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Volume 452 Issue 7189, 17 April 2008

Greenland, home to about a tenth of the worldãƒâ‚ã‚â’s ice, might be melting. Data from the dual-spacecraft GRACE project (the Gravity Recovery and Climate Experiment) revealed a dramatic loss of between 150 and 250 cubic kilometres of ice per year between 2002 and 2006. But other indicators have been contradictory and there is the vexed question of just what effect such melting would have on global sea level. In a News Feature this week Alex Witze attempts to pin down the current consensus on just what is going on in Greenland by posing three closely linked questions. The first is whether the warming already ãƒâƒã‚â‚ãƒâ‚ã‚â“in the pipelineãƒâƒã‚â‚ãƒâ‚ã‚â” as a result of todayãƒâƒã‚â‚ãƒâ‚ã‚â’s carbon dioxide will warm tomorrowãƒâƒã‚â‚ãƒâ‚ã‚â’s oceans sufficiently to push the ice sheet past a point of no return. The second is, how far from that threshold are we? The third is, as time goes on, how much faster will the melt go? Assumptions that such processes take millennia are now being re-examined on the basis of the changes already seen. [News Feature p. 798] Cover graphic by Danny

Editorial

  • The Arctic — particularly Greenland — needs to become a major focus of research for years to come.

    Editorial

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  • The US veterans' administration should go ahead with a much-delayed study of Agent Orange.

    Editorial
  • Efforts to boost science in the Islamic world need financial commitment from the nations themselves.

    Editorial
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Research Highlights

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Journal Club

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News

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News in Brief

  • Scribbles on the margins of science.

    News in Brief
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News

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News in Brief

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News Feature

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Correspondence

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Books & Arts

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Correction

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Books & Arts

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Essay

  • Modern science began several hundred years earlier than we have come to imagine. It got going in the twelfth century — and with it, the long-standing rift between reason and faith.

    • Philip Ball
    Essay
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News & Views

  • The application of new technology to sequence the genome of an individual yields few biological insights. Nonetheless, the feat heralds an era of 'personal genomics' based on cheap sequencing.

    • Maynard V. Olson
    News & Views
  • After a 30-year gap, all eyes are back on Mercury as the MESSENGER probe gives us our second glance at the Sun's nearest neighbour. Hints of intriguing results to come are already at hand.

    • H. Jay Melosh
    News & Views
  • For some viruses, the first step in infecting cells is to latch onto sugars on the cell membrane. The chemical basis of this virus-host recognition process has been identified using an NMR spectroscopic technique.

    • Andreas O. Frank
    • Horst Kessler
    News & Views
  • A particle-like object with a quarter of an electron's charge is the latest find in a hotbed of quantum-physical experimentation, the fractional quantum Hall fluid. Its significance is more than esoteric.

    • Eduardo Fradkin
    News & Views
  • Within a genome, genes are connected to each other through a complex network of interactions. One way to assess how robust and evolvable such genomic networks are is to introduce new links between unrelated genes.

    • Matthew R. Bennett
    • Jeff Hasty
    News & Views
  • Fishing of natural populations increases the variability of fish abundance. A unique data set from the southern California Current has allowed an evaluation of three hypotheses for why that should be so.

    • Nils Chr. Stenseth
    • Tristan Rouyer
    News & Views
  • X-ray data reveal that our Galaxy is shedding part of its gas, a phenomenon previously associated only with much more active star-forming galaxies. So what is driving the process in the Milky Way?

    • Dieter Breitschwerdt
    News & Views
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Article

  • This paper reports data of shot noise generated by the 5/2 fractional state in an ultraclean two-dimensional electron gas that compellingly points in the direction of the e/4 quasiparticles. It is believed that this observation is a first step towards understanding new fractional charges.

    • M. Dolev
    • M. Heiblum
    • D. Mahalu
    Article
  • Increased volatility of exploited fish stocks is due to amplified nonlinear behaviour caused by fishing. This paper shows how selective harvesting can alter the basic dynamics of exploited populations, and lead to unstable booms and busts that can precede systematic declines in stock levels.

    • Christian N. K. Anderson
    • Chih-hao Hsieh
    • George Sugihara
    Article
  • The first large-scale rewiring of a gene regulatory network (that of Escherichia coli) reveals that more than 95% of transcription site swaps are harmless, with many actually beneficial in several culture conditions. The results will help understanding how genomes tolerate pervasive shuffling of DNA segments during evolution.

    • Mark Isalan
    • Caroline Lemerle
    • Luis Serrano
    Article
  • Splicing is carried out within a large structure, the spliceosome, containing many RNAs and proteins. In this paper, two intermediary complexes of the splicing reaction have been purified. The differences in these complexes provide a significant advancement in understanding of the composition of the catalytic core.

    • Sergey Bessonov
    • Maria Anokhina
    • Reinhard Lührmann
    Article
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Letter

  • Tests of Einstein's general theory of relativity in a strong gravitational field may be best conducted in systems containing black holes. Such a test in a close binary system of two proposed black holes in the quasar OJ287 is reported. This quasar shows quasi-periodic optical outbursts at 12 year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black hole model and the general relativity.

    • M. J. Valtonen
    • H. J. Lehto
    • S. Dogru
    Letter
  • It is demonstrated that an isolated generic quantum many-body system does relax to a state well described by the standard statistical mechanical prescription. The thermalization happens at the level of individual eigenstates, allowing the computation of thermal averages from knowledge of any eigenstate in the microcanonical energy window.

    • Marcos Rigol
    • Vanja Dunjko
    • Maxim Olshanii
    Letter
  • The regions of aligned spins (magnetic domains) in a ferromagnet can influence the electrical properties of the material, but less is known about the domain structure of antiferromagnets, where neighbouring magnetic spins are opposed, rather than aligned. Pronounced spin-related effects can be seen in the electrical properties of the archetypical antiferromagnet, chromium. As the effects are at least as large as those seen in ferromagnets, they might prove of practical value.

    • Ravi K. Kummamuru
    • Yeong-Ah Soh
    Letter
  • An ice core record of carbon isotopic ratios in methane over the entire last glacial–interglacial transition is presented. The data show that the carbon in atmospheric methane is isotopically much heavier in cold climate periods. It is suggested that methane emissions due to biomass burning remained approximately constant throughout the glacial termination and that the atmospheric lifetime of methane is reduced during cold climate periods.

    • Hubertus Fischer
    • Melanie Behrens
    • Thomas F. Stocker
    Letter
  • Most Cambrian arthropods employed simple feeding mechanisms requiring only low degrees of appendage differentiation. But now, a sophisticated feeding apparatus from a Cambrian crustacean is described, showing that relatively large creatures were capable of manipulating fine food particles.

    • Thomas H. P. Harvey
    • Nicholas J. Butterfield
    Letter
  • Chromatin changes are examined in developing primordial germ cells during the time when the cells undergo a reprogramming step involving loss of DNA methylation and parental imprinting. Reprogramming is found to be linked to changes in histone modifications and to histone replacement through the action of histone chaperones. Histone replacement seems to occur subsequent to DNA demethylation.

    • Petra Hajkova
    • Katia Ancelin
    • M. Azim Surani
    Letter
  • An additional function for Sonic hedgehog (Shh) in the limb bud is identified, namely the control of expression of cell cycle regulators, thereby controlling growth and specifying the size of the field in which the digit specification gradient operates. It is found that when Shh signalling was inhibited in chick limb buds, all the digit precursors formed anterior structures. In contrast, when cell proliferation was inhibited, all the anterior structures were lost and all the digit-precursors formed posterior structures.

    • Matthew Towers
    • Ruth Mahood
    • Cheryll Tickle
    Letter
  • Use of transplantation to create mosaic zebrafish in which only one retinal ganglion cell develops in the eye enables the projection of this axon that innervates the tectum to be observed. It is found that these axons still navigate to their topographically correct target. The experiment rules out competition as essential for topographic specificity in the zebrafish.

    • Nathan J. Gosse
    • Linda M. Nevin
    • Herwig Baier
    Letter
  • Small interfering RNAs (siRNAs) can be systemically administered in non-human primates and significantly reduce expression from the mRNA against which they are directed. A therapeutic effect can also be achieved by targeting a microRNA (miRNA). A modified oligonucleotide directed against miR-122 was administered to monkeys, resulting in a reduction in serum cholesterol without detectable toxicity.

    • Joacim Elmén
    • Morten Lindow
    • Sakari Kauppinen
    Letter
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Corrigendum

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Erratum

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Technology Feature

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Prospects

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Regions

  • As North Carolina's Research Triangle Park nears its fiftieth birthday, Heidi Ledford investigates how research parks across the state are coping with mounting pressure from outside competition.

    • Heidi Ledford
    Regions
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Movers

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Bricks & Mortar

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Career View

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Futures

  • Who will save the servants?

    • C. N. Simms
    Futures
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Authors

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