Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 am and 4 am, before falling again. 3“It’s the neurohormone that controls our sleep and tells our body when to sleep and when to wake,”Says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body’s levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slept less well after a cup of caffeinated coffee than after drinking the same amount of decaf. On average, subjects slept 336 minutes per night after drinking
caffeinated coffee, compared with 415 minutes after decaf. They also took half an hour to drop off4— twice as long as usual _ and jigged around5 in bed twice as much. . In the second phase of the experiment, the researchers woke the volunteers every three hours and asked them to give a urine sample. Shilo measured concentrations of a breakdown product of melatonin. The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers. In a paper accepted for publication in Sleep Medicine, the researchers suggest6 that caffeine blocks production of the enzyme that drives melatonin production.
Because it can take many hours to eliminate caffeine from the body, Ohayon recommends that coffee lovers switch to decaf after lunch,
词汇： beware /b?'we?/ vi.当心；小心stimulant/'st?mj?l(?)nt/ n.兴奋剂 caffeine/'k?fi?n/ n.咖啡因melatonin/,mel?'t??n?n/ n.褪黑激素 hormone/'h??m??n/ n.荷尔蒙,激素
neurohormone /,n?ro'h?rmon; ,nj?ro'h?rmon/ n,神经激素
caffeinated /'k?fi?neitid/ adj.含咖啡因的;加入咖啡因的 halve /hɑ?v/ vt. 二等分;减半decaf/'di?k?f/ n.脱咖啡因咖啡 urine /'j??r?n; -ra?n/ n.尿enzyme /'enza?m/ n. 酶
1. have a quick “pick-me-up”cup of coffee:喝一杯快速提神的咖啡。pick-me-up 意为“提神饮料’这里用作定语。
2. play havoc with:干扰;对……造成严重破坏。例如:The noise of engines can play terrible havoc with a driver’s nerves.发动机的嘈杂声能严重扰乱驾驶员的神经。 3. Levels then peak between 2 am and 4 am, before falling again褪黑激素的
浓度在凌晨2点和4点之间达到最高值,然后再次下降。before在此处可以译为“然后”。
4. drop off:睡着。例如:He dropped off in the armchair.他在扶手椅上睡着了。 5. jig around:辗转反侧。jig:急蹦蹦跳跳。例如:Stop jigging about, Billy, and just stand still for a moment.别到处乱蹦,比利,稳稳地站一会儿。
6. suggest:在这里不作“建议”解,它的意思是“间接地表明；暗示”。例如:I’m not suggesting that the accident was your fault.我并不是说那事故是你的错。 练习：1. The author mentions “pick-me-up” to indicate that
A. melatonin levels need to be raised.B. neurohormone can wake us up. C. coffee is a stimulant.D. decaf is a caffeinated coffee.
2. Which of the following tells us how caffeine affects sleep?
A. Caffeine blocks production of the enzyme that stops melatonin production. B. Caffeine interrupts the flow of the hormone that prevents people from sleeping. C. Caffeine halves the body’s levels of sleep hormone. D. Caffeine stays in the body for many hours.
3. What does paragraph 3 mainly discuss?
A. Different effects of caffeinated coffee and decaf on sleep. B. Different findings of Lotan Shilo and a team about caffeine.
C. The fact that the subjects slept 415 minutes per night after drinking decaf. D. The evidence that the subjects took half an hour to fall asleep.
4. What does the experiment mentioned in paragraph 4 prove? A. There are more enzymes in decaf drinkers’ urine sample.
B. There are more melatonin concentrations in caffeine drinkers’ urine sample. C. Decaf drinkers produce less melatonin. D. Caffeine drinkers produce less sleep hormone.
5. The author of this passage probably agrees that A. coffee lovers sleep less than those who do not drink coffee. B. we should not drink coffee after supper.
C. people sleep more soundly at midnight than at 3 am. D. if we feel sleepy at night, we should go to bed immediately.
1. C pick-me-up指提神饮料,也就是一种刺激物,这篇文章里具体指咖啡。所以,答案应选C。
2. C第二段的第三个句子谈道,“控制我们睡眠的是神经激素”，而这一段的最后一个句子告诉我们“含咖啡因咖啡能使这种睡眠激素减半”。这正是咖啡因影响睡眠的原理。
3. A第三段涉及的是一个实验,这个实验的目的盛测试含咖啡因咖啡和脱咖啡因咖啡对睡眠的影响,该段主要谈论的是这个实验的结果。
4. D第四段是第三段实验的继续,是该实验的第二个阶段。研究人员通过对志愿者的尿进行化验发现,咖啡因摄人者体内的褪黑激素仅为非咖啡因摄人者的一半。褪黑激素就是睡眠激素,所以答案应该选D。
5. B文章的结尾谈道,“Ohayon建议爱喝咖啡的人午饭后应该换喝脱咖啡因咖啡”。另外,整个文章都在探讨咖啡因影响睡眠的机理,所以者大概会同意“晚饭后不应该喝咖啡”的说法。选项A是一个全称判断,这等于说“所有喜欢喝咖啡的人都比不喝咖啡的人睡觉少”。这不一定,因为如果咖啡适量,喝咖啡的时间适当,咖啡不影响睡眠。所以,作者可能不会会同意这种说法。根据文章第二段第二个句子,我们体内褪黑激素（睡眠激素）
的浓度在我们上床时间前两个小时开始上升,而这个时候我们会开始有困意。反过来说就是,人们并非一有困意就睡觉。所以,选项D 不是答案。
喜欢喝咖啡的人要小心了。晚上喝一杯快速提神的咖啡对你的睡眠造成严重破坏。并且咖啡因作为一种刺激物会打断褪黑激素的流动。褪黑激素是使人们进入睡眠的神经激素。 褪黑激素的浓度在睡前两小时开始上升。凌晨2点和4点之间达到最高植，然后再次下降。加利福尼亚斯坦福大学的斯坦福睡眠流行病学研究中心的Maurice Ohayon说：“控制我们睡眠是神经激素，它告诉我们的身体什么时候睡觉什么时候醒。”但是以色列的研究者发现含咖啡因咖啡能使人体中这种睡眠激素减半。
特拉维夫大学的塞帕医学中心的Lotan Shilo和一个小组发现六个志愿者在喝了一杯含咖啡因的咖啡后平均每晚睡336分钟，而喝完脱咖啡后平均每晚睡415分钟，他们用半个小时才能睡着——比平常长一倍，而且翻来覆去的时间比平常多一倍。
在试验的第二阶段，研究者每三个小时叫醒志愿者一次，并要他们提供一个尿样。Shilo测量了褪黑激素分解物的浓度。结果表明饮用含咖啡因咖啡的人体内的褪黑激素的浓度是饮用脱咖啡因咖啡的人体内褪黑激素浓度的一半。在《睡眠知学》上发表的一篇论文中，研究者表示咖啡因阻碍促使褪黑激素产生的酶的形成。
Ohayon建议爱喝咖啡的人午饭后应该换喝脱咖咖啡，因为要排除体内的咖啡因要用好几个小时。
第六篇 Making Light of1 Sleep
All we have a clock located inside our brains. Similar to your bedside alarm clock， your internal clock2 runs on a 24-hour cycle. This cycle，called a circadian rhythm，helps control when
you wake，when you eat and when you sleep.
Somewhere around puberty，something happens in the timing of the biological clock. The
clock pushes forward，so adolescents and teenagers are unable to fall asleep as early as they used to. When your mother tells you it's time for bed，your body may be pushing you to stay up3 for several hours more. And the light coming from your computer screen or TV could be pushing you to stay up even later.
This shift4 is natural for teenagers. But staying up very late and sleeping late can get your body's clock out of sync with the cycle of light and dark5. It can also make it hard to get out of bed in the morning and may bring other problems，too. Teenagers are put in a kind of a gray cloud6 when they don't get enough sleep，says Mary Carskadon，a sleep researcher at Brown University in Providence，RI7 .It affects their mood and their ability to think and learn.
But just like your alarm clock，your internal clock can be reset. In fact，it automatically resets
itself every day. How? By using the light it gets through your eyes.
Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal clocks. For years，researchers thought that the signals that synchronize the body's clock8 were handled through the same pathways that we use to see.
But recent discoveries show that the human eye has two separate light-sensing systems. One system allows us to see. The second system tells our body whether it's day or night.
词汇：circadian/s3:'keidi?n/ adj. 昼夜节奏的，生理节奏的
adolescent/?d?u'les?nt/ n．青少年；adj．青少年的puberty/ 'pju:b?ti/ n．发育；青春期 sync/si?k/ n. （口语）同步；和谐，协调
synchronize/'si?kr?naiz / V.（使）同时发生；（使）同步
注释：1.make light of ：轻视，不在乎。例如： We should not make light of their achievements．我们不应当低估他们的成就。
2. your internal clock ：指的是第一句中的a clock located inside our brains ，也即是第二段第一句中的the biological clock （生物钟）。
3. stay up：不睡觉，熬夜4. This shift：这种调整。指上文所描述的由于生理时间的变化青少年上床时间越来越晚的现象。
5. get your body's clock out of sync with the cycle of light and dark ：打乱了你的生物钟与昼夜时间循环之间的平衡
6. gray cloud ：提不起精神的状态7. Brown University in Providence， RI：位于美国罗得岛州普罗维登斯的布朗大学。RI是Rhode
Island（罗得岛）的首字母缩写；Providence 是罗得岛州的首府。布朗大学是美国一流大学，
创建于1764 年，是世界闻名的美国“常春藤联盟”（还包括哈佛大学、耶鲁大学、普林斯顿大学、布朗大学、哥伦比亚大学、宾夕法尼亚大学、达特茅斯大学和康奈尔大学）中的一员。
8. the signals that synchronize the body's clock：平衡生物钟的光信号 练习：
1 .The clock located inside our brains is similar to our bedside alarm clock because A it controls when we wake，when we eat and when we sleep. B it has a cycle of 24 hours.C it is a cycle also called circadian rhythm. D it can alarm any time during 24 hours. 2. What is implied in the second paragraph?
A Young children's biological clock has the same rhythm with that of the teenagers.
B People after puberty begin to go to bed earlier due to the change of the biological clock. C Children before puberty tend to fall asleep earlier at night than adolescents.
D Teenagers go to bed later than they used to due to the light from the computer screen. 3. In the third paragraph the author wants to tell the reader that A it is natural for teenagers to stay up late and get up late.
B staying up late has a bad effect on teenagers' ability to think and learn. C during puberty most teenagers experience a kind of gray cloud.
D it is hard for teenagers to get out of bed in the morning.
4. Which of the following statements is NOT true according to the fourth and fifth paragraphs?
A Our biological clock resets itself automatically.
B light gets through our eyes and resets our biological clock.
C Our internal clock as well as the alarm clock can be reset automatically. D Our internal clock，like the alarm clock，can be reset.
5. According to the last two paragraphs， what did the previous researchers think about
the human eye's light-sensing system?
A The human eye had two light-sensing systems
B The human eye had one light-sensing system.
C The human eye could sense the light of day more quickly than the dark of night. D The human eye could reset our internal clocks in accordance with the alarm clocks. 答案与题解：1.B 第一段第二句提供了答案。句中的your internal clock 即指a clock located inside ourBrains。
2. C 第二段主要内容是告诉读者，过了青春期（puberty），由于生物钟节奏的变化，青少年（adolescents and teenagers）比以前要晚睡几小时。所以C是该段所隐含的内容。 3. B 第三段的最后一句直接给出了答案。4. C 根据第四和第五段的内容，闹钟和生物钟都可以重新设定时间，但生物钟能通过眼睛接
受的日光来自动调节生理节奏。所以A、B和D都是这两段中所述内容，C是正确选择，因为闹钟不能自动重新设定时间。
5.B 问题使用的是过去时，问的是研究者在最新发现（recent discoveries）之前对眼睛感光系统的认识，即，the signals that synchronize the body's clock were handled through the samepathways that we use to see （眼睛所接受到的平衡生物钟的光信号同样作用于人类的视觉系统），也就是说，研究者之前认为人类的眼睛只有一个感光系统。但最新发现却是，人的眼睛有两个感光系统。
第六篇 不要太在意睡眠
我们每个人的大脑里都有一个像我们床边的闹钟一样的生物钟。人脑里的生物钟24小时走一圈，这一圈也就是一次完整的昼夜节律，正是这个节律决定了我们吃饭、睡觉和起床的时间。
青春期时，人的生物钟在定时方面会发生变化，生物钟会提前。这时，青少年会比以前睡得晚，所以当你妈妈告诉你该睡觉时，你的生物钟可能会让你多推迟几小时，并且电脑或电视光线可能会导致你熬夜到更晚。
生物钟的这种变化对青少年说是正常的，但熬夜到太晚会打乱你生物钟与昼夜时间循环之间的平衡，这样就会带来一些问题，例如：早晨很难按时起床。位于美国罗得州布郎大学睡眠方面的研究员Mary Carskadon说：“当青少年睡眠不足时会打不起精神，这将影响到他们心情、学习和思考问题的状态。”
其实生物钟与闹钟一样，也是可调的，事实上，生物钟每天都在进行着自我调节，其方式就是通过你眼睛接收到光线的变化。
很早之前，科学家就知道了昼夜光线强弱的变化对生物钟调节起到了重要的作用，长久以来，研究者们认为眼睛所接受到的平衡生物钟的光信号同样作用于人类的视觉系统。 但最近几年的研究发现，人类眼睛有两个感光系统，一个是视觉系统，而另一个是感知昼夜的系统。
第七篇Sugar Power for Cell Phones
Using enzymes commonly found in living cells，a new type of fuel cell produces small amounts of electricity from sugar.If the technology is able to succeed in mass production，you may some day share your sweet drinks with your cell phone.
In fuel cells，chemical reactions generate electrical currents.The process usually relies on precious metals，such as platinum.In living cells，enzymes perform a similar job，breaking down sugars to obtain electrons and produce energy.
When researchers previously used enzymes in fuel cells，they had trouble keeping