Friday, December 21, 2007

Marathon Save Lives

The last couple of months have featured two prominent marathoning deaths. The first happened during the October meltdown at the Chicago Marathon where extreme temperatures led to the race being shut down early and one runner died. The autoposy indicated that it wasn't the race conditions that killed him, though, but rather a pre-existing heart condition. The second was the surprising death of elite runner Ryan Shay around mile 5 of the US Olympic trials. Yet despite the press garnered by these events, running marathons is not only safe, but may actually lower the number of deaths.

There is, of course, overwhelming evidence that running has health benefits. But a new study published in the British Medical Journal indicates that not only is the chance of dying during a marathon slim, but that the number of motor vehicle fatalaties prevented by road closures drastically exceeds the number of people dying during the race.

If you don't feel like reading the journal article itself, the New York Times has a nice summary of the report.

This is good news for people like me who think that it's worth running in at-freezing temperature freezing rain to train for a marathon. Pictured here are my friend Jonathan and I after a recent run from my house. You can see the layer of ice that formed on the bill of my running hat below.

Speaking of which, here's my planned marathon schedule, which constitute the 5 races of the World Marathon Majors:

April 2008, Boston
October 2008, Chicago
April 2009, London
November 2009, New York City
September 2010, Berlin (click on the British flag at the top for English)

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Wednesday, December 12, 2007

Fresh Pasta

The other night, 19 people ate homemade pasta at my place. I can't take much credit beyond the dough, though, because everybody else brought the rest of the food and I was barely successful at rolling and cutting the dough. I used to roll out the dough with my mom growing up, but the past two years people have had to take over for me to make the magic with the pasta maker that my sister gave me last year for Christmas. This year, Craig and Suvda did the bulk of the pasta and managed to make a huge set of noodles out of an entire recipe of dough (we made five recipes worth). Here's my mom's super-simple recipe for the dough, which makes delicious fresh pasta:

2.5 cups flour
a little salt
~3 eggs

Mix in the food processor and add ~1T of water until the mixture balls up into a ball of dough.


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Tuesday, December 11, 2007

The Wiener Sausage

I was just introduced by my roommate to the mathematical Wiener sausage. My first introduction came from this abstract:

We consider the Wiener sausage among Poissonian obstacles. The obstacle is called hard if Brownian motion entering the obstacle is immediately killed, and is called soft if it is killed at certain rate. It is known that Brownian motion conditioned to survive among obstacles is confined in a ball near its starting point. We show the weak law of large numbers, large deviation principle in special cases and the moment asymptotics for the volume of the corresponding Wiener sausage. One of the consequence of our results is that the trajectory of Brownian motion almost fills the confinement ball.

I had trouble believing that this could be real, but it's very real indeed. In fact, it turns out that there's a Wiener measure.

Because I have the sense of humor of a 12-year old, I was dying to learn more. A quick search of Google Scholar yielded some great titles (links provided to prove that I'm not making this up):
Read any other good scholarly articles on the Wiener sausage lately?

UHV Part 2, the Bake-Out

Last month, I wrote about how we seal flanges using copper gaskets on our Ultra-High-Vacuum (UHV) system. Just sealing a system up, however, does not get rid of all the air and hooking a standard Hoover up to it won't do the job either. In fact, just hooking up all of our more sophisticated pumps won't do the job either. They work to keep us at UHV once the low pressures are achieved, but they won't do the job just by being turned on at atmosphere. In order to get to UHV pressures after venting the system to atmosphere, we have to do what is called a "bake-out."

The reason that UHV pumps cannot evacuate the chambers to UHV pressures from atmosphere is due to the fact that lots of atmospheric molecules (water is a particularly nasty one) stick to all of the surfaces. While the pumps can evacuate the gas molecules, they will be constantly replenished by molecules desorbing from the walls of the chambers to enter the gas phase. The idea of a bake-out is simple: heat the heck out of the chambers while pumping on them to encourage almost all of the molecules to come off of the walls to get pumped out over the course of a few days.

In practice, the basics of the bake-out are shown in these pictures. Once the system is completely sealed and leak tested, the entire system is wrapped with heating tapes and we place thermocouples everywhere on the system that we want to monitor. These heating tapes are phenomenally expensive and consist of nothing more than a piece of wire in some fiberglass that you plug into the wall; whoever manufactures these things must make a killing, particularly because they burn out all the time. Once the heating tapes are in place, we wrap the entire system in several layers of aluminum foil. This helps distribute the heat from the tapes over the entire chamber since the chambers themselves are made of the very poorly thermally conducting stainless steel. The tapes are then plugged into variacs, which let us apply however much voltage we want to them (to heat whatever parts of the chamber are wrapped in them to the desired temperatures) rather than just the 120 V from the wall.

For a few days, we slowly ramp the temperature up on the system without letting the pressure get too high. The goal is to get each part of the system as hot as we can without damaging any parts of the system (in this case, our microscope, which has a heat tolerance of about 150 C) or any of the seals, which vary from 150 C to 250 C. Once we have the system nice and hot, we say that it is at "full bake." We monitor the temperature at various places in and on the system with the thermocouples that we put on the system before wrapping it, plugging our thermocouple reader into each. We let the system sit at full bake for several days while we monitor the pressure, the presence of various atmospheric gases, and the temperature. Additionally, we do several procedures such as degassing filaments (turning any filaments on in the system to hot to desorb gases from them), regenerating our non-evaporable getters, and "burping" our ion pumps. (These terms are for another future UHV post on the five different types of pumps we use.) Finally, we switch the UHV side of the system over to the ion pumps and cool everything down. When we cool the system down, we cool the core of the system down first and the extremities last because we don't want gas molecules readsorbing at the extremities before the bake-out is complete. If all has gone well, when the system reaches room temperature, the pressures inside will be classified as ultra-high-vacuum!

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Sunday, December 09, 2007

How To Love The Long Run From Runner's

I was reading RW tonight and really enjoyed this article. I laughed in the first paragraph because when I'm on vacation with my family, they have to deal with me scheduling my long runs.

How To Love The Long Run From Runner's