July 02, 2016 at 01:59AM

Today I Learned: 1) Thermal cyclers, for those who don't work with thermal cyclers, are machines used in biology labs to heat up and cool down tiny tubes of liquid in a very controlled way on an automatic program. There used to be this problem with thermal cycling liquids that you typically have to ramp up the temperature to above 95 C more than once, which tends to evaporate your liquid mix. That might be fine, except that it could then condense on the top of the tube. This movement of liquid out of your sample could seriously concentrate your sample, which could easily make enzymatic reactions stop working as they got to salty or too overloaded. The old-school solution to this problem was to put a layer of mineral oil on top of your samples, which would prevent evaporation. Modern thermal cyclers instead cover the sample tubes with a metal lid heated to 105 C. That keeps the lids hot enough that water can't condense on them. There will still be some evaporation, but the air inside pretty quickly saturates with water vapor, and the effect is pretty small. Today I learned that some older heated-lid thermal cyclers will shut off their heated lid when the run is done. That matters because usually, when runs finish, the thermal cycler drops the samples down to 4 C (refrigerator temperature) to keep them cool and protected. With a heated lid, that isn't a problem. Without a heated lid, that's kind of a problem, because the block where you put your tubes starts to condense water out of the air. If you leave that running overnight, it can pool up quite a bit of water. 2) How window air conditioners are installed! More or less. At least, a little. In particular, I learned about the kinds of insulation material you can put around the outside of an air conditioner, and about some strategies for filling in parts of the window that aren't covered by the air conditioner. 3) A few pricing things: Doors can be bought surprisingly cheaply (~$50) and surprisingly expensively (~$1,000). 3D printing material goes for order-of-magnitude $25. Glass gets really expensive as you start trying to fill things like windows. Desktop computers are surprisingly not *that* much cheaper than the last time I checked, which was a couple of years ago. A $200 desktop at Fry's Electronics gives you an Intel i3 processor, 4 GB of RAM, a terabyte hard drive, and not much else. I guess that's really cheap, but I wasn't all that impressed. Water coolers cost in the range of $90-$200. Not really a pricing thing, but a lot of screw packs, especially for drywall screws, come with free drill bits. How nice!