theconversation.com – Andrew Dickerson, Associate Professor of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee – 2025-02-28 07:43:00
When wind or other disturbances detach winged maple seeds called samaras from their parent tree, they spin through the air – and can even spin when it’s raining. Impacts by high-speed raindrops only briefly interrupt the seed’s spinning because the seed can shed the drop rapidly and restart its spinning in less time than it takes to blink.
If you live somewhere with maple trees, you’ve probably seen their striking helicopter seeds – made up of a seed pod attached to a delicate wing. Maple samaras’ unique design and spinning movement can teach physicists like me about seed dispersal patterns and even engineering new types of flying vehicles.
The samaras’ spinning movement, called autorotation, keeps them in the air for longer so they travel farther.
The spinning flight of a maple samara.
In a February 2025 study, my colleagues and I filmed raindrops as they crashed into autorotating samaras. The samaras shed drops by shattering them, flinging the drops off, or rolling out of the way – like they’re turning away from a punch. If a drop falls in just the right place, the spinning seed can cut it in half.
The movement of a samara as it spins through the air. Our new study captured this pattern using a high-speed camera. Breanna Shaeffer and Andrew Dickerson, University of Tennessee-Knoxville
In order to keep flying, the samaras must shed the entire drop. Samaras shed drops fastest when the drops hit the heavier, round nutlet part of the seed, rather than the wing. Shedding is made easier by the samaras’ mildly water-repellent surface. We estimated that raindrop collisions reduce a samara’s time in flight and the distance it travels while spinning, but by less than 10%.
Why it matters
Maples are an important species to the Eastern United States. They provide syrup and timber, making them economically and commercially significant.
My team’s results provide context for other studies focused on how wind transports rotating and nonrotating seeds alike. Some seeds can even travel hundreds of miles.
From an engineering perspective, the insights gained from our study could inform the design of new types of aerial vehicles that use autorotation to ride the wind without a motor. Mimicking the shapes of these seeds could help such vehicles quickly recover from disruptions to flight.
Samaras are also visually intriguing. Discovering more about how small, beautiful parts of nature thrive could help scientists get people interested in the environment.
What still isn’t known
Maple samaras represent just one way that seeds use the wind to disperse farther. A dandelion’s parachute-like float relies on the seed’s light weight and high drag. A hop tree seed uses a single, wafer-shaped seed to flutter, while triplaris seeds have three wings that achieve a helicopter-like spin. Researchers still aren’t sure how raindrops can affect the flight of these seeds.
What’s next
Next, my colleagues and I hope to unravel the flight mechanics of the “rolling samaras” found on tulip poplar and ash trees. These seeds rotate like maple samaras, but the wing also rolls around the axis that runs across its wingspan as it does so.
Not only do we plan to compare their flight performance against the more recognizable maple samara, but we will also study how these seeds respond to perturbations such as wing damage and crosswinds.
How I do my work
I like to uncover the complexity in seemingly simple systems. So many of the brief, small and common interactions in our world are wonderfully beautiful. I seek to tell those stories through a camera lens and with mathematical flair.
Healthy coastal ecosystems play crucial roles in the U.S. economy, from supporting multibillion-dollar fisheries and tourism industries to protecting coastlines from storms.
They’re also difficult to manage, requiring specialized knowledge and technology.
That’s why the National Oceanic and Atmospheric Administration – the federal agency best known for collecting and analyzing the data that make weather forecasts and warnings possible – leads most of the government’s work on ocean and coastal health, as well as research into the growing risks posed by climate change.
The government estimates that NOAA’s projects and services support more than one-third of the nation’s gross domestic product. Yet, this is one of the agencies that the Trump administration has targeted, with discussions of trying to privatize NOAA’s forecasting operations and disband its crucial climate change research.
As a marine environmental historian who studies relationships among scientists, fishermen and environmentalists, I have seen how NOAA’s work affects American livelihoods, coastal health and the U.S. economy.
Here are a few examples from just NOAA’s coastal work, and what it means to fishing industries and coastal states.
Preventing fisheries from collapsing
One of the oldest divisions within NOAA is the National Marine Fisheries Service, known as NOAA Fisheries. It dates to 1871, when Congress created the U.S. Commission of Fish and Fisheries. At that time, the first generation of conservationists started to worry that America’s natural resources were finite.
By conducting surveys and interviewing fishermen and seafood dealers, the fish commissioners discovered that freshwater and saltwater fisheries across the country were declining.
Looking back on 150 years of NOAA’s fisheries history.
Oil spills and raw sewage were polluting waterways. Fishermen were using high-tech gear, such as pound nets, to catch more and more of the most valuable fish. In some areas, overfishing was putting the future of the fisheries in jeopardy.
One solution was to promote aquaculture, also known as fish or shellfish farming. Scientists and entrepreneurs reared baby fish in hatcheries and transferred them to rivers, lakes or bays. The Fish Commission even used refrigerated railroad cars to ship fish eggs across the country.
Men carry pails of fish specimens to a U.S. Fish Commission ‘fish car’ – a train car designed specifically for transporting fish or fish eggs to stock U.S. rivers, lakes and coastal waters – in this historical photo. Smithsonian Institution Archives
Corals build up reefs over centuries, creating “cities of the sea.” When they’re healthy, they provide nurseries that protect valuable fish species, like snapper, from predators. Reefs also attract tourism and protect coastlines by breaking up waves that cause storm-driven flooding and erosion.
The corals of Hawaii, Florida, Puerto Rico and other tropical areas provide over $3 billion a year in benefits – from sustaining marine ecosystems to recreation, including sport fishing.
A third important aspect of NOAA’s coastal work involves controlling invasive species in America’s waters, including those that have menaced the Great Lakes.
Zebra and quagga mussels, spiny water flea and dozens of other Eurasian organisms colonized the Great Lakes starting in the late 1900s after arriving in ballast water from transoceanic ships. These invaders have disrupted the Great Lakes food web and clogged cities’ water intake systems, causing at least $138 million in damage per year.
Zebra mussels found attached to this boat at an inspection station in Oregon show how easily invasive species can be moved. The boat had come from Texas and was on its way to Canada. Oregon Department of Fish & Wildlife, CC BY-SA
In the Northwest Atlantic, Caribbean and Gulf of Mexico, invasive lionfish, native to Asia and Australia, have spread, preying on native fish essential to coral reefs. Lionfish have become one of the world’s most damaging marine fish invasions.
When Republican President Richard Nixon proposed consolidating several different agencies into NOAA in 1970, he told Congress that doing so would promote “better protection of life and property from natural hazards,” “better understanding of the total environment” and “exploration and development leading to the intelligent use of our marine resources.”
The Trump administration is instead discussing tearing down NOAA. The administration has been erasing mentions of climate change from government research, websites and policies – despite the rising risks to communities across the nation. The next federal budget is likely to slash NOAA’s funding.
Commercial meteorologists argue that much of NOAA’s weather data and forecasting, also crucial to coastal areas, couldn’t be duplicated by the private sector.
As NOAA marks its 55th year, I believe it’s in the nation’s and the U.S. economy’s best interest to strengthen rather than dismantle this vital agency.
The Conversation asked epidemiologistAnnette Regan to explain why this flu season is different from last year’s and what people can do to help reduce the spread.
How do flu cases and hospitalizations this year compare with previous years?
Beginning in late January and extending through February 2025, flu hospitalizations have been higher than any other week since before 2009.
Most flu cases appear to be from influenza A strains, with a split between influenza A/H3N2 and influenza A/H1N1. These are two different subtypes of the influenza A virus.
Researchers believe that historically seasons that are predominated by influenza A/H3N2 infections tend to be more severe, but infections from influenza A/H1N1 can still be very severe.
This year’s season is also peaking “late” compared with the past three flu seasons, which peaked in early or late December.
Unfortunately, there have been a number of deaths from flu too this season. Since Jan. 1, 2025, alone, over 4,000 people, including 68 children, have died from flu. While the number of deaths do not mark a record number, it shows that flu can be a serious illness, even in children.
Unless directed otherwise, everyone ages 6 months and older should get a flu shot.
Why are flu cases so high this year?
There are a number of factors behind any severe season, including poor community protection from low immunization rates and low natural immunity, virus characteristics, vaccine effectiveness and increased human contact via travel, office work or schools.
Unfortunately, flu vaccination rates have declined since the COVID-19 pandemic. At the end of the 2023-24 flu season, 9.2 million fewer doses were administered in pharmacies and doctors’ offices compared with an average year before the pandemic.
Flu vaccination rates began dropping after the COVID-19 pandemic, especially in higher-risk groups. Flu vaccination in children has dropped from 59% in 2019-20 to 46% in 2024-25. In adults 65 years and older, the group with the greatest risk of hospitalization and death, flu vaccination rates dropped from 52% in 2019-20 to 43% in 2024-25.
Lower vaccination rates mean a greater portion of the population is not protected by vaccines. Data shows that vaccination reduces the risk of flu hospitalization. Even if a vaccinated person gets infected, they may be less likely to experience severe illness. As a result, low vaccination rates could contribute to higher flu severity this season.
However, low vaccination rates are probably not the only reason for the high rates of flu this season. In previous severe seasons, genetic changes to the viruses have made them better at infecting people and more likely to cause severe illness.
The effectiveness of annual flu vaccines varies depending on how well the vaccine matches the circulating virus. The effectiveness of vaccines ranges from 19% to 60% in any given season. In the 2023-24 flu season, the vaccine was 42% effective.
Similarly, early 2024-25 data from the U.S. shows that the vaccine was 41% to 55% effective against flu hospitalizations in adults and 63% to 78% effective against flu hospitalizations in children.
Something as simple as regular handwashing could keep you from getting the flu.
How do seasonal flu symptoms differ from COVID-19 and other illnesses?
It’s important to remember that people often incorrectly refer to “the flu” when they have a common cold. Flu is caused only by the influenza virus, which tends to be more severe than common colds and more commonly causes a fever.
Many of the signs and symptoms for flu, COVID-19 and other respiratory viruses are the same and can range from mild coldlike symptoms to pneumonia and respiratory distress. Common flu symptoms are fever, cough and fatigue, and may also include shortness of breath, a sore throat, nasal congestion, muscle aches and headache.
Some symptoms, such as changes in or loss of taste and smell, are more common for COVID-19. For both COVID-19 and flu, the symptoms do not start until about one to four days after infection, and symptoms seem to last longer for COVID-19.
The only way to know what virus is causing an infection is to test. This can be done using a rapid test, some of which now test for flu and COVID-19 together, or by seeing a doctor and getting tested using a nasal swab. There are prescription antiviral medications available to treat flu and COVID-19, but they need to be taken near the time that symptoms start.
Some people are at high risk of severe flu and COVID-19, such as those who are immunosuppressed, have diabetes or have chronic heart or lung conditions. In these cases, it is important to seek early care and treatment from a health care professional. Some doctors will also prescribe via telehealth calls, which can help reduce the strain on doctors’ offices, urgent care centers and emergency rooms when infection rates are high.
What can people do now to help steer clear of the flu?
There are a number of ways people can reduce their risk of getting or spreading flu. Since the flu season is still underway, it’s not too late to get a flu vaccine. Even in seasons when the vaccine’s effectiveness is low, it is likely to offer better protection compared with remaining unvaccinated.
Handwashing and disinfecting high-traffic surfaces can help reduce contact with the flu virus. Taking efforts to avoid contact with sick people can also help, including wearing a mask when in health care facilities.
Those who have been diagnosed with flu or are experiencing flu-like symptoms should avoid contact with other people, especially in crowded spaces. Covering coughs and sneezes can help reduce the amount of virus that is spread.
Texas records first US measles death in 10 years – a medical epidemiologist explains how to protect yourself and your community from this deadly, preventable disease
theconversation.com – Daniel Pastula, Professor of Neurology, Medicine (Infectious Diseases), and Epidemiology, University of Colorado Anschutz Medical Campus – 2025-02-28 07:46:00
Texas records first US measles death in 10 years – a medical epidemiologist explains how to protect yourself and your community from this deadly, preventable disease
In an interview with The Conversation U.S. associate health editor Alla Katsnelson, neurologist and medical epidemiologist Daniel Pastula explains why measles is so dangerous and how people and communities can protect themselves from the virus.
What is measles, and where does it come from?
Measles is an ancient disease caused by a virus that probably evolved in cattle and jumped into humans around 500 B.C. One of the first written accounts of it comes from a Persian physician named Rhazes in the ninth century C.E., and measles epidemics were described in medieval Europe and western Asia regularly beginning around 1100-1200. The virus got brought over to the Americas in the 1500s, and it wiped out large populations of native people as Europeans colonized the continent.
By the 1950s in the United States, there were 500,000 reported cases of measles each year – though the true number was probably closer to 4 million . It was so contagious, every kid was thought to have gotten measles by age 15. At that time, measles caused close to 50,000 hospitalizations annually and about 500 deaths, usually in children. It also caused over 1,000 cases of severe brain inflammation every year.
Since then, there have been occasional minor flare-ups, usually brought in by international travelers, but by and large, measles outbreaks have been rare. No one had died of it in the United States in nearly a decade.
Today, measles infections in the U.S. are almost completely preventable with vaccination.
About 10 to 14 days after infection, people suffering from measles experience a very high fever, cold-like symptoms including a runny nose and sneezing, and eye inflammation called conjunctivitis.
Next, they may develop white spots called Koplik spots inside their mouth and a diffuse, spotty, red rash that starts at the head and neck, then descends across the entire body. This rash is where the disease gets its name – the word “measles” is thought to come from a medieval Dutch word for “little blemishes.”
Symptoms of measles infection take about three weeks to resolve. People are contagious from about four days before symptoms emerge to four days after the rash starts.
What are the possible severe outcomes of measles?
Epidemiologists estimate that 1 in 5 people who are infected with measles get sick enough to be hospitalized. About 1 in 10 develop ear infections, some of which may result in permanent deafness.
About 1 in 20 people develop severe measles pneumonia, which causes trouble breathing. Reports from west Texas this month suggest that many infected children there have measles pneumonia.
About 1 in 1,000 people develop severe brain swelling. Both measles pneumonia and brain swelling can be fatal. About 3 in 1,000 people die after contracting measles.
In about 1 in 10,000 who get sick with measles and recover from it, the virus lies dormant in the brain for about a decade. It then can reactivate, causing a severe, progressive dementia called subacute sclerosing panencephalitis, which is fatal within one to three years. There is no treatment or cure for the disease. I have seen a couple of suspected cases of subacute sclerosing panencephalitis, and none of these patients survived, despite our best efforts.
Given how contagious measles is and how severe the outcomes can be, physicians and public health experts are gravely concerned right now.
How does measles spread?
Measles is one of the most contagious infectious diseases on the planet. The virus is so infectious that if you are in a room with an infected person and you are not vaccinated and have never had measles before, you have a 90% chance of becoming infected.
The measles virus is transmitted by droplets released into the air by infected people when they cough, sneeze or simply breathe. Virus particles can survive suspended in the air or on indoor surfaces for up to two hours, so people can get infected by touching a surface carrying virus particles and then touching their face.
Who should get the measles vaccine, and how effective is it?
The vaccine for measles has historically been called the MMR vaccine because it has been bundled with vaccines for two other diseases – mumps and rubella. Most children in the U.S. receive it as a two-dose regimen, which is 97% effective against measles.
Children generally get the first dose of the vaccine at 12-15 months old and the second dose when they are 4-6 years old. Infants who haven’t reached their first birthday generally do not receive it since their immune system is not yet fully developed and they do not develop quite as robust of an immune response. In an emergency, though, babies as young as 6 to 9 months old can be vaccinated. If an infant’s mother previously received the MMR vaccine or had been infected herself as a child, her transferred antibodies probably offer some protection, but this wanes in the months after birth.
People born before 1957 are considered immune without getting the vaccine because measles was so widespread at that time that everyone was presumed to have been infected. However, certain people in this age group, such as some health care workers, may wish to discuss vaccination with their providers. And some people who had the original version of the vaccine in the 1960s may need to get revaccinated, as the original vaccine was not as effective as the later versions.
In recent years, vaccination rates for measles and other diseases have fallen.
Based on available evidence, the vaccine is effective for life, so people who received two doses are most likely protected.
A single dose of the vaccine is 93% effective. Most people vaccinated before 1989 got just one dose. That year, an outbreak in vaccinated children with one dose spurred public health officials to begin recommending two doses.
People with certain risk factors who received only one dose, and everyone who has never received a dose, should talk to their health care providers about getting vaccinated. Because the vaccine is a live but weakened version of the virus, those who are severely immunocompromised or are currently pregnant cannot get it.
People who are immunocompromised, which includes those who have chronic conditions such as autoimmune disorders, are undergoing certain cancer treatments or have received an organ transplant, are more susceptible to measles even if they have been vaccinated.
In the current measles epidemic in Texas, the vast majority of people falling ill are unvaccinated. Public health officials there are urging unvaccinated people in affected areas to get vaccinated.
What measures can protect communities from measles outbreaks?
Vaccination is the best way to protect individuals and communities from measles. It’s also the most effective way to curb an ongoing outbreak.
High rates of vaccination are important because of a phenomenon called herd immunity. When people who are vaccinated do not get infected, it essentially stops the spread of the virus, thereby protecting those who are most susceptible to getting sick. When herd immunity wanes, the risk of infection rises for everyone – and especially for the most vulnerable, such as young children and people who are immunocompromised.
Because measles is so contagious, estimates suggest that 95% of the population must be vaccinated to achieve herd immunity. Once vaccine coverage falls below that percentage, outbreaks are possible.
Having robust public health systems also provides protection from outbreaks and limits their spread. Public health workers can detect cases before an outbreak occurs and take preventive steps. During a measles outbreak, they provide updates and information, administer vaccines, track cases and oversee quarantine for people who have been exposed and isolation for people who are contagious.
