon bond formation. Scanning tunneling spectroscopy revealed that this carbon allotrope is metallic. They expect the interpolymer HF-zipping method to complement the toolbox for the synthesis of other nonbenzenoid carbon allotropes.
氣候與生態(tài) Climate &Ecology
Global acceleration in rates of vegetation change over the past 18,000 years
過去18000年，全球植被變化加速
作者：Ondrej Mottl, Suzette G. A. Flantua, Kuber P. Bhatta1, John W. Williams, etc.
鏈接：
https://science.sciencemag.org/content/372/6544/860
摘要
在過去的18000年里，全球植被首先因伴隨最后一次冰川消失的氣候變化而發(fā)生變化，此后因為人類壓力的增加而發(fā)生變化；然而，對全球植被變化率的幅度和模式了解甚少。
通過對1181個花粉化石序列的匯編和新開發(fā)的統(tǒng)計方法，作者發(fā)現(xiàn)，從4.6萬年前到2.9萬年前，全球范圍內的植被組成變化速度在加速，這在過去1.8萬年里的全球范圍內都是前所未有的。
全新世晚期的變化速率等于或超過了所有大陸的除冰速率，這表明人類對陸地生態(tài)系統(tǒng)的影響規(guī)模甚至超過了氣候驅動的最后一次除冰。作者表示，從上個世紀的生態(tài)數(shù)據(jù)中可以看出，生物多樣性變化的加速始于數(shù)千年前。
Abstract
Global vegetation over the past 18,000 years has been transformed first by the climate changes that accompanied the last deglaciation and again by increasing human pressures; however, the magnitude and patterns of rates of vegetation change are poorly understood globally. Using a compilation of 1181 fossil pollen sequences and newly developed statistical methods, we detect a worldwide acceleration in the rates of vegetation compositional change beginning between 4.6 and 2.9 thousand years ago that is globally unprecedented over the past 18,000 years in both magnitude and extent. Late Holocene rates of change equal or exceed the deglacial rates for all continents, which suggests that the scale of human effects on terrestrial ecosystems exceeds even the climate-driven transformations of the last deglaciation. The acceleration of biopersity change demonstrated in ecological datasets from the past century began millennia ago.
Balancing conservation priorities for nature and for people in Europe
歐洲保護自然的優(yōu)先事項
作者：Louise M. J. O’Connor, Laura J. Pollock, Julien Renaud, Willem Verhagen, Peter H. Verburg, Sandra Lavorel, Luigi Maiorano, Wilfried Thuiller
鏈接：
https://science.sciencemag.org/content/372/6544/856
摘要
保護科學家一致認為，應該擴大保護區(qū)以保護生物多樣性和生態(tài)系統(tǒng)服務，但往往很難確定保護區(qū)的優(yōu)先級。
考慮到推動整個歐洲保護的因素，作者的分析囊括了，以（>800）脊椎動物物種的分布為代表的物種的價值；以自然 旅游 等活動為代表的景觀的文化價值；以及碳匯和防洪等生態(tài)系統(tǒng)服務的價值。
Abstract
There is consensus among conservation scientists that protected areas should be expanded to safeguard biopersity and ecosystem services, but it is often difficult to prioritize areas for protection. Considering factors that motivate conservation across Europe, an analysis by O'Connor et al. includes the value of species, represented by distribution of >800 vertebrate species; the cultural value of landscapes, represented by activities such as nature tourism; and the value of ecosystem services such as carbon sequestration and flood protection. Although these three main features often do not coincide in the landscape, the authors found that a focus on biopersity in spatial conservation planning is the most effective means of capturing a range of nature's values.
《科學》(20210521出版)一周論文導讀
https:\/\/science.sciencemag.org\/content\/372\/6544\/852 摘要 雖然石墨烯形成了二維的碳片,但其他排列的碳環(huán)也可以組裝成平面的薄片。 作者在金表面上合成了一種由 sp2 雜化碳原子組成的四元、六元和八元環(huán)的聯(lián)苯碳片。吸附的鹵代三苯分子經(jīng)過兩步互聚脫氫氟化聚合,通過碳-碳鍵形成四元環(huán)和八元環(huán)。 ...
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