SHIRLEY GRIFFITH: This is SCIENCE IN THE NEWS in VOA Special English. I'm Shirley Griffith.
STEVE EMBER: And I'm Steve Ember. Today, we tell about soft-bodied robots -- robots that can move more easily than those made of metal. We also tell about efforts to control the disease malaria. And we tell about how being president of the United States can be good for your health.
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SHIRLEY GRIFFITH: When many of us think of robots, we picture large, metal objects in the shape of humans, having difficulty moving around. But robots have come a long way. A team at Harvard University in Massachusetts recently developed a soft-bodied robot. The team based the design of its robot on sea creatures without hard shells or skeletons.
STEVE EMBER: The robotic device was made with soft materials called elastomers. It is about thirteen centimeters long and has four legs that can move separately. The movements are controlled by compressed air and can be operated from a computer.
George Whitesides led the Harvard researchers. The United States Department of Defense paid for the project.
The robot itself took two months to develop. In tests, researchers have guided the robot under a plate of glass less than three centimeters high. The researchers say their invention can move at a speed of about thirteen meters an hour.
A report about the robot was published in November in the journal Proceedings of the National Academy of Sciences.
SHIRLEY GRIFFITH: Increasingly, soft robots are being developed for difficult jobs like moving through a battlefield or wreckage from a natural disaster. The robot can move across uneven surfaces including small rocks and wet dirt.
Earlier this year, scientists from Tufts University in Massachusetts developed another kind of soft robot made of silicone rubber. This robot is about ten centimeters long and shaped like a caterpillar. It is able to roll up into a ball shape and move itself forward.
But researchers say there are difficulties in making these robots move. For one, they want to find a way for the robot to transport its own power source. They are also hoping to improve its speed.
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STEVE EMBER: The World Health Organization says malaria was responsible for seven hundred eighty-one thousand deaths in two thousand nine. Most of those deaths were in children in Africa. Worldwide there were two hundred twenty-five million cases of the disease.
Both of these numbers represent improvements. In two thousand there were an estimated two hundred thirty-three million cases of malaria and almost a million deaths.
Malaria remains a major problem in Africa, but there have been some successes. Deaths in Rwanda, for example, have been reduced by sixty percent.
SHIRLEY GRIFFITH: The main way for communities to control malaria is by controlling mosquitoes. The disease comes from a parasite spread through the bite of infected mosquitoes.
In a recent study, researchers in West Africa showed that an insecticide spray can greatly reduce malaria transmission. Researchers at the Center de Recherche Entomologique de Cotonou tested a chemical called bendiocarb. They tested it with indoor spraying at sites throughout Benin.
The study found there were fewer mosquito bites in homes sprayed with bendiocarb. More importantly, none of the three hundred fifty-thousand people who lived there got malaria-infected mosquito bites during the test.
STEVE EMBER:Malaria control efforts currently depend on things like chemically treated bed nets and spraying against mosquitoes. But scientists keep trying to find other ways to prevent the disease.
There are still no vaccines to prevent malaria. But a number of vaccines remain under development. Most contain genetically engineered versions of a few proteins from the Plasmodium parasite.
Plasmodium is the organism that causes malaria. Those modified proteins are designed to get the body's defenses to launch an immune response against the Plasmodium. But the parasite contains thousands of proteins.
SHIRLEY GRIFFITH: Another experimental vaccine includes a deactivated version of the entire parasite. Robert Seder works at the National Institute of Allergy and Infectious Diseases, near Washington.
ROBERT SEDER: "So instead of picking out one or two or three genes, you have the potential for what we call breadth -- generating an immune response that would be broad rather than narrower. And so that would be a good thing."
Radiation is used to weaken the parasite so it cannot make people sick or get spread by a mosquito. To make the vaccine, scientists use the parasite at a time in its growth when the organism is called a sporozoite.
This idea has been known since the nineteen sixties. But Mr. Seder says a discovery by a researcher at a vaccine company cleared the way for progress.
ROBERT SEDER: "The major breakthrough here was that my collaborator, Stephen Hoffman at Sanaria, developed a method where he could isolate the sporozoites and purify them so that they could administer it as a vaccine to humans. And no one thought that that was possible."
But no one knew either if the weakened sporozoites would activate the immune system to protect against malaria. So researchers tested it on volunteers and found that it was safe -- there were only minor side effects. But it was not very effective. Only two out of forty-four volunteers were protected when bitten by malaria-infected mosquitoes.
STEVE EMBER: To find out why, the researchers tested the vaccine on laboratory animals. They decided that the problem was the way the vaccine had been given to the volunteers. It was injected into the skin, to simulate the bite of a mosquito. Mr. Seder says it would have been more effective if it had been given directly into the blood.
For now, more testing is needed. A report on the testing appeared in Science magazine.
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SHIRLEY GRIFFITH: Finally, many Americans say the hardest job in the world is being president of the United States. The man, or woman, who lives and works in the White House must be able to deal with problems twenty-four hours a day, seven days a week. Even on holidays or in the middle of the night, the president may have to make decisions that affect both people in this country and the rest of the world.
That is why some news media tell about changes in a president's personal appearance during his time in office. Last August, President Obama celebrated his fiftieth birthday. Some pictures showed him as a man with grayer hair and more lines on his face than when he first took office. And that got researcher S. Jay Olshansky to thinking. He studies aging at the University of Illinois at Chicago.
STEVE EMBER: Doctors nearly always say that high levels of stress are bad for your health. So people would expect a president's life to be shorter than average. Some people even say that being president could cause a person to age two times as fast as normal. But Professor Olshansky was not persuaded. So he examined the lives of the thirty-four American presidents who died of natural causes. He found that twenty-three of them lived longer than most people born at the same time.
The average age of those thirty-four presidents when they died was seventy-three. If they had aged two times as fast as normal, they should have lived to be only sixty-eight point one years old. The professor also found that the first eight presidents lived an average of seventy-nine point eight years. At that time, modern medicines had not been invented, and most men lived only about forty years.
Four American presidents lived past ninety. John Adams, Herbert Hoover, and Ronald Reagan each lived ninety or more years. But Gerald Ford lived longer than any other president. He was ninety-three and a half when he died in two thousand six.
SHIRLEY GRIFFITH: Professor Olshansky says gray hair, hair loss and other changes are part of aging and may result from something in our genes. So presidents are no different from the rest of us. But the researcher thinks there are three reasons they outlive other people. Most presidents are well-educated. Many are wealthy when compared to other Americans. And they have the best medical care possible. They know how to stay healthy, and have the best doctors. As a result, they can afford to live a healthy life long after they leave the White House.
Professor Olshansky says, "It is a classic illustration of the benefits of socioeconomic status." His study was published last month in the Journal of the American Medical Association.
(MUSIC)
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disease malaria 疟疾
president ['prezɪd(ə)nt]
总统；董事长；校长
Massachusetts [,mæsə'tʃu:sits] 详细»
n. 马萨诸塞州（美国）
Harvard University 哈弗
creatures 生物
skeletons ['skɛlətn] 详细»
n. 骷髅；骨骼
elastomers详细»
n. 弹性体
led [led] 详细»
v. 领导；通向
defense [dɪ'fɛns] 详细»
n. 防卫，
academy [ə'kædəmɪ] 详细»
n. 学院；研究院；学会；专科院校
in the journal Proceedings of the National Academy of Sciences.
在《美国国家科学院院刊》上
battlefield ['bæt(ə)lfiːld] 详细»
n. 战场；沙场
wreckage ['rekɪdʒ] 详细»
n. （失事船或飞机等的）残骸；（船只等的）失事
uneven [ʌn'iːv(ə)n] 详细»
adj. 不均匀的；不平坦的；[数] 奇数的
silicone ['sɪlɪkəʊn] 详细»
n. 硅树脂；[口腔] 硅酮
rubber ['rʌbə] 详细»
n. 橡胶；橡皮；
caterpillar ['kætəpɪlə] 详细»
adj. 有履带装置的
n. [无脊椎] 毛虫；履带车
roll up详细»
卷起；滚滚上升；到达；出现；积累成；迫敌退向中央
transport [træn'spɔːt; trɑːn-] 详细»
n. 运输；运输机；狂喜；流放犯
vt. 运输；流放；使狂喜
was responsible for
负责
represent [reprɪ'zent] 详细»
vt. 代表；表现；描绘；回忆；再赠送
vi. 代表；提出异议
there were an estimated two hundred thirty-three million cases of malaria and almost a million deaths
communities [kə'mjʊnəti] 详细»
n. 社区；团体，群体（community的复数形式）
mosquitoes [məs'ki:təuz] 详细»
n. 蚊子（mosquito的复数）
parasite ['pærəsaɪt] 详细»
n. 寄生虫；食客
spread [spred] 详细»
n. 传播；伸展
adj. 伸展的
vt. 传播，散布；展开；伸展；铺开
vi. 传播；伸展
infected mosquitoes
受感染的蚊子
insecticide [ɪn'sektɪsaɪd] 详细»
n. 杀虫剂
spray [spreɪ] 详细»
n. 喷雾；喷雾器；水沫
vt. 喷射
vi. 喷
recherche详细»
adj. 精心设计的；异国风味的；精选的；矫揉造作的
DE [di:] 详细»
abbr. 判定元件（Decision Element）
网络释义┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈
特拉华州 消化能(Digestible Energy) 所属国家
bendiocarb详细»
n. 恶虫威（杀虫剂）
mosquito [mɒ'skiːtəʊ] 详细»
n. 蚊子
bed nets详细»
蚊帐（bed net的复数）
vaccines详细»
n. 疫苗
genetically [dʒe'netikəli] 详细»
adv. 从遗传学角度；从基因方面
engineered详细»
v. 设计；指导（engineer的过去分词）
adj. 设计的，工程
versions ['vɝʒən] 详细»
n. 版本；译本
proteins ['protiɪn] 详细»
n. 蛋白质（protein复数）
plasmodium [plæz'məʊdɪəm] 详细»
n. [无脊椎] 疟原虫；变形体；原形体；多核的原形质块
parasite ['pærəsaɪt] 详细»
n. 寄生虫；食客
organism ['ɔːg(ə)nɪz(ə)m] 详细»
n. 有机体；生物体；微生物
immune [ɪ'mjuːn] 详细»
n. 免疫者；免除者
adj. 免疫的；免于……的，免除的
response [rɪ'spɒns] 详细»
n. 响应；反应；回答
deactivated [di:'æktiveitid] 详细»
adj. 无效的
v. 使失效；去活化；释放（deactivate的过去式和过去分词）
parasite ['pærəsaɪt] 详细»
n. 寄生虫；食客
institute ['ɪnstɪtjuːt] 详细»
n. 学会，协会；学院
vt. 开始（调查）；制定；创立；提起（诉讼）
allergy ['ælədʒɪ] 详细»
n. 过敏症；反感；厌恶
infectious [ɪn'fekʃəs] 详细»
adj. 传染的；传染性的；易传染的
美国国家过敏症和传染病研究所
the National Institute of Allergy and Infectious Diseases
breadth [bredθ; -t-] 详细»
n. 宽度，幅度；宽宏
broad [brɔːd] 详细»
n. 宽阔部分
adj. 宽的，辽阔的；显著的；大概的
adv. 宽阔地
radiation [reɪdɪ'eɪʃ(ə)n] 详细»
n. 辐射；发光；放射物
sporozoite [,spɒrə(ʊ)'zəʊaɪt; ,spɔː-] 详细»
n. [无脊椎] 孢子体；孢子小体
major ['meɪdʒə] 详细»
n. [人类] 成年人；主修科目；陆军少校
adj. 主要的；重要的；主修的；较多的
vi. 主修
breakthrough ['breɪkθruː] 详细»
n. 突破；突破性进展
collaborator [kə'læbə'retɚ] 详细»
n. [劳经] 合作者；勾结者；通敌者
isolate ['aɪsəleɪt] 详细»
n. [生物] 隔离种群
vt. 使隔离；使孤立；使绝缘
adj. 隔离的；孤立的
vi. 隔离；孤立
purify ['pjʊərɪfaɪ] 详细»
vt. 净化；使纯净
vi. 净化；变纯净
laboratory [lə'bɒrə,t(ə)rɪ; 'læb(ə)rə,t(ə)rɪ] 详细»
n. 实验室，研究室
simulate ['sɪmjʊleɪt] 详细»
adj. 模仿的；假装的
vt. 模仿；假装；冒充
for now详细»
目前，暂时
affect [ə'fekt] 详细»
n. 情感；引起感情的因素
vt. 影响；感染；感动；假装
vi. 倾向；喜欢
Illinois [,ili'nɔi(z)] 详细»
n. 伊利诺斯州（美国州名）
expect [ɪk'spekt; ek-] 详细»
vi. 期待；预期
vt. 期望；指望；认为；预料
persuaded详细»
v. 说服，劝说（persuade的过去分词形式）
result from详细»
起因于；由……造成
they outlive other people
outlive [aʊt'lɪv] 详细»
vt. 比…活得长；比…经久；经受住；渡过…而存在
afford [ə'fɔːd] 详细»
vt. 给予，提供；买得起
illustration [ɪlə'streɪʃ(ə)n] 详细»
n. 说明；插图；例证；图解
socioeconomic ['səʊsɪəʊ,iːkə'nɒmɪk] 详细»
adj. 社会经济学的