Perspective: Time to unleash rice
Author: Robert Zeigler
Corporate inefficiency and government meddling are curbing production of the vital crop in the countries that need it most, says Robert Zeigler.
Nature 514, 7524 (2014). http://www.nature.com/doifinder/10.1038/514548b
The News Feature ‘The ethics squad’ (Nature514, 418–420; 2014) misspelled Susan Kornetsky’s name.
Evolutionary developmental biology: Ghost locus appears
Nature 514, 7524 (2014). doi:10.1038/514570a
Authors: James O. McInerney & Mary J. O'Connell
The sequences of two sponge genomes provide evidence that the ParaHox developmental genes are older than previously thought. This has implications for animal taxonomy and for developmental and evolutionary biology. See Letter p.620
Structural biology: Enzyme–chromatin complex visualized
Nature 514, 7524 (2014). doi:10.1038/514572a
Authors: Jürg Müller & Christoph W. Müller
The structure of an enzyme that is bound to a nucleosome — a protein complex around which DNA is wrapped — reveals how contacts between the two orient the enzyme so that it can modify a specific amino-acid residue. See Article p.591
Materials science: Radicals promote magnetic gel assembly
Nature 514, 7524 (2014). doi:10.1038/514574a
Authors: Christopher B. Rodell & Jason A. Burdick
Engineering complex tissues requires high-throughput, three-dimensional patterning of materials and cells. A method to assemble small gel components using magnetic forces from encapsulated free radicals could be just the ticket.
Crystal structure of the PRC1 ubiquitylation module bound to the nucleosome
Nature 514, 7524 (2014). doi:10.1038/nature13890
Authors: Robert K. McGinty, Ryan C. Henrici & Song Tan
The Polycomb group of epigenetic enzymes represses expression of developmentally regulated genes in many eukaryotes. This group includes the Polycomb repressive complex 1 (PRC1), which ubiquitylates nucleosomal histone H2A Lys 119 using its E3 ubiquitin ligase subunits, Ring1B and Bmi1, together with an E2 ubiquitin-conjugating enzyme,
Possible planet formation in the young, low-mass, multiple stellar system GG Tau A
Nature 514, 7524 (2014). doi:10.1038/nature13822
Authors: Anne Dutrey, Emmanuel Di Folco, Stéphane Guilloteau, Yann Boehler, Jeff Bary, Tracy Beck, Hervé Beust, Edwige Chapillon, Fredéric Gueth, Jean-Marc Huré, Arnaud Pierens, Vincent Piétu, Michal Simon & Ya-Wen Tang
The formation of planets around binary stars may be more difficult than around single stars. In a close binary star (with a separation of less than a hundred astronomical units), theory predicts the presence of circumstellar disks around each star, and an outer circumbinary disk surrounding a gravitationally cleared inner cavity around the stars. Given that the inner disks are depleted by accretion onto the stars on timescales of a few thousand years, any replenishing material must be transferred from the outer reservoir to fuel planet formation (which occurs on timescales of about one million years). Gas flowing through disk cavities has been detected in single star systems. A circumbinary disk was discovered around the young low-mass binary system GG Tau A (ref. 7), which has recently been shown to be a hierarchical triple system. It has one large inner disk around the single star, GG Tau Aa, and shows small amounts of shocked hydrogen gas residing within the central cavity, but other than a single weak detection, the distribution of cold gas in this cavity or in any other binary or multiple star system has not hitherto been determined. Here we report imaging of gas fragments emitting radiation characteristic of carbon monoxide within the GG Tau A cavity. From the kinematics we conclude that the flow appears capable of sustaining the inner disk (around GG Tau Aa) beyond the accretion lifetime, leaving time for planet formation to occur there. These results show the complexity of planet formation around multiple stars and confirm the general picture predicted by numerical simulations.
Quantum tomography of an electron
Nature 514, 7524 (2014). doi:10.1038/nature13821
Authors: T. Jullien, P. Roulleau, B. Roche, A. Cavanna, Y. Jin & D. C. Glattli
The complete knowledge of a quantum state allows the prediction of the probability of all possible measurement outcomes, a crucial step in quantum mechanics. It can be provided by tomographic methods which have been applied to atomic, molecular, spin and photonic states. For optical or microwave photons, standard tomography is obtained by mixing the unknown state with a large-amplitude coherent photon field. However, for fermions such as electrons in condensed matter, this approach is not applicable because fermionic fields are limited to small amplitudes (at most one particle per state), and so far no determination of an electron wavefunction has been made. Recent proposals involving quantum conductors suggest that the wavefunction can be obtained by measuring the time-dependent current of electronic wave interferometers or the current noise of electronic Hanbury-Brown/Twiss interferometers. Here we show that such measurements are possible despite the extreme noise sensitivity required, and present the reconstructed wavefunction quasi-probability, or Wigner distribution function, of single electrons injected into a ballistic conductor. Many identical electrons are prepared in well-controlled quantum states called levitons by repeatedly applying Lorentzian voltage pulses to a contact on the conductor. After passing through an electron beam splitter, the levitons are mixed with a weak-amplitude fermionic field formed by a coherent superposition of electron–hole pairs generated by a small alternating current with a frequency that is a multiple of the voltage pulse frequency. Antibunching of the electrons and holes with the levitons at the beam splitter changes the leviton partition statistics, and the noise variations provide the energy density matrix elements of the levitons. This demonstration of quantum tomography makes the developing field of electron quantum optics with ballistic conductors a new test-bed for quantum information with fermions. These results may find direct application in probing the entanglement of electron flying quantum bits, electron decoherence and electron interactions. They could also be applied to cold fermionic (or spin-1/2) atoms.
Room-temperature magnetic order on zigzag edges of narrow graphene nanoribbons
Nature 514, 7524 (2014). doi:10.1038/nature13831
Authors: Gábor Zsolt Magda, Xiaozhan Jin, Imre Hagymási, Péter Vancsó, Zoltán Osváth, Péter Nemes-Incze, Chanyong Hwang, László P. Biró & Levente Tapasztó
The possibility that non-magnetic materials such as carbon could exhibit a novel type of s–p electron magnetism has attracted much attention over the years, not least because such magnetic order is predicted to be stable at high temperatures. It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins, but it remains unclear under what conditions long-range magnetic order can emerge from such defect-bound magnetic moments. Here we propose that, in contrast to random defect distributions, atomic-scale engineering of graphene edges with specific crystallographic orientation—comprising edge atoms from only one sub-lattice of the bipartite graphene lattice—can give rise to a robust magnetic order. We use a nanofabrication technique based on scanning tunnelling microscopy to define graphene nanoribbons with nanometre precision and well-defined crystallographic edge orientations. Although so-called ‘armchair’ ribbons display quantum confinement gaps, ribbons with the ‘zigzag’ edge structure that are narrower than 7 nanometres exhibit an electronic bandgap of about 0.2–0.3 electronvolts, which can be identified as a signature of interaction-induced spin ordering along their edges. Moreover, upon increasing the ribbon width, a semiconductor-to-metal transition is revealed, indicating the switching of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferromagnetic configuration. We found that the magnetic order on graphene edges of controlled zigzag orientation can be stable even at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions.
Stochastic transport through carbon nanotubes in lipid bilayers and live cell membranes
Nature 514, 7524 (2014). doi:10.1038/nature13817
Authors: Jia Geng, Kyunghoon Kim, Jianfei Zhang, Artur Escalada, Ramya Tunuguntla, Luis R. Comolli, Frances I. Allen, Anna V. Shnyrova, Kang Rae Cho, Dayannara Munoz, Y. Morris Wang, Costas P. Grigoropoulos, Caroline M. Ajo-Franklin, Vadim A. Frolov & Aleksandr Noy
There is much interest in developing synthetic analogues of biological membrane channels with high efficiency and exquisite selectivity for transporting ions and molecules. Bottom-up and top-down methods can produce nanopores of a size comparable to that of endogenous protein channels, but replicating their affinity and transport properties remains challenging. In principle, carbon nanotubes (CNTs) should be an ideal membrane channel platform: they exhibit excellent transport properties and their narrow hydrophobic inner pores mimic structural motifs typical of biological channels. Moreover, simulations predict that CNTs with a length comparable to the thickness of a lipid bilayer membrane can self-insert into the membrane. Functionalized CNTs have indeed been found to penetrate lipid membranes and cell walls, and short tubes have been forced into membranes to create sensors, yet membrane transport applications of short CNTs remain underexplored. Here we show that short CNTs spontaneously insert into lipid bilayers and live cell membranes to form channels that exhibit a unitary conductance of 70–100 picosiemens under physiological conditions. Despite their structural simplicity, these ‘CNT porins’ transport water, protons, small ions and DNA, stochastically switch between metastable conductance substates, and display characteristic macromolecule-induced ionic current blockades. We also show that local channel and membrane charges can control the conductance and ion selectivity of the CNT porins, thereby establishing these nanopores as a promising biomimetic platform for developing cell interfaces, studying transport in biological channels, and creating stochastic sensors.
Centennial-scale changes in the global carbon cycle during the last deglaciation
Nature 514, 7524 (2014). doi:10.1038/nature13799
Authors: Shaun A. Marcott, Thomas K. Bauska, Christo Buizert, Eric J. Steig, Julia L. Rosen, Kurt M. Cuffey, T. J. Fudge, Jeffery P. Severinghaus, Jinho Ahn, Michael L. Kalk, Joseph R. McConnell, Todd Sowers, Kendrick C. Taylor, James W. C. White & Edward J. Brook
Global climate and the concentration of atmospheric carbon dioxide (CO2) are correlated over recent glacial cycles. The combination of processes responsible for a rise in atmospheric CO2 at the last glacial termination (23,000 to 9,000 years ago), however, remains uncertain. Establishing the timing and rate of CO2 changes in the past provides critical insight into the mechanisms that influence the carbon cycle and helps put present and future anthropogenic emissions in context. Here we present CO2 and methane (CH4) records of the last deglaciation from a new high-accumulation West Antarctic ice core with unprecedented temporal resolution and precise chronology. We show that although low-frequency CO2 variations parallel changes in Antarctic temperature, abrupt CO2 changes occur that have a clear relationship with abrupt climate changes in the Northern Hemisphere. A significant proportion of the direct radiative forcing associated with the rise in atmospheric CO2 occurred in three sudden steps, each of 10 to 15 parts per million. Every step took place in less than two centuries and was followed by no notable change in atmospheric CO2 for about 1,000 to 1,500 years. Slow, millennial-scale ventilation of Southern Ocean CO2-rich, deep-ocean water masses is thought to have been fundamental to the rise in atmospheric CO2 associated with the glacial termination, given the strong covariance of CO2 levels and Antarctic temperatures. Our data establish a contribution from an abrupt, centennial-scale mode of CO2 variability that is not directly related to Antarctic temperature. We suggest that processes operating on centennial timescales, probably involving the Atlantic meridional overturning circulation, seem to be influencing global carbon-cycle dynamics and are at present not widely considered in Earth system models.
Calcisponges have a ParaHox gene and dynamic expression of dispersed NK homeobox genes
Nature 514, 7524 (2014). doi:10.1038/nature13881
Authors: Sofia A. V. Fortunato, Marcin Adamski, Olivia Mendivil Ramos, Sven Leininger, Jing Liu, David E. K. Ferrier & Maja Adamska
Sponges are simple animals with few cell types, but their genomes paradoxically contain a wide variety of developmental transcription factors, including homeobox genes belonging to the Antennapedia (ANTP) class, which in bilaterians encompass Hox, ParaHox and NK genes. In the genome of the demosponge Amphimedon queenslandica, no Hox or ParaHox genes are present, but NK genes are linked in a tight cluster similar to the NK clusters of bilaterians. It has been proposed that Hox and ParaHox genes originated from NK cluster genes after divergence of sponges from the lineage leading to cnidarians and bilaterians. On the other hand, synteny analysis lends support to the notion that the absence of Hox and ParaHox genes in Amphimedon is a result of secondary loss (the ghost locus hypothesis). Here we analysed complete suites of ANTP-class homeoboxes in two calcareous sponges, Sycon ciliatum and Leucosolenia complicata. Our phylogenetic analyses demonstrate that these calcisponges possess orthologues of bilaterian NK genes (Hex, Hmx and Msx), a varying number of additional NK genes and one ParaHox gene, Cdx. Despite the generation of scaffolds spanning multiple genes, we find no evidence of clustering of Sycon NK genes. All Sycon ANTP-class genes are developmentally expressed, with patterns suggesting their involvement in cell type specification in embryos and adults, metamorphosis and body plan patterning. These results demonstrate that ParaHox genes predate the origin of sponges, thus confirming the ghost locus hypothesis, and highlight the need to analyse the genomes of multiple sponge lineages to obtain a complete picture of the ancestral composition of the first animal genome.
Corrigendum: Immune clearance of highly pathogenic SIV infection
Nature 514, 7524 (2014). doi:10.1038/nature13840
Authors: Scott G. Hansen, Michael Piatak, Abigail B. Ventura, Colette M. Hughes, Roxanne M. Gilbride, Julia C. Ford, Kelli Oswald, Rebecca Shoemaker, Yuan Li, Matthew S. Lewis, Awbrey N. Gilliam, Guangwu Xu, Nathan Whizin, Benjamin J. Burwitz, Shannon L. Planer, John M. Turner, Alfred W. Legasse, Michael K. Axthelm, Jay A. Nelson, Klaus Früh, Jonah B. Sacha, Jacob D. Estes, Brandon F. Keele, Paul T. Edlefsen, Jeffrey D. Lifson & Louis J. Picker
Nature502, 100–104 (2013); doi:10.1038/nature12519The Acknowledgements section of this Letter should have included the following sentence: “We acknowledge the contribution of M. A. Jarvis to the design, construction and initial in vitro characterization of all the strain
Bibliothque nationale, catalogues du Dpartment de la musique, Bibiothque nationale, catalogue du Dpartment de la musique, fonds du Conservatoire.
Subjects: Bibliothque nationale (France). Dpartement de la musique Catalogs. Bibliothque nationale (France). Dpartement de la musique. fast (OCoLC)fst00513041 , Music Bibliography Catalogs. Music Bibliography. fast (OCoLC)fst01761933 , Catalogs. fast (OCoLC)fst01423692
Das ungeliebte Frhwerk : Richard Wagners Oper "Das Liebesverbot" : Symposium Mnchen, Bayerischer Rundfunk, 2013 / herausgegeben von Laurenz Ltteken.
Subjects: Wagner, Richard, 1813-1883. Liebesverbot Congresses.
Salzburgs Musikgeschichte im Zeichen des Provinzialismus? : die ersten Jahrzehnte des 19. Jahrhunderts : Bericht einer Tagung der Forschungsplattform "Salzburger Musikgeschichte", 23. bis 25. September 2012 / herausgegeben von Dominik ediv.
Subjects: Music Austria Salzburg 19th century History and criticism Congresses.