Pasko Rakic of Yale Medical School in New Haven, Connecticut and his team were similarly scanning experimental mice, to help inject dye into embryos. When later studying the brain development of these mice, the team noticed that certain neurons in the growing cortex were not behaving normally.

Rakic discussed his preliminary results at the Society for Neuroscience meeting in 2004 (see 'Ultrasound scans accused of disrupting brain development'). But he says he wanted more results to be convinced - now, 335 mice later, he is.

Long exposure

Rakic says that he has no evidence that ultrasound scanning disrupts the brains of human fetuses. The affected mice in his study were exposed to continuous ultrasound for 30 minutes or more; a baby's brain would be exposed for only a fraction of this time during a 30-minute scan of its entire body. And a narrow ultrasound beam will hit and affect far more of a small mouse brain than a larger human one.

Some studies have hinted that ultrasound causes subtle brain changes in humans that increases the chance of a child being left-handed or developing speech problems. Others suggest that the risk is minimal. A 2004 study found that fetuses exposed to five ultrasound sessions rather than one are more likely to grow poorly, but that this difference disappears after the first year1.

"We don't want to push the panic button," Rakic says. "It would be very wrong if women stopped having medically indicated ultrasounds because of this."

At the same time, Rakic says that it is sensible to avoid the lengthy ultrasound scans that some parents now choose in order to make videos of their baby. The US Food and Drug Administration and other medical groups also discourage unnecessary ultrasound scans.

Scattered migration

Neurons are born deep inside an embryo's brain cortex and then migrate to the outer edge. This migration creates a series of parallel zones running through the cortex, like rock strata, each of which has specific functions in communicating to other areas of the brain.

These layers are vital for the processes directed by the cortex such as memory and language. In animals, alcohol, cocaine and viral infections can also disrupt the neurons' migration and affect behaviour.

Rakic marked some of these migrating neurons with a dye and then exposed the growing mice to between 5 minutes and 7 hours of ultrasound over the final three days of gestation, using a machine identical to that used for humans. He then examined the brains of the young mice a few days after birth.

In those exposed to 30 minutes or more of ultrasound, not all of the neurons destined for the outer layers of the cortex completed their journey. Instead, some remained scattered in interior layers of cortex, or even in neighbouring white matter. The more ultrasound the mice received, the more scattered their neurons. The results are reported in Proceedings of the National Academy of Sciences2.

Bad vibrations

The team also found that neuronal migration was disrupted in a group of animals that went through the experimental procedures for 7 hours, but were not exposed to ultrasound. This suggests that the stress caused by an extended period of handling could also affect the brains of a mother's babies. But stress can't explain all the results, says Rakic's team.

The scientists are not sure how the ultrasound waves disrupt neuron migration. One idea is that they make the neurons vibrate, preventing them from sticking to adjacent cells.

Rakic is repeating his experiments in monkeys, and looking for behavioural changes in the offspring. He says he does not yet have results.

Alma will open astronomers' eyes to the half of the universe that has, until now, been hidden to modern telescopes. When it is fully operational in 2012, the $1bn (£520m) observatory will discover a previously unseen galaxy every three minutes and study the formation of planets outside our solar system in the hope of understanding how the Earth was made.

After more than two decades of planning, astronomers have entered a critical phase in the construction of the observatory, with the imminent arrival of the first of 66 identical 12-metre diameter radio antennas that will eventually sit across the Chajnantor plateau.

"It turns out that half of the stars that form in the universe are obscured by dust," said John Richer, an astronomer at Cambridge University and the chair of Alma's science advisory committee. "If you want to study the universe and can't look through the dust, then you're missing a good deal of the universe with the optical and infrared telescopes."

Alma, Spanish for soul, will effectively see through the clouds of soot-like dust near stars. While this dust hides the stars, it also gets heated by them to a few degrees above absolute zero (-273C). The dust then emits radiation of its own at a wavelength of around one millimetre, 1,000 times smaller than the light we see with our eyes.

This radiation, from dust clouds all over the universe, will be picked up the 66 carbon-fibre dishes eventually sprawled across the Chajnantor plateau, allowing scientists to determine what stars lie behind the dust.

Astronomers chose the inhospitable Andean site because it is blessed with year-round clear skies and is one of the driest places in the world. Millimetre radiation is absorbed by water and there has been no rain in parts of the Atacama desert for several hundred years. The advantage of being so high up is the opportunity to capture images as sharp as anything the Hubble Space Telescope is capable of.

From a technical centre several thousand metres below the Chajnantor plateau, astronomers will control the movements of the antennas as they scan the skies for hitherto unseen galaxies and new stars.

The galaxies Alma will see are those in the early universe, which are still in the process of coming together but are so far away that their light has taken millions of years to reach us. Alma will witness these galaxies assembling themselves and forming vast spirals and ellipses of the kind we see in our part of the cosmos.

"You can start to put together a whole picture of how we got from the big bang, where everything was evenly distributed, to the more local set of galaxies we have today," said Dr Richer.

Astronomers will also study how the Earth was made. Five billion years ago, our planet formed out of a cloud of gas in the galaxy, but exactly how that happened is a mystery. "We fundamentally don't understand how planetary systems form. We don't know what a typical planetary system looks like - we don't know whether we are typical or atypical," said Dr Richer.

With Alma, astronomers will be able to look inside the dust clouds where planets and stars form with enough detail to study what is going on inside for the first time.

"What Alma will be able to do is look for many of these objects and see, through them, a sequence of different stages," said Massimo Tarenghi, the director of Alma.

"It will be able to study many stars and see the formation of these discs and the formation of proto-planets and maybe a planet."

He added that Alma would be able to analyse whether planets outside our solar system harbour the right conditions for life.

Alma is a collaboration between the 11 member countries of the European Southern Observatory with the US, Japan, Spain, Chile, Taiwan and Canada. The UK contribution, funded by the Particle Physics and Astronomy Research Council, includes detectors and design input from Cambridge and Manchester Universities and the Rutherford Appleton Laboratory in Oxfordshire.

The antennas are being built by American, Japanese and European manufacturers with the first 12-metre dish scheduled to arrive at Chajnantor in April next year.

Preliminary research using the antenna array can begin well before all the dishes are installed: Dr Tarenghi expects the first science results to be unveiled in 2009, three years before the construction is officially complete.

The Prudhoe Bay oilfield, which accounts for 8 percent of domestic output, is very different now from what it was when it was first brought onstream, said ING Financial Markets analyst Jason Kenney.

"The changing quality of the crude that is being produced has presented an issue with the infrastructure that's in place and the development and that is what BP are battling against," Kenney said.

The world's second-largest oil company announced Sunday it was shutting down the oil field after a small leak was found in one of its three transit lines, which bring oil to the 800-mile trans-Alaska pipeline. BP has 22 miles of transit lines and will be replacing two of the lines, or 16 miles of pipe.

The Prudhoe Bay field produces about 400,000 barrels a day - about half of all North Slope production - with production divided equally between the eastern and western sides.

The phased shutdown began Sunday on the east side, where the leak was discovered. It will likely move to the west side, where in March corrosion in another transit line caused a spill of up to 270,000 gallons - the biggest spill in the history of the North Slope or portion of Alaska north of the Brooks Range mountains.

Company officials said Tuesday they hope to avoid a complete shutdown on the west side.

Bob Malone, chairman of BP North America who took over July 1, defended the company Tuesday.

"I'm not able to see a systemic issue," Malone told analysts. "These are very, very unfortunate incidents. I can say with comfort I'm seeing a high level of focus on safety and operation integrity."

The discovery of the corroded pipe is not the first major problem at Prudhoe Bay - BP is already facing a criminal investigation over a March spill of up to 270,000 gallons on the west side of the field. Both spills are being blamed on corroded transit pipes.

BP is spending $72 million this year on its anticorrosion program, with about half that money going for millions of gallons of corrosion inhibiting chemicals placed in the pipelines. The amount of inhibitor is roughly double what it was a decade ago.

The company uses a variety of techniques to detect corrosion, including X-raying the pipe and gauging thickness by ultrasound. Workers place gel on sections of pipe and move a transducer along it to detect thin spots. More than 100,000 points along roughly more than 1,000 miles of Prudhoe Bay pipe are checked annually.

Flow pipes - the ones that carry oil, water and gas - also are cleaned and scraped and "smart pigged," where an ultrasound device is put into the pipe to check for the thin places in the wall of the pipe.

It was that test, ordered by the Federal Department of Transportation following the huge March spill, that revealed problems in the transit line that leaked Sunday.

BP had relied mostly on exterior ultrasound to monitor the integrity of its three transit pipes in the belief that they were low-risk for corrosion because they carried market-ready crude oil, the processed oil with the water, gas, and solids removed.

On any given day, between 60 and 70 workers are doing tests on Prudhoe Bay's aging pipeline system, Hedges said.

BP now says it will use a maintenance pig to scrape and smart pig all its transit lines.

CSFB analyst Edward Westlake said the outage in Alaska confirms that some non-
OPEC production infrastructure is becoming old.

"These are not new fears," he said. "However, they are causing more concern to company managements."

Sen. Charles Schumer, D-N.Y., said Tuesday that the corrosion in the Alaska pipeline could indicate other trouble in the U.S. system. He called on the Transportation Department to immediately survey the nation's pipeline network.

He urged the federal government to be more aggressive in seeking out and correcting flaws in the U.S. energy infrastructure.

"The bottom line is we cannot afford for this incident to be a canary in the mineshaft," Schumer said. "Now is the time to aggressively search for and fix any other problems before another disruption causes a national energy emergency."

Schumer said officials should review the inspection schedules companies file to determine whether pipeline operators are adhering to their required plans.

BP has said it determines how often to test its pipes depending on the particularities of the pipe and if it is likely to corrode.

The severe corrosion found in the pipe that leaked Sunday was a surprise.

"Others with operations with mature assets would no doubt be checking procedures for own infrastructure integrity," Kenney said.

Thomas J. Barrett, administrator of the Department of Transportation's Pipeline and Hazardous Materials Safety Administration, said his office has issued BP several compliance orders since the March 2 spill and will issue several more when the current onsite investigations are complete.

"Our goal is to restore the safe operations up there as quickly as we can. BP is doing the types of things we would like to have seen done sooner," he said.