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Volume 503 Issue 7475, 14 November 2013

The fireball that streaked across the skies above Chelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth of information. Two papers in this issue present detailed reconstructions of the Chelyabinsk event. From an analysis of videos, Jiř� Borovička et al. determined the trajectory and velocity of the superbolide with high precision. Its orbit was similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43), suggesting that the two bodies may be part of the same asteroid family. And they show that it broke into small pieces between the altitudes of 45 and 30 kilometres. In the companion paper, Peter Brown et al. analysed the damage caused by the airburst which they estimate was equivalent in energy to the detonation of 400 to 600 kilotons of TNT. They suggest that the number of impactors with diameters of tens of metres was an order of magnitude higher than current estimates, shifting much of the residual impact risk to these sizes. On the cover, a 3D simulation by Mark Boslough using CTH code on Sandia National Laboratories� Red Sky supercomputer, rendered by Brad Carvey using Houdini FX and LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.

Editorial

  • Editorial |

    Major African campaigns targeting malaria and HIV could help millions, but key concerns over their long-term effects should not be forgotten.

  • Editorial |

    Time is running out to comment on the NIH’s plan for sharing genomic data.

  • Editorial |

    Prejudice, not evidence, is too often the basis for government drug policies.

World View

Research Highlights

Seven Days

  • Seven Days |

    The week in science: Record storm ravages Philippines; open-genome effort comes to the UK; and US proposes a ban on artificial trans-fats.

News

News Feature

  • News Feature |

    Several African nations could strike a major blow against malaria by sacrificing the efficacy of some older drugs. Can they make it work?

    • Amy Maxmen

Comment

Books & Arts

Correspondence

Correction

News & Views

  • News & Views |

    A random array of holes etched in a semiconductor structure, consisting of a periodic series of thin layers, has been demonstrated that emits mid-infrared laser radiation. The device could have sensing and imaging applications.

    • Hui Cao
    • Stafford W. Sheehan
  • News & Views |

    Chemical analysis of the spliceosome's active site reveals that it is the RNA components of this enzyme complex that coordinate the catalytic metal ions responsible for production of a spliced messenger RNA. See Article p.229

    • Scott A. Strobel
  • News & Views |

    The recent entry of a 20-metre-wide celestial rock into Earth's atmosphere offered both a spectacular show and a source of invaluable data that advance our understanding of high-velocity impacts. See Letters p.235 & p.238

    • Natalia Artemieva
  • News & Views |

    Two independent studies show that, if push comes to shove, differentiated cells of the stomach and lung can act as adult stem cells, generating various cell types of the tissues, including a pool of stem cells. See Article p.218

    • Tushar J. Desai
    • Mark A. Krasnow
  • News & Views |

    Long-lived single electron spins are crucial for quantum computation and for understanding spin dynamics. A remarkably long lifetime — of the order of minutes — has now been obtained for a solid-state system. See Letter p.242

    • Michael E. Flatté
  • News & Views |

    The almost complete extinction of small mammals in forest islands within 25 years of the construction of a reservoir that fragmented the habitat provides a striking example of delayed biodiversity loss.

    • Andrew Gonzalez
  • News & Views |

    Efforts to make a prophylactic HIV vaccine have identified monoclonal antibodies that potently suppress viral replication. Studies in monkeys show that these reagents effectively treat HIV infection. See Article p.224 & Letter p.277

    • Louis J. Picker
    • Steven G. Deeks

Review Article

  • Review Article |

    The phonon is the physical particle responsible for the transmission of sound and heat; controlling the properties of phonons in materials could trigger many advances, which are reviewed here.

    • Martin Maldovan

Article

  • Article |

    Using in vivo lineage tracing in mice and sorted cells in culture, the ability of stably committed cells to dedifferentiate into basal stem cells in the mouse trachea is investigated: the findings suggest that the dedifferentiation of committed cell types into stem cells may contribute generally to regeneration in higher vertebrates in different organ and injury contexts.

    • Purushothama Rao Tata
    • Hongmei Mou
    • Jayaraj Rajagopal
  • Article |

    Treatment of SHIV-infected monkeys with potent broadly neutralizing anti-HIV-1 monoclonal antibodies resulted in rapid control of viral replication in both peripheral blood and tissues; viral rebound was linked to decreasing antibody concentrations and not the generation of escape mutations, and setpoint viral load following viral rebound remained lower than the initial baseline viral load.

    • Dan H. Barouch
    • James B. Whitney
    • Dennis R. Burton
  • Article |

    The spliceosome is shown to catalyse splicing through the RNA and not the protein components of the spliceosome; pre-messenger RNA splicing requires U6 snRNA acting by a mechanism similar to that used by group II self-splicing introns.

    • Sebastian M. Fica
    • Nicole Tuttle
    • Joseph A. Piccirilli

Letter

  • Letter |

    Single magnetic atoms on non-magnetic surfaces have magnetic moments that are usually destabilized within a microsecond, too speedily to be useful, but here the magnetic moments of single holmium atoms on a highly conductive metallic substrate can reach lifetimes of the order of minutes.

    • Toshio Miyamachi
    • Tobias Schuh
    • Wulf Wulfhekel
  • Letter |

    Different polymers can be used in combination to produce coexisting nanoparticles of different symmetry and tailored to co-assemble into well-ordered binary and ternary hierarchical structures.

    • André H. Gröschel
    • Andreas Walther
    • Axel H. E. Müller
  • Letter |

    Chemical, isotopic and physical evidence indicate that some of the groundwater in the Chesapeake Bay crater is remnant Early Cretaceous North Atlantic sea water, probably 100–145 million years old, with an average salinity of about 70‰, which is twice that of modern sea water.

    • Ward E. Sanford
    • Michael W. Doughten
    • Thomas D. Bullen
  • Letter |

    Fossils of four insects and one larva from the Carboniferous Pennsylvanian epoch are described; these are very small relative to other known Palaeozoic-era insects, and reveal a previously unknown diversity of early eumetabolan insects, although the lineage radiated more successfully only after the mass extinctions at the end of the Permian period.

    • André Nel
    • Patrick Roques
    • Alexander G. Kirejtshuk
  • Letter |

    Two-photon calcium imaging experiments reveal that ring neurons in the Drosophila central complex represent visual features and show direction-selective orientation tuning, resembling simple cells in mammalian primary visual cortex; future fly studies may enhance our understanding of circuit computations underlying visually guided action selection.

    • Johannes D. Seelig
    • Vivek Jayaraman
  • Letter |

    Deletions of chromosome 22q13.3 cause Phelan–McDermid syndrome (PMDS), a neurodevelopmental disorder associated with autism; here induced pluripotent stem cells from PMDS patients with autism are used to produce neurons, they are shown to have reduced SHANK3 expression and a defect in excitatory synaptic transmission which can be restored either by increasing SHANK3 or with insulin-like growth factor 1.

    • Aleksandr Shcheglovitov
    • Olesya Shcheglovitova
    • Ricardo E. Dolmetsch
  • Letter |

    Variation in ATG16L1, a protein involved in autophagy, confers risk for Crohn’s disease, but mice with hypomorphic ATG16L1 activity do not develop spontaneous intestinal inflammation; this study shows that autophagy compensates for endoplasmic reticulum stress — common in inflammatory bowel disease epithelium — specifically in Paneth cells, with Crohn’s-disease-like inflammation of the ileum originating from this cell type when both pathways are compromised.

    • Timon E. Adolph
    • Michal F. Tomczak
    • Richard S. Blumberg
  • Letter |

    A new protein, Arpin, is identified that inhibits the Arp2/3 complex and controls cell migration by decreasing cell speed and the directional persistence of migration; this inhibitory circuit is under the control of the small GTPase Rac1, and Arpin depletion causes faster lamellipodia protrusion and increased cell migration.

    • Irene Dang
    • Roman Gorelik
    • Alexis Gautreau
  • Letter |

    It is widely accepted that migrating cells and tissues navigate along pre-patterned chemoattractant gradients; here it is shown that migrating tissues can also determine their own direction by generating local gradients of chemokine activity, via polarized receptor-mediated internalization, that are sufficient to ensure robust collective migration.

    • Erika Donà
    • Joseph D. Barry
    • Darren Gilmour
  • Letter |

    A novel approach to analyse high-depth Hi-C data provides a comprehensive chromatin interaction map at approximately 5–10 kb resolution in human fibroblasts; this reveals that TNF-α-responsive enhancers are already in contact with target promoters before signalling and that this chromatin looping is a strong predictor of gene induction.

    • Fulai Jin
    • Yan Li
    • Bing Ren

Corrigendum

Feature

Column

  • Column |

    Expediting visa approval helps countries to attract the best researchers, says Conor O'Carroll.

    • Conor O'Carroll

Futures

  • Futures |

    Hard to swallow.

    • Anatoly Belilovsky

Outlook

  • Outlook |

    An injury to the spine — the long bony assemblage that supports the upper body and the spinal cord that carries nerve signals — can be grim and costly. By Bill Cannon.

    • Bill Cannon
  • Outlook |

    The first stem-cell therapies for spinal cord injuries are already being tested in clinical studies, but scientific and political uncertainty remain.

    • Cassandra Willyard
  • Outlook |

    Drugs to protect vulnerable neurons and encourage neural circuits to reform could one day improve the outlook for patients with acute spinal cord trauma.

    • Megan Cully
  • Outlook |

    Better data and technology could prevent many devastating injuries, says Peter Cripton.

    • Peter A. Cripton
  • Outlook |

    Mechanical suits known as exoskeletons can help people with spinal cord injuries stand up and walk away from their wheelchairs — but not without training.

    • Peter Gwynne
  • Outlook |

    There are easy ways to reduce the odds of suffering a life-changing injury, says Sara Klaas.

    • Sara J. Klaas

Nature Outlook

  • Nature Outlook |

    The spine

    Every year about a quarter of a million people suffer a spinal-cord injury. The consequences of such an injury can be devastating, with lifelong paralysis and economic burdens. Advances in healthcare — from stem-cell therapy and neuro-regenerative drugs to high-tech exoskeletons — can reduce pain and restore mobility.

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