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Volume 453 Issue 7194, 22 May 2008

Translucent materials such as milk, clouds and biological tissues owe their appearance to the way they interact with light, randomly scattering an incident ray many times before it re-emerges. This process ã‚â— analogous to the brownian motion of particles in a fluid ã‚â— is called a random walk, a concept central to statistical physics. It is used, for example, to describe the diffusion of heat, light and sound. An extension of this idea is the Lãƒâ©vy flight, where a moving entity can occasionally take unusually large steps, thereby transforming a systemã‚â’s behaviour. Lãƒâ©vy flights have been recognized in systems as diverse as earthquakes and animal food searches. Barthelemy et al. have now engineered such behaviour into an optical material (titanium dioxide particles in a glass matrix). In the resulting ã‚â‘Lãƒâ©vy glassã‚â’, rather than regular diffusion, light waves perform a Lãƒâ©vy flight, in which photons spread around extremely efficiently. This will be an ideal model for studying Lãƒâ©vy flights, and may also lead to novel optical materials. The cover the photonsã‚â’ path, with the light source top right. Photo by Diederik and Leonardo Wiersma

Editorial

  • Saving a handful of photogenic species — or iconic rainforests — is no substitute for a comprehensive plan that deals with climate, economics and the environment together.

    Editorial

    Advertisement

  • The Food and Drug Administration should rethink its rejection of the Declaration of Helsinki.

    Editorial
  • The digitization of astronomy is a transformation and a delight for both amateurs and professionals.

    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

  • An open-source software project could help unify every existing astronomical image into a single data set.

    • Eric Hand
    News
  • Polish leaders were disconcerted in January, when the nation's scientists came away empty-handed from the first round of applications for the European Research Council's starting-grant competition. The country is also performing poorly in other European Union research programmes (see page 558). Science minister Barbara Kudrycka explains how the Polish government plans to reform the country's science and higher-education system.

    • Quirin Schiermeier
    News
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News in Brief

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News Feature

  • Some researchers think that the evolution of languages can be understood by treating them like genomes - but many linguists don't want to hear about it. Emma Marris reports.

    • Emma Marris
    News Feature
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Correspondence

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Books & Arts

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Essay

  • Music provides unique opportunities for understanding both brain and culture. But globalization means that time is running out, warns David Huron, for the quest to encounter the range of possible musical minds.

    • David Huron
    Essay
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News & Views

  • Many laser diodes provide light in only a limited range of the visible spectrum. A hybrid laser made out of plastic, driven by a high-power light-emitting diode, looks to offer a more flexible approach.

    • John M. Lupton
    News & Views
  • Living cells must do away with regulatory proteins that are not needed. News comes of a considerable advance in understanding how the main agent of destruction, the proteasome, catches its targets.

    • Yasushi Saeki
    • Keiji Tanaka
    News & Views
  • A cell's shape changes as it moves along a surface. The forward-thinking cytoskeletal elements are all for progress, but the conservative cell membrane keeps them under control by physically opposing their movement.

    • Jason M. Haugh
    News & Views
  • The stellar explosions known as supernovae are spectacular but common cosmic events. A satellite telescope's chance observation of a burst of X-ray light might be the first record of a supernova's earliest minutes.

    • Roger Chevalier
    News & Views
  • In recombinational DNA repair, nearly identical sequences in chromosomes are found and swapped. Structures of the RecA–DNA complexes involved provide insight into the mechanism and energetics of this universal process.

    • Stephen C. Kowalczykowski
    News & Views
  • The vaccinia virus acts like a Trojan Horse to enter its host cells: it envelops itself in the membrane of a dying cell, and is then taken up by healthy cells.

    • Kirsten Sandvig
    • Bo van Deurs
    News & Views
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Correction

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Article

  • Supernovae are usually discovered through their 'delayed' light, which becomes visible some hours after the actual event. Now Soderberg et al. report the discovery of a supernova at the time of the explosion, marked by an extremely luminous X-ray outburst.

    • A. M. Soderberg
    • E. Berger
    • D. G. York
    Article
  • Theriot and colleagues use fish keratocytes to study variations in cell shape that occur during motility. They report a model that quantitatively accounts for their experimental measurements and provides an explanation for the observed morphology of motile cells.

    • Kinneret Keren
    • Zachary Pincus
    • Julie A. Theriot
    Article
  • The 26S proteasome is a multisubunit complex that selectively degrades ubiquitin conjugated proteins. Two studies (this Article and the Letter Dikic doi:10.1038/nature06924) show that a known component of the proteasome, Rpn13, functions as a novel ubiquitin binding receptor, and structural studies reveal a novel mode of ubiquitin recognition. Rpn13 is also a receptor for a deubiquitinating enzyme, suggesting a linkage between ubiquitin chain recognition and disassembly.

    • Koraljka Husnjak
    • Suzanne Elsasser
    • Ivan Dikic
    Article
  • DNA damage can be reversed by the homologous pairing of an undamaged DNA with a damaged DNA. Pavletich and colleagues report the structure of the E. coli strand-exchange protein, RecA, bound to DNA, offering new insight into the process by which homologous DNAs are paired.

    • Zhucheng Chen
    • Haijuan Yang
    • Nikola P. Pavletich
    Article
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Letter

  • An extension of the concept of a random walk is the Lévy flight, in which the moving entity can occasionally take unusually large steps. Pierre Barthelemy and colleagues show how such behaviour can be engineered into an optical material.

    • Pierre Barthelemy
    • Jacopo Bertolotti
    • Diederik S. Wiersma
    Letter
  • Solid-like behaviour arises in a wide variety of complex fluids upon gelation — aggregation of particles to form mesoscopic clusters and networks. The authors show that gelation of spherical particles with isotropic, short-range attractions is initiated by spinodal decomposition.

    • Peter J. Lu
    • Emanuela Zaccarelli
    • David A. Weitz
    Letter
  • Lavallee and colleagues have performed rheological experiments on the lavas involved in volcanic dome-building eruptions. They find that these dome lavas are seismogenic, the nature of the seismicity changing across the ductile-to-brittle transition, and conclude that monitoring such magma seismicity may lead to improved forecasting for some volcanic eruptions.

    • Y. Lavallée
    • P. G. Meredith
    • J. H. Kruhl
    Letter
  • Tuffen and colleagues present experiments in which high-temperature silica-rich magmas are deformed under simulated volcanic conditions. Acoustic emissions recorded during the experiments indicate that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

    • Hugh Tuffen
    • Rosanna Smith
    • Peter R. Sammonds
    Letter
  • Anderson and colleagues describe a fossil amphibian from the Early Permian of Texas that has the chassis of a temnospondyl but with the addition of many features seen in modern frogs, toads and salamanders. A phylogenetic analysis splits modern Amphibia into two groups, with frogs, toads and salamanders related to temnospondyls, and caecilians to leopspndyls.

    • Jason S. Anderson
    • Robert R. Reisz
    • Stuart S. Sumida
    Letter
  • Smith and colleagues show that embryonic stem cell self-renewal does not rely on extrinsic instruction, and can be enabled by the elimination of factors that induce differentiation and by inhibition of glycogen synthase kinase 3. They interpret the data as showing the ground state of the embryonic stem cell in the absence of extrinsic instruction is self renewal.

    • Qi-Long Ying
    • Jason Wray
    • Austin Smith
    Letter
  • Keller and colleagues report a method for differentiation and isolation of one of the earliest human cardiac progenitors from human ES cells. They show that these cardiac progenitors can form cardiac, endothelial and vascular smooth muscle in vivo and in vitro, and can form a population of contracting cardiomyocytes when plated in culture.

    • Lei Yang
    • Mark H. Soonpaa
    • Gordon M. Keller
    Letter
  • Over evolutionary time genes can undergo duplication, and may accumulate mutations that render them non-functional pseudogenes, which are thought to be uninteresting. This study (and that of the group of Sasaki) shows that pseudogenes can in fact influence gene expression.

    • Oliver H. Tam
    • Alexei A. Aravin
    • Gregory J. Hannon
    Letter
  • Over evolutionary time genes can undergo duplication, and may accumulate mutations that render them non-functional pseudogenes, which are thought to be uninteresting. This study (and that of the group of Hannon) shows that pseudogenes can in fact influence gene expression.

    • Toshiaki Watanabe
    • Yasushi Totoki
    • Hiroyuki Sasaki
    Letter
  • Even in clonal populations of cells, there is significant phenotypic variation from cell to cell: Huang and colleagues analyse the behaviour of an 'outlier', which had very high expressions of the stem cell marker Sca-1, and conclude that clonal heterogeneity of gene expression level is a manifestation of metastable states of a slowly fluctuating transcriptome. These fluctuations may govern the reversible, stochastic priming of multipotent progenitor cells in cell fate decision. (See Nature Reports Stem Cells).

    • Hannah H. Chang
    • Martin Hemberg
    • Sui Huang
    Letter
  • The 26S proteasome is a multisubunit complex that selectively degrades ubiquitin conjugated proteins. Two studies (this Letter and the Article Dikic doi:10.1038/nature06926) show that a known component of the proteasome, Rpn13, functions as a novel ubiquitin binding receptor, and structural studies reveal a novel mode of ubiquitin recognition. Rpn13 is also a receptor for a deubiquitinating enzyme, suggesting a linkage between ubiquitin chain recognition and disassembly.

    • Patrick Schreiner
    • Xiang Chen
    • Michael Groll
    Letter
  • The parasite Encephalitozoon cuniculi contains mitosomes instead of functional mitochondria. Although mitochondrial carrier proteins are known to be responsible for ATP transport from the mitochondria to the cytosol, Hirt et al. now show this process to be reversed in E. cuniculi, where ATP appears to be transported from the cytosol to the organelle.

    • Anastasios D. Tsaousis
    • Edmund R. S. Kunji
    • T. Martin Embley
    Letter
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Prospects

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Regions

  • Scientists in newer member countries are learning how to use what the European Union offers.

    • Quirin Schiermeier
    Regions
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Movers

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Networks and Support

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Career View

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Futures

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Authors

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