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Graphene Under Strain Creates Gigantic Pseudo-Magnetic Fields
Berkeley Lab ^ | July 29, 2010 | Paul Preuss

Posted on 07/29/2010 12:43:12 PM PDT by decimon

Graphene, the extraordinary form of carbon that consists of a single layer of carbon atoms, has produced another in a long list of experimental surprises. In the current issue of the journal Science, a multi-institutional team of researchers headed by Michael Crommie, a faculty senior scientist in the Materials Sciences Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley, reports the creation of pseudo-magnetic fields far stronger than the strongest magnetic fields ever sustained in a laboratory – just by putting the right kind of strain onto a patch of graphene.

“We have shown experimentally that when graphene is stretched to form nanobubbles on a platinum substrate, electrons behave as if they were subject to magnetic fields in excess of 300 tesla, even though no magnetic field has actually been applied,” says Crommie. “This is a completely new physical effect that has no counterpart in any other condensed matter system.”

Crommie notes that “for over 100 years people have been sticking materials into magnetic fields to see how the electrons behave, but it’s impossible to sustain tremendously strong magnetic fields in a laboratory setting.” The current record is 85 tesla for a field that lasts only thousandths of a second. When stronger fields are created, the magnets blow themselves apart.

The ability to make electrons behave as if they were in magnetic fields of 300 tesla or more – just by stretching graphene – offers a new window on a source of important applications and fundamental scientific discoveries going back over a century. This is made possible by graphene’s electronic behavior, which is unlike any other material’s.

A carbon atom has four valence electrons; in graphene (and in graphite, a stack of graphene layers), three electrons bond in a plane with their neighbors to form a strong hexagonal pattern, like chicken-wire. The fourth electron sticks up out of the plane and is free to hop from one atom to the next. The latter pi-bond electrons act as if they have no mass at all, like photons. They can move at almost one percent of the speed of light.

The idea that a deformation of graphene might lead to the appearance of a pseudo-magnetic field first arose even before graphene sheets had been isolated, in the context of carbon nanotubes (which are simply rolled-up graphene). In early 2010, theorist Francisco Guinea of the Institute of Materials Science of Madrid and his colleagues developed these ideas and predicted that if graphene could be stretched along its three main crystallographic directions, it would effectively act as though it were placed in a uniform magnetic field. This is because strain changes the bond lengths between atoms and affects the way electrons move between them. The pseudo-magnetic field would reveal itself through its effects on electron orbits.

In classical physics, electrons in a magnetic field travel in circles called cyclotron orbits. These were named following Ernest Lawrence’s invention of the cyclotron, because cyclotrons continuously accelerate charged particles (protons, in Lawrence’s case) in a curving path induced by a strong field.

Viewed quantum mechanically, however, cyclotron orbits become quantized and exhibit discrete energy levels. Called Landau levels, these correspond to energies where constructive interference occurs in an orbiting electron’s quantum wave function. The number of electrons occupying each Landau level depends on the strength of the field – the stronger the field, the more energy spacing between Landau levels, and the denser the electron states become at each level – which is a key feature of the predicted pseudo-magnetic fields in graphene.

A serendipitous discovery

Describing their experimental discovery, Crommie says, “We had the benefit of a remarkable stroke of serendipity.”

Crommie’s research group had been using a scanning tunneling microscope to study graphene monolayers grown on a platinum substrate. A scanning tunneling microscope works by using a sharp needle probe that skims along the surface of a material to measure minute changes in electrical current, revealing the density of electron states at each point in the scan while building an image of the surface.

Crommie was meeting with a visiting theorist from Boston University, Antonio Castro Neto, about a completely different topic when a group member came into his office with the latest data.

“It showed nanobubbles, little pyramid-like protrusions, in a patch of graphene on the platinum surface,” Crommie says, “and associated with the graphene nanobubbles there were distinct peaks in the density of electron states.”

Crommie says his visitor, Castro Neto, took one look and said, “That looks like the Landau levels predicted for strained graphene.”

Sure enough, close examination of the triangular bubbles revealed that their chicken-wire lattice had been stretched precisely along the three axes needed to induce the strain orientation that Guinea and his coworkers had predicted would give rise to pseudo-magnetic fields. The greater the curvature of the bubbles, the greater the strain, and the greater the strength of the pseudo-magnetic field. The increased density of electron states revealed by scanning tunneling spectroscopy corresponded to Landau levels, in some cases indicating giant pseudo-magnetic fields of 300 tesla or more.

“Getting the right strain resulted from a combination of factors,” Crommie says. “To grow graphene on the platinum we had exposed the platinum to ethylene” – a simple compound of carbon and hydrogen – “and at high temperature the carbon atoms formed a sheet of graphene whose orientation was determined by the platinum’s lattice structure.”

To get the highest resolution from the scanning tunneling microscope, the system was then cooled to a few degrees above absolute zero. Both the graphene and the platinum contracted – but the platinum shrank more, with the result that excess graphene pushed up into bubbles, measuring four to 10 nanometers (billionths of a meter) across and from a third to more than two nanometers high.

To confirm that the experimental observations were consistent with theoretical predictions, Castro Neto worked with Guinea to model a nanobubble typical of those found by the Crommie group. The resulting theoretical picture was a near-match to what the experimenters had observed: a strain-induced pseudo-magnetic field some 200 to 400 tesla strong in the regions of greatest strain, for nanobubbles of the correct size.

“Controlling where electrons live and how they move is an essential feature of all electronic devices,” says Crommie. “New types of control allow us to create new devices, and so our demonstration of strain engineering in graphene provides an entirely new way for mechanically controlling electronic structure in graphene. The effect is so strong that we could do it at room temperature.”

The opportunities for basic science with strain engineering are also huge. For example, in strong pseudo-magnetic fields electrons orbit in tight circles that bump up against one another, potentially leading to novel electron-electron interactions. Says Crommie, “this is the kind of physics that physicists love to explore.”

“Strain-induced pseudo-magnetic fields greater than 300 tesla in graphene nanobubbles,” by Niv Levy, Sarah Burke, Kacey Meaker, Melissa Panlasigui, Alex Zettl, Francisco Guinea, Antonio Castro Neto, and Michael Crommie, appears in the July 30 issue of Science. The work was supported by the Department of Energy’s Office of Science and by the Office of Naval Research.

Additional information

Lawrence Berkeley National Laboratory provides solutions to the world’s most urgent scientific challenges including clean energy, climate change, human health, novel materials, and a better understanding of matter and force in the universe. It is a world leader in improving our lives and knowledge of the world around us through innovative science, advanced computing, and technology that makes a difference. Berkeley Lab is a U.S. Department of Energy (DOE) national laboratory managed by the University of California for the DOE Office of Science.


TOPICS: Science
KEYWORDS: graphene; stringtheory
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Pseudo-magnetism = futile attraction?
1 posted on 07/29/2010 12:43:16 PM PDT by decimon
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To: SunkenCiv

Ping


2 posted on 07/29/2010 12:44:05 PM PDT by decimon
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To: decimon

Woo hoo!

This may well solve the problem of the energy required to maintain a magnetic bubble around a fusion reaction.

May well be the KEY!


3 posted on 07/29/2010 12:47:32 PM PDT by roaddog727 (It's the Constitution, Stupid!)
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To: decimon; KevinDavis

interesting


4 posted on 07/29/2010 12:47:40 PM PDT by GeronL (http://libertyfic.proboards.com <--- My Fiction/ Science Fiction Board)
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To: decimon

B4L8r


5 posted on 07/29/2010 12:50:14 PM PDT by AFreeBird
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To: decimon
When stronger fields are created, the magnets blow themselves apart.

LOL! Understatement of the year award. Nothing about reverse EMF toasting breakers, EMP killing equipment, or the startling noise and flash.

/johnny

6 posted on 07/29/2010 12:51:45 PM PDT by JRandomFreeper (Gone Galt)
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To: decimon

Its always nice to hear about the real science going on in the world and not just the political cult babble surrounding AGW. But then, I doubt that many climate scientists would be able to hang with this crowd.


7 posted on 07/29/2010 12:53:05 PM PDT by centurion316
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To: decimon

Wow! This reminds me of the 1950s, when semiconductors replaced vacuum tubes.

Again ... Wow!


8 posted on 07/29/2010 12:56:56 PM PDT by OldNavyVet (One trillion days, at 365 days per year, is 2,739,726,027 years ... almost 3 billion years)
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To: decimon

Ok, now that they have made electrons act as if they are in a very intense magnetic field what are the possible applications if any?

How much strain is required? If the strain is cycled is current flow produced?


9 posted on 07/29/2010 1:01:03 PM PDT by Wurlitzer (Welcome to the new USSA (United Socialist States of Amerika))
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To: Wurlitzer
Ok, now that they have made electrons act as if they are in a very intense magnetic field what are the possible applications if any?

How much strain is required? If the strain is cycled is current flow produced?

Well, it's pseudo-magnetism so what's induced is pseudo-current. Works fine with pseudo-appliances.

IOW, I don't know.

10 posted on 07/29/2010 1:04:53 PM PDT by decimon
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To: decimon

They’re calling it a “pseudo” magnetic field for a reason: it’s not a magnetic field.

This is just one more grant sucking scheme.


11 posted on 07/29/2010 1:09:56 PM PDT by Born to Conserve
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To: centurion316
I hope no one tells the oil companies about this.

I'm sure this advance could be used to solve the world's energy problems. But if the oil companies find out they'll surely buyout all the patents and kill anyone that tries to talk!

/sarc

12 posted on 07/29/2010 1:13:20 PM PDT by who_would_fardels_bear (These fragments I have shored against my ruins)
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To: decimon
"it's pseudo-magnetism so what's induced is pseudo-current. Works fine with pseudo-appliances"

Is it quasi-stable?

13 posted on 07/29/2010 1:14:50 PM PDT by who_would_fardels_bear (These fragments I have shored against my ruins)
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To: decimon
a very intense magnetic field what are the possible applications

Compact atom smashers, clyclotrons, magnets, amplifiers, electric motors ...

14 posted on 07/29/2010 1:15:30 PM PDT by OldNavyVet (One trillion days, at 365 days per year, is 2,739,726,027 years ... almost 3 billion years)
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To: decimon
Graphene Under Strain

Wasn't that a Star Trek episode? Graphen was a real hottie as I recall...

15 posted on 07/29/2010 1:15:38 PM PDT by frithguild (Joe Wilson was wrong when he shouted "You lie!" Obama doesn't just lie - he lies all the time.)
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To: decimon

I wonder if we could make electric guitar strings out this stuff.


16 posted on 07/29/2010 1:23:45 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: who_would_fardels_bear

......Is it quasi-stable?....

Except in the presence of a plasma fark array


17 posted on 07/29/2010 1:24:58 PM PDT by bert (K.E. N.P. N.C. +12 ..... The winds of war are freshening)
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To: Wurlitzer

It could make people’s peas stay on their knives.

You know, for people who don’t like honey.


18 posted on 07/29/2010 1:25:10 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: who_would_fardels_bear

Yup.

Just like they did with the 200 mpg carbeurator!


19 posted on 07/29/2010 1:26:33 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: who_would_fardels_bear

Yup.

Just like they did with the 200 mpg carbeurator!


20 posted on 07/29/2010 1:26:33 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: who_would_fardels_bear

Yup.

Just like they did with the 200 mpg carbeurator!


21 posted on 07/29/2010 1:26:42 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: WayneS

Sorry about the triple post, I’m having some computer issues.


22 posted on 07/29/2010 1:27:32 PM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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To: roaddog727
Well, that and the platinum coated chickenwire.

One does wonder what this thing cost ! $19.98 ~ not sold in stores.

There are some other uses of very powerful pseudo magnetic fields ~ e.g. antigrav units!

23 posted on 07/29/2010 1:30:26 PM PDT by muawiyah
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To: WayneS
I wonder if we could make electric guitar strings out this stuff.

Hmmmmm...think of the output of a pickup with this stuff used as the magnet. You'd only need a few windings, making for a very compact pickup. In theory, of course.

24 posted on 07/29/2010 1:33:37 PM PDT by randog (Tap into America!)
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To: muawiyah
"antigrav units"

Can't wait 'til they come out with the AntiGravJordans.

White men will be able to jump!

25 posted on 07/29/2010 1:34:57 PM PDT by who_would_fardels_bear (These fragments I have shored against my ruins)
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To: randog
You mean, of course, the neighborhood kid's S-10 pickup TRUCK where he's replaced the passengerside with a soundsystem.

Doggone, he could get his seat back ~ and make that baby buck like the world's most powerful Low Rider!

BTW, this, of course, means that the Chicom miniature speaker industry is now KAPUT!

26 posted on 07/29/2010 1:35:53 PM PDT by muawiyah
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To: decimon

How long before EPA declares it to be a pollutant and tries to limit it.


27 posted on 07/29/2010 1:37:14 PM PDT by KosmicKitty (WARNING: Hormonally crazed woman ahead!!)
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To: decimon


Michael Crommie, a faculty senior scientist in the Materials Sciences Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley (just kidding)
28 posted on 07/29/2010 1:37:21 PM PDT by rdax
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To: decimon

You’ve got it decimon, pseudo-automobiles produced by GM (government motors).

Once bHo gets energy cost to skyrocket, we can use pseudo-dollars to buy pseudo-cars running on pseudo-electricity.

We can even have a pseudo-Constitution...oh wait, we already have that.


29 posted on 07/29/2010 1:40:41 PM PDT by Wurlitzer (Welcome to the new USSA (United Socialist States of Amerika))
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To: decimon

Does this have anything to so with an anti-gravity look-alike?


30 posted on 07/29/2010 1:42:12 PM PDT by GOPJ (..Liberalism is Intolerance..- - Freeper Eric in the Ozarks)
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To: JRandomFreeper
Understatement of the year award. Nothing about reverse EMF toasting breakers, EMP killing equipment, or the startling noise and flash.

Not to mention the laundry bill for anyone in close proximity. :)

- Traveler

31 posted on 07/29/2010 2:07:54 PM PDT by Traveler59 (Truth is a journey, not a destination.)
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To: Wurlitzer

Yeah, if there is no ACTUAL magnetic field produced then the discovery is of little use ... but it is interesting.


32 posted on 07/29/2010 2:24:22 PM PDT by dartuser ("Palin 2012 ... nothing else will do.")
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To: WayneS
I wonder if we could make electric guitar strings out this stuff.

Yes, but strumming will pull the fillings out of your teeth.

33 posted on 07/29/2010 2:26:09 PM PDT by decimon
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To: OldNavyVet

I dimly remember one of my company’s scientists had a project to use powerful magnetic fields to affect the rate of radioactive decay in nuke waste. He said he could hasten the half life to make it give up it’s energy much faster. This could provide a usable energy source while destroying nuke waste.

Dunno if it worked.


34 posted on 07/29/2010 4:18:39 PM PDT by darth
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To: decimon; AdmSmith; bvw; callisto; ckilmer; dandelion; ganeshpuri89; gobucks; KevinDavis; ...
Thanks decimon! There is a surprising number of topics about graphene here on FR. :') Burnt City still roooools though. ;') Carbon nanotubes conduct electricity at low resistance, carry metal molecules along for the ride.
...pseudo-magnetic fields far stronger than the strongest magnetic fields ever sustained in a laboratory -- just by putting the right kind of strain onto a patch of graphene. "We have shown experimentally that when graphene is stretched to form nanobubbles on a platinum substrate, electrons behave as if they were subject to magnetic fields in excess of 300 tesla, even though no magnetic field has actually been applied," says Crommie. "This is a completely new physical effect that has no counterpart in any other condensed matter system."

· List topics · post a topic · subscribe · Google ·

35 posted on 07/29/2010 5:23:26 PM PDT by SunkenCiv ("Fools learn from experience. I prefer to learn from the experience of others." -- Otto von Bismarck)
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To: decimon
For example, in strong pseudo-magnetic fields electrons orbit in tight circles that bump up against one another, potentially leading to novel electron-electron interactions. Says Crommie, “this is the kind of physics that physicists love to explore.”

But the kind of English that grammarians love to deplore.
36 posted on 07/29/2010 5:30:16 PM PDT by aruanan
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To: roaddog727
This may well solve the problem of the energy required to maintain a magnetic bubble around a fusion reaction.

Around a pseudo fusion reaction.
37 posted on 07/29/2010 5:31:44 PM PDT by aruanan
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To: SunkenCiv
There is a surprising number of topics about graphene here on FR.

Pencil-necks and graphite just go together. ;-)

38 posted on 07/29/2010 5:53:08 PM PDT by decimon
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To: decimon; ALASKA; ActionNewsBill; A knight without armor; albertp; aragorn; areafiftyone; aruanan; ..

IIRC,

THAT’S DINKING AROUND in the area of UFO type technologies.

. . . both in terms of the graphene as well as the results.


39 posted on 07/29/2010 6:38:47 PM PDT by Quix (THE PLAN of the Bosses: http://www.freerepublic.com/focus/religion/2519352/posts?page=2#2)
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To: decimon

I’m sure someone has named their daughter graphene by now.


40 posted on 07/29/2010 6:51:42 PM PDT by SunkenCiv ("Fools learn from experience. I prefer to learn from the experience of others." -- Otto von Bismarck)
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To: OldNavyVet
This reminds me of the 1950s, when semiconductors replaced vacuum tubes.

We owe a great deal to semiconductors ... but I kindof like tubes. I downloaded about 2.4G of tube documentation; and, it is really interesting and extremely complex. I think I might make some tubes, just like that Frenchman on YouTube. The trick is the high vacuum.

41 posted on 07/29/2010 7:47:11 PM PDT by GingisK
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To: Quix
THAT’S DINKING AROUND in the area of UFO type technologies.

I've often told people that we don't know enough about physics to say for certain that UFOs can't reach Earth. Our "advanced" technology is just a wee bit over 100 years old; and, only since WWII has it advanced in spectacular ways.

I really don't think we have a clue about the way things REALLY work.

42 posted on 07/29/2010 7:52:15 PM PDT by GingisK
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To: GingisK

I agree entirely.

And even less of a clue about . . . spiritual dimensions,

n dimensions etc.


43 posted on 07/29/2010 8:08:00 PM PDT by Quix (THE PLAN of the Bosses: http://www.freerepublic.com/focus/religion/2519352/posts?page=2#2)
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To: GingisK
and, only since WWII has it advanced in spectacular ways.

Hmmmm....that was somewhere around 1947 wasn't it? Just sayin'...

44 posted on 07/29/2010 8:30:12 PM PDT by BreezyDog
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To: aruanan
IIRC that usage is correct because there are more than two circles bumping (i.e. "each other" where there are only two, "one another" where there are more than two)?

Have I got it wrong?

45 posted on 07/30/2010 3:23:41 AM PDT by SonOfDarkSkies (Satan's greatest trick is convincing some men he doesn't exist!)
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To: OldNavyVet
Another application might be the possible replacement for silicon-based semiconductors with a material which is a significantly faster conductor of electricity and data (and probably significantly cooler).
46 posted on 07/30/2010 3:28:42 AM PDT by SonOfDarkSkies (Satan's greatest trick is convincing some men he doesn't exist!)
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To: OldNavyVet

And batteries.


47 posted on 07/30/2010 3:29:18 AM PDT by SonOfDarkSkies (Satan's greatest trick is convincing some men he doesn't exist!)
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To: SonOfDarkSkies
in strong pseudo-magnetic fields electrons orbit in tight circles that bump up against one another, potentially leading to novel electron-electron interactions.

The electrons are what could bump into each other. It was just a poor choice of words to refer to their orbits as things that could interact.
48 posted on 07/30/2010 3:56:17 AM PDT by aruanan
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To: aruanan

Oh, you mean the use of the word “bump” [to describe what is probably a very complex interaction]?


49 posted on 07/30/2010 4:04:55 AM PDT by SonOfDarkSkies (Satan's greatest trick is convincing some men he doesn't exist!)
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To: randog

Exactly what I was thinking.


50 posted on 07/30/2010 4:43:22 AM PDT by WayneS (Respect the 2nd Amendment; Repeal the 16th)
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