March 29, 2016 at 01:50AM

Today I Learned: 1) ...that there's no direct linkage between the brain and lymphatic system. EXCEPT THAT THERE IS! UVA researchers have just discovered previously unknown lymphatic vessels entwined in the membranes surrounding the brain. This is big news for understanding neurological disorders with possible immune components, like Alzheimer's Disease. Got this information here: http://ift.tt/1USeccq Thanks Sarah Seid for pointing me to this! 2) ...a bit more about Kalman filters. In brief, a Kalman filter is an algorithm you used to guess at the state of a changing system (example -- the temperature of a pot of water, or the position of a moving car) from a potentially noisy set of measurements (example -- a bunch of inaccurate thermometer readings, or noisy GPS locations). In particular, a Kalman filter is the *optimal* algorithm for finding the maximum-likelihood solution for a particular Bayesian inference problem roughly equivalent to a hidden markov model with continuous state values and Gaussian noise. I knew that Kalman filters were supposedly "optimal", but I didn't know what that meant, exactly. Until today! 3) Not really a Thing I Learned as a Number I Crunched, but I thought this was a kind of interesting number -- a typical table is, order of magnitude, several tens of billions of atoms across. That's WAY smaller than I would have naively predicted, but I guess that's because when I think of Numbers of Molecules in things, I'm usually thinking about volume, and volume is, in some sense, much bigger than length.