理工类和卫生类新增的文章更体现专业性在线赌场网址大全:

C [u]Surface tension[/u](表面张力).

At this point, we said, "Let's just stop. Let's not go down that same road. Let's just figure out what's missing. What are we not dealing with? What are we not doing that needs to be done?" It's like in "The Godfather," right? When Fredo betrays his brother Michael, we all know what needs to be done. Fredo's got to go.

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(Laughter)

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And we were doing it -- and by we I mean my whole generation of graduate students. We were trying to make blazing fast computers using nanomaterials. We were constructing quantum dots that could one day go in your body and find and fight disease. There were even groups trying to make an elevator to space using carbon nanotubes. You can look that up, that's true. Anyways, we thought it was going to affect all parts of science and technology, from computing to medicine. And I have to admit, I drank all of the Kool-Aid. I mean, every last drop.

The Tiniest Electric Motor in the World

I know that's an absurd notion. It's probably impossible. The only way you get a statue from a pile of dust is if the statue built itself -- if somehow we could compel millions of these particles to come together to form the statue.

A An introduction of a Toyota’s 225 horsepower V6 engine.

So our group's role and our group's mission is to innovate by employing carbon nanotubes, because we think that they can provide a path to continue this pace. They are just like they sound. They're tiny, hollow tubes of carbon atoms, and their nanoscale size, that small size, gives rise to these just outstanding electronic properties. And the science tells us if we could employ them in computing, we could see up to a ten times improvement in performance. It's like skipping through several technology generations in just one step.

A An introduction of a Toyota’s 225 horsepower V6 engine.

As an example: if I took the room-sized computer that sent three men to the moon and back and somehow compressed it -- compressed the world's greatest computer of its day, so it was the same size as your smartphone -- your actual smartphone, that thing you spent 300 bucks on and just toss out every two years, would blow this thing away. You would not be impressed. It couldn't do anything that your smartphone does. It would be slow, you couldn't put any of your stuff on it, you could possibly get through the first two minutes of a "Walking Dead" episode if you're lucky --

C [u]Surface tension[/u](表面张力).

Now, as it turns out, this is not that alien of a problem. We just don't build anything this way. People don't build anything this way. But if you look around -- and there's examples everywhere -- Mother Nature builds everything this way. Everything is built from the bottom up. You can go to the beach, you'll find these simple organisms that use proteins -- basically molecules -- to template what is essentially sand, just plucking it from the sea and building these extraordinary architectures with extreme diversity. And nature's not crude like us, just hacking away. She's elegant and smart, building with what's available, molecule by molecule, making structures with a complexity and a diversity that we can't even approach. And she's already at the nano. She's been there for hundreds of millions of years. We're the ones that are late to the party.

D Previous inventions of nanoscale(纳米级的) products.

Let's imagine a sculptor building a statue, just chipping away with his chisel. Michelangelo had this elegant way of describing it when he said, "Every block of stone has a statue inside of it, and it's the task of the sculptor to discover it." But what if he worked in the opposite direction? Not from a solid block of stone, but from a pile of dust, somehow gluing millions of these particles together to form a statue.

指定的四个段落都没有明显的段落主题句(2007年理工类A/B级概括大意题中四个指定段落都没有明显段落主题句),考生可以通过通读指定段落的大意来归纳出段落主题, 或借助一些有效的答题技巧确认段落主题。以确认段落第4段的段落主题为例分析答题技巧:

When I was a graduate student, it was one of the most exciting times to be working in nanotechnology. There were scientific breakthroughs happening all the time. The conferences were buzzing, there was tons of money pouring in from funding agencies. And the reason is when objects get really small, they're governed by a different set of physics that govern ordinary objects, like the ones we interact with. We call this physics quantum mechanics. And what it tells you is that you can precisely tune their behavior just by making seemingly small changes to them, like adding or removing a handful of atoms, or twisting the material. It's like this ultimate toolkit. You really felt empowered; you felt like you could make anything.

F Possible fields of application in the future.

But that was 15 years ago, and -- fantastic science was done, really important work. We've learned a lot. We were never able to translate that science into new technologies -- into technologies that could actually impact people. And the reason is, these nanomaterials -- they're like a double-edged sword. The same thing that makes them so interesting -- their small size -- also makes them impossible to work with. It's literally like trying to build a statue out of a pile of dust. And we just don't have the tools that are small enough to work with them. But even if we did, it wouldn't really matter, because we couldn't one by one place millions of particles together to build a technology. So because of that, all of the promise and all of the excitement has remained just that: promise and excitement. We don't have any disease-fighting nanobots, there's no elevators to space, and the thing that I'm most interested in, no new types of computing.

  1. Scientists recently made public the tiniest electric motor ever built. You could stuff hundreds of them into the period at the end of this sentence. One day a similar engine might power a tiny mechanical doctor that would travel through your body to remove your disease.

  2. The motor works by shuffling(来回运动) atoms(原子) between two molten metal droplets(小滴) in a carbon nanotube(纳米管). One droplet is even smaller than the other. When a small electric current is applied to the droplets, atoms slowly get out of the larger droplet and join the smaller one. The small droplet grows – but never gets as big as the other droplet – and eventually bumps into the large droplet. As they touch, the large droplet rapidly sops up (吸入)the atoms it had previously lost. This quick shift in energy produces a power stroke(动力行程).

  3. The technique exploits the fact that surface tension -- the tendency of atoms or molecules to resist separating -- becomes more important at small scales. Surface tension is the same thing that allows some insects to walk on water.

  4. Although the amount of energy produced is small -- 20 microwatts(百万分之一瓦) -- it is quite impressive(给人印象深刻的) in relation to(与...相比) the tiny scale of the motor. The whole setup is less than 200 nanometers on a side, or hundreds of times smaller than the width of a human hair. If it could be scaled up to the size of an automobile engine, it would be 100 million times more powerful than a Toyota Camry’s 225 horsepower V6 engine.

  5. In 1988, Professor Richard Muller and colleagues made the first operating(工作的, 运行的) micromotor(微型发动机), which was 100 microns(微米) across, or about the thickness of a human hair. In 2003, Zettl's group created the first nanoscale motor. In 2006, they built a nanoconveyor(纳米传送带), which moves tiny particles along like cars in a factory.

  6. Nanotechnology(纳米技术) engineers try to mimic nature, building things atom-by-atom. Among other things, nanomotors could be used in optical circuits to redirect light, a process called optical switching. Futurists envision(预想) a day when nanomachines(纳米机器), powered by nanomotors(纳米发动机), travel inside your body to find disease and repair damaged cells.

(Laughter)

2.B.解析:段落中没有明显的段落主题句, 但是段落中出现了大量反映典型细节信息的词语:20 microwatts(微瓦), 200 nanometers(纳米), hundreds of times smaller than the width of a human hair, 100 million times more powerful, 225 horsepower(马力), 这些细节信息贯穿全段, 从性质上它们分别用于描述功率和尺寸大小, 因此可直接判断B(描述了纳米发动机的功率和尺寸大小)是答案。

Now that last one, that's a really important one. We just have come to expect the pace of computing advancements to go on indefinitely. We've built entire economies on this idea. And this pace exists because of our ability to pack more and more devices onto a computer chip. And as those devices get smaller, they get faster, they consume less power and they get cheaper. And it's this convergence that gives us this incredible pace.

E The working principle of the nanomotor.

But Michael -- he puts it off. Fine, I get it. Their mother's still alive, it would make her upset. We just said, "What's the Fredo in our problem?" What are we not dealing with? What are we not doing, but needs to be done to make this a success?" And the answer is that the statue has to build itself. We have to find a way, somehow, to compel, to convince billions of these particles to assemble themselves into the technology. We can't do it for them. They have to do it for themselves. And it's the hard way, and this is not trivial, but in this case, it's the only way.

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