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托福听力练习-科学美国人60秒:根据血液判断年龄

2017-06-11 09:27:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：根据血液判断年龄

　　科学美国人60秒听力练习：根据血液判断年龄

　　科学美国人60秒英文文本

　　Taking advantage of T cell by-products, a new technique may make it possible to estimate the age of a victim using only a blood sample. Cynthia Graber reports

　　You’ve seen it on TV. Crime scene investigators show up at what might be a murder scene. There are blood spatters—but no body. Who’s the victim? Now, a new technique developed in the Netherlands might help real-world investigators establish the age of the victim using only blood. The research was published in the journal Current Biology. [Dmitry Zubakov et al., "Estimating human age from T-cell DNA rearrangements"]

　　Usually, age is determined by physical characteristics, such as teeth or bones. Great—if you have a body. Researchers have tried unsuccessfully to use blood. But in this study, the scientists used immune cells called T-cells. T-cells recognize invaders through receptors that match molecules on bacteria, viruses, even tumors. The cellular activity that produces these receptors also produces a type of circular DNA molecule as a by-product.

　　The number of these receptor by-products declines regularly over time. So scientists devised a test to measure the molecules—and use that to infer someone’s age based on his or her blood. The results apear to be accurate to within plus or minus nine years. So forensic scientists could use a bloodstain to narrow a victim’s age to within two decades. That’s a big range—but it could help solve crimes when the victims can’t be found.

　　—Cynthia Graber

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人60秒

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