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Volume 512 Issue 7512, 7 August 2014

The electronic properties of single-walled carbon nanotubes (SWCNTs) are extraordinarily sensitive to their precise structure. To exploit their technological potential fully, samples containing only one SWCNT type are needed. Juan Ramon Sanchez-Valencia et al. have combined synthetic chemistry with materials engineering to develop a strategy that, with further optimization, could provide a route to nanotube-based materials for use in light detectors, photovoltaics, field-effect transistors and sensors. They use a surface-catalysed cyclodehydrogenation reaction to fold rationally designed precursor molecules deposited on a Pt(111) surface to produce end caps� that act as seeds for the growth of defect-free and structurally pure SWCNTs. The technique requires only modest temperatures and is fully compatible with todays complementary metal oxide semiconductor technologies. Cover: Konstantin Amsharov.

Editorial

  • Editorial |

    A US proposal to regulate medical diagnostics from individual labs reflects the tests’ growing complexity. Such guidance should be welcomed, not resisted.

World View

  • World View |

    The next research commissioner for the European Union will need the drive and confidence to clear a daunting in-tray, argues Colin Macilwain.

    • Colin Macilwain

Research Highlights

Seven Days

  • Seven Days |

    The week in science: Death of top Japanese stem-cell scientist; instruments picked for Mars rover; and drought tightens grip on California.

News

Correction

News Feature

  • News Feature |

    The race is on to build a machine that can synthesize any organic compound. It could transform chemistry.

    • Mark Peplow

Comment

  • Comment |

    Mahlon C. Kennicutt II, Steven L. Chown and colleagues outline the most pressing questions in southern polar research, and call for greater collaboration and environmental protection in the region.

    • Mahlon C. Kennicutt
    • Steven L. Chown
    • William J. Sutherland

Books & Arts

  • Books & Arts |

    Philip Ball unveils the scientific iconography in Albrecht Dürer's enigmatic engraving Melencolia I.

    • Philip Ball

Correspondence

Correction

News & Views

  • News & Views |

    'Seed' molecules have been made that enable synthesis of just one kind of single-walled carbon nanotube, rather than a mixture of species. This paves the way for the preparation of pure samples of any nanotube species. See Letter p.61

    • James M. Tour
  • News & Views |

    A comparison of colorectal cancer and normal cells from 103 patients identifies dozens of genes that are differently expressed in tumour cells as a result of altered regulation of transcription. See Letter p.87

    • Greg Gibson
  • News & Views |

    Two studies of amyloid-β protein aggregates, which cause Alzheimer's disease, find that different conformations of the aggregates can define different strains of the disorder, drawing parallels with prion diseases.

    • Adriano Aguzzi
  • News & Views |

    Some stars explode in thermonuclear supernovae, but understanding of why this occurs comes mainly from indirect clues. Now, the progenitor of a member of a strange class of such explosions may have been detected directly. See Letter p.54

    • Stephen Justham
  • News & Views |

    Giving monkeys antiretroviral therapy from just three days after exposure to simian immunodeficiency virus does not prevent a subsequent rebound of viral replication, suggesting that viral reservoirs are established early. See Letter p.74

    • Kai Deng
    • Robert F. Siliciano
  • News & Views |

    Mice deficient in the EDA protein lack normal tooth features. Restoring EDA in embryonic teeth at increasing doses has now been found to recover these dental features in a stepwise pattern that mimics evolution. See Article p.44

    • Zhe-Xi Luo

Article

  • Article |

    Net primary production is affected by temperature and precipitation, but whether this is a direct kinetic effect on plant metabolism or an indirect ecological effect mediated by changes in plant age, plant biomass or growing season length is unclear — this study develops metabolic scaling theory to be able to answer this question and applies it to a global data set of plant productivity, concluding that it is indirect effects that explain the influence of climate on productivity, which is characterized by a common scaling relationship across climate gradients.

    • Sean T. Michaletz
    • Dongliang Cheng
    • Brian J. Enquist
  • Article |

    Gradual changes that occur to mammalian tooth morphology across evolutionary time were modelled in vitro and in vivo by modulation of signalling pathways in the mouse, and computer modelling was used to provide further analysis of the parameters influencing tooth morphology.

    • Enni Harjunmaa
    • Kerstin Seidel
    • Jukka Jernvall
  • Article |

    The crystal structures of thalidomide and its derivatives bound to the E3 ligase subcomplex DDB1–CRBN are shown; these drugs are found to have dual functions, interfering with the binding of certain cellular substrates to the E3 ligase but promoting the binding of others, thereby modulating the degradation of cellular proteins.

    • Eric S. Fischer
    • Kerstin Böhm
    • Nicolas H. Thomä

Letter

  • Letter |

    The detection of the luminous, blue progenitor system of the type Iax supernova 2012Z suggests that this supernova was the explosion of a white dwarf accreting material from a helium-star companion.

    • Curtis McCully
    • Saurabh W. Jha
    • Maximilian D. Stritzinger
  • Letter |

    The ability of individual ions trapped in separate potential wells to simulate spin–spin interactions is demonstrated by tuning the Coulomb interaction between two ions, independently controlling their local wells and entangling their internal states with a fidelity of approximately 0.82.

    • A. C. Wilson
    • Y. Colombe
    • D. J. Wineland
  • Letter |

    Present preparation methods fail to meet fully the demand for structurally pure single-walled carbon nanotubes; surface-catalysed cyclodehydrogenation reactions are now shown to convert precursor molecules deposited on a platinum(111) surface into ultrashort nanotube seeds that can then be grown further into defect-free and structurally pure single-walled carbon nanotubes of single chirality.

    • Juan Ramon Sanchez-Valencia
    • Thomas Dienel
    • Roman Fasel
  • Letter |

    GEOTRACES sampling of deep water from the Atlantic, Pacific and Southern oceans allows an estimate of the amount (tripled in surface waters) and distribution (two-thirds increase in water less than a thousand metres deep) of anthropogenic mercury accumulating in the global ocean.

    • Carl H. Lamborg
    • Chad R. Hammerschmidt
    • Mak A. Saito
  • Letter |

    Reservoirs of virus infection represent the most important reason why HIV-1 cannot be cured with current antiretroviral drugs; now the refractory viral reservoir is shown to be seeded as early as 3 days after infection in a monkey model, even before the virus is detected in the blood.

    • James B. Whitney
    • Alison L. Hill
    • Dan H. Barouch

    Collection:

  • Letter |

    Myeloproliferative neoplasms are caused by mutations in the haematopoietic stem cell (HSC) compartment, and here the authors show that the HSC niche contributes to the pathogenesis; sympathetic innervation of mesenchymal stem cells (MSCs) is reduced in the bone marrow of patients, which leads to reduced MSC numbers and increased mutant HSC expansion, and restoring sympathetic regulation of MSCs with neuroprotective/sympathomimetic drugs prevents mutant HSC expansion.

    • Lorena Arranz
    • Abel Sánchez-Aguilera
    • Simón Méndez-Ferrer
  • Letter |

    Examination of allele-specific expression identifies 71 genes with excess somatic cis-regulatory effects in colorectal cancer (CRC), and 1,693 and 948 expression quantitative trait loci (eQTLs) in normal samples and tumours, respectively (with 36% of tumour eQTLs exclusive to CRC); tumour-specific eQTLs are more enriched for low CRC genome-wide association study P values and accumulate more somatic mutations than shared eQTLs, suggesting a role as germline-derived cancer regulatory drivers.

    • Halit Ongen
    • Claus L. Andersen
    • Emmanouil T. Dermitzakis
  • Letter |

    Systematically assaying the activity of 7,705 candidate enhancers during Drosophila embryogenesis shows that nearly half are active in the embryo and display dynamic spatial patterns during development; enhancer activity is matched to expression patterns of putative target genes and predictive cis-regulatory motifs are identified.

    • Evgeny Z. Kvon
    • Tomas Kazmar
    • Alexander Stark
  • Letter |

    A high-resolution map of enhancer three-dimensional contacts during Drosophila embryogenesis shows that although local regulatory interactions are frequent, long-range interactions are also very common; unexpectedly, most interactions appear unchanged between tissues and across development and are formed prior to gene expression, indicating that transcription initiates from preformed enhancer–promoter loops, which are associated with paused polymerase.

    • Yad Ghavi-Helm
    • Felix A. Klein
    • Eileen E. M. Furlong

Feature

  • Feature |

    Interest in energy-storage research is growing, opening up opportunities for chemists with interdisciplinary skills.

    • Katharine Gammon

Career Brief

Futures

Brief Communications Arising

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