Dear All:
Wow! I think I struck a chord asking these questions. I can't thank you
enough for your replies.
The concensus seems to be that
1: low-field rated tubes and disposable tubes can usually be used satisfactorily
in high-field magnets provided that they are not bowed and fit in the spinner
turbines properly.
2. don't use a shim to keep the tube from slipping
I should have mentioned in my original message that the particular tube
in question was very definitely of a smaller diameter than most of the
tubes used here and wouldn't fit properly into any of our spinners. 4.8 mm
as opposed to an average of 4.9 mm. I don't think that the o-rings need
replacing yet.
Here is the (very long) summary of the replies to date:
=======================================================================
You might have two problems, one, the spinner turbines have loose o-rings and
need to be replaced, two, the od of the nmr tubes varies too much. Try a
different brand of tubes. Aldrich gets theirs from several sources. Stick with
major brand high-throughput tubes that are used in most of the auto-sampling systems.
=======================================================================
Many years ago, I prepared a discussion on NMR tube quality for Wilmad
customers. It's still available (see
http://www.wilmad-labglass.com/services/NMR_001.jsp). Dan Traficante
makes this required reading in his NMR courses!
Basically, your problem with spinner fit comes down to OD precision.
Your "clients" are using tubes that are selected from drawn tubing,
which has a varying OD. You want your "clients" to use tubes that have
been precision ground and polished tubes on the OD to prevent the
variation that plagues you currently. These can a bit more expensive,
for sure, but -PS (polished/selected) tubes in the Wilmad product line
will not be as expensive since the IDs are not formed but rather
selected from drawn glass (the ODs are ground and polished, though).
=======================================================================
I had the same problem with similar cheap tubes. My solution was to require
all users to use Wilmad 507's and the problem was cured. The main problem
here is that most users will leave the sample-solution in the NMR tube until
they need to run the next sample and by that time the NMR tube has a solid
plug at the bottom, hence consider a disposable NMR tube. If they clean
the tube right after use, you can argue for a good quality tube. Also I
did not like the shimming range that the poor tubes required.
=======================================================================
Withing the last year, I am having the same issue with even the 500MHz
medium priced Wilmad tubes. I have NOT had the problem for >20 years, but,
have had a lot of tubes lately that are too small in OD. Unfortunately, the
users are also shimming them with kimwipe pieces!
=======================================================================
My candid opinion: Don't let your users do that. The kimwipe solution may
cause you problems.
In my NMR lab I have two key rules that I strongly enforce everyday and they
are:
- Never touch the spinner with your bare hands. Always use a kimwipe
- Use always a good NMR tube. I strongly recommend the use of
Wilmad-507-pp-7
The 507-pp is the lowest price good quality NMR tube. They do not wobble
when spinning and the fitting in the spinner is very consistent. Not like in
the case of cheap tubes. If you have a BBO probe and you spin the samples, a
bad tube will end up breaking the quartz insert.
=======================================================================
We have a 400 MHz instrument, and we frequently use disposable 5mm tubes
from any of three sources: Wilmad, Norell and/or NewERA. While some
tubes seem to be tighter or looser than others, it seems that (for us)
the problem has usually been the o-ring in the spinner-holder.
Sometimes they get dirty or greasy. An acetone cleaning seems to
generally solve the problem our problems. Those few tubes that are
truly too tight or loose, we just toss.... they are disposable, after
all.
=======================================================================
We have encountered these problems, except to the best of my knowledge,
our users haven't tried the Kimwipe trick. We tell them during training
that they must use their heads about the sample being snug enough to not
slip in the spinner. We sometimes encounter some tubes that are just too
big to go through. We also tell them that one consequence of buying very
cheap tubes is that a few will not be usable. Also, to the best of my
knowledge, they are not using disposable tubes. That could be going too
far.
=======================================================================
Use of disposable NMR tubes is generally not recommended for most modern
NMR spectrometers because they break easily and don't fit spinners properly
as you've discovered. The data quality is also lower particularly for higher
field spectrometers. When you start seeing cheap fixes to get disposable
tubes to work, it's time to set a policy about the type of NMR tubes that
you want in your instruments. I use fairly inexpensive Norell HP tubes
that I've tested against other manufacturers at 400 and 500 MHz. I also
get excellent results for these tubes up to 800 MHz. For our purposes,
we use them as disposable tubes because the time and effort to clean them
properly costs more than a new tube. However, I'm basing this on an
industrial setting where we get a small discount off the regular price
when we buy in bulk. At $3-$4 per tube for good quality NMR tubes,
these can be cleaned and re-used many times to save money.
=======================================================================
In the quest for sensitivity, probes are designed with very little
clearance between the tube and the coil/support. I have had bowed tubes
(specified as camber) rub and damage the probe. Any tube loose enough to
require a mechanical shim to retain it in the spinner body is likely to be a problem.
A second issue is that homogeneity will suffer since the shims (especially
the radial shims) presumably were set using a high-quality tube. I have seen
problems with spinning sidebands and lineshape degradation (especially near
the base) from inferior tubes.
Because of these issues, my coworkers and I banned "disposable" tubes,
requiring the use of mid-range Wilmad tubes or better.
=======================================================================
We have been using the Optima ES-400 tubes for routine work on all our
instruments, including the 500, without any problems. They seem to be
manufactured to a good degree of precision, and there have been no problems
of slippage in the autosampler. However, they are not made of Pyrex,
and so cannot be used for VT work.
Like you, I would be very uncomfortable plugging with a Kimwipe.
=======================================================================
we routinely use Wilmad "HIP" tubes (WG-1000). They work great. Spinning
sidebands are only negligibly higher than the 527 tubes.
I haven't noticed any issues of looseness with these tubes. I have noticed
the occasional loose tube brought in by users.
Your users trick with the kimwipes does sound like a very bad idea. It
could also lodge the tube at an angle in the spinner. Suggest you offer
exchange of any loose tubes for a good disposable that works.
I saw one 15 minutes ago. What I did was clean the spinner so the O-ring
got a tighter grip on it. If you take a Kimwipe and twist one corner ...
keep twisting until it looks like 3 inches of string with a bloom of
Kimwipe at the end. Thread the string end through the spinner, squirt
some acetone onto the O-ring, and pull it through.
Users could put a ring of scotch tape on the tube to keep it from
descending too far into the spinner.
Another solution is getting the spinners with teeth that grip the tube,
instead of an O-ring. (Wilmad has them). But not at automation prices.
=======================================================================
We do have the same problem as you stated. We have sent out several
e-mails to NMR users not to use those cheap tubes (disposable, thrift,
economy tubes from Aldrich, Norell, Wilmad...), but some users are still
using them on the NMR's to do their "paper chemistry".
I do require the user to use, at least, Kimble-Chase's (formally Konte's)
897240 NMR tubes, or other better quality tubes (such as 897245 or Wilmad's
528 or 535 tubes) for routine NMR experiments. If we see any user using
those low quality tubes with kimwipe, we will suspend his/her access to
the NMR spectrometers for at least a week. We also notice that in many
cases, one could not get good shimming for the samples in those cheap tubes.
=======================================================================
We do not let students use disposable or thrift nmr tubes in any of our
nmr instrument. We do allow student to use the economy tubes from the major
manufacturers. These tubes have mostly the same specifications at the precession
tubes but are made of a lower cost glass. Just think about how much money
the researchers save with the thrift tubes vs how much it will cost to repair
a probe and the down time of the instrument.
=======================================================================
I have had this exact thing happen. My users tore out pieces of the logbook
to make their wedges. The problem with those cheap tubes is not only in the
diameter but in the camber. The tubes are not straight and as they spin
they bump against the probe inserts. This lead to scratches and eventual
cracking of the insert. I have absolutely banned that tube from my facility.
I require that all tubes have specs that match the Wilmad 535 or better.
=======================================================================
I have encountered Kimwipe "shimming" and it is not acceptable. We require
a minimum specification for our 500 MHz NMR. It is particularly important
for samples that spin. Under no circumstances should anything go in the
probe other than a tube in spin turbine. In our department, anything else
in the probe is grounds for loss of NMR privileges since a mishap could
result in loss of instrument use by other users.
=======================================================================
As a general rule, we're not too concerned with tube quality as long as a
certain minimum is maintained. I'm not so sure we'd allow tubes explicitly
sold as disposable though. We've been using a lot of Norell 502-7 tubes
lately at 500, 600, and 800 MHz with no problems - these cost something like
$1.70(U.S.)/tube in boxes of 50, as opposed to the Wilmad 535 tubes that the
stockroom sells for somewhere between $12-14 each. Quality is high enough
that the tube OD is fairly consistent.
Unless you're spinning, the better specs of a higher field rated tube aren't
all that meaningful so anything above an acceptable minimum quality is fine.
Shimming hasn't been an issue, especially with gradient shimming.
If I were you, I'd decide what you consider the "cheapest" allowable NMR
tube and insist on that "or better". I don't know what enforcement power you
may have. In addition to Norell, New Era and Optima make reasonable quality,
affordable NMR tubes (I've used both), and lower field rated Wilmads (507)
are fine as well, so groups have plenty of options.
While I would doubt that the Kimwipe "fix" will lead to problems, why take
the risk?
=======================================================================
This should open a good can of worms for you... generally if you ask 20
people this questions, you'll get 20 different opinions. From my > 25 years
experience I'll give you my take on the situation.
1) Cheap tubes have poorer quality control, with some being slightly
bigger/smaller, or "bent" (camber), or whatever. Any of these can end up
damaging your probe (I've lost multiple probe-inserts due to
cheap/poorly-maintained tubes). These disposable tubes are forbidden in all
of my spectrometers, but this is difficult to police, since they often give
them away at ACS meetings and such, and people use them anyway. I caught one
user trying to use one of these that was slightly "too big" for the Varian
spinner-turbine. After a good scolding, I posed the question.. if it's too
big for the spinner, don't you think it might be too big for the probe? Of
course, if it is too small, it can slip, and move out of coil-center, which
is another set of problems. Probably > 90% of disposable tubes are probably
ok, but I worry about the 10% or 5% that could damage something.
2) Even the most expensive "Royal Imperial" (or other Wilmad-created buzz
word) tube will warp and become dangerous if poorly cared for. If stored
standing up in a beaker (leaning at an angle) in a hot oven long enough, it
will bend, and can damage the probe. So, it's important to remember that
even the most expensive NMR tube can go out of tolerance if poorly cared
for.
3) I've never found the tube quality/precision to have a dramatic effect on
shimming. Yes, it might take a little more work to shim a lower quality
tube, but it's been shown many times (i.e. the old Norell advertisements
(from the 1980s) that their XR-55 disposable tubes are as good as the most
expensive tubes, as evinced by spectra acquired at Harvard at 500MHz... they
were passing this around for more than a decade). I agree that running a
lot of samples in automation will benefit from tubes that are very similar
from one sample to the next (saving shimming time), but with my AV-III
using ICON and Topshim, it seems to be able to shim about anything better
than any of my users could do using older shimming methods.
4) Wilmad still sells an "NMR Tube Checker"
(
http://www.wilmad-labglass.com/group/2099 ), a piece of glass with a
precision-ground hole that can check the diameter and straightness of the
tube. If it slides through smoothly, and doesn't "catch", it's probably ok
to use. Funny, when my old Wilmad-Glass sales-rep gave me one of these (to
convince me to stop buying tubes from another vendor), the only tubes that
failed the test were older 528-PP tubes that had been poorly handled for a
longtime (proving my point in #2 above). I need to get some of these again
(note to self).
=======================================================================
I have used the same "fix" for NMR tubes, but I wouldn't do it with a sample
changer for just the reason you've said. Tubes for lower NMR fields work
just fine at higher fields, though sometimes they take more shimming. Notable,
if you have a cold probe, use a good tube. You do increase sensitivity
with ultra-high field tubes, which are more concentric and thinner. If it is
important enough to use a cryoprobe, use a better tube.
I find that cheap tube Norell XR-55s are concentric enough to use, but not
forever. Organometallic reagents take their toll on these tubes.
=======================================================================
tell your users to buy their "disposable" tubes from the Bruker online
store - cost is less than $2 each and they work fine in our new Bruker 400, 500
and 600s (with cryoprobes) all with sample changers as per Bruker's recommendation.
I bought 3000 tubes, replaced all the low grade ones in our science stores
(so that anyone buying tubes gets the good ones) and then billed each group about $50
and did a 1 for 1 exchange (old tubes for new). This had the added benefit
of purging all old cracked or broken tubes from various research groups as well.
Much cheaper than the possible consequences Ifelt.
=======================================================================
In a former position I used to run 100 sample lots using Norell 5mm throw
away NMR tubes. I did not experience the QC problems you have mentioned
regarding OD fluctuations. I found the spectra to be of very good quality
as well. Like any automation situation, I found that a small percentage
of samples did not shim well. Revisiting these samples yielded good spectra.
I never had time to investigate why a few samples did not shim. But I
saved a great deal on supplies.
I know that commercial for profit NMR spectra vendors use the throw
away tubes routinely (particularly when they supply the solvent and tube
for the spectra). They are in the business of producing the best quality
spectra for a profit.
Regarding Kimwipes--take a good look at a Kimwipe under a microscope
and you will find a myriad of small fibers--far more than what you see
in normal paper. These fibers are being deposited (like dust) directly into
your spinner housing where they grind into the wall and spin shuttle. I don't
recommend keeping Kimwipes near the spectrometer at all. A small soft cotton
cloth is far better for removing smudges and finger oil from the outer
edge of the NMR tube. A better approach to keep tubes from dropping through
the spin shuttle would be to wrap a single turn of scotch tape around the NMR
tube at the top of the spin shuttle. Nothing would be forced into position
and gravity will not take the NMR tube out of position.. Of course if your
autosampler grabs the NMR tube rather than the shuttle then you risk dropping
the shuttle on the pathway from the carousel to the top of the bore.
Then you risk dropping a bare tube down the bore.
=======================================================================
Since our polymer samples are impossible to clean out of 5 mm tubes, we use
the cheapest ones we can find for work at 500 MHz to toss them out
afterwards.
We have found the cheap Norell tubes to be consistently tighter in the
Bruker 5-mm spinners than the Aldrich or Wilmad ones. For Wilmad, we have
often had to throw away up to 20% of the tubes because they are too loose,
and I don't remember the last time I had to toss out a Norell tube. A
couple have been a little loose, but I could usually find a spinner that
was tight enough within 2 tries.
When we had a Varian, those spinners were more forgiving and we could get
away with the Wilmad and Aldrich ones.
Norell's part number is ST500-7, about $121 for 100 tubes if you buy at
least 10 packs, which I think is about 20% more expensive that the Wilmad
cheapest ones, but still much cheaper than a Wilmad 528 or better tube.
I think Wilmad also sells one level better than the HIP-7s that have
tighter specs on the OD and may work more consistently.
For our uses (polymers), the cheaper tubes are quite satisfactory for
shimming under automation, but our lines are very broad to begin with. For
true high resolution work, you will certainly see more sidebands and
strange out of phase things around the sharper peaks, especially if you are
using an inverse probe. Also good enough for basic 2D COSY, HSQC, HMBC.
May be an issue if you are looking for tiny peaks next to something sharp.
=======================================================================
My laboratory uses Wilmad disposable 5 mm NMR 8 inch tubes and we have had
no difficulties with fit or performance. We run all of our experiments
non-spinning so the need for trueness of the tube dimensions is minmized
(our gradient shimming and magnet homogeneity are very good. We have Varian
Mercury, 400MR and VNMRS 600 instruments (all with autosamplers); all 5 mm
probes and use all the same tubes. The problems I have encountered with
spinning (even with expensive tubes) are not worth it in my book; that is
why I do not spin samples anymore. My lineshape non-spin is almost the same
as my spinning lineshape with the test sample (CHCl3 in acetone-d6). I
just tweek my non-spin shims once every couple months to keep the lineshape
good after gradient shimming.
Your concerns are all justified as well. I have had not experience with
Aldrich tubes, just Wilmad. Are you sure that your turbine o-rings are
not worn out? The same turbine with a loose disposable tube is tight with
a high precision tube?
=======================================================================
The kimwipe fix seems quite dangerous to me.
The tube probably won't spin concentrically anymore (if you spin) and might
over time damage the glass insert inside the probe.
I usually keep several spinners around with varying degree of "looseness".
Maybe it's time to replace the O-ring in the spinner.
=======================================================================
FWIW I think the "MHz" rating on NMR tubes is pure marketing hype. What
matters is the manufacturing tolerances in terms of OD, concentricity and
camber. A crappy "300 MHz" tube could still damage a 200 MHz instrument,
especially if mishandled by a sample changer.
That being said, I have essentially banned such "disposable" tubes from
our lab. With the price of a probe now approaching (or exceeding) that
of a Porsche Boxter, it is simply not worth the risk. If your users insist
on using them then every tube should be checked in the spinners and also
checked for straightness on a straightness gauge (available from Wilmad).
Using Kimwipes as a "shim" is simply unacceptable. Decent NMR tubes will
last a long time it treated and cleaned properly, and are well worth the
added cost.
We have found that Wilmad 507 (or equivalent) tubes to be pretty consistent,
with only the odd one failing to fit the spinner properly. Even though the
Wilmad 507 tubes are only rated at "300 MHz", we even use them at 500 and
600 MHz - although I personally use Wilmad 528 and 535 tubes on the higher
field instruments. For most spectra, you won't notice the difference
between a 507 and a 528 at 500 MHz. To see the benefits of the better
tubes you would also likely need to filter the sample.
=======================================================================
Definitely see similar problems here, with a variety of tubes. I try to
not fight the groups about the tubes they are using; once thought about it,
but over last 10 yrs or so, have not have probe glass etching problems
that used to worry (tube out-of-round rubbing on the probe inner glass and
etching it). We have worked pretty hard to get groups to understand the
proper way to dry tubes (Wilmad write-up; keep tubes standing, and don't
"cook" overnight), which I think was the major cause of glass etching.
In any event, we do see some tubes that are "loose" in spinners, and
occasionally see students trying things like the piece of paper trick.
I do keep a mix of Bruker's blue and white spinners, as they pinch a bit
different. Students will try different ones; seems one or another will
often work; but not always. I don't see this problem as often with Varian spinners.
I do the following wrt to tubes: I emphasize my general satisfaction to
users about Wilmad. I'm don't test other vendors' tubes; I truly don't
have time for that. Don't reject them, but don't recommend either. My
experience shows that Wilmad tubes work as [better than] advertised, so
that's what I recommend.
One vendor, A [Ace glass], I do have the opposite experience with. Went
through an agonizing year (first half anyway, till I figured out the problem)
where an appreciable fraction of tubes (maybe 20%) would not shim even at
300 MHz. We got to where we'd immediately transfer the sample over to a
new tube (sometimes not that trivial); then started throwing out a lot of
A tubes. If poor shimming happens only occasionally, it's still too often,
as a lot of time will be wasted figuring out that the problem is the tube,
and not something to do with the probe, sample, or user. So no joy with
vendor A. Never seen the problem with vendor Wilmad.
We get good results with the Wilmad Economy tubes, even at 500 MHz. Have
to be a bit careful, as any sample that needs a good quality 1H at 500 MHz,
I put in a 506. If it needs water suppression, we often go to 528. But
Economy seems to work fine always on our 300s, and for many purposes are ok at 500.
=======================================================================
Having worked at GSK and now at Merck I have used resp. introduced
disposable NMR tubes from Aldrich resp. GPE/ Narolac. During the evaluation
period we have found out that the o-rings of our spinners - we are unsing
BRUKER spectrometers - have become loose and weak. A replacement of the
o-ring (100 pieces cost approx. ? 200,-) fixed the problem. We observed
a non-suitable NMR tube only once during 8 years. The bottom of the tube
was like a bulb. The tube could not even be passed through the bore of the spinner.
A more expensive solution are the latest BRUKER spinner which are of
greater length. Therefore they can accommodate with less "precise" outer
tube diameters. Regarding precision of NMR tubes: One supplier informed
me that all NMR tubes called "disposable" or "high-precision" are coming
from the same machine. The only difference is the number of quality
controls per lot.
=======================================================================
We also use "disposable" NMR tubes in our instruments and although we
use Wilmad rather than Aldrich, I suspect the tolerances are similarly
"lax". What we have discovered is that the spinners also have quite a
large tolerance and so a tube that is very loose in one spinner will
grip quite nicely in another spinner and the converse is also true. I
should add here that we use the "cheap" Bruker blue PLA/POM spinners.
Armed with this knowledge, it is simply a case of educating the users
that if they find that their tube is too tight or loose, simply try
another spinner until, as per Goldilocks, they find one that is just
right. It seems that the biggest variance is with the oldest type of
spinner (ca. 1988) that we use on our open-access system, the newer
spinners do seem better.
We use these disposable tubes on all our instruments upto 500MHz without
too many problems and both "autotune" & "gradshim" work well. If you
are looking for the ultimate in resolution then a very high quality tube
might be justified but for most cases the disposable tubes are fine.
=======================================================================
My two cents: The cheap tubes are so cheap that you could just collect
the less fitting ones and keep them for a spinner which might be a bit
tighter (new rubber rings) or just discard them alltogether.
There might be a difference in shimming. But I wouldn't be concerned as
long as you don't face problems this! A trick one of my teachers told
me: let them roll over the table. If they wobble just let them cross the
edge... :-)
=======================================================================
Often you can find a spinner-tube combination that gives a snug fit just
by switching spinners. This has been the solution here when using the
low grade tubes; out of a box of 30 spinners for the autosampler, the
students and staff are required to select one that gives a proper grip
on the tube. I do not force the users to use high grade tubes. The cost
has become prohibitive in an environment where there are two major problems
with the users - students and staff too lazy to keep their tubes clean and
then stealing clean tubes from each other and students and staff using tubes
as long-term storage vessels after running their experiments. I have
found that in the majority of cases, the tube is not the limiting factor,
it is rather the quality of the sample. There are occasional shimming problems,
spinning side-bands are larger (if you use spinning) and line-shape suffers
but this is usually only visible on a good quality sample and then it is only
a matter of transferring the sample to a higher grade of tube, if warranted
(I keep a stock of high grade tubes for this purpose). The majority of
users here wouldn't notice one way or the other and the low grade tubes
are substantially cheaper.
I would not allow users to use any form of accessory ("Kimwipe") - either
the tube sits tight in a spinner or it doesn't go anywhere near the magnet.
=======================================================================
I've given up trying to police tube usage beyond pointing out
that the time and product in the tube are usually worth over
$100, so why would you want to use a $3 tube. Cheap tubes
are useful if your product is difficult to remove. When tubes are
loose in the spinner, I usually wrap a small strip of parafilm
around the tube to keep it from slipping down.
=======================================================================
If you can't ban the students or confiscate the tubes, make sure the O-ring
in your spinner is nice and new. Over time they get loose. I'm very glad
our students haven't figured out this workaround.
=======================================================================
We had Varian machines with Plexiglas rotors. Quite often the
sample fails to spins. So quite routinely I use a wooden 'Q-tip' stick that
is cut at an angle to give a sharp wedge to dig out the O-ring. Then I
dig/clear the recessed area which housed the O-ring. Followed by a final
cleaning with a 'Q-tip' soaked in methanol. If the O-ring is loose ie the
NMR tube slides in and out too easily, I replaced the O ring. My o-rings
for the rotors are red --> they are made of silicon rubber. They can use
any nmr tubes they want. But they should never be allowed to use a Kimwipe
tissue to because it put the tubes way off alignment.
=======================================================================
Keith, We use Norell 502-7 tubes at up to 600MHz with no problems with
slippage in the spinner. Resolution is also adequate. We do not spin the tubes.
=======================================================================
We routinely re-use 100MHz tubes (Norell 502-7 which cost about 70-pence
per tube) and they cause no problems with fit etc. If we notice loose-fitting
tubes these are caused by old o-rings in the spinners (this is JEOL kit,
but I believe other spinners have the o-rings too). If we replace them,
the problem goes away.
I would NEVER let our users put anything into the spinner to tighten it
up.... if this is really the tubes, change the supplier!
We also replaced ALL of our tubes about 3 years ago (by changing from Wilmad
to Norell, we effectively forced all groups to change their tubes - this meant
we didn't have tubes that were 15 years old still floating around!).
We have never seen systematic problems with shimming related to tubes
on 300/400 instruments, and we are fully automated at 300/400 but we
do remind people that they cannot expect perfect results with cheap tubes,
so they are welcome to buy high res if they like (they never do).
We use 500MHz tubes for our 500/600 systems.
=======================================================================
Keith - do not allow them to use little pieces of kimwipe. Not only is
there a concern of the kimwipe getting lodged in the probe, of even more
concern is the students who will use too much kimwipe and then try and force
their tube into the spinner and break their tube, risking a serious cut. My
feeling is the only real solution is to enforce a higher quality tube
standard. Replacing the o-rings on the spinner (or replacing the spinner)
also helps to minimize the number of tubes that are too loose.
=======================================================================
Dr. Keith Brown
Department of Chemistry/
Saskatchewan Structural Sciences Center
University of Saskatchewan
Saskatoon, Saskatchewan
306-966-1725
http://chem4823.usask.ca/kbrown.html
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Quantum Mechanics: The dreams stuff is made of.
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Received on Fri Jul 09 2010 - 04:59:25 MST