Everything we do with electrons depends on their charge, for example the whole of electronics is based around an electron’s negative charge. But electrons have another property, their spin, that could also be used to manipulate them. So a lot of engineers are trying to think up ways we can fiddle with an electron’s spin to do interesting things. The resultant field is called spintronics and it’s exciting cos it opens the possibility of an entirely new form of computing based on spin rather than charge.

But it ain’t just computing that depend son an electron’s charge. Piezoelectric materials also depend on the way charge is distributed within their crystalline structure. When squeezed, this symmetry changes in way that generates a voltage. Conversely, when a voltage is applied, the crystals themselves change shape.

Now Alexy “Koala” Kovalev at Texas A&M University at College and some egghead pals are proposing that electron spin can do a similar thing. Pass a spin-polarized current (one in which all the electron spins point in the same direction) through the right kinda crystal and it will bend or vibrate. That ain’t so useful cos we can make things vibrate pretty good now.

But the converse effect could be very useful. Send a current through an oscillatin’ wire and it’ll spin-polarize it. Koala is calling it the piezo-spintronic effect and it’s handy cos there ain’t that many ways to generate spin-polarized currents right now and none that look as simple as this.

One problem: Koala Kovalev and pals have done some neat thinkin ‘n’ theorizin’ but ain’t built nothin’ yet. The chances are that this kinda piezo-spintronic material ain’t gonna be easy to come by. Time for some metamaterial brainstorming.

Ref: arxiv.org/abs/0711.4430: Nanomechanical Spin-polarizer

Quantum mechanics is seriously sexy . That’s what keeps the public coming back for more with the drool hangin from their spittle-flecked lips (repeat this often enough and it might actually come true).

Without a sexy lingo to bamboozle and baffle, physics eggs ain’t got nothing to keep people’s attention ‘cept their rugged good looks and scintillatin’ personalities.

So labs hire hampers of postdocs whose sole task is to invent new words that’ll keep the public a-gazin’ and a-gawpin at every shiny new pebble that is thrown their way.

Yer probably didn’t realise it but all the latest buzzwords were invented in this way: atomtronics, quamputing, brane theory and the ballsheet model of particle physics (OK, ah made that one up).

Normally, these postdocs are thrown a stale crust to keep em happy but otherwise kept under strict lock and key. But this week, one of em has escaped and posted a buzzword on the arXiv without permission.

Charles “Manhat” Tahan is normally locked in the bowels of the Cavendish lab in Cambridge. Let loose, he is brayin’ that physicists are a-stuttering and a-stumblin for want of a word to describe technology that depends on quantum effects that have no classical counterpart. We’re talkin things like entanglement, coherence and superposition–the so-called spooky properties of quantum physics.

Manhat Tahan says the word we need is “spookytechnology”.

Whadaya’ll think? Don’t send no shivers down my spine, I gotta tell yer. Surely ya’ll can come up with something better for this kinda strange stuff. How about quantech or ungodly gear or maniacal machinery or EPR matter or subsubstance or whatever.

And then maybe, just maybe, we can persuade Manhat Tahan to get back into the dungeon before he does some real damage.

Ref: arxiv.org/abs/0710.2537: Spookytechnology and Society

The squeeze ‘n’ shove of Mecca pilgrimages are a-mighty frightenin. Thousands of people have been died in em. Now video analysis shows that a remarkable new phenomenon called crowdquakes are behind these stampedes. The analysis  also suggests how stampedes might be prevented.

Dizzy Dirk Helbing and his mates at the Swiss Federal Institute of Technology in Zurich have been a-studyin videos of crowd panic and stampedes at the Jamarat Bridge near Mecca, where 350 pilgrims were trampled to death in 2005 (250 also died in 2004).

Conventional models of crowd behaviour assume that the velocity of the flow is smooth and that it drops to zero as the density of people rises–in other words the crowd drifts to a halt.

That ain’t what happens at all though. Dizzy Dirk reckons that at densities of more than 7 people per square meter, an individual is no longer able to control his movement and the crowd begins to move as a whole.

The density within crowds varies from place to place. So where the density is above the threshold, whatcha get is regions that take on a life of their own, a-heavin and a-shovin and a- sendin pressure waves through less dense regions of the crowd.

Now here’s the interestin bit. Dizzy Dirk says that under these circumstances, chains of people can become so tightly compressed that they become momentarily locked, like sand jamming as it passes through an hour glass. When these force chains break, they release sudden, uncontrollable amounts of energy, like earthquakes.

It is these crowdquakes that knock people off their feet causing them to be trampled. Dizzy Dirk says he seen it happen in the Jamarat videos.

The solution? Prevent crowd densities exceeding 7 bodies per square meter. In the videos of the 2006 event in which a crowdquake killed more than 350 people, Dirk says the warning signs were clearly visible 11 minutes before it occurred. That should give the authorities some warning.

Ref: arxiv.org/abs/0708.3339: Crowd turbulence: the physics of crowd disasters