### Bioreactor growth rates

My home bioreactor took 48 hours to get going where the instructions said 24-36 hours was typical, but it got going. About two weeks after startup the active cell culture had matured and I decided to put it into production. The instructions indicated that 1.5 hours at room temperature would be an adequate first stage reaction period. Four hours into it the first reaction stage wasn't finished, so I put the lot into the fridge and went to bed; clearly the time estimates were not representative.

I knew putting it in the fridge would slow the reaction down to the point where I could pick it up again the next day, because it's a bioreactor and they're sensitive to temperature - specifically, the reproduction rate of the cell culture slows down dramatically when cooled.

That's when I realized that my bioreactor had been reacting more slowly than the instructions suggested was normal every step of the way.

### Calcium Catastrophe

Generally speaking, a sudden drastic change in the chemistry of your environment is catastrophic. From bacteria to humans, there is a range of chemistry we can tolerate, and outside that range we tend to die.

I mentioned one major geochemical event last year, when free atmospheric oxygen first became common. That was a pretty catastrophic change for the living creatures (bacteria) who were adapted to the pre-oxygen conditions of the early earth.

Some time after that, another major geochemical event happened. Some researchers now think that this led directly to the cambrian explosion and to more complex life on earth. Even so, it was a catastrophic change—from the point of view of the creatures who didn't survive it.

### Home bioreactor

I now have a home bioreactor.

This is what it looks like 48 hours after startup:

Of course, I only realized after the bugs started farting all that CO2 that I didn't actually have a microscope at home to see what they were doing and what was there. I may have to start a second bioreactor after finding myself a microscope capable of seeing who's at home in that jar, to see how the population changes over time.

Hmm, it looks like telescope stores often sell microscopes as well. Magnifying optics are magnifying optics, I guess!

### Boiling with salt

Getting back into chemistry after last week's fun little diversion into mechanics, I feel like doing some more math. I was looking for a recipe not long ago and ran across repeated mentions that one adds salt to water when boiling food in order to raise the temperature at which the water boils, thus cooking the food faster.

Boiling point elevation is a real thing, as is freezing point depression, and it's not hard to calculate.

The boiling point of pure water at sea level is 100oC. In order to calculate the change in temperature, we need the following equation:

$\Delta T = K_b m$

### Inspired by: snakes

More fantastic robots! These ones are inspired by one of the creatures I find the most fascinating: snakes.

This little guy from Carnegie Mellon Biorobotics (still tethered to its power source and remote control) can move in all kinds of ways; as the video says, not just slithering. Quite a few of these types of movement are actually very simple repetitive motions, while others are much more complicated, with more steps in the movement.