Posted by: Patrick Allen Foster | January 10, 2015

Saturday Link Collection

1. “Matching donors and recipients is a bit like the traveling salesman problem”: Ars Technica on the math of kidney donation networks:

The typical donor chain generated by hospitals starts with an unconnected donor, someone who’s just willing to give up a kidney to anyone who needs it. From there, it goes through donor-recipient pairs, before ending at someone who doesn’t have a paired donor. The longer the chain, the better the chances are of optimizing matches among donors and recipients so that there’s a minimal chance of immune rejection.

The authors of the new paper try two different computational approaches for optimizing the chains. The first involves what are termed “integer programming” techniques, which are exactly what they sound like: the values used by the system to handle values for things like the suitability of a match and the amount of time spent waiting for an organ. Using this approach, they simply start with an unmatched donor and recurse through potential chains, checking for how optimal they are.

Separately, they note that the kidney donor problem is just a specialized case of what’s called the prize-collecting traveling salesman problem. In this version, a person has to visit as many cities on a list as possible, but can skip some at the cost of a penalty. Using a modification of an algorithm designed for the traveling salesman, they implement one that is specialized for kidney donations.

2. “British Elections Aren’t as British as They Used to Be”: “Over the past decade, U.K. politics have taken on a mix of features of both the U.S. and Continental European systems.”

3. “How the West selectively promotes democracy through sanctions.”

4. Schrödinger’s Coup.

5. Pagans against faith.

6. The past year in movies.

7. Radly Balko’s civil liberties predictions for 2015. (H/T: Will Truman.)

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