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Volume 506 Issue 7487, 13 February 2014

A representation of hysteresis in a quantized superfluid atomtronic circuit based on an image of a trapped ring-shaped Bose–Einstein condensate (BEC). Hysteresis, a phenomenon by which the physical properties of a system depend strongly on the history of the applied perturbation, is widely exploited in electronic circuits including hard disk drives and flux-gate magnetometers and is essential to the function of radio-frequency SQUIDs (superconducting quantum interference devices). Hysteresis is also fundamental to superfluidity and has been predicted to occur in superfluid atomic-gases, such as BECs. Gretchen Campbell and colleagues now report the first direct detection of hysteresis between quantized circulation states in a circuit formed from a ring of superfluid BEC obstructed by a rotating weak link. The presence of hysteresis in this system is of importance in the emerging field of ‘atomtronics�, in which ultracold atoms have a role analogous to that of the electrons in electronics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices. Cover: Emily Edwards.

Editorial

  • Despite a high death toll, public-health efforts to combat suicide lag far behind those focused on preventing accidents and diseases such as cancer. A US initiative aims to redress the balance.

    Editorial

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  • A declining island wolf population underlines the influence that humans have on nature.

    Editorial
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World View

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Research Highlights

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Seven Days

  • The week in science: Italian space head resigns; NIH teams up with big pharma; and US court rules some stem-cell treatments should be regulated as drugs.

    Seven Days
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News

  • Front-line services being trained in new approach to dealing with decontamination of victims in direct aftermath of an event.

    • Declan Butler
    News
  • Sequencing of DNA from Native American ‘Clovis boy’ forces researchers to rethink handling of tribal remains.

    • Ewen Callaway
    News
  • Some clinical trials funded by US agency resume, but strict regulations have put off others.

    • Sara Reardon
    News
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News Feature

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Comment

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Books & Arts

  • Rupert Till at the University of Huddersfield, UK, studies the sonic properties of caves containing prehistoric paintings. As he addresses a conference in Malta on the archaeology of sound, he talks about the hum of Stonehenge, acoustic fingerprinting and simulating primeval concerts in the dark.

    • Jascha Hoffman
    Books & Arts
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Correspondence

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News & Views

  • The whole-genome sequence of a human associated with the earliest widespread culture in North America confirms the Asian ancestry of the Clovis people and their relatedness to present-day Native Americans. See Letter p.225

    • Jennifer A. Raff
    • Deborah A. Bolnick

    Collection:

    News & Views
  • Simulations of the cosmos cast doubt on assumptions about the temperature of primordial hydrogen gas when it was ionized by the first stars and galaxies, complicating the interpretation of ongoing observations. See Letter p.197

    • Judd D. Bowman
    News & Views
  • An analysis reveals that satellite-observed increases in canopy greenness during dry seasons, which were previously interpreted as positive responses of Amazon forests to more sunlight, are in fact an optical artefact. See Letter p.221

    • Kamel Soudani
    • Christophe François
    News & Views
  • The observation of path dependence in the response of a superfluid to stirring promises potential applications in precision rotation sensing, and provides a test bed for microscopic theories of ultracold atomic gases. See Letter p.200

    • Matthew J. Davis
    • Kristian Helmerson
    News & Views
  • Globally consistent surveys of five factors influencing the success of marine protected areas — age, size, isolation, protection and enforcement — reveal that only when all five are present does nature thrive. See Letter p.216

    • Benjamin S. Halpern
    News & Views
  • Ocean eddies tens of kilometres in radius can delineate local ecosystems and contribute to biogeochemical budgets. The characterization of three such eddies in a coastal upwelling region provides insight into these wonders of nature.

    • Amala Mahadevan
    News & Views
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Review Article

  • In the ΛCDM paradigm, 95% of the Universe consists of dark energy and cold dark matter, but the low-density cores of dark matter measured at the centre of galaxies are hard to explain using this model; here a review of recent work shows that the action of stars and gas can significantly alter the distribution of cold dark matter through a coupling based on rapid gravitational potential fluctuations.

    • Andrew Pontzen
    • Fabio Governato
    Review Article
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Article

  • The authors report the largest family-trio exome sequencing study of schizophrenia to date; mutations are overrepresented in genes for glutamatergic synaptic proteins and also genes mutated in autism and intellectual disability, providing insights into aetiological mechanisms and pathopshyisology shared with other neurodevelopmental disorders.

    • Menachem Fromer
    • Andrew J. Pocklington
    • Michael C. O’Donovan
    Article
  • Exome sequence analysis of more than 5,000 schizophrenia cases and controls identifies a polygenic burden primarily arising from rare, disruptive mutations distributed across many genes, among which are those encoding voltage-gated calcium ion channels and the signalling complex formed by the ARC protein of the postsynaptic density; as in autism, mutations were also found in homologues of known targets of the fragile X mental retardation protein.

    • Shaun M. Purcell
    • Jennifer L. Moran
    • Pamela Sklar
    Article
  • The 1.8 Å high-resolution X-ray crystal structure of the human δ-opioid receptor is presented, with site-directed mutagenesis and functional studies revealing a crucial role for a sodium ion in mediating allosteric control in this receptor.

    • Gustavo Fenalti
    • Patrick M. Giguere
    • Raymond C. Stevens
    Article
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Letter

  • The hard spectra of X-ray binaries make them ineffective at heating primordial gas, which must have resulted in a delayed and spatially uniform heating during the epoch of reionization; this means that the signature of reionization in spectra of the 21-cm transition of atomic hydrogen will produce a more complex signal than has been predicted, including a distinct minimum at less than a millikelvin.

    • Anastasia Fialkov
    • Rennan Barkana
    • Eli Visbal
    Letter
  • Hysteresis is observed between circulation states in an ‘atomtronic’ circuit formed from a ring of superfluid Bose–Einstein condensate obstructed by a rotating weak link (a region of low atomic density), and may prove as crucial in future atomtronic devices as it has done in electronic devices.

    • Stephen Eckel
    • Jeffrey G. Lee
    • Gretchen K. Campbell
    Letter
  • Error correction is central to fault-tolerant quantum computation, but although various schemes have been developed in theory, there are few experimental realizations; a quantum error correction process is now reported for a single system of electron and nuclear spins residing in a diamond crystal.

    • G. Waldherr
    • Y. Wang
    • J. Wrachtrup
    Letter
  • The unusual structures of quasicrystals, such as the 18-fold symmetry observed in polymer micelles, lack the repeating cell pattern of conventional hard crystals; here their origin is shown to be an extension of Penrose tiling with a simple, generic interparticle interaction.

    • T. Dotera
    • T. Oshiro
    • P. Ziherl
    Letter
  • The long-term record of atmospheric carbon dioxide growth rate shows that the sensitivity of this growth rate to tropical temperature variability has increased by a factor of about two in the past five decades, and was greater when tropical land regions experienced drier conditions, implying that moisture regulates this sensitivity.

    • Xuhui Wang
    • Shilong Piao
    • Anping Chen
    Letter
  • Marine protected areas (MPAs) are an important and increasing component of marine conservation strategy, but their effectiveness is variable and debated; now a study has assembled data from a global sample of MPAs and demonstrates that effectiveness depends on five key properties: whether any fishing is allowed, enforcement levels, age, size and degree of isolation.

    • Graham J. Edgar
    • Rick D. Stuart-Smith
    • Russell J. Thomson
    Letter
  • The first individual genome from the Clovis culture is presented; the origins and genetic legacy of the people who made Clovis tools have been under debate, and evidence here suggests that the individual is more closely related to all Native American populations than to any others, refuting the hypothesis that the Clovis people arrived via European (Solutrean) migration to the Americas.

    • Morten Rasmussen
    • Sarah L. Anzick
    • Eske Willerslev
    Letter
  • Diffuse white matter injury is common in very preterm infants; here, enhanced epidermal growth factor receptor signalling in oligodendrocyte precursor cells in a mouse model of such injury is shown to increase cellular and functional recovery.

    • Joseph Scafidi
    • Timothy R. Hammond
    • Vittorio Gallo
    Letter
  • A pulse of C/EBPα followed by overexpression of the transcription factors Oct4, Sox2, Klf4 and Myc leads to fast and very efficient reprogramming of B cell precursors to induced pluripotent stem cells; C/EBPα facilitates transient chromatin accessibility and accelerates expression of pluripotency genes through a mechanism that involves activation of the Tet2 enzyme.

    • Bruno Di Stefano
    • Jose Luis Sardina
    • Thomas Graf
    Letter
  • Here it is proposed that RNA viruses can adapt to use the antiviral properties of microRNAs to limit viral replication and suppress innate immunity in particular cell types, and this restriction can lead to exacerbation of disease severity.

    • Derek W. Trobaugh
    • Christina L. Gardner
    • William B. Klimstra
    Letter
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Corrigendum

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Erratum

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Corrigendum

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Feature

  • An eye-pleasing website can boost the appeal of a laboratory, and creating one has never been easier.

    • Roberta Kwok
    Feature
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Column

  • Junior researchers can learn career-boosting skills by forming their own groups, says Alexandra Lucs.

    • Alexandra Lucs
    Column
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Futures

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Brief Communications Arising

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