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Questions 14 to 17 are based on a talk by a tourist agent on the Canyonland in Utah. You now have 20 seconds to read Questions 14 to 17. Which tour is commercially-operated
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Questions 22 to 25 are based on the conversation you have just heard.
Scientists have come up with a theory for why time flies when you are having fun and drags when you are bored. Scans have shown that (62) of activity in the brain change depending on how we focus on a task. Concentrating on time passing, as we do when bored, will (63) brain activity which will make it seem as though the clock is ticking more (64) . The research, by the French Laboratory of Neurobiology and Cognition, is published in the magazine Science. In the study, 12 volunteers watched an image while researchers (65) their brain activity using MRI(核磁共振成像) scans. Volunteers were given a (66) of tasks. In one they were told to concentrate simply on the duration of an image, in (67) they were asked to focus on the (68) , and in a third they were asked to concentrate on both duration and color. The results showed that a network of brain regions was (69) when more subjects were paid attention to duration. It is thought that if the brain is busy focusing on many aspects of a task, then it has to spread its resources thinly, and pays less (70) to time passing. Therefore, time passes without us really (71) it, and seems to go quickly. (72) , if the brain is not stimulated in this way, it concentrates its (73) energies on monitoring the passing of time. This may make time seem to (74) , but in fact it is probably a more accurate perception of reality. (75) the researchers found that the more volunteers concentrated on the duration of the images, the more (76) were their estimates of its duration.Lead researcher Dr. Jennifer Coull said many of the areas of the brain (77) in estimating time were the same that played a key role in controlling movement, and (78) for action. She said this overlap suggests that the brain may make sense of time as (79) between movements, in much the same way (80) musicians mark time with his foot, or (81) anticipate the sound of a starter’s pistol.
煌绿、胆盐、硫代硫酸钠、枸橼酸盐是SS琼脂培养基的
Most Adults in U. S. Have Low Risk of Heart Disease More than 80 percent of US adults have a less than 10 percent risk of developing heart disease in the next 10 years, according to a report in the Journal of the American College of Cardiology. Just 3 percent have a risk that exceeds 20 percent. "I hope that these numbers will give physicians, researchers, health policy analysts, and others a better idea of how coronary heart disease is distributed in the US population, " lead author Dr. Earl S. Ford, from the Centers for Disease Control and Prevention in Atlanta, said in a statement. The findings are based on analysis of data from 13,769 subjects, between 20 and 79 years of age, who participated in the Third National Health and Nutrition Examination Survey from 1988 to 1994. Overall, 82 percent of adults had a risk of less than 10 percent, 15 percent had a risk that fell between 10 to 20 percent, and 3 percent had a risk above 20 percent. The proportion of subjects in the highest risk group increased with advancing age, and men were more likely than women to be in this group. By contrast, race or ethnicity had little effect on risk distributions. Although the report suggests that most adults have a low 10-year risk of heart disease, a large proportion have a high or immediate risk, Dr. Daniel S. Berman, from Cedars-Sinai Medical Center in Los Angeles, and Dr. Nathan D. Wong, from the University of California at Irvine, note in a related editorial. Aggressive treatment measures and public health strategies are needed to shift the overall population risk downward, they add. Elderly people have a higher risk of heart disease than younger people.
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