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What's So Premium About Premium Gasoline?

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They must call it premium for a reason, right? Let's find out if we're missing out on something big by not shelling out the extra 20 cents.

Knock knock. Who's there?
While you're cruising around town, your car's engine is hard at work, repeating its four-stroke cycle. The piston drops from the top of the cylinder, which fills with a mix of gasoline and air (intake stroke). The piston moves up, compressing the fuel mix (compression stroke), and the spark plug ignites the mix, pushing the piston down (power stroke) again so it can expel what's left of the spent fuel through the exhaust valves and start the process over again (exhaust stroke).

Normally, this cycle keeps repeating without a hitch. But sometimes the mix of gasoline and air loses its patience, and it ignites on its own under compression instead waiting for the spark plug. This is called "pre-ignition," but you may know it as "knocking." The results are actual pinging or knocking sounds, as well as mechanical stress on the engine as the premature ignition pushes downward on the piston before it's completed its stroke. In extreme cases, pre-ignition can burn holes in engine parts.

All in the Numbers

Gasoline is a grab bag of hydrocarbon molecules, and each one behaves differently under pressure. During the auto industry's early days, there was no way to know if a given gasoline would knock in a given engine except for filling up the tank and going for a spin. In 1927, Dr. Graham Edgar of the Ethyl Gasoline Corporation (then a division of General Motors and Standard Oil) suggested using the ratio of two hydrocarbons "“ heptane and iso-octane, which have similar volatility properties and could be produced in sufficient quantity "“ as a reference number for computing a fuel's ability to resist knock.

iStock_000006429094XSmall-gaspumps.jpgA range of test engines and test conditions have popped up over time, but today the most common are the Research Octane Number (RON, which comes from running the fuel in a test engine* and represents typical mild driving), and the Motor Octane Number (MON, which comes from running preheated fuel in a similar test engine at a higher engine speed and with variable ignition timing to represent sustained high speed, high load driving).

What we get from these tests are the numbers you see on the yellow stickers on a gas pump. These numbers, called the octane rating or anti-knock index, are the average of the two different test methods (hence the pump label (RON + MON)/2) and are the measure of the fuels' resistance to knock. If you're pumping "regular," for example, its octane rating of 87 (this varies from state to state; in higher altitude areas, "regular" is sometimes 85) means the gasoline has the same knocking properties as a mixture of 13% heptane and 87% iso-octane.

So what makes premium so great?
What's behind its higher octane rating? It won't make your car faster, give you better gas mileage or make your teeth whiter.

A higher octane rating correlates to higher activation energy, meaning that the fuel needs more energy to start a chemical reaction and is less likely to pre-ignite under compression. That's right. It's simply more resistant to knock.

Modern engines are designed with specific compression ratios "“ the ratio of the combustion chamber's volume, from its largest capacity to its smallest capacity "“ and high-performance engines usually have high compression ratios (higher compression = more power). Premium's anti-knock properties allow it to maintain grace under all that pressure.

Even if you do drive a high-performance car, regular gas isn't going to knock like a woodpecker. Most cars today have knock sensors and engine management systems that use auditory detection to actually "hear" knocking and retard the spark timing to avoid detonation and minimize knocking. If you don't have a high-performance ride, using premium if you don't need it (your manual will tell you which octane rating you should use) just gets rid of more unburned fuel during the engine's exhaust stroke, putting unnecessary stress on the emissions system and sometimes producing a rotten egg smell.

*For the curious, the test engine is a Cooperative Fuels Research (CFR) engine. It's a single-cylinder engine with a variable compression ratio and a special four-bowl carburetor that can adjust individual bowl air-fuel ratios. The only company that makes them is the Waukesha Engine Division of Dresser Industries in Waukesha, Wisconsin, and the complete Octane Rating System package costs $200,000.

If you've got a burning question that you'd like to see answered here, shoot me an email at flossymatt (at) Twitter users can also make nice with me and ask me questions there. Be sure to give me your name and location (and a link, if you want) so I can give you a little shout out.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Cs California, Wikimedia Commons // CC BY-SA 3.0
How Experts Say We Should Stop a 'Zombie' Infection: Kill It With Fire
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Cs California, Wikimedia Commons // CC BY-SA 3.0

Scientists are known for being pretty cautious people. But sometimes, even the most careful of us need to burn some things to the ground. Immunologists have proposed a plan to burn large swaths of parkland in an attempt to wipe out disease, as The New York Times reports. They described the problem in the journal Microbiology and Molecular Biology Reviews.

Chronic wasting disease (CWD) is a gruesome infection that’s been destroying deer and elk herds across North America. Like bovine spongiform encephalopathy (BSE, better known as mad cow disease) and Creutzfeldt-Jakob disease, CWD is caused by damaged, contagious little proteins called prions. Although it's been half a century since CWD was first discovered, scientists are still scratching their heads about how it works, how it spreads, and if, like BSE, it could someday infect humans.

Paper co-author Mark Zabel, of the Prion Research Center at Colorado State University, says animals with CWD fade away slowly at first, losing weight and starting to act kind of spacey. But "they’re not hard to pick out at the end stage," he told The New York Times. "They have a vacant stare, they have a stumbling gait, their heads are drooping, their ears are down, you can see thick saliva dripping from their mouths. It’s like a true zombie disease."

CWD has already been spotted in 24 U.S. states. Some herds are already 50 percent infected, and that number is only growing.

Prion illnesses often travel from one infected individual to another, but CWD’s expansion was so rapid that scientists began to suspect it had more than one way of finding new animals to attack.

Sure enough, it did. As it turns out, the CWD prion doesn’t go down with its host-animal ship. Infected animals shed the prion in their urine, feces, and drool. Long after the sick deer has died, others can still contract CWD from the leaves they eat and the grass in which they stand.

As if that’s not bad enough, CWD has another trick up its sleeve: spontaneous generation. That is, it doesn’t take much damage to twist a healthy prion into a zombifying pathogen. The illness just pops up.

There are some treatments, including immersing infected tissue in an ozone bath. But that won't help when the problem is literally smeared across the landscape. "You cannot treat half of the continental United States with ozone," Zabel said.

And so, to combat this many-pronged assault on our wildlife, Zabel and his colleagues are getting aggressive. They recommend a controlled burn of infected areas of national parks in Colorado and Arkansas—a pilot study to determine if fire will be enough.

"If you eliminate the plants that have prions on the surface, that would be a huge step forward," he said. "I really don’t think it’s that crazy."

[h/t The New York Times]