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中美研究指出对流和燃料可用性对全球野火具有调控作用 快报文章
气候变化快报,2025年第5期
作者:  刘莉娜
Microsoft Word(15Kb)  |  收藏  |  浏览/下载:392/0  |  提交时间:2025/03/05
Near-surface Weather   Wildfire   Convective   Fuel Availability  
Accelerated discovery of CO2 electrocatalysts using active machine learning 期刊论文
NATURE, 2020, 581 (7807) : 178-+
作者:  Lan, Jun;  Ge, Jiwan;  Yu, Jinfang;  Shan, Sisi;  Zhou, Huan;  Fan, Shilong;  Zhang, Qi;  Shi, Xuanling;  Wang, Qisheng;  Zhang, Linqi;  Wang, Xinquan
收藏  |  浏览/下载:128/0  |  提交时间:2020/07/03

The rapid increase in global energy demand and the need to replace carbon dioxide (CO2)-emitting fossil fuels with renewable sources have driven interest in chemical storage of intermittent solar and wind energy(1,2). Particularly attractive is the electrochemical reduction of CO2 to chemical feedstocks, which uses both CO2 and renewable energy(3-8). Copper has been the predominant electrocatalyst for this reaction when aiming for more valuable multi-carbon products(9-16), and process improvements have been particularly notable when targeting ethylene. However, the energy efficiency and productivity (current density) achieved so far still fall below the values required to produce ethylene at cost-competitive prices. Here we describe Cu-Al electrocatalysts, identified using density functional theory calculations in combination with active machine learning, that efficiently reduce CO2 to ethylene with the highest Faradaic efficiency reported so far. This Faradaic efficiency of over 80 per cent (compared to about 66 per cent for pure Cu) is achieved at a current density of 400 milliamperes per square centimetre (at 1.5 volts versus a reversible hydrogen electrode) and a cathodic-side (half-cell) ethylene power conversion efficiency of 55 +/- 2 per cent at 150 milliamperes per square centimetre. We perform computational studies that suggest that the Cu-Al alloys provide multiple sites and surface orientations with near-optimal CO binding for both efficient and selective CO2 reduction(17). Furthermore, in situ X-ray absorption measurements reveal that Cu and Al enable a favourable Cu coordination environment that enhances C-C dimerization. These findings illustrate the value of computation and machine learning in guiding the experimental exploration of multi-metallic systems that go beyond the limitations of conventional single-metal electrocatalysts.


  
Noninvasive 2D and 3D Mapping of Root Zone Soil Moisture Through the Detection of Coarse Roots With Ground-Penetrating Radar 期刊论文
WATER RESOURCES RESEARCH, 2020, 56 (5)
作者:  Liu, X.;  Chen, J.;  Butnor, J. R.;  Qin, G.;  Cui, X.;  Fan, B.;  Lin, H.;  Guo, L.
收藏  |  浏览/下载:30/0  |  提交时间:2020/05/13
ecohydrology  in situ  near-surface geophysics  soil mapping  soil-plant-water relationships  subsoil  
Liquid flow and control without solid walls 期刊论文
NATURE, 2020, 581 (7806) : 58-+
作者:  Hellmuth, Susanne;  Stemmann, Olaf
收藏  |  浏览/下载:52/0  |  提交时间:2020/07/03

Wall-free liquid channels surrounded by an immiscible magnetic liquid can be used to create liquid circuitry or to transport human blood without damaging the blood cells by moving permanent magnets.


When miniaturizing fluidic circuitry, the solid walls of the fluid channels become increasingly important(1) because they limit the flow rates achievable for a given pressure drop, and they are prone to fouling(2). Approaches for reducing the wall interactions include hydrophobic coatings(3), liquid-infused porous surfaces(4-6), nanoparticle surfactant jamming(7), changes to surface electronic structure(8), electrowetting(9,10), surface tension pinning(11,12) and use of atomically flat channels(13). A better solution may be to avoid the solid walls altogether. Droplet microfluidics and sheath flow achieve this but require continuous flow of the central liquid and the surrounding liquid(1,14). Here we demonstrate an approach in which aqueous liquid channels are surrounded by an immiscible magnetic liquid, both of which are stabilized by a quadrupolar magnetic field. This creates self-healing, non-clogging, anti-fouling and near-frictionless liquid-in-liquid fluidic channels. Manipulation of the field provides flow control, such as valving, splitting, merging and pumping. The latter is achieved by moving permanent magnets that have no physical contact with the liquid channel. We show that this magnetostaltic pumping method can be used to transport whole human blood with very little damage due to shear forces. Haemolysis (rupture of blood cells) is reduced by an order of magnitude compared with traditional peristaltic pumping, in which blood is mechanically squeezed through a plastic tube. Our liquid-in-liquid approach provides new ways to transport delicate liquids, particularly when scaling channels down to the micrometre scale, with no need for high pressures, and could also be used for microfluidic circuitry.


  
Temperate rainforests near the South Pole during peak Cretaceous warmth 期刊论文
NATURE, 2020, 580 (7801) : 81-+
作者:  Johann P. Klages;  Ulrich Salzmann;  Torsten Bickert;  Claus-Dieter Hillenbrand;  Karsten Gohl;  Gerhard Kuhn;  Steven M. Bohaty;  ;  rgen Titschack;  Juliane Mü;  ller;  Thomas Frederichs;  Thorsten Bauersachs;  Werner Ehrmann;  Tina van de Flierdt;  Patric Simõ;  es Pereira;  Robert D. Larter;  Gerrit Lohmann;  Igor Niezgodzki;  Gabriele Uenzelmann-Neben;  Maximilian Zundel;  Cornelia Spiegel;  Chris Mark;  David Chew;  Jane E. Francis;  Gernot Nehrke;  Florian Schwarz;  James A. Smith;  Tim Freudenthal;  Oliver Esper;  Heiko Pä;  like;  Thomas A. Ronge;  Ricarda Dziadek
收藏  |  浏览/下载:28/0  |  提交时间:2020/05/13

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years(1-5), driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume(6). In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf-the southernmost Cretaceous record reported so far-and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82 degrees S during the Turonian-Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120-1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.


  
Urban Near-Surface Seismic Monitoring Using Distributed Acoustic Sensing 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (6)
作者:  Fang, Gang;  Li, Yunyue Elita;  Zhao, Yumin;  Martin, Eileen R.
收藏  |  浏览/下载:24/0  |  提交时间:2020/07/02
distributed acoustic sensing  urban seismology  near surface  passive seismic  seismic monitoring  
A pause in Southern Hemisphere circulation trends due to the Montreal Protocol 期刊论文
NATURE, 2020, 579 (7800) : 544-548
作者:  Imai, Yu;  Meyer, Kirsten J.;  Iinishi, Akira;  Favre-Godal, Quentin;  Green, Robert;  Manuse, Sylvie;  Caboni, Mariaelena;  Mori, Miho;  Niles, Samantha;  Ghiglieri, Meghan;  Honrao, Chandrashekhar;  Ma, Xiaoyu;  Guo, Jason J.;  Makriyannis, Alexandros;  Linares-Otoya, Luis;  Boehringer, Nils;  Wuisan, Zerlina G.;  Kaur, Hundeep;  Wu, Runrun;  Mateus, Andre
收藏  |  浏览/下载:42/0  |  提交时间:2020/05/13

Observations show robust near-surface trends in Southern Hemisphere tropospheric circulation towards the end of the twentieth century, including a poleward shift in the mid-latitude jet(1,2), a positive trend in the Southern Annular Mode(1,3-6) and an expansion of the Hadley cell(7,8). It has been established that these trends were driven by ozone depletion in the Antarctic stratosphere due to emissions of ozone-depleting substances(9-11). Here we show that these widely reported circulation trends paused, or slightly reversed, around the year 2000. Using a pattern-based detection and attribution analysis of atmospheric zonal wind, we show that the pause in circulation trends is forced by human activities, and has not occurred owing only to internal or natural variability of the climate system. Furthermore, we demonstrate that stratospheric ozone recovery, resulting from the Montreal Protocol, is the key driver of the pause. Because pre-2000 circulation trends have affected precipitation(12-14), and potentially ocean circulation and salinity(15-17), we anticipate that a pause in these trends will have wider impacts on the Earth system. Signatures of the effects of the Montreal Protocol and the associated stratospheric ozone recovery might therefore manifest, or have already manifested, in other aspects of the Earth system.


  
Action of a minimal contractile bactericidal nanomachine 期刊论文
NATURE, 2020, 580 (7805) : 658-+
作者:  Peng, Ruchao;  Xu, Xin;  Jing, Jiamei;  Wang, Min;  Peng, Qi;  Liu, Sheng;  Wu, Ying;  Bao, Xichen;  Wang, Peiyi;  Qi, Jianxun;  Gao, George F.;  Shi, Yi
收藏  |  浏览/下载:29/0  |  提交时间:2020/07/03

The authors report near-atomic resolution structures of the R-type bacteriocin from Pseudomonas aeruginosa in the pre-contraction and post-contraction states, and these structures provide insight into the mechanism of action of molecular syringes.


R-type bacteriocins are minimal contractile nanomachines that hold promise as precision antibiotics(1-4). Each bactericidal complex uses a collar to bridge a hollow tube with a contractile sheath loaded in a metastable state by a baseplate scaffold(1,2). Fine-tuning of such nucleic acid-free protein machines for precision medicine calls for an atomic description of the entire complex and contraction mechanism, which is not available from baseplate structures of the (DNA-containing) T4 bacteriophage(5). Here we report the atomic model of the complete R2 pyocin in its pre-contraction and post-contraction states, each containing 384 subunits of 11 unique atomic models of 10 gene products. Comparison of these structures suggests the following sequence of events during pyocin contraction: tail fibres trigger lateral dissociation of baseplate triplexes  the dissociation then initiates a cascade of events leading to sheath contraction  and this contraction converts chemical energy into mechanical force to drive the iron-tipped tube across the bacterial cell surface, killing the bacterium.


  
Design and synthesis of multigrain nanocrystals via geometric misfit strain 期刊论文
NATURE, 2020, 577 (7790) : 359-+
作者:  Oh, Myoung Hwan;  Cho, Min Gee;  Chung, Dong Young;  Park, Inchul;  Kwon, Youngwook Paul;  Ophus, Colin;  Kim, Dokyoon;  Kim, Min Gyu;  Jeong, Beomgyun;  Gu, X. Wendy;  Jo, Jinwoung;  Yoo, Ji Mun;  Hong, Jaeyoung;  McMains, Sara;  Kang, Kisuk;  Sung, Yung-Eun;  Alivisatos, A. Paul;  Hyeon, Taeghwan
收藏  |  浏览/下载:34/0  |  提交时间:2020/07/03

The impact of topological defects associated with grain boundaries (GB defects) on the electrical, optical, magnetic, mechanical and chemical properties of nanocrystalline materials(1,2) is well known. However, elucidating this influence experimentally is difficult because grains typically exhibit a large range of sizes, shapes and random relative orientations(3-5). Here we demonstrate that precise control of the heteroepitaxy of colloidal polyhedral nanocrystals enables ordered grain growth and can thereby produce material samples with uniform GB defects. We illustrate our approach with a multigrain nanocrystal comprising a Co3O4 nanocube core that carries a Mn3O4 shell on each facet. The individual shells are symmetry-related interconnected grains(6), and the large geometric misfit between adjacent tetragonal Mn3O4 grains results in tilt boundaries at the sharp edges of the Co3O4 nanocube core that join via disclinations. We identify four design principles that govern the production of these highly ordered multigrain nanostructures. First, the shape of the substrate nanocrystal must guide the crystallographic orientation of the overgrowth phase(7). Second, the size of the substrate must be smaller than the characteristic distance between the dislocations. Third, the incompatible symmetry between the overgrowth phase and the substrate increases the geometric misfit strain between the grains. Fourth, for GB formation under near-equilibrium conditions, the surface energy of the shell needs to be balanced by the increasing elastic energy through ligand passivation(8-10). With these principles, we can produce a range of multigrain nanocrystals containing distinct GB defects.


  
Frequency-Dependent P Wave Polarization and Its Subwavelength Near-Surface Depth Sensitivity 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2019
作者:  Park, Sunyoung;  Tsai, Victor C.;  Ishii, Miaki
收藏  |  浏览/下载:20/0  |  提交时间:2020/02/17
body-wave polarization  depth sensitivity  near-surface structure  site characterization  seismic hazard assessment  Japan