Some people can quite accurately time the end of their
night's sleep at will, without using an alarm clock, demonstrating that it is
possible to voluntarily control a state of consciousness that is characterized
by a loss of volition and attentional guidance. Here we show that the
expectation that sleep will come to an end at a certain time induces a marked
increase in the concentration of the hormone adrenocorticotriopin(促肾上腺皮质激素) in
the blood one hour before waking. The regulation of adrenocorticotropin release
during nocturnal sleep is therefore not confined to daily rhythms; {{U}}(46)
{{/U}} {{U}}(47) {{/U}} Normally, the release of adrenocorticotropin
and cortisol(皮质醇)increases during late stages of sleeping, reaching a daily
maximum at the time of spontaneous waking. Adrenocorticotropin and cortisol are
also released from the pituitary-adrenal system in a major adaptive response to
stress, and are secreted in anticipation of stressful events. We investigated
whether the increase in the secretion of pituitary-adrenal hormones during the
late stages of sleeping in part reflects anticipation of the 'stress' of the
waking phase. {{U}}(48) {{/U}} We made recordings of
electroencephalogram, electrooculogram and electromyogram throughout the night,
and took blood samples every 15 minutes to determine plasma concentrations of
adrenocorticortropin and cortisol. Lights were turned off at
midnight, after subjects had been told they would be woken at either 6:00
('short sleep', on one night) or 9:00('long sleep', on the other two nights). On
one of the long-sleep nights they were woken at 9:00 as they expected, but on
the other night they were instead woken at 6:00 ('surprise')under the pretence
of a technical problem. {{U}}(49) {{/U}} We interviewed the volunteers
at the end of the experiments, and found that all but one of the subjects had
expected to be woken up at the specified time. The order of the three
experimental nights was balanced across subjects, with five subjects starting
with short sleep, five with long sleep, and five with the surprise condition.
The increase in adrenocorticotropin release before the
expected time of waking indicates that anticipation, which is generally
considered to be a unique characteristic of the regulation of conscious action,
pervades sleep {{U}}(50) {{/U}} The regulation of adrenocorticotropin
release points to a mechanism that quickly adjusts endocrine activity to sharp
changes in the duration.
A. The regulation of sleep termination has been thought to embedded in a
daily rhythm controlling in paralleling the release of pituitary and adrenal
hormones.
B. Fifteen healthy volunteers with regular sleep-wake rhythms were studied
during three nights.
C. It also reflects a preparatory process in anticipation of the end of
sleep
D. After being woken, subjects stayed in bed for another three hours
E. The anticipatory adrenocorticotropin increase may also facilitate
spontaneous waking F. About 10 million Americans consult doctors
sleep problems each year
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{{B}}Can Loud Music Cause Hearing
Impairment (损伤)?{{/B}} Have you ever gone to a concert and
realized that your seats were right next to the booming speakers? Are you
guilty______(51) turning up the volume on your portable cassette or CD player to
drown out the whining (哭哭啼啼) of your little brother? Sometimes it's difficult to
avoid loud music or noises, but they can be bad news because loud noises
can______(52) temporary or permanent hearing loss. Extremely
loud music and noises that go on for long periods of______(53) are common causes
of deafness. If a noise is so loud that you have to shout to make
yourself______(54), there is a______(55) that the mechanism inside your ear can
be injured. Temporary hearing loss can happen after you've
been______(56) to loud noise for only 15 minutes. If you have temporary hearing
loss, you won't be able to hear as______(57) as you normally can, and you may
have tinnitus (耳鸣), which is a fancy word for ringing in the ears. Your ears can
feel "full", too.______(58), these things usually go away and your hearing soon
returns to normal. Permanent hearing loss can happen when
someone is exposed to loud noise ______(59) and over. Construction workers and
people who work in factories must ______(60) ear protectors because the
equipment they use can be extremely loud. But even some lawn mowers (割草机) and
power tools can permanently______(61) a person's ability to hear high-pitched
noises and can also give him permanent tinnitus. Listening to extremely loud
music over and over can also have the same effect on a person's______(62). And
using headphones on a portable cassette or CD player can be dangerous______(63)
if the volume is too high and the headphones are used a lot, the noise can
damage the ears. The best way to avoid hearing loss is to wear
ear protectors when working with machinery and earplugs when going to
a______(64). Headphones are OK to wear when you're listening to music; just be
sure the volume isn't too high, and give them a rest______(65) once in a
while.
阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。
{{B}}
Eat for a Good
and Healthful Life{{/B}} Food{{U}} (1) {{/U}}us alive. It
is our sustenance and our pleasure. But recently, research has shown that the
eating habits of the average Americans may be dangerous to future
health. The foods Americans now choose are oftentimes too{{U}}
(2) {{/U}}in calories and fats, so this article reports a new study:
Diet and Health, Implications for Reducing Chronic Disease Risk.
The study, conducted{{U}} (3) {{/U}}the National Research
Council's Committee on Diet and Health,{{U}} (4) {{/U}}that balancing
nutrition, calories and activity is key{{U}} (5) {{/U}}enjoying a long
and healthful life. The report recommends that most Americans
increase{{U}} (6) {{/U}}activity to a moderate level and make changes in
food{{U}} (7) {{/U}}and calories intake to maintain ideal weight. Most
of us-- even those of us at ideal weight--need to eat{{U}} (8) {{/U}}fat
so that no more than 30% of our dally calories will come from fat.
That means cutting{{U}} (9) {{/U}}on red meat and whole milk dairy
products.{{U}} (10) {{/U}}, eat fish, chicken without skin, lean meats,
and low-fat and no-fat dairy products. The report of the
Committee on Diet and Health recommends we eat five or more 1/2-cup servings of
vegetables and fruits{{U}} (11) {{/U}}-- especially green and yellow
vegetables and citrus fruits. Eating more fruits and vegetables
doesn't have to mean increased calories intake. Many plant foods are
nutrient-rich: they provide many vitamins and minerals for very few{{U}}
(12) {{/U}}. Nutrient-rich foods are particularly
important for Americans{{U}} (13) {{/U}}age 50. As we{{U}} (14)
{{/U}}, we need to eat less because our bodies need{{U}} (15)
{{/U}}calories to function properly. But we still need full measures of
vitamins and minerals to release the energy in our foods and make us feel strong
and healthy.
语法与词汇John has always remained (loyal) to his family and friends.
语法与词汇Einstein''s theory of relativity seemed (incredible) when it was first introduced.
语法与词汇It is taken for granted that a piano without any (defects) would produce very grand music.
语法与词汇During the United States Civil war, many people in the south were forced to (flee) their home.
语法与词汇Experiments enable young scientists to judge accurately what must be accepted and what must be viewed with (suspicion).
语法与词汇The development of the transistor and integrated circuits revolutionized the electronics industry by allowing components to be packaged more (densely).
语法与词汇Everybody {{U}}was glad to{{/U}}see Mary back
语法与词汇He has (thought out) the best way of saving oil for your car.
语法与词汇The price is (somewhat) higher than I expected.
语法与词汇John is {{U}}crazy {{/U}} about pop music
语法与词汇I (spotted) my father in the crowd.
语法与词汇The farmers worried about the (lack) of rain.
语法与词汇He (maintained) that the opinion was wrong.
语法与词汇Putting in a new window will (bring about) cutting away part of the roof.
语法与词汇There was a (number) of children on the playground.
语法与词汇I wonder who first (conceived) the idea of cutting a hole in the door.
语法与词汇At the sports meet, athletes (compete) with each other for the gold medals.