六级听力

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听力材料：

　　Some people who have naturally curly hair prefer tohave it straightened.

　　Others with straight hair want to have curls.

　　“It is kind of like the way I see the world, like thelens through which I see the world and I always waswondering about how we can think about this from amechanical engineering perspective."

　　Hair irons can take many shapes but are essentially clips or rods with heated surfaces.

　　“If you go to the mall right now you see an aisle full of straightening irons, and they have termslike iron technology and twirling."

　　The heat weakens or breaks a protein called keratin, responsible for the hair's shape, andtemporarily changes it.

　　But nobody knows exactly at what level the heat can actually cause permanent damage.

　　“If we understand the onset at which that happens than we might be able to intervene beforeor give some suggestions before you get to that point."

　　In a Purdue University lab, a movable flat hair iron goes over a hair strand while an infraredmicroscope measures the changes in the hair's structure.

　　Researchers say early results are a bit inconclusive.

　　It turns out that everyone's hair is different and that there's no exact temperature where hairstraightening becomes hair damage.

　　For example, people with naturally curly hair can suffer more damage from heat irons thanthose with straight hair.

　　Reid says they will continue their research in the hopes of finding that heat sweet spot forstylists.