2014年12月英语六级听力备考练习9

英语自学网

　　英语六级听力部分算是同学们考试时的难点吧。听力这部分不能急于求成，需要时间来练习。对于这部分同学们平时在积累词汇的基础上多加练习就可以，听的多了就能掌握技巧，距离12月份的四六级考试还有一段时间，同学每天练习一点听力，考试时听力就能取得高分了。
　　

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听力材料：
　　Three-dimensional printers are rapidlybecoming everyday appliances, much like colorprinters a couple of decades ago. Increasingly,the technology is being used in medicine forprinting bone replacements. And now,researchers in South Carolina are working onprinting living tissue replacements.
　　Researchers at the Medical University of South Carolina have been working on fabricating livingtissue, or biofabrication, since 2003.
　　Researcher Sarah Grace Dennis says new technology, such as the Palmetto bioprinter,advanced the process considerably.
　　“When I got here a year ago, we were printing just a-cellular bio-inks to see if patterns couldbe printed," she said. "Now we are printing skeletal muscle replica implants that we have beenimplanting into rats.”
　　Researchers prepare complex nutritious solutions, called bio-inks, made of glucose, proteinsand living cells taken from the animal that will be the recipient of the new, printed tissue.
　　“So this would typically have at least 1.5 million cells in it,” Dennis said
　　The bio-inks are placed in three interchangeable dispensers of the printer’s head. Position ofthe printing surface and dispensing tip-ends is controlled by lasers.
　　Associate Chairman of Surgery for Research, Dr. Michael Yost, says the printing process is fullyautomated.
　　“And with our 3-D bio-printer, we have been able to create new microvascular networks that wecan then grow new tissues in very key areas such as pancreas, liver and kidney,” he said.
　　Researchers point out the technique is in its early stages, but they hope in a few years theymay be able to print replacement tissue for damaged human organs.
　　“Tissue biofabrication is a reality, and it is a reality now, and if you get to come here you get tosee it," Yost said. "You will get to see it. You can not touch it, but you will see it and think thisis real. And this is really human.”
　　But scientists warn they have to overcome large obstacles, such as how to supply thereplacement tissue with the blood vessels essential for its survival.