Eating One US Fish Is Equivalent To Drinking a Month's Worth of Contaminated Water, Study Finds 117
To find out PFAS contamination in locally caught fish, a team of researchers analyzed more than 500 samples from rivers and lakes across the United States between 2013 and 2015. The median level of PFAS in the fish was 9,500 nanograms per kilogram, according to a study published in the journal Environmental Research. Nearly three quarters of the detected "forever chemicals" were PFOS, one of the most common and hazardous of the thousands of forms of PFAS. Eating just one freshwater fish equalled drinking water with PFOS at 48 parts per trillion for a month, the researchers calculated. Last year, the Environmental Protection Agency lowered the level of PFOS in drinking water it considers safe to 0.02 parts per trillion. The total PFAS level in the freshwater fish was 278 times higher than what has been found in commercially sold fish, the study said. "This study is important because it provides the first evidence for widespread transfer of PFAS directly from fish to humans," said David Andrews, a senior scientist at the non-profit Environmental Working Group, which led research. He's calling for much more stringent regulation to bring an end to all non-essential uses of PFAS.
The new findings appear in the journal Environmental Research.
Lab-Grown Alternatives Aim To Cut Palm Oil Dependence (bbc.com) 59
Palm oil remains the world's most-produced vegetable oil, accounting for 40% of the total, according to the World Wide Fund for Nature (WWF). [...] The widely-documented problem with this usage is that this demand for palm oil has led to significant deforestation in areas where oil palm trees can grow -- low-lying, hot, wet areas near the equator. The use of this land for palm oil cultivation, 85% of which is in Indonesia and Malaysia, has increased almost nine-fold from 3.3 million hectares (eight million acres) in 1970 to 28.7 million hectares in 2020. In financial terms, one report valued the worldwide palm oil industry at $62.3 billion in 2021. And such is the continuing growth in demand, this figure is expected to increase to $75.7 billion by 2028.
To try to reduce the world's reliance on palm oil, Ms Ticku, who was formerly an investment banker, and her co-founders set up C16 Biosciences in New York City in 2018. Backed by multi-million dollar funding from Microsoft founder Bill Gates, the company has spent the past four years developing and finessing their product, which is called Palmless. They grow a strain of yeast that naturally produces an oil with very similar properties to palm, which they harvest. The yeast is fed on sugars from sugar cane plants grown on land already used for arable farming. "Our process takes less than seven days from start to finish," says a spokeswoman for C16 Biosciences. "For a traditional oil palm tree, the oil wouldn't be ready to harvest until years after the seed is planted, and most trees don't reach peak production until seven years later." She adds that the company is now "actively collaborating on partnerships in the beauty and home categories -- for example, moisturizers, nourishing oils, soaps and cancels". "[And] we plan to enter into food in 2024." Chris Chuck, professor of bioprocess engineering at the University of Bath, leads another team that has created its own yeast-sourced alternative. "After hundreds of generations of yeast, and years of trial and error, they arrived at a unique strain called metschnikowia pulcherrima, or MP for short," reports the BBC. "MP is said to be hardy and not fussy what it eats. It can be fed on grass and food waste. And at the point of harvesting, its cells are full of oil. Even the leftover yeast cell biomass need not go to waste. It can be used for other products, for example creating a substitute for soya protein."
Prof Chuck says the aim is for the oil to be as sustainable as possible. "In the best case scenarios we've modeled," he says, "it could be even just a couple of percent of the greenhouse gas emissions from palm oil grown in Indonesia or Malaysia."
High-Powered Lasers Can Be Used To Steer Lightning Strikes 57
["The experiment was performed on Santis Mountain, in northeast Switzerland," adds The Washington Post. "A 407-foot (124-meter) communications tower there, equipped with a lightning rod, is struck roughly a hundred times a year."] The design ionizes nitrogen and oxygen molecules, releasing electrons and creating a plasma that conducts electricity. As the laser fires at a very quick 1,000 pulses per second, it's considerably more likely to intercept lightning as it forms. In the test, conducted between June and September 2021, lightning followed the beam for nearly 197 feet before hitting the rod. The findings have been published in the journal Nature Photonics. A video of the work has also been published on YouTube.
Human Waste Safe for Growing Vegetables, Researchers Say (yahoo.com) 83
In terms of safety, the researchers screened human waste for 310 chemicals, from pharmaceuticals to insect repellents, and found that only 6.5% of these were above the limit for detection and at low concentrations. "In general, the risk for human health of pharmaceutical compounds entering the food system by means of fecal compost use, seems low," the authors concluded. While they detected two pharmaceutical products in edible parts of cabbages, the painkiller ibuprofen and the anticonvulsant drug carbamazepine, the concentrations were markedly low. This means that more than half a million cabbage heads would need to be eaten to accumulate a dose equivalent to one carbamazepine pill, they said.
FDA Vaccine Advisers 'Disappointed' and 'Angry' That Early Data About New Covid-19 Booster Shot Wasn't Presented For Review Last Year (cnn.com) 168
The pharmaceutical company Moderna didn't present a set of infection data on the company's new Covid-19 booster during meetings last year when [FDA] advisers discussed whether the shot should be authorized and made available to the public
That data suggested the possibility that the updated booster might not be any more effective at preventing Covid-19 infections than the original shots. The data was early and had many limitations, but several advisers told CNN that they were concerned about a lack of transparency.
Specifically, Moderna hid data on actual infection rates among patients who were administered the original booster and those who got the bivalent vaccine. The data showed that the original booster resulted in slightly fewer infections than the bivalent version - though CNN points out that "the primary purpose of the study was not to study infection rates but to do immunogenicity analyses, taking blood from participants and examining their antibody responses to the vaccine."
CNN reports that Moderna "shared the infection data with the FDA and posted the study manuscript before the agency's panel meeting in June," but with an FDA spokesperson complaining that they received the preprint less than a day prior to the advisory committee meeting, and "therefore not provided in an adequate timeframe for it to be included in the agency's meeting materials..."
1.9% of the study participants who received the original booster became infected. Among those who got the updated bivalent vaccine -- the one that scientists hoped would work better -- a higher percentage, 3.2%, became infected.
Both versions of the shot were found to be safe. This infection data was far from complete. The number of study subjects who became infected was very small, and both the patients and the researchers were aware of who was getting the original shot and who was getting the new booster.... [S]ix FDA and CDC advisers interviewed by CNN said that this infection data wouldn't have changed how they voted, because the data had such limitations, but it still should have been presented to them.
Research released by the New England Journal of Medicine found that "boosting with new bivalent mRNA vaccines targeting both the BA.4-BA.5 variant and the D614G strain did not elicit a discernibly superior virus-neutralizing peak antibody response as compared with boosting with the original monovalent vaccines. Limitations of our study include the small sample size and follow-up period of our groups. We also note that the between-group comparisons were not controlled for factors such as age, vaccine type, and health status, which may have had an effect on antibody responses. These findings may be indicative of immunologic imprinting, although follow-up studies are needed to determine whether antibody responses will deviate over time, including after the administration of a second bivalent booster."
Watch SpaceX's Falcon Heavy Launch - the First of Its Five Missions This Year (youtube.com) 31
"Nearly five years have passed since the massive Falcon Heavy rocket made its successful debut launch in February 2018," writes Ars Technica.
"Since then, however, SpaceX's heavy lift rocket has flown just three additional times." Why? It's partly because there is simply not all that much demand for a heavy lift rocket. Another factor is that SpaceX has increased the performance of its Falcon 9 rocket so much that it can complete a lot of the missions originally manifested on the Falcon Heavy. However the main reason for the low cadence has been due to a lack of readiness of payloads for the new rocket, particularly from the US Department of Defense. But now this trickle of Falcon Heavy launches may turn into a flood. [Sunday's launch is the first of potentially five launches this year]
SpaceX completed a hot fire test of the rocket on Tuesday, and declared that the vehicle was ready for liftoff. The rocket will use a brand new core stage, and side-mounted boosters that have flown into space one time, as side-mounted boosters on the USSF-44 Falcon Heavy mission that launched on November 1 2022.
What's it carrying? Space.com writes: The main payload is a military communications satellite called Continuous Broadcast Augmenting SATCOM 2, which the Falcon Heavy will send to geostationary orbit, about 22,200 miles (35,700 kilometers) above Earth. Also flying Saturday is a rideshare spacecraft called Long Duration Propulsive ESPA (LDPE)-3A, a payload adapter that can hold up to six small satellites, according to EverydayAstronaut.com. LDPE-3A will carry five Space Force payloads on USSF-67. Among them are "two operational prototypes for enhanced situational awareness and an operational prototype crypto/interface encryption payload providing secure space-to-ground communications capability," Space Force officials said in an emailed statement on Friday....
If all goes according to plan, the two side boosters will come back to Earth shortly after liftoff on Sunday, making vertical touchdowns at Cape Canaveral Space Force Station, which is next door to NASA's Kennedy Space Center. The central booster will not return, instead ditching into the Atlantic Ocean....
USSF-67 is part of a busy week for SpaceX. The company also plans to launch 51 of its Starlink internet satellites to low Earth orbit atop a Falcon 9 on Thursday, January 19.
Harvard's 'RoboBee' Project Finally Lifts Off as a Surgical-Tech Company (msn.com) 8
"RoboBee was funded by $10 million in grants from the National Science Foundation. Its evolution into a company says a lot about how schools like Harvard are doing more to encourage entrepreneurship." The RoboBee first took flight in 2012, connected to a tether that provided a power supply. In 2019, it became the lightest object to take off and fly on its own.... When it takes off, its little wings flap about 150 times per second, but a slowed-down video of the wings resembles a human treading water. Many wonder what tiny, flying robots that weigh less than one-tenth of a gram might be useful for. Pollinating crops? Surveillance? Wood said he never paid too much attention to that.
"It's never really been about, 'Oh, I'm going to start a company based upon this,'" he said. But that changed recently, he said, mostly because of a growing push at Harvard to move research from its labs into the real world.... Wood was connected to venture capitalist and Harvard alum Andrew Chung by the school's School of Engineering and Applied Sciences dean, Frank Doyle, during the pandemic. The managing partner of 1955 Capital said he's been investing in surgical-robotics companies for the past decade. "The one key thing that we have been dreaming about is how we can make the robotic arms a lot smaller," Chung said. "Not necessarily what other VCs might be thinking, which is maybe 15 to 20 percent smaller. We're thinking 90 percent smaller."
Chung noticed how the RoboBee was designed and manufactured — Wood got his inspiration from origami and children's-book layering and folding techniques — and thought it could help make better small-scale surgical robots. "Thinking about how to shrink these devices to insect size or smaller opens up a whole range of possibilities that even surgeons haven't quite imagined," Chung said. For now, the startup is called Project 1985, a reference to the year the first robotic-assisted surgery took place. The company will initially focus on neurosurgery, urology, and lung surgery. Wood will serve as an advisor.
How NASA's Planned Moon Presence Will Practice Living in Space (msn.com) 49
First, unlike in the 1960s — we now know that the moon has water. Water is not only key to sustaining human life, but its component parts — hydrogen and oxygen — can be used as rocket propellant, making the moon a gas station in space. That could be critical for long-duration missions, allowing spacecraft to refuel on the moon instead of lugging all the fuel from Earth. And since the moon's gravity is one-sixth of Earth's, it is a relatively easy springboard to other points of the solar system.
NASA is also considering building a nuclear reactor on the moon: It's one of several initiatives NASA has begun under its Artemis program, designed to help astronauts stay for extended periods when they'll need power, transportation and the ability to use the moon's resources.... The effort is still very much in its nascent stages, and the funding NASA would need for the long term has not materialized in full.... A sustainable presence, despite the rosy predictions coming from the top echelons of the agency, is still years away, and the technical challenges are immense.
But NASA has begun developing the technologies that would be needed to sustain astronauts on the surface for extended periods. In June of last year, the agency and the Energy Department awarded contracts, worth $5 million each, to three companies to develop nuclear power systems that could be ready to launch by the end of the decade for a test on the moon. The systems would generate 40 kilowatts of power, enough energy to power six or seven American households, and last about 10 years....
NASA is also looking to build solar farms, using arrays that point vertically and catch the angle of the sun over the horizon. And it's exploring how best to exploit what are called "in situ resources" — meaning those that already exist, such as the regolith.
The article even broaches the idea of "a lunar economy that would help sustain a permanent presence."
Scientists Invent an Entirely New Way To Refrigerate Things (sciencealert.com) 55
It's all based on the idea that melting absorbs heats. "The landscape of refrigerants is an unsolved problem," says mechanical engineer Drew Lilley, from the Lawrence Berkeley National Laboratory in California. "No one has successfully developed an alternative solution that makes stuff cold, works efficiently, is safe, and doesn't hurt the environment. We think the ionocaloric cycle has the potential to meet all those goals if realized appropriately...."
A current running through the system would move the ions in it, shifting the material's melting point to change temperature. The team also ran experiments using a salt made with iodine and sodium, to melt ethylene carbonate. This common organic solvent is also used in lithium-ion batteries, and is produced using carbon dioxide as an input. That could make the system not just GWP [global warming potential] zero, but GWP negative.
A temperature shift of 25 degrees Celsius (45 degrees Fahrenheit) was measured through the application of less than a single volt of charge in the experiment, a result that exceeds what other caloric technologies have managed to achieve so far.... "Now, it's time for experimentation to test different combinations of materials and techniques to meet the engineering challenges," says mechanical engineer Ravi Prasher, from the Lawrence Berkeley National Laboratory.
Thanks to long-time Slashdot reader schwit1 for sharing the article.
Old Mice Grow Young Again in Study. Can People Do the Same? (cnn.com) 80
The combined experiments, published for the first time Thursday in the journal Cell, challenge the scientific belief aging is the result of genetic mutations that undermine our DNA, creating a junkyard of damaged cellular tissue that can lead to deterioration, disease and death. "It's not junk, it's not damage that causes us to get old," said Sinclair, who described the work last year at Life Itself, a health and wellness event presented in partnership with CNN. "We believe it's a loss of information — a loss in the cell's ability to read its original DNA so it forgets how to function — in much the same way an old computer may develop corrupted software. I call it the information theory of aging."
Jae-Hyun Yang, a genetics research fellow in the Sinclair Lab who coauthored the paper, said he expects the findings "will transform the way we view the process of aging and the way we approach the treatment of diseases associated with aging."
While Sinclair is now testing "genetic resets" in primates, the article warns that "decades could pass before any anti-aging clinical trials in humans begin, get analyzed and, if safe and successful, scaled to the mass needed for federal approval."
But Sinclair suggests damage could probably also be repaired through healthy behaviors like exercise and sufficient sleep, social support and lower stress levels, eating less often and focusing on plants.
Thanks to long-time Slashdot reader 192_kbps for sharing the story.
Virgin Orbit's Sixth Launch Became a 'Fireball' on Monday (gizmodo.com) 12
But instead "at an altitude of approximately 180km (111 miles), the upper stage experienced an anomaly which 'prematurely ended' the first burn. The company said this event ended the mission, with the rocket components and payload falling back to Earth within the approved safety corridor.,,,"
At this point the unmanned rocket became "a slow moving fireball in the sky," astrodynamics lecturer Marco Langbroek told Gizmodo in an email. The rocket's hellish descent was captured on video, revealing the unfortunate journey back from space. Ramón López, an observer at the Spanish Meteor Network, caught the rocket reentering Earth's atmosphere from Lanzarote, one of the Canary Islands off the west coast of Africa. He released the footage on YouTube, as well as on Twitter.
Earlier this week Space.com noted that four previous Virgin Orbit missions have all been successful, deploying a total of 33 satellites into orbit.
Research Summaries Written By AI Fool Scientists (scientificamerican.com) 59
Since its release, researchers have been grappling with the ethical issues surrounding its use, because much of its output can be difficult to distinguish from human-written text. Scientists have published a preprint2 and an editorial3 written by ChatGPT. Now, a group led by Catherine Gao at Northwestern University in Chicago, Illinois, has used ChatGPT to generate artificial research-paper abstracts to test whether scientists can spot them. The researchers asked the chatbot to write 50 medical-research abstracts based on a selection published in JAMA, The New England Journal of Medicine, The BMJ, The Lancet and Nature Medicine. They then compared these with the original abstracts by running them through a plagiarism detector and an AI-output detector, and they asked a group of medical researchers to spot the fabricated abstracts.
The ChatGPT-generated abstracts sailed through the plagiarism checker: the median originality score was 100%, which indicates that no plagiarism was detected. The AI-output detector spotted 66% the generated abstracts. But the human reviewers didn't do much better: they correctly identified only 68% of the generated abstracts and 86% of the genuine abstracts. They incorrectly identified 32% of the generated abstracts as being real and 14% of the genuine abstracts as being generated. Wachter says that, if scientists can't determine whether research is true, there could be "dire consequences". As well as being problematic for researchers, who could be pulled down flawed routes of investigation, because the research they are reading has been fabricated, there are "implications for society at large because scientific research plays such a huge role in our society". For example, it could mean that research-informed policy decisions are incorrect, she adds. On the contrary, Arvind Narayanan, a computer scientist at Princeton University in New Jersey, says: "It is unlikely that any serious scientist will use ChatGPT to generate abstracts." He adds that whether generated abstracts can be detected is "irrelevant."
"The question is whether the tool can generate an abstract that is accurate and compelling. It can't, and so the upside of using ChatGPT is minuscule, and the downside is significant," he says.
We Exist Inside a Giant Space Bubble, And Scientists Have Finally Mapped It (vice.com) 39
Now, a team of scientists has added another layer to our evolving picture of the Local Bubble by charting the magnetic field of the structure, which is thought to play a major role in star formation. Astronomers led by Theo O'Neill, who conducted the new research during a summer research program at the Center for Astrophysics at Harvard & Smithsonian (CfA), presented "the first-ever 3D map of a magnetic field over a superbubble" on Wednesday at the American Astronomical Society's 241st annual meeting in Seattle, Washington. The team also unveiled detailed visualizations of their new map, bringing the Local Bubble into sharper focus.
"We think that the entire interstellar medium is really full of all these bubbles that are driven by various forms of feedback from, especially, really massive stars, where they're outputting energy in some form or another into the space between the stars," said O'Neill, who just received an undergraduate degree in astronomy-physics and statistics from the University of Virginia, in a joint call with their mentor Alyssa Goodman, an astronomer at CfA who co-authored the new research. [...] "Now that we have this map, there's a lot of cool science that can be done both by us, but hopefully by other people as well," O'Neill said. "Since stars are clustered, it's not as if the Sun is super special, and is in the Local Bubble because we're just lucky. We know that the interstellar medium is full of bubbles like this, and there's actually a lot of them nearby our own Local Bubble." "One cool next step will be looking at places where the Local Bubble is nearby other feedback bubbles," they concluded. "What happens when these bubbles interact, and how does that drive start formation in general, and the overall long-term evolution of galactic structures?"
US Cancer Death Rate Falls 33% Since 1991, Report Says (cnn.com) 50
In their report, researchers from the American Cancer Society also pointed to HPV vaccinations as connected to reductions in cancer deaths. HPV, or human papillomavirus, infections can cause cervical cancer and other cancer types, and vaccination has been linked with a decrease in new cervical cancer cases. Among women in their early 20s, there was a 65% drop in cervical cancer rates from 2012 through 2019, "which totally follows the time when HPV vaccines were put into use," said Dr. William Dahut, the society's chief scientific officer. "There are other cancers that are HPV-related -- whether that's head and neck cancers or anal cancers -- so there's optimism this will have importance beyond this," he said. The lifetime probability of being diagnosed with any invasive cancer is estimated to be 40.9% for men and 39.1% for women in the US, according to the new report.
The new report includes data from national programs and registries, including those at the National Cancer Institute, the US Centers for Disease Control and Prevention and the North American Association of Central Cancer Registries. Data showed that the US cancer death rate rose during most of the 20th century, largely due to an increase in lung cancer deaths related to smoking. Then, as smoking rates fell and improvements in early detection and treatments for some cancers increased, there was a decline in the cancer death rate from its peak in 1991. Since then, the pace of the decline has slowly accelerated. The new report found that the five-year relative survival rate for all cancers combined has increased from 49% for diagnoses in the mid-1970s to 68% for diagnoses during 2012-18. The cancer types that now have the highest survival rates are thyroid at 98%, prostate at 97%, testis at 95% and melanoma at 94%, according to the report. Current survival rates are lowest for cancers of the pancreas, at 12%. The report does have some bad news: new cases of breast, uterine and prostate cancer have been "of concern" and rising in the United States.
Exxon Climate Predictions Were Accurate Decades Ago. Still It Sowed Doubt 126
Over the last few years, journalists and researchers revealed that Exxon did in-house research that showed it knew that human-caused climate change is real. The new study looked at Exxon's research and compared it to the warming that has actually happened. Researchers at Harvard University and the Potsdam Institute for Climate Impact Research analyzed Exxon's climate studies from 1977 to 2003. The researchers show the company, now called ExxonMobil, produced climate research that was at least as accurate as work by independent academics and governments -- and occasionally surpassed it. That's important because ExxonMobil and the broader fossil fuel industry face lawsuits nationwide claiming they misled the public on the harmful effects of their products. "The bottom line is we found that they were modeling and predicting global warming with, frankly, shocking levels of skill and accuracy, especially for a company that then spent the next couple of decades denying that very climate science," says lead author Geoffrey Supran, who now is an associate professor of environmental science and policy at the University of Miami.
"Specifically, what we've done is to actually put a number for the first time on what Exxon knew, which is that the burning of their fossil fuel products would heat the planet by something like 0.2 [degrees] Celsius every single decade," Supran says.
The report notes that ExxonMobil "faces more than 20 lawsuits brought by states and local governments for damages caused by climate change." These new findings could provide more evidence for those cases as they progress through the courts, says Karen Sokol, a law professor at Loyola University in New Orleans.
"What Exxon scientists found and what they communicated to company executives was nothing short of horrifying," says Sokol. "Imagine that world and the different trajectory that consumers, investors and policymakers would have taken when we still had time, versus now when we're entrenched in a fossil fuel based economy that's getting increasingly expensive and difficult to exit," says Sokol.
Fossil Fuel Producers Must Be Forced To 'Take Back' Carbon, Say Scientists (theguardian.com) 158
"The technology exists -- what has always been lacking is effective policy," he said. "The failure has been policy, not technology -- we know how to do this." The companies that profit from extracting fossil fuels -- oil, gas and coal producers around the world -- should be paying for an equivalent quantity of carbon dioxide to be stored geologically as a condition of being allowed to operate, he argued.
Allen is a co-author, along with four other scientists from Oxford, the US and the Netherlands, of a paper published on Thursday in the journal Environmental Research Letters that sets out how such an "extended producer responsibility" could work. Under a "carbon takeback obligation," all fossil fuels extracted or imported into a nation or group of nations would be offset by storing underground an amount of carbon dioxide equivalent to that generated by that fuel. Phased in over time, it could be used to store 100% of emissions by 2050, to help the world reach net zero.
NASA's Webb Telescope Discovers Its First Exoplanet (npr.org) 22
Russia To Rescue ISS Crew On Backup Rocket After Capsule Leak (reuters.com) 27
Russia said a new capsule, Soyuz MS-23, would be sent up on Feb. 20 to replace the damaged Soyuz MS-22, which will be brought back to Earth empty. "Having analyzed the condition of the spacecraft, thermal calculations and technical documentation, it has been concluded that the MS-22 must be landed without a crew on board," said Yuri Borisov, the head of Russian space agency Roscosmos. Russian cosmonauts Sergey Prokopyev and Dmitry Petelin and U.S. astronaut Francisco Rubio had been due to end their mission in March but will now extend it by a few more months and return aboard the MS-23.
"They are ready to go with whatever decision we give them," Joel Montalbano, NASA's ISS program manager, told a news conference. "I may have to fly some more ice cream to reward them," he added. The MS-23, which had been due to take up three new crew in March, will instead depart from the Baikonur cosmodrome in Kazakhstan as an unmanned rescue mission next month. If there is an emergency in the meantime, Roscosmos said it will look at whether the MS-22 spacecraft can be used to rescue the crew. In this scenario, temperatures in the capsule could reach unhealthy levels of 30-40 degrees Celsius (86-104 degrees Fahrenheit). "In case of an emergency, when the crew will have a real threat to life on the station, then probably the danger of staying on the station can be higher than going down in an unhealthy Soyuz," Sergei Krikalev, Russia's chief of crewed space programs, said.
Nuclear Reactor Mystery Solved, With No Need For New Particles (science.org) 33
In a reactor's core, uranium and plutonium nuclei split in a chain reaction, and the antineutrinos come from the radioactive "beta decay" of the lighter nuclei left behind. In such decay, a neutron in a nucleus changes into a proton while emitting an electron and an electron antineutrino. To predict the total flux of antineutrinos, physicists had to account for the amounts and decays of myriad different nuclei. That accounting pointed to a shortfall, but in 2017, physicists from the Daya Bay Reactor Neutrino Experiment in China called it into question. They studied antineutrinos from six commercial reactors, burning fuel with 4% uranium-235 atoms, which can sustain a chain reaction, and 96% uranium-238 atoms, which can't. As the uranium-235 is consumed, neutrons from its fission convert uranium-238 into plutonium-239, which also sustains a chain reaction. Daya Bay physicists found the antineutrino deficit shrank as the amount of uranium-235 fell, suggesting theorists had overestimated the flux of antineutrinos originating from uranium-235.
Now, physicists working at a small research reactor in France have confirmed that suspicion. The reactor at the Laue-Langevin Institute (ILL) produces copious neutrons for studies of materials. It also uses fuel containing 93% uranium-235. So, by studying the antineutrinos from it, researchers working with a neutrino detector called STEREO could measure the flux of antineutrinos from uranium-235 alone. The detector consists of six identical oil-filled segments lined up like teeth and spanning a distance of 9 to 11 meters from the reactor's core. Rarely, a proton in the oil will absorb an electron antineutrino to turn into a neutron while ejecting a positron -- sort of the reverse of beta decay. As the positron streaks through the oil, it produces light in proportion to the energy of the original neutrino. STEREO researchers showed the spectrum of energies of electron antineutrinos remained the same as distance from the core increased. That observation clashes with the idea that some are morphing into sterile neutrinos, because lower energy neutrinos should morph faster than higher energy ones, changing the spectrum as the neutrinos advance. STEREO researchers also showed the total flux of antineutrinos from uranium-235 was lower than the one used in theorists' models, as they report today in Nature. Taken together, the observations put an end to the reactor antineutrino deficit as evidence for a 1-eV sterile neutrino, says David Lhuillier, a neutrino physicist at France's Atomic Energy Commission and spokesperson for the 26-member STEREO team. "Can it be explained by a sterile neutrino of mass around 1 eV? The answer is no."
Other experiments -- such as one called PROSPECT at Oak Ridge National Laboratory -- had reached similar conclusions, Lhuillier notes.