Man has known about them for thousands of years. But the first scientific observation of circadian rhythms was not made until 1729. In that year French astronomer, Jean-Jacques d'Ortous de Mairan, noted that one of his plants opened its leaves at the same time every morning, and closed them at the same time every night. The plant did this even when he kept it in a dark place all the time. Later scientists wondered about circadian rhythms in humans. They learned that man's biological clock actually keeps time with a day of a little less than 25 hours instead of the 24 hours on a man-made clock. About four years ago an American doctor, Eliot Weitzman, established a laboratory to study how our biological clock works. The people in his experiments are shut off from the outside world. They are free to listen to and live by their circadian rhythms. Dr. Weitzman hopes his research will lead to effective treatments for common sleep problems and sleep disorders caused by aging and mental illness. The laboratory is in the Monteflore Hospital in New York City. It has two living areas with three small rooms in each. The windows are covered, so no sunlight or moonlight comes in. There are no radios or television receivers. There is a control room between the living areas. It contains computers, one-way cameras and other electronic devices for observing the person in the living area. The instruments measure heartbeat, body temperature, hormones in the blood, other substances in the urine and brain waves during sleep. A doctor or medical technician is on duty in the control room 24 hours a day during an experiment They do not work the same time each day and are not permitted to wear watches, so the person in the laboratory has no idea what time it is. In the first four years of research, Dr Weitzman and his assistant have observed 16 men between the ages of 21 and 80. The men remained in the laboratory for as long as six months. Last month, a science reporter for The New York Times newspaper, Dava Sobol, became the first woman to take part in the experiment. She entered the laboratory on June 13th and stayed for 25 days. Miss Sobol wrote reports about the experiment during that time, which were published in the newspaper.
The biological clock is believed to play an essential role in ______.
A.the regulation of body temperature
B.the secretion of hormones
C.animal reproduction
D.many aspects of plant and animal physiology
第5题
A、关节骨性强直,X线征为关节间隙消失,且有骨小梁贯穿其中
B、关节间隙变窄是由于关节腔消失所致
C、骨质增生是由于骨量增多的结果
D、骨质坏死的主要X线表现是有密度增高的死骨片存在
E、关节肿胀的X线表现为关节周围软组织肿胀,密度较高
第6题
A、关节骨性强直,X线征为关节间隙消失,且有骨小梁贯穿其中
B、关节间隙变窄是由于关节腔消失而关节软骨正常所致
C、骨质增生是由于骨量增多的结果
D、骨质坏死的主要X线表现是有密度增高的死骨片存在
E、关节肿胀的X线表现为关节周围软组织肿胀,密度增高
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