CLOSE
Original image

Messing with Mother Nature: Snakeheads

Original image

Fish normally are found in three places: in the wild water, in aquariums, and on our dinner plates. But fish can move from one of these worlds to another. Fish imported to eat or to keep as pets sometimes get into the local ecosystem, which is not their native habitat. The population controls of the species' native environment might not be present in the new place, or they may take over another species' spot in the food chain. That's pretty much the story of the snakehead fish.

The Northern Snakehead (Channa argus) is a fish native to China and Korea that will eat all the fish in a pond, then start on the other animals living there. In Asia they are grown for food, and they are kept in rice paddies in order to kill pests that may damage crops. Photograph by Flickr user Brian Gratwicke.

The snakehead is traditionally considered to have medicinal value. In 2000, a man in Crofton, Maryland ordered two snakeheads from a fish market in New York to make soup for his ailing sister. However, the woman recovered, so he put the live fish in his aquarium. When they grew too large for the aquarium, he let them go in a nearby pond. The snakeheads thrived and reproduced. Two years later, the infestation was discovered and officials made the decision to kill all the fish in the pond with the poison rotenone to eradicate the invasive species. The dead fish included six adult snakeheads and about a thousand juveniles. Photograph from the Maryland Department of Natural Resources.

But here's the kicker -snakeheads can walk.

They can travel from one water source to another by maneuvering on their fins, and young fish can survive days without water, as they have tiny sacs above their gills that can draw oxygen from air! In 2004, snakeheads were found in the Potomac River. You can't just poison all the fish in a river like they did at the Crofton pond.

The Crofton incident inspired two movies. One was the 2004 film Frankenfish, about genetically-engineered man-eating snakeheads that escaped and bred in the bayou country. It was released on home video about three weeks after debuting in theaters. The other, the SyFy Channel movie Snakehead Terror, also from 2004, is about snakeheads that grow to monster size after growth hormones are dumped in a Maryland lake. The fish crawl out onto the land searching for food. And, of course, that means people!

Snakehead importation was banned in 2002, and some authorities believe that people who owned live snakeheads at the time may have dumped them into public waters to get rid of the evidence. Northern Snakeheads were spotted in Piney Creek in Lee County, Arkansas in 2009. The source may have been a nearby fishery that once raised snakeheads for consumers, but "disposed" of them in 2001. Years later, a farmer found one wiggling across the road, and more in a ditch on his farm. The state Game and Fish Commission went into attack mode after the sightings, and poisoned Piney Creek and its tributaries, all 400 miles, with rotenone, which kills all fish. Native fish were restocked after the kill. Photograph from the Arkansas Game and Fish Commission.

p8171248

The Giant Snakehead (Channa micropeltes) is native to Southeast Asia, notably Malaysia and Indonesia. They can grow to over a meter in length! A 24-inch Giant Snakehead was caught in Wisconsin in 2003, but was thrown back before it was identified from a photograph. It was not seen again, probably because the tropical fish couldn't deal with the climate, but environmentalists are concerned that they could flourish in warmer industrial runoff sites. A 2008 report of a Giant Snakehead sighting in England turned out to be a hoax. Photograph by Flickr user Mohd Fahmi Mohd Azmi.

The Great Snakehead, Cobra Snakehead, or Bullseye Snakehead (Channa marulius) is indigenous to India and all of South Asia. Specimens were discovered in Florida waters in 2000, and are now part of the permanent ecosystem. Fishing for snakeheads is encouraged and embraced, as they get pretty big. Throwing them back is illegal.

Snakeheads have been found in Massachusetts, Maine, and Rhode Island, but those are believed to be isolated incidents of abandoned aquarium fish. Officials hope that New England waters are too cold for their proliferation. But a little further south, they thrive. Snakeheads were found in New York in 2005. Just a couple of weeks ago, a Northern Snakehead was found in the John Heinz National Wildlife Refuge in Tinicum, Pennsylvania. It was the second sighting in the refuge, as one was reported found last year. Photograph by Emma Lee for NewsWorks.

See also: Messing with Mother Nature: 5 Cautionary Tales and Messing with Mother Nature: The Macquarie Island Ecosystem.

Original image
iStock // Ekaterina Minaeva
technology
arrow
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
Original image
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!

Original image
Stephen Missal
crime
arrow
New Evidence Emerges in Norway’s Most Famous Unsolved Murder Case
May 22, 2017
Original image
A 2016 sketch by a forensic artist of the Isdal Woman
Stephen Missal

For almost 50 years, Norwegian investigators have been baffled by the case of the “Isdal Woman,” whose burned corpse was found in a valley outside the city of Bergen in 1970. Most of her face and hair had been burned off and the labels in her clothes had been removed. The police investigation eventually led to a pair of suitcases stuffed with wigs and the discovery that the woman had stayed at numerous hotels around Norway under different aliases. Still, the police eventually ruled it a suicide.

Almost five decades later, the Norwegian public broadcaster NRK has launched a new investigation into the case, working with police to help track down her identity. And it is already yielding results. The BBC reports that forensic analysis of the woman’s teeth show that she was from a region along the French-German border.

In 1970, hikers discovered the Isdal Woman’s body, burned and lying on a remote slope surrounded by an umbrella, melted plastic bottles, what may have been a passport cover, and more. Her clothes and possessions were scraped clean of any kind of identifying marks or labels. Later, the police found that she left two suitcases at the Bergen train station, containing sunglasses with her fingerprints on the lenses, a hairbrush, a prescription bottle of eczema cream, several wigs, and glasses with clear lenses. Again, all labels and other identifying marks had been removed, even from the prescription cream. A notepad found inside was filled with handwritten letters that looked like a code. A shopping bag led police to a shoe store, where, finally, an employee remembered selling rubber boots just like the ones found on the woman’s body.

Eventually, the police discovered that she had stayed in different hotels all over the country under different names, which would have required passports under several different aliases. This strongly suggests that she was a spy. Though she was both burned alive and had a stomach full of undigested sleeping pills, the police eventually ruled the death a suicide, unable to track down any evidence that they could tie to her murder.

But some of the forensic data that can help solve her case still exists. The Isdal Woman’s jaw was preserved in a forensic archive, allowing researchers from the University of Canberra in Australia to use isotopic analysis to figure out where she came from, based on the chemical traces left on her teeth while she was growing up. It’s the first time this technique has been used in a Norwegian criminal investigation.

The isotopic analysis was so effective that the researchers can tell that she probably grew up in eastern or central Europe, then moved west toward France during her adolescence, possibly just before or during World War II. Previous studies of her handwriting have indicated that she learned to write in France or in another French-speaking country.

Narrowing down the woman’s origins to such a specific region could help find someone who knew her, or reports of missing women who matched her description. The case is still a long way from solved, but the search is now much narrower than it had been in the mystery's long history.

[h/t BBC]

SECTIONS
BIG QUESTIONS
BIG QUESTIONS
JOB SECRETS
QUIZZES
WORLD WAR 1
SMART SHOPPING
STONES, BONES, & WRECKS
#TBT
THE PRESIDENTS
WORDS
RETROBITUARIES