VOA标准英语2011--Doctors Achieve Milestone Using Artifici

Doctors Achieve Milestone¹ Using Artificial Heart With No Beat

In March, two doctors at the Texas Heart Institute in Houston achieved what medical experts call a major milestone by implanting a continuous-flow artificial heart in a human patient. The mechanical heart worked flawlessly. But the patient, who suffered from other grave illnesses, eventually died after he and his family decided³ not to prolong treatment. The success of the artificial heart used in that case has opened the way to greater use of the device in other cardiac patients.
Since the first artificial heart was implanted in a human here in Houston in 1969, the field has advanced steadily⁴. But it hasn't kept pace with the need for devices that can keep patients alive until they can get a real organ transplant. Heart disease remains⁵ the number one killer⁶ of Americans each year. Of the estimated 5 million people in the United States with failing hearts, only around 2,000 are likely to get a transplant this year.
That is where various types of artificial pumps have come into play. Last month, at the Texas Children's Hospital here in Houston, Jordan Merecka, 17, became the first patient in a U.S. pediatric hospital to have his congenitally deformed⁷ heart removed and replaced with an external mechanical heart pump. Meeting with reporters a few days ago, he told how he almost ran out of time, waiting to have the procedure.
"This is just a godsend. A couple months earlier and I would not be here right now," said Merecka.
Merecka, who now awaits a transplant, has limited mobility⁸ in the hospital as he remains tethered to the artificial heart beating loudly beside him.
But nearby, at the Texas Heart Institute, doctors and researchers are working with another type of artificial heart, one that is much smaller, much more efficient and does not beat.
Lead researcher Dr. Bud Frazier explained its advantages over devices like the one keeping Jordan Merecka alive at Children's Hospital.
"It is a good life-saving pump, but the limitation of it is that it is externally powered and externally driven, and it requires a large console," said Frazier. "So, if we are really going to impact the premature⁹ death from heart failure, we have to have a pump that is implantable and can replace the heart."
The artificial heart Frazier and his colleague, Dr. William Cohn, developed is small enough to be implanted in the human chest. But, unlike an animal or human heart, it produces no pulse because it is a continuous-flow mechanism¹⁰. It uses a small spinning turbine to keep blood flowing at a steady rate rather than a pump that mimics¹² the action of the heart found in humans or in the calves¹³ the doctors have used for trials.
To provide the blood flow of a natural human heart, vibrating pumps must beat 100,000 times a day, 35 million times a year, leading to mechanical breakdowns¹⁴. The continuous-flow pumps are much more durable¹⁵ and can last years without a problem.
These continuous-flow devices have been used for some time to assist the left ventricle of the heart, which is the part that sends blood throughout the body and is the part that most often fails. But the doctors at Texas Heart Institute use a device that is essentially¹⁶ two such pumps put together to replace the functions of both sides of the heart.
Doctors Frazier and Cohn carried out the first successful implant² of a continuous-flow artificial heart in a 55-year-old man here in Houston in March. The patient later died because of conditions unrelated to the heart operation, but Cohn says the implanted heart worked well.
"He went five weeks and his blood pressure and the flow through his body and his oxygenation was beautiful throughout that interval," recalled Cohn.
Cohn says the work he and Frazier have done shows that such a device can function much like the natural heart, even though it has no pump action to increase the pulse.
Normally when a person works or exercises, the heart beats faster so that more blood can flow to the muscles in need of energy and to the lungs where the blood is oxygenated. But Cohn says the continuous-flow heart does the same without the pulsation¹⁷.
"If the conditions change so that the amount of blood arriving to the pump increases, the flow through the pump will increase," added Cohn. "It sort of has the ability to automatically increase its flow like the mammalian heart, which is, perhaps, the biggest advantage of all."
One of the biggest problems with this kind of small, implantable device is powering it without having the patient tethered to an external source of electricity. The device Doctors Frazier and Cohn developed uses small externally connected batteries that can be easily replaced without interrupting the machine's operation. But they are investigating the use of new highly efficient batteries, even ones using a tiny amount of plutonium as a power source.
Frazier says that while this may sound exotic and dangerous, the use of plutonium for such medical devices goes back to the 1970s, when they were used in heart pacemakers and studied closely.
"The thing we were concerned about was increased instance of malignancies, but we followed over a thousand of those patients over 20 years and there was no increased instance," Frazier explained. "It is bulky, though, and expensive. We came out for pacemakers with lithium-powered batteries."
Cohn says they are studying batteries that may be able to mimic¹¹ the human body's natural power system. "There is a lot of other research looking at biological cells, cells that are actually powered by oxygen and glucose¹⁸, much in the way the human body is," Cohn noted¹⁹. "So there is a lot of battery technology that is in the works."
Since the continuous-flow artificial heart is so efficient and durable, might some future version actually work better than the heart nature has provided? Science fiction writers have speculated that one day there might be "bionic" humans, partially²⁰ made up of artificial components²¹ that make them more powerful than normal people. That is something Doctors Frazier and Cohn also debate.
FRAZIER: "I don't think so."
COHN: "Well, you never know. Never try to second guess progress and human innovation. I always joke that in the 2090 Olympics there will be 'stock and modified.' You never know where it is all going to end up."
FRAZIER: "Well, we are also.. I think we are limited in time. You know, nature has had a million years or so on us in designing these things."
Doctors Bud Frazier and William Cohn are continuing their work with artificial hearts at the Texas Heart Institute in hopes of helping²² prevent at least some of the more than 300,000 heart disease-related deaths in the United States each year. Support for the research was provided by the National Institutes of Health as well as engineers at NASA and researchers from the University of Houston and Rice University.

1 milestone   

n.里程碑；划时代的事件

参考例句：

• The film proved to be a milestone in the history of cinema.事实证明这部影片是电影史上的一个里程碑。
• I think this is a very important milestone in the relations between our two countries.我认为这是我们两国关系中一个十分重要的里程碑。

2 implant   

vt.注入，植入，灌输

参考例句：

• A good teacher should implant high ideals in children.好教师应该把高尚理想灌输给孩子们。
• The operation to implant the artificial heart took two hours.人工心脏植入手术花费了两小时。

3 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

4 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

5 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

6 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

7 deformed   

adj.畸形的；变形的；丑的，破相了的

参考例句：

• He was born with a deformed right leg.他出生时右腿畸形。
• His body was deformed by leprosy.他的身体因为麻风病变形了。

8 mobility   

n.可动性，变动性，情感不定

参考例句：

• The difference in regional house prices acts as an obstacle to mobility of labour.不同地区房价的差异阻碍了劳动力的流动。
• Mobility is very important in guerrilla warfare.机动性在游击战中至关重要。

9 premature   

adj.比预期时间早的；不成熟的，仓促的

参考例句：

• It is yet premature to predict the possible outcome of the dialogue.预言这次对话可能有什么结果为时尚早。
• The premature baby is doing well.那个早产的婴儿很健康。

10 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

11 mimic   

v.模仿，戏弄；n.模仿他人言行的人

参考例句：

• A parrot can mimic a person's voice.鹦鹉能学人的声音。
• He used to mimic speech peculiarities of another.他过去总是模仿别人讲话的特点。

12 mimics   

n.模仿名人言行的娱乐演员，滑稽剧演员( mimic的名词复数 )；善于模仿的人或物v.（尤指为了逗乐而）模仿( mimic的第三人称单数 )；酷似

参考例句：

• Methods:Models were generate by CT scan,Mimics software and Abaqus software. 方法：采用CT扫描，Mimics软件和Abaqus软件的CAD进行三维有限元模型的创建。 来自互联网
• Relaxing the mind and body mimics the effect that some blood-pressure pills would have. 放松身心会产生某些降压药才能产生的效果。 来自辞典例句

13 calves   

n.(calf的复数)笨拙的男子，腓；腿肚子( calf的名词复数 )；牛犊；腓；小腿肚v.生小牛( calve的第三人称单数 )；（冰川）崩解；生（小牛等），产（犊）；使（冰川）崩解

参考例句：

• a cow suckling her calves 给小牛吃奶的母牛
• The calves are grazed intensively during their first season. 小牛在生长的第一季里集中喂养。 来自《简明英汉词典》

14 breakdowns   

n.分解( breakdown的名词复数 )；衰竭；（车辆或机器的）损坏；统计分析

参考例句：

• Her old car was unreliable, so the trip was plagued by breakdowns. 她的旧车老不听使唤，一路上总是出故障。 来自辞典例句
• How do we prevent these continual breakdowns? 我们如何防止这些一再出现的故障？ 来自辞典例句

15 durable   

adj.持久的，耐久的

参考例句：

• This raincoat is made of very durable material.这件雨衣是用非常耐用的料子做的。
• They frequently require more major durable purchases.他们经常需要购买耐用消费品。

16 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

17 pulsation   

n.脉搏，悸动，脉动；搏动性

参考例句：

• At low frequencies, such as 10 per sec., pulsation is sensed rather than vibration. 在低频率（譬如每秒十次）时，所感觉到的是脉冲而非振动。 来自辞典例句
• If the roller pulsation, the pressure on paper as cause misregister. 如果滚子径向跳不静，则差纸的不张辛有不小有小，致使套印禁绝。 来自互联网

18 glucose   

n.葡萄糖

参考例句：

• I gave him an extra dose of glucose to pep him up.我给他多注射了一剂葡萄糖以增强他的活力。
• The doctor injected glucose into his patient's veins.医生将葡萄糖注入病人的静脉。

19 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

20 partially   

adv.部分地，从某些方面讲

参考例句：

• The door was partially concealed by the drapes.门有一部分被门帘遮住了。
• The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静，宵禁部分解除。

21 components   

（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分

参考例句：

• the components of a machine 机器部件
• Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

22 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。