2011年公共英语二级考试考前每日一练（3.11）

文章作者 100test 发表时间 2011:03:11 18:08:06
来源 100Test.Com百考试题网

2011年公共英语二级考试考前每日一练（3.11）。百考试题#0000ff>公共英语等级考试站为您接下来的考试做足准备，一举拿下公共英语等级考试！ 　　Putting Plants to Work
　　Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels for
　　decades. But plants are the real experts : Theyve been using sunlight as an energy source for billions of years.
　　Ceils in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into1 sugars and
　　starches, stored energy that the plants can use. This conversion process is called photosynthesis. Unfortunately, unless
　　youre a plant, its difficult and expensive to convert sunlight into storable energy. Thats 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 miniature photosynthetic power
　　stations. For example, Mafia Ghirardi of the National Renewable Energy Laboratory in Golden, Colo. 2, is working with green
　　algae3. Shes trying to trick them into producing hydrogen4 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 air free environment. Its the
　　oxygen in the air that prevents algae from making hydrogen most of the time.
　　Working in an air free environment, however, is difficult. Its not a practical way to produce cheap energy. But Ghirardi and
　　her colleagues have discovered that by removing a chemical called sulfate 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 algaes 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.
　　Theres a lot of flexibility in how you can use these organisms. "
　　词汇:
　　panel n. 嵌板，发热板，仪器板 miniature adj. 口巧.微型的
　　carbon dioxide 二氧化碳 algae n. 水藻，海藻
　　starch n. 淀粉 sulfate n. 硫酸盐，硫酸酯
　　photosynthesis n. 光合作用
　　注释:
　　1. convert.., into... : 将……转换为……
　　2. Colo. : Colorado，(美国科罗拉多州)的缩写形式
　　3. Green algae: 绿藻
　　4.trick them into producing hydrogen: 想方设法使它们产生氢。trick作为动词，有“欺骗、哄骗”的意思，但是在这里的意思是“设法”
　　或“采取措施”。

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