Jud Ready, Georgia Institute of Technology

Imagine – it’s the mid-1800s, and you’re riding your high-wheeled, penny-farthing bicycle down a dusty road. Sure, it may have some bumps, but if you lose your balance, you’re landing on a relatively soft dirt road. But as the years go by, these roads are replaced with pavement, cobblestones, bricks or wooden slats. All these materials are much harder and still quite bumpy.

As paved roads grew more common across the U.S. and Europe, bicyclists started to suffer gruesome skull fractures and other serious head injuries during falls.

As head injuries became more common, people started seeking out head protection. But the first bike helmets were very different than helmets of today.

I’m a materials engineer who teaches a course at Georgia Tech about materials science and engineering in sports. The class covers many topics, but particularly helmets, as they’re used in many different sports, including cycling, and the materials they’re made of play an important role in how they work. Over the decades, people have used a wide variety of materials to protect their heads while biking, and companies continue to develop new and innovative materials.

In the beginning, there was the pith helmet.

Pith helmets

The first head protection concept introduced to the biking world was a hat made from pith, which is the spongy rind found in the stem of sola plants, aeschynomene aspera. Pith helmet craftsmen would press the pith into sheets and laminate it across dome-shaped molds to form a helmet shape. Then, they’d cover the hats in canvas as a form of weatherproofing.

Pith helmets were far from what we would consider a helmet today, but they persisted until the early 20th century, when bicycle-racing clubs emerged. Since pith helmets offered little to no ventilation, the racers began to use halo-shaped leather helmets. These had better airflow and were more comfortable, although they weren’t much better at protecting the head.

Leather halo helmets

The initial concept for the halo helmet used a simple leather strip wrapped around the forehead. But these halo helmets quickly evolved, as riders arranged additional strips longitudinally from front to back. They wrapped the leather bands in wool.

For better head protection, the helmet makers then started adding more layers of leather strips to increase the helmet’s thickness. Eventually, they added different materials such as cotton, foam and other textiles into these leather layers for better protection.

While these had better airflow than the pith hats, the leather “hairnet” helmets continued to offer very little protection during a fall on a paved surface. And, like pith, the leather helmets degraded when exposed to sweat and rain.

Despite these drawbacks, leather strip helmets dominated the market for several decades as cycling continued to evolve throughout the 20th century.

Then, in the 1970s, a nonprofit dedicated to testing motorcycle helmets called the Snell Foundation released new standards for bike helmets. They set their standards so high that only lightweight motorcycle helmets could pass, which most bicyclists refused to wear.

New materials and new helmets

The motorcycle equipment manufacturing company Bell Motorsports responded to the new standards by releasing the Bell Biker in 1975. This helmet used expanded polystyrene, or EPS. EPS is the same foam used to manufacture styrofoam coolers. It’s lightweight and absorbs energy well.

Constructing the Bell Biker involved spraying EPS into a dome shaped mold. The manufacturers used small pellets of a very hard plastic – polycarbonate, or PC – to mold an outer shell and then adhere it to the outside of the EPS.

Unlike the pith and leather helmets, this design was lightweight, load bearing, impact absorbing and well ventilated. The PC shell provided a smooth surface so that during a fall, the helmet would skid along the pavement instead of getting jerked around and caught, which could cause abrupt head rotation and lead to concussions and other head and neck injuries.

Over the next two decades, as cycling became more popular, helmet manufacturers tried to strike the perfect balance between lightweight and ventilated helmets, while simultaneously providing impact protection.

In order to decrease weight, a company called Giro Sport Design created an all-EPS helmet covered by a thin lycra fabric cover instead of a hard PC shell. This design eliminated the weight of the PC shell and improved ventilation.

In 1989, a company called Pro Tec introduced a helmet with a nylon mesh infused in the EPS foam core. The nylon mesh dramatically increased the helmet’s structural support without the added weight of the PC shell.

Meanwhile, as cycling became more competitive, many riders and manufacturers started designing more aerodynamic helmets using the existing materials. A revolutionary teardrop style helmet debuted in the 1984 Olympics.

Now, even casual biking enthusiasts will don teardrop helmets.

Helmets on the market today

Helmet makers continue to innovate. Today, many commercial brands use a hard polyethylene terephthalate, or PET, shell around the EPS foam in place of a PC shell to increase the helmet’s protection and lifespan, while decreasing cost.

Meanwhile, some brands still use PC shells. Instead of gluing them to the EPS foam, the shell serves as the mold itself, with the EPS expanding to fit inside it. Manufacturing helmets this way eliminates several process steps, as well as any gaps between the foam and shell. This process makes the helmet both stronger and cheaper to manufacture.

As helmets evolve to provide more protection with still lighter weight, materials called copolymers, such as acrylonitrile-butadiene-styrene, are replacing PC and PET shell materials.

Materials that are easier and cheaper to manufacture, such as expanded polyurethane and expanded polypropylene, are also starting to replace the ubiquitous EPS core.

Just as the leather and pith helmets would look strange to a cyclist today, a century from now, bike helmets could be made with entirely new and innovative materials.

Jud Ready, Principal Research Engineer in Materials Science and Engineering, Georgia Institute of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Roger Alford, University of Notre Dame

Of all the reasons it could be hard to pay rent each month, did you have an algorithm-powered illegal cartel on your list?

Millions of people across the United States are paying far more rent than they can reasonably afford, with rental housing prices rising far quicker than household income. In 2022, 22.4 million U.S. households were spending more than 30% of their income on rent and utilities, up from 20.4 million in 2019.

Many of these households faced severe cost burdens, with an all-time high of 11.6 million struggling with housing costs that consume more than half of their income. In Chicago, Cincinnati, Minneapolis, Virginia Beach and Washington, year-over-year rental prices are climbing at double-digit rates.

Several factors drive the high cost of rentals, including increasing demand, a dwindling supply of low-rent units, the rising cost of capital to build new rentals, and regulatory barriers restricting the construction of multifamily units.

But there’s another surprising factor driving up rental prices: landlords colluding with the help of technology. The U.S. Justice Department is suing the company RealPage, Inc., accusing it of selling software to landlords that allows them to collectively set prices – the illegal practice of price-fixing. As a former official in the Justice Department’s Antitrust Division and a law professor, I’ve been following the case closely.

The perils of price-fixing

The Federal Trade Commission defines price-fixing as an agreement, conspiracy or combination among competitors to raise, fix or otherwise maintain the price at which their goods or services are sold.

Any agreement that restricts price competition violates the antitrust laws. Examples of price-fixing agreements include commitments among competitors to hold prices firm, adopt a standard formula for computing prices, or adhere to a minimum fee or price schedule.

So when competitors share proprietary, confidential current price information – directly or indirectly through an intermediary – to stabilize or control industry pricing, they have crossed the line into illegal collusion, according to the FTC. That is the case in major portions of the U.S. rental market, the Justice Department argues.

One algorithm for all

In August 2024, the Justice Department and eight states filed a lawsuit in a federal court in North Carolina against RealPage. The Justice Department accused the company of selling software to landlords that collects nonpublic information from competing landlords and uses that combined information to make pricing recommendations.

Landlords who use the software input the rental prices they charge, and the software aggregates all the data from the company’s customers. The software’s algorithm then makes recommendations for what to charge. The recommendations are generally higher than the current market rate, and most customers take the recommendations, which push prices in a market higher.

Even if landlords retain some authority to deviate from the algorithm’s recommendations, it is illegal for competing landlords to jointly delegate key aspects of their pricing to a common algorithm, according to the Justice Department suit. The Justice Department declared that “RealPage replaces competition with coordination. It substitutes unity for rivalry. It subverts competition and the competitive process. It does so openly and directly – and American renters are left paying the price.”

The case is unusual in that, unlike a typical price-fixing cartel, the landlords used RealPage’s algorithms to dramatically improve their ability to engage in price-fixing. Algorithmic price-fixing is typically easier and more effective than other types of cartel behavior. The software can easily aggregate massive amounts of proprietary data, optimize cartel gains, monitor real-time deviations from cartel pricing and minimize incentives to cheat.

“It’s much easier to price-fix when you’re outsourcing it to an algorithm versus when you’re sharing manila envelopes in a smoke-filled room,” Justice Department antitrust chief Jonathan Kanter told The New York Times.

Since 2022, RealPage and various property managers have been named as defendants in more than 30 class action lawsuits alleging the RealPage software is used to unlawfully fix rental prices. Federal courts tend to be sympathetic to such arguments, as shown in the denial of a motion to dismiss the case in one of the private lawsuits filed against RealPage.

In that case, the court held that a price-fixing agreement could exist as a matter of law. Landlords provided RealPage’s algorithmic system with their proprietary commercial data, knowing that RealPage would require the same from their competitors and would use all of that data to recommend rental prices to all of the company’s clients.

Classic price-fixing or data-driven decisions?

Some landlords seem to be aware that in sharing confidential price information to RealPage’s software, they were facilitating the unlawful monitoring and raising of rental prices. The Justice Department complaint quoted a landlord commenting on RealPage’s software, “I always liked this product because your algorithm uses proprietary data from other subscribers to suggest rents and term. That’s classic price-fixing.”

Even RealPage’s own executives have boasted that when landlords collectively use their software, they can use “every possible opportunity to increase price,” according to the complaint.

RealPage argued that its software “simply helps landlords make data-driven decisions” in a competitive market. The company claims its tools are designed to reflect market conditions and optimize occupancy rates, not to engage in price-fixing.

The company describes the impact of its alleged collusion with landlords as “a rising tide [that] raises all ships.” Perhaps a better description for their service is a rising tide that raises all ships for those who have one.

The Justice Department’s case and the private cases are in the early stages of litigation. If the department is successful, RealPage will be barred from engaging in the anticompetitive practices related to helping landlords share proprietary pricing information.

Roger Alford, Professor of Law, University of Notre Dame

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Beth Ann Malow, Vanderbilt University

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Why do I feel better rested when I wake myself up than I do if my alarm or another person wakes me up? – Calleigh H., age 11, Oklahoma

We’ve all experienced this: You’re in the middle of a lovely dream. Perhaps you’re flying. As you’re soaring through the air, you meet an eagle. The eagle looks at you, opens its beak and – BEEP! BEEP! BEEP!

Your alarm goes off. Dream over, time to get up.

Many people – kids and adults alike – notice that when they wake up naturally from sleep, they feel more alert than if an alarm or another person, like a parent, wakes them up. Why is that?

I’m a neurologist who studies the brain, specifically what happens in the brain when you’re asleep. I also take care of children and adults who don’t sleep well and want to sleep better. My research involves working with parents to help them teach their children good sleep habits.

To understand how to sleep better, and why waking up naturally from sleep helps you feel more alert, you need to start by understanding sleep cycles.

The sleep cycle

The sleep cycle consists of four stages. One of these is REM, which stands for rapid eye movements. The other three are non-REM stages. When you fall asleep, you first go into a state of drowsiness called non-REM Stage 1.

This is followed by deeper stages of sleep, called non-REM stages 2 and 3. Each stage of non-REM is deeper than the one before. Then, about 90 minutes after you first fall asleep, you enter the fourth stage, which is REM sleep. This is a stage of lighter sleep where you do much of your dreaming. After a few minutes, you return to non-REM sleep again.

These cycles repeat themselves throughout the night, with most people having four to six cycles of non-REM sleep alternating with REM sleep each night. As the night goes on, the cycles contain less non-REM sleep and more REM sleep. This is why it’s important to get enough sleep, so that the body can get enough of both REM sleep and non-REM sleep.

REM vs. non-REM sleep

How do researchers like me know that a person is in non-REM vs. REM sleep? In the sleep lab, we can tell from their brain waves, eye movements and the tension in their muscles, like in the chin. These are measured by putting sensors called electrodes on the scalp, around the eyes and on the chin.

These electrodes pick up brain activity, which varies from waves that are low in amplitude (the height of the wave) and relatively fast to waves that are high in amplitude (a taller wave) and relatively slow. When we are awake, the height of the waves is low and the waves are relatively fast. In contrast, during sleep, the waves get higher and slower.

Non-REM Stage 3 has the tallest and slowest waves of all the sleep stages. In REM sleep, brain waves are low in amplitude and relatively fast, and the eye movements are rapid, too. People need both non-REM and REM stages for a healthy brain, so they can learn and remember.

Waking up naturally

When you wake up in the morning on your own, it’s usually as you come to the end of whatever stage of sleep you were in. Think of it like getting off the train when it comes to a stop at the station. But when an alarm or someone else wakes you up, it’s like jumping off the train between stops, which can feel jolting. That’s why it’s good to wake up naturally whenever possible.

People can actually train their brains to wake up at a consistent time each day that is a natural stopping point. Brains have an internal 24-hour clock that dictates when you first start to feel sleepy and when you wake up. This is related to our circadian rhythms.

Training the brain to wake up at a consistent time

First, it’s important to go to bed at a consistent time that allows you to get enough sleep. If you stay up too late doing homework or looking at your phone, that can interfere with getting enough sleep and make you dependent on an alarm – or your parents – to wake you up.

Other things that can help you fall asleep at a healthy time include getting physical activity during the day and avoiding coffee, soda or other drinks or foods that contain caffeine. Physical activity increases brain chemicals that make it easier to fall asleep, while caffeine does the opposite and keeps you awake.

Second, you need to be aware of light in your environment. Light too late in the evening, including from screens, can interfere with your brain’s production of a chemical called melatonin that promotes sleep. But in the morning when you wake up, you need to be exposed to light.

Morning light helps you synchronize, or align, your circadian rhythms with the outside world and makes it easier to fall asleep at night. The easiest way to do this is to open up your shades or curtains in your room. In the winter, some people use light boxes to simulate sunlight, which helps them align their rhythms.

Benefits of a good night’s sleep

A good sleep routine entails both a consistent bedtime and wake time and regularly getting enough sleep. That usually means 9-11 hours for school-age kids who are not yet teens, and 8-10 hours for teens.

This will help you be at your best to learn at school, boost your mood, help you maintain a healthy weight and promote many other aspects of health.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Beth Ann Malow, Professor of Neurology and Pediatrics, Vanderbilt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.