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Abrupt increase in harvested forest area over Europe after 2015 期刊论文
NATURE, 2020, 583 (7814) : 72-+
作者:  Guido Ceccherini;  Gregory Duveiller;  Giacomo Grassi;  Guido Lemoine;  Valerio Avitabile;  Roberto Pilli;  Alessandro Cescatti
收藏  |  浏览/下载：50/0  |  提交时间：2020/07/06

Fine-scale satellite data are used to quantify forest harvest rates in 26 European countries, finding an increase in harvested forest area of 49% and an increase in biomass loss of 69% between 2011-2015 and 2016-2018.


Forests provide a series of ecosystem services that are crucial to our society. In the European Union (EU), forests account for approximately 38% of the total land surface(1). These forests are important carbon sinks, and their conservation efforts are vital for the EU'  s vision of achieving climate neutrality by 2050(2). However, the increasing demand for forest services and products, driven by the bioeconomy, poses challenges for sustainable forest management. Here we use fine-scale satellite data to observe an increase in the harvested forest area (49 per cent) and an increase in biomass loss (69 per cent) over Europe for the period of 2016-2018 relative to 2011-2015, with large losses occurring on the Iberian Peninsula and in the Nordic and Baltic countries. Satellite imagery further reveals that the average patch size of harvested area increased by 34 per cent across Europe, with potential effects on biodiversity, soil erosion and water regulation. The increase in the rate of forest harvest is the result of the recent expansion of wood markets, as suggested by econometric indicators on forestry, wood-based bioenergy and international trade. If such a high rate of forest harvest continues, the post-2020 EU vision of forest-based climate mitigation may be hampered, and the additional carbon losses from forests would require extra emission reductions in other sectors in order to reach climate neutrality by 2050(3).


  
Revealing enigmatic mucus structures in the deep sea using DeepPIV 期刊论文
NATURE, 2020, 583 (7814) : 78-+
作者:  Nguyen, Ngoc Uyen Nhi;  Canseco, Diana C.;  Xiao, Feng;  Nakada, Yuji;  Li, Shujuan;  Lam, Nicholas T.;  Muralidhar, Shalini A.;  Savla, Jainy J.;  Hill, Joseph A.;  Le, Victor;  Zidan, Kareem A.;  El-Feky, Hamed W.;  Wang, Zhaoning;  Ahmed, Mahmoud Salama;  Hubbi, Maimon E.;  Menendez-Montes, Ivan
收藏  |  浏览/下载：49/0  |  提交时间：2020/06/09

Advanced deep-sea imaging tools yield insights into the structure and function of mucus filtration houses built by midwater giant larvaceans.


Many animals build complex structures to aid in their survival, but very few are built exclusively from materials that animals create (1,2). In the midwaters of the ocean, mucoid structures are readily secreted by numerous animals, and serve many vital functions(3,4). However, little is known about these mucoid structures owing to the challenges of observing them in the deep sea. Among these mucoid forms, the '  houses'  of larvaceans are marvels of nature(5), and in the ocean twilight zone giant larvaceans secrete and build mucus filtering structures that can reach diameters of more than 1 m(6). Here we describe in situ laser-imaging technology(7) that reconstructs three-dimensional models of mucus forms. The models provide high-resolution views of giant larvacean houses and elucidate the role that house structure has in food capture and predator avoidance. Now that tools exist to study mucus structures found throughout the ocean, we can shed light on some of nature'  s most complex forms.


  
Observation of Bose-Einstein condensates in an Earth-orbiting research lab 期刊论文
NATURE, 2020, 582 (7811) : 103-+
作者:  Yamamoto, Keisuke;  Venida, Anthony;  Yano, Julian;  Biancur, Douglas E.;  Kakiuchi, Miwako;  Gupta, Suprit;  Sohn, Albert S. W.;  Mukhopadhyay, Subhadip;  Lin, Elaine Y.;  Parker, Seth J.;  Banh, Robert S.;  Paulo, Joao A.;  Wen, Kwun Wah;  Debnath, Jayanta;  Kim, Grace E.;  Mancias, Joseph D.;  Fearon, Douglas T.;  Perera, Rushika M.;  Kimmelman, Alec C.
收藏  |  浏览/下载：47/0  |  提交时间：2020/07/03

Quantum mechanics governs the microscopic world, where low mass and momentum reveal a natural wave-particle duality. Magnifying quantum behaviour to macroscopic scales is a major strength of the technique of cooling and trapping atomic gases, in which low momentum is engineered through extremely low temperatures. Advances in this field have achieved such precise control over atomic systems that gravity, often negligible when considering individual atoms, has emerged as a substantial obstacle. In particular, although weaker trapping fields would allow access to lower temperatures(1,2), gravity empties atom traps that are too weak. Additionally, inertial sensors based on cold atoms could reach better sensitivities if the free-fall time of the atoms after release from the trap could be made longer(3). Planetary orbit, specifically the condition of perpetual free-fall, offers to lift cold-atom studies beyond such terrestrial limitations. Here we report production of rubidium Bose-Einstein condensates (BECs) in an Earth-orbiting research laboratory, the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with free-expansion times extending beyond one second, providing an initial demonstration of the advantages offered by a microgravity environment for cold-atom experiments and verifying the successful operation of this facility. With routine BEC production, continuing operations will support long-term investigations of trap topologies unique to microgravity(4,5), atom-laser sources(6), few-body physics(7,8)and pathfinding techniques for atom-wave interferometry(9-12).


  
Detection of metastable electronic states by Penning trap mass spectrometry 期刊论文
NATURE, 2020, 581 (7806) : 42-+
作者:  Rauch, Jennifer N.;  Luna, Gabriel;  Guzman, Elmer;  Audouard, Morgane;  Challis, Collin;  Sibih, Youssef E.;  Leshuk, Carolina;  Hernandez, Israel;  Wegmann, Susanne;  Hyman, Bradley T.;  Gradinaru, Viviana;  Kampmann, Martin;  Kosik, Kenneth S.
收藏  |  浏览/下载：23/0  |  提交时间：2020/07/03

State-of-the-art optical clocks(1) achieve precisions of 10(-18) or better using ensembles of atoms in optical lattices(2,3) or individual ions in radio-frequency traps(4,5). Promising candidates for use in atomic clocks are highly charged ions(6) (HCIs) and nuclear transitions(7), which are largely insensitive to external perturbations and reach wavelengths beyond the optical range(8) that are accessible to frequency combs(9). However, insufficiently accurate atomic structure calculations hinder the identification of suitable transitions in HCIs. Here we report the observation of a long-lived metastable electronic state in an HCI by measuring the mass difference between the ground and excited states in rhenium, providing a non-destructive, direct determination of an electronic excitation energy. The result is in agreement with advanced calculations. We use the high-precision Penning trap mass spectrometer PENTATRAP to measure the cyclotron frequency ratio of the ground state to the metastable state of the ion with a precision of 10(-11)-an improvement by a factor of ten compared with previous measurements(10,11). With a lifetime of about 130 days, the potential soft-X-ray frequency reference at 4.96 x 10(16) hertz (corresponding to a transition energy of 202 electronvolts) has a linewidth of only 5 x 10(-8) hertz and one of the highest electronic quality factors (10(24)) measured experimentally so far. The low uncertainty of our method will enable searches for further soft-X-ray clock transitions(8,12) in HCIs, which are required for precision studies of fundamental physics(6).


Penning trap mass spectrometry is used to measure the electronic transition energy from a long-lived metastable state to the ground state in highly charged rhenium ions with a precision of 10(-11).


  
Formation of liquid-like cellular organelles depends on their composition 期刊论文
NATURE, 2020, 581 (7807) : 144-145
作者:  Sengupta, Partho P.;  Adjeroh, Donald A.
收藏  |  浏览/下载：7/0  |  提交时间：2020/07/03

Phase separation of the nucleolus is composition dependent.


Liquid-like organelles in cells form when key constituents reach a certain concentration and then condense. Evidence now indicates that the concentration at which condensation occurs can vary, contrary to previous assumptions.


  
Layered nanocomposites by shear-flow-induced alignment of nanosheets 期刊论文
NATURE, 2020, 580 (7802) : 210-+
作者:  Rollie, Clare;  Chevallereau, Anne;  Watson, Bridget N. J.;  Chyou, Te-yuan;  Fradet, Olivier;  McLeod, Isobel;  Fineran, Peter C.;  Brown, Chris M.;  Gandon, Sylvain;  Westra, Edze R.
收藏  |  浏览/下载：59/0  |  提交时间：2020/07/03

Layered nanocomposites fabricated using a continuous and scalable process achieve properties exceeding those of natural nacre, the result of stiffened matrix polymer chains confined between highly aligned nanosheets.


Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness(1-3). Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix(4-6). Inspired by these biological structures, several assembly strategies-including layer-by-layer(4,7,8), casting(9,10), vacuum filtration(11-13) and use of magnetic fields(14,15)-have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 +/- 80 megapascals and a Young'  s modulus of 198.8 +/- 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 +/- 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre  meanwhile, the tensile strength is 1,195 +/- 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.


  
Demonstration of cooling by the Muon Ionization Cooling Experiment 期刊论文
NATURE, 2020, 578 (7793) : 53-+
作者:  Zheng, Wen;  Zhao, Wenjing;  Wu, Meng;  Song, Xinyang;  Caro, Florence;  Sun, Ximei;  Gazzaniga, Francesca;  Stefanetti, Giuseppe;  Oh, Sungwhan;  Mekalanos, John J.;  Kasper, Dennis L.
收藏  |  浏览/下载：19/0  |  提交时间：2020/07/03

The use of accelerated beams of electrons, protons or ions has furthered the development of nearly every scientific discipline. However, high-energy muon beams of equivalent quality have not yet been delivered. Muon beams can be created through the decay of pions produced by the interaction of a proton beam with a target. Such '  tertiary'  beams have much lower brightness than those created by accelerating electrons, protons or ions. High-brightness muon beams comparable to those produced by state-of-the-art electron, proton and ion accelerators could facilitate the study of lepton-antilepton collisions at extremely high energies and provide well characterized neutrino beams(1-6). Such muon beams could be realized using ionization cooling, which has been proposed to increase muon-beam brightness(7,8). Here we report the realization of ionization cooling, which was confirmed by the observation of an increased number of low-amplitude muons after passage of the muon beam through an absorber, as well as an increase in the corresponding phase-space density. The simulated performance of the ionization cooling system is consistent with the measured data, validating designs of the ionization cooling channel in which the cooling process is repeated to produce a substantial cooling effect(9-11). The results presented here are an important step towards achieving the muon-beam quality required to search for phenomena at energy scales beyond the reach of the Large Hadron Collider at a facility of equivalent or reduced wfootprint(6).


  
A multidisciplinary framework to derive global river reach classifications at high spatial resolution 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2019, 14 (2)
作者:  Dallaire, Camille Ouellet;  Lehner, Bernhard;  Sayre, Roger;  Thieme, Michele
收藏  |  浏览/下载：18/0  |  提交时间：2019/04/09
river classification  global scale  freshwater management  sustainability  river reach type  
Assessment of the Species Composition, Densities, and Distribution of Native Freshwater Mussels along the Benton County Shoreline of the Hanford Reach, Columbia River, 2004 科技报告
来源：US Department of Energy (DOE). 出版年： 2011
作者:  Phyllis C. Weaver
收藏  |  浏览/下载：13/0  |  提交时间：2019/04/05
mussels  Hanford Reach  assessment  
Development of a high-resolution bathymetry dataset for the Columbia River through the Hanford Reach 科技报告
来源：US Department of Energy (DOE). 出版年： 2010
作者:  Coleman, Andre M.;  Ward, Duane L.;  Larson, Kyle B.;  Lettrick, Joseph W.
收藏  |  浏览/下载：8/0  |  提交时间：2019/04/05
bathymetry  topography  Hanford Reach  Columbia River  hydrographic  survey  GIS