VOA标准英语2010年-Our World - 6 March 2010（在线收听）

This week on Our World: A newly documented and source of climate-changing greenhouse gas ... Rubber-stamping the nuclear power option ... and how second-hand tobacco smoke is putting teenagers at risk for heart disease.

LaVAN:  "Now, this is important because these kids are at higher risk for the development of plaque in their arteries as time goes by."
 
Those stories, a one-click solution for translating web pages, and more.

I'm Art Chimes. Welcome to VOA's science and technology magazine, "Our World."

New Global Warming Threat as Methane Bubbles Up from Under Arctic Ocean

Among the various kinds of greenhouse gases that accumulate in the atmosphere, trap solar heat and contribute to global warming, carbon dioxide gets the most attention. It comes from burning wood or fossil fuels like coal and oil, and many other sources.

But an even more powerful greenhouse gas is methane. Methane comes from human activities, too, but also from many natural sources, including animals and from gas released from melting permafrost.

Scientists have been tracking the release of methane in Siberia, but new research out this week identified permafrost offshore, under the Arctic Ocean, as a significant contributor of methane escaping into the atmosphere.

An international research team headed by scientists at the University of Alaska Fairbanks described the methane emissions this week in the journal Science.

Lead author Natalia Shakhova and her colleagues measured methane bubbling up from the East Siberian Arctic Shelf at about seven teragrams a year, or seven million metric tons. That's only about one percent or so of global methane emissions.

SHAKHOVA:   "But considering that we deal with [East Siberian] Arctic shelf, which has never been considered a source of methane to the atmosphere, this is a significant amount, and especially if compared with the total emissions from the world's oceans."

In this study, the researchers measured methane levels in the water and in the air above the Arctic Sea over a six-year period. They found lots of ups and downs in their measurements.  In a Science magazine podcast, Shakhova said that it's too soon to know whether their measurements are typical, or to predict future releases of a key greenhouse gas, but it's important to establish a baseline.

SHAKHOVA:   "It's definitely not a linear process. This is what I mean. This is just the very first phase in our work. This is kind of to set up a reference point. From this reference point we can focus on, because having no background, having no initial estimates it's hard to provide details."

The East Siberian Arctic Shelf, where Shakhova and her colleagues did their research, is rich in methane, and it's also relatively shallow, so it's more susceptible to warming than deeper waters. And methane release from this area appears to be part of the kind of feedback loop that some climate scientists have described.  In this case, the methane is released as warmer temperatures melt the permafrost, which releases the greenhouse gas methane, which contributes to warming, which melts more permafrost, which releases more methane ... and on and on.

Rare Polar Bear Fossil Traces Origin to Common Brown Bears

And another story this week from the northern latitudes ... A scientific analysis of a rare polar bear fossil indicates that the large, white-coated mammals evolved in the relatively recent past from common brown bears.  As VOA's Jessica Berman reports, the discovery suggests polar bears' ancestors migrated toward the North Pole in response to global warming thousands of years ago, and adapted quickly to their new Arctic habitat.

BERMAN:  Scientists analyzing the rare fossil, found in Norway's northern Svalbard islands in 2004, conclude that polar bears appear to have evolved from brown bears 150-thousand years ago  - a mere blink of an eye on the earth's geological  timeline. 
 
The genetic evidence comes from an unusually well-preserved polar bear jawbone with a canine tooth still attached to it - a rare find because most polar bear carcasses are consumed by scavengers or sink to the sea bottom.  The DNA mapped from the jawbone is the earliest mammalian genome ever sequenced.

Researchers have long suspected that the arctic-dwelling animals evolved from brown bears because of their present-day genetic similarities.  But scientists could not confirm an evolutionary timeline.   Estimates of the origins of polar bears have ranged all the way from 150,000 years ago to one million years ago.   But a comparison of the DNA in the polar bear fossil and in a group of modern brown bears living on a group of islands off the Alaskan coast showed the two genomes more closely related than they are today.

The researchers were able to estimate that the polar bears' ancestors branched off from the brown bear population when they headed north and adapted to the Arctic habitat, becoming a separate species about 150,000 years ago.

Charlotte Lindqvist, an evolutionary biologist at the University of Buffalo in New York, led the research.  Lindqvist says the fossil appears to be that of an adult male approximately the same size as modern polar bears.

LINDQVIST:  "We found that it probably had a diet similar to polar bears today.  And from the stratus from where the fossil was found, we can see that it lived in an environment probably similar as today.  So, this means that very rapidly polar bears probably adapted to a habitat very similar to what we see today."

BERMAN:  Lindqvist and colleagues theorize that one reason for the migration of brown bears to the Arctic may have been to escape the interglacial warming of the late Pleistocene period.

It's possible that Svalbard, where the fossil was found, served as a refuge for bears attempting to survive rising temperatures during this climate change, according to co-researcher Stephan Schuster of the University of Pennsylvania Center for Comparative Genomics.

SCHUSTER:  "It is questionable how they would survive this, and I think the most logical scenario would be that they were following the cold weather. And Svalbard would have been this kind of environment, where the polar bears could have gone and survived this warming period."
 
BERMAN:  Even today, notes the University of Buffalo's Charlotte Lindqvist, brown bears have been spotted wandering into areas considered to be polar bear habitats in the Canadian Arctic, suggesting that current warming trends may once again be impacting brown bear populations.

Lindqvist and her research team plan further genetic analysis of the polar bear fossil, which should yield clues about the migration routes taken by brown bears to the Arctic and the bears' rapid adaptation to the polar environment.

An international team of researchers described the polar bear fossil in the Proceedings of the National Academy of Sciences. 

Jessica Berman, VOA News, Washington

Teens Exposed to Tobacco Smoke Show Blood Vessel Damage

A new study has found that teenagers who are exposed to second-hand tobacco smoke are more likely to experience changes to their blood vessels that could lead to heart disease later in life.

Lead researcher Katariina Kallio of the University of Turku in Finland told me that her study on teenagers extends previous research, which found cardiovascular damage in grown-ups who breathed in other peoples' smoke.

KALLIO:  "We know previously that that in adults there is that kind of association, but we didn't know that in adolescents. So somehow it was a surprise that there is already in adolescents these kinds of changes."

The changes include thicker walls in the youngsters' blood vessels. American Heart Association spokesman Dr. Donald LaVan explains why that change in the arteries is significant.

LaVAN:  "Now, this is important because the blood vessel wall, when it becomes thickened and the lining is disturbed, is more sensitive to the effects of cholesterol deposition. So therefore, these kids are at higher risk for the development of plaque in their arteries as time goes by."

Plaque inside the artery can restrict blood flow, and it makes blood clots more likely, blood clots that can block an artery and cause a heart attack.

In their study, the Finnish researchers tested blood for a chemical [cotinine], which is produced when nicotine is metabolized, so they got an objective measure of how much smoke the teenagers were exposed to. They also did ultrasound and other tests to measure blood vessel function and the thickness of the artery wall.

Dr. LaVan agreed with Dr. Kallio that the results support the recommendation that kids need to be kept away from tobacco smoke.

KALLIO:  "Exposure to tobacco smoke is a risk factor for cardiac disease already in adolescents, and that's why this study supports that children and adolescents need smoke-free environments."

Although there is some evidence that artery damage caused by second-hand smoke in adults may be reversible, LaVan says it's unclear whether that's also true for adolescents.

LaVAN:  "That's a good question. We think that they may be. We do know that people who are taken out of high tobacco smoke environments have a definite drop in developing coronary artery disease. There's been studies that show that in adults, when they're taken away, it is a prevention."

Dr. Donald LaVan is a medical school professor and he is also a spokesman for the American Heart Association, which publishes the journal where this research paper appears this week - Circulation: Cardiovascular Quality and Outcomes.

Earliest Signs of Glaucoma Seen in the Brain

Another health story now: Glaucoma is one of the leading causes of blindness, especially for people over age 60 and those with a family history of the disease.

Now, researchers report that the first sign of glaucoma begins in the brain, and it may have global implications for the treatment of the disease known as the 'silent thief of sight'.

Philip Graitcer reports.

GRAITCER:  Worldwide, glaucoma is the leading cause of irreversible loss of vision.

CALKINS:  "Some estimations predict that by the year 2020, we will have 80 million cases of glaucoma worldwide."

GRAITCER:  Dr. David Calkins is the director of research at the Vanderbilt Eye Institute in Tennessee. He explains that increased fluid pressure inside the eye, known as ocular pressure, damages the optic nerve, which sends visual images to the brain. Damaged nerve cells cannot be replaced or repaired, so vision is gradually lost permanently.

Presently, there is only one treatment for glaucoma - reduce ocular pressure. Doctors test for glaucoma by measuring pressure inside the eye and checking peripheral vision.

But Calkins and his colleagues have discovered that the earliest signs of glaucoma are not in the eye … but in the brain.

CALKINS:  "We don't really understand why it is that there is a loss of communication at the brain first."

GRAITCER:  Calkins says the finding suggests that at least in the early stages of glaucoma, the disease may be reversible, because the nerve structures between the brain and the optic nerve do not degenerate right away.

CALKINS:  "The structure that allows the communication remains in place for a very, very long time."

GRAITCER:  And that, says Calkins, opens up new ways to treat glaucoma and puts it in an entirely new perspective.

CALKINS:  "Instead of treating it just as a disease of the eye, we now understand that it is really a neurological disease that involves loss of communication between the optic nerve and the brain."

GRAITCER:  And, by studying glaucoma as a neurological disease, Calkins says researchers may be able to learn more about other age-related neuro-degenerative disorders like Alzheimer's and Parkinson's Disease.

The study appeared in Proceedings of the National Academy of Sciences. I'm Philip Graitcer.

Website of the Week Explores World of Sub-Atomic Particles

Time again for our Website of the Week, when we showcase interesting and innovative online destinations.

The world of physics has changed a lot since I went to school. More powerful particle accelerators - atom smashers, they used to call them - have allowed physicists to learn ever more about the sub-atomic particles that are the basic building blocks of all matter. This week we feature a website where you can learn your physics from some of the people on the forefront of the most fundamental science there is.

BARNETT:   "Essentially, The Particle Adventure is an interactive tour of the world of quarks, neutrinos, antimatter, extra dimensions, dark matter, Higgs boson, as well as accelerators and particle detectors."

Michael Barnett is a physicist at the Lawrence Berkeley Laboratory in California and one of the people behind The Particle Adventure at particleadventure.org.

When visitors go to the site, they have a choice about how to begin their adventure.

BARNETT:   "Well, there's three basic paths they can go through. The first one is the Standard Model, which is basically the theory of what we know now. There's another path by which they can learn about accelerators and particle detectors - essentially, how do we know any of this. Finally, there's a section that talks more about the unsolved mysteries and particularly the role that the Large Hadron Collider would play in that."

The Large Hadron Collider, of course, is the world's largest particle accelerator located near Geneva, where we reached Barnett.

The website is overseen by a group of working physicists, but you don't need a Nobel Prize to join in the adventure of sub-atomic particles.

BARNETT:   "Our target audience originally was high school students, but I think it's also the general public, people who are interested in science in general, and we certainly have had tremendous feedback from both groups. We've even heard of people as young as a fifth grader who got a lot out of the site."

For a free and highly readable introduction to the world of particle physics - available in 15 languages as well as English - transport yourself to particleadventure.org, or get the link from our site, VOAnews.com.

MUSIC:  DeWolfe Music - "Clockwerk"

You're listening to Our World, the weekly science and technology magazine from VOA News. I'm Art Chimes in Washington. 

The latest beta release of the free Google web browser, Chrome, has a new feature you might find of interest: automatic translation of web pages to your own language.

When the browser detects that a web site is in another one of Google's 50-odd languages, it offers to present the information translated - almost instantly, with just one click - into your preferred language.

Translation is still a bit of a black art, and computer translation is rarely perfect. Sometimes it's pretty good, but we're still a long way from the universal translator device that has been a fixture of science fiction for years.

Perfect translation or not, Google software engineer Jay Civelli explains in a video that the feature will give you at least an idea of what the page is about.

CIVELLI:   "Sometimes the translations come out better than other [times], but you can usually get the gist of what the page is about. You can use the translate feature for whatever you're into, whether it's Korean phones, French cooking, or Brazilian soccer."

If you would like to see for yourself, you can get the free download at google.com/chrome, and click on the link "Try the latest BETA version."
And finally today ... A big chunk of the world's electricity is generated by burning fossil fuels, like coal.

They're burning coal more cleanly these days - producing less sulphur and particulates - but fossil fuels are still a big source of greenhouse gases that cause global warming.

There are alternatives, such as wind and solar, but many analysts feel they can't meet all our energy needs, and may never be able to.

Which is why even some environmentalists are looking again at nuclear power. Nuclear reactors produce radioactive wastes, but no greenhouse gases.

President Barack Obama has recently announced loan guarantees to kick-start construction of the first new reactor in the U.S. in 30 years. But as Shawn Allee reports, the real action in the nuclear industry is focused on extending the life of the old reactors, most of which are decades old.

ALLEE:  To run a reactor, you have to have the federal government's permission, but that permission lasts 40 years. If a company wants more time, it's got to renew that license - for 20 years at a pop. Companies are flooding the government with renewal applications. To understand why, I talk with Don Kreis. He teaches environmental law at the Vermont Law School.

KREIS:  "Think about an automobile that you own, that you've had for a really long time, but it's still working fine."

ALLEE:  Okay. You've got two choices .... you can bet your car repair costs will be low ... or you fork over a hefty wad of cash for a new car.

KREIS:  "Which of those two things are you going to do? Well, you're going to hold onto your old machine ... and run it for as long as it  possibly can be run. Nuclear power plants run in exactly the same way. "

ALLEE:  This is an understatement. It is much cheaper to run an existing nuclear reactor than to build a new one.

In Kreis' home state of Vermont, a company bought an old reactor in 2002. It paid $180 million. To build the same-sized plant new would cost $2.4 billion today.

That's the industry's motivation for license renewal, but only the Nuclear Regulatory Commission can give the final okay. In the past decade, the NRC's approved renewal at 59 reactors, more than half the nuclear fleet. This is too fast for critics.

LYMAN:  "We haven't been happy with the process and I think there are issues with license renewal and the NRC needs to address those."

ALLEE:  That's Edwin Lyman. He's a physicist with the Union of Concerned Scientists, an environmental group. Lyman worries the NRC downplays risk from old reactors. Take the case of the Crystal River reactor in Florida. Last year, workers tried to replace old steam turbines.

LYMAN:  "To do that you have to cut a hole in the containment building. When they did that, they found there was a huge gap that had developed in the containment building that you couldn't see or detect from the outside and they only saw when they cut through it. And so, the question is, was this an age-related issue that people didn't know about."

ALLEE:  The containment building keeps the public safe [from radiation] during accidents. The power company caught the problem after it submitted an application for renewal. Lyman also worries about corroding pipes and reactor vessels.

LYMAN:  "So, there are uncertainties, and these will probably only grow as the fleet of power plants gets older."

ALLEE:  The Nuclear Regulatory Commission says critics like Lyman shouldn't worry about aging reactors.

Samson Lee oversees renewal applications at the NRC. He says old reactors meet the same safety standards new ones do, plus companies have to show they'll manage aging parts.

LEE:  "So if they continue to meet the requirement to ensure the plants are safe, then, you know, we can issue a renewal license."

But as for the charge the renewal process is too quick or easy? Lee says the NRC can say "no."

LEE:  "NRC has returned one application for license renewal."

ALLEE:  "What was that for?"

LEE:  "That was because of poor quality of application."

ALLEE:  "Did that reflect at all on the plant or just the application process?"

LEE:  "It's the application process. This is how they chose to prepare the application."

ALLEE:  So, for now, the biggest problem the NRC has seen during license renewal has been in the paperwork.

Right now, the federal government's handing out renewal licenses, allowing nuclear power plants to run up to 60 years. But there is more to come. The government's prepared to evaluate renewals to let plants run up to 80 years.

For The Environment Report, I'm Shawn Allee.

Support for The Environment Report comes from the Park Foundation, the Gaylord and Dorothy Donnelly Foundation, and the Great Lakes Fishery Trust. You can find more stories - and post your comments - at EnvironmentReport.org.
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That's our show for this week.

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Our program was edited by Rob Sivak. Bob Doughty is the technical director.

And this is Art Chimes, inviting you to join us online at voanews.com/ourworld or on your radio next Saturday and Sunday as we check out the latest in science and technology in Our World.