This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.
VOICE TWO:
And I'm Steve Ember. This week, we will tell about an effort to place 2,000 year old documents on the Internet. We will tell why two American scientists are concerned about frogs. And we tell about Down syndrome -- a disorder that has been noted in the American election campaign.
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Israeli officials have announced plans to make the Dead Sea Scrolls available on the Internet. Officials say scientists have begun using space technology to take pictures of the scrolls. They say the technology will help uncover some writings that have been hidden for years.
The Dead Sea Scrolls are about two thousand years old. They include pieces from about nine hundred documents. The scrolls contain the oldest known copies of the Hebrew holy book or Bible. They also include descriptions of life for Jews and early Christians during the time of Jesus.
The scrolls were found near the Dead Sea in 1947. They are written on two kinds of paper: parchment or papyrus. Some parts of the documents have become difficult to read over the years.
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The Dead Sea Scrolls are in the possession of the Israel Antiquities Authority. Last month, officials announced that all of the scrolls would be digitally copied and placed on the Internet. The scientists say they are using non-damaging, high-tech imaging technology. Infrared cameras were used to make pictures of the Dead Sea Scrolls not long after they were found. Since then, infrared technology has greatly improved.
Scientists say the new method will show never before seen details. Officials say the imaging process will be done in way that protects the documents from the harmful effects of light and heat.
VOICE ONE:
The imaging technology being used on the scrolls now has also been used in space. Scientist Greg Bearman is taking part in the project. Mr. Bearman recently retired from the American space agency. He says the imaging equipment is used to study planets, but that it also works on the Dead Sea Scrolls.
Officials say the goal of the project is make the scrolls more widely available to researchers and the public. The work is expected to take about five years.
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VOICE TWO:
Two American scientists believe many kinds of wildlife life are in great danger. The scientists say these animals and plants could permanently disappear from Earth. They also say a widespread loss of amphibians in recent years shows that a biological disaster has begun.
Amphibians are land animals that reproduce in water. The scientists studied a well-known amphibian -- the frog. They found that some frog populations are only two to five percent of their normal size. David Wake and Vance Vredenburg reported the finding in the Proceedings of the National Academy of Sciences.
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Mr. Wake teaches at the University of California at Berkeley. Mr. Vredenburg works at the university's Museum of Vertebrate Zoology and teaches at San Francisco State University. Their joint observations represent almost fifty years of research.
The report says at least two hundred species, or kinds of life, have died out during the past twenty years. But the scientists are hopeful about some amphibians. They believe at least some will live through the current threat of extinction.
Professor Wake says people are mainly responsible for conditions that threaten wildlife. He blames human beings for destruction of the animals' habitats or living areas. This often happens when unoccupied land is developed for human use.
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The men and their team did some of the research in the Sierra Nevada Mountains of California. Five of seven amphibian species at the top of the mountains are threatened.
The scientists walked along forty kilometers of streams and lakes to observe the frogs. Mr. Vredenburg says one area -- Yosemite National Park -- is especially well protected. Yet its population of two kinds of frogs dropped sharply in recent years. Ninety-five to ninety-eight percent of the Sierra Nevada Yellow-legged Frog and the Southern Yellow-legged Frogs disappeared during that time.
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Professor Vredenburg says the frogs may have started disappearing in the 1990s. At that time, people were adding rainbow trout to streams and lakes. The fish like to eat frog eggs and young frogs. When the trout were removed, the frogs stopped dying for a time.
Mr. Vredenburg says they came back by the thousands, but later died off again. He says a few hundred yellow legged and Sierra frogs are alive today. That compares with many thousands in the past.
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The University of California team said the frogs died from an infection caused by a fungus. This disease, chytridiomycosis, also has killed many other animals over the past five years. And it has spread to other species around the world.
It is not known how the disease is spread. Birds or wind may be responsible. But experts now have been able to complete a genetic map of the fungus. They hope to develop prevention methods within a year. Mr. Wake notes that new kinds of animal and plant life have developed and died off over the centuries. Sometimes, however, an extinction event takes place. During this time, many more species die out permanently than develop. Mr. Wake says humanity is living in the sixth great extinction event of history. He says human responsibility makes it different from the first five extinction events.
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Scientists disagree about when the present mass extinction began. Some say it may have started about ten thousand years ago. That is when humans began to hunt.
Many large mammals disappeared from Earth during that period. Or, Mr. Wake said, it may have started in the nineteenth century, when the Industrial Revolution began. But he and Mr. Vredenburg believe it already has started.
Mr. Wake says amphibians have lived for two hundred fifty million years. He says they survived when dinosaurs did not. And he warns the fact that amphibians are dying out should send people an important message.
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This month, the governor of Alaska, Sarah Palin, accepted the Republican Party's nomination for vice president. Governor Palin has a son who was born with Down syndrome. She and her husband also have four other children who do not have the disorder.
Human genes are normally organized along forty-six chromosomes -- twenty-three from each parent. But as a result of a mistake in cell division, some people have three copies of the twenty-first chromosome. There are supposed to be just two.
About one in every seven hundred babies has this extra copy. A British doctor, John Langdon Down, first described the condition in the eighteen sixties.
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Many babies with Down syndrome have low muscle tone, so they need extra support when they are held. Their heads are smaller than average and they can have unusually shaped ears. Also, their eyes often point upward.
People with Down syndrome often have other symptoms. These include problems with their heart and with their breathing and hearing. But a lot of the problems are treatable.
As a result, people with Down syndrome are living longer. In nineteen eighty-three, they lived an average of just twenty-five years. Today the average life expectancy is fifty-six. But that longer life has led to a sad discovery. People with Down syndrome may have an increased risk for Alzheimer's disease at an early age. The disease slowly destroys memory, thinking and reasoning skills.
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Down syndrome is the most common genetic cause of mental retardation. Most people with Down syndrome are mildly to moderately retarded. Many are able to attend classes with other students. Later, as adults, many hold jobs and lead independent lives.
There are tests to look for Down syndrome during pregnancy. The risk of it is higher for older mothers. The rate for those under thirty is one in one thousand births. In women age forty-four, like Governor Palin, that number is one in thirty-five.
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VOICE ONE:
This SCIENCE IN THE NEWS program was written by Jerilyn Watson, Caty Weaver and Brianna Blake, who was also our producer. I'm Barbara Klein.
VOICE TWO:
And I'm Steve Ember. Join us again at this time next week for more news about science in Special English on the Voice of America.
Down syndrome:唐氏综合症（最常见的严重出生缺陷病之一。临床表现为：患者面容特殊，两外眼角上翘，鼻梁扁平，舌头常往外伸出，肌无力及通贯手。患者绝大多数为严重智能障碍并伴有多种脏器的异常，如先天性心脏病、白血病、消化道畸形等。）
