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This press release is copyright Nature.
VOL.454 NO.7200 DATED 03 JULY 2008
This press release contains:
· Summaries of newsworthy papers:
Space science: A lop-sided Solar System
Extinction: A game of chance
Materials: Going with the flow
Virology: Viral sedatives
Collision course: Another type of brief encounter
And finally… Carbon on early Earth
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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[1] — [6] Space science: A lop-sided Solar System (pp 63-83; N&V)
The Solar System is not round, but has an asymmetric, squashed shape, according to recent data streamed back from the Voyager 2 spacecraft. The results are reported as part of a series of papers in this week’s Nature analysing recent observations from the outer limits of the Solar System, and help build up a picture of how the Sun interacts with the rest of the Galaxy.
Launched in 1977, the Voyager spacecraft were originally sent to fly by and observe Jupiter and Saturn. The two probes eventually continued their mission into the outer Solar System, with Voyager 1 becoming the most distant man-made object in space in the 1990s. Operating in remote, cold and dark conditions, and powered by long-life nuclear batteries in the absence of solar energy, the probes are still transmitting data back to Earth, over thirty years after they were first launched and long after their original missions ended.
The current mission of both spacecraft is to reach and study the outer limits of the heliosphere — a magnetic ‘bubble’ around the Solar System created by the solar wind. The transition zone between the heliosphere and the rest of interstellar space is known as the ‘termination shock’. Edward Stone and colleagues report that Voyager 2 crossed this boundary closer to the Sun than expected, suggesting that the heliosphere in this region is dented, or pushed in, closer to the Sun by a local magnetic field. Companion papers explore more details of Voyager 2’s crossing of the termination shock, analysing the plasma, magnetic field, plasma-wave and lower-energy particle observations.
John Richardson and colleagues show in their paper that most of the solar wind energy is transferred to ‘pickup’ ions or other energetic particles both upstream of and at the termination shock. Leonard Burlaga and colleagues describe magnetic field observations revealing a complex shock of moderate strength undergoing reformation on a scale of a few hours, rather than the expected days. Donald Gurnett and William Kurth report the detection of intense plasma-wave electric fields at the solar wind termination shock.
Robert Decker and colleagues study the changes in electron and ion intensity observed by Voyager 2. They suggest that acceleration of ions extracts a large fraction of bulk-flow kinetic energy from the solar wind. Finally, Linghua Wang and colleagues report the detection and mapping of energetic neutral atoms produced by charge exchange between ions and neutral atoms. Much of the energy associated with the shock wave of the solar wind hitting the boundary is carried away by these energetic neutral atoms.
CONTACT
John Richardson (Massachusetts Institute of Technology, Cambridge, MA, USA) Author paper [1]
Tel: +1 617 253 6112; E-mail: [email protected]
Robert Decker (Johns Hopkins University, Laurel, MD, USA) Author paper [2]
Tel: +1 240 228 8696; E-mail: [email protected]
Edward Stone (California Institute of Technology, Pasadena CA, USA) Author paper [3]
Tel: +1 626 395 8321; E-mail: [email protected]
Leonard Burlaga (NASA/Goddard Space Flight Center, Greenbelt, MD, USA) Author paper [4]
Tel: +1 301 286 5956; E-mail: [email protected]
Donald Gurnett (University of Iowa, Iowa City, IA, USA) Author paper [5]
Tel: +1 319 335 1697; E-mail: [email protected]
William Kurth (University of Iowa, Iowa City, IA, USA) Author paper [5]
Tel: +1 319 335 1926; E-mail: [email protected]
Linghua Wang (University of California, Berkeley, CA, USA) Author paper [6]
Tel: +1 510 642 3668; E-mail: [email protected]
Jack Jokipii (University of Arizona, Tucson, AZ, USA) N&V author
Tel: +1 520 621 4256; E-mail: [email protected]
[7] Extinction: A game of chance (pp 100-103)
The risk of extinction for endangered species is greatly underestimated, finds a study in this week’s Nature. The authors call for an urgent re-evaluation of many species with conservation concerns.
Extinction is a fundamental process in biological systems and is central to our understanding of biodiversity and evolution. Like a game of Russian roulette, the demise of a species is the culmination of a series of chance events. Brett Melbourne and Alan Hastings describe a mathematical theory using all the random events that contribute to a dwindling population — such as birth and death rates, environmental factors and the male to female ratio — to predict the likelihood of a species becoming extinct. Linking with experiments on insect populations, they show that changes in sex ratio have a greater impact than random environmental events when populations are small and vulnerable.
The research reveals flaws in current models used to predict extinction — finding the risk to be many times higher than previously thought possible.
CONTACT
Brett Melbourne (University of Colorado, Boulder, CO, USA)
Tel: +1 530 848 1805; E-mail: [email protected]
[8] Materials: Going with the flow (pp 84-87)
Glassy substances such as creams and pastes have a unique behaviour as they flow, different from the behaviour of the material as a whole. In this week’s Nature, scientists discover that this behaviour is strongly dependent on the thickness of the paste and on the type of surface on which it is spread. The results have applications in diverse contexts; ranging from the industrial processing of food and cosmetics through to the geophysical hazards associated with debris flows.
The spreading of a paste or emulsion on a surface is a familiar everyday process — for example the application of skin cream — yet the underlying physics is highly complex. This sort of ‘granular’ material is neither solid or liquid, but has properties that lie somewhere in between. Individual grains are ‘jammed’ together like sand on a beach, forming a disordered structure, and giving the material its solid-like character. But when enough stress is applied, it begins to flow more like a liquid. These complex flow dynamics make materials like this ideal for use in many applications, such as industry, food and cosmetics.
Lydéric Bocquet and colleagues propose a theoretical framework to try and explain these unique rheological properties. They characterize the flow of thin layers of concentrated emulsions, in gaps of varying thicknesses and roughness, showing the existence of finite size effects in the flow properties. The team then develop a law to reproduce quantitatively all their experimental results in various flow configurations, revealing that how the material flows is highly dependent on both the film thickness and the roughness of the surface.
CONTACT
Lydéric Bocquet (Technical University Munich, Garching, Germany)
Tel: +49 89 289 14336; E-mail: [email protected]
Annie Colin (Université Bordeaux 1, Pessac, France) Co-author
Tel: +33 5 56 46 47 14; E-mail: [email protected]
[9] Virology: Viral sedatives (AOP)
DOI: 10.1038/nature07103
***This paper will be published electronically on Nature's website on 02 July 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 03 July, but at a later date. ***
A study published online this week in Nature reveals how herpesviruses are able to switch off their volatile life cycle in order to maintain lifelong dormant infections. This research could lead to new therapies to control infection.
One of the key viral genes associated with latent infections, LAT, does not encode any proteins but somehow manages to keep the virus in the dormant state. Bryan Cullen and colleagues found that LAT encodes single strands of regulatory genetic material known as microRNAs. These miRNAs seem to act by switching off the viral genes that kick-start the infectious life cycle — effectively lulling the virus to sleep.
The virus can remain in this restful state for many years, establishing a reservoir of virus that can sporadically erupt at any time, meaning that the host is never fully cured. The authors suggest that their findings could lead to new combination treatments; driving the virus out of latency with drugs to inhibit these miRNAs could set-off a normal virus infection that can be resolved with antiviral drugs.
CONTACT
Bryan Cullen (Duke University Medical Center, Durham, NC, USA)
Tel: +1 919 684 3369; E-mail: [email protected]
[10] Collision course: Another type of brief encounter (pp 88-91; N&V)
When a hydrogen atom crashes into a relatively heavy deuterium–deuterium molecule without chemically reacting with it, the incident hydrogen atom scatters off with reduced kinetic energy, the energy lost being converted into vibrational excitations. In such ‘inelastic’ processes the scattering of the incident atom is predominantly backwards, but a paper in this week’s Nature reveals that a different mechanism for inelastic scattering is also possible.
Richard Zare and his colleagues study collisions of fast hydrogen atoms with supersonically cooled deuterium–deuterium molecules. They found that the inelastic scattering process led mainly to forward scattering — the opposite of what was expected.
The explanation is that even if the hydrogen atom flies at some distance past the deuterium–deuterium molecule in a ‘grazing collision’, it can tug on the deuterium atom nearest to it and thereby extend — and vibrationally excite — the bond connecting the two deuterium atoms. Normally, inelastic collisions occur in a more ‘head-on’ fashion and result in a transient compression of the molecular bond. The authors suggest that this ‘tug-of-war’ behaviour may come into play whenever strong attraction can develop between the collision partners.
CONTACT
Richard Zare (Stanford University, CA, USA)
Tel: +1 650 723 3062; E-mail: [email protected]
Mark Brouard (University of Oxford, UK) N&V author
Tel: +44 1865 275457; E-mail: [email protected]
[11] And finally… Carbon on early Earth (pp 92-95)
Scientists report a light carbon reservoir recorded in mineral-hosted diamonds that may have formed over four billion years ago. They speculate that this could indicate the presence of biogenic activity on early Earth.
The recent discovery of diamond–graphite inclusions in the Earth's oldest zircon grains from the Jack Hills sediments in Western Australia is a unique opportunity to investigate Earth's earliest known carbon reservoir. These minerals help scientists to understand conditions during the planet’s development.
In Nature this week, Alexander Nemchin and colleagues analyse the carbon isotope composition of the diamond–graphite inclusions. They find low carbon isotopic ratios, which may reflect deep subduction of biogenic surface carbon.
The authors caution that these isotope values could also have been produced by inorganic chemical reactions and therefore do not prove the existence of life on Earth as early as 4,250 million years ago. Regardless, the results suggest that a reservoir of low carbon isotopic ratios may have existed on early Earth.
CONTACT
Alexander Nemchin (Curtin University of Technology, Bentley, WA, Australia)
Tel: +61 892 662 445; E-mail: [email protected]
ALSO IN THIS ISSUE…
[12] Functional asymmetry in Caenorhabditis elegans taste neurons and its computational role in chemotaxis (pp 114-117)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 02 July 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 them on this release to avoid multiple mailings they will not appear in print on 03 July, but at a later date. ***
[13] Structural basis for translation termination on the 70S ribosome
DOI: 10.1038/nature07115
[14] The cohesin ring concatenates sister DNA molecules
DOI: 10.1038/nature07098
[15] Oligomerization of STIM1 couples ER calcium depletion to CRAC channel activation
DOI: 10.1038/nature07065
[16] Crystal structure of the neurotrophin-3 and p75NTR symmetrical complex
DOI: 10.1038/nature07089
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.
AUSTRALIA
Bentley: 11
CANADA:
Toronto: 12
CHINA
Beijing: 1, 16
FRANCE
Champs-sur-Marne: 8
Paris: 8
Pessac: 8
Villeurbanne: 8
GERMANY
Garching: 8
Heidelberg: 14
Münster: 11
GREECE
Athens: 2
SWEDEN
Stockholm: 11
UNITED KINGDOM
Cambridge: 12
Coventry: 14
Durham: 10
Oxford: 14
UNITED STATES OF AMERICA
California
Berkeley: 6
Davis: 7
La Jolla: 12
Pasadena: 3
Santa Cruz: 13
Stanford: 10, 15
Colorado
Boulder: 7
District of Columbia
Washington: 4
Illinois
Chicago: 15
Iowa
Iowa City: 5
Kansas
Lawrence: 2
Maryland
College Park: 2, 3
Laurel: 2
Greenbelt: 3, 4
Massachusetts
Boston: 9
Cambridge: 1, 4
Michigan
Ann Arbor: 2
New Jersey
Murray Hill: 2
Newark: 2
New Mexico
Las Cruces: 3
North Carolina
Durham: 9
Oregon
Eugene: 12
Texas
San Antonio: 15
PRESS CONTACTS…
From North America and Canada
Katherine Anderson, Nature New York
Tel: +1 212 726 9231; E-mail: [email protected]
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; 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/Europe/other countries not listed above
Jen Middleton, Nature London
Tel: +44 20 7843 4502; E-mail [email protected]
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