自给自足的人体生物能发电

①随着煤炭、石油等资源日趋枯竭，环境恶化日趋严重，一些科学家为了开发更多的新能源，已把研究课题转向人类自身的生物能这一领域，利用人体生物能发电现已初见成效。

②人体中存在着一些化学物质，它们之间在发生反应时会产生化学能量。像新陈代谢过程中，葡萄糖和氧分子的反应就有能量释放出来，若稍加利用，这种能量就可以转化为电能。根据这一原理，科学家开始了人体生物电池的研究。

③据专家介绍，人体生物电池的电极是由两根长2厘米、直径约1/7 000纳米的碳纤维制成，在每根碳纤维的外层还涂有一种聚合物，此外还有一种作为催化剂的葡萄糖氧化酶。聚合物的作用是将碳纤维与葡萄糖氧化酶连接成一个电路，而葡萄糖氧化酶则是用来加速葡萄糖与氧分子的化学反应。这种人体生物电池在37℃、pH为7.2的环境下工作，这很接近人体血液的温度和酸碱度。它产生的动力可以驱动一个监控糖尿病的小型传感器。

④人体生物能发电还有其他形式。当一个人坐着或站立时，就会持续产生重力势能。此时，若能采用特制的重力转换器就能将这种能转换成电能。美国有一家公司将发电装置埋在行人拥挤的公共场所，外面是一排踏板。当行人从板上走过时，体重压在板上，使与踏板相连的摇杆向另一个方向运动，从而带动中心轴旋转，使与之相连的发电机启动。

⑤除此以外，人体生物能中的热能也可被利用。人每天都要散发大量的热能，而且是通过辐射传播出去。一般一个50千克重的成年人一昼夜所散发的热量约为2 500千卡。利用人体的热能制成的温差电池，可以将人体的热能转换成电能。这种温差电池做得很精致，只要放在衣服口袋里就能工作。它可以起到电源的作用，给助听器、袖珍电视机、微型发电机等供电，可谓是自己发电自己使用。

⑥人体能源可以说取之不尽，用之不竭，而且没有污染。如此神奇的能源是我们每个人都具有的，充分利用它，便会为我们的社会节约更多的能源，希望这种新型的能源会越来越多地造福于人类。

（选自《能源科学的奥秘》，有改动）

某篮球队甲、乙两名运动员练习罚球，每人练习10轮每轮罚球30个．命中个数的茎叶图如下．若10轮中甲、乙的平均水平相同，则乙的茎叶图中x的值是(     )

Should Children Be Allowed to Get Bored?

    Children need time to stand and stare. They should be allowed to get bored to that they can develop their ability to be creative.

    Children are expected by their parents to be reading a textbook all the time. However, research shows that it may hamper the development of their imagination, while boredom can give them opportunities to develop creativity.

    Boredom is often linked with loneliness, but a writer named Meera Syal said boredom had helped here in developing her mind. She told researchers about her childhood. Having few things todo, Syal often talked with her neighbors. She also tried to do things like learning to bake cakes. “But importantly, I Thought and wrote a lot, because I was bored,” Syal said. She kept a diary, filling here time with short stories and poems she made up.

    Grayson Perry, an artist, grew up in a family with little money. He enjoyed himself by making up stories, drawing pictures for his stories and reading many books in the library. Bored but free, he spent hours looking out of the window, watching the changing clouds and seasons. Perry filled up his free time with what he liked. He became creative, because he could think freely.

    Dr. Belton is an expert on the effects of emotions on learning. “Boredom could be an uncomfortable feeling,” she said. “But some young people cannot deal with that boredom creatively. So sometimes they may break a classroom window, or drive a car out for a mad race.”

    Usually, when children have nothing to do, they would turn on the TV, the computer, or the phone. Their time on these things has increased, yet they need to have time to think about their experiences through play or just watching the world around them.

    It is this kind of thinking that can inspire the imagination. On the other hand, the TV or phone may cut short the thinking process. That can be harmful to the development of creativity. “For developing the ability to be creative,” Dr. Belton advised, “perhaps we need to stand and stare, and stay off-line from time to time.”