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.

I guess there is no room for scientists to have a say? They must be whack-jobs too. How the hell was this modded up to insightful? Total flamebait.

I am a scientist who believes strongly that government funding of R&D needs to be increased. Often times, I hear the argument that it is not the government's role to do this. Most of our basic R&D now occurs in the universities and the national labs. But it wasn't always so.

Several years ago, I was an intern at Bell Labs, in Murray Hil, NJ, the main research engine of AT&T before the 1984 breakup. Some of the greatest inventions of the 20th century were created there, including the transistor and the laser. The cosmic microwave background was discovered at Murray Hill as well, an example of a pure scientific discovery, serendipitous but yet made more likely by the concentration and dynamic of the brilliant minds working there. As time went on, the research became more and more applied, less basic, less fundamental.

By the time I got there, Bell Labs was part of Lucent, which was a slave to its stock price. All kinds of financial shenanigans were going on in the background, and the business had become focused almost solely on fiber optics and other communications media/equipment. Some of the leftovers from the glory days of basic R&D were retiring, but there were still quite a few more recent hires. These people were let go during my summer. It was sad. It was the death of Bell Labs. All that were left were the old fogies and the people doing work related to the core business. Lucent's stock tanked, and the whole company became a shell of what it once was, and Bell Labs became special only in the history books.

Bell Labs was the greatest death of the old industrial research powerhouses. Few are left, most notably IBM. But even these are more application-oriented than in the past. They depend on the government to fund basic R&D in its labs and universities to keep the technology engine revving. Should that process stop, perhaps industry will revert to its old way, but that will not be a quick process. For almost a generation, we would be left with our pants down while our global competitors assert the lead in the technology race. This will put us at not just an economic disadvantage, but in poor strategic positioning politically. It is paramount that we fund basic R&D via government funds now. If we desire a different system where private industry does the brunt of basic R&D, then we must redesign the system via proper incentives to allow for a smooth transition to such a paradigm. Maintaining science funding at the levels they are at right now is not sustainable in the short term- the quicker we enhance funding, the better off we will be.

If you are a Democrat, blame Bush. If you are a Republican, blame Obama. And if you are neither, blame Bill Gates. Personally, I blame the Flying Spaghetti Monster. His noodley appendages have a way of getting into everything.