Cooling by Heating

PRX - When a bulk piece of material is heated at its surface, does its center become hotter or cooler? It turns out that the answer to this seemingly banal question is not obvious at all at a fundamental level. In this paper, we report, first through a theoretical analysis and prediction and then with experimental confirmation, an extraordinary phenomenon of cooling at the center of a supercooled liquid drop heated at its free surface.

Friends of friends key to job and mate searches

Physical Review E - Imagine that you are searching for a job, a date or an expert opinion on a social network. What do you do? Until recently, you had to rely on your friends or acquaintances, but nowadays, using social network sites (like Facebook, Twitter or LinkedIn) you can go beyond that and start to search not only using your direct friends but also the friends of your friends, or the friends of your friends of your friends, and so on. That is, you can find out not only people that is one degree of separation from you in the social network, but people that is two or three degrees from you on the social network. Since, we live in a small world perhaps with only six degrees we can span the whole network. In a recent paper, published on November 19 in Physical Review E, researchers found a navigation strategy that does precisely that: to jump directly to more than one degree of separation on a network. They found that this strategy, named Levy walks, akin to the one used by foraging animals, can be very efficient to search and navigate the social network.