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Safety warning?!!! ;)

  • Thread starter William J. Beaty
  • Start date
U

Uncle Al

Jan 1, 1970
0
Gregory L. Hansen said:
On a Swedish chainsaw, "Do not attempt to stop chain with your hands or
genitals."

Uncle Al professes new respect for Swedish genitalia - or are their
women capable of opening a Nehi bottle without a church key?
 
D

Damien

Jan 1, 1970
0
On a Swedish chainsaw, "Do not attempt to stop chain with your hands or
genitals."

One should of course note that that warning was only inserted into the
manual for the US Market...
 
D

DarkMatter

Jan 1, 1970
0
The 1.4 megagauss number is absurd; kilogauss, maybe. I seriously
doubt the part about separating the iron out from one's blood, too;
superconductive MRI magnets are far more powerful than any PM can ever
be, and have no such problems. And no small magnet is going to affect
a color TV from three feet away.

This guy sounds like a fathead, hardly a humorist.

We are working on a single pass PET scanner with Philips that makes
an image in a single pass under the detector array, as opposed to the
older method of making passes for each detector cell.

One's blood does not separate. Does anyone here even know where the
iron molecules are in the bloodstream?
 
S

Sir Charles W. Shults III

Jan 1, 1970
0
They are bound in the center of the heme complex, which is attached to
two pairs of alpha and beta protein chains.

Cheers!

Chip Shults
 
D

DarkMatter

Jan 1, 1970
0
They're also farther away. Inverse cube law, right?

No. Magnetic flux dissipates at the square of the distance.
But anyway, if I
remember correctly (which I might not), the magnetic field in MRI is pulsed,
and is pretty even throughout the cavity, meaning that it shouldn't pull
things strongly in any particular direction. By contrast, I believe Kevin's
talking about being within a centimeter of the magnet for a prolonged period
of time. Obviously, he handles the things himself.

He still isn't separating his blood with them.
I shop at his store pretty regularly.

Hopefully, you don't wear tin foil hats.
There's probably not much point in my
vouching for him since you don't know me either, but for what it's worth,
you might want to at least have a conversation with him before labeling him
as a fathead.

Or a foilhead.
In my experience he's not one, at least no more so than most
of us.
Hahahah.... that's funny.
 
D

DarkMatter

Jan 1, 1970
0
Yeah, one of those days. I'm battling Green's function for crystal
lattices, too. Both surviving neurons are chuggng flat out (if you
remember the 60s you weren't there). The rest of today is flying on
impulse engines.

He merely pointed out a math boo boo. A megaguass is 100 Teslas.
 
J

John Larkin

Jan 1, 1970
0
On 4 Mar 2004 19:37:27 GMT, "Walter Harley"
<[email protected]> Gave us:

No. Magnetic flux dissipates at the square of the distance.

Far-field from a magnetic dipole, it's inverse with the cube of
distance.

John
 
D

DarkMatter

Jan 1, 1970
0
They are bound in the center of the heme complex, which is attached to
two pairs of alpha and beta protein chains.
In other words, not ever able to be attracted magnetically.
Magnetic attraction relies partly on the media being magnetically
attracted as in when all the atom align, the force is greater.

In single molecule arrays, one would hardly think enough attractive
force even exists. I am not a believer in this guys tripe.
 
T

Tim Auton

Jan 1, 1970
0
DarkMatter said:
The 1.4 megagauss number is absurd; kilogauss, maybe. I seriously
doubt the part about separating the iron out from one's blood, too;
superconductive MRI magnets are far more powerful than any PM can ever
be, and have no such problems. And no small magnet is going to affect
a color TV from three feet away.

This guy sounds like a fathead, hardly a humorist.
[snip]
One's blood does not separate. Does anyone here even know where the
iron molecules are in the bloodstream?

Hemoglobin contains iron and is a molecule, but I wouldn't choose to
call it an "iron molecule".

I'm very dubious about the effects of magnetism on the blood too.


Tim
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that DarkMatter <DarkMatter@thebaratthe
endoftheuniverse.org> wrote (in <scek40d33f7b9cuq49mpmouejm9cic1ppn@4ax.
com>) about 'Safety warning?!!! ;)', on Sat, 6 Mar 2004:
Does anyone here even know where the
iron molecules are in the bloodstream?

In the middle of each haemoglobin molecule. I can't remember the
oxidation state (2?), but I doubt that it has an unpaired electron, so
presumably no magnetic moment.
 
U

Uncle Al

Jan 1, 1970
0
John said:
I read in sci.electronics.design that DarkMatter <DarkMatter@thebaratthe
endoftheuniverse.org> wrote (in <scek40d33f7b9cuq49mpmouejm9cic1ppn@4ax.
com>) about 'Safety warning?!!! ;)', on Sat, 6 Mar 2004:


In the middle of each haemoglobin molecule. I can't remember the
oxidation state (2?), but I doubt that it has an unpaired electron, so
presumably no magnetic moment.

Christ... nobody is keeping it a secret.

Hemoglobin is an AABB protein tetramer, MW=65,000. Each of the four
heme prosthetic groups chelates one high spin Fe(II).

http://www.crystal.uwa.edu.au/~ddb/bio3hhb.pdb

High spin is defined as having unpaired electrons in both the eg and
t2g orbitals, while low spin is unpaired electrons in only the t2g
orbitals. In deoxy-globins the iron atom is five-coordinate, high
spin, and sited below the plane of the porphyrin ring towards an axial
imidazole ligand. Upon oxygenation, the iron in Hb moves towards the
porphyrin plane (from 0.60 A to 0.13 A from the plane) and pulls this
histidine, thus commencing the cooperativity shown by Hb in binding
dioxygen. In Mb this change is not so pronounced (from 0.42 A to 0.18
A). It is still high spin.

Fe(0) has 2 s-electrons and 6 d-electrons. Fe(II) then has 6
d-electrons. If we model an octahedral ligand field,

eg _ _
t2g _ _ _

then four unpaired electrons. Each Fe(2+) is paramagnetic. Now, how
do things vary with tetramer spin coupling overall and with
oxygenation? Oxygenated hemoglobin is diamagnetic. Deoxygenated
hemoglobin is very weakly paramagnetic by measurement,

http://www.fmrib.ox.ac.uk/~peterj/lectures/fMRI_Exp_V/sld004.htm
faraday.ufbi.ufl.edu/~thmareci/bch6741/lecture10.pdf
middle

/_\chi=0.08 ppm.

The red color is from ligand to metal charge transfer. No high
gradient supercon magnet is about to pull the red goo from your veins.

OTOH, intense high divergence magnetic fields have a distinct affect
upon mental function. There is a old (magnet poorly shielded)
multi-nuclear 360 MHz NMR in the basement of the UVic chemistry
building. One must bloody crawl under the supercon magnet with one's
head pushing against the bottom of the armored dewar to get at the
probe switchbox for changing nuclei. That is the field divergence
sweet spot. Everybody who goes underneath comes up giggling - even
the flesh-eating NMR lady. Uncle Al was careful never to be checked
out on that machine.
 
R

Ray Drouillard

Jan 1, 1970
0
DarkMatter said:
We are working on a single pass PET scanner with Philips that makes
an image in a single pass under the detector array, as opposed to the
older method of making passes for each detector cell.

One's blood does not separate. Does anyone here even know where the
iron molecules are in the bloodstream?

The iron atoms are part of the hemoglobin molecule. Hemoglobin is used
inside the red blood cells.

Interestingly enough, hemoglobin is similar in structure to chlorophyll.
Chlorophyll is built around a different metal, however. I can't
remember if it's Mn or Mg. I think it's Mg.


Ray Drouillard
 
J

John Larkin

Jan 1, 1970
0
OTOH, intense high divergence magnetic fields have a distinct affect
upon mental function. There is a old (magnet poorly shielded)
multi-nuclear 360 MHz NMR in the basement of the UVic chemistry
building. One must bloody crawl under the supercon magnet with one's
head pushing against the bottom of the armored dewar to get at the
probe switchbox for changing nuclei. That is the field divergence
sweet spot. Everybody who goes underneath comes up giggling - even
the flesh-eating NMR lady. Uncle Al was careful never to be checked
out on that machine.

Maybe it's the helium boiloff that got'em. Or maybe there's a really
good Dilbert pasted to the bottom of the dewar.

I'll ask my buddies at Varian NMR if the magnets make them goofy;
they've got 900 MHz magnets with spiral staircases wrapped around the
outside.

John
 
D

Don Klipstein

Jan 1, 1970
0
They're also farther away. Inverse cube law, right? But anyway, if I
remember correctly (which I might not), the magnetic field in MRI is pulsed,
and is pretty even throughout the cavity, meaning that it shouldn't pull
things strongly in any particular direction.

The modulation of the field is pulsed, but the main component of the
magnetic field is steady and usually either 1.5 Tesla (15,000 gauss) or
5 Tesla (50,000 gauss).

The main magnetic field is achieved with a supercunducting
electromagnet.

And by the way, do not ever hit one of those emergency shutoff switches
for the main magnetic field unless there is some real emergency requiring
this. I am under the impression that restoring the main magnetic field
involves more than just moving that switch back to its normal position,
and that the main magnetic field is not turned off for nights, weekends,
holidays, or whatever.
Keep in mind that the energy in 1 cubic meter of 1.5 Tesla magnetic
field is about 142 megajoules if I figured correctly, and 11.11 times that
at 5 Tesla if I figured correctly. Dissipating that much energy quickly
is not trivial, and restoring it is even less trivial!

Pull is not much in the cavity where the field is even, but just outside
the cavity I would not want to be holding an oxygen tank! And do not let
go of anything magnetic outside the cavity - it can become a missile,
crashing hard just below the cavity or maybe getting pulled through and
crashing into something on the way out (or back in). Heed those signs
against magnetic objects! Heck, I wonder what a nonmagnetic metallic
implant in my body would do if rotated - maybe develop enough voltage to
cause electrocution risk or shbad shocks? (There are horror stories
about how little voltage under the skin can cause electrocution!)

- Don Klipstein ([email protected])
 
J

John Larkin

Jan 1, 1970
0
The main magnetic field is achieved with a supercunducting
electromagnet.

And by the way, do not ever hit one of those emergency shutoff switches
for the main magnetic field unless there is some real emergency requiring
this. I am under the impression that restoring the main magnetic field
involves more than just moving that switch back to its normal position,
and that the main magnetic field is not turned off for nights, weekends,
holidays, or whatever.

The field persists as long as the magnet stays cold; no power supply
is needed.

If it quenches, a lot of helium will boil out pronto. It will have to
be refilled with liquid nitrogen and liquid helium, and it will have
to be recharged with a power supply. The charging supplies are usually
brought in, and are not kept on site.

Do they really have a quench switch?
Pull is not much in the cavity where the field is even, but just outside
the cavity I would not want to be holding an oxygen tank! And do not let
go of anything magnetic outside the cavity - it can become a missile,
crashing hard just below the cavity or maybe getting pulled through and
crashing into something on the way out (or back in). Heed those signs
against magnetic objects! Heck, I wonder what a nonmagnetic metallic
implant in my body would do if rotated - maybe develop enough voltage to
cause electrocution risk or shbad shocks? (There are horror stories
about how little voltage under the skin can cause electrocution!)

My wife had an MRI when she had braces on her teeth. The MRI was
almost useless, terribly distorted, but she didn't have any associated
discomfort. She got them removed and it worked better.

John
 
D

Don Klipstein

Jan 1, 1970
0
We are working on a single pass PET scanner with Philips that makes
an image in a single pass under the detector array, as opposed to the
older method of making passes for each detector cell.

One's blood does not separate. Does anyone here even know where the
iron molecules are in the bloodstream?

They are in hemoglobin molecules. I give a chance that hemoglobin is
"paramagnetic", which is a class where the permeability is only slightly
greater than that of vacuum or "thin air". Most substances where most
atoms have "unpaired electrons" (first column of the periodic table,
columns 3a-7a and 3b-7b and most of the "rare earths") are paramagnetic.
The opposite (permeability slightly less than that of a vacuum, or
slightly less than 1) is true of most elements with all electrons paired
(second and last columns of the periodic table, as well as [I hope I got
this right] the one with zinc, cadmium and mercury.) Then again, bismuth
is diamagnetic - I saw it very slightly repelled by a magnet at the
Franklin Institute science museum in Philadelphia.
Most iron compounds are paramagnetic (permeability is only slightly
above 1 or that of vacuum) as opposed to ferromagnetic (permeability in
the 10's to 100,000's and usually notably nonlinear and prone to
"saturation" at field intensities anywhere from around a couple tenths of
a tesla to around a couple tesla).
Ferromagnetism is largely limited to iron, nickel and cobalt, a few
select compounds thereof (including ferrites), chromium (maybe a few
compounds thereof) in some special favorable cases, possibly in
favorable cases maybe other elements in that region of the periodic
table (I have yet to hear of this), and solidified hydrogen and not much
else.

- Don Klipstein ([email protected])
 
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