Theory and Evolution
First the obvious (that is, if you’re not brainwashed by economic orthodoxy): the economy doesn’t reach equilibrium. It isn’t static—it’s dynamic, constantly changing. And changes can happen suddenly and non-linearly. In other words, unlike a ball that you might push on a flat surface, the economy is more like pushing a ball into a series of curved surfaces and connected bowls of different heights. The track is always changing and different balls might be at different heights at different times. More on this in a bit.Second: While most economic theories presume people will optimize and take all available information into account—we, err, I mean they—don’t. We use rules of thumb: heuristics. There are volumes covering the various kinds of cognitive biases from which we suffer. And while most economists assume we are rational agents—it just ain’t so. People are irrational. Whether its information cascades, fads or cults (dot-com bust, pet rocks, Jonestown massacre) for every rational person you show me, I’ll dig out five irrational ones from the graveyard of folly and foible. Of course as has been said, it ain’t the things we don’t know that get us into trouble—it’s the things we know that just ain’t so.Next: networks. All the people and all the companies interact in networks and those networks are in themselves hard to predict. Have you ever met someone you judged to be of average intellect and ability but turned out to be connected to another of great power and influence? People always wonder, “how did HE meet HIM, and how are they still friends?” Small worlds indeed and when networks morph, merge into larger ones and break-off into sub-networks, it’s even harder to predict.
Once you have these networks, interesting and unpredictable things can happen. In a sand pile there is a network of potential energy, “fingers of instability” where a small input can trigger an avalanche. And that network—like a market—can change quickly and suddenly. You can also get the emergence of a phenomenon known as “emergence”. Emergence is a fancy way of saying that the whole is greater than the some of the parts. Ant colonies, brains, cities, behavior in markets all exhibit this phenomenon of emergence where the constituent components give rise to higher order.
January 22,
2007 Volume 85, Number 04 p. 10 Nanoscience
Nanoparticles Act Like Atoms
Gold spheres, bestowed with valency, are strung together in polymer-like chain
© Science 2007Coated gold nanoparticles strung together via linker molecules.
Using a little topology and a few thiol ligands, materials scientists have managed to corral a gold nanoparticle's thousands of atoms and make them behave like one divalent atom (Science 2007, 315, 358).
Transformed from a multivalent mass to tidy two-handled building blocks, the nanoparticles can then be hooked together into a tiny string of golden beads. "It's the nanoscale equivalent of a polymer," says Francesco Stellacci, the Massachusetts Institute of Technology professor who spearheaded the research.
To establish an orderly divalent bonding motif in the unruly nanoparticles, Stellacci's group took advantage of what topologists call the "hairy-ball theorem." Basically, the theorem states that if you've got a sphere covered in hair, it's impossible to comb those hairs so they all lie flat. No matter what you do, two hairs at opposite points on the sphere will stand straight up.
Applying the theorem to a gold nanoparticle "sphere" coated with a mixture of two types of thiol ligand "hairs," the researchers reasoned they could swap the thiols at those polar positions with thiol chains bearing a terminal carboxylic acid. "We knew that the exchange reaction would take place orders of magnitude faster there than at any other point on the sphere," Stellacci explains.
With an acid-functionalized chain at each of its poles, the particle selectively bonds with other molecules as though it were a divalent atom. Once they'd done the thiol swap, Stellacci's group simply condensed the divalent particles with 1,6-diaminohexane, creating polymer-like strands up to 20 nanoparticles long.
"Introducing valency into nanostructures through face- or edge-selective functionalization" is a major fundamental advance, comments Northwestern University's Chad A. Mirkin, an expert in controlling nanoscale architecture. The work will help researchers "realize more sophisticated and highly functional architectures," Mirkin adds. "It is analogous to transitioning from atoms to molecules."
- Chemical & Engineering News
- ISSN 0009-2347
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