Science news in brief: From the physics of chocolate to why snails lean left
And other news from around the world
What do chocolate and concrete have in common? More than you might think.
Chocolate is made by mixing liquid and finely ground cacao beans in a device that bears more than a passing resemblance to a cement mixer. In both cases, stirring tiny granules in a fluid results in a substance with very specific properties – for chocolate, it’s a meltingly smooth mouthfeel, and for concrete, it’s a cohesive, consistent texture.
However, while physicists have studied the physics of mixing concrete, few have taken a close look at the forces at work in chocolate conching, as the process is called. Now a team of physicists, funded in part by Mars, the confectionery company, is showing just what happens as the ingredients of chocolate are given a stir on their way to deliciousness.
When conching was invented in 1879 by Rodolphe Lindt, it could take more than a day of steady mixing for gritty chocolate to grow smooth. Today, it is a shorter process. For this study, the researchers spun cacao powder and oil in a conching machine for 40 minutes. What they saw was that much like what happens in a cement mixer, the dry paste formed from the powder and the fluid made shaggy clumps. Then it morphed into a more liquid-like state and started to flow. Adding oil near the end just encouraged the process.
Understanding the physics may help chocolatiers decide just how long and at what speed to conch chocolate, and when to add the right amounts of ingredients.
“Conching is one of the more energy expensive steps of chocolate making,” says Wilson Poon, a professor of physics at the University of Edinburgh who led the study. “We think that once you understand the actual process, it may well be possible to reduce the amount of energy used.”
The particular chocolate made in this study, alas, went untasted. “We don’t have a food grade lab,” says Daniel Hodgson, a researcher also at the University of Edinburgh and one of the co-authors, “so any samples prepared in our labs are only for experimentation.”
How Yosemite’s most famous rock is holding up
But this behemoth is also the site of frequent rockfalls. More than 20 have occurred in the past decade, including one in 2017 that killed a climber. The majority of these falls have been linked to rock formations known as flakes, sheets of rock that are peeling off El Capitan like layers of onion skin.
With infrared imaging, scientists have now essentially peered behind two of the largest flakes, Boot Flake and Texas Flake, to determine how well they’re connected to El Capitan. The results, presented at a meeting of the European Geosciences Union in Vienna in April, suggest that the underlying structures linking each flake to the 100 million-year-old granite are surprisingly small. By visualising these attachment points, scientists can monitor them to keep climbers safe.
Allen Glazner, a geologist at the University of North Carolina at Chapel Hill not involved in the research, says the study shows how much “glue” is holding these rocks up.
Hundreds of flakes dot the face of El Capitan. They’re unnerving to look at because they appear so precarious. “You can’t tell what holds those things up there,” Glazner says.
Boot Flake and Texas Flake are among El Capitan’s largest flakes: Boot Flake is about a third the size of a tennis court, and Texas Flake is about two times larger. They’re both located roughly halfway up a popular climbing route called The Nose. Climbers ascending The Nose move around these flakes, sometimes even shimmying between Texas Flake and the underlying rock face using a technique called “chimneying”.
In October 2015, researchers set up a camera capable of thermal imaging in El Capitan Meadow and photographed Boot Flake and Texas Flake. In all of the frames, the flakes stood out – they were a few degrees colder than the surrounding rock. That was consistent with cool air circulating around the backsides of the detached parts of the flakes, the scientists reasoned.
But a closer inspection of the images revealed something unexpected. Small sections of each flake – near the centre of Boot Flake and in the middle and lower part of Texas Flake – were slightly warmer than the rest of the formation. These thermal anomalies revealed the rock bridges where Boot Flake and Texas Flake are connected to the face of El Capitan, the researchers realised.
“We know that there are points of attachment,” says Greg Stock, a Yosemite National Park geologist and member of the research team. “But we’ve never been able to see them.”
Boot Flake is stable, at least for now, the researchers say. But Texas Flake’s tiny rock bridge likely isn’t sufficient to glue it in place. This formation is probably held up by another feature, an intact rock attachment that runs along its base.
Mouse may show dinosaurs’ true colours
What colour was T-rex? Or the triceratops? Until recently, the palette of prehistory was the stuff of daydreams, artists or kids with crayons. Advances in imaging technology are bringing us closer to real answers. In the past decade, we’ve learned that sinosauropteryx’s tail was striped, and microraptor’s head was blue-black and shiny.
And now a discovery in a fossilised mouse may help us find the true colours of dinosaurs and other ancient creatures. In a “false colour” synchrotron X-ray image of a mouse in Germany, the yellow regions are rich in zinc and sulphur, suggesting the mouse’s fur had red pigments. The researchers believe the creature contained pheomelanin – the same pigment that gives a red hue to chicken feathers, tiger fur and your freckles. Their findings will allow researchers to search for more evidence of this colouring across the fossil record.
Even in well-preserved fossils, pigments deteriorate quickly. Researchers have a few workarounds to find clues to colour. Some look for melanosomes, the organelles in animal cells that make and store pigments. The shape of a melanosome can indicate what type of pigment was once inside, while the organisation of melanosomes within a feather can suggest whether a bird (or dinosaur) was dull or iridescent.
Another technique is to look for more persistent molecules known to be associated with pigments. That’s the preferred tactic of this research group, which previously found evidence of eumelanin – a brown and black pigment – in the plumage of the feathered dinosaur Archaeopteryx.
The researchers worked with two specimens of an extinct field mouse. Three million years ago, when several of these mice died, they were washed into a pond in what is now Willershausen, Germany. Quickly buried by sediment, they were spared many of the ravages of bacteria and time, and ended up in a University of Göttingen fossil drawer.
“By understanding that delicate relationship between zinc and sulphur, for the first time, we can confidently say, ‘Yes, this is pheomelanin pigment in the fossil record,’” says Phillip Manning, a geologist at the University of Manchester and the paper’s lead author.
More important than their conclusion about the mouse’s colour is what their process makes possible. Previous approaches to detecting colour were piecemeal or destructive. But “this new method appears to allow mapping of colour-giving pigments across a whole fossil”, without chipping any of it away, says Mike Benton, a palaeontologist at the University of Bristol who was not involved in the study.
The group is working on further streamlining of the scanning method, “so that it’s easy for anyone to come and bring in fossils”, Bergmann says.
In test, warm women and cold men excel
It is a truth universally acknowledged – or at least much discussed on social media – that a woman who works in an office is in want of a sweater.
Office air conditioning is often set at a temperature that women find chilly; the resulting water-cooler debate has been called the “battle of the thermostat”. One study even suggested that because women have slower metabolic rates, the formula used to set temperatures in workplaces, which was developed decades ago based on the comfort of men, may overestimate women’s body heat production by 35 per cent.
But does temperature affect the productivity of men and women differently? A new study reports that at colder temperatures, men scored higher than women on verbal and math tests. But as a room grew warmer, women’s scores rose significantly. The findings require further confirmation under an assortment of conditions. But they add to a scientific rethinking of the spaces where we work and study, which sometimes have been devised with a limited set of physical requirements in mind.
Researchers asked more than 500 college students to take tests for an hour in rooms with temperatures between 61 and 90 degrees. The students performed math problems and rearranged a set of letters into as many words as they could. They were also asked to solve a series of logic problems. A pattern emerged. Scores on the logic problems did not vary among men and women as temperatures changed, but the math and verbal test scores did.
“If temperatures are cold, men are much better than women,” says Agne Kajackaite, an author of the study. “So there is this gender gap.” She adds: “But then when temperature increases, the gender gap disappears” on the math test, and women outpace men on the verbal test.
Why snails lean right, or left for that matter
Most snails live in shells that coil to the right. But some turn the other way. And then there was Jeremy, the garden snail with a left-coiled shell, whose struggle to find a left-coiled mate made him famous. He was finally paired up, leaving behind a litter that was born all right.
How Jeremy and other chiral or mirror-image snails – including a few species that are all-left – turn out like this has long baffled scientists. Studying these snails offers clues to the evolution of body plans in many animals. It also could be important for understanding why approximately one in 10,000 people are born with situs inversus, a condition where their internal organs are flipped like a lefty snail’s shell.
Now scientists are turning to Crispr – the powerful gene editing tool – to figure out why some snails turn out this way. A team in Japan led by Reiko Kuroda, a chemist and biologist, has successfully used the technique to manipulate a single gene responsible for shell direction in a species of great pond snail. The research, published in the journal Development, offers definitive proof of the genetic underpinnings of handedness in this species, and could lead to clues about left and right-handed mysteries in other organisms.
“Ten years ago you might not imagine there were any similarities in the left/right asymmetry of a snail and the left/right asymmetry of humans. But it’s becoming increasingly obvious that is the case,” says Angus Davison, an evolutionary geneticist who has studied Jeremy the lefty snail as well as chiral pond snails, but was not a part of Kuroda’s study.
As for Jeremy, Davison will be studying the lefty garden snail’s great-grand-snails for clues to what made their progenitor’s unusual coil.
“We’ve got a lab full of snails, lots and lots of them, but we’re still working to try and understand what it was that made Jeremy a lefty,” says Davison. “Unfortunately, snail research doesn’t move quickly.”
© New York Times