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How do Olympic skateboarders catch serious airtime? Physicists crunched the numbers

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How do Olympic skateboarders catch serious airtime? Physicists crunched the numbers

Skateboarders call it “pumping,” and it’s a skill that both Olympic medalists and aspiring thrashers use to build launch speed from what seems like thin air.

But what separates the steeziest pro from the sketchiest beginner is the years’ worth of practice it takes to develop the know-how to execute the cleanest pump — or at least that was the case until now.

In a paper published Monday in the journal Physical Review Research, scientists have revealed the secret of achieving serious airtime.

A skateboarder rides the bowls at Etnies skatepark in Lake Forest. (Allen J. Schaben / Los Angeles Times)

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With a bit of coding, researchers were able to describe the optimal technique for pumping — a tactic where skateboarders crouch down low momentarily and then push their body upright on inclines. To get the highest jump, they need to do it once as they descend into the bowl, and then again as they shoot back up toward the sky.

The trick is knowing when and where to execute the maneuver.

“Pumping is the foundation of skateboarding in skate parks,” said professional skater Haden McKenna, during a morning session at the Venice Beach Skatepark. “You build off of that and learn tricks. Then the pumping just becomes something in the back of your brain.”

However, the likeliest users of the researchers’ perfect pump equation are non-humans.

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After skateboarding’s Olympic debut at the Tokyo Games, a research arm of the Japanese government reached out to Shigeru Shinomoto, a scientist at the Advanced Telecommunications Research Institute International in Japan. The organization had wondered if it was possible to build a skateboarding robot that could compete in the X Games.

The robot is still a ways off — right now it’s more like a toy that rides back and forth on a mini half-pipe — but the researchers discovered that the mechanics for good skateboarding technique can be surprisingly simple (well, at least compared to the complex fluid dynamics and neuroscience that they’re normally working on).

Kokona Hiraki of Japan crouches on her board before popping upright to pump at the Tokyo Olympics.

(Associated Press)

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“It’s just this cute little project which became much bigger than we expected,” said Florian Kogelbauer, an author on the paper and a mechanical engineering professor at the public university ETH Zürich. “People like it — it’s a fun topic. It’s easy to explain, but some serious math and computational work went into it.”

To test their calculations, study authors recruited an expert skater with over a decade of experience, and a novice with just two years under their belt. They told the skaters to catch as much air as possible on a half-pipe erected in a research lab.

The result: The pro much more closely matched their calculated optimal motion than the amateur. (Ideally the skater would pop up instantaneously, but the researchers conceded that humans lack the unlimited muscle strength to do this — plus it would send the skater flying off their board.)

“The experiment seems to agree well,” said Frank Feng, a mechanical engineering professor at the University of Missouri who was not involved with the paper, but studied similar motions in half-pipe snowboarding.

Feng said the simple physics model gets researchers most of the way there, then the computer optimization is able to account for complexities that the physics equations can’t handle.

While the study was mostly just for fun, it snowballed into a fairly big project, and ended up getting published in one of the world’s premier physics journals. Part of the reason is that it may have some serious implications for how to get robots to move effectively without face-planting all the time.

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It could help human skateboarders, too. Feng said the results could be used as a straightforward guide to help skateboarders train.

However, some question whether skaters would be able to use the information in the moment.

“This graph, showing the mass going up, is very helpful for somebody that can understand that,” said pro skater McKenna, who was not involved in the research. “But when you’re teaching kids and you’re trying to teach somebody that’s focused in the moment of skateboarding, they’re not going to be able to bring math into the equation.”

Also, out in the complex terrain of the park, the technique gets a bit more nuanced than a simple model the physicists developed. You need to flow as “one with the wall,” said McKenna. “Like what Bruce Lee says, ‘Be like water.’”

A skateboard descends a steep ramp.

Skateboarder Greyson Godfrey, 20, of Rancho Santa Margarita drops into the bowl at Etnies Skate Park Lake Forest.

(Allen J. Schaben / Los Angeles Times)

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While the researchers’ optimal solution may not always be the best suited for real-world conditions, it does help to illustrate the physics behind the technique.

Studio Gutierrez, who teaches skateboarding as a sports instructor to middle schoolers in the Los Angeles Unified School District, finds understanding the science helpful for new skaters. “I explain it to them in physics motions,” he said. “The more motion, the faster you go, the higher you get.”

The physics works similarly to how ice skaters increase the speed of their spinning in the Winter Olympics, said Kogelbauer. They start out spinning slow with their limbs extended outward. Then, they tuck their arms and legs in, causing them to spin faster.

Skateboarders also gain speed by using this technique on curved surfaces.

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When a skateboarder hits the circular section of the half-pipe, they start crouched down, positioning their center of mass further from the center of rotation above their head. As they climb the curved ramp, they pop up and bring their center of mass closer to the center of rotation, and they speed up.

While the pumping paper is one of the first to capture the physics of pumping, its authors aren’t the only ones studying the motion of skateboarding.

Google has also taken a stab at a more complex understanding with its Project Skate. It’s using AI to identify different tricks and motions — but AI requires a lot of computing power that many researchers who aren’t Google don’t have access to.

“They have [essentially] unlimited resources. If they want to, they can take a new server farm and then run trajectories as much as they want.” said Kogelbauer. “That’s what Google does. We’re not Google.”

If you’d like to study pumping physics on your own, you can tune in to the Paris Olympics. The women skateboarders are scheduled to compete in the park event (as opposed to the street event, which has fewer curved surfaces for pumping) Tuesday morning. The men are scheduled for Wednesday.

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McKenna has always seen skating more as an art form and community than a sport, but he’s stoked to watch nonetheless. “When I was a kid, which doesn’t seem that long ago, skateboarding was a crime, literally,” he said. “Now we’re winning gold medals in the Olympics.”

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‘Grief into action.’ Philanthropists give historic $150 million donation to City of Hope for pancreatic cancer research

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‘Grief into action.’ Philanthropists give historic 0 million donation to City of Hope for pancreatic cancer research

For entrepreneur and philanthropist Emmet Stephenson Jr., seeing his wife and friends die from pancreatic cancer served as a wake-up call.

His wife, Toni, a patient at Duarte, Calif.-based cancer center City of Hope, died at 74 after a four-month battle with pancreatic cancer.

Now Emmet and his daughter Tessa are donating a historic $150 million to the City of Hope to help advance research into finding a cure for what’s known as the “silent killer.”

“We decided we were going to turn our grief into action and we wanted as few people as possible to go through what we did,” said Tessa Stephenson Brand. “It was fast. It was painful.”

The donation is the largest single gift the City of Hope has ever received, surpassing the $100 million Panda Express founders Andrew and Peggy Cherng gave to the nonprofit last year.

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World-renowned geneticist and diabetes expert Dr. Arthur Riggs also donated $100 million in 2021 to his longtime employer City of Hope before he passed away from a battle with a type of blood cancer known as lymphoma.

To help fuel the development of treatment and cures for pancreatic cancer, the Stephensons’ donation will help fund a $1 million prize that will be awarded annually (beginning in 2025) to a scientist or team that’s leading innovation in this field.

Pancreatic cancer research is underfunded and the City of Hope is trying to find new ways to cut down on bureaucracy so researchers and scientists can make progress at a faster rate, said Robert Stone, the chief executive of City of Hope. The gift equals nearly two-thirds of the total annual research budget for pancreatic cancer from the National Cancer Institute, City of Hope said in a news release about the donation.

“We’re trying to leapfrog and bring new ideas to challenge how research has been done traditionally,” Stone said.

Emmet Stephenson said the donation, which is expected to be spread out over 10 years, will also help fund grants, an annual symposium and a facility that collects tissues, blood and other materials needed for pancreatic cancer research.

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“If we were to get lucky and find a cure for pancreatic cancer soon, then we’re happy to have the money go to the next most deadly disease in the cancer arena,” he said. Stephenson is the retired co-founder and chairman of tech company StarTek .

Pancreatic cancer is the third-leading cause of cancer death in the United States, according to the National Cancer Institute. In 2024, about 66,440 people nationwide will be diagnosed with pancreatic cancer and 51,750 people will die from this disease, according to estimates from The American Cancer Society.

Located behind the stomach, the pancreas is a large gland that helps people digest food and regulate blood sugar. Pancreatic cancer occurs when abnormal cells in the gland multiply, forming a tumor.

Dr. Daniel D. Von Hoff, a professor and cancer scientist at the Translational Genomics Research Institute in Phoenix, that is a part of the City of Hope, said pancreatic cancer is hard to detect early partly because the pancreas is tough to image and people often don’t show symptoms.

Some of the risk factors include smoking, obesity, alcohol and diabetes that can cause inflammation in the body. Pancreatic cancer is also on track to become the second-leading cause of cancer-related deaths before 2030 as the population ages. It’s most frequently diagnosed in people between the ages of 65 to 74, according to the National Cancer Institute.

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Known as the “silent killer,” people often don’t show symptoms, which includes fatigue, belly pain and a loss appetite, before the cancer cells have multiplied.

“It’s like a toothache many people describe and so it’s kind of throbbing,” Von Hoff said. “By that time, it’s probably too late.”

Genetic testing, especially if you have a history of cancer in your family, could help detect a tumor early. Still, it’s possible to get pancreatic cancer at a young age.

Toni Bravo, a 21-year-old student who grew up in Tarzana, said she went to the emergency room last year because she was experiencing anxiety. After she got a CT scan, doctors in Indiana found a rare tumor on her pancreas. She became a patient at the City of Hope where she underwent surgery to remove the tumor from her pancreas.

The scariest part, she said, was she didn’t really have any symptoms or a history of pancreatic cancer.

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As a pancreatic cancer survivor, Bravo isn’t letting the diagnosis define her life and urges people to listen to their bodies.

“The journey is hard,” she said. “Having the love of others makes it easier…and having that mental strength makes the journey possible.”

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Are tiny black holes zipping through our solar system? Scientists hope to find out

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Are tiny black holes zipping through our solar system? Scientists hope to find out

A mind-bending hypothesis is gaining traction among scientists: The universe may be teeming with microscopic black holes the size of an atom, but with the mass of a city-sized asteroid.

Created just a split second after the Big Bang, these hypothetical black holes would whip quietly through the solar system roughly once every few years, traveling over a hundred times faster than a bullet.

Some have even argued that an immense explosion that flattened a Siberian forest in 1908 could have been the result of one of these micro black holes impacting Earth.

Now, researchers say they’ve figured out a way to test whether these cosmic bullets truly exist.

In a study published Tuesday in the journal Physical Review D, physicists at MIT say the presence of a tiny black hole speeding through the solar system could be identified by the gentle gravitational nudge it exerted on the Earth and other planets, which would alter their orbital paths by no more than a few feet.

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The possibility of proving the existence of micro black holes is generating excitement among some astrophysicists because it could help them to explain a mystery that has taunted them for almost a century: the nature and composition of dark matter.

In the 1930s, astronomers started noticing anomalies in the way galaxies were moving. Lurking in the dark and empty expanse of intergalactic space, something was generating tremendous amounts of gravity to tug on the galaxies — yet it seemingly refused to interact with light or any other force.

Scientists found this mysterious gravitational tugging everywhere. In order to account for it, they hypothesized that it was being caused by invisible mass, or dark matter, that made up roughly 85% of all matter in the universe.

Some physicists have suggested dark matter may be made up of exotic undiscovered particles. Others, such as the MIT researchers, think dark matter probably is just regular matter that is extremely hard to detect. And black holes, the researchers say, are a prime example of the properties of dark matter.

“It’s just fantastic that the most conceptually conservative response is to say, ‘It’s just super tiny black holes that were made a split second after the Big Bang,’” said David Kaiser, a physics professor at MIT and an author on the study.

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“It’s not inventing new forms of matter that have not yet been detected. It’s not changing the laws of gravity,” he said.

Still, black holes are not the sole potential culprit and there remains a lot of debate in the field.

Physicists have, in their quest to find dark matter, searched for new exotic particles, as well as regular matter that may have been overlooked — such as black holes of varying sizes. So far, they have come up empty-handed.

Until now, astronomers have been unsure how to search for black holes of a particularly pesky size — those that are too small for their gravity to bend star light.

The MIT researchers determined, through modeling, that these tiny black holes may have formed from pockets of dense matter that collapsed on themselves immediately following the Big Bang.

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The researchers simulated what might happen if one of these primordial black holes made a flyby within the orbit of Jupiter. They found that the orbits of Earth, Mars, Venus and Mercury could veer off their original course by up to 3 feet over a decade.

The researchers said they would expect to detect a black hole nudge somewhere between once a year to once every century — depending on the abundance and masses of the black holes.

To put their own minds at ease, the researchers also calculated the likelihood that one of these tiny black holes would strike Earth and found it would only happen roughly once in a billion years.

Even then, the black hole wouldn’t lead to an apocalypse.

Instead, it would pass straight through the Earth, leaving the planet relatively unbothered.

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Scientists in the 1970s even showed that a black hole impact would look strikingly similar to an streaking light and explosion over Russia 116 years ago that scientists believe was caused by a small asteroid or comet. (Although, a black hole would also leave an “exit wound.”)

Detecting the existence of mini black holes will require extremely precise measurements of where planets are and models of where they’re supposed to be. Fortunately, scientists have the tools to accomplish this.

NASA’s Jet Propulsion Laboratory in La Cañada Flintridge, for example, has created a detailed model of the solar system that uses Albert Einstein’s general relativity theory of gravity to calculate the expected orbits of the planets and account for hundreds of asteroids in excruciating detail. (They even calculated how the Earth’s ocean tides affect the moon’s orbit.)

NASA scientists also have developed an extremely precise means of determining the distance between the Earth and Mars. By measuring the time it takes radio signals to travel from Earth to spacecraft orbiting Mars, or to rovers on its surface, scientists can calculate the red planet’s distance from Earth within two feet.

“It’s really only a few decades where we’ve had that level of accuracy,” Kaiser said. “From a series of space program missions, we can worry about if Mars is 50 centimeters off from where we expect it to be.”

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To convince the skeptics, the scientists also would have to show that the nudge wasn’t caused by a passing asteroid.

The researchers say that the speed of the black holes — which would be traveling more than two times faster than anything else in our solar system — would create an unmistakably unique wobble in the planets’ orbits.

And astronomers are pretty good at spotting objects with a mass similar to that of the hypothetical black holes. In 2017, researchers identified the first object from another star to enter our solar system, which had far less mass than a microscopic black hole would.

Whether or not they detect a passing black hole, the scientists say it will push forward humanity’s understanding of dark matter.

“Of course I’d love to discover dark matter in the solar system,” said Benjamin Lehmann, a postdoctoral student at MIT and an author of the study. However, “if this kind of observation is what helps us to close this window and say dark matter is not in the form of these primordial black holes, that’s really important information.”

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By proposing a method for simply testing this possibility, “they’ve done … exactly what we should be doing in dark matter searches,” said Vera Gluscevic, a cosmology professor at USC who was not involved with the study. “We should not leave any stone unturned.”

Although the scientists plan to keep refining planetary motion models and dig through historical observations from the last few decades for signs of the black holes, the main test will be to simply watch and wait.

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Tooth decay still plagues California kids nearly a decade after Medi-Cal promised change

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Tooth decay still plagues California kids nearly a decade after Medi-Cal promised change

Eight years after an independent state watchdog agency harshly criticized the state for failing to provide dental care to low-income children, California has failed to remedy the problem or fully implement the commission’s recommendations, according to a follow-up review published last week.

The Little Hoover Commission found that less than half of the children in Medi-Cal received an annual dental visit in 2022 — 3% higher than when the initial report was released in 2016, which implored the state to do more to ensure that children have access to needed care.

“California is still doing a miserable job,” said Pedro Nava, chair of the commission and a former member of the state Assembly. “We have failed generations of children. We and they deserve better.”

The 2016 report was one of the most scathing reports that the commission had generated in years, Nava said. It found that only 44.5% of children in the Medi-Cal program had a visit with a dentist in 2016, a key indicator of whether children are receiving the care they need to prevent painful dental decay, and recommended that the state increase the rate to 66%. Lawmakers responded with a law requiring the health department to set a target of at least 60% of children.

Last fall, after the publication of an L.A. Times story on high rates of dental disease among California children, the commission initiated a follow-up review of the state’s progress.

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It found that the state had fallen far short of the goal; in 2022, the most recent data provided in the report, 47.6% of children with Medi-Cal visited a dentist, a 3-percentage-point increase from 2016.

“If you were an investor in a private company, and that was the best they could do, you’d sell your stock and invest it somewhere else,” Nava said. “It is a disappointment that low-income families with children have to shoulder the burden of this every day.”

Engage with our community-funded journalism as we delve into child care, transitional kindergarten, health and other issues affecting children from birth through age 5.

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California has made some improvements since 2016, the report said, fully implementing one recommendation and partially implementing seven of the commission’s eight others.

The state health department, however, disputes those findings and said they have fully implemented all of the recommendations from the 2016 report. The percentage of kids going to the dentist had been increasing significantly, they said — up to 49.6% in 2019 — but the pandemic interrupted that growth.

“California, along with every other state in the nation, was profoundly impacted by the effects of the COVID-19 pandemic. Virtually every state within the U.S. decreased and had a recovery period that lasted at least two years to return to pre-COVID figures,” the Department of Health Care Services wrote in a statement provided to The Times.

Since 2016, the department has made a number of important changes, the department wrote, including expanding the use of tele-dentistry to reach members across the state, increasing provider networks and creating a public education and outreach media campaign for Medi-Cal patients and providers.

In 2023 the percentage of children who visited the dentist “recovered to 2019 levels. Even higher utilization is projected in 2024,” the health department said, although data have not been been released on this upward trend.

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“I don’t think this response really questions the fact that they have not come close to reaching the recommendation set by the Legislature of 60% of kids getting in to see the dentist, let alone our rate of 66%,” said Ethan Rarick, executive director of the Little Hoover Commission. “Kids’ dental health is among the worst in the country, and much more needs to be done.”

California children have among the worst rates of dental disease in the nation. A national survey from 2020 to 2021 found that 14.8% of the state’s children ages 1 to 17 had decayed teeth or cavities in the last 12 months studied — ranking 47th out of 51 among all the states and the District of Columbia, with only Louisiana and Wyoming faring worse. “I don’t understand,” Nava said. “If you’re the fifth-largest economy in the world, you ought to be a leader in children’s health.”

Nationwide, more than half of children develop cavities by the age of 8, usually because of poor nutrition, bad hygiene habits or a lack of dental care.

The reality of dental disease can be devastating to children, causing pain and difficulty eating, sleeping and focusing in school, and low-income children of color are at greatest risk. L.A. County’s Smile Survey, which was conducted by the public health department, found that on any given day, more than 4,500 Los Angeles County kindergarten and third-grade children need urgent dental care, which means they may be experiencing mouth pain or a serious infection.

The state increased the payment rate for evaluating a child’s teeth, for example, from $15 to $45, and up to $100 if a dentist sees the same child two years in a row, according to the California Dental Assn. The reimbursement for a filling increased from $48 to $67.20. These rate increases were funded by Proposition 56, a 2016 tobacco tax that raised money for Medi-Cal payments, and by CalAIM, a state initiative to transform Medi-Cal. The Proposition 56 money was also used to fund county oral health plans and repay student loans for new dentists.

The state has made it easier for dentists to enroll as Medi-Cal providers by simplifying the enrollment forms and putting them online, the report said. It also began a pilot program for telehealth to help bring care to healthcare deserts through the Dental Transformation Initiative.

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Between the Medi-Cal payment rate and fewer administrative burdens, dentists appear to have taken note: 40% of all California dentists in the state now take Medi-Cal, a 34% increase since 2017, according to the dental association.

“The program had such a huge hole to dig out of, and COVID really derailed everything,” said Brianna Pittman-Spencer, senior director of government affairs at the California Dental Assn. “There have been improvements but obviously still a long way to go for the impact we want.”

Eileen Espejo, who leads the oral health project at Children Now, said she was pleased to see that the state had at least started to implement most of the recommendations, but that the numbers suggest the approach may not be working. “If we’re going to do better, it doesn’t seem like we should do more than the same,” she said.

In particular, she worries about children in far northern counties and those bordering Nevada, where dentists are hard to find. Twenty-one counties have five or fewer dental providers that take Medi-Cal, the report found. “How are we going to get providers to live in parts of the state where they aren’t yet?” she asked, adding that using more telehealth dentistry and allowing dental hygienists to provide more care could be part of the solution.

“Hopefully this report will light a fire and get more people engaged,” Espejo said. “I certainly think it opens the pathway for advocates to ask for more resources to help improve the program.”

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This article is part of The Times’ early childhood education initiative, focusing on the learning and development of California children from birth to age 5. For more information about the initiative and its philanthropic funders, go to latimes.com/earlyed.

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