A new type of fallout forensics can reconstruct nuclear blasts decades after detonation. By measuring the relative abundance of various elements in debris left over from nuclear explosions, researchers say they can accurately estimate the amount of energy released during the initial blast.
As proof of concept, the researchers estimated the yield of the 1945 Trinity nuclear test in New Mexico — the world’s first detonation of a nuclear device. The work pegged the explosion as equivalent to 22.1 kilotons of TNT, close to the official estimate of 21 kilotons. Applying the method to modern blasts could help regulators identify nuclear tests long after the fact and better enforce nonproliferation treaties, the researchers propose in a paper to appear in the Proceedings of the National Academy of Sciences the week of July 4. Regulators currently monitor nuclear tests by detecting tremors and radioactive material emanating from blasts. Those effects are short-lived, however, so the techniques can only be used within a few days or weeks of a test.
Chemist Susan Hanson and colleagues at New Mexico’s Los Alamos National Laboratory looked at the element molybdenum in glassy debris created by the Trinity test. Stable molybdenum forms when zirconium from the bomb’s fireball radioactively decays. The relative abundance of different molybdenum isotopes created from this process differs from that found naturally. By measuring the overabundance of certain molybdenum isotopes, researchers can determine the original amount of zirconium created by the explosion. Pairing the amount of remnant plutonium in the debris with the zirconium estimate, the researchers can estimate a blast’s explosive yield.
The Los Alamos group declined to comment on the method’s usefulness for measuring the yield of more recent nuclear tests, such as the test North Korea conducted in January (SN Online: 1/6/16).
A remote galaxy might harbor a type of black hole that arises directly from a massive cloud of gas rather than forming after the death of a star. This rare specimen could explain how some galaxies built gargantuan black holes in the first billion years or so after the Big Bang.
The galaxy, known as CR7, is unusual (SN: 7/25/2015, p. 8). It blasts out more ultraviolet radiation than other galaxies that lived at the same time, roughly 13 billion years ago (about 800 million years after the Big Bang). The gas in CR7 also appears to lack elements such as carbon and oxygen, which are forged within stars and then ejected into space. One idea is that CR7 is giving birth to first-generation stars, similar to the first stars ever created in the universe. Another hypothesis is that CR7 harbors the first known “direct collapse” black hole, one that forms when a blob of interstellar gas collapses under its own weight without first forming stars. A black hole is more likely, suggest Aaron Smith of the University of Texas at Austin and colleagues in the Aug. 11 Monthly Notices of the Royal Astronomical Society. The researchers developed computer simulations that explore how interstellar gas interacts with the harsh radiation from primordial stars or a large black hole. Smith and colleagues find that the light from a cache of hot, young stars can’t explain why a parcel of gas is racing away from CR7 at about 580,000 kilometers per hour. What can push the gas, they report, is radiation from a superheated disk of debris swirling around a black hole roughly 100,000 times as massive as the sun.
If CR7 does host a black hole, it would be the first evidence of one forming out of clouds that haven’t given birth to stars yet. Astronomers struggle to explain how some supermassive black holes could form in about 1 billion years out of just smaller black holes merging together. “There’s just not enough time to do that,” Smith says. A direct collapse black hole, however, creates a massive seed all in one go, jump-starting the growth of a behemoth that will eventually weigh as much as several billion suns.
“This is definitely a good step forward,” says David Sobral, an astrophysicist at Lancaster University in England who discovered CR7 in 2015. But it’s too early to say whether a black hole or a group of stars is powering CR7, he says. “I’ve tried to stay a bit away from it and argue that what we need is new observations instead of taking sides.”
With the data that are available, it’s hard to distinguish between stars or a black hole, says Sobral. That’s why he and colleagues have reserved time with the Hubble Space Telescope in January and are awaiting new data from the Atacama Large Millimeter/submillimeter Array in Chile. Data from both observatories will help researchers look for traces of heavy elements in CR7. If these more sensitive data still show no sign of atoms such as carbon, says Sobral, then CR7 probably hosts a nest of first-generation stars. A black hole, on the other hand, probably would have formed long enough ago that there would be enough time for stars to form and pollute CR7 with a smidgen of heavy elements, he says.
A growing census of similar locales will help as well. “We’re now finding that CR7 is not alone,” Sobral says. He and his colleagues have since found four other galaxies comparable to CR7 in the early universe, results presented June 27 at the National Astronomy Meeting in Nottingham, England. “We don’t have to discuss one single thing,” he says, “but we can put [CR7] into a broader picture.”
As the saying goes, “It’s difficult to make predictions, especially about the future.” The website Metaculus.com aims to make this challenging task easier by harnessing collective wisdom.
Metaculus solicits answers to questions about the future — on topics spanning science, politics and economics — and combines these predictions to infer the likely outcomes. Will 2016 be the hottest year yet recorded? Will we find evidence for aliens soon? Will we hail self-driving taxis in the next few years? The hive mind might provide answers. The website, created by physicists Anthony Aguirre and Gregory Laughlin of the University of California, Santa Cruz, along with former postdoc Max Wainwright, is an experiment to test whether our pooled instincts can produce reliable predictions. The site may also help scientists make informed decisions about which research to prioritize. Organizations funding research on pandemics, for instance, might want to know whether people are more concerned about bioterrorism, powerful germs escaping laboratories or naturally circulating diseases like the flu.
There’s a precedent for successful crowdsourcing of predictions. A U.S. government–funded geopolitical forecasting effort, the Good Judgment Project, has found that collective predictions can be remarkably accurate, and that prediction is a skill that can be honed.
After completing a free sign-up process, Metaculus users click through yes-or-no questions and make predictions, moving a slider from zero to 100 percent to indicate their level of certainty. The site provides relevant background information on each question, and additional research is encouraged. Prognosticators can hash things out in the comments section and share resources to help others make their predictions. Users rack up points — and bragging rights — when their predictions turn out to be correct.
The hive mind isn’t perfect — Metaculus users pegged the probability that the United Kingdom would vote to leave the European Union at just 32 percent. The United Kingdom did vote to leave, but that doesn’t mean the method is flawed. “The point of this is not to get a ‘yes’ or ‘no,’ ” Aguirre says, “but to get what is the probability.” Most events aren’t predictable with complete certainty, he says, but attaching a probability to such events can be useful in planning for the future.
So far, Metaculus has about 1,300 registered participants. In a review of more than 2,000 user predictions, the results were about as expected. When users predicted an event would happen with 80 percent certainty, they were correct about eight times out of 10. When many minds join forces, even nonexperts may collectively become capable guesstimators.
Pinky and The Brain‘s smarts might not be so far-fetched. Some mice are quicker on the uptake than others. While it might not lead to world domination, wits have their upside: a better shot at staying alive.
Biologists Audrey Maille and Carsten Schradin of the University of Strasbourg in France tested reaction time and spatial memory in 90 African striped mice (Rhabdomys pumilio) over the course of a summer. For this particular wild rodent, surviving harsh summer droughts means making it to mating season in the early fall.
The team saw some overall trends: Females were more likely to survive if they had quick reflexes, and males were more likely to survive if they had good spatial memory. Cognitive traits like reacting quickly and remembering the best places to hide are key to eluding predators during these tough times but may come with trade-offs for males and females. The results show that an individual mouse’s cognitive strengths are linked to its survival odds, suggesting that the pressure to survive can shape basic cognition, Maille and Schradin write August 3 in Biology Letters.
Training the brain could give paraplegics more control over their bodies.
After a year working with devices that link machine to brain, people paralyzed by spinal cord injuries were able to regain some movement and feeling in their legs, Miguel Nicolelis and colleagues report August 11 in Scientific Reports.
The training included an assortment of therapies with futuristic-looking gizmos, including virtual reality goggles and robotic exoskeletons that fasten over the body. All patients were better able to sense pain and touch, and half had their diagnosis upgraded from complete to partial paralysis. “This is a very key milestone in the field of brain-machine interfaces,” Nicolelis said in a news briefing August 9.
But some scientists aren’t convinced that it’s such an advance.
Researchers have already proposed (and demonstrated) the benefits of brain-machine interface technology before, says Brendan Allison, a neuroscientist at the University of California, San Diego. While the new work is impressive and stands out for such long-term brain training, he says, “it’s simply not a breakthrough.”
Paralyzing spinal cord injuries can sever the bundle of nerves that carries messages from the brain to the body. So even if the brain tells the toes to move, the message dead-ends when it hits the injury site. For people with these severe injuries, there’s not much doctors can do to help, said Nicolelis, of Duke University. “They basically just try to get you adapted to life in a wheelchair.”
In 2012, he and colleagues started a project to help paraplegics walk, with assistance. With a stretchy cap placed over their heads to capture brain signals, patients would use their thoughts to control an exoskeleton, a robotic walker that held their bodies upright. The device would give paraplegics some mobility again — at least that was the goal. What the team found was far more exciting, Nicolelis said. For one year, Nicolelis’ team worked with eight people who had been paralyzed for between three and 13 years. Twice a week for one hour, patients trained on a variety of rehabilitation tools. They learned how to control an avatar in virtual reality by imagining moving their legs, and later, how to use the brain-controlled exoskeleton. Patients also did hours of traditional physical therapy, including strengthening and stretching exercises. About seven months into the project, the researchers noticed that all patients were beginning to regain control of one or more muscles below their spinal cord injury. And after 12 months, all patients experienced improvements in sensing touch and pain. One woman even gave birth to a child, and could feel the contractions during the delivery, Nicolelis said.
Though all patients had severe spinal cord injuries, he thinks some nerve cells must have survived and that the training rekindled their activity.
The amount of clinical recovery “is almost like a dream,” Nicolelis said. It may be enough to upgrade brain-machine interfaces, he said, from an assistive therapy (something that helps people walk — like crutches or a cane) to something that actually that helps people recover.
Again, that’s not a new idea, says Donatella Mattia, a neurophysiologist at the Institute for Research and Health Care in Rome. Other scientists working with paralyzed stroke patients have already shown improvements in arm mobility after using brain-machine interfaces.
What’s more, teasing out cause and effect in the new study isn’t easy, says University of Houston neural engineer José Contreras-Vidal. Patients underwent a complicated blend of therapies, with different lengths of training. Despite the caveats, though, he thinks the work is a step forward. And in clinical research, he says, “even incremental is good.”
WASHINGTON — In the short-term, ways to beat the heat are cool. But for desert birds, even simple panting or flying into the shade have some sneaky long-term costs.
When male southern yellow-billed hornbills pant, they’re less able to snap up food, Susan Cunningham reported August 18 at the North American Ornithological Conference. The hornbills are the third bird species that Cunningham, of the University of Cape Town in South Africa, and various colleagues have shown face hidden costs of trying not to overheat. Birds certainly have ways to ease the immediate dangers of heat. But determining the full consequences of all those small accommodations becomes more urgent as the climate changes.
Yellow-billed hornbills (Tockus leucomelas) could be especially vulnerable to hidden costs of heat because males become the sole provisioners of their families during breeding season. A female walls herself and her eggs into a cavity (or a research nest box), leaving open a hole big enough only for her mate to poke food through. In southern Africa’s Kalahari region, a female may stay walled in the cavity for a month or more, leaving the male to scour hot, dry land for her food, his own and eventually, the chicks’.
During bouts of panting, males caught less food than they did in minutes before or after while not panting, Cunningham’s student Tanja van de Ven has found. A specially rigged perch on nest boxes registered a male’s weight every time he landed on it. When the temperature rose above 36.5° Celsius, males typically failed to maintain weight, raising concerns about their ability to care not only for themselves, but for dependents, too.
Cunningham had already seen costs of chronic panting in another Kalahari species, the southern pied babbler (Turdoides bicolor). A population of these social birds had become blasé about nearby scientists taking notes thanks to patient effort by Amanda Ridley of the University of Western Australia in Crawley. The birds even hopped onto a portable scale, allowing weight monitoring in the field. Ridley, Cunningham and other babbler chroniclers found that on hot days, the birds persevered in foraging but caught less for their effort. As temperatures rose above 35.5° C, the scales showed that birds were struggling to maintain body weight. Typically they lost more weight overnight than they could make up during a day, the team reported in 2012
Even a cooling strategy as simple as taking shelter in the shade can cut into a bird’s ability to collect resources in arid lands. Southern fiscals (Lanius collaris), chunky predators with fierce bills, prefer high, sunny perches from which to scan for the rodents and insects they attack in lightning-bolt dives. As the Kalahari’s temperatures rose, these birds spent more and more time on shady perches, usually lower to the ground. The birds didn’t catch as much from such spots, the researchers found, and growth slowed among younger chicks when parents had to hunt from substandard posts. Each day with a temperature above 35° C kept chicks in the nests a half day longer. That’s perilous, Cunningham and colleagues argued in a 2013 report on fiscals. The risk that predators will scavenge a nest, or it will fail in some other way, increases 4 percent for every day the chicks remain in it. Uncovering the downsides of such simple behaviors “is pretty cool,” said Blair Wolf of the University of New Mexico in Albuquerque. Birds can’t sweat, he pointed out, and the many species that pant as a cooldown technique have to compensate for the water lost in the process. Birds let their body temperatures rise to heights that would cook a human, and Wolf’s work has shown that this tolerance lessens water loss. Whether there are some hidden costs to this heat-fighting measure, as there are to panting and shade-seeking, remains to be seen.
Scientists have created giant molecules — the size of bacteria — that may be useful in future quantum computers.
The molecules of unusual size are formed from pairs of Rydberg atoms — atoms with an electron that has been boosted into a high-energy state. Such electrons orbit far from their atom’s nucleus and, as a result, can feel the influence of faraway atoms.
To create the molecules, researchers cooled cesium atoms nearly to absolute zero, hitting them with lasers to form Rydberg atoms that bound together in pairs. These molecules are about one thousandth of a millimeter in size — a thousand times the size of a typical molecule — scientists report August 19 in Physical Review Letters. “I think it’s fundamentally interesting and important because it’s such a curious thing,” says physicist David Petrosyan of the Institute of Electronic Structure & Laser at the Foundation for Research and Technology–Hellas in Heraklion, Greece. “The size of these molecules is huge.”
This is not the first time such molecules have been created, but the previous evidence was not clear-cut. “Before, maybe it wasn’t clear if this is really a molecule in the sense that it’s vibrating and rotating. It could have been just two atoms sitting therewith very weak interactions or no interactions,” says Johannes Deiglmayr, a physicist at ETH Zürich and a coauthor of the study.
Deiglmayr and collaborators measured the molecules’ binding energies — the energy that holds the two atoms together. Additionally, the scientists made detailed calculations to predict the molecules’ properties. These calculations were “extensive and seemed to match really well with their measurements,” says physicist Phillip Gould of the University of Connecticut in Storrs.
The result has practical implications, Petrosyan notes. In quantum computers that use atoms as quantum bits, scientists perform computations by allowing atoms to interact. Rydberg atoms can interact with their neighbors over long distances, and when bound together, the atoms stay put at a consistent distance from one another — a feature that may improve the accuracy of calculations.
Previously, researchers have used rubidium atoms to make another type of large molecule, formed from Rydberg atoms bonded with normal atoms. But these wouldn’t be useful for quantum computation, Petrosyan says, as they rely on a different type of bonding mechanism.
Remarkably preserved bones of rat-sized creatures excavated in an Indian coal mine may come from close relatives of the first primatelike animals, researchers say.
A set of 25 arm, leg, ankle and foot fossils, dating to roughly 54.5 million years ago, raises India’s profile as a possible hotbed of early primate evolution, say evolutionary biologist Rachel Dunn of Des Moines University in Iowa and her colleagues. Bones from Vastan coal mine in Gujarat, India’s westernmost state, indicate that these tiny tree-dwellers resembled the first primates from as early as 65 million years ago, the scientists report in the October Journal of Human Evolution. These discoveries add to previously reported jaws, teeth and limb bones of four ancient primate species found in the same mine. “The Vastan primates probably approximate a common primate ancestor better than any fossils found previously,” says paleontologist and study coauthor Kenneth Rose of Johns Hopkins University School of Medicine. The Vastan animals were about the size of living gray mouse lemurs and dwarf lemurs, weighing roughly 150 to 300 grams (roughly half a pound), the investigators estimate. Dunn’s group has posted 3-D scans of the fossils to Morphosource.org ( SN: 3/19/16, p. 28 ) so other researchers can download and study the material. Most Vastan individuals possessed a basic climbing ability unlike the more specialized builds of members of the two ancient primate groups that gave rise to present-day primates, the researchers say. One of those groups, omomyids, consisted of relatives of tarsiers, monkeys and apes. The other group, adapoids, included relatives of lemurs, lorises and bushbabies. The Indian primates were tree-dwellers but could not leap from branch to branch like lemurs or ascend trees with the slow-but-sure grips of lorises, the new report concludes.
Vastan primates probably descended from a common ancestor of omomyids and adapoids, the researchers propose. India was a drifting landmass headed north toward a collision with mainland Asia when the Vastan primates were alive. Isolated on a huge chunk of land, the Indian primates evolved relatively slowly, retaining a great number of ancestral skeletal traits, Rose suspects.
“It’s possible that India played an important role in primate evolution,” says evolutionary anthropologist Doug Boyer of Duke University. A team led by Boyer reported in 2010 that a roughly 65-million-year-old fossil found in southern India might be a close relative of the common ancestor of primates, tree shrews and flying lemurs (which glide rather than fly and are not true lemurs).
One possibility is that primates and their close relatives evolved in isolation on the island continent of India between around 65 million and 55 million years ago, Boyer suggests. Primates then spread around the world once India joined Asia by about 50 million years ago.
That’s a controversial idea. An increasing number of scientists suspect primates originated in Asia. Chinese primate fossils dating to 56 million to 55 million years ago are slightly older than the Vastan primates (SN: 6/29/13, p. 14; SN: 1/3/04, p. 4). The Chinese finds show signs of having been omomyids.
And in at least one respect, Boyer says, some of the new Vastan fossils may be more specialized than their discoverers claim. Vastan ankle bones, for instance, look enough like those of modern lemurs to raise doubts that the Indian primates were direct descendants of primate precursors, he holds.
Dunn, however, regards the overall anatomy of the Vastan fossils as “the most direct evidence we have” that ancestors of early primates lacked lemurs’ leaping abilities, contrary to what some researchers have argued.
Where you live and what you eat can rapidly affect the types of friendly bacteria inhabiting your body. To see how the microbes that inhabit the mouth and intestines change over time, Duke University computational biologist Lawrence David zealously chronicled his microbiome for an entire year. (For more on David and this experiment, see “Lawrence David’s gut check gets personal.”)
A stream plot (below, top graph) shows the ebb and flow of phyla of bacteria in his gut over time. The thickness of each stream indicates a bacterial group’s relative abundance in daily fecal samples. David peered closer at the data in a horizon plot (above, bottom graph; colored squares at left indicate the phylum of the bacteria represented in each row). He first determined each type of bacteria’s normal abundance in his gut, then calculated how much they differed from the median abundance. Warmer colors (red, orange, yellow) indicate that bacteria in that group increased in abundance, and cooler colors (blue, green) indicate a decrease in abundance. Living abroad from day 71 to day 122 had a dramatic — but short-lived — effect on David’s microbiome.
Using records unearthed from library storage vaults, researchers recently revealed that the sugar industry paid nutrition experts from Harvard University to downplay studies linking sugar and heart disease. Although the incident happened in the 1960s, it appears to have helped redirect the scientific narrative for decades.
The documents — which include correspondence, symposium programs and annual reports — show that the Sugar Research Foundation (as it was named at the time) paid professors who wrote a two-part review in 1967 in the New England Journal of Medicine. That report was highly skeptical of the evidence linking sugar to cardiovascular problems but accepting of the role of fat. The now-deceased professors’ overall conclusion left “no doubt” that reducing the risk of heart disease was a matter of reducing saturated fat and cholesterol, according to researchers from the University of California, San Francisco, who published their report online September 12 in JAMA Internal Medicine.
“Why does it matter today? The sugar industry helped deflect the way the research was developing,” says study coauthor Cristin Kearns, a dentist at UCSF’s Institute for Health Policy Studies. The Harvard team’s scientific favoritism had a role in directing research and policy attention toward fat and cholesterol. And in fact, the first dietary guidelines published by the federal government in 1980 said there was no convincing evidence that sugar causes heart disease, stating “the major health hazard from too much sugar is tooth decay.” Following the publication of the Harvard report, fat and cholesterol went on to hijack the scientific agenda for decades, and even led to a craze of low-fat foods that often added sugar. Kearns points out that it was only in 2015 that dietary guidelines finally made a strong statement to limit sugar. Researchers writing this year in Progress in Cardiovascular Diseases note that current studies estimate that diets high in added sugars carry a three times higher risk of death from cardiovascular disease. (For its part, the Sugar Association says in a statement on its website that “the last several decades of research have concluded that sugar does not have a unique role in heart disease.”)
The level at which the food industry continues to influence nutrition research is still a much-debated topic. The Sugar Association’s statement acknowledged the secret deal occurred, but pointed out that “when the studies in question were published, funding disclosures and transparency standards were not the norm they are today.” Journals now require all authors to list conflicts of interest, especially funding from a source has a vested interest in the outcome.
That doesn’t mean that trade groups and industry associations no longer have an influence on scientists, says Andy Bellatti, cofounder and strategic director of Dietitians for Professional Integrity, which has campaigned to push the Academy of Nutrition and Dietetics to sever its ties with industry, While a modern researcher could not take corporate money, even for speaking fees, without disclosure, the influences may be more subtle, he says. “We’re not talking about making up data, but perhaps influencing how a research question is framed.”
In a commentary published with the JAMA study, Marion Nestle, a nutrition researcher at New York University, wrote that industry influence has not disappeared. She cited recent New York Times investigations of Coca-Cola–sponsored research and Associated Press stories revealing that a candy trade group sponsored research attempting to show that children who eat sweets have a healthy body weight.
Bellatti says that researchers don’t necessarily want to be cozy with industry, but sometimes turn to commercial sources because non-biased research money is lacking. “The reason the food industry is able to do this is because there is such little public funding for nutrition and disease,” Bellatti says. For that reason, the scientific community should not reject industry money wholesale, says John Sievenpiper, a physician and nutrition researcher at the University of Toronto. A study of his was once ridiculed on Nestle’s blog because the disclosures covered two full pages. He believes that any scientist who takes industry money should adhere to an even higher standard of openness, including releasing study protocols ahead of time so reviewers can make sure the research question was not changed midstream to favor a certain conclusion.
While many parallels have been made between the food and tobacco industries, Sievenpiper believes those comparisons miss the complicated nature of the human diet. Tobacco is always bad, never good. Sugar, fat, cholesterol and other components of diet are some of both, making research into their effects much more nuanced, he says. And unlike with tobacco, the solution can’t be to never eat them. He believes solutions won’t involve turning single nutrients like fat or sugar into villains, but promoting better overall patterns of eating, like the Mediterranean diet.
Kearns, who has spent the past 10 years looking into the sugar industry’s influence on science, isn’t finished yet. She says her curiosity first arose during a conference on gum disease and diabetes in 2007, when she noticed a lack of scientific discussion of sugar. She started out simply Googling industry influences. The trail eventually led her to scour library archives, until she came across dusty boxes of records from a closed sugar company in Colorado. “The first page I looked at in that archive had a confidential memo,” she says. “I knew I had something no one else had never talked about before.”
She doesn’t see the research going sour any time soon. “This was their 226th project in 1965,” she says. “There’s a lot more to the story.”