Interesting Snippets from 2012-05-14

• The Wisdom of Slime - NYTimes.com

  There is a slime mold known as Physarum polycephalum that lives in forests around the world. It feeds on various kinds of microscopic particles. As it forages for food, protoplasmic tubes of slime extend out and bifurcate like tree branches; whenever it happens upon a source of nutrients, it gathers into a bloblike formation. The whole thing — blobs connected by tubes — is a single organism, and the network serves to transport nutrients throughout its “body.”

  An interesting fact about this slime mold is that it is highly intelligent — or at least it behaves as if it is. In locating food in its environment, it builds networks that have been shown to be optimally efficient in transporting the nutrients over the area in question. If placed in a maze, for instance, with a source of food outside the maze, the slime mold will discover the shortest path out.

  The Japanese researcher Toshiyuki Nakagaki and his colleagues have demonstrated that the slime mold’s foraging behavior can be used to perform sophisticated computations, as long as the problems are represented spatially. Problems solved by the slime mold include not only the shortest path out of a maze, but also other complex mathematical challenges (like creating a Voronoi diagram and a Delaunay triangulation).

• Lucene conference touches many areas of growth in search - O'Reilly Radar

  With a modern search engine and smart planning, web sites can provide visitors with a better search experience than Google. For instance, Google may well turn up interesting results if you search for a certain kind of shirt, but a well-designed clothing site can also pull up related trousers, skirts, and accessories. It's not Google's job to understand the intricate interrelationships of data on a particular web property, but the site's own team can constantly tune searches to reflect what the site has to offer and what its visitors uniquely need.

  Hence the important of search engines like Solr, based on the Lucene library.

• Every odd integer larger than 1 is the sum of at most five primes « What’s new

  The main result of the paper is as stated in the title, and is in the spirit of (though significantly weaker than) the even Goldbach conjecture (every even natural number is the sum of at most two primes) and odd Goldbach conjecture (every odd natural number greater than 1 is the sum of at most three primes). It also improves on a result of Ramaré that every even natural number is the sum of at most six primes. This result had previously also been established by Kaniecki under the additional assumption of the Riemann hypothesis, so one can view the main result here as an unconditional version of Kaniecki’s result.

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