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Volume 453 Issue 7196, 5 June 2008

The mapping of large-scale human movements is important for urban planning, traffic forecasting and epidemic prevention. Work in animals suggested that their movements might be explained in terms of a random walk, a mathematical rendition of a series of random steps, or a Lã©vy flight, a random walk punctuated by an occasional larger step. The role of Lã©vy statistics in animal behaviour is controversial, but the idea of extending it to human behaviour was boosted in 2006 by a report of Lã©vy flight-like patterns in human movement tracked via dollar bills. A new human study, based on tracking the trajectory of 100,000 cell-phone users for six months, reveals behaviour close to a Lã©vy pattern, but deviating from it as individual trajectories show a high degree of temporal and spatial regularity: work and other commitments mean we are not as free to roam as a foraging animal. But by correcting the data to accommodate individual variation, simple and predictable patterns in human travel begin to emerge.

Editorial

  • The next head of the US National Human Genome Research Institute will need to be equipped to deal with the scientific, political and societal challenges presented by the burgeoning era of personal genomics.

    Editorial

    Advertisement

  • It is less specific policies and more the approach to science that will distinguish the next US president.

    Editorial
  • Social scientists have a new handle on group behaviour — but its causes remain a challenge.

    Editorial
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Research Highlights

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Correction

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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

  • Steven Kurtz, an art professor at the State University of New York at Buffalo, was cleared in April of wire and mail fraud charges, four years after the FBI seized art supplies from his home that included laboratory equipment and bacterial cultures. Kurtz is a founding member of the Critical Art Ensemble, which recently exhibited an installation called Immolation at the Foundation for Art and Creative Technology in Liverpool, UK, showing the effects of incendiary weapons on samples of human skin.

    • Rachel Courtland
    News
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News in Brief

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Correction

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News in Brief

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News Feature

  • Animal behaviour is an endless challenge to mathematical modellers. In this, the first of two features, Mark Buchanan looks at how a mathematical principle from physics might be able to explain patterns of movement. In the second, Arran Frood asks what current models can teach us about ecological networks half a billion years old.

    • Mark Buchanan
    News Feature
  • Animal behaviour is an endless challenge to mathematical modellers. In the first of two features, Mark Buchanan looks at how a mathematical principle from physics might be able to explain patterns of movement. In this, the second, Arran Frood asks what current models can teach us about ecological networks half a billion years old.

    • Arran Frood
    News Feature
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Correspondence

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Books & Arts

  • A biography of botanist Joseph Dalton Hooker illustrates how science switched in the nineteenth century from being a hobby of aristocrats to a profession paid for by governments.

    • Sandra Knapp
    Books & Arts
  • A new translation of Theodor Boveri's 1914 monograph brings the early origins of contemporary cancer research to a wider readership, contends Robert A. Weinberg.

    • Robert A. Weinberg
    Books & Arts
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Essay

  • To appreciate how our species makes sense of sound we must study the brain's response to a wide variety of music, languages and musical languages, urges Aniruddh D. Patel.

    • Aniruddh D. Patel
    Essay
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News & Views

  • Pseudogenes constitute many of the non-coding DNA sequences that make up large parts of genomes. Once considered merely protein fossils, it now emerges that some of them have active regulatory roles.

    • Rajkumar Sasidharan
    • Mark Gerstein
    News & Views
  • The generation of ultrashort light pulses by atomic ionization and recombination doesn't come cheap. But by niftily exploiting the play of light on a nanostructured surface, it can be done on a table-top.

    • Mark I. Stockman
    News & Views
  • Given the lung's thousands of branching airways, its development might be expected to be a highly complex process. Yet a surprisingly simple picture now emerges of when, where and in what order these branches form.

    • David Warburton
    News & Views
  • Transition metals come in different oxidation states with different electric charges. So at least we are told at school. Detailed calculations lead to a heretical conclusion — those variable charge states are a myth.

    • Raffaele Resta
    News & Views
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News and Views Q&A

  • Optical lattices have rapidly become a favoured tool of atomic and condensed-matter physicists. These crystals made of light can be used to trap atoms at very low temperatures, creating a workshop in which to pore over and tinker with fundamental properties of matter.

    • Markus Greiner
    • Simon Fölling
    News and Views Q&A
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Article

  • A report giving direct evidence of moonlets embedded in the bright core of Saturn's F ring, and showing that most of the F ring's morphology results from the continual gravitational and collisional effects of small satellites, often combined with the perturbing effect of Prometheus.

    • Carl D. Murray
    • Kevin Beurle
    • Sébastien Charnoz
    Article
  • A complete three-dimensional branching pattern and lineage of the mouse bronchial tree, reconstructed from an analysis of hundreds of developmental intermediates, is described. The branching process is stereotyped and generated by three simple modes of branching used in three different orders throughout the lung.

    • Ross J. Metzger
    • Ophir D. Klein
    • Mark A. Krasnow
    Article
  • A study showing that homophilic E-cadherin complexes partition in very stable microdomains. Stability and lateral mobility of these microdomains depend on two distinct actin populations: small, stable actin patches stabilize homophilic E-cadherin clusters, whereas a rapidly turning over, contractile network constrains lateral diffusion by a tethering mechanism.

    • Matthieu Cavey
    • Matteo Rauzi
    • Thomas Lecuit
    Article
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Letter

  • A paper demonstrating high harmonic generation that requires no extra amplifier cavities. This is achieved by exploiting the local field enhancement induced by resonant plasmons within a metallic nanostructure consisting of bow-tie-shaped gold elements on a sapphire substrate.

    • Seungchul Kim
    • Jonghan Jin
    • Seung-Woo Kim
    Letter
  • A report on the discovery of bulk superconductivity in samarium-arsenide oxides SmFeAsO1−xFx with a transition temperature as high as 43 K.

    • X. H. Chen
    • T. Wu
    • D. F. Fang
    Letter
  • A paper looking at the response of hybrid bonds, formed between the transition-metal atom and its host crystal, to the addition or removal of electrons. A self-regulating process is identified that shifts the energy levels of these bonds in such a way that the local charge on the transition-metal atom remains approximately constant.

    • Hannes Raebiger
    • Stephan Lany
    • Alex Zunger
    Letter
  • This paper reports molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 million years. The findings suggest that the Early Cambrian animal radiation may have been triggered by a major change in ocean circulation, terminating a long period during which the Proterozoic ocean was stratified, with sulphidic deep water.

    • Martin Wille
    • Thomas F. Nägler
    • Jan D. Kramers
    Letter
  • This report combines long-period surface-wave observations with simultaneous GPS measurements of ice displacement to study the tidally modulated stick–slip motion of the Whillans Ice Stream in West Antarctica. Such long period seismic waves are useful for detecting and studying sudden ice movement, but are insensitive to the total amount of slip.

    • Douglas A. Wiens
    • Sridhar Anandakrishnan
    • Matt A. King
    Letter
  • This paper adopts a new approach to phylogenetic analysis that captures large-scale, biologically meaningful shape variation, treats the data using conventional statistical approaches and uses the output to inform a cladistic analysis. Their test case, applied to the human lineage, could provide a benchmark for future studies of the evolutionary relationships of groups in which there are many similar members.

    • Rolando González-José
    • Ignacio Escapa
    • Héctor M. Pucciarelli
    Letter
  • This study used a sample of 100,000 mobile phone users whose trajectory was tracked for six months to study human mobility patterns. Displacements across all users suggest behaviour close to the Lévy-flight-like pattern observed previously based on the motion of marked dollar bills, but with a cutoff in the distribution. The origin of the Lévy patterns observed in the aggregate data appears to be population heterogeneity and not Lévy patterns at the level of the individual.

    • Marta C. González
    • César A. Hidalgo
    • Albert-László Barabási
    Letter
  • This paper finds that the number of fat cells is set during childhood and adolescence, and adipocyte numbers for lean or obese individuals are subject to little variation during adulthood. Even after significant weight loss in adulthood and reduced adipocyte volume, adipocyte number remains the same.

    • Kirsty L. Spalding
    • Erik Arner
    • Peter Arner
    Letter
  • This paper shows that ClC-7 is a Cl/H+ antiporter in lysosomal membranes, the activity of which maintains the correct membrane voltage during acidification of the organelle. This work reinforces the idea that plasma membrane CLCs are Cl channels whereas 'intracellular' CLCs are antiporters.

    • Austin R. Graves
    • Patricia K. Curran
    • Joseph A. Mindell
    Letter
  • The identification of esiRNAs, a class of small RNAs, many of which are expressed from (and repress) retrotransposons, but in somatic cells. esiRNAs and piRNAs interact with different subfamilies of Argonaute proteins involved in RNAi.

    • Yoshinori Kawamura
    • Kuniaki Saito
    • Haruhiko Siomi
    Letter
  • This paper identifies a class of small RNAs in fly: endogenous siRNAs (endo-siRNAs). These RNAs are present in both somatic and gonadal cells, and their processing is different than that of miRNAs or piRNAs.

    • Benjamin Czech
    • Colin D. Malone
    • Julius Brennecke
    Letter
  • This paper shows that the Drosophila genome encodes endogenous siRNAs. Derived from long hairpin RNA genes, these siRNAs downregulate protein expression. Their processing pathway from the hairpin into the mature 21-nucleotide siRNA involves factors of two pathways thought to be distinct.

    • Katsutomo Okamura
    • Wei-Jen Chung
    • Eric C. Lai
    Letter
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Prospects

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Regions

  • Huntsville, Alabama, the original home of NASA and of military weapons development, makes a move into biology. Paul Smaglik reports from Rocket City.

    • Paul Smaglik
    Regions
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Futures

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Authors

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