This press release is copyright Nature.
VOL.449 NO.7159 DATED 13 SEPTEMBER 2007
This press release contains:
· Summaries of newsworthy papers:
Solar system: Planet survives the red-giant phase
Relics: Pinpointing the end of Neanderthals
Particle physics: Interesting state of matter made
Planetary science: Two-score ice ages for Mars
Commentary: Universities and the money fix
Outlook: Neglected diseases
Ecology: Power-law patterns seen in nature
Geology: Pulsed model for continent growth
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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 Solar system: Planet survives the red-giant phase (pp 189-191; N&V)
A planet has been discovered that has survived the red-giant phase of its star, reports a paper in this week’s Nature.
Stars become red giants when the hydrogen in their cores runs out and they expand, engulfing their inner planets. This is expected to happen to our Solar System in about five billion years, when the fate of the Earth is uncertain. The planet found by Roberto Silvotti and colleagues demonstrates that planets with orbits similar to the Earth’s can survive the red-giant expansion phase of their parent star.
Roberto R. Silvotti (Istituto Nazionale de Astrofisica, Naples, Italy)
Tel: +39 081 55 75 583; E-mail: [email protected]
Jonathan Fortney (NASA-Ames Research Center, Moffett Field, CA, USA)
Tel: +1 650 604 5514; E-mail: [email protected] N&V author
 Relics: Pinpointing the end of Neanderthals (pp 206-208)
What caused the demise of Neanderthals in Europe, some time around 28,000 years ago? Was it climate, or the arrival of modern humans? The conundrum exists partly because of problems establishing when events in the past actually happened. Polychronis Tzedakis and colleagues report, in Nature this week, a way to relate Neanderthal remains to the palaeoclimate record.
All living things use carbon, mostly in the form of the isotope 12C, but a small proportion of carbon in the environment is the radioactive 14C. When an animal dies, the proportion of 14C is fixed and decays at a fixed rate. By measuring the amount of 14C in a fossil, and comparing it with the proportion thought to exist in the creature when it was alive, researchers can estimate the date the creature died.
The problem is that the proportion of 14C in the environment itself varies, which means that ‘radiocarbon’ years and actual calendar years don't always match. The discrepancy was especially marked at around the time the Neanderthals went extinct, making it hard to work out the chronology of their last days. Tzedakis and colleagues got round the problem by ignoring actual chronology completely. They relate radiocarbon years directly to palaeoclimate through a deep-sea core drilled in the Cariaco Basin, Venezuela, in which records of past climate can be related directly to radiocarbon date.
The team investigate three proposed dates for the end of the Neanderthals and find that the oldest two do not coincide with any extreme climate events. The youngest, and most controversial, occurs just before the final expansion of ice sheets, but this was a several 1000-year long gradual transition rather than an abrupt cold snap that would explain a sudden extinction.
Polychronis Tzedakis (University of Leeds, UK)
Tel: +44 113 343 3300; E-mail: [email protected]
Please note the author is travelling but will be available on his mobile:
Tel: +30 697 221 9198
Katerina Harvati (Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany)
Tel: +49 341 355 0358; E-mail: [email protected] Co-author
Konrad Hughen (Woods Hole Oceanographic Institute, USA)
Tel: +1 508 289 3353; E-mail: [email protected] Co-author
Isabel Cacho (University of Barcelona, Spain)
Tel: +34 93 403 4641; E-mail: [email protected] Co-author
 Particle physics: Interesting state of matter made (pp 195-197; N&V)
At long last, researchers have made molecules of positronium. Positronium is a metastable hydrogen-like atom made from an electron and a positron, and the molecular form, described in this week's Nature, paves the way for future multi-positronium work that may lead to the development of an annihilation gamma-ray laser.
For many years it's been known that an electron and its antiparticle, the positron, can combine to form positronium. But making molecules of positronium — di-positronium — has proved elusive. David Cassidy and A. P. Mills Jr achieved this by firing intense positron bursts into a thin film of porous silica. Di-positronium is formed on the internal pore surfaces, experimentally confirming the existence of the molecule.
The discovery could one day aid the production of an annihilation gamma-ray laser. As particle and antiparticle combine, they would annihilate each other, releasing an intense burst of energy in the form of gamma-rays. Using a more intense positron source, it may be possible to generate a Bose–Einstein condensate of positronium, where the particles are in a coherent state — a prerequisite for lasing.
David Cassidy (University of California, Riverside, CA, USA)
Tel: +1 951 827 2919; E-mail: [email protected]
Clifford Surko (University of California, San Diego, CA, USA)
Tel: +1 858 534 6880; E-mail: [email protected] N&V author
 Planetary science: Two-score ice ages for Mars (pp 192-194)
The forty major ice ages experienced by Mars over the past five million years can explain the present distribution of subsurface ice, a modelling study in this week's Nature shows.
More so than the Earth, Mars experiences dramatic changes in incident sunlight that can redistribute ice on a global scale. By numerically simulating the retreat and growth of ground ice, Norbert Schorghofer has shown how the subsurface ice sheets would have evolved over the many ice ages that occurred on Mars over the past five million years, to end up in the state we see them today. These processes have given rise to a three-layer sequence of ice at high latitudes, and ice in the pores of rocks at mid-latitudes. Combined, these provide enough ice to be compatible with that predicted from spacecraft observations of Mars.
The dynamic nature of martian ice sheets makes them an ideal system in which to test our knowledge of astronomical climate forcing. Furthermore, a great deal might be learned about terrestrial ice ages from the study of martian ice layering — a longer, cleaner and simpler record than Earth’s.
Norbert Schorghofer (University of Hawaii, Honolulu, HI, USA)
Tel: +1 808 956 9086; E-mail: [email protected]
Commentary: Universities and the money fix
Biomedical researchers in the United States have been feeling increasingly anxious. Many are angry that it is harder to get funded today than before the doubling of the NIH budget. Why is this? Although Congress increased funding for NIH research between 1998 and 2003, the number of researchers applying for NIH grants, and the number of applications, also grew at a rapid rate. The result has been a steady drop in success rates for grant applications: from above 50% in 1998 to 20% in 2006. With the current flat budget, no end to the funding woes is in sight.
The NIH is receiving the brunt of the criticism for this shortfall, and is responding with several regional meetings in September and October to review its systems of research support and peer review. But as Brian Martinson argues in a Commentary in Nature this week the blame, and responsibility for change, may lie elsewhere.
Martinson argues that many US universities have become overly dependent on NIH funds. He points to financial and structural incentives that push universities to produce more and more scientists. Rather than going to Congress to ask for more money for the NIH, Martinson says the universities should consider whether they are producing too many scientists. To reduce the pressure on NIH funds, he suggests that universities that have benefited handsomely from NIH largesse should now return the favour by paying for the salaries of older faculty, freeing up money for hard-pressed younger researchers.
Brian Martinson (Health Partners Research Foundation, Minneapolis, MN, USA)
Tel: +1 952 967 5021; E-mail: [email protected]
Outlook: Neglected diseases
One-sixth of the world’s population is affected by tropical diseases, yet the drug ‘pipeline’ for these diseases is almost dry. An Outlook in Nature this week explores why this urgent need for development of effective therapies is not being met.
Although the factors hindering drug development are well understood in the developed-world environment, the process becomes significantly more complicated when dealing with diseases that disproportionally afflict poor and marginalized populations. Peter Singer and colleagues investigate what additional problems exist in the developing world. Practical issues are paramount — many areas have no electricity, which means that drugs cannot be stored appropriately. And cultural considerations are vital to encourage uptake of a new treatment or technology — often scientists arrive with plans that do not suit the local populations. Singer presents a model for the future, the result of interviews with 70 key experts from academic, industrial, civil and governmental sectors, which takes into account ethical and practical factors.
Also in the supplement, Declan Butler investigates the role of academia in bridging the gap between basic research and effective therapies for neglected diseases. Benedicte Callan and Iain Gillespie write about the path to new medicines and the need for greater government involvement in this process. And Patricia Danzon argues that subsidies coupled with differential pricing could provide incentives for the development of drugs for diseases that have no market in the developed world.
Peter Singer (McLaughlin–Rotman Centre for Global Health, University of Toronto, Canada)
E-mail: [email protected]
 &  Ecology: Power-law patterns seen in nature (pp 209-212 & 213-217; N&V)
Some patterns in nature are obvious to the human eye, whilst others need a little help from statistics to be noticed. In this week’s Nature, two studies do just that, revealing that patterns of plant growth can follow power laws, a finding that lends insight into the driving forces underlying their formation.
Todd M. Scanlon and colleagues used high-resolution satellite imagery to study the prevalence of self-organized vegetation patterns across a regional rainfall gradient in southern Africa. Tree canopy cluster sizes follow power-law distributions, a result that can be explained by the positive feedbacks operating in this water-limited ecosystem as a result of preferential environments formed within the vicinity of existing trees.
Sonia Kéfi and colleagues also report a plant-related power law, but this time in the Mediterranean. The team modelled the effect of grazing on vegetation patchiness in three arid ecosystems. The patch-size distribution of the vegetation followed a power law, a finding that can be explained by invoking local positive interactions among plants. Deviations from power laws occur when grazing pressure is high, as predicted by the model, and may be a harbinger of imminent desertification.
Todd M. Scanlon (University of Virginia, Charlottesville, VA, USA)
Tel: +1 434 924 3382; E-mail: [email protected] Author paper 
Sonia Kéfi (Utrecht University, Netherlands) Author paper 
Tel: +31 302 533 147; E-mail: [email protected]
Please note the authors for paper  will be at a conference from 10-13 September, but can be contacted on their mobiles:
Sonia Kéfi +31 647 802 126
Max Rietkerk +31 644 908 961 Co-author paper 
Additional media contact:
Peter van der Wilt (Press Office, Utrecht University, Netherlands)
E-mail [email protected]
Ricard Solé (Universitat Pompeu Fabra, Barcelona, Spain)
Tel: +34 3 401 6967; E-mail: [email protected] N&V author
 Geology: Pulsed model for continent growth (pp 202-205)
The Earth's continental crust has grown in pulses linked to large melting events in the mantle, suggests a report in Nature this week. The study builds on previous research using different chemical isotopes to track mantle melting events throughout Earth's geological history.
The origin and timing of the continental crust's extraction from the mantle has been controversial. It has been debated whether the continental crust accumulated all at once, gradually, or in stages, as the chemical evidence for such processes has largely been destroyed by crustal recycling, through mantle convection.
Graham Pearson and colleagues found that the rhenium–osmium isotope system can be used to track continent growth through time, as it retains the imprint of ancient melting events. They analysed large numbers of osmium alloy grains in order to gauge exactly when melt was extracted from the Earth's mantle, and found that the ages were not evenly distributed but clustered in distinct periods — around 1.2, 1.9 and 2.7 billion years ago. These dates coincide with peaks in the ages of continental crust.
The authors conclude that this is a clear chemical record of a strong link between major melting events in the Earth's interior and the formation of continental crust. They suggest that the crust was extracted in pulses, dominated by melting events in hot thermal plumes in the mantle.
Graham Pearson (University of Durham, UK)
Tel: +44 191 33 42324; E-mail: [email protected]
Please note the author is travelling 07-14 September with limited access to email. It may be easier to contact his co-author:
Stpehen Parman (University of Durham, UK)
Tel: +44 191 334 2331 wk; E-mail: [email protected]
Additional media contact:
Leighton Kitson (Press Office, University of Durham, UK)
Tel: +44 191 334 6074; E-mail: [email protected]
ALSO IN THIS ISSUE…
 Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era
 A general integrative model for scaling plant growth, carbon flux, and functional trait spectra (pp 218-222)
 Dscam diversity is essential for neuronal wiring and self-recognition (pp 223-227)
 The structural basis for activation of plant immunity by bacterial effector protein AvrPto (pp 243-247)
 Structure of Dnmt3a bound to Dnmt3L suggests a model for de novo DNA methylation (pp 248-251; N&V)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 12 September 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 they will not appear in print on 13 September, but at a later date.***
 Snapshots of nuclear pore complexes in action captured by cryo-electron tomography
 Conversion of mature B cells into T cells by dedifferentiation to uncommitted progenitors
 Structural basis for AMP binding to mammalian AMP-activated protein kinase
 Light adaptation in cone vision involves switching between receptor and post-receptor sites
 Crystal structure of the heterotrimer core of Saccharomyces cerevisiae AMPK homologue SNF1
 A histone H3 lysine 27 demethylase regulates animal posterior development
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.
Vienna: 10, 14
St Catherines: 8
Beer Sheva: 13
Tel Aviv: 1
Utrecht: 6, 16
Wageningen : 6
UNITED STATES OF AMERICA
Los Angeles: 10
Pasadena: 1, 8
Woods Hole: 2
Santa Fe: 9
New York: 17
For North America and Canada
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]
For the UK/Europe/other countries not listed above
Katherine Anderson, Nature London
Tel: +44 20 7843 4502; E-mail [email protected]
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