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Volume 493 Issue 7433, 24 January 2013

Laser cooling of solids, or optical refrigeration, is attractive as a route to compact, cryogen-free and vibration-free refrigeration devices. Laser cooling, based on removing heat due to blue-shifted emission, has been reported previously in rare-earth-metal-doped glasses and crystals. Now Jun Zhang et al. demonstrate a substantial net laser cooling of a semiconductor CdS nanobelt � by about 40 K from 290 K pumped by a 514-nm laser. This achievement opens up a route to optical refrigeration based on semiconductors, where the mechanisms involve excitonic rather than atomic resonances. Laser cooling media based on II VI semiconductors are potentially highly efficient, capable of achieving extremely low temperatures and readily integrated into optoelectronic devices. On the cover, a false-colour scanning electron micrograph of a suspended CdS nanobelt with a representation of luminescence up-conversion pumped by a green laser.

Editorial

  • Editorial |

    The ability to identify an individual from their anonymous genome sequence, using a clever algorithm and data from public databases, threatens the principle of subject confidentiality.

  • Editorial |

    Experiments that make deadly pathogens more dangerous demand the utmost scrutiny.

  • Editorial |

    With the Royal Institution in trouble, Britain’s crowded public-science scene must evolve.

World View

  • World View |

    Health systems must transcend clinical medicine and emphasize public-health approaches aimed at the drivers of disease, argues James D. Shelton.

    • James D Shelton

Research Highlights

Seven Days

  • Seven Days |

    The week in science: Barack Obama vows to tackle climate change; scientists resume research on flu viruses; and an international treaty to cap mercury emissions gets the green light.

News

News Feature

Comment

  • Comment |

    To get the best out of big data, funding agencies should develop shared tools for optimizing discovery and train a new breed of researchers, says Chris A. Mattmann.

    • Chris A. Mattmann
  • Comment |

    Increasing energy efficiency brings emissions savings. Claims that it backfires are a distraction, say Kenneth Gillingham and colleagues.

    • Kenneth Gillingham
    • Matthew J. Kotchen
    • Gernot Wagner

Books & Arts

  • Books & Arts |

    Monique Borgerhoff Mulder assesses an exploration of how modern industrial and traditional societies differ.

    • Monique Borgerhoff Mulder
  • Books & Arts |

    Edmund Stump welcomes a history of Antarctica that covers the glory, the rivalries and the scientific legacy.

    • Edmund Stump

Correspondence

News & Views Forum

  • News & Views Forum |

    A process called long-term potentiation mediates information storage — learning and memory — at the level of neurons. An in vitro study turns the molecular understanding of this process on its head. But researchers' opinions differ as to what can be inferred from these data. See Article p.495

    • Morgan Sheng
    • Roberto Malinow
    • Richard Huganir

News & Views

  • News & Views |

    An analysis shows that fuel made from wild, herbaceous vegetation grown on land currently unsuitable for cultivating field crops could contribute substantially to the United States' targets for biofuel production. See Letter p.514

    • Klaus Butterbach-Bahl
    • Ralf Kiese

    Special:

  • News & Views |

    Determining the real scale of structures in the Sun's corona has proved difficult because of limited spatial resolution. Now high-resolution imaging has allowed dynamic structures on scales of 150 kilometres to be observed. See Letter p.501

    • Peter Cargill
  • News & Views |

    A comparison of the wearing effect of plant-derived silica and desert dust on tooth enamel suggests that extreme wear on teeth might not be caused by food. The findings may change some thoughts about the diets of human ancestors.

    • Bernard Wood
  • News & Views |

    Two studies shed light on the role of cellular transitions between the epithelial and mesenchymal states during cancer metastasis, and provide food for thought as to which cellular processes should be targeted in cancer treatment.

    • Bryce J. W. van Denderen
    • Erik W. Thompson

Article

  • Article |

    Reconstruction of the Eemian interglacial from the new NEEM ice core shows that in spite of a climate warmer by eight degrees Celsius in Northern Greenland than that of the past millennium, the ice here was only a few hundred metres lower than its present level.

    • D. Dahl-Jensen
    • M. R. Albert
    • J. Zheng
  • Article |

    The minimal possible requirement for AMPA receptor trafficking during long-term potentiation is explored, revealing that no region of the receptor subunit is necessary, in contrast with previous work; the only requirement for LTP seems to be a large reserve of glutamate receptors.

    • Adam J. Granger
    • Yun Shi
    • Roger A. Nicoll

Letter

  • Letter |

    Net laser cooling from 290 kelvin to about 250 kelvin is achieved in semiconductor cadmium sulphide ‘nanobelts’ and attributed to strong coupling between excitons and longitudinal optical phonons.

    • Jun Zhang
    • Dehui Li
    • Qihua Xiong
  • Letter |

    When molecules of a phenalenyl derivative, which has no net spin, are deposited on a ferromagnet, they develop into a magnetic supramolecular layer with spin-filtering properties; this could be the basis for a new approach to building molecular magnetic devices.

    • Karthik V. Raman
    • Alexander M. Kamerbeek
    • Jagadeesh S. Moodera
  • Letter |

    A comparative assessment of six alternative cropping systems over 20 years shows that, once well established, successional herbaceous vegetation grown on marginal lands has a direct greenhouse gas emissions mitigation capacity that rivals that of purpose-grown crops.

    • Ilya Gelfand
    • Ritvik Sahajpal
    • G. Philip Robertson

    Special:

  • Letter |

    An earthquake source model in which stable, rate-strengthening behaviour at low slip rates is combined with coseismic weakening due to rapid shear heating of pore fluids, allowing unstable slip to occur in segments that can creep between events, explains a number of both long-term and coseismic observations of faults that hosted the 2011 Tohoku-Oki earthquake and the 1999 Chi-Chi earthquake.

    • Hiroyuki Noda
    • Nadia Lapusta
  • Letter |

    Biomarker and stable isotopic analysis of lipid residues from perforated pottery vessels from sixth millennium bc Europe are consistent with these vessels having been used for making cheese, a low-lactose dairy product with digestion and storage advantages for the prehistoric lactose-intolerant farming communities.

    • Mélanie Salque
    • Peter I. Bogucki
    • Richard P. Evershed
  • Letter | | Open Access

    Comparative analysis of the genomes of one mollusc (Lottia gigantea) and two annelids (Capitella teleta and Helobdella robusta) enable a more complete reconstruction of genomic features of the last common ancestors of protostomes, bilaterians and metazoans; against this conserved background they provide the first glimpse into lineage-specific evolution and diversity of the lophotrochozoans.

    • Oleg Simakov
    • Ferdinand Marletaz
    • Daniel S. Rokhsar
  • Letter |

    Optogenetic induction of phasic, but not tonic, firing in VTA dopamine neurons induces susceptibility to stress in mice undergoing a subthreshold social-defeat paradigm and in previously resilient mice that have been subjected to repeated social-defeat stress, and this effect is projection-pathway specific.

    • Dipesh Chaudhury
    • Jessica J. Walsh
    • Ming-Hu Han
  • Letter |

    Specific manipulation of midbrain dopamine neurons in freely moving rodents shows that their inhibition or excitation immediately modulates depression-like phenotypes that are induced by chronic mild stress, and that their activation alters the neural encoding of depression-related behaviours in the nucleus accumbens.

    • Kay M. Tye
    • Julie J. Mirzabekov
    • Karl Deisseroth
  • Letter |

    The crystal structure of rubella virus E1 glycoprotein in its post-fusion form reveals a class II fusion protein with distinct features so far unseen in any other crystallized fusion protein; the location of an antibody-neutralization epitope also suggests that rubella-specific antibodies may function through prevention of E1 glycoprotein trimer formation during cell entry.

    • Rebecca M. DuBois
    • Marie-Christine Vaney
    • Félix A. Rey
  • Letter |

    In the fission yeast Schizosaccharomyces pombe RNA interference (RNAi) machinery promotes heterochromatin assembly and silencing of centromeric repeats; here it is shown that RNAi participates in silencing other genomic regions, such as sexual differentiation genes and retrotransposons, and this process is regulated by developmental and environmental signals.

    • Soichiro Yamanaka
    • Sameet Mehta
    • Shiv I. S. Grewal
  • Letter |

    TET2 is shown to associate with OGT, which catalyses O-GlcNAcylation, and the two enzymes are found together at transcription start sites; TET2 facilitates the activity of OGT in O-GlcNAcylation of histone 2B, and epigenetic modifications to both DNA and histones by TET2 and OGT may be important in gene transcription regulation.

    • Qiang Chen
    • Yibin Chen
    • Xiaochun Yu

Feature

Career Brief

  • Career Brief |

    Foundation restructures application requirements.

  • Career Brief |

    Researchers in US industry far out-earn those in academia.

Futures

  • Futures |

    Time management.

    • Adam Kucharski
Nature Briefing

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