Link's not working for me. but, the Science Daily one does - http://www.sciencedaily.com/releases/2007/06/070620115358.htm.
It doesn't show the spiral image, but I get the idea. Believe it or not, this jives with a hypothesis I came up with a long time ago, but took down after realizing I don't have the ability to prove it, and even if I could, it wouldn't matter. Somebody with letters after their name is going to have to do it.
Essentially, it involves two kinds of substances. One is just the basic building block of matter and energy. I'll call it ones, for lack of a better term. The other is something else, which I'll call zeros. Zero's attract ones, but don't absorb them and the two cannot occupy the same space. One's tend to be surrounded by zeros, so when matter comes together, some zeros are expelled. It's the expelled zeros that attract more matter, not the matter itself. The concentration of expelled zeros is higher closer to a collection of matter, which is why the pull of gravity is stronger. It's higher still near the center of a collection of matter, where the concentration of merging matter is higher. The vortex area, in this fantasy, would be an area of concentrated zero's. Matter passing through wants to stay there. It's external energy is internalized, so it spins. The tendex area might be an area of highly concentrated one's. Matter has no use for this environment, so it zips through it. It's internal energy is externalized and it stretches. The one's eventually make their way to the zero's and precipitate into matter, but both areas are constantly being repopulated from the expulsion by the colliding black holes, and everyone lives happily ever after.