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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: A big idea in small planes ...

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Scientists find that even on a bad hair day, the famous male lions of Tsavo still look good to the females ...

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And the science of autumn leaves.

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Make room for some new arrivals in the market for small aircraft. The new airplanes are called very light jets. They are also known by other names including mini jets, microjets and air taxis. The Federal Aviation Administration in the United States expects nearly five thousand to be in service by two thousand seventeen.

The new planes will cost up to fifty percent less than business jets now on the market.

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Eclipse Aviation of Albuquerque, New Mexico, proudly calls itself the manufacturer of the world's first very light jet. The plane is called the Eclipse Five Hundred. It can carry as many as six people. The cost? Just over one and one-half million dollars.

Eclipse has just produced the first plane for the first buyer, businessman David Crowe. And the company says it already has more than two thousand five hundred orders to meet over the next few years.

The Eclipse Five Hundred can fly at a top speed of six hundred eighty kilometers an hour. And it can travel one thousand six hundred kilometers without the need for more fuel.

The company says a top flight level of almost twelve thousand five hundred meters will avoid most severe weather.

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Another very light jet, the A-Seven Hundred AdamJet, is currently under flight testing by Adam Aircraft of Englewood, Colorado. The AdamJet is twelve meters long and can carry up to eight people.

With bigger planes, travelers often have to fly into big cities, then get a car and drive to smaller towns. The mini jets will be able to use smaller airports. In many cases the new aircraft are expected to be used as air taxis for short flights.

Very light jets are designed to be easier to fly than other jet planes. And some versions even include a bathroom for long flights.

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Other companies have also entered the market for very light jets -- including one of Japan's top carmakers. Honda Motor has developed the HondaJet.

Honda expects to produce seventy jets a year. It hopes to have them on the market in two thousand ten.

In August, Honda established the Honda Aircraft Company, with headquarters in Greensboro, North Carolina. Honda appointed HondaJet chief engineer Michimasa Fujino to lead the new business. He spent the past twenty years working to develop a Honda aircraft.

The HondaJet can carry up to eight people. And, like the Eclipse Five Hundred and the AdamJet, it has two engines. But Honda officials say their plane will fly faster than other light jets of its kind. They say it will be able to reach speeds of almost seven hundred eighty kilometers per hour.

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Honda began sales of the HondaJet on October seventeenth. The price is more than three and one-half million dollars.

Very light jets are expected to be popular not just with air taxi companies and businesses whose employees travel a lot. They are also expected to appeal to wealthy people who want something a little sportier than a sports car.

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VOICE TWO:

You are listening to SCIENCE IN THE NEWS in VOA Special English.

In eighteen ninety-eight, two male lions attacked railway workers in the Tsavo [pronounced SAH-voh] area of what is now Kenya. It is said that the lions, over a period of nine months, ate more than one hundred thirty people.

A British military officer finally killed the two animals. He observed that they had no manes. Male lions are known for the thick hair along the top and sides of their necks. Yet other lions that the officer saw also had no manes.

The lions of Tsavo captured people's imaginations. They became the subject of scientific papers and books. The story was also told in the nineteen ninety-six motion picture "The Ghost and the Darkness."

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Researchers, however, now report that most fully grown Tsavo lions do have manes. They found that this was true of eighty-seven percent of the ones they observed. But the Tsavo lions do not develop their manes as fast as other lions they were compared with.

The Journal of Zoology recently published the results of a study by a team from the Field Museum in Chicago, Illinois.

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The scientists followed the development of lions living in different parts of East Africa during a period of about seven years. They observed the lions in the hot Tsavo valley area of Kenya. They also studied lions in the cooler Serengeti mountains of Tanzania. The team reported that the difference in mane growth appears most closely linked to climate.

The Tsavo lions took eight years to fully develop their manes. The team observed that the lions began to develop their manes later and at a slower rate than the Serengeti lions. The Serengeti lions had longer, thicker manes that were fully grown by age four or five.

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The Serengeti lions reached sexual maturity about the same time their manes were fully developed. The Tsavo lions did not have full manes until after their most sexually active years. But the researchers say even fully grown Tsavo lions with poor manes still mated actively.

The findings suggest that a delay in mane development does not compromise the ability to reproduce. These findings conflict with other recent studies of lions. Some research found that female lions like to mate with males that have darker and more developed manes.

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Leaves on many trees change color in autumn. But why?

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The falling leaves drift by the window

The autumn leaves of red and gold

I see your lips, the summer kisses

The sun-burned hands I used to hold

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OK, more of Nat King Cole later. Here is how scientists explain why leaves change color in the fall.

In the spring and summer, leaves produce a green substance called chlorophyll. Chlorophyll changes sunlight, water and carbon dioxide in the air into food energy. Chlorophyll is also what makes leaves green.

Other chemicals in trees produce other colors. Carotenoids are orange, xanthophylls are yellow and anthocyanins are red.

Scientists say chlorophyll, carotenoids and xanthophylls are present in leaf cells all through the spring and summer. But the green chlorophyll blocks the yellow and orange colors.

In autumn, those colors can be seen because the leaves produce less and less chlorophyll, until the production stops.

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Red leaves are the result of anthocyanin production in autumn. Yet scientists are not sure about the purpose of anthocyanins. Some believe they protect the leaves from too much of the sun's radiation and protect cells from freezing during the cool autumn nights.

Others think anthocyanins may help leaves stay on a tree longer. They say the chemicals may make it possible for the tree to receive more growth chemicals from the leaves before the leaves fall off. The anthocyanins then stay inside the tree and its roots until they are needed again in the spring.

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Leaves fall off many kinds of trees when the weather cools. The leaves slowly close the veins that carry the growth chemicals. And special cells form where the leaves attach to the branches of the tree. These cells cause the leaves to separate from the tissues that connected them to the tree.

The color of autumn leaves may not be the same each year. The colors are affected by the amount of rain that a tree receives. Lack of rain can delay the appearance of the colors.

Warm, wet weather in the autumn will reduce the brightness of the colors that do appear. And extremely cold weather will kill the leaves and cause them to drop early in the season.

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Since you went away the days grow long

And soon Ill hear old winters song

But I miss you most of all my darling

When autumn leaves start to fall

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SCIENCE IN THE NEWS was written by Brianna Blake, Jerilyn Watson and Nancy Steinbach. And special thanks to Kevin Tunison at the National Arboretum in Washington. I'm Bob Doughty.

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And I'm Faith Lapidus. Learn more about science, and download MP3 files of our programs, at WWW.51VOA.COM And be sure to listen again next week for more news about science in Special English on the Voice of America.