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Earth"s Inner CoreScientists have long struggled to understand what lies at the planet"s center. Direct observation of its center is impossible, so researchers must 1 to other evidence.In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves 2 jolts (晃动) from one side of Earth through the center to the other side. Then in 1936, Danish geophysicist lnge Lehmann studied the waves" 3 to determine that within Earth"s core of molten (熔化了的) iron lies a solid inner core—but 4 that core was made of eluded (难倒) her. Other geophysicists quickly determined that Lehmann"s inner core was composed mostly 5 iron. Since then, Lehmann"s discovery has 6 conventional Earth science.But now scientists are challenging traditional theory with new and radical 7 . For example, Earth"s center could actually contain an "inner core within the inner core", claim Ishii and colleague Adam Dziewonski.Analyzing hundreds of thousands of earthquake wave 8 , they maintain that the inner core has at its heart a tiny, even more solid sphere (球体). This sphere "may be the oldest fossil 9 from the formation of Earth," says Dziewonski.Dziewonski and Ishii speculate that shortly 10 Earth formed around 4.8 billion years ago, a giant asteroid (小行星) smashed into the young planet and nearly melted it. But Earth"s center didn"t quite melt; it 11 mass as the planet cooled. The core within a core may be the kernel (核心) that endured. "Its presence could change our basic ideas about the 12 of the planet," Dziewonski says.Dziewonski"s idea is tame (温和的) compared to the 13 theories of independent geophysicist J. Marvin Herndon. Earth"s inner core is made not of iron, he claims, but a 14 of nickel and silicon. Herndon has a truly revolutionary notion: Within the nickel silicide (硅化物) inner core is also an "inner" inner core—an 8 km-wide ball of the element uranium. Uranium is radioactive. Herndon thinks the uranium releases heat energy as its atoms 15 fission-split and crash into one another in a chain reaction. In other words, we may live on top of a gigantic, "natural" nuclear power plant.
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The Exploding Lakes of CameroonWhat comes to mind when you think of a lake You probably imagine a pretty scene with blue water, birds, and fish. For the people in the northwestern Cameroon, however, the image is very different. For them, lakes may mean terrible disasters. In 1984, poisonous gases exploded out of Lake Monoun and came down into the nearby villages, killing thirty-seven people. Two years later, Lake Nyos erupted. A cloud of gases rolled down the hills and into the valleys and killed 1,700 people.Lake Nyos and Lake Monoun are crater (火山口) lakes. They were formed when water collected in the craters of old volcanoes. The volcanoes under Lake Nyos and Lake Monoun are not active anymore. However, poisonous gases from the center of the earth continue to flow up through cracks in the bottom of the lake. This is normal in a crater lake. In most crater lakes, these gases are released often because the water "turns over" regularly. That is, the water from the bottom of the lake rises and mixes with the water at the top, allowing the gases to escape slowly.However, in Lakes Nyos and Monoun, there is no regular turning over. No one knows the reason for this fact, but as a result, these lakes have more gases trapped at the bottom than other crater lakes. In fact, scientists who have studied Lakes Nyos and Monoun have found 16,000 times more gases. When a strong wind, cool weather, a storm, or a landslide (滑坡) causes the water to turn over suddenly, the gases escape in a violent explosion.In the past, no one knew when the gases might explode, so there was no way for the villagers to escape disaster. Now scientists from the United States, France, and Cameroon have found a way to reduce the gas pressure at the bottom of Lake Nyos. They stood a 672-foot plastic pipe in the middle of the lake, with one end of the pipe near the bottom and the other end in the air. Near the top of the pipe, the team put several holes that could be opened or closed by a computer. Now, when the gas pressure gets too high, the holes are opened and some of the gas-filled water shoots up through the pipe into the air like a fountain. With less pressure, a disastrous explosion is much less likely. However, the scientists are not sure that one pipe will be enough to prevent explosions. They hope to put in others soon and they plan to install a similar pipe and a computer system at Lake Monoun as well.To protect people nearby until all of the pipes are in place, the scientists have installed early warning systems at both lakes. If the gas pressure rises to a dangerous level, computers will set off loud sirens (警报) and bright lights to warn the people in the villages. That way, they will have time to escape from the dangerous gases. A team of scientists has
More Than a Ride to SchoolThe National Education Association claims, "The school bus is a mirror of the community." They further add that, unfortunately, what appears on the exterior does not always reflect the reality of a chosen community. They are right—sometimes it reflects more! Just ask Liesl Denson. Riding the school bus has been more than a ride to school for Liesl.Bruce Hardy, school bus driver for Althouse Bus Company has been Liesl"s bus driver since kindergarten. Last year when Liesrs family moved to Parkesburg, knowing her bus went by her new residence, she requested to ride the same bus.This year Liesl is a senior and will enjoy her last year riding the bus. She says, "It"s been a great ride so far! My bus driver is so cool and has always been a good friend and a good listener. Sometimes when you"re a child adults do not think that what you have to say is important. Mr. Hardy always listens to what you have to say and makes you feel important." Her friends Ashley Batista and Amanda Wolfe agree.Bruce Hardy has been making Octorara students feel special since 1975. This year he will celebrate 30 years working for Althouse Bus Company. Larry Althouse, president of the company, acknowledges Bruce Hardy"s outstanding record: "You do not come by employees like Bruce these days. He has never missed a day of work and has a perfect driving record. He was recognized in 2000 by the Pennsylvania School Bus Association for driving 350,000 accident free miles. Hardy"s reputation is made further evident through the relationships he has made with the students that ride his bus."Althouse further adds, "Althouse Bus Company was established 70 years ago and has been providing quality transportation ever since. My grandfather started the business with one bus. Althouse Bus Company is delighted to have the opportunity to bring distinctive and safe service to our local school and community and looks forward to continuing to provide quality service for many more years to come."Three generations of business is not all the company has enjoyed. Thanks to drivers like Bruce Hardy, they have been building relationships through generations. Liesl"s mother Carol also enjoys fond memories of riding Bruce Hardy"s bus to the Octorara School District. Althouse Bus Company pays much attention to
The Exploding Lakes of CameroonWhat comes to mind when you think of a lake You probably imagine a pretty scene with blue water, birds, and fish. For the people in the northwestern Cameroon, however, the image is very different. For them, lakes may mean terrible disasters. In 1984, poisonous gases exploded out of Lake Monoun and came down into the nearby villages, killing thirty-seven people. Two years later, Lake Nyos erupted. A cloud of gases rolled down the hills and into the valleys and killed 1,700 people.Lake Nyos and Lake Monoun are crater (火山口) lakes. They were formed when water collected in the craters of old volcanoes. The volcanoes under Lake Nyos and Lake Monoun are not active anymore. However, poisonous gases from the center of the earth continue to flow up through cracks in the bottom of the lake. This is normal in a crater lake. In most crater lakes, these gases are released often because the water "turns over" regularly. That is, the water from the bottom of the lake rises and mixes with the water at the top, allowing the gases to escape slowly.However, in Lakes Nyos and Monoun, there is no regular turning over. No one knows the reason for this fact, but as a result, these lakes have more gases trapped at the bottom than other crater lakes. In fact, scientists who have studied Lakes Nyos and Monoun have found 16,000 times more gases. When a strong wind, cool weather, a storm, or a landslide (滑坡) causes the water to turn over suddenly, the gases escape in a violent explosion.In the past, no one knew when the gases might explode, so there was no way for the villagers to escape disaster. Now scientists from the United States, France, and Cameroon have found a way to reduce the gas pressure at the bottom of Lake Nyos. They stood a 672-foot plastic pipe in the middle of the lake, with one end of the pipe near the bottom and the other end in the air. Near the top of the pipe, the team put several holes that could be opened or closed by a computer. Now, when the gas pressure gets too high, the holes are opened and some of the gas-filled water shoots up through the pipe into the air like a fountain. With less pressure, a disastrous explosion is much less likely. However, the scientists are not sure that one pipe will be enough to prevent explosions. They hope to put in others soon and they plan to install a similar pipe and a computer system at Lake Monoun as well.To protect people nearby until all of the pipes are in place, the scientists have installed early warning systems at both lakes. If the gas pressure rises to a dangerous level, computers will set off loud sirens (警报) and bright lights to warn the people in the villages. That way, they will have time to escape from the dangerous gases. What do we learn from the last paragraph
A Phone That Knows You"re BusyIt"s a modern problem: you"re too busy to be disturbed by incessant (连续不断的) phone calls so you turn your cellphone off. But if you don"t remember to turn it back on when you"re less busy, you could miss some important calls. If only the phone knew when it was wise to interrupt you, you wouldn"t have to turn it off at all. Instead, it could let calls through when you are not too busy.A bunch of behavior sensors (传感器) and a clever piece of software could do just that, by analyzing your behavior to determine if it"s a good time to interrupt you. If built into a phone, the system may decide you"re too busy and ask the caller to leave a message or ring back later.James Fogarty and Scott Hudson at Camegie Mellon University in Pennsylvania based their system on tiny microphones, cameras and touch sensors that reveal body language and activity. First they had to study different behaviors to find out which ones strongly predict whether your mind is interrupted.The potential "busyness" signals they focused on included whether the office doors were left open or closed, the time of day, if other people were with the person in question, how close they were to each other, and whether or not the computer was in use.The sensors monitored these and many other factors while four subjects were at work. At random intervals, the subjects rated how interruptible they were on a scale ranging from "highly interruptible" to "highly not-interruptible". Their ratings were then correlated with the various behaviors. "It is a shotgun (随意的) approach: we used all the indicators we could think of and then let statistics find out which were important," says Hudson.The model showed that using the keyboard, and talking on a landline or to someone else in the office correlated most strongly with how interruptible the subjects judged themselves to be.Interestingly, the computer was actually better than people at predicting when someone was too busy to be interrupted. The computer got it right 82 per cent of the time, humans 77 per cent. Fogarty speculates that this might be because people doing the interrupting are inevitably biased towards delivering their message, whereas computers don"t care.The first application for Hudson and Fogarty"s system is likely to be in an instant messaging system, followed by office phones and cellphones. "There is no technological roadblock (障碍) to it being deployed in a couple of years," says Hudson. The computer performed better than people in the study because
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