So in fluid mechanics we were learning about carbon nanotubes. These tiny cylinders (about 10E-09 m in diameter, hence the name) are likely to revolutionize many sectors of industry. They are made out of carbon, with a unique chemical structure making them extremely strong. Like diamonds, they are made of carbon, and their bond structure makes them even stronger than diamonds, depending on which way you try and break them. They tend to aggregate into ropes, and you can fuse them together, creating the possibility of making them into extremely strong wires. They are also good at conducting heat.

So. How does this have to do with a pair of water scissors?

Well, given that carbon nanotubes are so strong, they are exceedly difficult to cut. Engineers would like to cut them to whatever length they desire for their projects, but now they have to deal with the fact that they're going to be whatever length they grow to be (perhaps a couple microns). Thus the problem was put to researchers: How can we cut a micron-scale nanotube accurately when its bonds are stronger than a diamond's? We must make a pair of nanoscissors!

One group tried to do it chemically, sort of how some people cut DNA. But they had to use extremely strong chemicals, and they always ended up destroying the carbon nanotubes instead of cutting them.

Another laboratory decided to cut them physically by mixing them with extremely tiny bits of zircon (a very hard and resilient mineral), and then shaking the container. Unfortunately, this method also usually reduced the carbon nanotubes to bits or damaging them instead of cutting them.

Enter the group at Brown. Fluid mechanicians, they decide to cut the carbon nanotubes using water. How? Cavitation, of course!

Cavitation is a process by which turbulence or disturbences (pressure waves, what have you) in a liquid cause tiny areas where the pressure is low enough for the liquid to turn into a gas. This is kind like boiling, except boiling is usually accompanied by temperature rising enough to turn the liquid to a gas, because the state of a material is dependent on both temperature and pressure. But even when boiling, the first bubbles usually nucleate on contaminating particles or along the wall of the container, where local pressure is slightly lower.
After these bubbles form, they almost immediately collapse after the pressure goes back to normal. They collapse at super-sonic speed, and because the process is adiabatic, as the volume shrinks, the temperature goes way up-- to the tune of some 5000 degrees C. The energy produced very locally by this process is so high that the popping bubbles often give off sparks as they collapse, as well as pressure waves that can be heard as very loud sounds.

This aspect of cavitation makes it a huge engineering concern, and a big concern for secret spy nuclear submarines (see: Hunt for the Red October, "We're cavitating!!!") Cavitating makes a huge number of extremely loud pops, which can be easily picked up by the sonar on other vessels (i.e., Commies!!). The skins of submarines are optimized to reduce cavitation as much as possible, but it depends on what maneuvers you are doing. Cavitation can also happen in pistons and pipes and near the propellors of ships. The energy from the popping bubbles wears huge pits into the metal in these systems, incurring a large cost and necessitating the replacement of parts well before they should be worn out.

Cavitation is also a concern when using ultrasound on the body, because pressure waves like those used in ultrasound, if it's turned up too high, can induce cavitation in your blood, wreaking havoc on the nanostructures in your vessels. (Don't worry, they never turn it up that high!)

Cognizant of the effect of cavitation on nanostructures, the people at Brown decided to see how carbon nanotubes reacted to cavitation. As it turns out, if you put a lot of carbon nanotubes into water, when the bubbles form, the nanotubes are attracted to the low pressure region and in a sense adhere to the surface of the bubble. When it collapses, the surface area over which the nanotubes are spread decreases drastically, and the nanotubes buckle... along eigenmodes!

If you imagine pushing a rug from either side, the rug will buckle in a series of folds that are usually evenly spaced. These are the eigenmodes of the rugs, and the spacing between them would be the eigenspacing, as eigen just means "characteristic" in german. But you can change the eigenspacing of your rug by pushing it together with different energies. (It will also have different eigenspacing depending on how stiff a rug it is. You can imagine that a doormat might have only one eigenmode, while a blanket would have a lot.)

So, by controlling the size of the bubbles that form (by controlling the kind of sonic waves that initiate the cavitation), you can cut the carbon nanotubes to pretty much any length you want!

Using scissors.... MADE OF WATER!!!

Anyway, that was a really cool class.

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So it's the day after Valentine's Day. We've been hearing all the stories drifting in of what everyone did last night. One guy made dinner with his sweetie-pie and they consumed half a salmon, a loaf of bread, a wheel of cheese, and untold glasses of wine. That didn't sound half bad. Another fellow just talked about the massive amount of wine that was involved. Hm...
The Welshman took his darling to a play in the next town over. It was rather experimental, written by a British-Irish playwright... but it was about this author who always writes stories about children being murdered, until children start being murdered in the very same way that he described. Then he gets incarcerated by his government and tortured so that they can try and find the truth. Doesn't really sound very Valentinesy, but I dare say, the Welshman's idea of Valentine's Day sounds quite civilised. (Note the use of the British orthography.)

As for my Valentine's Day, I had a bunch of amazing plans and they were all completely ruined.

I was all ready to sit in my office working on my proposal, then I was going to eat a Hot Pocket for dinner (the fiesta kind, my fav!). Then around 9:15 I was going to go see a movie by myself. After the movie I would return to my office where I would pretend to work but actually write enigmatic Nutang entries and refresh my facebook page a thousand times. Then I was going to look for free polka music online while listening to french news radio, finally driving home around 1am and being so tired that I'd sleep through my meeting this morning.

HOWEVER, I told my roommate about my desire to see this movie. "So... you're going to this movie with some people from work?" she probed. "Uh... well... actually I was just going to go by myself." I answered. It had sounded very "scene" and "emo" in my mind, me, going to the movie, looking mysteriously melancholy... but saying it out loud just made it sound pretty lame. Turns out she wanted to know who I was going with to see if she could go, too. Naturellement!

SOooo we ended up having a hilarious time eating Mexican food at the Azteca local restaurant, going to the movie [Persopolis, very good!], and admonishing the cats in unconjugated French for never pulling their weight in the household [nous travaillons pendant toute la journee, et voila, quand nous arrivons a la maison, vous n'avez pas fait la vaisselle! Vous n'avez rien fait!] until wee hours of the morning.

And I didn't sleep through my meeting. I fairly leaped out of bed this morning.

Vive la France!

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So apparently I got a 5/40 on my first advanced fluid mechanics homework. Oops.
But today we learned how the famed physicist/mathematician Boltzmann (like Boltzmann's Constant!) killed himself after his work was roundly criticized by Mach (like Mach number!) and some other contemporaries (except for Maxwell, like Maxwell's Equations, who worked with him... hence Maxwell-Boltzmann!)

He had just discovered the second law of thermodynamics, the law of Entropy, that is, the law that says that the net state of the universe will always tend towards increasing disorder. So basically, if you have a closed system, (no energy is entering it!) then everything will get more and more disordered as a function of time. It was rejected by many scientists for whom he had great respect. He actually killed himself *just* before experiments proved that he was right.

I may be appallingly bad at advanced fluid mechanics, but I am smart enough to know that killing yourself is a really stupid idea.

Which technically makes me smarter than Boltzmann.


Sweet.


Boltzmann's actual tombstone:

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Well today is G-bird's birthday. He's come to visit. Naturally our furnace took the opportunity to break, and naturally the last two days have been the coldest it's been this entire winter.

Thalweg made him a birthday cake that looks like a bicycle! Quite grand.

Our very own brilliant and charming french climate modeler colleague Francois has been here for the last couple of days... he described radiative transfer to me in about 15 minutes. We decided that he and his equally charming student Jean-Baptiste should travel a circuit reinspiring worn out graduate students everywhere with their contagious enthusiam.

I also went crazy and bought a bunch of DVDs since they were on sale:

Rambo: First Blood
Total Recall
Clue
and Milo and Otis

Hopefully the weather will improve so T & G can have a fun weekend riding bicycles. As for me, I spent the evening cleaning the bathroom. Then I ate an entire can of baked beans for dinner. BECAUSE I CAN.

For Valentine's Day I intend to eat a curried garlic onion chive dish with beans and lentils. BECAUSE I CAN.

vive la france!

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It's late again.

I'm in the lab.

Doing fluid mechanics homework. Tensor space. Blasius discovered how to mathematically express the velocity fields of viscous incompressible fluids near the leading edge of a blade.

I don't know why you would be cutting water with a blade.

Ok, propellers. Shut up, smart guy. Yah got any other smart comments, smart guy?

But anyway, thanks to Blasius and his devious goings-on in 1908, I now have to manipulate his equations.

Reminds me of the grossest math book passage I've ever read, saying something about, "After massaging the equation for a bit..." (aka doing "simple" algebra that it would take you 30 minutes to work out, which they don't write out because they're lazy)

I really don't want to read about math nerds massaging their equations. tmi, math nerds. tmi.

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I am finding it lame that when I ask people to do awesome things, they're just like, "well, I can't say yet because I have to ask my boyfriend what he's going to do."

Welllllll then, why don't you spend your whole life with your boyyyyfriend? Why don't you just not do awesome things ever again, because your boyfriend is laaaaammme and you just want to hang out doing laaaaame things together???

I mean, ok, maybe if your boyfriend lives an hour away and only comes to visit sometimes, and if next friday is both his birthday and the first time you've seen him in like three weeks, then I would give you a pass on that.

But that isn't the case for some people. Therefore, beest thou now informed: I find your actions to be supremely Lame*.



*Note the use of the capital L.

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