April 26, 2016 at 02:05AM

Tody I Learned: 1) ...that it's possible to debug the Windows kernel, live. This is a process known as "kernel debugging", appropriately enough, and it's done by using one computer as a debugger and one as a test machine. There's some built-in Windows software that makes it relatively easy to set up and run. Pretty cool, Microsoft! Pretty cool! 2) There's an inherent instability in maintaining cell populations that pops up above and beyond what you see in, say protein populations in a cell. See, a cell can keep a protein at a constant (steady state) concentration very easily, by producing at a constant rate and letting the protein degrade at a constant rate *per protein molecule*. Because the total amount of protein degradation increases when there's more *total* protein in the cell, degradation becomes stronger relative to production as the concentration of protein increases. As the cell produces more protein, degradation and production eventually balance out, and the cell reaches a steady-state protein concentration. This doesn't work for cell populations (i.e., the population of white blood cells in the blood), at least not naively. The problem is the way you get "constant production" of a cell population. In the protein case, absolute production is fixed beacuse there's exactly one genome (well, probably two copies of any particular chromosome, but you get the idea) and it produces at some fixed rate. For that to work with cells, they would have to come from a fixed population of progenitor ("stem") cells... but then you have to have some way to maintain *that* population at a fixed size, so that solution really begs the question of how you maintain a constant population. You could also just have each cell in the population divide at a fixed rate, but unfortunately that gives you growth that's proportional to the size of your population. If that growth is *just perfect*, you can get perfect balance and have a constant population, but that's an unstable situation. If the growth rate is just a little too low, then the cells will die off too quickly and the population will crash to zero. If the growth rate is just a little too high, then the population explodes and probably gives you a tumor. How does the body handle this dynamic instability? Tune in on Wednesday to find out. In the meantime, care to take a guess? 3) ...about "The Next Rembrandt". The Next Rembrandt (which I will abbreviate TNR) is a rather complex piece of software deisgned to produce novel paintings in the style of Rembrandt. By which I don't just mean "kind of like Rembrandt's paintings" -- TNR was built to mimic Rembrandt in exquisite detail, from his overall composition to the size and shape of his figures' eyes to the technique and order of his brush strokes. TNR's debut painting was created by instructing it to paint a white man with certain facial features, in a black outfit, facing to the right. TNR designed a painting, then 3D-printed it, presumably out of paint, to give it the full texture of a Rembrandt painting. Go Google Image search "the next rembrandt" to see the result.