Nature contents: 26 September 2013

Can't view this email? Click here to view in your browser.     Volume 501 Number 7468      nature •Visit Nature homepage •Subscribe to Nature •View Table of Contents The science that matters. Every week.               See what nature is hiding  BD Horizon™ Brilliant Violet™ polymer conjugates are brighter than traditional dyes and can help identify cell populations with lower receptor density than previously possible. Learn how to resolve rare and dim cell populations with our expanded set of tools and information and request a free sample at bdbiosciences.com/go/brilliant.       Jump to the content that matters to you View Table of Contents ▶ ▼ News & Comment   ▼ Biological Sciences   ▼ Chemical Sciences   ▼ Physical Sciences   ▼ Earth & Environmental Sciences   ▼ Careers & Jobs       This week's highlights     Specials - Outlook: Agriculture and drought     Climate change means more frequent episodes of severe drought with potentially devastating effects on the world's ability to feed a growing population. We need to improve agricultural practice to make the most efficient use of water and reduces the intensity of fertilizers and pesticides. ▼ more       Earth & Environmental Sciences More Earth & Environmental sciences ▼   Heat-pipe Earth   The Hadean era of Earth's history, around four billion years ago, is the dark age of geology, illuminated by occasional scraps of data. William Moore and Alexander Webb throw new light onto this period using a geodynamical model developed to explain events on Jupiter's volcanically active moon Io. They propose a 'heat-pipe' model to account for heat transport and lithospheric dynamics of an early Earth in transition between the early magma ocean and the era of plate tectonics.       Physical Sciences More Physical sciences ▼   Carbon nanotube computer   Carbon nanotubes have long been touted as promising building blocks for computers based on carbon rather than silicon. Max Shulaker et al. now reach a true milestone in the fields of carbon electronics and nanoelectronics with the construction of a simple but functional computer made entirely from carbon nanotube transistors. Composed of 178 transistors, each containing between 10 and 200 carbon nanotubes, it runs a simple operating system and is capable of multitasking.           Frontiers research network enables you make the most of your valuable professional network through our unique platform. Connect to colleagues, increase your impact and benefit from a 30% increase in downloads to any publication you link to your profile. Over 100,000 researchers are already here - We are just waiting for you: Register today           Biological Sciences More Biological sciences ▼   Integrating abundance and functional traits reveals new global hotspots of fish diversity   Traditional measures of biodiversity record species richness across different areas: they just count the number of species. This ignores the fact that different species have different abundances, or that the range of functional traits present in a community is not dependent solely on the number of species. This study presents a new measure of functional diversity, incorporating species abundances and functional traits into a global census of a vertebrate group – 2,473 marine reef fish species – at 1,844 sites. The results reveal previously unknown diversity hotspots in temperate regions and in the tropical Eastern Pacific.       Podcast & Video     In this week's podcast: a computer built from carbon nanotubes, what the Earth looked like before tectonic plates, and should we tweak genes to save species from extinction?         News & Comment Read daily news coverage▶ ▲top               THIS WEEK           Editorials                   Counting the cost ▶     As more and more of its ocean-sciences budget is eaten up by operational and maintenance costs, the US National Science Foundation should learn to take a long view when investing in major projects.             Time for change ▶     Angela Merkel needs to tackle the issue of Germany's uneven university funding.             Homes for bones ▶     A dispute over the skull of an Italian cheese thief highlights the enduring debate over repatriation.             World View                   Behavioural insights are vital to policy-making ▶     Governments should embrace the scientific approach and use controlled trials to test the impact of policies on people's behaviour, says Olivier Oullier.             Seven Days                   Seven days: 20–26 September 2013 ▶     The week in science: Nobel-prizewinning neuroscientist dies, jailed Iranian physics student wins human-rights prize, and Russian Academy of Sciences moves towards major overhaul.             NEWS IN FOCUS           Drilling hit by budget woes ▶     US funding for research vessel uncertain as international programme reorganizes.             Mystery over obesity 'fraud' ▶     Researcher baffled after his results appear in bogus paper.             Universities struggle to make patents pay ▶     Surfeit of unlicensed intellectual property pushes research institutions into unseemly partnerships.             Mozilla plan seeks to debug scientific code ▶     Software experiment raises prospect of extra peer review.             Regulation stacks up for e-cigarettes ▶     Devices may be the 'healthy' future of smoking — or a menace.             Interface superconductivity found in single crystal ▶     Iron-based compound revives search for room-temperature superconductors.             Features                   Biotechnology: The start-up engine ▶     Third Rock Ventures made its name by placing big bets on the biotechnology companies it launched. Now, everyone is waiting for the pay-off.             Marine science: Oceanography's billion-dollar baby ▶     A mammoth undersea US project will soon start streaming data to researchers. But some wonder whether the system is worth its high price.             COMMENT           Innovation: Bridging the market gap ▶     Physicists and engineers must do more than peddle ideas if their technologies are to translate effectively beyond the lab, says Hans Zappe.             Ecology: Gene tweaking for conservation ▶     It is time to weigh up the pros and cons of using genetic engineering to rescue species from extinction, say Michael A. Thomas and colleagues.             Books and Arts                   Molecular genetics: A revolutionary meeting of minds ▶     Jan Witkowski relishes the interwoven stories of Nobel laureates Jacques Monod and Albert Camus.             Atomic science: Winston and the warheads ▶     Richard Rhodes explores a history of Britain's little-known role in the race to develop an atomic bomb.             Books in brief ▶             Military science: Fight in flight ▶     Ann Finkbeiner ponders a chronicle of airborne war.             Technology: Pulp, pilcrows and interrobangs ▶     Andrew Robinson savours a pair of lively studies on paper and punctuation.             Correspondence                   Citations: In defence of Brazilian journals Marilia Sá Carvalho, Claudia Travassos, Claudia Medina Coeli | Citations: Ethical ways to grow impact Rafael Dias Loyola, José Alexandre Felizola Diniz Filho | Citations: Overcome the language barrier Ralf Buckley, Fernanda de Vasconcellos Pegas, Zhong Lin-sheng | Global hunger: Food crisis spurs aid for poverty Mara P. Squicciarini, Andrea Guariso, Johan Swinnen | Alternative careers: Once a scientist, always a scientist Robert E. Buntrock             Correction                   Corrections ▶               Biological Sciences ▲top             RESEARCH           Latest Online                   Microbiology: RNAs at fever pitch ▶     Franz Narberhaus             Palaeontology: A jaw-dropping fossil fish ▶     Matt Friedman, Martin D. Brazeau             Biological techniques: Chromosomes captured one by one ▶     Job Dekker, Leonid Mirny             Single-cell Hi-C reveals cell-to-cell variability in chromosome structure ▶     Takashi Nagano, Yaniv Lubling, Tim J. Stevens et al.     A novel genomic technique, single-cell Hi-C, detects thousands of simultaneous chromatin contacts in a single cell; this is used to show that individual chromosomes maintain domain organization at the megabase scale, but that chromosome structures vary from cell to cell at larger scales.             A Silurian placoderm with osteichthyan-like marginal jaw bones ▶     Min Zhu, Xiaobo Yu, Per Erik Ahlberg et al.     Although the origin of jaws is one of the key episodes in the evolution of vertebrates, the jaw bones of modern bony fishes and limbed vertebrates differ so much from those in any other groups that the individual evolutionary steps in the transition are still unknown; here Entelognathus is described, an early placoderm fish with full body armour, but with marginal jaw bones similar to those of modern bony fishes and limbed vertebrates.             Nanog, Pou5f1 and SoxB1 activate zygotic gene expression during the maternal-to-zygotic transition ▶     Miler T. Lee, Ashley R. Bonneau, Carter M. Takacs et al.     This study investigates how zygotic transcription is initiated and the maternal transcripts cleared in the zebrafish embryo: using loss-of-function analyses, high-throughput transcriptome sequencing and ribosome footprinting, the important roles of pluripotency factors Nanog, Pou5f1 and SoxB1 during these processes are identified.             Hidden specificity in an apparently nonspecific RNA-binding protein ▶     Ulf-Peter Guenther, Lindsay E. Yandek, Courtney N. Niland et al.     A novel high-throughput sequencing kinetics approach is used to measure functional binding of the apparently nonspecific RNA-binding protein C5 to all possible sequence variants in its substrate binding site; C5 binds different substrate variants with affinities varying widely, and with a similar affinity distribution to that of highly specific nucleic-acid-binding proteins, but it does not bind its physiological RNA targets with the highest affinity.             Adrenaline-activated structure of β2-adrenoceptor stabilized by an engineered nanobody ▶     Aaron M. Ring, Aashish Manglik, Andrew C. Kruse et al.     Here, by developing a high-affinity camelid antibody fragment that stabilizes the active state of the β2-adrenoceptor, the X-ray crystal structures of the receptor in complex with three agonists, including adrenaline, were determined.             Discovery of new enzymes and metabolic pathways by using structure and genome context ▶     Suwen Zhao, Ritesh Kumar, Ayano Sakai et al.     Pathway docking (in silico docking of metabolites to several enzymes and binding proteins in a metabolic pathway) enables the discovery of a catabolic pathway for the osmolyte trans-4-hydroxy-l-proline betaine.             Temperature triggers immune evasion by Neisseria meningitidis  ▶     Edmund Loh, Elisabeth Kugelberg, Alexander Tracy et al.     Three Neisseria meningitidis RNA thermosensors important for resistance against complement-mediated immune killing are identified, located in the 5′ untranslated regions of genes necessary for capsule biosynthesis, expression of factor H binding protein and sialyation of lipolysaccharide; increased temperature may act as a warning signal for the bacterium, prompting it to enhance mechanisms of immune evasion.             Temperature-dependent regulation of flowering by antagonistic FLM variants ▶     David Posé, Leonie Verhage, Felix Ott et al.     Temperature-dependent alternative splicing of FLOWERING LOCUS M (FLM) results in two protein products, FLM-β and FLM-δ, that regulate the onset of flowering in Arabidopsis; at cooler temperatures FLM-β represses flowering, whereas at higher temperatures, the plant preferentially produces FLM-δ, which promotes flowering.             Directional tissue migration through a self-generated chemokine gradient ▶     Erika Donà, Joseph D. Barry, Guillaume Valentin et al.     It is widely accepted that migrating cells and tissues navigate along pre-patterned chemoattractant gradients; here it is shown that migrating tissues can also determine their own direction by generating local gradients of chemokine activity, via polarized receptor-mediated internalization, that are sufficient to ensure robust collective migration.             Articles and Letters                   Transcriptome and genome sequencing uncovers functional variation in humans ▶     Tuuli Lappalainen, Michael Sammeth, Marc R. Friedländer et al.     Sequencing and deep analysis of mRNA and miRNA from lymphoblastoid cell lines of 462 individuals from the 1000 Genomes Project reveal widespread genetic variation affecting the regulation of most genes, with transcript structure and expression level variation being equally common but genetically largely independent, and the analyses point to putative causal variants for dozens of disease-associated loci.             The ubiquitin ligase parkin mediates resistance to intracellular pathogens ▶     Paolo S. Manzanillo, Janelle S. Ayres, Robert O. Watson et al.     Mutations in the ubiquitin ligase parkin are associated with increased susceptibility to Parkinson's disease; parkin is already known to have a role in mitophagy and this work identifies a new innate immunity role for parkin in ubiquitin-mediated autophagy of intracellular bacterial pathogens.             Integrating abundance and functional traits reveals new global hotspots of fish diversity ▶     Rick D. Stuart-Smith, Amanda E. Bates, Jonathan S. Lefcheck et al.     Global reef fish diversity is studied with metrics incorporating species abundances and functional traits; these identify diversity hotspots corresponding to the diversity of functional traits amongst individuals in the community, and greater evenness in the abundance of reef fishes at higher latitudes, findings that contrast with patterns reported previously using traditional richness-based methods.             A disinhibitory microcircuit initiates critical-period plasticity in the visual cortex ▶     Sandra J. Kuhlman, Nicholas D. Olivas, Elaine Tring et al.     The role of parvalbumin (PV)-positive interneurons in ocular dominance plasticity (ODP) has been a point of contention; here PV-positive cells are shown to initiate competitive periods of plasticity during the critical periods of eye development when ODP occurs, and transient reductions in inhibitory firing from PV-positive cells provides a return to normal firing rates in excitatory neurons, a key step in ODP progression.             The BC component of ABC toxins is an RHS-repeat-containing protein encapsulation device ▶     Jason N. Busby, Santosh Panjikar, Michael J. Landsberg et al.     The crystal structure of the complex formed by the B and C toxin complex proteins is reported, revealing how toxin complexes are processed and protected; the proteins assemble to form a large hollow structure that sequesters the cytotoxic portion of the C protein, and a β-propeller domain mediates attachment to the A protein in the native ABC complex.             Characterization of H7N9 influenza A viruses isolated from humans ▶     Tokiko Watanabe, Maki Kiso, Satoshi Fukuyama et al.     Here, biological attributes of two early human isolates of the newly emerged H7N9 influenza viruses are characterized: the potential of these viruses to infect and/or transmit within various animal models is discussed, as is their relative sensitivity to neuraminidase inhibitors and experimental polymerase inhibitors compared to an H1N1 pandemic strain.             Pathogenesis and transmission of avian influenza A (H7N9) virus in ferrets and mice ▶     Jessica A. Belser, Kortney M. Gustin, Melissa B. Pearce et al.     The new H7N9 influenza virus, recently emerged in China, can replicate in human airway cells and in the respiratory tract of ferrets to a higher level than can seasonal H3N2 virus and shows higher lethality in mice than genetically related H7N9 and H9N2 viruses, but shows limited transmission in ferrets by respiratory droplets.             Limited airborne transmission of H7N9 influenza A virus between ferrets ▶     Mathilde Richard, Eefje J. A. Schrauwen, Miranda de Graaf et al.     An investigation into the transmissibility of the H7N9 influenza A virus in ferrets finds that although the virus has some determinants associated with human adaptation and transmissibility between mammals, the airborne transmission between ferrets is limited.             Wapl is an essential regulator of chromatin structure and chromosome segregation ▶     Antonio Tedeschi, Gordana Wutz, Sébastien Huet et al.     Depletion of the cohesin-associated protein Wapl in mice is shown to increase the residence time of cohesin on DNA, which leads to clustering of cohesin in axial structures, and causes chromatin condensation in interphase chromosomes; the findings suggest that cohesin could have an architectural role in interphase chromosome organization.             Two replication fork maintenance pathways fuse inverted repeats to rearrange chromosomes ▶     Lingchuan Hu, Tae Moon Kim, Mi Young Son et al.     Stalling of replication forks in sequences that have non-allelic repeats can lead to genomic rearrangements; here two pathways consistent with homologous recombination and error-free post-replication repair fuse identical and mismatched repeats, respectively, thus inducing chromosomal rearrangements in mouse embryonic stem cells.             A two-domain elevator mechanism for sodium/proton antiport ▶     Chiara Lee, Hae Joo Kang, Christoph von Ballmoos et al.     The X-ray crystal structure of NapA, a Na+/H+ antiporter from Thermus thermophilus, in an active, outward-facing state is reported; comparisons to the structure of a related transporter in a low pH/inactivated, inward-facing state show the conformational changes that occur when the membrane protein moves from an inward-facing to an outward-facing state, suggesting that Na+/H+ antiporters operate by a two-domain rocking bundle model.             News & Views                   Biodiversity: Temperate hotspots ▶     Derek P. Tittensor             Cell biology: A table for two ▶     Marcel A. Behr & Erwin Schurr             Microbiology: RNAs at fever pitch ▶     Franz Narberhaus             Palaeontology: A jaw-dropping fossil fish ▶     Matt Friedman, Martin D. Brazeau             Biological techniques: Chromosomes captured one by one ▶     Job Dekker, Leonid Mirny             Corrigendum                   Corrigendum: LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling ▶     Xiaomeng Wang, Sabu Abraham, Jenny A. G. McKenzie et al.             Research Highlights                   Metabolism: Thyroid disease tips body's thermostat | Psychology: Young people resist bad news | Gene regulation: RNA boosts genes on a loop | Neuroscience: Lit neurons show sleep patterns | Microbiology: Termite turns to its dung for defence | Evolution: Cool eggs make for longer legs | Diagnostics: Virus revealed by host response | Animal models: Lab rats reveal genetics of selection         NEWS & COMMENT           Behavioural insights are vital to policy-making | Biotechnology: The start-up engine | Ecology: Gene tweaking for conservation | Regulation stacks up for e-cigarettes | Molecular genetics: A revolutionary meeting of minds | Books in brief | Mystery over obesity 'fraud' | Mozilla plan seeks to debug scientific code             More Biological Sciences ▶                 Nature Geoscience Insight: Marine cycles in flux In this Nature Geoscience Insight we highlight some of the most intriguing advances in the microbial biogeochemistry of the oceans, a field that is very much in flux. Free online for a limited time    Produced with support from: Gordon and Betty Moore Foundation          Chemical Sciences ▲top             RESEARCH           Articles and Letters                   Alkane desaturation by concerted double hydrogen atom transfer to benzyne ▶     Dawen Niu, Patrick H. Willoughby, Brian P. Woods et al.     Benzynes are capable of concerted removal of two vicinal hydrogen atoms from a hydrocarbon, a discovery enabled by the thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates.             More Chemical Sciences ▶               Physical Sciences ▲top             RESEARCH           Latest Online                   Condensed-matter physics: Quantum togetherness ▶     Sougato Bose             Attractive photons in a quantum nonlinear medium ▶     Ofer Firstenberg, Thibault Peyronel, Qi-Yu Liang et al.     By coupling light to strongly interacting atomic Rydberg states in a dispersive regime, it is possible to induce individual photons to travel as massive particles with strong mutual attraction, such that the propagation of photon pairs is dominated by a two-photon bound state.             Microscopic observation of magnon bound states and their dynamics ▶     Takeshi Fukuhara, Peter Schauß, Manuel Endres et al.     Bound states of elementary spin waves (magnons) have been predicted to occur in one-dimensional quantum magnets; the observation of two-magnon bound states in a system of ultracold bosonic atoms in an optical lattice is now reported.             Articles and Letters                   Swings between rotation and accretion power in a binary millisecond pulsar ▶     A. Papitto, C. Ferrigno, E. Bozzo et al.     A neutron star with a low mass companion star was observed at different times as a millisecond pulsar powered either by the rotation of its magnetic field or by the accretion of mass, demonstrating the evolutionary link between these two classes of pulsars, and probing the short timescales on which the transitions between the two states may occur.             Observation of dipolar spin-exchange interactions with lattice-confined polar molecules ▶     Bo Yan, Steven A. Moses, Bryce Gadway et al.     In a step towards developing a system in which to study quantum magnetism, the long-range dipolar interactions of polar molecules pinned in a three-dimensional optical lattice are used to realize a lattice spin model.             Carbon nanotube computer ▶     Max M. Shulaker, Gage Hills, Nishant Patil et al.     A computer built entirely using transistors based on carbon nanotubes, which is capable of multitasking and emulating instructions from the MIPS instruction set, is enabled by methods that overcome inherent challenges with this new technology.             Alkane desaturation by concerted double hydrogen atom transfer to benzyne ▶     Dawen Niu, Patrick H. Willoughby, Brian P. Woods et al.     Benzynes are capable of concerted removal of two vicinal hydrogen atoms from a hydrocarbon, a discovery enabled by the thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates.             News & Views                   Electronics: The carbon-nanotube computer has arrived ▶     Franz Kreupl             Condensed-matter physics: Rotating molecules as quantum magnets ▶     Andrew J. Daley             Condensed-matter physics: Quantum togetherness ▶     Sougato Bose             Brief Communications Arising                   Low-voltage magnetoresistance in silicon ▶     Jun Luo, Peisen Li, Sen Zhang et al.             Zhang et al. reply ▶     X. Z. Zhang, C. H. Wan, X. L. Gao et al.             Research Highlights                   Physical chemistry: Vitamin coating blocks static         NEWS & COMMENT           Atomic science: Winston and the warheads | Books in brief | Military science: Fight in flight | Mozilla plan seeks to debug scientific code | Interface superconductivity found in single crystal | Innovation: Bridging the market gap             More Physical Sciences ▶               Earth & Environmental Sciences ▲top             RESEARCH           Articles and Letters                   Heat-pipe Earth ▶     William B. Moore, A. Alexander G. Webb     A heat-pipe model of Earth, whereby interior heat is brought to the surface through localized channels, yields predictions that agree with craton data and the detrital zircon record, and offers a global geodynamic framework in which to explore Earth's evolution before the onset of plate tectonics.             Atmospheric oxygenation three billion years ago ▶     Sean A. Crowe, Lasse N. Døssing, Nicolas J. Beukes et al.     The distribution of chromium isotopes and redox-sensitive metals in the Nsuze palaeosol and in the Ijzermyn iron formation from the Pongola Supergroup, in South Africa, suggests that there were appreciable levels of atmospheric oxygen about three billion years ago, some 300–400 million years earlier than previous indications for Earth surface oxygenation.             News & Views                   Earth science: A resolution of the Archaean paradox ▶     Louis Moresi             Corrigendum                   Corrigendum: Weakened stratospheric quasibiennial oscillation driven by increased tropical mean upwelling ▶     Yoshio Kawatani & Kevin Hamilton             Erratum                   Erratum: Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage ▶     Mohamed F. Haroon, Shihu Hu, Ying Shi, Michael Imelfort, Jurg Keller et al.             Research Highlights                   Climate: Waiting to reduce emissions is costly         NEWS & COMMENT           Counting the cost | Drilling hit by budget woes | Marine science: Oceanography's billion-dollar baby | Ecology: Gene tweaking for conservation | Books in brief             More Earth & Environmental Sciences ▶               Specials - Nature Outlook: Agriculture and Drought Free Access ▲top               Agriculture and drought ▶     Michelle Grayson             The dry facts ▶     Drought has wreaked havoc throughout history, destroying crops and causing famine and conflict. And it could be getting worse.             Water: The flow of technology ▶     Farmers must develop new approaches if they are to keep producing crops as water supplies dwindle.             Plant breeding: Discovery in a dry spell ▶     Improved crops have helped farmers maintain yields in times of drought. But as climate change looms, will the gains keep coming?             Modelling: Predictive yield ▶     Farmers would benefit from better long-range weather forecasts. What else can science provide to help them decide what to plant?             Perspectives: Legislating change ▶     What should governments do to enhance sustainable agriculture and mitigate droughts?             Crop pests: Under attack ▶     The threat of insects to agriculture is set to increase as the planet warms. What action can we take to safeguard our crops?             Microbiome: Soil science comes to life ▶     Plants may be getting a little help with their tolerance of drought and heat.         Sponsors             LEARNING IN THE DIGITAL AGE Nature and Scientific American collaborate to probe the revolution underway in education and discuss what it means for learning, teaching and research.   Access the Special online or via specials in the NatureJournals app          Careers & Jobs ▲top               Education: Financial burden ▶     Graduate students face big decisions about money. They can benefit from wise counsel and careful forethought.             Careers related news & comment                   Seven days: 20–26 September 2013 | Biotechnology: The start-up engine Heidi Ledford | Marine science: Oceanography's billion-dollar baby Alexandra Witze | Regulation stacks up for e-cigarettes Daniel Cressey | Citations: Overcome the language barrier Ralf Buckley, Fernanda de Vasconcellos Pegas, Zhong Lin-sheng | Alternative careers: Once a scientist, always a scientist Robert E. Buntrock | Time for change | Universities struggle to make patents pay Heidi Ledford | Mozilla plan seeks to debug scientific code Erika Check Hayden | Innovation: Bridging the market gap Hans Zappe               naturejobs.com Science jobs of the week       Faculty Position     Vanderbilt University            Research Associate     Cardiff School of Biosciences            PhD Research Associate     University of Natural Resources and Life Sciences, Vienna            Postdoctoral Fellow In Developmental Neuroscience     CNRS and École Normale Supérieure          No matter what your career stage, student, postdoc or senior scientist, you will find articles on naturejobs.com to help guide you in your science career. Keep up-to-date with the latest sector trends, vote in our reader poll and sign-up to receive the monthly Naturejobs newsletter.           • Natureevents Directory featured events           natureevents directory featured events         Alzheimer’s Research UK Conference 2014     25.03.14 London, UK         Natureevents Directory is the premier resource for scientists looking for the latest scientific conferences, courses, meetings and symposia. Featured across Nature Publishing Group journals and centrally at natureevents.com it is an essential reference guide to scientific events worldwide.               Futures                   The rumination on what isn't ▶     Alex Shvartsman                 Your email address is in the Nature mailing list. You have been sent this Table of Contents Alert because you have opted in to receive it. You can change or discontinue your e-mail alerts at any time, by modifying your preferences on your nature.com account at: www.nature.com/nams/svc/myaccount (You will need to log in to be recognised as a nature.com registrant). For further technical assistance, please contact subscriptions@nature.com For other enquiries, please contact feedback@nature.com Nature Publishing Group | 75 Varick Street, 9th floor | New York | NY 10013-1917 | USA Nature Publishing Group's offices: Principal offices: London - New York - Tokyo Worldwide offices: Basingstoke - Boston - Buenos Aires - Delhi - Hong Kong - Madrid - Melbourne - Munich - Paris - San Francisco - Seoul - Washington DC Macmillan Publishers Limited is a company incorporated in England and Wales under company number 785998 and whose registered office is located at Brunel Road, Houndmills, Basingstoke, Hampshire RG21 6XS. © 2013 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.