It detects the oxygenation of blood. The mechanism behind this is a different magnetic moment of oxygenated hemoglobin, oxygenated hemoglobin is diamagnetic vs paramagnetic while deoxygenated. This is called the BOLD effect (Blood Oxygen Level Dependent). The difference in the two conditions magnetic property affects the MRI signal lifetime in the near vicinity. This results in contrast developing between tissues with oxygenated blood vs tissue with deoxygenated blood. The idea behind fMRI is that when you use a certain part of the brain, it requires oxygenated blood, which will lead to contrast. Unfortunately, due to low overall signal strength/contrast-to-noise ratio, the image must be signal averaged. Hence if you were tapping your finger to see which part of your brain "lights up", you would have to repeat this action, and have your MRI scan be synced to your action so that the same part of the brian is being imaged over the same interval each time. It's tricky, but my understanding is that it's quite feasible. There are many other mechanisms for causing localized signal lifetime changes, without having RTFA, I can't be sure what they took under consideration.

I am a Colombian-American, Caleño to be exact. Bogotà is very temperate, whereas Cali is very very tropical: hot and humid most of the year. But the escape to the mountains is still the same, just oh so much more dramatic. I prefer *up* the hill, I can't take 80s and 90s with humidity all the time. So sticky... but the nights are wonderful. Up the hill gets a bit chilly... some panela will take care of that, perhaps sancochito... or in your case, ajiaco.

Disclaimer: I'm an MR Physicist.

Regarding gradients: The gradients used in MRI vary in *position*. Yes in time, as well, but only because they are pulsed. We can ignore ramping issues to first order. Since the field varies as a function of position, when you move around, indeed the flux is changing which can induce currents in looped conductors so as to oppose the change. This is called induction. Many people, my self included, notice a strange sensation when first entering an MRI magnet. This is because the field is only homogeneous over a relatively small volume, outside of which there are once again field gradients (these are different than the intentional field gradients used to obtain an MRI image). It is probably not axons but something in the ear that is picking this up, I am not sure. Also, field strength has *nothing* to do with this effect. It's how fast the field changes as a function of position, i.e. the gradient, combined with the velocity of the pickup object.

Regarding repulsion: Water is diamagnetic. That means that the little spins (i.e. electrons) orbiting the atoms of a water molecule tend to align *against* the applied field direction. These spins will experience a repulsive force, hence the levitation.

magnets aren't nearly strong enough, that's why

Have them build a clock radio, with alarm. Lots of digital logic, cheap. A breadboard is useful so as to avoid soldering, and some kits to go with the breadboard (little wire segments). If you make them run it off of wall current, they'll have to learn how to go from AC to DC. Might take a few months of working in groups to do, but you can learn a lot that way.

I LOVE inkscape. That coupled with GIMP enables just about any graphic manipulation you want. Plus, inkscape has some plugins that allow you directly enter (and in one case edit) LaTeX code. All for free. Unbelievably useful. I have futzed with LyX, but because I am used to handcoding my tags, I doubt I will start using it. I use WinEdt to create my documents, though IMO the autotabbing leaves something to be desired.

This should have appeared as a preprint on the xxx archives first, if it wants to be taken seriously. I see a bunch of math, and a disjointed argument. That sounds alarm bells in my head. I would not really pay close attention to this article until it was cleaned up and resubmitted and/or I heard the author present his ideas live, with the ability to ask questions and get clarifications.

not 50mT. 50 MICROtesla. like .05 mT. or 5*10^-5 tesla.