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Current Issue of Nature


Volume 573 Issue 7773, 12 September 2019

Volume 573 Issue 7773, 12 September 2019

A matter of time

The current standard for timekeeping is the atomic clock, which measures time based on transitions between two states of an atom. In this week’s issue, two papers edge closer to the realization of the first nuclear clock — one that would be based on transitions between states in a nucleus and so would compete with atomic timekeepers. The nucleus in question is that of thorium-229. This is the only nucleus known to have a first excited state (229mTh) in the energy range of a few electronvolts, which makes it the lowest of all known nucleii and, crucially, accessible by lasers. But thorium poses challenges, including the accurate determination of its excitation energy and the direct optical excitation of 229mTh. In one paper, Benedict Seiferle and his colleagues present the direct measurement of the transition energy from the ground state to the first excited state. And in a second paper, Noboru Sasao and his colleagues report the direct X-ray excitation of thorium-229 to the second excited state, which then quickly decays to 229mTh.

Cover image: Daria Bilou

This Week

News in Focus

Comment

Technology

    Technology Feature

  • Technology Feature |

    Some advocates are betting that documenting experimental plans online will improve animal research, but uptake has been slow.

    • Monya Baker

Careers

Futures

  • Futures |

    Time for a civilized conversation.

    • Jeff Hecht

Research

    News & Views

  • News & Views |

    Silicon anodes in lithium batteries expand during discharge, causing failure. This expansion has been used constructively in a material whose architecture controllably and reversibly changes to alter its function.

    • Seung-Yeol Jeon
    •  & Sung Hoon Kang
  • News & Views |

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    • Edwin W. McCleskey
  • News & Views |

    A 3.8-million-year-old hominin fossil reveals what the cranium of the oldest known Australopithecus species looked like, casting doubt on assumptions about how these ancient relatives of humans evolved.

    • Fred Spoor
  • News & Views |

    Clocks that are based on the nucleus of a single thorium atom could be more precise than existing timekeepers. Such clocks have not yet been realized, but two experiments provide keys steps towards this goal.

    • Jason T. Burke
  • News & Views |

    An analysis of the dynamics of online hate groups on social-media platforms reveals why current methods to ban hate content are ineffective, and provides the basis for four potential strategies to combat online hate.

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  • Articles

  • Article |

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    • Xiaoxing Xia
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    • , Carlos M. Portela
    • , Dennis M. Kochmann
    • , Claudio V. Di Leo
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  • Article |

    Two related studies describe a newly discovered cranium of Australopithecus anamensis, the environment in which this hominin would have lived approximately 3.8 million years ago and how it is related to Australopithecus afarensis.

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    • , Stephanie M. Melillo
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  • Article |

    Two related studies describe a newly discovered cranium of Australopithecus anamensis, the environment in which this hominin would have lived approximately 3.8 million years ago and how it is related to Australopithecus afarensis.

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    • , Alan Deino
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    • , Naomi E. Levin
    • , Stephanie M. Melillo
    • , Mark D. Peaple
    • , Sarah J. Feakins
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    • , Doris Barboni
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    • , Stanley A. Mertzman
    •  & Yohannes Haile-Selassie
  • Article |

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    • Li Wang
    • , Heng Zhou
    • , Mingmin Zhang
    • , Wenhao Liu
    • , Tuan Deng
    • , Qiancheng Zhao
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    • , Xueming Li
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  • Article |

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    • Yi-Chih Lin
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  • Letters

  • Letter |

    Radio observations show a bipolar bubble structure of size 140 parsecs by 430 parsecs both above and below the Galactic Centre.

    • I. Heywood
    • , F. Camilo
    • , W. D. Cotton
    • , F. Yusef-Zadeh
    • , T. D. Abbott
    • , R. M. Adam
    • , M. A. Aldera
    • , E. F. Bauermeister
    • , R. S. Booth
    • , A. G. Botha
    • , D. H. Botha
    • , L. R. S. Brederode
    • , Z. B. Brits
    • , S. J. Buchner
    • , J. P. Burger
    • , J. M. Chalmers
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    • , M. A. Dikgale-Mahlakoana
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    • , S. W. P. Esterhuyse
    • , B. L. Fanaroff
    • , A. R. Foley
    • , D. J. Fourie
    • , R. R. G. Gamatham
    • , S. Goedhart
    • , S. Gounden
    • , M. J. Hlakola
    • , C. J. Hoek
    • , A. Hokwana
    • , D. M. Horn
    • , J. M. G. Horrell
    • , B. Hugo
    • , A. R. Isaacson
    • , J. L. Jonas
    • , J. D. B. L. Jordaan
    • , A. F. Joubert
    • , G. I. G. Józsa
    • , R. P. M. Julie
    • , F. B. Kapp
    • , J. S. Kenyon
    • , P. P. A. Kotzé
    • , H. Kriel
    • , T. W. Kusel
    • , R. Lehmensiek
    • , D. Liebenberg
    • , A. Loots
    • , R. T. Lord
    • , B. M. Lunsky
    • , P. S. Macfarlane
    • , L. G. Magnus
    • , C. M. Magozore
    • , O. Mahgoub
    • , J. P. L. Main
    • , J. A. Malan
    • , R. D. Malgas
    • , J. R. Manley
    • , M. D. J. Maree
    • , B. Merry
    • , R. Millenaar
    • , N. Mnyandu
    • , I. P. T. Moeng
    • , T. E. Monama
    • , M. C. Mphego
    • , W. S. New
    • , B. Ngcebetsha
    • , N. Oozeer
    • , A. J. Otto
    • , S. S. Passmoor
    • , A. A. Patel
    • , A. Peens-Hough
    • , S. J. Perkins
    • , S. M. Ratcliffe
    • , R. Renil
    • , A. Rust
    • , S. Salie
    • , L. C. Schwardt
    • , M. Serylak
    • , R. Siebrits
    • , S. K. Sirothia
    • , O. M. Smirnov
    • , L. Sofeya
    • , P. S. Swart
    • , C. Tasse
    • , D. T. Taylor
    • , I. P. Theron
    • , K. Thorat
    • , A. J. Tiplady
    • , S. Tshongweni
    • , T. J. van Balla
    • , A. van der Byl
    • , C. van der Merwe
    • , C. L. van Dyk
    • , R. Van Rooyen
    • , V. Van Tonder
    • , R. Van Wyk
    • , B. H. Wallace
    • , M. G. Welz
    •  & L. P. Williams
  • Letter |

    Excitation to the second excited state of 229Th is used to populate the metastable state 229mTh, enabling accurate determination of the isomer’s energy, half-life and excitation linewidth.

    • Takahiko Masuda
    • , Akihiro Yoshimi
    • , Akira Fujieda
    • , Hiroyuki Fujimoto
    • , Hiromitsu Haba
    • , Hideaki Hara
    • , Takahiro Hiraki
    • , Hiroyuki Kaino
    • , Yoshitaka Kasamatsu
    • , Shinji Kitao
    • , Kenji Konashi
    • , Yuki Miyamoto
    • , Koichi Okai
    • , Sho Okubo
    • , Noboru Sasao
    • , Makoto Seto
    • , Thorsten Schumm
    • , Yudai Shigekawa
    • , Kenta Suzuki
    • , Simon Stellmer
    • , Kenji Tamasaku
    • , Satoshi Uetake
    • , Makoto Watanabe
    • , Tsukasa Watanabe
    • , Yuki Yasuda
    • , Atsushi Yamaguchi
    • , Yoshitaka Yoda
    • , Takuya Yokokita
    • , Motohiko Yoshimura
    •  & Koji Yoshimura
  • Letter |

    The transition energy of the first excited state of 229Th to the ground state is determined through the measurement of internal conversion electrons to correspond to a wavelength of 149.7 ± 3.1 nanometres.

    • Benedict Seiferle
    • , Lars von der Wense
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    • , Ines Amersdorffer
    • , Christoph Lemell
    • , Florian Libisch
    • , Simon Stellmer
    • , Thorsten Schumm
    • , Christoph E. Düllmann
    • , Adriana Pálffy
    •  & Peter G. Thirolf
  • Letter |

    Investigation of a free-standing graphene monolayer using a technique based on transmission electron microscopy allows identification of atomic vibrations characteristic of the bulk or the edge of the sample.

    • Ryosuke Senga
    • , Kazu Suenaga
    • , Paolo Barone
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    • , Francesco Mauri
    •  & Thomas Pichler
  • Letter |

    Human scientists make unrepresentative chemical reagent and reaction condition choices, and machine-learning algorithms trained on human-selected experiments are less capable of successfully predicting reaction outcomes than those trained on randomly generated experiments.

    • Xiwen Jia
    • , Allyson Lynch
    • , Yuheng Huang
    • , Matthew Danielson
    • , Immaculate Lang’at
    • , Alexander Milder
    • , Aaron E. Ruby
    • , Hao Wang
    • , Sorelle A. Friedler
    • , Alexander J. Norquist
    •  & Joshua Schrier
  • Letter |

    Comparisons between past regional drivers of precipitation extremes found time series data from Lake Ohrid and modern climate models of the Mediterranean may help to reduce simulation uncertainties in predictions of the Mediterranean climate.

    • Bernd Wagner
    • , Hendrik Vogel
    • , Alexander Francke
    • , Tobias Friedrich
    • , Timme Donders
    • , Jack H. Lacey
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    • , Eleonora Regattieri
    • , Laura Sadori
    • , Thomas Wilke
    • , Giovanni Zanchetta
    • , Christian Albrecht
    • , Adele Bertini
    • , Nathalie Combourieu-Nebout
    • , Aleksandra Cvetkoska
    • , Biagio Giaccio
    • , Andon Grazhdani
    • , Torsten Hauffe
    • , Jens Holtvoeth
    • , Sebastien Joannin
    • , Elena Jovanovska
    • , Janna Just
    • , Katerina Kouli
    • , Ilias Kousis
    • , Andreas Koutsodendris
    • , Sebastian Krastel
    • , Markus Lagos
    • , Niklas Leicher
    • , Zlatko Levkov
    • , Katja Lindhorst
    • , Alessia Masi
    • , Martin Melles
    • , Anna M. Mercuri
    • , Sebastien Nomade
    • , Norbert Nowaczyk
    • , Konstantinos Panagiotopoulos
    • , Odile Peyron
    • , Jane M. Reed
    • , Leonardo Sagnotti
    • , Gaia Sinopoli
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    • , Roberto Sulpizio
    • , Axel Timmermann
    • , Slavica Tofilovska
    • , Paola Torri
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    • , Thomas Wonik
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  • Letter |

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    • , R. Leahy
    • , N. Johnson Restrepo
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    • , M. Zheng
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    •  & S. Wuchty
  • Letter |

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    • , Teresa Ferraro
    • , Flora Llense
    • , Pierre Mahou
    • , Julien Pontabry
    • , David Rodriguez
    • , Samantha Kim
    • , Shoichiro Ono
    • , Emmanuel Beaurepaire
    • , Christelle Gally
    •  & Michel Labouesse
  • Letter |

    The effect of vitamin C deprivation on mouse germline development is analysed, revealing that maternal vitamin C is required for proper DNA demethylation and the development of fetal oocytes, whereas the lack of vitamin C during pregnancy leads to reduced female fecundity in the offspring.

    • Stephanie P. DiTroia
    • , Michelle Percharde
    • , Marie-Justine Guerquin
    • , Estelle Wall
    • , Evelyne Collignon
    • , Kevin T. Ebata
    • , Kathryn Mesh
    • , Swetha Mahesula
    • , Michalis Agathocleous
    • , Diana J. Laird
    • , Gabriel Livera
    •  & Miguel Ramalho-Santos
  • Letter |

    The re-seeding of antibiotic-resistant persister subpopulations of Salmonella enterica into the gut lumen favours the transfer of resistance plasmids to gut-resident enterobacteria, showing that even small reservoirs of persister bacteria facilitate the spread of antibiotic resistance.

    • Erik Bakkeren
    • , Jana S. Huisman
    • , Stefan A. Fattinger
    • , Annika Hausmann
    • , Markus Furter
    • , Adrian Egli
    • , Emma Slack
    • , Mikael E. Sellin
    • , Sebastian Bonhoeffer
    • , Roland R. Regoes
    • , Médéric Diard
    •  & Wolf-Dietrich Hardt
  • Letter |

    H3K36me2 targets DNMT3A to intergenic regions and this process, together with H3K36me3-mediated recruitment of DNMT3B, has a key role in establishing and maintaining genomic DNA methylation landscapes.

    • Daniel N. Weinberg
    • , Simon Papillon-Cavanagh
    • , Haifen Chen
    • , Yuan Yue
    • , Xiao Chen
    • , Kartik N. Rajagopalan
    • , Cynthia Horth
    • , John T. McGuire
    • , Xinjing Xu
    • , Hamid Nikbakht
    • , Agata E. Lemiesz
    • , Dylan M. Marchione
    • , Matthew R. Marunde
    • , Matthew J. Meiners
    • , Marcus A. Cheek
    • , Michael-Christopher Keogh
    • , Eric Bareke
    • , Anissa Djedid
    • , Ashot S. Harutyunyan
    • , Nada Jabado
    • , Benjamin A. Garcia
    • , Haitao Li
    • , C. David Allis
    • , Jacek Majewski
    •  & Chao Lu
  • Letter |

    Structures of RNA polymerase of human and avian influenza A viruses reveal that the interface of the RNA polymerase dimer is required to initiate viral RNA synthesis in viral genome replication.

    • Haitian Fan
    • , Alexander P. Walker
    • , Loïc Carrique
    • , Jeremy R. Keown
    • , Itziar Serna Martin
    • , Dimple Karia
    • , Jane Sharps
    • , Narin Hengrung
    • , Els Pardon
    • , Jan Steyaert
    • , Jonathan M. Grimes
    •  & Ervin Fodor

Amendments & Corrections

Nature Outlook

  • Nature Outlook |

    Opioids

    Addiction to opioid drugs is an urgent health-care crisis. Researchers and policymakers are pursuing strategies that range from developing non-opioid pain relief to establishing new norms for prescribing these problematic medications.

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