Volume 457 Issue 7233, 26 February 2009

The fourth International Polar Year began in 2007 and is only now drawing to a close. This week we look back at the achievements of ‘IPY4’, and forward to the fate of the poles in a warming climate. The cover image, taken in Nunavut, Canada, in 2000, shows an Inuit hunter walking on summer ice floe in midnight sun (Rob Howard/CORBIS).



  • Editorial |

    The fourth International Polar Year is coming to an end. But the Arctic and Antarctic must remain top scientific priorities.

  • Editorial |

    A political impasse over transgenic crops has left the European Commission with no good options.

  • Editorial |

    More researchers should engage with the blogosphere, including authors of papers in press.

Research Highlights

Journal Club


News in Brief

News Feature

  • News Feature |

    The International Polar Year (IPY) has covered two full annual cycles at both poles. Consisting of 170 projects, it has involved more than 60 countries and cost about US$1.2 billion.

  • News Feature |

    As scientists celebrate the end of the International Polar Year, they see causes for concern on the frozen horizon, reports Quirin Schiermeier.

    • Quirin Schiermeier
  • News Feature |

    As change in the Arctic accelerates, scientists and indigenous peoples have pressing reasons to work together, reports Richard Monastersky.

    • Richard Monastersky



  • Commentary |

    Brain-implantable devices have a promising future. Key safety issues must be resolved, but the ethics of this new technology present few totally new challenges, says Jens Clausen.

    • Jens Clausen


  • Essay |

    A theory of how microbes 'wake up' from dormancy could help to solve scientific mysteries and improve disease control, says Slava S. Epstein.

    • Slava S. Epstein

Books & Arts

  • Books & Arts |

    Ralph Bagnold's wartime posting to map the dunes of North Africa was like a desert epic — and it inspired his classic text on how wind-blown grains self-organize into regular patterns, explains Philip Ball.

    • Philip Ball
  • Books & Arts |

    Charles Darwin's relationship with his wife Emma is the subject of the film Creation. Actor Paul Bettany describes portraying Darwin's turmoil over his daughter's death and religious conflict with his wife.

    • Adam Rutherford

News & Views

  • News & Views |

    The collapse of the Soviet Union had diverse consequences, not least the abandonment of crop cultivation in many areas. One result has been the vast accumulation of soil organic carbon in the areas affected.

    • Geoffrey M. Henebry
  • News & Views |

    More than 20 million people worldwide have Alzheimer's disease, yet its causes remain mostly uncertain. Fresh findings provide molecular clues, linking this disease to another neurodegenerative disorder.

    • Moustapha Cisse
    •  & Lennart Mucke
  • News & Views |

    A study of the main asteroid belt, which lies between Mars and Jupiter, reveals an excess depletion of asteroids that was triggered by the migration of giant planets in the early history of the Solar System.

    • Kevin J. Walsh
  • News & Views |

    The bipolar see-saw hypothesis provides an explanation for why temperature shifts in the two hemispheres were out of phase at certain times. The hypothesis has now passed a test of one of its predictions.

    • Jeffrey P. Severinghaus
  • News & Views |

    The discovery of embryos in certain fossil fishes not only shows that internal fertilization and live birth evolved early in vertebrate history, but also raises questions about the origin of jawed vertebrates.

    • Per E. Ahlberg
  • News & Views |

    • Sadaf Shadan


  • Article |

    An analysis of the last deglaciation shows that the South Atlantic cooled essentially instantaneously with warming in the North Atlantic. This first concrete evidence of an immediate seesaw connection provides a link between the rapid warming in the North Atlantic and the more gradual Antarctic response.

    • Stephen Barker
    • , Paula Diz
    • , Maryline J. Vautravers
    • , Jennifer Pike
    • , Gregor Knorr
    • , Ian R. Hall
    •  & Wallace S. Broecker
  • Article |

    Rho signalling is shown to regulate angiogenesis in response to mechanical signals such as extracellular matrix elasticity, or the angiogenic factor VEGF. The pathway modulates the antagonistic functions of two transcription factors, TFII-I and GATA2, which regulate the expression of VEGFR2.

    • Akiko Mammoto
    • , Kip M. Connor
    • , Tadanori Mammoto
    • , Chong Wing Yung
    • , Dongeun Huh
    • , Christopher M. Aderman
    • , Gustavo Mostoslavsky
    • , Lois E. H. Smith
    •  & Donald E. Ingber


  • Letter |

    The main asteroid belt has gaps cleared by the giant planets. This paper shows that the observed distribution of main belt asteroids does not fill uniformly even those regions that are dynamically stable over the age of the Solar System. There is a pattern of excess depletion of asteroids that is not accounted for by planetary perturbations in the current structure of the Solar System, but are consistent with dynamical ejection of asteroids by the sweeping of gravitational resonances during the migration of Jupiter and Saturn 4 Gyr ago.

    • David A. Minton
    •  & Renu Malhotra
  • Letter |

    This paper finds an unusually large magnetoresistance — dependence of electrical resistance on magnetic field — of 1,000% at room temperature in a simple device based on lightly doped silicon between two non-magnetic metallic contacts. The size of the effect is comparable to that of 'colossal magnetoresistance' found in certain magnetic systems, although the underlying mechanism is very different. The observed magnetoresistance effect could be used to develop new magnetic devices based on silicon.

    • Michael P. Delmo
    • , Shinpei Yamamoto
    • , Shinya Kasai
    • , Teruo Ono
    •  & Kensuke Kobayashi
  • Letter |

    For large objects sliding over one another, the friction force is proportional to the true contact area between the two bodies — this is smaller than the apparent contact area as the surfaces are rough, consisting of a large number of smaller features (asperities) that actually make contact. Here a related idea holds for contacts at the nanoscale: the friction force depends linearly on the number of atoms (rather than asperities) chemically interacting across the sliding interfaces.

    • Yifei Mo
    • , Kevin T. Turner
    •  & Izabela Szlufarska
  • Letter |

    This paper shows that the growth of aeolian giant dunes, ascribed to the non-linear interaction between small-scale superimposed dunes, is limited by the confinement of the flow over the average depth of the atmospheric boundary layer. The findings explain the mean spacing of aeolian giant dunes ranging from 300 metres in coastal deserts to 3.5 kilometres.

    • Bruno Andreotti
    • , Antoine Fourrière
    • , Fouzia Ould-Kaddour
    • , Brad Murray
    •  & Philippe Claudin
  • Letter |

    This paper reveals evidence of embryos within Incisoscutum (a member of the arthrodires, a large, important and diverse group of placoderms). Incisoscutum had pelvic girdles of the right structure to support organs like the claspers of sharks, which are used in internal fertilization. The find confirms that internal fertilization and viviparity were much more widespread among the earliest jawed vertebrates than had previously been appreciated.

    • John A. Long
    • , Kate Trinajstic
    •  & Zerina Johanson
  • Letter |

    This paper shows that the effects of amyloid-beta oligomers on long-term potentiation are mediated by the cellular prion protein — notorious for its involvement in diseases such as bovine spongiform encephalopathy, new variant Creutzfeldt–Jakob disease and kuru.

    • Juha Laurén
    • , David A. Gimbel
    • , Haakon B. Nygaard
    • , John W. Gilbert
    •  & Stephen M. Strittmatter
  • Letter |

    Using quadruple whole-cell recordings, this study tested for synaptic connections among heterogeneous populations of cortical excitatory cells (pyramidal neurons), and found highly connected local circuits of neurons, each reflecting the neurons' long-range projections to a different brain region. The findings illustrate a diversity of dense cortical microcircuitry associated with the variety of information streams that produce our repertoire of behaviours and internal states.

    • Solange P. Brown
    •  & Shaul Hestrin
  • Letter |

    This study uses a new fibre-optic method to record dendritic calcium signals in freely moving animals. The strength of a sensory stimulus is gradually encoded in somatosensory cortex neurons' dendrites, under the control of local inhibitory circuitry. The findings illustrate that the representation of sensory stimuli by cortical neurons cannot be fully described by traditional integrate-and-fire models.

    • Masanori Murayama
    • , Enrique Pérez-Garci
    • , Thomas Nevian
    • , Tobias Bock
    • , Walter Senn
    •  & Matthew E. Larkum
  • Letter |

    A recent optogenetic method has been adapted to map long-range inputs onto various segments of the dendritic arborizations of cortical pyramidal neurons. Specific inputs tend to cluster in distinct domains within dendritic trees. Such spatial segregation of different axonal inputs within dendrites may strengthen coupling of coherent cell populations during neuronal information processing and learning.

    • Leopoldo Petreanu
    • , Tianyi Mao
    • , Scott M. Sternson
    •  & Karel Svoboda
  • Letter |

    Beta-arrestin-2, an adaptor protein, is necessary for efficient insulin signalling by scaffolding downstream kinases, Akt and Src, to the insulin receptor. Without beta-arrestin-2 insulin resistance develops.

    • Bing Luan
    • , Jian Zhao
    • , Haiya Wu
    • , Baoyu Duan
    • , Guangwen Shu
    • , Xiaoying Wang
    • , Dangsheng Li
    • , Weiping Jia
    • , Jiuhong Kang
    •  & Gang Pei
  • Letter |

    In the plant root system it is thought that the stem cell niche is a local pattern 'organizer' required for both continuous post-embryonic growth and regeneration. Here, the root stem cell niche is shown to be not necessary for pattern formation and re-establishment of cell identity, separating growth from re-patterning.

    • Giovanni Sena
    • , Xiaoning Wang
    • , Hsiao-Yun Liu
    • , Hugo Hofhuis
    •  & Kenneth D. Birnbaum
  • Letter |

    This paper reports a novel link between calcium signalling and salicylic-acid-mediated responses (both important for plant immunity). AtSR1, a calcium/calmodulin-binding transcription factor, is shown to be a negative regulator of plant immunity by suppressing biosynthesis of salicylic acid.

    • Liqun Du
    • , Gul S. Ali
    • , Kayla A. Simons
    • , Jingguo Hou
    • , Tianbao Yang
    • , A. S. N. Reddy
    •  & B. W. Poovaiah
  • Letter |

    Here, subdiffraction-resolution STED fluorescence microscopy is used to detect the diffusion of single lipids or GPI-anchored proteins on the plasma membrane of a living cell. Tuning the probing spot area 70-fold below that of a confocal microscope reveals that unlike phosphoglycerolipids, sphingolipids and GPI-anchored proteins are trapped for 10 ms in cholesterol-mediated complexes within <20 nm space.

    • Christian Eggeling
    • , Christian Ringemann
    • , Rebecca Medda
    • , Günter Schwarzmann
    • , Konrad Sandhoff
    • , Svetlana Polyakova
    • , Vladimir N. Belov
    • , Birka Hein
    • , Claas von Middendorff
    • , Andreas Schönle
    •  & Stefan W. Hell
  • Letter |

    This paper shows that Desulfitobacterium hafniense pyrrolysyl-tRNA synthetase–tRNAPyl is an orthogonal pair in vivo and in vitro. The structure of the co-complex reveals the distinct interactions of the protein and tRNA that distinguish this pair from those which function with the twenty standard amino acids.

    • Kayo Nozawa
    • , Patrick O’Donoghue
    • , Sarath Gundllapalli
    • , Yuhei Araiso
    • , Ryuichiro Ishitani
    • , Takuya Umehara
    • , Dieter Söll
    •  & Osamu Nureki





  • Prospects |

    Career-conscious scientists should heed advice given to governments and institutions about coping with the downturn.

    • Gene Russo


  • Regions |

    Despite an economy that is sputtering, Ireland has recommitted to investing in science. Quirin Schiermeier examines the latest research investments on the Emerald Isle.

    • Quirin Schiermeier


Networks and Support

Career View


Brief Communications Arising

  • Brief Communications Arising |

    • Sanjay K. Singh
    • , Mohamedi N. Kagalwala
    • , Jan Parker-Thornburg
    • , Henry Adams
    •  & Sadhan Majumder


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