Why Heated Concrete Can Explode Like Popcorn

iStock.com/Salistock
iStock.com/Salistock

Unlike wood, insulation, and other building materials, concrete doesn't burn. Modern civilization has practically built its infrastructure on it, from stairs to floors to office towers. While not bursting into flames is a good thing, concrete does have vulnerability—exposed to high temperatures, it can explode like a bag of microwaved popcorn. And scientists are getting better at understanding why.

A recent paper published in the journal Cement and Concrete Research offered some insight into this unusual phenomenon. Researchers at Empa, the Swiss Federal Laboratories for Materials Science and Technology; the University of Grenoble, and Institut Laue-Langevin conducted an experiment using blocks of concrete, which typically consists of cement, sand, water, and other additives to increase strength or reduce permeability. Heated to 1112°F, portions of the block exploded.

Using neutron tomography, researchers were able to visualize the accumulation of water as the block heats up.

The principle behind it is largely the same as popping popcorn kernels. In both instances, heated water vaporizes and becomes trapped. With nowhere to go, the built-up energy is released, with the concrete becoming pressurized and breaking apart.

Part of the reason the vapor becomes trapped is because water moves away from the heat source—say, a fire in an interior room—and toward the cooler portion of the concrete. In doing so, the water acts as a moisture barrier, preventing vapor from coming through pores. High-performance concrete, which is often used in commercial applications, has few pores, which makes the pressure from the vapor more concentrated. The water in the mix can turn to vapor when temperatures reach 392°F.

Why is understanding this process important? By exploring how and why concrete can burst, additives can be developed to reduce or eliminate the effect. The result will be safer, more fire-resistant buildings.

[h/t Live Science]

Sssspectacular: Tree Snakes in Australia Can Actually Jump

sirichai_raksue/iStock via Getty Images
sirichai_raksue/iStock via Getty Images

Ophidiophobia, or fear of snakes, is common among humans. We avoid snakes in the wild, have nightmares about snakes at night, and recoil at snakes on television. We might even be born with the aversion. When researchers showed babies photos of snakes and spiders, their tiny pupils dilated, indicating an arousal response to these ancestral threats.

If you really want to scare a baby, show them footage of an Australian tree snake. Thanks to researchers at Virginia Tech, we now know these non-venomous snakes of the genus Dendrelaphis can become airborne, propelling themselves around treetops like sentient Silly String.

That’s Dendrelaphis pictus, which was caught zipping through the air in 2010. After looking at footage previously filmed by her advisor Jake Socha, Virginia Tech Ph.D. candidate Michelle Graham headed for Australia and built a kind of American Ninja Warrior course for snakes out of PVC piping and tree branches. Graham observed that the snakes tend to spot their landing target, then spring upward. The momentum gets them across gaps that would otherwise not be practical to cross.

Graham next plans to investigate why snakes feel compelled to jump. They might feel a need to escape, or continue moving, or do it because they can. Two scientific papers due in 2020 could provide answers.

Dendrelaphis isn’t the only kind of snake with propulsive capabilities. The Chrysopelea genus includes five species found in Southeast Asia and China, among other places, that can glide through the air.

[h/t National Geographic]

9 Facts About Narcolepsy

Korrawin/iStock via Getty Images
Korrawin/iStock via Getty Images

Everyone experiences occasional daytime sleepiness, but just a small fraction of the population knows what it’s like to have narcolepsy. The disorder is defined by persistent drowsiness throughout the day, and in some cases, sleep paralysis, hallucinations, and the sudden loss of muscle control known as cataplexy. Having narcolepsy can make doing everyday activities difficult or dangerous for patients, but unlike some chronic conditions, it’s also easy to diagnose and treat. Here are some facts you should know about the condition.

1. There are two types of narcolepsy.

If everything you know about narcolepsy comes from movies and TV, you may think of it as the disease that causes people to go limp without warning. Sudden loss of muscle control is called cataplexy, and it’s the defining symptom of type 1 narcolepsy. Type 2 narcolepsy, on the other hand, is mainly characterized by fatigue. Losing motor function while awake isn’t a problem for those with type 2.

2. Type 1 narcolepsy stems from a chemical deficiency.

Almost every patient with type 1 narcolepsy has low levels of hypocretin. Hypocretin is a neurochemical that regulates the wake-sleep cycle. When there isn’t enough of this chemical in the brain, people have trouble staying conscious and alert throughout the day. Most people with the second, less severe type of narcolepsy have normal hypocretin levels, with about a third of them producing low or undetectable amounts. Type 2 narcoplepsy has been studied far less than type 1 of the disorder, and scientists are still figuring out what causes it.

3. The exact causes of narcolepsy aren’t always clear.

So why do some people’s brains produce less hypocretin than others? That part has been hard for scientists to figure out. One possible explanation is that certain autoimmune disorders cause the body to attack the healthy brain cells that make this chemical. This disorder can be the result of genetic and environmental factors. Although people with narcolepsy rarely pass it down to their offspring (this happens less than 1 percent of the time), the sleep condition does occasionally crop up in family clusters, suggesting there is sometimes a genetic component at play. Head trauma that impacts the area of the brain responsible for governing sleep can also lead to narcolepsy in rare cases.

4. There are tests to diagnose narcolepsy.

If patients believe they might have narcolepsy, their doctors might ask them to detail their sleep history and keep a record of their sleep habits. There are also a few tests potential narcoleptics can take to determine if they have the condition. During a polysomnography test, patients spend the night at a medical facility with electrodes attached to their heads to monitor their breathing, eye movement, and brain activity. A multiple sleep latency test is similar, except it gauges how long it takes patients to fall asleep during the day.

5. Strong emotions can trigger cataplexy.

Cataplectic spells can sometimes be predicted by triggers. In some patients, feeling strong emotions—whether they’re crying, laughing, angry, or stressed—is all it takes for them to lose muscle control. These triggers vary from patient to patient, and they can even affect the same person randomly. Some people deal with them by avoiding certain situations and closing themselves off emotionally, which can disrupt their social lives.

6. Narcolepsy can make sleep terrifying.

Narcoleptics don’t just worry about their disorder during their waking hours. When they’re trying to fall asleep at night or wake up in the morning, narcolepsy can complicate things. One symptom is experiencing vivid, dream-like hallucinations while transitioning in or out of consciousness. These visions are often scary and may involve an intruder in the room with the sleeper. If they happen as the patient falls asleep, the hallucinations are called hypnagogic, and if they occur as they wake up, they’re hypnopompic.

A related symptom is sleep paralysis. This happens when a person’s brain cuts off muscle control of their body before they’re fully asleep or as they’re waking up. This combined with hypnagogic or hypnopompic nightmares can cause frightening experiences that are sometimes confused for real encounters.

7. Narcoleptics sometimes do activities half-asleep.

To outside observers, narcolepsy is sometimes hard to spot. A narcoleptic patient overcome by sleepiness won’t necessarily pass out in the middle of what they’re doing. Some act out “automatic behavior,” which means they continue with their actions—whether that’s walking, driving, or typing—with limited consciousness. This can cause poor performance at work or school, and in worst case scenarios, accidents while driving a car or operating machinery.

8. Harriet Tubman may have had narcolepsy.

One of the most famous likely narcoleptics in history is Harriet Tubman. The African American abolitionist was known to suffer from what were probably sudden narcoleptic episodes. The condition may have stemmed from the severe head trauma she sustained when a slave master threw an iron at another slave and hit her instead. The injury left her with permanent brain damage: In addition to narcolepsy, she also experienced chronic seizures and migraines throughout her life.

9. Medications and lifestyle changes are common narcolepsy treatments.

Though there’s no way to cure narcolepsy completely, there are many treatment options available. Taking medication is one of the most common ways to manage the disorder. Stimulants such as modafinil and armodafinil can be used to combat mild sleepiness, while amphetamines are often prescribed for more severe forms of fatigue. For hallucinations and sleep paralysis, selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors—drugs that suppress REM sleep—can help.

As an alternative or supplementary treatment to medications, doctors may recommend lifestyle changes. Sticking to a sleep schedule, exercising regularly, avoiding nicotine and alcohol, and taking naps during the day can all reduce the symptoms of narcolepsy.

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