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Two More Things I Just Learned About Fish

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When I'm not blogging for mental_floss, I can usually be found wearing bright orange rubber pants and gutting, cutting and selling fish at my local Whole Foods (and winning awards for it). Sometimes, my two worlds collide and I find some scientific research involving my ocean-dwelling friends that begs for a blog post. This is one of those times.

1. There are salmon in Paris

"¦and they're not just on plates, but alive and kicking in the Seine. For the first time in over a century, some 1,000 Atlantic salmon (Salmo salar) used the river to pass through the City of Lights on their migration to their spawning waters.

Before the Industrial Revolution, Atlantic salmon were abundant in the Seine, but as the river became increasingly polluted the fish were killed off. By 1900 the salmon had completely disappeared and most other species of fish followed in the early 20th century. By 1995, only five species of fish "“ carp, bream, roach and eel "“ still swam in the Seine around Paris (and no people "“ summer beaches on the Right Bank had numerous signs warning people to stay out of the water).

Now, 25 years after clean-up efforts began in the river, 32 species of fish—including sea trout, herring, shad, lampreys and the Atlantic Salmon—call Paris home.

Researchers are most excited about the return of the salmon, given the species status as a bioindicator, a species used to determine and monitor the health and integrity of an environment or ecosystem. [Image credit: David Monniaux.]

2. For plankton, global warming isn't such a bad thing

The increasing water temperatures associated with global warming are a problem for all aquatic life, but the creatures that call Arctic waters home have another problem to deal with. A research team from the University of Alaska, Fairbanks has suggested that the Arctic Ocean is especially susceptible to ocean acidification "“ increasing acidity of oceans resulting from seawater absorbing carbon dioxide from the atmosphere "“ and that this will cause problems for Alaska's famous salmon and crab fisheries.

One consequence of the acidification is that increased acidity and decreased pH leaves shellfish like crabs, clams and oysters struggling to pull the minerals they need to build their shells from the water. The team found several areas in the Gulf of Alaska where concentrations of the shell-building minerals were low enough that the shellfish there wouldn't be able to build shells of normal strength. Shellfish aren't going to start disintegrating any time soon, but the change in acidity and shell composition can cause their metabolisms to slow and their stress hormones to fire up, diverting energy from growth and reproduction.

planktonOne organism already feeling the effects of acidification is the sea butterfly, also known as the flapping snail, pteropod or swimming sea snail. Sea butterflies are tiny (about the size of a lentil) mollusks that account for up to 50% of the diet of pink salmon. They're already having trouble building shells at current acidity levels and if they cannot survive, a 10% decrease in their population could mean a 20% decrease in the body weight of adult salmon. By 2050, the sea butterflies may not be able to make shells at all and go extinct, wreaking havoc on the local food web.

BUT"¦researchers at the University of North Carolina, Chapel Hill think that plankton, the base of many other marine food webs, might thrive in warming oceans. The researchers found, after warming 4-liter bottles of seawater over time, that phytoplankton grew slightly faster with every degree that the water temperature rose. Zooplankton, which feed on phytoplankton, grew even faster. This effect could work its way up the food chain, meaning more food for bigger and bigger fish. The number and growth rates of the phytoplankton would have to be sustainable, though, or top-heavy food webs would be unstable and could crash.


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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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Live Smarter
Working Nights Could Keep Your Body from Healing
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The world we know today relies on millions of people getting up at sundown to go put in a shift on the highway, at the factory, or in the hospital. But the human body was not designed for nocturnal living. Scientists writing in the journal Occupational & Environmental Medicine say working nights could even prevent our bodies from healing damaged DNA.

It’s not as though anybody’s arguing that working in the dark and sleeping during the day is good for us. Previous studies have linked night work and rotating shifts to increased risks for heart disease, diabetes, weight gain, and car accidents. In 2007, the World Health Organization declared night work “probably or possibly carcinogenic.”

So while we know that flipping our natural sleep/wake schedule on its head can be harmful, we don’t completely know why. Some scientists, including the authors of the current paper, think hormones have something to do with it. They’ve been exploring the physiological effects of shift work on the body for years.

For one previous study, they measured workers’ levels of 8-OH-dG, which is a chemical byproduct of the DNA repair process. (All day long, we bruise and ding our DNA. At night, it should fix itself.) They found that people who slept at night had higher levels of 8-OH-dG in their urine than day sleepers, which suggests that their bodies were healing more damage.

The researchers wondered if the differing 8-OH-dG levels could be somehow related to the hormone melatonin, which helps regulate our body clocks. They went back to the archived urine from the first study and identified 50 workers whose melatonin levels differed drastically between night-sleeping and day-sleeping days. They then tested those workers’ samples for 8-OH-dG.

The difference between the two sleeping periods was dramatic. During sleep on the day before working a night shift, workers produced only 20 percent as much 8-OH-dG as they did when sleeping at night.

"This likely reflects a reduced capacity to repair oxidative DNA damage due to insufficient levels of melatonin,” the authors write, “and may result in cells harbouring higher levels of DNA damage."

DNA damage is considered one of the most fundamental causes of cancer.

Lead author Parveen Bhatti says it’s possible that taking melatonin supplements could help, but it’s still too soon to tell. This was a very small study, the participants were all white, and the researchers didn't control for lifestyle-related variables like what the workers ate.

“In the meantime,” Bhatti told Mental Floss, “shift workers should remain vigilant about following current health guidelines, such as not smoking, eating a balanced diet and getting plenty of sleep and exercise.”