US lifts HIV/Aids immigration ban

he US has lifted a 22-year immigration ban which has stopped anyone with HIV/Aids from entering the country.

President Obama said the ban was not compatible with US plans to be a leader in the fight against the disease.

The new rules come into force on Monday and the US plans to host a bi-annual global HIV/Aids summit for the first time in 2012.

The ban was imposed at the height of a global panic about the disease at the end of the 1980s.

It put the US in a group of just 12 countries, also including Libya and Saudi Arabia, that excluded anyone suffering from HIV/Aids.

The BBC's Charles Scanlon, in Miami, says that improving treatments and evolving public perceptions have helped to bring about the change.

Rachel Tiven, head of the campaign group Immigration Equality, told the BBC that the step was long overdue.

"The 2012 World Aids Conference, due to be held in the United States, was in jeopardy as a result of the restrictions. It's now likely to go ahead as planned," she said.

In October, President Obama said the entry ban had been "rooted in fear rather than fact".

He said: "We lead the world when it comes to helping stem the Aids pandemic - yet we are one of only a dozen countries that still bar people with HIV from entering our own country."

France follows Britain and US in shutting Yemen embassy

France has become the third Western nation to shut its Yemen embassy, after threats from an al-Qaeda offshoot, the foreign ministry in Paris announced.

The US and UK missions, which closed on Sunday, remain shut.

Reports that the closures were prompted by Yemeni security forces losing track of six trucks full of arms were denied by British officials.

Al-Qaeda in the Arabian Peninsula last week said it was behind an alleged plot to bomb a US airliner.

It urged attacks on "crusaders" in embassies.

US Secretary of State Hillary Clinton said Yemen was a threat both regionally and globally.

Threats to US interests in Yemen pre-dated the Christmas holiday period, and the embassy would be re-opened only when circumstances permitted, she said in Washington.

From Monday all travellers flying to America are being subjected to new security measures, introduced by the US government.

Airport staff will now carry out extra screening of people from 14 countries, including those the US considers to be state-sponsors of terrorism - Cuba, Iran, Sudan and Syria.

Yemen and Nigeria - through which the alleged bomber travelled - also face the new restrictions.

Passengers flying from other countries will be checked at random.

On Monday in Paris, French foreign ministry spokesman Bernard Valero told reporters their Yemen ambassador had decided the previous day to suspend public access to the embassy.

French citizens in the country had been warned to be vigilant and limit their movements, he added.

The US was the first to announce the closure of its embassy on Sunday, citing "ongoing threats" by al-Qaeda in the Arabian Peninsula (AQAP), and the UK followed suit.

A US diplomat told the Reuters news agency on Monday: "The embassy is still closed again today... We are continuing to make the security review."

The Japanese foreign ministry said consular services had been suspended at its embassy in Yemen but other business was continuing, AFP news agency reported.

The German foreign ministry confirmed security had been tightened at its mission but that the embassy remained open

Spain restricted public access to its embassy.

The Yemeni authorities have tightened security measures at Sanaa's airport, as well as around several other embassies.

Yemeni security forces, meanwhile, shot dead two militants north of the capital, Sanaa, said officials.

The US embassy was the target of an attack in September 2008 in which 19 people died, including a young American woman. The attack was blamed on AQAP.

On Sunday, the US deputy national security adviser for homeland security and counter-terrorism said there were "indications that al-Qaeda is planning to carry out an attack against a target inside of Sanaa, possibly our embassy".

John Brennan told ABC the group had "several hundred members" in Yemen and Saudi Arabia, and was posing an increasing threat.

Last week, AQAP urged Muslims to help in "killing every crusader who works at their embassies or other places".

The group also said it was behind an alleged failed attempt to destroy an Amsterdam-Detroit flight with nearly 300 people aboard on Christmas Day.

Mr Brennan told CNN there were "indications" a radical US cleric of Yemeni origin had links both to the Nigerian charged with the bomb plot, and the man accused of November's shootings at a Texas military base.

He said the preacher, Anwar al-Awlaki, had had contact with Umar Farouk Abdulmutallab, while he was allegedly being trained by AQAP operatives last year.

It was clear, he said, that Mr Awlaki had also been in touch with Nidal Malik Hasan, the US Army major charged with shooting dead 13 people at Fort Hood.

On Saturday, the head of US Central Command, Gen David Petraeus, visited Yemen's President Ali Abdallah Saleh to pledge support for its fight with al-Qaeda, after Washington doubled its counter-terrorism aid.

Yemeni officials last week said they had sent more troops to hunt down al-Qaeda militants in the provinces of Abyan, Baida and Shabwa.

Correspondents say the security situation in Yemen is complicated by an abundance of firearms, an insurgency in the north and a secessionist movement in the south.

But the prospects of re-asserting central government authority over the lawless areas where al-Qaeda is based look, in the opinion of some analysts, remote - even with beefed-up American support.

World's tallest building opens in Dubai

The world's tallest building has been opened with a dramatic fireworks ceremony in the Gulf emirate of Dubai.

The Burj Khalifa was revealed to be 828m (2,716ft) high, far taller than the previous record holder, Taipei 101.

Known as the Burj Dubai during construction, the tower has been renamed after the leader of Dubai's oil-rich neighbour, Abu Dhabi.

Last month, Abu Dhabi gave Dubai a handout of $10bn (£6.13bn) to help it pay off its debts.

Construction of the Burj Dubai began in 2004, at the height of an economic boom.

Clad in 28,000 glass panels, the tower has 160 floors and more than 500,000 sq m of space for offices and flats.

The tower also lays claim to the highest occupied floor, the tallest service lift, and the world's highest observation deck - on the 124th floor.

The world's highest mosque and swimming pool will meanwhile be located on the 158th and 76th floors.

Technical challenges

The opening ceremony, held 1,325 days after excavation work started, was attended by some 6,000 guests.

Though not complete on the inside, it was officially opened by Dubai's ruler, Sheikh Mohammed Bin Rashid Al Maktoum

In a surprise move he renamed it Burj Khalifa - after the president of the United Arab Emirates and emir of Abu Dhabi, Sheikh Khalifa bin Zayed Al Nahayan.

Sheikh Mohammed described the tower as "the tallest building ever created by the hand of man".

"This great project deserves to carry the name of a great man. Today I inaugurate Burj Khalifa," he said.

Sheikh Mohammed also unveiled a plaque inside the tower bearing the new name.

A dramatic fireworks and lights show took place around the tower while a screen displayed its exact height, which had previously been kept secret.

At 828m, Burj Khalifa dwarfs the 508m Taipei 101 and the 629m KVLY-TV mast in the US, the tallest man-made structure. Its spire can been seen 95km (60 miles) away.

"We weren't sure how high we could go," said Bill Baker of Skidmore, Owings & Merrill, the building's structural engineer. "It was kind of an exploration... a learning experience."

Man arrested over missing Degas

Police have arrested a man over the theft of an artwork by the Impressionist artist Edgar Degas from a museum in Marseilles.

A judicial official said "an employee of the museum, a night watchman" had been arrested on Thursday.

A security guard noticed Les Choristes (The Chorus) - on loan from the Musee d'Orsay in Paris - was missing from the city's Cantini Museum on 31 December.

Public prosecutor Jacques Dallest said there were no signs of a break-in.

A colourful depiction of a group of male singers performing on stage, France's national museum service valued the pastel artwork at £710,000.

The diminutive work - measuring just 32 by 27 centimetres (13 by 10 inches) - formed part of an exhibition featuring some 20 works by the 19th century artist.

The exhibition was due to come an end on 3 January before touring Italy and Canada.

Earlier this year, Degas' bronze sculpture of a young female dancer sold at auction in London for £13.3m.

New visa proposal to help create the next big thing

A proposal that will make it easier for foreign entrepreneurs in the US to start the next Google or Yahoo will be debated in the new year.

Congressman Jared Polis has proposed a start-up visa to entice "foreigners with good ideas" to stay in the US.

The issue has been gathering steam in Silicon Valley where half of all tech company founders are immigrants, according to Duke University research.

The idea is part of a proposed overhaul of the US immigration system.

"Every day the American economy is losing ground - not to mention high-tech jobs and technologies - to India and China because foreign-born entrepreneurs cannot secure a visa to stay in the US," he said.

Lost opportunity

Eric Diep, who has just turned 22, could be regarded as one entrepreneur who got away.

He came to Silicon Valley as a student like many immigrant founders who have helped start companies such as Google and PayPal.

Mr Diep was one of the first developers to get into social games with his application called Quizzes, initially launched on the social networking site Facebook.

Over a year ago he started to apply for a visa to allow him to carry on working in the Valley, but he soon encountered problems.

"The reason it was so difficult for me was because I dropped out of university and the stipulation for a lot of visas is undergraduate experience. My age also seemed to be an issue for the attorneys

"At the beginning it wasn't the expense in terms of legal fees but the big problem soon became one of distraction. I was trying to spend as much time working on perfecting my product but then I would have to go away and figure out the legalities of applying for the visa," Mr Diep told BBC News.

In the end, Mr Diep decided to base himself in his native Canada and travel back and forth to Silicon Valley.

"The flying is so tiring between the two places and it's expensive. At one point, I had no money left in my bank account but at the last minute money came in and now I feel pretty fortunate that I can still do this.

"It was a pretty close call," he added.

He backs a start-up visa because, for him, being in Silicon Valley is where he needs to be.

"Being there at the time really launched me. I would never have spotted the social gaming opportunity had I not been there."

Visa details

The start-up visa is aimed at streamlining the country's EB-5 visa system which was initially introduced in 1990 to attract foreign capital to the US.

Each year 10,000 EB-5 visas are available but to get one, applicants need to invest $1m and create 10 full-time jobs.

Mr Polis said he wants "a new class of eligibility" with the start-up visa.

It would be granted to foreign entrepreneurs if their business plan attracts either $250,000 from a venture capital operating company that is primarily US based or $100,000 from an angel investor.

They must also show that the business will create five to ten jobs or generate a profit and at least $1m in revenue.

Some of these requirements may well be changed when the bill goes to committee in the new year.

"Immigration reform is a big discussion in Washington," said supporter Brad Feld, who is also a managing director with venture company the Foundry Group.

"We think the start-up visa is an easy thing to talk about and get consensus around in terms of having a positive spin on entrepreneurship and creating jobs."

Job creation

Some critics fear that making it easier for entrepreneurs to set up shop will hurt Americans by taking jobs away from them.

"I feel incredibly strongly that that is a misinterpretation of the proposal," said Eric Ries a venture advisor and author.

"Some people have called those opposed to new immigration reform xenophobes and that is why I think it is important we craft this proposal so it addresses those concerns. This is not a new visa category but reform of an existing but flawed category," he told BBC News.

The proposal's backers say that far from taking away jobs, new jobs will emerge that were never there in the first place.

"If the capital is available for the market, we should jump to bring those people here. Those jobs only get created once the founders get funded. This is a market driven decision," said Dave McClure, an internet entrepreneur, investor and start-up advisor.

YouNoodle is a start-up company founded by two British entrepreneurs. It tracks the start-up sector and said the figures speak for themselves.

"If just ten thousand start-up visas were made available this would mean over 3000 additional new innovative and funded companies would be based in the US every year," said Kirill Makharinsky, YouNoodle co-founder.

"They would generate more than 10,000 jobs on average every year. In the first 10 years that would add up to over 500,000 highly-skilled new jobs

"So the upside is huge and the downside is negligible because no jobs are being taken away from US citizens," Mr Makharinsky told BBC News.

And for Mr McClure, the consequences of not establishing a start-up visa class are obvious.

"We will lose out because we are not being competitive with the rest of the world," he said.

"There are similar programmes in Canada, the UK and Australia. They are all vying for the top entrepreneurs and if we only look at our own citizens, we are only taking 10-20% of the world's talent into consideration here. That would be short-sighted in the extreme."

US radio star Rush Limbaugh's health scare over

Right-wing US talk show host Rush Limbaugh says tests taken after he was admitted to hospital with chest pains showed nothing wrong with his heart.

Mr Limbaugh said he was being released from the Queen's Medical Center, in Honolulu, Hawaii, where he had been since Wednesday.

He said he did not know what had caused the chest pains.

Mr Limbaugh, 58, is highly influential in the US and his radio show is one of the most popular in the country.

It is broadcast on some 600 stations across the country and heard by more than 14 million people every week.

Earlier, standing in on Mr Limbaugh's radio show, guest host Walter E Williams had described the radio star's pains as similar to the feeling of a "heart attack coming on".

But doctors said Mr Limbaugh had not had a heart attack and did not suffer from heart disease, the Associated Press news agency reported.

Mr Limbaugh is in Hawaii on holiday.

'Lifeless' prion proteins are 'capable of evolution'

Scientists have shown for the first time that "lifeless" prion proteins, devoid of all genetic material, can evolve just like higher forms of life.

The Scripps Research Institute in the US says the prions can change to suit their environment and go on to develop drug resistance.

Prions are associated with 20 different brain diseases in humans and animals.

The scientists say their work suggests new approaches might be necessary to develop therapies for these diseases.

In the study, published in the journal Science, the scientists transferred prion populations from brain cells to other cells in culture and observed the prions that adapted to the new cellular environment out-competed their brain-adapted counterparts.

When returned to the brain cells, the brain-adapted prions again took over the population.

Charles Weissmann, head of Scripps Florida's department of infectology who led the study, said: "On the face of it, you have exactly the same process of mutation and adaptive change in prions as you see in viruses.

"This means that this pattern of Darwinian evolution appears to be universally active.

"In viruses, mutation is linked to changes in nucleic acid sequence that leads to resistance.

"Now, this adaptability has moved one level down- to prions and protein folding - and it's clear that you do not need nucleic acid (DNA or RNA) for the process of evolution."

Mammalian cells normally produce cellular prion protein or PrPC.

During infections, such as the human form of mad cow disease known as vCJD, abnormal or misfolded proteins convert the normal host prion protein into its toxic form by changing its conformation or shape.

"It was generally thought that once cellular prion protein was converted into the abnormal form, there was no further change", Mr Weissmann said.

"But there have been hints that something was happening.

"When you transmit prions from sheep to mice, they become more virulent over time.

"Now we know that the abnormal prions replicate, and create variants, perhaps at a low level initially.

"But once they are transferred to a new host, natural selection will eventually choose the more virulent and aggressive variants."

Professor John Collinge, of the Medical Research Council's (MRC) Prion Unit, described the research as exciting confirmation of a hypothesis that he had proposed two years ago, that there could be a "cloud" or whole array of prion proteins in the body.

He called it the cloud hypothesis.

He said: "The prion protein is not a clone, it is a quasi-species that can create different protein strains even in the same animal.

"The abnormal prion proteins multiply by converting normal prion proteins.

"The implication of Charles Weissmann's work is that it would be better to cut off that supply of normal prion proteins rather than risk the abnormal prion adapting to a drug and evolving into a new more virulent form.

"You would do this by trying to block the sites on the normal prion protein that the abnormal form locks on to to do its conversion.

"We know there is an antibody that can do this in mice and the Medical Research Council's Prion Unit have managed to engineer a human antibody to do this.

Chemical libraries

"It is currently undergoing safety tests and we hope to move to clinical trials by the end of 2011"

Professor Collinge said the MRC was also trying to find more conventional chemical compounds to do this and has been collaborating with the chemical company GlaxoSmithKline (GSK).

He said: "They have given us access to their chemical libraries, which contain millions of compounds, and we have already identified some that may work well.

"This is a timely reminder that prion concerns are not going away and that controls to stop abnormal prions being transmitted to humans through the food system or through blood transfusions must be vigorously maintained."