Entropy Lives Here

Sorry about the light posting lately - suffice it to say that life has gotten a bit exhausting. More on that later, but for example, the past three weekends have involved Rachel traveling to Atlanta for USAV nationals, Chad going to Portland for Railscon*, and then Rachel heading to Gaithersburg MD to shoot some neutrons and Chad heading to Boston.

At any rate, I'm back at NIST, and was informed when I arrived at the gate this morning that there is a bear on site.

A BEAR.

NIST is a totally fenced in, guarded, federal lab. Apparently one that is now inhabited by a bear. You know scientists, not satisfied with working in close proximity to a nuclear reactor, might like having a bear around for extra excitement.

I guess the story is that bear was in someone's back yard, and when animal control came after it it jumped the fence into NIST. Apparently the plan is to just wait for it to leave on its own accord. Which is fine with me (I don't think I'm in any bear danger as I walk the short distance from my car to the building), but funny. The gatehouse has a big "bear warning" sign up. Such silliness.

*Did you see the first picture on the railscon website? I guess there are places with a more narrow demographic than WPI. And I thought physics conferences were bad!

So I’m at NIST, doing some scattering experiments at the National Center for Neutron Research this weekend. Please hold back your comments about what a party animal I am and how I live it up on the weekend.

**disclaimer: if you don't want to endure my lengthy description of Neutron scattering targeted to third grade teachers and musicians already familiar with x-ray scattering (perhaps that is a small demographic but whatever) please skip to the last paragraph.**

I actually think this Neutron stuff is pretty cool. Neutron scattering is similar to x-ray scattering, but the contrast mechanisms are different. When you shoot x-rays at a material, they scatter off of the atoms inside. The heavier the atom, the more the x-rays scatter (so P (atomic mass = 31) is a better scatterer than C (mass = 12), and H (mass = 1) is practically invisible). When you shoot neutrons at a material, they also scatter off the atoms inside. But the heavier atoms aren’t necessarily better than the light ones. For Neutrons, scattering is larger for atoms with a higher "scattering length" (I'll call it "b" for short), which doesn’t necessarily increase with atomic weight. For example, for C, b = 6.65, and for P, b = 5.13 .

There is a huge difference in scattering length between Hydrogen and Deuterium. Deuterium is Hydrogen with one extra neutron, so it's molar mass = 2. However, for D, b = 6.67, for H, b = -3.4. Big difference! Most molecules that have H in them can be made with D instead of H without really changing any other properties, so scientists can swap Ds for Hs in their molecules to get different scattering in the Neutron beam (so I don’t have to go into a whole shpiel about contrast matching, take my word for it that this is really really useful).

What all this boils down to is that you can do a very similar experiment with x-rays and neutrons and see totally different things. Below is an example of the difference between the contrast available from x-ray and neutron imaging, from UT Nuclear Engineering. "Neutron Imaging" is similar to "Neutron Scattering" in that you expose the material to neutrons, but the optics are different such that you get an image in real space. The contrast mechanisms are the same as with scattering, though, and you can see that each neutrons and x-rays allow you to see totally different things.

Here is an x-ray image of a camera.
The plastic parts of the camera are basically invisible (they're made up of light elements) and the metal parts are basically opaque (they're made of heavy elements).

Here is a neutron image of the same camera.
Now we can see the details in the plastic parts, including the film, because the metal parts are basically invisible. Isn't that cool?

They use neutron imaging a lot for fuel cell research. Inside a fuel cell there is water moving through channels in a plastic membrane, and the whole thing is enclosed in metal. Because of the metal casing, we can't use regular or x-ray imaging to see what's going on inside when the cell is running. But turns out Neutron imaging is perfect for this sort of thing, because the casing is basically invisible but the water shows up great. I would encourage you to read more just because I think it's such an elegant way to study fuel cells.

In case you are tired of my neutronbable, I will switch subjects entirely, to one less science-heavy. I think the picture on my NIST badge is one of the best taken of me in a really long time. Which is too bad because the badge is used for security purposes and belongs to the government, so I am quite sure it would be inappropriate for me to take a picture of it and post it here. Basically I am saying this great picture will be seen by no one, so it’s entirely useless to me. And you’ll just have to take it on faith that it actually exists.

P.R. = Public Relations, of course. I opened the Ambler Enterprise (our newspaper with an average length of 10 pages) to just skim through it for concerts or something interesting to do before I threw it in the recycling, and found this (click on the article to see it large enough to read).


I was totally surprised. Well, shocked to see my name in a headline but really not surprised after I did, since our director of communications asked me a bunch of questions before I went. My immediate reaction was to be really embarrassed, but then I tried to remember Mom's advice about dealing with the fishy-handed reporter at the Free Press: smile and be gracious. Smile and be gracious. And this isn't that embarrassing after all, since half of the article is the R&H standard press blurb. At any rate take a look, I'm famous.

The entire Spring House Technical Center (~950 people) got the following email from the site director:

to: Employees at the Spring House Site

As part of their exciting Pennsylvania primary campaign, we've just learned that Senators Hillary Clinton and Barak Obama will be visiting Spring House this afternoon for a townhall meeting in Emmons Auditorium. The meeting will start at 4:00 and should last about 1 hour. Seating will be on a first come basis so be sure to get their early if you want a seat. Sorry for the very short notice but we've had to keep this very quiet for security reasons. The Senators will be arriving by helicopter at 3:55 on the lawn in front of Building 6. Please keep clear of this area. The Secret Service will start clearing the geese from the site at 3:45 to insure that there is no interference with the helicopters. The TV crews should start arriving and setting up by 2:00. Please do not park in the parking spots by building 6. We need to keep these spaces open.

Thanks, I hope you can join us for this exciting and newsworthy event

Signed, the director of the site. I reacted to this with the following (in somewhere near this order):

- wow! That is so exciting!
- I wonder if Chad can come. He didn't say anything about guests.
- How early will I have to get there to get a seat? Can I get all my measurements done before then?
- Wait a second.... why would the secret service have to get rid of the geese and not our facilities people?
- Hillary and Barak in the same place and the same time, and that place is building 6? None of this makes any sense.

And then I remembered what day it was. And then I confirmed with some co-workers (not without some disappointment on my part) that our site director was messing with us. And went about my business, until we got the following email a few hours later.

to: Employees at the Spring House Site

Unfortunately the geese were too aggressive and it does not look like we can move them. Maybe next year on APRIL 1st we can invite the candidates back.

So at any rate, apparently the spring house geese are even scarier than I realized. In other news, Max and Entropy have learned how to ride a bicycle while singing the score from Les Miserables, and Chad has decided to sell his shares of Thoughtbot to Microsoft so he can take the cats on their European tour.

Booya. There it is. PhD senior scientist. It must be true because it's in print. :)

Things are going pretty well with the job so far. I'm not as exhausted as I was the first week, but my energy seems to be coming in spurts. For example, Tuesday night I felt great and played volleyball until ~10:30pm (so I didn't get to bed until ~11:30) and then got up at 5 so I could be at work early to meet with someone and decided to ride my bike to work. Then Wednesday night I crashed and went to bed at 8pm. So now that I can handle being awake and paying attention for eight hours straight every day we'll have to work on spacing out the out-of-work activities.

In other news this evening I cleaned our floors with murphy's oil soap (I've been waiting to do this until the urethane had a month to cure). Did I mention I love our floors? They are so great. Also I learned that Max is scared of the mop. Shocking, I know.

Who said yesterday she was sad she couldn't be there to bring me pencils (like my first day of school). Here I am, all ready to go to work, holding pencils that Grandma gave me years ago. My first day of work was good, the people I'm going to be working with are fun, and I'm excited in general about my new job. We'll see how this report changes by the end of several days of nothing but safety training...

9.5. Weehee!

Not much happened on the home front this weekend. We had a great time at a wedding yesterday, where we barely knew anyone other than the groom. Luckily they sat us with his engineer friends from work and apparently we geeks get along just fine. Today we spent a few hours running and walking around Valley Forge National Historic Park (we didn't actually do any historic stuff, just enjoyed the river). We saw several deer (who are apparently NOT very scared of people - they would hang out and chew a branch or something while we walked by 20 feet away), birds, butterflies, etc., and really not too many people. It was nice. Then we relaxed, cleaned a bit, and unpacked and hung the rest of our artwork. This means that several of our walls are now less bare. However, now that we have so many walls, we'll have to do a bit more work to fill them all.

So now the only box yet unpacked is the one with our casserole dishes. Unfortunately, we have no idea where this box is. Hopefully we will discover it in the basement eventually.