题干

如图甲所示,小明用弹簧测力计拉木块,使它沿水平木板匀速直线滑动,图乙是他两次拉动同一木块得到的距离随时间变化的图像。下列说法正确的是(   )

A:木块第一次受到的拉力较大

B:拉力第一次做的功多

C:拉力第一次做功的功率大

D:两次拉力做的功一样多

上一题 下一题 0.0难度 选择题 更新时间:2019-11-19 05:39:41

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C

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    The technique can lead to new ways to produce medicines, the researchers from the universities of Istanbul and Hawaii hope.

    As part of an effort to improve treatments for life-threatening illnesses, a team of scientists have created rabbits that glow(发光) in the dark.

    Their efforts produced two rabbits out of a litter of eight that went from being a normal, fluffy white to glowing green in the dark. The rabbits were born at the University of Istanbul as part of a collaboration(合作) between scientists from universities in Turkey and Hawaii.

    The rabbits glow to show that a genetic manipulation technique can work efficiently, though the specific color is more cosmetic than scientific. "The green is not important at all – it's just a marker to show the experiment can be done successfully," said University of Hawaii associate professor Stefan Moisyadi.

    To produce the glowing effect, researchers injected jellyfish DNA into a mother rabbit's embryos. Those altered embryos(胚胎). Those altered embryos were then inserted back into the mother. Similar experiments have resulted in glowing cockroaches and cats.

    Eventually, the researchers hope the technique can lead to new ways to produce medicines, Moisyadi said. “The final goal is to develop animals that act as barrier reactive to produce beneficial molecules in their milk that can be cheaply extracted, especially in countries that can't afford big pharma plants that make drugs, that usually cost $1bn to build, and be able to produce their own protein-based medication in animals," Moisyadi said.

    The rabbits are expected to have the same life span as their non-glowing counterparts(副本), but Moisyadi said he understands people can object to this kind of experimentation involving live animals.

    "To the people against, I say: think about, what are the benefits and what are the injuries?" Moisyadi said. "And if the benefits outweigh the injuries, let's go with the benefits."

    Moisyadi, a native of Turkey who is now with the University of Hawaii, started developing the project in 2006, and researchers are now waiting to see if pregnant sheep produce similar results.