Thursday, February 22, 2007

Too bad Apple's got that name locked up

I gravitated toward this paper's title, "Reversible, Erasable, and Rewritable Nanorecording on an H2 Rotaxane Thin Film".
the ref: JACS 2007 129, 2204-2205.
This paper's about a new material that makes a promising step toward atom-scale data storage devices. As computers store more and more large files (and I don't just mean home movies from your family trip to the world's largest ball of twine, I'm talking government use, scientific number crunching, and the like), the logical progression points to further miniaturized data drives.

Computers store data in bits and bytes, and the system boils everything down to a string of digits with only two possible values: zero or one. Because of this, the fundamental storage unit needs to be capable of switching reversibly between two different forms.

The authors of the paper pulled that feat off by making their new material from a molecule called a rotaxane, which is mechanically interlocked, like those metal toy puzzles that drive me crazy. Basically, the ring can move to each side of the dumbbell.

The "recording device", a scanning tunneling microscope, reminds me of a tiny turntable needle. This kind of microscope is a little different from the ones in every high school science classroom. It's used to measure properties at surfaces down to the nanometer (billionth of a meter) scale, and with an applied voltage, it can manipulate material down to individual atoms and molecules. Those school microscopes couldn't come close to being able to "see" something that small, and there's no voltage involved with them, either.

Put those two things together and the tiny tip can "move" the ring on the dumbbell molecule reversibly, which would translate to recording and erasing.

These researchers published a similar paper last year, but the new work tweaks the molecular structure of the dumbbell that makes erasing "data" easier. The next questions are ones of lifetime (how long-lasting is this material and how stable is the switch once it's put in position? etc.)

Sunday, February 18, 2007

Death, Taxes, and Grad School

One of the many differences between me and my friends who got "real jobs" after college is how Uncle Sam (and his state- and city-level brethren) decide we should be classified in the tax code. Since it's getting to be that time of year again, I figured I'd try to relate some of the confusion I've experienced because of the non-intuitive-ness of it all.
Back in high school and college, I got a W-2 at the end of the year for any job I held, listing how much had been withheld from my paycheck for federal and state tax, etc. All it took to do my taxes (and get my refund!) was the aptly named 1040-EZ.
In grad school, I was lucky enough to be awarded a fellowship. There is a difference in the way the federal government regards the various forms of grad-student income.
Princeton required me to TA for one semester, and that year I had a combination of fellowship and salaried income, so I remember that mess particularly fondly.
Permit me to explain:
If you're TA'ing a class (or, as Princeton calls it, acting as an AI or a preceptor), that is considered salaried work, so you still receive a W-2 and have federal and state taxes withheld. There is no money withheld from fellowship income at Princeton. (Is this different anyplace else?) That means I don't get a W-2.
Instead of the 1040-EZ, I have to use the tax tables to estimate what my tax will be for the coming year and send in a stub with a check to the U.S. Treasury quarterly. Then, I have to use a 1040-A form to report my estimated payments and deduct that from my calculated tax. There's a fine if you don't pay a certain amount of estimated tax in advance, so that's why I don't just pay up in one chunk on April 15th. The state-level taxes have the potential to add another layer of complexity, but I've been lucky because fellowship stipends are not taxable in the state of NJ, so I'd always get a little bit of a refund there. I grew up in NJ, so I didn't bother changing my residency or anything, either. (Now that I live in PA, I need to look into whether I'll owe tax at state level). City-dwelling grad students, how complicated is the tax situation for you?
Just for kicks, I'll link to Princeton's tax requirement sheet. I don't think you need to have an on-campus IP address to access it.
You always hear tell of random grad students who don't pay their taxes, figuring that it isn't worth the government's time to audit someone who only makes 19K a year. Good luck with that. I don't have the cojones for it.