Seeing Red Means Danger Ahead
The color red often means danger - and by paying attention, can be prevented. At railroad crossings, flashing red fights warn cars to stay back. A red light at a traffic intersection tells cars to stop, so dont run into other cars.
In the future, the color red also may help prevent danger construction sites. Thanks to1 new work by engineers, bridge supports2 - or other kinds of materials - could one day contain a color-changing material. It will turn red a structure collapses or falls . A tiny molecule may make a big difference in future warning systems.
A polymer a color-changing molecule called a mechanophore turns red seconds before it snaps3. The technology may one day allow damage to materials or structures4 to be easily .
The secret behind the color-changing material is a particular type of molecule. A molecule is a group of atoms held together by bonds. Molecules come in all shapes and sizes, and make up you can see, touch or feel. How a molecule behaves depends on what kinds of atoms it contains, and how theyre held together.
When a polymer containing a color-changing molecule called a mechanophore is about to breaks, it produces a color. When a polymer with mechanophore molecules becomes injured or , one of the mechanophore bonds breaks and the material turns red. Its a really simple detection method, says Nancy Sottos, one of the scientists who worked on the project. Were up this one bond, and it changes color. Sottos and her team tested the color-changing polymers in their lab. The test proved encouraging.
There is a way to get rid of~ the red color: . When a bright light is shone on the mechanophore, the broken bond is fixedrn and the red color disappears. This self-healing may be a problem for engineers. They need to use the color-changer in big construction projects that will be , in sunlight. And sunlight will make the mechanophores warning system useless.
Sottos and her fellow scientists still have work to do before the color-changing molecules can. be used outside the lab.
词汇：
crossing n.十字路口 mechanophore n.机械响应性聚合物 intersection n.交叉路口
molecule n.分子 snap v.折断，断裂 polymer n.聚合物 atom n.原子
注释：
1. Thanks to：多亏，由于
2. bridge supports：桥梁支柱
3. seconds before it snaps：聚合物断裂前几秒钟。Seconds 修饰状语从句 before it snaps。It 指代 polymer。
4. damage to materials or structures：材料或建筑物的损坏。to 是介词。介词短语 to materials or structures 修饰 damage。
5. is about to break：即将断裂。be about to 意为刚刚，行将。
6. get rid of：除去。
7. the broken bond is fixed：断裂的键被修复。Fix 意为修理，修复。
练习：
1 A measures B accidents C actions D collapses
2 A they B it C some D most
3 A with B over C at D in
4 A before B after C once D while
5 A together B behind C down D apart
6 A contacting B conducting C containing D considering
7 A controlled B spotted C repaired D changed
8 A technical B electronic C physical D chemical
9 A everything B something C nothing D anything
10 A weak B strong C tough D soft
11 A using B opening C turning D finishing
12 A laws B theories C tools D results
13 A air B electricity C light D sound
14 A aside B beside C inside D outside
15 A a part of B a pair of C a piece of D a lot of