❌

Normal view

There are new articles available, click to refresh the page.
Before yesterdayMain stream

Mice made transparent with a dye used in Doritos

✇Ars Technica
By: Jacek Krywko
16 September 2024 at 18:58
Zihao Ou, who helped develop this solution, holds a tube of it.

Enlarge / Zihao Ou, who helped develop this solution, holds a tube of it.

One key challenge in medical imaging is to look past skin and other tissue that are opaque to see internal organs and structures. This is the reason we need things like ultrasonography, magnetic resonance, or X-rays. There are chemical clearing agents that can make tissue transparent, like acrylamide or tetrahydrofuran, but they are almost never used in living organisms because they’re either highly toxic or can dissolve away essential biomolecules.

But now, a team of Stanford University scientists has finally found an agent that can reversibly make skin transparent without damaging it. This agent was tartrazine, a popular yellow-orange food dye called FD&C Yellow 5 that is notably used for coloring Doritos.

Playing with light

We can’t see through the skin because it is a complex tissue comprising aqueous-based components such as cell interiors and other fluids, as well as protein and lipids. The refractive index is a value that indicates how much light slows down (on average, of course) while going through a material compared to going through a vacuum. The refractive index of those aqueous components is low, while the refractive index of the proteins and lipids is high. As a result, light traveling through skin constantly bends as it endlessly crosses the boundary between high and low refractive index materials.

Read 11 remaining paragraphs | Comments

Remembering where your meals came from key for a small bird’s survival

✇Ars Technica
By: Jacek Krywko
13 September 2024 at 15:07
a small, black and grey bird perched on the branch of a fir tree.

Enlarge (credit: BirdImages)

It seems like common sense that being smart should increase the chances of survival in wild animals. Yet for a long time, scientists couldn’t demonstrate that because it was unclear how to tell exactly if a lion or a crocodile or a mountain chickadee was actually smart or not. Our best shots, so far, were looking at indirect metrics like brain size or doing lab tests of various cognitive skills such as reversal learning, an ability that can help an animal adapt to a changing environment.

But a new, large-scale study on wild mountain chickadees, led by Joseph Welklin, an evolutionary biologist at the University of Nevada, showed that neither brain size nor reversal learning skills were correlated with survival. What mattered most for chickadees, small birds that save stashes of food, was simply remembering where they cached all their food. A chickadee didn’t need to be a genius to survive; it just needed to be good at its job.

Testing bird brains

“Chickadees cache one food item in one location, and they do this across a big area. They can have tens of thousands of caches. They do this in the fall and then, in the winter, they use a special kind of spatial memory to find those caches and retrieve the food. They are little birds, weight is like 12 grams, and they need to eat almost all the time. If they don’t eat for a few hours, they die,” explains Vladimir Pravosudov, an ornithologist at the University of Nevada and senior co-author of the study.

Read 13 remaining paragraphs | Comments

❌
❌