This press release contains:
· Summaries of newsworthy papers:
Seismology: 'Stealth' earthquake doublet
Astronomy: Massive stars make waves
Quantum physics: Imaging quantum fluids
Materials science: A new role for graphene
Cell biology: From thymus to skin
Physics: A ferroelectric ferromagnet created by strain
Physics: High-pressure competition in a high-temperature superconductor
And finally… Faithful females foster cooperative breeding
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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[1] & [2] Seismology: 'Stealth' earthquake doublet (pp 959-968; N&V)
The tsunami that devastated Samoa and Tonga in September 2009 was caused by two giant, near-simultaneous earthquakes, one of which was hidden by the other, according to research published in Nature. A large intraplate earthquake was previously recognised as having occurred on the outer slope of the oceanic trench, but this event seems to have triggered an equally large subduction-zone 'megathrust' event that had not previously been identified. This reverses the pattern previously observed for such sequences and indicates that when such strong shaking triggers thrust faulting, tsunami wave generation can be significantly increased.
Large megathrust earthquakes often occur at subduction zones, where one tectonic plate sinks beneath another. Occasionally there are also large 'outer-rise' earthquakes as the top of the plate flexes and bends upwards before it sinks down, and such outer-rise events have been observed to be triggered by megathrust earthquakes, but the reverse has not previously been seen.
The September 2009 earthquakes along the Tonga subduction zone puzzled scientists, as the tsunami waves did not arrive at the anticipated time, and had anomalous polarities and amplitudes. John Beavan and colleagues now explain that this unprecedented sequence was a 'double whammy'. By studying GPS data and tsunami models, they discovered that the outer-rise earthquake occurred almost simultaneously with an equally large megathrust earthquake in the adjacent Tonga subduction zone.
In a separate paper, Thorne Lay and colleagues analyse seismic waves from the earthquake sequence, to find that the magnitude 8.1 outer trench-slope earthquake triggered extensive megathrust faulting, equivalent to another magnitude 8 earthquake in itself. Earthquakes such as this could therefore provide a possible mechanism for the occasional large tsunamis generated at the Tonga subduction zone.
Author contact
John Beavan (GNS Science, Lower Hutt, New Zealand) – Author paper [1]
Tel: +64 4 570 1444
E-mail: [email protected]
Thorne Lay (University of California, Santa Cruz, CA, USA) – Author paper [2]
Tel: +1 831 459 3164
E-mail: [email protected]
Kenji Satake (University of Tokyo, Japan) N&V author
E-mail: [email protected]
[3] Astronomy: Massive stars make waves (pp 947-949; N&V)
Periodic ripples have been observed at the surface of the Orion molecular cloud, close to a region where massive stars are forming. As described in this week’s Nature, the ripples seem to have formed in the same way as wind-driven waves on the ocean — but the ‘wind’, in this case, is high-velocity gas heated and ionized by massive stars.
Young massive stars emit intense radiation that interacts with their surrounding birth-cloud of molecular gas and dust. It has long been suspected that this interaction might give rise to hydrodynamical instabilities, which could compress or fragment the cloud, but clear evidence of an instability has been lacking.
Olivier Berné and colleagues now provide such evidence, with their observation of ripples in the gas of the Orion cloud. The authors combine new radio observations of carbon monoxide emission with archival images of infrared emission from hydrocarbon molecules to construct a detailed picture of the wave-like structures. They propose that the structures arise from a Kelvin–Helmholtz instability — an effect that occurs at the interface between fluids of contrasting density and velocity. So, just as the wind whips up water waves, it seems that the Orion ripples are produced by high-velocity gas from massive stars, blowing over the denser, slower-moving gas of the molecular cloud.
Author contact
Olivier Berné (Leiden University, Netherlands)
Tel: +31 71 527 8423
E-mail: [email protected]
John Bally (University of Colorado, Boulder, CO, USA) N&V author
Tel: +1 303 492 5786
E-mail: [email protected]
[4] Quantum physics: Imaging quantum fluids (AOP)
DOI: 10.1038/nature09378
Researchers have recorded in situ images of a quantum fluid in which each underlying quantum particle is detected. Their work is published in Nature and represents the attainment of a goal to which the field has aspired for years.
Immanuel Bloch and colleagues demonstrate fluorescence imaging of strongly interacting bosonic Mott insulators in an optical lattice with single-atom and single-site resolution. From the images, the team fully reconstruct the atom distribution on the lattice and identify individual excitations with high fidelity.
The ability to address individual lattice sites directly opens up new avenues for the manipulation, analysis and applications of strongly interacting quantum gases on a lattice.
Author contact
Immanuel Bloch (Max Planck Institute of Quantum Optics, Garching, Germany)
Tel: +49 89 32905 238
E-mail: [email protected]
[5] Materials science: A new role for graphene (AOP)
DOI: 10.1038/nature09379
***This paper will be published electronically on Nature's website on 18 August at 1800 London time / 1300 US Eastern Time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 19 August, but at a later date. ***
Atomically thin, isolated layers of graphite, known as graphene, find yet another potential role in this week’s Nature — as unique membranes for a range of chemical sensing applications and acting as single-molecule detectors with very high spatial resolution. These uses tap into the unique electrochemical properties displayed by graphene when it separates two ionic solutions each contacted with an electrode.
Graphene has attracted intense interest in recent years, for its exceptional electronic and chemical properties. Jene Golovchenko and colleagues now add to this list, by showing that although an atomically thin graphene membrane prevents most ions from moving between the two membrane-separated ionic solutions, it attracts cations and anions to its opposing surfaces; this affects the membrane conductivity and could be used for chemical sensing.
The thinness of the graphene membrane allows it to locate with a spatial resolution of less than one nanometre the composition or conformation changes in translocating DNA strands that modify the ionic conductivity through the pore. This, and potential improvements discussed in the paper, could make graphene membranes ideal substrates for high-resolution single-molecule detectors.
Author contact
Jene Golovchenko (Harvard University, Cambridge, MA, USA)
Tel: +1 617 495 3905
E-mail: [email protected]
[6] Cell biology: From thymus to skin (pp 978-982)
Cells present in the thymus can be reprogrammed to form skin stem cells without the need for genetic manipulation, a study in this week’s Nature shows. The finds shed light on several fundamental aspects of stem cell biology, and may have future therapeutic implications.
Cultured thymic epithelial cells can be induced to form hair follicle stem cells simply by changing the environment they are grown in, Yann Barrandon and colleagues demonstrate. Exposing the cells to a skin-like microenvironment seems to provide the signals necessary for cellular reprogramming without the need for genetic modification.
The study demonstrates the importance of the microenvironment in cell fate, and shows how cells from one embryonic tissue layer can be coaxed into cells more usually derived from a different germ layer. The experiments are also of interest because it was previously thought that thymic epithelial cells were less versatile and more restricted in nature.
Author contact
Yann Barrandon (Ecole Polytechnique Fédérale Lausanne, Switzerland)
Tel: +41 21 314 24 60
E-mail: [email protected]
[7] Physics: A ferroelectric ferromagnet created by strain (pp 954-958)
A material that is normally neither ferroelectric nor ferromagnetic has been induced to display both properties simultaneously, by applying strain to the crystal lattice. The transformation of europium titanate, EuTiO3, into a strong ferroelectric ferromagnet opens a new route to the fabrication of these rare materials, which should find use in a wide range of new technologies.
Ferroelectric ferromagnets — materials that display both spontaneous electrical polarization and spontaneous magnetization — are of great technological interest, combining the desirable properties of both types of material. Besides being rare, existing single-phase ferroelectric ferromagnets are weak; their spontaneous polarizations or magnetizations are typically 1,000 times smaller than those of useful ferroelectrics or ferromagnets. For this reason, attempts to fabricate new ferroelectric ferromagnets have centred on engineering composite materials, made from separate ferroelectric and magnetic phases.
Countering this trend, Darrell Schlom and colleagues report in Nature the fabrication of a strong, single-phase ferroelectric ferromagnet. Guided by a recent theoretical proposal, the authors grew thin films of EuTiO3 on a slightly mismatched substrate, which expanded the crystal lattice by about 1%. This change was sufficient to induce both ferroelectricity and ferromagnetism — confirming that the single parameter of lattice strain can be used to control both properties. Although strained EuTiO3 itself has an impractically low transition temperature for ferromagnetism, the present results confirm an experimental approach that should yield useful materials in future.
Author contact
Darrell Schlom (Cornell University, Ithaca, NY, USA)
Tel: +1 607 255 6504
E-mail: [email protected]
[8] Physics: High-pressure competition in a high-temperature superconductor (pp 950-953)
A two-step increase in the superconducting transition temperature (Tc) of a multilayer copper-oxide superconductor under applied pressure is reported in this week’s Nature. This unexpected behaviour may reflect competition between superconductivity and other ordered electronic phases.
The factors controlling superconductivity in the high-Tc superconductors are still not well understood. In the multilayer copper oxides, such as Bi2Sr2Ca2Cu3O10+δ (Bi2223), superconductivity has recently been shown to compete with another type of electronic order, such as antiferromagnetism or charge density waves. In other superconductors that display such competition, the superconducting Tc is maximized under conditions that suppress the competing order, but it is not known whether this can be done in the high-Tc materials.
Xiao-Jia Chen and colleagues have subjected single crystals of Bi2223 to extremely high pressures (up to 360,000 times atmospheric pressure, or 36 gigapascals), using magnetic and optical measurements to monitor the variation of Tc with increasing pressure. Up to about 24 gigapascals, the authors observe the expected behaviour, with Tc first increasing to a maximum and then decreasing again. But at even higher pressures, Tc increases again, eventually surpassing the first maximum.
The authors suggest that the change in behaviour at 24 gigapascals reflects a pressure-driven crossover from the competing order to superconductivity in the ‘inner’ CuO2 planes of Bi2223, which do not participate in the superconductivity at lower pressures. They further discuss how these observations might point to a possible strategy for increasing Tc in these materials.
Author contact
Xiao-Jia Chen (Carnegie Institution of Washington, DC, USA)
Tel: +1 202 478 8924
E-mail: [email protected]
[9] And finally… Faithful females foster cooperative breeding (pp 969-972; N&V)
Differences between bird species in levels of cooperation can be explained by the level of promiscuity in the species, reports a paper in this week’s Nature.
Ashleigh Griffin and colleagues conducted a phylogenetic analysis of breeding behaviour in 267 bird species, ranging from strictly monogamous puffins to highly promiscuous superb fairy-wrens. They found that levels of promiscuity are significantly lower in cooperative breeding species — where individuals prioritise the care of young that are not their own over their own reproduction — than in non-cooperative species. This may be because helpers can be more certain they are helping relatives when cooperation is low.
The study provides empirical support for E. O. Wilson’s statement that “sex is an antisocial force in evolution” and may also help to explain why cooperative breeding has been completely or partially lost in some bird species.
Author contact
Ashleigh Griffin (University of Oxford, UK)
Tel: +44 1865 271255
E-mail: [email protected]
Andrew Cockburn (Australian National University, Canberra, Australia) N&V author
Tel: +61 2 6125 3727
E-mail: [email protected]
ALSO IN THIS ISSUE…
[10] Non-canonical inhibition of DNA damage dependent ubiquitination by OTUB1 (pp 941-946; N&V)
[11] Trans-acting small RNA determines dominance relationships in Brassica self-incompatibility (pp 983-986; N&V)
[12] A mechanically stabilized receptor–ligand flex-bond important in the vasculature (pp 992-995)
[13] Crystal structure of the alpha6beta6 holoenzyme of propionyl-coenzyme A carboxylase (pp 1001-1005)
ADVANCE ONLINE PUBLICATION
***This paper will be published electronically on Nature's website on 18 August at 1800 London time / 1300 US Eastern Time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 19 August, but at a later date. ***
[14] Mediator and Cohesin Connect Gene Expression and Chromatin Architecture
DOI: 10.1038/nature09380
GEOGRAPHICAL LISTING OF AUTHORS…
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
BELGIUM
Brussels: 6
CANADA
Toronto: 10
CHINA
Guangzhou: 8
CZECH REPUBLIC
Prague: 7
DENMARK
Aarhus: 4
FRANCE
Strasbourg: 2
GERMANY
Berlin: 7
Garching: 4
Jülich: 7
Munich: 4
Stuttgart: 8
JAPAN
Ikoma: 11
Mie: 11
Morioka: 11
Osaka: 11
Sendai: 11
Shizuoka: 11
Tokyo: 10
NETHERLANDS
Leiden: 3
NEW ZEALAND
Lower Hutt: 1
SPAIN
Torrejón de Ardoz: 3
SWITZERLAND
Lausanne: 6
TONGA
Nuku’alofa: 1
UNITED KINGDOM
Edinburgh: 6
London: 9
Oxford: 9
UNITED STATES OF AMERICA
California
Los Angeles: 13
Pasadena: 2
Santa Cruz: 2
Colorado
Boulder: 14
Denver: 2
District of Columbia
Washington: 8
Illinois
Argonne: 7
Massachusetts
Boston: 12
Cambridge: 5, 14
Worcester: 14
Missouri
St Louis: 2
New Jersey
Piscataway: 7
New York
Ithaca: 7
New York: 13
Ohio
Columbus: 1, 7
Pennsylvania
Bethlehem: 12
University Park: 2, 7
Texas
Houston: 13
PRESS CONTACTS…
From North America and Canada
Neda Afsarmanesh, Nature New York
Tel: +1 212 726 9231
E-mail: [email protected]
From Japan, Korea, China, Singapore and Taiwan
Mika Nakano, Nature Tokyo
Tel: +81 3 3267 8751
E-mail: [email protected]
From the UK
Rebecca Walton, Nature, London
Tel: +44 20 7843 4502
E-mail: [email protected]
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