A team of physicists at the University of Edinburgh, working with an infection and immunity specialist, has, via experimentation, validated a theory to explain why paint dries at the same rate regardless of humidity (湿度) levels.     

Generally, paint should dry faster on an outdoor fence on a dry day than when it is humid because evaporation (蒸发) occurs faster when the air around a liquid source is drier. But evidence suggests this is not the case for paint and some other liquids. Chemist Salmon and his colleagues developed a theory to explain why. They suggested it is because large molecules in the liquid are pulled to the surface during evaporation, forming a “polarization layer” that prevents evaporation, and by extension, drying. In this new effort, the research team worked to test this theory.

The researchers drilled five holes into a short cylinder (圆柱体) and inserted glass tubes in a horizontal position — each was then sealed in place. They then added a quantity of PVA, a kind of chemical substance, into the cylinder, which they placed on a scale. They poured a thin layer of oil on top of the liquid to prevent surface evaporation. The final touch involved placing an air flow box over the top of the cylinder to allow for controlling humidity levels. The team then ran multiple 17-hour trials to determine evaporation rates, using the scale to measure how much liquid evaporated from the tubes at different humidity levels, ranging from 25% to 90%.

The researchers found that as expected, evaporation rates remained constant for approximately three hours. But then, rates plummeted, as was theorized by Salmon, regardless of humidity levels. The evaporation rate didn’t decrease as humidity increased during the initial three hours. However, the theory only appeared to hold for humidity levels up to 80% — at rates higher than that, evaporation did slow down, which the team suggested was likely due to some other forces.

The researchers suggested their work could have medical applications as recent research efforts have shown that respiratory droplets (呼吸道飞沫) tend to form skins similar to those seen in the experimental equipment.

Salvador Dali had a strange way of refreshing his mind — “slumber (睡眠) with a key”. In a book, he described how it worked. “You were to grasp a heavy key, hanging above a plate.” Then, he continued, “As you were progressively asleep, the key would slip from your fingers and fall on the plate, awakening you.” He claimed the brief moment spent between wake and sleep would refresh your physical and mental being.

Now Dali’s mysterious-sounding method has been, to some degree, proven by science — napping with an object in hand might help to tap into this creative sweet spot.

Delphine Oudiette is a sleep researcher at the Paris Brain Institute. She was curious to find out why — so she and her colleagues asked 103 volunteers to complete a series of math problems.

Unknown to the participants, there was a quick shortcut to solve all the problems. ( Sixteen of the volunteers figured that out and were excluded from the rest of the study. ) The volunteers who didn’t determine the secret were asked to emulate (模仿) Dali’s method — but grasping a plastic bottle with their fingertips rather than a key. Some took a Dali-style micro nap (小睡), some napped longer and others didn’t nap at all. After the nap, the researchers asked all the volunteers to do hundreds more of these math problems. And they found that volunteers who took micro naps were nearly three times as likely to figure out the problem-solving trick, compared to those who didn’t nap at all.

Oudiette said, “We think that’s maybe in this short period, you have the best of the two worlds: sleep and wake. So you lose control of your thoughts and have loose associations, which could be helpful for creativity. But at the same time, you still keep some awareness that might help you to recognize when you have a great idea. Those who slept for longer periods actually did worse than both those who briefly slept and those who stayed awake. The next step of my work will involve repeating the experiment with other creative tasks to know more about the mechanism — and maybe to teach people to reach this creative sweet spot.”

To look inside an ant nest is to meet with an alien civilization. The boiling mass of worker ants beneath an upturned stone is both strangely reminiscent of (联想到) human society and strikingly different. There is an organization that fascinates us and a long line of myrmecophiles (or ant lovers) leads back all the way to King Solomon, who in fact advised people to “go to the ant, consider her ways and be wise”. This was exactly the inspiration behind Planet Ant, a TV program showcasing what we know about the kingdom of ants, and what ants can teach us about the human world.

Like us, ants build structures, find food, defend their societies and manage waste, and-also like us-they must be well organized. For example, the leaf-cutting ants of Planet Ant have special waste disposal areas for storing harmful waste and a team of “waste-disposal ants” dedicated to keeping the nest clean. But ants achieve this familiar final result in a very different way to humans. Human societies have centralized control. In other words, someone tells us what to do. Ants, on the other hand, have decentralized control and neither the queen nor any other ant directs work. Ant workers are the final self-starters, following specific, but potentially flexible, rules in certain situations.

Chemical trails underpin much of this self-organization. Foragers (觅食者) lay a mix of chemicals known as trail pheromone (信息素) behind them as they walk. Other ants follow the trail and if they find food they reinforce it, laying more pheromone as they return to the nest. Stronger trails are more likely to be followed, so trails leading to food become progressively reinforced, while trails with no food at the end fade away.

This combination of positive feedback and evaporation (蒸发) produces an effective foraging system that is very good at finding the quickest routes to food. This simple guiding principle, and others like it, have provided some useful solutions to the complex problems faced by engineers, computer scientists and businesses.