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The Time Paul Revere Worked as a Dentist

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Paul Revere was a man of many talents. Outside of his military accomplishments (about which several misconceptions persist), Boston’s most famous messenger also enjoyed a unique medical career that saw him become the first forensic dentist in American history.

Like his father, Revere was a silversmith by trade, who dutifully took over the family shop for several years before handing it down to his own son in the 1780s. Yet even working with precious metals wasn’t enough to fully insulate him from economic hardships.

During the early 1760s, an English “dental surgeon” named John Baker arrived in the colonies. Smelling opportunity, Revere began eagerly studying under Baker, who taught him how to create and insert false teeth (usually made of ivory) for those whose real ones had decayed (Baker himself eventually wound up building a few of George Washington’s dentures).

In 1768, the silversmith ran an advertisement in the Boston Gazette to promote his fledgling dentistry practice, which was followed up by a second ad in 1770. “Paul Revere…,” boasted the latter, “can fix [teeth] as well as any surgeon dentist who ever came from London, he fixes them in such a manner that they are not only an ornament but of real use in speaking and eating.”

After the Revolutionary War broke out, Revere summoned his newfound knowledge to locate the body of a colonial soldier who’d been slain at the Battle of Bunker Hill on June 17, 1775. The victim was Massachusetts Major General Joseph Warren, who’d sent Revere on his famous “midnight ride” to Lexington earlier that year. 

Warren had been buried by the British in a mass grave with several of his comrades after the fray. Naturally, his loved ones wanted to search for the body to give it a proper funeral, which was made possible after the rebels took control of the area in 1776. But by then, the pile of corpses had decayed, making them almost impossible to tell apart—until Revere spotted one that was wearing a dental prosthetic he’d built to replace two of Warren’s teeth a few years earlier.

According to the National Museum of Health and Medicine, “Revere’s confirmation of General Warren’s identity was the first instance in this country of an identification of a military service member using dental remains.”

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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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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May 23, 2017
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