Scientists report progress in tests of a vaccine against the AIDS virus-英语点津

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This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty.

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And I'm Faith Lapidus. This week, we will tell about an experimental vaccine against the disease AIDS. We also will tell about a newly-found hiding place for harmful bacteria. And, we will tell about a discovery that could change scientific beliefs about dinosaurs.

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Researchers say they still have much work to do on a vaccine against the virus that causes AIDS. But the first reports of some success have raised hopes. Scientists say an experimental vaccine reduced the risk of infection in human beings by 31 percent and was safe.

Scientists report progress in tests of a vaccine against the AIDS virus

The study was designed to test for two abilities. One was the ability of the vaccine to prevent infections from the human immunodeficiency virus, better known as H.I.V. The other was the vaccine's ability to reduce the amount of virus in the blood of people who became infected during the study.

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Volunteers received vaccinations over a period of six months. They were tested for H.I.V. for an additional three years. The testing began six years ago. It was the largest AIDS vaccine study yet. It involved more than 16,000 adults in Thailand. Half received the vaccine. The other half received a placebo, or harmless substance. The volunteers did not know which they were getting.

74 people in the placebo group became infected during the study. The researchers say that was compared with only 51 of those who received the vaccine.

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Doctor Supachai Rerks-Ngarm led the study for Thailand's Ministry of Public Health. The United States government paid for the study. Doctor Anthony Fauci of the National Institutes of Health called the findings, an important step forward. He said it represents the first time an investigational H.I.V. vaccine has shown some ability to prevent infection. But he also said additional research is needed to better understand how the vaccine reduced the risk in those individuals.

The vaccine did not lower the amount of virus in the blood of volunteers who became infected during the study.

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The study was based on versions of H.I.V. commonly found in Thailand. The volunteers received a combination of two vaccines. The first, or prime, vaccine came from Sanofi Pasteur. The second, or booster, vaccine was developed by another company, VaxGen. The non-profit group Global Solutions for Infectious Diseases now has rights to it.

Neither vaccine had been successful by itself when tested earlier. More detailed results of the study are expected to be presented at a conference in France later this month.

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We all have heard about harmful bacteria hiding in the home. Studies have discovered evidence of harmful bacteria in toilets, on surfaces where food is prepared, even on home telephones.

Recently, American researchers found harmful bacteria in a place most of us would never suspect. They found that the bathroom showerheads people use to wash up may be covering us with more than water.

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The researchers used a molecular genetics test to examine 50 showerheads from nine American cities. Those showerheads came from homes and public places in Colorado, Illinois, New York, North Dakota and Tennessee.

30 percent of the devices had high levels of Mycobacterium avium, an organism linked to lung disease. The researchers say the bacteria were grouped together in a thin, but sticky area of cells on the inside of showerheads. They say the levels of Mycobacterium avium were 100 times higher than that of normal household water. And, showerheads made of plastic seemed to have higher bacteria levels than metal ones.

One of the showerheads was cleaned with a bleach solution in an effort to destroy the bacteria. Bleach is often used as a whitening agent when washing clothes. Tests showed that instead of killing the bacteria, the bleach actually caused the bacteria levels to increase.

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A report about the study appeared last month in the Proceedings of the National Academy of Sciences.

The lead writer of the report was Norman Pace of the University of Colorado at Boulder. Professor Pace has a warning for people who let water hit their face when they first turn on the shower. He says they probably are getting a full face of the unhealthy bacteria. He says the bacteria can also float around in the air and be easily pulled into the lungs.

The professor says earlier research at National Jewish Hospital in Denver supports this theory. The research suggested that increases in pulmonary infections in the United States may be linked to people taking more showers than traditional baths.

Signs of pulmonary disease caused by Mycobacterium avium can include shortness of breath, a continual dry cough, and feelings of tiredness or weakness.

The researchers say showers may not be a big problem for healthy people. But, they warn that persons with weakened defenses for fighting disease are at greater risk. This includes pregnant women, older adults and people with other diseases.

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Many young children can describe the well-known prehistoric dinosaur, Tyrannosaurus Rex. T. Rex had a big head, long legs and small arms. Its teeth filled a fierce-looking mouth that was heavy with muscles.

Now, try to imagine a dinosaur that looked like T. Rex. But the creature you are imagining is only one-hundredth of T. Rex's size. This describes Raptorex Kriegsteini -- a distant relative of T. Rex. Researchers say Raptorex might have looked like a toy version of the huge creature.

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Raptorex was not a T.Rex. Instead, it belonged to a tyrannosaurid species that lived many millions of years before its T. Rex relative. An examination of Raptorex and its meaning to dinosaur development appeared recently on the Internet version of "Science" magazine.

The small dinosaur is thought to have lived about 125 million years ago. T. Rex lived between 65 and 85 million years ago.

Researcher Stephen Brusatte says scientists have believed that the physical qualities of Tyrannosaurus developed because of its large body. But he notes similar qualities in the smaller Raptorex.

For example, the small arms on T. Rex did not develop as the creature got bigger. Instead, such arms were also present earlier. The researcher says traditional beliefs about Tyrannosaurus' development were too simple -- or wrong.

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Stephen Brusatte is a doctoral candidate at Columbia University in New York. He works with the city's American Museum of Natural History. He helped write about Raptorex Kriegsteini with Paul Sereno of the University of Chicago, the lead writer and researcher.

Professor Sereno says Raptorex Kriegsteini was probably just as effective at killing as T. Rex. He notes that Raptorex's body was about two and seven-tenths meters long. The creature weighed only 68 kilograms, about the same as many people. The professor said it probably died at an early age, living only about five or six years.

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The head of Raptorex Kriegsteini shows evidence of a well-developed olfactory system. The researchers suspect Raptorex had a strong sense of smell. The professor says the body design of the creature made it a kind of jaw on legs. It appeared to be a successful finder and killer of other animals.

Professor Sereno received fossilized remains of the creature three years ago from a private collector in the American state of Massachusetts. The Raptorex Kriegsteini reportedly was discovered inside a single piece of rock in the Inner Mongolia area of China. The fossil was removed from China under mysterious conditions. It had reached the collector, Henry Kriegstein, through sales.

Doctor Kriegstein later sent it to an expert who recognized its importance. The doctor then contacted Professor Sereno. Doctor Kriegstein named the fossil to honor his parents and donated it to science. Paul Sereno said the fossil will be returned to China and put in a museum when the scientists have finished their studies.

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VOICE TWO:

This SCIENCE IN THE NEWS was written by June Simms, Jerilyn Watson and Caty Weaver. Our producer was Brianna Blake. I'm Faith Lapidus.

VOICE ONE:

And, I'm Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.

placebo: a substance containing no medication and prescribed or given to reinforce a patient's expectation to get well 安慰剂

Mycobacterium: rod-shaped bacteria some saprophytic or causing diseases 分枝杆菌属

pulmonary: of, relating to, or affecting the lungs 肺的

Tyrannosaurus Rex: large carnivorous bipedal dinosaur having enormous teeth with knifelike serrations; may have been a scavenger rather than an active predator; later Cretaceous period in North America 暴龙

Raptorex Kriegsteini: 霸王龙

tyrannosaurid: a carnivorous dinosaur family whose name is derived from the Greek words tyrannos, meaning 'tyrant' and sauros, meaning 'lizard'.

olfactory: of or relating to the sense of smell 嗅觉的