June 2011

DNA Takes Square Roots

Around these parts we’ve been known to discuss whether it makes any sense to say that the universe is a computer. There’s little doubt, of course, that parts of the universe are computer-like. And in case you are wondering, you can now officially remove DNA from your personal list of “things I suspect are not computers.”

Caltech researchers Lulu Qian and Erik Winfree have managed to coax 130 strands of DNA into performing what is unquestionably a calculation: taking the square root of a number. (Ars Technica post; Science paper behind paywall; open-access background paper.) Not a big number: we’re talking about four-digit binary numbers, so 15 at the biggest. And not very efficiently: with prodding, the calculation took eight hours. Moore’s Law isn’t really in danger here.

Still, pretty cool stuff. Mostly it’s interesting because it seems scalable: the authors claim that this kind of circuit architecture could be made much larger. It’s not the first biochemical circuit; RNA and bacterial colonies have been made into logic gates. But it’s the first to do something as elaborate as taking a square root.

Best of all, the authors decided to illustrate their method for a wide audience by means of a … whimsical YouTube video! Let’s hope this idea catches on.

The seesaw magic book: the computational power of DNA molecules

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Unsolicited Advice: Non-Academic Careers

Since I know nothing very useful about the job market outside academia, I solicited suggestions for specific pointers and helpful websites. A bushel of useful advice and thought-provoking comments resulted.

My original idea was to summarize what I thought was the best advice, and turn it into a single post. This idea has been undermined by (1) me not knowing which advice is best, and (2) a wide variety of occasionally-contradictory advice, presumably all applicable in different circumstances.

So instead here I’m just going to link to some of the most promising-looking resources that were mentioned. I encourage you to read the comments on the original post to get more ideas, and chime in here to keep the conversation going.

Collections of Online Resources

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