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Newswise — On the 58th anniversary of the Hiroshima bomb it is time to close the book on the doses of radiation felt by its victims. Research published in this week's Nature confirms previous estimates of radiation-induced cancer risk.
Because humans are so rarely exposed to dangerous levels of radiation, the estimated radiation exposure of Hiroshima and Nagasaki victims has been used since the blasts to calculate radiation-related cancer risks in a wealth of settings.
Researchers were unsure, however, about the radiation levels of fast neutrons emitted during the explosion. Some studies had suggested that fast neutron doses were higher than originally estimated. This would mean that the danger of these particles have been underestimated from the Hiroshima and Nagasaki data and makes predictions about cancer risk from other exposures possibly too conservative.
Using a new chemical technique, Tore Straume and colleagues isolated an isotope of nickel — 63Ni — produced when fast neutrons hit copper. They measured minute amounts of 63Ni from copper lightning conductors, rain gutters, and even a shrine's roof, located at different distances from the bomb's hypocentre to re-estimate the number of fast neutrons at different distances from the blast.
It turns out that fast neutron exposure between 900 and 1,500 metres from the blast — the distance at which most irradiated survivors were found — was very similar to previous estimates. There is no need to alter existing estimates of the health effects of fast neutrons, the authors conclude. "The collective data from the survivors of the atomic bomb are likely to remain a valuable predictor of the risks of ionizing radiation," says Mark P. Little in an accompanying News and Views article.
 Chemistry: Catalysts go green (pp530-532)
Green chemistry moves one step closer with the development of a soluble, reusable catalyst. In this week's Nature, researchers describe a tungsten-based catalyst that drops out of solution once its work is done.
Catalysts are widely used in industry to make chemical reactions go faster. Soluble catalysts dissolve in the reaction mixture, but because of this they are difficult to separate out and reuse. Vladimir K. Dioumaev and R. Morris Bullock report a catalyst that dissolves in liquid reactants and converts them into liquid product, but then precipitates out as a solid at the reaction's end. The product can then be simply poured off, leaving the solid catalyst for reuse. The overall process requires no solvents, transforming most of the reactants into the desired product, so waste production is minimal.
The experiment serves as proof of principle, but the authors hope to adapt their system to practically important chemical reactions. They aim to investigate the processes that keep the catalyst in solution until the reaction is complete. This may help them tailor other catalysts and substrates suitable for efficient and solvent-free reaction schemes that might make for a cleaner chemical industry.
 Health and Medicine: Protective protein may prevent degenerative brain disease (pp556-561)
A protein may help prevent some degenerative brain disorders, such as Alzheimer's disease, from developing. Research in this week's Nature reveals how ageing mice lacking the Pin1 gene develop some of the classical hallmarks of degenerative brain disease. Future therapies may be based on this protective protein. Kun Ping Lu and colleagues analysed the behaviour and brains of Pin1 knockout mice. As the mice aged, they began to develop problems with coordination and balance. Abnormal protein tangles were seen inside vulnerable brain cells, and over time neurons began to die off. The brains of patients with Alzheimer's disease, Down's syndrome and Pick's disease show similar features. So, the Pin1 knockout mouse may prove a valuable tool for studying these diseases. It is also the first animal model of Alzheimer's disease to produce protein tangles because of the wiping out of a gene. Other well-known models achieve their effects by increasing the levels of various abnormal proteins.
 Ecology and Evolution: Key to tropical lizard community structure (pp542-545)
Researchers have identified the main organizing force behind a community of Caribbean lizards. The results could have important implications for future studies of community ecology, suggests a report in this week's Nature.
Jonathan B. Losos and colleagues headed off to the tropical island of Cuba to study a group of 11 species of Anolis lizard. They expected to find closely related species sharing a similar niche, but instead the lizards shifted to new niches in a bid to avoid tussles with other species over the same resources. The team combined records of habitat use, behaviour and prey size with an in-depth molecular study of relatedness between the 11 species. They conclude that it is the stiff competition between species and not relatedness that has shaped the community.
The team's two-pronged approach should prove valuable in studies looking at how species sharing a common ancestor adapt to their habitat — an area that has generated a lot of recent interest among ecologists.
 Ecology and Evolution: Deep-vent larvae stay close to home (pp545-549)
Strong currents are suppressed in the North Pacific's Endeavour ridge valley, research in this week's Nature reveals. This prevents larvae, living in and around hydrothermal vents, from drifting away into the inhospitable deep ocean. Oceanic researchers have yet to pinpoint how hydrothermal vent larvae manage to colonize neighbouring regions of the mid-ocean ridge system. In an effort to understand this, Richard E. Thomson and colleagues measured the speed of underwater currents at the Endeavour ridge, 300 kilometres seaward of British Columbia and Washington State. Here, a 10-kilometre-long, 1-kilometre-wide valley splits the ridge crest from its vent-filled base. The team found that strong tidal and wind-generated currents are suppressed within the valley. In addition, hydrothermal plumes drive a constrained pattern of circulation within the ridge — warm water rises and flows out of the ridge, whilst cooler water flows in near the valley base.
Together, these features may help vent larvae stay close to home, the researchers conclude. Every now and then, the currents may be over-ridden by other regional flow events. This may drive larvae out of the valley to form new colonies downstream, they speculate.
 Health and Medicine: The sunny side of surgery (p510)
Concentrated sunlight can be used to kill tissue in live animals, according to a Brief Communication in this week's Nature. Solar surgery may one day provide a low-cost alternative to conventional laser fibre-optic therapy.
Jeffrey M. Gordon and colleagues used the technique to destroy a section of liver tissue in anaesthetized rats. They used their prototype solar concentrator to transport several watts of radiation into the operating theatre through a flexible optical fibre. The concentrated sunlight was then shone directly onto the exposed liver in two short bursts, causing tissue in the area to wither in the same way as it does after laser therapy.
This alternative technique may also be of practical use in people — for example, in destroying some types of tumour tissue — though only in sunny climates with clear skies, say the researchers. As well as utilizing a free natural resource, the procedure carries a lesser risk of eye injury than does laser fibre-optic therapy.
 Earth: Slow climate changes had far-flung impact (pp532-536; N&V)
Slow climate changes in the Southern Ocean around Antarctica may have had important far-field effects in the North Atlantic, research in this week's Nature suggests. Southern Ocean currents may have been responsible for the abrupt climate warmings recorded in the palaeoclimatic archives of the Northern Hemisphere.
Nineteen thousand years ago, the Earth was emerging from the grip of the last ice age. Previous data and modelling studies have hinted that an acceleration of the North Atlantic thermohaline circulation (THC) — which transports massive amounts of heat northwards — played a dominant role in the abrupt climate changes seen at that time. Now, Gregor Knorr and Gerrit Lohmann look for the causes of this invigorated circulation. Using a three-dimensional ocean circulation model, the duo suggests that sea surface temperatures around Antarctica built up gradually. Then, at a threshold level, they triggered the North Atlantic THC into life. The results demonstrate that "slow changes in the south can trigger abrupt changes in the THC, far away from the location of origin of the perturbation," says Thomas F. Stocker in an accompanying News and Views article. "This provides a natural link between processes operating on multi-millennial time scales," he adds.
 Chemistry: Superconductor gets charged (pp527-529)
A new breed of superconductor is similar to its copper oxide alternatives, according to a report in this week's Nature. These findings could help us to understand how the mysterious copper oxides can conduct electricity without resistance at relatively high temperatures. They may also help researchers dream up new materials that can superconduct at room temperature.
This new superconductor, known as sodium cobalt oxyhydrate, was discovered earlier this year. It is striking because of its structural similarity to the well-known copper oxides, but it contains no copper. Now R. J. Cava and colleagues have tweaked the sodium content of this compound to vary the amount of charge flowing through its layered, cobalt-oxide lattice. As the amount of charge increased, so did the temperature at which the material was able to superconduct — up to a point. After this, the superconducting temperature decreased as the charge continued to rise. Intriguingly, copper oxide superconductors show a very similar response. Although the new materials can only manage a maximum superconducting temperature of four degrees above absolute zero, their similarities in structure and behaviour could point to a deeper connection with their copper oxide rivals. They may show that copper is not essential for obtaining superconductivity in transition metal oxides, as some have argued in the past.
 And Finally: Froghopper crowned as top insect jumper (p509)
The insect world has a new high-jump champion — and the chances are it lives in your back garden. Froghoppers (Philaenus spumarius) can outleap even fleas, previously thought to be the top athletes.
Writing in a Brief Communication in this week's Nature, Malcolm Burrows reports that the six-millimetre-long insects can reach heights of 70 centimetres — equivalent to an average-sized man hurdling a 210-metre skyscraper. In making their prodigious leaps, the bugs accelerate at more than 400 times the force of gravity. Their hind legs contain immensely powerful muscles, and act as a 'catapult' to release stored energy in an explosive burst.
Froghoppers — also called spittle bugs for their habit of creating 'cuckoo spit' on garden foliage — are distributed widely throughout the world, making it surprising that their prowess has only just been realized. "The amazing thing is that they were sitting on everyone's doorstep but no one ever measured them," says Burrows.
ALSO IN THIS ISSUE"¦
 Transformation and control of ultrashort pulses in dispersion-engineered photonic crystal fibres (pp511-515)
 The break-up of heavy electrons at a quantum critical point (pp524-527; N&V)
 Possible thermal and chemical stabilization of body-centred-cubic iron in the Earth's core (pp536-539)
 Evolutionary capacitance as a general feature of complex gene networks (pp549-552; N&V)
 Organization of cell assemblies in the hippocampus (pp552-556)
 Essential role for the peroxiredoxin Prdx1 in erythrocyte antioxidant defence and tumour suppression (pp561-565)
 Machinery for protein sorting and assembly in the mitochondrial outer membrane (pp565-571; N&V)
 Dimers of the N-terminal domain of phytochrome B are functional in the nucleus (pp571-574)
 Processivity of the single-headed kinesin KIF1A through biased binding to tubulin (pp574-577)
AHEAD OF PRINT PUBLICATION"¦
***This paper will be published electronically on Nature's website on 30 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 31 July, but at a later date.***
 Replication of a cis"syn thymine dimer at atomic resolution (DOI: 10.1038/nature01891) (http://dx.doi.org/10.1038/nature01898)
GEOGRAPHICAL LISTING OF AUTHORS"¦
The following list of places refers to the whereabouts of authors on the papers numbered in this release. 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.
CANADABritish Columbia Sidney: 5
GERMANYBremen: 7Dresden: 11Freiburg: 16Garching: 1, 11Halle: 16Hamburg: 7Heidelberg: 19Munich: 1
ISRAELBeer Sheva: 6Sede Boger: 6
JAPANKanagawa: 3Kyoto: 17Sendai: 3, 18Tokyo: 18
SINGAPORESingapore City: 3
UNITED KINGDOMBath: 10Cambridge: 9London: 12Oxford: 14
UNITED STATES OF AMERICACalifornia La Jolla: 3 Livermore: 1 San Diego: 1 Stanford: 13Georgia Atlanta: 3Kentucky Lexington: 3Massachusetts Boston: 3, 15 North Grafton: 15Missouri St. Louis: 4New Jersey Newark: 14Piscataway: 11 Princeton: 8New Mexico Los Alamos: 10New York Broadway: 4 Schenectady: 4 Upton: 2Pennsylvania Villanova: 4Tennessee Nashville: 4Utah Salt Lake City: 1Washington Seattle: 5
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Nature, 31-Jul-2003 (31-Jul-2003)