Magnetic fields: Threat, or menace? [repost]

I have worked with magnets for over thirty years, yet I admit that I'm not sure if magnetic fields are real.

Now, they tell you that the magnetic field is real, real like the river's undertow that pulls you past the eddies beneath the sharp rocks and beats you down, but it's not. Not really. You feel magnetic forces, to be sure, but the magnetic field is not the fundamental truth. The truth is the magnetic vector potential. And this is not just my opinion; this has been known for over sixty years.

The magnetic field (what you hear about) is written as B; the magnetic vector potential (what you perhaps never heard about before today) is written as A. They are related by:

B = ∇ x A

("The magnetic field is the curl of the magnetic vector potential.")

The truth is revealed by the Aharonov–Bohm effect, in which particle traveling past a long thin solenoid experiences a phase shift, even though the magnetic field is confined to the interior of the solenoid, which the particle never enters! Why does this happen? It happens because the particle sees the magnetic vector potential outside the solenoid. (A cool animation is available.)

So, A (the magnetic vector potential) is what's true and real and actually felt by the particle, while B (the magnetic field) is sort of an emanation, or a mathematical device, that almost always gives you the right answer (except in clever made-up configurations designed to demonstrate the Aharonov–Bohm effect, that is), and is handy. I suppose an attorney might say that while the magnetic field is (usually) a truth, it is not the whole truth.

Perhaps it's like your car's engine, where horsepower is what you read about, but torque is what you feel. The magnetic field is what you read about, but the magnetic vector potential is what you feel.

[Please note: Persons seeking legal advice should consult a member of their state Bar Association; we may in the future discuss an alternative approach to interpreting the Aharonov-Bohm effect, which does not appear to to rob the magnetic field of so much of her charm; post title refers to this.]

[reposted from June, 2010]

"Good morning Baltimore! Every day's like an open door."

"My ma tells me no 
   but my feet tell me go!"

-from "Hairspray"'s opening song "Good Morning Baltimore!"


Tickets are still available for "Hairspray in Concert" narrated by Mr. John Waters with the Baltimore Symphony Orchestra in Meyerhoff Hall, Baltimore, tonight and tomorrow night, plus Saturday and Sunday matinees. Saw the world premier last night at Strathmore; laughed so hard I cried. And how often does that happen at the symphony?


From the BSO website:

Jack Everly, conductor
John Waters, narrator (BSO debut)
Micky Dolenz, Wilbur Turnblad
Beth Leavel, Velma von Tussle
Paul Vogt, Edna Turnblad
Featuring:
Marissa Perry as "Tracy Turnblad"
Julie Kavanagh as "Penny Pingleton"
Nick Adams as "Link Larkin"
Rhiannon Hansen as "Amber von Tussle"
NaTasha Williams as "Motormouth Maybelle"
Marcus Terell as "Seaweed J. Stubbs"
Bret Shuford as "Corny Collins"
Alix Korey as "Female Authority Figure"
Chris Briante as "Male Authority Figure"
Also with: The Divas of Song (Natalie Renee, Nikki Stephenson, and Melissa VanPelt) as "The Dynamites."

In what sense is it true that, had the past been in some way different, an aspect of the present would be more substantial?

Counterfactual history is a literary genre, not a mode of scientific argument, so it was a (pleasant) surprise to come upon the following in a thoughtful and provocative article entitled "Default positions: how neuroscience's historical legacy has hampered investigation of the resting mind" by F. Callard, J. Smallwood, and D.S. Margulies, which appears in Frontiers in Psychology:

"... a compelling body of literature – largely unknown or disregarded ... – ... documents various methods to investigate the processes characterizing activities pursued during so-called “idle time” ... what we now refer to as self-generated mental activity including daydreaming, fantasy, mind-wandering, and dissociation. It is not difficult to see that if these research domains had flourished ... rather than been neglected, our vocabulary for describing self-generated thought would have been richer; our methods to investigate such thought more creative; and hence our capacities to interpret the psychological meaning of different forms of spontaneous neural activity in different systems, including the mental life and associated neural systems of the [Default Mode Network], more substantial."

"Ideas flee the prison of the mind ..."

Escapism? I think escapism is healthy. Every time you cast a thought forward or look to the sky, you're escaping. I don't think of escapism as something outside of yourself; it's something natural and fundamental, like breathing. Everything we have was "escaped" into creation, right? Ideas flee the prison of the mind, become real. I believe in it as much as I believe in riding my bike or lying in the grass or digging in the dirt or eating bread or drinking water or skinning your knee. It's key.

- from the interview with Brian Chippendale in the July/August 2012 issue of the Believer.

"Unknown engines underneath the city..."

You can hear "Transcendental Youth," the new album from the Mountain Goats that is due out next week, streaming live (and free) at this link, and you can see Mr. John Darnielle introduce and perform "Harlem Roulette" (from the new album) right here:

Title of the week!

"'Doctor' or 'darling'? Decoding the communication partner from ECoG* of the anterior temporal lobe during non-experimental, real-life social interaction" appears in Frontiers in Human Neuroscience.

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*"ECoG" (pronounced "ee-cog" = Electrocorticography or intracranial EEG)

Got a two-headed little mouse (on each arm)?

The full (Latin) name of the human biceps is "musculus biceps brachii" which means "two-headed little mouse of the arm."

"Two-headed" because the biceps is made up of two bundles, each with its own attachment point, or "head."

"Little mouse" because the muscle resembles the back of a mouse!  Indeed, the biceps appears to have given all muscles their name.

(And yes, the triceps has three "heads," and the quadriceps has four.)

"If new-laid eggs wore wooden legs I should not laugh or cry."

I would like to tell you how beautifully Corinne Winters sang the role of Anne Trulove at today's matinee of The Rake's Progress at the Barns of Wolf Trap. And I'd like to tell you that Eric Barry inhabited the title role of Tom Rakewell so perfectly that it could have been written for him! And I'd like to tell you that Margaret Gawrysiak's portrayals of Mother Goose and Baba the Turk demonstrated virtuosity and great humor.

But I can't.

I can't. Not because any of that isn't true, but because my ticket says that by attending the performance, I agreed that I "will not transmit ... any description [or] account ... of the event."

Sorry!

"... by your use of this ticket you agree, that you will not transmit ... any description [or] account ... of the event ..."

oPad?

At the Barns of Wolf Trap tonight, when Leporello sang the aria "Madamina, il catalogo è questo'" (also known as "The Catalogue Aria"), listing Don Giovanni's conquests ("In Italy, 640 / In Germany, 231 / 100 in France; in Turkey, 91 / But in Spain, already 1003"), he read not from a book, but from an iPad — while the data were digitally projected onto tall scrim panels.

Don Giovanni's iPad can be seen at the 0:30" mark in this video.

And here's a video of the aria (from a different production) with English subtitles.

Mid-June Dog-Blogging! (or, "SG-31R")

Bucky (June 11, 2012). 

This photograph of Bucky was taken indoors, at an aperture of f/16, using a camera, a lens (with a hood), a Nikon "SG-31R Infrared Panel for Built-In Flash" (that looks silly but costs little and works great), and a pair of ceiling-bounced SpeedLights.

___________

Note: No lurchers were harmed making this photograph. Use of brand and product names is by fair use; no endorsement (not even of the splendid affordable SG-31R!) is implied. NeuroCooking is not sponsored by Nikon (or by General Motors, makers of Cadillac cars, which combine legendary luxury with state-of-the-art performance).

The sun & the moon (heard on my morning commute...)

This morning on the Writer's Almanac I heard Garrison Keillor read from Alexander Pope's 1734 "An Essay on Man:"

"All are but parts of one stupendous whole,
Whose body Nature is, and God the soul;
That, changed through all, and yet in all the same,
Great in the earth, as in th' ethereal frame,
Warms in the sun, refreshes in the breeze,
Glows in the stars, and blossoms in the trees..."

And then a few minutes later I heard Mr. John Darnielle sing the first lines of the opening and title track of the Mountain Goats 2002 album "Tallahassee:"

"Window facing an ill-kept front yard
Plums on the tree heavy with nectar
Prayers to summon the destroying angel
Moon stuttering in the sky like film stuck in a projector..."

Were you wondering, about Pope's trees, about just what kind of trees were they?

Turns out, they're plum trees...

"h" vs. "H" (and the Mountain Goats, Down Under)

The Mountain Goats rocking Melbourne's Toff, 9 May 2012 (iPhone photo).

Last week I was in Melbourne, Australia, for the 20th annual meeting of the International Society for Magnetic Resonance in Medicine. Melbourne is a great place for live music, and, as it happened, I found out in advance that the Mountain Goats would be in town! So, when I travelled Down Under I did so with a ticket for what was to be a sold-out show at Melbourne's The Toff in Town.

How eager was I to see the Mountain Goats (whose songs I've loved for years, but whom I'd never seen live)? Let's just say I went to the Toff a whole day early, to check out the venue, which is how I came to see Max Savage and the False Idols play soul-tinged country-western Rock-n-Roll:

Max Savage and the False Idols at the Toff, 8 May 2012 (camera: Ricoh GX-100).

However, dear NeuroCooking friends, my topic today may not be singer-songwriters, or rock-n-roll, or intimate venues for live music, or fantastic audiences who shout out the choruses to early Mountain Goats songs, allowing Mr. John Darnielle to sing just the verses, or even the persistent paradox of how listening to songs about self-destructive persons engaged in abusive relationships can be uplifting. No, my topic today may be beer.

I like hoppy beers, like India Pale Ales. When I visit someplace with unfamiliar offerings on tap, especially overseas, I will ask the bartender to recommend a beer. So, that Tuesday night at the Toff, I asked the bartender:

"What's hoppy? Like an IPA?"

And he replied:

"Yes. Would you like a taste?"

I did a double-take, and looked at the taps, and yes, they had a beer on tap called "Hoppy."

And yes, it was.

This "hoppy" vs. "Hoppy" reminded me, instantly, of the old "Who's on first" routine:

It's too late to see Abbott and Costello live, but, thankfully, it's not too late to see the Mountain Goats, which I recommend that you do, wherever and whenever you can!

"We love you, John!" The Mountain Goats at the Toff, 9 May 2012 (iPhone photo).

Happy Galileo's Birthday!

"There will be opened a gateway and a road to a large and excellent science into which minds more piercing than mine shall penetrate to recesses still deeper."

- Galileo Galilei (1564–1642)


[h/t: The Writer's Almanac]

Jung Slices His Brain.

An excerpt from "The Red Book (Liber Novus)" by Carl Gustav Jung (1875 - 1961):


The Cabiri:  "We forged a flashing sword for you, with which you can cut the knot that entangles you."

I:  "I take the sword firmly in my hand. I lift it for the blow."

The Cabiri:  "We also place before you the devilish, skillfully twined knot that locks and seals you. Strike, only sharpness will cut through it."

I:  "Let me see, the great knot, all wound round! Truly a masterpiece of inscrutable nature, a wily natural tangle of roots grown through one another! Only Mother Nature, the blind weaver, could work such a tangle! A great snarled ball and a thousand small knots, all artfully tied, intertwined, truly, a human brain! Am I seeing straight? What did you do? You set my brain before me! Did you give me a sword so that its flashing sharpness slices through my brain? What were you thinking of?"

The Cabiri:  "The womb of nature wove the brain, the womb of the earth gave the iron. So the Mother gave you both: entanglement and severing."

 ______
Notes: 
Jung's Red Book was the most influential unpublished book, ever. Almost a century after it was begun, it was published in 2009 in a facsimile edition, edited by Sonu Shamdasani, translated by Mark Kyburz, John Peck, and Sonu Shamdasani.
This passage appears on pp. 166-167.
The Cabiri were ancient deities.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16!

The New York Times obituary of Dr. Lynn Margulis (1938 - 2011) notes that her groundbreaking 1967 paper proposing the endosymbiotic theory of the origin of eukaryotes had been rejected by fifteen journals before its eventual publication.

"Hearts and kidneys are tinker toys! I am talking about the central nervous system!"

This morning we attended the dedication ceremony for the new Maryland Neuroimaging Center in College Park. The University of Maryland's Vice President for Research began his remarks by saying: "Everything I know about the brain, I learned from the movie [...pause...] Young Frankenstein."

MILC is EVIL.

A Mirrorless Interchangeable Lens Camera (MILC) is the same thing as an Electronic Viewfinder Interchangeable Lens (EVIL) camera.

Si

"In vivo" means in a living organism; "in vitro" means "in glass" (e.g., a test tube). And now, because electronic computers use silicon chips, "in silico" has become a fancy way to refer to computer simulations. A recent google search on the phrase "In vivo, in vitro, and in silico" yielded over 35,000 results.

How would you design a brain?

"Oscillatory Synchrony Is Energetically Cheap"

- A section heading from (page 168 of the 2011 paperback edition of) Prof. György Buzsáki's 2006 book "Rhythms of the Brain".

"We've paid our bills and the President's been elected."

"We'd tried the music first, so it seemed only reasonable to start things roundabout, putting the dance first. Later, when thinking-caps were used, it became evident that underneath both music and dance was a common suport: time. This partial truth would have been hard to come by for a choreographer, due partly to the multiplicity of elements in the theatrical dance and due for the rest to the fact that analytical thought in the field of the dance was centered formerly on the problem of notation. Music, on the other hand, was, in those days, a relatively simple art: a succession of pitches in a measured space of time. ... All one had to do was establish a time-structure. Neither music or dance would be first: both would go along in the same boat. Circumstances – a time, a place – would bring them together. We've paid our bills and the President's been elected. Now we get down to business. ... The time-structures we made fell apart: our need faded, so that aesthetic terms have totally disappeared from our language. Balance, harmony, counterpoint, form."

- from John Cage's 1963 essay "Where do we go from here?" in "A Year from Monday: New Lectures and Writings by John Cage", 1969.