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Article Released Wed-15th-July-2009 22:37 GMT
Contact: Ruth Institution: Nature Publishing Group
 Press Release - Photons manipulated at crystal surface

Summaries of newsworthy papers include Diversity dynamics, Decoding bilharzia, Diversity without barriers, An inverse photoconductor, Sea ice in the Eocene Arctic, Look south, A new window on the past


This press release is copyright Nature.

VOL.460 NO.7253 DATED 16 JULY 2009

This press release contains:

· Summaries of newsworthy papers:

Space science: Diversity dynamics

Genomics: Decoding bilharzia

Ecology: Diversity without barriers

Chemistry: An inverse photoconductor

Geoscience: Sea ice in the Eocene Arctic

Palaeoclimate: Look south

Material science: Photons manipulated at crystal surface

And finally… A new window on the past

· Mention of papers to be published at the same time with the same embargo

· Geographical listing of authors

Editorial contacts: While the best contacts for stories will always be the authors themselves, in some cases the Nature editor who handled the paper will be available for comment if an author is unobtainable. Editors are contactable via Ruth Francis on +44 20 7843 4562. Feel free to get in touch with Nature's press contacts in London, Washington and Tokyo (as listed at the end of this release) with any general editorial inquiry.

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[1] Space science: Diversity dynamics (pp 364-366)

The main asteroid belt, located between the orbits of Mars and Jupiter, may have evolved very differently from what was previously thought, which could explain why its composition is now so varied. A paper in Nature this week suggests that primitive bodies in the outer main asteroid belt formed beyond the giant planets and were inserted into their current orbits as the planets migrated.

Scientists believe that the gas giant planets — Jupiter, Saturn, Uranus and Neptune —originally formed closer together than they now are, surrounded by a ‘primordial disk’ of comet-like planetesimals. In a theory known as the Nice model, the orbits of the planets are thought to have interacted with the disk and eventually to have become somewhat unstable, with Jupiter migrating inwards while Uranus and Neptune migrated outwards. Both migrations scatter the contents of the disk.

Harold Levison and colleagues used collision models to track the disk particles and the long-term evolution of the captured comet-like population. They show that the violent evolution of the giant planets’ orbits required by the Nice model leads to the insertion of primitive objects from outside Neptune’s orbit into the asteroid belt. This result suggests that the observed diversity of the asteroid belt – which has been puzzling – is not a direct reflection of the original composition of the proto-planetary disk, but rather of dynamical evolution.

Harold Levison (Southwest Research Institute, Boulder, CO, USA)
Tel: +1 303 546 9670; E-mail:

[2] & [3] Genomics: Decoding bilharzia (pp 352-358; 345-351)

The first of the flatworm genomes are detailed this week in Nature. The work is important because the two parasites studied cause the important neglected tropical disease schistosomiasis, and it’s hoped that the research will open doors for the development of targeted interventions.

Schistosomiasis — also known as bilharzia or ‘snail fever’ — is endemic across the developing world and poses a major public health concern. Najib El-Sayed and colleagues decoded the genome of S. mansoni, the most widespread of the human-infecting schistosome parasites, whereas Zhu Chen and colleagues looked at S. japonicum, which is largely confined to Asia. Both teams identify genes that are important for the parasites’ metabolism and how they interact with the host to establish infections. Notably, S. mansoni lacks the important enzyme fatty acid synthase, which is required for making essential fats. The parasite must therefore rely on the host to provide these, revealing a potential Achilles’ heel that could be exploited for drug development.

The information generated provides an invaluable resource to the research community, and it’s hoped that it will give new leads to develop new treatments and diagnostics.

Najib El-Sayed (University of Maryland, College Park, MD, USA) Author paper [2]
Tel: +1 301 405 2999; E-mail:

Zhu Chen (Chinese National Human Genome Center at Shanghai, China) Author paper [3]
Tel: +86 21 643 77 859; E-mail:

[4] Ecology: Diversity without barriers (pp 384-387; N&V)

Why is biodiversity like a traffic jam? The answer is revealed in a Nature paper that explains how biological diversity is spread in characteristic patterns, perhaps the single biggest problem in ecology.

In recent years, the ‘neutral theory’ of biodiversity has modelled the distribution of species in a very simple way, without reference to species interactions or history — rather like point mutations in a population without sexual reproduction. Yaneer Bar-Yam and colleagues now add sexual reproduction, mutation and dispersal to this model and find that it simulates reality on many levels, comparing well with real data sets, from shrubs in Panama to fossil mammals in Kansas.

The results also show that biodiversity can arise without specific physical barriers, similar to the way that traffic jams in heavy traffic flows form spontaneously without accidents or barriers.

Yaneer Bar-Yam (New England Complex Systems Institute, Cambridge, MA, USA)
Tel: +1 617 547 4100; E-mail:

Jayanth Banavar (The Pennsylvania State University, University Park, PA, USA) N&V author
Tel: +1 814 863 1089; E-mail:

[5] Chemistry: An inverse photoconductor (pp 371-375)

A new type of photoconductor becomes less, rather than more, conducting in the presence of light. It’s thought that nanoparticle-based photoconductors based on the underlying principles could find use as chemical sensors.

A photoconductor is a material whose electrical conductivity changes when illuminated, invariably increasing in response to the impinging light. In this week’s Nature, Bartosz Grzybowski and colleagues show how nanoparticle-based materials can be engineered, through careful choice of the molecules used, to make them less conducting in the presence of light.

The plasmonic material is made up of self-assembled monolayers (SAMs), which stabilize the nanoparticles. And altering the charge of the molecules within the monolayer can lead to positive or negative photoconductance — SAMs with electrically neutral molecules show increased conductivity with light, whilst SAMs containing electrically charged groups show decreased conductivity with light.

Bartosz Grzybowski (Northwestern University, Evanston, IL, USA)
Tel: +1 847 491 3024; E-mail:

[6] Geoscience: Sea ice in the Eocene Arctic (pp 376-379)

Sea ice first appeared in the Arctic Ocean no later than the middle Eocene epoch around 47.5 million years ago, a Nature paper suggests. The findings are important because previous research in this area failed to distinguish between land-based glacial ice and sea ice, both of which carry different climate implications.

Catherine Stickley and colleagues analysed a sediment core from the middle Eocene Arctic. They found an unusual abundance of a group of fossilized, needle-shaped diatom algae that are dependent on sea ice. Alongside analyses of the quartz grains present in the sediment core, the results establish the dominant presence of sea ice. At this time, freezing is likely to have occurred on a seasonal basis, forming in autumn and winter and melting in spring and summer.

The discovery is unusual because sea-ice-dwelling algae are generally too delicate to be preserved in the fossil record — the data here pre-date other evidence for algae diatoms by 16 million years. The finding, which pushes back the debut of Arctic sea ice by around 1.5 million years, boosts our understanding of the climate mechanisms that drove the Earth into a polar glaciated state.

Catherine Stickley (University of Tromso, Norway)
Tel: +47 94 88 23 53; E-mail:

[7] Palaeoclimate: Look south (pp 380-383; N&V)

Dynamic ocean currents in the Southern Hemisphere may have played a critical role in modulating Atlantic ocean circulation, and therefore global climate, suggests a paper in Nature this week.

Edouard Bard and Rosalind Rickaby analyse an 800,000-year record of sea surface temperature and ocean productivity from a sediment core in the path of the Agulhas current — a fast-moving, warm ocean current that flows south between Madagascar and the African coast. This current is thought to be the Indian Ocean’s equivalent of the Gulf Stream, supplying warm salty water to the South Atlantic in the region of the subtropical front — where it meets the colder Southern Ocean around Antarctica.

The isotopic data from the core reveal the position and migration of the subtropical front over time, indicating that as it moves northwards it modulates the severity of glacial periods by acting as a ‘gatekeeper’: affecting the strength of the Agulhas current, and controlling how much heat and salt are carried into the Atlantic. During cooler periods, the subtropical front moved northwards nearly 7° of latitude, nearly shutting off the Agulhas current completely.

Edouard Bard (Université Paul-Cézanne Aix-Marseille, Aix-en-Provence, France)
Tel +33 4 42 50 74 18; Email:

Rosalind Rickaby (Oxford University, UK)
Tel: +44 1865 272034; E-mail:

Please note this author is currently travelling and is best contacted by e-mail.

Rainer Zahn (Autonomous University of Barcelona, Spain) N&V author
Tel: +34 93 581 3324; E-mail:

[8] Material science: Photons manipulated at crystal surface (pp 367-370; N&V)

Photons have been manipulated at the surface of photonic crystals, an important step towards realizing novel optical devices.

Photonic crystals are periodic optical nanostructures designed to affect the motion of photons — particles of light — much as semiconductor periodicity affects the movement of electrons. So far, photonic crystals have been used to direct and manipulate photons inside the material, but in this week’s Nature, Kenji Ishizaki and Susumu Noda show that photons can be controlled and manipulated at the surface of such crystals. This new method of manipulating photons using photonic crystals may one day enable the control of photons in optical circuits.

Susumu Noda (Kyoto University, Japan)
Tel: +81 75 383 2315; E-mail:

Kenji Ishizaki (Kyoto University, Japan)
Tel: +81 75 383 2319; E-mail:

Sajeev John (University of Toronto, Canada) N&V author
Tel: +1 416 978 3459; E-mail:

[9] And finally… A new window on the past (pp 339-344)

An examination of the past and present material record of primates reveals new perspectives in our own origins. Overlaps between primatology and archaeology are uncommon, but a review in Nature this week makes the case for a new field of primate archaeology.

Archaeologists dig for evidence of past human activity, using artefacts such as tools, pottery and the detritus of day-to-day existence to build up a picture of life at the time. Non-human species feature rarely, appearing in the detritus if they were eaten, as domestic animals or for early archaeology, as dating evidence.

Michael Haslam and colleagues argue that important questions can be tackled from a new perspective. Primates use tools, create living sites and construct social groups. All these activities leave their mark in the archaeological record, and with it the evidence that puts the evolution of cognition and tool use in humans into context.

Michael Haslam (University of Cambridge, UK)
Tel: +44 1223 764 719; E-mail:


[10] The active form of DNA polymerase V is UmuD'2C•RecA•ATP (pp 359-363)


***This paper will be published electronically on Nature's website on 15 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 16 July, but at a later date. ***

[11] Proteome-wide cellular protein concentrations of the human pathogen Leptospira interrogans
DOI: 10.1038/nature08184


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.

Brisbane: 3
Townsville: 3

Belo Horizonte: 2
Campinas: 4
Sao Paulo: 2

Calgary: 9
Waterloo: 3

Beijing: 3
Shanghai: 3

Aix-en-Provence: 7
Lille: 2
Nice: 1
Paris: 1, 9

Goettingen: 2

Thessaloniki: 1

Cork: 2

Tel Aviv: 5

Rome: 9

Inuyama: 2, 9
Kyoto: 8
Yamagata: 6

Leiden: 2

Tromsø: 6

Singapore: 3

Barcelona: 9

Zurich: 11

Cambridge: 2, 9
Edinburgh: 2
Hinxton: 2, 3
London: 2, 9
Norwich: 2
Oxford: 7
Southampton: 2, 6
Sutton: 2
York: 2


Los Angeles: 10
San Francisco: 2

Boulder: 1

District of Columbia
Washington: 3

Chicago: 2
Evanston: 5
Normal: 2

Ames: 2

Baltimore: 2
Bethesda: 10
College Park: 2
Rockville: 2

Boston: 4
Cambridge: 2, 4

New Jersey
Montclair: 6
New Brunswick: 9

New York
Buffalo: 2

Gambier: 9
Oxford: 9

Pittsburgh: 2

San Antonio: 2

Harrisonburg: 6

Seattle: 11

Madison: 10


From North America and Canada
Neda Afsarmanesh, Nature New York
Tel: +1 212 726 9231; E-mail:

Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail:

From Japan, Korea, China, Singapore and Taiwan
Mika Nakano, Nature Tokyo
Tel: +81 3 3267 8751; E-mail:

From the UK/Europe/other countries not listed above
Jen Middleton, Nature London
Tel: +44 20 7843 4502; E-mail

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