Posted on 11/27/2004 10:23:36 PM PST by neverdem
No, but you're thinking. The stuff they inject you with is actually injected to bring out contrast in the picture. There are plenty of MRI's done without using the contrast enhancer.
Here, with a tremendous number of oversimplifications is how MRI works: the nuclei of certain atoms have a small intrinsic spin. In the presence of a large magnetic field, nuclei in one spin state have a higher probably of aligning with the field than the other, so the spin tends to align with the magnetic field. Now, if you could put energy into those nuclei, some of them would get enough of a bump to "flip" over into the higher energy state, opposing the magnetic field. By applying an oscillating magnetic field (like that produced by alternating current) in addition to the large static field already applied, you can get the spins to flip in a predictable way. This release photons as the nuclei transition from one state to another, which can be read by a detector.
So MRI essentially amounts to reading the states of magnetic nuclei inside your body. The nuclei resonating with the magnetic fields in medical uses of MRI are certain hydrogen nuclei in water. Your body is mostly water. As I say, this is so oversimplified that some of it isn't quite right. But it's the basic idea.
Here's a very good, highly technical introduction: The Basics of NMR
As I read through this thread, images of Lysenko and Eugenics keep coming to mind - other examples where science was subservient to ideology. Then it was Marxism and Nazism. Today it is Environmentalism.
I had to check your profile page. That's quite a quote from Garfield!
Every Rebel guerrilla and jayhawker, every man who ran to Canada to avoid the draft, every bounty-hunter, every deserter, every cowardly sneak that ran from danger and disgraced his flag, every man who loves slavery and hates liberty,... and every villain, of whatever name or crime, who loves power more than justice, slavery more than freedom, is a Democrat.
--James A. Garfield, 1866
I was just reading on a thread, maybe this one late last night, about how the Nazis were enviro-nuts who hounded their businessmen too.
"The most efficient, and safe, hydrogen storage medium has already been found.
Its called->> Gasoline..
Yep. About 15% to 16%, versus 11% for water, and extraction is EXOTHERMIC - it fuels itself. I suspect that when supplies run low, we will just make more. Perhaps we will make pure iso-octane, or perhaps something lower weight, like propane, that can fuel the same engine. Diesel might be better, but much harder to manufacture.
Finally, I think that hybrid vehicles - or actually, what might be called "pure-hybrid" vehicles, that use pure electric drive and a disconnected generator, are an important step forward. It's not new - a major sector of commercial transportation already runs this way, on rails all across the country.
First, the generator can then be any technology, depending only on the state of the art. Diesel rotary and various fuel cell types, both PEM (H2) and solid-oxide (gasoline, alcohol, or LNG) come to mind. But the most intriguing possibility in my mind is something like a trolley or slot-car pickup device, that could bring in external electric power directly from the grid. This is so much more efficient that running ALL of our vehicles on the electric grid would require a generation capacity expansion of only a few percent.
Perhaps it's a wild idea, and I don't pretend to know how to do it. The infrastructure required would be expensive, and potentially intrusive. A foolproof metering system would be required. But the convenience factor would be very high - you would move on and off the grid at your own convenience, using self-generation only when needed. Unadapted vehicles could share the road with adapted ones. Oil consumption AND pollution would be minimized drastically. I would think that city centers and major intercity routes would be the places to start.
Oh, I agree 100% that hydrogen we intentionally produce for a fuel is a storage material for energy. However, so is anything we burn, actually. We may not have produced it, but that is what it is. "Energy can neither be created or destroyed"...etc...etc.... We know that there is never 100% conversion of energy from one source to another. Energy is lost somewhere (heat, etc.), so the use of hydrogen as an energy-saving means is definitely a myth. I didn't mean to nit-pick...was more for clarification. It isn't just semantics.
Most of whose passengers lived, IIRC.
Incidentally, within the city of London overhead tram (trolley) wiring was forbidden, so the electric trams received power from cables buried in slots in the tracks.
Oh! That is so true!!! The GANG-GREEN movement was invented by German Pagans!!! That's why the GREEN PARTY is so prevalent there, today!!!
I wish you could find that and link it here! That's going on bigtime in CA with the encouragement of a Republican Governator pushing Land-Grabbing CONservancies and a "Hydrogen Highway, etc."!!!
But at least you can see those burning your little body. You can't see hydrogen burning!!!
Bless you for being here and pushing back the frontiers of blissful ignorance!!!
Aw, shucks (eyes down, kicking at the dirt).
Let me make the following substitution, which should be completely noncontroversial (though one never knows). "Since the initial lowest-entropy state at the beginning of the world."
The most promising improvements in fuel economy will not be found in changes to vehicles themselves, so much as in our USE of transportation.
As the economy increasingly takes advantage of the net to conduct business, the amount of petroleum spent for many routine routine activities will decrease.
Our success/failure in making this transition could be seen by charting national petroleum consumption as a fraction of GDP.
most US corporate attempts at wide scale, structured virtual office work, eliminating people needing to commute to work, have failed. the management culture in this country doesn't facilitate it - managers want to see their employees and feel they have some control over their behavior and their "organization".
right now, the infrastructure exists for a large number of US workers to be able to work from home. any evidence of it occurring, on a wide scale basis? at least where I work, VPN technology isn't being used to avoid people needing to commute, its being used to have people work extra hours when they get home (without compensation).
Another kind of net-related saving occurs when an organization allows part of itself to exist in a lower-cost locale where it normally wouldn't operate. Employees in those places do not personally telecommute, but the organization as a whole is doing the equivalent.
The savings may come from lower employee commuting and housing costs, which the employer sees as lower salaries.
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