Americans mark 10th anniversary of September 11 attacks

Americans Sunday remembered the horror of September 11, 2001, and the nearly 3,000 people who died in the hijacked plane attacks as authorities worked to ensure the emotional 10th anniversary was peaceful.

Law enforcement authorities in New York and Washington were on high alert against what was described as a "credible but unconfirmed" threat of an al Qaeda plot to attack the United States again a decade after the toppling of the World Trade Center's twin towers by hijacked airliners.

Security was especially tight in Manhattan, where police set up vehicle checks on city streets as well as bridges and tunnels coming into the city.

President Barack Obama and former President George W. Bush, who was president at the time of the attacks, were scheduled to be among the dignitaries at the Ground Zero site in New York.

They were set to join victims' families to hear the reading of the names of those who died on September 11. Bells will toll across the city.

In the attacks, 19 men from the Islamic militant group al Qaeda hijacked airliners and crashed them into the World Trade Center, the Pentagon outside Washington and a field in Shanksville, Pennsylvania.

Zeros to heroes: The tragic fate of a genetic pioneer

WHEN Paul Kammerer shot himself on an Austrian hillside in 1926, he seemed destined to be remembered only as a scientific fraudster who had faked his results to prove a controversial theory. In fact, he might well have glimpsed epigenetics, influential changes in gene activity that do not involve alterations to the DNA sequence.

Kammerer was infamous for his experiments on the midwife toad, Alytes obstetricans (pictured above), an unusual amphibian which mates and raises its eggs on dry land. By keeping toads in unusually hot, dry conditions, he drove them to breed and raise their eggs in water.

Only a few eggs hatched, but the offspring of these aquatic unions also bred in water. Kammerer claimed this as proof of Lamarckian inheritance - the idea (now known to be wrong) that traits acquired during an individual's lifetime can be passed on to its offspring.

In August 1926, Kammerer was condemned as a fraud in the pages of Nature (vol 118, p 518). He killed himself six weeks later. The sad story was largely forgotten until 1971, when Arthur Koestler published a book claiming that the biologist's experiments may have been tampered with by a Nazi sympathiser. Kammerer was a socialist who was planning to build an institute in the Soviet Union, which would have made him a target of Vienna's burgeoning Nazi movement.

Then, last year, biologist Alex Vargas of the University of Chile in Santiago re-examined Kammerer's work. He was not a fraud, Vargas suggests, but had inadvertently discovered epigenetics (Journal of Experimental Zoology B, vol 312, p 667). "Kammerer had the right approach," says Vargas, who hopes that the toad experiments will one day be repeated.

We now know that the patterns of inheritance of the kind Kammerer claimed to have seen can be due to epigenetics. This process is central to molecular biology, and numerous drugs based on it are in development. It would have been discovered regardless of Kammerer - but perhaps we would not still be waiting for those drugs if he had been taken seriously.