鈥淭here was an explosion on the Mojave Airport at 2:30 this afternoon (2130 GMT),鈥� fire engineer Roberto Figueroa of the Kern County Fire Department said. 鈥淭here are two confirmed fatalities and four seriously injured. What exploded was a rocket.鈥�

The cause of the explosion was not immediately known.

The airport is located 130 kilometres (80 miles) north of Los Angeles.

Local television CBS2 broadcast images taken from a helicopter showing debris scattered over a wide area and semi-trailer split by the blast.

According to the station, the explosion erupted from tanks filled with rocket fuel during engine tests carried out at the airport.

The Mojave desert site near the US Edwards Air Force Base is home to several private spaceflight companies.

The Mojave desert is the site of the aerospace company Scaled Composites, run by US engineer Burt Rutan, who in 2004 won the $10 million X Prize by launching a rocket to space twice within a two-week period.

Scaled Composites, which is currently working with British billionaire Richard Branson鈥檚 Virgin Galactic to send tourists to space by 2010, did not respond to calls for comment late on Thursday.

A super-thin carbon 鈥減aper鈥� that is super-strong, yet also flexible and light, has been developed by US scientists.

The substance, graphene oxide paper, was created by a team of scientists led by , Chicago. It is derived from graphite, oxidised to form graphite oxide, that is then formed into layers, each just 1 micron, or a millionth of a metre, thick.

The paper may have many potential applications, the researchers say, either alone or as a composite within plastics, ceramics or metals. It could be employed anywhere flexible reinforcement is needed, for example, in aircraft, cars or in body armour.

The researchers made small sheets of the dark-brown paper with thicknesses ranging from one to 100 microns, and tested it for stress and tensile resilience against high-tech competitors. It was superior to everything, including so-called bucky paper, which is made of carbon nanotubes.

Superior material

Graphene oxide paper owes its exceptional physical qualities to unique interlocking-tile lattices formed on the atomic scale. It also has intriguing electrical qualities, because the oxidisation process turns the material from a conductor into an insulator.

鈥淚n the future, it will be possible to tune the material as a conductor, semiconductor or insulator,鈥� Ruoff says. 鈥淥ne will be able to control the electrical properties without sacrificing exceptional mechanical properties.鈥�

It could also be used in batteries, Ruoff says, since its unique lattice structure could be electrically tuned to make membranes with controllable permeability.

So far, only experimental sheets of the paper have been made, each of them around 12 centimetres in diameter, but Ruoff believes that it would be quite easy to scale up to large sheets, helped by the fact that graphite is cheap and plentiful.

In theory, graphene sheets could be superior to all other materials, Ruoff says, 鈥渨ith the possible exception of diamond鈥�.

Journal reference:

They had been sentenced to death, but that was commuted to life imprisonment on 17 July. However, the five nurses and one Palestinian-born doctor were pardoned immediately on arrival in Sofia by Bulgarian President Georgy Parvanov.

The pardon ends an eight-year ordeal for the six, who always protested their innocence. They say confessions were extracted from them under torture. Foreign experts blamed poor hygiene at the hospital for the HIV infections.

Libya said it ordered their release after it was satisfied the conditions it laid down for extradition had been met. 鈥淲e received guarantees for the normalisation of relations with European countries, and for a partnership agreement with the European Union,鈥� a Libyan official told AFP.

In Brussels, European Commission chief Jos茅 Manuel Barroso confirmed that a deal on improving ties had been struck in order to secure the medics鈥� release. 鈥淚 told Libyan leader Muammar Gaddafi that, if this matter were settled, we would do our best to further normalise these relations,鈥� he said.

鈥楥onjecture and supposition鈥�

The medics had been behind bars since February 1999. They were convicted of infecting 438 children with HIV-tainted blood at a hospital in Libya鈥檚 second city, Benghazi, and sentenced to death in May 2004. Fifty-six of the children have since died.

But foreign health experts have cited poor hygiene as the probable cause of the infections.

Robin Weiss, an AIDS virologist at University College London, UK, said in 2006: 鈥淭here are no grounds for suspicion of deliberate infection by any staff, and strong evidence of hospital-acquired infection before the arrival, and after the departure, of the Palestinian physician and the Bulgarian nurses.鈥�

The journal Nature published a study that concluded a scientific report being used in the case against the six was nothing but .

Another journal, Science, published a , including Robert Gallo (who co-discovered that the human immunodeficiency virus (HIV) causes AIDS), which stated: 鈥淭he Libyan court chose to exclude expert testimony from independent scientists, and to prevent access to crucial pieces of evidence to test for HIV contamination.鈥�

Million dollar compensation

The families of the infected children have been paid compensation. According to the Gadhafi Foundation, run by Gadhafi鈥檚 son Seif al-Islam, and which has been involved in mediating the crisis, the compensation amounts to about $1 million per child.

EU External Relations Commissioner Benita Ferrero-Waldner had travelled to the Libyan capital Tripoli with C茅cilia Sarkozy, the wife of the French president, to help free the medics and flew with them to Sofia.

Ferrero-Waldner signed a two-page deal with Libya, laying out how ties could be boosted, a European source told Reuters. 鈥淚t covers everything 鈥� trade, support for archaeology, illegal immigration, grants for students and visa questions,鈥� the source said. A Libyan close to the negotiations said the EU also agreed to help upgrade a hospital in Benghazi.

The EU currently has no bilateral agreements with Libya since imposing sanctions following the , and has not started negotiations for an accord since UN sanctions were lifted in 2003.

鈥淭he Judicial Council decided to commute the death sentence to life in prison,鈥� said the source, who spoke on condition of anonymity.

The five Bulgarian nurses and a Palestinian doctor, who has been granted Bulgarian citizenship, could serve out their sentences in Bulgaria, as the two countries have an extradition treaty. It was not immediately clear if the six would be sent to Bulgaria.

However, the Bulgarian chief prosecutor will initiate on Wednesday procedures for seeking their extradition, spokesman Kamen Mikhov said. 鈥淔rom tomorrow, the prosecutor鈥檚 office will take steps to activiate the Bulgarian-Libyan extradition treaty,鈥� he said. 鈥淚t is a routine procedure that we have launched immediately in other cases.鈥�

Washington and the European Union joined in calling on Libya to send the six medics home. 鈥淲e urge the Libyan government to now find a way to allow the medics to return home,鈥� US State Department spokesman Sean McCormack said.

The European Commission described it as a 鈥渞elief鈥� while adding that the objective remained 鈥渢heir transfer to the EU as soon as possible.鈥� Bulgaria joined the EU in January.

Bulgaria鈥檚 Foreign Minister Ivaylo Kalfin welcomed Libya鈥檚 decision. 鈥淭he decision of Libya鈥檚 Supreme Judicial Council is a big step in the right direction, but for us the case will be over when our compatriots return to Bulgaria,鈥� Kalfin told journalists in the Bulgarian capital, Sofia.

Poor hygiene

The decision came after the children鈥檚 families dropped their call for the death penalty following a compensation deal worth millions of dollars. 鈥淲e have renounced the death penalty 鈥� after all our conditions were met,鈥� said Idriss Lagha, spokesman for the families. 鈥淎ll the families have received compensation.鈥�

The Gaddafi Foundation involved in mediating a resolution to the case that has dragged on for eight years and strained ties with the West, has previously said the compensation amounts to about $1 million per child.

The medics, who have been behind bars since 1999, were convicted of deliberately injecting 438 children in a Benghazi hospital with HIV-tainted blood. Lagha has said the number of victims has risen to about 460 after several mothers were infected. Fifty-six children have since died.

The death penalty had been confirmed by the Supreme Court last Wednesday, sparking renewed international concern over their fate.

Nurses Snezhana Dimitrova, Nasya Nenova, Valya Cherveniashka, Valentina Siropulo and Kristiana Valcheva and doctor Ashraf Juma Hajuj have always pleaded their innocence.

They say confessions were extracted under torture and foreign experts have blamed poor hygiene at the hospital for the AIDS outbreak in Libya鈥檚 second city of Benghazi on the Mediterranean coast.

Both EU External Relations Commissioner Benita Ferrero-Waldner and Bulgaria鈥檚 Prime Minister Sergey Stanishev had urged Libya鈥檚 Judicial Council to make a swift and clement ruling.

Last week, the medics sought 鈥減ardon and mercy鈥� from the council, which can uphold, modify or overturn the Supreme Court verdict.

Torture accusations

The Gaddafi Foundation, headed by Libyan leader Muammar Gaddafi鈥檚 son Seif al-Islam, said the money was paid to the victims鈥� families out of a special Benghazi AIDS fund created in 2005 by Tripoli and Sofia under EU auspices.

Among the victims are eight Palestinians, two Egyptians, two Syrians, two Sudanese and a Moroccan as well as Libyans, according to Lagha.

Last week, Libyan Foreign Minister Abdel Rahman Shalgham said the compensation would be paid by 鈥渃ertain European countries and charitable organisations, and from the Libyan state鈥�.

He refused to reveal how much money was already in the fund, except to say it ran into 鈥渉undreds of millions of dollars鈥�.

The French Le Figaro daily had reported on Saturday that some EU countries could be involved in the compensation but the European Commission, which has already committed 聙2.5 million to the fund, has denied it played any role in the deal.

The six medics also face defamation charges brought by a senior police officer over their torture accusations, although this case could also be resolved.

鈥淚t has been repeatedly proved that information blocking is like walking into a dead end,鈥� the state-run newspaper quoted Wang Guoqing, a vice minister with the , as saying.

Wang says local governments need to be more transparent, describing some as being 鈥渢oo na茂ve鈥� in thinking they can simply hide damaging information.

Wang reportedly revealed that some local government representatives used to believe that 90% of bad news could be concealed, and only 10% would be unluckily exposed by the media. He cited the recent case of a slavery scandal that emerged in China鈥檚 Shanxi and Henan provinces as proving that bad news needs to be managed, rather than covered up.

Scandal revealed

In that case, hundreds, perhaps thousands, of people had been forced to work as slaves in brickyards for years, but the authorities there refused to acknowledge any problem until relatives of victims posted information about the scandal on the internet.

Wang said that the central government鈥檚 commitment to transparency, as well as new information technologies such as the internet and cellphones, were making it more and more difficult for local authorities to hide bad news (see Behind the Great Firewall of China).

However, (RWB) describes the Chinese government as an 鈥渆nemy of the internet鈥�.

Bypassing controls

In RWB鈥檚 annual report, published in February 2007, the global media watchdog said that China was spearheading an increasingly sophisticated movement by repressive regimes around the world to restrict information on the internet.

Various prominent websites, including the BBC and Wikipedia are routinely blocked within China. Certain search terms are also restricted from popular search engines, including the Chinese versions of Yahoo and Google.

But there are also many tools for bypassing such state controls. These range from simple proxy servers, which reroute information but can also be blocked with ease, to peer-to-peer routing programs such as TriangleBoy and , which are much harder to block.

In a speech in January, Chinese President Hu Jintao said that the central government intended to keep as tight a rein on the internet as it does on traditional forms of the media, such as newspapers and television.

However, tightened controls have caused unrest among some internet users within the country (see Users rage against China鈥檚 鈥榞reat firewall鈥�).

The five Bulgarian nurses and a Palestinian doctor 鈥� who now has Bulgarian nationality 鈥� were not in court for the verdict, announced one day after a compensation deal was reached with the children鈥檚 families that could see the death sentences commuted to prison terms.

鈥淭he court has decided not to accept the defendants鈥� appeal and confirms the death penalty against them,鈥� chief judge Fathi Dahan said.

Libya鈥檚 top legal body, the Supreme Judicial Council, is due to meet next week to examine the compensation deal negotiated by the Gaddafi Foundation, a charitable body headed by the son of Libyan leader Muammar Gaddafi.

鈥淚t will be up to this body to cancel or commute the verdict pronounced today by the supreme court,鈥� said foreign minister Abdel Rahman Shalgham.

The medics have been behind bars since February 1999 (see timeline below), but have always protested their innocence.

鈥楴o grounds鈥�

They were convicted of infecting 438 children with HIV-tainted blood at a hospital in Libya鈥檚 second city, Benghazi, and sentenced to death in May 2004. Fifty-six of the children have since died.

But foreign health experts have cited poor hygiene as the probable cause of the infections.

Robin Weiss, an AIDS virologist at University College London, UK, said in 2006: 鈥淭here are no grounds for suspicion of deliberate infection by any staff, and strong evidence of hospital-acquired infection before the arrival, and after the departure, of the Palestinian physician and the Bulgarian nurses.鈥�

The journal Nature published a report that concluded a scientific report being used in the case against the six was nothing but .

The journal Science published a , including Robert Gallo (who co-discovered that the human immunodeficiency virus (HIV) causes AIDS), which stated: 鈥淭he Libyan court chose to exclude expert testimony from independent scientists, and to prevent access to crucial pieces of evidence to test for HIV contamination, while relying instead on 鈥榗onfessions鈥� extracted under torture.鈥�

Negative responses

Reaction in Europe to the decision has been negative but diplomatic. 鈥淲e regret that these decisions have been taken, but I would also like to express my confidence that a solution will be found,鈥� EU Commission President Jos茅 Manuel Barroso told the European Parliament.

Portuguese Prime Minister Jose Socrates, whose country holds the EU鈥檚 rotating presidency, said: 鈥淲e will do everything we can to ensure that we have a happy ending,鈥� adding that political rhetoric would not help reach a good outcome.

Bulgaria鈥檚 Deputy Foreign Minister Feim Chaushev also said Sofia was pursuing talks with Tripoli. But Bulgarian lawyers for the nurses condemned the verdict. 鈥淟ibyan justice wrote a sad and shameful page in its book,鈥� said the Bulgarian coordinator of the defence Trayan Markovski.

Failure to free the medics would carry a heavy diplomatic cost for Libyan leader Muammar Gaddafi.

Charges remain

Saad Djebbar, a commentator on Libya based in London, UK, said the Gaddafi Foundation鈥檚 announcement of a deal with the families on the eve of the ruling appeared to be an attempt by the authorities to tell international public opinion: 鈥淒on鈥檛 worry. The sentences will be commuted.鈥�

Salah Abdessalem, director of the Gaddafi Foundation, said on Tuesday that a compromise acceptable to the children鈥檚 families had been reached: 鈥淭his accord satisfied all the parties and puts an end to this crisis.鈥�

The deal was between the families and a special aid fund for victims set up by Tripoli and Sofia in 2005 under EU auspices, he added.

A representative of the victims鈥� families has said the compromise deal would see the death penalty commuted to jail terms, which could be served in the medics鈥� country of origin, as Libya and Bulgaria have an extradition treaty.

The six medics still face defamation charges brought by a senior police officer after being acquitted in May on similar charges. The cases arise from claims that the medics鈥� confessions in the AIDS trial were forced from them under torture, including beatings, electric shocks and being threatened with dogs.

If found guilty in the new trial, brought by Salim Jomaa Salim, head of the police dog unit, the accused face sentences of up to three years in jail.

Timeline of the AIDS tragedy

聲 February 1999: Bulgaria says 19 of its health workers, employed at a hospital in Benghazi, have been arrested on suspicion of deliberately infecting 438 children. At the time there had been no confirmed cases of HIV infection or AIDS in the North African country.

聲 2000: Five Bulgarian nurses and two doctors, one Bulgarian and one Palestinian, go on trial over the allegations. The Bulgarian government says its nationals have complained of being tortured.

聲 2001: Libyan prosecutors call for the death sentence against the six Bulgarians and the Palestinian. All plead not guilty.

聲 2002: The court throws out the case for lack of proof, but the public prosecutor launches a new procedure. Three of the Bulgarians who had made written admissions of guilt retract them, saying they were obtained under duress.

聲 2003: French AIDS specialists testify that the infection of the children was caused by poor hygiene at the hospital.

聲 2004: The court sentences the nurses and the Palestinian doctor to death, while the Bulgarian doctor gets four years in prison for currency smuggling.

聲 2005: A Libyan court acquits 10 officers accused of torturing the health workers. Libya鈥檚 supreme court orders a new trial of the six. Libya and Bulgaria set up a special aid fund for the child victims, under the aegis of the European Union.

聲 2006: The journal Nature publishes a study which finds that the strain of virus which infected the children must have been introduced to the hospital before the foreign medics began working there.

鈥淧rimary reasons for the move were a combination of highly limited launch opportunities for Dawn in July and the potential impact to launch preparations for the upcoming Phoenix Mars Lander mission, set for early August,鈥� the agency said in a statement on Saturday.

鈥淎 September launch for Dawn maintains all of the science mission goals a July launch would have provided,鈥� NASA added.

Dawn鈥檚 launch was originally scheduled for Saturday, but was delayed until Monday because of threatening weather at the launch site in Florida, US, and problems with an aircraft meant to observe the launch.

NASA was anxious to prevent any of Dawn鈥檚 launch delays from affecting the launch of its Phoenix mission to Mars. If Phoenix were to miss its first Florida launch window from 3 to 25 August, it would have to wait two years for its next chance to lift off.

Dawn鈥檚 eight-year mission is designed to shed light on the earliest moments in the birth of the solar system 4.6 billion years ago by examining the two celestial bodies Ceres and Vesta in the asteroid belt between Mars and Jupiter.

Dawn is scheduled to enter orbit around Vesta in October 2011, proceed to Ceres in May 2012 and then begin orbiting Ceres in February 2015 鈥� travelling a total distance of 5.1 billion kilometers.

Dawn鈥檚 launch window will remain open until the end of October, when the two asteroids begin pulling away from each other, making a rendezvous with both practically impossible. This will be the first NASA

mission to orbit two separate bodies.

快猫短视频s hope the mission will shed light on why its two target asteroids are so different 鈥� the more 鈥渆volved鈥� Vesta was once covered by liquid magma oceans and has an iron core, while the much larger Ceres may have a subsurface layer of water ice covering a liquid water ocean. Dawn is also the first NASA science mission to rely on ion propulsion to reach its targets.

鈥淧rimary reasons for the move were a combination of highly limited launch opportunities for Dawn in July and the potential impact to launch preparations for the upcoming Phoenix Mars Lander mission, set for early August,鈥� the agency said in a statement on Saturday.

鈥淎 September launch for Dawn maintains all of the science mission goals a July launch would have provided,鈥� NASA added.

Dawn鈥檚 launch was originally scheduled for Saturday, but was delayed until Monday because of threatening weather at the launch site in Florida, US, and problems with an aircraft meant to observe the launch.

NASA was anxious to prevent any of Dawn鈥檚 launch delays from affecting the launch of its Phoenix mission to Mars. If Phoenix were to miss its first Florida launch window from 3 to 25 August, it would have to wait two years for its next chance to lift off.

Asteroid belt

Dawn鈥檚 eight-year mission is designed to shed light on the earliest moments in the birth of the solar system 4.6 billion years ago by examining the two celestial bodies Ceres and Vesta in the asteroid belt between Mars and Jupiter.

Dawn is scheduled to enter orbit around Vesta in October 2011, proceed to Ceres in May 2012 and then begin orbiting Ceres in February 2015 鈥� travelling a total distance of 5.1 billion kilometres.

Dawn鈥檚 launch window will remain open until the end of October, when the two asteroids begin pulling away from each other, making a rendezvous with both practically impossible. This will be the first NASA mission to orbit two separate bodies.

快猫短视频s hope the mission will reveal why its two target asteroids are so different 鈥� the more 鈥渆volved鈥� Vesta was once covered by liquid magma oceans and has an iron core, while the much larger Ceres may have a subsurface layer of water ice covering a liquid water ocean. Dawn is also the first NASA science mission to rely on ion propulsion to reach its targets.

A system that makes three dimensional images solid enough to grasp has been unveiled by Japanese firm NTT. It could let businesspeople shake hands from across the globe or allow museum visitors to feel precious exhibits that are normally out of reach, the company says.

The prototype Tangible 3D system combines a 3D display with a 鈥渉aptic glove鈥�. The display creates lifelike images appear in just in front of a flat screen. It creates the illusion of depth by showing slightly different images to each of the viewer鈥檚 eyes. This means no special glasses are needed.

Attached to the display is a haptic glove. Once inside, a user鈥檚 hand is touched by numerous force-feedback components to make it feel as if it interacting with something solid.

The system can also translate real-world objects into virtual representations. Two cameras image the items in 3D so that they can be displayed on the screen. A connected computer then processes the 3D image to generate a tactile representation of the object.

This set up means that if the object being filmed is moved, the three-dimensional image also moves in real-time and the user will feel the movement with their hand.

Projected hand

NTT engineer Shiro Ozawa, who developed the system, envisages various applications. 鈥淵ou would be able to take the hand, or gently pat the head, of your beloved grandchild who lives far away from you,鈥� he says.

Anthony Steed, who works with haptic systems at University College London, UK, says the real-time image capture made possible by the Tangible 3D system is especially interesting.

His own research group has performed related work. But this involved connecting a haptic device to a 2D display on which the user鈥檚 hands are projected, rather than allowing users to manipulate virtual objects directly. He thinks the NTT system could make the interaction feel much more real, although the haptic glove could hinder this.

Steed鈥檚 group wants to use such technology to make valuable museum exhibits touchable and is working with the British Museum in London towards this goal.

Embryonic stem cells from mice are usually taken from very early stage embryos, called blastocysts (see Instant Expert: Stem Cells). These cells are significantly different from human cells and so have limited value.

Roger Pedersen at Cambridge University, UK, and colleagues took cells from the mouse embryo at a later stage in its development, when it is an epiblast. They found that epiblast stem cells, taken from the innermost layer of week-old rodent embryos, shared many of the same properties of human embryonic stem cells.

鈥淭hey are a missing link between mouse and human embryonic stem cells,鈥� says Pedersen, who led the study. The new cells will provide a better model in testing potential therapies for human diseases and injuries, he adds.

New therapies

Another group, led by Richard Gardner at Oxford University, UK, has announced similar findings.

Both studies were hailed by other scientists as a breakthrough that would shed light on the origin of human embryo stem cells and help fulfil the rich promise of cell-based medicine.

Adult bone-marrow stem cells are already used in the treatment of leukaemia, and experiments suggest stems cells could also yield effective treatments for numerous other illnesses, including Alzheimer鈥檚 and spinal-cord injury.

快猫短视频s have successfully grown mice embryo stem-cell lines in the laboratory for decades, and human ones since the late 1990s.

But until now, human and mice stem cells looked and behaved very differently, limiting the parallels that could be drawn between the two species, and raising questions about what accounted for the divergence.

Late breakthrough

鈥淚t was perplexing,鈥� Pedersen says. 鈥淲as is it the evolutionary divergence of mice and men, or was there a developmental explanation, reflecting different stages of growth?鈥�

This question spurred Pedersen and his team to challenge conventional wisdom and see whether the bio-chemical conditions used to maintain human embryo stem cells might work for mice too.

Previous attempts had failed. But when the researchers applied the human-specific molecular cocktail to a later stage of the mouse embryo, rather than the three-day old blastocyst stage from which stem cells had always been drawn, suddenly it worked.

鈥淐omparative analyses suggest that the new cells may have more in common with human embryo stem cells鈥� than the ones taken earlier in the life cycle from mice, says stem cell biologist Ian Chambers, the University of Edinburgh.

Exciting findings

鈥淭hese are exciting findings that hint at ways in which it may be possible to alter the culture conditions for human embryo stem cells in order to make their maintenance more straightforward and malleable,鈥� says Chambers, who was not involved in the studies.

Kevin Eggan, at the Harvard Stem Cell Institute, US, also welcomed the studies, saying they could 鈥渟hed light on the origin and nature of human embryonic stem cells鈥�.

The discovery of the epiblast stem cells in mice should make it easier to isolate stem cells in other species, including livestock, as well as mice genetically modified to express a disease so that it can be studied, Pederson says.

Journal references: (DOI:10.1038/nature05972 and DOI:10.1038/nature05950).