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32 Scientists study how photosynthesis works because they want to_____.
A improve the efficiency of it.
B turn plant sugars to a new form. of energy.
C get more sugars and starches from plants.
D make green plants a new source of energy.
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51.
A increase
B threat
C risk
D decline
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels(太阳能电池板) for decades. But plants are the real experts. They’ve been using sunlight as an energy source for billions of years.
Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide(二氧化碳), and water into sugars and starches(淀粉), stored energy that the plants can use. This conversion process is called
photosynthesis(光合作用). Unfortunately, unless you’re a plant, it’s difficult and expensive to convert sunlight into storable energy. That’s why scientists are taking a closer look at exactly how plants do it.
Some scientists are trying to get plants or biological cells that act like plants, to work as very small photosynthesis power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden. Colo., is working with green algae(水藻). She’s trying to trick them into producing hydrogen instead of sugars when they perform. photosynthesis. Once the researchers can get the algae working efficiently the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity.
The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches. “But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen.” Ghirardi says. For example, algae will produce hydrogen in an airfree environment. It’s the oxygen in the air that prevents algae from making hydrogen most of the time.
Working in an airfree environment, however, is difficult. It’s not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate(硫酸盐) from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present.
Unfortunately, removing the sulfate also makes the algae's cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells’ activity and produce larger quantities of hydrogen.
The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: “You can grow them in a reactor, in a pond. You can grow them in the ocean. There’s a lot of flexibility in how you can use these organisms.”
31 How do plants relate to solar energy？
A They have been using it for billions of years.
B They are the real experts in producing it.
C They have been a source of it.
D They have been used to produce it.
Engineers who build and program robots have fascinating jobs. These researchers tinker(修补) with machines in the lab and write computer software to control these devices. “They’re the best toys out there,” says Howle Choset at Carnegie Mellon University in Pittsburgh. Choset is a roboticist, a person who designs, builds or programs robots.
When Choset was a kid, he was interested in anything that moved — cars, trains, animals. He put motors on Tinkertoy cars to make them move. Later, in high school, he built mobile robots similar to small cars.
Hoping to continue working on robots, he studied computer science in college. But when he got to graduate school at the California Institute of Technology in Pasadena, Choset’s labmates were working on something even cooler than remotely controlled cars: robotic snakes. Some robots can move only forward, backward, left and right. But snakes can twist(扭曲) in many directions and travel over a lot of different types of terrain(地形). “Snakes are far more interesting than the cars,” Choset concluded.
After he started working at Carnegie Mellon, Choset and his colleagues there began developing their own snake robots. Choset’s team programmed robots to perform. the same movements as real snakes, such as sliding and inching forward. The robots also moved in ways that snakes usually don’t, such as rolling. Choset’s snake robots could crawl(爬行) through the grass, swim in a pond and even climb a flagpole.
But Choset wondered if his snakes might be useful for medicine as well. For some heart surgeries, the doctor has to open a patient’s chest, cutting through the breastbone. Recovering from these surgeries can be very painful. What if the doctor could perform. the operation by instead making a small hole in the body and sending in a thin robotic snake？
Choset teamed up with Marco Zenati, a heart surgeon now at Harvard Medical School, to investigate the idea. Zenati practiced using the robot on a plastic model of the chest and they tested the robot in pigs.
A company called Medrobotics in Boston is now adapting the technology to surgeries on people. Even after 15 years of working with his team’s creations, “I still don’t get bored of watching the motion of my robots,” Choset says.
16. Choset began to build robots in high school.
A. Right
B. Wrong
C. Not mentioned
A they are grown in narrow-necked bottles.
B there is no oxygen in the air.
C there is enough oxygen in the air.
D enough starches is stored.
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