## Saturday, June 17, 2017

Summer travel and other activities have slowed blogging, but I'll pick back up again soon.  In the meantime, here are a couple of interesting things to read:

• Ignition!  An Informal History of Liquid Rocket Propellants (pdf) is fascinating, if rather chemistry-heavy.  Come for discussions of subtle side reactions involved in red fuming nitric acid slowly eating its storage containers and suggested (then rejected) propellants like dimethyl mercury (!!), and stay for writing like, "Miraculously, nobody was killed, but there was one casualty — the man who had been steadying the cylinder when it split. He was found some five hundred feet away, where he had reached Mach 2 and was still picking up speed when he was stopped by a heart attack."  This is basically the story from start to finish (in practical terms) of the development of liquid propellants for rockets.   That book also led me to stumbling onto this library of works, most of which are waaaaay too chemistry-oriented for me.  Update:  for a directly relevant short story, see here.
• Optogenetics is the idea of using light to control and trigger the activation/inactivation of genes.  More recently, there is a big upswing in the idea of magnetogenetics, using magnetic fields to somehow do similar things.  One question at play is, what is the physical mechanism whereby magnetic fields can really do much at room temperature, since magnetic effects tend to be weak.  (Crudely speaking, the energy scale of visible photons is eV, much larger than the thermal energy scale of $k_{\mathrm{B}}T \sim ~$26 meV, and readily able to excite vibrations or drive electronic excitations.  However, one electron spin in a reasonably accessible magnetic field of 1 Tesla is $g \mu_{\mathrm{B}}B \sim ~$ 0.1 meV.)  Here is a nice survey article about the constraints on how magnetogenetics could operate.
• For a tutorial in how not to handle academic promotion cases, see here.