课程咨询

托福考试网 托福资料下载 托福资讯 0元讲座 水平测试

托福考试练习
新东方在线 > TOEFL > 托福听力 > 正文
托福培训

扫码免费领资料

内含托福全科备考资料

更有免费水平测试及备考规划

托福培训

扫码关注掌握一手留学资讯

回复XDF免费水平测试

录播精讲 直播课HOT

托福听力练习-科学美国人60秒:凝血易代价高

2017-04-17 09:04:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：凝血易代价高

　　科学美国人60秒听力练习：凝血易代价高

　　科学美国人60秒英文文本

　　They say what doesn’t kill you makes you stronger. But sometimes what makes you stronger can kill you, at least when it comes to blood clotting. Because the stickiness that allow platelets to heal your wounds also raises your risk of heart attack.

　　All mammals use platelets to help prevent blood loss after traumatic injury. But birds don’t have ‘em, nor do reptiles or fish. Instead, these critters have blood cells called thrombocytes, which are about twice the size of platelets. But is bigger necessarily better when it comes to clotting? Scientists took thrombocytes from parakeets and put them to the test. The work appears in the journal Blood. [Alec A. Schmaier et al., "Occlusive thrombi arise in mammals but not birds in response to arterial injury: evolutionary insight into human cardiovascular disease"]

　　They focused their attention on birds because our feathered friends have a cardiovascular system much like our own, in that blood exerts pressure on walls of blood vessels.

　　The results: parakeet thrombocytes don’t stick together like platelets do. They also don’t block blood flow in the birds’ arteries the same way that platelets do when they form clots in mice.

　　Which means that mice may be more likely to survive a bloodletting-pecking. But birds are far less likely to suffer from the clot formation called economy class syndrome—despite being frequent fliers.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人 科学60秒sss

上一页 1 2 下一页

托福辅导

关注新东方在线托福

托福机经·Official题目练习

考前重点突破·听说读写海量资料

更多资料

关注新东方在线托福，
回复【XDF】获取大礼包

托福辅导
  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加】，回复对应关键字领取学习资料。
更多>>
更多内容

免费获取托福备考大礼包

微信扫描下方二维码 立即领取

托福辅导
更多>>
更多公益讲座>>
更多>>
更多资料
托福TPO 托福听力练习 托福口语练习 托福阅读练习 托福写作练习
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10