Linkage

Photobucket raises its hosting rates to “go away we don’t want your business”, Flickr kicks out users of competing email servers, Unsplash ditches open access, and Dropbox stops photo sharing (G+). This is why I don’t like relying on cloud services: they go away or add unacceptable terms of service without warning.

How to construct the seams on a tennis ball from four semicircles, or more generally cover a sphere with rope of a constant width.

Zip files that contain themselves (G+). Or see this alternative link if you want to work out how to do it as a puzzle without the spoilers.

Turn your ascii art into vector graphics!, via MF).

Mitzenmacher and Upfal’s “Alice book” updated (G+). An essential reference for randomized algorithm analysis. Not to be confused with that other Alice book on databases nor with the Alice who’s been saving us from bad “on a computer” patents.

Connections between modal logic and bitwise Boolean arithmetic (G+). See also a later post where Dan Piponi connects both modal logic and bit-manipulation to digital circuit design.

Lensless cameras based on phased arrays, via YC). They don’t necessarily cover less area than current cell phone cameras, but they can be a lot flatter.

In memory of Alejandro (Alex) López-Ortiz (G+).

Trump administration proposes making foreign students re-apply for entry every year (G+). In case you weren’t already certain that the Trump administration hates higher education.

Quanta on Rao’s new pentagonal tiling proof. Thomas Hales vouches for correctness of “the most important half”.

Why net neutrality is essential, not just for idealistic reasons but for the health of the national economy.

Subhash Khot and Unique Games. Not very in-depth, but another nice popularization of current research from Quanta.

Pink Pineapple Pavilion (G+). An outdoor shade structure in southwest England, built of metal and fabric but “based on a piece of origami” by its designers.