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Volume 517 Issue 7532, 1 January 2015

Dunes on Titan in a Cassini radar mapper image taken on 21 December 2008 (upper part of cover) resemble those in Conception Bay in the Namib desert, seen here from 283 km altitude in NASA crew image STS107-E-5380 (lower image). NASA’s Cassini spacecraft mission � still out there sending data from the Saturnian system � has revealed extensive aeolian (wind-formed) dunes on the surface of Titan, Saturn’s largest satellite. Devon Burr et al. used a high-pressure wind tunnel to simulate the thick near-surface atmosphere on Titan and, with numerical modelling of the low gravity and low sediment density, derived the wind speeds necessary to move dune sand on Titan. These speeds are significantly higher than those predicted by present models of sediment entrainment by wind that are based on wind-tunnel experiments under conditions relevant for Earth and Mars. Experimental results and theoretical work can be reconciled if the extremely low ratio of particle to fluid density on Titan is taken into account, a correction that is not required for high density ratio environments such as jets on comets. Cover: NASA/JPL-Caltech/ASI/ Johnson Space Center

Editorial

  • Governments that want the natural sciences to deliver more for society need to show greater commitment towards the social sciences and humanities.

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  • From Gradzilla to coffee consumption: the research enterprise quantified for the year to come.

    • Mark Zastrow
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Books & Arts

  • Explore the gory glories of forensic science, grapple with Tom Stoppard's take on consciousness, learn what it takes to live on Mars, re-enter Jurassic Park, dive into a coral reef and dally with Robert Oppenheimer. Daniel Cressey reports.

    • Daniel Cressey
    Books & Arts
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Correspondence

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News & Views

  • Certain structural elements allow messenger RNAs not usually processed by the protein-synthesis apparatus to be translated. It now seems that they also control the expression of genes involved in embryonic development. See Article p.33

    • Jonathan D. Dinman
    News & Views
  • The properties of articular cartilage, which lines bones in joints, depend partly on repulsion between components of the material. A new synthetic gel that mimics this feature has rare, direction-dependent properties. See Letter p.68

    • Anne Ladegaard Skov
    News & Views
  • Photosystem II, a photosynthetic protein complex, is prone to X-ray damage during crystallography. A high-resolution structure of the undamaged complex now offers a detailed view of its catalytic centre. See Letter p.99

    • Ilme Schlichting
    News & Views
  • The finding that protein A of Staphylococcus aureus diverts the immune response so that it ineffectively responds to other structures from the bacterium explains the failure of ongoing attempts to develop working S. aureus vaccines.

    • Gordon Y. C. Cheung
    • Michael Otto
    News & Views
  • Mitotic cell division separates chromosome pairs into two genetically identical daughter cells. A study in fission yeast reveals that this separation is guided by the sequential activation of three phosphatase enzymes. See Letter p.94

    • Mathieu Bollen
    News & Views
  • High-resolution data on ocean circulation during the last glacial cycle suggest that the formation of North Atlantic Deep Water and associated heat transport may be more stable than previously thought. See Letter p.73

    • Ellen E. Martin
    News & Views
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Article

  • Specialized ribosomes (with a particular protein composition) carry out translation of specific transcripts; analysis of Hox mRNA translation in mice reveals that unique RNA structural elements within their 5′ UTRs, including internal ribosome entry sites and translation inhibitory elements, are responsible for this specialized mode of translation.

    • Shifeng Xue
    • Siqi Tian
    • Maria Barna
    Article
  • Using electron cryomicroscopy, the closed-state structure of rabbit RyR1 is determined at 4.8 Å resolution; analysis confirms that the RyR1 architecture consists of a six-transmembrane ion channel with a cytosolic α-solenoid scaffold, and suggests a mechanism for Ca2+-induced channel opening.

    • Ran Zalk
    • Oliver B. Clarke
    • Andrew R. Marks
    Article
  • Using electron cryomicroscopy, the structure of the closed-state rabbit ryanodine receptor RyR1 in complex with its modulator FKBP12 is solved at 3.8 Å; in addition to determining structural details of the ion-conducting channel domain, three previously uncharacterized domains help to reveal a molecular scaffold that allows long-range allosteric regulation of channel activities.

    • Zhen Yan
    • Xiao-chen Bai
    • Nieng Yan
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Letter

  • Wind tunnel experiments designed to simulate the conditions on Saturn’s moon Titan yield threshold wind speeds for particle saltation higher than those predicted by models derived from simulations of terrestrial-planet conditions; the results can be reconciled by modifying the models to take into account the low ratio of particle density to fluid density on Titan.

    • Devon M. Burr
    • Nathan T. Bridges
    • Joshua P. Emery
    Letter
  • Quantized conductance in the transport of neutral atoms is observed in an optically produced channel — either a quantum point contact or a quantum wire — between two atom reservoirs; the lowest non-zero conductance value is the universal conductance quantum, the reciprocal of Planck’s constant.

    • Sebastian Krinner
    • David Stadler
    • Tilman Esslinger
    Letter
  • Usually materials design focuses on attractive interactions, but here a hydrogel is described whose properties are dominated by electrostatic repulsion between negatively charged titanate nanosheets embedded within it; the material, inspired by articular cartilage, deforms easily when sheared parallel to the sheets but resists compressive forces applied orthogonally.

    • Mingjie Liu
    • Yasuhiro Ishida
    • Takuzo Aida
    Letter
  • Reconstruction of the Atlantic meridional overturning circulation from a highly resolved marine sedimentary record shows that a deep, vigorous overturning circulation mode has persisted for most of the last glacial cycle, dominating ocean circulation in the Atlantic, but that a shallower glacial mode prevailed during glacial maxima.

    • E. Böhm
    • J. Lippold
    • M. Deininger
    Letter
  • A comparison of protein-coding genes from 134 archaeal genomes with their homologues in 1,847 bacterial genomes reveals that, during evolution, genes are transferred more often from bacteria to archaea than vice versa, and that gene influxes from bacteria can bring about the origin of major archaeal groups.

    • Shijulal Nelson-Sathi
    • Filipa L. Sousa
    • William F. Martin
    Letter
  • Hepatitis A virus is a picornavirus that causes significant morbidity but remains poorly understood; this paper now provides high-resolution crystal structures of both the mature and the empty hepatitis A virus particle, which show that the three-dimensional structure resembles insect picorna-like viruses.

    • Xiangxi Wang
    • Jingshan Ren
    • Elizabeth E. Fry
    Letter
  • The activation and coordination of phosphatase activity is important during mitotic exit; here, a mitotic phosphatase relay is described in fission yeast between the two major phosphatases, PP1 and PP2A, a mode of regulation that may be a feature of signalling networks across eukaryotes.

    • Agnes Grallert
    • Elvan Boke
    • Iain M. Hagan
    Letter
  • Solving the X-ray crystal structure of a Δ14-sterol reductase and homologue of human C14SR and DHCR7, two enzymes that reduce specific carbon–carbon double bonds in the cholesterol biosynthetic pathway, may provide insight into how specific mutations in DHCR7 and lamin B receptor lead to human diseases.

    • Xiaochun Li
    • Rita Roberti
    • Günter Blobel
    Letter
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  • To kick off 2015, Nature's Careers section asked several young scientists — all 40 or under — about their plans for the year ahead and their wishes for the future of science.

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Futures

  • Rapid progress.

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