【托福培训-阅读】新托福阅读相关背景知识汇总(45)

快速阅读的技巧在于每一段的第一句。想想，TOEFL考试中的每篇文章都是经过千锤百炼的，而好的文章都有一个很好的思路，这种思路经常体现在文章段落的第一句。所以，从理论上来说，你只需阅读文章每个段落的第一句，而不必顾及段落的其他内容。既然，考试不以你对文章的理解计分(而是以你答案对错计分)，你没有理由去关注那些对你答题没有帮助的内容。

polymer gels一种聚合凝胶

　　The following information was part of our display for the SET96 and SET98 Scientific Power to the People Exhibition, The Galleries, Bristol, 20th and 21st March 1998.

　　A POLYMER is a very long molecule rather like a very long piece of string.

　　The borax joins two molecules together to make a large network - rather like a flexible scaffolding. This is cross-linking.

　　This turns the fluid dissolved polymer into a GEL.

　　In oilwells water is pushed down to push oil up. If this breaks through to the production well bore, the well will just produce water. A solution is to block the rock pores with polymer gel to make the well produce oil again. These gels can be made from naturally occurring sugar-based polymers such as Guar and they can be cross-linked with Cobalt or Chromium.

　　Other everyday examples of polymer gels are to be found in non-drip emulsion paints, foods, car tyres and agrochemicals.

　　The polymer that we are using is POLYVINYL ALCOHOL and we are joining the strands together with BORAX. This gel, when coloured, is sold in toyshops as SLIME.