Hierarchical Equal Area isoLatitude Pixelization from NASA JPL

HEALPix is an acronym for Hierarchical Equal Area isoLatitude Pixelization of a sphere. As suggested in the name, this pixelization produces a subdivision of a spherical surface in which each pixel covers the same surface area as every other pixel. The figure below shows the partitioning of a sphere at progressively higher resolutions, from left to right. The green sphere represents the lowest resolution possible with the HEALPix base partitioning of the sphere surface into 12 equal sized pixels. The yellow sphere has a HEALPix grid of 48 pixels, the red sphere has 192 pixels, and the blue sphere has a grid of 768 pixels (~7.3 degree resolution).

Another property of the HEALPix grid is that the pixel centers, represented by the black dots, occur on a discrete number of rings of constant latitude, the number of constant-latitude rings is dependent on the resolution of the HEALPix grid. For the green, yellow, red, and blue spheres shown, there are 3, 7, 15, and 31 constant-latitude rings, respectively.

Text copied from JPL, NASA: Source

Invisibility cloak? There might be a way

Researchers using nanotechnology have taken a step toward creating an "optical cloaking" device that could render objects invisible by guiding light around anything placed inside this "cloak."

The Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design that uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked. Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

More details at: Engineers create 'optical cloaking' design for invisibility, Purdue University

RFIDs, a library thing

I've been helping out a library to retrieve books from a floor that was damaged by storm a few weeks ago. Things went pretty fine at the beginning, finding books by the Library of Congress call numbers, taking them back, putting them on trolleys, giving them to the readers... Until one night, when I was totally exhausted, I had a thought about the RFIDs used in libraries. Wouldn't it be sweet to track down a book with a 'book detector' rather than going through all the shelves?

Now, RFIDs, this page from ALA explains the basics:

http://www.ala.org/ala/pla/plapubs/technotes/rfidtechnology.htm

However, a $0.85 ID for each book means it'll cost a lot for a library with thousands books in its collection.