The Belousov Zhabotinsky (BZ) reaction is the classical example of an oscillating reaction. Now. But it wasn't always accepted and loved by the scientific community.
The story of the BZ starts with something we all learned/memorized in high school biology-- the Kreb's cycle. Which apparently should be properly called the Szent Gyรถrgyi - Krebs cycle to give credit where credit is due. This is a component of the metabolic pathway which generates energy from the acetate derived from fats, proteins, and carbohydrates. Citric acid is consumed and regenerated in this cycle.
Boris Belousov was looking to create an inorganic analog of this cycle but happened upon a chemical oscillator where the reaction turned from colorless to yellow and back. He tried to publish this new thing, but the journals rejected it -- because it "obviously" conflicted with the second law of thermodynamics(something I can write about later). They didn't try it themselves or they would have seen it work. Ultimately he published the work in an obscure non-peer reviewed journal.
It all could have ended there if it weren't for Anatol Zhabotinsky.
The Women in Science Initiative at Brandeis has put together a nice series of talks : Art of Science.
This month's featured Professor Diana Dabby and her work creating musical variation utilizing chaos.
The term "chaos" means something specific in mathematics. It's reserved for dynamical systems, that is systems that change over time according to mathematical rules, that exhibit sensitivity to initial conditions.
We're familiar with this idea in terms of the "butterfly effect": that something as small as the flap of a butterfly's wings can be the deciding factor as to whether a hurricane forms half-way round the globe. This term was coined by Edward Lorenz, an american meteorologist and mathematician. He discovered it while running simulations for the weather patterns in the early 1960's. In one of these simulations, he decided to save time and put in fewer numbers after the decimal, and was surprised to find that the behavior was completely different.
Professor Dabby uses a set of equations that Lorenz created to describe the weather to generate her musical variations. Solutions to these equations tend to have a similar shape, a little bit like a butterfly.
One is shown in the poster. Dabby finds a solution to these equations and then connects that solution to the musical notes of the original song. She then changes the initial conditions to get a different solution, and uses the connection she built before to make a new song.
An interesting thing that she shared was that she had actually met Lorenz and that she's tried to find other chaotic systems that make aesthetically pleasing variations and no others have worked as well. She played a number of variations that she had created and discussed their similarities when considered through the lens of Schenkerian analysis.
The Belousov Zhabotinsky oscillating chemical reaction is the reason I ended up in a graduate program because I learned about it in one of my upper division mathematics courses : the geometry and dynamics of chaos. Oscillating reactions tie together cool mathematics and chemistry. We'll get to heart of the mechanism and math later, but here's an intro.
Here's a sweet little vid from youtube. This reaction is able to sustain oscillations for up to an hour depending on the recipe. The oscillations and spatio-temporal patterning that you see is the state of one of the chemicals in the system, the catalyst Ferroin. Feriin which is blue can be reduced (given an electron) to form Ferroin which is red. The red Ferroin can in turn be oxidized back into Feriin.
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If you stir the reaction, the reaction oscillates in time, which in this particular reaction mixture has a period of about 20 seconds. ( 2 video seconds * the time-lapse rate of about 10 x). At 0:56/3:47 in the vid, the stirring is stopped, and you can see the patterns start to form in space. This happens where symmetry is broken in the system. A little bit of dust or a local fluctuation in concentration of the chemicals at one point in space makes that point in space just different enough from its neighbors to trigger a wave.
You see about thirty of these points to start out-- more appear later, and as the video goes on you see that some of them oscillate at different frequencies, which you see as how close the waves are together. The ones with small wavelengths will win and kill off the ones with larger wavelengths. Another feature that is neat in this system is phase wave which shows up at 1:02/3:47, see the fast propagation of blue through the system? Ultimately, the spatiotemporal pattern formation will stop as the system comes to equilibrium and dies.
Many research groups use the BZ. Some use it to look at pattern formation and dynamics. Shout out to the Solomon Lab at Bucknell who uses the BZ to look at chaotic mixing. And the the Steinbock group in Florida who has their own youtube channel. Some people focus more on the materials aspect. If you put the BZ in a gel, you can couple the chemical oscillations to the mechanical ones, many people are working with different aspects of this, but MIT has a nice video for you. We use the BZ a couple of different ways in our lab and on campus with some nice basic research into dynamics as well as a some applied work for patterning of neurons and the heart.
Straight up. Patterns ( in space and time! spatiotemporal patterns!) are the coolest. And they are everywhere!
We see and recognize patterns when we can pick out something that's regular and repeats. Patterns can be made from and in pretty much anything!
We appreciate patterns in art and fashion:
And nature:
Seashells!
Animal skins!
And in the laboratory of course!
One of the main research thrusts of our lab ( and hey, I didn't come up with that terminology!) and my research passion is spatio-temporal pattern formation. The pattern I've been working with lately is the spiral. Look forward to more detail in the future, but here's the teaser photo:
Segmententing Spirals in the Belousov Zhabotinsky Aerosol OT Reaction
