Laser helps detect roadside bombs

19 September 2011 Last updated at 15:05 GMT By Katia Moskvitch Technology reporter, BBC News Roadside bombs have been one of the leading causes of deaths and injuries in places like Iraq and Afghanistan A laser beam that makes molecules vibrate could help detect improvised explosive devises, say scientists.

Every molecule vibrates with a unique frequency - so the laser could "sense" bombs while scanning the ground from a safe distance.

The Michigan State University team's work is another attempt to curb the number of deaths from roadside bombs in places such as Afghanistan.

The research appears in the journal Applied Physical Letters.

An improvised explosive device is a homemade bomb and more than half the deaths of coalition soldiers in Iraq and Afghanistan have been as a result of IEDs.

The lead developer of the laser sensor, Dr Marcos Dantus, said detecting IEDs has always been a challenge because of the chemical compounds present in the environment that mask the bomb's molecules.

"Having molecular structure sensitivity is critical for identifying explosives and avoiding unnecessary evacuation of buildings and closing roads due to false alarms," he said.

The invention uses a laser beam to probe the chemical composition of an object at a certain distance from the laser.

The beam combines short pulses that "kick" the molecules to make them vibrate with longer pulses.

"The laser and the method we've developed were originally intended for microscopes, but we were able to adapt and broaden its use to demonstrate its effectiveness for standoff detection of explosives," said Dr Dantus.

The researcher said he was not able to describe the technology behind the invention in great detail because of the project's sensitive nature.

"I cannot give you more specific information regarding its implementation," he told BBC News.

"All we are saying is that it could detect explosives from a standoff distance."

In 2010, a team of UK scientists developed a "plastic laser" able to sense hidden explosives Bombs in airports

Many different devices and techniques have been developed to help safely detect roadside bombs.

A UK scientist Dr Graham Turnbull from University of St Andrews, who has done a lot of research in this area, told the BBC that the latest study is an exciting step forwards for stand-off detection of explosives - despite still being in the exploratory phase.

"The work demonstrates that a laser spectroscopy technique called 'coherent anti-Stokes Raman spectroscopy' can be used for high-sensitivity stand-off detection of explosives," he said.

"The researchers show that their technique is sensitive - they can detect low concentrations of explosives, of a few millionths of a gram per square centimetre, from a distance of one metre.

"They also show that it is highly selective and can even tell apart very similar explosive molecules - this could be important in complex environments like airports where there could be innocent substances that give false positives with other stand-off detection techniques."

Robot dog's nose

In mid-2010, Dr Turnbull and his team developed laser technology able to sense hidden explosives by "pumping" a type of plastic called polyfluorene with photons from another light source.

They found the laser reacted with vapours from explosives such as TNT.

Dr Turnbull suggested placing such a laser on a robotic, perhaps remotely controlled, vehicle that would be able to "sniff around" in a mine field, looking for vapour clouds.

"On a dusty road in Afghanistan there are relatively few things that might give you a false positive and it certainly could have potential in that area," said Dr Turnbull.

"Essentially it's making an artificial nose for a robot dog."

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Roadside graves found in Tripoli

11 September 2011 Last updated at 18:06 GMT It is not known who the victims are or who killed them The corpses of up to 20 people have been found in two roadside graves on the outskirts of Tripoli.

Forensic experts are investigating the deaths, thought to have occurred last month.

The graves are located just off the 11th June highway, in the Souk al-Jumua area to the east of the capital.

Separately, the charred remains of two bodies were uncovered on airport road in Tripoli.

The corpses were found near the oil tanks of a site known as the Hadba Project, a witness has told the BBC. Local residents in the area said the men were killed on the 22 August.

Libyan rebels captured Tripoli about three weeks ago. Areas of pro-Gaddafi resistance to the rebels remain, notably in Sirte and Bani Walid.

Anti-Gaddafi forces have resumed their attack on Bani Walid, supported by Nato air strikes. Rebel officials says their forces are now within reach of the centre of the town.

The whereabouts of Col Gaddafi and several of his sons remain unknown, though some of his family have fled to Algeria.

Several convoys of former Gaddafi loyalists are also said to have recently streamed over Libya's southern border with Niger.

Grave sites

Local people said there were around 15 bodies buried at one grave site.

Continue reading the main story Peter Biles BBC News, Tripoli

A mechanical digger was brought in to clear the area initially, then workers with picks and shovels set to work. Many wore surgical masks and gowns.

We saw mobile phone video from a local man who said it showed people in the neighbourhood burying the bodies because of the smell. The smell today was extreme as the bodies were exhumed.

The four bodies at the site down the road had been exhumed and placed in plastic body bags. Locals said one site contained approximately 15 bodies - one Libyan, and others African mercenaries.

It is not clear who killed them or how they died.

They were said to be mostly the remains of African mercenaries who had been fighting for Col Gaddafi.

A few hundred metres away, at a separate site, another four bodies had already been dug up.

Daily, the search goes on for thousands of Libyans still unaccounted for as a result of the conflict, says the BBC's Peter Biles in Tripoli.

But speaking in Tripoli this weekend the head of the National Transitional Council, Mustafa Abdul Jalil, said this was not the time for retribution.

On Saturday, Mr Jalil was greeted by hundreds of cheering, flag-waving supporters when he arrived in the capital for the first time since rebels took over the city.

Until now he had remained in the eastern city of Benghazi. His presence in the capital is aimed at sending a message about his authority.

Correspondents say he now faces big challenges as he tries to stabilise the country and form an effective national administration.

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