答案:C
B
Recently,a study showed that changes found in astronauts’eye tissue might cause vision problems,and possibly even blindness.As well as threatening the health of astronauts,this could influence longdistance missions into space.
Larry Kramer of Texas Medical School in Houston and his colleagues carried out MRI scans on 27 NASA astronauts after they had spent an average of 108 days in space.About half of them had some problems in their optic nerve(视神经)or eyeball.
The changes match those seen in people with idiopathic intracranial hypertension,a rare condition in which the pressure of blood is abnormally high in the brain.People with the condition experience headaches,nausea(反胃)and vision problems including blindness.
In space,the changes are probably caused by living in free fall.“It is not because of the sunlight in space or the spacecraft’s function.One likely reason is that blood which normally pools in the legs is shifted toward the skull(头颅骨),raising pressure,”says Kramer.
The findings are similar to the results of a survey of 300 astronauts carried out in 2011.The damage in vision was reported by 29 percent of astronauts on shortterm missions,and 60 percent on longterm missions.
“If astronauts are exhibiting these changes after only 100 days in space,what will happen on a threeyear flight to Mars?”asks Jason Kring,who studies human performance in extreme conditions at the EmbryRiddle Aeronautical University in Florida.
【2017届高三(人教版)英语复习全国通用活页作业35】相关文章:
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (19)
★ 【北师大版】2014届高考英语一轮复习指导课时作业:Unit 5 A卷 Word版含解析
★ 2017届高考英语二轮复习书面表达限时测验:1(含解析)
★ 山西省永济市涑北中学高三英语总复习:美文欣赏(2)(Last Respects)
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21