According to the service experts, "A strong seismic event that continued for about half an hour" was registered on the volcano early on Tuesday. It was accompanied by spew of ash from the volcano crater and volcanic rock descent from the slopes.

According to data obtained from satellites, the volcano has spewed a cloud of ash to a height of about six kilometres. The plume moved to the north at a distance of 100 kilometres. An avalanche came down on the volcano slope along the Baidarnaya River bed. There has been no damage and threat to nearby settlements. The nearest populated locality - Klyuchi is located 50 kilometres from the volcano.

Shiveluch is one of the most active Kamchatka volcanoes. It is 3,283 metres high. Its eruptions are of explosive nature and are difficult to forecast. The volcano's preceding eruption was registered in September 2005.

Their work, reported on Thursday in the weekly British journal Nature, builds on a two-year-old discovery in which scientists ionized helium, forming a plasma wave on which the electrons rode, like surfers catching an ocean break.

The French advance is to improve the technique so that the electron beam, previously unstable and highly variable, is stable and regulated, thanks to a second laser pulse that fires electrons like a slingshot into the plasma wave.

Particle accelerators are used in deep physics to try to understand the nature of fundamental matter and also have medical uses, such as destroying cancer cells by radiotherapy.

The work by Faure and Malka is still in its infancy, accelerating only electrons and not the other particles used in radiotherapy.

An early use would be to provide very short pulses of accelerated particles that could be used in radiography. It could delve beneath the surface of alloys, such as aircraft landing gear, to test for metal fatigue, Faure told AFP.

"Higher viral load causes more HIV transmission, and malaria causes high HIV viral load," said lead study author Laith Abu-Raddad of the Fred Hutchinson Cancer Research Center in Seattle and the University of Washington.

Abu-Raddad, an AIDS researcher, estimated that malaria has helped HIV infect hundreds of thousands and perhaps millions of people in sub-Saharan Africa. AIDS was first identified a quarter century ago.

At the same time, HIV fuels malaria's spread because HIV-infected people are more susceptible to malaria as a result of HIV ravaging the immune system, the body's natural defenses, the researchers said.

AIDS and malaria are concentrated in sub-Saharan Africa. Abu-Raddad said scientists were puzzled when they realized that the risky sexual behavior by people in the region was not by itself sufficient to explain the swift spread of HIV, so other factors must be involved.

They focused their work on Kisumu, a Kenyan city by Lake Victoria where HIV and malaria are both common. They said 5 percent of HIV infections can be blamed on the increased HIV viral load due to malaria, and 10 percent of adult malaria cases can be blamed on HIV.

Since 1980, 8,500 more people got HIV infections, and there were 980,000 more episodes of malaria (a person can get it more than once) in a city whose adult population is 200,000, the study found.

PUBLIC HEALTH EFFORTS

The findings have implications for public health efforts, Abu-Raddad said, showing the importance for authorities to tackle these diseases together.

Of the 39.5 million people worldwide infected with HIV, 24.7 are in the poor countries of sub-Saharan Africa. About 2.1 million of the world's 2.9 million AIDS deaths in the past year were in this region.

Malaria kills more than a million people annually, mostly young children in sub-Saharan Africa.

The researchers produced their results with a mathematical model using HIV and malaria infection data gathered in Malawi by James Kublin of the Hutchinson Center. This enabled them to quantify for the first time the synergy between malaria on HIV and its toll on people.

Scientists previously determined that a lack of male circumcision and the incidence of genital herpes also were facilitating the spread of HIV. Abu-Raddad noted that circumcised men are much less likely to get HIV, and that genital herpes opens a door for HIV to infect a person.

Abu-Raddad said malaria now can be considered a third serious factor facilitating the spread of HIV.

The two diseases drive one another even though they have different modes of transmission -- malaria by mosquito and HIV predominantly by sexual intercourse, Abu-Raddad noted.

Abu-Raddad said once an HIV person gets malaria, his or her viral load goes up and stays higher for six to eight weeks, making the person far more infectious to others.

Plastic rubbish, from drinks bottles and fishing nets to the ubiquitous carrier bag, ends up in the world's oceans.

Sturdy and durable plastic does not bio-degrade, it only breaks down physically, and so persists in the environment for possibly hundreds of years.

Among clumps of seaweed or flotsam washed up on the shore it is common to find mermaids' tears, small plastic pellets resembling fish eggs.

Some are the raw materials of the plastics industry spilled in transit from processing plants. Others are granules of domestic waste that have fragmented over the years.

Either way, mermaids' tears remain everywhere and are almost impossible to clean up.

Raw materials

Dr Richard Thompson at the University of Plymouth is leading research into what happens when plastic breaks down in seawater and what effect it is having on the marine environment.

He and his team set out to out to find out how small these fragments can get. So far they've identified plastic particles of around 20 microns - thinner than the diameter of a human hair.

In 2004 their groundbreaking study reported finding particles on beaches around the UK. Historical records of samples taken by ships plying routes between Britain and Iceland confirmed that the incidence of the particles had been increasing over the years.

Now the team has extended its sampling elsewhere in Europe, and to the Americas, Australia, Africa and Antarctica.

They found plastic particles smaller than grains of sand. Dr Thompson's findings estimate there are 300,000 items of plastic per sq km of sea surface, and 100,000 per sq km of seabed.

So plastic appears to be everywhere in our seas. The next task was to try and find out what kind of sea creatures might be consuming it and with what consequences.

Thompson and his team conducted experiments on three species of filter feeders in their laboratory. They looked at the barnacle, the lugworm and the common amphipod or sand-hopper, and found that all three readily ingested plastic as they fed along the seabed.

"These creatures are eaten by others along food chain," Dr Thompson explained. "It seems an inevitable consequence that it will pass along the food chain. There is the possibility that chemicals could be transferred from plastics to marine organisms."

Other contaminants

There are two ways in which this might happen. Firstly, the Plymouth scientists want to establish whether there is the potential for chemicals to leach out of degraded plastic over a larger area after the plastic has been ground down.

The second aspect of this research is focusing on what happens when plastic absorbs other contaminants.

So-called hydrophobic chemicals such as PCBs and other polymer additives accumulate on the surface of the sea and latch on to plastic debris.

"They can become magnified in concentration," said Richard Thompson, "and maybe in a different chemical environment, perhaps in the guts of organisms, those chemicals might be released."

Whether plastics present a toxic challenge to marine life and subsequently to humans is one of the biggest challenges facing marine scientists today.

The plastics industry's response is that much of the research is speculative at this stage, and that there is very little evidence that this transfer of chemicals is taking place in the wild.

It says it is doing its bit by replacing toxic materials used as stabilisers and flame retardants with less harmful substances.

Whatever the findings eventually show, there is little that can be done now to deal with the vast quantities of plastic already in our oceans. It will be there for decades to come.

Costing The Earth: Mermaids' Tears will be broadcast on Friday 8 December on BBC Radio 4 at 1500 GMT.

You can also listen online for 7 days after that at Radio 4's Listen again page.

On Nov 17, 1986, he told the Kyodo journalists, he was chief pilot on JAL flight 1628, Narita-bound from Paris. The first stop was Keflavik, Iceland; the second, Anchorage, Alaska. At 5:10 p.m. local time the plane, a Boeing-747 jumbo, was flying 10,600 meters over Alaska. It was dusk, not quite dark.

"Suddenly," Terauchi said, "600 meters below, I saw what looked like two belts of light. I checked with the Anchorage control tower. They said nothing was showing on their radar."

But something was emitting those lights, and whatever it was seemed interested in the jumbo, for it adjusted its speed to match to match the plane's - "like they were toying with us," said Terauchi.

That went on for seven minutes or so. "Then there was a kind of reverse thrust, and the lights became dazzlingly bright. Our cockpit lit up. The thing was flying as if there was no such thing as gravity. It sped up, then stopped, then flew at our speed, in our direction, so that to us it looked like it was standing still. The next instant it changed course. There's no way a jumbo could fly like that. If we tried, it'd break apart in mid-air. In other words, the flying object had overcome gravity."

Five minutes later, the object vanished in the gathering darkness, but soon another, much larger object, "several tens of times larger than a jumbo jet," which itself is some 70 meters long, appeared, bathed in blue light. Again the control tower radar registered nothing. Terauchi noticed unusual silhouettes over Fairbanks, Alaska. The object vanished. The jumbo landed at 6:24 p.m. and the passengers disembarked, not so much as suspecting what a harrowing experience their pilot had been through.

What to make of this? It's tempting to say Terauchi's imagination got the better of him; but he's an ex-fighter pilot with more than 10,000 flying hours under his belt. He would know, if anyone would, how to keep his imagination in check. Another theory Shukan Shincho hears is that the lights the pilot saw were from Jupiter and Mars, which in fact would have been visible on the jumbo's flight path on the night in question. It's possible, but again - would a man with Terauchi's experience and training be so easily fooled?

There are other possibilities, among them a secret U.S. military operation or development, about which nothing is known precisely because it is secret. Or maybe it really was what Terauchi says it was - a UFO. In any case, Terauchi was shortly afterwards grounded by JAL for talking to the press. He was given a desk job, and only reinstated as a pilot years afterwards. Now 67 and retired, he lives quietly with his wife in a small town in north Kanto, and talks about the adventure as little as possible.

"I spoke to a doctor - he said it was an illusion," he tells Shukan Shincho. "You saw something you weren't meant to see," his wife says consolingly. That, if nothing else, seems certain.

But now a new exhibition marking the 800th anniversary of the foundation of the Mongol empire wants to challenge popular perceptions of the man who did it.

Genghis Khan and his Heirs: the Great Mongol Empire, which opened in Istanbul yesterday, suggests the warrior chief's reputation as a bloodthirsty warrior has been warped. Instead, it hails him as a tolerant, meritocratic law-giver whose reign - and that of his many descendants - led to the profitable flourishing of commerce and ideas from the Mediterranean to China for 200 years. Though no surprise to the Mongolians, who have long revered Genghis as thefather of their nation, the show looks like quite a makeover.

Opening the exhibition at the Sakip Sabanci Museum, its director, Nazan Olcer, said Genghis Khan's major achievement was the creation of the so-called Pax Mongolica which offered security to the entire region and enabled travellers such as Marco Polo to move freely along the Silk Road.

"This great come-and-go meant an immense commercial and artistic exchange between the West and the East," she said. "That was his long-lasting legacy."

For a man once voted one of the most important political leaders of all time by National Geographic, and man of the millennium by The Washington Post, the blanks in his known history are numerous.

Even the face peering out from giant posters across Istanbul is a 14th-century depiction. And the primary source for the biography of Genghis Khan is The Secret History of the Mongols, written in China after his death.

What is accepted is that Temujin was born around 1162 to an impoverished family of nomads. He was married at around the age of 16 to Borte, and pledged his allegiance to Toghrul, a close ally of his father who was the leader of the Keraits. When his wife was kidnapped by the Merkits he raised an army to get her back, and succeeded. Further conquests followed until he had united the Merkits, Naimans, Mongols, Uighurs, Tatars and other previously warring tribes under his rule, an unprecedented achievement.

In 1206 he was acknowledged the leader of the tribes, and within a century the Mongol empire had extended across the steppe lands of Iran and Russia to the plains of Hungary - provoking panic across Europe.

"Last year a people invaded the Ruthenian empire and destroyed an entire clan," wrote Caesarius von Heisterbaen in Germany in 1222. "We do not know who they are, where they came from and where they are going."

Genghis Khan and his heirs brooked no resistance. When Pope Innocent IV wrote in 1245 asking Genghis's son Ogedei, known as the Great Khan, to stop slaughtering people, especially Christians, the response was a scarcely disguised threat to Christendom to submit, or else.

But although he could be brutal, Genghis Khan was meritocratic compared with earlier tribal chiefs. His sons, who continued his work in China - under the fabled Kubla Khan - Persia and Russia, allowed indigenous culture to remain, so that Mongol influence can be hard to discern.

Dr Susanne Wichert-Meissner, of the Art and Exhibition Hall in Bonn - which has previously hosted the exhibition - said: "The conquered people were not forced to adopt a foreign culture, as Genghis Khan chose to use their diverse skills and cultures to his own benefit."

The Mongols remained nomadic, and Khan did not establish a city base until 1220, when the need for an administrative centre to support his mission prompted the founding of Karakorum - where German, French and Turkish archaeologists are now digging up new information.

But gaps in our understanding remain. Genghis Khan died on a military campaign in 1227, but the site of his burial remains unknown. "He built an empire like no other in history, the largest in the world," Dr Wichert-Meissner said. "He's one of the most famous personalities in history, but he didn't leave palaces or a magnificent grave behind."