# User:Brian P. Josey/Notebook/2010/05/17

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## End of Finals

I didn't update my notebook on Friday with what I did in lab that day. I did this because it was the last day of finals, and I just wanted to go home and enjoy the start of summer vacation. So I updated my notebook today with what I did on Friday, and the page is completely updated.

## New Forces and Terminal Velocities

I calculated the average forces, and speed of ferritin moving through water for a few new cases today. I simulated one of the cone magnets by itself, opposite the small cylinder magnets, and attached to the long cylinder magnets. I've also simulated the neodymium yoke without magnets opposite of the gap. I had hoped that with all of these simulations, I could show that a yoke is needed, but the numbers are a little off.

All forces are in fN, and speeds are in μm/s

Cone Alone

• Force Tip: 0.970
• Velocity: 8.579
• Force Flow Cell: 0.1865
• Velocity: 1.649
• Force Tube: 0.041
• Velocity: 0.361

Cone and Small Cylinder

• Force Tip: 0.986
• Velocity: 8.715
• Force Flow Cell: 0.178
• Velocity: 1.576
• Force Tube: 0.032
• Velocity: 0.280

Cone and Long Cylinder

• Force Tip: 0.992
• Velocity: 8.774
• Force Flow Cell: 0.179
• Velocity: 1.583
• Force Tube: 0.032
• Velocity: 0.279

"Broken"

• Force Tip: 0.991
• Velocity: 8.760
• Force Flow Cell: 0.179
• Velocity: 1.583
• Force Tube: 0.032
• Velocity: 0.279

Here again are the numbers for the control, the full neodymium yoke, that I calculated:

Force

• Near Tip: 0.975
• Flow Cell: 0.186
• Tube: 0.041

Velocity

• Near Tip: 8.620
• Flow Cell: 1.646
• Tube: 0.3583

It appears that the yoke provides a greater force on ferritin in both the flow cell and in the micro-centrifuge tube, but not near the tip of the cone magnet. Near the tip, it appears that the yoke actually hinders the magnetic field in some way, while the addition of more magnets helps it. I am still thinking about this, and checking my code. It could be that there is relaxation in the magnets, a lateral effect from the extra magnets in the yoke, or something else that I haven't thought of yet.

## Another Idea

I was just throwing ideas, and I came up with another one that might be useful to look into. If the force on the ferritin is not large enough to get the desired affect, then I can use an intermediate magnetic bead say 500 nm in diameter, to help move the ferritin. The larger magnetic bead would be attracted to the magnetic yoke, and the ferritin would be attracted to the bead. Because it is so much closer to the ferritin than the magnet, it could help move the ferritin in the cell.