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A remnant planetary core in the hot-Neptune desert 期刊论文
NATURE, 2020, 583 (7814) : 39-+
作者:  David J. Armstrong;  Thé;  o A. Lopez;  Vardan Adibekyan;  Richard A. Booth;  Edward M. Bryant;  Karen A. Collins;  Magali Deleuil;  Alexandre Emsenhuber;  Chelsea X. Huang;  George W. King;  Jorge Lillo-Box;  Jack J. Lissauer;  Elisabeth Matthews;  Olivier Mousis;  Louise D. Nielsen;  Hugh Osborn;  Jon Otegi;  Nuno C. Santos;  ;  rgio G. Sousa;  Keivan G. Stassun;  Dimitri Veras;  Carl Ziegler;  Jack S. Acton;  Jose M. Almenara;  David R. Anderson;  David Barrado;  Susana C. C. Barros;  Daniel Bayliss;  Claudia Belardi;  Francois Bouchy;  ;  sar Briceñ;  o;  Matteo Brogi;  David J. A. Brown;  Matthew R. Burleigh;  Sarah L. Casewell;  Alexander Chaushev;  David R. Ciardi;  Kevin I. Collins;  Knicole D. Coló;  n;  Benjamin F. Cooke;  Ian J. M. Crossfield;  Rodrigo F. Dí;  az;  Elisa Delgado Mena;  Olivier D. S. Demangeon;  Caroline Dorn;  Xavier Dumusque;  Philipp Eigmü;  ller;  Michael Fausnaugh;  Pedro Figueira;  Tianjun Gan;  Siddharth Gandhi;  Samuel Gill;  Erica J. Gonzales;  Michael R. Goad;  Maximilian N. Gü;  nther;  Ravit Helled;  Saeed Hojjatpanah;  Steve B. Howell;  James Jackman;  James S. Jenkins;  Jon M. Jenkins;  Eric L. N. Jensen;  Grant M. Kennedy;  David W. Latham;  Nicholas Law;  Monika Lendl;  Michael Lozovsky;  Andrew W. Mann;  Maximiliano Moyano;  James McCormac;  Farzana Meru;  Christoph Mordasini;  Ares Osborn;  Don Pollacco;  Didier Queloz;  Liam Raynard;  George R. Ricker;  Pamela Rowden;  Alexandre Santerne;  Joshua E. Schlieder;  Sara Seager;  Lizhou Sha;  Thiam-Guan Tan;  Rosanna H. Tilbrook;  Eric Ting;  Sté;  phane Udry;  Roland Vanderspek;  Christopher A. Watson;  Richard G. West;  Paul A. Wilson;  Joshua N. Winn;  Peter Wheatley;  Jesus Noel Villasenor;  Jose I. Vines;  Zhuchang Zhan
收藏  |  浏览/下载:20/0  |  提交时间:2020/07/06

The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to large uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary processes provide a route to understanding planetary interiors. Planets found in and near the typically barren hot-Neptune '  desert'  (1,2)(a region in mass-radius space that contains few planets) have proved to be particularly valuable in this regard. These planets include HD149026b(3), which is thought to have an unusually massive core, and recent discoveries such as LTT9779b(4)and NGTS-4b(5), on which photoevaporation has removed a substantial part of their outer atmospheres. Here we report observations of the planet TOI-849b, which has a radius smaller than Neptune'  s but an anomalously large mass of39.1-2.6+2.7Earth masses and a density of5.2-0.8+0.7grams per cubic centimetre, similar to Earth'  s. Interior-structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than3.9-0.9+0.8 per cent of the total planetary mass. The planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it could have avoided substantial gas accretion, perhaps through gap opening or late formation(6). Although photoevaporation rates cannot account for the mass loss required to reduce a Jupiter-like gas giant, they can remove a small (a few Earth masses) hydrogen and helium envelope on timescales of several billion years, implying that any remaining atmosphere on TOI-849b is likely to be enriched by water or other volatiles from the planetary interior. We conclude that TOI-849b is the remnant core of a giant planet.


Observations of TOI-849b reveal a radius smaller than Neptune'  s but a large mass of about 40 Earth masses, indicating that the planet is the remnant core of a gas giant.


  
International evaluation of an AI system for breast cancer screening 期刊论文
NATURE, 2020, 577 (7788) : 89-+
作者:  McKinney, Scott Mayer;  Sieniek, Marcin;  Godbole, Varun;  Godwin, Jonathan;  Antropova, Natasha;  Ashrafian, Hutan;  Back, Trevor;  Chesus, Mary;  Corrado, Greg C.;  Darzi, Ara;  Etemadi, Mozziyar;  Garcia-Vicente, Florencia;  Gilbert, Fiona J.;  Halling-Brown, Mark;  Hassabis, Demis;  Jansen, Sunny;  Karthikesalingam, Alan;  Kelly, Christopher J.;  King, Dominic;  Ledsam, Joseph R.;  Melnick, David;  Mostofi, Hormuz;  Peng, Lily;  Reicher, Joshua Jay;  Romera-Paredes, Bernardino;  Sidebottom, Richard;  Suleyman, Mustafa;  Tse, Daniel;  Young, Kenneth C.;  De Fauw, Jeffrey;  Shetty, Shravya
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/03

Screening mammography aims to identify breast cancer at earlier stages of the disease, when treatment can be more successful(1). Despite the existence of screening programmes worldwide, the interpretation of mammograms is affected by high rates of false positives and false negatives(2). Here we present an artificial intelligence (AI) system that is capable of surpassing human experts in breast cancer prediction. To assess its performance in the clinical setting, we curated a large representative dataset from the UK and a large enriched dataset from the USA. We show an absolute reduction of 5.7% and 1.2% (USA and UK) in false positives and 9.4% and 2.7% in false negatives. We provide evidence of the ability of the system to generalize from the UK to the USA. In an independent study of six radiologists, the AI system outperformed all of the human readers: the area under the receiver operating characteristic curve (AUC-ROC) for the AI system was greater than the AUC-ROC for the average radiologist by an absolute margin of 11.5%. We ran a simulation in which the AI system participated in the double-reading process that is used in the UK, and found that the AI system maintained non-inferior performance and reduced the workload of the second reader by 88%. This robust assessment of the AI system paves the way for clinical trials to improve the accuracy and efficiency of breast cancer screening.


  
Monumental architecture at Aguada Fenix and the rise of Maya civilization 期刊论文
NATURE, 2020
作者:  Bedding, Timothy R.;  Murphy, Simon J.;  Hey, Daniel R.;  Huber, Daniel;  Li, Tanda;  Smalley, Barry;  Stello, Dennis;  White, Timothy R.;  Ball, Warrick H.;  Chaplin, William J.;  Colman, Isabel L.;  Fuller, Jim;  Gaidos, Eric;  Harbeck, Daniel R.;  Hermes, J. J.;  Holdsworth, Daniel L.;  Li, Gang;  Li, Yaguang;  Mann, Andrew W.;  Reese, Daniel R.;  Sekaran, Sanjay;  Yu, Jie;  Antoci, Victoria;  Bergmann, Christoph;  Brown, Timothy M.;  Howard, Andrew W.;  Ireland, Michael J.;  Isaacson, Howard;  Jenkins, Jon M.;  Kjeldsen, Hans;  McCully, Curtis;  Rabus, Markus;  Rains, Adam D.;  Ricker, George R.;  Tinney, Christopher G.;  Vanderspek, Roland K.
收藏  |  浏览/下载:30/0  |  提交时间:2020/07/03

Archaeologists have traditionally thought that the development of Maya civilization was gradual, assuming that small villages began to emerge during the Middle Preclassic period (1000-350 bc  dates are calibrated throughout) along with the use of ceramics and the adoption of sedentism(1). Recent finds of early ceremonial complexes are beginning to challenge this model. Here we describe an airborne lidar survey and excavations of the previously unknown site of Aguada Fenix (Tabasco, Mexico) with an artificial plateau, which measures 1,400 m in length and 10 to 15 m in height and has 9 causeways radiating out from it. We dated this construction to between 1000 and 800 bc using a Bayesian analysis of radiocarbon dates. To our knowledge, this is the oldest monumental construction ever found in the Maya area and the largest in the entire pre-Hispanic history of the region. Although the site exhibits some similarities to the earlier Olmec centre of San Lorenzo, the community of Aguada Fenix probably did not have marked social inequality comparable to that of San Lorenzo. Aguada Fenix and other ceremonial complexes of the same period suggest the importance of communal work in the initial development of Maya civilization.


Lidar survey of the Maya lowlands uncovers the monumental site of Aguada Fenix, which dates to around 1000-800 bc and points to the role of communal construction in the development of Maya civilization.


  
Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (9) : 4505-4510
作者:  Veres, Patrick R.;  Neuman, J. Andrew;  Bertram, Timothy H.;  Assaf, Emmanuel;  Wolfe, Glenn M.;  Williamson, Christina J.;  Weinzierl, Bernadett;  Tilmes, Simone;  Thompson, Chelsea R.;  Thames, Alexander B.;  Schroder, Jason C.;  Saiz-Lopez, Alfonso;  Rollins, Andrew W.;  Roberts, James M.;  Price, Derek;  Peischl, Jeff;  Nault, Benjamin A.;  Moller, Kristian H.;  Miller, David O.;  Meinardi, Simone;  Li, Qinyi;  Lamarque, Jean-Francois;  Kupc, Agnieszka;  Kjaergaard, Henrik G.;  Kinnison, Douglas;  Jimenez, Jose L.;  Jernigan, Christopher M.;  Hornbrook, Rebecca S.;  Hills, Alan;  Dollner, Maximilian;  Day, Douglas A.;  Cuevas, Carlos A.;  Campuzano-Jost, Pedro;  Burkholder, James;  Bui, T. Paul;  Brune, William H.;  Brown, Steven S.;  Brock, Charles A.;  Bourgeois, Ilann;  Blake, Donald R.;  Apel, Eric C.;  Ryerson, Thomas B.
收藏  |  浏览/下载:23/0  |  提交时间:2020/05/13
dimethyl sulfide  marine sulfur  autoxidation  marine aerosols  aerosol sulfate  
Wintertime spatial distribution of ammonia and its emission sources in the Great Salt Lake region 期刊论文
ATMOSPHERIC CHEMISTRY AND PHYSICS, 2019, 19 (24) : 15691-15709
作者:  Moravek, Alexander;  Murphy, Jennifer G.;  Hrdina, Amy;  Lin, John C.;  Pennell, Christopher;  Franchin, Alessandro;  Middlebrook, Ann M.;  Fibiger, Dorothy L.;  Womack, Caroline C.;  McDuffie, Erin E.;  Martin, Randal;  Moore, Kori;  Baasandorj, Munkhbayar;  Brown, Steven S.
收藏  |  浏览/下载:10/0  |  提交时间:2020/02/17
OH chemistry of non-methane organic gases (NMOGs) emitted from laboratory and ambient biomass burning smoke: evaluating the influence of furans and oxygenated aromatics on ozone and secondary NMOG formation 期刊论文
ATMOSPHERIC CHEMISTRY AND PHYSICS, 2019, 19 (23) : 14875-14899
作者:  Coggon, Matthew M.;  Lim, Christopher Y.;  Koss, Abigail R.;  Sekimoto, Kanako;  Yuan, Bin;  Gilman, Jessica B.;  Hagan, David H.;  Selimovic, Vanessa;  Zarzana, Kyle J.;  Brown, Steven S.;  Roberts, James M.;  Mueller, Markus;  Yokelson, Robert;  Wisthaler, Armin;  Krechmer, Jordan E.;  Jimenez, Jose L.;  Cappa, Christopher;  Kroll, Jesse H.;  de Gouw, Joost;  Warneke, Carsten
收藏  |  浏览/下载:20/0  |  提交时间:2020/02/17
Uncovering hidden genetic variation in photosynthesis of field-grown maize under ozone pollution 期刊论文
GLOBAL CHANGE BIOLOGY, 2019
作者:  Choquette, Nicole E.;  Ogut, Funda;  Wertin, Timothy M.;  Montes, Christopher M.;  Sorgini, Crystal A.;  Morse, Alison M.;  Brown, Patrick J.;  Leakey, Andrew D. B.;  McIntyre, Lauren M.;  Ainsworth, Elizabeth A.
收藏  |  浏览/下载:10/0  |  提交时间:2019/11/27
air pollution  FACE  global climate change  heritability  maize  ozone (O-3)  photosynthesis  
The Role of Vegetated Coastal Wetlands for Marine Megafauna Conservation 期刊论文
TRENDS IN ECOLOGY & EVOLUTION, 2019, 34 (9) : 807-817
作者:  Sievers, Michael;  Brown, Christopher J.;  Tulloch, Vivitskaia J. D.;  Pearson, Ryan M.;  Haig, Jodie A.;  Turschwell, Mischa P.;  Connolly, Rod M.
收藏  |  浏览/下载:6/0  |  提交时间:2019/11/27
Historical and current fire regimes in ponderosa pine forests at Zion National Park, Utah: Restoration of pattern and process after a century of fire exclusion 期刊论文
FOREST ECOLOGY AND MANAGEMENT, 2019, 445: 1-12
作者:  Brown, Peter M.;  Gentry, Christopher;  Yao, Qichao
收藏  |  浏览/下载:10/0  |  提交时间:2019/11/27
A highly resolved food web for insect seed predators in a species-rich tropical forest 期刊论文
ECOLOGY LETTERS, 2019, 22 (10) : 1638-1649
作者:  Gripenberg, Sofia;  Basset, Yves;  Lewis, Owen T.;  Terry, J. Christopher D.;  Wright, S. Joseph;  Simon, Indira;  Fernandez, D. Catalina;  Cedeno-Sanchez, Marjorie;  Rivera, Marleny;  Barrios, Hector;  Brown, John W.;  Calderon, Osvaldo;  Cognato, Anthony I.;  Kim, Jorma;  Miller, Scott E.;  Morse, Geoffrey E.;  Pinzon-Navarro, Sara;  Quicke, Donald L. J.;  Robbins, Robert K.;  Salminen, Juha-Pekka;  Vesterinen, Eero
收藏  |  浏览/下载:9/0  |  提交时间:2019/11/27
Apparent competition  Barro Colorado Island  host specialisation  interaction network  Janzen-Connell hypothesis  Panama  plant traits  quantitative food web  seed predation