Geophysics: Depth constraints on quiet earthquakes

Summaries of newsworthy papers include Astronomy: A sunshade for seeing planets, Neuroscience: Monkey brain 'tuned' for face recognition, Virology: Retroviral invasion of the koala genome, Microscopy: Spot the nanoflaw and Low-temperature physics: Spot the difference


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* Summaries of newsworthy papers:

Astronomy: A sunshade for seeing planets

Neuroscience: Monkey brain 'tuned' for face recognition

Virology: Retroviral invasion of the koala genome

Geophysics: Depth constraints on quiet earthquakes

Microscopy: Spot the nanoflaw

Low-temperature physics: Spot the difference

* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors

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[1] Astronomy: A sunshade for seeing planets (pp 51-53)

Planets around other stars could be imaged directly by using a shield far away from the observing telescope to block out light from their parent star, according to a study by Webster Cash in this week’s Nature. Cash says that the screen should be shaped rather like the petalled silhouette of a sunflower. This shape, he calculates, is the most effective for blocking out the light of a distant star, so that any planets orbiting around it would show up as bright specks. The shield would be attached to a manoeuvrable spacecraft that would sit tens of thousands of kilometres away from a space telescope, and could be moved into position when the telescope was trained on a star to look for orbiting planets.

Although nearly two hundred extrasolar planets are now known, only last year were two of them seen directly, from the infrared light that they emit. The light from these planets, especially small, Earth-sized ones, is simply swamped by that of their parent star. One solution is to place a shield, called a coronagraph, inside the telescope to blot out the light - this is used to study the Sun. But the wave nature of light gives rise to diffraction and some light bleeds around the circular edge; not very much, but enough to swamp the light from the planet. Cash's proposed petal-shaped shield would diffract the light away from the immediate vicinity of the image of the star, enabling the planets to be seen.
His calculations show that a shield about 30-50 m across would enable Earth-sized planets to be seen by existing or planned space telescopes around stars 30 or more light years away. Seeing ‘planet-light’ directly would also allow astronomers to figure out what the planet’s composition is like - whether or not they could be like Earth, for instance.


Webster Cash (Univesity of Colorado, Boulder, CO, USA)
Tel: +1 303 492 4056; E-mail: [email protected]

[2] Neuroscience: Monkey brain 'tuned' for face recognition (AOP)

DOI: 10.1038/nature04951

***This paper will be published electronically on Nature's website on 05 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 06 July, but at a later date.***

Monkeys' brains seem to be fine-tuned for spotting tiny differences between different faces, according to research published online by Nature this week. The process, which allows them to recognize familiar faces easily, may be the same as that which gives humans our own skilful talent for face recognition.

Monkeys, like humans, are known to possess 'face cells' in a part of the brain called the inferotemporal cortex. These nerve cells fire up in response to the visual image of a face, although it was not clear exactly how they are primed to do this. But researchers led by David Leopold now show that these cells are fine-tuned to recognize neutral faces, and that they show the greatest response to small deviations from this 'internal norm'.

The researchers studied two macaques (Macaca mulatta) previously trained to recognize a series of computer-generated human faces. They then showed them a range of different pictures that differed by varying amounts from the familiar images. The results suggest that monkey, and perhaps human, face-recognition cells are fine-tuned to pick up tiny deviations from the internal norm, which might help us to recognize different individuals or even to spot signs of emotion or intent in others.


David Leopold (National Institute of Mental Health, Bethesda, MD, USA)
Tel: +1 301 594 0582; E-mail: [email protected]

[3] Virology: Retroviral invasion of the koala genome (pp 79-81)

The koala genome is being invaded by an RNA-based virus called the koala retrovirus (KoRV), a study to be published in this week’s Nature suggests. As the virus slowly becomes incorporated into the animals’ genomes it presents a unique, natural opportunity to study the process of retroviral endogenization.

Endogenous retroviruses, where a virus becomes integrated into a host genome and then gradually inactivated, are widespread in the animal kingdom. Koalas are no exception, with all animals previously tested being positive for KoRV.

But when Paul Young and his colleagues studied blood samples from koalas on Kangaroo Island off the south coast of Australia, the animals tested negative for KoRV. Other populations in southern Australia showed a mixed prevalence of KoRV, whereas animals further north in Queensland uniformly tested positive.

The finding, combined with high levels of viral activity and variability in individual koalas, suggests that the virus is in transition between exogenous and endogenous forms.

Paul R Young (University of Queensland, Australia)
Tel: +61 7 3365 4646; E-mail: [email protected]

[4] Geophysics: Depth constraints on quiet earthquakes (pp 71-74)

'Silent' earthquakes, in which deep geological faults slip slowly without creating seismic tremors, can be located more accurately through the use of associated microseismicity, say Paul Segall and colleagues in Nature this week. They find that 'slow slip' of a fault 7-8 kilometres below Kilauea volcano on Hawaii in early 2005 seems to have triggered a series of small earthquakes in the same region. The researchers say that this microseismicity may have the potential to help quantify the danger posed by such silent events.

Slow slip is a kind of fault movement halfway between smooth, steady sliding, like a well lubricated surface moving across another, and the earthquake-generating phenomenon of stick-slip motion, when the two sides of the fault move over one another in a series of juddering lurches. In slow slip the motion is gradual but not completely smooth. Because it doesn't in itself generate seismic waves, slow slip isn't detected as an earthquake as such, but the ground movement can be seen at the surface from a shift in the distance between reference points, detectable for example by the satellites of the Global Positioning System.

Such a 'silent earthquake' below Kilauea in 2000 caused surface displacements of around 1.5 centimetres in a day and a half. Segall and colleagues now report similar events in 1998, 2003 and 2005. And they say that the 2005 event happened at more or less the same time as - in fact, it started just before - a swarm of small earthquakes. They conclude that although the slow slip did not itself produce an earthquake, it seems to have set off these mini-quakes that were poised to happen elsewhere on the fault system.

Paul Segall (Stanford University, CA, USA)
Tel: +1 650 725 7241; E-mail: [email protected] <mailto:[email protected]>

[5] Microscopy: Spot the nanoflaw (pp 63-66; N&V)

A team of scientists show in Nature this week how it is possible to study atomic-scale imperfections in a nanocrystal by exploiting some unexpected effects observed when using coherent X-ray diffraction imaging, a technique for deducing the material’s crystal structure. Such imperfections can play a crucial role in determining a material’s properties.

By shining X-rays through crystals, scientists can generate a two-dimensional pattern of bright spots, called a diffraction pattern, which can then be used to figure out where the atoms in the crystals are. Recent advances in producing X-ray beams have made it possible to obtain diffraction patterns of discrete crystals just a few nanometres across by taking a diffraction pattern which can then be ‘inverted’ mathematically to get a three-dimensional image of the crystal, a technique known as coherent X-ray diffraction imaging. It is believed that this kind of imaging will be very useful in nanotechnology, where scientists and engineers strive to control the structure and thus the properties of materials on the scale of nanometres.

When working on this imaging technique, Ian Robinson and colleagues noticed asymmetries in their diffraction peaks, which they ultimately identified as disruptions to the atomic lattice due to the presence of a strain field. In the paper, the team show that asymmetries in the diffraction peaks of a nanocrystal of lead, about 200 nanometres across, sitting on a surface of silicon dioxide (silica) provide enough information to reveal, in three dimensions, the strained region within the nanocrystal lattice. They think that the deformation observed stems from an imperfection on the silica surface, which could well constitute the ‘seed’ around which the nanocrystal grew in the first place.


Ian K Robinson (University College London, UK)
Tel: +44 20 7679 8313; E-mail: [email protected] <mailto:[email protected]>

Eric D Isaacs (Argonne National Laboratory, IL, USA)
Tel: +1 630 252 6742; E-mail: [email protected] <mailto:[email protected]>

[6] Low-temperature physics: Spot the difference (pp 54-58; N&V)

An exotic state of matter has been directly observed for the first time and is reported in this week’s Nature. Martin Zwierlein and colleagues watched a gas of lithium atoms cooled to just a few tens of billionths of a degree above absolute zero 'condense' into a so-called superfluid state, where all the atoms act coherently like a single entity. This is a form of Bose-Einstein condensation, a quantum-mechanical effect first seen over ten years ago in a similar cloud of ultracold metal atoms.

Where the present experiment differs from previous ones is that here the atoms feel each other's presence strongly - they are 'strongly interacting'. In weakly interacting gases, Bose-Einstein condensation is easy to spot because the gas cloud acquires a dense central core. But for strongly interacting particles the superfluid and normal parts of the cloud are no longer so distinct, so condensation must be inferred by an indirect method, which is less well understood. Zwierlein and colleagues have got round this problem with the trick of using an unequal mixture of atoms in two different quantum-mechanical states. Because the superfluid state formed by condensation consists of pairs of each type of atom, the gas cloud separates into blobs of different densities, with the excess 'singletons' making it easy to distinguish the normal outer regions from the superfluid core.


Martin W Zwierlein (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 617 253 6677; E-mail: [email protected] <mailto:[email protected]>

J E Thomas (Duke University, Durham, NC, USA)

Tel: +1 919 660 2508; E-mail: [email protected] <mailto:[email protected]>


[8] Intracellular pattern recognition receptors in the host response (pp 39-44)

[9] Selective elimination of messenger RNA prevents an incidence of untimely meiosis (pp 45-50)

[10] Resonance in the electron-doped high-transition-temperature superconductor Pr0.88LaCe0.12CuO4-delta (pp 59-62)

[11] The effect of energy feedbacks on continental strength (pp 67-70)

[12] Local migration promotes competitive restraint in a host-pathogen ‘tragedy of the commons’ (pp 75-78)


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: 11

Clayton: 11

Kensington: 11

Melbourne: 5

Perth: 11

St Lucia: 3


Hamburg: 5

Mainz: 11

Tubingen: 2


Kobe: 9

Tokyo: 9


Luxembourg: 7


Rotterdam: 7


Ibadan: 7


Moscow: 2


Lausanne: 8


London: 5



Anchorage: 4


La Jolla: 8

Stanford: 4, 12


Boulder: 1


Hawaii National Park: 4


Urbana: 5


Bethesda: 2

College Park: 10


Cambridge: 6


St Paul: 12


Eugene: 5


Knoxville: 10

Oak Ridge: 10


Seattle: 12


For North America and Canada

Katie McGoldrick, Nature Washington

Tel: +1 202 737 2355; E-mail: [email protected] <mailto:[email protected]>

For Japan, Korea, China, Singapore and Taiwan

Rinoko Asami, Nature Tokyo

Tel: +81 3 3267 8751; E-mail: [email protected] <mailto:[email protected]>

For the UK/Europe/other countries not listed above

Helen Jamison, Nature London

Tel: +44 20 7843 4658; E-mail [email protected] <mailto:[email protected]>

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Published: 05 Jul 2006

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