What 'Chornobyl dogs' can tell us about survival in contaminated environments

In the first step toward understanding how dogs -- and perhaps humans -- might adapt to intense environmental pressures such as exposure to radiation, heavy metals, or toxic chemicals, researchers atNorth Carolina State, Columbia University Mailman School of Public Health, University of South Carolina, and the National Institutes of Healthfound thattwo groups of dogs living within the Chornobyl Exclusion Zone, one at the site of the former Chornobyl reactors, and another 16.5 km away in Chornobyl City, showed significant genetic differences between them. The results indicate that these are two distinct populations that rarely interbreed. While earlier studiesfocused on the effects of the Chornobyl Nuclear Power Plant disaster on various species of wildlife, this is the firstinvestigation into the genetic structure of stray dogs living near the Chornobyl nuclear power plant.

The 1986 Chornobyl nuclear power plant disaster displaced more than 300,000 people living nearby and led to the establishment of an Exclusion Zone, a "no man's land" of an approximately 30 km radius surrounding the damaged reactor complex, While a massive steam explosion releasing enormous amounts of ionizing radiation into the air, water, and soil was the direct cause of the catastrophe, radiation exposure is not the only environmental hazard resulting from the disaster. Chemicals, toxic metals, pesticides, and organic compounds left behind by years-long cleanup efforts and from abandoned and decaying structures, including the nearby abandoned city of Pripyat and the Duga-1 military base, all contribute to an ecological and environmental disaster.

"Somehow, two small populations of dogs managed to survive in that highly toxic environment," noted Norman J. Kleiman, PhD, assistant professor of Environmental Health Sciences at Columbia Mailman School of Public Health, and a co-author. "In addition to classifying the population dynamics within these dogs at both locations, we took the first steps towards understanding how chronic exposure to multiple environmental hazards may have impacted these populations."

"The overarching question here is: does an environmental disaster of this magnitude have a genetic impact on life in the region?" says Matthew Breen, Oscar J. Fletcher Distinguished Professor of Comparative Oncology Genetics at NC State, and a corresponding author. "And we have two populations of dogs living at and near the site of a major environmental disaster that may provide key information to help us answer that question."

Earlier research by the co-authors, led by collaborators at NIH, used a much smaller set of genetic variants, but a larger number of dogs, to show that the two populations were separate and that each had complicated family structures.

In this parallel study, the team analyzed the dog DNA samples with four times the number of genetic variants, which provided a closer look at the genomes. In addition to confirming that the two populations are indeed genetically distinct, the team were also able to identify 391 outlier regions in the genomes of the dogs that differed between dogs living at the two locations. "Think of these regions as markers, or signposts, on a highway," Breen says. "They identify areas within the genome where we should look more closely at nearby genes. Moreover, some of these markers are pointing to genes associated with genetic repair; specifically, with genetic repair after exposures similar to those experienced by the dogs in Chornobyl." He went on to say "at this stage we cannot say for sure that any genetic alterations are in response to the multigenerational and complex exposures; we have a lot more work to do to determine if that is the case"

"The question we must answer now are why are there striking genetic differences between the two dog populations?" says Megan Dillion, PhD candidate at NC State and a lead author of the published study. "Are the differences just due to genetic drift, or are they due to the unique environmental stressors at each location?"

"The dog is a sentinel species," Breen says. "By and teasing out whether or not the genetic changes we detected in these dogs are the canine genome's response to the exposures the populations have faced, we may be able to understand how the dogs survived in such a hostile environment and what that might mean for any population -- animal or human -- that experiences similar exposures."

"Though 37 years have passed since the accident, the ~30-year-long half-lives of lingering radioisotopes means the danger posed by radiation exposure is still very much real," notes Kleiman, who is also director of the Columbia University Radiation Safety Officer Training course. "When radiation exposure is combined with a complex toxic chemical mixture of uncertain composition, there are very real human health concerns raised for the thousands of people who continue to work within the Exclusion Zone on continuing cleanup efforts as well as at two newly constructed nuclear fuel reprocessing plants."

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An experimental loop for simulating nuclear reactors in space

Nuclear thermal propulsion, which uses heat from nuclear reactions as fuel, could be used one day in human spaceflight, possibly even for missions to Mars. Its development, however, poses a challenge. The materials used must be able to withstand high heat and bombardment of high-energy particles on a regular basis.

Will Searight, a nuclear engineering doctoral student at penn State, is contributing to research that could make these advancements more feasible. He published findings from a preliminary design simulation in Fusion Science and Technology, a publication of the American Nuclear Society.

To better investigate nuclear thermal propulsion, Searight simulated a small-scale laboratory experiment known as a hydrogen test loop. The setup mimics a reactor's operation in space, where flowing hydrogen travels through?the core and propels the rocket -- at temperatures up to nearly 2,200 degrees Fahrenheit. Searight developed the simulation using dimensions from detailed drawings of tie tubes, the components that make up much of the test loop through which hydrogen flows. Industry partner Ultra Safe Nuclear Corporation (USNC) provided the drawings.

"Understanding how USNC's components behave in a hot hydrogen environment is crucial to bringing our rockets to space," Searight said. "We're thrilled to be working with one of the main reactor contractors for NASA's space nuclear propulsion project, which is seeking to produce a demonstration nuclear thermal propulsion engine within a decade."

Advised by Leigh Winfrey, associate professor and undergraduate program chair of nuclear engineering, Searight used Ansys Fluent, a modeling software, to design a simulation loop from a stainless steel pipe with an outer diameter of about two inches. In the model, the loop connects to a hydrogen pump and circulates hot hydrogen through a test section adjacent to a heating element.

Searight found that while consistent heating of hydrogen to 2,200 degrees Fahrenheit was possible, it was necessary to include a heating element directly above the test section to prevent a reduction in heating. Data collected from the modeling software showed that the flow of hydrogen through the test section was smooth and uniform, reducing uneven distribution of heat through the loop that could jeopardize the setup's safety and lifespan. Analysis of the results also verified that stainless steel would allow for more convenient and cost-effective construction of the loop.

"We are excited to take the first steps in developing a unique capability for extreme environment simulation at Penn State," Winfrey said. "This preliminary work will enable us to pursue research that could have a major impact on the future of space exploration."

With further research, Searight's preliminary work could enable expanded testing of materials that could one day be implemented to create faster, more efficient space travel using reactor-fueled rockets.

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Explosive nuclear astrophysics

 Analysis of meteorite content has been crucial in advancing our knowledge of the origin and evolution of our solar system. Some meteorites also contain grains of stardust. These grains predate the formation of our solar system and are now providing important insights into how the elements in the universe formed.

Working in collaboration with an international team, nuclear physicists at the U.S. Department of Energy's (DOE's) Argonne National Laboratory have made a key discovery related to the analysis of "presolar grains" found in some meteorites. This discovery has shed light on the nature of stellar explosions and the origin of chemical elements. It has also provided a new method for astronomical research.

"Tiny presolar grains, about one micron in size, are the residue from stellar explosions in the distant past, long before our solar system existed," said Dariusz Seweryniak, experimental nuclear physicist in Argonne's Physics division. The stellar debris from the explosions eventually became wedged into meteorites that crashed into the Earth.

The major stellar explosions are of two types. One called a "nova" involves a binary star system, where a main star is orbiting a white dwarf star, an extremely dense star that can be the size of Earth but have the mass of our sun. Matter from the main star is continually being pulled away by the white dwarf because of its intense gravitational field. This deposited material initiates a thermonuclear explosion every 1,000 to 100,000 years, and the white dwarf ejects the equivalent of the mass of more than thirty Earths into interstellar space. In a "supernova," a single collapsing star explodes and ejects most of its mass.

Nova and supernova are the sources of the most frequent and violent stellar eruptions in our Galaxy, and for that reason, they have been the subject of intense astronomical investigations for decades. Much has been learned from them, for example, about the origin of the heavier elements.

"A new way of studying these phenomena is analyzing the chemical and isotopic composition of the presolar grains in meteorites," explained Seweryniak. "Of particular importance to our research is a specific nuclear reaction that occurs in nova and supernova -- proton capture on an isotope of chlorine -- which we can only indirectly study in the lab."

In conducting their research, the team pioneered a new approach for astrophysics research. It entails use of the Gamma-Ray Energy Tracking In-beam Array (GRETINA) coupled to the Fragment Mass Analyzer at the Argonne Tandem Linac Accelerator System (ATLAS), a DOE Office of Science User Facility for nuclear physics. GRETINA is a state-of-the-art detection system able to trace the path of gamma rays emitted from nuclear reactions. It is one of only two such systems in the world.

Using GRETINA, the team completed the first detailed gamma-ray spectroscopy study of an astronomically important nucleus of an isotope, argon-34. From the data, they calculated the nuclear reaction rate involving proton capture on a chlorine isotope (chlorine-33).

"In turn, we were able to calculate the ratios of various sulfur isotopes produced in stellar explosions, which will allow astrophysicists to determine whether a particular presolar grain is of nova or supernova origin," said Seweryniak. The team also applied their acquired data to gain deeper understanding of the synthesis of elements in stellar explosions.

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'Strange' glimpse into neutron stars and symmetry violation

New results from precision particle detectors at the Relativistic Heavy Ion Collider (RHIC) offer a fresh glimpse of the particle interactions that take place in the cores of neutron stars and give nuclear physicists a new way to search for violations of fundamental symmetries in the universe. The results, just published in Nature Physics, could only be obtained at a powerful ion collider such as RHIC, a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at DOE's Brookhaven National Laboratory.

The precision measurements reveal that the binding energy holding together the components of the simplest "strange-matter" nucleus, known as a "hypertriton," is greater than obtained by previous, less-precise experiments. The new value could have important astrophysical implications for understanding the properties of neutron stars, where the presence of particles containing so-called "strange" quarks is predicted to be common.

The second measurement was a search for a difference between the mass of the hypertriton and its antimatter counterpart, the antihypertriton (the first nucleus containing an antistrange quark, discovered at RHIC in 2010). Physicists have never found a mass difference between matter-antimatter partners so seeing one would be a big discovery. It would be evidence of "CPT" violation -- a simultaneous violation of three fundamental symmetries in nature pertaining to the reversal of charge, parity (mirror symmetry), and time.

"Physicists have seen parity violation, and violation of CP together (each earning a Nobel Prize for Brookhaven Lab[ -- ), but never CPT," said Brookhaven physicist Zhangbu Xu, co-spokesperson of RHIC's STAR experiment, where the hypertriton research was done.

But no one has looked for CPT violation in the hypertriton and antihypertriton, he said, "because no one else could yet."

The previous CPT test of the heaviest nucleus was performed by the ALICE collaboration at Europe's Large Hadron Collider (LHC), with a measurement of the mass difference between ordinary helium-3 and antihelium-3. The result, showing no significant difference, was published in Nature Physics in 2015.

Spoiler alert: The STAR results also reveal no significant mass difference between the matter-antimatter partners explored at RHIC, so there's still no evidence of CPT violation. But the fact that STAR physicists could even make the measurements is a testament to the remarkable capabilities of their detector.

Strange matter

The simplest normal-matter nuclei contain just protons and neutrons, with each of those particles made of ordinary "up" and "down" quarks. In hypertritons, one neutron is replaced by a particle called a lambda, which contains one strange quark along with the ordinary up and down varieties.

Such strange matter replacements are common in the ultra-dense conditions created in RHIC's collisions -- and are also likely in the cores of neutron stars where a single teaspoon of matter would weigh more than 1 billion tons. That's because the high density makes it less costly energy-wise to make strange quarks than the ordinary up and down varieties.

For that reason, RHIC collisions give nuclear physicists a way to peer into the subatomic interactions within distant stellar objects without ever leaving Earth. And because RHIC collisions create hypertritons and antihypertritons in nearly equal amounts, they offer a way to search for CPT violation as well.

But finding those rare particles among the thousands that stream from each RHIC particle smashup -- with collisions happening thousands of times each second -- is a daunting task. Add to the challenge the fact that these unstable particles decay almost as soon as they form -- within centimeters of the center of the four-meter-wide STAR detector.

Precision detection

Fortunately, detector components added to STAR for tracking different kinds of particles made the search a relative cinch. These components, called the "Heavy-Flavor Tracker," are located very close to the STAR detector's center. They were developed and built by a team of STAR collaborators led by scientists and engineers at DOE's Lawrence Berkeley National Laboratory (Berkeley Lab). These inner components allow scientists to match up tracks created by decay products of each hypertriton and antihypertriton with their point of origin just outside the collision zone.

"What we look for are the 'daughter' particles -- the decay products that strike detector components at the outer edges of STAR," said Berkeley Lab physicist Xin Dong. Identifying tracks of pairs or triplets of daughter particles that originate from a single point just outside the primary collision zone allows the scientists to pick these signals out from the sea of other particles streaming from each RHIC collision.

"Then we calculate the momentum of each daughter particle from one decay (based on how much they bend in STAR's magnetic field), and from that we can reconstruct their masses and the mass of the parent hypertriton or antihypertriton particle before it decayed," explained Declan Keane of Kent State University (KSU). Telling the hypertriton and antihypertriton apart is easy because they decay into different daughters, he added.

"Keane's team, including Irakli Chakeberia, has specialized in tracking these particles through the detectors to 'connect the dots,'" Xu said. "They also provided much needed visualization of the events."

As noted, compiling data from many collisions revealed no mass difference between the matter and antimatter hypernuclei, so there's no evidence of CPT violation in these results.

But when STAR physicists looked at their results for the binding energy of the hypertriton, it turned out to be larger than previous measurements from the 1970s had found.

The STAR physicists derived the binding energy by subtracting their value for the hypertriton mass from the combined known masses of its building-block particles: a deuteron (a bound state of a proton and a neutron) and one lambda.

"The hypertriton weighs less than the sum of its parts because some of that mass is converted into the energy that is binding the three nucleons together," said Fudan University STAR collaborator Jinhui Chen, whose PhD student, Peng Liu, analyzed the large datasets to arrive at these results. "This binding energy is really a measure of the strength of these interactions, so our new measurement could have important implications for understanding the 'equation of state' of neutron stars," he added.

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Animal life thriving around Fukushima

Fukushima, Japan map.

Nearly a decade after the nuclear accident in Fukushima, Japan, researchers from the University of Georgia have found that wildlife populations are abundant in areas void of human life.

The camera study, published in the Journal of Frontiers in Ecology and the Environment, reports that over 267,000 wildlife photos recorded more than 20 species, including wild boar, Japanese hare, macaques, pheasant, fox and the raccoon dog -- a relative of the fox -- in various areas of the landscape.

UGA wildlife biologist James Beasley said speculation and questions have come from both the scientific community and the general public about the status of wildlife years after a nuclear accident like those in Chernobyl and Fukushima.

This recent study, in addition to the team's research in Chernobyl, provides answers to the questions.

"Our results represent the first evidence that numerous species of wildlife are now abundant throughout the Fukushima Evacuation Zone, despite the presence of radiological contamination," said Beasley, associate professor at the Savannah River Ecology Laboratory and the Warnell School of Forestry and Natural Resources.

Species that are often in conflict with humans, particularly wild boar, were predominantly captured on camera in human-evacuated areas or zones, according to Beasley.

"This suggests these species have increased in abundance following the evacuation of people."

The team, which included Thomas Hinton, professor at the Institute of Environmental Radioactivity at Fukushima University, identified three zones for the research.

Photographic data was gathered from 106 camera sites from three zones: humans excluded due to the highest level of contamination; humans restricted due to an intermediate level of contamination; and humans inhabited, an area where people have been allowed to remain due to "background" or very low levels of radiation found in the environment.

The researchers based their designations on zones previously established by the Japanese government after the 2011 Fukushima Daiichi accident.

For 120 days, cameras captured over 46,000 images of wild boar. Over 26,000 of those images were taken in the uninhabited area, compared to approximately 13,000 in the restricted and 7,000 in the inhabited zones.

Other species seen in higher numbers in the uninhabited or restricted zones included raccoons, Japanese marten and Japanese macaque or monkeys.

Anticipating questions about physiological condition of the wildlife, Hinton said their results are not an assessment of an animal's health.

"This research makes an important contribution because it examines radiological impacts to populations of wildlife, whereas most previous studies have looked for effects to individual animals," said Hinton.

The uninhabited zone served as the control zone for the research.

The scientists said although there is no previous data on wildlife populations in the evacuated areas, the close proximity and similar landscape of the human-inhabited zone made the area the ideal control for the study.

The team evaluated the impact of other variables: distance to road, time of activity as captured by the cameras' date-time stamps, vegetation type and elevation.

"The terrain varies from mountainous to coastal habitats, and we know these habitats support different types of species. To account for these factors, we incorporated habitat and landscape attributes such as elevation into our analysis," Beasley said.

"Based on these analyses, our results show that level of human activity, elevation and habitat type were the primary factors influencing the abundance of the species evaluated, rather than radiation levels."

The study's results indicate the activity pattern of most species aligned with their well-known history or behavior patterns. Raccoons, who are nocturnal, were more active during the night, while pheasants, which are diurnal animals, were more active during the day. However, wild boar inside the uninhabited area were more active during the day than boar in human-inhabited areas, suggesting they may be modifying their behavior in the absence of humans.

One exception to these patterns was the Japanese serow, a goat-like mammal. Normally far-removed from humans, they were most frequently seen on the camera footage in rural human-inhabited upland areas. The researchers suggest this might be a behavioral adjustment to avoid the rapidly growing boar population in the evacuated zone.

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Microrobots clean up radioactive waste

According to some experts, nuclear power holds great promise for meeting the world's growing energy demands without generating greenhouse gases. But scientists need to find a way to remove radioactive isotopes, both from wastewater generated by nuclear power plants and from the environment in case of a spill. Now, researchers reporting in ACS Nano have developed tiny, self-propelled robots that remove radioactive uranium from simulated wastewater.

The accidental release of radioactive waste, such as what occurred in the Chernobyl and Fukushima nuclear plant disasters, poses large threats to the environment, humans and wildlife. Scientists have developed materials to capture, separate, remove and recover radioactive uranium from water, but the materials have limitations. One of the most promising recent approaches is the use of metal-organic frameworks (MOFs) -- compounds that can trap specific substances, including radioactive uranium, within their porous structures. Martin Pumera and colleagues wanted to add a micromotor to a rod-shaped MOF called ZIF-8 to see if it could quickly clean up radioactive waste.

To make their self-propelled microrobots, the researchers designed ZIF-8 rods with diameters about 1/15 that of a human hair. The researchers added iron atoms and iron oxide nanoparticles to stabilize the structures and make them magnetic, respectively. Catalytic platinum nanoparticles placed at one end of each rod converted hydrogen peroxide "fuel" in the water into oxygen bubbles, which propelled the microrobots at a speed of about 60 times their own length per second. In simulated radioactive wastewater, the microrobots removed 96% of the uranium in an hour. The team collected the uranium-loaded rods with a magnet and stripped off the uranium, allowing the tiny robots to be recycled. The self-propelled microrobots could someday help in the management and remediation of radioactive waste, the researchers say.

From Science Daily

Measuring the laws of nature

There are some numerical values that define the basic properties of our universe. They are just as they are, and no one can tell why. These include, for example, the value of the speed of light, the mass of the electron, or the coupling constants that define the strength of the forces of nature.

One of these coupling constants, the "weak axial vector coupling constant" (abbreviated to gA), has now been measured with very high precision. This constant is needed to explain nuclear fusion in the sun, to understand the formation of elements shortly after the Big Bang, or to understand important experiments in particle physics. With the help of sophisticated neutron experiments, the value of the coupling constant gA has now been determined with an accuracy of 0.04 % The result has now been published in the journal "Physical Review Letters."

When particles change

There are four fundamental forces in our universe: electromagnetism, strong and weak nuclear force, and gravity. "To calculate these forces, we have to know certain parameters that determine their strength -- and especially in the case of weak interaction, this is a complicated matter," says Prof. Hartmut Abele from the Institute of Atomic and Subatomic Physics at TU Wien (Vienna). Weak interaction plays a crucial role when certain particles are transformed into others -- for example, when two protons merge into a nucleus in the sun and one of them becomes a neutron. To analyze such processes, the "weak axial vector coupling constant" gA has to be known.

There have been different attempts to measure gA. "For some of them, however, systematic corrections were required. Major disturbing factors can change the result by up to 30%," says Hartmut Abele.

A different measuring principle called "PERKEO" was developed in the 1980s in Heidelberg by Prof. Dirk Dubbers. Hartmut Abele has been involved in the work on the PERKEO detectors for many years, he himself has developed "PERKEO 2" as part of his dissertation. He works together with his former student Prof. Bastian Märkisch from TU Munich and Torsten Soldner from the Institut Laue-Langevin in Grenoble to significantly improve the measurement. With "PERKEO 3," new measurements have now been carried out in Grenoble, far exceeding all previous experiments in terms of accuracy.

The PEREKO detector analyzes neutrons, which decay into protons and emit a neutrino and an electron. "This electron emission is not perfectly symmetric," explains Hartmut Abele. "On one side, a few more electrons are emitted than on the other -- that depends on the spin direction of the neutron." The PERKEO detector uses strong magnetic fields to collect the electrons in both directions and then counts them. From the strength of the asymmetry, i.e. the difference in the number of electrons in the two directions, one can then directly deduce the value of the coupling constant gA.

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In ‘Shocking’ Discovery, Lightning Triggers Nuclear Reactions

Cloud-to-ground lightning discharge, Tucson, Arizona

If stars are nature’s fusion reactors, then lightning is its particle accelerator. The powerful electrical and magnetic fields generated by a lightning strike emit a flash of gamma rays that burst out in all directions, colliding with atmospheric gases like a celestial game of billiards.

For years, scientists have wondered if these collisions were powerful enough to knock neutrons out of stable nuclei, creating radioactive isotopes of gases like nitrogen and oxygen. Thanks to a powerful winter thunderstorm and some well-placed radiation detectors, a team of Japanese researchers captured the first definitive proof that lightning can trigger a type of nuclear reaction.

As reported Nov. 22 in the journal Nature, a cluster of radiation detectors at the Kashiwazaki-Kariwa nuclear power station on the Sea of Japan recorded gamma ray and positron emissions from an offshore lightning strike on February 6, 2016. The lightning data was exactly what you’d expect to see following photonuclear reactions, the collision of high-energy photons with atmospheric nuclei.

The result of such reactions is a radioactive isotope. Nitrogen-14, for example, is the most abundant particle in the atmosphere, with seven protons and seven neutrons. If a neutron is knocked out of nitrogen-14, it becomes the radioactive isotope nitrogen-13, which quickly decays after just nine seconds into the stable isotope carbon-13.

Before this new lightning discovery, it was believed that all isotopes, both radioactive and stable, were formed in only two ways: from nucleosynthesis in stars, or from collisions in the upper atmosphere between cosmic rays and atmospheric nuclei. The isotope carbon-14, for example, famous for its slow and steady rate of decay, is formed when cosmic rays collide with nitrogen-14 nuclei in the atmosphere, adding a neutron and popping out a proton.

What the Japanese lightning researchers found was an entirely new channel for producing isotopes of nitrogen, carbon, and oxygen, some of which are abundant in nature.

Teruaki Enoto is a physicist and astronomer at Kyoto University in Japan. Back in 2006, he and some collaborators launched the Gamma-Ray Observation of Winter Thunderclouds project, or GROWTH, to try to capture definitive radiation data from lightning storms. After a stint at NASA Goddard Space Flight Center as an X-ray astronomer, Enoto returned to Japan in 2015 and installed several highly sensitive radiation detectors at the nuclear power plant.

Winter storms along the coast of Japan have the dual advantages of being both very powerful and very low to the ground, Enoto told Seeker, making it easier for ground-based detectors like his to capture gamma-rays and other particle emissions.

Enoto said the radiation data captured from a single lightning strike in 2016 points to several exciting new ways of understanding lightning and its role in the universe. First and foremost, the data proved that lightning is a source of at least a small fraction of all radioactive and stable isotopes on Earth, although much more research is needed to figure out how many different isotopes are generated by lightning storms and at what volume.

Second, said Enoto, the new data expands our understanding of lightning’s effects on atmospheric particles, which scientists used to believe was limited to electrons.

“This detection of nuclear reactions implies that nuclei can change in the lightning, which means that nuclear physics can be applied to lightning physics,” he said.

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