Controlling Machines with Brain Power / Navy Limits New Sonar Use / African Slaves Reburied

This is SCIENCE IN THE NEWS, from VOA Special English. I'm Sarah Long. And I'm Bob Doughty. This week -- getting monkeys, and possibly humans, to control machines with their brain.

Also, the United States Navy agrees to limits on a new sonar that some call a risk to whales. And, in New York, remains of African slaves are reburied after intensive study.

A device connected to the brain permits monkeys to control a robotic arm with their thoughts. These are the findings of experiments by scientists in the United States. Researchers say this is great news for hundreds of thousands of people who are disabled. Someday, people who cannot move their arms or legs might have the ability to control machines just by thinking.

Scientists at Duke University in North Carolina reported their work in P-L-O-S Biology. This is a new research publication offered free of charge over the Internet by the Public Library of Science. You can read the full report at publiclibraryofscience -- all one word -- dot o-r-g.

The experiments involved two rhesus monkeys with tiny wires placed in several areas of their brains. Each monkey learned to hold a stick to control the movement of a robotic arm. The arm appeared on a computer screen as part of a game.

Later, the researchers disconnected the stick. They wondered if the monkeys could still move the robotic arm on the screen just by thinking. The researchers were not the only ones surprised. They say the monkeys were surprised, too. And their ability at brain control improved over time.

There are different ways such a system could help people who are paralyzed. It might help them communicate by computer through their thoughts. It might help them come to think of robotic arms and other devices as extensions of themselves. It might even help them send messages from the brain directly to the muscles to move their own arms and legs again.

The researchers in North Carolina hope to begin experiments on people next year. They have already shown that people produce brain signals like those the monkeys used in the experiment. But longer studies are needed to prove that the devices are safe and good for more than just simple tasks.

Then, in the future, a person might control a computer or other machine in only the time it takes to think.

The remains of more than four-hundred Africans who died during the Colonial period in American history have been reburied in New York.

The people had been slaves or freed slaves. Workers found the remains in nineteen-ninety-one, as they dug ground for a federal office building in New York City.

The bones were part of a burial ground where historians estimate that twenty-thousand slaves from Africa were buried. The people were brought to North America three-hundred years ago. The African Burial Ground was the largest and oldest known burial place for enslaved and freed blacks.

Earlier this month, many people gathered in New York City to attend a "ceremony of return." The reburials took place in an area of the city where one of the largest slave markets in America once stood. People sang prayers, and political leaders spoke to the crowd.

In nineteen-ninety-three, scientists took the bones found in New York to Howard University in Washington. A team led by Doctor Michael Blakey examined the remains. They wanted to learn more about the lives of slaves in the northern United States. They compared the remains with a collection of bones at Howard University.

The researchers say up to half of the black population in colonial New York died at birth or in the first years of life. Almost half of the remains were those of children under fifteen years old.

Many of the remains showed evidence of poor nutrition and disease. Many had signs of violent wounds to the head. Evidence also suggested that many of the people had been forced to carry heavy loads.

The scientists also examined more than one-million cultural objects recovered from the burial ground. These included beads, tools and children's toys.

Many people were surprised to learn that New York State permitted slavery early in its history. Most people think of the Southern states where slave labor was widely used until the Civil War in the eighteen-sixties. In fact, historians say New York City once had the second most slaves in the United States after Charleston, South Carolina. The Dutch first brought them to colonial New York in the early sixteen-hundreds.

The reburial and research project cost twenty-five-million dollars and took thirteen years to complete. The federal government paid for it. Plans for building on the burial place have been canceled. The ground is now considered an important historic area.

The United States Navy has agreed to limit its use of a new sonar system that critics say could harm whales and other sea animals. The Natural Resources Defense Council, an environmental group, led the effort to restrict the use.

The sonar system is designed to search for submarines that are especially quiet. It sends loud, low frequency sound waves through the water. When the sound waves hit an object, its presence is confirmed. The sound waves can travel farther than sonar in common use today. The noise can be as loud as a rocket launch.

This sonar system and others that produce sound waves are called active sonar. Researchers say there is evidence that all active sonar may threaten sea animals.

Nature magazine recently published findings by British and Spanish researchers. They examined fourteen whales that died on the beach in the Canary Islands last year. The whales got trapped on land a few hours after the start of international naval exercises led by Spain. One American ship took part. The exercises involved the use of mid-frequency sonar.

The scientists found that ten of the whales had bubbles in their blood system. They also discovered evidence that major organs had bled. The researchers say the most likely cause was a form of decompression sickness, also called the bends. This can happen to divers when they rise from deep water too quickly. The pressure change releases bubbles of nitrogen gas into the blood system. These bubbles can block passages.

Traditional thinking is that whales and other ocean mammals are protected against the bends.

The study leader, Paul Jepsen, says more research is needed to learn how the whales got sick. But he says he is sure the mid-frequency sonar was connected. He says the noise may have frightened the whales and led them to surface too quickly. Or, he says, the mid-frequency sonar may have caused the nitrogen bubbles to form in their blood system. Mr. Jepsen is a scientist with the London Zoological Society.

United States Navy officials say there has been no evidence that their new low-frequency sonar harms ocean animals. They say it will improve national security. But Navy officials agreed this month to limit the use to an area off the coast of east Asia. The area includes China, Japan, North and South Korea and the Philippines. But it represents only one percent of the area in which the Navy had first received approval to use the sonar.

Under the agreement, the Navy cannot use the sonar within fifty to one-hundred kilometers of coastlines. It also bars use during seasonal times when whales travel through the area.

Researchers say the sonar could interfere with whale communication. Many whales produce sounds at the same low frequencies.

In August, a federal judge in California had restricted the use of the system, and ordered the negotiation of a final settlement.

All restrictions would be suspended in time of war or increased threat.

The National Resources Defense Council says it is extremely pleased with the agreement. And it says it will start an international effort to seek similar rules about the use of active sonar around the world.

Science in the News was written by Nancy Steinbach, Caty Weaver and Cynthia Kirk, who was also our producer. This is Sarah Long. And this is Bob Doughty. Join us again next week for more news about science, in Special English, on the Voice of America.