PSW at MBI: Day 1

Got off the plane (ok technically it’s the night of Day 0) and had my first taste of Ohio. I’ve included a couple shots of the display that met me in the lobby. Day 1 starts with an 8:15am bus ride in a bus labelled Nth degree transportation which was mildly amusing.

The first thing to do is to listen to all the problems being presented and then deciding on one to choose. For myself the calcium problem looked quite interesting and I’d recently done some work that used calcium reactions but in the dissolution of rocks rather than how the uptake of calcium is handled in the body.


Another problem that was quite interesting was the magnetic field problem where cells are labelled with an antigen and that process allows them to stick to small magnetite particles and be subsequently pulled through a layer of tissue serum and into a scaffold.  After looking at all the talks I think I’ll base myself here.

Now for the physics of the problem… well at least the day one physics.  What is really important is to try to understand just what is driving the particles.  There is a magnetic field that is pulling the magnetite particles down and these are in turn joined to relatively large (ten times the radius) stem cells.  There is also a viscous drag term and the classical Stokes drag should suffice since the flow rate is slow and cells are essentially spherical.  Finally there is a buoyancy effect but it’s a slightly more complicated since the cells are slightly more dense than water and the magnetite particles are tiny in comparison yet about five times the density of water.

A back of the envelope calculation seems to indicate that if the magnetic field is ignored then it should take about five minutes for the cells to travel the 4 mm through the serum and reach the scaffold.  What this seems to imply is that the magnetic field is not even necessary.

For tomorrow there are really two jobs.  1) Find an expression for the magnetic field or force that aligns with the field strength seen in the literature.  2) Get a handle on what the dominant process is and verify that the predicted time scales correspond to what is observed.

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