【Phat Yeti出品】60-SECOND SCIENCE 官方听力文稿 + 讨论帖 （更新至：2008.03.07）

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60-Second Science_ Aug 6, 2008

Ancient Bones Hold TB Clues
A team of Israeli, Palestinian and German scientists is analyzing DNA from human remains that date back to the ancient city of Jericho to try to understand more about the origins of tuberculosis. Cynthia Graber reports
Clues about modern-day tuberculosis could be found in some 6,000 year old bones. Israeli, Palestinian and German scientists have teamed up to investigate the remnants of diseases in bones excavated from the ancient city of Jericho. It’s an exercise in paleoepidemiology, the study of ancient diseases in mummified bodies and other human remains. The Jericho bones were unearthed by Dr. Kathleen Kenyon half a century ago. The DNA in the samples will be tested for tuberculosis, leprosy, leishmania and malaria. But the focus is on tuberculosis, which is the biggest killer today.
Scientists believe that tuberculosis originated in the Fertile Crescent 9-10,000 years ago. And Jericho is one of the earliest cities on earth, about 11,000 years old. So there’s a good chance TB could have gotten a start there. Researchers will be studying how early cities—the first time people lived in crowds—affected the DNA of microbes and their human hosts. They’ll also be looking at the remains of animals, which could have been disease vectors. Scientists on the team believe there’s sufficient DNA in the samples to provide new information about the origin and evolution of TB, which could help us combat it today.

—Cynthia Graber

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60-Second Science_ Aug 7, 2008

Neandertal Mitochondrial DNA Sequenced
The first full sequence of a Neandertal genome doesn't fully negate the possibility that they mixed with us. But the mitochondrial DNA sequence falls outside the range of current human variation. Steve Mirsky
Neandertals were our closest relatives. And now we know a lot more about them. Because researchers have for the first time sequenced a complete Neandertal genome—that of their mitochondrial DNA. The study appears in the August 8th issue of the journal Cell.
We all have a large genome in our cell nuclei. Then there’s a separate genome only in mitochondria, those organelles forever immortalized in textbooks as the powerhouse of the cell. The Neandertal DNA sequence falls outside the variation range found in humans today. It also confirms that the last common ancestor of us and Neandertals lived some time between 800,000 and 520,000 years ago.

The new info shows that a disproportionate number of Neandertal sequence differences change the amino acid sequences in proteins. One explanation would be that Neandertals had a smaller population size. Which would give natural selection fewer options to choose from. So, did Neandertals mix with our direct ancestors? The sequence finds no evidence for such mixing. But we’ll have to wait for a full nuclear genome sequence to be sure.
—Steve Mirsky

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60-Second Science_ Aug 8, 2008

Solid-State Future Fridge
By taking advantage of polymers that cool down in the presence of an electric field, researchers are on the way toward refrigeration and air conditioning units free of compressors and coils. Steve Mirsky reports
Ever been woken up by the sound of the refrigerator compressor kicking on? Well, such clumsy heat exchange units featuring long metal coils may be on their way out. Because Penn State scientists are investigating the possibility of solid-state refrigerators that take advantage of electric fields to exchange heat.
The researchers work with what are called ferroelectric polymers. When you apply an electric field to these substances, their internal structure goes from random to highly organized. And that makes the material colder. Turn off the electricity and the stuff sucks heat back in.  
In the August 8th issue of the journal Science, the researchers report an electrically induced temperature change of over 22 degrees Fahrenheit. Throw a heat exchanger into the mix and repeatedly zapping the polymers with electricity could make it possible to heat or cool a space over a wide range of temperatures. Before you get a solid-state fridge, though, look for electronics applications. The polymers could cool circuit boards, making it possible to jam more electronics closer together, leading to smaller devices.

—Steve Mirsky

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60-Second Science_ Aug 11, 2008

Civic Planning for Thinner People
Densely populated urban neighborhoods designed to be walkable have thinner people than the car-oriented suburbs. Adam Hinterthuer reports
Apparently all of the gyms in the suburbs can't compensate for a good old walk. At least that's the story told by a report in the September issue of the American Journal of Preventive Medicine. According to the study, people lower their risk of obesity when they live in densely populated, urban neighborhoods.

University of Utah researchers looked at census data from half a million state residents and found that, along with bigger cars and houses, the suburbs have bigger people as well. On average, a male suburbanite weighed 10 pounds more than his city-dwelling counterpart. Women had a weight difference of six pounds. The trend towards slimmer waistlines was especially pronounced in urban neighborhoods that were developed before the 1950's. These neighborhoods were built before our car culture took over, and they boast plenty of parks, restaurants and shops worth walking to, and the sidewalks needed to get people there.

The researchers say their study shows how America's civic planners can help fight the obesity epidemic. By designing new neighborhoods with pedestrians in mind, they can promote slimmer lifestyles and cut down on this new kind of suburban sprawl.
—Adam Hinterthuer

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60-Second Science_ Aug 12, 2008

Pepper Heat Battles Bugs
Hot peppers' heat is a defense against insect-borne infection. Cynthia Graber reports
Some peppers have a mild, fresh flavor. But others burn your lips and leave a lingering, numbing kick. If you enjoy that tingling thrill, you might want to say thanks. But not to the peppers themselves—to bugs. Peppers are tasty so they’ll be eaten and have their seeds dispersed. But the snacker has to be the right creature—which the peppers need to be birds. Some insects also like to munch peppers, and they may puncture the skin. The wound leaves an opening for a microbial fungus. The fungus wriggles inside and snacks on the seeds, destroying them.
Researchers from the U.S. and Bolivia tested whether a pepper’s heat offers it protection. They published August 11th in the Proceedings of the National Academy of Sciences. First, they collected chilies from seven populations of the same pepper species over a thousand-mile area. Then they counted insect-induced scars and tested pepper heat. In regions with lots of insects, and a greater risk of death by microbe, plants tended to be much hotter. And the hot chemicals, called capsaicinonids, slow microbial growth. Birds can’t sense capsaicin. So the hot peppers kill bugs, and still attract birds. And many humans, too.
—Cynthia Graber