How do the researchers conduct the study？ 查看材料A.By

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A.They are the second killers to smoking as cause of lung cancer.

B.They can compensate for the abnormal DNA.

C.High dosage and low dosage of them have the same effect on people"s health.

D.Their effect can"t be found immediately.

Alpha particles directly come from__________. 查看材料

A.decaying uranium

B.decaying radon atoms

C.air from the ground

D.radiation particles

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Alpha Particle

From decaying radon （ 氡） atoms can destroy the living cells they strike and increase the likelihood that those cells will later become cancerous.Researchers have now directly demonstrated that neighboring cells not suffering direct hits can be harmed， too. They"ve also taken a step toward showing how this type of radiation，called alpha particles， indirectly hurts those bystanders.

Radon derives from the decay of uranium （ 铀） and seeps naturally into the air from the ground.lt"s the primary environmental source of alpha particles， which contribute to cancer risk by causing aberrations （失常）in DNA.Alpha particles from inhaled radon are second only to smoking as a cause of lung cancer.

Because a person"s exposure to alpha particles typically is low， researchers have had to estimate public health threats from radon by guess from the effects of higher doses of alpha radiation.Such data comes primarily from studies of survivors of the atomic bombs that destroyed Hiroshima and Nagasaki in Japan. The customary extrapolation （ 推测 ） assumes that cancer risk is proportional to the dose of radiation even at low doses.

Radiation"s effects in cell structure don"t necessarily reflect what happens in "a whole organism， with its full range of defense repair mechanisms， " says Duport.Processes such as DNA repair and cell death triggered by radiation damage could cancel the effect on by stander cells observed in the lab， he suggests.

Furthermore， while a bystander effect can contribute to cancer， other cell-to-cell interactions in living tissue "may relieve increased risk." says Barry Michael， a radiation biophysicist at the Gray Cancer Institute in Northwood， England.One of these interactions halts cell division and hence cancer. "The jury is still out on whether cell-to-cell effects lead to a greater or lower risk， " Michael says.

The passage‘s main topic is__________. 查看材料

A.The experiment done by researchers

B.Uranium is the key killer of neighboring cells

C.Cell-to-cell interaction can make up for the hurt cells

D.Bystander cells can be indirectly damaged by alpha particles

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A.doctors will be able to repair the destroyed cells of human bodies

B.cancer and other infected diseases will be cured

C.there will be more accurate diagnoses of diseases

D.the medical devices will become smaller and devices with single function are produced

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A.tiny

B.lighter

C.costly

D.diversified

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A.Nanotechnology will be used to change the structures of materials.

B.Nanotechnology will make an operation more precisely.

C.Nanotechnology will change the properties of materials.

D.Nanotechnology will cure diseases that can"t be solved at present.

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Nanotechnology

Many of the grand challenges of today and the future are found in the question: "How are we going to solve the problems and make serious improvements in industrial manufacturing, disease control, environmental pollution control, global climate change, food production, transportation, communication, and others?"

Nanotechnology ( 纳米技术 ) promises to make revolutionary contributions.Within the next few years we can expect to see major improvements. Here are some possibilities the things to come.Nanotechnology is fundamentally changing the way materials and devices will be produced in the future.

Nanostructures, ceramics, polymers, metals, and other materials will have greatly improved mechanical properties.In fact, with the ability to build things atom-by-atom and molecule-by-molecule there will be new classes of structural materials.Nanotechnology will enable products to be lighter, stronger, smarter, cheaper,cleaner, and more precise.

The ability to synthesize nanoscale budding blocks with precisely controlled size and composition and then to assemble them into larger structures with unique properties and functions will revolutionize segments of the materials manufacturing industry. Nanotechnology is expected to bring about lighter, stronger, and programmable materials ; reductions in life-cycle costs through lower failure rates; innovative devices based on new principles and architectures ; and use of molecular cluster manufacturing.

Nanotechnology will provide new tools for medicine.It could radically change the way surgery is done.It will make it possible to do molecular scale surgery to repair and rearrange cells.Since disease is the result of physical disorder, misarranged molecules and cells, medicine at this level should be able to cure most diseases.

Mutations in DNA could be repaired and cancer cells, toxic chemicals, and viruses could be destroyed through use of medical Nan devices.

Nanotechnology enabled increases in computational power will permit the characterization of macromolecular networks in realistic environments.Such simulations will be essential elements in the development of biocompatible implants and in the drug discovery process. Nanotechnology has the potential to significantly impact energy efficiency, storage, and production, Nanotechnology can change the economics of energy production.

The passage deals mainly with__________. 查看材料

A.grand challenge in manufacturing， medicine and computer industry

B.possibilities of nanotechnology"s contributions in the future

C.great changes caused by nanotechnology

D.practical application of nanotechnology

料

A.books

B.lecture

C.tricks

D.fact

E.memory

F.list

Paragraph 5__________. 查看材料

A.Good results

B.An ancient skill

C.Gaining attention

D.Memory tricks

E.A lecture on memory techniques

F.Ways to improve memory

Paragraph 4__________. 查看材料

A.Good results

B.An ancient skill

C.Gaining attention

D.Memory tricks

E.A lecture on memory techniques

F.Ways to improve memory